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Biomedical subjects

R Cahn

Publications and source records attributed to R Cahn.

At least 19 recordsLinked to original sources
PubMed1998

Trophic support promotes survival of bcl-x-deficient telencephalic cells in vitro.

Survival of immature neurons is regulated by Bcl-xL, as targeted disruption of bcl-x significantly increases cell death in vivo and in vitro. Death of cultured bcl-x-deficient and wild-type telencephalic cells can be prevented by fetal calf serum or chemically-defined medium (ITS), suggesting trophic factors in these media potentiate survival through a pathway independent of Bcl-xL. Addition of trophic factors to basal medium revealed that insulin and insulin-like growth factors (IGFs), but not other trophic factors, reduced apoptosis of wild-type and bcl-x-deficient telencephalic cells. Antibodies raised against IGF-I receptors and wortmannin both attenuated the effects of IGF-I, indicating survival was mediated by IGF-I receptors and phosphatidylinositol 3'-kinase signaling, whereas effects of ITS were only partially reduced by these agents. The survival promoting effects of ITS were reduced in cells lacking both bcl-x and bcl-2, indicating Bcl-2 plays a supportive role to Bcl-xL in maintaining telencephalic cell survival. Furthermore, the ratio of expression of the pro-apoptotic bax gene to the anti-apoptotic bcl-2 gene was reduced in bcl-x-deficient cultures grown in ITS, suggesting that the interaction between these bcl-2 family members may, in part, regulate a Bcl-xL independent survival pathway. Finally, the pro-apoptotic bad gene does not appear to play a role in these interactions as targeted disruption of bad did not alter apoptosis in telencephalic cultures.

Animals↗
PubMed1997

Inactivation of the Fanconi anemia group C gene augments interferon-gamma-induced apoptotic responses in hematopoietic cells.

Hematopoietic progenitor cells (HPC) from mice nullizygous at the Fanconi anemia (FA) group C locus (FAC -/-) are hypersensitive to the mitotic inhibitory effects of interferon (IFN-gamma). We tested the hypothesis that HPC from the bone marrow of Fanconi group C children are similarly hypersensitive and that the fas pathway is involved in affecting programmed cell death in response to low doses of IFN-gamma. In normal human and murine HPC, IFN-gamma primed the fas pathway and induced both fas and interferon response factor-1 (IRF-1) gene expression. These IFN-gamma-induced apoptotic responses in HPC from the marrow of a child with FA of the C group (FA-C) and in FAC -/- mice occurred at significantly lower IFN doses (by an order of magnitude) than did the apoptotic responses of normal HPC. Treatment of FA-C CD34+ cells with low doses of recombinant IFN-gamma, inhibited growth of colony forming unit granulocyte-macrophage and burst-forming unit erythroid, while treatment with blocking antibodies to fas augmented clonal growth and abrogated the clonal inhibitory effect of IFN-gamma. Transfer of the normal FAC gene into FA-C B-cell lines prevented mitomycin C-induced apoptosis, but did not suppress fas expression or inhibit the primed fas pathway. However, the kinetics of Stat1-phosphate decay in IFN-gamma-treated cells was prolonged in mutant cells and was normalized by transduction of the normal FAC gene. Therefore, the normal FAC protein serves, in part, to modulate IFN-gamma signals. HPC bearing inactivating mutations of FAC fail to normally modulate IFN-gamma signals and, as a result, undergo apoptosis executed through the fas pathway.

Anemia, Aplastic↗
PubMed1990

Effect of halothane on ischemic brain edema.

Halothane anesthesia (2%) given continuously during the ischemic and post-ischemic period in gerbils does not protect against cytotoxic edema but counteracts superimposed vasogenic edema due to the first BBB opening to serum protein during the reflow period, thus allowing specific gravity values at 1-hour reflow to return to initial levels. It seems likely that this effect of halothane is due to a reduction of the hyperemia by halothane, which reduces both blood pressure and brain metabolism. CBF measurements in halothane-treated animals also indicated that intense early postischemic hypoperfusion may well exist in the absence of brain edema.

Animals↗
PubMed1989

The effects of dihydroergocryptine on the neurological and enzyme disorders induced by cerebral ischaemia in rats.

