PubMed Health⌕ Search

Biomedical subjects

D V Rayner

Publications and source records attributed to D V Rayner.

At least 37 records · Page 2Linked to original sources
PubMed1995

Acute cold-induced suppression of ob (obese) gene expression in white adipose tissue of mice: mediation by the sympathetic system.

The effect of acute exposure to cold on the expression of the ob (obese) gene, which encodes a protein that plays a critical role in the regulation of energy balance and body weight, has been examined in epididymal white adipose tissue of mice. Overnight (18 h) exposure of mice to a temperature of 4 degrees C led to the disappearance of ob mRNA in epididymal white fat, and subsequent studies showed that a cold-induced loss of ob mRNA could occur in as little as 2-4 h of exposure to 4 degrees C. When mice exposed to cold for 18 h were returned to the warm (24 degrees C), there was a rapid stimulation of the expression of the ob gene, the mRNA returning within 2.5 h. Administration of noradrenaline led to a reduction in the level of ob mRNA in mice maintained in the warm, while isoprenaline resulted in the disappearance of the mRNA; these changes in ob mRNA were paralleled by similar changes in lipoprotein lipase mRNA. In contrast to white fat, the level of lipoprotein lipase mRNA in brown adipose tissue was increased by noradrenaline and isoprenaline. It is concluded that there is a cold-induced suppression of ob gene expression in white adipose tissue of mice and that this is mediated primarily by the sympathetic system. The profound effect of cold on ob gene expression indicates that the ob system relates to energy expenditure, as well as to satiety.

Adipose Tissue↗
PubMed1995

Effects of fasting and refeeding on ob gene expression in white adipose tissue of lean and obese (oblob) mice.

A 33-mer antisense oligonucleotide has been utilized as a probe for the rapid chemiluminescence-based detection of ob (obese) mRNA. Expression of the ob gene was evident in several white adipose tissue depots of mice (epididymal, highest; subcutaneous and omental, lowest), but not in other organs. Fasting (24 h) induced a substantial fall in ob mRNA in the epididymal fat of lean mice, which was rapidly reversed on refeeding, responses consistent with the putative role of ob in energy balance. Fasting had no effect, however, on ob mRNA levels in obese (oblob) mice.

Adipose Tissue↗
PubMed1995

Rapid chemiluminescent detection of mRNAs on northern blots with digoxigenin end-labelled oligonucleotides.

A simplified, nonradioactive procedure for the detection of specific mRNAs on Northern blots has been developed, utilizing digoxigenin-labelled oligonucleotides and chemiluminescence. Antisense oligonucleotide (30-35 mer) probes were designed and synthesised based on published cDNA and gene sequences. These probes were end-labelled (5') with digoxigenin. Total RNA was fractionated by agarose gel electrophoresis and capillary blotted onto positively charged nylon membranes. After hybridization, the mRNA/digoxigenin-labelled oligonucleotide complex was detected by a chemiluminescence-based method using disodium 3-(4-methoxyspiro-[1,2-dioxetane-3-2'(5'chloro)- tricyclo[3.3.1.13.7]decane]-4-yl)phenyl phosphate (CSPD) as substrate. The advantages of this simplified technique for detecting mRNAs in physiological and nutritional studies are described.

Animals↗
PubMed1995

Control of gastric emptying in the pig: influence of cholecystokinin, somatostatin and prokinetic agents.

The influence of systemic arterial infusions of cholecystokinin octapeptide (CCK8) and somatostatin, and injections of cisapride, metoclopramide and atropine on gastric emptying were studied in eight pigs. Gastric emptying of dry matter (DM) and liquids (Cr-EDTA as marker) was measured, in pigs fitted with a gastric cannula, by evacuation of gastric contents either immediately after the pigs had finished feeding, or 3 h after being fed a meal containing 1200 g of a finely ground barley diet mixed with 2.41 water. Gastric emptying of DM and liquids during the feeding period was not significantly altered by cisapride (0.15 and 0.3 mg kg-1-1), metoclopramide (0.2 mg kg-1), CCK8 (250 ng kg-1 h-1) or somatostatin (1.8 and 4.5 micrograms kg-1 h-1); atropine (0.06 mg kg-1) slowed emptying of DM (by 53 +/- 6%; P < 0.001) and of liquids (by 51 +/- 7%, P < 0.01). In contrast, the amount of DM emptied within 3 h of feeding was significantly reduced with CCK8 (250 ng kg-1 h-1; by 14 +/- 3%, P < 0.001) and with somatostatin (1.8 microgram kg-1 h-1; by 10 +/- 4%; P < 0.001). There was no increase in emptying of DM or liquids with cisapride or metoclopramide; indeed, there was actually a reduction in liquid emptying (by 13 +/- 6%; P < 0.05) with cisapride (0.3 mg kg-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Chemiluminescent detection of mRNAs on northern blots with digoxigenin end-labeled oligonucleotides.

