Effects of partially hydrolysed guar gum (PHGG) or intact guar gum (GG) on iron utilization in rats fed on several iron-deficient diets were examined. Hemoglobin, serum iron and iron storage in liver of rats fed on iron-deficient diets as a control group (without PHGG and GG) significantly decreased, while those of the test group fed together with PHGG or GG were unchanged. In an iron balance test for 3 days, administration of PHGG or GG caused an increase in iron absorption. The results suggested that PHGG or its metabolites increase the bioavailability of dietary iron in deficiency.
Although innate immunity has been well studied in laboratory animal models, no such documentation exists for wild species possessing a diversity of physiological adaptations to their environment. We examined the blood sera of 188 hispid cotton rats (Sigmodon hispidus) for naturally occurring hemolytic activity against heterologous erythrocytes. Ninety-two percent of the blood sera samples from cotton rats lysed sheep erythrocytes. All sera tested against chicken erythrocytes showed hemolytic activity, while only 44% of the same sera could lyse bovine erythrocytes. No hemolytic activity was present in cotton rat sera against erythrocytes from other rodent species (Eastern woodrat, Neotoma floridana, and pine vole, Microtus pinetorum). Hemolytic activity was heat labile and appeared to be mediated through the classical complement pathway. The protective nature of this hemolytic factor is unclear but it is probably directed at a more relevant molecule. These data, along with other reports of naturally occurring target specific serum factors in the cotton rat, may reflect the importance of innate protective mechanisms to small mammal populations.
Muscle respiration experiments on inhibitor dosage (experiment 1), muscle preparation (tendons removed vs. unstretched vs. stretched muscles; chick muscle only; experiment 2) and media temperature (26.5, 32, 37, 42 degrees C; experiment 3) were conducted on chick (Gallus domesticus) gastrocnemius and tilapia (Tilapia mossambica) epaxial muscle in vitro. Experiment 1: The dosage of cycloheximide and ouabain required for maximum inhibition of protein synthesis and Na+,K+ ATPase, respectively, in chick and tilapia muscle was approximately 6 x 10(-5) M. Experiment 2: Removing the tendons of chick muscle decreased (% inhibition, P = 0.05) cycloheximide-sensitive respiration compared to stretched and unstretched muscles (tendons intact). However, muscle preparation had little influence on ouabain-sensitive respiration. Experiment 3: Cycloheximide-sensitive respiration tended to increase (microliter O2/mg DNA.hr, P = 0.054) with media temperature in tilapia muscle. Chick muscle was less responsive in this respect. Ouabain-sensitive respiration increased at lower temperature in chick muscle (% inhibition, cubic relationship, P = 0.001) and at higher temperature in tilapia muscle (% inhibition, quadratic relationship, P = 0.0002).
The effect of repeated oral administration of prostaglandin analogue (dmPGE2) on intestinal macromolecular transport and digestive enzymes development were investigated in the suckling rats. By the administration of dmPGE2 for 7 days, precocious induction of maltase activity, depression of amylase activity and enhancement of trypsin activity in the pancreas occurred. Absorption of bovine IgG was dose dependently depressed by dmPGE2 treatments. The intestinal cessation was also observed in the adrenalectomized pups, but was not influenced by difluoromethyl ornithine administration. These results suggest that oral administration of PGE2 induces precocious maturation of the small intestine and exocrine pancreas and that the intestinal cessation is not directly related to ornithine decarboxylase activity in the suckling rats.
