Distribution of glutamate dehydrogenase and glutamine synthetase activity in the sheep and chicken digestive tract.

Glutamate dehydrogenase (GLDH, EC 1.4.1.3) and glutamine synthetase (GS, EC 6.3.1.2) activity were determined in the contents and tissues of the various parts of the sheep and chicken digestive tract, GLDH activity in the tissues of the sheep omasum, duodenum, rumen, reticulum, colon, caecum, jejunum and ileum ranged from 3.25+/-0.7 U (mumol/g dry weight . min) to 5.94+/-2.28 U; in the abomasum it was 9.67+/-1.27 U. GLDH activity in the contents of the ileum, abomasum, jejunum and duodenum varied from 0.85+/-0.19 U to 3.29+/-0.53 U and in the colon, caecum, reticulum, omasum and rumen from 6.34+/-2.64 U to 16.96+/-3.83 U. GS activity in the tissues of these parts of the digestive tract varied from 2.8+/-0.59 U to 8.6+/-1.4 U and their contents from 2.49+/-0.85 U to 10.76+/-2 U. GS activity in the contents of the colon was very low (0.26+/-0.07 U). In the tissues of the chicken duodenum, caecum, jejunum and ileum we found GLDH activity of 4.68+/-1.64 U to 7.96+/-1.73 U; in their contents it was 3.31+/-1.06 U to 3.8+/-0.73, but in the caecum it attained up to 66.7+/-24.3 U. GS activity was high from 57.6+/-2.0 U to 231+/-84 U in the tissues and 357+/-53 U to 383+/-76 U in the contents (in the caecum up to 2,500+/-233 U). The results show that conditions for the utilization of ammonia are present in the tissues and the contents in the whole of the sheep and chicken digestive apparatus. The hypothesis is confirmed that the different ability of ruminants and fowls to utilize ammonia formed from urea added to their feed, including ammonia formed by hydrolysis of blood urea, is due to the different GLDH and GS activity in their digestive tract as well as in their liver.     

DNA stability and thiol-disulphide status of rat sperm nuclei during epididymal maturation and penetration of oocytes.

DNA stability and thiol-disulphide status of rat sperm nuclei was observed in vivo during maturation in the epididymis and penetration of oocytes. When spermatids and spermatozoa were stained with acridine orange after fixation with acetic alcohol, the red/green fluorescence ratio observed under a confocal microscope was not different between spermatids (3.81 +/- 0.16) and testicular spermatozoa (4.03 +/- 0.34), and then decreased sharply (p < 0.01) as the spermatozoa descended the epidymis to the caput epididymis (1.13 +/- 0.03). However, the ratio was not different among corpus (0.69 +/- 0.01), cauda epididymis (0.68 +/- 0.11) and ejaculated spermatozoa (0.63 +/- 0.01). On the other hand, when spermatozoa were labelled with monobromobimane (mBBr), the fluorescence intensities gradually decreased (p < 0.01) during passage of spermatozoa from testis (4.74 +/- 0.16) through epididymis (caput, 2.72 +/- 0.08; corpus, 1.07 +/- 0.03; cauda, -0.05 +/- 0.05; ejaculated, 0.08 +/- 0.03). The acridine orange red/green fluorescence ratio increased (p < 0.01) during zona penetration (binding sperm, 0.52 +/- 0.09; perivitelline sperm, 0.64 +/- 0.16) and sperm decondensation (decondensed sperm, 0.69 +/- 0.12). When spermatozoa in the perivitelline space were labelled with mBBr, the fluorescence was detected. These results demonstrate that DNA stability against acid appears to be ahead of the oxidation of protamine during sperm maturation in the epididymis and is an initial event of the unpackaging process in rat genome occurring during or just after zona penetration but before ooplasm penetration.     

