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Biomedical subjects

S Yehuda

Publications and source records attributed to S Yehuda.

At least 19 recordsLinked to original sources
PubMed1998

Fatty acids and brain peptides.

The role of fatty acids (FA) as a mediator and modulator of central nervous system activity in general, and peptides in particular, is only recently becoming understood. This paper reviews numerous findings concerned with the activity of fatty acids, particularly with their interaction with diverse neurochemical systems and their consequences for better understanding neurotransmitters, hormones and peptides. The effects include FA as precursors in the manufacture of neurochemical elements, including enzymes, neurotransmitters, and hormones. Of particular interest is the important changes in neuronal membrane composition that have been attributed to FA. Such changes may account for the changes in thermoregulation, learning, and other functions that accompany dietary manipulation of FA intake. While the total level of FA has been the object of many investigations, this report addresses the need to focus on the ratio of FA, especially alpha-linolenic/linoleic acid, which has been shown to be a critical factor in a number of research studies.

Animals↗
PubMed1998

Essential fatty acids and sleep: mini-review and hypothesis.

The neurochemical basis of sleep mechanisms (onset and maintenance) is still controversial although the phenomenon itself is known to be mediated by more than a single molecule. The list of suggested endogenous sleep substances is rather long, and there is no single 'sleep center' identified in the brain. The role of fatty acids, and essential fatty acids in particular, has been ignored in sleep research. This review proposes an integration of the current knowledge about the effects of fatty acids in sleep neurochemistry, wherein fatty acids are seen to exert a direct effect on neuronal membrane structure or indirectly on the dynamics of biochemical compounds (complex lipids, prostaglandins, neurotransmitters, amino acids, interleukins) necessary for the initiation and maintenance of sleep.

Alzheimer Disease↗
PubMed1998

Modulation of learning and neuronal membrane composition in the rat by essential fatty acid preparation: time-course analysis.

Previous studies have shown that chronic administration of SR-3 (a 1:4 mixture of alpha-linolenic and linoleic acid) affects spatial learning, thermoregulation, pain threshold and protection from seizures. The mode of action is unknown. One possible explanation is that the preparation induces changes in the fatty acids profile and in the cholesterol level in the neuronal membrane. This study used 15 independent groups of rats (n = 12) which were given either saline, mineral oil (vehicle) or SR-3 (25 mg/kg) for 0, 1, 2, 3, or 4 weeks. The learning performance was measured in the Morris Water tank and the fatty acids profile and the cholesterol level were examined by the GC method in synaptosomes obtained from the frontal cortex of the rats. SR-3 improved the learning performance and induced major changes in the neuronal membrane composition, such as an increase in the total level of fatty acids, an increase in the level of essential fatty acids and a decrease in the cholesterol level. Those changes occurred after 3 weeks of treatment. The biochemical variables can predict the behavioral variables but not vice versa. The changes in the neuronal membrane may result in a modification of the membrane fluidity, which may, in turn, enhance cognitive and neuropharmacological effects.

Animals↗
PubMed1997

Essential fatty acid preparation improves biochemical and cognitive functions in experimental allergic encephalomyelitis rats.

This study examined the possible effects of a novel mixture of fatty acids, SR-3 (a specific ratio of alpha-linolenic acids), on brain biochemistry and on learning deficits induced by injection of an agent that induces experimental allergic encephalomyelitis. Treatment with SR-3 caused a decrease in myelin and changes in the fatty acid profile of brain synaptosomes, and a learning deficit. Eighteen days of treatment with SR-3 reversed the biochemical and learning deficit significantly, but did not restore them to normal levels. We propose that, most probably, the main action of SR-3 is the modulation of the cholesterol level, which in turn causes the modulation of the fatty acid profile and enhances learning by allowing improved neuronal communication.

Analysis of Variance↗
PubMed1997

Attention deficit disorder and hyperactivity--changes in hypothalamic function in hyperactive children: a new model.

This presentation proposes a dynamic integrative model for understanding attention deficit disorder and hyperactivity. The proposed model-the lapses model-is based on principles found in control systems. It suggests the existence of a compensatory system employed by the organism in order to correct its internal overload and homeostatic disturbances resulting from a hypothalamic dysfunction. The restoration of internal homeostasis requires resources needed for the interaction with the environment. Allocation of such resources results in lowered control ability to the point of total loss of contact with the environment. Thus, the compensatory system influences the data-processing ability and determines the cognitive style. The limitation of resources directed to coping with the surrounding environment, already creates a disturbance at the input level. This results in continuity-loss and data-loss due to the temporary saturation and oscillations in the arousal level. When balance is regained, the arousal level comes back to the optimal range, until such time when accumulated load will again cause a disturbance. The cycle repeats itself at varying intervals. The model relates to the interaction between three behavioral levels: biochemical-hormonal, physiological and cognitive-communicative.

Arousal↗
PubMed1996

Essential fatty acid preparation reduces cholesterol and fatty acids in rat cortex.

