bluuebunny/crossref_metadata_2025 huggingface dataset:
The structure of the pulmonary acinus in a child of six years and eight months
Authors: Boyden Edward A.
Published: February 2005

So far as known this is the first portrayal of the detailed structure of a pulmonary acinus as seen both from within its cavities and from without. Some 200 serial sections (× 50) were traced upon transparent plastic plates and then viewed as translucent objects in packets of ten. This method was supplemented by wax‐plate and graphic reconstructions of the whole and of its parts.

The pulmonary acinus is a terminal bronchiole and all its branches. In this example there were three generations of respiratory bronchioles and from two to five generations of alveolar ducts ending in saccules. This acinus had a volume of 15.6 mm3, comparable to a cube measuring 2.5 mm on each side. The two halves (medial and lateral semiacini) interdigitated. Only the lateral, forming 53.4% of the whole, was analyzed in detail. It consisted of a roof having three portions with varying patterns (namely a proximal wing, a distal wing extending to the connective tissue septum, and a rudimentary lateral component); a septal portion resting on the septum and consisting of four pairs of alternating small and large clusters of alveolar ducts, to the lower half of which a cluster of vesicles was appended; and a paired lateral envelope of ducts which in one place communicated with an adjacent acinus, thereby revealing a third mode of collateral ventilation.

This acinus, reconstructed over a period of three years, is replete with numerous variations such as dilated atria and saccules, supernumerary structures, recurrent ducts, irregular branches and differing lengths of airways. Thus, it records the “fight for space” in earlier periods of growth. Knowing the pattern of this particular acinus, it has been possible to calculate the rate of diffusion of gases between the terminal bronchiole and the peripheral saccules, and vice versa. Yet the impression persists that no two acini are alike in either proximal or distal portions; therefore, it is questionable whether diffusion of gases in the peripheral airways of the living individual are really subject to precise mathematical measurement.
Fine structural observations on cell death in the epidermis of the external gills of the larval frog, Rana pipiens
Authors: Michaels John E. , Albright John T. , Patt Donald I.
Published: February 2005

The fine structure of the epidermis of the external gills of the larval frog, Rana pipiens, was observed during the period of gill degeneration. Many of the epidermal cells underwent morbid alterations. In typical degenerating epidermal cells the nucleus became irregular in outline, chromatin formed electron‐dense clumps and the nuclear envelope increased in width. Lysosomes became prevalent in the cytoplasm of these cells and progressively larger autophagic vacuoles appeared. As degeneration continued, apical epidermal cells were found embedded deeper within the epidermis. In some instances cell processes from two neighboring epidermal cells extended partially around the relocated degenerating apical epidermal cells probably contributing to their translocation; phagocytosis was completed by a single cell in other instances. The degree of participation of the phagocytic epidermal cells in the degenerative process was uncertain. The distribution of acid phosphatase activity was followed in specimens treated by the Gomori technique. Profiles of cisterna‐like elements, positive for the enzyme, suggested that perhaps entire Golgi cisternae contributed to the formation of autophagic vacuoles in combination with small vesicles. Heterophils and macrophages observed in the degenerating gills were believed to participate in the removal of the dying cells.
The effects of cortisol and BUDR on cellular differentiation in the small intestine in suckling rats
Authors: Clark Sam L.
Published: February 2005

In suckling rats absorptive cells in the distal two‐thirds of the small intestine ingest colloids by pinocytosis. In the middle third of the intestine pinocytosis ceases 17 to 21 days after birth and can be halted prematurely by glucocorticoids. The adrenal cortex is relatively inactive in newborn rats and begins to secrete glucocorticoids two weeks after birth; this secretion has been suspected to cause the termination of pinocytosis.

Glucocorticoids do not stop pinocytosis in absorptive cells already present on the villi but induce the renewing population of cells in the crypts to replace the cells on the villi with new ones that do not engage in pinocytosis. Therefore, glucocorticoids act by inducing a new direction of cellular differentiation.

BUDR (5‐bromodeoxyuridine) is reported to inhibit cellular differentiation reversibly in vitro. When injected into 8 to 9‐day‐old rats, simultaneously with cortisol, it inhibited the change in cellular differentiation induced by cortisol; that is, pinocytosis continued unabated. BUDR did not appear to be toxic and did not interfere with cellular replacement in the small intestine, as judged autoradio‐graphically.

Thus it appears that BUDR inhibits the initiation of cellular differentiation by cortisol but does not interfere with cellular proliferation or the pre‐established program of cellular differentiation that leads to pinocytosis. The mechanism of action of BUDR is still unknown; it is discussed in light of the possibility that BUDR may after cellular differentiation without acting directly on the genome.
Cerebral cortex of the mouse after prenatal chemical insult
Authors: Langman Jan , Shimada Morimi
Published: February 2005