NORADRENALINE IN THE GUINEA PIG ALIMENTARY CANAL: REGIONAL DISTRIBUTION AND SENSITIVITY TO DENERVATION AND RESERPINE

The concentrations of noradrenaline, dopamine and 5-hydroxytryptamine were studied in the stomach, duodenum, ileum, caecum (taenia coli), colon and rectum of the guinea pig. The wall of the alimentary canal was dissected into two fractions, one formed by the longitudinal muscle and myenteric plexus, the other formed by circular muscle, submucous plexus, submucosa and mucosa. In the longitudinal muscle-myenteric plexus, the amount of noradrenaline was lower in the ileum (0.56 μg/g of fresh tissue), higher in the duodenum and caecum (0.75 μg/g and 0.82 μg/g respectively) and even higher in the stomach and rectum (0.85 μg/g and 0.91 μg/g). The highest value was found in the colon (1.33 μg/g), probably related to the occurrence of intramural adrenergic neurons. When extrinsic nerves to the ileum were damaged, the amount of noradrenaline in the corresponding ileal segment was reduced to less than 5 per cent within 3 days in both fractions of the wall. 6-Hydroxydopamine (35 mg/kg intravenously) reduced to approx. one-third the amount of noradrenaline in longitudinal muscle-myenteric plexus of ileum and colon. Reserpine (1 mg/kg, subcutaneously injected 72 h-earlier) reduced the amount of noradrenaline in the longitudinal muscle-myenteric plexus of both ileum and colon to 0.01 μg/g. Doses of reserpine as small as 0.02 mg/kg were still effective in causing a great reduction in noradrenaline concentration. No difference in the effects on ileum and colon was observed.     

The effects of xylanase supplementation on performance, characteristics of the gastrointestinal tract, blood parameters and gut microflora in broilers fed on wheat-based diets

The aim of this study was to investigate the effects of xylanase supplementation on performance, characteristics of the gastrointestinal tract, blood parameters and gut microflora in broilers fed on wheat-based diets. The experimental diets consisted of a wheat-based diet supplemented with 0 or 1 g/kg enzyme preparation (xylanase activity was 1218 U/g). The diets were fed between 7 and 49 days of age. Enzyme supplementation (ES) improved (P<0.05) growth performance and feed conversion efficiency. The addition of enzyme to a wheat-based diet reduced the relative weights of the duodenum, jejunum, pancreas (P<0.05) and colon (P<0.01) in 21-day-old broiler chickens. Enzyme preparation reduced digesta viscosity in the proventriculus and jejunum of 21-day-old broiler chickens (P<0.05) and in colon of 49-day-old broiler chickens (P<0.05). The pH of the digesta in the crop, duodenum and jejunum was increased (P<0.05) in 21-day-old broiler chickens and was reduced in the caecum of 49-day-old broiler chickens (P<0.05) with enzymes. There was no significant difference between the two experimental groups in counts of lactobacillus and coliform bacteria in the caecum. Enzyme supplementation increased the concentration of blood insulin-like growth factor I (IGF-I) (P<0.01) of 21-day-old broilers, triiodothyronine (T₃) and insulin (P<0.05) at 49 days. ES reduced the concentrations of blood thyroxine (T₄) (P<0.01) and uric acid (P<0.05) at 49 days, but had no effect on glucose concentration (P>0.05). In conclusion, ES can improve performance and digestive parameters and can change some blood parameters in broiler chickens fed a wheat-based diet.     

Enzymatic degradation of luteinizing hormone releasing hormone (LHRH) by mucosal homogenates from the intestine of the common brushtail possum (Trichosurus vulpecula)

The peptidolytic activity of fresh and frozen mucosal homogenates from five regions (duodenum, jejunum, ileum, caecum and colon) of possum intestine from Trichosurus vulpecula towards human Luteinizing Hormone Releasing Hormone (LHRH) was investigated. The rank of order of specific peptidolytic activity of the mucosal homogenates was jejunum > ileum > caecum> duodenum = colon, with a 3 to 4 fold difference between the least and the most active segment in both frozen and fresh samples. The formation of peptides LHRH (1-3), LHRH (1-4) and LHRH (1-5) suggest endopepetidase-24.18, endopeptidase-24.15 and angiotensin converting enzyme (ACE) might be responsible for the peptide degradation in mucosal homogenates. The inhibition of LHRH degradation by mucosal homogenates was evaluated in four regions (jejunum, ileum, caecum and colon) of possum intestine. Ethylenediaminetetraacetic acid (EDTA, 5 mM), sodium deoxycholate (SDA, 10 mM) and bacitracin (3.5 or 9 mM) inhibited the degradation of LHRH in mucosal homogenates from small intestine and hindgut. However, the serine protease inhibitor, soybean trypsin-chymotrypsin inhibitor (SBTI), did not prevent degradation of LHRH. It is concluded that combining peptides with inhibitors may enhance oral delivery of bioactive peptides or proteins to possums.     

