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S Lewin

Publications and source records attributed to S Lewin.

At least 19 recordsLinked to original sources
PubMed2001

The use of 99mTc-phytate for sentinel node mapping in melanoma, breast cancer and vulvar cancer: a study of 100 cases.

Sentinel node mapping reduces surgical morbidity and allows the use of more accurate tumour staging techniques. Radionuclide studies are preferentially performed using small colloids, which have limited availability in our country. The possibility of using phytate for sentinel node mapping was raised because of the similarity between its biodistribution and that of nanocolloids in the reticulo-endothelial system. In this paper we evaluated the use of 99mTc-phytate for sentinel node mapping, correlating the histopathological results with the status of the rest of the lymph node chain in different malignant tumours. A total of 100 patients were studied. group 1 consisted of 62 patients with breast cancer, group 2 of 20 patients with melanoma and group 3 of 18 patients with vulvar carcinoma. Lymph node scintigraphy was carried out after injecting 99mTc-phytate subdermally, and the sentinel node projection was marked on the skin. After 18-24 h, intraoperative sentinel node localisation was performed using a gamma probe (combined with visual localisation using patent blue dye) in 75 patients, and lymph node dissection was then carried out. Radionuclide scintigraphy identified the sentinel node in 98% of all studies. Intraoperative detection using the gamma probe was equally efficient: group 1=93% (38/41), group 2=95% (18/19) and group 3=100% (15/15). The sentinel node was involved in 41%, 31% and 20% of cases in groups 1, 2 and 3, respectively. Among the patients with positive nodes, the sentinel node was the only one affected in 53% of group 1, 50% of group 2 and 67% of group 3 cases. The method's negative predictive value was 91% in group 1 and 100% in the other groups. One false-negative study occurred in a patient who had a multifocal tumour and an intraparenchymatous lymph node; another occurred in a patient with a macroscopically affected node found during surgery. There were no side-effects related to the 99mTc-phytate. It is concluded that scintigraphic and intraoperative sentinel node identification was satisfactorily performed using 99mTc-phytate. The results were comparable to those previously described in the literature using other radiopharmaceuticals. Easy availability and low cost justify the use of phytate in our practice.

Adult↗
PubMed2001

Molecular epidemiology and population genetics in Leishmania.

Polymorphic DNA sequences have been amplified using different PCR-based techniques and used for species identification, strain discrimination and population genetic studies in Leishmania. A PCR fingerprinting method that uses single non-specific primers generates species-specific banding patterns with some intraspecies variation. This approach can be used to identify Leishmania species and also to discriminate strains of different Leishmania species. Cultivation of the parasites is, however, mandatory. PCR-restriction fragment length polymorphism of the internal transcribed spacer (ITS) in the ribosomal operon differentiates all Leishmania species, except members of the L. donovani and L. brasiliensis complexes. ITS-single-strand conformation polymorphism or ITS sequencing can detect strain specific-variation (except in L. infantum); culturing is not required. Species of Leishmania exhibit different degrees of genetic variation (L. tropica > L. aethiopica > L. major > L. donovani). Population analysis using co-dominant DNA markers developed by sequence-confirmed amplified region analysis revealed a primarily clonal structure in a L. donovani population from Sudan and suggested that occasional recombination events may occur in this population.

Animals↗
PubMed2001

Ethics that exclude: the role of ethics committees in lesbian and gay health research in South Africa.

Prevailing state and institutional ideologies regarding race/ethnicity, gender, and sexuality help to shape, and are influenced by, research priorities. Research ethics committees perform a gatekeeper role in this process. In this commentary, we describe efforts to obtain approval from the ethics committee of a large medical institution for research into the treatment of homosexual persons by health professionals in the South African military during the apartheid era. The committee questioned the "scientific validity" of the study, viewing it as having a "political" rather than a "scientific" purpose. They objected to the framing of the research topic within a human rights discourse and appeared to be concerned that the research might lead to action against health professionals who committed human rights abuses against lesbians and gay men during apartheid. The process illustrates the ways in which heterosexism, and concerns to protect the practice of health professionals from scrutiny, may influence the decisions of ethics committees. Ethics that exclude research on lesbian and gay health cannot be in the public interest. Ethics committees must be challenged to examine the ways in which institutionalized ideologies influence their decision making.

