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Biomedical subjects

J M Forbes

Publications and source records attributed to J M Forbes.

At least 73 records · Page 4Linked to original sources
PubMed1987

Effects of intraportal infusion of glucose and lysine on food intake in intact and hepatic-vagotomized chickens.

Cockerels of a laying strain were prepared at 16 weeks of age with catheters whose tip lay in the hepatic portal vein, to study the effect of 3-h infusions of nutrients into the liver on food intake. L-Lysine (300 mg) and D-glucose (1.26 mg) reduced food intake by up to 25 and 24% respectively when infused into the portal vein and gave an additive effect (-47%) when infused together. Bilateral abdominal vagotomy prevented the reduction in food intake caused by the infusions, although when no infusion was given intakes were lower than in intact birds and the birds ate significantly fewer meals which were of a greater size. These results suggest a role for the liver in the control of food intake of the domestic fowl, with the vagus nerves communicating between this organ and the central nervous system.

Afferent Pathways↗
PubMed1987

Effects of infusions of lysine, leucine and ammonium chloride into the hepatic portal vein of chickens on voluntary food intake.

1. Adolescent cockerels of a laying strain were prepared with catheters whose tip lay in the hepatic portal vein, to study the effect of 3-h infusions of nutrients on food intake. 2. Lysine, infused into the hepatic portal vein at rates of 150-450 mg/3 h reduced 3-h food intake by up to 58%, for a period of 6 h in previously starved birds, but had no effect on birds allowed free access to food. Infusions made into the jugular vein had no effect, suggesting a role for the liver in monitoring lysine levels. 3. Portal infusion of leucine had a delayed effect while ammonium chloride, infused at isosmolar rates to those of the lysine infusions, had very little effect on intake. 4. The results support the concept of liver sensitivity to amino acids, but the mode of action is not clear; it appears not to be via the effects of ammonia.

Ammonium Chloride↗
PubMed1987

Stimulation of food intake and growth of chickens by cyproheptadine: lack of interaction with the effects of pinealectomy and melatonin.

Cyproheptadine stimulates food intake and growth in some species of mammal; its effects are reported here in chickens. Growing cockerels of an egg-laying strain were given 0.32 mg/d by mouth, which resulted in significant increases in weight gain and food intake, including feeding during the night. Increasing daily doses of up to 1.6 mg/kg body weight stimulated intake in a dose-related manner, while 1.92 mg/kg had the same effect as 0.96 mg/kg. Neither pinealectomy, which is known to stimulate food intake, nor treatment with melatonin, which depresses intake, interacted with the effects of cyproheptadine on food intake, showing that its effect is not mediated by the pineal gland.

Animals↗
PubMed1987

Feeding responses to infusions of glucose solutions into the duodenum of cockerels and the influences of pre-fasting or vagotomy.

1. The duodenum of cockerels was chronically catheterised, to study the effects of 3 h infusions of glucose solutions on voluntary food intake. 2. Compared to water, solutions containing 30, 60 and 90 g glucose/l infused at 1 ml/min induced significant, dose-related depressions in intake after the first 30 min of infusion. 3. Fasting the birds for 3 h before the start of infusion resulted in higher intakes during the period of infusion than in unfasted birds. 4. Vagotomy at the level of the proventriculus prevented the inhibitory effects of glucose infusion into the duodenum, except at the highest concentration (120 g/l).

Animals↗
PubMed1984

Melatonin in the plasma of growing sheep subjected to short and skeleton long photoperiods.

The levels of melatonin in plasma were measured at hourly intervals for 24 h in 8 sheep, 4 under 8L:16D (short day) and 4 under 7L:10D:1L:6D (skeleton long day) after 38 days of exposure. Mean concentrations did not differ significantly between treatments (52 pg/ml under short days; 91 pg/ml for skeleton long days), but the levels were more stable during 24 h in the SD treatment. Under skeleton long days there were 3 peaks during the 10D scotophase, with low levels during the 6D scotophase and the 7L photophase.

Animals↗
PubMed1984

Effects of thyroxine on the reproductive organs and growth of young chickens.

Male chicks of an egg-laying strain were injected with 0, 1, 2 or 4 micrograms/100 g b. wt thyroxine s.c. daily from 7 to 12 weeks of age. Increasing dose suppressed testicular development and puberty was completely blocked by the highest level. Live weight gain was enhanced by thyroxine treatment. Similar treatment of females prevented normal development of the ovaries at puberty.

Animals↗
PubMed1984

The effect of short and skeleton long photoperiods on the plasma concentrations of prolactin and cortisol in sheep.

