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R Burstein

Publications and source records attributed to R Burstein.

At least 55 records · Page 3Linked to original sources
PubMed1991

The cells of origin of the spinohypothalamic tract in cats.

Various cutaneous and visceral stimuli alter the discharge rates of neurons in the hypothalamus. Changes in the activity of hypothalamic neurons are thought to play important roles in eliciting neuroendocrine, autonomic, and affective responses to somatosensory and visceral stimuli. Information from peripheral structures has been considered generally to reach the hypothalamus via multisynaptic ascending pathways. Recently, a direct projection from the spinal cord to the hypothalamus was demonstrated in rats. The goal of this study was to determine whether a similar projection exists in cats. Either wheat germ agglutinin conjugated to horseradish peroxidase, a mixture of this tracer and the B subunit of cholera toxin conjugated to horseradish peroxidase, or fast blue was injected into the hypothalamus of cats. Injections were centered in the hypothalamus in seven cats and did not spread to the thalamus, zona incerta or midbrain. After these injections, retrogradely labeled neurons were observed bilaterally in each of the 17 spinal segments that were examined. A total of approximately 400-500 labeled neurons was observed in alternate sections through these segments in the most effective cases. Roughly 70% of the labeled neurons were located contralaterally. Labeled neurons were found predominantly in the deep dorsal horn, the intermediate zone/ventral horn and in the area surrounding the central canal. A few were also noted in the superficial dorsal horn. The first and second sacral segments contained the largest numbers of retrogradely labeled neurons in the spinal cord. The number of spinohypothalamic tract neurons observed in this study in cats was roughly an order of magnitude smaller than that previously reported for rats. This finding suggested either that the spinohypothalamic tract is relatively small in cats or that our tracing techniques did not label many spinohypothalamic tract neurons in cats. To test the sensitivity of one of our tracing techniques, control injections of wheat germ agglutinin conjugated to horseradish peroxidase that filled the ventrobasal thalamus were made in two cats. In both cases, thousands of spinal cord neurons were labeled. In summary, our results indicate that a spinohypothalamic tract exists in cats. However, our findings also suggest that the total number of spinohypothalamic tract neurons in cats may be an order of magnitude smaller than it is in rats.

Animals↗
PubMed1991

Autoantibodies in male homosexuals and HIV infection.

We have used ELISA to study the frequency of autoantibodies to several antigens in the serum of 17 male homosexuals (MHS) negative for HIV (HIV-), 11 asymptomatic HIV seropositive MHS (HIV+) and patients with ARC (N = 15) or AIDS (N = 13), and compared them to 20 matched healthy heterosexual controls. Serum antibody binding to histones, cardiolipin, ss-A, ss-B and Sm was found to be significantly higher in each of the MHS groups studied as compared to controls (P less than 0.001), and was also increased in the HIV+ patients vs. the HIV- group (P less than 0.05). In contrast, no increase in autoantibodies to ss-DNA, ds-DNA, poly(I), poly(G) or RNP were found in any of the groups tested. These results enlarge the spectrum of autoimmunity previously reported in HIV infection and identify a similar pattern to a lesser degree, already present in HIV- MHS, suggesting a role for HIV or concomitant virus infections in its pathogenesis.

AIDS-Related Complex↗
PubMed1991

Physiological characterization of spinohypothalamic tract neurons in the lumbar enlargement of rats.

