F plasmid CcdB killer protein: ccdB gene mutants coding for non-cytotoxic proteins which retain their regulatory functions.

The ccd locus of the F plasmid codes for two gene products, CcdA and CcdB, which contribute to the plasmid's high stability by post-segregational killing of plasmid-free bacteria. Like the quinolones, the CcdB protein is a poison of the DNA-topoisomerase II complexes, while CcdA acts as an antidote against CcdB. In addition to these poison-antipoison properties, the CcdA and CcdB proteins act together at transcription level to repress their own synthesis. In this work, we have isolated, in vivo, and characterized several non-killer CcdB mutants. All missense mutations which inactivate CcdB killer activity are located in the region coding for the last three C-terminal residues. However, the resulting mutant CcdB proteins retain their autoregulatory properties. We conclude that the last three C-terminal residues of CcdB play a key role in poisoning but are not involved in repressor formation.

The antidote and autoregulatory functions of the F plasmid CcdA protein: a genetic and biochemical survey.

The ccd operon of the F plasmid contributes to the high stability of the episome by postsegregational killing of plasmid-free bacteria. It contains two genes, ccdA and ccdB, which are negatively autoregulated at the level of transcription, probably by a complex comprising the two gene products. Using the bacterial gyrA462 CcdB resistance mutation and a Pccd-lacZ transcriptional fusion, we have obtained evidence that the CcdB protein by itself has no regulatory activity or operator DNA-binding affinity and needs CcdA in order to effect transcriptional control. The ccd killing mechanism is based on the poison-antidote principle. The CcdB protein is cytotoxic, poisoning DNA-gyrase complexes, while CcdA antagonizes this activity. In order to define functional domains of the CcdA antidote involved in the anti-killer effect, autoregulation or both, we introduced several missense or amber mutations into the CcdA protein by directed mutagenesis. We report on missense CcdA proteins that have lost their autoregulatory properties but are still able to antagonize the lethal activity of CcdB. We show that the five carboxy-terminal amino acid residues of the antidote protein are not required for the antidote effect or for autoregulation. Several missense CcdA polypeptides were generated by suppression of nonsense codons. Two substitutions lead to CcdB-promoted killing: glutamine 33-->cysteine and glutamine 33-->phenylalanine.

The continuum of care revisited: a rural perspective.

This study examines resource data for a variety of services in North Carolina's continuum of care for older adults. It qualifies the widespread contention that older adults in urban areas receive a greater number and more varied services than their rural counterparts. It also demonstrates that one of the most important differences between these communities is the greater variability of services among rural compared to urban counties. The comparative findings on urban and rural variations in the continuum of care for older adults have implications for further research and future policy development.

Self-help quit smoking interventions: effects of self-help materials, social support instructions, and telephone counseling.

Smokers requesting self-help materials for smoking cessation (N = 2,021) were randomized to receive (a) an experimental self-quitting guide emphasizing nicotine fading and other nonaversive behavioral strategies, (b) the same self-quitting guide with a support guide for the quitter's family and friends, (c) self-quitting and support guides along with four brief counselor calls, or (d) a control guide providing motivational and quit tips and referral to locally available guides and programs. Subjects were predominantly moderate to heavy smokers with a history of multiple previous quit attempts and treatments. Control subjects achieved quit rates similar to those of smokers using the experimental quitting guide, with fewer behavioral prequitting strategies and more outside treatments. Social support guides had no effect on perceived support for quitting or on 8- and 16-month quit rates. Telephone counseling increased adherence to the quitting protocol and quit rates.

A survey of smoking and quitting patterns among black Americans.

A sample of adult Black policyholders of the nation's largest Black-owned life insurance company was surveyed in 1986 to add to limited data on smoking and quitting patterns among Black Americans, and to provide direction for cessation initiatives targeted to Black smokers. Forty per cent of 2,958 age-eligible policyholders for whom current addresses were available returned a completed questionnaire. Population estimates for smoking status agree closely with national estimates for Blacks age 21-60 years: 50 per cent never-smokers; 36 per cent current smokers; 14 per cent ex-smokers. Current and ex-smokers reported a modal low-rate/high nicotine menthol smoking pattern. Current smokers reported a mean of 3.8 serious quit attempts, a strong desire and intention to quit smoking, and limited past use of effective quit smoking treatments and self-help resources. Correlates of motivation to quit smoking were similar to those found among smokers in the general population, including smoking-related illnesses and medical advice to quit smoking, previous quit attempts, beliefs in smoking-related health harms/quitting benefits, and expected social support for quitting. Methodological limitations and implications for the design of needed Black-focused quit smoking initiatives are discussed.

Platelet alpha-adrenergic receptor activity and pizotifen in migrainous children.

Adrenoceptors have been measured in the platelets from migrainous children, using (3H) yohimbine. Maximum binding (Bmax) was not significantly different in migrainous children and controls, 259 +/- 21 and 265 +/- 19 f moles per mg of protein respectively. Dissociation constants (KD) were significantly higher in the migraine group than in the controls 2.62 +/- 0.18 and 2.17 +/- 0.07 respectively (p less than 0.02). Bmax values were lower in 6 out of 9 cases following treatment with pizotifen. In 8 out of 9 cases KD values were lower following pizotifen treatment; in one case there was no change.

The acro-renal syndrome of Curran.

A nine-year-old girl with symmetrical acral deformities and anomalies of the renal tract is described. There have been four previous reports of this association, all in phenotypic males. In each case there was moderate intellectual retardation and in two cases dermatoglyphic analysis revealed abnormalities. It is suggested that there is now sufficient evidence to give the acro-renal syndrome independent status.