Calcium Dependence of Vasoactive Intestinal Peptide-Stimulated Cyclic AMP Accumulation in Rat Hippocampal Slices

Previous work has shown that incubation of hippocampal slices in medium without added calcium markedly attenuates the capacity of vasoactive intestinal peptide (VIP) to elevate cyclic AMP levels. The present studies examined the mechanism that confers calcium dependence on VIP stimulation of cyclic AMP accumulation in hippocampal slices. Calcium dependence was apparent immediately on slice preparation and was reversible only if calcium ions were added back very early during slice incubation (within 5 min). The cyclic AMP response to VIP was not abolished by preincubating slices in 100 microM adenosine, suggesting that calcium-dependent, VIP-induced release of adenosine does not mediate VIP elevation of cyclic AMP. VIP-stimulated cyclic AMP accumulation was not decreased by agents that block calcium influx (verapamil, nifedipine, magnesium ions), or by calmodulin antagonists (trifluoperazine, calmidozolium). In fact both verapamil (100 microM) and magnesium (14 mM) augmented VIP stimulation of cyclic AMP generation. Incubation of slices with the phosphodiesterase inhibitor 1-methyl-3-isobutylxanthine (MIX) did not affect VIP activation of cyclic AMP accumulation if slices were incubated without added calcium, but MIX did enhance VIP elevation of cyclic AMP content in slices incubated with calcium. Thus calcium dependence of the cyclic AMP response to VIP in hippocampal slices is unlikely to result from VIP-dependent calcium influx, from interactions with calmodulin, or from calcium-inhibited phosphodiesterase(s).(ABSTRACT TRUNCATED AT 250 WORDS)     

Behavioral responses of red hake,Urophycis chuss,to decreasing concentrations of dissolved oxygen

Synopsis Laboratory experiments were conducted to examine changes in behavior of red hake,Urophycis chuss, under decreasing concentrations of dissolved oxygen (DO). Since the ecological requirements of this species change with age, responses were measured for three different groups: (1) age 0+, = 89 mm total length (TL); (2) age 1+, = 238 mm TL; and (3) age 2–3+, = 397 mm TL. As DO decreased from 8–10 mg l^-1 to < 0.5 mg l^-1, changes were evident in active time, water column activity, range of horizontal movement, food searching, and agonistic behavior. Age 0+ fish were most sensitive, moving up into the water column and swimming continuously as DO levels fell below 4.2 mg l^-1. Age 2–3+ fish were the least responsive, remaining on the substrate and increasing only their range of movement at concentrations below 3 mg l^-1. Responses of age 1 + fish were variable, possibly reflecting a transition stage between the younger and older fish. Common to all groups was the decrease and eventual cessation of food searching.     

Stability of Lanatoside C content in thein vitro propagatedDigitalis lanata clones

In vitro culture was established from shoot tips ofDigitalis lanata cotyledonous plants. The propagated plant material was rooted, transplanted into soil and grown under field conditions. Lanatoside C content was determined in a total of 20 clones and statistically evaluated by means of variance analysis of unequal-sized samples.In vitro clonal propagation ofD. lanata was found not to affect lanatoside C content. Drug level was dependent on a plant genotype.     

A reply to Holmes on Gendercide

Warren's book, Gendercide: The Implications of Sex Selection (Totowa, N.J.: Rowman and Allanheld; 1985), was reviewed by Helen Bequaert Holmes in the January 1987 issue of Bioethics. Here, Warren responds to the review by clarifying some of her moral arguments and continuing to defend the point of view that selecting the sex of children before conception or before birth is not always sexist, socially harmful, or disrespectful of the child as an end in itself.     

Glomerular ultrastructure of the trout,Salmo gairdneri: Effects of angiotensin II and adaptation to seawater

Summary The effect of angiotensin infusion on the glomerular ultrastructure of freshwater- and seawater-adapted rainbow trout, Salmo gairdneri, has been examined by scanning and transmission electron microscopy. Adaptation of trout to seawater resulted in epithelial podocyte flattening, primary process broadening and apparent loss of foot processes in almost all glomeruli, features which were uncommon in freshwater-adapted trout. Similar changes were induced by infusion of freshwater-adapted animals with angiotensin, suggesting that the renin-angiotensin system plays a role in the modification of glomerular epithelial ultrastructure. Adaptation of trout to seawater also reduced glomerular diameter, but infusion of freshwater-adapted animals with angiotensin did not mirror this effect. Infusion of angiotensin into seawater-adapted animals increased the overall thickness of glomerular basement membrane by increasing the lamina rara interna and lamina densa. This did not occur when freshwater-adapted fish were either infused with angiotensin or adapted to seawater. These findings suggest that other humoral systems are involved in the control of glomerular diameter and basement membrane thickness as part of an integrated response to increased environmental salinity.     

