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Biomedical subjects

S Johnson

Publications and source records attributed to S Johnson.

At least 469 records · Page 26Linked to original sources
PubMed1985

Laboratory monitoring of rubella.

A study was undertaken to determine the level of immunity to rubella in the population on the basis of findings in serum specimens sent to the laboratory of the National Institute for Virology. A total of 4791 sera taken between August 1982 and October 1983 were examined for rubella-specific IgG antibodies by enzyme-linked immunosorbent assay (ELISA). A disquietingly high proportion (18,4%) of women of child-bearing age were not immune; 59 cases of primary infection occurred in pregnant women, as documented by the presence of rubella-specific IgM antibodies on ELISA. The need to ensure the protection of susceptible women of child-bearing age by prepubertal immunization and screening for immunity is emphasized.

Adult↗
PubMed1985

Electrophysiological and neurochemical correlates of the neurotoxic effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on central catecholamine neurons in the mouse.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is an agent which produces a parkinsonian syndrome in man. To explore the use of MPTP in a rodent model of parkinsonism, male albino mice (NMRI) were given MPTP (50 mg/kg, s.c.) twice with a 6-8 h interval. Up to 10 weeks after injection, mice were killed and high-pressure liquid chromatography was used to assay dopamine (DA) and noradrenaline (NA) concentrations in various regions of the CNS. At 4 and 10 weeks after injection, DA levels were significantly reduced in occipital cortex (-40%), hippocampus (-30%), and striatum (-60%). NA levels were reduced by 60-80% in frontal and occipital cortex, hippocampus, and cerebellum. Neither DA nor NA concentration was reduced in spinal cord. Dopaminergic denervation was also suggested by electrophysiological data which showed that treatment with MPTP increased the spontaneous discharge rate of caudate neurons and decreased the potency of locally administered phencyclidine, an indirect DA agonist. However, denervation was evidently not complete enough to produce postsynaptic receptor supersensitivity, as MPTP treatment did not increase the potency of locally applied DA, and it did not increase 3H-spiperone binding in striatal membrane preparations. These results suggest that MPTP causes regionally selective and long-term reductions of catecholamine transmission in the CNS of the mouse.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1985

Reinnervation of dopamine-denervated striatum by substantia nigra transplants: immunohistochemical and electrophysiological correlates.

This study evaluated whether or not fetal substantia nigra tissue, grafted to striatum previously lesioned with 6-hydroxydopamine, provides functional dopaminergic reinnervation of striatum. Falck-Hillarp histochemistry and immunofluorescent staining for tyrosine hydroxylase demonstrated extensive networks of nerve fibers which extended 1-1.5 mm from the nigral grafts into striatal tissue. Multibarrel micropipettes were used to record neurons electrophysiologically and test neuronal responses to phencyclidine which was applied locally by pressure microejection. "Distal" neurons, defined as those striatal neurons more than 2.0 mm from the nigral graft, fired at an average spontaneous rate of 13.4 spikes/s and were relatively insensitive to the effects of locally applied phencyclidine. However, "proximal" neurons, defined as those neurons less than 1.0 mm from nigral grafts, fired at a significantly lower average rate of 4.9 spikes/s, and were significantly more sensitive than distal neurons to the effects of phencyclidine. These results suggest that fetal substantia nigra grafts can provide functionally significant reinnervation of striatum previously lesioned with 6-hydroxydopamine.

Animals↗
PubMed1985

Stress management training as a prevention program for heavy social drinkers: cognitions, affect, drinking, and individual differences.

The effectiveness of cognitive-affective stress management training (SMT) as a drinking reduction program for heavy social drinking college students was investigated. The SMT package included muscle relaxation and meditation training, cognitive restructuring, and coping skill rehearsal during induced affect. Treated and control subjects rated the frequency and intensity of their anxiety, anger and depression and recorded their alcohol consumption on a daily basis over a 6-month period. SMT significantly reduced posttreatment daily anxiety ratings and was associated with changes in four of ten irrational beliefs and a shift toward more internal locus of control in treated subjects. Reduction in anxiety was no longer evident at the 2 1/2- and 5 1/2-month follow-ups. The men in the SMT group showed a significant decrease in daily drinking rates at posttreatment and at the 2 1/2-month follow-up, but drinking returned to baseline levels by 5 1/2 months for the group as a whole. However, significant improvement variance in daily moods and in drinking rates over all posttreatment periods was accounted for by individual difference variables in the trained subjects but not in the control group, suggesting that these cognitive, personality, and social support variables are associated with response to stress management training. Implications of these results for future prevention research are discussed.

