Showing papers in "Anatomical Record-advances in Integrative Anatomy and Evolutionary Biology in 1963"

Autoradiographic investigation of cell proliferation in the brains of rats and cats

Abstract: Cell proliferation in the brains of rats and cats was investigated autoradiographically Two young adult rats were injected intraperitoneally with 2 mc of thymidine-H3 and killed after a two weeks' exchange period Two adult cats were injected intraventricularly with 05 mc of thymidine-H3 and killed one week later Labeling of cell nuclei in the brain, presumed to reflect DNA turnover and cellular proliferation, was investigated In the rats, some neuroglia cells were found labeled in all parts of the brain, suggesting a low rate of glial proliferation In addition, circumscribed small regions with numerous labeled neuroglia and microglia cells were seen in several brain regions, suggesting the occurrence of local glial proliferative reactions in these presumably normal brains A few apparently labeled neurons were seen in the neocortex, and a proliferative region of granule cells was identified in the dentate gyrus of the hippocampus In the cats labeling of glia cells was highest in the midline region, near the point of injection of the radiochemical, with a gradient of decreasing number of labeled cells both laterally and in the anteroposterior direction of the neuraxis Neurons with apparently labeled nuclei were observed in the midline cortex bilaterally in both animals These results indicate that glia cells can multiply in the brains of young adult rats and adult cats and they support the possibility that new neurons may be formed in forebrain structures, both in rodents and carnivores

Adrenergic synaptic vesicles in the anterior hypothalamus of the rat

Abstract: After formaldehyde perfusion a small area of the anterior hypothalamus was extirpated, identified neuroanatomically and studied under the electron microscope. The preparative technique consisted in refixation of the piece in 1% osmium tetroxide for two hours, immersion in 2% uranyl acetate and embedding in Epon 812. Sections were stained with lead acetate. The main areas comprised in the tissue were the nucleus hypothalamicus anterior, nucleus periventricularis inferior and anterior hypothalami area. In the neuropiles of these regions varicose axons containing neurotubules and granular vesicles are observed. There are also numerous nerve endings containing typical synaptic vesicles in addition to some having a dense granule of reduced osmium. Measurements demonstrate that there are two different populations of vesicles with means of 510 A and 1,300 A respectively. The possible significance of the granular vesicles is discussed and related to the high content of catecholamines in this region of the CNS. The possibility that these nerve endings may synthesize and store more than one transmitter substance is also discussed. The wide variety of vesicles found in axons and synaptic endings of the anterior hypothalamus is also considered as supporting a unified theory of neurosecretion postulated by one of the authors.

The postnatal development and differentiation of the boundary tissue of the seminiferous tubule of the rat.

Abstract: The morphology of the boundary tissue of the seminiferous tubule of the rat has been investigated in testes from animals aged from birth to four months. In the adult, the boundary tissue consists of four layers: (1) an inner non-cellular layer comprising a network of collagen fibrils sandwiched between two basement membranes (2) an inner cellular layer of flattened cells showing many of the characteristics of smooth muscle, including intracytoplasmic filaments and micropinocytotic vesicles, (3) an outer non-cellular layer containing scattered colagen fibrils and associated usually with a single basement membrane and (4) an outer cellular layer, component cells of which contain no fine filaments. At birth, the seminiferous tubule rests upon a basement membrane which separates it from a layer of low cuboidal cells. External to this, there is a narrow intercellular zone containing scattered fibrillar material and a region consisting of numerous processes of mesenchyme cells. By ten days postnatal, four definite layers are established due to the differentiation of an outer cellular layer of flattened cells from the mesenchyme, and intracytoplasmic filaments have made their appearance within the inner cellular layer. In subsequent stages there is progressive thinning and specialization of the cellular layers and increased fibril content within the non-cellular layers. By 22 days postnatal the boundary tissue appears virtually adult in morphology.