Pituitary adenylate cyclase activating polypeptide stimulates gallbladder motility in conscious dogs.

We investigated whether pituitary adenylate cyclase activating polypeptide (PA-CAP27 and PACAP38) had any effect on gallbladder motility in conscious dogs, in which force transducers were chronically implanted in the gastric antrum, duodenum and gallbladder. PACAP27 and PACAP38 were administered intravenously during the digestive and interdigestive states at doses of 30, 100 and 300 pmol/kg. By way of comparison, cholecystokinin octapeptide (CCK-OP) was administrated at doses of 3, 9 and 27 pmol/kg. As a result, each peptide evoked transient and tonic contractions both in the digestive and interdigestive states, and the effect on the motor index was dose dependent. PACAP27 and PACAP38 were 0.11 +/- 0.03 and 0.04 +/- 0.01 as potent as CCK-OP in the digestive state, and 0.18 +/- 0.04 and 0.02 +/- 0.01 in the interdigestive state, respectively, on a molar basis. Although PACAP27 and PACAP38 belong to the vasoactive intestinal polypeptide (VIP) family, intravenous administration of 300 pmol/kg of VIP had no effect on interdigestive gallbladder motility, but on the other hand inhibited gallbladder motility in the digestive state. The contractile effects of PACAP27 and PACAP38 were almost completely abolished by pretreatment with atropine or hexamethonium, but not with L364718. An in vitro study using canine gallbladder strips showed that PACAP27 and PACAP38 had no effect on spontaneous gallbladder motor activity evoked by electric field stimulation, CCK-OP or acetylcholine. It was concluded that PACAP27 and PACAP38 stimulate gallbladder motility in conscious dogs through a preganglionic cholinergic mechanism.     

The effects of insulin on glucose and fluid transport in the isolated small intestine of normal rats

Chronically administered insulin returns enhanced maximal glucose transport capacity induced by diabetes to its normal state. In this study, the direct and acute effects of insulin on glucose transport in different parts of isolated small intestine were investigated. Mucosal Fluid Transport (MFT), Mucosal Glucose Transport (MGT) and Serosal Glucose Transport (SGT) were measured in the presence and absence of insulin in averted sacs, prepared from female Wistar rats. This study shows that the presence of insulin in vitro (40 and 80 microU/mL) can reduce MGT and SGT in different segments of the small intestine (duodenum, jejunum and ileum) after 30 min whereas it had no effect on MFT. Mucosal glucose transfer rates in the duodenum, jejunum and ileum of the controls were 6.07+/-0.4, 6.34+/-0.62 and 6.43+/-0.47 mg/g tissue respectively which were significantly reduced to 3.82+/-0.93, 3.60+/-0.50 and 1.17+/-0.45 in the presence of 80 microU/mL of insulin. Serosal glucose transfer too was decreased significantly from 0.3+/-0.05, 0.57+/-0.07 and 0.43+/-.07 in the duodenum, jejunum and ileum to 0.16+/-0.03, 0.16+/-0.04 and .07+/-.02 respectively. Mucosal fluid transfer was not affected by insulin. Insulin was as effective whether it was added on the mucosal or the serosal side. The results of this study show that insulin can directly affect glucose transport in the small intestine; its physiological role must be examined. Direct effect of insulin deficiency on glucose absorption in diabetic patients may play a role in the pathophysiology of the disease.     

