Class I-like MHC molecules expressed by baboon placental syncytiotrophoblast

Human placental villous trophoblast is known to be unreactive with W6/32 and other monoclonal antibodies recognizing monomorphic determinants of human class I MHC heavy chains, whereas extravillous cytotrophoblast in the placental bed is W6/32-reactive by immunohistology. We have now demonstrated, in contrast, that syncytiotrophoblast is the only cellular component of baboon early placental villous tissue which is reactive with any of these antibodies. Radioimmunoprecipitation of detergent-solubilized baboon placental membrane preparations, and subsequent SDS-PAGE, has shown the W6/32-reactive component to have an m.w. of 41,000 and to be associated with beta 2-microglobulin, whereas baboon peripheral lymphocytes express 45,000 m.w. W6/32-reactive antigens comparable with the HLA-A,B,C heavy chains of human lymphocytes.     

A 5'----3' exoribonuclease of Saccharomyces cerevisiae: size and novel substrate specificity

The purification scheme for a 5'----3' exoribonuclease of Saccharomyces cerevisiae has been modified to facilitate purification of larger amounts of enzyme and further extended to yield highly purified enzyme by use of poly(A)-agarose chromatography. As determined by either sodium dodecyl sulfate-polyacrylamide gel electrophoresis or physical characterization, the enzyme has a molecular weight of about 160,000. Further studies of its substrate specificity show that poly(C) and poly(U) preparations require 5' phosphorylation for activity and that poly(A) with a 5'-triphosphate end group is hydrolyzed at only 12% of the rate of poly(A) with a 5'-monophosphate end group. DNA is not hydrolyzed, but synthetic polydeoxyribonucleotides are strong competitive inhibitors of the hydrolysis of noncomplementary ribopolymers. Poly(A).poly(U) and poly(A).poly(dT) are hydrolyzed at 60 and 50%, respectively, of the rate of poly(A) at 37 degrees C. The RNase H activity of the enzyme can also be demonstrated using an RNA X M13 DNA hybrid as a substrate. When poly(dT).poly(dA) with a 5'-terminal poly(A) segment on the poly(dA) is used as a substrate, the enzyme hydrolyzes the poly(A) "tail," removing the last ribonucleotide, but does not hydrolyze the poly(dA).     

The effect of the H2 partial pressure on the metabolite pattern ofLactobacillus casei,Escherichia coli andClostridium butyricum

Summary The metabolite pattern of batch cultures ofLactobacillus casei LMG 6400,Clostridium butyricum LMG 1213t1 andEscherichia coli LMG 2093 was effected only for the latter organism when the H₂ partial pressure was below 1 atmosphere: high hydrogen partial pressures increased the formate formation, low pressures gave rise to increased acetate production and higher cell yields.     

Metal complexes of antiinflammatory drugs. Part VII: Salsalate complex of copper(II)

The preparation and properties of the Cu(II) complex Cu(SAS)2.H2O are reported for the antiinflammatory drug Salsalate (SAS). The diffuse reflectance spectra and magnetic moments are consistent with a dinuclear structure as found for [Cu(aspirinate)2(H2O)]2. The Cu(II) complex exhibits an increased superoxide dismutase activity compared with the parent drug molecule in the nitroblue tetrazolium assay.     

Characterization of genes required for protein sorting and vacuolar function in the yeast Saccharomyces cerevisiae.

To further our studies of protein sorting and biogenesis of the lysosome-like vacuole in yeast, we have isolated spontaneous mutations in 11 new VPL complementation groups, as well as additional alleles of the eight previously described VPL genes. These mutants were identified by selecting for cells that mislocalize vacuolar proteins to the cell surface. Morphological examination of the vpl mutants indicated that most contain vacuoles of normal appearance; however, some of the mutants generally lack a large vacuole, and instead accumulate smaller organelles. Of the 19 VPL complementation groups, 12 were found to be identical to 12 of 33 VPT complementation groups identified in a separate study. Moreover, the end1 mutant and all of the previously reported pep mutants, with the exception of pep4, were found to exhibit a profound vacuolar protein sorting defect, and complementation tests between the PEP, VPL VPT and END1 groups demonstrated that there are extensive overlaps between these groups. Collectively, mutants in these four collections define 49 complementation groups required to deliver or retain soluble vacuolar enzymes, including carboxypeptidase Y (CPY) and proteinase A. We have also isolated 462 new mutants that lack normal levels of vacuolar CPY activity. Among these latter mutants, only pep4 mutants were found to be specifically defective in vacuolar zymogen activation. We conclude that there is a large number of gene products required for sorting or retention of vacuolar proteins in yeast, and only a single gene, PEP4, that is essential for activation of CPY and other vacuolar zymogens.     

