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Biomedical subjects

M Roberts

Publications and source records attributed to M Roberts.

At least 289 records · Page 16Linked to original sources
PubMed1984

Black fertility patterns--Cape Town and Ciskei.

The reproductive and contraceptive experience of 491 Black women in urban and rural areas (Cape Town and Ciskei) is presented. The 'average woman' in the sample was 31 years old and first became pregnant by the age of 19,8 years; she had had 3,5 pregnancies, 2,9 living children and wished for 3,9 children. Family size was related to the level of education, degree of urbanization and age of the mother. A sizeable minority of the women experienced at least 1 miscarriage or the death of at least 1 child. Most of the women (65,5%) used some method of contraception between pregnancies, and 57% were using contraception when interviewed. All but 20,7% of those using contraception were receiving an injectable progestogen (Depo-Provera). In urban areas a significant minority used oral contraceptives or sterilization for contraception. Very few women used an intra-uterine contraceptive device. The results of our survey suggest that it is more difficult for the poor to maintain their desired family size. There is a need for family-planning services to be accessible to all, and especially to teenagers. The strongest motivation for a decrease in family size probably results from the settled family life and job opportunities which characterize urban life.

Adolescent↗
PubMed1984

Anomalous expression of the E. coli lac operon in Proteus mirabilis. I. Effects of L8 and L8 UV5.

The lac operon shows anomalous expression in Proteus mirabilis: the maximal induced level is 10% or less of that in E. coli, while repression reduces this by a factor of only 2-5. We have sought to determine whether this effect relates in any way to CRP-mediated activation of expression, by comparing expression in P. mirabilis of lac operons (introduced for technical reasons on IncP1 plasmids) either regulatorily wild-type or bearing L8 or L8UV5. Derivatives of RP1 bearing L8UV5 were obtained by homogenotisation of pGC9114 (RP1::Tn951) in a L8UV5 background; while derivatives of RP4 bearing lac+, L8 or L8UV5 were obtained by Mu-mediated translocation of chromosomal regions bearing these alleles, following partial heat-induction of Mucts62 on pGM14 (RP4::Mucts62) in the appropriate hosts. These plasmids could be readily transferred to, and stably maintained in, the P. mirabilis strains employed. It was found that L8 reduced the maximal level of beta-galactosidase activity, and L8UV5 restored this activity to around wild-type, in P. mirabilis quantitatively very much as in E. coli. Nevertheless, the low maximal level of expression and high basal level characteristic of the former host were unchanged. The simplest explanation of these results is that P. mirabilis contains a protein that mimics the E. coli CRP protein in interacting with the appropriate DNA binding site and thereby stimulating transcription; and that the anomalous regulation of lac in this host is unconnected with the CRP system.

Escherichia coli↗
PubMed1984

Anomalous expression of the E. coli lac operon in Proteus mirabilis. II. Effects of lacI and lacP mutations.

The lac operon introduced into Proteus mirabilis shows two anomalies of expression: the maximal induced level is reduced by about an order of magnitude, and the basal level becomes about 100 times higher than in E. coli, as a result of which the induction ratio appears very small, around 2-5 in contrast to as much as 1000 in E. coli. It was suggested by Baumberg and Dennison (1975) that the two anomalies might be manifestations of a single effect whereby some exogenous promoters give poor expression in this host, since they could result from poor expression of the lacZYA and lacI promoters respectively. We show here that when the lacP class II promoter mutation L305 was transferred on an F-prime into P. mirabilis, its effect on lac expression was much as in E. coli. However, when Flac bearing the IQ1 up-promoter mutation was introduced into P. mirabilis, the basal level decreased by three orders of magnitude, in accord with poor expression of lacI+ being responsible for the usual low induction ratio. These results are consistent with the hypothesis of Baumberg and Dennison (1975) but do not prove it: poor expression of lacI and/or lacZYA could also result from weak translation initiation, problems of continuation of transcription or translation (e.g. due to pause sequences or differences in codon use), or diminished mRNA stability.

Escherichia coli↗
PubMed1984

IgE against ethylene oxide-altered human serum albumin in patients who have had acute dialysis reactions.

