Biomedical subjects

D M Denbow

Publications and source records attributed to D M Denbow.

At least 91 records · Page 5Linked to original sources

PubMed1986

Food intake in the domestic fowl: effect of intrahepatic lipid and amino acid infusions.

Five experiments were conducted to determine the effect of hepatic and jugular infusions of amino acid and lipid solutions on short-term food intake of cockerels. Neither jugular nor hepatic infusions of amino acids had any effect on food intake of Single-Comb White Leghorn (SCWL) cockerels. Lipid infusions had no effect on SCWL cockerels when administered intrajugularly but decreased food intake significantly when infused intrahepatically. In contrast, no effect on food intake was observed when Rock-Cornish (RC) cockerels were infused intrahepatically with lipid. Thus, it appears that the liver of the SCWL cockerel is not responsive to plasma amino acid concentrations but is sensitive to circulating lipid levels. This lipid sensitive mechanism may be important in the peripheral control of food intake in a chicken such as the SCWL which has been bred for egg production but may be desensitized in fowl such as the RC broiler which has been selected for large body size and feed consumption.

Amino Acids↗

PubMed1986

Selection for growth alters the feeding response to injections of biogenic amines.

Two experiments were conducted to determine if selection for growth altered the response to intracerebroventricular (ICV) injections of methoxamine and 5-hydroxytryptamine (5-HT). Lines of chickens divergently selected over 25 generations for 8-week body weight were used. The ICV injection of methoxamine into fully fed birds significantly increased food intake in the high-weight line but had no effect on food intake in the low-weight line. Conversely, the ICV injection of 5-HT had no effect in fully fed birds but significantly decreased food intake in 24-hr fasted birds in both weight-lines. Food intake was affected by 5-HT for a much longer period in the high-weight line than in the low-weight line. These results suggest that selection for growth alters the brain response to biogenic amines.

Animals↗

PubMed1986

alpha-Melanocyte-stimulating hormone infused ICV fails to affect body temperature or endotoxin fever in the cat.

Permanent cannulae for intracerebroventricular (ICV) infusion were implanted bilaterally in cats following stereotaxic procedures. After colonic temperature was recorded for a one-hour baseline, a 300 microliter ICV infusion was given of CSF control vehicle, 1:100 dilution of W3110 E. coli endotoxin (10(8) organisms/ml) or alpha-melanocyte-stimulating hormone (alpha-MSH) in one of seven doses ranging from 50.0 ng to 50.0 micrograms. Whereas ICV E. coli always induced an intense and prolonged fever of rapid onset, alpha-MSH infused similarly was essentially without effect on the deep body temperature of the normothermic cat. When each of the doses of alpha-MSH was infused ICV, either during the rising phase of an E. coli fever or after the febrile response had reached its asymptote, the core temperature of the cat was unaffected. Similarly, a mixture of E. coli combined with alpha-MSH given ICV failed to alter the characteristics of the rapidly developing fever produced in the cat by this endotoxin. On the other hand, either excess Ca++ ions (50 mM) given ICV or the antipyretic drug. Dipyrone, administered systematically during the course of an endotoxin fever effectively attenuated the animal's elevated body temperature. These results demonstrate that alpha-MSH is apparently neither involved in the central mechanisms underlying normal thermoregulation, nor does it act as an endogenous antipyretic in the cat as has been postulated in another species.

Animals↗

PubMed1986

CCK and other peptides modulate hypothalamic norepinephrine release in the rat: dependence on hunger or satiety.

The purpose of this investigation was to determine the functional relationship between putative satiety peptides and endogenous norepinephrine (NE) activity in the hypothalamus. Permanent guide cannulae for push-pull perfusion were implanted stereotaxically in Sprague-Dawley rats so as to rest above the medial or lateral hypothalamus (LH). Post-operatively, the animals were either satiated with food and water, both available ad lib, or fasted for 18-22 hr prior to an experiment. To perfuse a site in the LH, paraventricular (PVN) or ventromedial nucleus (VMN), a concentric 29-23 ga push-pull cannula system was lowered to a pre-determined site, in most cases after catecholamine stores had been pre-labeled with [3H]-NE. During control tests, an artificial CSF was perfused at a rate of 20-25 microliter/min for 5-8 min with a 5 min interval between each sample. The addition of cholecystokinin (CCK) in a concentration of 2.0-6.0 ng/microliter to the CSF perfused in PVN or VMN of the satiated rat enhanced the efflux of NE; however, in the fasted animal CCK often suppressed the catecholamine's release. Perfused in the LH, CCK exerted opposite effects, typically augmenting NE output when the rat was fasted but not affecting the amine's activity during the sated condition. Proglumide (1.2 micrograms/microliter) attenuated CCK's effect in releasing NE when the antagonist was perfused in the PVN of the satiated rat. Similar experiments in which neurotensin (NT) was perfused in the LH, PVN and VMN revealed virtually the same inverse effects on NE release in the fasted and satiated rat, which again were anatomically specific. Finally, insulin and 2-deoxy-D-glucose (2-DG) exerted similar state-dependent effects on the release of NE within LH and PVN. Overall, the results suggest that CCK or other neuroactive peptide could serve as a "neuromodulator" of the pre-synaptic release of NE within classical hypothalamic structures which are thought to underlie both hunger and satiety. The state-dependent nature of the peptides' activity on the noradrenergic feeding mechanism implies that these substances constitute a pivotal portion of the profile of factors which impinge functionally upon the hypothalamic neurons responsible for the feeding response and its cessation.

