ATP-dependent proteolysis of hemoglobin alpha chains in beta-thalassemic hemolysates is ubiquitin-dependent

beta-Thalassemia is an inherited human disorder which is characterized by a deficient production of hemoglobin beta chains and an attendant accumulation of structurally normal alpha chains in the erythropoietic cells. The objective of this work is to understand the mechanism of intracellular proteolysis of these excess alpha chains. Dialyzed stroma-free hemolysates (32 mg/ml hemoglobin) of blood reticulocytes from four individuals with beta-thalassemia intermedia were incubated with human hemoglobin 3H-alpha chains (0.13 mg/ml) at 37 degrees C in a reaction mixture supporting protein degradation. In the presence of ATP and an ATP-generating system, the fraction of alpha chain 3H radioactivity made acid-soluble after 4 h ranged from 4 to 12% among the different hemolysates; in the absence of ATP or when hemolysates of normal human erythrocytes were used, only 1 to 2% of the 3H-alpha chains were degraded. It is likely that the ATP-dependent proteolysis of 3H-alpha chains in the beta-thalassemic hemolysates corresponds to the ATP-dependent turnover of newly synthesized soluble alpha chains in intact beta-thalassemic reticulocytes observed previously (Shaeffer, J. (1983) J. Biol. Chem. 258, 13172-13177) because of the following similarities between the two systems: (a) free 3H-alpha chains, but not 3H-labeled tetrameric hemoglobins, were readily degraded; (b) the rate of 3H-alpha chain proteolysis in the cell-free system was at least one-half of that observed for the turnover of newly synthesized alpha chains (t1/2 approximately 6 h) in intact cells; and (c) the ATP-dependent proteolytic activity of both systems was inhibited substantially by certain chemical agents (orthovanadate, N-ethylmaleimide, o-phenanthroline, and phenylmethylsulfonyl fluoride) but only slightly, if at all, by others (epsilon-aminocaproic acid and leupeptin). When excess human erythrocyte ubiquitin was added to the beta-thalassemic cell-free systems, a stimulation in ATP-dependent proteolysis of 3H-alpha chains ranging from 30 to 58% was observed. Conversely, addition of from 1.25 to 2.50 mg/ml affinity-purified rabbit antiubiquitin inhibited almost all (greater than 90%) of the ATP-dependent 3H-alpha chain proteolysis; in control experiments, antiubiquitin neutralized with excess ubiquitin inhibited only 13 to 30% of the total (including ubiquitin-stimulated) ATP-dependent proteolysis.(ABSTRACT TRUNCATED AT 400 WORDS)     

Structure-activity relations of the molluscan neuropeptide FMRFamide on some molluscan muscles

Analogs of the molluscan neuropeptide FMRFamide were tested on four different molluscan muscle preparations which show qualitatively different responses to the peptide; the structure-activity relations are basically similar, but not identical. The C-terminal amide and the Arg³ residue are critical for FMRFamide-like activity on all four preparations. In contrast, analogs extended at the N-terminal or with conservative substitutions for the Phe¹ or Met² residue are approximately equipotent to FMRFamide. These structural requirements parallel those for the C-terminal tetrapeptide amide of gastrin.     

Alanine metabolism in the perfused rat liver. Studies with (15)N.

We have utilized [(15)N]alanine or (15)NH(3) as metabolic tracers in order to identify sources of nitrogen for hepatic ureagenesis in a liver perfusion system. Studies were done in the presence and absence of physiologic concentrations of portal venous ammonia in order to test the hypothesis that, when the NH(4)(+):aspartate ratio is >1, increased hepatic proteolysis provides cytoplasmic aspartate in order to support ureagenesis. When 1 mm [(15)N]alanine was the sole nitrogen source, the amino group was incorporated into both nitrogens of urea and both nitrogens of glutamine. However, when studies were done with 1 mm alanine and 0.3 mm NH(4)Cl, alanine failed to provide aspartate at a rate that would have detoxified all administered ammonia. Under these circumstances, the presence of ammonia at a physiologic concentration stimulated hepatic proteolysis. In perfusions with alanine alone, approximately 400 nmol of nitrogen/min/g liver was needed to satisfy the balance between nitrogen intake and nitrogen output. When the model included alanine and NH(4)Cl, 1000 nmol of nitrogen/min/g liver were formed from an intra-hepatic source, presumably proteolysis. In this manner, the internal pool provided the cytoplasmic aspartate that allowed the liver to dispose of mitochondrial carbamyl phosphate that was rapidly produced from external ammonia. This information may be relevant to those clinical situations (renal failure, cirrhosis, starvation, low protein diet, and malignancy) when portal venous NH(4)(+) greatly exceeds the concentration of aspartate. Under these circumstances, the liver must summon internal pools of protein in order to accommodate the ammonia burden.     

