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Biomedical subjects

A M Johnson

Publications and source records attributed to A M Johnson.

At least 271 records · Page 15Linked to original sources
PubMed1990

Evaluation of a nonisotopic probe for detection of Chlamydia trachomatis in endocervical specimens.

A nonisotopic probe (Gen-Probe PACE; Gen-Probe, Inc., San Diego, Calif.) for detection of Chlamydia trachomatis in endocervical specimens was evaluated in 344 women attending a dysplasia clinic or an obstetrics clinic and 158 women who visited an emergency room. For each patient, the probe, a tissue cell culture, and a direct immunofluorescent-antibody test (DFA; MicroTrak; Syva Co., Palo Alto, Calif.) were used. C. trachomatis was detected in 54 specimens by at least one method. Forty-four, 44, and 37 specimens were positive by culture, probe, and DFA, respectively, and 31 were positive by all three methods. Considering culture-positive plus both probe- and DFA-positive results as the "gold standard," we determined the overall sensitivity, specificity, and positive and negative predictive values of the probe to be 80, 98, 82, and 98%, respectively. These values were 94, 98, 84, and 99%, respectively, in emergency room patients and 71, 98, 80, and 97%, respectively, in clinic patients. The sensitivities, specificities, and negative predictive values of the DFA and probe were comparable. The positive predictive values of the DFA in all patients and in emergency room and clinic patients were 97, 100, and 95%, respectively. Given the number of probe-positive results that were not confirmed by culture, we do not recommend using the Gen-Probe PACE to screen for C. trachomatis in women with a low to moderate risk for infection.

Cervix Uteri↗
PubMed1990

A study of humor and the right hemisphere.

65 male and 65 female subjects rated 32 jokes for funniness and solved 14 visually displayed mental-rotation problems. Subjects with faster mental-rotation times tended to rate the jokes as funnier, which is consistent with previous evidence implicating the right hemisphere in the processing of humor. The hypothesis that right-hemisphere processing speed or problem-solving ability are the common factors in mental rotation and humor processing is discussed. Furthermore, sex differences suggest that gender-differentiating preferences for type of humor and mental-rotation abilities may involve basic cognitive functions.

Adult↗
PubMed1990

The speed of mental rotation as a function of problem-solving strategies.

40 subjects solved seven identical and seven mirror image visually-displayed mental-rotation problems, a measure of right hemisphere processing. Subjects who indicated that they had inferred that, if two objects were not identical, then they must be mirror images showed faster rotation times. This evidence supports the hypothesis that expedient problem-solving strategies may contribute to right-hemisphere processing speed as measured by mental rotation. That mental rotation and humor processing may draw on the same right hemisphere processes is also discussed.

Adult↗
PubMed1990

Prevalence of Toxoplasma gondii antibodies in dingoes.

Serum samples from 62 dingoes (Canis familiaris dingo) trapped in five areas of southeastern New South Wales, Australia were tested for antibodies to Toxoplasma gondii. Six (10%) of the dingoes had direct agglutination test titers for T. gondii of greater than or equal to 1:64, and four of these animals had T. gondii-specific IgM, suggesting recent exposure.

Agglutination Tests↗
PubMed1990

Cigarette smoking-associated changes in blood lipid and lipoprotein levels in the 8- to 19-year-old age group: a meta-analysis.

In this meta-analysis it was demonstrated that, when compared with nonsmokers of similar age, smokers in the 8- to 19-year-old age group have significantly higher serum levels of triglyceride (+11.8%), very-low-density lipoprotein (VLDL)-cholesterol (+12.4%) and low-density lipoprotein (LDL)-cholesterol (+4.1%) and significantly lower serum levels of high-density lipoprotein (HDL)-cholesterol (-8.5%) and total cholesterol (-3.7%). All of these smoking-associated changes are in the same direction as those found in adults, with the exception of total cholesterol levels, which are significantly increased in adult smokers. The extent to which mean triglyceride, LDL-cholesterol, and HDL-cholesterol levels are shifted is significantly greater in the 8- to 19-year-old smokers than in adult smokers. The changes in mean total cholesterol levels among smokers in both age groups represent only the net shifts in the lipoprotein fractions and are therefore likely to be a less sensitive indicator of the possible lipid-related excess coronary artery disease risk in smokers.