Suffolk-cross lambs, aged eight weeks, were exposed to either short photoperiods (8L : 16D, SP; 7 castrated males and 6 females) or skeleton long photoperiods (7L : 10D : 1L : 6D, SLP; 6 castrated males and 7 females). They were fed individually on a complete pelleted diet at 70 g/kg live weight 0.75/day. Blood samples were taken monthly by jugular puncture for three months and, after 39 days on experiment, jugular catheters were inserted for frequent sampling over a 24 h period. The samples were assayed for prolactin using radioimmunoassay and for cortisol by competitive protein binding. SLP caused a large and significant increase in plasma prolactin throughout the experiment, with no effect on sex. During the 24 h period there were consistent peaks of prolactin at the start of both dark phases under SLP, with lower levels around the start of both light phases; under SP, prolactin tended to be higher in the middle of the light phase and the middle of the dark phase than at other times. Considerable hourly fluctuations were observed in cortisol levels but an obvious 24 h rhythm was not. Mean levels were, however, significantly higher under SP (38.3 nmol/l) than under SLP (26.8 nmol/l).

Animals↗
PubMed1984

Effects on voluntary food intake of infusions of glucose and amino acids into the hepatic portal vein of chickens.

The hepatic portal veins of cockerels were catheterised to study the effects of 3-h infusions of nutrient solutions on voluntary food intake. An amino acid mixture, infused at rates up to 800 mg N/3 h, depressed intake of a standard diet in a significant linear manner (intakes with the highest dose and control: 1.6 g and 22.6 g/3 h respectively). Infusion of the highest dose into the jugular vein had a smaller and nonsignificant effect (17.2 and 25.3 g/3 h). The effects of combined infusion of amino acids and glucose into the portal vein on food intake were approximately additive.

Amino Acids↗
PubMed1984

Effect of pinealectomy on the plasma concentrations of prolactin, cortisol and testosterone in sheep in short and skeleton long photoperiods.

Two experiments were carried out to investigate the effects of pinealectomy on the responses of prolactin, cortisol and testosterone to skeleton long photoperiods (7 h light: 10 h darkness: 1 h light: 6 h darkness; 7L: 10D: 1L: 6D) compared with short photoperiods (8L: 16D) in lambs. The first experiment included 23 female Suffolk cross sheep aged 10 months, of which six were pinealectomized. The skeleton long photoperiod significantly increased plasma levels of prolactin but this was blocked by pinealectomy; there was a peak around dusk and a trough around dawn and at the time of the 1-h period of light. There was no effect of either photoperiod or pinealectomy on plasma levels of cortisol. Testosterone was not measured in this experiment. In the second experiment there were 12 intact males and 11 castrated males aged 3 months; six of the lambs in each group were pinealectomized. Prolactin was again greatly stimulated by skeleton long photoperiods and the effect was blocked by pinealectomy; there was a trough in plasma prolactin at dawn in all groups. In addition, castration increased prolactin levels on two of the four sampling days. Plasma cortisol concentrations were significantly lower under skeleton long photoperiods and this was also blocked by pinealectomy; there was no effect of castration. Testosterone was much higher in intact males. After 10 weeks of exposure, skeleton long photoperiods produced significantly lower concentrations than short photoperiods in the intact ram with pineal glands but not in those which were pinealectomized.

Animals↗
PubMed1983

Growth and food intake of intact and pinealectomised chickens treated with melatonin and triiodothyronine.

Male chickens of an egg-laying strain were used in an investigation of the effects of pinealectomy at 1 d after hatching. Pinealectomised birds killed at 28 d of age were significantly heavier than sham-operated chickens; intraperitoneal treatment of intact birds during the same period with 10 mg melatonin/kg d depressed weight gain, while 200 micrograms triiodothyronine (T3)/kg d given intramuscularly had no effect. Pinealectomized birds aged 11 weeks ate some food during the night, in contrast to intact birds, and ate significantly more food per 24 h; their short-term food intake responded to melatonin and T3 in a manner similar to that of intact birds. The electroencephalogram (EEG) of pinealectomised birds was affected to a slight degree of darkness, while in intact chickens there is a rapid and marked change in the EEG.

Animals↗
PubMed1983

Involvement of melatonin and thyroid hormones in the control of sleep, food intake and energy metabolism in the domestic fowl.