Dynamic condition of proteins in the visual cells of rats and mice as shown by radioautography with labeled amino acids

Abstract: The behavior of proteins in retinal rods was examined by injecting various labeled amino acids (methionine-S35 and -H3, tyrosine-, leucine-, and arginine-H3) into rats and mice, which were sacrificed at different time intervals between 10 minutes and 30 days. The retina of these animals was then radioautographed. Within minutes after injection of any one of the listed amino acids, a radioautographic reaction appears over the inner segment of the rods. This region of the cell is therefore a site of protein synthesis. Since this synthesis may be seen at any time of the day, it must be a continuous phenomenon. At 24 hours after injection, the radioautographic reaction appears over the junction of the inner and outer segments, and at 1.5–4 days, over the outer segment. Hence, the recently synthesized protein progressively migrates from the inner, toward and into the outer segment. Analysis of the decay of the specific activity in the inner segment reveals that two categories of proteins are synthesized there. One is a slowly turning over protein, presumably catabolized in situ and referred to as “sedentary.” The other is a fast turning over protein, which migrates into the outer segment and is referred to as “exportable”. The exportable protein may be opsin.

Studies on the fine structure of teleost blood cells. I. Peripheral Blood

Abstract: The fine structure of goldfish peripheral blood cells was studied by electron microscopy correlated with light microscopy. Various methods of specimen preparation are described. Optimal preservation for electron micoscopy was attained with fixation in 1% OsO4 in acetate-veronal buffer (pH 7.3) and embedding in Epon. Electron micrographs of erythrocytes reveal division of nucleoplasm into chromatin and interchromatin material, and continuity between the latter and cytoplasm via nuclear pores. Erythrocyte mitochondria contain longitudinally oriented tubular internal structures. Variations in lymphocyte morphology are noted and the close association between membranes of the nuclear envelope, Golgi apparatus and endoplasmic reticulum is shown. Compound granules, the azure granules of stained blood smears, are described. A distinguishing feature of the granulocytes is their specific granulation. Neutrophilic granules appear to be membrane-enclosed and contain varying amounts of dense material, the amount depending upon maturation, physiological state or degree of preservation. Specific eosinophilic granules are characterized by a dense matrix enclosing one or more crystalloid bodies. The specific granules of the basophil are large, membrane-enclosed bodies, demonstrating different degrees of electron density. Similarities between thrombocytes and lymphocytes are evident from light and electron microscope studies. A phylogenetic relationship between vertebrate blood cells in indicated.

Lipid-depleted white adipose cells: An electron microscope study†

Abstract: This report presents an electron microscope study of white adipose cells depleted of their lipid inclusion by prolonged low food intake. The tissue was fixed in phosphate-buffered 1% osmium tetroxide, embedded in Vestopal W, and sections were stained with lead hydroxide. Such cells differ in shape and size from signet-ring cells. They are ovoid, diminished in size, and the cell surface has become indented in all planes of the cell. The intercellular space is expanded with concentrations of collagen fibers in close association with the cell surface. These changes are presumed to be mechanical events associated with loss of lipid from the cell. Subcellular changes include the appearance of an extremely large number of pinocytotic vesicles and cytoplasmic vesicles similar in appearance, membrane-bound dense bodies, five-layered membranous structures, vesiculated bodies, and areas of flocculent material. Mitochondria and nuclei appear to be similar to their counterparts in signet-ring cells. Observations are discussed with relation to ultrastructural changes reported in other studies in which adipose cells were depleted of fat by acute starvation or experimental deprivation of insulin. It is suggested that intracellular structural changes are probably associated with adaptive alterations in the metabolism of the cell.

Fine structure of the rectal (salt-secreting) gland of the spiny dogfish, Squalus acanthias

Abstract: The rectal gland of the spiny dogfish, Squalus acanthias has been described by light and electron microscopy. The cell outline shows remarkable complexity in electron micrographs. The basal plasma membrane has numerous complex infoldings and interdigitations separated by groups of mitochondria. The lateral plasma membrane also shows extensive interdigitation. The apical region demonstrates profiles of interleafing cell processes with much membrane interdigitation occurring between them but containing few mitochondria. The apical surface has microvilli which extend into the tubular lumen and are covered with nap-like filaments. Glands of some fish were catheterized and attempts were made to correlate the fine structure of these glands with the known secretory rates. The cellular morphology of the secretory cells of the rectal gland correlates well with that seen in other ion-transporting tissues, although some unique specializations were noted.

