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Y Cohen

Publications and source records attributed to Y Cohen.

At least 235 records · Page 13Linked to original sources
PubMed1991

Surface coil spectroscopic imaging: time and spatial evolution of lactate production following fluid percussion brain injury.

Detailed temporal and spatial distributions of lactate production are presented for graded fluid-percussion brain injury in the rat. A one-dimensional proton spin-echo spectroscopic imaging (1D SESI) technique, performed with a surface coil, is presented and evaluated. This technique, which represents a practical compromise, provides spatially localized proton nuclear magnetic resonance (NMR) brain spectra from a series of small voxels (less than 0.15 cm3) in less than 10 min, thus enabling both spatial and temporal monitoring of lactate production. These high-resolution lactate maps are correlated with hyperintense regions observed in T2-weighted images taken 10 h after impact, which, in turn, correlate with histology. The data demonstrate that, following severe trauma there is delayed production and propagation of lactate to regions of the brain that are remote from the trauma site. The extent of lactate production depends on the severity of impact. More significantly, the data show that following severe trauma, local lactate concentrations exceed 15 mumol/g, the concentration that has been claimed as the threshold for brain injury. Therefore high lactate levels cannot be ruled out a priori as a possible factor in brain injury following severe head trauma.

Animals↗
PubMed1991

Comparison of diffusion- and T2-weighted MRI for the early detection of cerebral ischemia and reperfusion in rats.

The sensitivity of diffusion-weighted MRI was compared to that of T2-weighted MRI following temporary middle cerebral artery occlusion (MCA-O) for 33 min followed by 4 h of reperfusion in rats. Diffusion-weighted spin-echo images using strong gradients (b value of 1413 s/mm2) demonstrated a significant increase in signal intensity in ischemic regions as early as 14 min after onset of ischemia in comparison to the normal, contralateral hemisphere (p less than 0.05). This hyperintensity returned to baseline levels during reperfusion. T2-weighted images showed no evidence of brain injury during the temporary occlusion. In three rats subjected to permanent MCA-O, diffusion-weighted MRI demonstrated an increased signal intensity on the first image following occlusion and continued to increase during the 4-h observation period. T2-weighted images failed to demonstrate significant injury until approximately 2 h after MCA-O. Signal intensity ratios of ischemic to normal tissues were greater in the diffusion-weighted images than in the T2-weighted MR images at all time points (p less than 0.05). Close anatomical correlation was found between the early and sustained increase in diffusion-weighted MRI signal intensity and localization of infarcts seen on post-mortem histopathology.

Animals↗
PubMed1991

Effects of dexfenfluramine and opioid peptides, alone or in combination, on food intake and brain serotonin turnover in rats.

Dexfenfluramine (d-FF) and opiate agonists both act on food intake but in opposite ways. Serotonin is known to be involved in the pharmacological action of both d-FF and opiates, but not necessarily in the feeding effect of the latter. In order to test this hypothesis, the effects of three opioid agonists, beta-endorphin, dynorphin and D-Ser2-Leu-Enk-Thr6 (DSLET) and of an antagonist, naltrexone, were investigated individually and in combination with d-FF on food intake and brain serotonin turnover. The opioid agonist-d-FF combinations generally produced a similar anorectic effect to that of d-FF alone, with the exception of DSLET which showed a reciprocal antagonism. The serotonergic effects varied according to the opioid tested, alone or in combination with d-FF. This does not allow to highlight a general pattern of serotonin involvement in the feeding effects of these peptides. However, all the treatments which decreased feeding (d-FF, naltrexone and the combinations dynorphin-d-FF and beta-endorphin-d-FF) displayed similar trends in hypothalamic serotonergic variations. This study evidences a role of serotonin in the feeding effect of opiates, although not similar for all of them. The use of d-FF provides a tool for assessing this involvement.

Animals↗
PubMed1991

Effects of insulin on brain monoamine metabolism in the Zucker rat: influence of genotype and age.