Surface pH responses of muscles of different fiber-type composition to catecholamines

Catecholamines were infused intravenously for 45 min into pentobarbital sodium-anesthetized rabbits. Physiologically low-dose epinephrine (0.125 microgram . min-1 . kg-1) decreased medial gastrocnemius (MG) surface pH (SpH) 0.16 +/- 0.03 (SD) (P less than 0.001) to a low of 7.25 +/- 0.11 and soleus (S) SpH 0.09 +/- 0.04 (P less than 0.01) to a low of 7.33 +/- 0.08 without changing blood pressure significantly. Surface temperature measurements suggested a statistically insignificant small increase in local blood flow in both muscles. With 1.25 microgram . min-1 . kg-1 epinephrine, MG SpH decreased 0.22 +/- 0.05 (P less than 0.001) to a low of 7.17 +/- 0.06 and S SpH decreased 0.10 +/- 0.05 (P less than 0.02) to a low of 7.26 +/- 0.04. The MG SpH decrease exceeded the S SpH decrease in each experiment for both epinephrine infusion levels, and the incremental difference was significantly greater (P less than 0.02) with the higher dose, demonstrating a dose-response effect more pronounced for glycolytic compared with oxidative fibers. Norepinephrine infusions of 1.25 and 2.5 micrograms . min-1 . kg-1 did not change SpH of either muscle significantly, despite increases in blood pressure of 10 +/- 3 (P less than 0.002) and 19 +/- 10 mmHg (P less than 0.02), respectively.     

Protein and peptide degradation in the intestine of the common brushtail possum (Trichosurus vulpecula)

A protein (bovine serum albumin: BSA) and a peptide (luteinizing hormone releasing hormone: LHRH) were used to evaluate proteolytic activity in the intestine of common brushtail possums (Marsupiala, Trichosurus vulpecula). Luminal and mucosal extracts were isolated from the duodenum, jejunum, ileum, caecum, proximal colon and distal colon, their protein content assessed and specific activities in metabolising LHRH and BSA determined in vitro. The degradation of LHRH by luminal extracts was compared with that by the pancreatic enzymes, chymotrypsin, trypsin, and elastase. The protein concentration (microg x mg-1) of mucosal extract in the duodenum was higher ( P<0.05) than in the proximal colon, but that of luminal extracts did not differ significantly between regions. Proteolytic activity of luminal extracts was greater ( P<0.01) in the jejunum and ileum than in the hindgut. In the small intestine, proteolytic activity of luminal enzymes far exceeded that of mucosal enzymes ( P<0.05). All three pancreatic enzymes hydrolysed LHRH, but chymotrypsin had the greatest activity. This study has demonstrated that, in possums, proteolysis occurs primarily in the small intestine through luminal enzymes, with chymotrypsin playing a major role. The possum hindgut contributes little to the metabolism of peptides and proteins, identifying it as a potential site to target for their absorption following oral delivery.     

Liver metal concentrations in Greater Sage-grouse (Centrocercus urophasianus)

Greater Sage-grouse (Centrocercus urophasianus) are a species of concern due to shrinking populations associated with habitat fragmentation and loss. Baseline health parameters for this species are limited or lacking, especially with regard to tissue metal concentrations. To obtain a range of tissue metal concentrations, livers were collected from 71 Greater Sage-grouse from Wyoming and Montana. Mean +/- SE metal concentrations (mg/kg wet weight) in liver were determined for vanadium (V) (0.12 +/- 0.01), chromium (Cr) (0.50 +/- 0.02), manganese (Mn) (2.68 +/- 0.11), iron (Fe) (1,019 +/- 103), nickel (Ni) (0.40 +/- 0.04), cobalt (Co) (0.08 +/- 0.02), copper (Cu) (6.43 +/- 0.40), mercury (Hg) (0.30 +/- 0.09), selenium (Se) (1.45 +/- 0.64), zinc (Zn) (59.2 +/- 4.70), molybdenum (Mo) (0.93 +/- 0.07), cadmium (Cd) (1.44 +/- 0.14), barium (Ba) (0.20 +/- 0.03), and lead (Pb) (0.17 +/- 0.03). In addition to providing baseline data, metal concentrations were compared between sex, age (juvenile/adult), and West Nile virus (WNv) groups (positive/negative). Adult birds had higher concentrations of Ni and Cd compared to juveniles. In addition, Zn and Cu concentrations were significantly elevated in WNv-positive birds.     

Effects of high fat provision on muscle PDH activation and malonyl-CoA content in moderate exercise.

