Postnatal development of sarcolemmal invaginations in right atrial myocardium of the rat

Postnatal development of the sarcolemmal invaginations of right atrial cells of the rat has been studied using standard fixation combined with tannic acid mordanting. T tubules were seen to form at Z lines as simple tubular invaginations starting at the 14th postnatal day. T tubules were present in most cells by the 18th postnatal day but, as in the adult, were restricted to peripheral regions. Also, between the 16th and 18th postnatal day a proliferation of caveolae was seen, both as single vesicles and as complexes with up to a dozen caveolae sharing the same neck. The caveolar complexes persisted in the adult and did not seem to contribute significantly to the formation of the T tubules. Dyadic couplings were seen to become more abundant as T tubules and caveolae proliferated. These findings are discussed in relation to transsarcolemmal Ca2+ movements and excitation-contraction coupling during postnatal development.     

Regioselectivity of metabolic activation of acetylenic steroids by hepatic cytochrome P450 isozymes

Liver cytochrome P450 monooxygenases (P450), a group of isozymes that catalyze the reductive cleavage of molecular oxygen, dominate hepatic metabolism of xenobiotic lipophilic substances. These P450 enzymes exhibit broad and overlapping substrate specificities, in contrast to the P450 isozymes of the steroid biosynthetic pathways, which are highly substrate specific. Hepatic heme pigments, N-alkylated porphyrins, accumulate following the self-catalyzed destruction of P450 by the metabolic activation of 17 alpha-ethynyl steroids. Acetylenic substituted steroidal aromatase inactivators, norethisterone (NET), and 10-(2-propynyl)estr-4-ene-3,17-dione (MDL 18,962) were administered to rats to determine if the acetylenic substituent was activated by hepatic P450 mixed-function oxidases. This metabolism could result in the formation of a reactive species that would alkylate a pyrrole nitrogen atom of heme. Male Sprague-Dawley rats were treated with 0, 10, 30, or 100 mg/kg NET or MDL 18,962 intraperitoneally. Four hours later, these animals received 40 mg/kg sodium pentobarbital and their sleeping times were recorded. On arousal, the rats were killed and their livers were taken for determination of P450 content and formation of N-alkylated porphyrins (green pigments). Norethisterone inhibited hepatic P450 isozymes, resulting in a dose-related increased sleeping time (89.2 +/- 3.5 to 156.3 +/- 7.6 minutes) and decreased P450 levels (maximum 25% decrease at 100 mg/kg), and the amount of green pigments increased with doses of 10 to 100 mg/kg. In contrast, MDL 18,962 treatment did not increase sleeping time and caused only a 15% decrease in hepatic P450 content at 100 mg/kg, with no detectable green pigments.(ABSTRACT TRUNCATED AT 250 WORDS)     

Helium Tracer Tests for Assessing Contaminant Vapor Recovery and Air Distribution During In Situ Air Sparging

Helium tracer tests are used as an alternative to soil-gas pressure measurements to assess the effectiveness of soil vapor extraction (SVE) systems for capturing contaminant vapors liberated by in situ air sparging (IAS). The tracer approach is simple to conduct and provides more direct and reliable measures than the soil-gas pressure approach. The tracer test described here can be used to both determine SVE system capture efficiency and to evaluate air distribution during IAS pilot tests. The tests can also be conducted on operating, full-scale systems to confirm system performance. In addition, the tests can be easily repeated, which allows system parameters to be modified and the impact of those modifications to be quickly assessed. Whether used alone or in conjunction with other diagnostic tools, helium tracer tests provide an important measure of IAS system performance.     

The sequence of a porcine cDNA encoding α-lactalbumin

A cDNA clone encoding porcine α-lactalbumin (αLA) was isolated and sequenced. The longest clone was 688 nucleotides (nt) long and encoded a preprotein of 141 amino acids (aa) including a leader peptide of 19 aa. The porcine cDNA exhibited a nt similarity of between 72.2%–83.5% to other αLA cDNAs and an aa similarity of between 50.8%–85.2% with other αLA aa sequences. The derived aa sequence varied at three positions from a previously reported sequence for porcine αLA obtained by direct aa sequencing.     

Amoeba proteus: the nuclear periphery.

This study extends previous work on the nuclear envelope and associated structures. It illustrates that the cylindrical structures of the honeycomb lattice are not attached to the nuclear envelope, although generally perpendicular and closely apposed to it, and that there is a complex arrangement of fibrillar material between the cylinders of the lattice. The relationship of nuclear helices to these structures is described and the possible mode of their transfer from nucleus to cytoplasm is discussed.     

Spiro-naphthyridinone piperidines as inhibitors of S. aureus and E. coli enoyl-ACP reductase (FabI)

Spiropiperidine naphthyridinone inhibitors of Staphylococcus aureus and Escherichia coli FabI have been prepared. Compounds 14a and 14c were identified as having sub-nanomolar E. coli FabI activity and are among the most potent FabI inhibitors yet described. The structural model of 14a bound to E. coli FabI is shown.