Ergot alkaloids are commonly used as cerebroprotective drugs. Their efficacy has been demonstrated experimentally in animals submitted to acute cerebral anoxia or ischaemia, at dose levels hugely superior to dose levels usually administered in humans. In the present experiments, dihydroergocryptine (DHEC), a constituent of dihydroergotoxine (DHET), was administered at doses closely related to human doses, preventively (in experiments where animals survived only for a short while after ischaemic insult) or curatively, and its efficacy tested through refined neurological and biochemical evaluation of experimental cerebral ischaemia sequelae. DHEC was administered orally (30 micrograms or 150 micrograms/kg body weight (bwt) twice daily) for 3 days, following transient cerebral ischaemia induced by a 60-min carotid occlusion plus sodium nitroprusside (1.1 mg/rat s.c.) injection, or, in a second experiment, prophylactically (60 micrograms or 300 micrograms/kg bwt/day) for 4 days prior to multiple cerebral infarct induced by sodium arachidonate injection into the left internal carotid artery. The neurological sequelae were evaluated by the Irwin visual placing response or by a battery of behavioural tests. Na-K-ATPase enzyme activity in cerebral homogenates was measured; decreases in this enzyme activity are considered to reflect the neuronal membrane consequences of the neurocell energetic metabolism alterations caused by cerebral ischaemia. Low dose oral DHEC treatment prevented the behavioural abnormalities and memory impairment arising after transient cerebral ischaemia and there was a marked trend in improving the behavioural abnormalities observed in animals submitted to massive cerebral infarction, in spite of the model severity. DHEC prevented reduction in cerebral Na-K-ATPase activity after cerebral multiinfarction. These effects of DHEC were observed with doses and administration route close to the usual therapeutic regimen.

Animals↗
PubMed1989

Effect of brain gangliosides on early and late consequences of a transient incomplete forebrain ischemia in the rat.

Rat transient incomplete forebrain ischemia was induced by 60 min of bilateral carotid artery occlusion associated with systemic hypotension. Intraperitoneal treatment with either GM-1 monosialoganglioside or its inner ester AGF-2 started 1 h after release of carotid clamps and was repeated twice a day. Ganglioside treatment was effective in reducing the increase of cerebral water content, nonetheless AGF-2 reduces significantly not only cerebral edema, but also potassium efflux and calcium overload. With respect to ischemic untreated rats, GM-1- and AGF-2-treated rats showed a higher incidence of conditioned response retention of a single training trial, associated with improvement in cerebral blood flow and electrocorticographic patterns. In addition, 4 weeks following ischemia, the extent of tissue necrosis was reduced, although not statistically significant, in both ganglioside-treated groups. However, all these improvements are more evident in the AGF-2-treated rats than in the GM-1-treated ones. In conclusion, these results suggest that, except in some cases with different potency, both monosialoganglioside GM-1 and its inner ester derivative, AGF-2, are able to improve outcome after brain ischemia.

Animals↗
PubMed1989

Influence of monosialoganglioside inner ester on neurologic recovery after global cerebral ischemia in monkeys.

We assessed the consequences of transitory global cerebral ischemia and the influence of monosialoganglioside inner ester (AGF 2) treatment on neurologic outcome, cerebral blood flow, and cerebral metabolic rate in monkeys over 48 hours. Global cerebral ischemia was produced by a cervical tourniquet and a lowering of blood pressure to 6.65 kPa; recirculation followed after 30 minutes. AGF 2 (30 mg/kg) was administered intravenously immediately after initiation of recirculation and intramuscularly twice a day for 48 hours. Our results show that treatment with AGF 2 significantly accelerated the rate of neurologic recovery. Improvement was evident 5 hours after ischemia; full neurologic recovery was observed in half of the monkeys 48 hours after ischemia. This recovery was associated with a less severe reduction in cerebral blood flow without a concomitant increase in the cerebral metabolic rate.

Animals↗
PubMed1988

Effects of new chemically and metabolically stable prostacyclin analogues (iloprost and ZK 96480) on early consequences of a transient cerebral oligemia, in the rat.

Transient incomplete cerebral ischemia (oligemia) has been obtained in rats by associating mild systemic hypotension with bilateral carotid artery occlusion for 60 min. Continuous i.v drug administration for 3 days, performed with Alzet osmotic minipumps so that to deliver 167 ng.kg-1.min-1 Iloprost, 5 ng.kg-1.min-1 ZK 96480 or their respective vehicle, started 1 hour post-oligemia. Both compounds which are stable prostacyclin analogues reduced the edematous reaction and the post-oligemic accumulation of calcium in the brain tissue but above all they improved, mainly ZK 96480, the learning capacity of injured animals. These results indicate that regarding its therapeutic effect toward early consequences of a transient cerebral oligemia, ZK 96480 has the same profile as Iloprost at a dose 20-fold lower. Thus, these data encourage further clinical studies, in ischemic stroke, in which PGI2 and Iloprost have been shown promising.