Adolescent↗
PubMed1989

Cloning, expression and nucleotide sequence of the gene fragment encoding an antigenic portion of the nucleoside triphosphate hydrolase of Toxoplasma gondii.

Toxoplasma gondii expresses high levels of an active nucleoside triphosphate hydrolase (NTPase; EC 3.6.1.3) with several unique properties. It has been detected as a circulating antigen in mice, making it an ideal candidate for diagnostic tests for toxoplasmosis. A cDNA library constructed from T. gondii poly(A)+RNA was made in lambda gt11. One hundred thousand members of this library were immunoscreened with a rabbit polyclonal antibody to the purified NTPase. Six positive clones were subcloned into the plasmid, pGEX-IN, and the inserts were restriction-mapped. All clones had identical partial restriction enzyme maps. One insert was subcloned into M13mp18 and sequencing by the deoxy/dideoxy method showed an NTPase-encoding gene (ntp) fragment of 571 bp. The insert was also purified, radiolabelled, and used to hybridize to Northern blots of tachyzoite RNA and quantitative Southern blots of tachyzoite DNA. Northern blotting revealed that the NTPase mRNA was in great abundance and had a length of about 2800 nucleotides. Southern blotting showed a gene copy number of between one and five, and the possibility that ntp is tandemly repeated over a large length of DNA. The NTPase was expressed as a glutathione S-transferase (EC 2.5.1.18) fusion protein of about 50 kDa, which reacted with polyclonal rabbit antibody on Western blotting.

Amino Acid Sequence↗
PubMed1989

Evidence for recent changes in sexual behaviour in homosexual men in England and Wales.

Over 80% of cases of Acquired Immune Deficiency Syndrome (AIDS) in England and Wales have occurred in homosexual men. Changes in sexual behaviour in this group may have a substantial influence on the incidence of Human Immunodeficiency Virus (HIV) infection and will therefore be crucial in determining future cases of AIDS. This paper critically weighs the indirect and direct evidence for changes in behaviour in homosexual men since the advent of the AIDS epidemic. The paper reports on falling incidence of gonorrhoea, hepatitis B and syphilis in homosexual men, the changes being most marked from 1985 onwards. Data on temporal trends in HIV prevalence and incidence in homosexual men are reviewed. These suggest that the maximum incidence of HIV infection occurred in 1982-84 and may have fallen since then. Evidence for a concomitant change in sexual behaviour is reported from several sources. This points towards a recent change in sexual behaviour characterized by reduction in the numbers of partners and adoption of safer sexual practices. In some places change may have occurred as early as 1983. A change became apparent generally in 1985 and this appears to have been sustained in 1986-87. Nevertheless, a substantial proportion of homosexual men studied continue to practice high risk sexual practices, such as anal intercourse, including relationships with casual partners.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Risk behaviours for HIV infection among injecting drug users attending a drug dependency clinic.

To study a range of possible risk factors for HIV among injecting drug user patients attending a clinic in London were interviewed from November 1986 to November 1987. Serum samples were tested for viral markers. Of 116 patients, 101 had shared injecting equipment, 75 on the first occasion of injecting and 76 during the past year. Seventy said that sharing was because equipment was not available. In the past year 102 had been sexually active, a third having two to 20 partners; a quarter of the women had exchanged sexual intercourse for money. The four patients who were positive for antibody to HIV antigen had shared equipment or had intercourse with drug users from areas with a high prevalence of HIV. Eleven patients had injected drugs while in prison. Despite a low prevalence of HIV infection this infection remains a threat to drug users in London; strenuous efforts are still needed to prevent its further transmission.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Haemolytic activity of Campylobacter pylori.

