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Biomedical subjects

A A Travill

Publications and source records attributed to A A Travill.

12 recordsLinked to original sources
PubMed1978

The relation of aberrant vasculogenesis to skeletal malformation in the hamster fetus.

Oral administration of teratogenic doses of retinoic acid to pregnant hamsters on day 10 of gestation is associated with dysmorphogenesis of the appendicular skeleton. During the 24 h following retinoic acid treatment, the developing limb bud vasculature was disorganized, with blood vessels encroaching on areas where mesenchymal condensation of the skeletal blastemata normally occurs. Large, branching marginal folds and endothelial cell vesiculations protruded into the blood vessel lumina. It is suggested that the vascular changes observed may affect the concurrent early development of the skeleton and contribute to the skeletal malformation seen in near-term fetuses.

Abnormalities, Drug-Induced↗
PubMed1978

Structure and carbohydrate histochemistry of the stomach in eight species of teleosts.

The histology and carbohydrate histochemistry of eight teleostean stomachs are compared. Three gross anatomical types of stomachs are described and their shapes appear to correlate somewhat with feeding habits. Each type can be divided histologically into a corpus and pylorus. Gastric glands, containing only one cell type, occur in the copora of all species, but are present in the pylori of esocids only. As a single cell can produce both enzymes and hydrochloric acid such cells may be comparable to those of amphibians but not mammals. Lamina propria and submucosa are indistinctly separated in corpora but better defined in pylori by an intervening muscularis mucosa. The arrangement of the muscularis into inner circular and outer longitudinal layers is the opposite of that seen in the esophagus. Gastric mucous cells show species variations in localization of epithelial mucosubstances, which in broad terms are recognized as sulfomucins, sialomucins and neutral mucosubstances. A piscivorous diet does not appear to demand any particular type of carbohydrate. Within the Centrarchidae, gastric pit cells vary in carbohydrate content from only neutral mucosubstance to only weakly acidic sulfomucin; two species contain both types. A positive PAS reaction on the surface of gastric epithelial cells is suggestive of a striated border and thus possibly absorptive function. The absence of stomachs in some teleosts and the evolutionary and dietary significances are discussed.

Animals↗
PubMed1978

The effect of retinoic acid on chondrogenesis in the fetal hamster tibia in vivo.

Chondrogenesis in the fetal hamster tibia was examined 24, 36 and 48 h after maternal administration of retinoic acid at a known teratogenic dose (80 mg/kg) on day 10 of gestation. Twenty-four hours after treatment the tibial chondroblasts were more closely packed with less intervening fibrillar or granular matrix than in the controls. By 36 h post treatment, an intercellular matrix containing wide clumped fibrils unassociated with matrix granules had begun to accumulate, while the condroblasts had a relatively poorly developed Golgi apparatus and smooth, non-scalloped cell outlines. Cells frequently maintained contact chondroblasts appeared similar to controls of the same age. It is suggested that the paucity and abnormality of the extracellular matrix prevents the chondroblasts from assuming their normal spatial relations with each other, resulting in a small skeletal blastema.

Abnormalities, Drug-Induced↗
PubMed1978

Gross morphology of the alimentary canal in 10 teleostean species.

The gross morphology of 10 teleostean alimentary canals was compared. Each short, tubular esophagus was connected either to a stomach or, in the agastric species, to a proximal intestinal swelling. 3 stomach types were differentiated according to their shapes, which appeared to be correlated somewhat with diet. Intestines showed variations in amount of coiling and in numbers of pyloric ceca. Ratios of gut lengths to body lengths (RGL, relative gut length) were calculated and the results of previous studies were confirmed in that the RGL of a planktivore was small, while that of an organic detritus feeder was large, and that of a carnivore fell in between.

Animals↗
PubMed1977

Structure and carbohydrate histochemistry of the esophagus in ten teleostean species.