The purpose of this study was to examine whether a short term chemical insult to neuroepithelial cells (the matrix cells of neurons) causes a clearly defined neuronal deficit in the neocortex and hippocampal region. In the first experiment 15‐day pregnant mice were given a single dose of 5‐azacytidine (4 mg/kg); 30–60 minutes later they were injected with tritiated thymidine (6 μc/g). The fetuses were sacrificed at various hours and days after treatment. No cellular abnormalities were observed one or two hours after treatment with 5‐azacytidine, but at three to four hours abnormal mitotic figures became visible at the lumen. Usually the chromosomes were clumped together, forming commaand circle‐shaped structures. Sometimes chromosome breaks were observed. The number of cells with chromosomal abnormalities increased during the following hours, but ten hours after treatment a few normal mitotic figures appeared again. In the meantime the affected cells moved from the lumen toward the cortical plate. Their number gradually decreased and 48 hours after treatment all had disappeared. Since in the controls many labeled cells reached the cortex but in the experimental animals none, a neuronal deficit resulted from the treatment. It was difficult, however, to pinpoint the type of neuron lacking in the brain of the treated newborn. In the second experiment pregnant animals were given several doses of 5‐azacytidine (2 mg/kg on days 13, 14 and 15 of gestation) and sacrificed at various days after birth. The neocortex as well as the hippocampal region of the treated animals contained fewer cells than the same structures in the controls. In addition many neurons both in the cortex and hippocampus were morphologically abnormal. It is thus concluded that single and repeated shortterm chemical insults to neuroepithelial cells during the later stages of fetal life, result in a shortage of neurons and the presence of morphologically abnormal neurons.
“Sternzellen” in the liver: Perisinusoidal cells with special reference to storage of vitamin A
Authors: Wake Kenjiro
Published: February 2005

The “Sternzellen” (von Kupffer, 1876) in the liver of normal animals and of those injected with excess vitamin A were examined with the light and electron microscopes. These cells were stellate perisinusoidal cells located in the space of Disse and were separated from the sinusoidal lumen by the endothelium. Their cytoplasm contained a number of lipid droplets which reacted intensely with gold chloride. These lipid droplets imparted intense vitamin A fluorescence under the fluorescence microscope. Following the administration of excess vitamin A, these lipid droplets increased remarkably. The “Sternzellen” were identical with cells described as “interstitial” or “fat‐storing” cells by others, and were quite different from the so‐called Kupffer cells of the liver reticulo‐endothelial system.
The brain venous system of the dog
Authors: Armstrong L. D. , Horowitz A.
Published: February 2005

The venous system of the canine brain was investigated by gross dissection and by radiographs. The system was divided into four major groups of vessels: cerebral veins, central veins, cerebellar veins, and pontomedullary veins.

The dorsal cerebral veins emptied into the dorsal sagittal sinus and the ventral cerebral veins entered the dorsal petrosal or transverse sinus. The internal system of cerebral veins, and the central veins, were drained by the great cerebral vein which entered the straight sinus. Cerebellar and pontomedullary veins flowed mainly to the sigmoid sinus.

The venous system of the dog differed from the human configuration in several ways. In the dog the major dorsal cerebral veins entered the dorsal sagittal sinus by independent lacunae in the same direction as the flow of blood. A middle cerebral vein was not present in the dog but was replaced by a continuation of the caudal ventral cerebral vein. There was a basal vein in the dog but its main flow of blood was to the dorsal petrosal sinus; in man, this vein passes to the great cerebral vein. The entire venous system of the brain was plexiform and collateral circulation was prominent. The larger veins were identified radiographically.
The fusion of dorsal and ventral endocardial cushions in the embryonic chick heart: A study in fine structure
Authors: Hay Don A. , Low Frank N.
Published: February 2005

Fusion of atrioventricular endocardial cushions begins during Hamburger‐Hamilton stage 27 and is completed during stage 28 (5 to 6 days incubation age). Connective tissue cells of these cushions are derived from the proliferating endocardial cell layer. The character of the organelles in cells of these cushions changes progressively as the cushions approach, meet and fuse: granular endoplasmic reticulum accumulates; Golgi complexes become extensive, and nuclei develop irregular shapes. These occur first in the connective tissue cells of the cardiac jelly and later in the endocardial cells. Fusion apparently is accomplished by liberation of the endocardial endothelial cells into the cardiac jelly, where, along with pre‐existing connective tissue cells, they become cells of the membranous interventricular septum. Gradually the cells appear to merge into one morphological population and thus become indistinguishable from each other. Both endocardial cells and connective tissue cells exhibit uptake of tritiated thymidine and undergo mitosis before, during and after fusion of the cushions. An outstanding characteristic of these cells is their continuing vitality throughout the entire process of fusion.
Olfactory and non‐olfactory epithelia in the nasal cavity of the mouse, Peromyscus
Authors: Adams Donald R.
Published: February 2005

The nasal cavities of 14 deer mice, Peromyscus maniculatus, were examined histologically to determine the variability in surface area of the olfactory epithelium and its correlation with nasal cavity volume, area of non‐olfactory epithelial surface, and body size.

Forty‐four per cent of the nasal cavity surface of P. maniculatus is covered by a non‐olfactory epithelium with an area of 129.8 mm2; the epithelial surface consists of gradations in type from keratinized stratified squamous rostrally to ciliated pseudostratified columnar caudally. An extensive portion of this epithelium is non‐ciliated and devoid of goblet cells. Situated dorsocaudal to the non‐olfactory epithelium is the olfactory epithelial surface measuring 166.8 mm2 in area.