To establish a simplified, nonradioactive approach for identifying mRNAs on Northern blots, antisense oligonucleotides have been used as probes in combination with chemiluminescence-based detection. Oligonucleotides (approximately 32-mer) were end-labeled with digoxigenin (DIG) and used in conjunction with adamantyl 1,2-dioxetane aryl phosphate substrates (Lumigen PPD and CSPD). Oligonucleotides were designed as probes for several mRNAs in tissues of rats and mice, including the mitochondrial uncoupling protein, lipoprotein lipase, GLUT1, GLUT4, and beta-actin. Uncoupling protein mRNA was detected in total RNA from brown adipose tissue with a 32-mer DIG-labeled oligonucleotide, within 2 min of exposure to film. This mRNA could also be detected when as little as 250 ng of total RNA was applied to the gel, following 4 h exposure to film, and was present only in brown fat. The mRNA for lipoprotein lipase was detectable with a 30-mer DIG-labeled oligonucleotide in 1 micrograms of total RNA from mouse heart, within 2 h of exposure. The mRNA for the GLUT1 glucose transporter was detected in total RNA from rat midbrain using a 32-mer DIG-labeled oligonucleotide, while beta-actin mRNA was detected with a 30-mer oligonucleotide. The mRNA for the insulin-sensitive glucose transporter GLUT4 was detected with a 32-mer DIG-labeled oligonucleotide and found only in those tissues in which glucose uptake is stimulated by insulin. The speed of detection was greater with CSPD and was augmented by exposure of membranes to film at 37 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Actins↗
PubMed1994

Glucose transporters (GLUTs 1-4) and their mRNAs in regions of the rat brain: insulin-sensitive transporter expression in the cerebellum.

Major regions of the rat brain have been examined for the presence of glucose transporters (GLUTs 1-4) and their mRNAs. Both the mRNA and immunoreactive protein for GLUT1 and GLUT3 were found in each brain region (medulla, pons, cerebellum, midbrain, hypothalamus, thalamus, hippocampus, parietal cortex). The mRNA and protein for GLUT4 were identified in the cerebellum, but not elsewhere in the brain. GLUT2 protein and mRNA were not detected in any region of the brain. Although GLUT1 and GLUT3 are the major brain glucose transporters, the presence of GLUT4 in the cerebellum suggests that insulin-sensitive glucose uptake may occur in a specific part of the brain.

Animals↗
PubMed1993

Voluntary intake and gastric emptying in pigs: effects of fat and a CCK inhibitor.

The influence of the cholecystokinin (CCK) antagonist MK-329 (0.1 mg/kg) on short-term control of voluntary food intake and gastric emptying was studied in five pigs. Arterial injection of MK-329 abolished the inhibition of intake resulting from duodenal infusion of emulsified fat (Intralipid, 24 g/h). However, MK-329 only reduced the inhibition of dry matter (DM) and liquid emptying, and hence increased stomach volume at satiety. Intralipid infusion decreased the rise in gastric pressure during feeding. All these changes are consistent with endogenous CCK, released by Intralipid, inhibiting intake independent of the concomitant slowing of gastric emptying. MK-329 alone significantly increased intake using two different diets, but had no effect on gastric emptying so that gastric volume at satiety was significantly increased. These results suggest that endogenous CCK may be part of short-term satiety control in the pig.

Animals↗
PubMed1991

The relationships between glucose absorption and insulin secretion and the migrating myoelectric complex in the pig.

