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Biomedical subjects

A Stuart

Publications and source records attributed to A Stuart.

At least 73 records · Page 4Linked to original sources
PubMed1991

Behavior changes after notification of HIV infection.

BACKGROUND: To learn more about how people who did not volunteer for testing react to information about HIV infection, we assessed short-term behavior changes in HIV-positive blood donors. METHODS: Blood donors who were notified at the New York Blood Center that they were HIV positive were asked to participate in a study. A nurse elicited a medical history, performed a limited medical examination, and asked participants to complete a questionnaire that included questions about drug use, sexual behavior, and psychological characteristics. Participants were asked to return in 2 weeks to complete another questionnaire. RESULTS: Many fewer men and women reported engaging in unsafe sexual behaviors in the 2 weeks preceding the follow-up visit than had reported such behaviors prior to notification. These changes were greater than those other investigators have reported, but about 40% of the participants still reported unsafe sexual activity at the follow-up interview. CONCLUSIONS: To make nonvolunteer screening programs for HIV infection more effective in reducing the spread of HIV infection, we need to learn more about how to help people change their high-risk behaviors.

Adolescent↗
PubMed1991

Test-retest variability in audiometric threshold with supraaural and insert earphones among children and adults.

The effect of age and earphone condition on test-retest intrasubject variability in audiometric threshold was investigated. Ten subjects in each of the following age groups were investigated: 6-9 years, 10-13 years and young adults. Test-retest audiometric thresholds were collected at six frequencies (250, 500, 1,000, 2,000, 4,000 and 8,000 Hz) under three earphone conditions (Telephonics TDH-50P supraaural and Etymotic Research ER-3A insert earphone coupled to an immittance probe cuff or a foam insert). No statistically significant differences were found in variability of test-retest differences as a function of age, earphone condition or test frequency (p greater than 0.05). The clinical application of the insert earphone is recommended with children and adults as it affords no greater test-retest variability and at the same time provides a solution to a number of limitations incurred with the use of the supraaural earphone.

Adolescent↗
PubMed1990

Critical differences in aided sound field thresholds in children.

Variability of aided sound field thresholds (ASFTs) was examined in 30 children comprising two age groups (5-9 and 10-14 years). Test-retest ASFTs were collected at six frequencies (250, 500, 1000, 2000, 3000, and 4000 Hz). No statistically significant difference was found in mean test and retest ASFTs between the two groups (p greater than .05). Test-retest difference data from both groups of children were combined and used to generate critical differences (in dB) for two ASFTs. At a 95% confidence level, two ASFTs would have to differ by more than 10 dB across signal test frequencies to attain statistical significance. In clinical decision-making, if one accepts smaller differences in ASFTs as statistically significant, larger probabilities of error must be assumed.

Acoustics↗
PubMed1990

Effect of temporal area bone vibrator placement on auditory brain stem response in newborn infants.

The effect of bone conduction vibratory placement on the temporal area, revealed by the auditory brain stem response (ABR), in newborn infants, was investigated. Twenty-five full term neonates were tested at 48 to 72 hours postparturition. ABR wave V latencies were obtained from three different temporal area postauricular vibrator placements at 15 and 30 dB nHL stimulus intensity levels. Results showed that significant ABR wave V latency shifts were observed with changes in the three vibrator placements (p less than 0.05). It is suggested that, with ABR testing in newborn infants using bone conducted stimuli, bone vibrator placement on the temporal area remain consistent.

Audiometry, Evoked Response↗
PubMed1989

High-dose combination cyclophosphamide, cisplatin, and melphalan with autologous bone marrow support. A clinical and pharmacologic study.

A total of 23 patients were treated at five dose escalations with high-dose combination cyclophosphamide, cisplatin, and melphalan with autologous bone marrow support. The maximum tolerated doses of cyclophosphamide, cisplatin, and melphalan were 5,625, 180, and 80 mg/m2, respectively. The dose-limiting toxicity was cardiac toxicity. Objective tumor regression occurred in 14 of 18 evaluable cases, with a median duration of 3.5 months. Pharmacokinetic evaluation of melphalan in 20 patients revealed a dose-related increase in maximum plasma concentration (Cmax) and area under the curve (AUC). Perturbation of the melphalan plasma half-life and AUC, associated with severe toxicity, resulted when renal insufficiency occurred. The results suggest that high-dose combination cyclophosphamide, cisplatin, and melphalan produces frequent, rapid responses in breast cancer, melanoma, and sarcoma, although with significant extramedullary toxicity. The pharmacokinetics suggest that modification of the treatment schedule may result in a reduction of treatment-related toxicity.

