Characterization of a heat-stable NADP-dependent isocitrate dehydrogenase from the obligate thermophile Thermoleophilum minutum YS-4

Summary A thermostable NADP-dependent isocitrite dehydrogenase (IDH; EC. 1.1.1.42) was purified from the obligately thermophilic hydrocarbonoclastic bacterium Thermoleophilum minutum YS-4 (ATCC 35265). This was accomplished by affinity chromatography and electroelution from a nondenaturing polyacrylamide gel. The enzyme has an M _r of 60 000 and is composed of two identical subunits of M _r 30 500. The amino acid composition has an Arg/Lys ratio of 4:1 and very high levels of glycine. Under nondenaturing conditions, the enzyme has a distinct difference in electrophoretic mobility relative to IDHs obtained from other genera including the genus Thermus. The secondary strcuture consists of 16% -helix, 20% -sheet, 25% -turn and 37% random coil as determined by circular dichroism spectroscopy. The optimum pH and temperature for activity were 7.2 and 75° C respectively and the apparent K _mvalues for DL-isocitrate adn NADP⁺ were 33 M, and 48 M, respectively. The enzyme requires divalent cations, such as Mn²⁺ or Mg²⁺ for activity. NAD⁺ cannot substitute for NADP⁺. Oxaloacetate plus glyoxylate exert considerable inhibition on IDH activity while other glycolytic and tricarboxylic acid cycle intermediates have a lesser effect. p-Chloromercuribenzoic acid was inhibitory to the IDH although isocitrate and Mn²⁺ offered some protection from this inactivation. The enzyme is thermostable, retaining 84% and 57% of initial activity after incubation for 1 h at 60° and 70° C, respectively. Isocitrate provided protection from thermal inactivation allowing the IDH to maintain 21% activity after 1 h at 80° C. Offprint requests to: J. J. Perry     

Interference Competition among Coprophilous Fungi: Production of (+)-Isoepoxydon by Poronia punctata

(+)-Isoepoxydon has been established as the major causative agent of interference competition between Poronia punctata (NRRL 6457), a late fungal colonist of cattle dung, and two early-occurring dung colonists, Ascobolus furfuraceus (NRRL 6460) and Sordaria fimicola (NRRL 6459). This compound was isolated from ethyl acetate extracts of liquid cultures of P. punctata by silica gel chromatography and identified by mass spectrometry and proton and carbon nuclear magnetic resonance spectroscopy. The isolation process was guided by in vitro bioassays for antifungal activity against A. furfuraceus and S. fimicola. (+)-Isoepoxydon has been implicated as an intermediate in the biosynthesis of patulin, a mycotoxin produced by Penicillium spp., but no patulin could be detected in cultures of P. punctata.     

The effect of glucocorticoids on the in vivo conversion of androstenedione to oestrone

In vitro studies have previously shown that the activity of the aromatase enzyme system, which is responsible for the conversion of androstenedione to oestrone, can be stimulated by natural and synthetic glucocorticoids and also by ACTH. In view of the potential physiological importance of such a regulatory mechanism we have examined the effect of administration of dexamethasone, and of ACTH on the conversion of androstenedione to oestrone in vivo. The transfer constants for the conversion of androstenedione to oestrone [( rho]AEBU) measured in two women before administration of dexamethasone were 1.0% and 1.1% and after were 0.9% and 1.2%. Similarly no increase in conversion of androstenedione to oestrone [( rho]AE1BB) was detected after ACTH stimulation (pre = 0.74%, post = 0.77%). It is concluded from this study that glucocorticoids and ACTH do not have a role in regulating aromatase activity in vivo.     

Changing patterns of cerium reactivity in developing ovarian oocytes of the hamster

In developing ovarian oocytes of 2-day-old, 12-day-old and adult hamsters, oxidative enzyme activity as demonstrated by the cerium technique is strongest at 12 days and occurs principally in those oocytes which have begun rapid growth. The reaction is associated with the outer mitochondrial membrane, nearby cytoplasm, endoplasmic reticulum and nuclear envelope. Once antrum formation has begun and the mitochondria have reached the dormant (storage) stage, cerium reactivity ceases. In adults, reaction occurs at the same stages of oocyte development but is weaker and limited to the mitochondria and their immediate vicinity.     

Rationalization of some genetic anticodonic assignments

The genetic code appears to be a logic matrix in which, generally speaking, there is a correlation between the hydrophobicities of amino acids and their anticodonic nucleotides. There are several exceptions to this generality, however, and using previous data on hydrophobicity and binding constants, coupled with new data on reaction rates, we rationalize several of the anticodonic assignments.     

Age and growth of a colonizing minnow,Barbus anoplus,in a man-made lake in South Africa

Synopsis Aspects of the life history of Barbus anoplus were studied in Lake le Roux, a turbid man-made lake on the Orange River, South Africa. This minnow underwent a population explosion and successfully colonized the shoreline of the newly-formed lake during the early phases of reservoir filling. Male and female B. anoplus reach sexual maturity in one year at about 40 mm fork length. They have a multiple spawning habit with the first spawning in November–January and the second in February–March. The growth of the two resulting cohorts is discussed. It is proposed that the offspring from the second spawning not only acts as a ‘back-up’ but is capable of prolonging the life of that year-class into an additional reproductive season. Most of the minnows die after their second summer, but more offspring from the second spawning, especially females, live into a third summer. Females attain a larger maximum size (73 mm FL) and age (3–4 years) than males (60 mm FL, 2–3 years). B. anoplus is small and short-lived with a high seasonal reproductive potential, which is in contrast to the larger Barbus species in the Orange River system. These life-history traits enable the species to colonize and successfully inhabit unstable environments and probably account for its widespread distribution.     

Reduction in headache patients' medical expenses associated with biofeedback and relaxation treatments

Comparisons are made of self-reported medical costs from a sample of headache patients who underwent various combinations of relaxation training and biofeedback training. The average costs for the 2 years prior to self-regulatory treatment were $955±480 (3 SEM) for 45 patients; for the 2 years after completing treatment the average costs were $52±28 (3 SEM) for patients. Within the limitations of the study, medical costs do seem to have been markedly reduced.This research was supported by a grant from NINCDS, NS-15235.