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Biomedical subjects

M K Schwartz

Publications and source records attributed to M K Schwartz.

At least 19 recordsLinked to original sources
PubMed2005

Serum HER2 extracellular domain in metastatic breast cancer patients treated with weekly trastuzumab and paclitaxel: association with HER2 status by immunohistochemistry and fluorescence in situ hybridization and with response rate.

PURPOSE: We explored the relationship between circulating HER2 extracellular domain (ECD) and tissue HER2 status as determined by immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). We also examined its predictive value in a cohort of metastatic breast cancer patients treated with weekly trastuzumab and paclitaxel. METHODS: Eligible patients had pre- and post-treatment stored serum specimens and were treated on a previously reported phase II trial. Retrospective analysis evaluated: the association between pretreatment serum HER2 ECD and tissue HER2 status by IHC and FISH; and the association between change in serum HER2 ECD after 12 weeks of therapy and response proportion. RESULTS: Stored serum samples were available for 55/95 (58%) patients. Statistically significant associations were found between HER2 status as assessed by IHC and FISH, and baseline serum HER2 ECD level. Patients whose ECD normalized after 12 weeks of therapy had a higher response proportion compared with patients with persistently high ECD levels (68% versus 15%, P=0.005). A relative decline of over 55% from baseline HER2 ECD predicted response to therapy. CONCLUSION: A statistically significant association was observed between pretreatment serum HER2 ECD and tissue HER2 status as assessed by IHC and FISH. A decrease in serum HER2 ECD level was a significant predictor of response to trastuzumab-based therapy.

Adult↗
PubMed2005

Behavioral and neurochemical phenotyping of Homer1 mutant mice: possible relevance to schizophrenia.

Homer proteins are involved in the functional assembly of postsynaptic density proteins at glutamatergic synapses and are implicated in learning, memory and drug addiction. Here, we report that Homer1-knockout (Homer1-KO) mice exhibit behavioral and neurochemical abnormalities that are consistent with the animal models of schizophrenia. Relative to wild-type mice, Homer1-KO mice exhibited deficits in radial arm maze performance, impaired prepulse inhibition, enhanced 'behavioral despair', increased anxiety in a novel objects test, enhanced reactivity to novel environments, decreased instrumental responding for sucrose and enhanced MK-801- and methamphetamine-stimulated motor behavior. No-net-flux in vivo microdialysis revealed a decrease in extracellular glutamate content in the nucleus accumbens and an increase in the prefrontal cortex. Moreover, in Homer1-KO mice, cocaine did not stimulate a rise in frontal cortex extracellular glutamate levels, suggesting hypofrontality. These behavioral and neurochemical data derived from Homer1 mutant mice are consistent with the recent association of schizophrenia with a single-nucleotide polymorphism in the Homer1 gene and suggest that the regulation of extracellular levels of glutamate within limbo-corticostriatal structures by Homer1 gene products may be involved in the pathogenesis of this neuropsychiatric disorder.

Animals↗
PubMed2003

Landscape location affects genetic variation of Canada lynx (Lynx canadensis).

The effect of a population's location on the landscape on genetic variation has been of interest to population genetics for more than half a century. However, most studies do not consider broadscale biogeography when interpreting genetic data. In this study, we propose an operational definition of a peripheral population, and then explore whether peripheral populations of Canada lynx (Lynx canadensis) have less genetic variation than core populations at nine microsatellite loci. We show that peripheral populations of lynx have fewer mean numbers of alleles per population and lower expected heterozygosity. This is surprising, given the lynx's capacity to move long distances, but can be explained by the fact that peripheral populations often have smaller population sizes, limited opportunities for genetic exchange and may be disproportionately affected by ebbs and flows of species' geographical range.

Alleles↗
PubMed2000

Complexed prostate specific antigen provides significant enhancement of specificity compared with total prostate specific antigen for detecting prostate cancer.

