CARBOHYDRATE AND ENERGY METABOLISM IN PERINATAL RAT BRAIN: RELATION TO SURVIVAL IN ANOXIA

The ability of rats of different ages to survive exposure to anoxia was correlated with rates of high energy phosphate consumption (metabolic rates) of the fore-brain. Fetal rats at term, delivered by hysterotomy following maternal decapitation, survived in nitrogen at 37°C twice as long as 1-day-old neo-nates, 5 times longer than 7-day-old rats, and 45 times longer than adults. During ischemia induced by decapitation, the cerebral concentrations of the labile energy reserves (ATP, ADP, P-creatine, glucose and glycogen) and of lactate were determined in fetuses, 1- and 7-day post-natal animals. From the changes, the cerebral energy use rates were calculated to be 1·57 mmol/kg/min in fetuses, 1·33 mmol/kg/min in 1-day-olds and 2·58 mmol/kg/min in 7-day-olds. Maximal rates of lactate accumulation during ischemia, as a measure of glycolytic capacity, were comparable in fetuses and neonates, but were about twice as great in 7-day-old rats. It is concluded that in post-natal animals survival in anoxia and cerebral energy consumption are inversely, and nearly quantitatively, related. However, the reduced cerebral energy requirement cannot entirely account for the greater anoxic resistance of fetuses.     

“Unblocking” Serum Activity <Emphasis Type="Italic">in vitro</Emphasis> in the Polyoma System may Correlate with Antitumour Effects of Antiserum <Emphasis Type="Italic">in vivo</Emphasis>

In a variety of tumour systems, individuals carrying progressively growing neoplasms have lymphoid cells with a specific cytotoxic effect on cultured tumour cells from the same individual^1–4. Since the sera of tumour-bearing individuals have been shown to prevent tumour cell destruction by immune lymphocytes in vitro^2,5–8 and since this serum blocking activity appears early in primary and transplant tumour development^5,7, it has been suggested that the appearance of this serum blocking activity might be responsible for the progressive growth of tumours in individuals having cytotoxic lymphocytes. Counteraction of this blocking activity would thus be of primary importance in facilitating the function of an already existing or bolstered cell-mediated immunity. The serum blocking activity might be inhibited in various ways, by preventing the formation of blocking antibody or by interfering with its action (“unblocking”), as demonstrated in Moloney sarcoma regressor sera⁹. This type of serum also has a therapeutic effect on Moloney sarcomas in vivo^10,11, which has been tentatively attributed to its unblocking activity^8,9 or, possibly, to a complement-dependent cytotoxicity¹⁰. Tumour growth in the Moloney sarcoma system, however, might be due in part to continuous recruitment of neoplastic cells by virus-induced transformation and so the therapeutic effect could be due to a virus-neutralizing serum activity^9,10.     

Developmental Expression of GLUT1 and GLUT3 Glucose Transporters in Rat Brain

Abstract: Two glucose transport proteins, GLUT1 and GLUT3, have been detected in brain. GLUT1 is concentrated in the endothelial cells of the blood-brain barrier and may be present in neurons and glia; GLUT3 is probably the major neuronal glucose transporter. Of the few studies of glucose transport in the immature brain, none has quantified GLUTS. This study used membrane isolation and immunoblotting techniques to examine the developmental expression of GLUT1 and GLUT3 in four forebrain regions, cerebral microvessels, and choroid plexus, from rats 1–30 days postnatally as compared with adults. The GLUT1 level in whole brain samples was low for 14 days, doubled by 21 days, and doubled again to attain adult levels by 30 days; there was no regional variation. The GLUT3 level in these samples was low during the first postnatal week, increased steadily to adult levels by 21–30 days, and demonstrated regional specificity. The concentration of GLUT1 in microvessels increased steadily after the first postnatal week; the GLUT1 level in choroid plexus was high at birth, decreased at 1 week, and then returned to near fetal levels. GLUT3 was not found in microvessels or choroid plexus. This study indicates that both GLUT1 and GLUT3 are developmentally regulated in rat brain: GLUT1 appears to relate to the nutrient supply and overall growth of the brain, whereas GLUT3 more closely relates to functional activity and neuronal maturation.     

