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Biomedical subjects

C Chavez

Publications and source records attributed to C Chavez.

At least 19 recordsLinked to original sources
PubMed2002

Comparison of eggshell surface microbial populations for in-line and off-line commercial egg processing facilities.

The objective of this project was to evaluate the aerobic plate counts (APC) of eggshells at in-line and off-line egg processing facilities at selected sites, throughout the processing procedure. Samples were collected from four sites in the processing plant and five time periods during the daily processing shift. Site 1 was from the conveyor system before the eggs passed through the washing system. Site 2 was after detergent wash but before sanitizer application. Site 3 was immediately after sanitizer treatment. Site 4 was immediately before packaging. Samples were collected from the sites at five equally spaced intervals beginning 15 min after the processing shift began and ending 15 min before the processing shift ended. At each sampling time, eggs were aseptically collected from each site and placed into sterile plastic bags containing 50 mL of PBS that was serially diluted immediately. The dilutions were plated on APC agar within 8 h of collection and were incubated at 37 C for 48 h. APC counts of in-line and off-line eggs were compared within time periods across sites. As the processing shift progressed, off-line APC counts were significantly higher than in-line counts at Site 1. At Site 2, off-line APC counts were significantly higher than in-line counts for Periods 2 through 5. At Site 3, off-line APC counts were significantly higher than in-line counts for Periods 2 through 5. Site 4 off-line counts were significantly higher than in-line counts at all time periods.

Animals↗
PubMed2002

Reduction of eggshell aerobic plate counts by ultraviolet irradiation.

The effects of 254 nm ultraviolet light (UV) radiation on aerobic plate count (APC) of egg shells were investigated. In the first experiment, eggs were exposed to UV treatment (7.35 mW/cm2) for 0, 15, 30, and 60 s. Three eggs from each treatment were aseptically collected and placed into sterile plastic bags containing 50 mL of sterile phosphate-buffered solution. Serial dilutions of the phosphate-buffered solution were plated on aerobic plate count agar and incubated at 37 C for 48 h. Exposure of eggshells to 30 and 60 s UV significantly reduced aerobic plate counts compared to untreated eggs. Exposure to 60 s of UV resulted in a 2 to 3 log10 cfu/egg APC reduction and reduced counts below detectable levels. In the second experiment, UV lights were placed in a chamber equipped with a commercial-style egg conveyor. A UV treatment of 7.5 mW/cm2 and time intervals of 0, 12, 36, and 48 s were used. Three eggs were placed consecutively on the conveyor and passed through the chamber. The center egg was selected for APC evaluation. Sample size, dilution, plating, and incubation procedures were used as described for the first experiment. A significant 1 to 2 log10 reduction in colony-forming units per egg between the eggs treated 48 s to the untreated eggs was detected. The results of these studies show that UV light treatment at high intensities and low time intervals has the potential to reduce aerobic plate counts of eggshells.

Animals↗
PubMed1999

The evolving role of advanced practice nursing within the new Veteran's Health Administration.

The Veteran's Health Administration (VHA) is experiencing profound change in focus and organization of service delivery. The focus of the evolving VHA system includes improvements in performance outcomes, such as actual costs, better access, higher levels of customer satisfaction, and improved functional status of patients. Given the changing nature of service delivery in the VHA system and the contributions of the Advanced Practices Nurses (APNs), this article explores the expanding role of the APN within the VHA and presents a best practice model for achieving the full potential of advanced nursing practice.

Hospitals, Veterans↗
PubMed1998

EGF-Receptor phosphorylation and signaling are targeted by H2O2 redox stress.

