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Notes: Abstract  The development of visual thalamocortical projections was analyzed quantitatively by comparing, in cresyl violet-stained brain sections of early postnatal (10–17 days) and adult cats, the cell body dimensions and total cell packing density (CPD) of neuronal populations in different laminae (A, A1 and C) of the dorsal lateral geniculate (dLGN), medial interlaminar nucleus (MIN), and in lateral (LPl), intermediate (LPi) and medial (LPm) subdivisions of the lateral posterior complex. Following injections of different fluorescent tracers (FB, NY, EB, RITC) into cortical visual areas 17/18, posterior medial (PMLS) and posterior lateral (PLLS) lateral suprasylvian and anterior ectosylvian (AEV), the thalamic distribution and densities of retrogradely labeled neurons were analyzed. Projection CPDs and ratios of projection/total CPDs were determined and compared within the different thalamic components in the kitten and adult cat. A significant decrease in total cell packing density was observed in the various thalamic components of the adult cat, varying between 43% and 65%, and a marked increase in mean cell body diameter in the A, A1 and C laminae and MIN from kitten to adult (8.4±1.8 and 11.8±2.8 µm respectively) compared to the LP subnuclei (9.0±1.3 and 9.1±1.5 µm). The ratios of projection/total CPDs decreased significantly for projections upon areas 17/18 stemming from layers A and A1 (20 and 25%, respectively) and from LPi upon both PMLS (34%) and AEV (16%). Thalamocortical projections observed in the kitten from LPi upon areas 17/18 and from the A-laminae upon PMLS were absent in the adult cat. The data indicate that, in comparison to the lateral posterior nucleus, the maturation of neurons within the dLGN and MIN is incomplete with respect to cell body size during the early postnatal period. In addition, the developmental changes observed involve both reductions in the total number of thalamic neurons and a differential loss of cortical projections. The selective elimination of early cortical connections stemming from dorsal lateral geniculate laminae A and A1 and from the intermediate division of the lateral posterior nucleus may occur through a process of axon collateral withdrawal from the expanded cortical sites, thereby giving rise to the adult pattern.

Notes: Abstract  Membrane potential changes and discharges from 28 laryngeal motoneurons were recorded intracellularly in the caudal nucleus ambiguus of decerebrate, paralyzed and ventilated cats. Electrical activities were recorded from 17 expiratory laryngeal motoneurons (ELMs) with maximal depolarizing membrane potential in early expiration, and from 11 inspiratory laryngeal motoneurons (ILMs) with maximal depolarizing membrane potential in inspiration. Activities during breathing were compared with those observed during fictive coughing and swallowing evoked by electrical stimulation of the superior laryngeal nerves. These non-respiratory behaviors were evidenced in paralyzed animals by characteristic discharge patterns of the phrenic, abdominal nerves and pharyngeal branch of the vagus nerve. We recorded the activity of 11 ELMs and 5 ILMs during coughing in which ELMs, but not ILMs, exhibited increased membrane depolarization and discharge frequencies. Membrane depolarization and discharge frequencies of all ELMs were also significantly increased during swallowing. In addition, membrane depolarization of most ELMs (15/17) was preceded by a short-lasting hyperpolarization due to chloride-dependent inhibitory mechanisms occurring at the onset of swallowing. Out of 10 ILMs tested during swallowing, 7 exhibited membrane depolarization, preceded in 5 cases by a short-lasting hyperpolarization. Discharge frequencies of ILMs were significantly reduced during swallowing. The same pattern of phasic activities of ILMs and ELMs was observed during coughing and breathing, suggesting the involvement of similar excitatory pathways in both behaviors. These results imply that the duration of activation and the discharge frequency of neurons of the central generator for breathing that drive laryngeal motoneurons are enhanced during coughing. During swallowing, in addition to central excitatory mechanisms, laryngeal motoneurons are subjected to an initial inhibition of unknown origin. This inhibition probably contributes to the temporal organization of the swallowing motor sequence.

Notes: Abstract Clinical applications of flow cytometry to certain diseases of the dog and cat are now possible. The utility of such applications for diagnosis, prognosis and follow-up are illustrated here by a number of examples: feline AIDS resulting from FIV infection, Leukocyte Adhesion Deficiency in Irish setters, deep pyoderma in German shepherds, Immune-mediated Thrombocytopenia, canine Systemic Lupus Erythematosus and Leishmaniasis, Leukemia and Lymphoma.

Notes: Abstract A 49-year-old man had three episodes of bacterial peritonitis in the 8 months after he started nocturnal intermittent peritoneal dialysis (NIPD) at home, using an automated cycler device. When peritonitis was first diagnosed, Enterobacter agglomerance was cultured in his peritoneal fluid. In the second and third episodes, Pasteurella multocida and alpha-Streptococcus were isolated, respectively. These bacteria are unusual pathogens in continuous ambulatory peritoneal dialysis (CAPD) peritonitis. Detailed questioning revealed that a domestic cat had bitten the dialysis tube before the patient experienced the second episode of peritonitis. Pasteurella multocida is part of the normal oral flora in cats and dogs. We isolated Pasteurella multocida from the teeth of the patient's cat. Enterobacter agglomerance is part of the common bacterial flora in animal's alimentary tract, and alpha-Streptococcus is commonly found in animal's respiratory tracts. Since the patient removed the cat from his bedroom, he has had no peritonitis. NIPD is a very convenient sysytem for patients in the final stage of renal failure; however, patients must be aware of the risks associated with keeping pets in their homes. This case is the first report of cat-associated peritonitis in Japan.

Notes: Abstract  Functional connections of single reticulospinal neurons (RSNs) in the nucleus reticularis gigantocellularis (NRG) with ipsilateral dorsal neck motoneurons were examined with the spike-triggered averaging technique. Extracellular spikes of single NRG-RSNs activated antidromically from the C6, but not from the L1 segment (C-RSNs) were used as the trigger. These neurons were monosynaptically activated from the superior colliculus and the cerebral peduncle. Single-RSN PSPs were recorded in 43 dorsal neck motoneurons [biventer cervicis and complexus (BCC) and splenius (SPL)] for 21 NRG-RSNs and 135 motoneurons tested. All synaptic potentials were EPSPs, and most of their latencies, measured from the triggering spikes, were 0.8–1.5 ms, which is in a monosynaptic range. The amplitudes of single-RSN EPSPs were 10–360 µV. Spike-triggered averaging revealed single-RSN EPSPs in multiple motoneurons of the same species (SPL or BCC), their locations extending up to nearly 1 mm rostrocaudally. Synaptic connections of single RSNs with both SPL and BCC motoneurons were also found with some predominance for one of them. The results provide direct evidence that NRG-RSNs make monosynaptic excitatory connections with SPL and BCC motoneurons. It appears that some NRG-RSNs connect predominantly with SPL motoneurons and others with BCC motoneurons.

Notes: Abstract  Postsynaptic potentials (PSPs) evoked in motoneurons innervating the back and abdominal muscles in the lumbar part of the body by stimulating hindlimb cutaneous afferents were investigated in unanesthetized decerebate and spinal cats. Various types of PSP: pure excitatory postsynaptic potential (EPSP), pure inhibitory postsynaptic potential (IPSP), and mixed PSP (i.e., EPSP followed by IPSP, EPSP/IPSP; and IPSP followed by EPSP, IPSP/EPSP) were observed. The weak stimulation at 2 times threshold (2T) produced predominantly the EPSP, while at 5T the incidence of IPSP or EPSP followed by IPSP was increased. In about 20–50% of the various groups of motoneurons, PSPs evoked by ipsi- and contralateral nerves were qualitatively and quantitatively similar. For the other motoneurons, PSPs evoked by ipsi- and contralateral nerves were markedly different with respect to magnitude and/or polarity. These findings suggest that, within each motoneuron pool, some neurons act to increase stiffness of the trunk or to move vertically in response to an increased activity of cutaneous afferents, while the other motoneurons act to produce lateral bending of the trunk.

Notes: Abstract  Receptive-field properties of retinal ganglion cells (RGCs) that had regenerated their axons were studied by recording single-unit activity from strands teased from peripheral nerve (PN) grafts apposed to the cut optic nerve in adult cats. Of the 286 visually responsive units recorded from PN grafts in 20 cats, 49.7% were classified, according to their receptive-field properties, as Y-cells, 39.5% as X-cells, 6.6% as W-cells, and 4.2% were unclassified. The predominant representation of Y-cells is consistent with a corresponding morphological study (Watanabe et al. 1993a), which identified α-cells as the RGC type with the largest proportion of regenerating axons. Among the X-cells, we only found ON-center types, whereas both ON-center and OFF-center Y-cells were found. As in intact retinas, the receptive-field center sizes of Y-cells and W-cells were larger than those of X-cells at corresponding displacements from the area centralis. Within the 10° surrounding the area centralis, the receptive fields of X-cells with regenerated axons were larger than those in intact retinas, suggesting that some rearrangement of retinal circuitry occurred as a consequence of degeneration and regeneration. Receptive-field center responses of Y-, X-, and W-type units with regenerated axons were similar to those found in intact retinas, but the level of spontaneous activity of Y- and X-type units was, in general, less than that of intact RGCs. Receptive-field surrounds were weak or not detected in more than half of the visually responsive RGCs with regenerated axons.

Notes: Abstract  Corticospinal (CS) axon terminations in several species are widespread early in development but are subsequently refined into a spatially more restricted distribution. We studied the role of neural activity in sensorimotor cortex in shaping postnatal development of CS terminations in cats. We continuously infused muscimol unilaterally into sensorimotor cortex to silence neurons during the postnatal CS refinement period (weeks 3–7). Using anterograde transport of WGA-HRP, we examined the laterality of terminations from the muscimol-infused (i.e., silenced) and active sides in the spinal cord, as well as in the cuneate nucleus and red nucleus. We found that CS terminations from the muscimol-infused cortex were very sparse and limited to the contralateral side, while those from the active cortex maintained an immature bilateral topography. Controls (saline infusion, noninfusion) had dense, predominantly contralateral, CS terminations. There was a substantial decrease in the spinal gray matter area occupied by terminations from the side receiving the blockade and a concomitant increase in the area occupied by ipsilateral terminations from the active cortex. Optical density measurements of HRP reaction product from the active cortex in muscimol-infused animals showed substantial increases over controls in the ratio of ipsilateral to contralateral CS terminations for all laminae examined (IV–V, VI, VII). Our findings suggest that ipsilateral dorsal horn terminations reflect new axon growth during the refinement period because they are not present there earlier in development. Those in the ventral horn are present earlier in development and thus could reflect maintenance of transient terminations. Increased ipsilateral terminations from active cortex were due to recrossing of CS axons in lamina X and not to an increase in labeled CS axons in the ipsilateral white matter. Examination of brain stem terminations suggested that, between postnatal weeks 3 and 7, development of corticocuneate terminations also is activity-dependent but that development of corticorubral terminations is not. Activity-dependent CS development is a plausible mechanism by which early motor experiences could shape the anatomical and functional organization of the motor systems during a critical postnatal period.

Notes: Abstract  Pontine omnipause neurons (OPNs) have so far been considered as forming a homogeneous group of neurons whose tonic firing stops during the duration of saccades, when the head is immobilized. In cats, they pause for the total duration of gaze shifts, when the head is free to move. In the present study, carried out on alert cats with fixed heads, we present observations made during self-initiated saccades and during tracking of a moving target which show that the OPN population is not homogeneous. Of the 76 OPNs we identified, 39 were found to have characteristics similar to those of previously described neurons, ”saccade” (S-) OPNs: (1) the durations of their pauses were significantly correlated with the durations of saccades; (2) the discharge ceased shortly before saccade onset and resumed before saccade end; (3) visual responses to target motion were excitatory; and (4) during tracking, S-OPNs interrupted the discharge for the duration of saccades and resumed firing during perisaccadic ”drifts”. However, the characteristics of 37 neurons (”complex” (C-) OPNs) were different: (1) the pause duration was not correlated with the duration of self-initiated saccades; (2) time lead of pause onsets relative to saccades was, on average, longer than in the group of S-OPNs, and firing resumed after the saccade end; (3) visual target motion suppressed tonic discharges; and (4) during tracking, firing was interrupted for the total duration of gaze shifts, including not only saccades but also perisaccadic ”drifts”. We conclude that cat OPNs can be subdivided into two main groups. The first comprises neurons whose firing patterns are compatible with gating individual saccades (”saccade” OPNs). The second group consists of ”complex” OPNs whose firing characteristics are appropriate to gate total gaze displacements rather than individual saccades. The function of these neurons may be to disinhibit pontobulbar circuits participating in the generation of saccade sequences and associated perisaccadic drifts.

Notes: Abstract  Connections from the otolithic organs to sternocleidomastoid (SCM) motoneurons were studied in 20 decerebrate cats. The electrical stimulation was selective for the saccular or the utricular nerves. Postsynaptic potentials were recorded from antidromically identified SCM motoneurons; these muscles participate mainly in neck rotation and flexion. Partial transections of the brainstem at the level of the obex were performed to identify the possible pathway from the otolithic organs to the SCM motoneurons. Saccular or utricular nerve stimulation mainly evoked inhibitory postsynaptic potentials (IPSPs) in the ipsilateral SCM motoneurons. Some of the sacculus-induced IPSPs were preceded by small-amplitude excitatory PSPs (EPSPs). The latencies of the PSPs ranged from 1.8 to 3.1 ms after saccular nerve stimulation and from 1.7 to 2.8 ms after utricular nerve stimulation, indicating that most of the ipsilateral connections were disynaptic. In the contralateral SCM motoneurons, saccular nerve stimulation had no or faint effects, whereas utricular nerve stimulation evoked EPSPs in about two-thirds of neurons, and no visible PSPs in about one-third of neurons. The latencies of the EPSPs ranged from 1.5 to 2.0 ms, indicating the disynaptic connection. Thus, the results suggest a difference between the two otolithic innervating patterns of SCM motoneurons. After transection of the medial vestibulospinal tract (MVST), saccular nerve stimulation did not evoke IPSPs at all in ipsilateral SCM motoneurons, but some (11/40) neurons showed small-amplitude EPSPs. Most (24/33) of the utricular-activated IPSPs disappeared after transection, whereas the other 9 neurons still indicated IPSPs. In the contralateral SCM motoneurons, no utricular-activated EPSPs were recorded after transection. These MVST transection results suggest that most of the otolith-SCM pathways are located in the MVST at the obex level. However, the results also suggest the possibility that other otolith-SCM pathways exist at the obex level.

