Biomedical subjects

J H Cutts

Publications and source records attributed to J H Cutts.

At least 37 records · Page 2Linked to original sources

PubMed1985

Morphological observations on the mesodermal cells in the 8 day opossum embryo.

Cells of the mesodermal layer of the 8 day opossum were examined by scanning and transmission electron microscopy after removal of the ectoderm. The mesodermal layer is formed by a multilayered network of large somewhat flattened, stellate-shaped cells, whose broad surfaces usually lie parallel to the external surface of the embryo. The mesodermal cells show numerous cytoplasmic processes which often appear as long delicate threads that may branch. The processes may course for considerable distances and establish contact with adjacent mesodermal cells. Contact points between processes, processes and cells, and between adjacent cell bodies showed junctional complexes. Most of the junctional complexes appeared morphologically similar to the nexus (communicating) type. Occasional desmosome-like junctions also were observed. Extracellular fibers were not observed.

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PubMed1985

Placentation in the opossum, Didelphis virginiana.

For the first 9 days of gestation, opossum embryos float in uterine secretions, separated from maternal tissues by a shell membrane. Each embryo is part of the wall of its hollow embryonic sphere. By the 10th day of development, the embryo becomes enveloped by both the amnion and yolk-sac. The yolk-sac consists of vascular and non-vascular portions and, together with the surrounding trophectoderm (trophoblast), forms the yolk-sac placenta of the opossum: the allantois does not contribute to formation of the placenta. The vascular portion of the yolk-sac placenta establishes an intimate relationship with the uterine epithelium soon after loss of the shell membrane. The yolk-sac placenta is non-invasive. Cells of the trophoblast exhibit numerous microvilli, an apical endocytic complex and the lateral and basal cell membrane are elaborately folded. These features suggest a cell that is active in the transport of materials. Junctional complexes between cells of the trophoblast and uterine epithelium were not observed. The uterine epithelium changes from ciliated pseudostratified columnar with few infoldings of lateral and basal cell membranes, to non-ciliated simple columnar in which these membranes show elaborate infoldings. The cells show numerous inclusions and mitochondria are polarized to the basal half of the cell. These features suggest a cell that also is active in the transport of materials.

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PubMed1985

Quantitative distribution of enteroendocrine cells in the gastrointestinal tract of the adult opossum, Didelphis virginiana.

The distribution and quantification of enteroendocrine cells exhibiting immunoreactivities to nine peptides and one amine were examined in the gastrointestinal mucosa of the adult opossum using specific immunocytochemical methods. In the stomach, 90% of the enteroendocrine cells are confined to the pyloric glands and this region contained 73% of the gastrin-containing cells, 60% of the somatostatin-containing cells and 9% of cells reactive for 5-HT. Enteroendocrine cells showing immunoreactivities to glucagon, pancreatic polypeptide, somatostatin and 5-HT were observed scattered within the oxyntic glands. Only somatostatin and 5-HT positive cells were found in the cardiac glands. Immunoreactivities to CCK, glucagon, gastrin, BPP, somatostatin, secretin, motilin, neurotensin, GIP and 5-HT were observed in the epithelium of the small intestine. Although considerable variation exists in the distribution of individual enteroendocrine cell types along the intestinal tract, nearly equal numbers of enteroendocrine cells were observed in each segment. The percentage of enteroendocrine cells increases distally in the colon. Of the three enteroendocrine cell types present, somatostatin- and 5-HT-immunoreactive cells are evenly distributed, whereas neurotensin-immunoreactive cells increase in numbers distally, resulting in an increase in total number.

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PubMed1984

Scanning electron microscopic observations on the 9-day opossum (Didelphis virginiana) embryo.

