PubMed Health⌕ Search

Biomedical subjects

M H Fox

Publications and source records attributed to M H Fox.

69 records · Page 4Linked to original sources
PubMed1980

Enhanced light collection in a flow cytometer.

A modified flow cell in a conventional flow cytometer is described. The refraction of light in the flow cell-to-air interface is analyzed. The analysis shows that much of the light that can be collected is refracted out of the collection optics. The efficiency of light collection is doubled by the addition of a plano-convex lens to the flow cell. Also, more stable operation of the flow cell is achieved with the addition of a secondary sheath.

Flow Cytometry↗
PubMed1980

A model for the computer analysis of synchronous DNA distributions obtained by flow cytometry.

A new model for obtaining the distributions of cells in the cell cycle by computer analysis of flow cytometry data is proposed. The model is able to analyze distributions from both asynchronous and synchronous cell populations. A culture of HeLa cells is pulse-labeled with tritiated thymidine at various times after synchronization by the mitotic selection method, then analyzed by flow cytometry and autoradiography. The results show good agreement between the percentage S-phase cells determined by the model and by autoradiography.

Autoradiography↗
PubMed1975

Variability of polymorphic cellular enzymes in medical students with different serum lipid levels: a preliminary survey.

Groups of male Caucasian medical students who had, relative to their classmates, eitherhigh or low lipid levels were screened for electrophoretic variants of haptoglobin, transferrin, and 10 polymorphic erythrocyte enzymes. Members of both the "high" and "low" lipid groups were found to be polymorphic at 7 genetic loci, 6 of which were enzymatic. Consistently, at most polymorphic loci the high lipid groups had somewhat higher frequencies of nonpredominant phenotypes (patterns other than the phenotype reported to occur most frequently in U.S.A. Caucasian populations). A higher frequency of the less common nonpredominant phenotypes (reported Caucasian population frequency less than 0.200) in the high lipid groups was primarily responsible for the observed variations in the phenotypic distributions. Gene frequency distributions were correspondingly skewed. In 14 comparisons between the high and low lipid groups the least common allele of the 7 polymorphic series had a higher frequency in the high lipid group 9 times and in the low lipid group only once. Collectively, our preliminary observations suggest quantitative and qualitative genetic trends related to serum lipid levels that warrant more extensive investigation.

Alleles↗
PubMedDate not supplied

Tumour cell kinetics as predictors of response in canine lymphoma treated with chemotherapy alone or combined with whole body hyperthermia.

Kinetic parameters including potential doubling time (Tpot), duration of S phase (Ts), labelling index (LI), and DNA index (DI) were obtained from 42 dogs with previously untreated lymphoma. Standard flow cytometric techniques using BrdUrd were employed. All dogs were treated with L-asparaginase and remission was induced in 26 dogs, which were then randomized to receive chemotherapy only (doxorubicin [DOX] alone or with lonidamine) or chemotherapy plus whole body hyperthermia (WBH). Dogs were treated every 3 weeks for up to five treatments and evaluated every 3 weeks for evidence of tumour recurrence. Within this subset of animals there was no difference in outcome based on treatment group. Median values for Tpot, Ts and LI were 3.4 days, 7.23 h and 12.49%, respectively. Dogs that had tumours with LI > or = 20% had a shorter time until recurrence than dogs with tumours characterized by LI < 20%. In dogs treated only with chemotherapy, dogs bearing tumours with longer than median Tpot and Ts values and lower than median LI had significantly longer remission duration than dogs with more rapidly proliferating tumours. Dogs treated only with chemotherapy, which had longer than median Tpot and Ts values and lower than median LI, had significantly longer remission duration than all other dogs in the study. The mechanisms in which kinetics are associated with response to chemotherapy are not clear and vary depending on tumour type and treatment regimen. More work is needed to understand factors involved in cell killing during in vivo hyperthermia.

Animals↗
PubMedDate not supplied

Building pharmacoepidemiological capacity to monitor psychotropic drug use among children enrolled in Medicaid.

This study's objective was to develop a methodology to apply pharmacoepidemiological research toward understanding and improving psychotropic drug use among children enrolled in Medicaid. Using Kansas Medicaid data for 1995-1996, we summarized drug claims, diagnoses, and demographics for children under 20 who received at least one psychotropic drug prescription over either year. The sequence of steps needed to assure a quality improvement role is discussed. Use of key personnel in less regulatory and more clinical data applications is critical. Illustrating this approach, we found disproportionate numbers of children receiving psychotropic drugs who were young boys and larger numbers of white children receiving psychotropic prescriptions relative to their Medicaid enrollment than either African-American or Hispanic children. Medicaid agencies can expand epidemiological capacity to understand service use among segments of the population they insure as part of an overall commitment to improving quality.

Adolescent↗
PubMedDate not supplied

Effects of hyperthermia and membrane-active compounds or low pH on the membrane fluidity of Chinese hamster ovary cells.

Chinese hamster ovary (CHO) cells heated in the presence of the membrane-active agents procaine, ethanol, butylated hydroxytoluene (BHT) and glycerol were analysed for changes in fluorescence polarization of the lipid probe (1-[4(trimethylamino)phenyl]-6-phenyl-1,3,5-hexatriene, an indicator of plasma membrane fluidity). Cells were heated in normal and acid (pH 6.6) medium. Procaine, ethanol, BHT and low pH sensitized cells to heat-killing. Procaine, ethanol and BHT decreased fluorescence polarization (increased plasma membrane fluidity) significantly. Polarization distributions for cells heated with these sensitizers were broadened substantially and were skewed toward lower polarization values. Glycerol, a heat-protector, inhibited changes in fluorescence polarization due to heating at temperatures up to 45.0 degrees C. Heating cells at either 42 or 45 degrees C in pH 6.6 medium had no significant effect on the fluorescence polarization compared with controls, while survival was reduced substantially. Thus, heat-sensitization of low pH cannot be ascribed to changes in membrane fluidity. The changes in membrane fluidity caused by other sensitizers and protector indicate that membrane fluidity changes may be a contributing cause of cell killing by hyperthermia.

