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Notes: The surfaces of palatal shelves from carefully staged A/Jax mouse embryos were examined with the scanning electron microscope prior to and during palatal fusion. No change was observed in the appearance of cells covering the oral and nasal surfaces of the shelves. A change was observed, however, in the region of presumptive fusion, and was detectable on vertical shelves just prior to transposition. This change initially involved surface cells along the future medial edge of the shelf at the level of the second to third rugae. It was characterized by a loss of distinct cellular boundaries, the appearance of intercellular gaps caused by apparent retraction of adjacent cells, and a progressive accumulation of filamentous material at the surface. These alterations spread posteriorly along the medial edge of the shelf during transposition and fusion. While it was impossible to determine the precise nature of the surface change from S.E.M. data alone, the fact that it both preceded closure and was restricted to the region of subsequent contact and fusion between the shelves suggests it may be a prerequisite for normal palatal fusion and may represent an expression of the acquisition of a potential to fuse similar to that proposed for palatal fusion in vitro.

Notes: The day-by-day developmental changes which occur in the respiratory system, mesenteries and celom of the sheep embryo from 14 to 34 days coital age are documented chronologically and described. This work provides standards of normal development which can be used as a basis for future work on abnormal development of these structures.The respiratory diverticulum which first appears on the seventeenth day is seen as a primitive lung bud on the nineteenth day and becomes bilobed on day 20. By the twenty-first day a laryngotracheal tube is present and the larynx develops in the next ten days.The dorsal mesogastrium forms on the eighteenth day and the omental bursa is seen as an invagination by the twenty-first day. A splenic primordium associated with the omentum is present by the twenty-seventh day.The dorsal mesentery appears on the eighteenth day and undergoes torsion, herniation and coiling on the twentieth, twenty-second and twenty-seventh days. The ventral mesentery is present on the seventeenth day but disappears centrally between the eighteenth and twenty-first days.An extraembryonic celom is seen on the fourteenth day and the formation of the intraembryonic celom occurs on day 15. Development of the pleuroperitoneal membranes commences on the twenty-first day. Complete separation of pericardial and pleural cavities is completed by the twenty-eighth day.

Notes: Using an indirect immunofluorescent technique sera from a group of patients suffering from a variety of liver diseases have been shown to contain an antibody which will specifically stain the bile canaliculi of a wide variety of mammals, birds and amphibia. It is suggested that this method is an effective alternative to the methods presently available for demonstration of bile canaliculi.

Notes: Rostral pores are epidermal invaginations which occur on the internarial region of most chelonians. Representatives of all Recent chelonian families and 67 of the 74 extant genera were examined grossly and/or histologically. Pores are absent only in the families Carettochelyidae, Cheloniidae, and Dermochelyidae. The number and microscopic structure of pores vary markedly within and between taxa. Morphological data suggest that rostral pores could function in mechanoreception. The possible origin and evolution of rostral pores are discussed in the context of other chelonian integumentary speializations.

Notes: During development of the secondary palate, mouth-opening reflexes and swallowing movements have been observed previously. They have been assumed to be necessary in order to allow the descent of the tongue, thus enabling movement of the palatine shelves from a vertical position lateral to the tongue, to a horizontal position superior to the tongue. Interpretation of fixed, paraffin-embedded sections, showing large spaces in the oral cavity, has added to the concept that the tongue descends into a space.Hexane-quenched, cryostat-cut, frozen sections of fetal mice heads show that no oral space exists at any time during elevation of the palatine shelves. Interpretation of static micrographs indicates that prior to shelf elevation the tongue is in contact with the nasal septum above and the vertical palatine shelves laterally. When the shelves elevate they seem to “flow” dorsally and interpose themselves between the tongue inferiorly and the nasal septum superiorly.

Notes: The biosynthesis of pyridine nucleotides has been examined in a number of mammalian cell lines in culture. In all lines examined, nicotinamide is incorporated by a biochemical pathway distinct from the Preiss-Handler pathway for nicotinic acid.In at least the human cell line D98/AH2, there is no detectable endogenous synthesis of the pyridine ring from tryptophan. Although most cell lines examined (hamster BHK 21/13, mouse L929 and human D98/AH2) use either nicotinic acid or nicotinamide as a precursor for DPN and TPN, two mouse cell lines, 3T3-4E and LM CIID, are unable to utilize nicotinic acid as a source of the pyridine ring.If nicotinic acid is present in the medium, substantial amounts of intracellular desamido DPN accumulate suggesting that the last step (desamido DPN→DPN) is limiting in the Preiss-Handler pathway. With nicotinamide, the only compound which accumulates in substantial amounts apart from DPN and TPN is nicotinamide ribose; there is no detectable NMN. The results of pulse-labeling experiments suggest that nicotinamide ribose may be an intermediate in the nicotinamide pathway.Following growth of D98/AH2 cells in high concentrations of niacin, biosynthesis of DPN from nicotinamide was completely inhibited for at least six hours. The converse experiment revealed no inhibition of niacin incorporation. This observation suggests that a niacin pathway intermediate, which present evidence indicates is desamido-DPN. can inhibit nicotinamide utilization.Newly synthesized DPN turns over with a half-life of two hours in azaserine-treated D98/AH2 cells. In the absence of azaserine, the nicotinamide moiety of newly synthesized DPN is lost from D98/AH2 cells to the medium with a half-life of eight hours. About 80% of the nicotinamide is lost to medium as nicotinamide ribose.

