Arginase,an s-phase enzyme in a human cell line

Suspension cultures of ‘Chang liver’ cells were synchronized by preincubation in a glutamine-deficient medium or by thymidine blockade. Specific arginase activity varied in the synchronized cultures, being high when the number of S-phase cells was maximal. A relationship between high arginase activity and a high percentage of (S+G₂) cells was also found when unsynchronized cells were separated by velocity sedimentation. The increase in arginase activity near the G₁/S border was totally inhibited in the presence of cycloheximide. The rate of decrease in activity after addition of the drug indicated that the variations in the rate of synthesis of the enzyme, while the rate of degradation was more or less constant, corresponding to 4–6% per h. The role of arginase in cells lacking a urea cycle and the regulation of arginase activity in ‘Chang liver’ cells is discussed.     

Amino acid sequence homologies between rabbit, rat, and human serum retinol-binding proteins

The main transporting protein for vitamin A in rabbit serum, the retinol-binding protein (RBP), was isolated and its amino acid sequence determined. Rabbit RBP was found to be highly homologous to human RBP, whose amino acid sequence was elucidated earlier, and to rat RBP. The rat RBP sequence was obtained by combining information deduced from the nucleotide sequences of two overlapping cDNA clones with the NH2-terminal sequence of the isolated protein determined by automated Edman degradation. The identity between the three proteins is approximately 90%. The high degree of homology between RBP molecules from different species is probably explained by the fact that RBP participates in at least three types of molecular interactions: in the binding of prealbumin, in the interaction with retinol, and in the recognition of a specific cell surface receptor. All these interactions should lead to a conservation of RBP structure. The amino acid differences between rabbit, rat, and human RBP are discussed in light of the recent elucidation of the three-dimensional structure of human RBP. Hybridization of a probe isolated from a rat RBP cDNA clone to restriction enzyme-digested genomic DNA from rat and mouse suggests that RBP is encoded by a single gene.     

Z → B transition in poly[d(G-m5C)2] induced by interaction with 4′,6-diamidino-2-phenylindole

The Z form of poly[d(G-m⁵C)₂], in presence of Mg²⁺ ion, is found to be transformed into B form upon interaction with 4′,6-diamidino-2-phenylindole (DAPI). The Z → B transformation is complete at a mixing ratio of about 0.07 DAPI per DNA base pairs, i.e., each DAPI molecule may be related to the conversion of 6–7 base pairs. An interaction between DAPI and poly[d(G-m⁵C)₂] in its Z form at low drug: DNA ratios is suggested from optical dichroism and time-resolved luminescence anisotropy results. The spectroscopic behaviour of DAPI indicates that the Z conformation of DNA does not provide normal binding sites for DAPI, such as groove or intercalation sites, but that the initial association may be of external nature. © 1993 John Wiley & Sons, Inc.     

Determination of (R)- and (S)-Disophyramide in human plasma using a chiral α1-acid glycoprotein column

The direct resolution and quantitation of (R)- and (S)-disopyramide, isolated from human plasma, was accomplished using a chiral α₁-acid glycoprotein column. A LiChrosorb RP-2 column (50 × 3.0 mm I.D.) was used as a precolumn. Phosphate buffer, pH 6.20, containing 2-propanol and N,N-dimethyloctylamine was used as mobile phase, expressed as the relative standard deviation, was 1.8% and 3.3% for (R)- and (S)-disopyramide, respectively, at a drug level of 0.5 μg/ml. In two subjects who received a single capsule of racemic disopyramide (150 mg), the plasma levels of the (R) isomer were about half those of the (S) isomer. The half-lives of (R)- and (S)-disopyramide were similar.     

