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E Yavin

Publications and source records attributed to E Yavin.

At least 37 records · Page 2Linked to original sources
PubMed1998

Direct administration and utilization of [1-13C]glucose by fetal brain and liver tissues under normal and ischemic conditions: 1H, 31P, and 13C NMR studies.

Three distinct, maternal-independent routes (e.g. intraamniotic, intraperitoneal and intracerebral), for [1-13C]glucose utilization by fetal brain and liver tissues, were examined by multinuclear magnetic resonance (NMR) spectroscopy before and after vascular occlusion of the maternal-fetal blood flow. Labeled lactate was the major glycolytic product by all routes, but in addition labeled TCA cycle products were also generated. Fractional 13C enrichment in both glucose and lactate were always higher in the ischemic state compared to controls using either one of the three routes studied. After intraperitoneal injection total glucose in the fetal brain was decreased by 85% after 20 min reperfusion following 20 min ischemia, but was elevated up to 170% after 60 min. [1-13C]glucose increased continuously by up to 370% after 60 min. Total glucose in the fetal liver remained unchanged while [1-13C]glucose increased up to 380%. Total lactate level in brain was 50-80% above the control apart from a transient increase (140%) notable after 40 min reperfusion. The kinetics of [3-13C]lactate followed a similar time course. At the same time when lactate was transiently increased in fetal brain, total lactate as well as 13C-labeled lactate showed a transient decrease in liver after 40 min. While the ways of mobilization of energy substrates for maintaining adequate metabolic activity in the fetal brain remain still unclear, the present 13C NMR studies suggest that both liver glucose and lactate can contribute to brain metabolism particularly under ischemic stress.

Adenosine Triphosphate↗
PubMed1998

Mechanisms of docosahexaenoic acid accretion in the fetal brain.

Docosahexaenoic acid (DHA, 22:6 n-3) is the major polyunsaturated fatty acid (PUFA) in the adult mammalian brain. DHA is an essential fatty acid (FA) since it, or its short chain precursor, alpha-linolenic acid (LnA, 18:3 n-3), have to be obtained in the diet. Moreover, dietary n-3 FA deficiency is associated with biochemical changes in the brain and with disturbances in vision and other neurological parameters. Under normal nutritional conditions, fetal brain DHA accumulation is substantial, with a "DHA accretion spurt" being demonstrated in the last period of gestation. This accumulation is supported by the maternal supply of DHA or LnA, but selectivity of DHA accumulation is probably a placental function whose mechanism is lately being clarified. The fetal gastrointestinal (G-I) tract may be instrumental in supplying DHA to the fetal brain under certain conditions, such as following intra-amniotic administration of ethyl-docosahexaenoate (Et-DHA). In this pathway, DHA is supplied independently of the maternal metabolism, and the fetal liver is apparently involved. The fetal G-I tract may be advantageous for DHA supply in cases of maternal-placental insufficiency resulting in intrauterine growth retardation. The fetal brain itself is capable of metabolizing LnA to DHA, without the participation of the fetal liver, thus contributing to the accumulation of its own DHA during one of the most crucial periods of its development.

Animals↗
PubMed1998

Tetanus toxin enhances protein kinase C activity translocation and increases polyphosphoinositide hydrolysis in rat cerebral cortex preparations.

Tetanus toxin (TeTx) has been recently demonstrated to be a Zn2+-dependent endopeptidase that cleaves synaptobrevin, a protein in part responsible for neurotransmitter release. Nevertheless, certain aspects of TeTx action, for example, the causal relationship between TeTx and protein kinase C (PKC; EC 2.7.1.37) activity cannot be explained by this cleavage alone. In the present study, primary neurons from fetal rat brain, synaptosomes, and whole slices have been used to examine this issue. Low doses of TeTx (< or = 10(-8) M) caused PKC activity translocation in a manner similar to that produced by 12-O-tetradecanoylphorbol 13-acetate (TPA). TPA (< or = 10(-7) M) caused sustained PKC activity translocation, whereas TeTx produced translocation followed by relocation, depending on the dose and time of exposure. Immunoidentification with a monoclonal antibody recognizing both alpha and beta isoforms revealed that TeTx induced moderate losses of PKC in the cytosolic fraction, without a comparable increase in the particulate fraction. Although moderate losses of activity were also noticed in the cytosolic fraction, the inconsistency with respect to activity translocation may be explained by translocation of additional PKC isoforms that are not identified by the antibody. Comparable levels of water-soluble inositol phosphate-labeled intermediates were obtained after treatment of cerebral cells and/or cortical brain slices with TeTx. Significant increases of 19 and 114% in the water-soluble myo-[2-(3)H]inositol-labeled inositol phosphate metabolites were found in cerebral cell culture and brain slices, respectively, after treatment with 10(-8) M TeTx. TeTx (10(-8) M) increased to the same degree the water-soluble inositol phosphate levels as did serotonin (10(-5) M) or carbachol (10(-6) M). It is suggested that part of the signaling cascade of TeTx consists of a component involving inositol phospholipid hydrolysis, which is associated with PKC activity translocation.

