Bibliothek

Notizen: The synthesis of zymogen-like secretory granules in convoluted tubules of mouse submandibular gland (SMG) was investigated by histometry, light microscopy and electron microscopy. In normal males secretory granules in the SMG increased greatly from 25 days after birth and reached a maximum level 50 days after birth. Castration of adult male mice markedly decreased the level, but it was completely restored by testosterone administration. A parallel was found between change in the granule level and the amount of rough endoplasmic reticulum (RER) in the convoluted tubular cells during development or after various treatments. Development of the Golgi apparatus was also observed in the cells when the granules increased. Both the increase in the granules and in the RER induced by testosterone were prevented by actinomycin D or puromycin. These results indicate that the granule contents are synthesized on the RER under the control of testosterone, and then condensed in the Golgi apparatus.

Notizen: The ultrastructure of the intercellular junctions of rat endocardium has been characterized following lanthanum exposure in vitro and uranyl acetate staining en bloc. The interendothelial clefts of the endocardium run either a relatively straight or convoluted course and possess one or two loci where the plasma membranes are in close apposition or form punctate fusions. Elongate restrictions, that exhibit hexagonal arrays of subunits following lanthanum immersion (gap junctions), are also present in the intercellular endocardial clefts. The occurrence of interendothelial clefts of endocardium lacking occlusive foci can account for the permeability properties of ventricular endocardium, where the direction of diffusion of macromolecules has been attributed to pressure gradients between ventricular cavity and myocardium. The relationship of gap junctions to possible electrical phenomena within the endocardium is also discussed.

Notizen: The ultrastructure of the median eminence of neonatal (newborn, 1-, 3-, 5-, and 10-day old) and adult guinea pigs was studied to determine the dynamic changes occurring in this structure during early life. At birth the portal vasculature consists of the Mantelplexus and a few, non-fenestrated capillary loops. The number of ansae and the degree of fenestration increase rapidly after birth. The abundance of cytoplasmic and ciliary projections into the ventricular recess and the large numbers of organelles indicate that the ependymal cells are more active in the neonatal period than in the adult male. Moreover, the ependymal endfeet cover most of the surface area of the primary portal plexus during this time. The neuronal layers of the median eminence are difficult to distinguish at birth due to the lack of myelinated fibers in the zona interna. Significant myelination appears on day 3 but is not complete until day 10. There is a progressive increase in the numbers of Herring bodies and large neurosecretory granules (1,500-1,700 Å) during this same time period. In the zona externa, few nerve terminals abut on the perivascular space until day 3. Increases in numbers of granules per axon profile were noted for each day after birth. Despite the relatively long gestation period of the guinea pig (68-72 days), the morphologic appearance of the median eminence at birth suggests that the neurovascular link controlling anterior pituitary function is not yet complete.

Notizen: Renewal of the cell populations of the incisor was studied in 100 gm male rats injected with a single dose of 3H-thymidine and sacrificed at various times from one hour to 32 days after injection. Radioautographs showed that a cohort of labeled cells within the enamel organ, odontoblast layer, and pulp was carried passively with the erupting incisor from the apical end toward the gingival margin where the life cycle of these cells was terminated. Labeled cells in the upper and lower incisor, although traversing different absolute lengths, were found in approximately the same functional stage of their life cycle at similar times after the injection. Thus, by one and one-half days labeled ameloblasts began inner enamel secretion. By 32 days labeled ameloblasts had traversed the entire maturation zone and were located at the gingival margin. Labeled odontoblasts followed closely the movement of labeled ameloblast. The mean rate of ameloblast migration was 567 μm/day on the upper incisor and 651 μm/day on the lower. For the odontoblasts this rate was 500 μm/day (upper) and 631 μm/day (lower). Finally, it was found that as the rat aged, the duration of the life cycle for epithelial and pulp cell populations of the incisor increased because of growth within the longitudinal axis of the tooth. It was concluded that the apical end of the incisor literally “grows backward” in the bony socket, and hence, the duration of the life cycle becomes greater simply because it takes cells longer to physically reach the gingival margin.

Notizen: The venous channels responsible for the intracranial drainage were dissected in a series of 25 male and female adult tufted or brown capuchin monkeys (Cebus apella).It was found that Cebus have a venous arrangements fundamentally the same as in man, differing only in that: 1. the monkey has no inferior sagittal sinus, sphenoparietal sinus, and emissary parietal and condylar veins; 2. the occipital sinus is not in connection with other sinuses; 3. there are a sphenopetrosal sinus, a petrosquamous sinus, and an unpaired inferior cerebellar vein; 4. besides the internal jugular vein, there is additional intracranial drainage through the petrosquamous sinus and the postglenoid vein; 5. the superficial middle cerebral vein opens into the petrosquamous sinus; 6. the lingual and facial veins are not tributaries of the internal jugular vein; 7. there is a bilateral uniform division of the superior sagittal sinus at the confluence of the sinuses to drain equally into both transverse sinuses; 8. the vascular pattern appears to be quite stable; anatomical variations appear to be few and unimportant.

Notizen: The trophospongial layer of the near-term kangaroo rat placenta was examined in the electron microscope. Two ultrastructurally different cellular zones were distinguishable - an inner zone adjacent to the labyrinth and a basal zone located mesometrial to the inner zone. Inner zone cells contained a well developed granular ER and Golgi apparatus as well as polymorphous membrane-limited granules. The cells also contained modest amounts of glycogen and lipid droplets. Basal zone cells were also rich in ER; some cells had dilated ER cisternae containing a highly structured material which appears as a sheet of hexagons when viewed en face. Basal zone cells may, among other things, function as glycogen storage cells, since they had large cytoplasmic accumulations of glycogen. Unlike the situation in some other rodents, maternal blood draining from the trophospongial layer was always contained in channels lined by a layer of squamous cells which, in turn, was separated from the trophospongial cells by a basal lamina. The trophospongial zones are compared with the trophosngial regions of other rodent placentas and possible functions are considered.

Notizen: The surface characteristics of the intrapulmonary airways and alveoli of the lungs from 12 young adult cattle examined by the scanning electron microscope are described. When compared with similar studies of the lungs of various other mammalian species, the bovine lung gneerally resmebles that of other mammals except for several important features: (1) Alveolar pores of Kohn are small and extremely rare; (2) Alveolar macrophages are seldom seen in alveolar air spaces; (3) Interlobular septa completely separate the lung into distinct lobules.

Notizen: Autoradiography and scintillation counting have been used after various schedules of 3H-thymidine injections to evaluate lymphocyte kinetics in normal and thymus-deprived BALB/C mice. The thymus was found to be an active production site of small lymphocytes, the majority of these cells having thymic residence times of three to five days. Peripheral lymphoid tissues - including spleen, lymph nodes and Peyer's patches - were dominated by long-lived lymphocytes and produced very few small lymphocytes. Nearly identical percentages of long-lived lymphocytes with comparable grain counts were found in the peripheral tissues. In adult thymectomized animals, and in mice thymectomized and reconstituted with bone marrow cells following total body irradiation, percentages and lifespan of long-lived lymphocytes were found to be of the same order as in normal or sham-operated controls. It is concluded that T cells in the peripheral long-lived pool can be formed outside the thymus and that the bone marrow probably produces long-lived B lymphocytes.

Notizen: Neuroblasts of the substantia gelatinosa at birth were small with large oval nuclei and scanty cytoplasm. The cytoplasm possessed ribosomes and mitochondria. Granular endoplasmic reticulum and Golgi complexes were generally absent or rudimentary. Electron dense bodies were seldom observed. By the end of the first week, the nuclei of several cells demonstrated early nuclear invaginations; cytoplasm exhibited growth cones, a well developed granular endoplasmic reticulum and Golgi complexes. At several points the channels of endoplasmic reticulum became continuous with the perinuclear space. By the end of the second week, differentiation of the neuroblasts was more advanced. More nuclei showed invagination of their contour. The cytoplasm revealed well developed granular endoplasmic reticulum and multiple Golgi complexes. Numerous vesicles and dense bodies were found adjacent to the Golgi complexes. Arrays of agranular endoplasmic reticulum also appeared late in the second week. By the third week, features of neuronal differentiation, such as nuclear invaginations, granular endoplasmic reticulum, agranular membrane configurations, multiple Golgi complexes and dense bodies in the cytoplasm became well established.

Notizen: The authors' previous report (Savostin-Asling and Asling, 1973) demonstrated that Meckel's cartilage is a favorable site for study of calcified cartilage resorption. In the present study the ultrastructural features at this resorption front have been examined by transmission and scanning electron microscopes (19-day rat fetus). Multinucleated giant cells (chondroclasts) dominated the erosion front. The many features which they showed in common with osteoclasts included abundant mitochondria, vacuolation, lysosomes, sparsity of roughsurfaced endoplasmic reticulum, and deep infoldings at loci of contact with calcified matrix. Crumbling of matrix (with mineral crystals penetrating between these foldings) and fragmentation of collagen fibrils were also seen. The propensity of chondroclasts for spanning several opened lacunae provided special opportunity to demonstrate cell surface modifications in presence or absence of matrix contact. Ameboid processes extending into lacunae were seen by both transmission and scanning procedures; they were sometimes tipped with a veil of filamentous processes as small as 0.3 μm in diameter. Most hypertrophic chondrocytes, when released from lacunae, appeared to be disintegrating. However, in accord with previous evidence of their possible merger with chondroclasts (in light microscopic studies) there was also evidence for breakdown of cell walls between a chondroclast and a chondrocyte in intimate contact, with possibility of cytoplasmic continuity.

Notizen: This study is concerned with the morphogenesis of the carpal elements in the regenerating forelimb of the adult newt. Blastema cells surrounding the remnant bony stumps begin to differentiate into cartilage on the twentieth post-amputation day. Subsequently, masses of cartilage build up from the radial and ulnar stumps. The radial mass is larger and differentiates more rapidly than the ulnar mass. By the fifty-fifth post-amputation day, the eight basic carpal elements are formed, with fusion of two of the units, intermedium with ulnare, occurring by the seventieth day. The complexed regenerate possesses the seven carpal elements characteristic of the normal adult limb. The present results show that during limb regeneration in the adult newt the carpal elements are restored to their original number and position and that the pattern of such carpal differentiation proceeds in a proximodistal direction influenced by the stump remnants of the radius and ulna.

Notizen: This study focuses on the confusion in existing literature concerning the presence of smooth muscle in the capsule and trabeculae of lymphnodes. Human and bovine nodes from several anatomical areas and several individuals of each species were examined by conventional light, electron and fluorescence microscopy. Smooth muscle cells, independent of blood vessels, were demonstrated in the trabeculae and capsules of lymph nodes of both species examined by all three techniques. The need for further study on the function of these cells is indicated.