This study examined the effects of elevated free fatty acid (FFA) provision on the regulation of pyruvate dehydrogenase (PDH) activity and malonyl-CoA (M-CoA) content in human skeletal muscle during moderate-intensity exercise. Seven men rested for 30 min and cycled for 10 min at 40% and 10 min at 65% of maximal O(2) uptake while being infused with either Intralipid and heparin (Int) or saline (control). Muscle biopsies were taken at 0, 1 (rest-to-exercise transition), 10, and 20 min. Exercise plasma FFA were elevated (0.99 +/- 0.11 vs. 0.33 +/- 0.03 mM), and the respiratory exchange ratio was reduced during Int (0.87 +/- 0.02) vs. control (0.91 +/- 0.01). PDH activation was lower during Int at 1 min (1.33 +/- 0.19 vs. 2.07 +/- 0.14 mmol. min(-1). kg(-1) wet muscle) and throughout exercise. Muscle pyruvate was reduced during Int at rest [0.17 +/- 0.03 vs. 0.25 +/- 0.03 mmol/kg dry muscle (dm)] but increased above control during exercise. NADH was higher during Int vs. control at rest and 1 min of exercise (0.122 +/- 0.016 vs. 0.102 +/- 0.005 and 0.182 +/- 0.016 vs. 0.150 +/- 0.016 mmol/kg dm), but not at 10 and 20 min. M-CoA was lower during Int vs. control at rest and 20 min of exercise (1.12 +/- 0.22 vs. 1.43 +/- 0.17 and 1.33 +/- 0.16 vs. 1.84 +/- 0.17 micromol/kg dm). The reduced PDH activation with elevated FFA during the rest-to-exercise transition was related to higher mitochondrial NADH at rest and 1 min of exercise and lower muscle pyruvate at rest. The decreased M-CoA may have increased fat oxidation during exercise with elevated FFA by reducing carnitine palmitoyltransferase I inhibition and increasing mitochondrial FFA transport.     

Microbial diversity in the rumen,reticulum, omasum,and abomasum of yak on a rapid fattening regime in an agro-pastoral transition zone

The ruminant digestive system harbors a complex gut microbiome, which is poorly understood in the case of the four stomach compartments of yak. High-throughput sequencing and quantitative PCR were used to analyse microbial communities in the rumen, reticulum, omasum, and abomasum of six domesticated yak. The diversity of prokaryotes was higher in reticulum and omasum than in rumen and abomasum. Bacteroidetes predominated in the four stomach compartments, with abundance gradually decreasing in the trend rumen > reticulum > omasum > abomasum. Microorganism composition was different among the four compartments, all of which contained high levels of bacteria, methanogens, protozoa and anaerobic fungi. Some prokaryotic genera were associated with volatile fatty acids and pH. This study provides the first insights into the microorganism composition of four stomach compartments in yak, and may provide a foundation for future studies in this area.     

Properties of phosphatidate phosphohydrolase and diacylglycerol acyltransferase activities in the isolated rat heart. Effect of glucagon, ischaemia and diabetes.

Myocardial triacylglycerol hydrolysis is subject to product inhibition. After hydrolysis of endogenous triacylglycerols, the main proportion of the liberated fatty acids is re-esterified to triacylglycerol, indicating the importance of fatty acid re-esterification in the regulation of myocardial triacylglycerol homoeostasis. Therefore, we characterized phosphatidate phosphohydrolase (PAP) and diacylglycerol acyltransferase (DGAT) activities, enzymes catalysing the final steps in the re-esterification of fatty acids to triacylglycerols in the isolated rat heart. The PAP activity was mainly recovered in the microsomal and soluble cell fractions, with an apparent Km of 0.14 mM for both the microsomal and the soluble enzyme. PAP was stimulated by Mg2+ and oleic acid. Oleic acid, like a high concentration of KCl, stimulated the translocation of PAP activity from the soluble to the particulate (microsomal) fraction. Myocardial DGAT had an apparent Km of 3.8 microM and was predominantly recovered in the particulate (microsomal) fraction. Both enzyme activities were significantly increased after acute streptozotocin-induced diabetes, PAP from 15.6 +/- 1.1 to 28.1 +/- 3.6 m-units/g wet wt. (P less than 0.01) and DGAT from 2.23 +/- 0.11 to 3.01 +/- 0.11 m-units/g wet wt. (P less than 0.01). In contrast with diabetes, low-flow ischaemia during 30 min did not affect PAP and DGAT activity in rat hearts. Perfusion with glucagon (0.1 microM) during 30 min did not affect total PAP activity, but changed the subcellular distribution. More PAP activity was recovered in the particulate fraction. DGAT activity was lowered by glucagon treatment from 0.37 +/- 0.03 to 0.23 +/- 0.02 m-unit/mg of microsomal protein (P less than 0.05). The role of PAP and DGAT activity and PAP distribution in the myocardial glucose/fatty acid cycle is discussed.     

