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Biomedical subjects

I Nir

Publications and source records attributed to I Nir.

At least 91 records · Page 5Linked to original sources
PubMed1988

The synthesis in vivo of proteins in various tissues in chickens adapted to intermittent feeding.

1. Protein synthesis was estimated in vivo in breast (superficial pectoral) and tibia (gastrocnemius) muscles, liver, kidney, pancreas, crop, duodenum, jejunum and ileum, using L-[U-14C]lysine injection. The effect on incorporation of [14C]lysine 1 and 2 h after injection was examined in five chickens adapted or not adapted to intermittent feeding. 2. Incorporation of [14C]lysine into tissue decreased in magnitude in the following descending order: pancreas greater than jejunum, duodenum greater than ileum, crop, liver greater than kidney greater than tibia, breast muscle and blood plasma. 3. The incorporation of [14C]lysine into muscle protein was higher in chicks after 24 h of refeeding than after 24 h of food deprivation. These differences were higher in adapted than in non-adapted birds. On days of refeeding the rate of incorporation exceeded that found in chickens fed ad lib. 4. Bound 14C from lysine in the intestinal segments was less than in control birds after food deprivation and greater after refeeding in non-adapted chicks only. 5. A negative relation was observed between bound and free 14C in muscles and in other tissues. 6. Short- and long-term adaptations to feeding regimens are discussed.

Adaptation, Physiological↗
PubMed1988

Melatonin receptors in discrete brain areas of the male rat. Impact of aging on density and on circadian rhythmicity.

The distribution of melatonin receptors in six discrete brain areas of mature (3-4 months old) and aged (greater than 24 months old) male rats was recorded every 4 h during a 24-hour light: dark cycle (L:D 14:10h). 125I-melatonin was used as a melatonin receptor probe. In the mature animals, specific binding of 125I-melatonin was found in all brain areas investigated, i.e. hypothalamus, medulla pons, hippocampus, cerebellum, parietal cortex and striatum. The density of 125I-melatonin-binding sites in the hypothalamus, medulla pons and hippocampus exhibited clear diurnal rhythms with different patterns and phases. No such rhythm was evident in the cerebellum, parietal cortex and striatum. The apparent affinity of the binding sites was similar in all the brain regions and did not change at any of the times recorded. In the old male rats, the density of 125I-melatonin binding sites in the hypothalamus was only 10% of that in the mature animals at 13 h after the onset of light and was vanishingly small throughout the 24-hour period. The 24-hour mean of the binding site density in the parietal cortex, hippocampus and medulla pons was significantly lower than in mature rats with no apparent diurnal variations. The age-related decrease in the density of melatonin-binding sites was less pronounced in the cerebellum and striatum. In all brain areas tested, apart from the hypothalamus, the decrease in receptor densities was not accompanied by changes in the apparent affinity towards the ligand.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1988

Two populations of mast cells on fibroblast monolayers: correlation of quantitative microscopy and functional activity.

We have previously shown that a confluent layer of mature mast cells is obtained when lymph node cells are grown on embryonic fibroblast monolayers. Two populations of mast cells may be observed, depending on treatment of the mice from which the lymph node cells are derived. We report now on the morphometric evaluation of these two mast cell entities, and we correlate this with cellular biochemistry and secretory behaviour. The first type of mast cell is small (265 +/- 20 microns 3). It arises from the embryonic monolayer and the cells have feathers resembling those of connective tissue mast cells. These cultured cells are filled with about 1000 homogeneous electron-dense granules, which usually range in diameter from 0.05 to 0.2 microns. The second type of mast cell arises from precursors originating from the lymph node and they have feathers of mucosal mast cells. These cells are larger (480 +/- 40 microns 3) and contain about 300 heterogeneous granules, which range from 0.1 to 0.8 microns. Both cell entities contain about equal amounts of histamine, serotonin and chymase. Biologically, the two cell entities secrete soluble mediators (histamine and serotonin) at different rates compared to the rate at which they secrete chymase. We suggest that such a pattern of secretion exhibits a form of degranulation that permits the release of freely diffusible mediators that are loosely bound to granules, but only partially permits the secretion of insoluble mediators, which are stored in the granules. Alternatively, there might be a mechanism that rapidly inactivates or binds chymase so that only the vasoamines will be free.

Animals↗
PubMed1988

Cisplatin ototoxicity in guinea pigs with special reference to toxic effects in the stria vascularis.