It was the aim of the present study to investigate the transport of tricarboxylates (citrate, tricarballylate) across the basolateral membrane (BLM) of the small intestine. Experiments were performed using BLM vesicles isolated from the jejunum of rats. For comparison, some experiments with brush border membrane (BBM) vesicles were also performed. Finally, transfer of citrate and tricarballylate across the intestinal wall was investigated using sacs of everted small intestine. Uptake of citrate by BBM vesicles occurs by a Na+ gradient-driven transport mechanism specific for tri- and dicarboxylates. The partially protonated forms of citrate seem to be much better transported than the completely dissociated form, since lowering the extravesicular pH from 7.8 to 5.6 resulted in a marked stimulation of Na+-dependent citrate uptake. In contrast to citrate uptake across the BBM, uptake of citrate across the BLM was neither influenced by Na+ nor by pH changes. Neither structurally related tri- and dicarboxylates (tricarballylate, succinate) nor other organic and inorganic anions (e.g. lactate, p-aminohippurate, sulfate, chloride, bicarbonate) significantly influenced citrate uptake by BLM vesicles under cis-conditions. Uptake of citrate as a function of the extravesicular substrate concentration was linear over a concentration range from 0.1 to 10 mmol/l. Thus, citrate uptake under these conditions seems to be Na+-independent and not to be mediated by a carrier. However, preloading the BLMV with citrate clearly trans-stimulated the uptake of citrate and tricarballylate, respectively. Furthermore, citrate significantly inhibited tricarballylate uptake into BLMV preloaded with citrate. These results indicate uptake of tricarboxylates across the BLM by an exchange mechanism. Using sacs of everted small intestine, no transfer of intact citrate against a concentration gradient occurred, but some evidence for metabolization of citrate within the intestinal wall was obtained. In contrast, the non-metabolizable tricarboxylate tricarballylate was significantly accumulated in the serosal compartment of everted intestinal sacs.
Obese (fa/fa) rats fed on control diet have lower proportions of linoleic acid (18:2n-6) and/or arachidonic acid (20:4n6) in IBAT and pancreas phospholipids compared with lean (Fa/-) rats. Lower stearic acid (18:0) to oleic acid (18:1n-9) mean ratios in fa/fa compared with Fa/- suggest enhanced Δ9-desaturase activity in the former. 18:220:4 mean ratios in pancreas, but not IBAT, are indicative of a reduced Δ6-desaturase activity in fa/fa rats. Absolute amounts of phospholipids (mg/unit tissue wt) were 2-fold greater in IBAT of fa/fa compared with Fa/- rats, irrespective of their diet. This was reflected in greater absolute amounts of 18:2n-6 and 20:4n-6 only in HSO and HTO fa/fa groups, but not in the control group. Adrenalectomy (Adx) or T3 treatment also modified phospholipid fatty acid composition of IBAT and pancreas phospholipids in animals fed on the control diet with fa/fa rats more sensitive to endocrine induced changes. In fa/fa rats T3 treatment increased docosahexaenoic acid (22:6n-3) in IBAT of both phenotypes compared with the control, but this effect was evident only in fa/fa and not Fa/- pancreas. T3 treatment also increased docosapentaenoic acid (22;5n-3) in IBAT from, both phenotypes, but no 22:5n-3 was evident in the pancreatic tissue of these animals. ADX also increased 22:6n-3 in the IBAT of fa/fa (Fa/- values were less than 1%) but not in the pancreas of fa/fa or Fa/-. ADX modified the relative proportions of 18:0 to 18:1 and 18:2 to 20:4 in IBAT and pancreas of fa/fa in a way that indicated decreased Δ9-desaturase and increased Δ6-desaturase activities; these effects tended toward normal again in pancreas of fa/fa rats on corticosterone replacement (CST).
Flies of the genus Drosophila, particularly D. melanogaster, have been mainstays of biological research on aging for more than 80 years. However, what was striking for most of those years was how little concrete progress was made on the problem of aging using the normally powerful Drosophila model system. To be sure, a great deal of longitudinal information was accumulated about Drosophila aging and various mutant or inbred stocks were characterized for longevity (Lints and Soliman, 1988). However, throughout the period from 1915 to 1980, there were none of the significant breakthroughs that characterized other research with Drosophila, from genetics to biochemistry to developmental biology to population genetics. In this respect, Drosophila aging research was like that with other organisms. Up until 1980, little demonstrable progress was made in aging research. The one powerful experimental system, in vitro cell culture, had revealed the finite replicative potential
Female miniature swine, 4-11 yr, were fed 15% fat diets containing n-3 and/or n-6 polyunsaturated fat for 6 months, at 1.95 g fat/kg body weight. Liver lipids from menhaden oil-fed minipigs were elevated in the n-3 fatty acids: 20:5, 22:5 and 22:6, but heart lipids only in 20:5 and 22:6. Liver cell plasma membrane was elevated in 20:5, 22:5 and 22:6 and lowered in the n-6 acids 18:2 and 20:4 in menhaden oil-fed animals, to a greater extent than in the total tissue lipids. Liver alpha-tocopherol tended to decrease upon feeding menhaden oil, but heart alpha-tocopherol concentrations were not affected.