Distribution of neurokinin-2 receptors in the guinea-pig gastrointestinal tract

The distribution of neurokinin-2 (NK2) tachykinin receptors was investigated by immunohistochemistry in the guinea-pig oesophagus, stomach, small and large intestine. Receptor immunoreactivity occurred at the surfaces of smooth muscle cells throughout the digestive tract. Nerve fibre varicosities in enteric ganglia were also immunoreactive. In myenteric ganglia, these varicosities were most numerous in the ileum, frequent, but less dense, in the proximal colon and caecum, rare in the distal colon, extremely infrequent in the rectum and duodenum, and absent from the stomach and oesophagus. Reactive varicosities were rare in the submucous ganglia. Reactive nerve fibres in the mucosa were only found in the caecum and proximal colon. Strong NK2 receptor immunoreactivity was also found on the surfaces of enterocytes at the bases of mucosal glands in the proximal colon. Receptors were not detectable on the surfaces of nerve cells or on non-terminal axons. Reactivity did not occur on nerve fibres innervating the muscle. Denervation studies showed that the immunoreactive varicosities in the myenteric plexus of the ileum were the terminals of descending interneurons. Immunoreactivity for nitric oxide synthase was colocalised with NK2 receptor (NK-R) immunoreactivity in about 70% of the myenteric varicosities in the small intestine. Bombesin immunoreactivity occurred in about 30% of NK2-R immunoreactive varicosities in the small intestine. Received: 10 April 1996 / Accepted: 13 May 1996     

Fluctuation in responsiveness of LH and lack of responsiveness of FSH to prolonged infusion of morphine and naloxone in the ewe

In ewes in the mid-luteal phase, LH pulse frequency (P less than 0.01) and amplitude (P less than 0.05) increased during a 24 h infusion of naloxone (0.5 mg/kg/h) compared to a 24 h infusion of vehicle (mean +/- s.e.m.; 0.25 +/- 0.03 vs 0.14 +/- 0.01 pulses/h and 0.84 +/- 0.08 vs 0.55 +/- 0.08 ng/ml serum, respectively). The increase in pulse amplitude was immediate, but was less (P less than 0.05) during the second 12 h, compared to the first 12 h, of naloxone infusion (0.52 +/- 0.14 vs 0.98 +/- 0.08 ng/ml serum). Oestradiol concentrations were higher (P less than 0.01) during naloxone than during control infusion (5.63 +/- 0.26 vs 4.13 +/- 0.15 pg/ml serum). In ovariectomized ewes in the breeding season, LH pulse frequency was lower (P less than 0.01) during a 24 h infusion of morphine (0.5 mg/kg/h) than during a 24 h infusion of vehicle (mean +/- s.e.m.; 1.17 +/- 0.08 vs 1.71 +/- 0.06 pulses/h). We conclude that long-term infusion of naloxone results in a sustained increase in LH pulse frequency but only a transient elevation in pulse amplitude. No effects on FSH secretion were noted. LH secretion was sensitive to morphine in the absence of ovarian steroids, suggesting that ovarian steroids are not required for the presence of functional opioid receptors capable of modulating LH release.     