The families of bitunicate ascomycetes

The morphology and nomenclature of ca. 195 families of bitunicate or alleged bitunicate ascomycetes are discussed. Available representatives of these families were studied especially with respect to the morphology of the asci and ascospores. The morphology of the ascomata, etc. was studied in the SEM in 73 species. The following morphological terms are introduced: hamathecium, pseudoprototunicate, pseudofis–situnicate, semifissitunicate, and umbilicus. The following taxa are described as new: Coccodiniaceae O. Erikss. fam. nov., Microtheliopsidaceae O. Erikss. fam. nov., Amarenomyces O. Erikss. gen. nov., and Euantennaria abietina O. Erikss. sp. nov. The name Lecanidiaceae is proposed to replace Patellariaceae Corda, and Cyanoder–mella to replace Cyanoderma Höhn. The Massariaceae are treated as Trypetheliaceae subfam. Massarioideae (Nits.) O. Erikss. The following new combinations are proposed: Amarenomyces ammophilae (Lasch) O. Erikss., Cyanodermella viridula (Berk. & Curt.) O. Erikss., C. Candida (Setch.) O. Erikss., Dictyotrichiella delicatula (Ves–tergr.) O. Erikss., Laurera sepulta (Mont.) O. Erikss., Splanchnonema superans (Mull. Arg.) O. Erikss. and Thelenella antarctica (M. Lamb) O. Erikss. The origin and evolution of the Ascomycetes are discussed, and the importance of paedomor–phosis in the transspeciation of the group is emphasized. The stratigraphic classification of the Ascomycetes is discussed. In a transitional classification of the Ascomycetes, 109 monophyletic entities (clades) are recognized. La morphologie et la nomenclature ?environ 195 families ?ascomycétes bituniques ou soit–disant bituniques sont étudiées, spécialement en respectant la morphologie des asques et des ascospores. La morphologie des ascocarpes, etc. de 73 espèces fut étudiée dans le SEM. Les termes morphologiques suivants sont introduits: hamathecium, pseudoprototunique, pseudofissitunique, semifissitunique et umbilicus. Ces nouveaux taxa sont decrits: Coccodiniaceae O. Erikss. fam. nov., Microtheliopsidaceae O. Erikss. fam. nov., Amarenomyces O. Erikss. gen. nov. et Euantennaria abietina O. Erikss. sp. nov. Le nom Lecanidiaceae est proposéà la place de Patellariaceae Corda, Cyanodermella à la place de Cyanoderma Höhn. Les Massariaceae sont traitées comme Trypetheliaceae subfam. Massarioideae (Nits.) O. Erikss. Les nouvelles combinations suivantes sont proposées: Amarenomyces ammophilae (Lasch) O. Erikss., Cyanodermella viridula (Berk. & Curt.) O. Erikss., C. Candida (Setch.) O. Erikss., Dictyotrichiella delicatula (Vestergr.) O. Erikss., Laurera sepulta (Mont.) O. Erikss., Splanchnonema superans (Müll. Arg.) O. Erikss. et Thelenella antarctica (M. Lamb) O. Erikss. ?origine et ?évolution des ascomycètes sont discutées, et I'importance de la paedomorphose dans la transspeciation du groupe est mise en évidence. La classification stratigraphique des ascomycètes est discutée. Dans une classification de transition des ascomycètes, 109 entités monophyletiques sont reconnues.     

Selective inactivation of the deoxyadenosine phosphorylating activity of pure human deoxycytidine kinase: stabilization of different forms of the enzyme by substrates and biological detergents