The response to an intravenous glucose load was evaluated in four groups of rats following fetal exposure to maternal diets containing 18, 12, 9 or 6% protein. The animals differed nutritionally only in terms of this prenatal experience. Animals in the 6% protein exposed group exhibited lower body weights at all ages, whilst the body weights of 9 and 12% protein exposed rats did not differ from the control group. At 9 weeks of age, a 2 g/kg body weight intravenous glucose load was cleared in 60 min by 18% protein exposed, control rats and 12% protein exposed rats. Peak blood glucose concentrations in these animals were 27.2 and 27.1 mM, respectively. Rats exposed to 9% protein in utero also cleared the glucose load in 60 min, but peak blood glucose concentrations were lower (24.4 mM), and the area under the glucose tolerance curve was 28% lower than in controls. Rats in the 6% protein exposed group cleared the glucose load in 40 min and peak blood glucose levels were only 22.1 mM. The area under the glucose tolerance curve was reduced by 40% relative to controls. When the glucose tolerance test was repeated in animals aged 44 weeks, no differences in peak glucose concentrations, area under the curve or rates of glucose clearance were observed. In utero exposure of rats to maternal low protein diets has been shown, therefore, to alter glucose tolerance in young adulthood through an, as yet, undefined mechanism.
The contraction-relaxation cycle of the heart represents the combined action of a variety of different components of the myocytes. For many years an ‘index’ of contractility has been sought as a means of describing and integrating the large amount of information available from the studies of heart muscle contraction. This review will undertake to show that dF/dt, recorded from the whole heart, and dT/dt, recorded in isometric studies of isolated heart muscle preparations, should not be considered as the ‘index’ of contractility. Examples will be presented in which an increasing dT/dt is paradoxically accompanied by a lower tension, while a decreasing dT/dt can occur concomitantly with an increased contractile tension. Arguments are further presented in support of the concept that Ca2+, in conjunction with troponin C, is the main determinant of cardiac contractility and that dT/dt reflects a dynamic equilibrium between free and troponin-bound Ca2+. Peak tension is thus the net result of overlapping events competing for Ca2+ during the latter part of contraction, that is, during Phase II of contraction as defined below. These suggestions are based upon the following considerations: (a) The Ca2+ pumps are active even during rest and serve to maintain low cytosolic Ca2+ levels, (b) As cytosolic Ca2+ concentration increases, Ca2+ pump activity also increases, (c) In addition, the Na+Ca2+ exchange is activated by elevated Ca2+ concentrations and serves to decrease cytosolic Ca2+ levels, (d) The net result is a decline in free Ca2+ concentration during Phase II and a reduction in the rate of cross-bridge formation until peak tension is reached. Thus, the Ca2+ handling elements of the myocyte serve as a finely tuned feedback device, regulating troponin C-Ca2+ interactions controlling the Ca2+ concentration of the cytosol and as a result, the actin and myosin interaction. Factors which influence the function of these elements will change the contractility of the heart.
Germ-free (GF) and heteroxenic (Hx) rats were given a hypocholesterolemic diet (Hyper) with or without 5% guar gum (GG) for 4 weeks. The GF and Hx rats fed GG diets showed a lower hepatic and plasmatic cholesterol level when compared with Hyper groups. This reduction of cholesterolemia was due to a decrease in the chylomicron + very low density lipoprotein (VLDL) fraction. The caecal and portal concentrations of propionate were 30% higher in Hx rats fed the GG diet than in Hx rats fed the Hyper diet. These results exclude the participation of the intestinal microflora in the hypocholesterolemic effect of GG, and show that guar gum nullifies the effect of the hypocholesterolemic diet in the GF rats.