Notes: A cinematographic analysis of the unrestrained walking, trotting, galloping, jumping and landing movements of 11 adult cats was undertaken to provide previously unavailable information concerning the demands imposed on the nervous system for the control of low and high speed movements and the demands imposed by such natural movements on muscle performance and proprioceptive response.With due regard for the swing (F and E1) and stance (E2 and E3) phases of the step cycle of an individual limb, single frame analysis of the film permitted measurement of instantaneous angles of the lower spine, hip, knee, ankle and metatarsophalangeal joints. Appropriate lever arm measurements were also made on 50 freshly dispatched cats and 25 cadavers such that the Law of Cosines could be used to calculate instantaneous lengths of select hind limb muscles that would apply to the natural movements of adult cats of small (1.5-2.5 Kg), intermediate (2.6-3.5 Kg) and large (3.6-4.5 Kg) size. Muscle displacements were analyzed relative to maximum and minimus in situ lengths and the lengths associated with quiet standing. Use was also made of a previous electromyographic analysis of hind limb muscles during unrestrained locomotion (Engberg and Lundberg, '69).The sequential relations between the four phases of the step cycle are maintained as forward speed increases from walking ( 〈 2 mph) to high speed galloping ( 〉 16 mph). There are significant differences in the time consumed by each phase, however, with a greater reduction in the E3 phase, little reduction in the E2 and E1 phases and virtually no reduction in the F phase. When each phase is expressed as a relative percentage of the duration of the total step cycle, the greatest reduction is again in E3 with little change in the E2 phase. In contrast F and E1 phases increase in the percent of time they occur in each cycle, with the greatest increase in the F phase. For all speeds, analysis of the phase relations between movements of various sections of the hind limb revealed a remarkable unity of knee and ankle joint movement. The hip joint is largely out of phase with the knee and ankle during E1 and E2, all three joints being in phase in F and E3. The digits are essentially out of phase with the other joints except in the stance phase of the gallop.Rates and extents of muscle displacement during natural movements are greater than might be anticipated when expressed in absolute mm's and mm/sec but not when considered in relation to maximum and minimum in situ length and the length associated with quiet standing (Ls). During stepping a progressive increase in forward speed results in: (a) a greater usage of muscles at lengths between Ls and maximum in situ length; (b) for knee and ankle extensors, pronounced increase in the lengthening contraction associated with the E2 (yield) phase of step; and, (c) for both flexor and extensor muscles, an increased active phase of lengthening or near isometric contraction immediately prior to periods of active shortening. In contrast to these changes in active muscle status, the change from walking to galloping has little effect on the extent and rate of passive muscle displacements, particularly the F phase stretch of extensors.For the soleus muscle, calculations were made of the relation between changes in overall muscle length during natural movements and the length of the average muscle fiber and the tendon of insertion. These measurements revealed that the increases in fiber length when passive and decreases in length during active shortening are less than would be anticipated from the extensive liteature on extirpated fibers. In contrast, the increase in fiber length when active is greater than would be expected from the admittedly sparse literature on this subject.The results of this study are discussed largely in relation to two points of neurophysiological interest: the physiological range of muscle stretch as it pertains to the responsiveness of muscle spindles and tendon organs; and those mechanical aspects of lengthening contractions that give insight into the neural control of stepping. For exciting both spindles and tendon organs passive muscle stretch and shortening contractions are shown to be relatively ineffective and lengthening and isometric contractions particularly effective movements. It is suggested that, just as recent literature has emphasized the co-activation of efferent alpha and gamma motoneurons as a muscle becomes active, so too is there a synchronous activation of afferents, particularly the Ia and group II endings of muscle spindles and Ib endings of tendon organs. Finally the thesis is advanced that, while it has been convenient to separate E2 from E3 in the description of the stance phase of the step cycle, extensor muscles are actually undergoing a single mechanical event: an active stretch-shorten cycle for knee and ankle extensors and an active isometric-shorten cycle for hip extensors. This hypothesis has significant implications for the neural control program that regulates the stepping sequence in that it emphasizes the extent to which appropriate changes must be preprogrammed in the mechanical properties of muscles for the smooth execution of stepping.