The haemolytic activity of several clinical and reference strains of Campylobacter pylori was determined using cell-free preparations of broth-grown organisms and human, horse, guinea pig, rabbit and sheep erythrocytes. Significant levels of haemolysis were produced only when the cell-free preparations were concentrated tenfold. However, three of 14 strains still gave haemolysis values of less than 50% when tested with guinea pig erythrocytes. Significant haemolytic activity could not be demonstrated with preparations derived from bacteria cultured on solid medium. Irrespective of the strain examined or the type of preparation, strong urease activity was demonstrable. Purified urease had no effect on erythrocytes, and thiourea failed to inhibit the haemolytic activity of Campylobacter pylori cell-free preparations. It was concluded that ureolytic activity was not implicated in the lysis of erythrocytes, either by direct action or via the generation of ammonia. Furthermore, the haemolytic activity produced by Campylobacter pylori was found to be due to a secreted factor, possibly a haemolysin.

Animals↗
PubMed1989

Gastrotracheal fistula: a late complication after transhiatal esophagectomy.

A 51-year-old woman underwent a transhiatal esophagectomy for a failed antireflux procedure. She did well for 15 months, when she developed evidence of hemoptysis followed by tracheogastric fistula. She underwent operative repair with the use of a pericardial patch to replace the membranous trachea and interposition of a latissimus dorsi flap to isolate the stomach from the tracheal suture line. She has done well after this operation.

Esophagus↗
PubMed1989

Blastocystis hominis: phylogenetic affinities determined by rRNA sequence comparison.

In 1912 Blastocystis hominis was identified as a new species and classified as a yeast (Brumpt 1912). In the early 1920s several groups confirmed its classification as a yeast, specifically a member of the genus Schizosaccharomyces (discussed by Zierdt et al. 1967). Apart from an occasional case report, the classification of B. hominis and its role as a harmless intestinal yeast was not questioned for another 50 years. Then, Zierdt (1967) suggested that it should be classified in the phylum Protozoa, subphylum Sporozoa, and that it should be considered as a potential pathogen. The likely role of B. hominis as a human pathogen has recently become more firmly established (Garcia et al. 1984; Sheehan et al. 1986) and its classification has been changed. Although the classification of B. hominis as a protozoon was assumed widely, classification as a sporozoon was not accepted, and the most recent definitive classification of the Protozoa did not even list B. hominis (Lee et al. 1985). Then, based essentially on a review of the known characteristics of the organism, it was recently reclassified into the subphylum Sarcodina (Zierdt 1988). Clearly, the phylogeny of this emerging human pathogen needs definitive analysis (Mehlhorn 1988).

Animals↗
PubMed1989

Rapid ribosomal RNA sequencing and the phylogenetic analysis of protists.

A newly described technique for rapidly obtaining the partial nucleotide sequence of ribosomal RNA is being applied to investigate phylogenetic relationships among living organisms. Alan Johnson and Peter Boverstock describe the importance of this method to parasitology in providing new information on the phylogenetic relationships of parasitic organisms previously placed in groups of convenience. The phylum Apicomplexo in particular, has been the object of much study using this technique, but the technology is likely to extend soon to the restructuring of the phylogenetic trees of many groups of parasites.

Journal Article↗
PubMed1989

Serodiagnosis of acute toxoplasmosis in macropods.