Animals↗
PubMed1998

Intraamniotic ethyl docosahexaenoate administration protects fetal rat brain from ischemic stress.

Studies were conducted on the prenatal rat given a single intraamniotic injection of ethyl docosahexaenoate (Et-DHA; 9.6-12 mmol per fetus) or subjected to an n-3 fatty acid-deficient diet to assess the role of docosahexaenoate on oxidative stress during episodes of ischemia. A time-dependent decrease in the ability of brain slices from animals treated with Et-DHA to produce thiobarbituric acid-reactive substance (TBARS), most pronounced after 1 day (from 58.1 +/- 4.22 to 15.9 +/- 1.6 nmol/mg of DNA), was noticed on stimulation with Fe2+. Brain slices from fetuses treated for 1 day with Et-DHA and those from untreated fetuses produced TBARS levels of 46.7 +/- 6.5 and 114.8 +/- 10.8 nmol/mg of DNA, respectively, after a 20-min occlusion of the fetal-maternal circulation at embryonic day 20, suggesting a protective effect of Et-DHA. The protective effect of a single dose of Et-DHA in utero remained high up to 3 days after injection (p < 0.001) and was long-lasting, yet not significant, up to 3 days following birth. In agreement with a reduction in TBARS production by slices, the endogenous levels of TBARS in brains of Et-DHA-treated animals were lower than in the controls. Et-DHA-injected fetuses exhibited significantly higher levels of esterified DHA than the noninjected controls. n-3-deficient diet given to dams for 2 weeks before birth did not affect the levels of TBARS production in control fetal brain slices but abolished the increase caused by ischemia. Et-DHA administration for 24 h to n-3-deficient fetuses reduced the amount of TBARS produced by the fetal brain slices from 49.1 +/- 8.5 to 31.7 +/- 4.1 nmol/mg of DNA. A protective effect from oxidative damage after postischemic oxidative stress in fetal brain following DHA supplements is suggested, whereas the effect of n-3 fatty acid deficiency in this regard is more ambiguous.

Amnion↗
PubMed1997

Replenishment of docosahexaenoic acid in n-3 fatty acid-deficient fetal rats by intraamniotic ethyl-docosahexaenoate administration.

A procedure for intraamniotic ethyl-docosahexaenoate (Et-DHA) administration was used to restore the docosahexaenoic acid (DHA; 22:6 n-3) levels in n-3-deficient fetal rats. The state of deficiency, characterized by a 34% and 60% decrease in DHA content of fetal brain and liver, respectively, was attained by feeding the pregnant dams from day 8 and up to 20 days gestation, with an n-3 linolenic acid-deprived diet. After a single intraamniotic administration of Et-DHA on day 18 or 19, a rapid increase in both fetal brain and liver DHA was achieved. This increase was accompanied by a decrease in the docosapentaenoic acid (DPA; 22:5 n-6) level. After 48 hr following Et-DHA administration, the major phospholipids (PLs) phosphatidylserine (PS), phosphatidylethanolamine (PE), and phosphatidylcholine (PC), together accounting for more than 90% of total lipid phosphorus in sunflower oil (SFO)-treated animals, regained the DHA content to levels similar to control animals in both fetal brain and liver tissues. Unlike brain, however, most of the DHA content in liver PLs was restored by 24 hr, suggesting that the fetal liver may have a higher metabolic turnover. The DHA/DPA ratio was used to assess the degree of DHA correction. Fetal brain PS, PC, and PE ratios following Et-DHA administration grew steadily over a period of 48 hr but reached only approximately 60% of the control levels. Liver PS regained a value similar to the control, while those of PC and PE were 33% and 46% lower than the controls, respectively. Alterations in the PL polar head-group composition were observed following the dietary manipulations and Et-DHA administration. Although the intraamniotic injection is an invasive approach, the ability to rapidly enhance DHA acylation during intrauterine life may hold potential clinical value whenever an indication for DHA deficiency exists.

