Inheritance of quantitative expression of erythrocyte glucose-6-phosphate dehydrogenase activity in the Negro—a twin study

Studies have been conducted on eight sets of monozygous and nine sets of dizygous female Negro twins, both members of whom were heterozygous for G-6-PD deficiency. Twins were studied both by assay of erythrocytic G-6-PD activity and by the methemoglobin elution test (MET). The MET is a procedure which identifies histochemically cells with appreciable G-6-PD activity and permits accurate determination of the percentage of such cells in heterozygotes. Monozygous twins showed significantly less within-pair variation than dizygous twins with both the MET and G-6-PD assay.Concerning the significantly greater agreement in MET results in monozygous twins than dizygous twins, our present working hypothesis is that X-chromosomal inactivation in the Negro female is genetically controlled, rather than random. However, certain alternate hypotheses allowing for random X-inactivation have not been excluded; these include somatic cell selection after random X-inactivation, and cell exchange between identical twins in utero/it. Studies in nontwin related heterozygotes now underway should help differentiate among these various possibilities.In addition to the studies on 17 pairs of female twins heterozygous for G-6-PD deficiency, 26 pairs of nondeficient female Negro twins have been studied by G-6-PD assay. Within-pair variation in monozygous twins was significantly less than within-pair variation in dizygous twins in all cases. The genetic influences detected with the G-6-PD assay in the female twins could theoretically be due to nonrandom X-inactivation, to genetically determined quantitative differences in enzyme activity (e.g., isoalleles), or to both. By appropriate calculations, based on the MET results, we have factored out the effects of X-inactivation on overall enzyme activity in the heterozygous deficient twins. After removal of the effect of X-inactivation, monozygous twins heterozygous for enzyme deficiency continue to show significantly less within-pair variation than dizygous twins. This finding indicates significant genetic influences on quantitative G-6-PD activity other than X-inactivation and other than the deficiency allele. This conclusion has been strengthened by studies on male twins where X-inactivation is not present.Supported by USPHS research grants AM-09381, HE-17544, AM-09919, and HE-03341, by USPHS Career Development Award 1-K3-AM-7959 (Dr. Brewer) and by U.S.A.E.C. Contract (11-1)-1552.     

The Influence of Morphology on Prognosis in Acute Leukemia

The presence of definite cytoplasmic granulation in at least some of the malignant cells was used as the sole criterion to separate 156 patients with acute leukemia into two groups: 110 with myeloblastic (AML), and 46 with lymphoblastic or stem cell leukemia (ALL). The median survival from the onset of symptoms in patients with AML was 20 weeks, and those with ALL 37 weeks. The difference in survival in these two groups is much greater for patients under the age of 25 than for those over the age of 25.     

U-21,963, a New Antibiotic: II. Isolation and Characterization

The isolation and characterization of antibiotic U-21,963 are discussed. This compound is a highly unsaturated monobasic acid with the molecular formula C(9)H(7)NO(3). The molecular weight is 177. It is dextrorotatory, [alpha](D) = +138 degrees , and has a pK(a) of 5.1. The ultraviolet absorption spectrum, which showed a maximum at 223 mmu (epsilon = 15,115), indicates unsaturation alpha-beta to the carboxyl group, and the infrared spectrum suggests the presence of an acetylenic group. Explosive decomposition of U-21,963 at 97 C conforms with the latter. U-21,963 is relatively insoluble in water, but readily soluble in ethyl alcohol, acetone, and halogenated hydrocarbons.     

Resonance Raman studies of iron spin and axial coordination in distal pocket mutants of ferric myoglobin

We have used resonance Raman spectroscopy to study 11 distal pocket mutants and the "wild type" and native ferric sperm whale myoglobin. The characteristic Raman core-size markers v4, v3, v2, and v10 are utilized to assign the spin and coordination state of each sample. It is demonstrated that replacements of the distal and proximal histidines can discriminate against H2O as a sixth ligand and favor a pentacoordinate Fe3+ atom. Soret absorption band blueshifts are correlated with the pentacoordinate heme environment. One E7 replacement (Arg) leads to an iron spin state change and produces a low spin species. The Glu and Ala mutations at position E11 leave the protein's spin and coordination unaltered. A laser-induced photoreduction effect is observed in all pentacoordinate mutants and seems to be correlated with the loss of the heme-bound water molecule.     