Notizen: The study was designed to determine whether or not the rat uterine luminal epithelium exhibits a mitotic circadian rhythm and to ascertain the effect of estrogen treatment at different time periods on the uterine epithelial mitotic response. Immature rats were injected with either sesame oil (controls) or 60 ng of estradiol-17 β at eight time periods and were necropsied 24 hours after treatment. Colchicine was administered IP two hours before autopsy. Peak mitotic activity was observed during the nocturnal phase (0300) for both the control and estrogen-treated rats. The nadirs were recorded during the diurnal phase (1800 and 1200 for the control and estrogen groups, respectively). The differences between low and high values were 1100% for the control rhythm and 101% for the estrogen animals. The data demonstrate the existence of overt circadian rhythms in the uterine epithelium for both control and estrogentreated rats.

Notizen: The arteries and veins of the fox testis were studied using an angiographic technique. The postnatal development of the testis involved only minor modification of the vasculature. In the non-breeding season both the arteries and veins of the adult fox testis undergo extensive spiralization which completaly disappears during the breeding season. When the sequence of morphological changes in blood vessels are related to available data on changes in testicular size, blood flow and connective tissue content, it is obvious that the vascular spiralization is passive and related to shrinkage of the organ and does not primarily influence the testicular blood flow.

Notizen: Cushion veins of the human nasal lining were studied in eight patients of both sexes ranging in age from 11 to 59 years. It was found that the subendothelial cushions were part of the tunica media and consisted of smooth muscle cells, collagen and elastic fibers and occasional fibrocytes. The muscle fibers of the cushion nearest to the endothelium were circular. They extended processes towards the endothelium through gaps in the endothelial basement membrane and formed appositional junctions with the endothelial cells. The rest of the cushion consisted of longitudinal muscle fibers. The sarcoplasm of the muscle cells was characterized by large areas filled with vesicles of various sizes. In addition, these cells possessed cytoplasmic processes which were devoid of a basement membrane and which did not show the regular structure of sarcoplasm. The subendothelial cushion possessed a rich, intrinsic nerve supply of adrenergic and cholinergic axons. It is suggested that the cushion veins regulate the drainage of the cavernous tissue and are under nervous and humoral control. The increase in girth of the subendothelial cushion is effected by contraction of the longitudinal muscle cells and probably by uptake of extracellular fluid by means of the specialized cytoplasmic processes. The single layer of circular muscle cells situated between the endothelial lining and the longitudinal musculature, may provide protection to the endothelium against distension when the cushion expands.

Notizen: The history of particle clearance was studied in lungs of mice serially sacrificed at intervals up to 14 months following single exposures to an aerosol of submicronic, particulate, iron oxide used as a similitude for atmospheric dust. Clearance was followed by light microscopy in unstained and Prussian blue stained frozen and plastic embedded sections, as well as by electron microscopy, where iron oxide can be recognized by its form. Related problems were investigated through histochemical demonstration of acid phosphatase activity in pulmonary lysosomes and Prussian blue staining of various tissues after administration of iron compounds by gastrointestinal and vascular routes.The iron particles settle extensively but not uniformly on pulmonary alveolar surfaces. Clearance is centripetal and involves two mechanisms, an extracellular mechanism fed by fluid currents sweeping across the surface, and a cellular mechanism principally involving alveolar macrophages. In the early post exposure period both actively remove deposited particles predominantly through the pulmonary airways. By 24 hours uncleared residues have become ingested and clearance thereafter results mainly from cellular action. Macrophages enter bronchial passages where they sometimes continue to pursue normal activities. A chronic phase of clearance begins when deposited particles become sequestered in macrophages of pulmonary connective tissues. These cells are reached by several routes, not least by crossing the bronchial epithelium. Particle clearance from these macrophages is very slow, and residue-containing cells eventually congregate in lymphoid tissues surrounding major bronchi. These findings are discussed as they help to develop an overall picture of clearance from the lungs and as they bear on related topics, such as functional roles of alveolar and pulmonary connective tissue macrophages and the pathogenesis of chronic bronchial disease.

Notizen: Wall structures of the arteries in the corpora cavernosa penis were observed in rabbits. The deep (central) arteries in the proximal part of the penis have five or more independent ridges of the wall which are formed by the internal layer of the media consisting of almost longitudinal muscle cell layers. Electron microscopy of these regions revealed that the endothelial cells are connected to each other by many maculae and zonulae adherentes, and that smooth muscle cells of the media are separated from one another by a wide intercellular space embedding abundant collagenous fibers.The epithelioid cells constituting the media of the helicine branches of the deep artery vary in their fine structure from close resemblance to muscle cells, to cells with easily identified special features. Frankly epithelioid cells have few scattered cytoplasmic filaments of a single type, 60-90 Å in diameter, abundant ribosomes, active Golgi, and other features different from the typical smooth muscle cells. There is no suggestion that these epithelioid cells are either degenerative or undifferentiated forms of smooth muscle cells, as postulated by light microscopists. Transitions froms muscle to epithelioid cells are consistent with, but not proved by, our data.

Notizen: The objective of this study was to determine the spatial distribution of fungiform papillae on the rat's tongue. Since each fungiform papilla in the rat has a single taste bud, the spatial distribution of fungiform papillae is equivalent to the location of taste buds on the anterior tongue. A mean total number of 187 fungiform papillae per tongue were found which were about equally divided between the two lateral halves of the tongue. Over 50% of the total number of fungiform papillae were located on the tongue tip for an average density of 3.4 papillae/mm2, while the dorsal surface of the tongue had an average density of 1.3 papillae/mm2 of tongue surface. Papillae were absent on the dorsal midline, but a paracentral line of papillae running from anterior to posterior was a consistent finding. Though not identical, the distribution of papillae was essentially the same on different tongues. The functional significance of the papilla distribution is not understood, but electrophysiological experiments show evidence of neural interaction of papillae which are clustered together. The distribution of papillae and the distribution of nerve fibers which innervate them must be evaluated together in order to appreciate the significance of the distribution of fungiform papillae and their associated taste bunds.

Notizen: The armadillo is rapidly emerging as an animal for biomedical research. A morphological study of the immune system of the armadillo was undertaken to try to demonstrate a possible defect in the morphogenesis of the lymphoid organs that could account for their susceptibility to leprosy. Blood from 20 domesticated adult armadillos revealed lymphocytes predominated among circulating leukocytes in the majority of animals, whereas in wild animals neutrophils predominated. Necropsies revealed well-developed thymus glands and the thymus-dependent areas in lymph nodes and spleens contained abundant lymphoid cells. Hence, we conclude that the susceptibility of the armadillo to leprosy cannot be explained on a morphological basis.

Notizen: Diuresis and natriuresis follow volume expansion by intravenous infusion of either blood or saline. However, the mechanisms underlying the renal responses seem different for the two types of expansion. It has been suggested that the response to saline expansion is due to changes in physical factors with alterations in the morphology of the lateral intercellular space (LIS). The present study examines the width of the LIS of the proximal tubule after a Ringer-Locke (1%, 2.3%, or 7% body weight) or whole blood (2.3% body weight) infusion and in nonexpanded control. After Ringer-Locke infusion, a significant widening of the LIS of the proximal tubule is seen at all levels of expansion. There is a linera relationship between the level of the Ringer-Locke infusion and the degree of expansion of the LIS. In contrast, after blood volume expansion, the width of the LIS is the same as nonexpanded controls. These studies are consistent with the view that the renal response to saline expansion is mediated at least in part by physical factors affecting the proximal tubule.

Notizen: Electron microscopic examination of samples from various regions of the rat small intestine was carried out. The number of mitochondria in the epithelial cells was estimated. The counts were made in sections of cells cut along their longitudinal central plane. The errors involved in extrapolating these counts to the whole cells were also estimated.The average mitochondrial number per cell section was 21 in the lower third of the crypts, it gradually increased in the mid and upper thirds and reached about double, 42, at the villus base. The known forms of dividing mitochondria were identified in the mid and upper third of the crypts. The counts remained around 42 along the epithelium of the villi.Crypt cells are continually produced in the lower crypt; these cells migrate to the villi while differentiating into nonproliferative absorptive cells. After inhibiting mitosis by methotrexate, this migration continued (Altmann, 1974) and mitochondrial division persisted. In segments of the jejunum isolated surgically from the functional intestine for three weeks, mitosis and cell migration continued, but no evidence of mitochondrial duplication was found.Each mitochondrion probably undergoes a division as the crypt cells migrate from the mid-crypts to the villus. As a result, the villus epithelial cells contain double numbers of mitochondria. It appears that the mitochondrial division is not directly related to mitosis and is elicited by a stimulus present only in the functional intestine.

Notizen: The myotendinous junction in the skeletal muscle of adult lamprey Lampetra japonica was studied with an electron microscope. Numerous finger-like sarcolemmal invaginations were present at the ends of muscle fibers to form the myotendinous junction. Parietal fibers of each muscle unit showed more closely distributed sarcolemmal invaginations than central fibers. Features of the myotendinous junction. Parietal fibers of each muscle unit showed more closely distributed sarcolemmal invaginations than central fibers. Features of the myotendinous junction generally conform to the accounts in the literature. The sarcolemmal invagination was covered on its sarcoplasmic aspect by the connecting filament layer and the dense amorphous attachment layer, and on the extracellular aspect by the intermediary layer and the external lamina with collagen fibrils arising from the myosepta. Sarcolemmal invaginations were sometimes seen to consist of a pair of sarcolemmas of adjacent muscle fibers within a muscle unit, which is characteristic to the myotendinous junction of lamprey. It is noteworthy that the connecting filament layer is much thinner than that, e.g., in the tadpole tail muscles (Nakao, '74). Furthermore, it is much thicker in the parietal fibers than in the central fibers. The sarcolemma of the terminal segment of the invagination frequently showed specific coupling with cisterns of the sarcoplasmic reticulum (terminal coupling). The external lamina is partially or completely deficient in the terminal segment of sarcolemmal invaginations which form terminal couplings so that collagen fibrils contained in the invagination appear to be in direct contact with the sarcolemma; however, definite relationships of collagen fibrils with the sarcolemma and the external lamina in the terminal segment of invagination still remain obscure. This type of coupling is considered to play a role in the coupling of excitation to contraction of muscle fibers as triads and diads.

Notizen: In early embryonic epithelia most cell divisions are oriented with their cleavage furrows perpendicular to the free surface of the tissue. This results in the generation of two daughter cells, which are equivalent with regard to their apical surface. Mitotic figures, in which the long axis through the centers of the chromosome plates (chromatin masses) is perpendicular to the surface, are seen only occasionally.The lens placode and early lens cup of mouse embryos homozygous for the gene aphakia show significantly greater numbers of maloriented mitoses than normal control lenses. The axis connecting the centers of the chromosomal plates is frequently perpendicular or oblique to the surface. This may result in the production of daughter cells, which are unequal as far as their position at the tissue surface is concerned.Later, the lumen of the mutant lens vesicle fills up with cells, which are apparently released from the lens epithelium. Further development of the lens and the eye is grossly disturbed.The release of these cells may be a consequence of the malorientation of their divisions, or both may be the result of a defect in the spatial orgnization of the lens tissue, possibly due to abnormal cellular adhesion.