Adult↗
PubMed1989

Computer assisted treatment planning for 125I ophthalmic plaque radiotherapy.

This paper describes a computer program for planning the treatment of ocular tumors with 125I plaques. The program permits the input of the tumor configuration into a model eye and facilitates the viewing of the relative geometry of the tumor and various eye structures in different perspectives. Custom-designed 125I plaques can be localized onto the globe, and dose distributions can be calculated and superimposed on the eye structures in any plane or on the inner eye surface. The program allows efficient evaluation of the plaque design in terms of radiation dose distribution relative to the tumor and critical structures.

Brachytherapy↗
PubMed1988

Neutrophil migration is defective during recombinant human granulocyte-macrophage colony-stimulating factor infusion after autologous bone marrow transplantation in humans.

We have previously reported that continuous intravenous (IV) administration of recombinant granulocyte-macrophage colony-stimulating factor (rHuGM-CSF) to humans following high-dose alkylating agent chemotherapy and autologous bone marrow support (ABMS) results in myeloid bone marrow maturation, accelerated granulocyte recovery, and reduced treatment-related toxicity. However, we found that leukocyte counts declined rapidly after discontinuation of rHuGM-CSF therapy, which suggests possible growth factor effects on leukocyte margination and migration. For these reasons we studied granulocyte margination by using 111In-labeled autologous granulocytes and found similar granulocyte margination before (21.5% +/- 13.4%) and during continuous IV rHuGM-CSF infusion (23.3% +/- 9.6%). Phagocytosis of Cryptococcus neoformans and granulocyte hydrogen peroxide production was similar before and during rHuGM-CSF infusion and similar to patients treated with the same high-dose chemotherapy and ABMS but not receiving growth factor. However, migration of granulocytes to a sterile inflammatory site was markedly reduced during continuous rHuGM-CSF infusion (1.2 +/- 0.9 WBCs/cm2, 24 hr) as compared with baseline (39.6 +/- 17.7 WBCs/cm2/24 hr; P less than .0008). These findings may be of relevance when extravascular granulocytes are required for host defense.

Bone Marrow Transplantation↗
PubMed1987

Clinical and pharmacologic effects of high dose single agent busulfan with autologous bone marrow support in the treatment of solid tumors.

A Phase I-II clinical trial of high dose single agent busulfan (16-20 mg/kg) administered over a 4-day period was undertaken. Pharmacokinetic measurements reveal that steady state total plasma busulfan levels between 2 and 10 microM were achieved by the second day and maintained through the remaining treatment period. Urinary excretion of mutagenic activity monitored by the Salmonella mutagenesis assay persisted for up to 48 h following the last dose of busulfan. The treatment showed specificity for myelocytic precursors as evidenced by selective depression of granulocytes with relative sparing of lymphocytic elements, and by differences in DNA damage as measured by a nucleoid sedimentation assay. Dose limiting toxicity was mucositis, anorexia, and hepatic toxicity. Transient autoimmune disorders were observed in three of the six patients. Partial responses were seen in two of five patients with melanoma, but these lasted for only 2 and 3 months. High dose busulfan represents an alkylating agent with marked myelocytic selectivity and may be useful for inclusion in intensive combination regimens.

Adult↗
PubMed1983

Restoration of functional continuity in dystrophic murine muscle after crushing.

The recovery of functional continuity after crush injury was measured by a simple electrophsiological technique in semitendinosus muscles of normal and dystrophic mice of the C57BL/6J(dy2Jdy2J) strain. In contrast to virtually complete restitution in normal muscles, only one-third of fibers regained continuity in dystrophic muscles. The study also confirmed the lower resting membrane potentials of dystrophic fibers and the presence of "functional" denervation in some of them.

Animals↗
PubMed1983

Absence of fibrillation after muscle injury.