The areas of total, non‐olfactory and olfactory epithelial surfaces are highly variable in a sample of mice containing two subspecies, both sexes and various ages. Surface area measurements of non‐olfactory and olfactory epithelia are correlated significantly with body length, body weight and volume of the nasal cavity. A relatively constant epithelial area to volume ratio is present in the nasal cavity of P. maniculatus. It is surmised that a stable ratio of molecules in the air to epithelial area may occur within a species.
Morphology of adipose cells in lambs at birth and during subsequent transition of brown to white adipose tissue in cold and in warm conditions
Authors: Gemmell R. T. , Bell A. W. , Alexander G.
Published: February 2005

Light and electron microscopy were used to study the morphology of adipose cells in newborn Merino lambs (Ovis aries). Postnatal changes in morphology were also examined in naturally fed Merino lambs held at 26°C or at 3°C for up to 32 days from the time of birth, and in lambs fasted for up to three days at 26°C or at 3°C since birth.

All adipose cells examined in the newborn lambs showed the morphological characteristics of brown adipose cells; no white adipose cells could be found. The brown adipose tissue in normally fed lambs was replaced progressively by white adipose tissue during the first two or three weeks of life, and this replacement was retarded in the lambs held at 3°C. During replacement a continuous spectrum of cells with morphological characteristics between those of brown and white adipose cells were seen. No degenerating brown adipose cells were observed; and, apart from brown adipose cells, no cells were identified that could have been precursors of white adipose cells. This evidence suggests that in various body regions of lambs white adipose cells are derived from brown adipose cells.

Lambs fasted at 3°C or under conditions that approached thermoneutrality (26°C) showed rapid depletion of lipid from brown adipose cells; hence brown adipose tissue of the lamb differs from that in the newborn rabbit in which this tissue is not readily depleted of fat during starvation under thermoneutral conditions.
Adrenergic innervation in ovaries of the rat and guinea pig
Authors: Burden Hubert W.
Published: February 2005

The ovarian adrenergic innervation of rats and guinea pigs was studied using a fluorescent technique. In both species, catecholamine‐containing nerves entered the ovary via hilar perivascular plexuses and extended into adjacent medullary and cortical tissue. The interstitial gland of the rat ovary was well innervated; however, cortical components of the ovary in this species, including corpora lutea and developing and mature follicles, were sparsely innervated. The interstitial gland and theca folliculi of developing and mature guinea pig follicles contained a dense network of beaded preterminal nerves. It is suggested that ovarian adrenergic nerves facilitate ovulation, either directly by stimulating perifollicular smooth muscle to contract or indirectly by influencing the steroid output of the interstitial gland.
Intracellular channels as a route for protein passage in the capillary endothelium of the shark brain
Authors: Hashimoto Paulo H.
Published: February 2005

Capillaries in the area postrema and other brain regions at the level of the obex were examined in Japanese sharks under the electron microscope with or without intravascular injection of horse‐radish peroxidase and histochemical incubation. The postremal capillaries were characterized by a relatively wide perivascular space filled with connective tissue elements including fine fibrils about 100 Å in diameter, and by endothelial fenestration; however, the space and fenestration were apparently less extensive than in rats and cats (Hashimoto, '66; Rivera‐Pomar, '66; Hashimoto and Hama, '68). In other brain regions, the capillary endothelium showed peroxidase‐filled intracellular channels that connected the luminal surface with the basement membrane soon after peroxidase injection. Many of the adjoining endothelial cells were linked by tight junctions. Perivascular astrocytic processes had long, tight contacts of about 125 Å in overall thickness. Discussion was focused on a possible endothelial route for passage of so‐called barrier‐free substances in the central nervous system of higher vertebrates.
Histochemical and electron microscopic observations on the sperm receptacles in the garter snake oviduct
Authors: Hoffman Loren H. , Wimsatt William A.
Published: February 2005

The sperm storage receptacles in the oviduct of the garter snake, Thamnophis sirtalis, were studied using histological, histochemical, and electron microscopic techniques. The receptacles are located in the posterior infundibulum and are readily distinguished from other structures within the oviduct. The luminal epithelium consists of secretory cells and ciliated cells. The latter cell type also lines the ducts leading to the receptacles. The distribution of lipids, carbohydrates, and several enzymes (succinic dehydrogenase, acid and alkaline phosphatases, nonspecific esterase, lipase, sorbitol dehydrogenase) in the infundibulum is described.

At the electron microscopic level sperm heads are seen to be closely associated with the surface of receptacle cells, often indenting the luminal plasma membrane. The possibility of a “Sertoli cell‐like” relationship is discussed. Formation of cytoplasmic vacuoles in receptacle cells is temporally associated with ovulation and may be part of a mechanism for sperm release from receptacle cells. No contractile elements were observed immediately around the receptacles.