Observations on the innervation of human long bones

Abstract: The innervation of some of the long bones of the extremities of the human was studied by methylene blue immersion. Small myelinated and amyelinated nerve fibers enter the numerous foramina of the epiphyseal and metaphyseal regions of long bones, traverse the thin cortex, and supply the interior of the bone. Small myelinated fibers wind about the trabeculae of the spongiosa or spread out on the undersurface of the articular cartilage. Small knob-like terminations end in close relationship to the endosteum. Other myelinated nerve fibers have branched free fiber endings associated with the walls of intertrabecular marrow arterioles. Amyelinated nerve fibers are usually associated with vascular walls but may also be associated with the connective tissue of the intertrabecular fat or marrow. Numerous myelinated and amyelinated nerve fibers traverse the nutrient foramen and supply the bone marrow and endosteum of the shaft of the bone. While the Volkmann's canals of the shaft receive nerve fibers from the overlying periosteum, the disposition of these fibers in the shaft of the bone has not been determined. No nerve fibers or endings were ever seen between the lamellae in any location. No function can yet be attributed to any particular type of nerve fiber or nerve ending.

The spinal arachnoid villi of the monkeys Cercopithecus aethiops sabaeus and Macaca irus.

Abstract: The spinal arachnoid villi have been studied in the monkey by the examination of serial sections of spinal nerve roots, particular attention being paid to the relations of the arachnoid to the dura mater and to the veins which are regularly applied to the emerging roots. Although the roots vary in their content of specialized arachnoid formations, in many, columns and clusters of arachnoidal cells occupy spaces between collagen bundles in the dura mater. In a few, leptomeningeal tissue extends completely through the dura. In approximately one of each six roots examined, arachnoidal tissue formed part of the wall of and projected into a vein associated with the root. This relationship to veins is considered an especially compelling point in dispelling the doubt which has been cast upon the conception of spinal arachnoid villi as specialized structures.

Closure of the spheno‐occipital synchondrosis

Abstract: Comparative anatomical and histologic methods have been responsible for the belief that the spheno-occipital synchondrosis in the human is an active growth center until the adult stage is reached. According to standard texts the suture closes between the eighteenth and twenty-fifth years. The present investigation was a re-examination of this question by means of midsagittal laminagraphy. The material consisted of 205 males 8 to 21 years; and 193 females 6 to 18 years. The midsagittal lamina of the spheno-occipital junction appears as a band of less radiopacity when the suture is open. Closure was found to occur first on the cranial border and to progress downward. Initial closure was found in a male of 10 years, 10 months; first complete closure at 13 years, 4 months. The last found completely open was at 15 years, 2 months. Complete obliteration was found at 8 years, 1 month in one female subject and the last completely open suture at 13 years, 9 months. In general, the closing age for the males was between 13–16 years, and the female between 11–14 years.

The pars distalis of the female rabbit hypophysis: an electron microscopic study.

Abstract: New Zealand virgin rabbits were used in this study. Normal males and castrated, thyroidectomized and recently mated females formed the control groups. Correlation with the light microscopical appearance using the method of alternate thin and thick sections, correlation with the control glands, and comparison with the descriptions in the rat, were used as criteria for the identification of five different types of secretory cells in the pars distalis. Two types of “acidophiles” were found, the more numerous and conspicuous having secretory granules of a maximum diameter of 380–400 mm (growth hormone-producing cell), and a second type with granules of 600–800 mm, very seldom seen in the virgin rabbit but increasing in number and granulation after mating (Prolactin-producing cell). Two types of “basophiles” that correspond to the “thyrotrophes” (angular shape, granules of 150 mm in diameter) and “gonadotrophes” (rounded shape, granules of 280–300 mμ), were also identified. In addition, a peculiar large cell with characteristic mottled cytoplasm and very few granules was tentatively identified as a “basophile” in the process of regranulation. Its functional significance was discussed. A stellate cell having fibrillar material and no secretory granules within its cytoplasmic processes, found between parenchymal cells and approaching basement membranes, was tentatively identified as a supporting element. In addition to the description of the fine structure and possible functional significance of the different cell types, some features as cilia, desmosomes, intranuclear fibrillar material, as well as vacuolization of cells in normal glands were also discussed.

Electron microscopic, observations on the vascular barrier in the cortex of the thymus of the mouse.