The possibility was examined that fibrillation potentials may occur in those parts of muscle fibers which become functionally denervated following segmental necrosis. Focal necrotic lesions were induced in rat semitendinosus muscles by crushing, ligating, or cutting muscle fibers. When the treated muscles were examined microscopically and recordings made with intracellular or extracellular electrodes, fibrillations were found to be either completely absent or extremely infrequent. Fibrillation potentials were also absent in the brachioradialis muscle of a human subject after myotomy. In contrast to these negative results, surgical denervation of the rat semitendinosus induced fibrillation activity within 3 days; when fully developed, fibrillations occurred in approximately one-half of the fibers at any time. The findings are considered to have significance for an understanding of the pathogenesis of those "myopathic" disorders in which fibrillations are found.

Action Potentials↗
PubMed1983

2,4-diamino-5-benzylpyrimidines and analogues as antibacterial agents. 6. A one-step synthesis of new trimethoprim derivatives and activity analysis by molecular modeling.

A new route to 2,4-diamino-5-(4-hydroxybenzyl)pyrimidines has been developed that involves the condensation of 2,4-diamino-5-(hydroxymethyl)pyrimidine with phenols in acidic medium. The use of phenol and its 2,6-dialkyl derivatives produces 5-(4-hydroxybenzyl)pyrimidines exclusively. However, 2,6-dimethoxyphenol produces a mixture of 5-(3-hydroxy-2,4-dimethoxybenzyl)- and 5-(4-hydroxy-3,5-dimethoxybenzyl)pyrimidines. The phenolic condensation has been used to prepare a series of alkyl-substituted 5-(4-hydroxybenzyl)- and 5-(4-alkoxybenzyl)pyrimidines. The use of 1,2,3-trimethoxybenzene in place of a phenol produces 2,4-diamino-5-(2,3,4-trimethoxybenzyl)pyrimidine, a trimethoprim isomer with low antibacterial activity. The use of molecular models of several of the new ortho-substituted derivatives in the active site of dihydrofolate reductase has provided a rational explanation for their activities relative to trimethoprim.

Anti-Bacterial Agents↗
PubMed1983

Zinc supplementation and its effect on taste acuity in children with chronic renal failure.

Diminished taste acuity (hypogeusia) and zinc deficiency have been reported in children on maintenance haemodialysis and with varying degrees of chronic renal failure. We have studied the effect of 6 weeks' zinc supplementation in 20 children with chronic renal impairment using a double-blind crossover trial. Although we achieved significant increases in serum zinc levels no significant improvement in taste acuity could be demonstrated. These studies provide no support for the belief that routine zine supplements are necessary in children with chronic renal failure.

Adolescent↗
PubMed1982

A new method of dosimetry-a study of comparative laser-induced tissue damage.

The use of lasers in medicine and surgery has increased slowly-its effectiveness based on trial-and-error clinical experience. Very little comprehensive data has been published that scientifically presents dosage, energy, absorption, and comparisons between types of lasers. Our laboratory has developed a method for taking the guesswork out of laser dosage using scientific data to optimize therapy and give reproducible responses. Experiments were conducted using an argon laser, a neodymium: YAG laser, and a broad-band infrared light source. This preliminary study uses a beam scan technique, which for the first time permits accurate measurement of the laser intensity incident on tissue. Therefore, this protocol allows the standardization of dosage measurements with good experimental reproducibility in biological models. By using this accurate method of measuring the intensity delivered to pigskin, we are able to reproduce for the first time similar histological damage with the different energy sources.

Animals↗
PubMed1975

Breast cancer rates in populations of single women.

The well known associations of breast cancer with fertility patterns and diet are interdependent and it is difficult to estimate the extent to which breast cancer is related to diet. This was attempted by analysing breast cancer rates in populations of single (never married) women for which the contribution of childbearing would be small. Age specific breast cancer rates for single women showed the same variation by country, social class, urban-rural area and with time, as did the corresponding rates for married women, suggesting that common or related factors determined breast cancer rates in single and married women. Also, dietary correlations of breast cancer rates at 55-64 years, around 1960, were not sifnificantly different for single women and the general female population. This supported the view that the dietary associations with breast cancer, observed in larger studies of general female populations, did not arise indirectly from an association with childbearing rates. It was pointed our that the positive association of breast cancer with sugar, observed for single and for all women, was accopanied by a negative association with starch. These opposite associations with two forms of varbohydrate seemed inconsistent on general nutritional grounds and could be explained as arising indirectly to the association of breast cancer with affluence. Otherwise, it would seem necessary to establish a nutritional difference between starch and sugar, which could reasonably influence breast cancer rates, before the association was accepted as indicating cause.

Age Factors↗