Biomedical subjects

M H Fox

Publications and source records attributed to M H Fox.

At least 19 recordsLinked to original sources

PubMed2005

The fluidity of Chinese hamster ovary cell and bull sperm membranes after cholesterol addition.

Cell plasma membrane fluidity is affected by membrane lipid and protein composition as well as temperature. Altering the cholesterol content of a membrane can change membrane fluidity at different temperatures and this may affect cell survival during cryopreservation. In these experiments, we examined the effect that adding cholesterol to the membranes of Chinese hamster ovary cells (CHO) and bull sperm had on cell plasma membrane fluidity and cell survival when cells were cooled to 5 degrees C or were cryopreserved. Cells were treated with 0, 1.5 or 5.0mg cholesterol-loaded cyclodextrin (CLC), stained with N-((4-(6-phenyl-1,3,5-hexatrienyl)phenyl)propyl)trimethylammonium-p-toluenesulfonate (TMAP-DPH) to evaluate membrane fluidity and with propidium iodide to evaluate cell viability, prior to analysis by flow cytometry at 23, 5 degrees C, and after cryopreservation. CHO cells exhibited a single cell population with all cells having similar membrane fluidity. Membrane fluidity did not change when temperature had been reduced and then returned to 23 degrees C (P<0.05), however, adding cholesterol to the cells induced membranes to become more rigid (P<0.05). Bull sperm samples consisted of two cell subpopulations, one having relatively higher membrane fluidity than the other, regardless of cholesterol treatment or temperature. In addition, cells possessing the highest membrane fluidity did not survive cooling or cryopreservation efficiently. CLC treatment did not significantly alter membrane fluidity after temperature changes, but did maintain higher percentages of spermatozoa surviving cooling to 5 degrees C and cryopreservation (P<0.05). In conclusion, adding cholesterol to cell resulted in detectable membrane fluidity changes in CHO cells and increased survival of bull sperm after cooling to 5 degrees C and after cryopreservation.

Animals↗

PubMed2003

Arsenic and benzo[a]pyrene differentially alter the capacity for differentiation and growth properties of primary human epidermal keratinocytes.

Normal human epidermal keratinocytes (NHEK) have been chosen as an in vitro model to test the hypothesis that chemicals which alter or interfere in cellular differentiation will concomitantly induce growth perturbations and are, thus, potential carcinogens. In these studies, we have focused on two known skin carcinogens, arsenic and benzo(a)pyrene (BaP). Our results demonstrated that BaP inhibits terminal differentiation in NHEK, as measured by cross-linked envelope (CLE) formation, up to 5.8-fold in control and 1.7-fold in calcium (Ca2+)-treated cells. In comparison, arsenic decreased CLE formation 20-fold in control cells and 5.5-fold in Ca2+-treated NHEK. To characterize the effects of these agents on the growth rate and cell cycle distributions of NHEK, flow cytometric analysis was used. BaP at 2 microM increased proliferation rates by 29%. Altered cell-cycle distribution in BaP-treated cells indicated a more rapid progression through the cell cycle, possibly by a shortened G2 phase. In contrast, arsenic at 5 microM inhibited proliferation by 25%; growth arrest (9%) was also observed in NHEK treated with 2 mM Ca2+. Our findings suggest that, although both BaP and arsenic inhibit CLE production in NHEK, different mechanisms may be involved. Studies in progress will attempt to identify molecular markers involved in the observed chemical effects. These markers will facilitate a mechanistic understanding of how an altered balance between growth and differentiation may play a role in the transformation process in NHEK.

Arsenic↗

PubMed2003

Alkaline subcritical-water treatment and alkaline heat treatment for the increase in biodegradability of newsprint waste.

