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Biomedical subjects

B Johnson

Publications and source records attributed to B Johnson.

At least 235 records · Page 13Linked to original sources
PubMed1990

A deletion linked to a poly(ADP-ribose) polymerase gene on chromosome 13q33-qter occurs frequently in the normal black population as well as in multiple tumor DNA.

The nuclear enzyme poly(ADP-ribose) polymerase (PADPRP) is thought to play a role in DNA recombination, replication, and repair. In view of the implication of these processes in tumorigenesis, and based on preliminary evidence which indicated the presence of an extraneous polymorphic restriction fragment for murine PADPRP loci in strains of mice susceptible to plasmacytomas, we investigated correlations between the restriction fragment length polymorphism of the PADPRP gene(s) and human Burkitt lymphoma. No increase in the frequency of polymorphisms on chromosome 1 (containing the active gene) or on chromosome 14 (a pseudogene) was observed. However, restriction fragment length polymorphism analysis of PADPRP sequences on chromosome 13 (either a processed pseudogene or a gene with extensive identity to PADPRP) revealed that of 19 DNA samples derived from endemic Burkitt lymphoma all contained at least one copy of a rare allele (B). Simple two-allele (A/B) polymorphisms in this PADPRP-like locus were identified by digestion with a number of restriction enzymes including HindIII, PstI, KpnI, and MspI. These restriction fragment length polymorphisms always segregated together, suggesting that they identify a deletion within or close to the PADPRP sequences on chromosome 13, which we mapped precisely to 13q33-qter. Based upon family studies the A and B alleles were shown to be transferred in a Mendelian codominant fashion. Subsequently, this probe was used as a linkage marker to study the frequency of this deletion in various tumors including B-cell follicular lymphomas, small cell lung carcinomas, breast carcinomas, and colorectal carcinomas. In noncancer control populations, the frequency of this deletion was 3-fold higher among Blacks as compared to Caucasians. When DNA from various tumors was compared to normal DNA from racially appropriate noncancer controls, the frequency of this deletion was still 2- to 3-fold higher in the tumor DNA. Matched samples provided instances of tumor-specific loss of heterozygosity but also revealed that the predominant source of this deletion is the germ line, suggesting that the chromosome 13 region neighboring the PADPRP locus may harbor a gene whose loss may predispose individuals to malignancy.

Alleles↗
PubMed1990

Primary sequence of the EcoRII endonuclease and properties of its fusions with beta-galactosidase.

The EcoRII endonuclease cleaves DNA containing the sequence CC(A/T)GG before the first cytosine. The methylation of the second cytosine in the sequence by either the EcoRII methylase or Dcm, a chromosomally coded protein in Escherichia coli, inhibits the cleavage. The gene for the EcoRII endonuclease was mapped by analysis of derivatives containing linker insertions, transposon insertions, and restriction fragment deletions. Surprisingly, plasmids carrying the wild-type endonuclease gene and the EcoRII methylase gene interrupted by transposon insertions appeared to be lethal to dcm+ strains of E. coli. We conclude that not all the EcoRII/Dcm recognition sites in the cellular DNA are methylated in dcm+ strains. The DNA sequence of a 1650-base pair fragment containing the endonuclease gene was determined. It revealed an open reading frame that could code for a 45.6-kDa protein. This predicted size is consistent with the known size of the endonuclease monomer (44 kDa). The endonuclease and methylase genes appear to be transcribed convergently from separate promoters. The reading frame of the endonuclease gene was confirmed at three points by generating random protein fusions between the endonuclease and beta-galactosidase, followed by an analysis of the sequence at the junctions. One of these fusions is missing 18 COOH-terminal amino acids of the endonuclease but still displays significant ability to restrict incoming phage in addition to beta-galactosidase activity. No striking similarity between the sequence of the endonuclease and any other protein in the PIR data base was found. The knowledge of the primary sequence of the endonuclease and the availability of the various constructs involving its gene should be helpful in the study of the interaction of the enzyme with its substrate DNA.

Amino Acid Sequence↗
PubMed1990

Molecular mapping of deletion sites in the short arm of chromosome 3 in human lung cancer.