Abstract: The thymus of newborn and young adult mice of the DBA strain was studied under the electron microscope after fixation in osmium tetroxide and embedding in araldite. In most of the animals several intravenous doses of Thorotrast were administered within 24 or 48 hours of thymectomy. The fine vessels in the cortex of the thymus appear unusually competent. Their endothelium is complete, their basement membrane broad, and their wall further increased by adventitial cells and extracellular tissue. The epithelial reticular cell is the most peripheral adventitial element of these vessels. It extends slender processes which encircle the vessel and, by similar processes, surrounds individual or clusters of perivascular lymphocytes. This cell is disposed to mediate influences passing between cortical lymphocytes and the blood. By cytoplasmic processes of the endothelium and the adventitial reticular cells a cellular pathway from the lumen to the outside of the these vessels is established. In smaller vessels, moreover, the adventitial enclosure by reticular cells is incomplete. After intravenous injection thorium dioxide may be found in the vessel wall and, to a limited degree, in the surrounding tissue. These vessels resemble both the fine vessels in the central nervous system where a blood-brain barrier is present, and the terminal arterial vessels in the spleen.

Cell proliferation and displacement in the adrenal cortex of young rats injected with tritiated thymidine.

Abstract: The origin and fate of cells within the growing adrenal cortex have been studied autoradiographycally in young rats injected with thymidine-H3 and sacrificed at intervals between one hour and ten weeks after injection. Cell proliferation (DNA synthesis and mitosis) was greatest in the zona glomerulosa, dropped off progressively deeper in the cortex, and was negligible in the inner fasciculata and reticularis. The shorter cell generation times in the glomerulosa, compared to the other zones, were due mainly to a decrease in duration of the G1 period of the cell proliferative cycle, although a slight diminution in the length of G2 + mitosis was also detected. The average duration of DNA synthesis was not appreciably modified. Growth of the cortex was achieved through peripheral addition of new cells produced by mitosis in the outermost regions of the gland. As the cortex thickened, some labeled cells within these outer layers were gradually displaced to progressively greater distances from the medullary surface. Since these cells remained within the zone of rapid proliferation, they continued to divide, thereby diluting their radioactivity. Other labeled cells were gradually displaced out of the proliferative regions towards the medullary surface, and into zones which did not support cell division (inner fasciculata and reticularis). In consequence, heavily labeled cells were ultimately restricted to the innermost zones. It was suggested that as cells are displaced within the growing adrenal cortex they encounter changing microenvironments which influence not only proliferative activity, but presumably enzymatic pathways of steroid synthesis as well.

The ultrastructure of capillaries and arterioles of the hamster dental pulp.

Abstract: The ultrastructure of capillaries and arterioles of the hamster dental pulp has been studied. Pieces of the incisor pulp were fixed in 1% OsO4 buffered with 0.14 M veronal acetate, embedded in epoxy resin and studied in an electron microscope. The basic cytoplasmic organization of endothelial cells confirmed observations on blood vessels of other organs made by previous investigators. A large number of intracytoplasmic fibrils were found in many endothelial cells, and their presence was discussed in relation to earlier reports on the contractility of endothelial cells. Previous observations on the structural details of the intercellular region of the endothelium were confirmed and elaborated upon. The manner in which the cytoplasmic flaps of adjoining cells were oriented indicated that, if the integrity of the capillary wall was maintained, only cells with capacity for ameboid movement could creep through the region. Thus they were thought to play a role as an effective barrier against the passage of red blood cells. Numerous micropinocytosis and pinocytosis vesicles were found in association with plasma membranes. The significance of their structure in the transport of materials across the capillary wall is discussed. The fine structure of the pericyte resembled that of the fibroblast. Portions of plasma membranes of adjacent smooth muscle cells in the media of arterioles were brought together closely and resembled attachment zones.

Microcirculation in the islets of Langerhans of the mouse.

Abstract: A technique for the study of microcirculation in living islets, using quartz rod and cinephotomicrography, is presented, together with results of a study of insular microcirculation. With this technique, conditions are standard, results are reproducible and the findings are recorded permanently. The pancreas, bathed constantly in Locke-Ringer's solution at 37°C, is lifted with the spleen from the body, supported on the tip of Knisely's hollow-tipped fused quartz rod, and the lobules are separated gently. Circulation in the transilluminated islets, which are pale yellow, spherical or ovoid bodies with a distinctive vascular pattern, is studied with the biobjective, binocular microscope. For cinephotomicrography, the camera is aligned over one eyepiece of the microscope and the film is exposed at 64 frames per second, using a 750 watt projection bulb as light source. Direct anastomoses of insular and acinar capillaries are not observed. Blood flow in the islets of the anesthetized mouse is rapid and constant, under these conditions of observation. Intravenous epinephrine and ephedrine cause temporary interruption of blood flow in the islets, whereas nor-epinephrine slows but does not stop the circulation. Pitressin also causes slowing of insular blood flow. Insulin, glucagon, hydrocortisone, glucose, alloxan and diphenylthiocarbazone have no acute effect upon the insular microcirculation. A possible relation between the circulatory effect and the hyperglycemic effect of epinephrine and ephedrine is suggested.