This work describes two alkaline semicontinuous processes for the conversion of refractory organic materials into biodegradable substances. Newsprint was used as a lignocellulosic waste. Methane conversion efficiencies and cellulose removals were investigated for the two following processes: alkaline subcritical-water treatment (ASWT) coupled with methane fermentation and alkaline heat treatment (newsprint heated with steam in an autoclave; AHT) coupled with methane fermentation with a neutral subcritical-water treatment (NSWT) recycle. Results showed that for ASWT coupled with methane fermentation higher methane conversion efficiencies and higher cellulose removals were achieved as HRT increased. At HRT = 20 days, average CH4 conversion efficiency and average cellulose removal reached 26% and 44%, respectively. After a final HRT of 40 days, average CH4 conversion efficiency and average cellulose removal reached 50% and 60%, respectively. On the other hand, for AHT coupled with methane fermentation, methane conversion efficiencies did not show a greater improvement using this pretreatment process. Average conversion reached 9% with an average cellulose removal of 20%. In order to improve the yield of the reactor, approximately one-third of the effluent was recycled using NSWT (150 degrees C; neutral pH). Methane conversion efficiency of this process increased as more recycles were performed. For the fifth operation, the total average methane conversion efficiency was 44% with a total average cellulose removal of 55%.

Bacteria, Anaerobic↗

PubMed2001

The effectiveness of CAHPS among women enrolling in Medicaid managed care.

The large-scale transition of public health insurance programs to managed care has shifted much of the responsibility for selecting appropriate coverage to beneficiaries--a role for which many have had little preparation. This study evaluates the impact of a CAHPS (Consumer Assessment of Health Plans Study) health care report card in assisting newly enrolled Medicaid case heads in selecting a managed care plan. The major finding is that the CAHPS report card helped consumers make more informed decisions. Those who received the report cards found judging quality between plans easier, felt that they had significantly more information on which to make decisions, and recognized the importance of their decision more often than those receiving only standard enrollment packets.

Adult↗

PubMed2001

A biologically based model of growth and senescence of Syrian hamster embryo (SHE) cells after exposure to arsenic.

We modified the two-stage Moolgavkar-Venzon-Knudson (MVK) model for use with Syrian hamster embryo (SHE) cell neoplastic progression. Five phenotypic stages are proposed in this model: Normal cells can either become senescent or mutate into immortal cells followed by anchorage-independent growth and tumorigenic stages. The growth of normal SHE cells was controlled by their division, death, and senescence rates, and all senescent cells were converted from normal cells. In this report, we tested the modeling of cell kinetics of the first two phenotypic stages against experimental data evaluating the effects of arsenic on SHE cells. We assessed cell division and death rates using flow cytometry and correlated cell division rates to the degree of confluence of cell cultures. The mean cell death rate was approximately equal to 1% of the average division rate. Arsenic did not induce immortalization or further mutations of SHE cells at concentrations of 2 microM and below, and chromium (3.6 microM) and lead (100 microM) had similar negative results. However, the growth of SHE cells was inhibited by 5.4 microM arsenic after a 2-day exposure, with cells becoming senescent after only 16 population doublings. In contrast, normal cells and cells exposed to lower arsenic concentrations grew normally for at least 30 population doublings. The biologically based model successfully predicted the growth of normal and arsenic-treated cells, as well as the senescence rates. Mechanisms responsible for inducing cellular senescence in SHE cells exposed to arsenic may help explain the apparent inability of arsenic to induce neoplasia in experimental animals.

Animals↗

PubMed2000

Factors influencing infant visits to emergency departments.

OBJECTIVES: To follow the 1995 birth cohort of infants, born in the State of Missouri, through their first birthday to: 1) examine their rates of visits to emergency departments (EDs), 2) identify predictors of any ED visit, 3) examine rates of nonurgent ED visits, and 4) identify predictors of nonurgent visits. METHODS: This was a retrospective population cohort study. Using deterministic linkage procedures, 2 databases at the Missouri Department of Health (DOH; (the patient abstract database and the birth registry database) were linked by DOH personnel. International Classification of Diseases, Ninth Revision-Clinical Modification codes for ED visits were classified as emergent, urgent, or nonurgent by 2 researchers. Eight newborn characteristics were chosen for analysis. Negative binomial regression was used to examine the rates and predictors of both total and nonurgent ED visits. RESULTS: There were 935 total ED visits and 153 nonurgent ED visits per 1000 infant years. The average number of visits was.94, with 59% of infants having no visits, 21% having 1 ED visit, and 20% having 2 or more visits. Factors associated with increases in both total and nonurgent ED visits were Medicaid, self-pay, black race, rural region, presence of birth defects, and a nursery stay of >2 days. Significant interactions were found between Medicaid and race and Medicaid and rural regions on rates of ED use and nonurgent use. The highest rate of ED use, 1.8 per person year, was seen in white, rural infants on Medicaid, and the lowest rate (.4 per person year) was seen in urban white infants not on Medicaid. The highest rates of nonurgent use,.3 per person year, were among urban and rural Medicaid infants of both races and among black infants on commercial insurance. The lowest nonurgent rate,.04 per person year, was seen in white urban infants on commercial insurance. CONCLUSION: Infants in the State of Missouri have high rates of ED visits. Nonurgent visits are only a small portion of ED visits and cannot explain large variations in ED usage. Increased ED use by Medicaid patients may reflect continuing difficulties in accessing primary care.

