Evidence for X-Linkage of Steroid Sulfatase in the Mouse: Steroid Sulfatase Levels in Oocytes of XX and XO Mice

The steroid sulfatase (STS) levels in mature oocytes of XX and XO mice were assayed along with lactate dehydrogenase (LDH), an autosomal marker, and glucose-6-phosphate dehydrogenase (G6PD), a known X-linked gene. LDH levels in XX and XO oocytes were equal, whereas STS and G6PD levels were approximately twice as high in XX oocytes as in XO oocytes. These results indicate that the STS gene is X-linked in the mouse just as it is in humans. Assays of STS in kidney tissue of XX and XO mice indicated dosage compensation for the gene, which is different from that observed in humans.     

Kinetics of UV-induced changes in deoxynucleoside triphosphate pools in Chinese hamster ovary cells and their effect on measurements of DNA synthesis

Measurements of dNTP pools following exposure of Chinese hamster ovary cells to ultraviolet radiation reveals a rapid accumulation of cellular dTTP and a rapid loss of cellular dCTP. Exposure to 3-, 10- or 20 Jm-2 results in a 3-, 4- or 5.4-fold increase in cellular dTTP, respectively, within the first 10 min after exposure. dTTP levels then decrease noticeably, approaching the control value 3 to 5 hr later. In contrast, dCTP levels decrease rapidly within 10 min after exposure, ultimately to 1/10 that observed in the unirradiated control population. Recovery to normal dCTP levels is slow, taking in excess of 12 hr. No change in dATP is observed for 1-2 hr; subsequently, a moderate decrease in dATP levels occurs which is then followed by recovery, beginning 8 hr after irradiation. These results contrast with changes in dNTP pools observed in Chinese hamster V-79 cells exposed to mutagens. Measurements of rates of DNA synthesis by pulse-labeling cells with [3H]thymidine are also apparently affected by UV-induced transient deviations in the endogenous radiospecific activity of the labeled precursor.     

Amino acid-specific ADP-ribosylation

[adenine-U-14C]ADP-ribose-agmatine and [adenine-U-14C ))ADP-ribose-histone were synthesized by an NAD:arginine ADP-ribosyltransferase from [14C]NAD and agmatine and histone, respectively. The pseudo-first order rate constants for breakdown of the two components either in 0.4 N NaOH or in 0.4 M neutral hydroxylamine were identical. Hydroxylamine treatment of [14C]ADP-ribose-agmatine or [32P]ADP-ribose-histone yielded a single radioactive product which was separated by high pressure liquid chromatography and identified as ADP-ribose-hydroxamate by the formation of a ferric chloride complex. Hydrolysis of ADP-ribose-hydroxamate with snake venom phosphodiesterase resulted in the formation of 5'-AMP, consistent with the presence of a pyrophosphate bond. Incubation of ADP-ribose-[14C]agmatine, synthesized by the ADP-ribosyltransferase from NAD and [14C]agmatine, with 0.4 M neutral hydroxylamine resulted in the release of [14C]agmatine rather than phosphoribosyl[14C]agmatine. In addition, neither NAD nor ADP-ribose reacts with hydroxylamine; i.e. there was no evidence of nucleophilic attack by hydroxylamine at the pyrophosphate bond. The ADP-ribosyl-protein linkage formed by the NAD:arginine ADP-ribosyltransferase is considerably more stable to hydroxylamine than is the ADP-ribose-glutamate bond. The presence of ADP-ribose-arginine and ADP-ribose-glutamate synthesized by the ADP-ribosyltransferase and poly(ADP-ribose) synthetase, respectively, may be the chemical basis for the "hydroxylamine-stable" and "hydroxylamine-labile" bonds described by Hilz (Hilz, H. (1981) Hoppe-Seyler's Z. Physiol. Chem. 362, 1415-1425).     

The fine structure of spermatozoa of Hydrolagus colliei (Chondrichthyes, Holocephali)

The ultrastructure of spermatozoa in Hydrolagus colliei is described. Basic similarities of structure to the sperm of the related elasmobranch fish are noted. The most significant features of sperm structure in Hydrolagus that differ from those of elasmobranch fish occur in the tail. The axoneme is eccentrically located and forms a double helix with a single longitudinal column. A second longitudinal column is reduced to a short remnant at the base of the tail. Microtubules within the axoneme are also helically disposed, a feature that is consistent with the rotating motion of the sperm. Abundant glycogen reserves are stored along the length of the tail.     