Serum samples obtained from seven hemodialysis patients with immediate-type allergic reactions, from six hemodialysis patients without reactions, and from three nonatopic control subjects were analyzed for IgE against human serum albumin exposed to ethylene oxide (ETO-HSA). ETO is used to sterilize medical equipment like dialyzers that cannot withstand heat sterilization. IgE to ETO-HSA, measured by a polystyrene tube technique was found in six of seven dialysis reactor patients but in only one of six nonreactor patients (p less than 0.05 two-tailed Fisher's exact test). No control sera from three nonatopic individuals had antibody. The reactor patients had 2.0 +/- 8.0 ng (SD) of ETO-HSA bound per milliliter of serum, whereas nonreactor patients had 0.2 +/- 8.0 ng per milliliter bound (p less than 0.05 one-tailed Student's t test on log transformed values). We suggest that there is an association between the presence of IgE to ETO-HSA and immediate-type allergic reactions to dialysis in this group of patients.

Antibody Specificity↗
PubMed1984

Familial idiopathic priapism: a case report.

Idiopathic priapism is a diagnosis made by exclusion of identifiable etiologies and is found in 43 to 58 per cent of the cases. We report a case of priapism that was investigated exhaustively and classified as idiopathic. In addition, 3 brothers also reported similar episodes of priapism. Although a common abnormality exists presumably, we were unable to define an etiology. Therefore, this case was designated as familial idiopathic priapism.

Adult↗
PubMed1984

Activation of pS2 gene transcription is a primary response to estrogen in the human breast cancer cell line MCF-7.

We have shown previously that an increase in the level of accumulated pS2 mRNA is first detectable in MCF-7 cells after 3 hr of estradiol treatment. Using in vitro nuclear run-on transcription with nuclei prepared from MCF-7 cells grown in the presence of estradiol or in estradiol-stripped medium, we demonstrate here that expression of the pS2 gene is controlled by estrogen at the transcriptional level. Induction of transcription is a very early event that is already apparent within 15 min after addition of estradiol to the culture medium. In addition, pretreatment of the cells with the protein synthesis inhibitor cycloheximide does not prevent induction of pS2 gene transcription, indicating that it corresponds to a primary effect of estrogen. The pS2 gene in MCF-7 cells represents a unique example of a human gene whose transcription is directly controlled by estrogen.

Breast Neoplasms↗
PubMed1984

Adherence of Haemophilus influenzae to monkey respiratory tissue in organ culture.

We studied the adherence of Haemophilus influenzae to monkey respiratory mucosa using nasal turbinates maintained in organ culture. Adherence of capsulated and rough strains was not inhibited by monosaccharides, sucrose, human albumin, foetal calf serum or polyribophosphate. However, antisera directed against surface components decreased bacterial adherence. Although variation in adherence capacity in individual strains was observed there was no correlation with capsulation, anatomical site of strain isolation or biotype. Bacterial surface structures other than capsular material appear important in effecting upper respiratory tract colonization.

Animals↗
PubMed1984

Replication, integration and expression of exogenous DNA injected into fertilized eggs of Xenopus laevis.

We have analyzed the fate of circular and linear DNA molecules following microinjection into the cytoplasm of fertilized eggs of Xenopus laevis. Recombinant plasmids containing sea urchin histone genes (pSp 102), Drosophila ADH genes (sAC-1), and SV40 (SV2 CAT) replicate during the development of the injected frog embryo. In contrast, pBR322 either as monomers or multimers does not appear to replicate as efficiently. Generally, injected circular DNAs were not detectable by the gastrula stage of development, although there were several examples in which these molecules persisted until larval stages. In 90% of the cases, injected linear DNAs persisted as discrete molecules into early embryonic stages. A portion of the DNA sequences complementary to injected linear and circular molecules was detected comigrating with the high-molecular-weight cellular frog DNA (48 kb or larger) from mid-cleavage stages onward. Restriction enzyme analysis of DNA from injected embryos suggested some copies of the injected DNAs were integrated into the frog genome. This occurred in about 10%-30% of the cases of injected circular DNA and approximately 60%-70% of the cases of injected linear DNA. We were able to rescue circular plasmids from the injected blastulae by retransforming Escherichia coli. Restriction enzyme analysis of this DNA suggested that the majority of injected circular DNAs were not modified following replication in the frog embryo. The DNA of Xenopus embryos was highly methylated. On the other hand, injected DNA sequences were not methylated de novo even after many replication cycles in the frog embryo. Ribonucleic acid (RNA) transcripts from the injected DNAs were detectable by the late blastula stage of development.