Age Factors↗

PubMed1999

Use of social services by pregnant Medicaid eligible women in Baltimore.

OBJECTIVES: To use linked health and social service databases to determine differences in the use of social services by pregnant women in different managed care systems. METHODS: Comparison of service use by women enrolled in a fee-for-service primary care case management program (Maryland Access to Care or MAC), in a capitated health maintenance organization (HMO), or not assigned to managed care using six state databases. Participants included 5181 women receiving Medical Assistance (MA) and delivering in Baltimore City in 1993. Outcome measures were receipt of WIC, AFDC, and Food Stamps. RESULTS: The overall proportions of women receiving WIC, AFDC, and Food Stamps at delivery were 52.7%, 89.2%, and 62.7%, respectively. Women enrolled in an HMO at delivery were less likely to be receiving WIC (adjusted odds ratios, 0.8, 95% CI, 0.69 to 0.93), AFDC (OR, 0.20; CI, 0.03 to 0.43 for women with prior children and OR 0.13; CI, 0.09 to 0.20 for women without prior children), and Food Stamps (OR 0.77; CI, 0.59 to 0.95 for women with prior children and OR, 0.49; CI, 0.35 to 0.67 for women without prior children) than their MAC counterparts. Women not assigned to managed care also generally were less likely than their MAC counterparts to receive WIC (OR 0.55; CI, 0.46, 0.66), AFDC (OR 1.07; CI 0.83, 1.30 for women with prior children and OR 0.24; CI 0.18, 0.34 for women without prior children), and Food Stamps (OR 0.31; CI 0.08, 0.55 for women with prior children and OR 0.31; CI 0.23, 0.41 for women without prior children). CONCLUSIONS: Although many low-income pregnant women qualify for select social services, receipt of WIC and Food Stamps was low. Increasing efforts are needed by managed care systems and public health agencies to ensure delivery of appropriate services for women.

Adolescent↗

PubMed1999

Activation of heat-shock transcription factor 1 in heated Chinese hamster ovary cells is dependent on the cell cycle and is inhibited by sodium vanadate.

Inducible heat-shock protein 70 (HSP72) is expressed in a cell cycle-specific manner in Chinese hamster ovary (CHO) cells after heating for 15 min at 45.0 degrees C, with the highest level in S-phase cells. Since heat shock induces the transcription of heat-shock proteins through the transactivation of heat-shock elements (HSEs) by heat-shock factor HSF1, we wished to determine whether the cell cycle-specific expression of HSP72 was regulated at the level of transcription. The levels of HSF1 did not vary through the cell cycle, as measured by polyclonal antibodies and flow cytometry. The binding of HSF1 to the heat-shock element was measured with the gel mobility shift assay using cell extracts from Hoechst 33342-labeled heated cells sorted from G1, S and G2/M phases. The HSF1-HSE binding activity was twofold higher in S phase than in G1 or G2/M phase. When CHO cells were exposed to 10 microM sodium vanadate, an inhibitor of tyrosine phosphatase, for 24 h before heat shock, the binding of HSF1 to HSE was reduced by a factor of 2 and the level of HSP72 was greatly reduced. The HSF1 binding to HSE was completely eliminated by using anti-HSF1 antibody in the gel mobility shift assays. Antibodies against HSP73 did not reduce the HSF1-HSE binding activity, but antibodies against HSP40 actually increased the binding activity. These results support the hypothesis that cell cycle-dependent binding of HSF1 to HSE is the cause of the cell cycle-specific expression of HSP72 in heated CHO cells and is regulated by phosphorylation.