Notes: Abstract  Accurate performance by the vestibulo-ocular reflex (VOR) is necessary to stabilize visual fixation during head movements. VOR performance is severely affected by peripheral vestibular damage; after one horizontal semicircular canal is plugged, the horizontal VOR is asymmetric and its amplitude is reduced. The VOR recovers partially. We investigated the limits of recovery by measuring the VOR’s response to ipsilesional and contralesional rotation after unilateral peripheral damage in cats. We found that the VOR’s response to rotation at high frequencies remained asymmetric after recovery was complete. When the stimulus was a pulse of head velocity comprising a dynamic overshoot followed by a plateau, gain was partially restored and symmetry completely restored within 30 days after the plug, but only for the plateau response. The overshoot in eye velocity remained asymmetric. The asymmetry was independent of stimulus velocity throughout the known linear velocity range of primary vestibular afferents. Sinusoidal rotation at 0.05–8 Hz revealed that, within this range, the persistent asymmetry was significant only at frequencies above 2 Hz. Asymmetry was independent of the peak head acceleration over the range of 50–500°/s2. When both horizontal canals were plugged, a small residual VOR was observed, suggesting residual signal transduction by plugged semicircular canals. However, transduction by plugged canals could not explain the enhancement of the VOR gain, at high frequencies, for rotation away from the plugged side compared with rotation toward the plug. Also, the high-frequency asymmetry was present after recovery from a unilateral labyrinthectomy. These results suggest that high-frequency asymmetry after unilateral damage is not due to residual function in the plugged canal. The findings are discussed in the context of a bilateral model of the VOR that includes central filtering.

Notes: Abstract  The purpose of this review is to assess the role of short-latency pathways in the vestibulocollic reflex (VCR). First the current knowledge about the disynaptic and trisynaptic pathways linking semicircular canal and otolith afferents with cat neck motoneurons is summarized. We then discuss whether these pathways are sufficient or necessary to produce the responses observed in neck muscles by natural vestibular stimulation and conclude that they are neither. Finally, alternate pathways are considered, most likely involving reticulospinal fibers, which are an important part of the neural substrate of the VCR.

Notes: Abstract  The retrograde axonal transport method was used to compare the topography and organization of the visual zone of the claustrum in rat, guinea pig, rabbit and cat. First, massive Fluoro-Gold injections were placed into the primary visual cortex and the secondary areas. Experiments showed differences in the location of the visual zone among the animals under study. In rat, the visual zone occupied the posteroventral part of the claustrum and spread to its anterior pole. In guinea pig, neurons projecting to the visual cortex were located dorsally in the posterior half of the claustrum. In rabbit, similarly to the rat, they were localized in the posteroventral part; however, they did not reach the anterior pole. In cat, neurons that project to the visual cortex were concentrated dorsally in the posterior fourth of the claustrum. In double-injection experiments, Fast Blue and Diamidino Yellow were placed into the primary and secondary visual areas in various combinations. The experiments showed that in the rat and the rabbit claustral neurons project to primary visual cortex (area 17) as well as to both secondary visual areas (areas 18a and b). Populations of neurons sending axons to the primary and secondary areas showed full overlap. The presence of double-labeled neurons indicates that some claustral neurons project both to the primary and secondary fields. In cat, neurons that project to the primary visual cortex appear to be clearly separated from those connected with the secondary visual area, as no double-labeled neurons were found. In all studied species, the double injections placed into the visual and primary somatosensory cortex did not result in any double-labeling neurons. Our results indicate that the location of the visual zone in the posterior part of the claustrum is a phylogenetically stable feature, whereas its dorsoventral shift as well as the extent toward the anterior pole is related to the particular species. The overlap of neurons projecting to the primary and secondary visual areas in the rat and rabbit as well as the separation of both projections in cat appear to reflect the higher degree of complexity of the visual system in the latter.

Notes: Abstract  In cats the global (gCBF) as well as the regional cerebral blood flow (rCBF) and blood pressure were measured before, during, and after noxious inward and outward rotations of normal and inflamed elbow joints. The animals were anesthetized with halothane and immobilized by gallamine triethiodide. The gCBF as well as the rCBF were measured using positron emission tomography (PET) with a camera specifically designed for use in small animals. Slow intravenous bolus injections of 15O-labeled water were followed by 3-min acquisition of regional radioactivity starting at the time of injection. In all experiments the gCBF as well as the blood pressure were increased by noxious inward-outward rotations of the normal and of the inflamed joint, whereas the blood pressure and the rCBF remained unchanged during bolus injections under control conditions (without any joint movement). Movements of the inflamed joint evoked significantly greater increases in blood pressure and gCBF than corresponding ones of the normal joint. These increases in gCBF were paralleled by increases in rCBF along the complete anterior to posterior axis of the brain. Again, the increases in rCBF were larger, more extensive and more uniform following the stimulation of the inflamed joint relative to the results obtained with stimulation of the normal joint. No significant laterality was seen, but when an atlas-based region of interest (ROI) analysis was carried out and when the individual variations in rCBF were removed with two-way ANOVA, significant differences were disclosed in rCBF between the stimulated condition and the resting condition in a large number of brain regions. In particular, noxious rotation of the normal (right) elbow joint induced a significant increase in rCBF over the cerebral cortex and in the right thalamus and hippocampus. The same stimulation of the (left) inflamed joint induced a significant increase in rCBF throughout the brain; the biggest increase being over the right posterior cortex. It is concluded that under the conditions of the present experiments the generally accepted autoregulation of the cerebral blood flow is not fully functioning, and various factors that may be responsible for this failure (which obscures rCBF differences) are discussed. The more pronounced increases in rCBF when moving inflamed joints instead of normal ones is thought to be a direct consequence of the peripheral sensitization of the articular nociceptors and the consequent central hyperexcitability induced in the articular nociceptive pathways.

Notes: Abstract  This study examined (1) how changes in head position affect postural orientation variables during stance and (2) whether changes in head position affect the rapid postural response to linear translation of the support surface in the horizontal plane. Cats were trained to stand quietly on a moveable platform and to maintain five different head positions: center, left, right, up, and down. For each head position, stance was perturbed by translating the support surface linearly in 16 different directions in the horizontal plane. Postural equilibrium responses were quantified in terms of the ground reaction forces, kinematics, dynamics (net joint torques), body center of mass, and electromyographic (EMG) responses of selected limb and trunk muscles. A change in head position involved rotation of not only the neck but also the scapulae and anterior trunk. Tonic EMG levels were modulated in several forelimb and scapular muscles but not hindlimb muscles. Finally, large changes in head orientation in both horizontal and vertical planes did not hamper the ability of cats to maintain postural equilibrium during linear translation of the support surface. The trajectory of the body’s center of mass was the same, regardless of head position. The main change was observed in joint torques at the forelimbs evoked by the perturbation. Evoked EMG responses of forelimb and scapular muscles were modulated in terms of magnitude but not spatial tuning. Hindlimb responses were unchanged. Thus, the spatial and temporal pattern of the automatic postural response was unchanged and only amplitudes of evoked activity were modulated by head position.

Notes: Abstract  Visually evoked potentials (VEPs) measured under conditions of retinal image stabilization that minimized the influences of visual masking and smearing were averaged from electroencephalographic records measured from striate cortex of three cats. The amplitudes of the VEPs increased around saccade initiation. The grating-evoked potentials obtained at different times relative to the saccade exhibited changes in waveform shape that could be attributed to a saccade-evoked potential. The changes in the shape of the waveform were reasonably accounted for by the summation of the grating-evoked potential (produced when the cat did not make a saccade) and an appropriately timed saccade-evoked potential. The fundamental amplitudes of the residual potentials were computed and found to vary across the time course of the saccade. These observations suggest that there are other influences besides visual masking that are exerted early in the visual pathway to modulate visual processing during saccadic eye movements. A corollary discharge process is the most likely candidate to exert these influences.

Notes: Abstract  The neuronal responsiveness to three-dimensional (3D) motion in cat posteromedial lateral suprasylvian (PMLS) cortex was studied using a computer-controlled, stereoscopic 3D graphic display capable of reproducing the major visual cues for natural 3D motion, including motion disparity, size, texture, and shading changes. The animals were anesthetized with nitrous oxide supplemented with alphaxalone, and paralysis prevented eye movement. Systematic investigation of neuronal responsiveness to 3D motions in 26 different directions revealed that more than half of the PMLS cells were selectively responsive to approaching (AP cells, 112 of 271) or recessive motion (RC cells, 64 of 271). The remaining cells were selectively responsive to frontoparallel motion (FP cells, 49 of 271) or nonselectively responsive to motion in multiple directions (NS cells, 46 of 271). The dependency on these visual cues was investigated as a reduction in the response amplitude or the response selectivity for the removal of a single cue from the motion stimuli containing the full visual cues. The AP and RC cells showed a strong dependency on the motion disparity cue, moderate dependency on the size cue, and weak dependency on the texture and shading cues. The FP cells showed no dependency on those visual cues. The cue dependency analysis indicated the existence of nonlinear interactions between those visual cues. Comparison of the responses to a combination of the motion disparity and size cues with the summed responses to each of the individual cues revealed that the responses to the combined cues are roughly predicted as a linear sum between the preferred responses. This comparison also showed nonlinear summation between the nonpreferred responses, i.e., responses to the combined cues were smaller than the summed responses. A similar quasilinear summation of the preferred responses between the two eyes and a nonlinear summation of the nonpreferred responses were found in the AP and RC cells for the motion disparity stimulus. All of these observations indicate that quasilinear and nonlinear interactions of the responses to various stimulus elements underlie the 3D motion responsiveness of the PMLS cells.

Notes: Abstract  The experiments reported here demonstrate that the mechanical sensitivity of peripheral nerve fibres typically seen after injury can be induced without overtly injuring the nerve, but by simply applying colchicine topically to the nerve. In cats anaesthetised with pentobarbitone sodium, the medial gastrocnemius nerve was exposed and 10 mM colchicine applied topically for 15 min. The animals recovered from the operation normally and showed no subsequent motor deficit. Six days later animals were re-anaesthetised, a laminectomy carried out and responses recorded in single afferents at the level of the dorsal root. It was found that many afferents, particularly those with conduction velocities in the group II–III range, had become sensitive to local mechanical stimulation of the nerve in the region treated with colchicine and showed slowly adapting responses to stretch of the nerve. Many of the smaller fibres exhibited spontaneous activity. Mechanically sensitive afferents exhibited impulse conduction blocks at the colchicine-treated site. Some afferents, which appeared to conduct impulses normally through the treated region, were associated with muscle receptors having normal response properties. However, other muscle receptors were clearly abnormal and were insensitive to muscle stretch or contraction or exhibited only phasic responses. When the nerve was cut proximal to the colchicine-treated site, some, but not all, spontaneous activity was abolished. It was subsequently shown using a collision technique that the activity in some axons had its origin in the cell body in the dorsal root ganglion. In one experiment, it was shown that after nerve section proximal to the colchicine-treated region three of five axons switched their activity from a peripheral to a central origin. It is postulated that colchicine disrupts fast axonal transport of mechanically sensitive or voltage-sensitive ion channels, from the cell body to the peripheral terminals of the axons, leading to an accumulation of these channels at the treated site. This induces mechanical sensitivity and spontaneous activity. It is postulated that interruption of a retrogradely transported signal induces the spontaneous activity in the cell body. These experiments suggest that an important influence is exerted by the cell body on the peripheral terminals of mechanoreceptors to confer on them their normal response properties.

Notes: Abstract The aim of this electron-microscopic study was to analyze the distribution of synaptic contacts on the cell bodies and dendrites of permanently axotomized adult cat spinal α-motoneurons. Following transection and ligation of the medial gastrocnemius nerve, the synaptic covering of the cell bodies and three different dendritic compartments of homonymous α-motoneurons was analyzed quantitatively at 3, 6, and 12 weeks postoperatively. The synaptic boutons were classified according to their size and the shape of their synaptic vesicles. On the soma, a transient increase in the number of boutons was noted at 3 weeks and 6 weeks postoperatively, while after 12 weeks the bouton number had decreased to half of its normal value. The transient increase was mainly due to an increase in the number of F-type boutons. At 12 weeks postoperatively, the synaptic covering was reduced by 83% on the soma and by 57% on the proximal dendrites. In the distal dendritic regions, the values for synaptic covering remained largely unchanged. In summary, axotomized motoneurons exhibit a reduction in synaptic covering which is maximal on the cell body and becomes less pronounced centrifugally along the dendrites. However, if also taking into account the loss of distal dendritic branches that occurs in axotomized motoneurons, the total loss of boutons is several times larger in the dendrites than on the soma.

Notes: Abstract  In our previous report we found that subcutaneous (s.c.) formalin injection into the cutaneous receptive field (RF) of dorsal horn wide-dynamic-range (WDR) units and nociceptive primary afferent units resulted in a tonic, long-lasting increase in firing. However, s.c. formalin injection only resulted in a short-lasting increase in firing of non-nociceptive primary afferent units. In the present study, by using extracellular single-unit recording techniques we further studied effects of s.c. formalin on response properties of identified superficial-layer nociceptive-specific (NS) units and deeper-layer, low-threshold mechanoreceptive (LTM) units of L7 dorsal horn in urethane-chloralose-anesthetized cats. s.c. formalin injection into the RF of NS units resulted in a tonic, long-lasting increase in firing (7.08 ± 0.42 spikes/s, n = 5), for more than 1 h, compared with the spontaneous background (1.42 ± 0.03 spikes/s, n = 5). Formalin injection into the RF of LTM units also resulted in an increase in firing; however, the duration was short-lasting, for 25–520 s (152.92 ± 46.73 s, n = 12). The present study demonstrated that s.c. injection of dilute formalin solution resulted in activation of not only nociceptive but also non-nociceptive dorsal horn units, suggesting that tissue injury caused by s.c. formalin results in vigorous injury discharges of peripheral nerve terminals, which subsequently leads to activation of primary afferent neurons and secondary dorsal horn neurons.