On the mechanism of ATP-induced shape changes in the human erythrocyte membranes: the role of ATP

In the preceding paper (Sheetz, M. and S.J. Singer. 1977. J Cell Biol. 73:638-646) it was shown that erythrocyte ghosts undergo pronounced shape changes in the presence of mg-ATP. The biochemical effects of the action of ATP are herein examined. The biochemical effects of the action of ATP are herein examined. Phosphorylation by ATP of spectrin component 2 of the erythrocyte membrane is known to occur. We have shown that it is only membrane protein that is significantly phosphorylated under the conditions where the shape changes are produced. The extent of this phosphorylation rises with increasing ATP concentration, reaching nearly 1 mol phosphoryle group per mole of component 2 at 8mM ATP. Most of this phosphorylation appears to occur at a single site on the protein molecule, according to cyanogen bromide peptide cleavage experiments. The degree of phosphorylation of component 2 is apparently also regulated by a membrane-bound protein phosphatase. This activity can be demonstrated in erythrocyte ghosts prepared from intact cells prelabeled with [(32)P]phosphate. In addition to the phosphorylation of component 2, some phosphorylation of lipids, mainly of phosphatidylinositol, is also known to occur. The ghost shape changes are, however, shown to be correlated with the degree of phosphorylation of component 2. In such experiment, the incorporation of exogenous phosphatases into ghosts reversed the shape changes produced by ATP, or by the membrane-intercalating drug chlorpromazine. The results obtained in this and the preceding paper are consistent with the proposal that the erythrocyte membrane possesses kinase and phosphates activities which produce phosphorylation and dephosphorylation of a specific site on spectrin component 2 molecules; the steady-state level of this phosphorylation regulates the structural state of the spectrin complex on the cytoplasmic surface of the membrane, which in turn exerts an important control on the shape of the cell.     

Selective inhibition of prostaglandin biosynthesis by gold salts and phenylbutazone

Gold salts and phenylbutazone selectively inhibit the synthesis of PGF_2α and PGE₂ respectively. Lowered production of one prostaglandin species is accompanied by an increased production of the other. Selective inhibition by these drugs was observed in the presence of adrenaline, reduced glutathione and copper sulphate under conditions when most anti-inflammatory compounds inhibited PGE₂ and PGF_2α syntheses equally. It is postulated that selective inhibitors may have a different mode of action and beneficial effects may be related to the endogenous ratio of PGE to PGF required for normal function.     

Wavelet change-point prediction of transmembrane proteins

MOTIVATION: A non-parametric method, based on a wavelet data-dependent threshold technique for change-point analysis, is applied to predict location and topology of helices in transmembrane proteins. A new propensity scale generated from a transmembrane helix database is proposed. RESULTS: We show that wavelet change-point performs well for smoothing hydropathy and transmembrane profiles generated using different scales. We investigate which wavelet bases and threshold functions are overall most appropriate to detect transmembrane segments. Prediction accuracy is based on the analysis of two data sets used as standard benchmarks for transmembrane prediction algorithms. The analysis of a test set of 83 proteins results in accuracy per segment equal to 98.2%; the analysis of a 48 proteins blind-test set, i.e. containing proteins not used to generate the propensity scales, results in accuracy per segment equal to 97.4%. We believe that this method can also be applied to the detection of boundaries of other patterns such as G + Cisochores and dot-plots. AVAILABILITY: The transmembrane database, TMALN and source code are available upon request from the authors.     

Hypoxic Preconditioning and Hypoxic-Ischemic Brain Damage in the Immature Rat: Pathologic and Metabolic Correlates

Abstract: It has been reported that immature rats subjected to cerebral hypoxia-ischemia sustain less brain damage if they are previously exposed to systemic hypoxia compared with animals not exposed to prior hypoxia. Accordingly, neuropathologic and metabolic experiments were conducted to confirm and extend the observation that hypoxic preconditioning protects the perinatal brain from subsequent hypoxic-ischemic brain damage. Six-day postnatal rats were subjected to systemic hypoxia with 8% oxygen at 37°C for 2.5 h. Twenty-four hours later, they were exposed to unilateral cerebral hypoxia-ischemia for 2.5 h, produced by unilateral common carotid artery ligation and systemic hypoxia with 8% oxygen. Neuropathologic analysis, conducted at 30 days of postnatal age, indicated a substantial reduction in the severity of brain damage in the preconditioned rats, such that only 6 of 14 such animals exhibited cystic infarction, but all 13 animals without prior preconditioning exhibited infarction ( p < 0.001). Measurement of cerebral glycolytic and tricarboxylic acid intermediates and high-energy phosphate reserves at the terminus of and at 4 and 24 h following hypoxia-ischemia showed no differences in the extent of alterations in the preconditioned and nonpreconditioned immature rats. A difference was seen in the restitution of high-energy stores during the first 24 h of recovery from hypoxia-ischemia, with a more optimal preservation of these metabolites in the preconditioned animals, reflecting the less severe ultimate brain damage. Accordingly, the neuroprotection afforded to the preconditioned animals was not the result of any differences in the extent of anaerobic glycolysis, tissue acidosis, or depletion in high-energy reserves during hypoxia-ischemia but rather the result of other mechanisms that improved the metabolic status of the immature brain during the early hours of reperfusion following hypoxia-ischemia.