Animals↗
PubMed1988

Curative effect of an almitrine-raubasine combination in the postischemic syndrome following transient cerebral ischemia in dogs.

Cerebral hemodynamic and metabolic changes, occurring during delayed hypoperfusion following transient cerebral ischemia, and the influence of treatment with almitrine plus raubasine were studied in mongrel dogs. 10 min of transient cerebral ischemia was induced by bilateral clamping of both carotid and vertebral arteries. After declamping, the mean time necessary until cerebral venous PO2 (cvPO2) reached a value of 3.6 kPa, threshold for tissue hypoxia, was 80 min. At this time (T0), venous cerebral blood flow (vCBF) and cerebral perfusion pressure (Perf P) were below (60 and 20%, respectively) preischemic values, while cerebral vascular resistance (CVR) and oxygen and glucose extraction rates increased despite a normal cerebral oxygen consumption (CMRO2). At T0 ventilatory assistance without (control group) or with (treated group) intravenous infusion of almitrine plus raubasine was applied for 110 min. Between T0 and T110 min, 2 dogs died in the control group. During this period vCBF decreased by more than 60% in the control group while it slightly increased in the treated group. A strong decrease in Perf P (40%) and increase in CVR (140%) was observed in the control group while in the treated group Perf P and CVR slightly decreased (14 and 35%, respectively). CMRO2 decreased by 60% in the control group but remained within the normal range in the treated group. The fact that cvPO2 remained constantly below the initial value of 3.6 kPa in the control group and, on contrary, above this value in the group infused with raubasine plus almitrine indicates that the vCBF improvement leads to an increase in oxygen supply and is involved in the keeping of the adequacy between flow and metabolism. Our results support the hypothesis that the post-ischemic syndrome may play an important role in the acute prognosis of stroke. They clearly indicate that early cerebral resuscitation by infusion of almitrine plus raubasine, maintaining oxygen availability and CBF above initial thresholds, should improve the long-term neurological outcome.

Almitrine↗
PubMed1988

[Evaluation of the institutional setting on psychotic adolescents. Psychoanalytic approach].

Based on a statistical check of how certain teenage psychotics have changed, these changes, even mutative effects on these kinds of problems because of steps taken in the institutional setting, were examined. Within the framework of the mental-health facility, through compulsive repetition, a process implicating both patient and healer in their interrelationship and the possibility of talking about family problems are developed. In the same way, such a setting allows a patient's virtualities to come out and be used because of the objective, transitional and narcissistic aspects that these various opportunities bring into play. Several clinical examples are given, regarding dialectic articulation, with their theory highlighted. The idea of accepting one's own exaggerated narcissism turns out to be fundamental in realizing a teenager's psychotic problems as much as different diachronic and synchronic ways of action, so that, without playing with language, we can qualify the setting as therapeutic.

Adolescent↗
PubMed1985

Role of extracellular proteins in the dynamics of vasogenic brain edema.

The relationship between extravasation of proteins into extracellular spaces of brain parenchyma and the water content of such regions were evaluated in an experimental model. In this model, a temporary opening of the blood-brain barrier (BBB) to proteins was produced without significant injury to the cellular elements of brain tissue. Rabbits were subjected to bolus injection of their own blood under 360-400 mm Hg pressure via the internal carotid artery. The opening of the barrier and its duration were evaluated with Evans blue (EB), horseradish peroxidase (HRP), and sodium fluorescein (NaFl) tracers. The water content of brain tissue was assessed by specific gravity (SG) measurements in 1-mm-diameter tissue samples. Quantitative evaluation of protein penetration into brain tissue was carried out using 125I bovine serum albumin (BSA). The opening of the BBB to proteins persisted up to 9 h, whereas the barrier remained permeable to small molecular NaFl for 24 h. The SG measurements indicated in the areas of EB extravasation a progressive increment in water content up to 9 h, i.e., the duration of BBB opening to proteins. Following this, there was a progressive clearance of edema in spite of the BBB remaining open for NaFl for 24 h. Quantitative evaluations of 125I-BSA and SG in the same tissue samples, supported by statistical analysis, indicated approximately linear relationship analysis, indicated approximately linear relationship between albumin and water, implying a strong correlation between the development of vasogenic edema and extravasation of proteins into extracellular spaces.

Animals↗