Previous studies have shown that chronic administration of SR-3 (a 1:4 mixture of alpha-linolenic and linoleic acid) affects spatial learning, thermoregulation, pain threshold, and protection from seizures. The mode of action of SR-3 is unknown. One possible explanation is that SR-3 induces changes in the FA profile and in the cholesterol level in neuronal membranes. This study used 10 independent groups of rats (ni = 12) given 4 weeks of either saline, mineral oil (vehicle), alpha-tocopherol (antioxidant), alpha-linolenic acid, linoleic acid, or one of 5 different ratios of alpha-linolenic acid:linoleic acid (1:3, 1:4, 1:5, 1:6, 1:7) as free fatty acids. FA profile and cholesterol level were examined by GC method in synaptosomes obtained from the frontal cortex of the rats. The mineral oil treated group served as the control group. No difference was found in the FA profile or cholesterol level except for the SR-3 treated group. The ratio of 1:4 was found to have a significant influence on decreasing the cholesterol level and in inducing major changes in the FA profile, such as an increase in EFA. These effects of SR-3 may result in modification of the membrane fluidity, which may, in turn, enhance cognitive and neuropharmacological effects.

Animals↗
PubMed1996

Essential fatty acids preparation (SR-3) improves Alzheimer's patients quality of life.

In a number of previous reports we showed the salutary effects on rats of SR-3, a compound comprising a 1:4 ratio of n-3 and n-6 fatty acids. Improvements were noted in learning tasks, thermoregulation, recovery from neurotoxins, and seizure protection. Because we were impressed that these effects are related to changes in membrane fluidity and neuronal functioning and because Alzheimer's Disease is also associated with lipid defects, we undertook a short term (4 week) double blind study with 100 Alzheimer patients (60 received SR-3 and 40 in a placebo control). The results indicated improvements in mood, cooperation, appetite, sleep, ability to navigate in the home, and short term memory. Overall improvement was reported for 49 patients, and in no case did a guardian report adverse effects to the compound. While not uniform or permanent, and while no mode of action for SR-3 can be precisely identified at this time, the promising results in quality of life for the patient and caregiver warrant further clinical trials and continued basic research into the neuropsychological substrate of the disease and its response to SR-3.

Activities of Daily Living↗
PubMed1996

Dead Sea mineral-based cosmetics--facts and illusions.

Modern Dead Sea cosmetics have developed in order to meet the demands of new regulations, technical opportunities, and today's consumer expectations for higher quality standards and proven performance. As an example of the application of this approach, the authors describe the development of a new cosmetic formulation, based on "Osmoter", a special Dead Sea mineral composition, and the evaluation of this formulation's effect on the depth of skin wrinkles, by a controlled assay. Possible mode of action is discussed.

Chemistry, Pharmaceutical↗
PubMed1995

Modification of cytokine secretion following mild emotional stimuli.

In the present study, changes in the cytokine system (IL-1 beta, IL-2, IL-3, IL-6 and TNF alpha) were assessed following exposure to mild mood induction (negative and positive) in humans. An increase in secretion of TNF alpha, a decrease in that of IL-2 and of IL-3 with no change in IL-1 beta and in IL-6 secretion levels, was observed in response to mild negative emotional changes. A reversed cytokine secretion profile was found following positive mood changes, suggesting the hypothalamic-pituitary-adrenal axis and the autonomic nervous system, as possible mediators underlying these effects, specific to the nature of the emotion.

Adolescent↗
PubMed1995

Essential fatty acid preparation (SR-3) rehabilitates learning deficits induced by AF64A and 5,7-DHT.

The purpose of this study was to examine the possible effects of a novel mixture of fatty acids, SR-3 (a specific ratio between alpha-linolenic and linoleic acids) on learning deficits induced by cholinergic (AF64A) and serotonergic (5,7-DHT) neurotoxins in rats. I.c.v. AF64A and 4th ventricle administration of 5,7-DHT induce severe learning deficit using the Morris Water Tank. Three weeks of treatment with SR-3 rehabilitated the learning capacity of rats. However, learning deficits induced by a lesion in area postrema was not rehabilitated by SR-3. The mode of action of SR-3 is unknown. We propose that this combination of free fatty acids modulates the composition of neuronal membrane lipids and allows better neuronal communication.

Animals↗
PubMed1994

Essential fatty acid preparation (SR-3) raises the seizure threshold in rats.

The anticonvulsant properties of a mixture of non-esterified alpha-linolenic acid and linoleic acid with a ratio of 1:4 (SR-3) were evaluated in four rat models of epileptic seizures: (1) i.p. injection of a single convulsant dose (50 mg/kg or 100 mg/kg) of pentylenetetrazol; (2) repeated subconvulsant doses of pentylenetetrazol; (3) cortical irritation by intraventricular administration of iron chloride (FeCl3); and (4) audiogenic seizure-prone preparation created by repeated pretreatment with p-cresol. Treatment with SR-3 (about 40 mg/kg i.p.) for a period of 3 weeks prior to challenge was found effective in each of these experimental models and caused up to a 22-fold increase in latency to major motor seizures, up to 84% reduction in the number of rats with seizures, and up to a 97% reduction in the duration of seizures. It is postulated that the anticonvulsant effects of SR-3 may be related to its stabilization of neuronal membranes. SR-3 should be evaluated further as a treatment for epilepsy.