All three germ layers are present in the opossum embryo by the 9th prenatal day. The embryo proper is part of, and continuous with, the remainder of the chorionic wall. The wall of the yolk sac-chorion away from the embryo consists only of an outer covering of ectoderm and an inner layer of endoderm. Ectodermal cells covering the neural folds have dome-shaped apices and often show large, bleb-like expansions. Microvilli are short and few in number. The apical surfaces of ectodermal cells that overlie the parietal mesoderm are relatively smooth and show scattered, short microvilli that tend to be concentrated at cell junctions. The apices of ectodermal cells that cover the extraembryonic region are more rounded, and the cells balloon from the surface. Each cell shows abundant elongate microvilli and occasional cytoplasmic blebs. Endodermal cells that line the chorion and form the third (innermost) layer of the embryo are similar in their surface morphology.

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PubMed1984

Scanning electron microscopic observations on the opossum yolk sac chorion immediately prior to uterine attachment.

The 10 day opossum embryo is enclosed by a yolk sac chorion in which distinct vascular and non-vascular regions are established before attachment to the uterine epithelium. The embryo is closely associated with the vascular region which becomes adherent to the uterine lining. Cells of the external layer bear abundant, closely packed, long microvilli, which may serve to absorb nutrients from the uterine secretions. Cells of the inner surface show only scattered microvilli and microplicae on their apical surfaces.

Animals↗

PubMed1983

Ultrastructural observations on the shell membrane of the North American opossum (Didelphis virginiana).

Each developing opossum embryo is surrounded by a shell membrane which completely separates embryonic and maternal tissues. During the eighth and ninth prenatal days, the embryos together with their limiting shell membranes float freely within the uterine lumen, surrounded only by the secretions of the uterus. The shell membrane is transparent, nonelastic, tough, and capable of extreme deformation. It consists of a mat of interwoven fibers which vary in external diameter, are electron dense, and show no apparent substructure. The morphology and arrangement of component fibers are similar throughout the width of the shell membrane.

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PubMed1983

Morphological observations on the parathyroid of the opossum (Didelphis virginiana).

Parathyroid III of the opossum, Didelphis virginiana, lies on the medial surface of the internal carotid artery at its origin just above the bifurcation of the common carotid artery. It is limited externally by a capsule and is subdivided into lobule-like structures by connective tissue septae. The parenchyma consists solely of chief (principal) cells, arranged in irregular cords and clumps supported by a delicate vascular connective tissue. Ultrastructurally, the chief cells are polyhedral in shape and have centrally placed nuclei. The cytoplasm contains small, randomly distributed, rod-shaped mitochondria, scattered profiles of granular endoplasmic reticulum, free ribosomes, and small perinuclear Golgi complexes. Secretory granules are small, electron-dense, and appear to be limited by a delicate membrane. The granules are related both to the Golgi complex and the basal cell membrane. Capillaries that lie immediately adjacent to the chief cells show an extensively fenestrated endothelium.

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PubMed1983

Postnatal development of the thyroid gland in the opossum (Didelphis virginiana).

Thyroid lobes of the newborn opossum consist of small epithelial cords or plates, the constituent cells of which are joined by tight junctions and surround a minute lumen that courses throughout the length of each cord. Occasional cells, not directly associated with the lumina of the cords, show central nuclei and clusters of small electron-dense granules: these may represent parafollicular cells at an early state of development. By the end of the 1st week after birth, parafollicular cells are well established and appear as groups between the epithelial cords and as scattered individual cells within the cords. Growth of the thyroid occurs as the cords continue to elongate and branch. 11 days after birth, thyroid development in the opossum corresponds morphologically to that of eutherians just prior to birth. Primary follicles are present near the periphery of the thyroid lobes, having formed from evaginations of the epithelial cords. There is evidence of synthetic activity by the epithelial cells and colloid is present. Secondary follicles form as a result of evaginations from the epithelium of the primary follicles. At the end of the 2nd postnatal week, epithelial cords are no longer a prominent feature of the opossum thyroid, and the organ is now characterized by numerous, small colloid-filled follicles. As development progresses, the follicles increase in size and number and, by 35 days after birth, the thyroid shows adult features.