1. Ninety-six neurons in the lumbar enlargement of urethananesthetized rats were antidromically activated from the contralateral hypothalamus. The antidromic stimulating electrode was moved systematically within the hypothalamus until antidromic activation could be produced with currents of less than or equal to 50 microA (18.6 +/- 10.8 microA; mean +/- SD). The points at which antidromic activation thresholds were lowest were found in several regions of the hypothalamus but were concentrated in the optic tract and the supraoptic decussation. 2. The recording locations of 79 spinohypothalamic tract (SHT) neurons were marked and recovered. Twenty-nine were located in the superficial dorsal horn (SDH), 42 in the deep dorsal horn (DDH), 4 in the intermediate zone, and 2 in the gray matter surrounding the central canal. Two additional marks were located in the dorsal lateral funiculus (DLF). 3. The responses of 46 SHT neurons were examined during innocuous and noxious mechanical stimulation of their receptive fields. Forty-eight percent of recorded SHT neurons responded to both innocuous and noxious stimuli (wide dynamic range, WDR) and 39% responded only to noxious stimuli (high threshold, HT). Therefore 87% of SHT neurons responded preferentially or exclusively to noxious mechanical stimulation. Nine percent of SHT neurons responded exclusively to innocuous manipulation of joints and muscles. Four percent of SHT neurons responded only to innocuous tactile stimul (low threshold, LT). WDR, HT, and LT neurons were recorded widely throughout the dorsal horn; no relationship was found between the locations of recording sites in the dorsal horn and the response types of the neurons. SHT neurons that responded to stimulation of muscle, tendon, or joint were recorded deep in the gray matter. 4. The effects of heating the receptive fields were determined for 25 SHT neurons. Fourteen (56%) responded to thermal stimuli. Six (43%) of the responsive neurons responded at low frequencies to innocuous warming (38-41 degrees C) but more vigorously to noxious (greater than or equal to 45 degrees C) heating. The other eight responded only to noxious heat. Eighteen percent (3/17) of tested SHT neurons were activated by noxious cooling of their receptive fields. 5. Cutaneous receptive fields of most recorded SHT neurons were small, typically involving areas as small as two or three toes on the ipsilateral hindlimb; the largest receptive fields covered the entire paw. These findings indicate that relatively precise information about the location of innocuous and noxious stimuli is conveyed directly to the hypothalamus by SHT neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Distributions of spinothalamic, spinohypothalamic, and spinotelencephalic fibers revealed by anterograde transport of PHA-L in rats.

Fibers projecting from several levels of the spinal cord to the diencephalon and telencephalon were labeled anterogradely with Phaseolus vulgaris leucoagglutinin injected iontophoretically. Labeled fibers in the thalamus confirmed projections previously observed. In addition, many labeled fibers were seen in the hypothalamus and in telencephalic areas not generally recognized previously as receiving such projections. In the hypothalamus, these areas included the lateral hypothalamus (including the medial forebrain bundle), the posterior hypothalamic area, the dorsal hypothalamic area, the dorsomedial nucleus, the paraventricular nucleus, the periventricular area, the suprachiasmatic nucleus, and the lateral and medial preoptic areas. In the telencephalon, areas with labeled fibers included the ventral pallidum, the globus pallidus, the substantia innominata, the basal nucleus of Meynert, the amygdala (central nucleus), the horizontal and vertical limbs of the diagonal band of Broca, the medial and lateral septal nuclei, the bed nucleus of the stria terminalis, the nucleus accumbens, infralimbic cortex, and medial orbital cortex. These results suggest that somatosensory, possibly including visceral sensory, information is carried directly from the spinal cord to areas in the brain involved in autonomic regulation, motivation, emotion, attention, arousal, learning, memory, and sensory-motor integration. Many of these areas are associated with the limbic system.

Afferent Pathways↗
PubMed1991

Hyponatremia induced by exercise: a 24-hour endurance march study.

