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Biomedical subjects

M S Smith

Publications and source records attributed to M S Smith.

At least 163 records · Page 9Linked to original sources
PubMed1991

Interference with neural crest migration by maternal hyperthermia as a cause of embryonic death due to heart failure.

Maternal hyperthermia has been demonstrated to be a teratogen in every animal species studied, and a minimum core temperature rise of 2.5 degrees C can produce a number of developmental defects. However, numerous embryos fail to survive to term. In the guinea-pig, heating the embryos prior to neural tube closure induces significant neural tube defects, but all embryos die within 20 days of heating. A number have aberrant cardiac development and many show spectacular pericardial effusions and congestion in the peripheral circulation. We suggest that maternal hyperthermia has interfered with neural crest migration which is a major component in the induction of these changes.

Animals↗
PubMed1991

Inhibition of human immunodeficiency virus type 1 morphogenesis in T cells by alpha interferon.

Some murine retroviruses exhibit altered release of virus when cells are treated with alpha interferon (IFN-alpha), resulting in the accumulation of intracellular virions in cytoplasmic vacuoles. In studies of the inhibitory effect of IFN-alpha (Wellferon) on acute human immunodeficiency virus type 1 infection of human T-cell lines, we found that in C3 cells, the 50% effective concentration was 9 U/ml and the 90% effective concentration was 310 U/ml. There was no apparent accumulation of intracellular particles detected by p24 antigen levels or by processing the cells for electron microscopy. Extracellular reverse transcriptase activity and p24 levels decreased in parallel with increasing IFN, whereas the intracellular viral proteins decreased only slightly. By electron microscopy, cells treated with higher concentrations of IFN (512 U/ml) disclosed very few particles budding into extracellular spaces; no intracellular particles could be seen, despite nearly normal levels of intracellular viral protein detected by the p24 antigen assay and correct processing detected by Western blot (immunoblot) analysis. Thus in human immunodeficiency virus-infected cells, the major block produced by IFN-alpha appeared to be late in the viral cycle at the morphogenesis stage of virion production. Chronically infected Jurkat cells treated with IFN appeared to be inhibited in growth rate, as virus production decreased proportionally with cell number.

Acquired Immunodeficiency Syndrome↗
PubMed1991

A prospective study of physical trauma and multiple sclerosis.

During an eight year period 170 multiple sclerosis (MS) patients and 134 controls without physical impairment were followed closely to record all episodes of physical trauma and to measure their effect on exacerbation rate and progression of MS. There was a total of 1407 instances of trauma, which were sorted into various categories. Overall there was no significant correlation between all-traumas and disease activity. There was, however, a statistically significant negative correlation between traumatic episodes and exacerbations in 95 patients who had exacerbations during the programme, due primarily to less activity of the disease during a three month period following surgical procedures and fractures. Electrical injury had a significant positive association with exacerbation using a three month at-risk period, but there were no other significant positive correlations in any other category of trauma, including minor head injuries; there were no cases of head injury with prolonged unconsciousness. There was no linkage between the frequency of trauma and progression of disability. MS patients had two to three times more trauma than controls.

Adult↗
PubMed1991

Differences in the luteinizing hormone and prolactin responses to multiple injections of kainate, as compared to N-methyl-D,L-aspartate, in cycling rats.