Characterization of brush border membrane-bound alkaline phosphatase activity in different segments of the porcine small intestine

This study was conducted to characterize enterocyte apical membrane-bound alkaline phosphatase activity in different segments of the porcine small intestine. Duodenal, jejunal, and distal ileal segments were isolated from three 26-kg pigs and enterocyte brush border membrane, enriched between 19- and 24-fold in sucrase specific activity, was prepared by Mg(2+) precipitation and differential centrifugation. With P-nitrophenyl phosphate as substrate, the optimum pH for porcine brush border membrane-bound alkaline phosphatase activity was defined to be 10.5 for all three segments. At the optimal pH, the kinetics of membrane-bound alkaline phosphatase were determined for the three intestinal segments. The affinity of this enzyme (K(m), mM) in the jejunum (0.64 +/- 0.07) was four times greater than that in the duodenum (2.75 +/- 0.59) and the distal ileum (2.71 +/- 1.14). These results indicate that different isomers of membrane-bound alkaline phosphatase might have been expressed in different segments of porcine small intestine. The maximal specific activity (V(max), micromol/mg protein . min) of this enzyme was highest in the duodenal (7.74 +/- 0.95), intermediate in the jejunal (4.31 +/- 0.18), and lowest in the distal ileal (3.53 +/- 0.84) brush border membrane. Therefore, the maximal specific activity of brush border membrane-bound alkaline phosphatase along the intestinal longitudinal axis in growing pigs decreases from the duodenum toward the distal ileum.     

Prostacyclin, prostaglandin F2 alpha and progesterone production by bovine luteal cells during the estrous cycle

Corpora lutea (CL) were collected from Holstein heifers on Days 5, 10, 15 and 18 (5/day) of the estrous cycle. Dispersed luteal cell preparations were made and 10(6) viable luteal cells were incubated with bovine luteinizing hormone (LH) and different amounts of arachidonic acid in the presence and absence of the prostaglandin (PG) synthetase inhibitor indomethacin. The concentrations of progesterone, PGF2 alpha and 6-keto-PGF1 alpha, the stable inactive metabolite of prostacyclin (PGI2), were measured. Day 5 CL had the greatest initial content of 6-keto-PGF1 alpha (1.01 +/- 0.16 ng/10(6) cells), and synthesized more 6-keto-PGF1 alpha (2.55 +/- 0.43) than CL collected on Days 10 (0.57 +/- 0.11), 15 (0.08 +/- 0.05) and 18 (0.19 +/- 0.03) during a 2-h incubation period. Arachidonic acid stimulated the production of 6-keto-PGF1 alpha by Days 10, 15 and 18 luteal tissue. PGF2 alpha was produced at a greater rate on Day 5 (0.69 +/- 0.17 ng/10(6) cells) than on Days 10 (0.06 +/- 0.01), 15 (0.04 +/- 0.02) and 18 (0.08 +/- 0.01). Arachidonic acid stimulated and indomethacin inhibited the production of PGF2 alpha, in most cases. The initial content of 6-keto-PGF1 alpha was higher than that of PGF2 alpha on all days of the cycle and more 6-keto-PGF1 alpha was synthesized in response to arachidonic acid addition. The ratio of 6-keto-PGF1 alpha content to PGF2 alpha content was 4.39, 2.30, 1.25 and 1.13 on Days 5, 10, 15 and 18, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of heat stress on the antimicrobial drug resistance of Escherichia coli of the intestinal flora of swine