Cerebral Blood Flow and Oxidative Metabolism in Conscious Fischer-344 Rats of Different Ages

Abstract: The cerebral metabolic rates for O₂ and for glucose were measured in conscious, fasted male Fischer-344 rats at the ages of 3, 12, and 24 months, and cerebral blood flow was determined with ¹⁴C-iodoantipyrine. The metabolic rates for oxygen and glucose were obtained by multiplying blood flow by the O₂ and glucose concentration differences, respectively, between blood in the femoral artery and in the superior sagittal sinus. Mean cerebral blood flow and the metabolic rates for oxygen and glucose did not differ significantly (p > 0.05) between 3 and 12 or between 12 and 24 months. Nor did the arteriovenous differences for O₂ and for glucose change significantly with age. Because the superior sagittal sinus drains blood mainly from the cerebral cortex, the results indicate that average cerebral cortical oxidative metabolism, and the coupling ratios between the cerebral metabolic rate for oxygen and cerebral blood flow and between the cerebral metabolic rate for glucose and cerebral blood flow, do not change significantly with age in the Fischer-344 rat.     

A calcium antagonist drug binding site in skeletal muscle sarcoplasmic reticulum: Evidence for a calcium channel

The sarcoplasmic reticulum (S.R.) of rabbit skeletal muscle has been found to contain a single, high affinity binding site for the Ca antagonist drug [³H] -nitrendipine. Two subfractions of the reticulum were studied, the heavy (HSR) and light (LSR) preparations, which exhibited similar nitrendipine equilibrium dissociation constants (K_D) of 1nM. Crude cardiac and brain membranes assayed under the same conditions exhibited K_D values of 0.2–0.3nM. The concentration of binding sites per mg. protein (B_max) in HSR was found to be very high, namely 6.7 picomoles/mg, some four times greater than that of LSR. [³H] -nitrendipine binding to HSR was reversible and inhibited by the Ca antagonists flunarizine and verapamil, and by the intracellular Ca release antagonist TMB-8 (8-diethylamino-octyl 3,4,5- trimethylbenzoate hydrochloride). However, unlabelled nitrendipine at 2 × 10^?5M had no effect on contraction of isolated electrically stimulated rabbit lumbrical or rat diaphragm muscles, nor did it affect the neuromuscular junction as studied in rat phrenic nerve-diaphragm preparations. Also, little effect of 2 × 10^?5M nitrendipine was seen on net ⁴⁵Ca uptake by HSR. These results suggest that [³H] -nitrendipine binding to skeletal muscle S.R. resembles that of brain membranes, which also contain a high affinity binding site for [³H] -nitrendipine and which similarly are pharmacologically insensitive to this dihydropyridine type of Ca channel blocking agent. Since HSR is also enriched in calsequestrin and terminal cysternae from which Ca is released in vivo, it seems likely that the [³H]- nitrendipine binding sites in S.R. are associated with Ca channels in the S.R.     

Temperature-dependence of intramolecular coupling of active sites in pyruvate dehydrogenase multienzyme complexes.

Intramolecular coupling of active sites in the pyruvate dehydrogenase multienzyme complexes of Escherichia coli, ox heart and Bacillus stearothermophilus was measured at various temperatures. As the temperature was raised, the extent of active-site coupling was found to increase, approaching a maximum near the physiological growth temperature of the organism. Under these conditions, a single pyruvate dehydrogenase (lipoamide) dimer appeared able to cause a rapid (20s) reductive acetylation of probably all 24 polypeptide chains in the dihydrolipoamide acetyltransferase core of the enzyme complex from E. coli at 37 degrees C, and of most if not all of the 60 polypeptide chains in the dihydrolipoamide acetyltransferase cores of the enzymes from ox heart and B. stearothermophilus at 37 degrees C and 60 degrees C respectively. Experiments designed to measure the inter-core and intra-core migration of enzyme subunits suggested that, in the bacterial enzymes at least, this was not a major contributor to active-site coupling.     

Antimicrobial Properties of Natural Phenols and Related Compounds: I. Obtusastyrene

Obtusastyrene (4-cinnamylphenol) displays effective antimicrobial activity in vitro against a variety of gram-positive bacteria, yeasts, and molds. The activity of obtusastyrene is not appreciably affected by pH, and its minimal inhibitory concentrations, 12 to 25 mug/ml for bacteria and 12 to 100 mug/ml for fungi, compare favorably with those of a number of synthetic, phenolic antimicrobial agents.