The toxic effects of cisplatin (cis-diamminedichloroplatinum [II]) on the organ of Corti are well established. Few and conflicting data on this drug's effects on the stria vascularis exist. The present study presents animal experiments on the toxic effects of cisplatin in the stria vascularis and in the organ of Corti. Cisplatin-induced toxicity in albino and pigmented guinea pigs was evaluated morphologically and functionally, using light and transmission electron microscopy as well as auditory brainstem-evoked potentials on the organ of Corti and the stria vascularis. The results showed variability in hearing thresholds, ranging from no change to hearing loss of 30 dB, and prominent damage in the organ of Corti and in the stria vascularis. The toxic effects to both the organ of Corti and the stria vascularis should be considered when cisplatin is used in chemotherapy.

Animals↗
PubMed1987

Effect of acute administration of delta 1-tetrahydrocannabinol on beta-endorphin levels in plasma and brain tissue of the rat.

Acute treatment with delta 1-tetrahydrocannabinol (delta 1-THC) elevated the concentration of beta-endorphin-like immunoreactivity (beta-ELIR) in plasma and in the hypothalamus, but not in the hippocampus of rats habituated to the injection procedure. These effects were not obtained with the psychotropically inert analog of delta 1-THC, cannabidiol. In animals that had not been habituated to the injection procedure, placebo treatment induced a decrease in hippocampal beta-ELIR.

Animals↗
PubMed1987

Water intake and water concentration in the body and gastrointestinal tract of intermittently fed broiler chickens.

The relationship between water intake and water concentration in the body and in the gastrointestinal contents was studied in meat-type chickens fed either intermittently or ad libitum, as controls. In experiment 1, male broilers were reared from 12 to 33 d of age and were fed every second day or ad libitum. The water consumption of the intermittently-fed birds on days of food removal was 31% of the consumption of the control group. On days of food restoration their water consumption exceeded that of the controls, by 27%. No significant differences in water:food ratios were found between birds fed intermittently or the controls on days of food restoration. The restricted birds had a lower fat and a higher protein concentration in the body. No relationship was found between water:food ratio and body composition. In experiment 2, birds were kept on the same feeding regimes from 12 to 46 d of age. The water content of the pancreas increased after food restoration compared with ad libitum feeding or food deprivation. The amount of water in the gastrointestinal contents increased progressively from crop to ileum. The feeding regimens had no effect on the water content of the intestine.

Animals↗
PubMed1987

Pineal, retinal, serum melatonin, and N-acetylserotonin rhythms in chicks on reversing light regimen and eye covering.

After reversing a 12:12-h light-dark regimen of environmental lighting, pineal and retinal melatonin levels of white leghorn chicks recorded at the first mid-darkness were greatly enhanced and reached maximum levels after three more days; those recorded during the light periods indicate gradual decline but were far from the nadir of the original light period, even at the end of the experiment. The first mid-darkness serum melatonin levels recorded after photoperiod reversal were not much different from their original mid-light values. However, on continuing with the reversed regimen, the next mid-darkness levels were sharply increased, and maximum levels were reached after a further 2 days. Under the same experimental conditions light had much more drastic effects, and 6 h on the reversed regimen were sufficient to bring down completely the high value of the original mid-darkness period to the level of the starting mid-light nadir. Retinal N-acetylserotonin (NAS) measured simultaneously had a pattern similar to that of melatonin, but the pineal NAS rhythm did invert completely, albeit gradually. Eye covering did not prevent inversion of pineal and serum melatonin rhythms, which were identical in eye-covered and sighted control chicks on the reversed regimen of light. However, retinal melatonin values of the light periods were significantly less depressed in eye-covered than in sighted control chicks. Moreover, eye covering completely prevented the retinal NAS depression under light but did not affect pineal NAS. During darkness retinal and pineal NAS elevation was sluggish in the eye-covered chicks.

Animals↗
PubMed1987

Muscle protein synthesis and degradation in chicks adapted to intermittent feeding: in vitro studies.

The effect of intermittent feeding (every 2nd day) on in vitro muscle protein synthesis and degradation was studied in adapted and nonadapted broiler chicks. Protein synthesis, estimated by in vitro incorporation of L-[14C]-tyrosine into muscle protein, was higher in the intermittently fed birds than that in ad libitum fed counterparts or nonadapted birds. In chicks exposed to one 24-hour cycle of food deprivation and restoration, protein synthesis was slightly depressed (nonsignificant). Protein degradation, estimated by free tyrosine released from muscle into the medium, decreased after 24 h of food deprivation and increased after 24 h of food restoration, to the same extent in both adapted and nonadapted birds.

Adaptation, Physiological↗
PubMed1987

Growth-associated traits in parental and F1 populations of chickens under different feeding programs. 1. Ad libitum feeding.