Adult↗
PubMed1985

Epidemic Coxsackie B virus infection in Johannesburg, South Africa.

A particularly extensive epidemic of Coxsackie B3 virus infection occurred in Johannesburg in the spring and summer of 1984. A total of 142 positive cases were diagnosed by isolation of the virus from stools and other specimens (60) or by serology (82). Coxsackie B3 accounted for 87% of the isolations and was also the dominant serotype on serology. The outbreak involved predominantly children and young adults, with no apparent sex differences being noted. The majority of specimens came from the white population and no significant difference in age or sex distribution could be observed between the two race groups. The major clinical presentation in the white group was Bornholm disease followed by cardiac involvement and then meningoencephalitis. In the black group, however, myocarditis was the major clinical presentation, which is of particular interest taking into account the extremely high incidence of acute rheumatic carditis in this population and the prevalence of chronic cardiomyopathy.

Age Factors↗
PubMed1984

Acyclovir in cytomegalovirus infection 3 1/2 years after renal transplantation. An unusual case and dramatic response.

Late cytomegalovirus (CMV) infection in renal allograft recipients is uncommon. The treatment of CMV infection is controversial, with numerous claims of successful treatment with different drugs. We report the successful use of acyclovir in a serious case of CMV infection occurring in a young woman 3 1/2 years after a renal transplant. This result is encouraging and supports the future use of acyclovir in the treatment of CMV infection in this and other settings.

Acyclovir↗
PubMed1984

Effects of phosphorylation of avian retrovirus nucleocapsid protein pp12 on binding of viral RNA.

The major nucleocapsid protein of avian retroviruses, pp12, preferentially binds to the single-stranded regions of 60 S viral RNA with a apparent binding constant (Kapp) of 1.2 X 10(11) M-1. If the phosphate associated with serine residues of pp12 is hydrolyzed by either alkali treatment or with partially purified phosphoprotein phosphatase activities isolated from virions, the Kapp for binding to 60 S RNA decreases 100-fold. The high affinity binding of pp12 to viral RNA can be restored by phosphorylation of the protein with a protein kinase, protease-activated kinase I. The same serine residues phosphorylated in vivo are phosphorylated by protease kinase I in vitro. These residues have been identified as serine residues 40 and either 76 or 77. The protein purified from virions is phosphorylated primarily at serine residue 40 (greater than 90%). This suggests that phosphoserine residue 40 is responsible for modulating the binding of the protein to RNA. Thus, the phosphorylation state of pp12 can be reversibly altered in vitro resulting in the interconversion of the protein between a state of high and low affinity for single-stranded viral RNA.

Avian Leukosis Virus↗
PubMed1984

Application of recombinant DNA technologies to studies on chicken growth hormone.

Messenger RNA isolated from chicken pituitaries was used to construct a chicken pituitary cDNA library. A chicken growth hormone cDNA clone was isolated using 32P-labeled mammalian growth hormone cDNA probes. The amino acid sequence (derived from the DNA sequence) of the mature form of chicken growth hormone shows 77% homology with that of bovine growth hormone. The chicken growth hormone cDNA clone was used to generate a vector capable of producing chicken growth hormone in Escherichia coli. The recombinant E. coli-derived chicken growth hormone was similar to pituitary chicken growth hormone in several biochemical and immunological properties. The recombinant-derived hormone has been used to establish a sensitive radioimmunoassay for growth hormone determinations made from chicken sera. The chicken growth hormone gene has also been introduced into a retroviral vector capable of establishing productive infections of chicken cells both in in vitro and in vivo. The resulting infections are accompanied by the production of radioimmunoassay-detectable growth hormone. The concentrations of growth hormone in sera of Leghorn chickens infected with the recombinant retrovirus are three- to tenfold higher than in control animals.

Amino Acid Sequence↗
PubMed1984

Poliomyelitis outbreak in South Africa, 1982. I. Epidemiology.

An epidemic of type 1 poliomyelitis in Gazankulu, which is a self-governing National State in the north-eastern part of South Africa, is described. 260 cases of paralytic poliomyelitis, included 42 deaths, were recorded between 1st May and 3rd September 1982. 92% of cases, who were all admitted to hospital, were in the age group 0 to 5 years. The vaccination status of cases was found to be low: 69% said they had received no vaccination and a further 15% were unsure. Recommendations on the steps to be taken to prevent a recurrence can be gleaned from the discussion in Part II of this article, Laboratory and vaccine aspects (see pp. 24-29 below).