Growing male domestic fowl of an egg-laying strain were fed ad libitum and injected intraperitoneally with melatonin or intramuscularly with triiodothyronine (T3) to study the effects on sleep, food intake, blood glucose, e.e.g., oxygen consumption and carbon dioxide production. Melatonin caused a dose-related depression of food intake with sleep and aphagia lasting for 2 1/2 hr following 8 mg, drowsiness and greatly reduced intake following 4 and 2 mg and a slight reduction in food intake after 1 mg. T3 injection was followed by increased feeding within the range 50-200 micrograms. The higher dose (200 micrograms) completely prevented the effects of 10 mg melatonin injected simultaneously. Melatonin (10 mg) depressed plasma glucose levels whereas T3 (200 micrograms) elevated blood glucose. Either darkness or melatonin (10 mg) caused an increase in amplitude and a decrease in frequency of the e.e.g. Birds fasted for 3 hr before injection showed significantly lower oxygen consumption and carbon dioxide production when given melatonin (10 mg); T3 had no effect within the 4 hr period after injection and did not modify the effects of melatonin. It is postulated that the rapid effects of melatonin and T3 which were observed result from direct effects of these hormones on the central nervous system.

Animals↗
PubMed1982

18S coding sequences in amplified ribosomal DNA from Xenopus laevis oocytes are highly homogeneous, unmethylated, and lack major open reading frames.

We have used two approaches to search for sequence variants in the 18S coding region of amplified ribosomal DNA (rDNA) from Xenopus laevis oocytes. First, using clones derived from amplified rDNA, we compared the equivalent of a complete 18S coding region from two clones and short regions from two other clones with the 18S sequence previously determined from a "reference" clone. The respective sequences in all the clones were identical. Secondly, we examined greater than 60% of the 18S sequence in "pooled 18S genes" in uncloned amplified rDNA. The predominant sequence corresponded to that in the reference clone and no heterogeneities were apparent. Since many chromosomal rDNA units contribute to rDNA amplification the findings indicate that 18S coding sequences in X. laevis are largely homogeneous. The previously established sequence is the predominant one, thus providing a reliable basis for studies on 18S rRNA. Sequencing gels on uncloned amplified rDNA confirmed the absence of methylated cytosine in this DNA. The 18S sequence lacks major open reading frames.

Animals↗
PubMed1981

Changes in somatomedin-like activity and growth hormone concentrations in the plasma of the domestic fowl (Gallus domesticus).

Variations to immunoreactive growth hormone (GH) and bioassayable somatomedin-like activity (SLA) were determined in the plasma of the domestic fowl. The plasma concentrations of SLA (potency relative to a pooled serum standard) and GH were both inversely age-related in growing cockerels (Thornber 909) between 3 and 20 weeks of age (SLA, r = 0.454; P less than 0.01, GH, r = 0.548; P less than 0.01) and directly related to each other (r = 0.54; P less than 0.01). In immature birds maintained on a photoperiod of 16 h light, 8 h darkness, plasma concentrations of SLA were highest during the first hour of darkness (1.19 +/- 0.18 units/ ml (u/ml) mean +/- S.E.M., n = 6) and significantly lower 1 h after dawn (0.78 +/- 0.07 u/ml n = 6). No diurnal variations in plasma concentrations of GH were observed. Deprivation of food in two strains of chickens (Thornber 909 and broiler) significantly reduced plasma concentrations of SLA in both strains and increased plasma concentrations of GH in the Thornber strain. Re-feeding fasted Thornber chickens caused the plasma concentrations of SLA and GH to return to normal within 24 h but had no effect in broilers. Deprivation of water, which also reduces food intake, for 12, 18 and 24 h markedly reduced plasma concentrations of SLA but had no effect on plasma GH concentration in Thornber cockerels.

Aging↗
PubMed1981

Factors affecting food intake in the domestic chicken: the effect of infusions of nutritive and non-nutritive substances into the crop and duodenum.

1. Infusions of 10 g of diet mashed in 20 ml of water, increasing glucose loads and hypertonic solutions of glucose, sorbitol and KCl, were introduced into the crop of the adolescent cockerel (1.5 to 2.0 kg body weight and 12 to 20 weeks of age). All caused a significant reduction of food intake over the following 3-h period. 2. Duodenal infusions of hyperosmotic solutions of sorbitol and KCl at 3 osm significantly decreased food intake within an hour of infusion. Glucose infusion decreased intake only in birds starved for 3 h before the experiment. 3. The results are discussed in relation to the site of infusion and nutritive visceral mechanisms of food intake control. It is likely that there is a major osmotic control in the duodenum which may affect a secondary control system in the upper gastro-intestinal tract.

Animal Feed↗