Search PubMed⌕ Search

Biomedical subjects

M Nelson

Publications and source records attributed to M Nelson.

At least 325 records · Page 18Linked to original sources
PubMed1991

An evaluation of the BD-100R rechargeable neutron bubble dosimeter.

The purpose of this paper is to present data gathered in the evaluation of the BD-100R neutron bubble dosimeter done at the University of Maryland and the Naval Research Lab. The performance of 12 dosimeters has been followed over 15 exposure-recharge cycles under a wide range of exposure conditions. Included in this paper are the results from tests on dose rate dependence, neutron energy dependence, beta and gamma exposure, and recharge cycle performance. A statistical analysis of the reusability performance of the dosimeter as a function of dose equivalent is also presented.

Evaluation Studies as Topic↗
PubMed1991

Shrinkage of thyrotrophin secreting pituitary adenoma treated with octreotide.

Thyrotrophin secreting pituitary adenomas are a rare cause of recurrent thyrotoxicosis. We report on a 47 year old woman with an 8-year history of this condition. In this case the somatostatin analogue, octreotide, normalized thyroid hormone levels. It was associated with marked tumour shrinkage, with striking reduction of the suprasellar extension and improved appearances in the region of the left cavernous sinus shown by high resolution computerized tomography. Following surgery she developed a biochemical relapse which responded to the reinstitution of octreotide. On long term treatment she developed stomach cramps and gallstones. Octreotide was discontinued. We review previous reports of this condition and discuss the role of octreotide in its management.

Adenoma↗
PubMed1991

Stroke as a late sequela of cranial irradiation for childhood brain tumors.

Cerebrovascular disease involving large and medium-size vessels is thought to be an uncommon sequela of treatment of childhood brain tumors. We reviewed 11 children who developed cerebrovascular disease manifested by strokes or transient ischemic attacks 6 months to 4 years after treatment of brain tumors, while their tumors were in remission. All had received radiation therapy, and seven had received chemotherapy. One child died of acute bilateral cerebral infarctions due to carotid occlusion on one side and marked stenosis on the other 2 years after receiving radiation therapy for an incompletely resected craniopharyngioma. Pathologically, there was marked subendothelial fibrosis of the vessels of the circle of Willis, with inflammatory changes surrounding some of the vessels. In addition to the widely recognized small-vessel damage caused by radiation and chemotherapy in children (mineralizing microangiopathy), damage to medium and large intracranial vessels may result in late sequelae, manifested by stroke or transient ischemic attacks.

Adolescent↗
PubMed1991

HIV infection and risk behaviors among intravenous drug users in low seroprevalence areas in the Midwest.

We studied behavioral factors that place intravenous drug users at risk for the acquisition and transmission of the human immunodeficiency virus (HIV) in a sample of 855 individuals not in drug treatment, living in central and southwestern Ohio. The HIV seropositivity rate for the sample was 1.5%. Three factors were significantly related to HIV infection: homeless shelter residence (odds ratio [OR] = 7.7, 95% confidence interval (CI) = 3.0-20.0), travel to northeastern HIV hyperendemic areas (OR = 5.2, 95% CI = 1.8-15.4), and recent male homosexual or bisexual behavior (OR = 11.2, 95% CI = 2.9-43.9).

Adult↗
PubMed1991

Pre- and postnatal growth retardation--severe mental retardation--acral limb deficiencies with poorly keratinized nails. Another example of a distinct syndrome of inherited intrauterine dwarfism?

In this report, we further delineate an autosomal recessive syndrome with prenatal growth retardation, severe postnatal growth failure, profound mental and motor retardation, characteristic face and acral limb deficiencies with poorly keratinized nails and hypoplastic distal phalanges.

Child Development↗
PubMed1990

The apparent specificity of NotI (5'-GCGGCCGC-3') is enhanced by M.FnuDII or M.BepI methyltransferases (5'-mCGCG-3'): cutting bacterial chromosomes into a few large pieces.

The restriction endonuclease (ENase) NotI is blocked by methylation within its recognition sequence at 5'-GCGGCmCGC-3'. This sensitivity to methylation can be used to enhance the specificity of NotI in vivo and in vitro. Modification by M.FnuDII or M.BepI methyltransferases (MTase) (5'-mCGCG-3') will block NotI (5'-GCGGCCGC-3') cleavage at overlapping MTase/ENase sites 5'-CGCGGCCGC-3' (equivalent to 5'-GCGGCCGCG-3'), and increase the apparent cleavage specificity of NotI about twofold. This 'cross-protection' procedure reduces the number of NotI fragments in the genomes of Escherichia coli and Bacillus subtilis, as resolved by pulsed field electrophoresis. Application of this method to large DNAs in vitro requires the preparation of highly purified DNA MTases.

Bacillus subtilis↗
PubMed1990

Inhibition of interleukin-2 production by tumor cell products and by CKS-17, a synthetic retroviral envelope peptide.