Disturbances of insulin or brain monoamine metabolism may play a role in the impaired regulation of food intake and body weight in the obese Zucker rat. We investigated a possible insulin-monoamine interaction by measuring monoamine levels in the hypothalamus and striatum of obese (fa-fa) and lean (Fa-Fa and Fa-fa) Zucker rats after peripheral insulin administration. The classically reported effects of insulin, i.e., increases in tryptophan, 5-hydroxy-indolacetic acid (5-HIAA) and dihydroxyphenylacetic acid (DOPAC) levels, were observed in the hypothalamus of Fa-Fa and Fa-fa rats, but not in obese fa-fa rats. Given the mechanism of action of insulin, this lack of effect in the obese rats may be related to the peripheral insulin resistance they exhibit. Furthermore, given the role of these monoaminergic systems, this reduced effect may be related to the impaired regulation of food intake and body weight. At 8 wk of age, however, insulin restored the decreased basal 5-HIAA levels observed in the obese rats. Increase in 5-HIAA levels following insulin administration appeared in the striatum of Fa-Fa rats only, suggesting that, as for brain insulin content, other central insulin-related disturbances may be related to the presence of the "fa" gene. In addition, certain effects of insulin on striatal dopamine release were observed in only the Fa-Fa and fa-fa rats, suggesting a particular disturbance related to the heterozygous character. This latter point calls for further investigations on the central dopaminergic effects of insulin.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1991

Interleaved 1H and 31P spectroscopic imaging for studying regional brain injury.

We present a new approach for in vivo localized spectroscopy which combines 1H and 31P one-dimensional spectroscopic imaging pulse sequences in an interleaved, time-shared manner using a surface coil. This approach was used to acquire metabolic information from a rat brain with regional ischemia at 4.7 Tesla. Spectra with very good signal-to-noise ratios, void of chemical shift artifacts, are obtainable from voxel sizes less than 0.3 cm3 in 40 min. Advantages and drawbacks of the proposed methodology are discussed.

Animals↗
PubMed1991

Grandiosity in children with narcissistic and borderline disorders. A comparative analysis.

I draw a distinction between two clinical pictures in children, borderline and narcissistic disorders. Both belong to the realm of personality disorder--or, perhaps, disorders in the development of the personality--but only the former has been widely reviewed and thoroughly investigated in the professional literature. I raise the question how and when these disorders emerge, stressing that both derive from the early, preoedipal period, and precede completion of the separation-individuation processes. Both disorders reveal manifestations of grandiosity which I view as a defense against the two underlying emotional experiences of the disorders: the experience of feeling alone in the borderline case, and the experience of "worthlessness" in the narcissistic personality.

Adult↗
PubMed1991

Cerebral uptake and elimination of desflurane, isoflurane, and halothane from rabbit brain: an in vivo NMR study.

The authors used in vivo 19F nuclear magnetic resonance spectroscopy to determine rates of cerebral uptake and elimination of desflurane, isoflurane, and halothane in rabbits. After anesthetizing animals by intramuscular and intravenous injection of methohexital and inhalation of 70% nitrous oxide, intravenous and intraarterial catheters were inserted and a tracheostomy and craniotomy performed. Ventilation was controlled to maintain arterial carbon dioxide tension (PaCO2) from between 35 and 45 mmHg. A 2-2.5-cm diameter circle of dura was exposed, over which a 0.9 x 1.0-cm elliptical surface coil was placed. Cerebral anesthetic concentrations (CC) were estimated from spectra acquired on a 4.7-Tesla spectrometer. Alveolar uptake and elimination also were assessed, using inspired (FI) and end-tidal (denoted FA0 at the end of administration) concentrations measured by gas chromatography. After baseline spectra were obtained, volatile agents were administered for 30 min, followed by a 120-min period of elimination. Our findings demonstrate that cerebral uptake and elimination correlate with solubility: they are most rapid for desflurane, next most rapid for isoflurane, and least rapid for halothane. During administration, cerebral uptake of desflurane (CC/FI = 0.690 +/- 0.049 at 9 min) was approximately 1.7 times faster than isoflurane (CC/FI = 0.691 +/- 0.020 at 15 min) and 3 times faster than halothane (CC/FI = 0.662 +/- 0.040 at 27 min). Similarly, elimination rates for desflurane (CC/FA0 = 0.238 +/- 0.015 at 9 min) were 1.7 times faster than isoflurane (CC/FA0 = 0.236 +/- 0.017 at 15 min) and three times faster than halothane (CC/FA0 = 0.212 +/- 0.033 at 27 min).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Cardiovascular effects of intracerebroventricular injections of (+/-)-nebivolol and its enantiomers--a comparison with those of metoprolol in the rat.

