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Biomedical subjects

M J Gentle

Publications and source records attributed to M J Gentle.

At least 55 records · Page 3Linked to original sources
PubMed1985

The fibre spectrum of the chorda nerve in the chicken (Gallus gallus var. domesticus).

Using transmission electron microscopy, the numbers and diameters of all nerve fibres were studied in the chorda tympani nerve of the domestic fowl. The mean diameter of the whole nerve was 64.6 micron and contained 203-407 (mean 302) myelinated and 205-345 (mean 265.6) unmyelinated fibres. Of the myelinated fibres (including sheath) 95% were in the range 0.5-3 micron in diameter and 94% of the unmyelinated fibres ranged from 0.2 to 0.9 micron in diameter. After section of the facial nerve within the facial canal, there was a marked reduction in the number of myelinated fibres present in the chorda tympani nerve (range 12-160, mean 103) but a less marked reduction in the unmyelinated fibres (range 94-362, mean 223). The loss of myelinated fibres was not confined to any one fibre size whereas the loss of unmyelinated fibres was mainly in the smaller fibres (range 0.1-0.5 micron). Since facial nerve section results in degeneration of efferent fibres it would seem that a large proportion of the afferent fibres are unmyelinated.

Afferent Pathways↗
PubMed1983

Effects of food deprivation, strain, diet and age on feeding responses of fowls to intravenous injections of cholecystokinin.

This paper presents new information about inhibitory effects of intravenous injections of cholecystokinin-octapeptide (CCK-8) on feeding activity in birds, with particular reference to variation in motivational state. With increasing food deprivation (0, 1, 2 or 3 h) before injection, doses of 2 and 8 micrograms/kg CCK-8 became progressively less effective in suppressing feeding of domestic fowls. As with mammals, latency to feed was shorter, and subsequent feeding activity greater, with deprived than with undeprived birds. Fowls of broiler (meat-type) and layer strains, which have different absolute food requirements but similar relative (per kg body weight) requirements, did not differ in their feeding responses to injections of 1, 8 and 16 micrograms/kg CCK-8. Food intake of fowls fed on a diet diluted with 40% powdered cellulose was suppressed less by the same three doses of CCK-8 than that of birds fed on undiluted food. This may have been because birds with the more bulky diluted food had to spend a greater proportion of time feeding. Broiler chicks aged 2 and 6 weeks, which may have different blood-brain resistance to circulating CCK and which have different relative food requirements, did not differ in their feeding responses to injections of 2 and 8 micrograms/kg CCK-8. These results do not satisfy one of the criteria proposed for demonstrating the action of a satiety agent, that feeding should be suppressed in a consistent manner regardless of motivational state. An alternative explanation for the apparent satiating properties of CCK-8 is suggested, based on similarities in their time-course, and dependence on deprivation level, to abnormal gastrointestinal responses with similar doses of the peptide.

Aging↗
PubMed1983

Toxic effects of high concentrations of zinc oxide in the diet of the chick and laying hen.

The effects of high dietary concentrations of zinc oxide on chicks and hens were studied in four experiments. Chicks given 2000, 4000 or 6000 mg zinc/kg diet from 2 to 6 weeks of age grew poorly, many showing gizzard erosion and lesions of the exocrine pancreas. Dissecting aneurysms occurred in a few birds receiving 6000 mg zinc/kg. Pancreatic lesions were found in chicks maintained on 1000, 2000 or 4000 mg zinc/kg from 0 to 4 weeks and the two higher concentrations reduced body weight and increased the incidence of gizzard erosion. Histologically, gizzard lesions varied from excessive desquamation of epithelial cells, heterophils and erythrocytes into an abnormally spongiform koilin, to erosion of koilin, glands and pits. Pancreatic lesions could be detected only microscopically and consisted of dilation of the acinar lumina, cytoplasmic vacuolation, cytoplasmic globule formation and necrosis of the exocrine cells with interparenchymal fibrosis. Similar lesions of the gizzard and pancreas were found in hens after they had received 10000 or 20000 mg zinc/kg diet for only 4 d. Hens given 10000 mg zinc/kg for 4 d followed by a normal zinc intake for 28 d had normal gizzards and pancreata.

Aortic Dissection↗
PubMed1981

The effects of zinc deficiency on oral behaviour and taste bud morphology in chicks.

The number of beak and tongue movements was measured in chickens (Gallus domesticus) following oral stimulation with different concentrations of quinine hydrochloride (0.01 to 0.25 M), acetic acid (0.25 to 5.0 M), sodium chloride (0.5 to 5.0 M) and distilled water. The birds showed an increase in behaviour with increasing concentration up to a certain point, when the response showed no further increase. 2. Two groups of chicks, one fed on a normal diet and one fed on a diet deficient in zinc, were stimulated orally every 3 to 4 d with 0.1 ml of sodium chloride (2 M), acetic acid (2 M), quinine hydrochloride (0.1 M) and water, and the numbers of beak and tongue movements were recorded. 3. All the birds fed on the zinc-deficient diet showed significant increases in beak and tongue movements compared with the control birds. The time of onset of this increase in behaviour was variable: with quinine hydrochloride it was 3 d whereas with acetic acid, sodium chloride and water it was between 6 and 9 d. 4. The morphology of the taste buds in zinc deficiency was investigated and there was no evidence of primary or preferential involvement of the taste buds; these structures were either morphologically normal or were involved in a generalised degeneration of the epithelium. 5. The increase in oral behaviour is discussed in relation to the possible ageing of the taste cells and to the general degeneration of the oral epithelium.