Notes: Cells in secretory glands of globiferous pedicellariae from Strongylocentrotus purpuratus (Stimpson) were studied with the electron microscope and subjected to preliminary light microscopic, histochemical analysis. Specimens for electron microscopic observation were fixed with chilled 2% glutaraldehyde in sea water postfixed in cold 1.33% osmic acid, and embedded in Araldite 502 epoxy resin Samples for histochemical analysis were fixed in the same manner, and then embedded in n-butylmethacrylate.Secretory cells line and fill partially bifurcated, muscular gland sacs located peripherally on each of three jaw elements comprising the pedicellarial head. Cells from venom glands are typically mucoid in appearance, possessing small volumes of basally displaced, vesiculated cytoplasm and an extensive system of vacuoles dominating the apical nine-tenths of each cell. These vacuoles enclose ground substances of various densities and staining affinities. Despite their extensive vacuolation, gland cells contain numerous cytomembrane complexes indicating metabolic activity just prior to fixation. Deciduous endoplasmic reticulum, Golgi complexes, large vacuoles, and various species of vesicles associated with these membrane systems are found in spatial proximity which indicates an apparent biosynthetic association.Preliminary histochemical tests on sections embedded in acrylic plastic indicate vacuolar products may consist of protein and nonsulfated acid mucosubstances.Gland cells are probably holocrine in function, releasing their vacuolar complement upon constriction of the muscular gland sac. There is no evidence indicating delivery of non-membrane bounded, granular secretion to an acellular lumen within the gland sac.

Notes: Basicranial anatomy of mammalian carnivores is significant in the determination of carnivore evolution. One of the least understood yet most often studied features of the basicranium is the auditory bulla, a bony capsule enclosing the middle ear. Although previously believed to be formed by a tympanic bone alone, or by tympanic and entotympanic, it is shown here that the carnivore bulla is formed by three and in some cases four ontogenetic elements: tympanic, rostral entotympanic, caudal entotympanic(s). These elements in Carnivora appear to correspond to bulla elements discovered over 50 years ago by Van der Klaauw in representative species of several other orders of mammals.Increased auditory sensitivity appears to have been attained in various carnivore lineages by increase in the volume of the middle ear cavity, principally by hypertrophy of the caudal entotympanic, but also by different yet less common anatomical strategies such as invasion of the mastoid bone by the middle ear space. Five basic types of bulla among living Carnivora can be recognized, based largely on the relationship of the caudal entotympanic to the other bulla elements.Closely associated with the bulla in the auditory region are the median and promontory branches of the internal carotid artery. These branches exhibit a precise relationship to the bulla elements, particularly the rostral entotympanic. The promontory branch is much reduced or completely lacking in all living carnivores. Reduction or loss of the median branch is explained as the result of the development of arterial retia on the anastomotic artery in the orbital region. Reduction of the median branch is particularly characteristic of the aeluroid Carnivora, in which a greater proportion of the cerebral blood supply passes to the brain in the external carotid artery via the anastomotic branch, and is cooled in the orbital region by a countercurrent heat exchange mechanism formed by arterial retia closely associated with venous blood in surrounding sinuses. The arctoid and cynoid Carnivora are characterized by only rudimentary development of retia along the anastomotic artery, and the median branch is much better developed than in the aeluroids. Among arctoids, ursids parallel the aeluroids in the development of a countercurrent mechanism but employ the median branch of the internal carotid rather than the anastomotic branch of the external carotid artery.Bulla structure and nature of the carotid circulation in the auditory region can be determined from fossil Carnivora as well as for living forms. This study attempts to define basicranial anatomical patterns characteristic of living Carnivora which then can be used to trace the evolution of lineages in the fossil record.

Notes: The authors describe the spermiogenesis of Polyxenus lagurus, a diplopod, in the male genital ducts and the transformations the spermatozoon successively undergoes in the spermatheca.The spermatozoon in the male genital ducts looks like a little barrel devoid of centriole and of any kind of rudimentary flagellum whatever. The organelles are markedly modified; cross sections present an elongated, flattened nucleus, an X-shaped body running parallel to it on the opposite side and two longitudinal mitochondrial strips interposed between them. The rest of this barrel-shaped spermatozoon is filled with peculiar Golgi formations, the spongy chambers, which open outwards through little vents.In the spermatheca the spermatozoon is quite different: it is shaped like a long ribbon. The basic structure of the spermatozoon is formed by the double folding of part of the cortical layer of the barrel-shaped spermatozoon. On the central part of this endo-skeleton are longitudinally ranged the nucleus and the acrosome flanked on both sides by a thread of mitochondria. Even in this phase the sperm has no flagellum.