It is well known that metabolic acidosis (MA), PGE2, and insulin stimulate H+ excretion in toad urinary bladder. In addition, PGE2 has been shown to increase in the toad bladder during MA. Our present experimental findings indicate that MA, PGE2 and insulin increase [Ca2+]i and this then may be the signal for stimulation of H+ excretion in this tissue. Isolated cells of the toad urinary bladder, obtained from toads in a chronic metabolic acidosis (MA) have a significantly higher intracellular Ca2+ ([Ca2+]i) than similar cells obtained from toads in normal acid-base balance. Protaglandin E2 (PGE2) (10−5M) was found to stimulate [Ca2+]i, in the same normal toad bladder cells, as determined by the fluorescence ratio technique using FURA 2/AM (P < 0.05). Insulin (100 mU/ml) was also found to stimulate [Ca2+]i, in toad bladder cells (P < 0.01). The increase in [Ca2+]i following PGE2 stimulation was not dependent on extracellular Ca2+, whereas the increase seen following insulin stimulation was dependent on extracellular Ca2+.
CHAPS-solubilized muscarinic receptors (mAChRs) retain selective agonist or antagonist binding and sensitivity to GTP and ADP-ribosylation by pertussis toxin that ribosylates a group of G protein called Gi. This suggests that CHAPS solubilizes the mAChR-Gi complex both from neonatal and adult neurons. The gradient centrifugation of solubilized samples indicated that the neonatal samples contain mostly Gi-coupled mAChR (mAChRn) exhibiting a high affinity for [3H]OxM, but the adult samples contain a comparable quantity of Gi coupled mAChR (mAChRa1) and uncoupled mAChRs (mAChRa2) exhibiting low affinity for the agonist. The binding of [3H]OxM to or the dissociation of [3H]OxM from mAChRn and mAChRa1 was sensitive to GTP. However, the effects of GTP were sensitive to Na+ for mAChRn but not for mAChRa1. ADP-ribosylation by pertussis toxin but not by cholera toxin abolished the effects of Na+ on agonist binding to solubilized mAChRn, suggesting that NaCl affects mAChRn not by interacting with the receptor but by interacting with the mAChR-Gi complex. The subtype composition of mAChRn, mAChRa1 and mAChRa2 was studied by determining the IC50 and the Ki values for the inhibition by subtype-selective antagonists in the binding of [3H]OxM to the receptors. The neonatal and adult samples exhibited differences in the distribution of the mAChR subtypes, the neonatal samples containing mostly the M1-mAChR subspecies but the adult samples containing M1-, M2- and M3-mAChR subspecies. The pirenzepine-induced inhibition in the binding of [3H]OxM both to M1-mAChRn and M1-mAChRa1 was sensitive to GTP. The GTP-induced effects on mAChRn were modulated by Na+, but the effect on M1-mAChRa1 was not. This suggests functional differences between Gi coupled M1-mAChRn and M1-mAChRa1.
A novel angiogenesis model using co-culture of endothelial and interstitial cells was developed, in which bovine capillary endothelial cells (BCEC) formed capillary-like structure on the monolayer of interstitial cells (like smooth muscle cells) isolated from rat skeletal muscle. The capillary formation of BCEC occurred even under serum-free conditions. Insulin stimulated the capillary growth under serum-free condition, but not BCEC growth in the single culture system. These results suggested that the insulin effect on the capillary growth was brought about indirectly through the interstitial cells, and that this co-culture system may be useful for the study of angiogenesis (especially in skeletal muscle).
