Opportunities for natural selection on DNA and protein at the Adh locus in Drosophila melanogaster

A study was made of environmental and genetic factors affecting the quantity and disposition of the alcohol dehydrogenase (ADH) protein in Drosophila melanogaster. It was found that the amount of enzyme per fly is greatly influenced by the environmental conditions in which it develops. A critical factor is the concentration of yeast in the medium. A high concentration of yeast can double the quantity of ADH. The yeast appears to act through the provision of protein, and the protein to act through the provision of threonine, which is already known to induce ADH in fungi. Various genetic factors affect the quantity of enzyme. Males have more ADH than females. Files homozygous for the Fast allele have more ADH than those homozygous for the slow allele, and the difference is greater in females than in males. One particular line (ve), homozygous for Slow, has approximately half the normal quantity of enzyme, and the quantity segregates with the electrophoretic allele. Lines differ in the relative amounts of ADH in the gut (including Malpighian tubules) and the fat body. In general it seems that slow lines have relatively more enzyme in the fat body. In a cross between ve and a line homozygous to Fast, the difference in tissue distribution segregated with the electrophoretic allele. It is argued, but not demonstrated, that the differences in quantity and tissue distribution are due to nucleotide substitutions in noncoding regions close to, or within, the structural gene. It seems likely that the observed environmental and genetic differences in the quantity and disposition of ADH will influence the relative selective values of the electrophoretic genotypes.     

Fertilization acid of sea urchin eggs: Evidence that it is H+, not CO2

The report of R. J. Gillies, M. P. Rosenberg, and D. W. Deamer (1981, J. Cell. Phys., 108, 115–122) that sea urchin fertilization acid is anaerobically produced CO₂, was reinvestigated by inseminating Strongylocentrotus purpuratus eggs in HCO^?₃-free seawater, then bubbling the seawater with N₂ to remove volatile acid. Fertilization acid production occurred in HCO^?₃-free seawater and with N₂-bubbling, the pH rose 0.28 ± 0.08 unit, significantly less than the rise of 0.63 ± 0.14 unit during N₂-bubbling of HCO^?₃-free seawater that had been acidified with CO₂ and similar to the rise of 0.18 ± 0.07 unit when acidification was with HCl. We conclude that most, if not all, of the sea urchin fertilization acid is nonvolatile and thus is not CO₂; since it is not a weak acid, it must be H⁺.     

Interaction of glutathione transferase from horse erythrocytes with 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole

7-Chloro-4-nitrobenzo-2-oxa-1,3-diazole reacts with two thiol groups of the dimeric horse erythrocyte glutathione transferase at pH 5.0, with strong inactivation reversible on dithiothreitol treatment. The inactivation kinetic follows a biphasic pattern, similar to that caused by other thiol reagents as recently reported. Both S-methylglutathione and 1-chloro-2,4-dinitrobenzene protect the enzyme from inactivation. Analysis of the reactive SH group-containing peptide gives the sequence Ala-Ser-Cys-Leu-Tyr, identical with that of the peptide that contains the reactive cysteine 47 of the human placental transferase. In the presence of glutathione, the enzyme is not inactivated by this reagent, but it catalyzes its conjugation to glutathione. At higher pH values, 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole reacts with 2 tyrosines/dimer and lysines, as well as with cysteines. Reaction with lysine seems essentially without effect on activity; whether the reactive tyrosines are important for activity could not be determined using this reagent only. However, 2 tyrosines among the 4 that are nitrated by tetranitro-methane are important for activity.     

A review of the salt sensitivity of the Australian freshwater biota

In Victoria, Australia, both dryland salinity and salinity in irrigation regions are serious agricultural problems. One option to control the latter is to pump groundwater to maintain it below the surface. However, this leaves a saline wastewater for disposal, probably into local streams or wetlands. This review of the salt sensitivity of the biota of Australian streams and wetlands gives information of interest to those responsible for developing controls on these discharges. The review addresses the lethal and sub-lethal effects of salinity on microbes (mainly bacteria), macrophytes and micro-algae, riparian vegetation, invertebrates, fish, amphibians, reptiles, mammals, and birds. Data suggest that direct adverse biological effects are likely to occur in Australian river, stream and wetland ecosystems if salinity is increased to around 1 000 mg L⁻¹. The review highlights a general lack of data on the sensitivity of freshwater plants and animals to salinity increases.     

The effect of polyamines on ethylene synthesis during normal and pollination-induced senescence of Petunia hybrida L. flowers

Senescence of Petunia hybrida L. flowers is accompanied by a climacteric pattern in ethylene production and a rapid decline in the levels of putrescine and spermidine during the preclimacteric phase. The decrease in spermidine is caused by the decline in the availability of putrescine which is initially synthesized from L-arginine via agmatine and N-carbamoylputrescine. Inhibition of putrescine and polyamine synthesis resulted in a rapid drop in the levels of putrescine and spermidine without resulting in a concomitant increase in ethylene production. These results indicate that polyamine synthesis is not involved in the control of ethylene synthesis through its effect on the availability of S-adenosylmethionine, and is confirmed by the results obtained with pollinated flowers. Treatment with polyamines may stimulate or suppress ethylene production in the corolla, depending on the concentrations applied. In unpollinated flowers the onset of the climacteric rise in ethylene production was accelerated after treatment with polyamines. However, in pollinated flowers this process was delayed as a result of treatment with low concentrations of polyamines. The effects of exogenous polyamines on ethylene production in both pollinated and unpollinated flowers indicate that ethylene synthesis in these flowers is not regulated by a feedback control mechanism. Although polyamines do not play a key role in the control of ethylene production during the early stages of senescence through their effect on the availability of S-adenosylmethionine, it appears that they play an important role in some of the other processes involved in senescence.Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - MGBG methylglyoxal bis-(guanylhydrazone) - SAM S-adenosylmethionine     

Introduction of Tn916 and pAM beta 1 into Streptococcus bovis JB1 by conjugation.

