The influence of early protein-calorie malnutrition on neuronal and glial protein synthesis

The effect of pre- and postnatal undernutrition, produced according to the method of Chow and Lee (3), on the rate of protein synthesis in the brains of rats 11, 21, 34 and 90 days of age was studied by measuring the incorporation ofl-[¹⁴C]valine in vivo andl-[³H]lysine in vitro. Both in vivo and in vitro experiments were performed with high concentration of the precursor to decrease the effects of pool variations and protein degradation. Particular interest was given to the effects of this form of early protein-calorie malnutrition (PCM) on neuronal and glial cells which were isolated from the brains by gradient centrifugation. Brain protein synthesis measured in vivo which showed a peak at 21 days in both animal series, was depressed by PCM at 11 days but stimulated at 34 days of animal age. Small effect was observed in the 90-day-old animals. A similar response as in whole brain was seen for neuronal cells, while glial cells showed a different reaction. Studies of in vitro protein synthesis did not reveal appreciable effects of undernutrition in whole brain. Both neuronal and glial cells showed a moderate but not statistically significant elevation of protein synthesis in animals subjected to early PCM.     

Specific binding and pharmacological interactions of apamin,the neurotoxin from bee venom,with guinea pig colon

This paper describes the interaction of apamin, the bee venom neurotoxin, with its receptor in the guinea pig colon. The pharmacological activity of the toxin was assayed by measuring its contracting effect on guinea pig colon preparations that had been previously relaxed by neurotensin. The IC₅₀ value of apamin in this $\text{in vitro}$ bioassay is 7 nM. These pharmacological data are compared to the binding properties of apamin to smooth muscle membranes prepared from guinea pig colon. The highly radiolabeled monoiododerivative of apamin binds to its colon receptor with a dissociation constant $\text{K}{}_{\mathrm{<mtext>d</mtext>}}{}^1\text{= 36}\text{pM}$. The maximal binding capacity of colonic membranes is 30^dfmol/mg of protein. The dissociation constant of the unmodified toxin is 23 pM. The difference between the toxin concentrations that produce half-maximal effects in the binding and pharmacological studies arises from the different experimental conditions used for the two assays.     

Hydrogen Production by the Thermophilic Alga Mastigocladus laminosus: Effects of Nitrogen, Temperature, and Inhibition of Photosynthesis

Hydrogen production by nitrogen-limited cultures of a thermophilic blue-green alga (cyanobacterium), Mastigocladus laminosus, was studied to develop the concept of a high-temperature biophotolysis system. Biophotolytic production of hydrogen by solar radiation was also demonstrated. Hydrogen consumption activity in these cultures was relatively high and is the present limiting factor on both the net rate and duration of hydrogen production.     

The modulation of membrane fluidity by hydrogenation processes. III. The hydrogenation of biomembranes of spinach chloroplasts and a study of the effect of this on photosynthetic electron transport

A method is reported for the in situ modification of the lipids of isolated spinach chloroplast membranes. The technique is based on a direct hydrogenation of the lipid double bonds in the presence of the catalyst, chlorotris(triphenylphosphine)rhodium (I). The pattern of hydrogenation achieved suggests that the catalyst distributes amongst all of the membranes. The polyunsaturated lipids within the membranes are hydrogenated at a faster rate and at an earlier stage than are the monoenoic lipids.Whilst addition of the catalyst to the chloroplast causes an initial 10–20% decrease in Hill activity, saturation of up to 40% of the double bonds present can be accomplished without causing further significant alterations in photosynthetic electron transport processes or marked morphological changes of the chloroplast structure as observed in the electron microscope.     

Serological detection of H-2K- and H-2D-gene products

Using the fluorescence-activated cell sorter (FACS II), we have analyzed the expression of H-2K- and H-2D-gene products on the membrane of various cellular components of the murine immune system. Using this serological technique we show a basic difference between T and B lymphocytes. Whereas all cellular components analyzed — hydrocortisone-resistant thymocytes, splenic T and B lymphocytes, macrophages and bone-marrow cells — expressed H-2K-subregion-encoded alloantigens at a high density, it seems that the high density expression of H-2D-encoded alloantigens is restricted mainly to B cells and to macrophages. Hydrocortisone-resistant thymocytes, splenic T lymphocytes and bone-marrow cells, on the other hand, showed significant expression of the H-2D alloantigens only at low membrane density. These results, then, provide evidence for the existence of an imbalance in serologically detectable expression of H-2K- and H-2D-region-gene products on the cell membrane of various cells comprising the murine immune system.Abbreviations usedin this paper DTH delayed type hypersensitivity - FCS fetal calf serum - FITC fluorescein isothiocyanate - HrT hydrocortisone-resistant thymocytes - Ig immunoglobulins P. De Baetselier is an EMBO and Euratom postdoctoral fellow     

Partial characterization of the plasma membrane ATPase from arho 0 petite strain ofSaccharomyces cerevisiae

Crude membrane preparations of arho ⁰ mutant ofSaccharomyces cerevisiae exhibit Mg²⁺-dependent ATPase activity. Over the optimal pH range, 5.0–6.75, the apparentV _max of the enzyme equals 590 nmoles of ATP hydrolyzed per minute per milligram protein, with an apparentK _m for ATP of 1.3 mM. ATP hydrolysis is insensitive to ouabain, venturicidin, aurovertin, and the protein inhibitor described by Pullman and Monroy; inhibited by oligomycin (at high concentrations) and sodium orthovandate, and it is sensitive to dicyclohexylcarbodiimide,p-hydroxymercuribenzoate, hydroxylamine, sodium fluoride, and sodium iodoacetate. The pH optimum and the inhibitor pattern distinguish the plasma membrane enzyme from the mitochondrial F₁ ATPase still present in these cells (this activity is sensitive to efrapeptin, aurovertin, and the protein inhibitor, but resistant to DCCD). In addition, the activity of the plasma membrane enzyme and its affinity for ATP are responsive to changes in the composition of the growth medium, with the highest activity observed in cells grown on methyl--d-glucoside, a sugar which results not only in partial release from catabolite repression but also requires the induction of an active transport system for growth.Author to whom correspondence should be addressed; recipient of a Research Career Award No. K06 05060 from the Institute of General Medical Sciences.     

Involvement of the cystathionine pathway in the biosynthesis of glutathione by isolated rat hepatocytes

The ability of l-methionine to support glutathione biosynthesis has been investigated in isolated rat hepatocytes under conditions of normal and depleted glutathione status. The addition of l-[³⁵S]methionine or [l-[³⁵S]homocysteine to incubation media containing hepatocytes results in the incorporation of ³⁵S into intracellular glutathione. Additionally both l-methionine and l-homocysteine are capable of supporting the resynthesis of glutathione in isolated hepatocytes after prior depletion with diethyl maleate. The inclusion in the incubation medium of 1 mm propargylglycine, which is an irreversible inhibitor of the terminal enzyme of the cystathionine pathway, substantially blocks the incorporation of ³⁵S from methionine and l-homocysteine into cellular glutathione. Propargylglycine treatment of hepatocytes in the presence of [³⁵S]methionine is shown to result in the intracellular accumulation of [³⁵S]cystathionine. These results strongly support the conclusion that in rat hepatocytes the cystathionine pathway enables methionine to provide a significant source of l-cysteine for the support of glutathione biosynthesis, under both normal and glutathione-depleted conditions.