Net glucose and free amino nitrogen absorption and insulin output in the pig hepatic portal vein were calculated from portal-arterial concentration differences and portal blood flow measured by thermodilution. Duodenal and jejunal motility were assessed by electromyography. In the fed pig, the migrating myoelectric complex (MMC) pattern of motility persisted; glucose and amino nitrogen absorption and insulin secretion all varied with the phase of the MMC, rising to maximum values 19.4 +/- 3.1 min before and falling to minimum values 16.7 +/- 4.4 min after phase III. The variations in glucose absorption with the MMC were caused primarily by changes in duodenal and jejunal motility rather than by changes in the rate of gastric emptying as glucose absorption and insulin secretion varied with the phase of the MMC during duodenal glucose infusions, with maximum values occurring 24.4 +/- 3.3 min before and minimum values 14.9 +/- 2.5 min after phase III activity. The mean glucose absorption time calculated by timing the appearance of glucose in the portal vein following an intraduodenal bolus injection was significantly longer when given in phase I showing that absorption was less rapid when the intestine was not contracting. A significant amount of glucose is metabolized by intestine, as during glucose infusion (500 mg min-1) the average portal glucose absorption (376 mg min-1) was less than the glucose infused.

Animals↗
PubMed1990

Pattern of gastric emptying in the pig: relation to feeding.

The aims of the present study were to compare the gastric emptying of dry matter (DM) and liquids during the feeding period with that following meal consumption, to clarify the relationship between feeding and gastric emptying, and to investigate how gastric emptying changes in growing animals. The studies were performed in pigs fitted with a gastric cannula and fed on a normal finely ground solid diet mixed with water containing CrEDTA as liquid marker. Gastric emptying was measured using a gastric evacuation technique. It was observed that between 0.75 and 6 h after feeding the total amounts emptied increased, but the proportion of the meal emptied fell, with increase in meal size; emptying of both DM and liquids with large and small meals followed an exponential pattern. In contrast, while the animals were feeding, there was linear and rapid emptying of both DM and liquids following a very short (approximately 2 min) lag phase before emptying began. The rate of emptying increased linearly with body-weight (by 0.055 g DM/min and by 0.24 ml/min per kg body-weight over the range 58-200 kg) such that the emptying of digestible energy per kg metabolic body-weight (W0.75) was roughly maintained (between 2.9 and 3.2 kJ/min per kg W0.75). This suggests that the rate of emptying may be linked in some way with the metabolic requirements of the body. The biphasic pattern of gastric emptying observed is probably the intrinsic pattern of emptying of a meal which does not require breakdown of particles before emptying can occur.

Animal Feed↗
PubMed1989

Duodenal infusion of fat, cholecystokinin secretion and satiety in the pig.

The influence of the cholecystokinin (CCK) antagonist L-364,718 (0.1 mg/kg) on short-term control of food intake was studied in 6 pigs. Arterial injection of L-364,718 abolished the inhibition of intake to CCK octapeptide infusion (4 micrograms/kg/hr; from 42% p less than 0.001, to 97% of control intake), but did not alter control intake (99%). Injection of L-364,718 also abolished the inhibition of intake to duodenal infusion of emulsified fat (12 g/hr; from 76% p less than 0.001 to 105%) and of monoglyceride (24 g/hr; from 64% p less than 0.001 to 101%), but did not alter the inhibition to oleic acid (60 g/hr; 48% p less than 0.01 and 61% p less than 0.02), to glycerol (127 g/hr; 84% p less than 0.05 and 89%) or to glucose (144 g/hr; 78% p less than 0.02 and 69% p less than 0.001). These results suggest that monoglyceride-induced CCK secretion is mainly responsible for the satiety to duodenal fat in the pig, but that there is also a CCK-independent effect via the fatty acid. The results further indicate that intake of a normal barley-based diet (2% fat) is controlled via CCK-independent mechanisms.

Animals↗
PubMed1989

Relation between gastric emptying and short-term regulation of food intake in the pig.