PURPOSE: Determining serum total prostate specific antigen (PSA) has proved to be a valuable diagnostic aid for detecting prostatic carcinoma, although the lack of specificity has limited its usefulness. Studies indicate that the use of percent free PSA would improve specificity while maintaining sensitivity. Since complexed PSA represents the major proportion of measurable PSA in serum, we determined whether it represents a single test alternative to the use of percent free PSA for the early detection of prostate cancer. MATERIALS AND METHODS: Archival serum was obtained from 385 men with no evidence of malignancy on biopsy and 272 with biopsy confirmed prostate cancer. We determined the concentration and proportion of total, complexed and free PSA. RESULTS: Receiver operating characteristics analysis using total PSA results from all samples (range 0.32 to 117 ng./ml.) indicated that the areas under the curve for complexed PSA alone as well as the free-to-total and complexed-to-total PSA ratios were similar and significantly greater than those for total PSA alone. Within the range of 85% to 95% sensitivity receiver operating characteristics analysis revealed that the specificity of complexed PSA was higher than that of total PSA and equivalent to that of the free-to-total PSA ratio. We noted a similar improvement in specificity in the 4 to 10 ng./ml. total PSA range. Using published cutoff values for complexed, total and percent free PSA when total PSA was in the 4 to 10 ng./ml. range the sensitivity and specificity of complexed and percent free PSA were similar. Within the 4 to 10 ng./ml. total PSA range the population of patients with no evidence of malignancy and complexed PSA below the upper limit was different with respect to total PSA from that with no evidence of malignancy and free PSA greater than 25%. CONCLUSIONS: The measurement of complexed PSA represents an alternative to the use of percent free PSA, although the patient populations identified by the 2 tests are different.

Humans↗
PubMed1999

Genetic testing and the clinical laboratory improvement amendments of 1988: present and future.

CLIA '88 superseded CLIA '67. CLIA '88 set standards designed to improve quality and expanded federal oversight to virtually all clinical laboratories in the United States. Presumably because genetics testing was then in its infancy, CLIA '88 did not devote a special section to genetics testing. Biochemical and immunochemical tests used to evaluate inborn errors of metabolism and other genetic entities were categorized as analytes in the Clinical Chemistry section, and DNA probes used primarily in infectious disease were included in Microbiology. The legal, social, economic, and ethical implications of genetic testing and the rapid commercialization of these tests led to recommendations that genetic testing be defined as a laboratory specialty with a subsection in CLIA. The advisory committee created under CLIA was assigned to review these recommendations. The committee agreed that genetics testing was sufficiently different from other areas already included in CLIA to warrant a separate section. Two definitions were adopted. The more clear-cut one is for molecular genetic and cytogenic tests. This includes the analysis of human DNA/RNA in evaluating genetic diseases. The second definition is not as clear-cut and is for the analysis of proteins and metabolites used predominantly to detect inborn errors of metabolism. Many of these analytes already are categorized according to their uses for other purposes. The recommendations for genetic testing include detailed and specific proposals concerning personnel, confidentiality and informed consent, quality control, contamination, proficiency testing, validation of tests, special reporting, retention of records, and reuse of tested specimens.

Clinical Laboratory Techniques↗
PubMed1998

Bayer Immuno 1 PSA Assay: an automated, ultrasensitive method to quantitate total PSA in serum.

The Bayer Immuno 1 PSA Assay measures total PSA in human serum and demonstrates excellent performance with an interassay CV < or = 3.4% and a biological detection limit of 0.03 microgram/L. No significant interference from common hormonal and chemotherapeutic drugs, kallikrein, prostatic acid phosphatase, and trypsin, or elevated levels of total bilirubin, hemoglobin, triglycerides, and IgG was observed. The 95th percentile values for healthy individuals increased with age from 3.0 micrograms/L for males 50-59 years and 3.3 micrograms/L for males 60-69 years, to 4.6 micrograms/L for males > or = 70 years. Clinical studies with retrospective samples demonstrated correspondence between serial measurements of PSA and clinical outcome for 98% of 159 prostate cancer patients. Clinical sensitivity for patients with clinical evidence of disease, untreated at the time of specimen draw, increased with increasing stage from 77.5-100%. Specificity of 60-70% for BPH and other benign urogenital diseases was consistent with previous findings. Bayer Immuno 1 PSA Assay values for 2131 specimens from healthy subjects and patients with prostate cancer, BPH, and other malignant and nonmalignant diseases correlated well with the Abbott IMx PSA Assay over the range 0.0-6,238 micrograms/L (Y = 1.10 x + 0.02). The Bayer Immuno 1 PSA Assay provides automated ultrasensitive, precise, and equimolar measurement of total PSA in human serum.

Aged↗
PubMed1998

Multicenter evaluation of the Bayer Immuno I CA 15-3 assay.