We used 10 restriction fragment length polymorphism (RFLP) probes spanning the length of the short arm of chromosome 3 (3p) to map deletion sites in human lung cancer. Two approaches were used. 1) When a patient's tumor and normal tissue were available, loci with allelic heterozygosity in the normal tissue were tested for loss of alleles at 3p. 2) When the corresponding normal tissue was not available, the frequency of heterozygosity at each locus in a panel of tumors was compared to the corresponding published frequencies in nontumor tissue of healthy individuals or patients with lung cancer. In 14 small cell lung carcinomas (SCLC) with normal DNA for comparison, allele loss was found at all heterozygous loci, with one exception at a locus near the 3p centromere (D3S4). In the total of 53 SCLCs, which included tumors without paired normal tissue, frequency of heterozygosity was significantly reduced in all 10 3p loci. Three loci, DNF 15S2, RAF1, and D3S18, were homozygous in all tumors in the SCLC panel. These loci, which are in regions 3p21 and 3p25, may thus be involved in the origin or evolution of SCLC. We also investigated 24 non-SCLC tumors. In this panel, frequency of heterozygosity was significantly reduced at seven of the 10 loci tested. Comparison of the results shows that the pattern of allele loss on 3p is different in SCLC and non-SCLC, suggesting a difference in pathogenesis at the genetic level.

Alleles↗
PubMed1990

Effects of methyldopa on psychometric performance.

Double-blind, crossover comparisons of methyldopa with placebo were performed in 16 patients with mild to moderate hypertension. Methyldopa (250 mg tid) for 14 days significantly reduced blood pressure, impaired card-sorting time and digital symbol substitution score, and caused trends for impairment of other psychometric tests. Effects of practice were greater than those of treatment on all tests other than card sorting, although no interaction between treatment and practice was seen. Continued dosage impairs psychometric performance, but practice effect is a major confounder. Simple crossover studies are inadequate for detecting moderate drug effects on intellectual performance.

Adult↗
PubMed1990

Use of multiple dipole analysis for the classification of benign rolandic epilepsy.

The clinical literature has suggested that while the clinical features and presentation of benign rolandic epilepsy in children (BREC) are known, the neuronal mechanism of the epileptic focus is poorly understood. Classification of clinical subtypes is usually made by determining whether there are supplementary clinical signs of brain damage, in which case the epilepsy is classified as non-benign or "atypical". Studies of EEG findings in BREC have suggested that the source of the epilepsy is in the Rolandic fissure. We investigated dipole source modelling in 24 children, comparing the results of one and two dipole models. The results indicate that atypical BREC patients have a more complex distribution of dipoles and that single dipole fits may be more predictive of typical BREC than multiple dipole fits. The implications of these results are discussed.

Brain Mapping↗
PubMed1990

Exploratory factor analysis of a sixty-item questionnaire concerned with fear of dental treatment.

701 dental-school outpatients rated the degree of fear occasioned by each of 60 events that occur routinely during dental treatment. The 4,206 ratings then were subjected to principal components factor analysis with oblique rotation. Four meaningful factors were deduced: fear of pain and its antecedents, anticipatory fear, fear of negative evaluation, and fear due to perceived absence of control over the dentist. This outcome is compared and contrasted with results of other attempts to delineate the components of dental fear.

Adult↗
PubMed1990

Evaluation of substance-abusing adolescents by primary care physicians.

Physicians are in a unique position to identify substance-abusing adolescents. To evaluate physician performance from the patient's perspective, we interviewed 54 substance-abusing adolescents and their parents about previous medical encounters. Although nearly all patients had seen a physician during the time they were using drugs or alcohol, 43% did not recall being asked by a doctor about alcohol or drug use. Of the 26 patients who recalled being asked, 12 (46%) stated that they responded dishonestly, usually because a parent was present. Of the 23 who didn't recall being asked, five (18%) wished they had been asked. Physicians tended to ask about substance abuse more often (p = .08) when they had previously discussed the problem with the parents, but many parents did not initiate such discussions. This survey suggests that physicians may not adequately assess high-risk adolescents for substance abuse because of physician-, patient- and/or parent-dependent factors.

Adolescent↗
PubMed1990

A model for group research by master's degree RNs in advanced roles.

Master's prepared RNs in advanced roles are ideally prepared to do clinical nursing research. Yet lack of time, resources, and a paucity of confidence have limited such scholarly pursuits among nurses in specialty roles. The article describes a group process by which five Master's prepared nurses (three clinical specialists, two Nursing Educators) successfully investigated and implemented a Nurse Research Interest Group (NRIG). The facilitators and obstacles are described as well as the past, present, and future activities of this group.

Clinical Nursing Research↗
PubMed1990

Outbreak of Bacillus Calmette-Guérin-associated lymphadenitis and abscesses in Jamaican children.