Notizen: Both the NZW and NZB mice exhibit an elevated fasting blood sugar level when compared to Swiss white mice. The NZB/NZW F1 hybrid mouse shows still a higher fasting serum glucose level than either of its parental strains. This elevated glucose level is noted very early in the animals' life, long before definitive signs or symptoms of pathology are evident, and remains elevated at least until the fortieth week of life, the last testing period in our series before sacrificing the animals. There are two major peaking periods for the glucose levels, namely at 4-10 weeks of age and then again at 31-40 weeks of age. These age periods correspond to the very young animal and to the animal that is beyond its prime and most likely sick and near the end of its lifespan due to the animals' inherent disease processes. The NZB and NZB/NZW F1 hybrid succumb to their disease processes at approximately 8-10 months of age. The NZW usually lives until 18 months.The questions are raised: does the altered immunologic state in the NZB and/or the NZB/NZW F1 hybrid produce the elevated blood sugar levels and the pancreatic histopatholgy or is it the early hyperglycemic condition coupled with pancreatic pathology which are in some measure instrumental in producing the lesions discussed and observed, in the beginning of the three to four month period of age, in the various organs? Is there a relationship between the hyperglycemic condition and the immune state or are these independent phenomena in a genetically “mixed up” mouse?

Notizen: To study the role of certain organelles in steroidogenesis, dissociated rat adrenocortical cells were incubated for two hours with ACTH at a concentration that induces a high level of steroid production. Sections of ACTH treated and untreated cells were photographed in the electron microscope, and morphometric analysis was undertaken to assess possible ACTH-induced changes in total cell volume, volume density and numerical density of lipid droplets and mitochondria.There was no change in total cell volume. Lipid droplet volume density and numerical density decreased. Mitochondrial volume density did not change, but numerical density increased.The decrease in lipid droplet volume density indicates a rapid depletion of cholesterol for steroid production. This depletion is almost entirely due to the disappearance of lipid droplets, rather than to an overall diminution in their size, as shown by the decrease in lipid droplet numerical density. The mitochondrial data suggest that the adrenocortical cell has an adequate mitochondrial apparatus to respond to acute ACTH stimulation with increased steroid output without an increase in mitochondrial volume.

Notizen: A rarely occurring structure that is apparently a modification of endoplasmic reticulum was observed in the epithelial cells of the ascending colon of the mouse. The structure consists of a stack of 3 to 15 parallel cisterna-like elements separated by about 67 nm. The stacked cisternae usually are located adjacent to the basal end of the nucleus or in the region between nucleus and basal cell membrane. Top and bottom cisternae of many of the stacks have patent lumens and their outer membranes are lined by ribosomes. Most frequently, middle cisternae have attenuated lumens in their central regions. In some instances the width of the cisternal lumens is similar throughout. Closely apposed pairs of cisternae also occur. Some stacks have a concentric configuration. The intercisternal space contains tightly packed vesicles (38 nm) arranged in a hexagonal array. Many of the vesicles are connected to the membranes of the cisternae by stalk-like projections. The vesicles also occur between the nuclear envelope and the adjacent parallel cistenae. Mitochondria are situated close to each stack.

Notizen: The effects of ZnSO4 irrigation on mouse nasal respiratory epithelium (NRE) and subsequent responses of the tissue were studied at the light and electron microscopic levels in two different strains of mice (C57B1/6J and SWR/J).The most marked effect of the ZnSO4 took the form of necrosis and sloughing of surface cells in both strains one-half day after ZnSO4 irrigation. This treatment caused maximal change in a different cell type in each of the two strains. Ciliated cells were most noticeably affected in the C57B1/6J strain, secretory cells in the SWR/J strain. Subsequent manifestations of recovery differed accordingly in each strain. In the C57B1/6J mice numerous dividing surface cells and large areas of tall nonciliated and ciliating cells were prominent two to five days after treatment. Secretory cells appeared normal but were reduced in numbers during this time, indicating that they were also affected by the treatment. The NRE of this strain was normal by the fourteenth day following treatment. The NRE of SWR/J animals, on the other hand, contained no visibly dividing cells and no large areas of nonciliated cells during the first four days following treatment, although a few ciliating cells were present at this time. The secretory cell population in these animals was normal after five days but individual cells deviated from normalcy by containing numerous dilated cisternae of rough endoplasmic reticulum which persisted in the secretory cells during the remainder of the experiment.

Notizen: Intact soleus and extensor digitorum longus muscles in the rat were freely grafted to the contralateral leg after either no preliminary tretment or 14 days prior denervation. Normal muscle grafts during the first week were characterized by a central zone of degenerating original muscle fibers (disappearing by 7-9 days) and a peripheral zone, containing regenerating muscle as well as small numbers of surviving original muscle fibers. A radial gradient of regeneration was established, with more mature muscle at the periphery and less mature muscle toward the center. Denervated grafts were characterized by rapid degeneration (within 2-3 days ) of original muscle fibers in the central area, rapid appearance of regenerating muscle fibers (e.g., cross striations by 5 days) with uniform levels of differentiation throughout the graft and larger numbers of surviving original muscle fibers at the periphery. During the first week, stages of muscle differentiation in denervated grafts were attained 1-2 days earlier than comparable stages in normal grafts. Later stages of muscle differentiation were similar in both types of grafts. Histochemical studies revealed a loss of enzyme activity (phosphorylase, ATPase and SDH) in the center of early (2-4-day) normal and denervated grafts. Denervated grafts, however, possessed a thicker peripheral rim of enzymatically active surviving muscle fibers than normal grafts. In both types of grafts the old muscle fibers in the center were replaced by enzymatically active regenerating muscle fibers which stained uniformly (ATPase) until 30 days. By 60 days a mixed fiber pattern had developed. Muscle spindles were found within the grafts.

Notizen: Autoradiographic methods were used to analyze cell kinetics in peripheral epithelium of the fetal mouse lung, days 15-18. The 3H labeling index decreased in proportion to increases in fetal lung and body weight from day 15 to day 18. Cell-cycle determination estimated from the percent of labeled metaphases at intervals after 3H thymidine injection showed the shortest cell-cycle time (12.25 hours) on day 15 during the precenal stage of growth. Total cycle time (Tc) increased by approximately one hour on each subsequent day. Between days 15 and 16 Tc increased due to a 1-hour increase in the post mitotic interphase (G1); thereafter increases in Tc could be ascribed almost entirely to lengthening of the DNA synthetic period. A comparison of cell-cycle time in central and peripheral tubules of the same lungs on day 15 showed a slower cell cycle in the central tubules than in the peripheral branches. An estimate of the growth fraction (GF) on each day based on calculated and observed cell-cycle times showed that GF was 1 on days 15 and 16, decreasing to 0.69 on day 17 and 0.27 on day 18. Thus cell-cycle time increases with lung maturation and it increases from peripheral to central zones of the bronchial tree. The greater part of the observed decline in growth rate as the prenatal phase of growth is completed was due largely to a decrease in the fraction of cells in the cell cycle.

Notizen: The effects of magnesium deficiency in ovariectomized and estrogen-treated rats were examined in histological sections of bones and various soft tissues. The changes observed in the femora of intact rats deprived of magnesium for three weeks were: 1. a general increase in diaphyseal thickness, 2. the presence of localized fibrous or bony-like masses in subperiosteal and metaphyseal sites, and 3. the occurrence, although rare, of endosteal hyperplasia. In ovariectomized, magnesium-deprived animals, the incidence and location of fibrous masses were similar to that in the femora of magnesium-deficient intact rats; however, no increase in diaphyseal thickness was noted. Daily injections of 25 μg estradiol caused a reduction of the frequency of skeletal hyperplasia from 80% to 20%, as well as a reduction in femoral diaphyseal thickness. Estradiol hormone administration also brought about a marked alleviation of the dermal and neural manifestations of magnesium deficiency, but, at the same time, caused an exacerbation of renal calcinosis.

Notizen: The surface epithelium in fetal guinea-pig ovaries was examined from the time of early sexual differentiation, about 34 days, until approximately ten days before birth.At day 34 the epithelium varied greatly in apperance as seen in the light microscope and possessed a superficial layer of flattened or cuboidal cells. By day 58 the epithelium had changed into one layer of regularly arranged columnar cells. During the same period the number of germinal cells decreased. Connections between the germinal cords and the surface epithelium were observed from day 34, being especially numerous and broad at days 34 and 42 and decreasing in number and size from day 46 onwards. The basement membrane beneath the epithelium gradually increased in thickness.In the electron microscope two types of somatic cells could be distinguished. One type formed a superficial single layer connected by junctional complexes and exhibited intracellular bundles of 60 Å microfilaments running straight through the apical part of the cell, attached to junctional complexes on either side. These bundles were found frequently between days 34 and 42, but were rarely seen after the forty-sixth day. Microvillous projections into the coelomic cavity were especially numerous from day 34 to day 46.The other type of somatic cells lay in close proximity to the germinal cells: microfilaments or junctional complexes were not observed.The subepithelial basement lamina was continous with that surrounding the connections and the germinal cords.

Notizen: A simple, inexpensive method of making accurate permanent casts of brain dissections is described. Dissected brain preparations are used to produce silicone rubber molds. Methyl methacrylate is used to make the hard plastic models.

Notizen: Changes in physiological reproductive states of female Long-Evans hooded rats were directly correlated with changes in the concentration of acidophilic and basophilic connective tissue granulated cells in the lamina propria of the duodenum. Acidophilic granulated cell numbers were significantly higher at estrus and metestrus than at other stages of the estrous cycle or in the immature state. Acidophilic granulated cell numbers during pregnancy were not significantly different from cell numbers quantified during metestrus, diestrus, or proestrus, but were significantly lower than cell numbers during estrus. Late lactation (21-25 days) was associated with significant decreases in the numbers of acidophilic granulated cells from numbers observed during the estrous cycle and during pregnancy. Basophilic granulated cell numbers did not differ significantly during the estrous cycle, although the highest numbers were observed during proestrus. Basophilic granulated cell numbers were significantly higher during pregnancy than during the estrous cycle. Basophilic granulated cell counts in late lactation were comparable to numbers quantified in estrus, metestrus, and diestrus, but were significantly lower than during proestrus and pregnancy.

Notizen: Electron microscopy of the normal human thymus demonstrates a characteristic vascular-parenchymal relationship. The vascular lumen is always separated from the thymic parenchyma by: the endothelial cell cytoplasm, a muscular coat in arterioles and veins, the vascular basal lamina, a perivascular space containing collagen fiber and cells, the epithelial-reticular cell basal lamina and the epithelial-reticular cell cytoplasm. The width of this perivascular space is proportional to the size of the vessel it surrounds; it is wide around the vessels in the septa and at the cortical-medullary junction, but narrow around capillaries. While many cells are present in this space around the larger vessels, only collagen is observed around the capillaries. Lymphocytes are the predominant cell type in the space; however, plasma cells, eosinophils, histiocytes, polymorphonuclear leukocytes, mast cells and unidentified granulated cells are also seen.The vascular complex described above may function as a blood-thymus barrier, as the initial site of exposure of the lymphocytes to circulating antigen and as the route of emigration of lymphocytes from the thymus.