Animals↗

PubMed1998

A comparison of ambulatory Medicaid claims to medical records: a reliability assessment.

This study compares the documentation of ambulatory care visits and diagnoses in Medicaid paid claims and in medical records. Data were obtained from Maryland Medicaid's 1988 paid claims files for 2407 individuals who were continuously enrolled for the fiscal year, had at least one billed visit for one of six indicator conditions, and had received the majority of their care from one provider. The patients sampled were also stratified on the basis of the case-mix adjusted cost of their usual source of care. The medical records for these individuals as maintained by their usual source of care were abstracted by trained nurse reviewers to compare claims and record information. Linked claim and medical record data for sampled patients were used to calculate: (i) the percent of billed visits documented in the record, (ii) the percent of medical record visits where both the date and the diagnosis agreed with the claims data, and (iii) the ratio of medical record visits to visits from billed claims. Included in the analysis were independent variables specifying place of residence, type and costliness of usual care source, level of patient utilization, and indicator condition on which patient was sampled. Ninety percent of the visits chronicled in the paid claims were documented in the medical record with 82% agreeing on both date and diagnosis. Compared to the medical records kept by private physicians and community health centers, a significantly lower percent of hospital medical records agreed with the claims data. Total volume of visits was 2.6% higher in the medical records than in the claims. Claims data substantially understated visits in the medical record by 25% for low cost providers and by 41% for patients with low use rates (based on claims information). Conversely, medical records substantially understated billed visits by 19% for rural patients and by 10% for persons with high visit rates. Although Medicaid claims are relatively accurate and useful for examining average ambulatory use patterns, they are subject to significant biases when comparing subgroups of providers classified by case-mix adjusted cost and patients classified by utilization rates. Medicaid programs are using claims data for profiling and performance assessment need to understand the limitations of administrative data.

Adult↗

PubMed1997

Variation of heat shock protein 70 through the cell cycle in HL-60 cells and its relationship to apoptosis.

Cells respond to a heat shock by synthesizing heat shock proteins, which help to protect the cells from further heating. Recent results indicate that heat shock protein 70 (hsp70) may help to protect cells from apoptosis. We have used flow cytometry to investigate the relationship between constitutive and inducible hsp70 and apoptosis through the cell cycle in HL-60 cells. Specific antibodies were used to measure hsp70 in cells costained with propidium iodide. In separate samples apoptosis was measured using the TdT assay. The apoptotic cells have a subdiploid DNA content, which allows them to be identified also in the bivariate histograms of heat shock protein vs DNA content. After HL-60 cells were heated at 45.0 degrees C for 7.5 min and incubated for various times at 37 degrees C, many of them underwent apoptosis. The level of inducible hsp70 (hsp72) was lower in the apoptotic cells than in the nonapoptotic population, but constitutive hsp70 (hsp73) was the same in both populations. Pretreatment with sodium vanadate increased the fraction of apoptotic cells twofold, slightly increased the level of hsp72 in the nonapoptotic cells, but did not affect hsp73. These results suggest that hsp72, but not hsp73, is involved in the development or prevention of apoptosis.

Apoptosis↗

PubMed1996

Levels of 70-kDa heat shock protein through the cell cycle in several mammalian cell lines.

Seven different cell lines were analyzed by flow cytometry to evaluate the variation in heat shock protein hsp70 through the cell cycle. Inducible (hsp72) or both constitutive and inducible (hsp70) heat shock proteins were measured with monoclonal antibodies, and the cell cycle distribution was simultaneously measured with propidium iodide. Cell lines analyzed were Rat-1, Hr-24 (Rat-1 transfected with human hsp 72 gene), CHO (Chinese hamster ovary), C3H-10T1/2, AG1522 (normal human foreskin), GM2149 (normal human female skin), and Hela. None of the cell lines had a substantial variation in hsp72 or hsp70 levels through the cell cycle if they were not heated. In contrast, after chronic heating at 42.0 degrees C for 7.5 h, different cell lines had different patterns of hsp72 or hsp70 through the cell cycle. These results demonstrate that the level of hsp70 is not regulated differentially through the cell cycle in a variety of mammalian cell lines under normal unheated conditions. However, heat shock does induce cell-cycle-specific regulation of hsp70, which varies for different cell lines.