The cardiovascular effects of (+/-)-nebivolol, a potent beta 1-adrenoceptor antagonist, and its enantiomers, (+)-nebivolol (SRRR) and (-)-nebivolol (RSSS) in normotensive anaesthetized rats, have been investigated using metoprolol as a reference substance. The drugs decreased blood pressure and heart rate immediately after i.c.v. injection. These effects paralleled the beta-blocking potencies ((+)- greater than (+/-)-greater than (-)-nebivolol). Metoprolol induced a weaker hypotension than (+/-)-nebivolol, and a long-lasting reduction in stroke volume. As reported after i.v. administration, (+/-)-nebivolol and isomers by the i.c.v. route decreased peripheral vascular resistance following i.c.v. administration while metoprolol increased it. These effects are centrally mediated since cardiovascular responses to isoprenaline i.v. remained unchanged.

Adrenergic beta-Antagonists↗
PubMed1991

Accumulation of trehalose and sucrose in cyanobacteria exposed to matric water stress.

The drought-resistant cyanobacteria Phormidium autumnale, strain LPP(4), and a Chroococcidiopsis sp. accumulated trehalose, sucrose, and both trehalose and sucrose, respectively, in response to matric water stress. Accumulated sugar concentrations reached values of up to 6.2 mug of trehalose per mug of chlorophyll in P. autumnale, 6.9 mug of sucrose per mug of chlorophyll in LPP(4), and 4.1 mug of sucrose and 3.2 mug of trehalose per mug of chlorophyll in the Chroococcidiopsis sp. The same sugars were accumulated by these cyanobacteria in similar concentrations under osmotic water stress. Cyanobacteria that did not show drought resistance (Plectonema boryanum and Synechococcus strain PCC 7942) did not accumulate significant amounts of sugars when matric water stress was applied.

Journal Article↗
PubMed1991

Tolerance of low cerebral intracellular pH in rats during hyperbaric hypercapnia.

BACKGROUND AND PURPOSE: Brain acidosis from cerebral ischemia is characterized by average intracellular pH levels of approximately 5.8-6.2, which appear in turn to worsen cellular injury. We report that the brain is not injured when hypercapnia is used to reduce intracellular pH to about 6.2 during adequate oxygenation. A hyperbaric chamber is needed to achieve intracellular pH values so low because inspired CO2 tensions must be increased to approximately 1 atm. SUMMARY OF REPORT: Using in vivo phosphorus-31 and proton nuclear magnetic resonance spectroscopy, we measured brain intracellular pH and lactate concentration of rats inside a nonmagnetic polycarbonate chamber at a barometric pressure of 1,500 mm Hg. Intubated rats were ventilated with a 50% O2/50% CO2 gas mixture for specific times. All six rats ventilated for 15 minutes with CO2 tensions of approximately 750 mm Hg woke up without neurological impairment, despite a decrease in intracellular pH to about 6.2. Higher CO2 tensions and longer exposures resulted in cardiovascular collapse and sudden death, followed by the postmortem appearance of brain lactate. CONCLUSIONS: Brain intracellular pH values near 6.2 can be induced briefly in vivo in ventilated rats without injury under hyperbaric hypercapnic conditions. If attempts are made to lower brain pH in vivo even further by increasing PCO2 beyond 750 mm Hg, mean arterial blood pressure and cerebral blood flow decrease to values incompatible with life.

Animals↗
PubMed1991

[Primary brain lymphoma].