Hemoglobin Dallas (alpha 97(G4)Asn-->Lys): functional characterization of a high oxygen affinity natural mutant.

Hemoglobin Dallas, an alpha-chain variant with a substitution of lysine for asparagine at position 97(G4), was found to have increased oxygen affinity (p1/2 = 1 mmHg at pH 7.3 and 20 degrees C), diminished cooperativity (n, the Hill coefficient = 1.7) and reduced Bohr effect (about 50%). Addition of allosteric effectors (such as 2,3-diphosphoglycerate, inositol hexakisphosphate and bezafibrate) led to a decrease in oxygen affinity and increase in cooperative energy. Kinetic studies at pH 7.0 and 20 degrees C revealed that (i), the overall rate of oxygen dissociation is 1.4-fold slower than that for HbA and (ii), the carbon monoxide dissociation rate is unaffected. The abnormal properties of this hemoglobin variant can be attributed to a more 'relaxed' T-state.     

Round robin investigation of methods for recovering human enteric viruses from sludge

To select a tentative standard method for detection of viruses in sludge the American Society for Testing and Materials D19:24:04:04 Subcommittee Task Group initiated round robin comparative testing of two procedures that, after initial screening of several methodologies, were found to meet the basic criteria considered essential by the task group. Eight task group member laboratories agreed to perform round robin testing of the two candidate methods, namely, The Environmental Protection Agency or low pH-AlCl3 method and the Glass or sonication-extraction method. Five different types of sludge were tested. For each particular type of sludge, a single laboratory was designated to collect the sludge in a single sampling, make samples, and ship it to the participating laboratories. In most cases, participating laboratories completed all the tests within 48 h of sample arrival. To establish the reproducibility of the methods, each laboratory tested each sludge sample in triplicate for the two candidate virus methods. Each processed sludge sample was quantitatively assayed for viruses by the procedures of each individual round robin laboratory. To attain a more uniform standard of comparison, a sample of each processed sample from all laboratories was reassayed with one cell line and passage number by a single laboratory (Environmental Protection Agency Environmental Monitoring and Support Laboratory, Cincinnati, Ohio). When the data were statistically analyzed, the Environmental Protection Agency method was found to yield slightly higher virus recoveries for all sludge types, except the dewatered sludge. The precisions of both methods were not significantly different.(ABSTRACT TRUNCATED AT 250 WORDS)     

The study of X-rays and TCDD effects on satellite associations may suggest a simple model for application in environmental mutagenesis

Summary Satellite associations were used as parameters to test nucleolar organizer activity. Assuming that toxic and/or mutagenic agents may affect the ribosomal genes, satellite associations in human lymphocytes were analysed following exposure to X-rays and compared with the satellite association pattern of subjects exposed to TCDD. A significant decrease in the satellite association frequency in D group chromosomes was found both in irradiated lymphocytes and in subjects exposed to Dioxin. The findings seem to be in accordance with the hypothesis based on random damage of functional nucleolar organizing regions.     

Use of low-dose insulin infusions in diabetics after myocardial infarction

Myocardial infarction in diabetics is often accompanied by poor diabetic control. An assessment of a low-dose insulin infusion regimen in 26 diabetic patients after myocardial infarction found this system to be simple, effective, and safe.     

Intraspecific interactions and their effect on habitat utilisation by the praying mantid <Emphasis Type="Italic">Ciulfina biseriata</Emphasis> (Mantodea: Liturgusidae)

Tree trunks are spatially separated habitat patches for the tree-running mantid Ciulfina biseriata (Mantodea: Liturgusidae). This paper investigates how intraspecific interactions may affect spacing patterns in C. biseriata. Many mantid species inhabit tree trunk surfaces, but little is known about how they interact with this type of habitat. Behavioural observations and choice tests investigated the effect of a conspecific on habitat utilisation. Field surveys were used to investigate patterns of movement in the field. The decision to inhabit a tree trunk may be affected by the presence of a conspecific. Whereas adult males seek out females when selecting habitat, females will actively avoid males. Habitat choice decisions are primarily based on aspects of their mating system rather than on competition for space or food resources. The behavioural interactions of C. biseriata are described, including novel observations of same-sex mating behaviour in adult males.