Holocrine secretory cells of the rat epididymis

Abstract: Epithelial cells of the rat epididymis are of two major types, principal and holocrine. So called basal, apical, and clear cells represent different stages of the holocrine cell cycle in which it accumulates secretion products, dies, and is replaced. The twocell types differ not only in their secretory behavior, but also in mitotic characteristics and staining properties. Condensed mitoses of holocrine cells occur in the basal epithelium, but larger mitotic figures of principal cells occur in their own apical regions. Holocrine cells are acid phosphatase positive only in their activated basal forms, but are strongly PAS and silver positive in all stages except when disintegrating. In principal cells, only the Golgi area is acid phosphatase and silver positive, and small scattered PAS granules also appear in this region. While secretory functions of both cell types are under testicular hormone control, frequent mating releases holocrine cellsfrom the epithelium into the lumen where they disintegrate. A shortened cycle in mated males occurs within 24 hours. Holocrine cells are also present in the rat vas deferens. Cells with similar staining reactions occur in ductuli efferentes and seminal vesicles of the rat, and in epididymides of hamsters and guinea pigs. Similar fixation methods and staining reactions applied to purified glycerylphosphorylcholine indicate that holocrine cells may accumulate and secrete this constituent of epididymal fluids.

Incidence of the ponticulus posticus of the first cervical vertebra between ages six to seventeen.

Abstract: Lateral cephalometric radiographs of 353 young caucasoid orthodontic patients from 6 years to 17 years were examined for the presence of ponticulus posticus of the first cervical vertebra. Visualization of the posterior fossa was not obstructed and in each case the squamous occipital and posterior arch of the atlas could be clearly defined. Of the 353 subjects, 56 (15.8%) showed some degree of a ponticulus posticus. Of these, 24 (14.6%) of 164 were males and 32 (16.9%) of 189 were females, with no apparent sex differences in the occurrence of this anomaly. Those showing a ponticulus were divided on the basis of bilateral complete or incomplete and unilateral complete or incomplete. There were numerous variations in the size and location of the ossification centers in the atlanto-occipital membrane. The youngest female with a ponticulus was six years seven months and the oldest 16 years 11 months, while the youngest male was six years four months and the oldest 16 years five months. Two females with a unilateral partial ponticulus were observed over a one to two year period. During this time a complete unilateral radiopaque ponticulus had developed.

The fine structural localization of some testicular phosphatases

Abstract: The distribution of several nonspecific and nucleoside phosphatase activities in rat testis fixed in glutaraldehyde was studied with the electron microscope. Seven apparently discrete distributions of activity were found. Nonspecific phosphatase activity at neutral pH was found in the basement membrane of seminiferous tubules, as well as in pinocytic vesicles in connective tissue cells underlying the tubules. Acid phosphatase activity was associated with the dense bodies of Sertoli cells, and with the Golgi apparatus of all spermatogenic cells. In addition, the Golgi apparatus of spermatogenic cells exhibited activity to both nucleoside di- and tri-phosphates. The Golgi apparatus of the Sertoli cells exhibited both di- and triphosphatase activity, but no glycerophosphatase activity. Triphosphatase activity was also found at the cell surfaces of spermatogenic cells in some stages of development. Spermatogonia and early spermatocytes exhibited activity to both ATP and ITP. Little triphosphatase activity was found at the cell surfaces of secondary spermatocytes or early spermatids, while pronounced activity was seen at the surfaces of late spermatids.

