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Biomedical subjects

S Green

Publications and source records attributed to S Green.

At least 541 records · Page 30Linked to original sources
PubMedDate not supplied

Comprehensive two-dimensional gas chromatography for fast screening of wash oils.

Fast screening of wash oils is demonstrated using comprehensive two-dimensional gas chromatography (GCxGC). Wash oils are used in ethylene production plants to minimize compressor fouling. The composition of a wash oil determines its effectiveness in solubilizing heavy hydrocarbons. In particular, the relative amount of 1- and 2-ring aromatics is important. The presence of oxygenates is undesirable because of adverse effects to the process. It is shown that GCxGC is well suited for this application. Species in wash oils are separated and grouped into three bands: a nonpolar aliphatics band, 1- and 2-ring aromatics band, and polyaromatics band. For a given polar secondary column, the spacing between bands in the second dimension can be adjusted in a broad range by selecting a primary column and an oven-temperature-programming rate. Integration of GCxGC peaks is evaluated using a standard GC integration program and a new GCxGC integration program. Consistent results are obtained using both programs for well-separated GCxGC peaks with relative differences for individual peak ranging from 0.04% to 1.6%. Peak responses are integrated by the GCxGC software, and the relative amounts of aromatics content and aliphatics content are estimated by peak response percent with relative standard deviations ranging from 0.15% to 2.8% (n = 3).

Journal Article↗
PubMedDate not supplied

Can we justify spermatid microinjection for severe male factor infertility?

During 1995 and 1996 the first spermatid pregnancies were announced with both round spermatid (ROSI) and elongated spermatid (ELSI) injections. These publications were flanked by live births from ROSI in a number of animal species, with resulting offspring appearing normal, healthy and fertile. However, the live births in humans heralded a scientific and ethical debate on the clinical use of this technology; and in a number of countries nationwide moratoria prohibiting spermatid microinjection were enjoined. Concerns surrounded the biological condition of spermatids and clinical implications of utilizing an immature spermatozoon for conception. Nevertheless, case reports and a few scientific studies on human spermatid conception have been published in recent years, and further polemic on testicular histopathology and prognosis has ensued. This paper reviews the current arguments on the clinical use of ROSI and ELSI, and evaluates the biology of the main contributory components of a spermatozoon to the subsequent embryo, namely the genetic material, the microtubular organizing complex and the putative oocyte activating factor. We also consider the relevant testicular histopathology and likely outcome in the context of the current birth rate from ROSI and ICSI. We conclude by considering the way forward for infertile men who require this technology to become genetic fathers, and whether the time is now appropriate to consider clinical trials.

Clinical Trials as Topic↗
PubMedDate not supplied

Reduction in needle sharing among community wide samples of injecting drug users.

Evidence of reduced levels of needle sharing among injecting drug users (IDUs) has largely been confined to IDUs attending needle exchanges or receiving treatment. In this paper we present the results of a serial cross-sectional study of needle sharing conducted in Glasgow using a multisite sampling strategy. Of the estimated 9400 IDUs in the city, 503 were interviewed in 1990 and 535 in 1991. The proportion of IDUs reporting injecting with, or passing on used needles and syringes in the last 6 months fell significantly as did the number of individuals from whom equipment was received or passed on to. The impact of this level of sharing has been limited in terms of HIV transmission; the prevalence of HIV among the 1990 sample was 2.0% and 1.1% for the 1991 sample. However, the fact that third of IDUs in Glasgow continue to inject, even occasionally, with used equipment gives cause for concern in view of the other pathologies known to be associated with poor injecting hygiene.

Adolescent↗
PubMedDate not supplied

T cell receptor Vbeta gene usage in Thai children with dengue virus infection.

T lymphocyte activation during dengue is thought to contribute to the pathogenesis of dengue hemorrhagic fever (DHF). We examined the T cell receptor Vbeta gene usage by a reverse transcriptase-polymerase chain reaction assay during infection and after recovery in 13 children with DHF and 13 children with dengue fever (DF). There was no deletion of specific Vbeta gene families. We detected significant expansions in usage of single Vbeta families in six subjects with DHF and three subjects with DF over the course of infection, but these did not show an association with clinical diagnosis, viral serotype, or HLA alleles. Differences in Vbeta gene usage between subjects with DHF and subjects with DF were of borderline significance. These data suggest that the differences in T cell activation in DHF and DF are quantitative rather than qualitative and that T cells are activated by conventional antigen(s) and not a viral superantigen.

Adolescent↗
PubMedDate not supplied

Present and future uses of mutagenicity tests for assessment of the safety of food additives.