Evidence is presented which suggests that free fructose and glucose are produced by the oviduct, possibly to be utilized for sperm metabolism at the time of ovulation and sperm release.
The effect of lithium carbonate on the structure of the rat kidney
Authors: Evan Andrew P. , Ollerich Dwayne A.
Published: February 2005

Female Sprague‐Dawley rats were used to study effects of lithium carbonate on the ultrastructure of the rat kidney. Experimental rats received daily intraperitoneal injections of lithium carbonate in dosages of 10, 30 or 100 mg/kg/day. These animals were killed on day 12 to 60. Control rats were either non‐injected or injected with either sodium chloride or sodium carbonate. Kidneys from control rats showed no abnormal changes. The 10 and 30 mg/kg lithium carbonate dosages caused progressive mitochondrial swelling, dilatation of cisternae of rough endoplasmic reticulum and occasional swelling of apical cytoplasm in tubular cells localized in the distal portion of the nephron. The 100 mg/kg lithium dosage produced damage in all portions of the nephron. However, the most severe damage, consisting of mitochondrial swelling, dilatation of the rough endoplasmic reticulum, apical cytoplasmic rarefaction and liquefaction, karyolysis and karyorrhexis was noted in the distal convoluted tubules and collecting ducts. The present study demonstrated that low dosages of lithium carbonate do affect the structure of the rat kidney.
The fine structure of the interstitial tissue of the rat prostate
Authors: Flickinger Charles J.
Published: February 2005

The structure of the interstitial tissue of the rat prostate has been studied using the light and electron microscopes in an attempt to determine the role of the fibromuscular stroma in the normal functioning of the gland. Smooth muscle cells and fibroblasts are the most numerous cell types. They are accompanied by macrophages, mast cells, and undifferentiated cells of low electron density. Smooth muscle cells have cytoplasmic protrusions that extend into corresponding depressions in adjacent muscle cells, and, at these points, the intercellular space is narrowed to 150–2000 Å. Smooth muscle cells and fibroblasts are arranged in parallel in septa between adjacent epithelial alveoli and form a sheath around each alveolus. Proceeding peripherally from the epithelium into the interstitial tissue, this sheath is composed of a layer of one or two highly flattened fibroblasts and a parallel layer of smooth muscle cells, followed subsequently by additional layers of fibroblasts and smooth muscle that merge into the remainder of the interstitial tissue. Most of the capillaries have an uninterrupted endothelium, but in some regions endothelial fenestrations are present. Unmyelinated axons contain aggregations of small granular and agranular vesicles. Vesicles are found in axons at distances up to several thousand angstroms from muscle cells and in axons that approach to within 150–200 Å of smooth muscle cells. In some cases an axon lies in a deep depression in the surface of a muscle cell. The type of innervation and variety of intercellular contact between muscle cells is discussed in relation to probable physiological characteristics of the tissue.
Placental development in the mongolian gerbil (Meriones unguiculatus). I. Early development to the time of chorio‐allantoic contact
Authors: Fischer Theodore V. , Floyd Alton D.
Published: February 2005

Early gerbil development was studied from days 4 through 12 of gestation. Implantation occurs on day 8 in a shallow antimesometrial implantation crypt. The proamniotic cavity forms from an invagination of basal trophoblast and a folding together of the rim of the cup thus produced. The approximation of this rim gives rise to the ectoplacental cone. The further development and expansion of the ectoplacental cone is much like the rat. Amniogenesis is by folding into the proamniotic cavity. Between large glycogen‐filled decidual cells occur many PAS‐positive eosinophilic granular cells. A massive subplacental gland forms from proliferating uterine epithelium within the decidua basalis. Epithelial proliferation begins shortly after implantation, and soon short thick cellular processes extend from the antimesometrial side of the lumen whereas long branching cords penetrate the decidua basalis mesometrially. The function of this structure is unknown.
Structure and carbohydrate histochemistry of postnatal canine salivary glands
Authors: Reifel Conrad W. , Travill Anthony A.
Published: February 2005

Structural changes in secretory units of developing canine salivary glands have been correlated with their histochemically demonstrable carbohydrate content. At birth, three and eight weeks, and six months, secretory cells and duct systems of parotid, submandibular, sublingual and zygomatic glands of mongrel puppies were examined for morphology and localization of sulfomucin, sialomucin, neutral polysaccharide and glycogen. Combining structural and histochemical criteria a classification was formulated to discriminate between mucous, serous, and seromucous cells. Within the first six months of life changes occur in the proportion of these cells in individual salivary glands. Structurally distinct typical and atypical mucous cells contained acidic carbohydrates, usually sulfomucin. In sublingual glands of more mature dogs, however, sialomucin was the predominant constituent in atypical mucous cells. Serous acinar cells containing neutral polysaccharide occurred only in these glands. Seromucous acinar cells secreting acidic carbohydrates, usually sialomucins, were recognized in parotid and zygomatic glands. Demilunes composed of sialomucin‐producing seromucous cells and neutral polysaccharide‐producing serous cells were observed in submandibular and zygomatic glands, respectively. From this investigation it appears that the structural and carbohydrate profile of developing canine salivary glands is distinctive to the particular age examined.
The ultrastructure of the thyrotropic cell during thyrotropin rebound in the adenohypophysis of the rat
Authors: Rosa Charles G. , D'Angelo Savino A.
Published: February 2005

Adenohypophyses of rats were studied ultrastructurally to ascertain the morphologic changes that occur in thyrotropic cells during the pituitary TSH Rebound Phenomenon. Rats were maintained on propylthiouracil (PTU) for 43–147 days and their adenohypophyses studied three to nine days after discontinuance of goitrogen treatment. TSH rebound was also induced in chronically hypothyroid rats by single intravenous injections of 0.8, 4, 20 and 200 μg of thyroxine. Pituitaries were studied from animals sacrificed 6–24 hours after thyroxine injection. Thyrotrophs of euthyroid rats were characterized ultrastructurally by the presence of numerous peripherally‐located, small secretory granules (storage phase) and by highly dilated cisternae of rough endoplasmic reticulum (secretory phase). The thyrotropic cells in PTU‐treated rats were sparsely granulated, displayed enlarged mitochondria with much loss of cristae and contained extensively dilated rough endoplasmic reticulum and expanded Golgi membranes.