The sera of 34 Australian macropods, the brains of which had been bioassayed for Toxoplasma gondii, were used to establish that a titre greater than 1/32 was significant for a direct agglutination test against toxoplasmosis. In addition, the concentration of 2-mercaptoethanol required to destroy the IgM fraction of macropod serum was confirmed in a modified direct agglutination test. To further validate the tests, the serological responses of three eastern grey kangaroos (Macropus giganteus) dosed orally with T. gondii oocysts and one M. giganteus injected with T. gondii cysts were studied. The tests were then used to investigate a diagnosis of acute toxoplasmosis in four Tasmanian pademelons (Thylogale billardierii) clinically suspected of acquiring toxoplasmosis naturally. One hundred and fifty-one Bennett's wallabies (Macropus rufogriseus rufogriseus) and 85 T. billardierii were also tested to determine the prevalence of acute toxoplasmosis of macropods in the wild. Four percent of M. r. rufogriseus and 1.2% of T. billardierii possessed T. gondii-specific IgM in their sera.

Acute Disease↗
PubMed1989

The clinical utility of renal concentrating capacity in polycystic kidney disease.

We studied 177 adult nonazotemic subjects with autosomal dominant polycystic kidney disease (ADPKD) and 123 unaffected family members (NADPKD). In order to assess the factors influencing renal concentrating capacity maximal urinary osmolality (UOsm) after overnight water deprivation and vasopressin was measured. UOsm was reduced in ADPKD (680 +/- 14) compared to NADPKD subjects (812 +/- 13 mOsm/kg). A greater severity of the architectural abnormality as assessed by cyst number and size and remaining volume of normal parenchyma was associated with a greater impairment of renal concentrating capacity. The concentrating defect was present in the youngest ADPKD subjects and the rate of decline of concentrating capacity with age in ADPKD paralleled that in NADPKD subjects. Based on the initial 135 subjects studied, we developed an algorithm for diagnostic screening for ADPKD utilizing blood pressure, serum creatinine and UOsm designed to maximize sensitivity. When applied to a subsequent population of 165 adults, 121 with ADPKD and 44 unaffected relatives, this algorithm would have spared 20% of unaffected subjects from the cost of ultrasound while failing to detect less than 2% of affected subjects. This simple protocol thus offers a rapid and inexpensive way to screen for ADPKD.

Adult↗
PubMed1989

srRNA evolution and phylogenetic relationships of the genus Naegleria (Protista: Rhizopoda).

A rapid RNA sequencing technique was used to partially sequence the small-subunit ribosomal RNA (srRNA) of four species of the amoeboid genus Naegleria. The extent of nucleotide sequence divergence between the two most divergent species was roughly similar to that found between mammals and frogs. However, the pattern of variation among the Naegleria species was quite different from that found for those species of tetrapods characterized to date. A phylogenetic analysis of the consensus Naegleria sequence showed that Naegleria was not monophyletic with either Acanthamoeba castellanii or Dictyostelium discoideum, two other amoebas for which sequences were available. It was shown that the semiconserved regions of the srRNA molecule evolve in a clocklike fashion and that the clock is time dependent rather than generation dependent.

Animals↗
PubMed1989

A pilot study of sexual lifestyle in a random sample of the population of Great Britain.

Rates of sexual-partner change and patterns of high-risk behaviour are important determinants of the spread of HIV. We carried out a survey to assess the feasibility of studying sexual lifestyle in a random sample of the British population, aged 16-64 years, in November 1987. Two thousand and seventy-seven households were selected using a multi-stage probability sampling procedure. Seven hundred and eight-five adults participated in a structured interview. The schedule included demographic details, attitudes to AIDS, numbers of sexual partners in different time periods, history of homosexuality and contact with prostitutes. An interview was obtained in 61% of households where contact was made, but the overall response rate was low (48%). There was marked variability between individuals in numbers of sexual partners in given time intervals. Men and women in younger cohorts had experienced first sexual intercourse earlier and had higher numbers of sexual partners than people in older cohorts. Surprisingly few reported high-risk behaviour such as homosexuality and use of prostitution. The methodological problems in trying to obtain unbiased and valid data on sexual behaviour are discussed. Further work is necessary to improve the response rate and questionnaire design.

Adolescent↗