Between 1973 and 1989, 739 patients with non-Hodgkin's lymphoma were referred here for treatment, of whom 10 (1.4%) had primary brain lymphoma (PBL) and 1 had acquired immunodeficiency syndrome (AIDS). There were 7 females and 3 males (mean age 58 years, range 35-77). Duration of symptoms ranged from several days to 3 weeks. The presenting symptoms were secondary to increased intracranial pressure. Computerized tomography (CT) performed in 8 revealed a solitary lesion in 7. Other CT scan features were various degrees of contrast enhancement, edema and midline shift. The most common site was the frontal lobe; infratentorially, the cerebellum was the most frequent site. The diagnosis was established in 8 patients by surgery and in 2 at autopsy. The most common subtype was the diffuse, large cell, immunoblastic lymphoma. 5 patients were irradiated following subtotal excision and 2 had combined radiation therapy and high-dose methotrexate-based chemotherapy; only 1 had no postoperative treatment. All patients treated by radiotherapy alone died within 3-5 months after diagnosis. The 2 who received combined therapy are alive, 15 and 48 months after diagnosis, respectively.

Adult↗
PubMed1991

Values, superego, adolescence and suicide.

We are noticing a decline in ideological and societal values among our youth and, at the same time, seeing an increase in anger, violence and extremism in their behavior. To better understand these developments, we turn to superego theory.

Adolescent↗
PubMed1991

Gender identity conflicts in adolescents as motivation for suicide.

One of the motivational factors for suicide in adolescents is examined in light of gender identity issues and conflicts. It is proposed that difficulties in the formation of a cohesive gender identity are related to the adolescent's motivation to attempt suicide. This paper makes use of Fast's (1984) distinction between "event-centered" and "self-centered" experiences in order to explore problems in the formation of gender identity with reference to regression to earlier stages of psychosexual development. Physiological changes and regressive pull may lead the adolescent to the "event-centered" mode of experience. Thus one minor event may become the focus of the adolescent's gender and self identities. The adolescent may then have regressive omnipotent fantasies of being able to change gender identity through suicidal acts.

Adaptation, Psychological↗
PubMed1990

Changes in hypothalamic neuropeptide Y concentrations induced by cholecystokinin analogues.

Neuropeptide Y (NPY) and cholecystokinin (CCK) are two peptides involved in opposite ways in the control of food intake. A possible interaction between NPY and CCK has not yet been well defined. Two CCK derivatives with agonistic and antagonistic properties were studied with regard to their effects on brain and plasma NPY levels. The CCK agonist decreased NPY levels in plasma and in the hypothalamus but not in the other brain areas assayed. The CCK antagonist reversed the agonist-induced decrease in both plasma and hypothalamus. These results suggest a negative relation between NPY and CCK peptides, which is not surprising given their opposite role in feeding regulation. The hypothalamus, a preferential site of this regulation, appears to be the brain area most involved in the NPY-CCK interaction. The plasma NPY level variations closely reflect the hypothalamic profile, suggesting a direct release of NPY by a mechanism that remains to be investigated.

Animals↗
PubMed1990

Survival of diffuse large cell lymphoma. A multivariate analysis including dose intensity variables.

Ninety-five newly diagnosed patients with diffuse large cell lymphoma (DLCL) treated by cyclophosphamide (CTX), doxorubicin (ADM), vincristine (VCR), and prednisone (CHOP regimen) chemotherapy were evaluated for survival factors including dose intensity (DI). DI calculations were done for the initial cycles needed to achieve maximal response. The medians of the relative DI for CTX, ADM, and VCR were 0.9, 0.86, and 0.79, respectively. The median of the average relative DI (ARDI) was 0.83 (range, 0.28 to 1.14). The univariate analysis of potential prognostic variables showed that the following significantly decreased the survival rate: age older than 60 years (P = 0.0005), Stage III to IV (P = 0.02), male sex (P = 0.03), and all four DI variables (CTX, ADM, VCR, and ARDI) less than the median (P = 0.01 to 0.0001). A multivariate analysis by the stepwise proportional hazards model of Cox indicated that the factors predicting a poor prognosis were ARDI less than the median (P = 0.0003) and age older than 60 years (P = 0.02). A multivariate survival analysis of those who achieved complete remission showed ARDI less than the median (P = 0.0003), CTX less than the median (P = 0.02), and Stage III to IV (P = 0.02) to be the most negative factors regarding survival. In conclusion, a high DI in the initial cycles of CHOP chemotherapy for DLCL has a significant positive impact on survival.

Adolescent↗