We have previously reported that repetitive iv injections of NMA [N-methyl-D,L-aspartate, the mixed analog acting on the N-methyl-D-aspartate (NMDA) receptor] can induce a consistent increase in LH and PRL secretion in cycling rats, but not in lactating rats. To further explore the use of excitatory amino acids (EAAs) as tools for understanding the regulation of the neuroendocrine reproductive axis, we have examined the effects of multiple injections of kainate, an agonist to another subclass of EAA receptor, on LH and PRL secretion in cycling rats. Recent studies suggest that kainate receptors may be more abundant than NMDA receptors in the hypothalamus. Five iv injections of kainate were administered at 50-min intervals to diestrous or estrous rats. Blood samples were collected every 10 min and assayed for LH and PRL. LH, but not PRL secretion, was stimulated by this regimen of kainate treatment. Surprisingly, the LH response to kainate, unlike NMA, decreased with repetitive injections of the drug. The response to the last pulse of kainate was approximately 30-40% of the first pulse. This decline in LH responsiveness to kainate was not due to desensitization at the level of the pituitary or to refractoriness of GnRH neurons, since further stimulation of LH release could be obtained by the administration of GnRH or NMA. The mechanisms responsible for the diminishing GnRH response to kainate remain unclear. However, we speculate that it might be due to the delayed activation of inhibitory inputs to GnRH neurons or to the desensitization of kainate receptors. On the other hand, the absence of a PRL response to kainate, in contrast to the stimulatory effect of NMA, most likely reflects differences in the distribution of kainate and NMDA receptors on dopamine neurons and neurons containing PRL-releasing factors, or on extrahypothalamic afferent neuronal populations projecting to the hypothalamus. In conclusion, the effects of systemic injections of kainate on LH and PRL secretion differed from NMA in that the LH response could not be sustained with multiple injections and PRL was unresponsive to kainate stimulation.

Animals↗
PubMed1991

Biofeedback.

Explore the source record for details and available documents.

Biofeedback, Psychology↗
PubMed1991

Variation of HIV infectibility of macrophages as a function of donor, stage of differentiation, and site of origin.

Heterosexual transmission of HIV-1 is likely to involve transmission of virus present in seminal fluid to inflammatory cells, particularly macrophages, present in the endometrium and peritoneal cavity. We have investigated the susceptibility of peritoneal macrophages and the corresponding autologous blood monocytes from normal women to infection by the BA-L strain of HIV-1. In 10 of 18 examples, peritoneal macrophages showed signs of infection within 4-5 days, which was earlier than the autologous monocytes. In contrast to peritoneal macrophages, lung macrophages from 10 of 11 normal donors failed to show significant reverse transcriptase (RT) values 3 weeks post infection. Monolayer cultures of monocytes cultured for 5 days prior to infection developed RT values similar overall to those of freshly isolated cells although individual donors varied as to which culture condition was optimal. The ease of infection of peritoneal macrophages did not correlate with levels of CD4 antigen or degree of pelvic inflammatory development, nor were macrophages harvested from women early in the menstrual cycle significantly more susceptible to infection than those collected from midcycle on. This unexplained heightened infectibility of peritoneal macrophages in a proportion of normal women suggests that those individuals could be more at risk for heterosexual transmission of HIV-1 infection.

CD4 Antigens↗
PubMed1991

Chronic fatigue in adolescents.

Nine female and 6 male adolescents (mean age 14.5 +/- 1.7 [SD] years) were evaluated for chronic fatigue associated with at least three additional symptoms present for 18.4 +/- 8.4 months. Eleven subjects experienced the onset of symptoms with an acute illness (seven Monospot-positive). Medical history, physical examination, and laboratory testing yielded little helpful information. Serologic testing for Coxsackie B viruses 1 through 6, cytomegalovirus, Epstein-Barr virus, human herpesvirus 6, and Toxoplasma gondii in subjects and healthy controls provided little evidence for an infectious cause of persistent fatigue. Children's Depression Inventory scores and psychiatric interviews with the Schedule for Affective Disorders and Schizophrenia-Children's Version (K-SADS) identified five subjects with major depression. On the K-SADS, the 10 fatigued subjects without major depression endorsed many secondary symptoms of depression but were less likely than depressed psychiatric clinic patients to endorse primary symptoms such as depressed mood, guilt, and suicidality. At telephone follow-up 13 to 32 months after intake, 4 subjects were completely well, 4 markedly improved, and 7 unimproved or worse. Further research is necessary to determine whether chronic fatigue in adolescents is prodromal depression, a discrete psychosomatic condition, or an infectious or immunologic disorder that mimics depression.

Adolescent↗
PubMed1991

Chlamydia trachomatis, Mycoplasma hominis and Ureaplasma urealyticum infections in women. Prevalence, risks and management at a South African infertility clinic.