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PubMed1983

Structure of the paws in Didelphis virginiana.

The paws of Didelphis virginiana show several unusual features. They possess dermatoglyphs on the foot pads, have opposable first digits and the pads show a peculiar vascular arrangement. The hallux lacks a claw. The degree of innervation and the number and size of Pacinian corpuscles indicates that the paws of the opossum are finely sensitive to pressure and vibration.

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PubMed1982

Morphological observations on the papillae of the opossum tongue.

The dorsum of the opossum tongue shows filiform, fungiform, conical and three vallate papillae. An additional type, the compound filiform papilla, is characteristic of most marsupials, including the opossum. These are unique structures in which the epithelium forms fringe-like, keratinized projections around the apical borders of the papillae. The covering epithelium is an extensively keratinized, stratified squamous type with a well-developed stratum granulosum containing numerous keratohyalin granules. Large, heavily cornified conical papillae occur in a patch near the anterior end of the tongue and the apex of each papilla is directed posteriorly. Taste buds are associated with only the three vallate papillae which form a triangle near the base of the tongue. They are not present on the fungiform papillae or in the posterolateral mucosal folds which appear to replace the foliate papillae of other species.

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PubMed1982

The notochord of the newborn opossum and its fate during postnatal development.

The notochord was examined by light, transmission and scanning electron microscopy, in 25 pouch young opossums (Didelphis virginiana) ranging in age from 6 hr to 25 days post natum. In the newborn opossum, the notochord forms a thin cylinder within developing vertebral centra and presents diamond-shaped expansions in regions of the developing intervertebral discs. The opossum notochord differs from that of other species in that it appears to consist of a heterogeneous population of light and dark cells, and also in the thinness of the notochordal sheath which never attains the degree of development seen in other animals. The sheath is made up of thin cytoplasmic processes which arise both from the light and dark cells. The processes cross a mucopolysaccharide-filled space and then expand to form a thin cytoplasmic sheath that forms the external boundary of the space. The matrix of the cartilage immediately adjacent to the cytoplasmic sheath shows an increased concentration of microfilaments as compared to the cartilage further from the notochord. During postnatal development the notochordal tissue in the centra of the vertebral bodies decreases, while in the regions of the developing discs, there is a corresponding increase. At the end of the first week, notochordal tissue in the vertebral centra is represented only by a thin cylinder of mucopolysaccharide which contains cell fragments. In subsequent weeks, as ossification of the centra occurs, both the cartilage and notochordal tissue are replaced by bone. Notochordal tissue in the intervertebral regions contributes to the formation of the nucleus pulposus of the intervertebral discs. Despite its short gestation period of only 12 1/2 days, the basic structure and fate of the notochord in the opossum is similar to that of other mammals.

Aging↗

PubMed1982

Histochemistry of the striated musculature in the opossum and human oesophagus.

The striated muscle component of the opossum oesophagus has been studied for fibre type as revealed by histochemical stains for succinic acid dehydrogenase, adenosine triphosphatase, nicotinamide adenine dinucleotide dehydrogenase and after staining with the periodic acid-Schiff reagent. The reactions were compared to those obtained in a single human oesophagus. In both species, the striated muscle consisted of Type II fibres throughout, but at the pharyngeal end, some Type I fibres passed into the muscularis externa from the lower pharyngeal constrictor and extended for a short distance along the oesophagus. Differences in the reactions to these histochemical stains indicated that the Type II fibres of the opossum oesophageal musculature are subtype A, while those of the human are subtype B.

Adenosine Triphosphatases↗

PubMed1982

Postnatal development of the spleen in Didelphis virginiana.

The postnatal development of the spleen has been examined in 85 opossums ranging in age from newborn to adult. At birth the spleen consists of a well vascularized mass of mesenchymal tissue and lacks lymphatic tissue or any evidence of haemopoietic activity. Haemopoiesis is evident at seven days, increases to a maximum at about two to three weeks and thereafter gradually declines. Although production of granulocytes has disappeared by 60 days postnatum, a small degree of erythropoiesis and megakaryocyte formation continues throughout life. Lymphatic tissue appears by the third week, but germinal centres do not appear until after weaning. A feature of the spleen during the first three to four days is the presence of a population of primitive 'blast' cells.

