Adaptation of Drosophila enzymes to temperature--I. Acetylcholinesterase and NADP-dependent isocitrate-dehydrogenase

1. The relationship between Km and assay temperature was examined in three tropical and two temperate Drosophila species, and in the cosmopolitan species, D. melanogaster, for isocitrate dehydrogenase and acetylcholinesterase. 2. For both enzymes Km patterns were similar among species from the same habitat, and different between habitats. No such parallelism was seen with respect to thermal inactivation. 3. The Q10 values in general reflected temperature dependent changes in Km, but exceptions were noted.

Calcium-induced damage of haemoglobin SS and normal erythrocytes

An ionophore specific for divalent cations has been used to load normal erythrocytes and erythrocytes from patients with sickle cell anaemia (Hb SS disease), with small amounts of calcium. Such calcium accumulation leads to decreased cellular water, potassium, adenosine triphosphate (ATP), and osmotic fragility, all characteristics of irreversibly sickled cells (ISCs). In addition, calcium loading of Hb SS, but not normal, erythrocytes causes a marked decrease of haemoglobin oxygen affinity; another, and specific, hallmark of ISCs. Ionophore-induced accumulation of calcium by deoxygenated Hb SS erythrocytes also leads to temporary retention of sickled shape following reoxygenation, despite the absence of detectable intracellular haemoglobin S fibres. All these effects require calcium in the incubation medium and support the idea that increased intracellular calcium is important in the formation of ISCs in patients with Hb SS disease.

Isozyme and allozyme patterns in embryonic Drosophila cell culture lines

Two independently derived embryonic Drosophila cell culture lines were examined for 19 gene-enzyme systems. At two loci, alpha-glycerophosphate dehydrogenase on chromosome 2, and isocitrate dehydrogenase on chromosome 3, allelic variation was detected. These can now serve as genetic markers to identify hybrid cell clones. Quantitative differences between cell lines were found for five enzymes.

Host heme catabolism in drug-sensitive and drug-resistant malaria

Chloroquine resistance has arisen in both human and murine forms of malaria. CR Plasmodium berghei in mice does not produce the malaria pigment which is characteristic of the CS form. Determinations of carbon monoxide production (i.e., host heme catabolism) by individual mice revealed that those infected with CS P. berghei produce only one fourth as much carbon monoxide as do CR infected mice at all levels of infection. These observations confirm the idea that malaria pigment is composed of precipitated host cell hemoglobin and suggest that drug resistance is accompanied by a basic alteration in parasite-mediated hemoglobin catabolism.

The ribosomes of Drosophila. Normal and defective ribosome biosynthesis in Drosophila cell cultures

The assembly of proteins and RNA into mature ribosomal subunits has been studied in Drosophila cell cultures by pulse-chase experiments. Pulse labeled rRNA has a transit time of 3 h, while the transfer of ribosomal protein occurs completely within 30 min. Inhibition of protein synthesis by cycloheximide results in an almost immediate cessation of ribosome assembly, a result which indicates that no large pool of free ribosomal proteins exists in the cell. Substituting pre-ribosomal RNA with the analogue 5-fluorouridine (5-FU) results in a cessation of ribosome muturation. Under these conditions at least three large subunit proteins continue to accumulate on pre-existing cytoplasmic subunits, indicating an exchange. A portion of ribosomal subunit proteins synthesized in the presence of 5-FU can be recovered in cytoplasmic subunits once the effect of 5-FU has been reversed. This is most easily interpreted in terms of their stabilization on substituted pre-rRNA within the nucleolus, and subsequent utilization on unsubstituted RNA.

The effect of intravenous potassium canrenoate in patients with severe heart failure and digitalis toxicity

In 16 patients with critical condition due to severe heart failure associated with digitalis toxicity, the effects of potassium canrenoate (AldactoneR) administered intravenously were studied. Rhythm and conduction disturbances disappeared or improved in all instances. This effect was well correlated with an increase of serum potassium concentration. In 13 patients, after 1-2 days of Aldactone therapy, heart failure improved, which could be explained by a diuretic effect and by a possible inotropic action of aldactone. It is concluded that intravenous Aldactone is useful in patients with severe heart failure and digitalis toxicity in whom diuretics are often ineffective and even dangerous.