Amnion↗
PubMed1997

Apoptotic death in cerebral hemisphere cells is density dependent and modulated by transient oxygen and glucose deprivation.

Flow cytometry, light and fluorescence microscopy, and designated biochemical techniques were used to examine the type of death which occurs in cerebral cortex cells when grown under crowded vs. sparse conditions or after brief anoxia/hypoglycemia. A 4 hr episode of anoxia combined with glucose deprivation enhanced apoptotic cell death as assessed by 4',6-diamidino-2-phenylindole (DAPI) staining and reduced neutral red eye uptake. An additional form of cell death involving exclusion of the nucleus was recorded by time lapse cinematography and DAPI stain. The presence of the endonuclease inhibitor aurintricarboxylic acid (0.1 mM) reduced cell death by 56.6%, while the protein and RNA synthesis inhibitors actinomycin D and cycloheximide (each at 5 micrograms/ml) effectively decreased cell death by 83.3% and 90.6%, respectively. In contrast, 5 mM glutamate had no effect on cell death in accord with the immature state of the cells. Growth of cells under crowded conditions improved cell survival; after 2 h or 4 days in culture, cells seeded at high density (34 microgram cellular DNA/cm2) showed a nearly 3-fold decline in the amount of cell death in comparison to cells seeded at low density (5 micrograms cellular DNA/cm2). At high cell density, anoxic episodes enhanced cell death most likely by preventing a cell density-mediated rescue. Neutral red dye uptake, an index for cell viability, was enhanced with increasing cell density and in vitro maturation, but was reduced in dense cultures exposed to anoxic/hypoglycemic conditions. The data suggest that cell density may play a critical role in brain organogenesis and that anoxic stress is more deleterious in dense than sparse cell assemblies.

Animals↗
PubMed1997

Lipid peroxides are generated by the fetal rat brain after episodes of global ischemia in utero.

Complete arrest of maternal-fetal blood supply for up to 30 min caused a time-dependent increase in the endogenous levels of lipid peroxides (LPO) in fetal brain and liver extracts and fetal blood and amniotic fluids as indicated by the appearance of thiobarbituric acid reactive substances (TBARS). A steady increase of TBARS from 48.0 +/- 2.2 pmol/g wet weight to 75.0 +/- 5.6 pmol/g wet weight up to 30 min restriction was noticed in the fetal brain. The fetal liver TBARS values increased by approximately 69% after 5 min restriction and remained high, above the control level, for 30 min. After two days reperfusion following 30 min restriction, the TBARS levels in the fetal brain were 1.8 fold higher above the control, while those of the liver returned to control values. The levels of the lipid-soluble antioxidant alpha-tocopherol were reduced by about 40% and 50% in the placenta and brain tissues after 5 min restriction, respectively. Slices of fetal brain incubated at 37 degrees C in DMEM under oxygen in the presence of 50 microM Fe2+ were able to generate LPO in a time- and tissue concentration-dependent manner. After 15 min incubation, about 6.3 fold increase in total TBARS levels could be measured in the presence of 50 microM Fe2+, most of which was released in the medium. The iron chelator desferrioxamine (25 microM) and the antioxidant alpha-tocopherol (10 microM) added to the incubation medium, each inhibited by about 88% TBARS production. After 20 min episode of ischemia, fetal brain slices released into the medium 138.5 +/- 9.8 nmol/15 min/mg DNA compared to 75.9 +/- 4.5 nmol/15 min/mg DNA released by the sham preparations. After 3 h reperfusion, brain slices from fetuses exposed to 20 min ischemia continued to produce TBARS above control levels, whereas those of brief ischemia (5 min) returned to control levels. The data indicate that the limited resistance of the fetal brain to brief, rather than prolonged, periods of ischemia, is likely due to a lack of free FA for LPO generation, rather than the levels of tissue lipid antioxidants.