Animals↗
PubMedDate not supplied

Modification of intracellular pH and thermotolerance development by amiloride.

The intracellular pH (pHi) of cells heated at 45.0 degrees C in the presence or absence of amiloride and in choline chloride substituted sodium-free medium was measured with flow cytometry using the pH sensitive dye, carboxy-seminaphthorhodafluor (SNARF-1). Chinese hamster ovary (CHO) cells at pH 7.3 and low-pH-resistant (PHV2) cells at pH 6.6 were studied. Bimodal population distributions of pHi were obtained for both CHO and PHV2 cells following a treatment in which cells were heated 10 min at 45.0 degrees C, incubated 4 to 10 h at 37 degrees C, then reheated at 45 min at 45.0 degrees C. Amiloride or sodium-free medium modified the changes in pHi, but did not eliminate them entirely. Cells were sorted from the higher pHi and lower pHi subpopulations and plated for cell survival. The survival after both heat treatments was three to five-fold higher for cells sorted from the higher pHi subpopulation than cells sorted from the low pHi subpopulation. The development of thermotolerance was delayed in CHO cells but not in PHV2 cells when amiloride was present throughout the treatment regimen. Combining low pH with amiloride caused an even greater delay in thermotolerance development in CHO cells. However, the final fraction of thermotolerant cells after 14 h incubation was nearly identical, regardless of medium pH or the presence of amiloride.

Amiloride↗
PubMedDate not supplied

The role of intracellular free calcium in the cellular response to hyperthermia.

The intracellular free calcium (Ca++i) concentration was measured in several cell lines after heating at 45.0 degrees C using flow cytometry with indo-1. Chinese hamster ovary 10B2 (CHO) cells do not stain well with indo-1, so a CHO mutant cell line (CHO IS1) isolated in our laboratory with much-improved stainability for indo-1 was used to study CA++i changes in heated CHO cells. BALB-3T3 (mouse) and EJ30 (human) cells were also studied. Cells were heated in the sample holder of the cell sorter in order to measure Ca++i within seconds after heating. Ca++i increased rapidly within the first 5 min of heating at 45.0 degrees C in all three lines, though the magnitude of the increase varied for each cell line. The Ca++i returned rapidly to baseline after heating in CHO IS1 cells and BALB-3T3 cells. After 5 min of heating, the Ca++i plateaued in the EJ30 and IS1 cells, but decreased in the 3T3 cells. There was an inverse relationship between the Ca++i after 10 min at 45 degrees C and survival for the different cell lines. Thermotolerant cells experienced a similar change in Ca++i during heating as non-thermotolerant cells, though the kinetics were somewhat different for the IS1 cells. A bimodal distribution of Ca++i developed in EJ30 cells by 2 min after heating. Cells sorted from the near-normal Ca++i region of the histogram had a 2-fold higher survival rate than the cells which had a high Ca++i concentration. These data support the view that Ca++i changes during heating are not the principal factor in heat-induced cell death.

3T3 Cells↗
PubMedDate not supplied

Do increases in payments for obstetrical deliveries affect prenatal care?

Raising fees is one of the primary means that State Medicaid Programs employ to maintain provider participation. While a number of studies have sought to quantify the extent to which this policy retains or attracts providers, few have looked at the impact of these incentives on patients. In this study, the authors used Medicaid claims data to examine changes in volume and site of prenatal care among women who delivered babies after the Maryland Medicaid Program raised physicians fees for deliveries 200 percent at the end of its 1986 fiscal year. Although the State's intent was to stabilize the pool of nonhospital providers who were willing to deliver Medicaid babies, it was also hoped that women would benefit through greater access to prenatal care, especially care rendered in a nonhospital setting. The authors' hypotheses were that (a) the fee increase for obstetrical deliveries would result in an increase in prenatal visits by women on Medicaid, and (b) the fee increase would lead to a shift in prenatal visits from hospital to community based providers. The data for Maryland's Medicaid claims for the fiscal years 1985 through 1987 were used. Comparisons were made in the average number of prenatal visits and the ratio of hospital to nonhospital prenatal visits before and after the fee increase. Data for continuously enrolled women who delivered in the last 4 months of each fiscal year were analyzed for between and within year differences using Student's t-test and ANOVA techniques. The findings indicate very little overall change in either the amount or location of prenatal care during the year after the large fee increase for deliveries.Though significant increases in the number of prenatal visits occurred for women who lived outside of Baltimore City, it is difficult to attribute these changes solely to the fee increase. Where an effect was observed, it appeared to be greatest in non urban areas of the State, probably because coordination of care by fewer Medicaid providers is more common in such areas.The findings do not support the hypotheses that raising fees for obstetrical deliveries uniformly increase community-based prenatal care. Instead, the findings suggest that tying fee increases for obstetrical deliveries to the amount of prenatal care provided for each patient may be the best way of increasing the commitment of Medicaid obstetrical providers to give their patients more comprehensive perinatal care.

Adult↗