Notizen: Lumbar and sacral afferent axons in the submucosa of the urinary bladder were recognized by degeneration in seven cats subjected to spinal ganglionectomies. Of 2,935 observed terminating axon profiles, 145 were found degenerating. Lumbar afferent axons were 3.7 times more numerous than sacral afferent axons in the submucosa, a reversal of the ratio reported for the muscle coat of the bladder. Sacral afferent axons were evenly distributed to different regions of the bladder, but lumbar afferents were concentrated in the bladder neck. Apparent endings in the submucosa of the urinary bladder were principally free nerve endings. Synaptic vesicles were found in 57% of observed terminating axon profiles. The bladder neck had more terminating axon profiles of all kinds than other regions of the urinary bladder.

Notizen: Electron microscopy of the rat cardiac ganglion shows occurence of small granule-containing cells that form reciprocal synaptic junctions with cholinergic terminals. At the synaptic junctions which are from axon to granule-containing cell, the intraaxonal vesicles are clustered against the junctional axolemma, but dense-cored vesicles in the postynaptic cell do not cluster towards the membrane densities in these synapses. By contrast, the synaptic zone polarized in the opposite direction shows an absence of axonal vesicles in close proximity to the postsynaptic axolemma, but there is a marked aggregation of dense-cored vesicles towards the presynaptic specializations of granule-containing cells. The synaptic zones are multifocal rather than bifocal, and the minimal distance separating each synaptic zone is about 0.3 μ. These findings may indicate that cholinergic excitation of some or all granule-containing cells causes a reciprocal inhibition of one or more cholinergic terminals.

Notizen: The ciliary ultrastructure is studied in the ciliated cells of the thymic cysts of the “nude” mouse. The cilium is made up of two segments: the intracellular basal body and the extracellular cilium shaft.The basal body extends in a rootlet and demonstrates three annexes: basal foot, anchoring system and tonofibrillar web. The rootlet, composed of one central and nine peripheral chambers, is closely and constantly associated with smooth endoplasmic reticulum. The classical periodicity of the basal foot can be explained by its internal structure. The anchoring system binds the upper part of the basal body to the cell membrane. The cilium shaft is divided into four segments: implantation base, proximal segment, intermediate segment and tip. The details of particular structures in the implantation base and in the proximal segment are given on transverse and longitudinal sections. In the intermediate part, a peculiar desmosome-like structure, binds some doublets with the ciliary membrane. At the tip level, A tubules end up in an opaque plate and membranes are covered with several intricated cristae.

Notizen: A variety of fixatives, buffers and fixation procedures were compared in rat and squirrel monkey lung in an attempt to preserve optimally both the cytologic details of pulmonary parenchyma as well as the acellular alveolar lining layer. In initial experiments utilizing the fixative of Ito and Karnovsky ('68), an electron-dense deposit was observed on the alveolar surface. Experiments were carried out in an attempt to determine what component of this fixative was responsible for the reaction product observed. In addition, immersion fixation of tissue blocks was compared to the whole lung fixation method of Kikkawa ('70). Kikkawa ('70) achieved excellent preservation of the acellular alveolar lining layer by such a fixation technique.In all lungs examined, whenever a phosphate buffer was utilized with primary aldehyde fixation, an electron-dense precipitate was observed on the luminal surfaces of the type I and II pulmonary epithelial cells. Additional sites of reaction product were pinocytotic vesicles of the type I cells and membranous arrays within the alveolar lumen. Such deposits were never observed when a sodium cacodylate buffer was used. No such granules were observed in areas of lung where the acellular alveolar lining layer had been preserved.The implications of these findings with regard to lung histochemical procedures and the possible relationship of these phosphate buffer-dependent granules to the surfactant system are discussed.

Notizen: A method for inducing paralysis in embryonic chicks is described. This involves single injections of the neuromuscular blocking agents, D-tubocurarine Chloride or decamethonium iodide, into 10-day embryos. The dose which optimises survival and paralysis is determined along with the effect of the drugs on embryonic growth. Decamethonium iodide at a dose of 1 mg per embryo gave maximum survival and paralysis to 18 days of incubation. Paralysis was assessed by observation of treated embryos in ovo and by examination of embryos removed from their shells between 11 and 18 days of incubation. Embryos were completely paralysed 24 hours post-injection and remained paralysed until 18 days of incubation. Paralysed embryos failed to hatch. Development of the leg musculature was severely retarded in paralysed embryos. This method of inducing paralysis has considerable advantages over previous continuous infusion methods. The growth and collagen content of the tibia in the paralysed embryos was reduced and these results, and other applications of the method, are discussed.

Notizen: The morphology and development of junctional complexes between blastomeres of the preimplantation rabbit embryo were investigated using several approaches. Electron microscopic examination of embryos stained en bloc with uranyl acetate, and the study of junction permeability using horseradish peroxidase and lanthanum nitrate provided information on structure, intermembrane spacing and permeability of the junctional complexes. In addition, the freeze fracture technique was used with day 5 and day 6 blastocysts, since the large size of these embryos facilitated use of this method. These experiments showed that although rudimentary junctions were present between blastomeres of the early cleavage stages, effective tight junctions were not present until the blastocyst stage. Electron microscopic examination of thin sections revealed apical foci of membrane approximation or “fusion” between trophoblast cells by day 4. Freeze fracturing revealed a lattice of interconnecting ridges (on the A face) and grooves (on the B face) in the apical region between trophoblast cells of the day 5 blastocyst. This lattice formed a continuous band along the apical margin of each cell, and therefore constituted a zonula occludens. The zonula occludens of the day 5 blastocyst averaged 2-3 ridges per lattice, while day 6 blastocysts had lattices that averaged 5-6 ridges. Also seen in the freeze fracture replicas from the day 5 and day 6 blastocysts were local accumulations of intramembranous particles on the A face. These particles were often observed in aggregates similar to those of previously described gap junctions. It could not be determined whether these small regions of particles were true gap junctions or a possible primitive form of gap junction because the complementary pitted surfaces (B face pits) were not demonstrated.

Notizen: Fertilized and unfertilized rabbit ova were exposed to ruthenium red with the zona intact or after machanical removal, for the demonstration of mucopolysaccharides on the surface coat. Ova were also exposed to Concanavalin A. Ruthenium red bound strongly to elements of the zona and increased the opacity of the plasmalemma. There was no notable change in staining of the vitellus following fertilization. Although there were ruthenium red stained bodies resembling cortical granules in crypts in the plasmalemma, there was no evidence for cortical granule extrusion of mucopolysaccharides. The Concanavalin reaction was seen over both unfertilized and fertilized ova, demonstrating receptors for terminal α-D-mannopyranosyl, α-D-glycopyranosyl, β-D-fructofuranyosyl residues. The deposit on the fertilized egg surface was enormously enhanced indicating a change in the distribution of receptor sites.

Notizen: Verhoeff's iron hematoxylin (VIH) followed by lead citrate (LC) applied to epoxy thin sections stained the dense component of elastic fibers heavily and the peripheral microfibrillar component lightly in guinea pig trachea and mouse testis fixed with a glutaraldehyde-osmium tetroxide sequence. This method stained large fimbriated fibers beneath tracheal epithelium, small fibers and stacked aggregates thereof in the deep lamina propria, cartilage and adventitia of the trachea and large stacked fibers in the fibroelastic band of the trachea. Fibers of the fetus differed from those of the adult, especially in the subepithelial elastic lamina of the trachea. Elastic fibers were intimately associated with fibroblasts and particularly slender fibroblast processes in tracheal stroma and with chondrocytes in tracheal cartilage. Fibroblasts associated with elastic fibers in the tracheal subepithelial lamina propria were often closely bordered by eosinophils, mast cells, or monocytes. Occasional mast cells extended slender processes around elastic fibers in the subepithelial lamina propria. In mouse testis and in many regions of the trachea, small elastic fibers were identified which were below the limits of resolution for the light microscope and were not apparent at the ultrastructural level in routinely stained thin sections.

Notizen: By use of lanthanum tracer and freeze-fracture procedures it was found that granulosa-lutein cells of the pregnant mouse and rat ovaries are connected by gap junctions and septate-like zones of contact. Lutein cell gap junctions enlarge and become partially internalized by the end of the first week of gestation. Expansion of the gap junction domain appears to be due initially to intercalation of particles along borders of small gap junctions devoid of smaller non-junctional particles. The number of gap junction lined processes appearing at the cell border increases concomitantly with hypertrophy of the lutein cell during the second week of pregnancy. Strands of particulate or grooved membrane emanate from the margin of larger gap junctions undergoing interiorization. Most large gap junctions are intimately associated with elements of the smooth endoplasmic reticulum. Spherical gap junctional profiles assume a deeper location in the lutein cell and may form concentric arrays by term while true surface gap junctions appear to fragment in the post-partum corpus luteum. The modifications observed are interpreted with respect to biogenesis of the gap junction and the hormonal control of lutein cell function.

Notizen: The surface patterns of the oviduct of Gallus domesticus were examined by scanning electron microscopy (SEM) using several preparatory techniques. Ciliated epithelial cells predominate throughout the oviduct with nonciliated cells approaching an equal proportion in the magnum and isthmus. Short, randomly oriented mucosal folds which characterize the infundibulum increase in height and longitudinal orientation as they approach the magnum. Here and in the isthmus they broaden and become dimpled with glandular apertures. The folds narrow again in the uterus and vagina. Cryofracture followed by SEM demonstrate the deeper mucosal folds and submucosal tubular system.

Notizen: Wallerian degeneration in the severed newt's (Triturus viridescens) optic nerve is complete between the 10-14th post operative day (p.o.d.). Consequently, the newt optic nerve displays one of the most rapid degenerative responses yet reported for the central nervous system of vertebrates. In most cases it also exhibits the speed of degenerative phenomena in the vertebrate peripheral nervous system.The degeneration of unmyelinated axons is most rapid and is completed by 2-3 p.o.d., compared to myelinated axons, most of which degenerate between 2-10 p.o.d. Myelin ring formation (vesicular transformation) is the principal form of lamellar breakdown and occurs in a highly organized manner which can be clearly staged.The glial cell response to Wallerian degeneration is two-fold: cytoplasmic hypertrophy and myelin-lytic. Glial hypertrophy subsides by the 10-14 p.o.d. with the ingrowth of numerous regenerating nerve fibers. The myelin-lytic response accounts for most of the myelin destruction. Leukocyte-like and microglialike cells also participate in myelin breakdown but to a lesser degree.

Notizen: Ovariectomized rabbits received 3H-estradiol via an ear vein and were killed one hour later. Autoradiograms were prepared and exposed up to six months. Labeled cells, as indicated by many silver grains over the nucleus of a neuron, were found in many nuclei of the brain. Thus, the bed nucleus of the stria terminalis had labeled cell bodies. The stria terminalis leads into the medial preoptic area where great numbers of cells concentrated the estrogen. Farther into the hypothalamus the labeled cells were numerous in the ventromedial and arcuate nuclei. Other locations with labeled cells were the lateral septal nucleus and nucleus accumbens septi, the periventricular preoptic nucleus, anterior hypothalamic nucleus, nucleus supraopticus diffusus, posterior hypothalamic nucleus, and premammillary nucleus. The labeled cells could be followed into the central gray surrounding the aqueduct of Sylvius. The amygdaloid nuclei, and in particular the medial amygdaloid nucleus, had labeled cells as did the most ventral posterior part of the hippocampal cortex. The results are discussed in comparison with those in the rat, and with reference to physiologic data.