Behavioral Research↗
PubMed2000

Genetic variability within the species Leishmania aethiopica does not correlate with clinical variations of cutaneous leishmaniasis.

Leishmania aethiopica infections in man result in a spectrum of diseases from LCL to DCL. These clinical manifestations have been attributed to genetic differences within the host or the parasites. In this study two different PCR-based methods were used to elucidate genetic variation within the species L. aethiopica. Inter- and intra-specific variations were detected in the ITS of the ribosomal operon in different strains and species of Leishmania, using a PCR-RFLP approach, and by a PCR fingerprinting technique that used single non-specific primers to amplify polymorphic regions of the genomic DNA. Both methods revealed genetic heterogeneity among ten L. aethiopica isolates examined. Unrooted distance trees separated the ten strains into two different genetic groups. This subdivision was correlated to the geographical origin of the isolates rather than to the clinical manifestation of the disease.

Animals↗
PubMed1999

Quantifying residual HIV-1 replication in patients receiving combination antiretroviral therapy.

BACKGROUND: In patients infected with human immunodeficiency virus type 1 (HIV-1), combination antiretroviral therapy can result in sustained suppression of plasma levels of the virus. However, replication-competent virus can still be recovered from latently infected resting memory CD4 lymphocytes; this finding raises serious doubts about whether antiviral treatment can eradicate HIV-1. METHODS: We looked for evidence of residual HIV-1 replication in eight patients who began treatment soon after infection and in whom plasma levels of HIV-1 RNA were undetectable after two to three years of antiretroviral therapy. We examined whether there had been changes over time in HIV-1 proviral sequences in peripheral-blood mononuclear cells, which would indicate residual viral replication. We also performed in situ hybridization studies on tissues from one patient to identify cells actively expressing HIV-1 RNA. We estimated the rate of decrease of latent, replication-competent HIV-1 in resting CD4 lymphocytes on the basis of the decrease in the numbers of proviral sequences identified during primary infection and direct sequential measurements of the size of the latent reservoir. RESULTS: Six of the eight patients had no significant variations in proviral sequences during treatment. However, in two patients there was sequence evolution but no evidence of drug-resistant viral genotypes. In one patient, extensive in situ studies provided additional evidence of persistent viral replication in lymphoid tissues. Using two independent approaches, we estimated that the half-life of the latent, replication-competent virus in resting CD4 lymphocytes was approximately six months. CONCLUSIONS: These findings suggest that combination antiretroviral regimens suppress HIV-1 replication in some but not all patients. Given the half-life of latently infected CD4 lymphocytes of about six months, it may require many years of effective antiretroviral treatment to eliminate this reservoir of HIV-1.

Adult↗
PubMed1999

Dramatic rise in plasma viremia after CD8(+) T cell depletion in simian immunodeficiency virus-infected macaques.

To determine the role of CD8(+) T cells in controlling simian immunodeficiency virus (SIV) replication in vivo, we examined the effect of depleting this cell population using an anti-CD8 monoclonal antibody, OKT8F. There was on average a 99.9% reduction of CD8 cells in peripheral blood in six infected Macaca mulatta treated with OKT8F. The apparent CD8 depletion started 1 h after antibody administration, and low CD8 levels were maintained until day 8. An increase in plasma viremia of one to three orders of magnitude was observed in five of the six macaques. The injection of a control antibody to an infected macaque did not induce a sustained viral load increase, nor did it significantly reduce the number of CD8(+) T cells. These results demonstrate that CD8 cells play a crucial role in suppressing SIV replication in vivo.

