Effects of N-alcohols on potassium conductance in squid giant axons

The effect of bath application of several short chain N-alcohols on voltage-dependent potassium conductance has been studied in intact giant axons of Loligo forbesi under voltage-clamp conditions. All tested alcohols (methanol, ethanol, propanol, butanol, heptanol and octanol) were found to depress potassium conductance only at concentrations much larger than those necessary to reduce sodium conductance. The efficacy of the different molecules was correlated with the carbon-chain length. In all cases the effects were found to be at least partly reversible. Low concentrations of propanol (100 mM) or heptanol (1 mM) were found to increase potassium conductance whereas higher concentrations had the usual depressing effect. The two alcohols were found to induce a slow inactivation of the potassium conductance. A detailed analysis of the time course of the turning-on of the potassium current for various pulse potentials in the presence of TTX revealed that, for membrane potential values more positive than -20 mV, the time constant of activation was reduced in the presence of propanol or heptanol. The delay which separates the change in potential and the turning-on of the potassium current, which was systematically analysed for different pulse and prepulse potential values, was increased by the two alcohols, the curve relating this delay to prepulse potential being shifted towards larger (positive) delays. This high degree of complexity in the effects on potassium conductance suggests that the alcohol molecules modify several more or less independent mechanisms associated with the turning-on of the potassium current.     

Interaction and combination of separate A and B chains of insulin effects of D-and L-tryptophan in position A1

The S-thiomethyl derivatives of insulin A chain with A1-Gly replaced by D- or L-Trp have been prepared and their respective interaction and combination with the S-thiomethyl B chain studied. The UV difference spectra of the mixed against the separated [Trp1]A chains with the B chain at pH 10.8 are similar to those obtained for the unmodified chains except that the 295-nm-negative peak for ionized Tyr residue appears to be less marked. Fluorescence studies show very little environmental changes at the A1-Trp residues when mixed with the B chain. The intact hormone with A1-Gly replaced by D-Trp is known to be considerably more active than the analog with L-Trp replacement. However, for both derivatives the resynthesis of the whole molecules correctly joined by disulfide bridges starting from the separated reduced chains, gives similar low yields as shown by HPLC analysis and by receptor-binding assay. The replacement of A1-Gly by D-Trp appears to affect the separated A chain more than the intact hormone and replacements at A1 by both D- and L-Trp probably lead to significant conformational changes of the A chain so as to prevent its correct pairing with the B chain.     

Locus determining the human sperm-specific lactate dehydrogenase, LDHC, is syntenic with LDHA

From the data presented in this report, the human LDHC gene locus is assigned to chromosome 11. Three genes determine lactate dehydrogenase (LDH) in man. LDHA and LDHB are expressed in most somatic tissues, while expression of LDHC is confined to the germinal epithelium of the testes. A human LDHC cDNA clone was used as a probe to analyze genomic DNA from rodent/human somatic cell hybrids. The pattern of bands with LDHC hybridization is easily distinguished from the pattern detected by LDHA hybridization, and the LDHC probe is specific for testis mRNA. The structural gene LDHA has been previously assigned to human chromosome 11, while LDHB maps to chromosome 12. Studies of pigeon LDH have shown tight linkage between LDHB and LDHC leading to the expectation that these genes would be syntenic in man. However, the data presented in this paper show conclusively that LDHC is syntenic with LDHA on human chromosome 11. The terminology for LDH genes LDHA, LDHB, and LDHC is equivalent to Ldh1, Ldh2, and Ldh3, respectively.     

Integration of hepatitis B virus: analysis of unoccupied sites.

Hepatitis B virus (HBV) sequences integrated in the PLC/PRF/5 cell line (Alexander cells), which was derived from a human primary liver carcinoma, were previously extensively studied. Here we describe the analysis of the unoccupied sites of two linearly integrated forms of HBV DNA, AL-14 and AL-26, that were characterized previously. No major cellular DNA rearrangements were seen at the integration sites except for small deletions of host sequences: 2 kilobases of DNA in AL-14 and 17 base pairs (bp) in AL-26. The unoccupied site of AL-26 was found to be missing 182 bp, which previously mapped next to the right end of the integration sites of several independent clones. These were believed to be of cellular origin, but we show here that these 182 bp are in fact from unusual HBV sequences. Surprisingly, a region of this newly detected HBV DNA sequence is more homologous to that of woodchuck HBV DNA. Our analysis shows that the normal counterparts of both AL-14 and AL-26 contain minisatellite-like repetitive sequences. Based on the data presented here and our previous finding of HBV DNA integration at satellite sequences, we propose that genomic simple repetitive sequences are hot spots for HBV DNA integration.     

Freeze-fracture localization of filipin-sterol complexes in plasma- and cyto-membranes of Pneumocystis carinii

The polyene antibiotic, filipin, was used as the probe for demonstrating sterols in the freeze-fractured plasma- and cytomembranes of Pneumocystis carinii. The distribution of filipin-sterol complexes was homogeneous on the plasma membrane throughout all developmental stages from trophozoite to cyst; however, the density of the complexes gradually decreased with the progress of development. In the trophozoite, the density of the complexes was 485 +/- 42/micron2 on the P face and 341 +/- 27/micron2 on the E face. It was 249 +/- 50 on the P face and 132 +/- 48 on the E face in the precyst and 138 +/- 24 and 59 +/- 20, respectively, in the cyst. The membranes of nucleus, mitochondria, and small round bodies showed more or fewer complexes while no complexes were found in the membranes of one endoplasmic reticulum. In nuclear and mitochondrial membranes, some small scattered clusters of complexes were observed. Two types of vacuoles were distinguished: one having many complexes in its membrane and the other having none at all.     