In our previous studies on the relationship between prolonged physical stress and muscle enzyme activities, a number of individuals suffered a hyponatremic state. The present study was conducted to evaluate the effect of prolonged physical stress on the development of hyponatremia. Seventeen physically fit male subjects were studied during a 24-hour endurance march. Serum sodium, that averaged 142 +/- 2 before the march, decreased during the march to 135 +/- 2 mEq/l (p less than 0.01 versus before the march). Blood and plasma volumes increased by 8 and 16% (p less than 0.05), respectively. Creatinine clearance before the march declined from 118 +/- 24 to 74 +/- 19 ml/min (p less than 0.005) during the march and correlated negatively with serum sodium (p less than 0.002; r = 0.59). Urinary sodium excretion before the march was 132 +/- 55 and during the march was 123 +/- 62 mEq/24 h. Free water clearance rose during the march and correlated negatively with serum sodium (p less than 0.001), suggesting an appropriate renal diluting response. However, the fall in serum sodium correlated positively with water intake (p less than 0.01; r = 0.59). These results show that hyponatremia develops during endurance marching in normal subjects on an unrestricted high water intake. The renal response to water intake is appropriate; however, the subjects fall to produce maximally diluted urine. Therefore, we suggest that water intake should follow physiological needs and not forced to cause hyponatremia during prolonged physical stress.

Adult↗
PubMed1991

The effect of prolonged intermittent exercise, combined with food deprivation, on plasma metabolite concentration.

To examine the effect of continuous fasting combined with prolonged, intermittent exercise on glucose homeostasis, 16 endurance-trained subjects, ranging in age from 18-21 years, were completely deprived of food during 81 h of field maneuvers. Water was supplied to avoid dehydration. Participants marched 10 h each night at an estimated intensity of 35-45% of mean VO2 max covering a total distance of 105 km, and had a relative rest during day time. Blood was sampled prior to the beginning of the march, at the end of 81 h, and after 24 h of recovery. Samples were analyzed for plasma glucose, insulin, alanine, free fatty acids (FFA), and 3-hydroxybutyrate (3-HB). Body weight decreased from a mean (+/- S.E.M.) of 73.0 +/- 0.6 kg at pre-march to 66.5 +/- 0.6 kg at 81 h of fasting (p less than 0.05), and remained unchanged at 24 h after march termination. Glucose, insulin, and alanine decreased, whereas FFA and 3-HB increased significantly at 81 h fast (p less than 0.05). Within 24 h of recovery all parameters changed significantly (p less than 0.05), approaching baseline values. The results indicate that in trained individuals under extreme survival conditions, as in the present study, blood glucose is maintained above hypoglycemic levels at the expense of fat and fat-derived substrates that become the main energy sources utilized.

Adult↗
PubMed1990

Evidence that Fluoro-Gold can be transported avidly through fibers of passage.

Small iontophoretic injections of the retrograde tracer Fluoro-Gold were restricted to the dorsal columns in the cervical enlargement of 6 rats. Large numbers of neurons were labeled in the lumbosacral dorsal horn in each rat. In the most effective case, more than 1800 neurons were labeled in alternate sections through nine examined segments. Many neurons were also labeled in lumbosacral dorsal root ganglia of all cases. This study, in contrast to previous reports, indicates that Fluoro-Gold can be transported avidly by axons passing through, but not terminating in, injection sites.

Animals↗
PubMed1990

The cells of origin of the spinothalamic tract of the rat: a quantitative reexamination.

We quantitatively reinvestigated the cells of origin of the spinothalamic tract (STT) of the rat. Injections of Fluoro-Gold that filled the thalamus on one side labeled large numbers of neurons throughout the length of the spinal cord. In 3 cases, we estimated the total number of STT neurons by counting labeled neurons in 18 of the 34 total segments, applying correction factors to these counts, and estimating the numbers of labeled neurons in the 16 remaining unexamined segments. The accuracy of these estimates was tested in two animals in which labeled neurons were counted in all 34 spinal segments. In both cases, the estimated totals of STT neurons differed from the counted totals by less than 5%. In the most effective case, we estimated that more than 9500 STT neurons were labeled. This study indicates that the number of STT neurons in rats is larger than previously reported and suggests that the STT may play an important role in nociception in rats, as it does in primates including humans.

Animals↗
PubMed1990

Cells of origin of the spinohypothalamic tract in the rat.