Inflammation of the respiratory tract is associated with the production of reactive oxygen species, such as hydrogen peroxide (H2O2) and superoxide (O2-), which contribute extensively to lung injury in diseases of the respiratory tract. The mechanisms and target molecules of these oxidants are mainly unknown but may involve modifications of growth-factor receptors. We have shown that H2O2 induces epidermal growth factor (EGF)-receptor tyrosine phosphorylation in intact cells as well as in membranes of A549 lung epithelial cells. On the whole, total phosphorylation of the EGF receptor induced by H2O2 was lower than that induced by the ligand EGF. Phosphorylation was confined to tyrosine residues and was inhibited by addition of genistein, indicating that it was due to the activation of protein tyrosine kinase (PTK). Phosphoamino acid analysis revealed that although the ligand, EGF, enhanced the phosphorylation of serine, threonine, and tyrosine residues, H2O2 preferentially enhanced tyrosine phosphorylation of the EGF receptor. Serine and threonine phosphorylation did not occur, and the turnover rate of the EGF receptor was slower after H2O2 exposure. Selective H2O2-mediated phosphorylation of tyrosine residues on the EGF receptor was sufficient to activate phosphorylation of an SH2-group-bearing substrate, phospholipase C-gamma (PLC-gamma), but did not increase mitogen-activated protein (MAP) kinase activity. Moreover, H2O2 exposure decreased protein kinase C (PKC)-alpha activity by causing translocation of PKC-alpha from the membrane to the cytoplasm. These studies provide novel insights into the capacity of a reactive oxidant, such as H2O2, to modulate EGF-receptor function and its downstream signaling. The H2O2-induced increase in tyrosine phosphorylation of the EGF receptor, and the receptor's slower rate of turnover and altered downstream phosphorylation signals may represent a mechanism by which EGF-receptor signaling can be modulated during inflammatory processes, thereby affecting cell proliferation and thus having implications in wound repair or tumor formation.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed1997

Determination of a substance P antagonist in human plasma and urine using high-performance liquid chromatography with ultraviolet absorbance and tandem mass spectrometric detection.

A high-performance liquid chromatographic (HPLC) assay using ultraviolet (UV) detection was developed and compared with a HPLC method with tandem mass spectrometric (HPLC/MS-MS) detection for the determination of a substance P receptor antagonist 2(S)-((3,5-bis(trifluoromethyl)benzyl)-oxy)-3(S)-phenyl-4-((3-oxo-1,2,4- triazol-5-yl) methyl)morpholine (Fig. 1, Ia, L-742 694) in human plasma and urine. The drug was isolated from the biological matrix through liquid-liquid extraction. In the HPLC/UV method, the samples were initially injected onto a cyano Hypersil column, and the chromatographic region containing the peaks of interest was heart-cut onto an analytical C-18 Hypersil column via a column switching device. The analyte was quantified by monitoring absorbance at 205 nm. The limit of quantification for I extracted from 1 ml of plasma or urine was 2.5 ng ml-1, and the assays were validated in the concentration range 2.5-500 ng ml-1. The HPLC/MS-MS method were validated in the concentration range 0.2-500 ng ml-1. Both assays provided data with precision, measured as coefficient of variation, better than 10% at all points within the standard curve range and with adequate accuracy.

Chromatography, High Pressure Liquid↗
PubMed1996

Geriatric targeting criteria as predictors of survival and health care utilization.

OBJECTIVE: To assess the utility of geriatric targeting criteria in predicting survival and health care utilization in a cohort of hospitalized older veterans. DESIGN: A prospective cohort study assessing geriatric targeting criteria, e.g., polypharmacy, falls, or confusion, with respect to adverse outcomes at 12 months. SETTING: A Tertiary Care VA Medical Center. PATIENTS: 507 acutely hospitalized male veterans aged 65 years or more. MAIN OUTCOME MEASURES: Survival status, nursing home placement, and total hospital days during 12 months following hospital admission. RESULTS: Patients who had a higher number of targeting criteria at admission showed a significantly increasing trend toward death (P < or = .001), nursing home placement (P < or = .01), and longer hospital stays (P < or = .01) at 12 months. In univariate analyses, weight loss (relative hazard 3.8, 95% CI 2.4, 5.9), appetite loss (relative hazard 3.3, 95% CI 1.9, 5.8), depression (relative hazard 2.5, 95% CI 1.4, 4.5), falls (relative hazard 2.2, 95% CI 1.2, 4.1), confusion (relative hazard 2.2, 95% CI 1.2, 4.0), and socioeconomic problems (relative hazard 1.6, 95% CI 1.0, 2.5) predicted death. Polypharmacy (OR 3.4, 95% CI 1.3, 8.8), confusion (OR 4.4, 95% CI 1.5, 13.0), and prolonged bedrest (OR 7.6, 95% CI 1.5, 39.3) predicted nursing home placement. Confusion (Beta 12.0, 95% CI 2.9, 21.3), falls (Beta 14.2, 95% CI 4.2, 24.3), and prolonged bedrest (Beta 22.4, 95% CI 3.9, 41.0) predicted total hospital days. In multivariate analyses, weight loss, depression, and socioeconomic problems predicted death; confusion and polypharmacy predicted nursing home placements; and falls predicted total hospital days. CONCLUSION: This prospective cohort study of hospitalized older veterans demonstrated geriatric targeting criteria as predictors of adverse hospital outcomes. Our findings suggest screening acutely hospitalized patients using chart abstracted geriatric targeting criteria is useful in identifying patients at risk for adverse outcomes of hospitalization.