The object was to determine if carnitine attenuated ethanol metabolism in broilers similar to that reported in the rats. Two groups (n = 5) of 5-week-old broilers were given for 10 days the feed with or without 0.5% L-carnitine supplement. A single oral dose of ethanol on day 8 was followed by serial blood samples which were analysed for ethanol. Another dose of ethanol was given on day 10 and 2 hr later, plasma and liver were collected and analysed for ethanol, total lipid, triglycerides and carnitine. The carnitine supplemented diet prolonged the half-life of ethanol due to attenuation of ethanol metabolism which is similar to that reported earlier in rodents. The increases in plasma and hepatic acylcarnitines indicate that supplementary carnitine lessens the load of free acyl groups in the liver by eventual oxidation or excretion.
Ex vivo studies have been carried out on roe and red deer erythrocytes using electron spin resonance spectroscopy. Free radical formation in cells challenged with the brassica-derived haemolysin, dimethyldisulphide, was measured using spin trapping techniques. Significantly greater amounts of radical were trapped in the roe deer cells which may relate to differences in the antioxidant profile of the two genotypes. Results suggest that roe deer have a greater risk of developing oilseed rape poisoning than red deer.
Responses of endogenous transporters/receptors of Xenopus oocytes to l-alanine, l-arginine, l-leucine and l-serine were investigated under voltage clamp conditions, (a) Concentrationresponse relations for the amino acids followed Langmuir's adsorption isotherm, (b) The neutral amino acids required Na+ to elicit the responses, whereas l-arginine did not. (c) The responses to l-alanine decreased with decreasing pH and became undetectable at pH 5.5. The present experiments supply criteria to judge if the oocytes translate exogenous mRNA coding taste or olfactory receptor proteins for the amino acids, the best characterized stimuli, especially in fishes.
Nitrogen and mineral (Fe, Mg, Na, K, and Ca) compositions of foodstuffs consumed by and dung produced by male, pregnant and lactating female adult Icelandic reindeer and calves were determined during May of 1992. Iron levels in foodstuffs are consistently above the reported toxicity level for similar-sized sheep (0.5 ppt) and may lead to iron toxicity when consumed by reindeer during periods of high lean body mass catabolism. Male and female reindeer meet nutrient requirements for all measured elements and nitrogen with the possible exception of calcium for males during antler growth.
Kalahari dwelling Damara mole-rats (Cryptomys damarensis) naturally feed on a high fibre diet of underground gemsbok cucumber tubers, Acanthosicyos naudinianus. We investigated the degree of fibre utilization and fermentation on this diet by measuring caecal characteristics (namely temperature, pH and weight) and in vitro rates of gas and short chain fatty acid (SCFA) production in these underground dwelling hind-gut fermentors. Rectal temperatures (33.8±0.6°C) were consistently higher than caecal temperatures (33.3 ± 0.6°C). Furthermore, a 0.8°C gradient of temperatures existed within the caecum, with the lowest temperature occurring in the corpus caeci. Both rates of gas production (4.74 ± 0.6 ml/g dry matter/hr) and SCFA production (266.80 ± 9.251 /i mol/caecum per hr) were high, with proportionately more acetic acid produced than any other SCFA. Nevertheless, the initial concentrations of SCFAs present in the caecum were low (52 ±17 mM) implying a rapid rate of absorption of these SCFAs. The high rates of fermentation provide a considerable amount of energy that would otherwise be trapped in fibre and thus unavailable to the animal. This highly efficient caecal fermentation enables the Damara mole-rat to maximally exploit the underground food resources in the arid-zone ecotope.
In vitro exposure of dogfish (Mustelus canis) lenses to near-UV energy not incompatible with that of the environment, causes an opalescence that is not present in unirradiated lenses or those irradiated after soaking in alpha-tocopherol or deferoxamine. The ability of whole lenses to destroy H2O2, as shown by their ability to produce O-2 bubbles in H2O2 containing media, is markedly diminished by UV exposure without these antioxidant/free radical scavengers added. The lens capsule epithelium is the major site of catalase activity. Bubble formation was prevented by presoaking the lenses in 3-amino-triazole (3-AT), a potent catalase inhibitor. Analytical measurements confirmed the above observations. Near-UV inhibition of catalase may allow H2O2 in, the aqueous humor to damage the lens by exerting oxidative stress.
