Electron microscopic studies on liver 5-aminolaevulinate synthase

The structure of chick embryo liver 5-aminolaevulinate synthase has been examined by electron microscopic studies using negative staining. From the different projections of the enzyme particles observed in electron micrographs, a model for the enzyme molecule has been proposed. In this model, an enzyme molecule consists of two curved and identical subunits associated in opposite polarities. From the dimensions of an enzyme molecule subunit measured from electron micrographs, the relative molecular mass of each subunit is estimated to be 70 000.     

Isolation and characterization of a unique protease from sporulating cells of Bacillus subtilis

Two proteases, designated I and II, have been isolated from sporulating cells of Bacillus subtilis. They were partially purified by ammonium sulfate fractionation, Sephadex chromatography and affinity columns. Protease I was found to be similar to an already characterized B. subtilis protease. Protease II is trypsin-like in its substrate specificity and is distinct from protease I in its pH optimum, pH stability, molecular weight, substrate specificity, heat stability and sensitivity to various inhibitors. While both enzymes were produced primarily during sporulation, they attained maximum levels of activity at different times. Distinct functions for these proteases in post exponential B. subtilis are likely.     

A study of the pollen grains of Amaranthus spinosus Linné and A. Dubius Mart ex Thellung and their hybrids

A pollen-morphology study of Amaranthus spinosus, A. dubius, and their hybrids has been carried out. Three pollen types have been observed, namely (1) Type A: micrograins; (2) Type B: grains with smaller pores; and (3) Type C: grains with larger pores. Type B is characteristic of A. spinosus, Type C of A. dubius, and the micrograins of the hybrids. Pollen size range, and frequency of the various morphotypes serve to throw light on the biosystematics of the plants studied.     

Modification of the rapidly reacting thiols of atrial and ventricular myosins. Evidence for structural variances around the SH-1 thiol of the two isozymes

Environmental variances were noted around the rapidly reacting SH-1 thiol of ventricular versus atrial myosin, based on electron paramagnetic resonance studies. Further studies, in which either SH-1 or SH-1 + SH-2 thiols were modified with N-ethylmaleimide, indicated the importance of the SH-2 moiety of both isozymes for generation of tension, when analyzed as synthetic actomyosin threads. Comparative EPR studies showed that the spin label was more strongly immobilized when complexed to ventricular SH-1 thiol as compared to when it was complexed to atrial myosin. Likewise, addition of PPi, ATP or ADP created a greater mobility in the spin label when added to ventricular spin-labeled myosin as compared to that of atrial myosin. comparative studies of spin-labeled actomyosin versus myosin analyzed at different EPR power settings also demonstrated disparaties surrounding the SH-1 thiol between the two myosin isozymes.     

Extractive lactic acid fermentation using ion-exchange resin

Lactic acid fermentation is an end-product-inhibited reaction. The restriction imposed by lactic acid on its fermentation can be avoided by extractive fermentation techniques. Studies were performed by attaching an ion-exchange resin packed column with a 2-L fermentor for separation of lactic acid. The fermentation, in a conventional batch mode, resulted in a lactic acid yield of 0.828 g . g(-1) and a lactic acid productivity of 0.313 g . L(-1) . h(-1). However, these could be further enhanced to 0.929 g . g(-1) and 1.665 g . L(-1) . h(-1) by extractive fermentation techniques. The effect of temperature on extractive fermentation was remarkable and has been included in this work.     

Genetic control of sucrose synthetase in maize endosperm

Summary Sucrose synthetase activity in endosperm extracts of seven shrunken(sh) mutants of spontaneous origin and three similar mutants due to the association of the controlling element Ds with the Sh locus is examined. A residual level of 3 to 5% as compared to the normal (Sh) endosperm is seen in all the mutants. The residual activity is similar to that of the Sh locus encoded endosperm sucrose synthetase by several criteria including an identical size of polypeptides and a similarity in antigenic properties. These two enzymes are, however, distinguishable by a slight difference in electrophoretic mobility in native gels and a difference in the relative abundance of enzyme molecules. The latter property is a reflection of a marked difference seen in the developmental profile of enzyme activity in the two genotypes. The earlier hypothesis (Chourey and Nelson 1976) that these two sucrose synthetases are encoded by two separate genes is strengthened by: (a) the presence of the residual enzyme in a sh deletion mutant and (b) an electrophoretic demonstration of two proteins, corresponding to the major and minor sucrose synthetase proteins, in the wild type (Sh) genotype. The two sucrose synthetase genes seem to provide a model system in plants for studying the molecular basis of temporal specificity of genes.Cooperative Investigation, United States Department of Agriculture and Institute of Food and Agricultural Sciences, University of Florida, Florida Agricultural Experiment Station Journal Series No. 3288. Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products or vendors that may also be suitable     

The fine structure of psychrophilic and mesophilic Rhodotorula rubra

Transmission electron microscopy of thin sections of two mesophilic and a psychrophilic Rhodotorula rubra revealed structures normally associated with yeast. The capsule of all three strains was thicker in the cells grown in glucose than those grown in glucose-free media. The cell wall of all three strains showed more lamellae in the cells grown in a medium containing glycerol. Budding was of the Rhodoturula type. Endoplasmic reticula running parallel to the nucleus were commonly observed in the psychrophiles but not in the mesophiles. In the psychrophile, in association with the plasmalemma, lomasomes and plasmalemmasomes were observed. Giant mitochondria were commonly seen in the cells grown in a fermentable carbohydrate-free medium. Vacuoles were mostly empty.     

A note on suxamethonium sensitivity and serum cholinesterase variants

Summary Sera from 21 cases of prolonged apnoea which showed normal phenotype (UU) on the basis of dibucaine and fluoride inhibition were re-examined by replacing the substrate benzoylcholine with succinylcholine (suxamethonium). 9 samples had normal enzyme activity but low dibucaine number (DN=<20) indicating the atypical variant; 6 sera showed no detectable enzyme activity. The remaining 6 samples had enzyme activity and DN comparable with healthy controls. The occurence of new variants of serum cholinesterase sensitive only to succinylcholine is suggested.Dedicated to Prof. Dr. med. J. Kühnau on his 75th birthday.