We recently demonstrated that large numbers of neurons in the spinal cord of rats project directly to the hypothalamus. In the present study, we used the retrograde tracer Fluoro-Gold (FG) to examine this projection more completely. In the first series of studies, we attempted to label the entire population of spinal cord neurons that project to the hypothalamus. Injections that virtually filled the hypothalamus on one side without spreading into any other diencephalic area labeled a large number of neurons (estimated to be more than 9,000 in the case with the most neurons labeled) bilaterally at all levels of the spinal cord. Approximately 60% of the labeled neurons were contralateral to the injection. The greatest number of labeled neurons was found within the deep dorsal horn. Many were also found within the lateral spinal nucleus, the superficial dorsal horn, and the gray matter surrounding the central canal. A small number of labeled cells was located in the intermediate zone and ventral horn of the spinal gray matter. Labeled neurons were distributed bilaterally within the sacral parasympathetic nucleus and trigeminal nucleus caudalis. Injections of FG restricted to the medial hypothalamus labeled neurons within the spinal cord in a distribution similar to that produced by injections that filled the hypothalamus. However, fewer neurons were labeled in the spinal cord (estimated to be more than 6,200) and trigeminal nucleus caudalis. Injections of FG restricted to the lateral hypothalamus also labeled fewer neurons (approximately 3,300) than did injections that filled the hypothalamus. In these cases, also, the pattern of labeled neurons within the spinal cord was similar to that produced by injections within either medial or both medial and lateral hypothalamus. However, few neurons were labeled in the sacral parasympathetic nucleus following injections into the lateral hypothalamus. These findings show the distribution of a large number of spinal cord neurons that project directly to medial or lateral hypothalamic regions that are involved in autonomic, neuroendocrine, and emotional responses to somatosensory stimulation, including painful stimuli.

Afferent Pathways↗
PubMed1990

Neurons in the sacral parasympathetic nucleus that project to the hypothalamus do not also project through the pelvic nerve--a double labeling study combining Fluoro-gold and cholera toxin B in the rat.

We recently reported that neurons in the sacral parasympathetic nucleus (SPN) project directly to the hypothalamus. In the present study, we examined the possibility that individual neurons in SPN send both an axon into the pelvic nerve and an ascending projection to the hypothalamus. We used a new double-labeling technique in which two sensitive retrograde tracers (Fluoro-gold and cholera toxin subunit B immunocytochemically stained with rhodamine-labeled antibodies) were combined. The effectiveness of this combination for singly and doubly labeling neurons was established in experiments in which both tracers were injected into overlapping areas of the tongue or ventrobasal thalamus. These injections doubly labeled large numbers of neurons in the hypoglossal or dorsal column nuclei, respectively. In studies of the projections of neurons in the SPN, injection of one tracer into the hypothalamus and the other into the pelvic nerve and/or pelvic ganglion singly labeled many neurons (more than 3300 in the 7 examined cases). However, no SPN neurons were doubly labeled. These findings indicate that the SPN in the rat consists of at least two distinct groups of cells, parasympathetic preganglionic neurons and neurons that project to the hypothalamus.

Animals↗
PubMed1990

Effect of fluid intake on renal function during exercise in the cold.

The effect of an imposed drinking discipline versus ad libitum drinking was studied on 21 healthy, well-trained volunteers, during a continuous 4.5-h march at an altitude of 1,700 m and an ambient temperature of 0 degree C, SD 1. Group I (n = 13) was instructed to drink 250 ml of warmed, artificially sweetened fluid every 30 min, whereas group II (n = 8) drank plain water ad libitum. The median fluid intake in group I was significantly higher than in group II (P less than 0.0002). Serum urea and osmolality decreased during the march in group I (P less than 0.05; P less than 0.002, respectively) with no significant change in group II. In both groups, a similar increase in haemoglobin concentration concomitant with a reduction in calculated blood and plasma volume was observed after exercise and did not correlate with the state of hydration. Total urine volume, creatinine clearance, urea clearance and potassium excretion were significantly higher and urinary osmolality was lower in group I than in group II (P less than 0.05). These results reflect a state of extreme "voluntary dehydration" in the control group when no fluid intake was obligatory. Thus, during exercise in the cold, under conditions similar to those in this study, a fluid intake of 150 ml.h-1 should be maintained in order to keep a urinary flow of about 1 ml.kg-1.h-1 and to achieve a good state of hydration.