Notes: Abstract  The dendritic tree constitutes more than 93% of the receptive membrane area of a spinal motoneuron, yet little is known about its synaptic inputs. In this study we examined the distribution of glutamate-, GABA- and glycine-like immunoreactivity in boutons apposing dendrites in the L7 spinal cord motor nucleus, by use of postembedding immunohistochemistry on serial sections. We examined 799 boutons apposing 401 cross-sectioned dendrites of different calibre (range 0.2–15 µm), and 14 first-order (stem) dendrites. Thirty-five percent (35%) of the boutons were immunopositive for glutamate and 59% for GABA and/or glycine. Among the latter, 30% showed glycine immunoreactivity only and 24% were immunoreactive for both GABA and glycine. Very few were immunoreactive only for GABA (5%). As few as 6% of the boutons were judged as not enriched for any amino acid analysed. The fine structural characteristics of the boutons were in accordance with previous descriptions. The sample of dendrites was arranged in calibre bins in order to facilitate distribution analysis. Stem dendrites differed from the other bins, with a high total bouton covering (61%) and a high bouton density. Sixty-nine percent of the membrane covering was by glycine- and/or GABA-immunoreactive boutons, whereas 18% was covered by boutons enriched in glutamate. For non-stem dendrites, bouton covering fell from 33% to 12% with decreasing calibre. However, bouton apposition length decreased in parallel, yielding a fairly uniform bouton density among dendrites of different calibre. The lack of correlation between packing density and dendrite calibre was also evident when the sample of dendrites was broken down into subsamples based on content of amino acid immunoreactivity. The latter analysis also revealed that both the relative covering and density of boutons containing inhibitory amino acids (57%; glycine and/or GABA) and glutamate (38%), respectively, did not vary systematically with dendrite calibre. Combined, the data indicate that in non-stem dendrites the proportion of excitatory and inhibition inputs does not change systematically throughout the dendritic arborizations of spinal α-motoneurons. Thus, spinal motoneurons can, with respect to the general synaptic architecture, be divided into two main compartments, i.e. the proximal soma-juxtasomatic compartment (including stem dendrites) and the distal dendritc compartment. The proximal domain is under a powerful glycine and/or GABA influence. Finally, based on the data presented here and previously published data, it was calculated that spinal α-motoneurons receive in the range of 50–140×103 synaptic boutons.

Notes: Abstract  The possibility of collateral segmental actions of spinocervical tract (SCT) neurones upon interneurones with input from cutaneous and group II muscle afferents was investigated in deeply anaesthetized cats. To this end, intracellular and/or extracellular recordings were made from 35 dorsal horn and 15 intermediate zone interneurones in midlumbar segments of the spinal cord and effects of stimulation of the ipsilateral dorso-lateral funiculus (DLF) at C3 and C1 levels, i.e. below and above the lateral cervical nucleus where axons of SCT cells terminate, were compared. The stimuli applied at the C3 segment were within the range of stimuli (50–100 μA) required for antidromic activation of SCT neurones in the same experiment. Those applied at the C1 segment (200–500 μA) were at least 3 times stronger than C3 stimuli. Under the same experimental conditions, long ascending and descending tract neurones (dorsal spino-cerebellar and rubro-spinal tract neurones) with axons in the DLF were activated at similar thresholds from the C1 and C3 segments. Intracellular recordings were made from 29 interneurnoes of which 19 (65%) were dorsal horn and 10 (35%) were intermediate zone interneurones. Excitatory postsynaptic potentials (EPSPs) evoked by single stimuli applied at the C3 segment, but not the C1 segment, were found in 14 (48%) of those interneurones; their latencies (3.0–5.7 ms) and frequency following with only minimal temporal facilitation were as required for potentials being evoked monosynaptically by the fastest conducting SCT neurones. Extracellular recordings were made from 30 interneurones (24 dorsal horn and 6 intermediate zone interneurones), and in these neurones spike potentials induced from the C3, but not from the C1 segment, were evoked only by short trains of stimuli. However, their latencies from the first effective stimulus (4.3–5.4 ms) were compatible with mono- or oligosynaptically mediated collateral actions of SCT neurones. They were found in 10 (33%) of the 30 investigated interneurones. Similar effects of C3 stimuli were found in similar proportions of dorsal horn interneurones and intermediate zone interneurones. Indications were also found for synaptic actions evoked by C3 stimuli that could not be attributed to direct collateral actions of SCT neurones. In some intracellularly recorded dorsal horn interneurones, short-latency EPSPs were evoked from the C3 segment by the 2nd or 3rd stimulus in the train, but not by single stimuli. In other dorsal horn and intermediate zone interneurones, inhibitory postsynaptic potentials (IPSPs) were evoked from the C3 segment at minimal latencies (2.7–3.2 ms), which might be too short to allow their mediation via SCT neurones. We conclude that SCT neurones might be used to forward information from muscle group II and cutaneous afferents not only to neurones in the lateral cervical nucleus and via them to thalamus and cerebral cortex but also to interneurones in spinal reflex pathways. Thereby reflex actions evoked from group II and cutaneous afferents might be co-ordinated with responses mediated by supraspinal neurones. We conclude also that dorsal horn and intermediate zone mid-lumbar interneurones might contribute to the previously reported di-and poly-synaptic excitation or inhibition of postsynaptic dorsal column (PSDC), spinothalamic tract (STT) and spinomesencephalic tract (SMT) neurones by collateral actions of SCT cells. Thereby these interneurones might contribute to the co-ordination of responses mediated by various populations of supraspinal neurones.

Notes: Abstract  The robust behavior, the degree of response linearity, and the aspect of contrast gain control in visual cortical simple cells are (amongst others) the result of the interplay between excitatory and inhibitory afferent and intracortical connections. The goal of this study was to suggest a simple intracortical connection pattern, which could also play a role in other cortical substructures, in order to generically obtain these desired effects within large physiological parameter ranges. To this end we explored the degree of linearity of spatial summation in visual simple cells experimentally and in different models based on half-wave rectifying cells (’’push-pull models’’). Visual cortical push-pull connection schemes originated from antagonistic motor-control models. Thus, this model class is widely applicable but normally requires a rather specific design. On the other hand we showed that a more generic version of a push-pull model, the so-called cascaded inhibitory intracortical connection scheme, which we implemented in a biologically realistic simulation, naturally explains much of the experimental data. We investigated the influence of the afferent and intracortical connection structure on the measured linearity of spatial summation in simple cells. The analysis made use of the relative modulation measure, which is easy to apply but is limited to moving sinusoidal grating stimuli. We introduced two basic push-pull models, where the order of threshold nonlinearity and linear summation is reversed. Very little difference is observed with the relative modulation measure for these models. Alterative models, like half-wave squaring models, were also briefly discussed. Of all model parameters, the ratio of excitation to inhibition in the simple cell exerts the most crucial influence on the relative modulation. Linearity deteriorates as soon as excitatory and inhibitory inputs are imbalanced and the relative modulation drops. This prediction was tested experimentally by extracellular recordings from cat area 17 simple cells and we found that about 62% showed a significant deviation from linear behavior. The problem that individual basic push-pull models are hard to distinguish experimentally led us to suggest a different solution. In order to generically account for the observed behavior (e.g., imbalance of excitation versus inhibition), we suggested a rather generic version of a push-pull model where it no longer mattered about (the hard-to-distinguish) fine differences in connectivity. Thus, we introduced a new class of biophysically realistic models (’’cascaded inhibition’’). This model class requires very little connection specificity and is therefore highly robust against parameter variations. Up to 25 cells are connected to each target cell. Thereby a highly interconnected network is generated, which also leads to disinhibition at some parts of an individual receptive field. We showed that the performance of these models simulates the degree of linearity and its variability in recal simple cells with comparatively high accuracy. This behavior can be explained by the self-regulating properties of a cascaded inhibitory connection scheme by which the balance between excitation and inhibition at a given cell is improved by the joint network effects. The virtues and the generic design of this connection pattern, therefore, allow to speculate that it is used also in other parts of the cortex.

Notes: Abstract  The generation of locomotor-like spinal rhythms has been proposed to involve two neural centres with mutual reciprocal inhibition (Graham Brown’s ”half-centre” hypothesis). Much later a particular set of segmental flexor reflex pathways were described as being organized in accordance with this half-centre hypothesis. As these pathways became operative following injection of monoaminoxidase inhibitors and l-3,4-dihydroxyphenylalanine (l-dopa), i.e. under the same conditions under which a spontaneous locomotor activity may develop, it was assumed that these particular pathways and spinal rhythm generators involve the same neuronal networks. In order to give further evidence to this hypothesis, we investigated whether short trains to ”flexor reflex afferents” (FRA) reset the spinal locomotor rhythm, i.e. shorten or lengthen the stimulated cycle after which the regular rhythm is resumed with step cycles of the original duration. The experiments were performed in anaemically decapitated, high-spinal curarized cats. A steady locomotor rhythm was induced by injection of nialamide and l-dopa and the influence of electrical stimulation (trains of 50–1000 ms) of FRA (joint, cutaneous, and group II and III muscle afferents) onto this rhythm was tested. Stimulation of FRA induced a clear resetting of the locomotor rhythm, which was mainly characterized by a flexion reflex pattern: during the extension phase the extensor activity was interrupted and a flexion phase was initiated; during the late flexion phase mainly a prolongation of that phase with a variable change of the following extension phase was induced. In addition to this prevailing pattern, stimulation of some nerves (in particular nerves to more distal extensors and the sural nerve) could often prolong extension, when stimulated during the late extension, or terminate the flexor burst and initiate a new extension phase, when stimulated during the late flexion phase. This pattern is probably due to the concomitant stimulation of group I afferents in the case of the muscle nerves and to separate non-FRA pathways in the case of the sural nerve. The results demonstrate that the interneurones of the FRA pathways, which are operative during l-dopa-induced locomotion in spinal animals, can be considered as neuronal elements of the rhythm-generating network for locomotion.

Notes: Abstract  Feline caudofemoralis (CF) is a promising preparation in which to study the properties of mammalian fast-twitch skeletal muscle, but little is known about its muscle fiber properties, architecture, and motor innervation. We used histochemical techniques to confirm that it contained predominantly type IIB fibers (95±2%, n=8, with six of eight muscles composed exclusively of type IIA and IIB fibers), but physiological experiments showed less fatiguability than for the type IIB component of medial gastrocnemius. This may be related to the surprisingly strong and regular recruitment of CF during repetitive tasks such as walking and trotting, which we demonstrated electromyographically. We measured muscle length over the anatomical range of motion for CF (∼0.6–1.2 L 0) and estimated working length during walking and trotting (∼0.95–1.15 L 0). The specific tension was similar to that of the exclusively slow-twitch soleus muscle (31.2±4.7 N/cm2 compared with 31.8±4.1 N/cm2; P〉0.8). Single fiber dissections of CF revealed a series-fibered architecture with a mean of 2.3 fibers, each 2.5 cm long, required to span the fascicle length. We identified two neuromuscular compartments in CF by cutting one of the two nerve branches innervating CF and depleting the glycogen stores in the intact motor units. These compartments were in parallel and extended the length of the muscle; their electromyographic activity was similar during various natural behaviors. CF and gluteus maximus motoneurons were labeled concurrently with a combination of fluorescent, retrograde tracers including Fluororuby, Fluorogold and Fast Blue. The CF motor nucleus was located in L7-S1, overlapping and intermingling extensively with the nucleus of the adjacent gluteus maximus muscle. Distributions of CF motoneuron diameter revealed one large peak around 50–55 µm, with relatively few small-diameter (less than 35 µm) cells. Using estimates of the total number of fibers in three muscles and the estimated number of α-motoneurons for those same muscles, we calculated a mean innervation ratio of ∼270, which is at the low end of the innervation ratios for type IIB motor units from other feline muscles and more similar to type IIA motor units. In general, CF appears to be a useful preparation in which to study the properties of fast-twitch muscle, but these properties may vary somewhat from type IIB fibers from different muscles.

Notes: Abstract  Micturition in the decerebrate cat is characterized by a coordinated bladder contraction and a simultaneous decrease in external urethral sphincter (EUS) efferent activity. Without the suppression of EUS activity, voiding is significantly impaired, resulting in a state sometimes referred to as bladder-sphincter dyssynergia. The aim of the present study was to determine whether glycinergic inhibition contributes to the suppression of EUS activity during micturition evoked by bladder distension or electrical stimulation of the pontine micturition center (PMC) in decerebrate cats. Using subconvulsive intravenous doses of strychnine (0.1–0.24 mg/kg), we examined changes in bladder and EUS electroneurographic (ENG) activity during micturition. Following subconvulsive doses of strychnine, tonic EUS ENG activity increased during bladder filling in five of six animals. In the presence of strychnine, it was possible to evoke reflex bladder contractions of similar duration and peak pressure to those observed before strychnine administration. However, there was an absence of suppression of EUS ENG activity during the bladder contractions in all the animals. To determine whether the changes in sphincter activity could be due to strychnine acting at glycine receptors on EUS motoneurons, sacral spinal tissue was processed for a structural protein (gephyrin) associated with the glycine receptor. Motoneurons in Onuf′s nucleus in S1 were identified using choline acetyltransferase immunohistochemistry and subsequently processed with a gephyrin monoclonal antibody. Abundant gephyrin labeling was evident throughout Onuf′s nucleus. Since Onuf′s nucleus is made up of EUS and other motoneuron populations, a sample of antidromically identified urethral and anal sphincter motoneurons were intracellularly labeled with tetramethylrhodamine dextran (TMR-D) and then processed with the gephyrin antibody. Using dual-beam confocal microscopy, gephyrin immunoreactivity was observed on the soma and proximal processes of individual EUS motoneurons in both male and female animals. It was concluded that a strychnine-sensitive mechanism contributes to the suppression of sphincter activity normally observed during voiding. Although glycinergic inhibition may affect several components of the circuitry responsible for micturition, it appears that the suppression of EUS motoneurons during micturition may be partly due to a direct glycinergic inhibition of the EUS motoneurons.