Tumor cells of all types and species tested have been found to produce, in culture, substances that depress the expression of cell-mediated immunity, in the form of delayed-type hypersensitivity reactions in mouse feet. The factors responsible appear related immunologically to the retroviral envelope protein p15E. We have measured the effects of tumor products and conjugates of a p15E-related peptide, CKS-17, on interleukin-2 (IL-2) production by cultured, mitogen-stimulated EL4 cells; in this system IL-2 production is independent of IL-1. Supernatants of cultures of mouse, human and guinea-pig tumor cells inhibited IL-2 production in a dose-dependent fashion. CKS-17 conjugates, but not control conjugates, also inhibited IL-2 production. Responses to IL-2 of the CTLL line used were less inhibited by tumor products and very slightly inhibited by CKS-17 conjugates. IL-2 receptor density, assayed by flow cytometry, was not inhibited. IL-2 production was inhibited whether the tumor products or CKS-17 conjugates were added early or late in the course of culture of stimulated EL4 cells. Inhibition by CKS-17 conjugates was selective in that IL-2 production was inhibited to a greater degree than general protein synthesis in EL4 cells, and general protein synthesis by fibroblasts was unaffected. Measurement of IL-2 mRNA suggested that inhibition of IL-2 production was mediated post-transcriptionally. Fractionation of six different tumor supernatants on Sephacryl S-300 revealed a single peak of activity with an apparent molecular mass of 18 kDa. Antibodies to CKS-17 conjugates neutralized the inhibitory effect of native tumor products on IL-2 production. Inhibition of IL-2 production, by factors related to p15E, provides a strategically effective means of subversion of host defenses by tumors, and abrogation of this inhibition by means of antibodies might promote host resistance to tumor growth.

Animals↗
PubMed1990

Nutrient intakes, vitamin-mineral supplementation, and intelligence in British schoolchildren.

Children (227), aged 7-12 years, weighed and recorded all food and drink consumed for seven consecutive days. Each child completed tests of verbal and non-verbal intelligence, and was then randomly allocated to one of two groups after matching for age, sex, IQ and height. In a double-blind trial lasting for 28 d, one group received a vitamin-mineral supplement daily and the other group a placebo. On re-testing, there were no significant differences in performance between the two groups. Furthermore, there was no consistent correlations between test scores and micronutrient intakes based on the weighed records. Thus, we found no evidence that learning ability in a cross-section of British schoolchildren was limited by the quality of their diets.

Body Height↗
PubMed1990

Pneumocystis carinii pneumonia treated with eflornithine in AIDS patients resistant to conventional therapy.

Eflornithine (DFMO) was used to treat 31 AIDS patients with confirmed Pneumocystis carinii pneumonia who had clinically failed treatment with pentamidine, sulphamethoxazole-trimethoprim or both agents as their first-line therapy. Twenty-one of 31 (68%) responded to second-line treatment with 400mg/kg per day of eflornithine. Five patients discontinued treatment because of bone marrow toxicity. Eflornithine appears to be a useful salvage therapy in patients failing first-line treatments.

Acquired Immunodeficiency Syndrome↗
PubMed1990

HIV infection in sexually transmissible disease practice in Sydney: the effects of legislation, public education and changing clinical spectrum.

The experience with human immunodeficiency virus (HIV) infection of a private inner-city sexually transmissible diseases (STD) clinic in Sydney was quantified. Between February 1984 and March 1988, 2073 of the Clinic's patients were tested for antibodies to HIV on 5095 occasions. Of those tested, 538 (26%) were positive for antibodies to HIV: 532 (98.9%) of the seropositives had practised male homosexual intercourse. This is the highest reported seroprevalence of HIV for any primary care service in Australia. Those individuals seropositive because of other risk behaviours were detected by voluntary contact tracing rather than by screening. Female prostitution was not found to be a risk factor for HIV. In general, rates of first HIV antibody tests were adversely affected by threatening legislation, and temporarily stimulated (among lower-risk persons) by a national television campaign. These data suggest that much of the counselling, detection and management of HIV infection in Australia is occurring in private practice, and that STD services (private and public) are at the forefront of the HIV epidemic. This has implications for disease surveillance and control, health services planning and medical education.

Adult↗
PubMed1989

Stomach cancer and food storage.

To examine the influence of food storage habits on the development of stomach cancer, we compared 95 patients and 190 controls selected from the general population. Information about food storage and diet was obtained from the patients and the controls by use of a questionnaire mailed to each subject followed by an interview. Low intake of salad vegetables and fruit and high intake of salt were clearly associated with stomach cancer development. No association was found with recent refrigerator use, but a halving of stomach cancer risk in subjects who had used a refrigerator for greater than or equal to 29 years persisted after allowance was made for recent diet. Risk was elevated in subjects who, when children, had lived in houses without a larder built specifically for the storage of food.

Adult↗