Two experiments were conducted to compare body composition, plasma concentrations of glucose, lipid and protein, gastrointestinal tract (GIT) morphology, and digestive enzyme activities among populations of chickens exhibiting wide differences in growth. In the first experiment, males from a high weight (HW) line, a low weight (LW) line, and crosses between the lines (HL) were examined. In the second experiment, the same high weight (HW') line, a White Leghorn (LEG) line and their crosses (HLEG) were compared. In both experiments, comparisons were made at both 25 and 61 days of age. The HW chicks were heavier and had larger breasts and longer shanks than the LW or LEG chicks. Although the crosses (HL, HLEG) exhibited values for these traits intermediate to those of the parental lines, HLEG chicks tended to resemble one of the parental lines more closely than did the HL chicks. Differences among all mating combinations were significant for body fat, but the crosses (HLEG, HL) tended to more closely resemble their HW parental line. The HW chicks had significantly higher concentrations of glucose, lipid, and protein in plasma at 25 but not 61 days of age. No differences in glucose, lipid, or protein concentrations in plasma were observed in the second experiment. When expressed as a percentage of body weight, LW and LEG chicks tended to have larger GIT than HW chicks, whereas crosses more closely resembled the HW line. Although significant differences in digestive enzyme activities were obtained, these differences were generally associated with differences in body weight. It was concluded that genetic variation in the traits examined was dependent on both population and age.

Animals↗
PubMed1987

Growth-associated traits in parental and F1 populations of chickens under different feeding programs. 2. Ad libitum and intermittent feeding.

Growth traits and digestive enzyme activities were compared in parental lines and F1 crosses under ad libitum and alternate-day feeding. Responses to the feeding regimens were, in general, dependent on the background genome and age. Population by feeding regimen interactions were more prevalent for growth traits than for enzymatic activities. Although chickens adapted morphologically and physiologically to the particular feeding regimen to which they were exposed, the degree of adaptation was population dependent. Moreover, a line of White Leghorns differed considerably in response compared to a line of White Rocks selected for low body weight, demonstrating that weight is primarily a result of metabolic and behavioral processes rather than the determiner of those processes.

Animals↗
PubMed1987

Growth-associated traits in parental and F1 populations of chickens under different feeding programs. 3. Eating behavior and body temperatures.

In two experiments, parental populations of chickens and their F1 crosses were fed ad libitum or on alternate days. Eating and drinking behaviors, ability to compensate for fasting, and surface and cloacal temperatures were measured. Genetic and environmental (due to fasting) differences in feeding and drinking behaviors were found. Chicks from lines selected for larger body weight were better able to compensate for a 24-hr fast than those selected for smaller weight. Crosses were similar to the parental line that was the better compensator. Correlations between surface temperatures and body weights were consistently positive.

Animals↗
PubMed1987

Growth-associated traits in parental and F1 populations of chickens under different feeding programs. 4. Growth and thyroid hormones.

Plasma levels of growth hormone (GH), triiodotyronine (T3), and thyroxine (T4) were compared at 25 and 61 days of age in parental lines and F1 crosses between parental lines under ad libitum and alternate day feeding. Parental lines included White Rocks selected for high and low body weight and a White Leghorn population. Differences among populations for hormone levels were more pronounced at 61 than at 25 d of age. Growth hormone decreased and T4 increased with age in all populations except the line selected for low body weight, whereas the pattern for T3 varied with genetic stock. On days when chicks were not fed, plasma GH and T4 increased and T3 decreased. On days of feeding, GH and T4 returned to the level of chicks fed ad libitum while T3 was either identical to or higher than that for the ad libitum chicks. Population by feeding regimen interactions were not significant at either age for any of the hormones measured showing that responses to the feeding regimens were similar for all populations.

Aging↗
PubMed1987

Opsin accumulation in photoreceptor inner segment plasma membranes of dystrophic RCS rats.

Opsin localization in photoreceptor plasma membrane was studied in 10- to 30-day-old dystrophic RCS rats. Preembedding cytochemical procedures with antiopsin antibodies and electron microscopy were employed. In the second postnatal week, opsin was sequestered to the outer segment plasma membrane in affected rat retinas. This distribution resembled that observed in the photoreceptors of normal rats at this age. As unphagocytosed debris accumulated in the subretinal space, the outer segments degenerated, and the distribution of opsin in the plasma membrane changed. Opsin reappeared in the inner segment plasma membrane as the outer segments were lost. Loss of the regionalized distribution of opsin was not associated with visible ultrastructural changes in the inner segments or connecting cilium. Severely damaged cells invariably were labeled on their inner segments at high density. Thus, the presence of an outer segment was correlated with the clearance of opsin from the inner segment, while damage to the outer segment was followed by reappearance of opsin in the inner segment plasma membrane.