Marked repletion of granules, both intracisternal and cytoplasmic, was seen during TSH rebound in the pituitary. It was observed in some thyrotrophs as early as three days after goitrogen withdrawal and was enhanced further at the 6‐ and 9‐day intervals. Granule repletion increased progressively with doses of thyroxine up to 20 μg and assayable thyrotropin in pituitary glands increased 500–700% over normal. Effects with the 20 μg dose could be detected as early as six hours. With higher doses of thyroxine, granule repletion in thyrotrophs was inhibited and mitcohondrial hypertrophy was largely reversed.

The electron microscopic findings reveal close correlation with previously published data on thyrotropin assays of the rat pituitary. They support the concept that the degree of cytoplasmic granulation in thyrotropic cells is quantitatively related to assayable stores of thyrotropin in the anterior pituitary gland.
A study on division of primordial germ cells in the early chick embryo
Authors: Swartz William J. , Domm L. V.
Published: February 2005

The purpose was to determine the sites, times and frequency of mitotic activity in primordial germ cells in the white Leghorn chick embryo during the period of migration. Colchicine was employed to facilitate the identification of dividing germ cells in embryos ranging in age from 18 hours to five days of incubation (stages 3–27). An increase in the number of germ cells was observed during the period of migration, due primarily to proliferation of intraembryonic cells, since no significant increase in the number of extra‐embryonic germ cells was seen during this period. The number of germ cells during this period ranged from 43 at 18 hours to 2211 at 120 hours. Two periods of intense proliferation were observed, the first between 48 and 72, the second between 96 and 120 hours. This coincided with a simultaneous increase in the number of germ cells during these periods. Dividing germ cells were present in the extraembryonic blood vessels anterior, lateral and posterior to the embryo at 28, 48 and 72 hours and within the intra‐embryonic circulatory network at 48, 72, 96 and 120 hours. At 72, 96 and 120 hours, dividing germ cells were numerous in the tissues of the dorsal mesentery adjacent to the developing gonads and within the gonads. Dividing germ cells were also located in head mesenchyme, limb buds and mesenchyme surrounding the notochord‐neural tube complex. Dividing germ cells were found in the chick embryo throughout the entire migratory period.
The demonstration of cilia in canine macula densa cells
Authors: Sottiurai Vikrom , Malvin Richard L.
Published: February 2005

Although the presence of cilia in mammalian epithelia is common, the finding of cilia in the macula densa cell of the kidney has never been reported. In this paper are reported electron microscopic observations of cilia in canine macula densa cells. The cilia observed have the classic 9+2 configuration. The centriole, basal body, foot process, ciliary rootlet and the substructure of the latter also were observed.
Cytochalasin‐B: Effects on cytokinesis, glycogen and 3H‐D‐glucose incorporation
Authors: Sanger J. W. , Holtzer H.
Published: February 2005

Time‐lapse pictures of He La cells grown in a medium with low concentrations of Cytochalasin‐B revealed that during division furrowing proceeds normally until the mid‐body forms. Only then was the centripetal contraction of the furrow blocked. In time the contracted furrow relaxed, resulting in a binucleated cell. Cytochalasin‐B exerted a profound depression on the level of glycogen in the cells and on the incorporation of 3H‐D‐glucose into glycogen, glycoprotein and mucopolysaccharides. These observations suggest that sensitivity to the drug may be due more to interference with glucose uptake and utilization than to disruption of putative contractile microfilaments in the cell cortex.
Circadian rhythms in mitotic activity and 3H‐thymidine uptake in the duodenum: Effect of isoproterenol on the mitotic rhythm
Authors: Scheving Lawrence E. , Burns E. Robert , Pauly John E.
Published: February 2005

Mitotic activity in the duodenum of the rat and mouse exhibits a circadian periodicity with a peak in the rat between 1200 and 1500 hours and a sustained trough between 1800 and 0600. Scintillation counts revealed a similar rhythm in the total uptake of 3H‐thymidine by the rat duodenum with a sustained but fluctuating crest occurring between 0800 and 1800 and a trough between 1900 and 0100. In the mouse the peak mitotic activity occurred at 0900 and the trough at 1700. Isoproterenol completely abolishes the rhythm in mitosis in mouse duodenum, when injected exactly 28 hours previous to sacrifice. The results are discussed in relation to reports that deny a circadian rhythm in mitotic activity in the duodenum.
Ultrastructural studies of the effects of various agents on the motor neurons of the spinal cord
Authors: Yates Robert D. , Yates Jane C.
Published: February 2005

In a previous study, morphological alterations of motor neurons were noted following an injection of strychnine. These changes consisted of dilated endoplasmic reticulum and the presence of intramitochondrial granules. In the current ultrastructural study rats were given either dihydrobetaerythroidine, metrazol, curare, botulinum toxin, fluoroacetate, fluorocitrate, Bungarus multicinctus venom, Naja naja venom, tetrodotoxin or potassium cyanide while other animals were given first one of these agents and then strychnine. Alterations in the endoplasmic reticulum and the presence of intramitochondrial granules were noted only when strychnine was given alone or in combination with one of the other agents.