Roles of neonatal and prepubertal testicular androgens on androgen-induced proliferative response of seminal vesicle cells in adult mice

Male mice were castrated at 0, 10, 20, 30, 40 and 60 days of age; daily injections of testosterone propionate (TP, 4 micrograms/g b. wt) were started from day 90. On various days after starting the TP injections, the incorporation of 5-[125I]iodo-2'-deoxyuridine into the whole seminal vesicles was determined as an index for proliferation. The seminal vesicle cells in mice castrated on days 0 and 20 were characterized by low weight (0.5-1 mg) before TP injection, long duration of androgen-induced proliferation (greater than 20 days) with a low peak, and involvement of both epithelial and fibromuscular cells (neonatal castration type). The seminal vesicle cells in mice castrated on days 60 and 40 were characterized by relatively high weight (5-10 mg) before TP injection, short duration of androgen-induced proliferation (10 days) with a high peak, and involvement of only the epithelial cells (adult castration type). In mice castrated on days 0 and 20, the neonatal castration type of androgen-induced proliferation was completely changed to the adult castration type when TP pretreatment (2 micrograms/g b. wt per 12 h) had been given from day 20 to day 40. However, the TP pretreatment given from day 90 to day 110 instead of days 20-40 had no such effect in 140-day old mice castrated on day 0. The present findings suggest that testicular androgens secreted from day 20 to day 40 play an indispensable role in the induction of irreversible proliferative response of the mouse seminal vesicle. The activity of the prepubertal androgens may not be completely compensated by androgen activity at adulthood.     

Dextrorphan: an antagonist for phencyclidine receptors

Radio-binding assay, bioassay and HPLC detection were used to observe the antagonistic effects of dextrorphan on PCP's actions. Dextrorphan displayed high affinity to PCP receptor in the rabbit mesenteric blood vessels. It had weak PCP-like bioactivity, but could antagonize PCP's action dose-dependently in vitro study with the rabbit ear artery preparation and shifted the dose-response curve of PCP to the right. After PCP administration, the content of norepinephrine in the vascular bath medium was increased, which was reversed by dextrorphan. Thus suggests that dextrorphan is an antagonist with very mild agonistic action for PCP receptors.     

Atrial natriuretic hormone secretion in patients with renal failure

To study the effects of volume overload and renal failure on plasma levels of immunoreactive atrial natriuretic hormone (IR-ANH), we measured levels of this hormone in normal subjects, in patients with advanced chronic renal failure (CRF) with and without clinically evident volume overload, and in patients with end-stage renal disease (ESRD) treated with chronic hemodialysis. The levels were 13 +/- 2 pmol/l in normal volunteers, 77 +/- 24 pmol/l in patients with CRF without volume overload, and 219 +/- 50 pmol/l in patients with CRF and clinically evident volume overload (analysis of variance, p less than 0.001, alpha = 0.05 compared to normals). In patients with ESRD, the levels of IR-ANH were 145 +/- 46 pmol/l before dialysis and decreased to 87 +/- 31 after dialysis (p less than 0.025). No correlation was found between the decrease in IR-ANH levels and the decrease in weight during dialysis. A significant positive correlation was found between the IR-ANH levels and blood urea nitrogen in patients with CRF (r = 0.658, p less than 0.01). Volume overload appears to be the most important stimulatory factor for ANH secretion in renal failure patients but other mechanisms, especially a decrease in metabolic clearance, may also contribute to elevated plasma levels. The increased secretion of ANH in patients with renal failure may be an important adaptive response to volume overload and hypertension.     

The effect of muscarinic and beta-adrenergic blockade on cysteamine-induced gastrin secretion by the isolated perfused rat stomach

Cysteamine-induced duodenal ulceration in rats is accompanied by increased circulating gastrin. Although cysteamine appears to exert a direct action on the gastrin cell some groups have provided evidence for an involvement of the autonomic nervous system. The current experiments were performed to determine whether beta-adrenergic or cholinergic (muscarinic) pathways are involved in the acute effect of cysteamine on gastrin secretion in the isolated perfused rat stomach. Cysteamine (1 mM) increased gastrin (IRG) secretion to a maximum ranging between 100% and 192% above basal. A cysteamine concentration of 5mM resulted in peak levels ranging between 150% and 1050% above basal. Addition of atropine or propranalol did not influence the responses obtained. The present results, therefore, do not support a role for either cholinergic or beta-adrenergic pathways in cysteamine-induced gastrin release at the level of the stomach and suggest that in vivo such autonomic effects are mediated extrinsically.     

Replication and cytopathic effects of ovine lentivirus strains in alveolar macrophages correlate with in vivo pathogenicity.

Ruminant lentiviruses share genomic sequences and biologic properties with human immunodeficiency viruses. Four ovine lentivirus strains were assessed for cytopathic effects and virus replication. Lentivirus isolate H/24 produced high virus titers and lysis of synovial cells but replicated slowly and caused no fusion of alveolar macrophages. Lentivirus isolates 84/28 and 85/14 produced low virus titers, less syncytia, and limited or no cell lysis in synovial cells and macrophages. In contrast, ovine lentivirus isolate 85/34 produced early peak virus titers and caused rapid fusion and lysis of both macrophages and synovial cells. Ovine lentivirus isolates which were cytopathic for macrophages induced lymphoproliferative disease when inoculated into lambs.