An outbreak of axillary lymphadenitis and abscesses after Bacillus Calmette-Guérin (BCG) vaccination (Pasteur Paris, Batch N5122) occurred in 139 Jamaican children between January and July, 1988. The overall rate of this complication was 0.95%. The attack rate was 1.92% among the 0- to 6-week age group and 0.6% in the 7- to 52-week age group. Of 139 patients there were 77 males and 62 females and the mean age at presentation was 4 months. The mean size of the BCG scar, duration of healing and Mantoux reaction size differed significantly in patients compared with those of control infants (P less than 0.01). Mycobacterium bovis was isolated from 11 patients. Immunologically index patients and controls differed significantly only with respect to T lymphocyte subpopulation percentages and concanavalin A stimulation indices. Evaluation of the BCG vaccine did not reveal either increased potency or microbial contamination. We conclude that increased susceptibility to the Pasteur strain of BCG might have contributed to the increased incidence of complications in these Jamaican children and hence caution should be exercised in switching one vaccine for another as is often done in the developing countries.

Abscess↗
PubMed1990

An in vivo study of neutrophil locomotion in relation to periodontal disease status and local chlorhexidine.

Neutrophil migration from skin window abrasions was studied in 10 patients with no history of periodontitis, 10 with localised juvenile or post-juvenile periodontitis, and 10 with chronic adult periodontitis. Filters contained either saline or chlorhexidine (0.002% or 0.02%). The leading front was measured in filters placed for 30 min after cell migration had been established for 2 h. Subjects in the juvenile/post juvenile group showed a reduced range of migration distances, but were still within the normal range when compared with the other 2 groups. Chlorhexidine at 0.002% tended to increase leading front distances, and 0.02% to decrease them. We conclude that: 1) migrating neutrophils in vivo may move less far in patients with a history of juvenile periodontitis; 2) chlorhexidine may inhibit cell migration, possibly decreasing the host response in vivo if applied at current therapeutic concentrations.

Adolescent↗
PubMed1990

Quantitative relationship between anticapsular antibody measured by enzyme-linked immunosorbent assay or radioimmunoassay and protection of mice against challenge with Streptococcus pneumoniae serotype 4.

We have recently shown that a substantial proportion of antibody to pneumococcal polysaccharide as measured by enzyme-linked immunosorbent assay (ELISA) or radioimmunoassay is removed by adsorption with pneumococcal cell wall polysaccharide (CWPS). The present study was undertaken to validate the hypothesis that only serotype-specific antibody that remains after adsorption with CWPS provides protection against pneumococcal infection. Serum samples were obtained from human subjects before and after they had been vaccinated with pneumococcal polysaccharide vaccine. Antibody to Streptococcus pneumoniae serotype 4 was measured by ELISA without adsorption or after adsorption of serum with CWPS. Groups of mice were injected with graded doses of serum and then challenged intraperitoneally with 10, 100, or 1,000 50% lethal doses (LD50) of S. pneumoniae serotype 4. Without adsorption, prevaccination sera from five healthy adults appeared to contain up to 33 micrograms of antibody to S. pneumoniae serotype 4 antigen per ml; adsorption with CWPS removed all detectable antibody, and pretreating mice with up to 0.1 ml of these sera (less than or equal to 3.3 micrograms of antibody) failed to protect them against challenge with 100 LD50. In contrast, postvaccination sera contained 2.9 to 30 micrograms of antibody per ml that was not removed by adsorption. Diluting sera to administer desired amounts of serotype-specific immunoglobulin G showed a significant relationship between protection and antibody remaining after adsorption (P less than 0.05 by linear regression analysis); 150 ng was uniformly protective against 1,000 LD50, and 50 ng was protective against 100 LD50. These studies have, for the first time, quantitated the amount of serotype-specific antibody that protects mice against challenge with S. pneumoniae type 4. In light of these observations, it is necessary to reassess current concepts regarding the presence of antipneumococcal antibody in the unvaccinated population, responses to pneumococcal vaccination, and protective levels of immunoglobulin G.

Adult↗
PubMed1990

Dietary modification with dairy products for preventing vertebral bone loss in premenopausal women: a three-year prospective study.