Animals↗
PubMed1996

Fatty acid composition of late embryonic and early postnatal rat brain.

The fatty acid (FA) composition and distribution in a variety of phospholipids (PL) and neutral lipids (NL) at two discrete stages during the embryonic rat brain development were investigated. Over 96% of the FA were acylated into fetal brain PL at embryonic day 17 after the peak of neuronal proliferation and at embryonic day 20, one day prior to delivery. Phosphatidylcholine constituted approximately 60% of the total PL pool, phosphatidylethanolamine (PE) 30%, phosphatidylserine (PS) 6%, and phosphatidylinositol (PI) 4%. The diacylglycerols and triacylglycerols constituted 1-2% of the fetal brain lipids. alpha-Linolenic acid (18:3n-3) and linoleic acid (18:2n-6) were found in very low amounts in all fetal brain PL and NL. The percentage of the n-6 polyunsaturated FA, consisting of arachidonic acid (AA), 22:4n-6 and 22:5n-6, remained unchanged in all the fractions, except in PI, in which the proportion of AA increased. The concentration of docosahexaenoic acid (DHA) increased with age in all the fractions, with the bulk of accumulation accounted for by its increase in PE and, to a lesser extent, in PS. This finding suggests a "DHA accretion spurt" during the last three days of pregnancy.

Animals↗
PubMed1996

Natural and accelerated docosahexaenoic acid accumulation in the prenatal rat brain.

The quantity and distribution of docosahexaenoic acid (DHA) in major brain phospholipids (PL) was examined in the fetal rat brain before birth, using thin-layer and capillary column gas chromatography. A rapid increment of DHA content of about 187 micrograms/g brain/day was observed between 17 to 20 days gestation, as opposed to 39.3 +/- 2.9 micrograms/g brain/day prior to that. Single intraamniotic injections of 5 microL ethyl-docosahexaenoate (Et-DHA) (12 microM, 4.25 mg) administered to 17-day-old fetuses were used to examine the uptake of DHA into brain PL. Three days following injection, the amount of n-3 polyunsaturated fatty acids increased by 28% compared to ethyl-oleate (Et-Ole) injected fetuses. Compared to the n-6 fatty acid family, the relative amount of DHA increased in the phosphatidylserine (PS), phosphatidylethanolamine and phosphatidylcholine (PC) lipids by 15 (P = 0.02), 13 and 14%, respectively. A major increase in the pool size of phosphatidylinositol and PS (110 and 50.3%, respectively), and a decrease in PC (8.2%) were observed 3 d after Et-DHA as compared to Et-Ole administration. The data suggest that a single intraamniotic administration of Et-DHA can modulate membrane PL content and alter PUFA composition.

Amnion↗
PubMed1996

Urinary excretion of prostacyclin in a rat model of uteroplacental vasculature occlusion: implications for fetal growth retardation.

An experimental model was devised in the pregnant rat to study by a combined high pressure liquid chromatography and radioimmunoassay technique the accumulation of prostanoids (PNs) in the urine after transient-complete or permanent-partial interruption of the maternal-fetal blood flow. After 8 min of complete restriction of the blood flow in the pregnant rat at 18 days of gestation, the urinary concentration of 6-keto-prostaglandin F1 alpha (6k-PGF1 alpha, the stable prostacyclin metabolite) increased from 4.97 +/- 1.27 ng mg-1 creatinine to 8.09 +/- 2.47 ng mg-1 creatinine and 13.02 +/- 4.5 ng mg-1 creatinine after the second and third post-operative day respectively. The urinary concentration of the 2,3-dinor derivative of prostacyclin reached 12.35 +/- 5.44 ng mg-1 creatinine after the second post-operative day and was reduced to 4.71 +/- 1.94 ng mg-1 creatinine after the third post-operative day. The concentration of thromboxane B2 (TxB2, the stable thromboxane A2 metabolite) increased approximately 7-fold and 13-fold over that of the control after the second and third post-operative day respectively. The urinary concentration of the 2,3-dinor derivative of TxB2 (d-TxB2) increased from about 1.42 +/- 0.3 ng mg-1 creatinine to 4.49 +/- 0.9 ng mg-1 creatinine and 7.76 +/- 2.63 ng mg-1 creatinine under the same experimental conditions. Increases in the urinary concentrations of 6k-PGF1 alpha and d-TxB2 to 94 +/- 27.76 ng mg-1 creatinine and 12.05 +/- 2.26 ng mg-1 creatinine, respectively, were observed on the second post-operative day, after the restriction time was increased to 30 min. Permanent-partial occlusion of the maternal fetal circulation resulted in excretion of PNs in the urine to similar levels produced after transient-complete restriction. High concentrations of prostacyclin (range, 0.8 ng min-1 mg-1 wet weight) were produced in vitro by uterine preparations from restricted animals after the second post-operative day. Placenta preparations from restricted animals generally exhibited a lower ability to synthesize PNS (up to 0.006 ng min-1 mg-1 wet weight) compared with uterine tissue but produced more thromboxane than their sham counterparts. The data suggest that the uterus constitutes the main source for urinary PN excretion following short episodes of maternal-fetal blood flow interruption.