Adult↗
PubMed1990

Lipid profile in trained subjects undergoing complete food deprivation combined with prolonged intermittent exercise.

Sixteen male subjects [18-21 years, maximal oxygen consumption (VO2max) = 59.2 ml.kg-1.min-1 +/- SEM 5.6] participated in a study to evaluate the effect of prolonged, complete food deprivation combined with physical effort, on plasma lipoprotein concentrations. The subjects were deprived of food for 81 h but were supplied with water: they walked for 10 h a day at 40% of VO2max, covering a total of 105 km. During this period the subjects' average mass decreased significantly (P less than 0.05) reflecting a marked catabolic process. Plasma concentration of low density lipoprotein-cholesterol [( LDL-C]) and triglycerides were significantly lower (P less than 0.05) and total cholesterol, high-density lipoprotein-cholesterol [( HDL-C]), and free fatty acid levels were significantly higher (P less than 0.05) at the end of the experimental period compared to the start. The ratio between plasma [HDL-C] to plasma [LDL-C] increased from 0.51 to 0.89 at the end of the exercise period, reflecting a marked anti-atherogenic effect. All changes were transient and reversible within 12 days of recovery.

Adolescent↗
PubMed1990

Androgenic response to long-term physical training in male subjects.

An increase in endogenous androgen production has been observed following long-term physical training and the beneficial effects of training have been attributed in part to this phenomenon. Other investigators, however, found, in contrast lower testosterone levels in trained compared with untrained subjects. The purpose of the present study was to follow the long-term changes in total testosterone (T) and cortisol (C) levels in intensely training individuals. The changes in the body's anabolic state, induced by intense long-term physical training, were determined using the plasma resting T/C ratio. T and C levels of 35 young untrained subjects were measured at 6 week intervals during 18 weeks of strenuous physical training. All samples were drawn within one half hour of awaking (05.30-06.00). Mean serum T levels increased significantly at 6 weeks (28.7%, p less than 0.02) and decreased significantly at 12 weeks (20.6%, p less than 0.02), but did not differ at 18 weeks compared with levels before training was commenced (mean +/- SE, 16.9 +/- 0.2, 21.8 +/- 0.3, 12.8 +/- 0.2 and 17.3 +/- 0.2 nmol/l at 0, 6, 12, and 18 weeks, respectively). Mean serum C was increased significantly (21.3%, p less than 0.005) at 18 weeks (463.5 +/- 19.3, 507.7 +/- 22.1, 480.1 +/- 19.3, and 565.6 +/- 22.1 nmol/l). T/C ratio decreased significantly after 12 and 18 weeks of training. Our results do not support an association between reduced total testosterone levels and prolonged training. However, hypercorticolism with a relative catabolic state may occur.

Adaptation, Physiological↗
PubMed1990

Effects of caffeine ingestion on body fluid balance and thermoregulation during exercise.

This study investigated the effects of caffeine supplementation on thermoregulation and body fluid balance during prolonged exercise in a thermoneutral environment (25 degrees C, 50% RH). Seven trained male subjects exercised on a treadmill at an intensity of 70-75% of maximal oxygen consumption to self-determined exhaustion. Subjects exercised once after caffeine and once after placebo ingestion, given in a double-blind crossover design. Five milligrams per kilogram body weight of caffeine followed by 2.5 mg.kg-1 of caffeine were given 2 and 0.5 h before exercise, respectively. Rectal temperature was recorded and venous blood samples were withdrawn every 15 min. Water loss and sweat rate were calculated from the difference between pre- and post-exercise body weight, corrected for liquid intake. Following caffeine ingestion, when compared with placebo, no significant difference in final temperature or in percent change in plasma volume were found. No significant differences were observed in total water loss (1376 +/- 154 vs. 1141 +/- 158 mL, respectively), sweat rate (12.4 +/- 1.1 vs. 10.9 +/- 0.7 g.m-2.min-1, respectively), rise in rectal temperature (2.1 +/- 0.3 vs. 1.5 +/- 0.4 degrees C, respectively), nor in the calculated rate of heat storage during exercise (134.4 +/- 17.7 vs. 93.5 +/- 22.5 W, respectively). Thus, in spite of the expected rise in oxygen uptake, caffeine ingestion under the conditions of this study does not seem to disturb body fluid balance or affect thermoregulation during exercise performance.