Chlamydia trachomatis, Mycoplasma hominis and Ureaplasma urealyticum infections not only jeopardize fertility but also pose a risk for infertility treatment and resulting pregnancies. Routine screening tests or empirical antibiotic treatment of infertile couples may be justified by the prevalence of these organisms. We studied the wives in 40 consecutive infertile couples. Monoclonal direct immunofluorescence (DIF) for C trachomatis was performed on fixed smears from endocervical swabs. M hominis and U urealyticum were isolated by inoculation of Hayflick (HF) medium, HF broth and Ureaplasma A7 agar with endocervical swabs. Using DIF, 11 (27.5%) specimens were positive, 25 (62.5%) were negative, and 4 (10.0%) were equivocal. DIF was repeated on smears from three of the last four patients; all three were positive for C trachomatis. One patient was lost to follow-up and excluded from the study. For the total 39 specimens the final results were 14 (35.9%) positive and 25 (64.1%) negative. M hominis was isolated from 3 (7.5%) endocervical swabs. None of the endocervical swabs yielded a culture positive for U urealyticum. Statistical analysis showed no correlation between the clinical history and presence of infection with any of the three organisms. The prevalence of 35.9% for C trachomatis was surprisingly high for an infertile population and, if supported by culture confirmation, justifies routine screening. The potential adverse effects of these organisms on the success rate of highly specialized infertility treatments are essentially unresolved. Since our analysis of cost effectiveness as applicable to our unit, all new infertile couples are treated empirically with lymecycline.

Adult↗
PubMed1991

Glycosylated hemoglobin and psychological adjustment in adolescents with diabetes.

The relationships between glycosylated hemoglobin levels as an index of metabolic control, life events occurring in the previous year, and general adjustment in the areas of attitude towards diabetes, independence, peer, school, and family relationships were investigated in 37 adolescents with insulin-dependent diabetes mellitus. The number or type of life events did not show a relationship with metabolic control. As measured by the Sullivan Diabetic Adjustment Scale, diabetic adolescents who were in better metabolic control reported more conflict regarding family relationships and issues of independence than did those in lesser control.

Adaptation, Psychological↗
PubMed1990

[The prevalence of Chlamydia trachomatis infections in new patients at the Infertility Clinic, UOFS, Bloemfontein].

Chlamydia trachomatis is a common sexually transmitted agent causing infertility. Routine screening tests or empirical antibiotic treatment of infertile couples may be justified by the prevalence of this organism. In this study the female partner of 40 consecutive infertile couples was investigated. As a screening test direct immunofluorescence (DIF) was performed on fixed smears from endocervical swabs. Of a total of 40 specimens, 11 (27.5%) were positive, 25 (62.5%) were negative and 4 (10.0%) were equivocal. DIF was repeated on smears from 3 of the last 4 patients and all 3 specimens were positive for C. trachomatis. One patient was lost to follow-up and excluded from the study. Of a total of 39 specimens the final results yielded 14 (35.9%) positive and 25 (64.1%) negative. Statistical analysis showed no correlation between the clinical history and the presence of C. trachomatis infection.

Adult↗
PubMed1990

Esophageal obstruction after ingestion of a fiber-containing diet pill.

Foreign bodies of the esophagus in adults may be the result of a food bolus that becomes lodged proximal to a structural abnormality of the distal esophagus. A case of peptic stricture of the esophagus in a patient who presented with acute dysphagia after ingesting an over-the-counter diet pill composed of guar gum is discussed. It is recommended that anorectics composed of dietary fiber should not be used in patients with a history of esophageal stricture.

Aged↗
PubMed1990

Effects of psychoactive and nonpsychoactive cannabinoids on the hypothalamic-pituitary axis of the adult male rat.

The acute dose-response effects of delta-9-tetrahydrocannabinol (THC), cannabinol (CBN) and cannabidiol (CBD) on gonadotropin and testosterone (T) secretion and on hypothalamic norepinephrine (NE) metabolism were tested in adult male rats. THC and CBN both produced an acute suppression of plasma-luteinizing hormone (LH) and T levels and median eminence NE turnover although a dose-response relationship could not be demonstrated. CBD had no significant effect on any of these parameters and none of these cannabinoids had any effect on plasma follicle-stimulating hormone levels or median eminence LH-releasing hormone (LHRH) content. Except for the highest dose of CBN, none of the in vivo cannabinoid treatments significantly altered in vitro LH secretion although there was a trend towards decreased LH secretion. These results suggest that the decrease in LH secretion in THC- or CBN-treated rats is due to reductions in NE stimulation of LHRH release rather than to changes in LHRH synthesis or pituitary LHRH response.

