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Notes: Abstract— The oxidation of l-[U-14C]leucine and l-[l-14C]leucine at varying concentrations from 0.1 to 5mM to CO2 and the incorporation into cerebral lipids and proteins by brain slices from 1-week old rats were markedly stimulated by glucose. Although the addition of S mM-dl-3-hydroxybutyrate had no effect on the metabolism of [U-14C]leucine by brain slices from suckling rats, the stimulatory effects of glucose on the metabolism of l-[U-14C]leucine were markedly reduced in the presence of dl-3-hydroxybutyrate. The stimulatory effect of glucose on leucine oxidation was, however, not observed in adult rat brain. Furthermore, the incorporation of leucine-carbon into cerebral lipids and proteins was also very low in the adult brain. The incorporation of l-[U-14C]leucine into cerebral lipids by cortex slices was higher during the first 2 postnatal weeks, which then declined to the adult level. During this time span, the oxidation of l-[U-14C]leucine to CO2 remained relatively unchanged. The incorporation in vivo of D-3-hydroxy[3-14C]butyrate into cerebral lipids was markedly decreased by acute hyperleucinemia induced by injecting leucine into 9-day old rats. In in vitro experiments, 5 mM-leucine had no effect on the oxidation of [U-14C]glucose to CO2 or its incorporation into lipids by brain slices from 1-week old rats. However, 5 mM-leucine inhibited the oxidation of d-3-hydroxy-[3-14C]butyrate, [3-14C]acetoacetate and [1-14C]acetate to CO2 by brain slices, but their incorporation into cerebral lipids was not affected by leucine. In contrast 2-oxo-4-methylvalerate, a deaminated metabolite of leucine, markedly inhibited both the oxidation to CO2 and the incorporation into lipids of labelled glucose, ketone bodies and acetate by cortex slices from 1-week old rats. These findings suggest that the reduction in the incorporation in vivo of d-3-hydroxy[3-14C]butyrate into cerebral lipids in rats injected with leucine is most likely caused by 2-oxo-4-methylvalerate formed from leucine. Since the concentrations of leucine and 2-oxo-4-methylvalerate in plasma of untreated patients with maple-syrup urine disease are markedly elevated, our findings are compatible with the possibility that an alteration in the metabolism of glucose and ketone bodies in the brain may contribute to the pathophysiology of this disease.

Notes: Cerebral cortex slices from 1-day old rats incorporated actively 3-hydroxy[3-14C] butyrate into lipids. The rate of synthesis increased moderately during the first postnatal week and then decreased rapidly reaching negligible rates by the end of the fourth postnatal week. The incorporation of [3-14C]acetoacetate (5 mM) and 3-hydroxy[3-14C]butyrate (5 mM) at non-physiological concentrations into lipids by cerebral cortex from 1-week old rats was markedly stimulated in the presence of added glucose; however, the addition of glucose had no effect on the oxidation of ketone bodies to 14CO2 At physiological concentrations of acetoacetate (0.5 mM) and 3-hydroxybutyrate (1 mM), glucose stimulated both the oxidation of ketone bodies to 14CO2 and the incorporation of ketone body-carbon into cerebral lipids. In contrast, the oxidation of [U-14C]glucose to CO2 and its incorporation into lipids by brain slices were markedly reduced in the presence of ketone bodies at physiological as well as non-physiological concentrations. However, the total rate of lipid synthesis, as determined by the incorporation of 3H from 3H2O, was maintained under these conditions. This indicated that the decreased contribution of the acetyl moiety from glucose was compensated to a similar extent by acetyl-CoA formed from ketone bodies. The findings show that both acetoacetate and 3-hydroxybutyrate are better precursors than glucose for in vitros lipid synthesis in developing rat brain.

Notes: Thermal imaging by an infrared television camera has been successfully employed as an in situ method for end-point detection during plasma etching of polycrystalline silicon layers on a SiO2/Si substrate. In addition, it is also shown that thermal imaging can be used for remote sensing of etch rate, heat of reaction, wafer temperature, and for measuring thermal time constants during plasma etching. From these measurements, the heat-transfer coefficient of the thermal contact between the silicon wafer and the water-cooled electrode can be determined.

Notes: A 120 mm, 27-gauge needle has recently been introduced for subarachnoid anaesthesia when using a single-space, combined spinal-extradural technique. The flow characteristics of this needle were compared with those of a 120 mm, 26-gauge needle using a pressure monitor infusion pump. Surprisingly, the resistance to fluid flow of the 26-gauge needle was twice that of the 27-gauge needle. The results of this experiment were confirmed by the findings of a clinical study undertaken in 100 obstetric patients who required regional anaesthesia. The time taken from dural puncture to appearance of cerebrospinal fluid at the hub of the needle was on average three times greater with the 26-gauge needle.

Notes: Single trilayer spin valves consisting of uncapped FeNi(60 A(ring))/Cu(60 A(ring))/Co(40 A(ring)) have been grown using ultrahigh vacuum (UHV) electron beam evaporation methods. Room temperature magnetoresistance (MR) measurements exhibit well defined plateaux corresponding to the full antiparallel alignment of the FeNi and Co magnetizations. This sharp switching behavior and precisely defined antiferrimagnetic state is in contrast with the corresponding behavior reported for FeNi/Cu/Co multilayers.

Notes: Several second messenger systems have been implicated in mediating the action of gonadotrophin-releasing hormone on the pituitary gonadotrophs and numerous studies have shown that activation of these systems induces luteinizing hormone (LH) secretion. However, it is not known how gonadotrophin-releasing hormone or the second messenger systems induce de novo LH biosynthesis and post-translational modification of the hormone. In these experiments hemipituitary glands have been perifused with drugs which activate second messengers or stimulate protein kinase C directly. The LH secretory responses have been correlated with measurements of common a and LHβ mRNA and the molecular species of LH which were present in the pituitary perifusate after exposure to the drugs.Gonadotrophin-releasing hormone (50 ng/ml, 42 nM), with and without the presence of extracellular Ca2+, the Ca2+ ionophore, A23187 (10 μM), and phorbol 12-myristate (1 μM) all stimulated an increase in LHβ mRNA compared with controls and the appearance of a different isoform of LH to that found stored in and released from the unstimulated pituitary gland. Phospholipase C was without effect on LHβ mRNA levels and showed minimal efficacy in inducing the appearance of the different LH isoform.

Notes: Spores of Clostridium botulinum type B (NCTC 7273) were sensitized to the inhibitory action of 2.5% and 3.5% w/w NaCl by heating at 85, 90 or 95°C at pH 6.0 and pH 6.5. Spores heated at 70 or 80°C were not significantly sensitized to these concentrations of NaCl but they were sensitized to 4.5% and 5.5% NaCl. A significant salt-nitrite interaction was observed only at NaCl levels of 4.5% and above. Heat-shocked spores and spores heated through a ‘1-D process’ at 70 or 95°C were more sensitive to nitrite heated in meat or in culture medium (121°/10 min) than to unheated nitrite added after heating. However, no differences in sensitivity to the heated nitrite (Perigo factor) were observed with spores heated at 70 and 95°C.