Notizen: The evolution of ultimobranchial bodies in Holtzman rats during the first 64 weeks after birth was studied by reconstructing three-dimensional models from serial sections stained by the periodic acid-Schiff technique. Radioautography with 125I was made to see if ultimobranchial cells and/or follicular cells lining the lumen of mixed follicles were able to iodinate proteins. The term ultimobranchial body designates herein an embryonic vesicular structure (derived from the third pharyngeal pouch) whose wall is made of a stratified squamous epithelium. During the first week after birth, the vesicular ultimobranchial body elongates rapidly and becomes a canal or a duct. During the second week, cell desquamation brings about local dilatations in the lumen of these ducts; with further enlargement ultimobranchial follicles will appear. In one-day-old rats, mixed follicles are present. Only the follicular component of mixed follicles iodinates proteins as is shown by radioautography. The reconstructed models enlarge rapidly up to the 56th day after birth at which time their weight has increased nineteenfold. These same models show that the three morphological components of ultimobranchial parenchyma, namely ducts, follicles and mixed follicles, are in continuity within the thyroid parenchyma. The formation of new thyroid follicles after birth and the possibility that the ultimobranchial parenchyma may function as an endocrine gland of holocrine type are discussed.

Notizen: The postnatal development of high-endothelial venules (HEvenules) in popliteal lymph nodes of normal and athymic mice was studied by light and electron microscopy.In the normal mice, undifferentiated postcapillary HEvenules are already present at birth. During the first four days after birth, ribosomes and mitochondria in the endothelial cells of the venules become more numerous, and the endoplasmic reticulum and in particular the Golgi complexes enlarge. At day four lymphocyte diapedesis through the venules becomes apparent. From the tenth day the HEvenules are structurally mature. However, diapedesis activity still increases till about a month postnatally. In mice with congenital aplasia of the thymus (nude mice) and in neonatally thymectomized mice the development of the HEvenules is similar to that in normal mice. In the athymic mice both lymphocytes and granulocytes migrate through the walls of the HEvenules. However, the blood level of lymphocytes in these mice is far below the value in normal mice.It is concluded that the development of the HEvenules during the first month of life is independent of the blood level of lymphocytes.

Notizen: Cat adrenal medulla was studied to determine whether or not an adrenergic nerve supply was available to medullary cells. The techniques used were those of routine electron microscopy, injection and uptake of “false” transmitter substance (5-hydroxydopamine), injection of 6-hydroxydopamine, which selectively destroys postganglionic adrenergic elements and a specific cytochemical method using glutaraldehyde and heavy metal techniques for cytochemical localization of biogenic amines. Each method consistently demonstrated adrenergic fibers and terminals in the adrenal medulla; these adrenergic elements contain dense, large core and small core vesicles which are not of the “dense cored” cholinergic type. Localization of adrenergic fibers and terminals is deemed significant since the latter had the bouton en passage configuration immediately adjacent to norepinephrine cells; adrenergic elements were not seen in close relationship to epinephrine cells. Consistency of the findings from the three techniques point to the fact that the norepinephrine cells of the adrenal medulla have a dual innervation, both cholinergic and adrenergic. This type of innervation pattern is not unique for the autonomic nervous system, but it has not been reported previously for adrenal medullary cells. It is believed that such an innervation pattern has functional and pharmacologic significance.

Notizen: The structural features of the development of the bursa of Fabricius in white Leghom chick embryos are depicted at carefully timed intervals during embryogenesis, with emphasis on the sequence of events between the ninth and twelfth days of incubation. The direction and character of the migration of lymphoid cell precursors and granulocytes from the intravascular space to intraepithelial sites, where the formation of the primitive lymphoepithelial nodule takes place, is demonstrated. The mechanism of the mode of migration of these cells through the stromal epithelial interface is described and illustrated with electron micrographs and their role in the development of the primitive lymphoid follicles is described and discussed.

Notizen: Following intravenous injection, cytochrome c traverses the capillary endothelium of the rat choroid plexus and permeates the perivascular space and the extracellular space between epithelial cells. The tracer is incorporated into pinocytotic vesicles adjacent to the lateral and basal plasmalemmas. There-after, cytochrome c is incorporated into multivesicular and dense bodies. Tracerladen vesicles were not found to fuse with the apical plasmalemma and cytochrome c was not discharged into the cerebral ventricles. Acid phosphatase activity of the choroidal epithelium after the administration of cytochrome c was greatly increased and localized in the same intracellular sites shown for cytochrome c. These data suggest that cytochrome c and possibly other proteins that penetrate the choroidal stroma are taken up by the choroidal epithelium and subsequently degraded in lysosomal vesicles. This heterolytic mechanism may be an important means for preventing the entry of certain substances such as proteins into CSF and subsequently into nervous tissue.

Notizen: Transection of a peripheral nerve not only elicits changes in the injured neurons but also results in an increase in non-neuronal cells, considered by most workers to be neuroglia, in the region of these neurons. Since studies in this laboratory have shown that the neuroglial population of spinal cords of immature rats can be reduced markedly by ionizing radiation, the present investigation was undertaken to determine if this reaction would occur in the irradiated spinal cord following transection of the sciatic nerve. In order to answer this question the sciatic nerve was sectioned unilaterally at 17 days of age (14 days post-irradiation). Sham-irradiated littermates served as controls. Light microscopic examination showed an increase in non-neuronal cells throughout the gray matter on the side of axotomy in spite of a decreased neuroglial population in the 2,000 R and 3,000 R groups. These cells were scattered in the neuropil or were adjacent to injured neuronal perikarya in the anterior horn. Qualitatively similar reactions occurred in the 500 R and 1,000 R groups and in shamirradiated controls. Whether the magnitude of response is the same in all groups is currently under investigation, as are questions dealing with the origins of the reactive cells.

Notizen: The development of the granular convoluted duct in the submandibular gland of male rats, 4 to 12 weeks of age, was investigated. During this period, the average weight of the gland increased from 213 to 526 mg, the total DNA and RNA contents doubled, and the protein content tripled. Radioautographs were prepared from Epon embedded sections of the gland of the rats given 3H-thymidine and stained with toluidine blue. The glands of 4-week-old rats consisted mainly of acinar cells (45%), intercalated ductal cells (20%) and striated ductal cells (16%). A few granular convoluted ductal cells were seen in the striated duct close to the intercalated duct. The frequency (and absolute number) of granular convoluted ductal cells increased linearly from 1% (3 × 106) at four weeks to 26% (68 × 106) at eight weeks, while the calculated number of striated ductal cells remained stationary. The absolute number of acinar cells and intercalated ductal cells nearly doubled between four to eight weeks of age. The proliferative activity of all cell types declined with age but between six and ten weeks of age the rate of proliferation of ductal cells was relatively higher than the rate of proliferation of the acinar cells. Morphologically the size and number of granules in the granular convoluted ductal cells increased with age. Based on the above data it is concluded that the granular convoluted ductal cells developed from that segment of the striated ductal cells which is in close proximity with the intercalated ductal cells. The heterogeneity of the granules in the granular convoluted ductal cells observed from six weeks of age might denote the functional diversity of the cells.

Notizen: Splitting the uterus longitudinally through implantation sites makes it possible to obtain access to blastocysts and implantation chambers during stages of implantation of the blastocyst in the rat. On the afternoon of day 5 of pregnancy, blastocysts lie in a shallow antimesometrial depression and tend to fall free of the uterus when the chamber is opened. On day 6, blastocysts are oriented in a mesometrial-antimesometrial plane, occupy a distinct implantation chamber, and tend to adhere to one side or the other of the uterus, leaving an imprint on the contralateral side. After about noon of day 6, some of the blastocysts split in half laterally, and by day 7 all blastocysts which are exposed are split. In addition to demonstrating increased adhesion of blastocyst to uterine epithelium, the procedure clearly shows the progressive elongation of the implantation chamber. The embryonic cell mass is specifically oriented on day 6, and is clasped but not distorted, whereas the abembryonic trophoblast is slightly compressed and indented by the uterine epithelium. The microvilli of the uterine epithelium within the imprint become progressively flattened when compared to the microvilli of the implantation chamber outside of the imprint. The method provides a means of gaining direct access to the surface of uterine epithelium precisely where it has been in association with the blastocyst not only for scanning electron microscopy but also for studies of the properties of the surface constituents.

Notizen: Contraction of the conus arteriosus (conus) is visibly delayed in the tubular heart of the chick embryo, and since the electromechanical coupling interval of isolated conal segment is similar to other areas of the embryonic heart, the delayed contraction of the conus indicated an impedance in the spread of the depolarization wave across the ventriculo-conal (VC) junction.A surface electrode placed on the conus of hearts obtained from the 72-hour chick embryo records a deflection, termed the C wave, appearing between the QRS complex and the T wave. To establish that the C wave arose from below the atrioventricular sulcus, atria were removed from a series of hearts from 96-hour embryos and the electrogram revealed a C wave without a P wave.The VC junction responds to digitoxin just as the atrioventricular tissue. Digitoxin prolongs the interval between the QRS and the C wave prior to a complete block in a manner analogous to the PR interval increase prior to the development of the Wenckebach phenomenon or complete atrioventricular block.As the embryonic heart developed after 96 hours, the C wave was no longer identifiable in the ECG.

Notizen: Female reproductive tracts from 84 bats were examined by light and/or electron microscopy to observe early embryology and implantation in Macrotus. The earliest pregnancy was observed in October and by the end of October all bats were pregnant. Implantation had begun in most specimens from late October. In late November females were carrying implanted blastocysts in which differentiation of endoderm was noted. Reichert's membrane was first observed in November.In early December the trophoblast had begun to differentiate into cytotrophoblast and syncytiotrophoblast and by the end of January this differentiation was most evident. Reichert's membrane persisted until late January. Endoderm in the January sample completely surrounded the yolk sac cavity.By late February the embryos were at the embryonic disc stage and had differentiated mesoderm. The uterine-fetal relationship was complex and an early placenta was recognized.In late March the embryos spanned a range of development from neural plate to limb-bud stages. Parturition occurred in June.This lengthy gestation period is characterized by an embryonic diapause of approximately four and one-half months. The roles of food supply and/or temperature in controlling this growth rate and the evolutionary implications of this development are discussed.

Notizen: A procedure for differential staining of decalcified bone with silver nitrate showed major histological features which appeared to correspond closely to microradiographic images. The extent to which this is actually the case was investigated directly by preparing microradiographs of ground sections of baboon and dog radii and then decalcifying and staining the same sections. The many detailed similarities indicate that this staining procedure is a useful adjunct to microradiography. Thus, poorly mineralized osteons or layers of circumferential lamellae are darker stained by silver nitrate, and the variably mineralized layers of circumferential lamellae are closely duplicated by light and dark bands in the stained sections. These similarities imply that there is a relationship between the mineral density of bone and some condition of the organic matrix which is probably related to maturation changes in the collagen.