Notes: Abstract  This study examined the role of trunk extensor muscles in the thoracic and lumbar regions during postural adjustments in the freely standing cat. The epaxial extensor muscles participate in the rapid postural responses evoked by horizontal translation of the support surface. The muscles segregate into two regional groups separated by a short transition zone, according to the spatial pattern of the electromyographic (EMG) responses. The upper thoracic muscles (T5-9) respond best to posteriorly directed translations, whereas the lumbar muscles (T13 to L7) respond best to anterior translations. The transition group muscles (T10-12) respond to almost all translations. Muscles group according to vertebral level rather than muscle species. The upper thoracic muscles change little in their response with changes in stance distance (fore-hindpaw separation) and may act to stabilize the intervertebral angles of the thoracic curvature. Activity in the lumbar muscles increases along with upward rotation of the pelvis (iliac crest) as stance distance decreases. Lumbar muscles appear to stabilize the pelvis with respect to the lumbar vertebrae (L7-sacral joint). The transition zone muscles display a change in spatial tuning with stance distance, responding to many directions of translation at short distances and focusing to respond best to contralateral translations at the long stance distance.

Notes: Abstract  This study examined the configuration of the vertebral column of the cat during independent stance and in various flexed positions. The range of motion in the sagittal plane is similar across most thoracic and lumbar joints, with the exception of a lesser range at the transition region from thoracic-type to lumbar-type vertebrae. The upper thoracic column exhibits most of its range in dorsiflexion and the lower thoracic and lumbar in ventroflexion. Lateral flexion is limited to less than 5° at all segments. The range in torsion is almost 180° and occurs primarily in the midthoracic region, T4-T11. Contrary to the depiction in most atlases, the standing cat exhibits several curvatures, including a mild dorsiflexion in the lower lumbar segments, a marked ventroflexion in the lower thoracic and upper lumbar segments, and a profound dorsiflexion in the upper thoracic (above T9) and cervical segments. The curvatures are not significantly changed by altering stance distance but are affected by head posture. During stance, the top of the scapula lies well above the spines of the thoracic vertebrae, and the glenohumeral joint is just below the bodies of vertebrae T3-T5. Using a simple static model of the vertebral column in the sagittal plane, it was estimated that the bending moment due to gravity is bimodal with a dorsiflexion moment in the lower thoracic and lumbar region and a ventroflexion moment in the upper thoracic and cervical region. Given the bending moments and the position of the scapula during stance, it is proposed that two groups of scapular muscles provide the major antigravity support for the head and anterior trunk. Levator scapulae and serratus ventralis form the lateral group, inserting on the lateral processes of cervical vertebrae and on the ribs. The major and minor rhomboids form the medial group, inserting on the spinous tips of vertebrae from C4 to T4. It is also proposed that the hypaxial muscles, psoas major, minor, and quadratus lumborum could support the lumbar trunk during stance.

Notes: Abstract  Cells in the superficial layers of the superior colliculus of the cat have mainly binocular receptive fields. The aim of the present experiment was to investigate the sensitivity of these cells to horizontal spatial disparity. Unit recordings were carried out in the superficial layers of the superior colliculus of paralyzed and anesthetized cats. Centrally located receptive fields were mapped, separated using prisms, and then stimulated simultaneously using two luminous bars optimally adjusted to the size of the excitatory region of the receptive fields. Only binocular cells were tested, and 65% of these units were found to be sensitive to spatial disparities. Some cells (20%) were clearly insensitive to spatial disparity and the remaining 15% showed complex, unclassifiable interactions. The sensitive cells could be divided into four classes based on their disparity-sensitivity profiles: 38% showed excitatory interactions, whereas 9% showed inhibitory interactions. Moreover, 11% and 7% of the cells responded, respectively, to crossed or uncrossed disparities, and were classified as near cells and far cells. Whereas the general shapes of the sensitivity profiles were similar to those of cells in areas 17–18, selectivity in the superior colliculus was significantly coarser. The superficial layers of the superior colliculus project topographically to the deep layers of the superior colliculus, which are known to contain circuits involved in the control of ocular movements. The results thus suggest that disparity-sensitive cells of the superior colliculus could feed information to these oculomotor neurons, allowing for the localization and fixation of objects on the appropriate plane of vision.

Notes: Abstract  The purpose of this study was to investigate changes in neck muscle and eye movement responses during the early stages of vestibular compensation (first 3 weeks after unilateral vestibular neurectomy, UVN). Electromyographic (EMG) activity from antagonist neck extensor (splenius capitis) and flexor (longus capitis) muscles and eye movements were recorded during sinusoidal visual and/or otolith vertical linear stimulations in the 0.05–1 Hz frequency range (corresponding acceleration range 0.003–1.16 g) in the head-fixed alert cat. Preoperative EMG activity from the splenius and longus capitis muscles showed a pattern of alternate activation of the antagonist neck muscles in all the cats. After UVN, two motor strategies were observed. For three of the seven cats, the temporal activation of the individual neck muscles was the same as that recorded before UVN. For the other four cats, UVN resulted in a pattern of coactivation of the flexor and extensor neck muscles because of a phase change of the splenius capitis. In both subgroups, the response patterns of the antagonist neck muscles were consistent for each cat independently of the experimental conditions, throughout the 3 weeks of testing. Cats displaying alternate activation of antagonist neck muscles showed an enhanced gain of the visually induced neck responses, particularly in the high range of stimulus frequency, and a gain decrease in the otolith-induced neck responses at the lowest frequency (0.25 Hz) only. By contrast, for cats with neck muscle coactivation, the gain of the visually induced neck responses was basically unaffected relative to preoperative values, whereas otolith-induced neck responses were considerably decreased in the whole range of stimulation. As concerns oculomotor responses, results in the two subgroups of cats were similar. The optokinetic responses were not affected by the vestibular lesion. On the contrary, otolith-induced eye responses showed a gain reduction and a phase lead. Deficits and short-term changes after UVN of otolith- and semicircular canal-evoked collic and ocular responses are compared.

Notes: Abstract  In pentobarbitone-anaesthetised spinal cats, a comparison was made of the effects of intravenous bicuculline hydrochloride, a GABAA-receptor antagonist, and several (-)-baclofen (GABAB-receptor) antagonists (CGP 35348, 46381, 56999A) on the prolonged inhibition of extensor-muscle monosynaptic reflexes, recorded from lumbar ventral roots, by brief or continuous tetanic stimulation of low-threshold afferent fibres of hindlimb flexor muscles. Two components of brief tetanus inhibition were detected. Whilst possibly of similar central latency, the inhibition associated with GABAB receptors had a longer time course than that reduced by bicuculline. Furthermore, whereas bicuculline reduced primary afferent depolarization, generated by the inhibitory volleys, and detected as dorsal-root potentials, such potentials were generally enhanced by intravenous baclofen antagonists. The inhibition of reflexes during and after continuous (333 Hz) tetanic flexor-nerve stimulation appeared to be predominantly associated with the activation of GABAB receptors. In the period following continuous tetanic flexor-nerve stimulation, during which monosynaptic extensor reflexes were reduced in amplitude, the action potentials of the intraspinal terminations of extensor-muscle group-Ia afferent fibres were reduced in duration, as detected by the time course of the recovery of the threshold to extracellular microstimulation following the arrival of an orthodromic impulse. A reduction in termination action-potential duration also accompanied the reduction by microelectrophoretic (-)-baclofen of the release of excitatory transmitter from group-Ia terminations, both presynaptic effects being blocked by microelectrophoretic baclofen antagonists. However, the reduction of the duration of the action potential of individual group-Ia terminations, which followed continuous flexor-nerve stimulation, was not sensitive to the baclofen antagonist CGP 55845A, but was diminished by bicuculline methochloride. Intravenously administered bicuculline hydrochloride, however, had little or no effect on the inhibition of reflexes following continuous flexor-nerve stimulation. These observations are discussed in the context of possible intraspinal pathways and pre- and postsynaptic mechanisms for GABAA and GABAB receptor-mediated inhibition of the monosynaptic excitation of spinal motoneurones and of the functional significance of central GABAB receptor-associated inhibitory processes, given the relatively minimal effects on motor activity and behaviour produced by baclofen antagonists that penetrate the mammalian blood-brain barrier.

Notes: Abstract Orofacial dyskinesia (OFD) is a disorder characterized by involuntary movements of the oral and facial muscles. OFD attacks can be elicited acutely in cats by local injections of dopaminergic agents into the anterodorsal part (r-CRM) of the caudate nucleus. Because the dopaminergic A8 cell group, being embedded in the retrorubral nucleus (RRN), gives rise to fibres which terminate in the r-CRM, two questions arose: (1) whether the A8 cell group forms part of the circuitry that directs and/or modulates OFD, and (2) whether GABA-ergic compounds in the RRN play a role in OFD, and if so, whether a pharmacological GABA-ergic intervention of the activity in the RRN modulates or mediates OFD. For this purpose, the activity of the RRN was manipulated with local injections of the GABAA agonist muscimol and antagonist bicuculline. These local injections into the RRN were subsequently combined with manipulations of dopamine transmission in the r-CRM with local injections of the selective DAi receptor agonist (3,4-dihydroxyphenylimino)-2-imidazoline. The present study shows that local injections of GABA-ergic compounds into the RRN do not elicit OFD attacks in cats, but can modulate oral behaviour elicited from the r-CRM. The latter effect is dose dependent and GABA-ergic specific.

Notes: Abstract  There is evidence that glycans carrying terminal galactose residues are differently expressed in the sarcoplasm of different muscle fiber types. In this study monoclonal antibodies directed against P blood group antigens Pk: Galα1–4Galβ1–4Glcβ- and P1: Galα1–4Galβ1–4GlcNAcβ- were used to detect terminal α-galactosylated glycoconjugates on muscle proteins. Electrotransfer of proteins, extracted from human masseter and biceps muscles, to nitrocellulose after polyacrylamide gel electrophoresis (PAGE) and incubation with anti-Pk (CD77) consistently showed two bands with apparent molecular weights of 66 kDa and 64 kDa. In fresh frozen muscle sections from some humans there was endothelial reaction with anti-CD77 in capillaries, venules and veins but not in arterioles and arteries. In muscle samples from other humans there was no staining of endothelial cells. Formalin-fixed human muscle displayed a CD77 reaction with highest accumulation of reaction product at the periphery of the fibers. This may be explained by the presence of Pk glycoconjugates on intermediate filaments in muscle fibers. In preparations of cat masseter muscle proteins the antibodies against P1Pk antigens reacted with a 170 kDa and a 55 kDa band while in preparations of cat biceps brachii only a 55 kDa band was reactive. The specificities of the antibodies were investigated by fluorescence-activated cell sorter (FACS), α- and β-galactosidase digestion and inhibitory sugars. This study indicates that glycans carrying Galα1–4Galβ1- epitopes are expressed on myofibrillar associated proteins.

Notes: Abstract Studies were carried out on the organization of the internal connections of the striate cortex in cats in the projection zone of the center (0–5°) of the field of vision by microintophoretic application of horseradish peroxidase to electrophysiologically identified orientational columns. The area containing neurons showing retrograde labeling in most cases extended in the mediolateral direction. Labeled cells were located in the upper (II, III) and lower (V, VI) layers of the cortex, and the shapes and orientations of the areas containing labeled neurons in these layers coincided. Spatial asymmetry was detected in the distribution of labeled neurons relative to the orientational column studied. Labeled cells were located predominantly medial to the columns, regardless of the distance from the projection of the area centralis. Considering the visuotopical map of field 17, the asymmetry detected here provides evidence that neurons in orientational columns have more extensive connections with neurons of the peripheral part of the cortex. An asymmetrical distribution of “silent” zones around the receptive fields of neurons in orientational columns is suggested, and that these appear to receive influences from the periphery of the visual field.

Notes: To get informations on both the structure and dynamics of hydrogen chelates 1 of heteroaromatic systems, a great variety of quinazoline-2-acetonitrile chelates were synthesized (see 2-4). Similarly to the situation of the corresponding H-chelates in the pyrimidine-2-acetonitrile series, the investigation of these new derivatives 2-4 by NMR spectroscopic methods (DNMR, COSY, NOESY, ROESY, EXSY, HMQC, HMBC) confirms the presence of an equilibrium of the two possible H-chelate structures (two ‘rotamers’ I and II, i.e., (E)/(Z) isomers; see Scheme). The corresponding equilibria I ⇌ II were determined by complete 1H-NMR signal assignment at low temperatures (after freezing the rotational processes). In addition, the tautomer equilibria A ⇌ B (relative energies of the two minima of the nonsymmetrical double-well potential) for both ‘rotamers’ are ascertained by H,H and C,H couplings. The results are an important basis for the interpretation of both the UV/VIS absorptions and the dependence of fluorescence and fluorescence quantum yields on temperature.

Notes: Stereoselective reactions of phthalimido-substituted radicals derived from (±)-threonine with different radical traps are reported (Scheme 3, Table 1). A strong influence of the nature of the radical trap on the stereoselectivity was noticed. Small nucleophilic radical traps gave preferentially the syn products. The observed selectivities are explained with the A1,3 strain model and depend on steric and electronic effects (Fig. 2). Reactions with electrophilic radical traps such as diphenyl diselenide gave the anti diastereoisomers with moderate stereocontrol, presumably due to stereoelectronic effects. The same stereochemical outcome, i.e., preferential formation of the anti products, was observed for the reactions of the related N-phthaloyliminium ion (Scheme 5, Table 2). The stereochemistry of the ionic reaction is rationalized by a Felkin-Anh model (Fig. 3).