Animals↗
PubMed1995

Modulation of fetal rat brain and liver phospholipid content by intraamniotic ethyl docosahexaenoate administration.

In an attempt to elucidate the role of docosahexaenoic acid (DHA; 22:6n-3) in the developing brain, a method was devised whereby rapid enrichment of fetal brain and liver lipid with DHA was achieved. Fetal rats at 17 days of gestation were injected intraamniotically with ethyl docosahexaenoate (EtDHA). Control fetuses were administered ethyl oleate (EtOle). Brain lipid DHA content increased by almost 21% (p = 0.02) 3 days after EtDHA administration as compared with EtOle-injected fetuses, whereas liver lipid DHA content increased by almost 60% (p = 0.0002). At this time brain phosphatidylinositol content doubled, whereas phosphatidylserine (PS) content increased by > 50% (p = 0.03). Increases in liver PS (+25.8%; p = 0.015) and sphingomyelin (+43.6%; p = 0.01) content were observed. A redistribution of total brain phospholipid (PL) DHA was observed following EtDHA administration, resulting in a 56.4% increase in PS-DHA abundance (p < 0.05) and an 8.8% decrease in phosphatidylethanolamine-DHA abundance (p = 0.05). These results suggest modulation of fetal brain and liver PL and provide a method for enrichment of DHA content in discrete PLs during intrauterine life.

Amniotic Fluid↗
PubMed1995

Ischemia-triggered translocation and inactivation of protein kinase C isoforms in the fetal brain.

The kinetics of protein kinase C (PKC) translocation and down-regulation in the 20-day-old fetal brain following short and long episodes of maternal-fetal blood flow occlusion were examined. Restriction for up to 15 min increased the specific enzymatic activity in the membrane by 73%, indicative of translocation. After a 30-min restriction and a 2.5-h reperfusion the total PKC activity in the cytosol was reduced to approximately 50%, consistent with down-regulation/inactivation. The total membrane PKC activity remained unchanged. Several PKC isoenzymes, including alpha, beta 1, beta 2, epsilon, and zeta, but not gamma, were identified in the fetal brain on western blots using specific antibodies. Compared with postnatal day 15, a greater proportion of the fetal PKC isoforms, particularly alpha and epsilon, were membrane bound, alpha, beta 2, epsilon, and zeta, but not beta 1, were translocated into the membrane compartment after episodes of ischemia alone or ischemia and reperfusion. There were no major identifiable proteolytic fragments in the 50-kDa region. Major losses in the total enzymatic activity were encountered in both cytosol and membrane fractions after storage of the enzyme for 10 days at 4 degrees C. These losses were less profound in membrane fractions from ischemic than control animals, suggesting a relative sparing of activity in the membrane as a result of the insult. Preincubation of DEAE-purified PKC for 30 min at 50 degrees C resulted in enzyme inactivation. This was accompanied by a size reduction (approximately 2-5 kDa) in the gel migration of several isozymes in both cytosol and membrane fractions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Differentiation of oligodendrocytes cultured from developing rat brain is enhanced by exogenous GM3 ganglioside.