The effects of heat stress on the antimicrobial drug resistance of Escherichia coli of the intestinal tract of swine were studied in animals from a farm that had not been supplementing antimicrobials in feed for the past 10 years. In one study, 10 finisher hogs were heat stressed (34 degrees C) for 24 h. Antimicrobial resistance levels after stress were significantly higher (P < 0.05) when compared with pre-stress levels for amikacin, ampicillin, cephalothin, neomycin and tetracycline from faecal samples. This high level of resistance persisted to slaughter that occurred at 10 days post-stress for most of the antimicrobials mentioned. In a second study, samples of different sections of the gastrointestinal tract were collected after heat stress and compared with control, non-stressed animals. Results indicated that E. coli which colonized the ileum and caecum had a higher level of resistance to ampicillin and tetracycline than the E. coli which colonized the colon and rectum. When animals were exposed to heat stress, resistance to ampicillin and tetracycline of E. coli in the lower digestive tract increased (P < 0.05) to a level similar to that observed in the ileum and caecum. Based on these findings, an investigation was made to test the hypothesis that (a) an increase in intestinal motility increases shedding of resistant E. coli and (b) heat stress induces a reduction in intestinal transit time in swine. For each study, two groups of three, randomly selected finisher hogs each were formed (treated and control groups). In study (a), induction of increased motility and peristalsis was obtained using an intramuscular injection of the cholinergic drug neostigmine methylsulphate. Escherichia coli isolates were obtained from the ileum, caecum, colon and rectum after animals were slaughtered. A higher level of ampicillin-resistant E. coli was found in the caecum (40%) than in other segments of the intestinal tract. In treated animals, level of resistance increased for organisms from the colon and rectum. Similar results were obtained for tetracycline resistance. In study (b), intestinal transit time was measured using chromium-EDTA as a marker. Swine were euthanized and samples were collected throughout the intestinal tract (duodenum to rectum) 8 h after administration of the marker to control and heat-stressed animals. Results indicated a reduced transit time for the stressed group. These findings corroborate the initial hypothesis that an outflow of resistant organisms moves from the upper tract (ileum and caecum) to the lower tract (colon and rectum).     

Contribution of prostaglandins to the dilation that follows isometric forearm contraction in human subjects: effects of aspirin and hyperoxia.

In 11 healthy volunteers, we evaluated, in a double-blind crossover study, whether the vasodilation that follows isometric contraction is mediated by prostaglandins (PGs) and/or is O2 dependent. Subjects performed isometric handgrip for 2 min at 60% maximal voluntary contraction (MVC), after pretreatment with placebo or aspirin (600 mg orally), when breathing air or 40% O2. Forearm blood flow was measured in the dominant forearm by venous occlusion plethysmography. Arterial blood pressure was also recorded, allowing calculation of forearm vascular conductance (FVC; forearm blood flow/arterial blood pressure). During air breathing, aspirin significantly reduced the increase in FVC that followed contraction at 60% MVC: from a baseline of 0.09 +/- 0.011 [mean +/- SE, conductance units (CU)], the peak value was reduced from 0.24 +/- 0.03 to 0.14 +/- 0.01 CU. Breathing 40% O2 similarly reduced the increase in FVC relative to that evoked when breathing air; the peak value was 0.24 +/- 0.03 vs. 0.15 +/- 0.02 CU. However, after aspirin, breathing 40% O2 had no further effect on the contraction-evoked increase in FVC (the peak value was 0.15 +/- 0.02 vs. 0.16 +/- 0.02 CU). Thus the present study indicates that prostaglandins make a substantial contribution to the peak of the vasodilation that follows isometric contraction of forearm muscles at 60% MVC. Given that hyperoxia similarly reduced the vasodilation and attenuated the effect of aspirin, we propose that the stimulus for prostaglandin synthesis and release is hypoxia of the endothelium.     

The thickness of the mucus layer in different segments of the rat intestine

Summary The thickness of the pre-epithelial mucus layer has been measured in different gut segments of rats kept under normal (ad libitum) feeding conditions, and after 48 h of fasting, using cryostat sections and celloidin stabilization from samples containing luminal contents. The mucus layer of the stomach, duodenum, jejunum, ileum, caecum, proximal colon, colon transversum, distal colon and rectum was studied in five groups of male rats (10, 40, 70 and 150 days of age, and older). Underad libitum feeding conditions, a distinct and continuous mucus layer, with a thickness of more than 3 μm, was only observed in the colon transversum, in the distal colon, in the rectum and in the stomach. No pre-epithelial mucus layer was observed in the duodenum and jejunum where the glycocalix from the apical membrane of the superficial cells appeared to be in a direct contact with the luminal ingesta. In the ileum, caecum and the proximal colon, the surface epithelium of the mucosa was only partly covered by a mucus layer of highly variable thickness. After 48 h of fasting, a mucus layer of 28.8 ± 25.6 μm and 93.3 ± 59.4 μm thickness, respectively, was found in the duodenum and jejunum of adult rats, but no increase in the thickness of the mucus layer was observed in the rat hind gut.