Directly observed 15N NMR spectra of uniformly enriched proteins

The proteins cytochrome c2, cytochrome c', and ribulosebisphosphate carboxylase/oxygenase from Rhodospirillum rubrum were enriched in 15N by growth of the organism on 15NH4Cl. The proteins were purified to homogeneity and studied by 15N NMR. Longitudinal and transverse relaxation times as well as the nuclear Overhauser effects were determined for various groups of the proteins which vary in molecular weight from 13,000 to 114,000. The values of these parameters for the amide resonances or for groups thought to be rigid were consistent with the molecular weights of the proteins. Relaxation times of the amino-terminal alpha-amino groups and the side chain nitrogen atoms of arginine and lysine were consistent with much more rapid motion. Nitrogen atoms having bound protons were generally found to be decoupled from the protons by chemical exchange. Demonstrable 1H-15N coupling was taken as an indication that exchange was hindered, either by hydrogen bonding interactions or by inaccessibility of the group to solvent. Histidine side chain nitrogen atoms, which experience a large chemical shift upon protonation/deprotonation, were often found to be broadened beyond detectability by chemical exchange and tautomerization. Strategies for improving sensitivity and for obtaining specific peak assignments are also discussed.     

A small one-band paracentric inversion inv (4) (p15.3p16.3).

A neonate with aniridia was found to have a one band paracentric inversion of the short arm of chromosome 4. This was initially difficult to interpret on high resolution banding. The inversion was present in three generations of the family.     

Characterization of p51/52, a cell-growth regulated protein of WI-38 cells.

A number of proteins have been identified whose expression or activity is regulated by cell growth. We have produced a monoclonal antibody against a new cell-growth regulated protein found in normal human fibroblasts. We have shown that this antibody recognizes a 51/52-kDa doublet (p51/52) found mainly in normal cells. This doublet is sensitive to degradation by the calcium-activated protease, calpain, breaking down to a 37/38-kDa doublet. The relative amount of the two members of the 51/52-kDa doublet changes when serum-starved cells reenter the cell cycle. Quiescent cells express mainly the 51-kDa form; the 52-kDa form becomes more abundant upon refeeding serum-starved cells. Transformed cells express either very small amounts of this doublet, and then predominantly the 52-kDa form, or no detectable amount of either form. These characteristics distinguish this molecule from several other known growth-regulated proteins such as statin and the anti-oncogene p53.     

Cardiopathic effects of dichloroacetate in the fetal Long-Evans rat.

Dichloroacetic acid (DCA) is a by-product of the chlorine disinfection of water and may occur in treated water at levels exceeding 100 micrograms/L. Previous studies revealed teratogenic effects, particularly heart malformations, at high doses (900-2,400 mg/kg given on days 6-15 of pregnancy). In a series of three studies, groups of 7-10 Long-Evans rats were dosed with 1,900 mg/kg of DCA on days 6-8, 9-11, or 12-15; with 2,400 mg/kg on days 10, 11, 12, or 13; and with 3,500 mg/kg on days 9, 10, 11, 12, or 13, in an attempt to determine the most sensitive period and further characterize the heart defect. In a fourth study, six dams were treated with 1,900 mg/kg of DCA days 6-15 of pregnancy, and 56 fetuses were harvested for light microscopy of the heart. Eight control fetuses from four litters were also examined. No heart malformations were seen in the groups treated with 1,900 mg/kg DCA days 6-8 but were present in the group treated on days 9-11 and 12-15, with the higher incidence occurring on days 12-15. Single doses of 2,400 mg/kg DCA given on days 10, 11, 12, or 13 resulted in a much lower incidence of cardiac malformations, which occurred only on days 10 and 12. The high dose of DCA (3,500 mg/kg) did not increase the incidence of heart defects but showed that dosing on day 9 as well as on days 10 and 12 would produce the defect. The defects seen were characterized as high interventricular septal defects (H-IVSD). Light microscopy showed that the defect was caudal to the semilunar valves, with the anterior right wall of the aorta communicating with the right ventricle. Another aspect of the defect is at the level of the semilunar valves, with the right cusp or sinus of Valsalva in communication with the right ventricle. The defects are discussed more fully and methods for further study suggested.     

Two novel loci underlie natural differences in Caenorhabditis elegans abamectin responses

Parasitic nematodes cause a massive worldwide burden on human health along with a loss of livestock and agriculture productivity. Anthelmintics have been widely successful in treating parasitic nematodes. However, resistance is increasing, and little is known about the molecular and genetic causes of resistance for most of these drugs. The free-living roundworm Caenorhabditis elegans provides a tractable model to identify genes that underlie resistance. Unlike parasitic nematodes, C. elegans is easy to maintain in the laboratory, has a complete and well annotated genome, and has many genetic tools. Using a combination of wild isolates and a panel of recombinant inbred lines constructed from crosses of two genetically and phenotypically divergent strains, we identified three genomic regions on chromosome V that underlie natural differences in response to the macrocyclic lactone (ML) abamectin. One locus was identified previously and encodes an alpha subunit of a glutamate-gated chloride channel (glc-1). Here, we validate and narrow two novel loci using near-isogenic lines. Additionally, we generate a list of prioritized candidate genes identified in C. elegans and in the parasite Haemonchus contortus by comparison of ML resistance loci. These genes could represent previously unidentified resistance genes shared across nematode species and should be evaluated in the future. Our work highlights the advantages of using C. elegans as a model to better understand ML resistance in parasitic nematodes.