Animals↗

PubMed1986

Pressor responses to central hypertonic NaCl stimulation in conscious turkeys.

The purpose of this investigation was to examine the possible involvement of the central renin-angiotensin system in the pressor response to the intracerebroventricular (icv) injection of hypertonic NaCl in conscious turkeys. The icv injection was accomplished via a stereotaxically implanted stainless steel guide cannula in the lateral cerebral ventricle. The arterial blood pressure (AP) of the turkey was measured by means of a PE catheter in the left brachial artery. The icv administration of hypertonic NaCl caused a dose-dependent increase of AP. The mean AP increases due to 10-microliter icv injections of 0.9, 3.6, and 7.2% NaCl were 1.4 +/- 1.4, 18.1 +/- 3.0, and 31.2 +/- 3.2 (SE) mmHg, respectively. These changes were statistically significant (P less than 0.001). The icv administration of captopril, [Sar1, Ile8]angiotensin II, or pentobarbital sodium markedly reduced the pressor response to the icv injection of hypertonic 7.2% NaCl. Blockade of central adrenergic receptors with phentolamine and propranolol was without effect. These results support the contention that the central renin-angiotensin system may directly contribute to pressor responses induced by central hypertonic NaCl stimulation.

Anesthesia↗

PubMed1986

Reduced food intake following intracerebroventricular administration of a low molecular weight fraction of plasma from free-feeding fowl.

Plasma was collected from free-feeding Leghorn cockerels and partitioned by gel filtration into fractions of different molecular weight ranges. The individual fractions were then lyophilized and reconstituted to four times the original concentration. The plasma was administered to 10-week-old Leghorn cockerels via a stainless steel guide cannula, stereotaxically implanted into the lateral cerebral ventricle. Sated cockerels received 10 microliters intracerebroventricular (ICV) injections of one of the concentrated plasma fractions or of a control injection of artificial cerebrospinal fluid. Food and water intake were monitored following injection. Food intake was significantly decreased by the ICV injection of plasma fractions less than 1500 mol wt, whereas water consumption was not significantly different from that of the controls. The 1500 to 5000 mol wt fraction and the fraction above 5000 did not alter either food or water intake. These results suggest that the plasma of free-feeding domestic fowl contains a low molecular weight factor that is involved in the regulation of food intake.

Animals↗

PubMed1986

Intraduodenal glucose infusions do not affect food intake in the fowl.

A series of experiments was performed to examine the role of the duodenum in food intake regulation in the fowl. In each of the experiments, birds were surgically fitted with intraduodenal cannulae. In Experiments 1 to 6, Single Comb White Leghorn (SCWL) or Rock Cornish cockerels were infused with isosmotic glucose, urea, or saline solutions. Glucose had no effect on food intake as compared with the saline and urea control treatments. In the final experiment, food intake of splanchnicectomized SCWL cockerels was contrasted to that of sham-operated controls, following intraduodenal glucose infusions. No difference between the denerved and intact birds was observed. The duodenum of the fowl, unlike the mammal, does not appear to play a significant role in food intake regulation.

Animals↗

PubMed1986

Intraperitoneal injections of tryptophan inhibit food intake in the fowl.

The effects of intraperitoneal injections of tryptophan on food intake in the chicken were examined. Four levels of tryptophan (12.5, 25, 50, 100 mg), and a saline control were tested in birds that were ad libitum fed or fasted 24 hr. The tryptophan treatments decreased food intake in the ad libitum-fed chickens in a dose-dependent manner. Food intake of the 24-hr fasted chickens was not influenced by the tryptophan injections. It is not known whether tryptophan is acting centrally or peripherally to decrease food intake of ad libitum-fed chickens.

Animals↗

PubMed1986

Avian cerebrospinal fluid: repeated collection and testing for a possible role in food intake regulation.