Notizen: Osteopetrosis is a disease in which diffuse sclerosis of the entire skeleton results from an imbalance between the processes of bone formation and bone resorption. The grey lethal is the most severely affected of the three mouse mutants which have been described and its osteopetrosis is transmitted as a simple autosomal recessive gene. Affected mice develop a grey coat at 8-10 days of age and die before one month of age.Recently we (Hollinshead and Schneider, 1973) reported that grey lethal mice could be identified at birth because the apex of their lower incisors lies anterior to the molar region in the mandible. In this study we show that it is possible to identify affected fetuses from day 18 of gestation using the same and other histologic criteria in examining their teeth.

Notizen: A method is described for the investigation of deep cerebral structures by freeze-substitution. The head of a mouse is sectioned in a guillotinelike apparatus. The exposed surface is subjected to freeze-substitution. Electron micrographs prepared from this material exhibit under a layer of sheared tissue, a layer of tissue comparable with that observed previously in micrographs of the cerebral and cerebellar cortices subjected to freeze-substitution of their natural surfaces. By varying the plane in which the head is sectioned any structure in the brain can be made accessible to freeze-substitution.

Notizen: The tibial tuberosity develops by a concomitant, and juxtaposed, outgrowth of hyaline cartilage and ingrowth of fibrovascular tissue. During the fetal period this hyaline cartilage outgrowth is progressively distally displaced to become situated adjacent to the anterior portion of the tibial metaphysis. About four to six months post-natally a growth plate develops under the tibial tuberosity. This growth plate shows structural adaptations that permit accommodation of large tensile stresses. The growth plate of the tibial tuberosity has three distinct regions  -  (a) a zone of endochondral bone formation, (b) a zone of intramembranous bone formation through fibrocartilage, and (c) a zone of intramembranous bone formation through fibrous tissue.

Notizen: Single palatal processes or homotypic paired palatal processes from 12-day mouse embryos (strain C57B1) were grown in organ culture on Millipore filters. The epithelium along the medial edge of each palatal process became disrupted, and, by 72 hours of culture, paired palatal processes achieved mesenchymal fusion at the site of disruption. The nasal epithelium of paired palatal processes became a recognizable pseudostratified ciliated columnar epithelium by 96 hours of culture, and the oral epithelium became a recognizable stratified squamous epithelium by 120 hours of culture. These events correspond temporally to the differentiation of palatal tissue in vivo. Differentiative changes of single palatal processes followed the same schedule as double processes. Observations also suggest that the epithelium at the tip of the vertically oriented young palatal process corresponds to the medial epithelium of the more advanced horizontal process  -  these observations have bearing on the mechanism of palatal movement. In addition, the results suggest that a re-evaluation of the terminology “potential for fusion” is necessary.

Notizen: The systemic arterial pattern of the guinea pig was studied to determine the arrangement of the major arterial trunks and their branches. Fiftynine specimens were examined by dissection, angiography or corrosion casting. The arterial arrangement was found to resemble a typical mammalian pattern, although some exceptions were noted. For example, the guinea pig usually has a single vessel, the celiacomesenteric trunk, instead of separate celiac and cranial mesenteric arteries. The celiac components of this vascular axis were found to originate in four different patterns. Also, the renal arteries were found to be single or double on either side with double origins more frequent.

Notizen: In order to study the behaviour of epiphyseal cartilage in a nonfunctional environment, the third metacarpal bone was transplanted intracerebrally as an isograft between 7-day-old litter-mate rats. Host animals were killed 1, 2, 3, 4, 5, 6 weeks post-operatively, and the cellular kinetics evaluated by means of tritiated thymidine autoradiography. The study was also used to compare the effects of function on chondrogenesis at the epiphyseal cartilage with that previously demonstrated for the condylar cartilage of the mandible (Meikle, '73a).Transplantation resulted in three major changes in the cartilage; there was a decreased rate of proliferative activity in the cell columns; the cartilage failed to maintain a satisfactory increase in transverse diameter; the cells of the perichondrium differentiated into osteoblasts instead of chondroblasts. Autoradiographic and histological findings suggested that the inability of the cartilage to increase in transverse diameter was related to the decreased rate of proliferative activity in the cell columns and not to the cessation of perichondrial chondrogenesis. On the basis of these findings two conclusions can be made.1. Extrinsic mechanical stresses associated with function appear to be necessary for the normal interstitial growth of epiphyseal cartilage during postnatal development, suggesting that functional activity can influence the rate of cell proliferation.2. Functional activity provides the stimulus for the differentiation of perichondrial cells into chondroblasts.

Notizen: Muscle fibers of the sternomastoid and the tongue of the rat were characterized histochemically according to mitochondrial distribution (succinic dehydrogenase), as well as reactivity for the alkali- and acid-stabile “myofibrillar” adenosine triphosphatases. The principal fiber types of the sternomastoid were the large, “white” AαβM fibers and the smaller, “intermediate” BβD and “red” CαL fibers (figs. 1, 2, 3). The unusual musculature of the tongue was populated by diminutive AαM and CαM fibers, and variants thereof; all with relatively high mitochondrial content (figs. 4, 5, 6).Reinnervation of the sternomastoid muscle by the hypoglossal nerve caused most fibers of the sternomastoid to assume histochemical profiles reminiscent of those commonly observed in the tongue. However, the BβD fibers of the sternomastoid persisted in near usual numbers and disposition (fig. 17), despite their reinnervation by a nerve normally destined for a muscle lacking that particular fiber type. Thus, there are as yet unrecognized factors, possibly of neural origin, though more likely of muscle origin (genetic), that impose restrictions on the metabolism-regulating functions of substitute motoneurons.

Notizen: Nuclei isolated from mouse thymus, kidney, and liver were fixed in ethanol-acetic acetic acid; treated with dilute acid to extract histones; stained by three protein end-group procedures; and measured by scanning, integrating microspectrophotometry. Measurements were also made of nuclei isolated from the same organs and stained by the Feulgen procedure for DNA. Protein end-group procedures included pH 2.8 Biebrich scarlet (for basic groups), mercury orange (for sulfhydryl groups), and mercury orange after thioglycolate reduction (for the sum of sulfhydryl and disulfide groups). With the exception of the comparison between Feulgen-stained 2C liver and kidney nuclei, the integrated extinction values obtained for nuclei of a given organ differed significantly from the measurements of nuclei from other organs, regardless of the staining procedure. Furthermore, the integrated extinction values for 2C nuclei were highest in larger, more vesicular nuclei (from liver and kidney) and lowest in condensed thymocyte nuclei, except in the case of measurements of the disulfide content of the nuclei. In this instance, the values of integrated extinction were highest in condensed thymocyte nuclei, intermediate in kidney nuclei, and lowest in 2C liver nuclei. When 2C, 4C, and 8C liver nuclei were compared, the integrated extinction values of 4C nuclei were found to be approximately twice those of 2C nuclei and half those of 8C nuclei. Exceptions included 8C nuclei whose disulfide and Feulgen values were, respectively, higher and lower than expected. The greater disulfide values and reduced Feulgen values obtained in thymocyte and 8C liver nuclei might be related to a greater degree of chrmoatin condensation in these nuclei, and, therefore, to a reduction or selective restriction of their RNA transcriptional capacities.

Notizen: The fine structure of spherulecytes, cell types with large, intracellular membrane-bound vacuoles termed spherules, was investigated in regenerating tips of spines of the sea urchin Strongylocentrotus purpuratus. Two categories of cell types were observed: red spherulecytes and colorless spherulecytes. Red spherulecytes were represented by a single cell type, the eleocyte, while colorless spherulecytes consisted of three morphologically distinct cell types termed morula cells, granulocytes, and vacuolecytes. Eleocytes and morula cells were distributed in both the epidermis and dermis, while granulocytes and vacuolecytes were present only in the dermis. After processing for light and electron microscopy, the spherules of eleocytes typically appeared empty, having lost their content of the red pigment, echinochrome. In contrast, the spherules of morula cells, granulocytes, and vacuolecytes enclosed a variety of granular and other material.The cell types reported in this paper resembled, to various degrees, spherulecytes in the coelomic fluid of echinoids described by other investigators.

Notizen: The fine structure of regenerating tips of spines of the sea urchin Strongylocentrotus purpuratus was investigated. Each conical tip consisted of an inner dermis, which deposits and contains the calcite skeleton, and an external layer of epidermis. Although cell types termed spherulecytes containing large, intracellular membrane bound spherules were also present in spine tissues, only epidermal and dermal cell types lacking such spherules are described in this paper.The epidermis was composed largely of free cells representing several functional types. Over the apical portion of the tip these cells occurred in groups, while proximally they were distributed within longitudinal grooves present along the periphery of the spine from the base to the tip. The terminal portions of apical processes extending from some of the epidermal cells formed a thin, contiguous outer layer consisting of small individual islands of cytoplasm bearing microvilli. Adjacent islands were connected around the periphery by a junctional complex extending roughly 200 Å in depth in which the opposing plasma membranes were separated by a narrow gap about 145 Å in width bridged by amorphous material. Other epidermal cells were closely associated with the basal lamina, which was 900 Å in thickness and delineated the dermoepidermal junction; some of these cells appeared to synthesize the lamina, while others may be sensory nerve cells.The dermis at the spine tip also consisted of several functional types of free cells; the most interesting of these was the calcoblast, which deposits the skeleton. Calcoblasts extended a thin, cytoplasmic skeletal sheath which surrounded the tips and adjacent proximal portions of each of the longitudinally oriented microspines comprising the regenerating skeleton, and distally, formed a conical extracellular channel ahead of the mineralizing tip. The intimate relationship between calcoblasts and the growing mineral surface strongly suggests that these cells directly control both the kinetics of mineral deposition and morphogenesis of the skeleton. Other cell types in the dermis were precalcoblasts and phagocytes. Precalcoblasts may function as fibroblasts and are possible precursors of calcoblasts. Closely associated with the basal lamina at the dermoepidermal junction were extracellular unbanded anchoring fibrils 150 Å to 200 Å in diameter. Scattered proximally among dermal cells were other extracellular fibrils, presumably collagenous, about 300 Å in diameter with a banding periodicity of 210 Å.

Notizen: Larvae removed at one-day intervals from laboratory infected intermediate hosts provided material for a comparative study of presomal development in Prosthorhynchus formosus (Van Cleave, '18) Travassos, '26, Prosthenorchis elegans (Diesing, 1851) Travassos, '15, and Moniliformis dubius Meyer, '33. Acanthellae begin development soon after entering intermediate hosts' hemocoels, and by the 18th day all three species possess three nuclear masses representing primordia of the proboscis, proboscis receptacle and ganglion, and trunk musculature and genitalia.Presomal development of P. formosus and P. elegans results in structures concurring with morphology of other adult palaeacanthocephalans and archiacanthocephalans. Development of M. dubius, however, differs from that of other archiacanthocephalans in that the muscular receptacle wall lines the entire surface of the nonmuscular sheath, failing to form a ventral cleft characteristic of other archiacanthocephalans. Unlike receptacle protrusor muscles of other archiacanthocephalan species, those of M. dubius spiral around the receptacle as they extend posteriad to attach individually to a pouchlike, muscular thickening at the receptacle's base. These protrusor muscles are distinct from the receptacle wall, as attested by their development alongside neck retractor muscles, not from the receptacle primordium, and the manner in which they are left to trail behind the receptacle when it is drawn anteriorly into the proboscis during larval development. The proboscis receptacle of M. dubius should not be thought of as being double-walled, as envisioned by previous workers.