Light and electron microscopy of the islets of langerhans of the saimiri monkey pancreas

Abstract: The distribution of alpha, beta, and other islet cells in the tail of the pancreas of the Central American monkey (Saimiri sciurea) revealed by the light and electron microscopes, is similar to that occurring in man. Differentiation of acinar, islet and duct cells is based on the presence or absence of specific granules and the special morphology of the cytoplasm and its membrane systems. Conspicuous lipid droplets appear in the islets, largely confined to beta and delta cells. An “intergrade” cell is present, possessing features of both alpha and beta cells, as well as a nongranular variety of delta cells. Nerve processes which display synaptic vesicles and clusters of mitochondria are present within the islets. Islet and acinar cells are sometime separated by connective tissue or a reticulum, as observed in light microscopy, but there may be simple apposition of their respective plasma membranes. The fine structure of this reticulum presents several levels of organization. Duct cells possess lipid masses similar to those in islet cells. These duct cells, unlike islet cells, are agranular and possess microvilli and cytoplasmic blebs, both of which show internal structures.

Comparative anatomical and neurohistological observations on the tongue of the marsupials.

Abstract: Macroscopic and neurohistological observations of the red, gray and tree kangaroo and wombat's tongues are described. On the dorsum, three circumvallate papillae, foliate papillae (gland-duct type), fungiform papillae and filiform papillae are observed. In the wombat, the vallate papillae are shaped like a “lotusnut.” Its summit is broadened, rough, and reaches the level of the dorsal surface. The papillae of the kangaroo are shaped like a “walnut” and are situated below the dorsal surface of the tongue. The vallate papilla is occupied with abundant nerves, thin non-myelinated and thick myelinated fibers, and ganglion cells, multipolar and unipolar. In the upper area of the wombat's papilla, however, there is a demarcated thin layer of non-innervated connective tissue. Therefore, taste buds are located in nearly the whole wall of the papilla in the kangaroo, but only in the lateral wall in the wombat, closely associated with the subgemmal nerve plexus. Foliate papillae of gland-duct type, which connect with the serous glands, have many taste buds innervated with thin fibers from the periductal nerve plexus. Also in this region there are many ganglion cells. This gland-duct type may be regarded as the primitive form of the common foliate and vallate papillae; i.e., foliate papillae may be developed from a linear gathering of its anlages, vallate ones from a circular gathering and bellshaped vallate form from an atypical type of the circular gathering. Taste buds may serve as a chemoreceptor for gland secretion in the tongue because their position does not exhibit any suitable form to receive the sense of taste. Richly innervated fungiform papillae contain a few taste buds, but poorly innervated ones have none in the upper epithelium. Filiform papillae are of a vascular nature. In the apical region of the tongue Vater-Pacinian corpuscles of simple type are found.

A histochemical study of the toad urinary bladder.

Abstract: Histochemical methods for the demonstration of enzyme activities and carbohydrates were applied to the bladder of the toad, Bufo marinus. The three cell types in the mucosa (ordinary epithelial cell, goblet cell, and mitochondria-rich cell) were found to be distinctive with the methods used. Dehydrogenase enzyme activities were highly concentrated in the mitochondria-rich cells. Membrane-associated ATPase activity was found in the basal cell-membranes of the mucosal cells, where active sodium transport is thought to occur. The potentialities of the various cell types for active electrolyte transport are discussed.

A hitherto undocumented variation of the inferior mesenteric artery in man.

Abstract: The variation appeared in a cadaver, male, Negro, 71 years old. Estimated stature and weight: 6′1″ and 180 lbs. Stated cause of death: Bronchopneumonia. In place of a single inferior mesenteric trunk, two arteies orginated from the aorta 2.6 cm apart, the inferior one located 3 cm superior to the bifurcation of the aorta. The superior artry was directed superiorly and gave origin to two branches: one to the superior portion of the descending colon and another which supplied the entirety of the transverse colon. The inferior artery also gave rise to two branches: one to the inferior portion of the descending colon and the other to the sigmoid colon and rectum. The superior mesenteric artery gave rise to one major trunk to the colon, which divided into ileocolic and right colic branches only. The marginal artery of the colon was well developed and patent throughout its length. Search of the literature, to date, has revealed no description of this variation. Two references to a variation in which the inferior mesenteric artery gave rise to a branch corresponding to the middle colic artery have been found. There is a paucity of literature regarding variations of the inferior mesenteric artery. Consequently it is uncertain whether this is due to lack of observation, small amount of variation, or both.