IgG-dependent generation of platelet-activating factor by normal and low density human eosinophils

We have compared normal and low density human eosinophils for their ability to generate platelet activating factor (PAF) in response to IgG-dependent and nonimmunologic stimulation. After 45 min incubation with IgG-coated Sepharose beads the concentrations of cell-associated PAF recovered from normal density eosinophils were significantly greater than from low-density eosinophils or neutrophils. Moreover, eosinophils stimulated with calcium ionophore A23187 had a considerably greater capacity to generate PAF than had previously been described. Although the quantities of cell-associated PAF recovered from normal and low density eosinophils and neutrophils after A23187 stimulation were similar, the amounts of extracellular PAF recovered from both eosinophil populations were significantly greater than from neutrophils. The amounts of PAF recovered from the low density eosinophils may not reflect the full synthetic capacity of these cells, because PAF-turnover was found to be more rapid than that observed with normal density eosinophils. When exogenous [3H]PAF was added to the two stimulated eosinophil populations subsequent analysis of the [3H]PAF metabolites by DIOL-HPLC revealed that low density eosinophils incorporated PAF into the phosphatidylcholine (PC) pool more rapidly than did normal density eosinophils or neutrophils. Alkaline hydrolysis of the PC fraction from whole cell extracts followed by treatment with acetic anhydride resulted in all the PC-associated radioactivity being converted to [3H]PAF, confirming PAF incorporation to PC via this pathway. These findings suggest that the contribution of eosinophils to inflammatory processes through the generation of PAF may be greater than previously appreciated, and that Ig-mediated stimulation may be important in initiating generation of the mediator. Low density eosinophils, that are presumed to be similar to tissue eosinophils, may have a role in regulating PAF concentrations in tissues through their enhanced rate of metabolism.     

Presymptomatic testing for Huntington's disease

Summary Presymptomatic testing for Huntington's disease (HD) is possible through the use of restriction fragment length polymorphisms (RFLPs) at the closely linked D4S10 locus. Recombination between the HD and D4S10 loci will occur in 4%–5% of meioses, and is a well-recognised complication of predictive testing. Recombination between RFLPs within the D4S10 locus is a rare event and can usually be ignored. We report a case where such an intra-locus recombination frustrated attempts to predict the chance of a high-risk individual inheriting the HD gene.     

An evolutionary relationship between the ColE5-099 and the ColE9-J plasmids revealed by nucleotide sequencing

The nucleotide sequence of a 1124 bp fragment of the ColE5-099 plasmid which encodes colicin E5 immunity, a lys gene involved in colicin release from the host cell, and the 3' end of the colicin E5 structural gene has been determined. Open reading frames corresponding to the three genes have been located by analogy with similar sequences from other E colicin plasmids. The location of these open reading frames corresponds with the position of the genes as determined by subcloning and transposon mutagenesis. The amino acid sequence of the carboxy-terminal 107 amino acid residues of the colicin E5 gene shows no homology with any other E colicin, suggesting a different mode of action in killing sensitive cells. A comparison of the nucleotide sequence of this region of the ColE5-099 plasmid with that of the equivalent region of the ColE9-J plasmid suggests a close evolutionary relationship between these two plasmids.     

Eradication of ear mites from naturally infested conventional research rabbits using ivermectin

Rabbits naturally infested with ear mites were treated with ivermectin injection for cattle, subcutaneously at the rate of 400 mcg/kg; which was repeated in 15 to 17 days. Rabbits treated as described and housed in a conventional vivarium environment were found to be free of mites during a subsequent 33 to 139 day observation period. Side effects were minimal and associated with occasional transient discomfort at the injection site. Ivermectin appears to be safe and effective for treating rabbits with ear mites. The prospects of eradicating mites from infested rabbit colonies using this method of treatment is promising.