The effect of dietary calcium on vertebral bone mass in women is controversial. In a randomized study we have investigated the effect of dietary modification in the form of dairy products on vertebral bone mass in 30- to 42-yr-old premenopausal women over a 3-yr period. Twenty women increased their dietary calcium intake by an average of 610 mg/day (P less than 0.03) for 3 yr, while 17 age- and weight-matched women served as controls. Calcium intake was monitored by 3-day diet histories and 24-h urinary calcium excretion. The consumption of the dairy products did not alter serum calcium or PTH levels or the fasting urinary calcium to creatinine ratio. Twenty-four-hour urinary calcium excretion increased by 28% (P less than 0.03) in the supplemented women. Dairy product intake was accompanied by increased dietary fat intake, but there were no statistically significant changes in serum cholesterol, low density lipoprotein cholesterol, or high density lipoprotein cholesterol levels. The vertebral bone density in the women consuming increased calcium did not change over the 3-yr period (-0.4 +/- 0.9%). In contrast, the vertebral bone density in the control women declined (-2.9 +/- 0.8%; P less than 0.001) and was significantly lower than that in the supplemented group at 30 and 36 months. The study suggests that dietary modification in the form of dairy products retards vertebral bone loss in premenopausal women. Therefore, increased calcium intake in estrogen-replete premenopausal women may prevent age-related bone loss.

Adult↗
PubMed1989

Chlamydia trachomatis infections--the Royal Women's Hospital experience.

During the 18-month period from December 1, 1985 to May 31, 1987 Chlamydia trachomatis was the most-common sexually-transmitted agent to be identified at the Royal Women's Hospital, Melbourne. It was isolated from 4% of all specimens for which such culture was requested and was found five-times more frequently than was Neisseria gonorrhoeae. A review of the clinical presentation and the management of the 100 public patient for this period whose cervical specimens were found to give positive results for the presence of chlamydiae revealed that 77% of the women were less than 25 years of age, 78% of the women were single and 65% of the women were nulliparous. Thirty-five women were asymptomatic carriers of chlamydiae. Of the remaining 65 patients with symptoms, 46% experienced pelvic pain, 39% experienced a vaginal discharge and 26% experienced irregular bleeding. The importance of abnormal bleeding is emphasized. In patients who presented for therapeutic abortions, morbidity occurred in 19% of those who were carriers of Chl. trachomatis; accordingly, screening for chlamydiae as routine is recommended in such patients. Furthermore, because of the risk of pelvic inflammatory disease and its consequences, it is important not only to treat female patients in whom chlamydiae have been isolated, but also to treat and to follow-up their sexual partners simultaneously.

Adolescent↗
PubMed1989

Technique for reconstituting fixed cadaveric tissue.

Dissecting room cadavers used over a prolonged period inevitably become desiccated, especially in well-ventilated surroundings. It is particularly desirable that dissections used for end-of-year examinations be restored to their original condition. We describe here a quick and simple procedure designed to restore neglected specimens to their former condition at dissection. Specimens were either soaked for 24 hr in a standard solution of fabric conditioner or sprayed with the same standard solution. The specimens were then wrapped with muslin soaked in the conditioner and covered with polythene sheeting for 1 week. The results obtained were excellent and much superior to a short soak in water. The results further indicate that this technique may have other applications in the preparation of fixed histological material.

Cadaver↗
PubMed1989

Epidemiology of hepatitis B in eastern Kenya.

A cross-sectional survey of outpatients attending the three distinct hospitals in the towns of Mombasa, Kilifi, and Malindi was conducted to determine the patterns of hepatitis B transmission in eastern Kenya. Of 1,533 study subjects (mean age 21.9 +/- 13.2 years; range, 4 months to 80 years), 11.4% were positive for HBsAg and 56.2% were seropositive for at least one hepatitis B marker (HBsAg, anti-HBs, or anti-HBc). Anti-delta antibody was found in 1.2% of HBsAg-positive samples. HBeAg was found in 36.0% of HBsAg-positive samples obtained from women of childbearing age. The prevalence of seropositivity for hepatitis B markers was positively correlated with age, increasing from 20% in subjects less than 4 years old to more than 80% in study subjects greater than 40 years old. On multivariate analysis, male sex was found to be associated with HBsAg positivity, and age and previous deliveries of children were associated with seropositivity for any hepatitis marker (HBsAg, anti-HBs, or anti-HBc). An effective hepatitis B immunization strategy in this region of Kenya would require vaccination early in life because a major portion of hepatitis B transmission occurs in childhood.

Adolescent↗
PubMed1989

Protooncogene structure in the cancer family syndrome.

Protooncogene loci in constitutional DNA from affected members of a kindred with the cancer family syndrome were studied by Southern blot hybridization analysis. No structural rearrangements or amplification of 16 protooncogenes were detected. These studies demonstrated that gross structural alteration of the tested protoocongenes is not responsible for cancer susceptibility in this syndrome.

Chromosome Mapping↗