Deoxycytidine kinase, purified from human leukemic spleen to apparent homogeneity, is a multisubstrate enzyme that also phosphorylates purine deoxyribonucleosides [Bohman & Eriksson (1988) Biochemistry 27, 4258-4265]. In the present investigation we show that the stability and temperature dependence of dCyd kinase activity differed appreciably from the dAdo kinase activity of the same pure enzyme. Selective inactivation of dAdo activity was observed upon an incubation of the enzyme at both 4 and 37 degrees C. The half-life of dAdo activity at 4 degrees C increased from 36 to 84 h, when the protein concentration was increased by addition of bovine serum albumin. However, the half-life of dCyd activity increased from 72 h to more than 7 days under the same conditions. dCyd activity was stable for at least 6 h at 37 degrees C while the half-life of dAdo activity was 2 h. The presence of substrates like ATP, dTTP, or dAdo stabilized dAdo activity at both temperatures, and full maintenance of both activities at 37 degrees C was obtained by the addition of the zwitterionic detergent CHAPS. Furthermore, thermal inactivation of the dAdo activity occurred at a lower temperature (48 degrees C) as compared to the dCyd activity (54 degrees C). The presence of protease inhibitors had no effect on enzyme inactivation, nor was there a difference in the subunit structure of the selectively inactivated enzyme as compared to the fully active form, as revealed by size-exclusion chromatography.(ABSTRACT TRUNCATED AT 250 WORDS)     

Fiber type composition of the human male trapezius muscle: enzyme-histochemical characteristics

The human trapezius muscle has an origin that is more extensive than that of any other body muscle; it has a complex macroscopic structure with fibers running in different directions. Histochemical analysis of multiple samples, obtained from different parts of the trapezius muscle from five males, showed marked differences in the distribution and the cross-sectional fiber area of the fiber types among different parts of the muscle as well as among individuals. As revealed by the mATPase activity, after different levels of alkaline and acidic preincubations, the lower third of the descending portion, the transverse, and the ascending portions of the muscle had a predominance of type I fibers (low mATPase activity at pH 9.4), whereas the most superior parts of pars descendens had a higher frequency of type II fibers (high mATPase activity at pH 9.4). The fibers of the most superior parts of the muscle were considerably smaller compared with those in all the other parts. In sections stained for NADH-TR, moth-eaten fibers were observed within parts of the descending portion. Their location and their larger fiber area, compared with that of ordinary type I fibers, may be related to frequent and/or continuous use of these fibers. In conclusion, the differences in fiber type composition between the different parts of the muscle probably reflect different functional demands on the trapezius muscle in various head, neck, and shoulder movements. We suggest that the interindividual differences in muscle fiber composition are due, at least in part, to genetic factors.     

The development and standardization of an ELISA for ovalbumin determination in influenza vaccines

A double antibody sandwich enzyme-linked immunosorbent assay (ELISA) for the detection of ovalbumin in influenza vaccines has been developed and standardized. Commercially available reagents were used. ELISA was compared to single radial immunodiffusion (SRD) and immunoelectro-osmophoresis (IEOP) techniques. The detection limit by ELISA was 0.5 ng/ml. This method was found to be at least 1000 times more sensitive than SRD and at least 200 times more sensitive than IEOP. It was concluded that ELISA is a specific, sensitive and reproducible method for the determination of the small amounts of ovalbumin found as an impurity in unconcentrated influenza vaccines.     

Learning of auditory equivalence classes for vowels by rats

Four male Long-Evans rats were trained to discriminate between synthetic vowel sounds using a GO/NOGO response choice task. The vowels were characterized by an increase in fundamental frequency correlated with an upward shift in formant frequencies. In an initial phase we trained the subjects to discriminate between two vowel categories using two exemplars from each category. In a subsequent phase the ability of the rats to generalize the discrimination between the two categories was tested. To test whether rats might exploit the fact that attributes of training stimuli covaried, we used non-standard stimuli with a reversed relation between fundamental frequency and formants. The overall results demonstrate that rats are able to generalize the discrimination to new instances of the same vowels. We present evidence that the performance of the subjects depended on the relation between fundamental and formant frequencies that they had previously been exposed to. Simple simulation results with artificial neural networks could reproduce most of the behavioral results and support the hypothesis that equivalence classes for vowels are associated with an experience-driven process based on general properties of peripheral auditory coding mixed with elementary learning mechanisms. These results suggest that rats use spectral and temporal cues similarly to humans despite differences in basic auditory capabilities.