The transposon Tn916 and self-mobilizing plasmid pAM beta 1 were conjugated from Enterococcus faecalis to the ruminal bacterium Streptococcus bovis JB1. Transconjugants were identified by resistance to tetracycline (Tn916) or erythromycin (pAM beta 1) and by Southern hybridization analyses. Transfer frequencies were 7.0 x 10(-6) and 1.0 x 10(-6) per recipient cell for Tn916 and pAM beta 1, respectively. The transconjugants JB1/Tn916 and JB1/pAM beta 1 were used as donors for matings with E. faecalis, Bacillus subtilis, and the ruminal bacterium Butyrivibrio fibrisolvens. While pAM beta 1 was successfully transferred to all three organisms, Tn916 was transferred only into B. subtilis and B. fibrisolvens at very low frequencies. This is the first report of conjugal DNA transfers between two ruminal organisms.     

Myb expression is higher in malignant human colonic carcinoma and premalignant adenomatous polyps than in normal mucosa.

Expression of the protooncogene c-Myb protein was assessed in normal mucosa and in tumor samples resected from six patients. We found that the tumor samples always expressed higher levels of full length Myb protein than the normal tissue. This contrasts with the situation in c-myb-associated hemopoietic malignancies of the mouse and chicken, in which Myb proteins are generally amino or carboxyl truncated. Tissues from five patients with colonic adenomatous polyps were also examined and found to express levels of Myb that were, in general, intermediate between those found in normal tissues and tumors. Of particular interest is that the more dysplastic polyps displayed higher Myb levels. In one patient with carcinoma and multiple colonic polyps, some polyps had intermediate levels of Myb, whereas one polyp with carcinoma in situ expressed tumor-like levels of Myb. To directly test the hypothesis that Myb expression may be important in determining the rate of colonic cell proliferation, we examined three colonic carcinoma cell lines and one polyp cell line. We found that the cell lines with the most rapid doubling times exhibited the highest Myb levels. In addition, we show that antisense myb oligonucleotides retard the proliferation of one of these colonic cell lines which expresses the highest level of Myb.     

Dose responses for Colletotrichum lindemuthianum elicitor-mediated enzyme induction in French bean cell suspension cultures

The induction of L-phenylalanine ammonialyase (PAL, EC 4.3.1.5) and flavanone synthase in French bean cell suspension cultures in response to heat-released elicitor from cell walls of the phytopathogenic fungus Colletotrichum lindemuthianum is highly dependent upon elicitor concentration. The elicitor dose-response curve for PAL induction shows two maxima at around 17.5 and 50 g elicitor carbohydrate per ml culture, whereas the flavanone synthase response shows one maximum at around 100 g ml^-1. The PAL response is independent of the elicitor concentration present during the lag phase of enzyme induction; if the initial elicitor concentration is increased after 2 h by addition of extra elicitor, or decreased by dilution of the cultures, the dose response curves obtained reflect the concentration of elicitor present at the time of harvest. PAL induction is not prevented by addition of methyl sugar derivatives to the cultures; -methyl-D-glucoside, itself a weak elicitor of PAL activity, elicits a multiphasic PAL response when increasing concentrations are added in the presence of Colletotrichum elicitor. Eight fractions with different monosaccharide compositions, obtained from the crude elicitor by gel-filtration, each elicit different dose-responses for PAL induction; the response to unfractionated elicitor is not the sum of the response to the isolated fractions. There is no correlation between the ability of the fractions to induce PAL in the cultures and their ability to act as elicitors of isoflavonoid phytoalexin accumulation in bean hypocotyls.Abbreviations PAL phenylalanine ammonia-lyase - PMS Phytophthora megasperma var sojae     

Prevention of venous thromboembolism after total knee replacement by high-dose aspirin or intermittent calf and thigh compression.

A prospective study of patients undergoing total knee replacement was carried out by using a combination of 125I-fibrinogen scanning and phlebography, and showed a high incidence of venous thromboembolic disease (TE). Ventilation-perfusion lung scanning was performed to detect pulmonary emboli in most patients. High doses of aspirin and an intermittent low-pressure pneumatic compression device (IPCD) were effective, even in women, in preventing TE. Low doses of aspirin and placebo were equally ineffective in preventing TE. Lung-scan abnormalities compatible with pulmonary emboli were found in six out of 10 patients with isolated calf-vein thrombi. Conventional tests of platelet function did not predict the development of TE. No significant differences were found between the patients receiving low and high doses of aspirin with respect to the mean template bleeding time or platelet aggregation in response to adenosine diphosphate, collagen, and epinephrine, although these variables were significantly abnormal in the two groups receiving aspirin compared with those treated with placebo and the IPCD. Thus high doses of aspirin and a new low-pressure IPCD were effective in preventing venous TE in patients (predominantly women) undergoing total knee replacement.