These results indicate that convulsive activity, release of transmitter substance at the neuromuscular junction, exhaustion of the transmitter substances from the motor neurons during excessive discharge, interruption of oxidative phosphorylation or the direct action of strychnine on the neuronal membrane does not result in changes such as are seen after an injection of strychnine alone. Tentatively, we propose that strychnine alters neuronal membrane permeability with consequent disruption of the ionic equilibrium of the neuron, which is reflected as dilated endoplasmic reticulum, and the presence of intramitochondrial granules.
Innervation of pulmonary alveoli of the mouse lung: An electron microscopic study
Authors: Hung Kuen‐Shan , Hertweck M. Sue , Hardy John D. , Loosli Clayton G.
Published: February 2005

The nerve supply to the alveolar ducts and alveoli of mouse lungs was studied with the electron microscope. In the alveolar ducts, nerve bundles consisting of as many as nine unmyelinated axons surrounded by connective tissue fibers were usually located in the interstitium surrounding the openings of the alveoli. In the alveolar walls, nerve bundles consisting of as many as five unmyelinated axons were located in the interstitium between pneumocytes and the capillaries. The unmyelinated axons contained neurotubules and some mitochondria, and were partially or completely surrounded by Schwann cells. Two distinct types of enlarged nerve endings were identified. The first type contained many small mitochondria and was either associated with the type I pneumocyte or located alone in the interstitium. The second type was packed with numerous large dense‐core vesicles and was in close contact with the type II pneumocyte. It is suggested that the first type of ending is sensory and the second type is motor in function.
Ultrastructure of developing germ cells in the fetal rabbit testis
Authors: Gondos Bernard , Conner Lucy A.
Published: February 2005

Testicular differentiation, as evidenced by the appearance of a distinct tunica albuginea and formation of plate‐like aggregates of germ cells and mesenchymal cells, occurs at 16 days in the rabbit fetus. The germ cells at this stage of development are isolated large, round to oval cells that are easily distinguished from the smaller elongated mesenchymal elements surrounding them. The germ cell nuclei have a smooth spherical contour and a prominent eccentric nucleolus. Cytoplasmic organelles are sparse, consisting of scattered polyribosomes and spherical or ovoid mitochondria distributed singly in the cell. At 18 days, the cell groups form into distinct cords of germ cells and supporting cells, the earliest stage of seminiferous tubule formation. Between 22 and 25 days, proliferating germ cells show increasing condensation of nuclear chromatin and increased nucleolar complexity. The cytoplasm contains groups of mitochondria, dense polyribosomal complexes, lipid aggregates, scattered smooth vesicles and prominent Golgi complexes. Intercellular bridges appear between germ cells on day 22 and increase in number on succeeding days. During the last week of fetal development, germ cells become aligned in rows at the periphery of the primitive tubules. Their arrangement at this time resembles that of spermatogonia in the adult testis. However, the fetal “prespermatogonia” lack some of the characteristic ultrastructural features of adult spermatogonia.
Oocyte structure and early vitellogenesis in the trout, Salmo gairdneri
Authors: Beams H. W. , Kessel R. G.
Published: February 2005

Light and electron microscopic studies have been made on young oocytes of the trout; i.e., during previtelline and early stages of vitellogenesis. Balbiani's basophilic body has been followed from its origin in the youngest oocyte to its disappearance at the beginning of vitellogenesis. It assumes the form of a duplex body composed of a non‐basophilic component (idiosome) and a highly basophilic portion, the pallial substance. Electron micrographs reveal the Balbiani body to be a dense, finely granular substance apparently unrelated to the Golgi apparatus or mitochondria. Its role in oogenesis is not clear, but probably constitutes an essential precursor substance (perhaps RNA) necessary for oocyte growth and vitellogenesis.

At given periods in early oocyte growth, an extensively developed system of endoplasmic reticulum is formed and the cisternae contain numerous granules. These intracisternal granules probably represent precursor elements for a specialized type of yolk substance. The granules collect in dilated regions of the smooth‐surfaced cisternae where the latter undergo anastomosis. Here the granules undergo transformation into a finely granular particle. Older and more vitellogenetic oocytes have not been included in this study.
Location of large core synaptic vesicles in the dorsal gray matter of the cat and dog spinal cord
Authors: Duncan Donald , Morales Ricardo
Published: February 2005

Cross sections of aldehyde‐perfused, Epon‐embedded cat and dog spinal cord examined with an electron microscope display numerous synaptic vesicles with electron‐opaque cores along the medial and lateral margins of the dorsal gray matter (laminae I, II, III). The cored vesicles, 750 – 1500 A in diameter are located in synaptic sacs and in small unmyelinated axons. They occur in small numbers throughout the apical gray matter but are much more numerous in a narrow band immediately adjacent to the white matter. Their numbers and location should be of value in studies on the nature and origin of this type of synaptic vesicle.
An in vivo and in vitro autoradiographic investigation of growth in synchondrosal cartilage
Authors: Servoss Joel M.
Published: February 2005