Animals↗
PubMed1999

Morphometric dual-energy X-ray absorptiometry of the spine: report of a large series and correlation with axial bone mineral density.

We studied vertebral morphometry and its relation to bone mineral density (BMD) in normal Brazilian women (n = 605). All women (age 22-97 years) were ambulatory and healthy. A lateral spine scan was done for morphometric X-ray absorptiometry using an imaging densitometer. In 429 of these women, BMD of the spine and proximal femur also were measured using dual-energy X-ray absorptiometry. All women were white with mean (+/- 1 SD) age of 53.7 (+/- 9.5) years. About 21% of the women over 50 years had a T score for spine BMD lower than -2.5 SD, and 7% had a femoral neck BMD below this osteoporosis threshold. Vertebral heights (anterior, HA; middle, HM; and posterior, HP) and ratios (HA/HP and HM/HP) were assessed. There was no systematic difference between younger (20-49 years) and older (50+ years) women in heights or ratios. The vertebral heights were normalized for those observed in each individual case for the L2-L4 sequence. This normalization was adequate for all vertebral heights; the Z score averaged about +0.1. The average Z score for HA/HP was +0.01, but that for the HM/HP was -0.72, indicating that the latter ratio might differ from the reference population used (white American and European women). We observed a small positive correlation between vertebral heights and spine or femur BMD, but this was due entirely to the influence of body size on BMD. On a group basis, the HM/HP showed a significant association with axial BMD; the 1 SD difference between the lowest and highest quartile was associated with a difference of 8-15% (0.5-1.0 SD) in axial BMD.

Absorptiometry, Photon↗
PubMed1998

Zimbabwe's hospital referral system: does it work?

BACKGROUND: Anecdotal evidence has suggested inefficiency in the pyramidal health care referral system established in Zimbabwe in 1980, as part of its primary health care (PHC) model. AIM: To assess the functioning of the pyramidal referral system in two rural districts surrounding Harare, Zimbabwe, with regard to two common indicator conditions: pneumonia in children and malaria in adults. METHODS: For a three-month period, all complete inpatient records with discharge diagnoses of pneumonia or malaria from three hospitals representing different levels of care were analyzed (n = 227). Data were collected on demographic and patient care variables. The appropriateness of admissions and referrals was determined by an assessment of the severity of illness and 'intensiveness' of care required. Data were analyzed for differences among the three hospitals and between the two indicator conditions. Per night inpatient bed costs for each hospital were also calculated. RESULTS: For pneumonia in children, 56.8% of patients admitted at the secondary level, 53.8% of patients at the tertiary level and 57.8% of patients at the quaternary level were of mild severity. For malaria in adults, 74.0% of patients seen at the secondary level, 81.5% of patients at the tertiary level and 54.3% at the quaternary level were of mild severity. For pneumonia, were no differences in severity between the three hospitals whereas for malaria significant case-mix differences among the hospitals were found. Most patients attending the highest level referral facility were inappropriate admissions who could have been treated at a lower level of care. The majority of patients at all the hospitals studied had used that hospital as their first or second point of contact with the health services. There were large variations in the inpatient per night bed costs between the three hospitals. CONCLUSIONS: Using the indicator diseases of pneumonia in children and malaria in adults, this study concluded that this network did not meet design expectations as the central level referral hospital cared for a similar case-mix of patients as the district level, but at six times the cost. The appropriateness of admissions and referrals could be improved by developing or strengthening intermediate level facilities, by changing mechanisms of access to specialist facilities and by training health professionals in community settings.

Adult↗
PubMed1997

Down syndrome with biparental inheritance of der(14q21q) and maternally derived trisomy 21: confirmation by fluorescent in situ hybridization and microsatellite polymorphism analysis.