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PubMed1980

Transitory cell attachments in the differentiating glomerular epithelium of the opossum metanephros.

Numerous transitory intercellular attachments are observed between the central, lateral surfaces of adjacent glomerular epithelial cells in the differentiating renal corpuscle. The junctions are characterized by an increased electron density of the adjacent cell membranes and cytoplasm. The intervening intercellular space may contain an amorphous material of moderate electron density. The distribution and position of such temporary cell attachments, together with their modification and subsequent loss during the differentiation of podocytes, suggest that they play an important role in the histogenesis of the glomerular epithelium.

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PubMed1980

Scanning electron microscopic observations on the eruption of primary teeth in the opossum.

Just prior to the emergence of the tooth into the oral cavity, a small circular crater forms in the gingival epithelium immediately above the crown. The craters appear to expand in diameter during eruption to accommodate the emerging crown of the tooth. The observations support the concept that the crown of the tooth does not actively push through and rupture the gingival epithelium, but rather that the epithelium degenerates and then the tip of the crown emerges into the formed defect.

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PubMed1980

Changes in the erythrocytes of the developing opossum, Didelphia virginiana.

Changes in the erythrocyte population during postnatal development of the opossum have been studied. At birth, the red cells of the peripheral blood number less than 600,000/cmm and the characteristic erythrocyte is a large nucleated cell ('megaloblast'). These are rapidly replaced by smaller, nonnucleated cells. The results indicate that the yolk-sac period of blood formation is short and that the hepatic phase of hemopoiesis begins prior to birth. The data also suggest that megaloblasts in the opossum may be able to transform into megalocytes.

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PubMed1980

Leukocytes in the peripheral blood of the developing opossum.

Changes in the blood leukocytes have been studied in 112 opossums ranging in age from newborn to adult. Very few circulating leukocytes are present at birth, and these consist mainly of neutrophil granulocytes, with many immature forms. Leukocytes increase rapidly in number during the first 2 weeks of postnatal life, due to an accumulation of granulocytes. While all three types of granulocyte share in this early increase, initially it is the neutrophils which predominate. However, eosinophil granulocytes increase rapidly and their number soon equals or exceeds that of the neutrophils. Eosinophils remain a prominent, but lesser, component of the blood leukocytes throughout all subsequent periods of development. Lymphocytes are present only in small numbers during the first 8--10 days of postnatal life, and during this time small lymphocytes are absent from the peripheral blood. Apart from increased lobation of the granular leukocytes, the white blood cells show no remarkable cytological changes during the postnatal period.

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PubMed1979

Pairing of spermatozoa in the epididymis of the opossum (Didelphis virginiana): a scanning electron microscopic study.

Spermatozoa of the opossum, Didelphis virginiana, were taken from three different regions of the epididymis and examined by scanning electron microscopy, phase-contrast and dark-field microscopy. It has been demonstrated that marked morphological changes occur in spermatozoa during their passage through the epididymis. In the first segment or head of the epididymis, spermatozoa are non-motile and the long axis of their nuclei is perpendicular to that of the tail. The nucleus is V-shaped with a thick and a thin arm. At the junction of the two arms. At the junction of the two arms, where the arms join, the articular fossa receives the capitulum of the connecting piece which attaches the head of the spermatozoon to the tail. Spermatozoa from the central region of the epididymis show a re-orientation of the nuclei which now lie parallel to the long axis of the tail. Both paired and unpaired spermatozoa are found and show an increase in motility. In the caudal region of the epididymis all spermatozoa are paired. Pairing occurs as a result of the close apposition of adjacent cell membranes covering the acrosomes of the larger arms.

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