The histology and carbohydrate histochemistry of ten teleostean esophagi were compared. Structurally, the four layers of atypical vertebrate digestive tract were consistently present. The epithelium was always stratified and in all but one species (Ictalurus nebulosus) contained taste buds. Esophageal mucous cells were not the typical goblet cells seen in other vertebrates but appeared to be of six different types, pairs of which were associated with particular families. In esocids, poorly developed mucous acini and serous monogranular cells were present. In all species, the subepithelial connective tissue was not divided into definitive lamina propriae submucosae due to the absence of muscularis mucosae. Variably present in this connective tissue region were argentophilic fibers and in esocids only, randomly dispersed striated muscle fibers. The arrangement of the muscularis was reverse to that of the general vertebrate plan. In mucous cells, three general types of epithelial mucosubstances were identified and in broad terms were recognized as sulfomucins, sialomucins and neutral mucosubstances. Morphological differences were accompained by differences in carbohydrate localization, each esophageal epithelium containing at least two different mucosubstances. However, the mucosubstances identified in each mucous cell had a profile of characteristics different in some respects from any other. Thus teleostean esophagi appear to perform an integrated diversity of functions as reflected by their complex morphology and carbohydrate histochemistry.

Animals↗
PubMed1977

The anatomical basis of clinical practice: an anatomy learning programme.

In an attempt to optimize medical students' enthusiasm to learn, rather than to be taught, 'The anatomical basis of clinical medicine: An anatomy learning programme' has been introduced into an evolving medical school curriculum. Initially, educational concepts were identified, the aims and goals clarified, then the learning process and its evaluation techniques were introduced. The programme encompasses the use of a specifically designed course guide, a weekly 35 mm topographic slide presentation, prosection by senior students and then peer-directed group tutorials under the guidance of teachers. Surgical and radiological teaching colleagues cooperate in reinforcing student understanding of the relevance of anatomical concepts and data to clinical medicine. Students are encouraged to dissect personally, use the departmental museum as a learning centre, and at any time take advantage of freely available audio-visual aids. Tutorial situations are used by the students for self-evaluation, while promotional evaluation (an honours-pass-fail system) is based on the tutors' assessments, two 'on demand' multiple choice, two laboratory identification and a final oral examination.

Anatomy↗
PubMed1976

Light and electron microscopic observations on hydrocortisone-induced cleft palate in hamsters.

Palatal histogenesis in hydrocortisone-treated hamster fetuses was studied by both light and electron microscopy. At an early stage in the hydrocortisone-affected fetuses, when the palatal shelves hung vertically on either side of the tongue, necortic changes could be seen in some of the basal epithelial cells which lay adjacent to the fragmented basal lamina. The normal looking cells lay on an intact basal lamina and were attached to the contiguous necrotic cells by desmosomes. With horizontal reorientation of the palatal shelves and their approach to the midline, cellular necrosis and fragmentation of the basal lamina increased. When compared with normal cells, the hydrocortisone-affected ones were seen to be lighter, to contain fewer ribosomes and no lysosomes. At a later stage, when midline palatal fusion was lacking, the epithelium underwent stratification and keratinization while the necrotic debris was removed by mesenchymal macrophages. It appears that the normal process of protein synthesis is inhibited following hydrocortisone administration and that this, in turn, during palatogenesis, disrupts normal cellular differentiation and the integrity of the basal lamina, which are associated with the production of a cleft palate.

Animals↗
PubMed1976

Morphogenesis of the secondary palate in normal and hydrocortisone-treated hamsters.

Fetal palate morphogenesis was studied in normal and hydrocortisone-treated hamsters. Formation of the normal palate was completed between day 12:00 and 13:00 of gestation, and during this period 8 distinct developmental stages were recognized. Following hydrocortisone administration the early stages, during which vertical-to-horizontal shelf reorientation occurs, appeared to be unaffected, but subsequent fusion between opposing shelves was inhibited. Both chronological age and fetal weight provided reliable criteria for stages of normal palatal development. Following hydrocortisone administration, however, fetal weight was a poorer indicator of stage of palate organogenesis than chronological age.

Abnormalities, Drug-Induced↗
PubMed1976

The teratogenic effects of hydrocortisone on palatal development in the hamster.

The effect of different doses of hydrocortisone, administered at various times during gestation, on the fetal hamster and its palatal development was studied. Both the frequency of cleft palate and that of resorption depended upon the dose of hydrocortisone and the time of its administration. Two peaks in the incidence of cleft palate were observed, which appeared to be due to inhibition of different events. Incidence of morphologically different types of cleft palate was related to the doses and gestational time of hydrocortisone treatment. A close association was observed between the frequency of cleft palate and fetal growth retardation and between the latter and the dose and time of drug administration. It was suggested that maternal physiology and the placental barrier may play a crucial role in cleft palate induction.

Animals↗