Adolescent↗
PubMed1984

Poliomyelitis outbreak in South Africa, 1982. II. Laboratory and vaccine aspects.

Between May and September 1982 an extensive epidemic of poliomyelitis occurred in Gazankulu in the north-eastern region of South Africa, with a total of 260 paralysed cases and 42 deaths. A three-part study was instituted, the first of which established the aetiological agent of the epidemic to be poliovirus type 1. This was determined initially by serology and later by isolation of the virus, chiefly from stool specimens. The potency of the trivalent oral polio vaccine manufactured at the National Institute for Virology, was evaluated in the second study by in vitro potency testing of samples recalled from the epidemic areas and also in vivo by determining the serological response of seronegative children immunized with fresh vaccine. Nearly half of the vaccine samples withdrawn from the field had sub-optimal titres whereas fresh vaccine produced a very satisfactory serological response. In order to plan immunization rationally, the third study, namely the determination of the immune status of the various populations throughout the country was instituted. This involved both serology, using a neutralization test on randomly collected sera and also an analysis of patient history and health card documentation. With the exception of the urban black area (Soweto), which had high levels of immunity both serologically (75%) and on history, other areas examined had poorer levels of immunity of approximately 52% on serological testing and 57% on history. It is clear that the epidemic was multifactorial in origin, with fall-offs in the level of immunization and evidence of breaks in the cold chain being the major factors.

Antibodies, Viral↗
PubMed1984

Tissue distribution and toxicity of cyclosporin A in the mouse.

Groups of mice were given cyclosporin A (CyA) subcutaneously for 6 wk at a dose of 12.5, 50 or 200 mg/kg/d. After 7, 21 and 42 days of CyA administration the CyA content of serum, thymus, mesenteric lymph nodes, spleen, kidney, liver, lung, small and large intestine and brain was measured, each organ was examined histologically, and the total viable nucleated cell content of thymus, mesenteric lymph nodes, spleen and femoral marrow was analysed. CyA was detected in every organ assayed at each concentration of CyA administered. The mean concentration of CyA per organ was consistently highest in organs of mice given CyA 200 mg/kg/d and lowest in those given 12.5 mg/kg/d at each time point, but there was pronounced variability in the concentration of CyA between individual mice. Repeated administration of CyA after the first week did not further elevate CyA tissue concentrations. At doses of 50 or 200 mg/kg/d CyA caused weight loss, diarrhea, intussusception and fatal neurotoxicity. In addition, the spleen, thymus and mesenteric lymph nodes of mice given CyA 50 or 200 mg/kg/d were hypocellular and disorganized, and all lymphoid organs contained numerous pyknotic lymphocytes. The liver showed fatty change and the kidney degeneration of proximal tubules. Femoral marrow showed enlarged and congested sinuses. No abnormalities were noted in mice given CyA 12.5 mg/kg/d.

Animals↗
PubMed1984

Chronic adaptations to physical conditioning in cardiac patients. Implications regarding exercise trainability.

Physical conditioning in patients with coronary heart disease can result in increased functional capacity, symptomatic relief of angina pectoris, favorable reduction of risk factors, enhanced psychological status, and improved quality of life. The mechanisms underlying the adaptations to training are poorly understood, but it is clear that several factors affect exercise trainability. Guidelines are available that suggest the appropriate intensity, frequency, and duration of exercise needed to obtain beneficial physiologic adaptations.

Adaptation, Physiological↗
PubMed1984

Cardiac exercise programs: role of continuous electrocardiographic monitoring.

The purpose of the present study was to determine the value of telemetry monitoring for detection of new and significant electrocardiographic (ECG) or blood pressure abnormalities during outpatient cardiac exercise therapy. Following preliminary graded exercise testing, 177 cardiac patients underwent a four-week monitored exercise program three days per week. During 2248 training sessions, 12 of the 177 patients (7%) showed significant ECG or blood pressure abnormalities not evident on initial exercise testing, eight (5%) requiring change in medical therapy. Abnormalities included significant (greater than 2mm) ST-T displacement (two patients), ventricular arrhythmias (seven patients), and hypertensive exercise response (three patients). Eleven of the abnormalities (92%) appeared during the first three weeks of the program. Results indicated that continuous ECG and blood pressure monitoring offered a small but significant diagnostic yield not evident on preliminary graded exercise testing. One-year experience suggested that short-term (four weeks) exercise monitoring may be adequate for cardiac patients who undergo careful preliminary screening.

Adult↗