The inherent growth potential of synchondrosal cartilage has been studied as follows. Sixty CD‐1 mice were injected with 3H‐thymidine on their first day of life. Thirty of these were sacrificed one hour after injection, and their cranial bases were removed and placed in an organ culture system. The explants were removed from culture at six‐hour intervals for one day and then every 24 hours for five more days. The remaining animals, which comprise the in vivo series, were sacrificed by decapitation at corresponding times. In order to detect cell movements, the spheno‐occipital synchondroses were divided into five zones, and labeled cell counts were done for each zone. The labeled cartilage cells spread apart with growth as new cells were formed in the central zone and moved toward the outer zones The labeled cells moving from the central resting zone to the outer hypertrophic zones were comparable in absolute number and in rate of movement in both the in vivo and in vitro cartilages. The fact that synchondroses grown in culture retained their capacity for growth without benefit of neighboring tissues seems to indicate that the spheno‐occipital synchondrosis possesses an inherent potential for growth and is not merely reactive or adaptive in nature.
Synaptic ultrastructure in the tangential nucleus of the goldfish (Carassius auratus)
Authors: Hinojosa Raúl
Published: February 2005

The synaptic ultrastructure in the tangential nucleus of the goldfish was studied with the electron microscope. The nucleus consists of cells measuring 30–40 μ in diameter receiving complex innervation from eighth nerve fibers and boutons. Two types of synaptic contacts by the eighth nerve, terminal and en passant, were recognized. Three varieties of the terminal type were described: calyciform, trilobated, and club endings. The three varieties of the terminal type, as well as the synapses en passant, showed gap junctions in their synaptic membrane complex. The morphological characteristics of these endings suggested electrical transmission.

The boutons synapsing on the tangential cells were of two types: terminal and en passant. Three varieties of boutons terminaux were described. One of these was classified as a mixed synapse. The morphological characteristics of the synaptic vesicles of the other two varieties suggested that the boutons could be inhibitory or excitatory.
Studies of the hemopoietic microenvironment. III. Differences in the splenic microvascular system and stroma between Sl/Sld and W/Wv anemic mice
Authors: McCuskey Robert S. , Meineke Howard A.
Published: February 2005

The differences in the splenic microvascular system and stroma between Sl/Sld and W/Wv anemic mice were investigated using in vivo microscopic and histochemical methods. Spleens of Sl/Sld anemic mice had increased numbers of sinusoids containing blood flow and an increased concentration of sulfated acid mucopolysaccharide in the splenic stroma when compared to spleens of non‐anemic littermates; in both groups of mice the undifferentiated hemopoietic cells in the red pulp were enveloped with a coating of sulfated acid mucopolysaccharide. In contrast, in the W/Wv anemic mice, the number of sinusoids containing blood flow was one‐half of that seen in non‐anemic littermates. While the concentration of mucopolysaccharides in the splenic stroma of the W/Wv mice and their non‐anemic littermates appeared similar, the W/Wv mice had a deficiency in the number of undifferentiated hemopoietic cells in the red pulp as well as a deficiency in the number of such cells enveloped with a coating of sulfated acid mucopolysaccharide. Transfusion of the W/Wv mice with stem cells from non‐anemic littermates corrected the anemia. Blood flow through the sinusoids was restored to near normal levels, and the number of undifferentiated hemopoietic cells increased in the red pulp; most were enveloped with a coating of sulfated acid mucopolysaccharide.

The histochemical results suggest specific defects in the composition of mucopolysaccharides in the hemopoietic microenvironment of Sl/Sld anemic mice and in the cell coatings of undifferentiated hemopoietic cells in W/Wv anemic mice. These results are consistent with our hypothesis that a cell coating of sulfated acid mucopolysaccharide is required for early erythroid differentiation but that a microenvironment which contains excessive concentrations of sulfated acid mucopolysaccharide is not conducive to supporting the later stages of erythroid development. In addition, the results obtained by in vivo microscopy of the microvascular system tend to support our hypothesis that erythropoietin‐sensitive stem cells respond to erythropoietin by producing a substance that is locally vasoactive.
Catecholamines and morphogenesis of the chick neural tube and notochord
Authors: Lawrence Irvin E. , Burden Hubert W.
Published: February 2005

Catecholamines in the early chick embryo (days 2–3) were studied using the Falck‐Hillarp technique. After treating specimens with nor‐epinephrine, specific catecholamine fluorescence was localized in the early neural tube of the youngest embryos (stages 7–9). In older embryos (stages 10–12) exposed to exogenous norepinephrine the fluorescence was seen in both the neural tube and notochord and by stage 13 fluorescence was brighter in the notochord than neural tube. Endogenous notochord catecholamine fluorescence was demonstrable in stages 13 through 17 without exposure to exogenous amines although treatment with a monoamine oxidase inhibitor (nialamide) or norepinephrine intensified the fluorescence. Treatment of embryos with nialamide or an inhibitor of catecholamine synthesis (α‐Methyltyrosine) caused numerous archencephalic anomalies, ventral flexure of the head without lateral rotation, and spina bifida. The results suggest that catecholamines in the early neural tube and notochord may provide the motive force for morphogenetic movements, including closure of the neural folds and torsion of the embryo.
The functional anatomy and evolution of the mammalian humero‐ulnar articulation
Authors: Jenkins Farish A.
Published: February 2005