Individuals with translocation Down syndrome (DS) often inherit the rearranged chromosome from a carrier parent. DS due to inheritance of one Robertsonian or derivative (14q21q) from one parent and a second der(14q21q) in addition to a free chromosome 21 from the other parent are rarely documented in liveborn infants. Presented here is such a propositus with DS and with a unique karyotype 45,XY,der(14;21) (p11.1;p11.1)pat,der(14;21)(p11.1;q11.1)mat, +21mat. Using conventional chromosome heteromorphisms, fluorescent in situ hybridization (FISH), and microsatellite polymorphism analyses, we established the biparental origin of the 2 der(14q21q) and the maternal origin of the extra chromosome 21 in the patient. A combination of both cytogenetic and molecular genetic techniques also enabled us to show that the 2 der(14q21q) were not identical by descent and hence the parents were nonconsanguineous. It has been a well-established fact that mothers with Robertsonian translocations have higher risk for nondisjunction than do carrier fathers. Our case, wherein the nondisjunctional event occurred in the mother, even though both parents are carriers of a 14;21 Robertsonian translocation, is yet another example of this.

Chromosome Banding↗
PubMed1997

Mating and hormonal triggers regulate accessory gland gene expression in male Drosophila.

Drosophila melanogaster males transfer accessory gland proteins, as part of their seminal fluid, to females during each mating. Since accessory gland proteins are important for male reproductive success, it is important that the male replenish the proteins he transferred during mating. Previous studies had shown that mating induces the resynthesis of accessory gland proteins, but since mating includes a set of stereotyped behavior patterns as well as the act of copulation, it was not known which aspect of the mating process induces accessory gland protein synthesis. By exposing males to females whose ovipositors had been sealed shut, we have shown that resynthesis of accessory gland proteins occurs only when seminal fluid is transferred to females. By applying juvenile hormone or 20-hydroxyecdysone topically to the cuticle of male flies, we showed that these hormones can act in vivo to stimulate the synthesis of accessory gland proteins to levels similar to those observed after mating.

Journal Article↗
PubMed1997

Most patients attending a 'walk-in' clinic at Red Cross War Memorial Children's Hospital could safely be managed at primary care level.

OBJECTIVES: (i) To ascertain what proportion of patients attending the general medical outpatient service at Red Cross War Memorial Children's Hospital (RXH) could safely be managed at peripheral primary care facilities; and (ii) to measure the effect of the introduction of free health care for children under 6 years of age on requirements for levels of care ranging from home to super-specialist referral centres. DESIGN: Prospective survey of patients attending on a stratified, randomised sample of 7 days in March 1994 (N = 1 962) and again in November 1994 (N = 1 404)-before and after the introduction on 6 June 1994 of free care for children under 6 years of age. SETTING: The general outpatient department of an academic/referral children's hospital. PATIENT SELECTION: All patients attending the outpatient department on the study days (7h00 to 6h59 the following day), excluding those who were referred, returning for follow-up, attending a specialist clinic or attending the surgical outpatient department. QUESTIONNAIRE: The questionnaire completed by medical officers recorded the following: patient's name, folder number, date and time of arrival, whether referred, clinic, treating doctor, disposal, diagnoses, home suburb and the level of care required: (i) home: (ii) clinic without a doctor; (iii) clinic with a doctor; (iv) hospital with non-specialists; (v) hospital with general paediatricians; or (vi) super-specialist hospital. MAIN RESULTS: In March 1994 the percentages of unreferred patients requiring the 6 levels of care defined for the study were 0.3, 25, 62, 8, 3 and 1, respectively. In November 1994 the percentages were 4, 41, 43, 8, 4 and 1. The graph of the number of patients seen at the outpatient department each month shows a large month-to-month variation but the trend is clearly towards an increase. CONCLUSIONS: The general medical outpatient department at RXH provides care to a large number of children, 48% of whom are unreferred. Of the unreferred patients 95% could be treated (more appropriately for the health services and more conveniently for their families) at a local primary health care facility. The situation has been aggravated by the introduction of free care for children under 6 years of age, who constitute 83% of the unreferred workload.

Child Health Services↗