Animals↗
PubMed1984

The reproducibility of hemodynamic, electrocardiographic, and gas exchange data during treadmill exercise in patients with stable angina pectoris.

Fourteen male patients with exercise test-induced angina and ST-segment depression underwent treadmill testing on three consecutive days to evaluate the reproducibility of certain treadmill variables. Computerized ST-segment analysis and expired gas analysis, including anaerobic threshold, were evaluated for reproducibility using an intra-class correlation coefficient analysis. Measured oxygen uptake at peak exercise displayed better reproducibility than total treadmill time, the onset of angina, and the gas exchange anaerobic threshold (ATGE). The double product, heart rate, and ST-segment displacement in lead X were found to be reproducible at peak exercise, the onset of angina, and the ATGE. The incorporation of gas exchange analysis can provide accurate physiologic determinants of exercise capacity in patients with angina pectoris. In addition, noninvasive estimates of myocardial oxygen demand and ischemia can be reproducibly determined. These findings have important implications for the design of studies evaluating the effects of an intervention on angina pectoris.

Adult↗
PubMed1984

Breast cancer: views of general practitioners on its detection and treatment.

A considerable proportion of women with breast cancer in this country present for treatment in late stages of the disease; Britain's primary health-care system means that in most cases the possible diagnosis of breast cancer is first made in general practice. This offers ample opportunity for early diagnosis and a better understanding about the way the general practitioners perceive the problems associated with the disease. With that specific aim, the present article reports on a survey conducted simultaneously in Oxford and in Edinburgh. Results show that general practitioners in the survey are deeply concerned about breast cancer and see a definite role for themselves in its early detection and long-term management. They also see a need for more health education that includes the encourgement of breast self-examination programmes. Most are in favour of open-access breast clinics for women and, in general, they feel positive about self-education programmes.

Adult↗
PubMed1983

Transmission of integrated sea urchin histone genes by nuclear transplantation in Xenopus laevis.

Sea urchin histone genes contained in a recombinant plasmid pSp102 were microinjected into the cytoplasm of fertilized eggs of Xenopus laevis. By the late blastula stage, plasmid DNA sequences were detected comigrating with the high molecular weight cellular DNA (greater than 48 kilobases). Analysis of the DNA from injected embryos digested with various restriction endonuclease demonstrated that the injected DNA was integrated into the frog genome. Clones of embryos containing the pSp102 DNA sequences were produced by means of nuclear transplantation. Individuals of the same clone contain the pSp102 sequences integrated into similar chromosomal locations. These sites vary between different clones.

Animals↗
PubMed1983

Genetic control of drug resistance: assignment of ama-1 to Chinese hamster chromosome 7, confirmation of assignment of genes coding for TK, GALK, and ACP to chromosome 7, and tentative assignment of TPI to chromosome 8.

The gene which specifies a subunit of RNA polymerase II, ama-1, is assigned to chromosome 7 in the Chinese hamster. The assignment of genes coding for TK, GALK, and ACP to chromosome 7 is confirmed, with a provisional regional assignment of TK and GALK to 7q. On the basis of one clone with six subclones, a provisional assignment of TPI to Chinese hamster chromosome 8 is made. With the assignment of tk and ama-1 to chromosome 7 in the CHO cell line Ama1, this chromosome is shown to have two selectable markers.

Acid Phosphatase↗
PubMed1983

The relationship of total serum IgE and blocking antibody in trimellitic anhydride--induced occupational asthma.