Notes: The cyclopalladation of 1,1′-azonaphthalene (= di(naphthalen-1-yl)diazene; 2) with bis(hexafluoroacetyl-acetonato)palladium(II) (3; [Pd(hfa)2]) yields the ortho-palladated complex (1,1,1,5,5,5-hexafluoropentane-2,4-dionato-κ2O,O′)[1-(naphthalen-1-ylazo-κN2)naphthalen-2-yl-κC2]palladium(II) (4) as well as the peri-palladated complex (1,1,1,5,5,5-hexafluoropentane-2,4-dionato-κ2O,O′)[8-(naphthalen-1-ylazo-κN2)naphthalen-1-yl-κC1]-palladium(II) (5); their structures were corroborated by X-ray analyses. The formation of the novel peri-metallated product 5 containing a six-membered palladacycle strongly depends upon the reaction conditions.

Notes: The photoisomerization behavior of three mono[(E)-3-(4-hydroxyphenyl)prop-2-enoyl]spermidines, 1, 2, and 3, and three bis[(E)-3-(4-hydroxyphenyl)prop-2-enoyl]spermidines, 4, 5, and 6, are investigated. The synthetic product (E)-1 could be almost quantitatively (〉 96%) converted into its isomer (Z)-1 under UV light irradiation. In the cases of (E)-2 and (E)-3, a mixture of (E)/(Z) ca. 1:2 was obtained, when the same conditions were applied. The comparison of their UV spectra provides the possible explanation for these different behaviors. Furthermore, it was noticed that the (Z) → (E) isomerization of the C=C bond took place during the purification by reverse-phase high-performance liquid chromatography (RP-HPLC), and the (E)/(Z)-mixture is thus inseparable. The same feature could be observed during the isolation of the (Z,Z)-N,N′-bis[3-(4-hydroxyphenyl)prop-2-enoyl]-spermidines, (Z,Z)-4, (Z,Z)-5, and (Z,Z)-6. Nevertheless, the fractions of (Z,Z)-5 and (Z,Z)-6 were in almost pure state collected, and their 1-NMR spectra are presented.

Notes: The synthesis, absolute configuration, and olfactive evaluation of (-)-(E)-α-trans-bergamotenone (= (-)-(1′S,6′R,E)-5-(2′,6′-dimethylbicyclo[3.1.1]hept-2′-en-6′-yl)pent-3-en-2-one; (-)-1), as well as its homologue (-)-19 are reperted. The previously arbitrarily attributed absolute configuration of 1 and of (-)-α-trans-bergamotene (= (-)-(1 S,6R)-2,6-dimethyl-6-(4-methylpent-3-enyl)bicyclo[3.1. 1]hept-2-ene; (-)-2), together with those of the structurally related aldehydes (-)-3a,b and alcohols (-)-4a,b, have been rigorously assigned.

Notes: (-)-(R)-4,4,4,4′,4′,4′-Hexafluorovaline hydrochloride ((R)-5) of 98% ee is prepared from β,β-bis(trifluoromethyl)acrylic acid (= benzyl 4,4,4-trifluoro-3-(trifluoromethyl)but-2-enoate; 1) in 4 steps with an overall yield of 9.6%. Key step is the separation of the TsOH salts of the diastereoisomers obtained by anti-Michael addition of (+)-(R)-1-phenylethylamine (2) to 1 (→ (R,R)-3). In contrast to the published (S)-chirality, the X-ray structure analysis of (R,S)-6 reveals, that (R)-chirality has to be assigned to the levorotatory (-)-4,4,4,4′,4′,4′-hexafluorovaline hydrochloride.

Notes: The synthesis and characterization of tripodal dodecadentate ligands with salicylamide and bipyridine binding sites for iron(II) and iron(III) are presented.

Notes: The reaction of CuO'Bu with CO2, and iPr2NH in the presence of PPh3, gives the dialkylcarbamato complex [Cu(O2CNiPr2)(PPh3)2] (1). The CO2/R2NH system (R = Me, Et) in an appropriate organic medium reacts with Ag2O giving the corresponding N,N-dialkylcarbamato complexes of analytical formula [Ag(C2CNR2)] (R = Me, 2; R = Et, 3). The methyl derivative 2 was characterized by X-ray diffraction methods. Crystal data of 2: for [Ag2(O2CNMe2)2], C6H12Ag2N2O4, mol. wt. 391.9; monoclinic, space group P21/c, a = 12.08(1), b = 3.797(2), c = 11.316(7) Å, β = 113.37(6)°, V = 476.3 Å3, Z = 2, Dc = 2.732 g cm-3; μ(MoKα) = 40.64 cm-1, F(000) = 376.0; R = 0.059, Rw = 0.067; g.o.f. 1.27. The structure consists of dinuclear [(Ag2OCNMe2)2] units with slightly distorted linearly two-coordinated Ag-atoms containing bridging carbamato groups to form a substantially planar eight-membered ring with an intra-annular Ag—Ag distance of 2.837(2) Å; the dinuclear units are further joined by Ag—O bonds to form an infinite array. Compound 3, which is presumably dinuclear, as suggested by cryoscopic measurements in benzene, undergoes a structural fission with PPh3, giving the mononuclear triphenylphosphine derivative [Ag(O2CNEt2)(PPh3)2] (4). The amine-catalyzed conversion of Ag2O into Ag2CO3, in the presence of the iPr2NH/CO2 system, is also reported. Cl-Exchange from [AuCl(PPh3)] with [Ag(O2CNEt2)] (3) gives the first N,N-dialkylcarbamato complex of gold, namely [Au(O2CNEt2)(PPh3)] (5), which crystallizes in the monoclinic system: C23H25AuNO2P · 0.5 C7H16, mol. wt. 625.5, space group P21/c; a = 13.212(5), b = 12.25(1), c = 16.795(6) Å, β = 109.09(2)°, V = 2568(2) Å3, Z = 4, Dc, = 1.618 g cm-3; μ(AgKα) = 31.40 cm-1, F(000) = 1236.0; R = 0.058; Rw = 0.064; g.o.f. 2.121. The compound contains two-coordinated Au-atom, namely to the P-atom and to the O-atom of the monodentate carbamato group, the P—Au—O bond angle being 174.7(3)°. The reaction with MeI showed these compounds to react predominantly at the carbamato O-atom giving the corresponding urethanes R2NCO2Me. Evidence was gathered for the transient coordination of CO to Ag in 3.

Notes: The reactions of α-diazo ketones 1a,b with 9H-fluorene-9-thione (2f) in THF at room temperature yielded the symmetrical 1,3-dithiolanes 7a,b, whereas 1b and 2,2,4,4-tetramethylcyclobutane-1,3-dithione (2d) in THF at 60° led to a mixture of two stereoisomeric 1,3-oxathiole derivatives cis- and trans-9a (Scheme 2). With 2-diazo-1,2-diphenylethanone (1c), thio ketones 2a-d as well as 1,3-thiazole-5(4H)-thione 2g reacted to give 1,3-oxathiole derivatives exclusively (Schemes 3 and 4). As the reactions with 1c were more sluggish than those with 1a,b, they were catalyzed either by the addition of LiClO4 or by Rh2(OAc)4. In the case of 2d in THF/LiClO4 at room temperature, a mixture of the monoadduct 4d and the stereoisomeric bis-adducts cis- and trans-9b was formed. Monoadduct 4d could be transformed to cis- and trans-9b by treatment with 1c in the presence of Rh2(OAc)4 (Scheme 4). Xanthione (2e) and 1c in THF at room temperature reacted only when catalyzed with Rh2(OAc)4, and, in contrast to the previous reactions, the benzoyl-substituted thiirane derivative 5a was the sole product (Scheme 4). Both types of reaction were observed with α-diazo amides 1d,e (Schemes 5-7). It is worth mentioning that formation of 1,3-oxathiole or thiirane is not only dependent on the type of the carbonyl compound 2 but also on the α-diazo amide. In the case of 1d and thioxocyclobutanone 2c in THF at room temperature, the primary cycloadduct 12 was the main product. Heating the mixture to 60°, 1,3-oxathiole 10d as well as the spirocyclic thiirane-carboxamide 11b were formed. Thiirane-carboxamides 11d-g were desulfurized with (Me2N)3P in THF at 60°, yielding the corresponding acrylamide derivatives (Scheme 7). All reactions are rationalized by a mechanism via initial formation of acyl-substituted thiocarbonyl ylides which undergo either a 1,5-dipolar electrocyclization to give 1,3-oxathiole derivatives or a 1,3-dipolar electrocyclization to yield thiiranes. Only in the case of the most reactive 9H-fluorene-9-thione (2f) is the thiocarbonyl ylide trapped by a second molecule of 2f to give 1,3-dithiolane derivatives by a 1,3-dipolar cycloaddition.

Notes: The synthesis of a series of chiral enantiomerically pure C2-symmetric binucleating ligands is reported. Ligands of type 1-4, which consist of a phenolic or heterocyclic unit bridging two chiral dihydrooxazole rings. are readily accessible from chiral amino alcohols. Ligands 5a and 5b are composed of a cyclic urea or thiourea unit, respectively, and two 3,4-dihydro-2H-pyrrole rings containing a stereogenic center next to the N-atom. Compounds of this type are readily assembled from ethane-1,2-diamine and an imidothioic ester derived from pyroglutamic acid. These new ligands, which can coordinate two metals in close proximity to each other, are of interest regarding possible applications in asymmetric catalysis.

Notes: Stability constants have been measured for a series of ligands based on a 2,2′-(pyridine-2,6-diyl)bis[1H-benzimidazole] unit which forms dinuclear double-stranded helical complexes with copper(I). Variation of different structural parameters confirms the importance of the coordinate bond, the stacking interactions, and the weakly bridging pyridine units observed by X-ray crystallography. The stabilities of the complexes depend strongly on the solvent, and in MeCN, which is a good solvent for copper(I), the complexes are less stable and assemble in a stepwise manner. The interconversion of the enantiomers may be followed by 1H-NMR and takes place on a millisecond time scale around room temperature. The trends in lability are similar to those found for the stability of the complexes.

Notes: Oligodeoxyribonucleotides containing 7-deaza-2′-deoxy-8-methylguanosine (m8c7Gd; 2b) were prepared. For this purpose, the phosphonate 3a and the phosphoramidite 3b were synthesized and employed in solidphase oligodeoxyribonucleotide synthesis. The structures and the thermodynamic data of duplex formation of oligodeoxyribonucleotides containing 2b were investigated by temperature-dependent CD and UV spectra and compared with those containing 7-deaza-2′-deoxy-7-methylguanosine (m7c7Gd) or 7-deaza-2′-deoxy-guanosine (c7Gd; 2a). In general, compound 2b reduces the duplex stability. In case of the sequence d(m8c7G-C)4 (18), the B → Z transition was facilitated by the incorporation of 2b. Moreover, a single 7-deaza-8-methylguanine residue present in an oligodeoxyribonucleotide tract of guanine residues destabilizes the dG quadruplex significantly. This destabilization is more pronounced than in the case of 7-deazaguanine or 7-deaza-7-methyl-guanine.

Notes: Absolute rate constants and their Arrhenius parameters are obtained for the addition of a cyclic malonyl radical derived from Meldrum's acid to 20 mono- or 1,1-disubstituted alkenes in (±)-propylene oxide and for the addition of the open-chain di(tert-butyl)malonyl radical to six mono- or 1,1-disubstituted alkenes in 1,1,2-trichloro-1,2,2-trifluoroethane by time-resolved electron spin resonance spectroscopy. At room temperature, the radicals add at the unsubstituted C-atoms with rate constants ranging from 1.1. 105 M-1S-1 (acrolein) to 2.4. 106 M-1S-1 (1,1-diphenylethene). The frequency factors are in the narrow ranges of log (A/M-1S-1) = 8.7 ± 0.1 for the cyclic and log (A/M-1S-1) = 8.2 ± 0.2 for the open-chain malonyl species, whereas the activation energies vary from 12.9 kJ/mol (1,1-diphenylethene) to 21.7 kJ/mol (acrylonitrile). They correlate with the alkene ionization potentials and, more weakly, with the reaction enthalpy. No correlation was found between the activation energies and the alkene electron affinities. Hence, the results confirm and quantify the electrophilic nature of malonyl radicals in addition reactions.

Notes: An asymmetric synthesis of (-)-(4R)-dihydroisomyricoidine (28), a 13-membered amino lactam of type A, was performed by a diastereoselective Michael addition between the spermidine derivative 3 and the commercially available optically active ethyl carboxylate 4, and the cyclization of the resulting ω-amino acid 7 using diethyl phosphorocyanidate ((EtO)2POCN), followed by a Wittig reaction to introduce the (Z)-side chain. Some side reactions are also discussed.

Notes: Natural free carboxylic acids from the hadromerid sponge Diacarnus levii (Kelly-Borges and Vacelet) were esterified to yield the new cyclic norditerpene peroxides ent-muqubilin benzyl ester (= (αR,3S,6R)-α,6-dimethyl-6-[(E)-4-methyl-6-(2,6,6-trimethyl-cyclohex-1-en-1-yl)hex-3-enyl]-1,2-dioxan-3-acetic acid benzyl ester; 6, diacarnoate B methyl ester(= (αS,3R,6R)-α,6-dimethyl-6-{2-(4aS,8aS)-3,4,4a,5,6,7,8,8a-octahydro-3-oxo-2,5,5,8a-tetramethylnaphthalen-1-yl)ethyl}-1,2-dioxan-3-acetic acid methyl ester; 9), and deoxydiacarnoate B benzyl ester (= (αS,3R,6R)-α,6-dimethyl-6-{2-[(4aS,8aS)-3,4,4a,5,6,7,8,8a-octahydro-2,5,5,8a-tetramethyl-1-naphthalenyl]ethyl}-1,2-dioxan-3-acetic acid benzyl ester; 10), which were isolated following extensive chromatography. The relative configuration of the peroxide/α-methylacetate moiety of 6, 9, and 10, was directly determined from their NMR spectra. The absolute configurations of the peroxide/α-methylacetate moiety was deduced from comparative 1H-NMR data of the (S)- and (R)-phenylglycine methyl ester derivatives 7 and 8 as well as 11/13 and 12/14, all obtained from a mixture of the precursors of 3, 6, and 10. The absolute configuration at the carbobicyclic moiety of enone 9 and of 10, is identical, as established by chemical interconversion, 9 and 10 belong to the normal labdane series according to empirical CD rules, applied either directly to 9 or to the parent (+)-sclareolide-derived enone 20. In contrast, molar rotation additivity rules suggest the ent-labdane configuration for 9 and 10. The epidioxides 1-3, 6, and 10 proved active in vitro against the malaria parasite Plasmodium falciparum; especially the previously isolated methyl 3-epinuapapuanoate (2) was active against a chloroquine-resistant strain, and this with a good security index.