Major stages in the structural and functional evolution of the mammalian humero‐ulnar joint are described on the basis of paleontological and cineradiograhic evidence. In pelycosaurs (the earliest known fossil reptiles with mammalian affinities), the humerus projected laterad and more or less horizontally; locomotor movements were principally rotation about its proximodistal axis. Because the forearm moved in a plane perpendicular to this axis, the flexed elbow was subjected to substantial torque. The humero‐ulnar joint consisted of two pairs of facets that engaged upon humeral rotation and was principally a stabilizing rather than a flexion‐extension mechanism.

Cynodonts (advanced mammal‐like reptiles ancestral to mammals) possessed an ulnar condyle rather than a trochlea. A condylar humero‐ulnar articulation, usually with a spiral configuration, was retained by early mammals and persists in slightly modified form among modern prototherians. The spiral joint allows the ulna to extend in a sagittal plane as the humerus rotates, adducts, and elevates.

The primitive therian trochlea evolved by enlargement of the intercondylar groove separating the ulnar and radial condyles and by retention of part of the ulnar condyle mechanism. Cineradiography demonstrates the relationship of diverse types of mammalian humero‐ulnar joints to limb posture and excursion characteristics.
Effects of short‐term low intensity light on the albino rat retina. An electron microscopic study (1)
Authors: R. Shear Charles , Keith O'Steen W. , V. Anderson Kenneth
Published: February 2005

Retinas of albino rats exposed to continuous, low intensity fluorescent light for periods of 6, 12, and 18 hr display fine structural changes in both pigment epithelial cells and in the outer segments of the photoreceptor cells. Adjacent pigment epithelial cells showed wide intercellular spacing (600 to 36,000 A) and retraction of the villous processes. As the rats were exposed to increasingly longer photoperiods, the lamellated discs, which are flattened in dark‐adapted retinas, became progressively more tubular.
A reexamination of the chorioallantoic placental membrane of a shrew, Blarina brevicauda: Resolution of a controversy
Authors: Wimsatt William A. , Enders Allen C. , Mossman Harland W.
Published: February 2005

The allantoic placenta of shrews has been classified as hemochorial, endotheliochorial and endothelioendothelial. Recent confusion has centered on the persistence of an intermediate cellular layer within the interhemal membrane and on its identity. Conflicting interpretations assert, (1) that the intermediate layer represents a continuous trophoblastic lamina (endotheliochorial placenta), or (2) that it consists of a discontinuous “maternal symplasma,” the trophoblast having disappeared early in development (endothelioendothelial placenta).

Utilizing thin plastic sections for light microscopy and electron microscopy we find that the disputed intermediate layer comprises an exceedingly thin, but continuous layer of syncytiotrophoblast, and that the shrew placenta is indeed endotheliochorial. However, the interhemal membrane displays a most unusual organization. The trophoblast is sieve‐like in that it is honeycombed with interstitial (extracellular) spaces which open freely at both its surfaces. Into these channels project numerous processes of the maternal endothelium, and where these contact trophoblast close junctions are often apparent; in rare instances endothelial processes were seen to penetrate to the fetal surface of the trophoblast, but not through its well‐defined basal lamina. Maternal endothelium and trophoblast are separated by an irregular space filled with a dense amorphous material, but it lacks fibrillar components normally found in basal membrane. Peculiarities of the hypertrophied maternal endothelium include an abundance of oriented cytoplasmic fibrillar elements, moderate endoplasmic reticulum and ribosomes, and a marked alignment of mitochondria against the basal cell membrane. Hypertrophied fetal mesenchymal cells often intervene between the fetal endothelium and the rest of the interhemal membrane. Seldom does either abut directly against the basal lamina of the trophoblast; they are usually separated from it by a welter of cytoplasmic processes from both elements, which project into the fetal interstitial space. The fetal endothelial cells are somewhat hypertrophied, and their external processes, like those of the mesenchymal cells, often contain glycogen. Peculiarly, the fetal endothelium lacks a basal lamina. The mesenchymal cells display all the usual ultrastructural characteristics of protein synthesizing cells and appear highly active. Functional implications of the organizational peculiarities of the interhemal membrane are discussed.
Monoamine‐containing cell bodies in the squirrel monkey brain
Authors: Felten David L. , Laties Alan M. , Carpenter Malcolm B.
Published: February 2005

Fifteen catecholamine‐containing cell groups and eight indoleamine‐containing cell groups are present in the brain of the squirrel monkey. Most of the catecholamine‐containing cell groups (12) are similar to catecholamine‐containing cell groups previously described in the rat. However, three catecholamine‐containing cell groups not previously noted are found in the squirrel monkey brain.

The indoleamine‐containing cell groups are found within, or adjacent to, the raphe nuclei. Differences between the localization of indoleamine‐containing cell bodies in the brain of the rat and the squirrel monkey are minor.