Cultures consisting primarily of O-2A progenitor cells and immature oligodendrocytes with a few microglia and astrocytes were obtained by shaking primary cultures from neonatal rat brain after 12-14 days in vitro. Addition of 50 micrograms/ml exogenous Neu-NAc alpha 2-3Gal beta 1-4Glc beta 1-1'ceramide (GM3 ganglioside) to the cultures resulted in an increase in the number and thickness of cell processes that stained intensely for sulfatide and galactocerebroside (galC) in comparison to control cultures without added GM3. The treated cultures also contained fewer astrocytes than control cultures as revealed by immunostaining for glial fibrillary acidic protein (GFAP). Cells that immunostained for both GFAP and sulfatide/galC were very rare in control cultures but were frequently seen in the GM3-treated cultures, suggesting that these may represent cells changing their direction of differentiation away from type II astrocytes toward oligodendrocytes under the influence of GM3. These effects on the developing rat oligodendrocytes were specific for GM3 ganglioside and were not produced by adding GM1, GM2, GD3, or GD1a to the cultures. Lactosyl ceramide and neuraminyl lactose were also ineffective. When control cultures were initially plated on polylysine and incubated with [14C]galactose, GD3 was the principal labeled ganglioside. However, as the control cells differentiated over time in culture without the addition of exogenous GM3 and produced increasing amounts of myelin-related components, the incorporation of [14C]galactose into endogenous GM3 increased to become the predominant labeled ganglioside by 6 days after plating. Metabolic labeling of the GM3-treated oligodendrocytes with [14C]galactose revealed increased incorporation into galC and sulfatide in comparison to control cultures, but a decreased labeling of endogenous GM3. Similarly, incorporation of an amino acid precursor into the myelin-associated glycoprotein (MAG) was increased by GM3 treatment, but incorporation into myelin basic protein (MBP) was not affected. Although the overall effect of added GM3 was to decrease the phosphorylation of most proteins in the oligodendrocytes, including MBP, GM3 enhanced the phosphorylation of MAG. These findings indicate that GM3 ganglioside has an important role in the differentiation of cells of the O-2A lineage toward myelin production, since differentiation is associated with increased metabolic labeling of endogenous GM3 in control cultures and is enhanced by the addition of exogenous GM3.

Animals↗
PubMed1994

Production and metabolism of platelet-activating factor in the normal and ischemic fetal rat brain.

Production and metabolism of platelet-activating factor (PAF) in the fetal rat brain under normal and under ischemic stress conditions were examined. Endogenous PAF levels, determined by a bioassay using PAF-stimulated platelet release of [3H]serotonin, averaged 2.32 +/- 2.14 pg/mg in control brains and was reduced to 1.10 +/- 1.06 pg/mg after 20 min of maternal-fetal blood flow occlusion. [3H]PAF administered intracranially into the fetuses in utero was removed in a biphasic, time-dependent manner: a rapid component with an estimated elimination rate constant of 0.067 min-1 and t1/2 of 10 min and a slower component with an elimination rate of 0.017 min-1 and t1/2 of 41 min. In fetal brains subjected to ischemia a delayed elimination of [3H]PAF was noticed in the slow component (t1/2 = 59 min), indicating a possible difference between the clearance of exogenous and endogenous PAF. The disappearance of [3H]PAF was accompanied by an increase in the radioactivity associated with lyso-PAF that reached a plateau after 2.5 min, possibly indicating the degradation of the fast component. A steady increase in the alkyl-acyl-glycerophosphorylcholine radioactivity commenced after 5 min and continued up to 30 min. The endogenous production of PAF and the rapid degradation due to maternal-fetal blood flow occlusion indicate an additional target for therapeutic intervention in the pathology of intrauterine ischemia. Addition of the calcium ionophore A23187 stimulated in vitro formation of PAF and lyso-PAF from [3H]-choline-labeled fetal brain phospholipids, suggesting that intracellular calcium may play a major stimulatory role in PAF production.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Transient rise of glucose uptake in the fetal rat brain after brief episodes of intrauterine ischemia.