The relative changes in isometric force and work during fatigue and recovery in isolated toad sartorius muscle

Toad sartorius muscle was subjected to sinusoidal varying length changes at 2 Hz to measure work. Both isometric tetanic force and work per cycle were measured before, during, and after a 3-min fatigue. Both isometric tetanic force and positive work, the work done by the muscle during the shortening part of the cycle, rapidly decreased in parallel in the first 40 s of fatigue. Thereafter, force continued to decrease, but at a slower rate, to about 10% of prefatigue values, whereas positive work levelled off at about 30% of prefatigue values. Negative work, the work done on the muscle during the lengthening part of the cycle, increased during fatigue to the extent that net work became negative. This was due to a prolonged relaxation, which resulted in active force still being generated while the muscle was being stretched. Work and force recovered at about the same rate. Isometric force measurements alone do not give any clear indication that net work will be negative under a particular set of experimental conditions.     

Effect of cycle frequency and excursion amplitude on work done by rat diaphragm muscle

Strips of isolated rat diaphragm muscle were attached to a servomotor-transducer apparatus, and the muscle length was cycled in a sinusoidal fashion about the length at which maximum isometric twitch force was developed, Lo. The amplitude of the length displacement (excursion amplitude) and rate of cycling were varied between 3 and 13% Lo and 1-4 Hz respectively. The muscle was tetanically stimulated (100 Hz, supramaximal voltage, stimulus duration (duty cycle) 20% of the length cycle period) during the shortening stage of the imposed length cycle at the phase that yielded maximum net positive work. The force and displacement of the muscle were recorded. Work per cycle was calculated from the area of the loop formed by plotting force against length for one full stretch-shorten cycle. Work per cycle decreased, but power increased, as cycle frequency was increased from 1 to 4 Hz. Maximum work done per cycle was about 12.8 J/kg at a cycle frequency of 1 Hz. Maximum mean power developed was about 27 W/kg and occurred at a cycle frequency of 4 Hz. Work and power were maximum at an excursion amplitude of 13% of Lo (i.e., Lo +/- 6.5%). Measured work and power output are considerably less than values estimated from length-tension and force-velocity curves.     

Methyl linoleate ozonide as a substrate for rat glutathione S-transferases: reaction pathway and isoenzyme selectivity

The 9,10-mono-ozonide of methyl linoleate was shown to be a substrate for rat hepatic cytosolic, rat lung cytosolic and rat hepatic microsomal glutathione S-transferases (GST). The activities of lung cytosol and liver microsomes with methyl linoleate ozonide (MLO) were found to be high relative to the activity demonstrated by liver cytosol, as compared with their respective activities towards 1-chloro-2,4-dinitrobenzene (CDNB). Only a slight catalytic activity towards the ozonide was noticed for rat lung microsomes. Isoenzyme 2-2 exhibited the highest specific activity (208 nmol/min/mg) when isoenzymes 1-1, 1-2, 2-2, 3-3, 3-4, 4-4 and 7-7 were compared. This isoenzyme accounts for approx. 25% of cytosolic GST protein in rat lung, while in rat liver it represents approx. 9%. This may partly explain the high activity towards the ozonide noticed for rat lung cytosol. No stable conjugates were formed as products of the reaction of MLO with glutathione; although two glutathione-conjugates were noticed on TLC, they were only formed as intermediate compounds. Coupling of an aldehyde dehydrogenase assay or a glutathione reductase assay to the GST-catalyzed conjugation, demonstrated that oxidized glutathione and aldehydes are formed as the major products in the reaction. To further confirm the formation of aldehydes, the products of the GST-catalyzed reaction were incubated with 2,4-dinitrophenylhydrazine, which resulted in hydrazone formation. In conclusion, the activity of the GST towards the ozonide of methyl linoleate is similar to their peroxidase activity with lipid hydroperoxides as substrates.