The calcified zone (basal layer) of articular cartilage of rabbits

Abstract: In the mammalian embryo, the articular end of a long bone consists of a mass of fetal cartilage which undergoes transformation into two types of tissue as the animal ages: The hyaline cartilage surface of the adjacent joint; and the bone of the ossific nucleus of the epiphysis. The junction of these two areas, the calcified zone (or basal layer) of the articular cartilage, was studied in the distal femur of 110 albino rabbits of various ages by: tritiated thymidine autoradiography; routine histologic staining and mitotic counts; special stain for glycogen; and special stain for calcium (murexide). In the immature rabbit (under two months) the cartilage cells are arranged in columns and there is evidence of active proliferation. In its most basal portion adjacent to the vascular tufts of the epiphyseal nucleus, the cells are hypertrophic and contain glycogen. The intervening matrix bars are calcified. It is apparent that, at this age, endochondral ossification, indistinguishable from that at the epiphyseal plate, is occurring. In the older rabbit (age four months) proliferation, columniation, and glycogen content are minimal, and the basal layer of cartilage is diffusely calcified. Proliferation is intense in and about the capillary loops and a thin layer of bone surrounds the capillary. In the adult (over six months) rabbit, calcification and ossification predominate. No proliferative activity is noted. Apparently growth has ceased completely or is so slow as to be unmeasurable by available techniques.

An electron microscopic study of the effects of reserpine on adreno-medullary cells of the syrian hamster†

Abstract: Adult Syrian hamsters were given daily subcutaneous injections of reserpine (1 mg/kg) for one or three days in order to study the fine structural changes in adreno-medullary cells. Initial alterations of fine structure in animals given one injection and sacrificed 15 hours later. Hamsters treated for three days were adrenalectomized on the left side 24 hours after the last reserpine injection. Following adrenalectomy, animals were allowed to recover for 48 or 96 hours after which the cells of the right adrenal medulla were compared with those of the left. Medullary cell changes 15 hours following one injection of reserpine included partial loss of electron opaque granules and an increase in the number of cytoplasmic vesicles and vacuoles. Medullary cells from the left adrenal glands removed following three subcutaneous injections of reserpine were characterized by a marked loss of electron opaque granules and by the presence of many vesicles and vacuoles distributed throughout the cytoplasm. Forty-eight hours following unilateral adrenalectomy medullary cells from the remaining right glands exhibited slightly electron opaque granules within the cytoplasm, each of which was surrounded by a smooth surfaced membrane. Cytoplasmic vesicles and vacuoles had decreased in number. Ninety-six hours following unilateral adrenalectomy medullary cells from the right glands showed further decreases in numbers of vesicles and vacuoles, and granules which possessed an electron opaqueness comparable to control medullary cells had reappeared within the cytoplasm.

Cardiovascular lesions in Swiss mice fed a high fat-low protein diet with and without betaine supplementation.

Abstract: Young adult mice of an albino stock (Taconic Swiss) were fed a hypolipotropic diet with a fat content (lard) of 28% and 8% protein (casien). The same diet containing betaine hydrochloride (2%) as a lipotropic supplement was fed to one-half the mice. After seven weeks of restriction to these diets (with and without betaine supplementation) pronounced lesions had developed in the hearts. These lesions consisted of myocardial necrosis and thrombi within atrial lumina. The thrombi increased progressively in size, reaching critical and lethal dimensions for 75% of the animals by 13 weeks. Atrial dilatation, as a compensating mechanism, was a typical response. Small foci of myocardial necrosis with calcification and fibrosis were common in the ventricles. All mice surviving for longer than 13 weeks showed the myocardial changes ventricles. All mice surviving for longer than 13 weeks showed the myocardial changes and the thrombosis described above. Mural necrosis was observed in the intramyocardial branches of coronary arteries but thrombosis was infreqent within these vessels. There was extreme weight loss which paralleled the onset and increasing severity of the cardiac lesions. Betaine, as a dietary lipotrope, did not prevent or alter the cardiovascular lesions.

Effects of transitory pteroylglutamic acid (pga) deficiency on embryonic and placental development in the rat.

