PubMed Health⌕ Search

Biomedical subjects

J H Cutts

Publications and source records attributed to J H Cutts.

At least 55 records · Page 3Linked to original sources
PubMed1979

Structure of the esophagus in the adult opossum, Didelphis virginiana.

The structure of the esophagus has been studied in the adult opossum, Didelphis virginiana. A thickening of both layers of the muscularis externa occurs at the origin of the esophagus and may represent the upper esophageal sphincter; a massive expansion of the muscularis mucosae occurs in the region of the lower esophageal sphincter. The distribution of striated, mixed and smooth muscle in the muscularis externa differs in the inner and outer layers and elements of the myenteric plexus are found to occur even in the region of striated muscle; however, the ganglia of this plexus become much more prominent as smooth muscle makes its appearance. Esophageal glands are found in the lamina propria where they are confined to the 2 ends. They are especially prominent at the distal end where they are responsible for the formation of permanent transverse folds. Similar glands are found in the submucosa, scattered throughout the length of the esophagus but distally, in the region of the transverse folds, the submucous glands disappear. In both of these layers, the glands contain mucous, serous and myoepithelial cells.

Animals↗
PubMed1979

Morphological observations on the mesonephros in the postnatal opossum, Didelphis virginiana.

The mesonephros of the opossum persists for 3-4 weeks into the postnatal period. Based on our observations of its structure, and the vital dye experiments of others, it appears that the opossum mesonephros is functional during the first 10 days of the postnatal period. The mesonephros of the newborn opossum consists of 35-45 nephron units which are structurally very similar to metanephric nephrons except that they lack a loop of Henle. By the end of the first postnatal week, regression which proceeds in a craniocaudal direction, is observed. By the end of the second week most nephrons show some signs of regression. The regressing mesonephric nephrons are replaced by connective tissue.

Animals↗
PubMed1979

Morphological observations on the metanephros in the postnatal opossum, Didelphis virginiana.

The metanephros of the newborn opossum is very immature, consisting only of collecting tubules and a few immature nephrons. Development during the postnatal period can be divided into two distinct phases. The initial phase occurs during the first 60 days of postnatal life and is concerned with nephronogenesis and the differentiation of nephrons that have formed during this period. The second phase lasts through the remainder of the postnatal period and is concerned with further differentiation and growth of established nephrons. During this latter period the tubular portion of the nephron increases in length and the renal corpuscle increases in diameter. Ultrastructural observations suggest that metanephric nephrons are not functional during the first 4 days of postnatal life, while the mesonephros reaches the height of its development during this period: there may be some functional overlap between the mesonephros and metanephros during the latter part of the first week of postnatal life. The pattern of nephron induction and differentiation in the opossum is discussed.

Animals↗
PubMed1978

Virus-like particles in the opossum submandibular gland.

Numerous inclusion bodies (virus-like particles) were observed in the lumina of the intercellular canaliculi, mucous tubules and intralobular ducts of the opossum submandibular gland. The particles are spherical in outline, show an electron dense core, and are surrounded by a peripheral membrane.

Animals↗
PubMed1978

Postnatal development of the pancreas in the opossum. Light microscopy.

The pancreas of the newborn opossum consists of a central region of forming islets surrounded by primitive tubules that end in proacinar cells. Paratubular buds, which are outgrowths from the tubular epithelium, characterize the newborn pancreas and eventually give rise to both exocrine and endocrine units. 4 days after birth, definite intralobular ducts, acini and centroacinar cells are observed. In addition to the central expanding islets (primary islets), endocrine cells are observed singly or in small groups in the ductal epithelium. The endocrine cells are believed to originate from the terminal cells of the ductal epithelium and, throughout the entire postnatal period, retain a close association with the exocrine epithelium. With the simultaneous proliferation of both endocrine and exocrine components from the ductal system, the majority of the islets observed at 24 days (5.0 cm) appear to be surrounded by a single layer of acinar cells. As acini develop and the ducts expand toward the periphery, this layer of acinar cells separates from the developing islets, the majority of which have become localized within the centers of lobules to form the secondary islets by the 10.0-cm stage (59 days). A marked development of lobules is observed by the 13.0-cm stage and the majority of acinar cells now are filled with zymogen granules. Acinar cells continue to proliferate late into the postnatal period and the majority of acini exhibit a tubular form in the juvenile and adult opossum.

Animals↗
PubMed1978

Development of the external muscle coats in the digestive tract of the opossum, Didelphis virginiana.

Development of the external musculature of the gastrointestinal tract has been studied in the stomach, small intestine and colon of the postnatal opossum. The muscle support is thin and poorly developed at birth, especially in the stomach and small intestine where only the inner layer is completely formed. The outer layer is discontinuous and formed by scattered myoblasts. The muscularis externa of the colon at birth is considerably thicker and both layers are present. Subsequent development of the muscularis externa consists of an early period of proliferative activity followed by hypertrophy. A low rate of mitotic activity continues throughout development and into the adult. Elements of the myenteric plexus are present at birth.