The objective of this study was to determine if a factor(s) involved in the regulation of food intake exists in the cerebrospinal fluid (CSF) of the domestic fowl. A technique was developed that allows blood-free CSF samples to be collected repeatedly from the cisterna magna for up to 6 weeks. Using this technique, CSF was collected from free-feeding and 24-hour fasted broiler cockerels and injected into the lateral cerebral ventricle of 8-week old Leghorn cockerels and 4-week old broiler cockerels. The free-feeding birds received 10 microliter intracerebroventricular injections of CSF either at normal concentration (1 X -CSF) (Experiments 1 and 3) or at four times normal concentration (4 X-CSF) (Experiments 2 and 4). Artificial CSF served as the control. Food and water consumption were monitored following injection. The 1 X- and 4 X-CSF collected from both the free-feeding and 24-hour fasted donors did not affect the food intake of either the Leghorn or the broiler recipients. Water intake, however, was significantly increased in the Leghorns and broilers receiving the 4 X-CSF collected from 24-hour fasted birds. Thus, there does not appear to be a factor(s) present in the CSF collected from the cisterna magna that alters food intake when injected into the lateral ventricle, but a factor may exist in the CSF collected from fasted donors that stimulates water intake.

Animals↗

PubMed1986

Tryptophan's influence on feeding and body temperature in the fowl.

The neurotransmitter, serotonin, has been implicated in both food intake and body temperature regulation. In this experiment, the effect of tryptophan, the amino acid precursor of serotonin, on food consumption and rectal temperature in the fowl was determined. Single Comb White Leghorn cockerels were intubated with a tryptophan solution or distilled water. Tryptophan significantly (P less than or equal to .05) decreased both food intake and body temperature of the birds. These results suggest that tryptophan may inhibit food intake via peripheral rather than central mechanisms.

Animals↗

PubMed1986

The influence of prolactin on food intake of turkey hens.

The effect of intracerebroventricular (ICV) injections of turkey prolactin on food intake of turkey hens was studied. Adult, nonlaying medium-weight turkey hens, exposed to 6 hr of light per day, were used in Experiment 1. In Experiments 2 and 3, medium-weight and large-weight turkey hens, respectively, exposed to a long photoperiod and in production, were used. Prolactin was injected into free-feeding hens at doses ranging from 800 to 3200 ng. The ICV injection of prolactin had no significant effect on food intake of hens maintained under 6 hr light per day and not in egg production. In hens exposed to long photoperiods and in egg production, the ICV injection of prolactin caused a significant decrease in food intake. These results suggest that prolactin, acting at the level of the central nervous system, decreases food intake in photostimulated turkey hens.

Animals↗

PubMed1986

Salinomycin toxicity in turkeys.

Five 7-day trials using 336, 24, 24, 40, and 40 Large White male turkeys when 7, 11, 15, 27, and 32 weeks of age, respectively, were conducted to determine the toxic effects of salinomycin. Salinomycin became more toxic as the age of the turkeys increased. When 7-week-old turkeys were fed diets containing 44 or 66 ppm salinomycin, only 1 of 84 died; when turkeys 27 or 32 weeks of age were fed those amounts, 13 of 20 died. Salinomycin at 22 ppm tended to depress rate of growth at young ages and to prevent or decrease growth and to increase mortality at older ages. Caution should be exercised to avoid salinomycin contamination of turkey diets.

Animals↗

PubMed1986

Influence of hatcher holding times on several physiological parameters associated with the immune system of chickens.

Two experiments were conducted with broiler chicks to study the effects of posthatch holding time in the incubator on physiological and disease parameters. In each experiment, half of the chicks were removed shortly after hatching and half of the chicks were allowed to remain in the hatcher for an additional 30 hr. Bursa weights, hematocrits, total plasma protein, and blood glucose concentrations were measured at various times up to 35 and 28 days of age in Experiments 1 and 2, respectively. In addition, chicks hatched from eggs with one of two specific gravities (less than or equal to 1.065 and greater than or equal to 1.075) were tested in the second experiment. Spleen weights, heterophil:lymphocyte ratios and the influence of an aerosol Newcastle disease-Mycoplasma gallisepticum vaccine challenge were also measured in the second experiment. In Experiment 1, when chicks were held in the hatcher for an additional 30 hr, bursa weights were reduced through 8 days of age; however, they were significantly heavier by 21 days of age. In Experiment 2, both bursa and spleen weights were significantly reduced through 14 days of age when chicks were held in the incubator. Total plasma protein and glucose concentrations, hematocrits, and heterophil:lymphocyte ratios were all significantly higher for chicks held in the incubator. Chicks held in the incubator and then exposed to an aerosol vaccine challenge at 1 day of age had a significantly greater percentage of air sac lesions and the lesions were more severe at 28 days of age. Egg specific gravity had no influence on any of the parameters measured.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1985

Effect of the ovulatory cycle on oviductal sperm storage in the domestic fowl.

