Association between clinical symptoms and lymphocyte abnormalities in a population with chronic domestic exposure to industrial solvent-contaminated domestic water supply and a high incidence of leukaemia

Summary An unusually high incidence of leukaemia and recurrent infections was noted in children exposed in utero to domestic water supply contaminated with industrial solvents including trichloroethylene, perchloroethylene and 1,2-transdichloroethylene. Medical and laboratory investigations were carried out on 28 family members of the patients with leukaemia with particular emphasis on the immunological system to determine if they displayed symptoms associated with acute or chronic exposure to these chlorinated hydrocarbons. The principal organ systems affected were neurological, immunological and cardiological. Damage to these systems was found in all subjects by history, physical and laboratory parameters. Damage to the immunological system was manifest by altered ratios of T lymphocyte subpopulations, increased incidence of auto-antibodies, increased infections and recurrent rashes.     

How does protein folding get started?

Three models for the initiation of protein folding are considered in the light of recent experiments. The three models emphasize the possible roles of: (1) a hydrophobic collapse, (2) formation of secondary structure, or (3) formation of one or more specific interactions. Whether these models are likely to be contradictory or complementary is discussed.     

Purification and initial characterization of an enzyme with deacetoxycephalosporin C synthetase and hydroxylase activities.

Deacetoxycephalosporin C synthetase (expandase) from Cephalosporium acremonium (Acremonium chrysogenum) was purified to near homogeneity as judged by SDS/polyacrylamide-gel electrophoresis. The enzyme (Mr about 40,000) exhibited a pH optimum around 7.5. It required 2-oxoglutarate (Km 0.04 mM), Fe2+ and O2 as cofactors, and ascorbate and dithiothreitol were necessary for maximum activity. It was stable for over 4 weeks at -70 degrees C in the presence of 1 mM-dithiothreitol. Activity was inhibited by the thiol-quenching reagent N-ethylmaleimide, the metal-ion-chelating reagent bathophenanthroline, and NH4HCO3. The highly purified enzyme also showed deacetoxycephalosporin C hydroxylase (deacetylcephalosporin C synthetase) activity, indicating that both expandase and hydroxylase activities are properties of a single protein. These activities could not be separated by ion-exchange, dye-ligand, gel-filtration or hydrophobic chromatography. A beta-sulphoxide and a 3 beta-methylene hydroxy analogue of penicillin N were synthesized to test as potential intermediates in the ring-expansion reaction, Neither compound was a substrate for the enzyme. A synthetic analogue in which the 3 beta-methyl group and the 2-hydrogen atom of penicillin N were replaced by a cyclopropane ring was not a substrate but was a reversible inhibitor of the enzyme.     

Selection of synchronous bacterial cultures by density sedimentation.

A procedure previously used to select synchronous cultures of Chlorella was found to produce similar results with the bacterium Lineola longa (Bacillus macroides). A midlog culture of L. longa was layered onto a 31-42% dialyzed Ficoll gradient and ceitruged at 51 000 3 g. The culture sedimented into a broad band in 30 min. Continued centrifugation failed to cause further migration. Cells taken from the top of the band and reinoculated into the broth in which they had previously grown, pH adjusted to 7.0, grew without a lag, doubled in optical density at the same rate as midlog cultures, and divided synchronously. Coulter counter sizing of these cells showed a doubling in volume just before division followed by a halving of volume after division. The major advantages of this method are the low osmolarity of Ficoll and the large volume of cells that can be separated.     

Iterative computation of metabolic flux and stoichiometric parameters for alternate pathways in rumen fermentation.

A model is presented which has been derived to compute the end-products of rumen fermentation from knowledge of the input of feedstuff. The model comprises a set of algebraic equations for the fermentation of each of the following feedstuff components: soluble sugars, starch, cellulose, hemicellulose and protein. The equations were derived from known biochemical stoichiometric relationships. A iterative, non-linear least sqares method (steepest descent) was used to estimate parameter values. In a sample run the inputs used were from an experiment where eight sheep were fed white clover. The model predicted values were in good agreement with the experimental values.     

Effect of the substitution Ala----Gly at each of five residue positions in the C-peptide helix

The substitution Ala----Gly has been studied in a unique-sequence peptide (related in sequence to the C-peptide of ribonuclease A) to determine its effect on C-peptide helicity at different residue positions. There is a substantial decrease in helicity for Ala----Gly at residue position 4, 5, or 6 but only a small decrease in helicity for Ala----Gly at end residue 1 and no decrease at end residue 13. The change for Ala----Gly is similar at position 4, 5, or 6; the change is caused chiefly by the difference in s, the helix growth parameter in the Zimm-Bragg model for alpha-helix formation, between Ala and Gly. Thus, the helicity of C-peptide depends sensitively on s at interior positions. The small change in helicity found for Ala----Gly at either end position suggests that the end residues are largely excluded from the helix, with the result that helicity is relatively unaffected by replacement of an end residue. Another possibility is that some helix-stabilizing effect is exerted by Gly only at an end position. Exclusion of an end residue from the helix might be caused either by fraying of the helix ends or by helix termination at an interior residue, resulting from a helix stop signal such as the Glu-2- -Arg-10+ salt bridge or the Phe-8-His-12+ ring interaction.     

Simultaneous Loss of Proteinase- and Lactose-Utilizing Enzyme Activities in Streptococcus lactis and Reversal of Loss by Transduction

During studies on spontaneous loss of lactose metabolism in Streptococcus lactis C2, it was found that the lactose-negative (lac(-)) mutants were also proteinase negative (prt(-)). This pleiotropic effect was observed in S. diacetilactis 18-16, but not in S. cremoris B1. The lac(-)prt(-) mutants from S. lactis C2 were able to grow in milk, but no pH change or measurable protein breakdown occurred. When the milk was supplemented with glucose, a slow decline in pH occurred. Addition of a protein hydrolysate to milk did not stimulate acid production. When both supplements were added to milk, normal growth and pH change were obtained. When the lac(-)prt(-) mutant of S. lactis C2 was transduced with the temperate phage from the lac(+)prt(+) parent culture, approximately equal numbers of lac(+)prt(-) and lac(+)prt(+) transductants were obtained. When the spontaneous lac(+)prt(-) strain of S. lactis C2 was converted to a lac(-)prt(-) derivative and transduced, similar results were obtained. The co-transduction of the lactose and proteinase markers suggest they are closely associated. The findings indicate that the transducing phage from S. lactis C2 can be used to examine the causes of instability in both the lactose and proteinase enzyme systems of this organism.