Adult↗
PubMed1990

Effect of an acute bout of exercise on glucose disposal in human obesity.

The effect of acute exercise on insulin action has been studied in six obese (150-250% ideal body weight) non-insulin-dependent diabetics (OD), seven obese normoglycemics (ON), and six lean healthy controls (LC). Using a three-stage euglycemic clamp, the metabolic clearance rate (MCR) of glucose under increasing insulin concentrations was measured. The insulin dose-response curve was assessed on two separate occasions: 1) a base-line test and 2) 1 h after aerobic treadmill exercise at a steady-state heart rate of 150-160 beats/min. In the base-line test, under all insulin levels, glucose MCR was significantly lower in obese compared with lean individuals (P less than 0.01). Exercise increased glucose MCR at the highest hormonal concentrations applied to 124 and 134% of base line in OD and in ON, respectively (P less than 0.05); the insulin concentration required for one-half of the maximal clearance rate of glucose achieved in this study decreased from 200 to 130 and from 160 to 95 microU/ml in OD and ON, respectively (P less than 0.05). The changes in these parameters were insignificant in LC. It is suggested that acute exercise affected the insulin dose-response curve in OD and in ON but not in LC; although enhanced by exercise, glucose MCR remained significantly lower in both obese groups compared with control subjects. We concluded that insulin resistance, which accompanies extreme obesity, could be markedly decreased but not completely reversed by one bout of exercise.

Adult↗
PubMed1990

Absence of T cell impairments in a unique group of anal-receptive transvestite and male prostitutes in Israel.

High rates of immunologic abnormalities in asymptomatic, clinically healthy urban homosexual men have been associated with promiscuous, unprotected receptive rectal intercourse, and related to infection by the human immunodeficiency virus (HIV), Epstein-Barr virus (EBV) and cytomegalovirus (CMV). In cohort studies in Israel, which is still a low risk country for HIV infection and AIDS, about 40% of asymptomatic, clinically healthy male homosexuals consistently showed T cell defects that were not correlated with anal-receptive sexual behavior and were independent of HIV antibody status. Since pre-existing immune impairments in HIV-seronegative individuals have been implicated as a risk factor for seroconversion, we have attempted to investigate more precisely the role of anal-receptive homosexual activity as a risk factor for the acquisition of immune defects. We compared T lymphocyte profiles and mean geometric titers of EBV and CMV in a homogeneous group of 14 transvestite and male anal-receptive homosexual prostitutes with those of 77 HIV-seronegative male homosexuals who were not exclusively anally passive with multiple sex partners. While 44% of the control group showed a decrease of total T cells or their subpopulations as compared with normal heterosexual men (P less than 0.001), T lymphocyte values of the anal-receptive prostitutes were within the normal range. In the prostitutes, serum antibodies to HIV were detected in only 1 individual, to CMV in 12 of 13, and to EBV in all. Despite high mean geometric titers of antibodies to CMV (86.6) and EBV (25.8), frequent anal-receptive intercourse was not sufficient, in itself, to cause immune impairment in this unique group. The results suggest that the problem of cofactors contributing to immune deficiency in male homosexuals should be reexamined in countries with a low incidence for HIV seropositivity and AIDS.

Adolescent↗