Clinical and immunologic evaluations were performed on workers who manufacture trimellitic anhydride (TMA), a chemical used widely in the plastics industry. Serum samples of 29 workers exposed to TMA dust and fumes were assayed for total IgE, as well as specific IgE and total antibody binding to radiolabeled trimellityl human serum albumin (TM-HSA). Fifteen workers were determined to have significant specific IgE to TM-HSA (greater than or equal to 1 ng of 125I-TM-HSA bound per milliliter). Of these 15 individuals, seven workers had immediate asthma and rhinitis and positive cutaneous prick tests and eight were nonasthmatic and skin test negative. Mean peak total serum IgE was significantly higher in the prick test positive group (p less than 0.02) and higher than in 12 exposed asymptomatic IgE antibody-negative workers (p less than 0.001). Total serum IgE followed rises and falls in TM-HSA--Specific IgE binding, correlating to the onset of allergic symptoms in all seven workers. Total antibody binding of 125I-TM-HSA, as determined by the ammonium sulfate precipitation technique, was higher in the skin test-negative group of eight (mean 12,062 ng per milliliter 125I-TM-HSA bound) than in the seven symptomatic skin test-positive workers (mean 2930, p less than 0.004). Determinations of total antibody divided by specific IgE (both in nanograms of 125I-TM-HSA bound per milliliter) or blocking ratios clearly discriminated the seven skin test-positive workers with TMA-induced asthma (range 10 to 666) from the eight skin test-negative workers (range 1580 to 16,000).(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies↗
PubMed1983

Assignment of the native Chinese hamster dihydrofolate reductase gene to chromosome 2.

The native Chinese hamster DHFR gene was localized to 2pter----q14 using a combination of somatic cell hybrid technology and molecular techniques. In addition, PGD, ENO1, and DTS, previously mapped to Chinese hamster chromosome 2, were localized to 2q14----qter. Localization of PGM1 to this region was confirmed. The relationship of the site of the native DHFR gene to the location of the homogeneously staining region in methotrexate-resistant cells is discussed.

Animals↗
PubMed1983

A radioimmunoassay index for allergic bronchopulmonary aspergillosis.

Differentiating patients with allergic bronchopulmonary aspergillosis from those with asthma who have immediate cutaneous reactivity to Aspergillus fumigatus may be difficult. Both groups have IgE and IgG antibodies against aspergillus antigen. We describe methods for establishing IgE and IgG antibody indices using sera from asthmatic patients as a control serum pool. The IgE and IgG antibody indices are usually both positive and at least one index was positive in all patients during the acute stage. The indices had diagnostic value in individual patients during the other four stages, but were not consistently positive in patients in any other stage. In a patient with a suspected case, serodiagnosis should be attempted before corticosteroid therapy is started; thus, acute-phase serum should be obtained and stored before therapy.

Acute Disease↗
PubMed1983

Dissociation of IgE from receptors on human basophils. I. Enhanced passive sensitization for histamine release.

Leukocytes of only one of 11 nonatopic donors could be passively sensitized for histamine release elicited by ragweed extract. A short incubation in an unbuffered isotonic saline at pH 3.9 or in an 0.01 M lactic acid/lactate-buffered isotonic saline at pH 3.9 dissociated from 4 X 10(5) to less than 3 X 10(4) IgE molecules per basophil from washed leukocytes of several in a series of six atopic and 11 nonatopic donors. After such treatment, leukocytes of only one of the 11 nonatopic donors could not be sensitized for histamine release. Basophils of the four ragweed-sensitive donors lost their sensitivity to ragweed after the treatment, but all could be passively resensitized; for three of these donors the level of release approximated their original reactivity. Leukocytes of the two mold-sensitive donors could be passively sensitized to ragweed allergens after but not before treatment. Four plasma samples from histamine release-positive volunteers were used for sensitization of treated leukocytes of each cell donor; three were consistently effective and one was consistently ineffective. The positive plasmas had concentrations of antigen E-specific IgE of over 100 ng/ml, which accounted for 17 to 23% of the total IgE; the inactive one had less than 5 ng/ml of specific IgE. For each cell donor, all three samples of active plasma mediated quite similar histamine release, but there was a spectrum of donor cell reactivity ranging from 23 to 70% release. These results suggest that basophils from each donor, atopic or nonatopic, had a maximal potential for in vitro sensitization, which was only attained if the plasma contained appropriate, but yet to be fully defined, concentrations of specific and total IgE. Several unexpected results were obtained. Treated leukocytes from some individuals were sensitized for mediator release to a greater extent by sixfold diluted than undiluted plasma. In addition, a 4-hr incubation with plasma at 37 degrees C, but not at 25 degrees C or 0 degrees C, was less effective than were shorter incubation periods. Treated leukocytes should be useful in studying kinetic and equilibrium parameters of IgE binding to specific receptors on human basophils. Analogous treatments should also be useful in sensitization and measurement of IgE-receptor interactions of mast cell populations.

Basophils↗