Animals↗
PubMed1978

General observations on the growth and development of the young pouch opossum, Didelphis virginiana.

A 3-year study of general growth and development revealed a uniform increase in body length of young pouch opossums during the first 10 weeks of life. Throughout this period, growth was linear and constant for all animals regardless of sex, litter size, or whether animals were obtained from first, second or third litters. Body weights were somewhat more variable, but there were no significant sex differences. Various aspects of external gross morphology are presented and discussed as they relate to growth of the young opossum.

Animals↗
PubMed1978

Postnatal development of the epidermis in a marsupial, Didelphis virginiana.

At birth the epidermis of the opossum is 43 micron thick and consists of a basal layer of columnar cells, an intermediate layer of fusiform cells, a layer of incompletely cornified cells and a single surface layer of cells (the periderm). The latter shows central nuclei and distinct cell boundaries. Adjacent surface cells. are contiguous and show extensive interdigitations of the lateral cell membranes. The periderm is lost during the first week of postnatal development. The epidermis attains its greatest thickness (58 micron) at the 4.0 cm stage (18 days postnatum), and this is due primarily to an increase in thickness of the spinous layer. After this the epidermis thins to 14 micron in the adult. The epidermis of the adult consists of a thin Malphighian layer and a desquamating cornified layer. Hair follicles begin to differentiate at the 2.5 cm stage (7 days postnatum). They continue to differentiate and develop while the epidermis is increasing, and then decreasing, in thickness. The young are fully furred prior to the time they first venture from the protection of the pouch.

Animals↗
PubMed1978

Postnatal development and differentiation of the opossum submandibular gland.

The postnatal development and differentiation of the submandibular salivary gland has been examined in sixteen groups of young opossums. At birth the glandular elements, dispersed in loose connective tissue, consist only of ducts that are immature in appearance and of irregular secretory end-pieces. Development occurs in two phases, the first from birth to approximately 31 days postnatum, and the second thereafter. During the first phase the ductular elements show separation into intercalated and intralobular ducts, and attain structural maturity. The larger ducts are concentrated centrally within each lobule and lie in a markedly vascular connective tissue. The secretory end-pieces, initially acinar in form, are lined by proacinar cells which exhibit intercellular canaliculi at the lateral cell membranes and a few dense granules in the apical cytoplasm. During the second phase of development extensive changes occur within the secretory end-pieces, which elongate to form a system of branching tubules. Component cells show an increased granular content, and those in the main body of the tubules differentiate into mucous cells. By 34 cm postnatum the proacinar cells in the bulbous endings of the tubules are replaced by special serous cells possessing intercellular canaliculi and secretory granules which are either electron-lucent or electron-dense. The sequence of changes that occur during postnatal development is discussed and related to possible functional activities. The early development of the ducts may be correlated with their role in homeostasis, while the later development of secretory tubules and the differentiation of secretory cell types may be related to the onset of weaning, and may possibly be induced by this major change in dietary habit.

Age Factors↗
PubMed1977

The postnatal development of the alimentary canal in the opossum. III. Small intestine and colon.

The duodenum of the newborn opossum exhibits a patent lumen containing scattered elongate villi, whereas the distal segments of the small intestine are smaller in diameter and are filled with short immature villi. The muscularis externa through the small intestine consists of a single layer of myoblasts. Interposed between the intestinal lining epithelium and the muscularis externa is an extensive capillary bed that occupies a considerable proportion of the intestinal wall. Additional villi appear to form during the postnatal period as a result of evaginations of the epithelium, together with underlying connective tissue and vasculature, into the intestinal lumen. Intestinal glands are not observed until 8.5cm, and are shallow in depth even in the adult. The epithelium of the entire small intestine is modified for absorption until just prior to weaning. The principal intestinal lining cells show an extensive apical endocytic complex, large supranuclear vacuoles and numerous cytoplasmic inclusions. Intestinal epithelial cells of the colon also appear to be modified for absorption during the first two weeks after birth. Although goblet cells and Paneth cells are present during the suckling period, they do not comprise a significant population in the intestinal epithelium until after weaning. In contrast to the small intestine, goblet cells are numerous in the colon by the ninth postnatal day. The significance of macromolecular absorption and the possibility of passive immunity being transmitted in the opossum during suckling are discussed and related to similar events that occur in the slckling young of several eutherian species. The possible functional significance of two large membranes that develop in the lamina propria of the intestines after weaning also is discussed.

Animals↗
PubMed1976

Type II pulmonary epithelial cells of the newborn opossum lung.