Animals↗
PubMed1987

Surface glycoconjugates on rat photoreceptor cilium. Effect of neuraminidase digestion.

In retinal photoreceptors the connecting cilium constitutes a boundary between the inner and outer segments. In previous studies we demonstrated that, while opsin could be localized in abundance in the distal ciliary membrane, very little opsin was detected in the proximal ciliary plasma membrane. In the present study we extended our view of molecular specialization on the ciliary membrane with respect to glycoconjugates. Saccharide moieties of ciliary glycoconjugates were studied in immature and mature rat photoreceptors. Surface saccharides were detected and localized by means of ferritin-labeled lectins and electron microscopy. Dense labeling of the ciliary membrane surface with wheat germ agglutinin (WGA) was observed. In immature photoreceptors the labeling was restricted to the proximal ciliary membrane, in a region where opsin molecules could not be detected. Neuraminidase digestion abolished WGA binding to the proximal ciliary membrane surface, indicating that sialic acids mediate WGA binding to this domain. Peanut agglutinin (PNA) did not label the ciliary surface, nor did it bind to the surface of other photoreceptor domains. Neuraminidase digestion exposed numerous PNA binding sites on the ciliary membrane surface. In view of the carbohydrate specificity of PNA, we suggest that a terminal trisaccharide sequence, sialic acid-galactose-(beta 1----3)-N-acetyl galactosamine, is present in high density on the proximal ciliary membrane surface.

Animals↗
PubMed1987

Cytochemical characterization of sialoglycoconjugates on rat photoreceptor cell surface.

Terminal saccharide sequences in rat photoreceptor cell surface glycoconjugates were characterized. Lectin cytochemistry and electron microscopy were used for preembedding cytochemical localization of surface carbohydrates. Neuraminidase digestion was employed for the exposure of penultimate saccharides in sialoglycoconjugates. Isolated rat retinas were incubated with ferritin-labeled wheat germ agglutinin (WGA), peanut agglutinin (PNA), and soybean agglutinin (SBA) prior to and after neuraminidase digestion. PNA and SBA did not label untreated photoreceptors. WGA densely labeled the photoreceptor surface and interphotoreceptor matrix (IPM) components. Following neuraminidase treatment, PNA, but not SBA, labeled the photoreceptor surface and the IPM. WGA labeling of the IPM was abolished, and the labeling of the photoreceptor surface was reduced. Based on the lectin specificity, it was concluded that photoreceptor surface glycoconjugates in the rat retina contain a terminal trisaccharide: sialic acid-D-galactose-(beta 1----3)-N-acetyl-D-galactosamine.

Acetylgalactosamine↗
PubMed1986

Accentuated response to soybean inhibitors by meal-feeding in various species.

Diets containing raw soybean products (RSD) fed ad libitum caused a reduction in food consumption and growth, pancreatic enlargement, hypersecretion of digestive enzymes, and enlargement of intestinal segments and their contents in rats, chicks and geese. These effects were found to be related to the concentration of trypsin inhibitor (TI) in the diet. Geese were more sensitive than rats and chicks. Calves fed RSD did not respond in pancreatic hypertrophy and hypersecretion of digestive enzymes, but growth was depressed. Meal-feeding also caused enlargement of the pancreas, digestive tract segments and their contents. The effects of feeding RSD and of meal feeding were found to be additive. In ad libitum feeding the animal can regulate food consumption and moderate the effects of antinutritional factors in the diet. Meal or tube-feeding interfered with this defense mechanism and the negative effects of RSD were accentuated and were lethal in non adapted rats and geese. In long-term studies the incidence of pancreatic nodules was correlated to the level of TI in the diet. Feeding RSD potentiated the carcinogenic effect of azaserine and meal feeding enhanced the incidence and size of the pancreatic nodules in rats fed RSD.

Amylases↗
PubMed1986

Horseradish peroxidase as a cytochemical marker of blood-brain barrier integrity in oxygen toxicity in the central nervous system.

The ultrastructural integrity of endothelial tight junctions in cerebral microvessels of the rat exposed to hyperbaric oxygen was examined to find whether or not there are alterations of the blood-brain barrier in the initial phase of central nervous system oxygen toxicity. Rats were pre-implanted with cortical electrodes for continuous EEG and provided with two polyethylene cannulae inserted into the common carotid artery. HRP was administered to unanesthetized rats through a cannula directed into the brain, before the onset of O2 pressurization. As soon as the early electrical discharges of oxygen toxicity were recorded (20 to 30 min), the animal was killed by injection with saturated KCl into the heart. Examination of small blood vessels in both LM and EM did not support the possibility that the blood-brain barrier is altered prior to the first electrical discharge appearing in central nervous system oxygen toxicity.

Animals↗