Stressful life events and affective illness.

OBJECTIVE: To investigate the association between the occurrence of affective illnesses and the number/type of experienced negative stressful life events in a twin material. A case-control study with an unrelated twin as control to the case and a co-twin control study were both undertaken with the same material. METHOD: Postal questionnaire responses were used for confirming diagnosis and to inventory stressful life events. Risk ratios (RR) for groups of events were calculated using conditional logistic regression. RESULTS: A dose-response relationship was observed for the association between stressful life events and affective illness. The RRs for specific groups of exposures were higher in the co-twin control study and higher for dizygotic twin pairs than for monozygotic twin pairs. CONCLUSION: Individuals with a history of affective illness select themselves into high-risk environments, in part due to their genetic propensity to the disease. Thus, the association represents a classic genotype-environment correlation.

Identification and sequence of a nifJ-like gene in Rhodospirillum rubrum: partial characterization of a mutant unaffected in nitrogen fixation.

A nifJ-like gene was identified in the photosynthetic purple non-sulphur bacterium Rhodospirillum rubrum. A DNA segment hybridizing to Klebsiella pneumoniae nifJ was isolated, the gene was inactivated, and a mutant strain, SNJ-1, was constructed by allele replacement. The mutation was confirmed by DNA sequencing. Northern blotting and by the lack of pyruvate oxidoreductase activity. This is the first report of a nifJ-like gene in photosynthetic bacteria. Unexpectedly, SNJ-1 was capable of nitrogen fixation, and growth was similar to the wild-type strain under all conditions investigated. Therefore, this is also the first demonstration that a nifJ homologue, when present, is not essential for nitrogen fixation in a diazotroph. The nifJ-like gene was sequenced and found to have considerable similarity to published nifJ gene sequences from other organisms. By primer extension, the initiation site for transcription was located, and a typical sigma 54 promoter sequence was identified.

Purification and partial characterization of a pyruvate oxidoreductase from the photosynthetic bacterium Rhodospirillum rubrum grown under nitrogen-fixing conditions.

A pyruvate oxidoreductase with the capacity to support pyruvate-dependent nitrogenase activity in vitro has been purified from the photosynthetic bacterium Rhodospirillum rubrum. The enzyme requires CoA for activity and is irreversibly inactivated by oxygen. The molecular properties and Km values for the substrates have been studied. In supporting nitrogenase activity addition of ferredoxin is required. Overall the enzyme is similar to the nif-specific pyruvate: flavodoxin oxidoreductase purified from Klebsiella pneumoniae.

Characterization of prolactin immunoreactivity in human cerebrospinal fluid.

Immunoreactive prolactin has been recovered from human cerebrospinal fluid (CSF) by hydrophobic interaction chromatography on Phenyl-Sepharose CL-4B and molecular sieving on Sephadex G-100. The hormone was obtained in a yield of about 1 microgram/liter CSF and was further analyzed by column electrophoresis on granular agarose at different pHs. All separation procedures were guided by radioimmunoassay. Upon chromatography on Sephadex G-100, the CSF prolactin coeluted with a pituitary reference preparation (molecular weight, 22,000 Da). A further relationship between the CSF prolactin and the pituitary hormone was demonstrated by the electrophoretic experiments. Thus, at alkaline pH, both preparations resolved into 3 or 4 active components, whereas only a single peak was observed in each preparation following runs performed at acidic pH. The results suggest that the prolactin activity present in the CSF specimens is identical with the hormone derived from the pituitary.