Animals↗

PubMed1996

Comparison of flow cytometry and western blotting to measure Hsp70.

The levels of constitutive and inducible forms of heat shock protein 70 (hsp73 and hsp72, respectively) through the cell cycle were measured in CHO cells by flow cytometry and Western blotting at various times after heating. Cells were labeled with antibody C92 (hsp72) or N27 (hsp73) and propidium iodide prior to analysis by flow cytometry. Cells were heated for 15 min at 45 degrees C, then analyzed from 3 to 36 h later. There was about a tenfold increase in hsp72 in early S phase cells beginning within 6 h after heating and these cells gradually cycled though S phase so by 36 h most of them had divided. When CHO cells were exposed to 10 microM sodium vanadate, an inhibitor of tyrosine phosphatase, for 24 h prior to heating, the induction of hsp72 in early S phase cells was almost completely inhibited. Heated cells did not express hsp73 in a cell-cycle-dependent manner. Hsp73 increased uniformly in all cells by 10 h after heating and sodium vanadate did not affect the expression. Quantitative comparisons of the relative levels of hsp72 and hsp73 measured by flow cytometry and Western blotting were in excellent agreement. Control and heated cells were labeled with Hoechst 33342 and sorted from G1, S, and G2/M phases and processed by Western blotting to verify the cell cycle dependent increase in hsp72 as measured by flow cytometry. Again there was excellent agreement between the Western blotting and flow cytometry results.

Animals↗

PubMed1996

Effects of hyperthermia on intracellular chloride.

Hyperthermia induces transient changes in [Na+]i and [K+]i in mammalian cells. Since Cl- flux is coupled with Na+ and K+ in several processes, including cell volume control, we have measured the effects of heat on [Cl-]i using the chloride indicator, MQAE, with flow cytometry. The mean basal level of [Cl-]i in Chinese hamster ovary cells was 12 mM. Cells heated at 42.0 degrees or 45.0 degrees C for 30 min had about a 2.5-fold increase in [Cl-]i above unheated control values when measured immediately after heating. There was about a 3-fold decrease in [Na+]i under the same conditions, as measured by Sodium Green. The magnitude of the increase in [Cl-]i depended upon time and temperature. The [Cl-]i recovered in a time-dependent fashion to control values by 30 min after heating. When cells were heated at 45.0 degrees C for 30 min in the presence of 1.5 mM furosemide, the heat-induced [Cl-]i increase was completely blocked. Since furosemide inhibits the Na+/K+/2Cl- cotransporter, Cl- channels, and even Cl-HCO3 exchange, these ion transporters may be involved in the heat-induced increase in [Cl-]i.

Animals↗

PubMed1996

Heat-induced changes in intracellular sodium and membrane potential: lack of a role in cell killing and thermotolerance.

Hyperthermia induces transient changes in intracellular free sodium levels and membrane potential. The possible role of these changes in cell killing by hyperthermia and thermotolerance has been evaluated using Chinese hamster ovary IS1 and HeLa cells. Intracellular sodium was measured with Sodium Green and SBFI, while membrane potential was measured with the oxonol dye diBAC4(3). Heating at either 42.0 or 45.0 degrees C caused nearly the same decrease in free [Na+]i from about 20 mM in unheated cells to 5-7 mM in heated cells. However, survival differed by over two orders of magnitude after heating for 30 min at these two temperatures. In addition, blockage of the heat-induced decrease in [Na+]i using ouabain and/or amiloride did not affect the survival curves for heated cells. Hyperthermia also induced a membrane hyperpolarization of 15 mV after 15 min at 42.0 degrees C or 35 mV after 15 min at 45.0 degrees C which could be blocked with ouabain and amiloride. Both the free [Na+]i and membrane potential recovered to near baseline levels within 30-40 min after heating. Induction of thermotolerance using a 45.0 degrees C, 10-min heat treatment also was not affected by ouabain and/or amiloride. Finally, thermotolerant cells experienced the same heat-induced changes in free [Na+]i and membrane potential as non-thermotolerant cells. We conclude that the heat-induced changes in free [Na+]i and membrane potential are not directly related to cell killing by hyperthermia or thermotolerance.