The tier approach has been employed for the past 3 years for investigating the potential mutagenicity of food additives and generally recognized as safe (GRAS) substances. This approach is used to set testing priorities, since a large number of substances must be investigated. Three tiers or testing levels are used. The first tier is a pre-screen to determine whether a chemical has the potential to cause genetic damage. The second tier is designed to ascertain whether mutagenic activity detected at tier one can be confirmed in the tests which are a part of tier two. The third tier is used for risk assessment and, as such, attempts to define the genetic risk to humans that is associated with use of a substance which is a confirmed mutagen as defined by one or more test methods in tier two. The future uses of mutagenicity test methods will probably be in the area of short-term tests for carcinogenicity and as a means of assessing the risk associated with the use of gentically active chemicals.

Animals↗
PubMedDate not supplied

The protection against trimetrexate cytotoxicity in human bone marrow by sequence-dependent administration of raloxifene, 5-fluorouracil/trimetrexate.

BACKGROUND: Currently, one of the most effective strategies for the treatment and prevention of breast cancer is the use of drugs that block estrogen action in the breast. The success of the first clinically relevant selective estrogen receptor modulator (SERM), tamoxifen, provided the foundation for further testing of this drug to reduce breast cancer incidence in high-risk women. However, the negative effects associated with the long-term use of tanrhoxifen have initiated the search for compounds that are more effective but less toxic. The discovery of raloxifene (RAL), which functions as a potent antiestrogen in the breast but an estrogen receptor (ER) agonist in the bone and cardiovascular system with very little uterotropic activity, provided an alternative strategy to the targeted use of tamoxifen. The aim of this study was to evaluate RAL in combination with 5-fluorouracil (5-FU)/trimetrexate (TMX) to determine the most effective regimes and cellular mechanism of action to mitigate trimetrexate cytotoxicity in human bone marrow cells. MATERIALS AND METHODS: The cell viability was performed using the Quick Cell Proliferation Assay by exposing the cells to TMX, 5-FU and RAL alone; RAL 24 h prior to 5-FU followed 2 h by TMX, and 5-FU 2 h prior to TMX followed 24 h by RAL determined the sequence-dependent interaction between TMX, 5-FU and RAL on the proliferation. RESULTS: The growth rate in MCF-7 in late RAL was 34.75 +/- 4.79% of the control, whereas in bone marrow the same drug combination exhibits a significant protection against TMX cytotoxicity with late RAL yielding 51.25 +/- 4.43% of the control. The findings were also supported by Cell flow cytometry and Western blot analysis. CONCLUSION: Sequence-dependent administration of RAL in combination with 5-FU/TMX can act against TMX toxicity in human bone marrow, while not affecting the maximum inhibitory effect of TMX in breast cancer.

Antineoplastic Agents↗
PubMedDate not supplied

Hair dye toxicity--a review.

This article reviews local and systemic effects which relate to hair dye formulation and hair dye ingredient tests and experiences in man and animals. Mutagenic and carcinogenic aspects are discussed. In a very limited way, safety and hazards of using hair dyes are interpreted for consumers.

Animals↗
PubMedDate not supplied

Partial expiratory flow-volume curves in infancy: technical aspects.

We have constructed a simple pressure-jacket with which to produce passive forced expiration in sleeping, supine infants by thoraco-abdominal compression. During expiration, flow and volume were measured at the airway opening with a face-mask and pneumotachograph. From partial expiratory flow-volume (PEFV) curves, peak expiratory flow rate (PEFR) and maximum expiratory flow at a lung volume equal to the functional residual capacity (VmaxFRC) were obtained. Using the jacket in groups of normal and wheezy infants, we have assessed the effects on PEFR and VmaxFRC of variable inflation pressure, rate and duration of jacket inflation, timing of chest compression in relation to the breathing cycle and subject interaction with the compression manoeuvre. The within-subject reproducibility of PEFR and VmaxFRC was measured. Consistent values were produced by inflating the jacket within 100 ms at end inspiration to a pressure of 3-4 kPa and maintaining the inflation (in wheezy infants) for at least 1 s. The median within-subject coefficients of variation of PEFR and VmaxFRC for both normal infants and wheezy infants were 9 and 12% respectively. The technique is clearly reproducible and can provide information about intrathoracic airway function in infancy.

Forced Expiratory Flow Rates↗
PubMedDate not supplied

The mutagenic assay of some hair dye components, using the thymidine kinase locus of L5178Y mouse lymphoma cells.

Five hair dye components were tested for their mutagenicity at the TK +/- locus of L5178Y cells. Three of the components, m-phenylenediamine, 2 nitro-p-phenylenediamine, and 4-nitro-o-phenylenediamine, gave a positive response that was dose related; 2,4-diaminoanisole gave a questionable response; and 2,5-diaminoanisole gave a negative response. The assay was carried out in vitro without metabolic activation during a 24-hr chemical exposure period. It is concluded that further in vivo tests are necessary to establish the safety of the hair dyes.

Animals↗