The relation between gastric emptying (GE), measured by gastric evacuation, and food intake (FI) was studied in pigs fed two meals to appetite per day. Duodenal infusion of emulsified fat (Intralipid; KabiVitrum) inhibited both FI and GE of digestible energy by more than the energy infused, but the gastric volume at satiety was more than 20% below the control. Duodenal infusions of glucose inhibited FI calorically, and generally inhibited GE calorically; but gastric volume at satiety was always equal to control volume. Thus GE (via gastric distension) may regulate FI to duodenal infusion of glucose but not to Intralipid. In pigs given no infusions, removal of the gastric contents immediately prior to the p.m. meal increased intake by 10%, However, when the contents were retained the pigs ate two equal-sized meals in the day, even though the gastric volume after the p.m. meal was 24% greater than after the a.m. meal. Therefore, although gastric volume may influence intake it cannot be the only factor determining satiety on this diet.

Animals↗
PubMed1989

Control of gastric emptying in the pig: influence of duodenal infusions of glucose and emulsified fat.

The influence of duodenal infusions of emulsified fat (20% Intralipid) and glucose (40%, w/v) on gastric emptying during the feeding period was studied in five pigs. Gastric emptying was measured by evacuation of gastric contents immediately the pigs had finished feeding in animals fitted with a gastric cannula and a duodenal catheter and fed a solid meal mixed with water. Infusions at various rates of Intralipid and glucose given either from the start of feeding or up to 30 min prior to feeding until the pigs had finished feeding inhibited gastric emptying of dry matter (DM) and liquids in a qualitatively similar but quantitatively different manner. With both infusions the rates of gastric emptying of DM and liquids were progressively reduced with pre-infusions of 0, 10, 20 and 30 min. Slow infusions of Intralipid (2.3 and 4.6 ml/min) inhibited gastric emptying of DM and liquids to a greater extent than equicaloric infusions of glucose (3 and 6 ml/min), but faster infusions of Intralipid (6 ml/min) inhibited emptying less than equicaloric infusions of glucose (8 ml/min). When the DM emptied was converted into digestible energy (DE) there was no evidence that Intralipid inhibited gastric emptying calorically. In contrast the results showed that there was caloric regulation of gastric emptying with infusions of glucose begun at the start of feeding. There was a linear reduction in the rate of DM emptied with increase in the rate of glucose infusion (2-8 ml/min) of 64.5 +/- 4.8 g DM per MJ/min glucose infused, i.e. equivalent to a reduction of 0.98 +/- 0.07 kJ/min DE emptied for each kJ/min glucose infused. These changes in gastric emptying with duodenal infusions of glucose and Intralipid mirror the changes previously observed in food intake following similar infusions, and the results are therefore compatible with control of gastric emptying being an important site of short-term regulation of food intake in the pig.

Animals↗
PubMed1987

The influence of gastrointestinal infusions of glucose on regulation of food intake in pigs.

The influence of gastrointestinal infusions of glucose on short-term and 24 h control of food intake was studied in sixteen pigs fed twice per day and nine fed three times per day. The pigs were fitted with up to four catheters each, placed in the stomach, the duodenum and at 2 and 8 m from the ligament of Treitz (l.t.). Infusions were given into the catheters, beginning 30 min before the first meal (two feeds) or second meal (three feeds) of the day, and continuing until the pigs stopped eating. The effects of the infusions on both short-term and 24 h intakes were the same whether the pigs were given two or three feeds per day. Infusions of glucose (400 g/l) into the stomach or small intestine altered short-term (meal) intake, but had no effect on intake at the following meal. With glucose infusion at rates above a threshold level (4 ml/min) to the stomach, duodenum or ileum (8 m from l.t.) food intake at that meal was suppressed such as to compensate for the amount of energy infused. Glucose infusions to the jejunum (2 m from l.t.) caused greater inhibition of short-term intake than infusions elsewhere, and 6 ml/min glucose inhibited intake by more than the amount of energy infused. Duodenal injection of the local anaesthetic lignocaine markedly suppressed the inhibition of intake caused by gastric infusion of glucose. The reductions in intake with glucose infusions at various rates into the stomach or duodenum were nearly identical to those with the same rates of infusion of NaCl at the same high osmolarity. It is concluded that glucose activation of receptors over a large part of the small intestine participates in the short-term control of energy intake in the pig, and that the receptors are activated equally by glucose in terms of an osmotic or caloric stimulus. It is suggested that activation of these receptors is involved in the caloric regulation of gastric emptying leading to gastric distension and inhibition of further intake.

Animals↗