In a rat model of intrauterine growth retardation and fetal brain ischemia, the maternal-fetal circulation was obstructed for up to 40 min in 20-day gestational age rats by occluding (restriction) the uterine blood vessels supplying the placenta. After restriction, flow was returned (reperfusion) for designated times. A time-dependent depletion of cerebral pyruvate levels (from 0.2 +/- 0.02 to 0.06 +/- 0.01 mumol/g wet weight) accompanied by an elevation in lactate concentration (from 1.95 +/- 0.03 to 7.00 +/- 0.56 mumol/g wet weight) was observed after 20 min restriction. During 20 min, reperfusion lactate levels continued to increase, then gradually decreased as the reperfusion continued for approximately 2 h. A drastic increase in the lactate/pyruvate ratio (from 10 to 117) suggested that the fetal brain was relying on anaerobic glycolysis to meet its energy demands. In addition, a time-dependent decrease in fetal brain phosphocreatine (PCr) content from 2.54 +/- 0.26 to 1.52 +/- 0.15 mM was observed after 20 min of maternal-fetal blood flow obstruction. ATP levels gradually decreased after 20 min restriction from 1.62 +/- 0.13 to 0.59 +/- 0.09 mM. After 30 min reperfusion ATP, PCr and pyruvate returned to their normal values. These metabolic changes observed are concordant with the ability of the ischemic fetal brain to sustain adequate levels of ATP for energy-requiring cellular processes. The capacity of glucose transporters to facilitate transport of glucose into brain tissue was assessed ex vivo, using [3H]2-deoxyglucose (2D-Glu).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1993

Gangliosides stimulate synthesis of prostaglandin E2 and prostacyclin in fetal rat brain hemispheres after episodes of global intrauterine ischemia.

The ability of brain preparations from 20-day-old rat fetuses to synthesize prostanoids in vitro before and after interruption of the maternal-fetal blood flow was examined using a radioimmunoassay technique. Synthesis of thromboxane B2 (TxB; the stable thromboxane A2 metabolite) decreased with increasing restriction time; conversely, it was elevated with reperfusion. Synthesis of 6-keto prostaglandin F1 alpha (PGF; the stable prostacyclin metabolite) and prostaglandin E2 (PGE) prostanoids remained unchanged after 20 min restriction and through a 2 hr reperfusion period. Intraperitoneal administration of GM1 (45 mg/kg) into the pregnant rat, 3 hr before restriction, stimulated synthesis of PGE and reduced synthesis of TxB. A prostanoid vasoactive index (PVI), which reflects the relative proportion of the three prostanoids synthesized and asserts the vasoactive potential of the brain tissue, was established. A rise in this value was attained after intrafetal administration into the peritoneal cavity of either GM1, GM3, or isopropyl-GM1 (AGF44) gangliosides, each given at 40 micrograms dose in 5 microliters volume, and N-dichloroacetyl-sphingosine (LIGA20; 15 micrograms/5 microliters) ganglioside analog, 1 hr before restriction. The effect was primarily due to an increase in the capacity of fetal brain tissue to synthesize PGE and, to a lesser extent PGF, vasodilating prostanoids. The N-methyl-D-aspartate (NMDA) receptor-blocker MK801 (6.6 micrograms/2 microliters) and the platelet activating factor (PAF) receptor antagonist BN52021 (0.1 mumol/2 microliters), given by the same route, effectively raised by 60-80% the vasodilating potential of the brain tissue following ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Ketoprostaglandin F1 alpha↗
PubMed1993

GT1b ganglioside prevents tetanus toxin-induced protein kinase C activation and down-regulation in the neonatal brain in vivo.

A single dose of 0.25 ng of tetanus toxin (TeTx), equivalent to approximately 5 minimal lethal doses, injected intracerebrally to 1-day-old rats, caused translocation, i.e., activation, of Ca(2+)-phosphatidylserine-dependent protein kinase C (PKC) from the cytosolic to the membrane compartment within 1 h. Six hours after treatment with the toxin, a 40-50% reduction in the total brain PKC (cytosolic plus membrane) activity was noticed. GT1b (2 micrograms per brain) ganglioside, a putative receptor for TeTx, completely prevented enzyme translocation when injected intracerebrally 30 min before toxin administration and abolished down-regulation after 6 h from the time of toxin injection. GM1 (2 micrograms per brain), a ganglioside of lesser affinity for TeTx, produced by itself a 20-30% reduction of the total PKC activity and did not reverse TeTx-induced PKC down-regulation after 6 h. 12-O-Tetradecanoylphorbol 13-acetate (TPA) phorbol ester, administered at a concentration of 5 x 10(-5) M, caused activation and down-regulation of the enzyme, although with several orders of magnitude lesser potency. GT1b prevented the TPA-induced down-regulation.

Animals↗