Phosphorylation on basic amino acids in myelin basic protein.

Isolated rat brain myelin when incubated with γ³²P labelled ATP yields proteins bearing acid labile, base stable phosphoryl groups. Phosphorylated myelin basic protein can be isolated and degraded with trypsin and pronase to yield principally phosphoarginine and phosphohistidine. Only a very small amount of phosphorerine survives the base treatment used in the isolation procedure.     

Randomised trial of two-drug and four-drug maintenance chemotherapy in advanced or recurrent Hodgkin's disease. Medical Research Council's working party on lymphomas.

Between 1970 and 1975, 108 patients who presented with advanced or recurrent Hodgkin''s disease and were free of disease after six courses of chemotherapy with mustine, vinblastine, procarbazine, and prednisone (MVPP) were allocated at random to one of two regiments of maintenance treatment: either intermittent treatment with vinblastine and procarbazine or intermittent treatment with MVPP. After a median follow-up period of nearly five years there was no significant difference between the two groups in either the rate of relapse or death rate. Six of the 55 patients given the two-drug regimen died compared with 10 of the 53 given the four-drug regimen. The four-drug required hospital attendance and was less agreeable than the two-drug regimen. The efficacy of maintenance chemotherapy with the two-drug regimen was no less than that with the four-drug regimen, but the two-drug regimen had several practical advantages.     

Specificity of GlcNAc-PI de-N-acetylase of GPI biosynthesis and synthesis of parasite-specific suicide substrate inhibitors.

The substrate specificities of Trypanosoma brucei and human (HeLa) GlcNAc-PI de-N-acetylases were determined using 24 substrate analogues. The results show the following. (i) The de-N-acetylases show little specificity for the lipid moiety of GlcNAc-PI. (ii) The 3'-OH group of the GlcNAc residue is essential for substrate recognition whereas the 6'-OH group is dispensable and the 4'-OH, while not required for recognition, cannot be epimerized or substituted. (iii) The parasite enzyme can act on analogues containing betaGlcNAc or aromatic N-acyl groups, whereas the human enzyme cannot. (iv) Three GlcNR-PI analogues are de-N-acetylase inhibitors, one of which is a suicide inhibitor. (v) The suicide inhibitor most likely forms a carbamate or thiocarbamate ester to an active site hydroxy-amino acid or Cys or residue such that inhibition is reversed by certain nucleophiles. These and previous results were used to design two potent (IC50 = 8 nM) parasite-specific suicide substrate inhibitors. These are potential lead compounds for the development of anti-protozoan parasite drugs.     

Female marmoset monkeys (Callithrix jacchus) can be identified from the chemical composition of their scent marks.

The present study analyzed 42 organic solvent extracts of scent mark pools from five dominant female common marmosets by gas chromatography (GC) and combined GC and mass spectrometry. We determined whether there were qualitative or quantitative differences between the chemical composition of scent marks from individual females. Gas chromatography and mass spectral analysis detected the same 162 chemicals in 86% (36/42) of scent mark pools from five dominant females. This near identical chemical composition of scent marks suggested there were few, if any, qualitative differences between the chemical composition of scent marks from individual females. Instead, quantitative differences in scent may provide the key factor distinguishing individual females. Using the relative concentration of highly volatile chemicals detected by GC in scent marks, linear discriminant analysis classified scent mark pools to their correct donor approximately 91% of the time. Such highly reliable statistical matching of scent to donor suggested that each individual female common marmoset has a unique ratio of highly volatile chemicals in their scent marks which may permit individual identification of females from odors in their scent alone.     

Effect of continuous infusion of a low dose of GnRH antagonist on serum LH and testosterone concentrations, spermatogenesis and semen quality in the rhesus monkey (Macaca mulatta)

Treatment of 4 adult male rhesus monkeys for 8-12 months with 100-400 micrograms of a GnRH antagonist/day by means of using osmotic minipumps led to suppressed serum concentrations of LH and testosterone followed by various degrees of recovery toward pretreatment values. The serum LH response to a challenge of native GnRH was reduced by 30-75% during antagonist treatment. The serum testosterone response to GnRH was exaggerated above the response in the pretreatment period, suggesting hypersensitivity of the testis to gonadotrophin. Antagonist administration under these conditions did not alter body weight or abolish ejaculatory response. Antagonist infusion caused a 96% decrease in sperm counts. Spermatozoa recovered during the final month of antagonist treatment showed a reduced ability to penetrate denuded hamster ova. Testicular biopsies performed at the end of antagonist treatment revealed persistent spermatogenesis. However, the cellularity of the seminiferous tubules was decreased below that of pretreatment biopsies. The results of this study suggest that the amount of testosterone needed to maintain normal spermatogenesis is greater than that needed to maintain electroejaculatory response in monkeys.     

Interaction of rat mammary gland thioesterase II with fatty acid synthetase is dependent on the presence of acyl chains on the synthetase

The interaction between rat mammary gland thioesterase II and fatty acid synthetase has been studied by a variety of physicochemical techniques. Pyrene-labeled thioesterase II does not exhibit increased fluorescence anisotropy when mixed with fatty acid synthetase, suggesting that the enzymes do not readily form a complex. Nevertheless, the functional interaction between the enzymes can be easily demonstrated by observing the hydrolysis, by unmodified thioesterase II, of acyl chains from their thioester linkage to the 4-phosphopantetheine of the fatty acid synthetase. This hydrolytic reaction is not inhibited even in the presence of a large excess of fatty acid synthetase with vacant 4'-phosphopantetheine thiols, indicating that interaction occurs only between thioesterase and fatty acid synthetase species which carry acyl chains on the 4'-phosphopantetheine thiols. A novel model system was devised which allowed us to explore the nature of the physical interaction between the two enzymes under conditions where the synthetase was actively engaged in acyl chain assembly. Fatty acid synthetase was treated with phenylmethanesulfonyl fluoride to inhibit its resident thioesterase activity, immobilized via a specific antibody to a column of Sepharose 4B, and exposed to the substrates required for acyl-enzyme assembly. When thioesterase II was introduced to the column, it passed through unretarded even though it efficiently catalyzed hydrolysis of the immobilized S-acyl synthetase en route. These results indicate that the two enzymes associate when an acyl chain is present on the synthetase and that they dissociate rapidly following completion of the catalytic process. Thus, the mammary system differs from that of the avian uropygial gland in which the two enzymes associate to form a stable complex even in the absence of substrates.