Notizen: The hearts and ascending aortae of 11 Weddell seals, Leptonychotes weddelli, three adult Crabeater seals, Lobodon carcinophagus, two adult Ross seals, Ommatophoca rossi, and one adult Leopard seal, Hydrurga leptonyx, were examined for comparison with terrestrial forms. The Weddell seal specimens were from animals ranging in age from midterm in fetal development to mature adults. All specimens were collected in 1971, 1972, and 1973, from McMurdo Sound and the Ross Sea, Antarctica.The phocid hearts were characteristically broader and flatter than those of other carnivore families and they tended toward bifid apices. The heart form indices (height/circumference) averaged 31.5 compared to 39.0 for felids. The right ventricular chambers of the Antarctic seals were found to average longer in Weddells and narrower in all, than those reported for four other carnivore families. An elastic enlargement was present in the ascending aortae of all seals. The largest diameter of the aortic bulb averaged 25.5 mm more than the base of the aorta in the adult Weddell seals which represented an increase of 72.5% over the base.It is suggested that the general heart form, and especially the ascending aortae, are anatomical adaptations to diving. The compressed heart makes possible unimpaired function when the chest is compressed during deep dives. The aortic bulb maintains mean arterial blood pressure and perfusion of the brain and cardiac tissue during diving bradycardia.

Notizen: Jaw movements of albino rats during biting and mastication of relatively hard food were recorded by means of conventional and X-ray cinematography. Mandibular kinetics have been analysed in the context of passive mechanical limits imposed by jaw morphology, particularly of the joints, and by the food itself. Movements have been described in terms of degrees of gape, condylar translation and horizontal rotation of the rami about the symphysis.During biting the condyle remains in the anterior two-thirds of the fossa, moves forward as the jaw opens and the converse. The rami usually spread well apart; the lower incisors are usually approximated. Incised food particles are transported toward the molars by means of coordinated jaw and tongue movements. The prominent palatal rugae of the diastemal region abet this process. In the power stroke of mastication, the mandible shifts forward as the lower toothrows move a little inward; the condyles occupy the posterior two-thirds of the fossa. All movements seen were bilaterally symmetrical. Simultaneous chewing occurred on both sides.It is suggested that the lingual components in the primarily anterior power stroke enhance grinding efficiency.A movable symphysis appears to be of critical importance in facilitating this type of mastication.

Notizen: The integument of the paddlefish (Polyodon spathula) is unusual as a relatively small amount of mucus is produced by epithelial cells that are not modified into regular mucous gland cells. A thick compact epidermis and dermis compensate for the slight amount of mucus secreted.Paddlefish have a variety of scales formed of concentric bony lamellae containing osteocytes. There are five kinds of scales: dorsal and ventral fulcra on the caudal fin, rhomboidal scales on the caudal lobe, horny denticles over the pectoral girdle, calcareous denticles on the trunk, and anchor-shaped plates on the rostrum. Except for the fulcra, the scales are undoubtedly vestigial.The numerous surface pits on the rostrum, head, operculum, and throat are epithelial invaginations which are not connected to lateral line canals. No nerves lead to the pits. The spherical to cuboidal and often ciliated cells at the base of the pits are considered to be aplasic cells of unformed neuromasts.

Notizen: Freshwater sponges of the family Spongillidae reproduce sexually through formation of a parenchymula larva. The cytochemical characteristics of parenchymula larval metamorphosis  -  beginning with the blastula and terminating with the motile escape stage  -  for the spongillid Eunapius fragilis (Leidy) have been defined using both absorption and fluorescent cytochemical methods, particularly those demonstrating protein end-groups. Morphogenesis of the parenchymula larva of E. fragilis involves the interrelated processes of cytodifferentiation and mobilization of reserve materials. Larval development has been categorized into five stages, from blastula (stage I) through the escape stage (stage V). Parenchymula development is characterized by morphogenetic precocity, a fact influencing the rate of mobilization of cytoplasmic reserves, cytodifferentiation, and the fate of individual cell types. With attainment of the stage V parenchymula, the larva is, essentially, a mobile adult sponge exhibiting flagellated chambers, canal systems, a well defined connective tissue stroma, a diverse cell population consisting of specialized elements and a totipotent archeocyte reserve, and a terminal epitheliocyte line. The present study recognizes differences in development within the spongillids as well as within more remote poriferan taxa  -  emphasizing the need for detiled understanding of particular processes in individual species before proposing major generalizations about development in this ancient but evolutionally specialized group.

Notizen: In Mytilus californianus, root lamellae of the byssus stem are formed by two morphologically distinct exocrine cell types. Type 1 cells contain large ellipsoid granules which are ultrastructurally identical to those of the collagen gland associated with byssus thread formation: these granules are secreted only at the base of the stem generator. Type 2 cells contain small cylindroid granules which are secreted only from the lateral surfaces of generator septa. The resultant matrix is biphasic because the two secretions are incompletely mixed. Lamellar sheets of matrix are propelled outward by the action of cilia and are molded into a cylinder at the neck region of the stem. However, the stem retains a lamellar pattern.Byssus threads are attached to the stem by flattened rings formed from thread material which is secreted into the cervical crevice surrounding the neck.The microanatomy of the stem forming region is described and a new term, “stem generator,” is proposed for this organ.

Notizen: As in other arthropods the exoskeleton of arachnids is subjected to loads generated by external stimuli and behavioral activities. Far from being mere by-products of various activities such loads act as signals for mechanoreceptors capable of detecting minute displacements caused by them in the cuticle. In arachnids the slit sense organs serve in this capacity.Spiders have the most elaborate system of slit sense organs. Our previous studies clearly pointed to a functional significance of their specific location and orientation, as well as degree and type of aggregation (isolated, grouped, compound or lyriform) on respective body parts.The present study extends our work to the slit sense organs of scorpions. It gives a detailed account of the topography of the organs on the walking legs. In general slits are less orderly arranged on the legs of scorpions than on those of spiders. In the scorpion they never aggregate to form lyriform organs. Instead there are groups at comparable locations forming much more irregular, but still specific patterns. Isolated slits are more numerous on the scorpion leg, but are also less regularly distrubuted there. A common feature of the majority of slits on both the spider and the scorpion leg is their position on the lateral surfaces and their orientation roughly parallel to the long axis of the leg.

Notizen: The spermatozoon of Cucumaria pseudocurata is unique among those of the echinoderms in that it is tabloid in shape, i.e., elongated and dorsoventrally compressed. The sperm consists of a dorsal surface which contains an extensive striated rootlet-like structure located within a dorsal groove and a ventral surface which contains a medially situated acrosome. A single mitochondrion lies at the base of the nucleus. The flagellum is unusual in that a 9 + 3 tubular arrangement is observed in the mid-tail region.The acrosome consists of an acrosomal granule bounded by a limiting membrane and a surrounding periacrosomal layer. The granule is irregular in shape with the anterior-posterior surfaces flaring out, forming pockets in the periacrosomal material. The ventral granule surface bulges forming a close association with the plasma membrane. The dorsal surface is indented. Ventral to the depression (within the granule) is a small area containing a particulate-fibrous material. To the inside of the granule limiting membrane there is a second membrane-like structure (incomplete) which extends from the anterior-posterior surfaces around the dorsal face of the granule. Dorso-medial to the granule the periacrosomal layer contains a particulate-fibrous region lodged within the granule depression. This material is presumably the precursor of the acrosomal filament.Prominent cytoplasmic folds extend off from the basal flagellar region. The proximal and distal centrioles are situated perpendicular to one another within the mitochondrion. Centriolar satellite materials are associated with both centrioles. Toward the base of the tail the satellite of the distal centriole consists of nine radiating arms extending at an angle of 45° to the axis of the centriole. Each arm terminates in a dense thickening. The striated rootlet extends anteriorly from the distal centriole to just below the level of the acrosome.

Notizen: The ecdysial glands of mature male Libinia emarginata are pale, yellowish organs composed of lobes of epithelial cells having oval nuclei which are often eccentric and which have one or two nucleoli containing amorphous granular material and coarse strands. The plasma membrane bordering the basal lamina consists of invaginations containing microtubules which may serve to increase the surface area for metabolic exchange. Masses of smooth endoplasmic reticulum and associated vesicles are scattered throughout the cytoplasm. Two or more vacuoles may coalesce. Larger vesicles lie close to the cell surface. Numerous mitochondria with tubular cristae surround the nucleus and frequently are associated with SER. A few Golgi complexes consisting of flattened sacs, cisternae or vesicles, lipid droplets and free ribosomes were seen. Adjacent plasma membranes may be in close apposition or separated by a space filled with vesicles, granules, or blood or supporting cells. This type of ultrastructure is associated with steroid-secreting cells.

Notizen: Recent behavioral studies have shown the primary organ of prehension used in capturing prey to be the claw equipped forelimbs. In light of its functional importance, the claw retractile mechanism for 15 felid species is described and its function studied. The anatomy of the claw retractile mechanism for felids is then compared to that of other carnivorans.For felids, claw retraction is mechanically possible due to the unique shape of the middle and distal phalanges. Claw retraction, however, is a function of the dorsal elastic ligaments and not of the forearm extensor muscles. The resistance provided by these ligaments allows for flexion of the wrist and digital joints without claw protrusion. Moreover, co-contraction of both forearm flexor and extensor muscles is necessary to produce claw protrusion.The functional anatomy of claw retraction for felids differs considerably from that of most other carnivorans. However, the claw retractile mechanism for some advanced viverrids is structurally similar to that of the felids. For these viverrids prey seizing, as in the felids, has become a function of the forelimbs. For the other families of carnivorans, the jaws and not the forelimbs are used as the primary organ of prehension and the anatomy of the claw retractile mechanism reflects functional demands placed on it other than grasping and holding prey.

Notizen: The gross relationships and light microscopic anatomy of the suprarenal gland of a prosimian primate, Galago senegalensis, is described. The left gland is located medial to the pole of the left kidney in a fascial compartment of its own. The right suprarenal is located medial to the pole of the right kidney in intimate apposition to the liver and inferior vena cava. The capsule of the right gland blends with the capsule of the right lobe of the liver and is also contiguous with the adventitia of the inferior vena cava.The histologic appearance of the gland is similar to that of other primate genera. The zona glomerulosa is poorly developed; the zona fasciculata is composed of cell cords and is relatively well developed and the zona reticularis shows no unusual characteristics. The organization of the lipid content of the various cortical zones show a considerably different pattern than previously reported. The zona glomerulosa contains numerous large lipid droplets. In contrast to the bi-laminar pattern of lipid deposition seen in other primates, the Galago shows three distinct layers of lipid droplets in the zona fasciculata. The zona reticularis has a moderate population of lipid droplets essentially similar to that reported in most other forms. The medulla, except for a sparse number of centrally displaced zona reticularis cells, is completely devoid of lipid deposits. The junction of the zona reticularis and medulla is distinct, although a connective tissue capsule is not present.