Notes: 3-Hydroxy-2-cyanoalk-2-enamides, and 2-cyano-2-(tetrahydrofuran-2-ylidene)- and 2-cyano-2-(tetrahydropyran-2-ylidene)acetamides with N-alkyl and N-aryl substituents have been synthesized in three steps from cyanoacetic acid. Their conformations were investigated by X-ray crystallography and 1H-NMR ROESY spectroscopy at room temperature. The enolic compounds 1-3 adopt an extended conformation stabilized by a strong intramolecular O—H … O=C bond both in the solid state and in (D6)DMSO solution. In contrast, the structure of the cyclic derivatives 5a,b-8a,b is solvent-dependent. In the solid state and in CDCl3 solution, the compounds adopt an extended conformation of type I or III, while, in (D6)DMSO solution, their structures undergo time-dependent (Z)/(E)-isomerization structures (of type II or IV). This observation is compatible with a dipolar transition state of rotation. The kinetics of the isomerization are controlled by the N-substituent, the N-(t-Bu) derivatives 7a and 7b having the highest barrier of rotation around the C=C bond. The whole body of experimental evidence together with the results of molecular-mechanics calculations with I-IV, indicate that, in DMSO, two (E)/(Z)-isomers with two conformations are present, and that they undergo interconversion at room temperature with four different constants. The very fast exchange rates kI,II and kIII,IV in the NMR time-scale might be responsible for the detection of only two isomers.

Notes: A new acylated dimeric secoiridoid glycoside, seemannoside A (2), has been isolated from the aerial parts of Lisianthius seemannii (GRISEB) O. KUNTZE (Gentianaceae). The structure was established by spectroscopic analysis (UV, MS, 1H- and 13C-NMR, and 2D-NMR experiments) and chemical reactions as (E-4′-O-p-coumaroyl)lisianthioside. The structure of the (Z)-isomer (seemannoside B, 3), also present in the plant, was confirmed by LC/UV/1H-NMR analysis. The active principle, 6, responsible for the antifungal activity of the apolar extract against Cladosporium cucumerinum, has been isolated. Its structure has been established by NMR spectroscopy and X-ray crystallographic analysis as a rare type of aglycone monoterpene dimer.

Notes: Asymmetric Diels-Alder reaction of the pentadienoic and hexadienoic acids 2a,b with the chiral chloronitroso derivative 3 gave the primary adducts 4a,b with good-to-excellent enantioselectivity. Subsequent as- or trans-dihydroxylation and hydrogenolytic cleavage of the N—O bond led to the 5-amino-5-deoxypentono-δ-lactams 13a, 14, 15a, and 16 in the D-ribose, L-arabinose, D-xylose, and L-lyxose series, respectively, and to the 5-amino-5,6-dideoxyhexono-δ-lactams 13b and 15b in the D-allose and D-glucose series, respectively.

Notes: The synthesis of the monomeric building block 13 and its constitutional isomer 12 of a new type of DNA analog, distamycin-NA, is presented (Schemes 1 and 2). This building block consists of a uracil base attached to a thiophene core unit via a biaryl-like axis. Next to the biaryl-like axis on the thiophene chromophore, a carboxy and an amino substituent are located allowing for oligomerization via peptide coupling. The proof of constitution and the conformational preferences about the biaryl-like axis were established by means of X-ray analyses of the corresponding nitro derivatives 10 and 11. Thus, the uracil bases are propeller-twisted relative to the thiophene core, and bidentate H-bonds occur between two uracil bases in the crystals. The two amino-acid building blocks 12 and 13 were coupled to give the dimers 15 and 16 using dicyclohexylcarbodiimide (DCC) in THF/LiCl and DMF, respectively. While the dimer 15 showed no atropisomerism on the NMR time scale at room temperature, its isomer 16 occurred as distinct diastereoisomers due to the hindered rotation around its biaryl-like axis. Variable-temperature 1H-NMR experiments allowed to determine a rotational barrier of 19 ± 1 kcal/mol in 16. The experimental data were complemented by AM1 calculations.

Notes: Heating of a mixture of N,N′-(thiocarbonyl)diimidazole (= 1,1′-(carbonothioyl)bis[1H-imidazole]; 1) and 2,5-dihydro-1,3,4-thiadiazole 2a or 2b gave the 1,3-dithiolanes 4a and 4b, respectively, via a regiospecific 1,3-dipolar cycloaddition of the corresponding ‘thiocarbonyl methanides’ 3a,b onto the C=S group of 1 (Schemes 1 and 2). The adamantane derivative 4b was not stable in the presence of 1H-imidazole and during chromatographic workup. The isolated 1,3-dithiole 5 is the product of a base-catalyzed elimination of 1H-imidazole from the initial cycloadduct 4b. The formation of the S,N-acetal 6 can be rationalized by a protonation of the ‘thiocarbonyl ylide’ 3b followed by a nucleophilic addition of 1H-imidazole. With the diazo compounds 8a-e (Scheme 3) 1 underwent a regiospecific 1,3-dipolar cycloaddition to give the corresponding 2,5-dihydro-1,3,4-thiadiazole derivatives 9, which spontaneously eliminated 1H-imidazole to yield (1H-imidazol-1-yl)-1,3,4-thiadiazoles 10. The structures of 10a and 10d were established by X-ray crystallography. In the case of diazodiphenylmethane (8f), the initial cycloadduct 9f decomposed via a ‘twofold extrusion’ of N2 and S to give 1,1′-(2,2-diphenylethenylidene)bis[1H-imidazole] (11; Scheme 3).

Notes: The synthesis of new deoxyribose nucleosides by coupling chloropurines with modified D-ribose derivatives is reported. The methyl 2-deoxy-N-methyl-3-O-(p-toluoyl)-α-D-ribofuranosiduronamide (α-D-8) and the corresponding anomer β-D-8 were synthesized starting from the commercially available 2-deoxy-D-ribose (1) (Scheme 1). Reaction of α-D-8 with the silylated derivative of 2,6-dichloro-9H-purine (9) afforded regioselectively the N9-(2′-deoxyribonucleoside) 10 as anomeric mixture (Scheme 2), whereas β-D-8 did not react. Glycosylation of 9 or of 6-chloro-9H-purine (17) with 1,2-di-O-acetyl-3-deoxy-N-methyl-β-D-ribofuranuronamide (13) yielded only the protected β-D-anomers 14 and 18, respectively (Scheme 3). Subsequent deacetylation and dechlorination afforded the desired nucleosides β-D-11, β-D-12,15, and 16. The 3′-deoxy-2-chloroadenosine derivative 15 showed the highest affinity and selectivity for adenotin binding site vs. A1 and A2A adenosine receptor subtypes.

Notes: (S)-5,5,5,5′,5′,5′-Hexafluoroleucine ((S)-13) of 81 % ee is prepared from hexafluoroacetone (l) and ethyl bromopyruvate (= ethyl 2-oxopropanoate) in 7 steps with an overall yield of 18% (Schemes 1 and 2). Key step in this sequence is the highly enantioselective reduction of the carbonyl group in α-keto ester 4 either by bakers' yeast (91 % ee) or by ‘catecholborane’ 6 utilizing an oxazaborolidine catalyst, yielding hydroxy ester (R)-5 with 99% ee. The absolute configuration was determined by X-ray analysis of the HCl adduct (S,R)-9b of (2S)-N-[(R)- l-phenylethyl]-5,5,5,5′,5′,5′-hexafluoroleucine ethyl ester.

Notes: N-Fmoc-Protected (Fmoc = (9H-fluoren-9-ylmethoxy)carbonyl) β-amino acids are required for an efficient synthesis of β-oligopeptides on solid support. Enantiomerically pure Fmoc-β3-amino acids β3: side chain and NH2 at C(3)(= C(β)) were prepared from Fmoc-protected (S)- and (R)-α-amino acids with aliphatic, aromatic, and functionalized side chains, using the standard or an optimized Arndt-Eistert reaction sequence. Fmoc-β2- Amino acids (β2 side chain at C(2), NH2 at C(3)(= C(β))) configuration bearing the side chain of Ala, Val, Leu, and Phe were synthesized via the Evans' chiral auxiliary methodology. The target β3-heptapeptides 5-8, a β3- pentadecapeptide 9 and a β2-heptapeptide 10 were synthesized on a manual solid-phase synthesis apparatus using conventional solid-phase peptide synthesis procedures (Scheme 3). In the case of β3-peptides, two methods were used to anchor the first β-amino acid: esterification of the ortho-chlorotrityl chloride resin with the first Fmoc-β-amino acid 2 (Method I, Scheme 2) or acylation of the 4-(benzyloxy)benzyl alcohol resin (Wang resin) with the ketene intermediates from the Wolff rearrangement of amino-acid-derived diazo ketone 1 (Method II, Scheme 2). The former technique provided better results, as exemplified by the synthesis of the heptapeptides 5 and 6 (Table 2). The intermediate from the Wolff rearrangement of diazo ketones 1 was also used for sequential peptide-bond formation on solid support (synthesis of the tetrapeptides 11 and 12). The CD spectra of the β2- and β3-peptides 5, 9, and 10 show the typical pattern previously assigned to an (M) 31 helical secondary structure (Fig.). The most intense CD absorption was observed with the pentadecapeptide 9 (strong broad negative Cotton effect at ca. 213 nm); compared to the analogous heptapeptide 5, this corresponds to a 2.5 fold increase in the molar ellipticity per residue!

Notes: On irradiation (350 nm) in the presence of excess 2,3-dimethylbut-2-ene, the newly synthesized title compound 5 affords as main products the unexpected cyclopropylpyrrolidine 10 (50%) and the spiro-oxetane 9 (25%).

Notes: Among seventeen different Lewis acids, TiCl4 was found to be the best catalyst for the [4 + 2] cycloaddition of cyclopentadiene to N,N′-fumaroylbis[(2R)-bornane-10,2-sultam] ((-)-1). Independently of the TiCl4 molar concentration, almost constant and complete (98-89% d.e.) diastereofacial π-selection was achieved in the Diels-Alder addition of (-)-1 to cyclopentadiene, cyclohexadiene, isoprene, and 2,3-dimethylbuta-1,3-diene.

Notes: A new facile synthesis of N,S- and N,Se-acetals starting from aldehydes and primary amines is presented (Schemes 3-5). These acetals are used as precursors for stereoselective radical deuteration and allylation reactions (Schemes 6 and 7, Tables 1 and 2). The stereochemical outcome of the reactions depends on the radical trap and the substituents at the N-atom. Deuterations give always anti products with moderate to high selectivities. The allylation reactions give either syn or anti products with low to moderate selectivities. The observed stereoselectivities can be explained with a model based on minimization of A1,3 strain and are controlled by steric and stereoelectronic effects.

Notes: Based on O-methylasparvenone (1), a N-free 5HT2C antagonist with moderate affinity (pKi = 6.7), derivatives bearing dimethylamino (7), (dimethylamino)methyl (17, 18, 21, and 22), and aminomethyl substituents (26) in place of the benzylic OH group of 1 as well as pyrrolidine- (33) and piperidine-fused derivatives (29, 43, and 45) were synthesized. In contrast to the lead structure 1, these new ligands were active in vivo in the rat. The tricycles 33 and 45 display high affinities for the 5HT2C receptor (pKi = 8).

Notes: Thermal reactions of 1,2,3-trisubstituted aziridines 1 with 1,3-thiazole-5(4H)-thiones 6 in toluene yielded, in general, a mixture of two diastereoisomeric spirocyclic [2+3] cycloadducts. The formation of these products can be explained by a stereoselective electrocyclic ring opening of 1 to give an azomethine ylide 2 as the reactive intermediate, which is trapped immediately by 6 via a stereoselective 1,3-dipolar cycloaddition. Only in the case of trans-dimethyl 1-(4-methoxyphenyl)aziridine-2,3-dicarboxylate (trans-1a), four diastereoisomeric cycloadducts were formed (Scheme 4). This result is rationalized by an isomerization of the intermediate azomethine ylide cis-2a to trans -2a.

Notes: Due to their small mass, adjacent protons (or H-atoms) of molecular systems may exhibit quantum entanglement (or quantum correlations), even at ambient conditions. The considerable thermal disturbance and/or manybody interactions of condensed matter and the associated decoherence effect, however, cause this protonic entanglement to be restricted in space and time. Some aspects of entanglement and decoherence are mentioned. Extending our previous theoretical work, in the present paper the focus is on the possible existence of entangled protons belonging to the H-bonds of adjacent base pairs of B-type DNA. Based on the ‘working hypothesis’ that this effect does really exist, the most probable ‘positions’ for the appearance of protonic entanglement in DNA sequences are qualitatively determined. Furthermore, these ‘positions’ appear to correspond uniquely to dimers of adjacent base pairs of DNA. As a consequence, one can straightforwardly search for an enhanced appearance of such entangled H-bonds in DNA sequences of living organisms, using the existing DNA databases. A quantitative analysis of protein-coding DNA sequences of various organisms has been performed, the results of which provide strong evidence for the existence of the considered effect. The most striking finding may be summarized as follows: Quantum entanglement appears preferably between the third base of a codon and the first base of the following one. Quantitative estimates of this and further obtained results are presented. It is also shown that quantum-chemical considerations of stacking energies cannot account for the results. The new findings provide first evidence for the biological significance of entangled H-bonds.