Abstract: Female Long-Evans rats, were given a purified PGA-deficient diet containing 10 mg% of the antimetabolite, 9-methyl-PGA, from days 8 to 10 of gestation, followed by a PGA-supplemented diet from day 10 to autopsy. Thisregimen resulted in 18% embryonic death by day 11, 65% by day 12, and 100% by day 13 of pregnancy. No morphological differences between PGA-deficient and control embryos were observed at nine or nine and one-half days but ten-day embryos showed retardation of growth and development and decreased mitosis, especially in the neural epithelium. In 11-day PGA-deficient embryos the cranial portion of the neural tube was markedly retarded or anomalous. PGA-deficient embryos still living on day 12 exhibited severely retarded or abnormal development of the cranial region with moderate retardation in other areas. The placentas of PGA-deficient embryos were normal until the twelfth or thirteenth day when vacuolization and pyknosis of giant cells in the junctional zone occurred. These changes as well as placental involution through day 16 appeared morphologically identical with those observed in placentas of embryosdestroyed surgically on day 12. PGA-deficiency appeared primarily to affect embryonic rather than placental tissues.

Electron microscopy of post-mortem changes in the rat myocardium.

Abstract: An electron microscopic study was made on specimens of rat myocardium taken at various intervals after death, in order to determine the extent and character of autolytic change occurring during the first ten hours. Specimens were taken immediately after death and at 15 minutes, one hour, three hours, five hours and ten hours after death, fixed in 1% phosphate-buffered osmium tetroxide and examined with the electron microscope. The first noticeable change was a rapid depletion of glycogen. The specimens taken one hour or more after death show a longer sarcomere length indicating a more relaxed state. This is believed to reflect the inability of these fibers to contract upon stimulation by the initial contact with the fixative. Nuclei, when encountered, showed more chromatin clumping than in fresh tissue, but the nuclear membranes were intact. Very little change was noted in the mitochondria, sarcoplasmic reticulum, or other cellular components.

Genetic influences on induced cleft palate in different strains of mice

Abstract: This paper reports some of the genetic aspects of induced cleft palate susceptibility in the Strong a mouse compared with another less susceptible strain (C3H) and with their intercrosses. Pregnant females were injected with 1.25 mg of cortisone (Cortone acetate Merck) daily on the eleventh, twelfth, thirteenth and fourteenth day of pregnancy and killed on the seventeenth and eighteenth day of pregnancy. The control animals were not treated. In treated animals, cleft palate was induced in 100% of the Strong a offspring and 36.3% in the C3H offspring. In cross matings between these two strains the same dose of cortisone induced 11.7% of cleft palate if the mother was of the Strong a strain and 43.7% if of the C3H strain. The same dose produced cleft palate in 29.7% of the offspring of the F1 generation when mated among themselves and in 42.5% of the white offspring of the F2 generation when mated among themselves. The incidence of induced cleft palate was independent of albinism in the offspring of the F1 and F2 generation. There was no significant correlation between the occurrence of cleft palate and the position in utero, the weight of the affected fetuses or the litter size; however, the more crowded the uterine horn, the more affected fetuses it contained. There was no significant correlation between weight of the mother and number of affected fetuses among her offspring when the effect of litter size was eliminated.

Age variations in the specific surface of howship's lacunae as an index of human bone resorption.

Abstract: Internal remodelling of bone occurs continually during life in discrete foci throughout cortex and large trabeculae. It is defined as the process of replacement of primaryappositional bone with Haversian bone occurring within the periosteal-endosteal envelope. The foci are produced by osteoclastic resorption of preexisting bone and are subsequently filled in by successive waves of osteoblasts that deposit new matrix. In this study, measurements of the surface area of Howship's lacunae in rib diaphysealcortex are presented for 137 relatively normal individuals of both sexes and ranging from one month to 84 years of age. Undecalcified cross-sections were prepared fresh from rib obtained at thoracotomy or post-mortem. Measurements were performed with a calibrated Zeiss Integrating Eyepiece II. It was found that the values for this resorption index were highest in infancy and lowest in middle and early adult life. The maximum adult values were attained in the seventh decade. No differences were noted that could be accounted for by sex. Correlation of these data with an index of secondary bone formation in this same group of bones enabled the authors to conclude that the internal remodelling rate of rib cortex is highest in infancy, lowest in the fourth decade and attains a secondary peak in the seventh decade. The authors suggest that the phasing of the changes noted are due to some as yet unknown programming of the mesenchymal cell. Since no increases coincided with growth spurts during childhood and adolescence, they conclude that the process of internal remodelling may be under a completely different mechanism of control from that governing skeletal growth and maturation.