Activities of Daily Living↗
PubMed1996

Passive hyperimmune therapy: buying time at what cost?

Some AIDS physicians are now turning to passive hyperimmune therapy as an alternative to try to protect and rebuild AIDS patients' ravaged immune systems. This is a labor-intensive and expensive treatment that raises many questions.

Double-Blind Method↗
PubMed1995

Development and comparison of high-performance liquid chromatographic methods with tandem mass spectrometric and ultraviolet absorbance detection for the determination of cyclobenzaprine in human plasma and urine.

Sensitive assays for the determination of cyclobenzaprine (I) in human plasma and urine were developed utilizing high-performance liquid chromatography (HPLC) with tandem mass spectrometric (MS-MS) and ultraviolet (UV) absorbance detections. These two analytical techniques were evaluated for reliability and sensitivity, and applied to support pharmacokinetic studies. Both methods employed a liquid-liquid extraction of the compound from basified biological sample. The organic extract was evaporated to dryness, the residue was reconstituted in the mobile phase and injected onto the HPLC system. The HPLC assay with MS-MS detection was performed on a PE Sciex API III tandem mass spectrometer using the heated nebulizer interface. Multiple reaction monitoring using the parent-->daughter ion combinations of m/z 276 --> 215 and 296 --> 208 was used to quantitate I an internal standard (II), respectively. The HPLC-MS-MS and HPLC-UV assays were validated in human plasma in the concentration range 0.1-50 ng/ml and 0.5-50 ng/ml, respectively. In urine, both methods were validated in the concentration range 10-1000 ng/ml. The precision of the assays, as expressed as coefficients of variation (C.V.) was less than 10% over the entire concentration range, with adequate assay specificity and accuracy. In addition to better sensitivity, the HPLC-MS-MS assay was more efficient and allowed analysis of more biological fluid samples in a single working day than the HPLC-UV method.

Amitriptyline↗
PubMed1995

Determination of a glycine/NMDA receptor antagonist in human plasma and urine using column-switching high-performance liquid chromatography with ultraviolet, fluorescence and tandem mass spectrometric detection.

High-performance liquid chromatography (HPLC) assays using ultraviolet (UV) and fluorescence (FL) detection were developed and compared with a liquid chromatography/tandem mass spectrometry (LC/MS-MS) method for determination of the glycine receptor antagonist 7-chloro-4-hydroxy-3-(3-phenoxy)phenyl-2(1H)-quinolone (L-701, 324, I) in human plasma and urine. The drug and internal standard (II) were isolated from the biological matrix through liquid-liquid extraction. In the HPLC-UV and HPLC-FL methods, the samples were initially injected onto a Cyano BDS Hypersil column, and the chromatographic region containing the peaks of interest was heart-cut onto an analytical C-18 BDS Hypersil column via a column-switching device. The analyte was quantified by monitoring either absorbance at 226 nm or fluorescence at 385 nm following 230 nm excitation. The limit of quantitation for I extracted from 1 ml of plasma or urine was 5 ng ml-1, and the assays were validated in the concentrated range of 5-200 ng ml-1. The LC/MS-MS method also utilized a column-switching protocol and was validated in the concentration range of 1-200 ng ml-1. Both assays provided data with precision and accuracy within less than 10% for all points in the standard curve range.