The air chambers of the newborn opossum are lined by a respiratory epithelium which appears similar to that lining alveoli of other species. The type II pulmonary epithelial cell is cuboidal in shape, shows apical microvilli, several Golgi complexes, lipid droplets, and numerous cytosomes. The cytosomes contain osmiophilic lamellae and are similar in appearance to whorls of osmiophilic material lying free within the alveolar lumina and on the surface of the respiratory lining epithelium. In the newborn opossum lung, examination of the air chambers with the scanning electron microscope permits the observation of several type II pulmonary epithelial cells in a single field. The potential use of the air chamber of the newborn opossum as an experimental model is suggested.

Animals↗
PubMed1976

The postnatal development of the alimentary canal in the opossum. I. Oesophagus.

The oesophageal epithelium of the newborn opossum generally is two to three cells in depth and in some regions appears pseudostratified. By the 9th postnatal day the epithelium shows two distinct strata. Ciliated cells and occasional goblet cells also are observed within the epithelium during this stage and in subsequent stages. Cilia persist in the oesophagus of the adult opossum, but are restricted to the depths of the transverse folds found in the distal part of the organ. The epithelium covering the transverse folds of the adult likewise has an immature appearance. By 4-5 cm (ca. 20 days), the epithelium has assumed a more mature appearance and is of greater depth. This and later stages show three basic strata: a germinal layer, a spinous layer and, adjacent to the lumen, a flattened layer of cells that retain their nuclei. The epithelium throughout the postnatal period and in the adult does not undergo complete keratinization. The oesophageal glands begin as outgrowths from the epithelium just prior to 4-5 cm (ca. 20 days). The glands continue their development throughout the remainder of the postnatal period. The secretory units of the oesophageal glands of the the major portion of the secretory elements, and a light, rounded cell type which is less numerous and which occupies the terminal portions of the secretory units. Secretory material of the former appears complex, consisting of both neutral and acid glycoproteins. The secretory product of the light cell type is unknown at present. Both cell types are encompassed by myoepithelial cells. The relationship of the mitotic sequences to the observations made by microscopic examination of the developing oesophagus is discussed.

Animals↗
PubMed1976

The postnatal development of the alimentary canal in the opossum. II. Stomach.

The postnatal development of the gastric mucosa in the opossum has been traced with the light, transmission and scanning electron microscopes. The formation of fovea and gastric glands occurs simultaneously during the postnatal period. During the first 60 postnatal days the developing gastric glands are composed of undifferentiated cells, parietal cells and scattered endocrine cells. Chief cells are not present until just before weaning (13 cm, i.e. ca. 75 days). Juvenile and adult animals show only a small population of chief cells, and these are confined to the bases of the gastric glands. The pH of stomach contents ranges from 6-0 to 6-5 until the time of appearance of solid food within the stomach, when it drops to 2-0-2-5. The surface cells lining the gastric lumen contain a considerable amount of what appears to be lipid during the first 3 weeks after birth, and this may indicate that the gastric mucosa is involved in the absorption of lipid during this period. The mode of lipid absorption appears to be different from that described for the intestinal tract of several other species.

Animals↗
PubMed1975

The postnatal development of the liver in a marsupial, Didelphis virginiana. 2. Electron microscopy.

The postnatal development of the liver has been examined with the electron microscope in 15 groups of young opossums. At birth, hepatic cells show little organization and large islands of haemopoietic elements occur between clusters of hepatic cells. Hepatocytes appear small and contain an abundance of granular endoplasmic reticulum. The cytoplasm is also characterized by scattered lipid droplets of varying sizes. Canaliculi occasionally are found between hepatocytes. Only a few scattered lining cells are found in relation to the sinusoids and extensive areas appear to lack a lining endothelium. By the 9th postnatal day large accumulations of glycogen are present in the majority of hepatic cells and large areas of the sinusoids remain devoid of a lining endothelium. Glycogen and lipid droplets remain abundant in hepatocytes of the 15 day old opossum and later stages. By the 69th postnatal day, hepatocytes are relatively mature in appearance and the principal cytological features appear similar in this and subsequent stages. The cytoplasm is characterized by the presence of glycogen, granular endoplasmic reticulum and numerous small, spherical mitochondria. A heterogeneous population of hepatic cells was noted in the majority of stages examined. This ultrastructural study confirmed the tendency for haemopoietic cells to remain in discrete foci of like kind, both with regard to cell lineage and stage of maturation.

Animals↗
PubMed1975

Megakaryocytopoiesis in the liver of the developing opossum (Didelphis virginiana).

The development of hepatic megakaryocytes has been examined in the livers of 35 young opossums at four different stages of postnatal development. Megakaryocytopoiesis is carried out within the sinusoidals and there appears to be a close relationship between the young megakaryocytes and the sinusoid lining cells. Megakaryocytes in the opossum are relatively small and lack the degree of nuclear complexity seen in other species. Both the nucleus and the cytoplasm undergo sequential maturational changes but, in the newborn especially, these sequences are not necessarily interrelated and there is a rapid cytoplasmic differentiation to provide for early platelet release. A scheme for the maturation of the hepatic megakaryocytes is presented.

Animals↗