Acoustic Stimulation↗
PubMed1994

Decrease of serum iron in acutely psychotic schizophrenic patients.

Iron deficiency has been shown to effect the dopaminergic system. Iron deficient rats have low dopamine D2 receptor levels and modified dopamine-mediated behaviors, including reversal of circadian cycles of these behaviors. Abnormal iron deposits have been found in the brains of schizophrenics in CT and post mortum studies. We examined serum iron levels at 0800, 1700 and 2400 hours in 26 medication free schizophrenic patients in acute psychotic relapse and compared them to iron levels in a normal control group. The results show significant decreases in the iron levels at 1700 and 2400, and a non significant drop in the 0800 levels. A feedback mechanism involving iron and dopamine is proposed.

Acute Disease↗
PubMed1993

Modulation of learning, pain thresholds, and thermoregulation in the rat by preparations of free purified alpha-linolenic and linoleic acids: determination of the optimal omega 3-to-omega 6 ratio.

Ingested polyunsaturated fatty acids are postulated to lead to changes in central nervous system activity, presumably by altering the lipid composition of neuronal membranes. In support of this hypothesis, we and other investigators have previously demonstrated cognitive effects in rats fed oils that contain both alpha-linolenic acid (18:3 omega 3) and linoleic acid (18:2 omega 6), with the relative content of alpha-linolenic acid being seen as the critical variable. The present study in rats examined the effects of preparations containing different ratios of highly purified free alpha-linolenic acid to linoleic acid (about 25 mg/kg of body weight daily) on learning performance (Morris water tank), pain thresholds (heated plate), and thermoregulatory control of d-amphetamine-induced hypothermia during 4 weeks of treatment. Preparations with omega 3-to-omega 6 ratios ranging from 1:3.5 to 1:5 (specifically a ratio of 1:4) produced significant favorable effects on all of these variables. Although the specific mode of action remains to be elucidated, these results suggest that such preparations of free fatty acids should be evaluated in the treatment of memory disorders and pain conditions.

Animals↗
PubMed1991

The effect of pain on pentylenetetrazol induced seizures.

Repeated administrations of subconvulsive doses of pentylenetetrazol (PTZ) leads to frank convulsions. The number of injections required to bring about such an effect is taken as an index of seizure vulnerability, and was studied in normal rats. This study examined the effect of pain induced by formaline injection or placement on a hot plate on seizure elicitation. The results could be accounted for by the role of arousal and/or endogenous opiates that are generated by the pain induction procedures, wherein the pain appears to provide some elevation of the threshold for seizure vulnerability.

Animals↗
PubMed1991

The effects of iron deficiency and electric shock on learning in rats.

It is hypothesized that electric shock can compensate for the learning deficit caused by iron deficiency in the experimental rat population, and that this effect will be sustained over a 3-week "rehabilitation" period. Forty-seven female Sprague-Dawley rats served as the experimental subjects. The learning capacity of the rats was assessed using a water Y-maze. The dependent variables were assessed twice, once after half had been made iron deficient, and again after the iron deficiency had been corrected. A 2 x 2 x 2 analysis of variance with repeated measures was employed, along with post-hoc tests, to assess the effects of the experimental manipulations on the rats' performance. The experimental results replicated previous findings regarding the damaging effects of iron deficiency on learning capacity in rats and confirmed that shock improves the performance of rats in the water Y-maze. Furthermore, it was found that shock and iron deficiency interact, such that the performance of iron-deficient rats subjected to electric shock is superior to that of rats not made iron deficient. This trend persists even after the hematological effects of iron deficiency are corrected, although to a less dramatic degree. A possible explanation for these findings is advanced.

Animals↗
PubMed1989

Putative biological mechanisms of the effect of iron deficiency on brain biochemistry and behavior.

An animal model of nutritional iron deficiency (ID) is described that demonstrates a reduction of brain nonheme iron. The most prominent feature of ID is the significant and selective diminution of central dopamine neurotransmission resulting from the decreased number of dopamine D2 receptors in the caudate nucleus, nucleus accumbens, pituitary, and in all probability the frontal cortex. The consequences of diminished dopaminergic neurotransmission is a modification of dopamine-dependent behaviors and biochemical reactions, the most important of which is the reduction in learning processes. The role of iron in maintaining the homeostasis of normally functioning dopamine neurons and their involvement in cognitive processes cannot be excluded. An interference with iron metabolism at an early age can result in irreversible damage to developing dopamine neurons, with consequences that may manifest themselves in adult life.

Animals↗