Amiloride↗

PubMed1995

Intracellular Na+ measurements using sodium green tetraacetate with flow cytometry.

Intracellular sodium concentration ([Na+]i) can be measured using SBFI with image analysis or spectrofluorometry. However, SBFI cannot be used with most flow cytometry systems, due to its requirement for dual excitation in the UV range. Recently a new sodium indicator, Sodium Green, was developed which can be used with flow cytometry to measure [Na+]i. Adequate staining of cells with Sodium Green is dependent upon both dye and cell concentration, time and temperature of loading, use of the non-ionic detergent Pluronic, and the cell line used. Both Sodium Green and SBFI give similar calibration curves using the ionophore gramicidin. Sodium Green has a small pH dependence, but this should not affect most applications. Since a fluorescence ratio technique cannot be used with Sodium Green, we used a ratio of dye fluorescence to forward angle light scatter to normalize for cell size variations in the population. The basal [Na+]i obtained using the Sodium Green technique in CHO ISI cells was 19 mM, in reasonable agreement with previous studies using SBFI in other cells.

3T3 Cells↗

PubMed1995

Expression of hsp70 induced in CHO cells by 45.0 degrees C hyperthermia is cell cycle associated and DNA synthesis dependent.

In response to a heat shock, the synthesis of heat shock proteins with a molecular weight of 72 kD (hsp72) is induced. To determine whether hsp72 expression in Chinese hamster ovary (CHO) cells is cell cycle associated, flow cytometry was used to measure DNA content and heat shock protein levels simultaneously. After 10 min at 45.0 degrees C and incubation at 37 degrees C for several hours, hsp72 was induced to a high level in early S phase. Inhibitors of DNA synthesis, aphidicolin, and 1-beta-D-arabinofuranosylcytosine (araC), suppressed the induction of hsp72 but did not inhibit it completely. Hsp73 (constitutive hsp70) was also induced by heat shock, but the induction was uniform through the cell cycle and it was not suppressed by araC.

Animals↗

PubMed1995

Cell cycle variation of Hsp70 levels in HeLa cells at 37 degrees C and after a heat shock.

The expression of the 72 kD inducible heat shock protein (hsp72) has been reported to be cell cycle associated in unheated, synchronized HeLa cells. In this study, flow cytometry was used to investigate hsp72 levels through the cell cycle in HeLa cells by dual labeling with propidium iodide and antibodies against hsp72. The entire cell cycle distribution of hsp72 could be measured in a single sample of asynchronously growing cells. For unheated cells, the level of hsp72 increased about 30% from G1 to S phase, with about a 65% increase in G2/M, probably due to cell size differences. Neither mitotic selection nor serum stimulation induced a higher level of hsp72 than in the control cells. Western blot analysis of hsp72 from Hoechst-stained cells sorted from G1, mid-S, or G2/M showed that G1 cells had the lowest level of hsp72, with about a 30% increase in S phase and a 60% increase in G2/M, in good agreement with the flow cytometry results. These data conflict with previous reports by other laboratories which showed a 3-fold higher level of hsp72 in S phase than in G1 or G2. In contrast, heat shock (both acute and chronic) led to a non-uniform increase in hsp72 through the cell cycle. Most cells in mid S phase had high levels of hsp72, and a larger range in the levels of hsp72 were found in G1 and late S/G2/M phase cells.

Blotting, Western↗

PubMed1995

Prolonged neuromuscular block associated with mivacurium.

Mivacurium is a relatively new short-acting nondepolarizing neuromuscular blocker. A recommended dose of 0.15-0.2 mg kg-1 provides tracheal intubating conditions within 2.5 min and duration of action of 15-30 min, making it a possible alternative to suxamethonium for short procedures requiring tracheal intubation. However, in common with suxamethonium its metabolism depends primarily on plasma cholinesterase and its duration of action is prolonged in patients with reduced plasma cholinesterase activity. We present a case of unexpected prolonged neuromuscular block in a child with previously undiagnosed plasma cholinesterase deficiency.

Anesthesia Recovery Period↗