Notizen: The projections of the accessory and main olfactory bulbs of the bullfrog are described as part of a long term analysis of the morphological differences in amphibian and reptilian telencephalons. Unilateral aspiration of the accessory olfactory bulb results in an ipsilateral projection to the pars lateralis of the amygdala via the accessory olfactory tract. Degenerating fibers from the accessory olfactory bulb are tracable into the cell-free zone between the dorsal striatum and the lateral pallium, and projections to these neural populations may also exist. Unilateral lesions of the main olfactory bulb reveal two major secondary pathways: an ipsilateral medial olfactory tract that projects to the rostral ventromedial portion of the medial pallium, the postolfactory eminence and the rostral, lateral and medial septal nuclei; and an ipsilateral lateral olfactory tract that projects to the dorsal striatum, the lateral pallium and the ventral half of the dorsal pallium. Two crossed secondary olfactory pathways to the contralateral telencephalon decussate via the habenular commissure after entering the ipsilateral stria medullaris. A crossed lateral pathway terminates in the dorsal striatum, the caudal, lateral pallium and the ventral portion of the dorsal pallium. A crossed medial pathway terminates in the internal granule layer of the main olfactory bulb.

Notizen: The brook stickleback, Culaea inconstans (Kirtland), in common with other bony fishes, lacks a germinal epithelium in the tubules of the testis, and the tubule wall is composed of a thin, discontinuous layer of myoid cells and collagenous fibers. Labelling of germ cells with tritiated thymidine has shown that the germ cells are derived from clumps of spermatogonia in the interstitial area. Large companion cells within the lumina of the tubules extend their processes to engulf spermatogonia from the interstitium which then enter the lumen of the tubule. Subsequent development of the germ cells takes place within individual compartments formed by folds of the plasma membrane of a companion cell. The companion cell, together with its complement of germ cells, constitutes a cyst. A companion cell may surround spermatogonia in the interstitium and at the same time encompass residual sperm of the previous season within the lumen. The plasma membranes of the germ cells and the companion cells remain discrete. Mature sperm are released into the lumen of the tubule and the companion cell again extends its processes into the interstitium and engulfs more spermatogonia for the following year.Companion cells may be homologous to the Sertoli cells of higher vertebrates although their processes penetrate the interstitium during the initial stages of spermatogenesis and they do not contain a permanent stock of spermatogonia.

Notizen: The cephalic clasper of the male Chimaera collei is a cartilaginous rod equipped with denticles and presumably used to grasp the female during copulation. It is attached to the skull by ligaments but there is no joint cavity or articular surface. It has no intrinsic muscles, its movements being provided by attachments to muscles of the lower jaw and labial cartilages. The cephalic clasper is apparently elevated by a branch of the preorbitalis muscle, whose main function is to elevate the lower jaw. It appears to be forcefully depressed during copulation by M. levator anguli oris, whose primary function is to move the labial cartilages. When not in use, the cephalic clasper is held passively depressed by an elastic tendon from M. preorbitalis. In the female the cephalic clasper is represented by an apparently functionless rudiment.

Notizen: A new pattern index, Ip, is introduced and used to compare patterns of wild type, burnsi, and kandiyohi chromatophores in the leopard frog, Rana pipiens. Wild type chromatophores are hyperdispersed over distances within cellular contact, and it is concluded that this hyperdispersion results from contact-mediated negative interactions. The hyperdispersion is less strong in spot cells than interspot, and extends over larger areas in burnsi than in wild type epidermis. Over areas greater than chromatophore size, patterns are either random or clumped. Patterning of kandiyohi melanophores is clumped into aggregates small enough to be within the range of cellular contact, suggesting a lack of contact inhibition among these cells. The possible roles of cellular properties and the extracellular environment in pattern determination are discussed.

Notizen: Interpretation of cross and tangential sections of the annulate lamellae and nuclear membrane of Rana pipiens oocytes provides evidence in these structures for the existence of diaphragms spanning the pores. The evidence appears to rule out explanations ascribing such diaphragms to an optical artifact. More detailed description is given of a component of the pore complex only briefly described heretofore and now called the “intracisternal ring.” The varied results and interpretations of studies of the pore complex in various cells are discussed.

Notizen: The masticatory apparatus in the albino rat was studied by means of electromyography and subsequent estimation of muscular forces.The activity patterns of the trigeminal and suprahyoid musculature and the mandibular movements were recorded simultaneously during feeding. The relative forces of the individual muscles in the different stages of chewing cycles and biting were estimated on the basis of their physiological cross sections and their activity levels, as measured from integrated electromyograms. Workinglines and moment arms of these muscles were determined for different jaw positions.In the anteriorly directed masticatory grinding stroke the resultants of the muscle forces at each side are identical; they direct anteriorly, dorsally and slightly lingually and pass along the lateral side of the second molar. Almost the entire muscular resultant force is transmitted to the molars while the temporo-mandibular joint remains unloaded. A small transverse force, produced by the tense symphyseal cruciate ligaments balances the couple of muscle resultant and molar reaction force in the transverse plane. After each grinding stroke the mandible is repositioned for the next stroke by the overlapping actions of three muscle groups: the pterygoids and suprahyoids produce depression and forward shift, the suprahyoids and temporal backward shift and elevation of the mandible while the subsequent co-operation of the temporal and masseter causes final closure of the mouth and starting of the forward grinding movement. All muscles act in a bilaterally symmetrical fashion.The pterygoids contract more strongly, the masseter more weakly during biting than during chewing. The wide gape shifts the resultant of the muscle forces more vertically and more posteriorly. The joint then becomes strongly loaded because the reaction forces are applied far anteriorly on the incisors. The characteristic angle between the almost horizontal biting force and the surface of the food pellet indicates that the lower incisors produce a chisel-like action.Tooth structure reflects chewing and biting forces. The transverse molar lamellae lie about parallel to the chewing forces whereas perpendicular loading of the occlusal surfaces is achieved by their inclination in the transverse plane. The incisors are loaded approximately parallel to their longitudinal axis, placement that avoids bending forces during biting. It is suggested that a predominantly protrusive musculature favors the effective force transmission to the lower incisors, required for gnawing. By grinding food across transversely oriented molar ridges the protrusive components of the muscles would be utilized best. From the relative weights of the masticatory muscles and their topographical relations with joints, molars and incisors it may be concluded that the masticatory apparatus is a construction adapted to optimal transmission of force from muscles to teeth.

Notizen: The description of stages of the molt cycle in mantis shrimp (emphasizing Gonodactylus but compared in a number of Gonodactylidae, Squillidae, and Lysiosquillidae) includes data on texture, hardness, and color of the exoskeleton; behavior; and the micromorphology of the integument and developing setae.After stage A1, When the exoskeleton feels soft and soapy, and A2, when the abdomen attains parchment consistency, the exoskeleton continues to harden until stage C1, when the telson carinae can no longer be depressed with a fingernail. The propodus (C2) and the merus (C3) of the raptorial appendage are the last elements to become rigid. The meral spot achieves indistinct coloration at B1 and distinct but pale coloration at B2; body color continues to intensify until C4.Changes in behavior are particularly marked before and after the molt. After the molt defensive and avoidance behaviors characterize A1 and A2. Threatening increases from low to intense levels in A2 and B1. Striking and offensive behavior increase from weak to normal intensities from B2 to C4. One or two days before the molt, animals lower activity and dominance and feeding levels, exhibit reclusive behavior, and sometimes seal the cavity entrance.The morphology of setagenesis is particularly valuable for determining the stage of the molt after the exoskeleton hardens. The ratio of setae containing cellular contents throughout the lumen to those condensed into strands separates stages A2 through C3. “Cones,” although variable within and between individuals in some species, form initially in B2 and continue to condense through D. Initiation of C4, D0 and D1 overlaps variously in some individuals. Apolysis (D0) and morphogenesis of new setae (D1-D3) provide cues for identifying approach of the molt. Setagenesis and setal morphology differ among families, genera and some species of stomatopods. The structure and functional morphology of setae can be explained by the form of setagenesis.Passive swelling and active muscular peristalsis effect the shedding of the exoskeleton and setal eversion at the molt. The carapace and rostrum are shed as one unit. Patterns of meral sutures vary among taxa with enlargement of the merus and with subterminal or terminal ischiomeral articulation. Middorsal sutures open only on the sixth and seventh thoracic segments, suggesting loss of the first rather than the last abdominal segment and therefore a distant relationship to other eumalacostracans.Approximate durations of the molt stages in stomatopods are compared to those of 11 crustacean taxa. Extensive overlap seems to occur among midinterval stages, particularly in stomatopods. The developmental plateau occurs in different stages in different taxa. Late postmolt (C), associated with calcification, requires longer in more heavily calcified than in thinly calcified species, except for stomatopods. The physiological events immediately surrounding the the molt (A1-B1 and D3-D4) are compressed in time in crayfish, brachyurans, and especially in stomatopods. Behavioral adaptations maximize this compression of physiological events at the molt in stomatopods. These three groups also possess the most asymmetrical molt cycles of the crustacean taxa examined. It is hypothesized that these modifications of the molt cycle allow opportunistic molting and represent adaptations to agonistic behavior.Temporal variation in behavior and in color over the molt cycle may increase the potential for speciation by processes resembling neoteny.

Notizen: Pheromone systems from seven species of noctuid are examined. Much of the structure of scales from the wings and/or the abdomen is interpreted as a modification for secretion or release of a pheromone. Scales with an extremely complex surface provide a large evaporation surface, while those connected to secretory cells show less superficial folding than body-covering scales.The development of the secretory gland and diseminatory scales in Mamestra configurata is followed from the exuvial pharate adult stage to emergence. Both components are paired and develop from epidermal cells lining a pair of large lateral invaginations. They may have resulted through division of a group of less specialized cells that originally combined the function of pheromone production and release.

Notizen: Examinations of stages of fibril development in muscle fibers of seven Rhesus monkey and six human fetuses reveal SR tubules encircling the Z lines at all stages of fibril development. The encircling SR tubules are continuous with the SR network of tubules which is found surrounding fibrils at all stages of development observed. The SR tubules encircling the Z lines show connections (electron-opaque strands) with the Z lines. The developing triadic junction shows a progressive increase in complexity of structures within the junction. First, membranes of T and SR become apposed with no visible structure between them. Second, tenuous connections are found traversing the space between apposed membranes. Third, well developed bridges are seen traversing the space. And finally, an intermediate density midway between the apposed membranes and parallel to them is found in favorable sections. Junctions between T tubule membranes were also observed and the structures in these junctions are somewhat similar to those found in junctions between T and SR membranes. The change in orientation of triads from predominantly longitudinal to predominantly transverse is complete in the 18-week monkey fetus and incomplete in the latest stage (28-week) of fetal development observed in humans.