Acetates↗
PubMed1981

The effects of vitamin A deficiency of oral gustatory behaviour in chicks.

1. Two groups of chicks (Gallus domesticus) were fed on a vitamin A-deficient diet for 24 d. Birds in one group, which acted as a control, were dosed orally with retinyl palmitate in corn oil, whereas the other group (experimental) was given corn oil only throughout the experiment. 2. At regular intervals birds in both groups were stimulated, orally with solutions of acetic acid, quinine hydrochloride and sodium chloride and the number of beak and tongue movements counted. 3. By the end of the experiment the vitamin A-deficient birds showed a significant decrease in their response to the oral stimulants compared with the control birds.

Acetates↗
PubMed1979

Effects of water temperature on short-term water intake and medullary neuronal responses in the hen.

1. The daily water intake of adult Brown Leghorn hens was measured at water temperatures of 0, 10, 20, 30, 40 and 45 degrees C. The electrical activity of neurones in the nucleus ventro-lateralis anterior solitarii (NVLAS) of the medulla was also measured when the mouth was stimulated with water at the same temperatures. 2. There was a significant decrease in water intake when the temperature of the water was 10 or 45 degrees C. 3. There was an increase in activity of some of the NVLAS neurones with decreasing water temperature and this activity was in response to specific "cold" receptors. 4. Some NVLAS neurones were identified which showed an increase in activity at temperatures of 45 degrees C and more; it was concluded that these represented responses to thermal pain. 5. It is concluded that the effects of temperature on water intake may in part be explained by the behaviour of the oral receptors.

Animals↗
PubMed1976

Using arousal changes in the EEG to indicate gustatory sensitivity following brain lesion in Gallus domesticus.

The EEG of Gallus domesticus was recorded before and after brain lesions following stimulation with light, sound and taste. 2. It was found that under the conditions of the experiment the lesions did not have any general effect on the arousal mechanism of the animal. 3. Bilateral lesions in the stratum cellulare externum of one animal had a specific effect on the arousal response to a quinine hydrochloride solution and it was concluded that it is possible to indicate deficits following brain lesion in the gustatory system using the EEG.

Acoustic Stimulation↗
PubMed1976

Effects of dietary dilution with fibre on the food intake and gut dimensions of Japanese quail.

Japanese quail (Coturnix coturnix japonica) were fed on either a conventional diet (low-fibre) or the same diet diluted with 200 g oak sawdust/kg (high-fibre). The lengths of the colo-rectum, small intestine, two caeca combined and empty gizzard weight were measured at 10 and 20 weeks of age. Food intake and rate of passage were measured and an approximate measure of digestibility was also made. 2. There were separate effects of dietary fibre, sex and age on gut size. It was larger in birds fed on high-fibre diet, in females and in older birds. 3. Increased dietary fibre caused increased food intake, but had no obvious effect on the rate of passage. 4. When quail were fed on the low-fibre diet or the same diet diluted with 200 or 400 g cellulose powder/kg gut size at 20 weeks of age was greatest when the most fibrous diet was fed and decreased concomitantly with dietary fibre concentration. 5. It appeared that differences in gut size between dietary treatments were more a reflection of variations in food intake than of fibre per se, and that the effects of sex and age on gut size were probably similarly explained.

Animal Feed↗
PubMed1976

Changes in food intake and gut size in Japanese quail in response to manipulation of dietary fibre content.

Adult Japanese quail (Coturnix coturnix japonica) which had been fed, since hatching, on either a conventional diet (low-fibre) or on the same diet diluted with 200 g oak sawdust/kg (high-fibre) took 8 to 10 d to adjust their food intake when their diets were interchanged. 2. Those fed on high-fibre weighed less than those fed on low-fibre diet, and body weight changed rapidly when the diets were interchanged. All the birds digested about the same weight of nutrients in a day, irrespective of diet, and this suggests that body weight differences were due mainly to differences in energy utilisation, birds fed on high-fibre diet having to expend more energy on feeding than those fed on low-fibre diet. 3. Gut size was greater in birds fed on high-fibre diet, presumably to accommodate the greater bulk of food eaten, and when the diets were interchanged the gut dimension of both groups changed at similar rates, reaching the appropriate sizes for the respective diets in 3 to 4 weeks.

Animal Feed↗
PubMed1975

The effect of dietary dilution on the intestinal anatomy of the Japanese quail (Coturnix coturnix japonica).

There was an increase in the length of the small intestine, caeca and colon when Japanese quail (Coturnix coturnix japonica)were fed on a diet diluted with fibre. No differences were found in the length of the villi and the thicknesses of the submucosal layers throught the large and most of the small intestine between birds fed on the normal diet compared with those fed on the diluted diet. The birds fed on the normal diet appeared to have more mucous goblet cells and lymph nodes in the caeca than those fed on the diluted diet.

Animals↗