Anovulatory domestic hens (pregnant mare serum-treated) and normally cyclic domestic hens were artificially inseminated with 0.034 ml of pooled semen. A subsequent microscopic assessment of the uterovaginal sperm storage glands on days 1, 3, 6, 9 and 12 post-insemination indicated that the sperm glands emptied over time in the normally cyclic hens, but not in the anovulatory hens. The data suggest that events associated with ovulation and/or oviposition are important to the sperm gland emptying process.

Journal Article↗

PubMed1985

Food intake control in birds.

The regulation of food intake has been a topic of intense investigation for several decades. Most investigators have used the rat in such studies while considerably fewer studies have been conducted using birds. Research concerned with the control of food intake in birds is discussed herein. In most instances, birds and mammals have similar control mechanisms. The alimentary tract and the liver are peripheral structures which function in the control of feeding in birds but much remains to be studied as to their role. Many brain loci, including the lateral hypothalamus, ventromedial hypothalamus, striatum and olfactory bulbs are also involved in controlling food intake. Studies with birds have revealed marked breed and line differences in the response to factors modulating food intake. The bird appears to provide an excellent model for studies designed to investigate how selection for growth can alter the mechanisms involved in food intake control.

Amino Acids↗

PubMed1985

Behavior and growth parameters of large white turkeys as affected by floor space and beak trimming. II. Females.

The effects of floor space allowance and beak trimming on behavior and growth performance of female Large White turkeys were studied. Floor space allowances were 5.6, 7.0, and 9.3 dm2/bird from 0 to 8 weeks of age and 14.0, 18.6, and 23.2 dm2/bird from 8 to 16 weeks of age. Floor space was adjusted by changing pen size to assure a constant number of birds per pen. Results showed that neither floor space allowance nor beak trimming had any significant effect of any of the variables under study through 8 weeks of age. At 16 weeks of age, growth, feed consumption, feed efficiency, feather scores, live market quality grades, and mortality were still unaffected. Beak trimming significantly reduced body weight gain, body weight, and feed consumption but had no significant effect on feed efficiency, feather scores, or mortality. Agonistic (aggressive) behavior was very low in this population of females. Of significance, however, were the nonaggressive behaviors of social "pecking" and "pecking and pulling" of feathers. Feather-pecking activity was unaffected by previous or subsequent floor space allowances through 16 weeks of age; however, the incidence of pecking and pulling of feathers was highest among females previously assigned the largest floor space allowance (9.3 dm2/bird) in the brooder house and subsequently allowed the smallest floor space allowance (14.0 dm2/bird) in the grower house. Beak trimming significantly increased the frequency of both "pecking" and "pecking and pulling" of feathers over that of their untrimmed contemporaries when the females were 12 and 16 weeks of age. Possible reasons for this are discussed.

Aggression↗

PubMed1985

Effect of intracerebroventricular glucose injection on feeding in Leghorn chicks.

The food and water intake response of Leghorn chicks to intracerebroventricular (ICV) injections of glucose was studied. Experiments were done in both free-feeding and 24-hr fasted birds. The ICV injection of 10 microliter of glucose solutions ranging from 5.5 to 30% had no significant effect on food or water intake in free-feeding or in 24-hr fasted Leghorns. This suggests that glucose does not influence food or water intake when injected into the lateral cerebro-ventricle. This effect is discussed in relationship to recent findings showing that injection of glucose into the third ventricle decreases food intake.

Animals↗

PubMed1985

Effect of intrahepatic glucose infusions on feeding in heavy and light breed chicks.

Although food intake regulation by the central nervous system in the fowl has received considerable attention, studies examining peripheral regulatory mechanisms are relatively few. The objective of these experiments was to determine the role of the liver in short-term regulation of feeding. Small volumes of isotonic glucose were infused into the hepatic circulation of undisturbed, unrestrained Single Comb White Leghorn (SCWL) and Rock-Cornish (RC) cockerels under both free-feeding and mildly-fasted conditions. Glucose infusions significantly decreased the food intake of free-feeding SCWL chicks but had no effect on mildly-fasted SCWL chicks. The RC chicks, whether free feeding or mildly fasted, were not influenced by the glucose infusions. These findings suggest that selection for increased growth rate has affected peripheral appetite regulatory mechanisms.

Animals↗