Chromatography, High Pressure Liquid↗
PubMed1989

Calcitonin, zinc, and testicular function.

Recent studies demonstrating decreases in transport kinetics of zinc (Zn) in testis in response to calcitonin (CT) and the presence of CT receptors on Leydig cells has suggested a physiological interrelationship between CT and cellular Zn metabolism in the testis. The present studies were undertaken to evaluate the acute effects of human synthetic calcitonin (hCT) on testosterone (T) synthesis and on transmembrane Zn transport as measured in a closed two-compartment model system in Leydig cells isolated from intact and thyroparathyroldectomized (TPTX) rats. Leydig cells acutely exposed to 1 ng/mL equine luteinizing hormone (LH) in vitro had a fivefold increase in medium T concentration. Calcitonin at 42 micrograms/mL had no effect on the basal T synthesis and did not affect the increase seen after LH administration. Lower doses of LH demonstrated a dose response for T production, but no alteration in the pattern of response. In TPTX rats pretreated with 167 micrograms/d (25 MRC U/d) hCT subcutaneously (sc) for three days before they were killed, a reduction to 73% of the control value was observed in the in vitro Leydig cell fractional influx coefficient for Zn transport (P less than .02). No difference was observed in the fractional efflux coefficient. Fractional flux coefficients from intact rats demonstrated qualitatively similar, but more variable, changes. These data demonstrate that there is no acute effect of CT on T synthesis in the isolated Leydig cell. There does appear, nevertheless, to be a role for CT in the modulation of transmembrane Zn transport. Clinically important Zn-dependent alterations of T synthesis may require long-term changes in Zn metabolism before they become manifest.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Molecular cloning of the Streptococcus mutans gene specifying antigen A.

A gene encoding a Streptococcus mutans surface protein antigen has been isolated from a strain GS-5 gene bank constructed via the Streptococcus-Escherichia coli shuttle vector pSA3. This E. coli recombinant clone, designated 4B2, expressed S. mutans proteins, as shown by Western immunoblot analysis with a specific rabbit antibody to S. mutans surface antigens. Three bands were observed, including a 52-kilodalton (kDa) protein (pI 5.7), a 29-kDa protein (pI 4.2), and a 20-kDa protein usually present in lower amounts. The 52- and 29-kDa proteins both reacted with a monoclonal antibody to S. mutans antigen A, a 29-kDa protein which has been characterized and used as a vaccine for the prevention of induced caries in rodents and monkeys. The 52-kDa protein, but not the 29-kDa protein, showed a capacity to bind to a broad number of carbohydrate polymers. The results from this study suggest that the recombinant 4B2 clone specifies a 52-kDa protein which is a precursor to the 29-kDa antigen A.

Antibodies, Bacterial↗
PubMedDate not supplied

Prickly business. The finer points of acupuncture.

Acupuncture, which is gaining credibility among the Western medical establishment, is just one element of traditional Chinese medicine (TCM) being used to treat fatigue, nausea, insomnia, diarrhea, menstrual problems, and HIV-related peripheral neuropathy. Acupuncture is often used in combination with exercise massage, meditation, and herbal therapy. Special combinations of Chinese herbs are used to treat HIV-conditions, promote digestion, increase energy, and fight fungal infections. "Enhance", "Resist", and "Combination A", are three such formulas. Another benefit of acupuncture and Chinese herbs is their ability to decrease side effects associated with Western medicine. The growing medical interest in acupuncture is evidenced in the progress of CPCRA 022, a phase II/III trial to study acupuncture alone or in combination with amitriptyline, an anti-depressant, as a treatment for peripheral neuropathy. The National Institutes of Health (NIH) recently awarded the Bastyr University in Seattle, with funds to study alternative therapies. Regardless of outcomes, these studies may encourage other organizations to pursue acupuncture trials.

Acupuncture Therapy↗