Animals↗
PubMed1990

Psychosomatic symptoms in adolescence.

This article provides the physician with an efficient and comprehensive method for the evaluation and management of adolescent psychosomatic symptoms in the medical care setting. The physician should make a firm statement of the nonorganic nature of the psychosomatic symptom, identify significant stressors, and provide strong recommendations for immediate action. Appropriate referrals should be arranged, and a follow-up visit to assess progress several weeks after the evaluation should be scheduled.

Adolescent↗
PubMed1990

Luteinizing hormone-releasing hormone neurons express Fos protein during the proestrous surge of luteinizing hormone.

The ability of luteinizing hormone-releasing hormone (LHRH) neurons to express the oncogene c-fos was examined during the estrous cycle in rats. The immunocytochemical localization of the c-fos-encoded antigen, Fos, was coupled with the immunocytochemical localization of LHRH. LHRH neurons showed no Fos immunoreactivity during diestrus-1, diestrus-2, estrus, or the morning of proestrus. However, Fos was expressed in LHRH neurons from 1600 to 2200 hours during proestrus. The timing of onset of Fos expression in LHRH neurons during proestrus suggests a strong correlation with increased LH secretion. Pentobarbital, which blocks the preovulatory LH surge, blocked Fos expression in LHRH neurons, but the LHRH neurons expressed Fos on the following afternoon at the time of the expected delayed LH surge. Not all LHRH neurons expressed Fos during the LHRH surge. Approximately half of the LHRH neurons were activated in the preoptic area and anterior hypothalamus; more anteriorly positioned LHRH neurons did not express Fos, resulting in an overall stimulation of 40% of the LHRH neurons. These data provide direct evidence that stimulation of LHRH neurons during proestrus takes place at the LHRH cell bodies, and identify the specific population of LHRH neurons which are activated.

Animals↗
PubMed1990

Establishment and characterization of a cell line from the mosquito Culex (Culex) theileri (Diptera: Culicidae) and its susceptibility to infection with arboviruses.

The mosquito Culex (Culex) theileri Theobald is probably the major vector of Rift Valley fever (RVF) virus during epizootics on the inland plateau of southern Africa. A cell line was established from the tissues of this mosquito species to facilitate laboratory studies on RVF and other arboviruses. After temperature pretreatment, egg rafts from a laboratory colony were disinfected, mechanically disrupted, and grown in preconditioned Eagles minimum essential medium supplemented with 10% fetal calf serum. The cells were characterized by their protein content, karyology, and their susceptibility to three arboviruses. Although high infectivity titers were obtained, no cytopathic effects were produced by these viruses. The cell line was shown to be free from latent viruses. These results show that this cell line may be employed fruitfully in arbovirus studies.

Animals↗
PubMed1990

Aerobic and anaerobic growth of rifampin-resistant denitrifying bacteria in soil.

The growth and survival of several rifampin-resistant isolates of denitrifying bacteria were examined under anaerobic (denitrifying) and aerobic conditions. Two isolates added to nonsterile Bruno soil at densities of between 10(4) and 10(6) CFU g dry soil-1 exhibited an initial period of growth followed by a gradual decline in numbers. After 28 days, both isolates maintained viable populations of between 10(4) and 10(5) CFU g dry soil-1 under both denitrifying and aerobic conditions. One of the isolates consistently grew better under denitrifying conditions, and the other isolate consistently grew better under aerobic conditions. The relative pattern of denitrifying versus aerobic growth for each organism was not affected by the addition of glucose. The growth yields of the two isolates varied with soil type, but the relative pattern of denitrifying versus aerobic growth was consistent in three soils with greatly different properties. Five of nine isolates introduced into Bruno soil at low population densities (approximately 10(5) CFU g dry soil-1) exhibited better growth after 2 days under denitrifying conditions. It was not possible to predict the prevalence of the denitrifying or aerobic mode of growth in nonsterile soil from the growth characteristics of the isolates in pure cultures or sterile soil.

Aerobiosis↗