Base sequence complexity of the stable RNA species of Drosophila melanogaster

The base sequence complexity of Drosophila transfer RNA (tRNA), 5S RNA, and 18S + 28S ribosomal RNA was determined by analyzing the kinetics of RNA-DNA hybridization on membrane filters. We find that Drosophila tRNA is made up from about 59 basic nucleotide sequences distinguishable by hybridization, suggesting that many of the 99 tRNA species resolved by reverse phase chromatography (RPC-5) are homogenic. In contrast 5S RNA was found to contain a single family of sequences. Either 18S ribosomal RNA (rRNA) alone, or 18S + 28S rRNA together, behaved kinetically as two sequence families, and the possible basis for this unexpected result is discussed.

The ribosomes of Drosophila. III. RNA and protein homology between D. melanogaster and D. virilis

The extent of interspecific homology between D. melanogaster and D. virilis for ribosomal RNA and ribosomal protein was examined using the techniques of two-dimensional gel electrophoresis, and RNA-DNA filter hybridization. Only 2 of the 71 ribosomal proteins resolved were found to be species specific, while comparisons of soluble larval hemolymph protein patterns showed little similarity. Depending on the technique employed, the sequence homology for 18S + 28S ribosomal RNA was found to be between 83-94%, and sequence homology for 5S rRNA was judged to be complete.

The ribosomes of Drosophila. IV. Electrophoretic identify among ribosomal subunit proteins from wild type and mutant D. melanogaster and D. simulans

One- and two-dimensional gel electrophoresis was employed to characterize and compare ribosomal subunit proteins from wild-type D. melanogaster and several mutants, including suppressor-of-forked and four X-linked cold sensitive lethals. The sibling species D. simulans was also studied. We found the electropherogram patterns indistinguishable in all cases.

Preserved allografts of dilated saphenous vein for vascular access in hemodialysis: an initial experience

Arteriovenous fistulas constructed from preserved (frozen) allograft veins provided vascular access for maintenance hemodialysis in 14 patients with inadequate vasculature for conventional autogenous fistulas. Electromagnetic flows ranged from 200 to 250 cc/min. Dialysis flow of 200 cc/min were accomplished consistently. The allografts were useable for dialysis much earlier than autogenous A-V fistulas. Arteriography demonstrated a wide vasculature channel very suitable for dialysis needles. Allografts seemed superior to bovine heterografts in both patency and susceptibility to infection. Scanning electron microscopy revealed smoother initimal surfaces if the donor received small amounts of heparin systemically while the veins were being removed. Allograft veins appear to be a useful alternative means of vascular access for hemodialysis.

Polymorphism at the alpha-glycerophosphate dehydrogenase locus in Drosophila melanogaster. I. Properties of adult allozymes

A biochemical comparison was made between alpha-glycerophosphate dehydrogenase allozymes from Drosophila melanogaster. Enzymes extracted from the three major genotypes were indistinguishable in terms of their pH optima and thermal stabilities. Distinctive differences were observed for three parameters; temperature dependence of specific activity, temperature dependence of K-m, and reaction rate constancy over a physiological temperature range. These results are discussed in terms of a model of balancing selection and the existence of spatial and temporal allele frequency clines in natural populations.

Survival at extreme altitude: protective effect of increased hemoglobin-oxygen affinity

Decreased hemoglobin-oxygen affinity is thought to be of adaptive value to humans and nonindigenous animals at high altitude. To test this, hemoglobin-oxygen affinity was modified by carbamoylation of hemoglobin in rats. Exposure of control (low oxygen affinity) and experimental (high oxygen affinity) animals to a pressure equivalent to high altitude revealed that increased, rather than decreased, hemoglobin-oxygen affinity will permit survival at greatly reduced environmental oxygen pressures.