Notes: The title compounds D-10 and L-10 were prepared from 1 in eight steps and in a combined overall yield of 41-49%.

Notes: The reaction of N,N'-dimethyl-2-nitroethene-1,1-diamine (8) with α,ß-unsaturated acyl isothiocyanates 9 affords 3,3-diamino-2-nitroacrylthioamides 10 (Scheme 2) in moderate-to-good yields. Cyclization of 10 under acidic conditions gives 1,3-thiazin-4-one derivatives of type 11. Oxidative cyclization of 10 with diethyl azodicaboxylate leads to 4-nitro-1,2-thiazol-5(2H)-imine derivatives 12.

Notes: The CH2Cl2 extract of Monotes engleri Gilg. (Dipterocarpaceae) showed antifungal activity against the yeast Candida albicans in our bioautographic TLC assays. After a first fractionation of the crude extract, the bioactivity was located in one of the fractions. To perform an efficient targeted isolation of the active compounds, LC/UV/MS and LC/UV/NMR analyses of the crude extract and the active fraction were performed. LC/UV/, LC/MS, and LC/NMR data (1D and 2D) allowed the identification of 1 as (2S)-2,3-dihydro-5,7-dihydroxy-{3-hydroxy-4-[(3-methylbut-2-enyl) oxy]phenyl}-4H-1-benzopyran-4-one, a new prenylated flavanone, named monoteson A. Subsequent isolation of 1 has permitted the determination of its absolute configuration on the basis of CD measurements. Theree other prenylated flavanoes 2-4 were isolated from the same extract. Compound 3 was identified as 2- (3, 5-dihydroxyphenyl) -2,3-dihydro-5, 7-dihydroxy-6, 8-bis (3-methylbut-2-enyl)-4 H-1-benzopyran-4-one, another new natural product, named monotesone B. The structures of 2 and 4 were established as selinone and lonchocarpol A, respectively. The antifungal activity against Candida albicans was determined for all compounds.

Notes: The disubstituted clusters[Ir4(CO)10(μ2-L—L)] with one edge-bridging ligand have a ground-state geometry with all COs terminal (L—L = (MeS)2CHMe, cluster 1) or with three edge-bridging COs (L—L = (Ph2P)2CHMe, cluste 2; L—L =Ph2P(CH2)3PPh2, cluster 3) in the solid state and in solution. A comparative 13C-NMR study of 1-3 shows that their respective ground-state geometries are merely relative minima of energy in the same kinetic profile of successive fluxional processes consisting of a merry-go-round of six COs about a unique trangular face and the rotation of terminal COs about one Ir-atom. The factors affecting the activation energy of the merry-go-round result from the relative bites of the bidentate ligands in the ground-state geometry, as shown by a comparison of the molecular structures of 2 and 3.

Notes: The kinetics of the reaction between pyridoxal 5′-phosphate (PLP) with carbidopa, hydralazine, and isoniazid, in aqueous solution at variable pH and constant ionic strength of 0.1M was studied spectrophotometrically. The rate constants of formation and hydrolysis of the resulting Schiff base, and its stability were determined in a wide range of pH. A comparison is made of the formation rate constants with those of PLP with hydrazine. The reactivity shows the sequence isoniazid 〉 hydrazine 〉 carbidopa 〉 hydralazine in the whole range of pH studied. The Schiff bases studied are more stable than those formed by PLP and hexylamine and as stable as those described for the reactions of PLP with poly(L-lysine) or copolypeptides containing L-lysine.

Notes: The coordination behavior of chiral binucleating ligands of type 1-4 with various transition metals has been investigated. 1H-NMR Titration experiments with zinc(II) salts gave detailed structural information about the structure of the resulting zinc complexes. Ligand 1 forms an unusual C3-symmetric dinuclear zinc complex [Zn2CIL3] (8a) which was characterized by X-ray crystallography. Treatment of complex 8a with various carboxylic acids resulted in ligand-exchange reactions. With ligand 2, a hydroxo-bridged dinuclear copper complex 15 was synthesized and its structure elucidated by X-ray analysis. Solution studies UV and 1H-NMR spectroscopy of the reaction of ligand 3 with ZnII and NII salts revealed the formation of dimeric species of the type [M2X4L2]. Ligand 4 formed well-defined dinuclear complexes with NiII and CuII salts of which the corresponding NiII complex [Ni2(AcO)2(ClO4)2L] (22a) was characterized by crystal-structure analysis.

Notes: Why Pentose- and Not Hexose-Nucleic Acids? Purine-Purine Pairing in homo-DNA: Guanine,Isoguanine, 2,6-Diaminopurine, and XanthineThis paper concludes the series of reports in this journal [1-4] on the chemistry of homo-DNA, the constitutionally simplifie dmodel system of hexopyranosyl-(6′ → 4′)-oligonucleotide systems stidued in our laboratory as potentially natural-nucleic-acid alternatives in the context of a chemical aetiology of nucleic-acid structure. The report describes the synthesis and pairing properties of homo-DNA oligonucleotides which contain as nucleobases exclusively purines, and gives, together with part III of the series [3], a survey of what we know today about purine-purine pairingin homo-DNA. In addition, the paper discusses those aspects of the chemistry of homo-DNA which, we think, influence the way how some of the structural features of DNA (and RNA) are to be interpreted on a qualitative level.Purine-purine pairing occurs in the homo-DNA domain in great variety. Most prominent is a novel tridentate Watson-Crick pair between guanine and isoguanine, as well as one between 2,6-diaminopurine and xanthinone, both giving rise to very stable duplexes containing the all-purine strands in antiparallel orientation. For the guanine-isoguanine pair, constitutional assignment is based on temperature-dependent UV and CD spectroscopy of various guanine- and isoguanine-containg duplexes in comparison with duplexes known to be paired in the reverse guanine is replaced by 7-carbauguanine. Isoguanine and 2,6-diaminopurine also have the capability of self-pariring in the reverse-Hoogsteen mode, as previously observed for adenine and guanine [3]. In this type of pairing, the interchangeably. Fig. 36 provides an overall survey of the relative strength of pairing in all possible purine-purine combinations.Watson-Crick pairing of isoguanine with guanine demands the former to participate in its 3H-tautomeric form; hitherto this specific tautomer had not been considered in the pairing chemistry of isoguanine. Whereas (cumulative) purine-purine pairing in DNA (reverse-Hoogsten or Hoogsteen) seems to occur in triplexes and tetrapalexes only, its occurrence in duplexes in a characteristic feature of homo-DNA chemistry. The occurrence of purine-purine Watson-Crick base pairs is probably a consequence of homo-DNA's quasi-linear ladder structure [1][4]. In a double helix, the distance between the two sugar C-atoms, on which a base pair is anchored, is expected to be constrained by the dimensions of the helix; in a linear duplex, however, there would be no restrictions with regard to base-pair length. Homo-DNA's ladder-like model also allows one to recognize one of the reasons why nucleic-acid duplexes prefer to pair in antiparallel, rather than parallel strand orientation: in homo-DNA duplexes, (averaged) backbone and base pair axes are strongly inclined toward one another [4]; the stronger this inclination, the higher the preference for antiparallel strand orientation is expected to be (Fig. 16).In retrospect, homo-DNA turns out to be one of the first artificial oligonucleotide systems (cf. Footnote 65) to demonstrate in a comprehensive way that informational base pairing involving purines and pyrimidines is not a capability unique to ribofuranosyl systems. Stability and helical shape of pairing complexes are not necessary conditions of one another; it is the potential for extensive conformational cooperativity of hte backbone structure with respect to the constellational demands of base pairing and base stacking that determines whether or nor a given type of base-carrying backbone structure is an informational pairing system. From the viewpoint of the chemical aetiology of nucleic-acid structure, which inspired our investigations on hexopyranosyl-(6′ → 4′)-oligonucleotide systems in the first place, the work on homo-DNA is only an extensive model study, because homo-DNA is not to be considered a potential natural-nucleic-acid altenratie. In retrospect, it seems fortunate that the model study was carried out, because without it we could hardly have comprehended the pairing behavior of the proper nucleic-acid alternatives which we have studied later and which will be discussed in Part VI of this series.The English footnotes to Fig. 1-49 provide an extension of this summary.

Notes: ‘Fully chiral’ dendrimers, containing a stereogenic center at each and every branching point, have been prepared using a chiral core triol with aromatic elongating units (cf. 27) and chiral branch diols (cf. 8, 12, and 24) as building blocks. The biggest dendrimer prepared is of the 4th generation (33: 46 building blocks, 93 stereogenic centers, 1028 possible stereoisomers), and has been obtained by a convergent growth approach in 32 steps starting from the biopolymer poly[(R)-3-hydroxybutanoic acid] (P(3-HB)). All compounds were shown to be monodisperse by MALDI-TOF mass spectrometry. Spin-lattice relaxation-time (T1) measurements and size-exclusion chromatography show typical features of structurally related achiral dendrimers. The influence of the chiral building blocks on the shape of the whole dendrimer has been investigated by chiroptical measurements: the specific rotation can be considered as average of all chiroptical properties of its constituent chiral units, independent of the solvent, the concentration, and the temperature. On the other hand, regularity in the circular dichroism (CD) spectra is completely lost with variation of the solvent (cf. Fig. 13).

Notes: The first steps, believed to be involved in the highly enantioselective copolymerization of styrene and carbon monoxide to poly[1-oxo-2-phenylpropane-1,3-diyl] with phosphinodihydrooxazole-palladium(II) complexes, were investigated. The insertion of carbon monoxide into [Pd(Me)(P^N)(solvent)] TfO (P^N = (S)-2-[2-(5H-benzo[b]phosphindol-5-yl)phenyl]4-benzyl-4,5-dihydrooxazole (1)) and of styrene into [Pd(Me)(P^N)(solvent)] TfO were highly regioselective (alkyl and acyl substituents trans to N); moreover, the olefin insertion took place with essentially complete enantioface discrimination.

Notes: The [4 + 2] cycloadduct 17 of 2,3-dimethylidene-1,2,3,4-tetrahydro-1,4-methanonaphthalene and 4-phenyl-4H-1,2,4-triazole-3,5-dione (PTAD) was subjected to a triplet-sensitized di-π-methane rearrangement. Hydrolysis of the resulting urazol 18 gave the hydrocarbon 7. Hydrolysis of 18 at lower base concentrations led to isomeric stable semicarbazides 24 and 25, which were submitted NiO2 or MnO2 oxidation, to give the target compound 7, and oxidation products 26 and 27.

Notes: The difference between the strong inhibition of retaining β-glucosidases by the tetrazole 1 and the weak inhibition by the triazole 3 has been explained by the protonation by the enzymic catalytic acid of N(3) of 1, replaced by CH in 3. One also expects a contribution to the inhibition from the charge-dipole interaction between the enzymic catalytic nucleophile and the azole ring. The extent of this contribution was estimated from the calculated, distance-dependent heats of formation of the acetate-azole complexes. The calculations were validated by comparison of the charge-dipole interaction between phosphate and the inhibitors 1 and 3 in the glycogen phosphorylase b (GPb)-azole-phosphate complexes, as derived from differences in the Ki values for 1 and 3, while the structural invariance of the complexes was demonstrated by X-ray analysis. The difference between the charge-dipole interactions of (dihydrogen) phosphate and 1 or 3 as derived from Δ Ki is 1.1 kcal mol-1, while the calculated difference is 1.3 kcal mol-1. The calculated difference for the interaction of 1 or 3 with acetate, representing the catalytic nucleophile in β-glycosidases, is 2.0 kcal mol-1, while the differences of the binding energies as derived from the Ki values for the inhibition by 1 or 3 of different β-glycosidases range from 2.4 to 5.3 5 kcal mol-1. The calculated difference for 1 and the imidazole 6 is 2.5 kcal mol-1 in favour of 1, whereas the Ki-derived difference is 3.7 kcal mol-1 in favour of 6, equal to the calculated difference between 1 and the protonated imidazole 6. Thus, protonation by the catalytic acid and the charge-dipole interaction with the catalytic nucleophile contribute cooperatively to the binding of inhibitors possessing a trigonal anomeric centre bonded to a heteroatom.

Notes: Described are the preparation of nanocrystals and the synthesis of molecules that may be covalently or noncovalently assembled in solution to yield heterosupermolecules possessing a well-defined heterosupramolecular function. Also described are preparative and synthetic methods that yield organized assemblies of heterosupermolecules possessing an addressable heterosupramolecular function. Finally, the development of these synthetic strategies to permit the covalent and noncovalent assembly and organization of a wide range of condensed phase and molecular components is outlined.

Notes: For a comparison with the corresponding α- and β-hexapeptides H-(Val-Ala-Leu)2-OH (A) and H-(β-HVal-β-HAla-β-HLeu)2-OH (B), we have now prepared the corresponding γ-hexapeptide 1 built from the homochirally similar (S)-4-aminobutanoic acid, (R)-4-amino-5-methylhexanoic acid, and (R)-4-amino-6-methylheptanoic acid. The precursors were prepared either by double Arndt-Eistert homologation of the protected amino acids Boc-Val-OH, Boc-Ala-OH, and Boc-Leu-OH (Schemes 1 and 2), or by the superior route involving olefination/hydrogenation of the corresponding aldehydes (Boc-valinal, Boc-alaninal, and Boc-leucinal; Scheme 3). Conventional peptide-coupling methodology (EDC/HOBt) furnished the γ-hexapeptide 1 (through the intermediate γ-di- and γ-tripeptide derivatives 9-11). Analysis of NMR measurements in (D5)pyridine and CD3OH solution (COSY, TOCSY, HSQC, HMBC, ROESY) reveals that the γ-hexapeptide 1 adopts a right-handed helical structure ((P)-2.61 helix of ca. 5-Å pitch, containing 14-membered H-bonded rings) which is to be compared with the left-handed helix of the corresponding β-peptide B ((M)-31 helix of 5-Å pitch, 14-membered H-bonded rings) and with the familiar right-handed, so-called α-helix of α-peptides ((P)-3.61 helix of 5.4-Å pitch, 13-membered rings). Like the helix sense, the helix dipole reverses when going from α-, (N + → C) to β-(C + → N) to γ-peptides (N + → C). The surprising difference between the natural α-, and the analogous β- and γ-peptides is that the helix stability increases upon homologation of the residues.