Molecular cloning of a pair of human pepsinogen A genes which differ by a Glu→Lys mutation in the activation peptide

Summary Three human cosmid clones containing pepsinogen A (PGA) encoding sequences were isolated from a genomic bank derived from a single individual. One cosmid contains two PGA genes in tandem in a head-to-tail orientation, while the other two cosmids each contain a single PGA gene. The three cosmids were characterized by restriction mapping and sequence analysis (exons 1 and 2 and flanking regions). As judged from these data, three of the four PGA genes isolated appear to be nearly identical, but one of the tandem genes is clearly different from the other genes. The first exon of all four genes codes for the same amino acid sequence. However, in the second exon of one of the tandem genes we found a nucleotide substitution giving rise to a GluLys substitution of the 43rd amino acid residue of the activation peptide, leading to a charge difference of the corresponding isozymogens. The presence of two distinct PGA genes in the isolated gene pair conclusively proves the multigene structure of the PGA system. These genes might be responsible for at least part of the electrophoretic polymorphism at the protein level.     

In vivo cytogenetic effects of cooked food mutagens

Using a variety of in vivo cytogenetic endpoints, we have investigated the effects of several compounds formed during the cooking of meat. C57Bl/6 mice were used to test for an increase in the frequency of sister-chromatid exchanges (SCEs), chromosomal aberrations, and micronucleated erythrocytes by 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx). 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (DiMeIQx), and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). MeIQx and DiMeIQx did not induce SCEs in mouse bone marrow cells. PhIP induced sister-chromatid exchanges, but not chromosomal aberrations in bone marrow. In peripheral blood lymphocytes, PhIP did induce aberrations at 100 mg/kg, the highest dose tested. PhIP induced a low but significantly increased frequency of micronuclei in normochromatic but not polychromatic erythrocytes in bone marrow and peripheral blood. However, dose responses were not observed. With the exception of the SCEs induced by PhIP, these results contrast with observations made in vitro, where these compounds were found to have significant genotoxicity in mammalian cells and a very high mutation frequency in prokaryotic systems.     

Differential expression within a family of novel wound-induced genes in potato

Summary Wounding in higher plants leads to an increased synthesis of specific messenger RNAs. A cDNA clone complementary to a wound-induced message from potato tubers was used to isolate a lambda clone from a genomic library of Salanum tuberosum var. Maris Piper. DNA sequence analysis has shown that this single genomic clone contains two novel wound-induced genes, called win1 and win2, organised in close tandem array. The coding sequences of these two genes are highly homologous and are interrupted by a single intron. However, the sequences of the introns and flanking regions have diverged widely. Win1 and win2 encode cysteine-rich proteins of 200 and 211 amino-acids, respectively, which show striking homologies to several chitin-binding proteins. Southern analysis of genomic DNA has shown that win1 and win2 are members of a small multi-gene family which is estimated to have a minimum of five members per haploid genome of Maris Piper and appears to be conserved within the Solanaceae. We have shown by Northern analysis and S1 mapping that the two genes exhibit differential organ-specific expression after the wounding of a potato plant.     

Aminoglycoside suppression at UAG, UAA and UGA codons in Escherichia coli and human tissue culture cells

Summary We have compared the suppression of nonsense mutations by aminoglycoside antibiotics inEscherichia coli and in human 293 cells. Six nonsense alleles of the chloramphenicol acetyl transferase (cat) gene, in the vector pRSVcat, were suppressed by growth in G418 and paromomycin. Readthrough at UAG, UAA and UGA codons was monitored with enzyme assays for chloramphenicol acetyl transferase (CAT), in stably transformed bacteria and during transient expression from the same plasmid in human 293 tissue culture cells. We have found significant differences in the degree of suppression amongst three UAG codons and two UAA codons in different mRNA contexts. However, the pattern of these effects are not the same in the two organisms. Our data suggest that context effects of nonsense suppression may operate under different rules inE. coli and human cells.