Notes: 7-O-Substituted analogs of deaminodeoxycolchinol thiomethyl ether were synthesized and evaluated for their inhibitory effects on tubulin polymerization in vitro. Ketone 9, a key compound in this study, was derived from thiocolchicone 6 by reaction with aniline. Reaction of compound 6 with MeNH2 or BuNH2 gave tetracyclic lactams 7 and 8, respectively. Optically active alcohols 11a and 11b were obtained from racemic 11 by chemical resolution including a separation of the comphanate diastereoisomers 12a and 12b, followed by basic hydrolysis. The (aR,7R)-configuration of 12b was verified by X-ray crystallographic analysis. Almost all racemic and optically active 7-O-acyl or 7-O-aroyl compounds had strong inhibitory effects on the tubulin polymerization reaction, with IC50 values from 1.7 to 5.1 μM. A few agents, such as the lactams 7 and 8, the camphanates 12a and 12b, the cyclohexanecarboxylates 19a and 19b, and, most notably, the (7S)-benzoate 15a, had negligible effects on polymerization, yielding IC50 values greater than 40μM. Ketone 9 showed strong inhibition of tubulin polymerization comparable to that of thiocolchicone (6). Optically active alcohol 11a and acyl esters 13a and 14a with a (7S)-configuration were more active than the (7R)-esters 13b and 14b. However, the esters 15a-17a with a (7S)-configuration were less active than the (7R)-isomers 15b-17b, in which the (7R)-benzoate 15b was at least 15-fold more inhibitory than the (7S)-isomer 15a. For the most part, the agents causing strongest inhibition of polymerization also caused the greatest inhibition of [3H]colchicine binding. NMR and optical rotatory data indicate that, in polar solvents, the equilibrium in esters with a 7-O-aroyl substituent, i.e., 15a,b, 16a,b, and 17a,b, is reversed from (aS) to (aR) or from (aR) to (aS), as compared to nonpolar solvents.

Notes: As a continuation of our previous studies on the synthesis and antiplatelet activity of quinolin-2(1H)-ones with an α-methylidene-γ-butyrolactone substituted at O(8), the O(6)- and N(1)-substituted isomers were synthesized and evaluated for antiplatelet activity against thrombin (Thr)-, arachidonic acid (AA)-, collagen (Col)-, and platelet-activating-factor (PAF)-induced aggregation in washed rabbit platelets. These compounds were synthesized from 6-hydroxyquinolin-2(1H)-one via alkylation and Reformatsky-type condensation (Schemes 1 and 2). All of them were found to inhibit the platelet aggregation perfectly which was induced by AA and Col. 6-Substituted isomers 5b-g exhibited very strong inhibitory activities against AA- and PAF- induced aggregation and are approximately ten times more potent than their 8-substituted counterparts. However, the 1-substituted (11a and 11b) and the 1,6-disubstituted (6) counterparts were relatively inactive. Their effects on the Ca2+-dependent vasoconstriction induced by high K+, and the phasic and tonic vasoconstrictions induced by norepinephrine (NE) in rat aorta were also evaluated. Except 5g, all of them were found to have significant inhibitory activity on the NE-induced phasic and tonic vasoconstrictions. Compounds 6 and 11b also exhibited strong inhibitory activity on high-K+ medium, Ca2+-induced vasoconstriction.

Notes: The photolysis of N-alkylpyridinium halides 9a-e in alkaline H2O gave 6-azabicyclo[3.1.0]hexenol derivatives 10a-e. N-Substituents bearing ether, acetal, and alcohol functions were found to do not adversely influence the photochemical reaction course. The free OH groups of the N-(3-hydroxypropyl) derivative 10d were protected by benzoylation. The ensuing dibenzoate 14 underwent stereocontrolled opening of the aziridine ring on reaction with MeSH/BF3 to give a thioether 15. With benzoic acid in CHCI3, 10d gave the 4-hydroxy-5-aminocyclopent-2-enyl benzoate 11. The meso-2-aminocyclopent-4-ene-1,3-diol 12 was obtained by hydrolysis of 11. On reaction with Boc2O and NaI, the aziridine ring of 14 was converted to a bicyclic compound 17. Hydrolysis of 17 provided the trans-1,3-diol 18, the epimer of 12. Face-selective dihydroxylation of Boc-protected 12 gave a meso-aminocyclopentanetetrol 23 which was characterized upon peracetylation. Dihydroxylation of 15 provided a racemic analogue of epi-mannostatin A (26).

Notes: An alternative synthesis of enantiomerically pure SDZ 220-881 (1a) and SDZ EAB 515 (1b) starting from L-Z-tyrosine is described.

Notes: Bicyclic thiohydantoins were synthesized in a stereoselective manner by reacting (2R)/(2S)-diastereoisomer mixtures of 1,3-thiazolidine-2,4-dicarboxylic acids or their dimethyl diesters with PhNCS. 5,5-Dimethyl-1,3-thiazolidine-2,4-dicarboxylic acid with PhNCS led to a cyclization involving the C=O group at the C(2) center of the thiazolidine ring, while the acid's dimethyl diester gave cyclization involving the C=O group at C(4). In contrast, reactions involving unsubstituted 1,3-thiazolidine-2,4-dicarboxylic acid or its dimethyl diester led to thiohydantoins in which the ring closure had taken place only with the COO group at C(4). Independently of the direction of the ring closure, all reactions produce exclusively products with the (R)-configuration at C(2). The configurational assignments were based on 1H- and 13C-NMR studies, and confirmed by X-ray crystallographic analyses.

Notes: The new, axially chiral bis(4,5-dihydrooxazoles) 4 have been synthesized in a straightforward manner, starting from the substituted, racemic 1,1′-biphenyl-2,2′-dicarboxylic acids 1 and optically active amino alcohols 2. The adducts were resolved by medium-performance liquid chromatography (MPLC; see Scheme 1). Formation of Cu1 complexes of 4 was followed by 1H-NMR spectroscopy. The catalytic behavior of these complexes has been investigated by asymmetric cyclopropanation of styrene with ethyl diazoacetate. Beside the influence of steric factors, a significant electronic effect on asymmetric induction could also be observed (see Scheme 2 and Table).

Notes: The synthesis of the enantiomerically pure, bridgehead-functionalized bicyclo[3.2.1]octanes 11 and 16, containing a conformationally fixed trihydroxypropyl (aminodihydroxypropyl) unit, as well as the X-ray structure of 11 are described. These compounds are of interest as sugar surrogates in the preparation of DNA analogs. Compounds 11 and 16 became available in 10 and 12 steps, respectively, and in an overall yield of 11 and 4% from D-arabinose via a highly stereoselective pinacol coupling as the key step.

Notes: New derivatives of campholenaldehyde (= 2-(2,2,3-trimethylcyclopent-3-enyl)ethanal bearing two cyclopropane moieties were synthesized, and the structure of the stereoisomer responsible for its exceptionally strong, diffusive, and natural sandalwood-oil scent, ((1S,2S)-1-methyl-2-{[1S,3R,5R)-1,2,2-trimethylbicyclo[3.1.0]hex-3-yl]methyl}cyclopropyl)methanol (13a), was elucidated.

Notes: Titanium-dioxide surfaces have been glycosylated with the benzyl-, 4-fluorobenzyl-, and acetyl-protected diazirines 1-3. The modified TiO2 surfaces were characterized by contact-angle measurement, X-ray photoelectron spectroscopy (XPES), and time-of-flight secondary-ion mass spectrometry (ToF-SIMS). The main by-products of the glucosidation (mostly azines and trehaloses) were identified. Their physisorption slightly reduces the efficiency of the glucosidation by 1 mM solution of 1 or 2 in CH2Cl2, but this influence is neutralized by repeating the glucosidation, or by using a 100 mM solution of the diazirines. The immobilized, acetylated glucosyl moieties were deacetylated in situ. Calculations based on the XPES peaks of Ti 2p and F 1s for the TiO2 surface modified with 2 indicated 1.5 ± 0.9 immobilized glucosyl moieties per nm2.

Notes: A Chemotaxonomic survey for biologically active compounds from Malaysian Calophyllum species led to the findings of the four new benzoylcoumarins 1a, 2, 3, and 4a (including the unusual prenylated 6-benzoylcoumann 1a), two uncommon coumarins 5 and 6a with a pyran-4-one moiety fused at C(6) and C(7), and compounds 7a, 9, and 10, all isolated from the bark of C. teysmannii var. inophylloide. Their structures were determined by spectroscopic analysis and chemical transformations. X-Ray crystal-structure determination of 2 provided information on the conformational preferences of substituents in this class of coumarins. The syntheses of the cytotoxic calanone (7a) and of some related coumarins are described.

Notes: The heme-thiolate protein chloroperoxidase (CPO) catalyzes the chlorination of activated C—H bonds. A reaction mechanism is proposed for this enzymatic transformation (Scheme 1), and a new iron(III) porphyrinate complex 13 is synthesized containing pentafluorophenyl groups at two meso-positions and a thiophenolato ligand coordinating to the Fe-atom (Schemes 2 and 3). Due to the presence of the electron-withdrawing substituents, the catalyst 13 is appreciably resistant to oxidants (HOCl) and chlorinates, e.g., monochlorodimedone (5), with turnover numbers up to 1530. The redox potential of 13, E0 = - 134 mV, and the Soret band (λmax 448 nm) of the CO adduct of the reduced state of 13 are close to the corresponding values of the enzyme CPO.

Notes: The chemical synthesis of 2′-amino-2′-deoxyribonucleosides of uracil, cytosine, adenine, and guanine, and their conversion into suitably protected 3′-phosphoramidite building blocks 35-40 for oligonucleotide synthesis are described. The aglycone and the 2′-amino functions were protected using the 2-(4-nitrophenyl)ethoxycarbonyl (npeoc) group. The synthesis of the 3′-O-succinyl (3′-O-(3-carboxypropanoyl))-substituted starting nucleoside 41 is described and its behavior examined in solution and on solid phase with regard to an anticipated migration during 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) deprotection. Oligonucleotides were prepared using the new building blocks, and their hybridization properties were studied by UV-melting techniques.

Notes: Chiral supermolecules may be obtained from suitable achiral molecular constituents associated through a dissymmetrizing interaction mode. This is the case for the supermolecules I-IV formed by hydrogen-bonding association between the achiral complementary components 1a,b and 2a,b,c. The crystal structures of the supermolecular pairs I-III and of the homochiral aggregate of two ternary supermolecules IV have been determined. The structural data are discussed.

Notes: Various bifunctional amino-protecting groups such as the phthaloyl, succinyl, and glutaryl group were investigated as potential linker molecules for attachment to solid-support materials. Pentane-1,3,5-tricarboxylic acid 1,3-anhydride (16) offered the best properties and reacted with the amino groups of differently sugar-protected adenosine (see 20 and 22), cytidine (see 29), and guanosine derivatives (see 32) to the corresponding 2-(2-carboxyethyl)glutaryl derivatives 23, 24, 30, and 33. The usefulness of the new linker-type molecules was demonstrated by the solid-support synthesis of the potentially antivirally active 3′-deoxyadenylyl-(2′-5′)-2′-adenylic acid 2′-{2-[(adenin-9-yl)methoxy]ethyl} ester (38) starting from the 2′-end with N6,N6-[2-(2-carboxyethyl)glutaryl]-9-{{2-[(4,4′-dimethoxytrityl)ethoxy]methyl}adenine (12).

Notes: An efficient stereocontrolled synthesis of (S)-N-Cbz-serine (Cbz = benzyloxycarbonyl; 12) and of its (R)-enantiomer is reported. Kinetic resolution of the easily available racemic 3-(hydroxymethyl)-1,4-benzodiazepin-2-ones is performed in the key step via acetylation by the immobilized Mucor miehei lipase (Lipozyme IM) at 60°. This method is characterized by high enantiomer purity (ee's ges; 99%) of the intermediary alcohols (+)-8 and (+)-9 and acetates (-)-10 and (-)-11, as well as of the final products (S)- and (R)-N-Cbz-serine, simple recycling of the biocatalyst, complete recovery of 2-aminobenzophenones (3 and 4) and their recycling into production of 1,4-benzodiazepines, and possibility to selectively racemize ‘wrong’ enantiomers of the alcohols 8 and 9 in the presence of Amberlite CG 400.

Notes: The fate of an insect juvenile hormone analog applied to the insect body of the flesh fly (Sarcophaga bullata) or the tsetse fly (Glossina palpalis), respectively, was studied using three different radiolabeled positions in the parent biologically active compound 1. Several metabolites were found and analyzed. A mechanism of degradation of the applied molecule was designed using a combination of several radioanalytical methods. A unique monitoring of the applied compound and its metabolites was provided, based on the different radiolabeling of the structure (cf. 1a-1c), and established their fate in an insect body during a 10-day experiment. A 14C and 3H radiolabeling, respectively, was employed to synthesize three different radiolabeled forms 1a-1c derived from the parent non-labeled 1. A combination of three different ways of radiolabeling resulted in an advantage in tracing the metabolic pathway of degradation of the employed compound 1 in its radiolabeled forms 1a-1c.

Notes: Previous work has indicated orbital-symmetry effects upon forward electron transfer in bimolecular systems, with magnitude similar to that encountered in rigid monomolecular systems. The present work, which employs back electron transfer, supports and extends these earlier findings.