We conducted a multicenter evaluation of the analytical and clinical features of the automated Bayer Immuno 1 CA 15-3 assay and compared assay performance to two manual tests. Results of the 10-day imprecision study of the Bayer Immuno 1 assay pooled across four evaluation sites and three lots of reagent produced total CV < or = 4%. Lot-to-lot reproducibility for 26 different lots of reagents and calibrators manufactured over a 2-year period was demonstrated (CV, 1.1%). Results for the Bayer Immuno 1 assay correlated well with the Biomira TRUQUANT BR 27.29 and Centocor CA 15-3 RIAs (r > or = 0.94). The upper limit of the reference interval for the Bayer Immuno 1 assay was 35.9 kilounits/L (35.9 units/mL); values were similar for all methods. Longitudinal monitoring of healthy women yielded assay values with an average CV of 11% and 21% for the Bayer Immuno 1 and Biomira assays, respectively. The Bayer Immuno 1 assay demonstrated the analytical features, intermethod correlation, and long-term performance characteristics that are essential for longitudinal monitoring of breast cancer patients.

Adolescent↗
PubMed1995

Tissue cathepsins as tumor markers.

In the metastatic process, proteolytic enzymes play an important role in mediating passage of the malignant cell through the cell membrane. The cathepsins are ubiquitous lysosomal proteases and are classified both functionally and according to their active site. Cathepsin D, cathepsin B and to a lesser extent other cathepsins have been described as prognostic markers in cancer. Measurements of cathepsin D in breast tissue may be significant in predicting recurrence as well as disease free and overall survival. Reported differences concerning the role of cathepsin D as a prognostic marker may be related in part to the methodology used and the employment in the assays of antibodies prepared to different portions of the molecule. The general consensus is that elevated concentrations of cathepsin D in breast cancer tissue are highly significant indicators of the potential for recurrence. Cathepsin B, which catalyzes the degradation of laminin, may play a role in the rupture of the basement membrane and may be of importance in pancreatic and colorectal cancer.

Biomarkers, Tumor↗
PubMed1995

Glutathione metabolism in newborns: evidence for glutathione deficiency in plasma, bronchoalveolar lavage fluid, and lymphocytes in prematures.

Respiratory distress in premature newborns is associated with deficiency of surfactant in the bronchoalveolar lining fluid; this may be influenced by a local deficiency of antioxidants. Severe L-buthionine-S,R-sulfoximine-induced depletion of glutathione (GSH, a major antioxidant) in rodents is associated with lung type 2 cell lamellar body damage and decreased concentrations in lung and bronchoalveolar lavage fluid (BALF) of phosphatidyl choline (a major component of surfactant). At birth, prematurely born newborns (30-34 weeks) had lower peripheral venous plasma GSH concentrations than term (> 36 weeks) babies; these levels decreased further with increasing prematurity (< 27 weeks, with respiratory distress). On day 2, the peripheral venous plasma GSH concentrations reached a nadir, and the lowest levels were found in the most premature newborns. Lymphocyte GSH concentrations were lowest on day 2 and day 7, and in prematures (< 27 weeks, with respiratory distress) remained below adult lymphocyte GSH levels for at least 4 weeks. At birth, prematures (< 27 weeks, with respiratory distress) had a central plasma arterio-venous (A-V) GSH gradient across the lung (an estimate of lung uptake of GSH) of 0.72 +/- 0.15 (mean +/- SD) mumol/L; on day 2, the A-V gradient did not change significantly (0.49 +/- 0.09 mumol/L). At birth, these prematures had markedly decreased BALF GSH concentrations (compared with adult levels), and they were not significantly changed during the first 4 weeks of life. These results suggest that GSH deficiency is present in prematures and that it increases with the degree of prematurity. At birth, GSH deficiency will compromise the lungs' defense against oxidative stress injury. Oxidative stress is likely to increase if hyperoxic treatment is given for respiratory distress in these infants.

Bronchoalveolar Lavage Fluid↗
PubMed1995

L-2-oxothiazolidine-4-carboxylate, a cysteine precursor, stimulates growth and normalizes tissue glutathione concentrations in rats fed a sulfur amino acid-deficient diet.

The efficiency of L-2-oxothiazolidine-4-carboxylate, a cysteine precursor, in stimulating glutathione synthesis and growth was evaluated in growing rats. Animals were fed a sulfur amino acid-deficient diet (0.25% L-methionine and no cysteine) supplemented with L-2-oxothiazolidine-4-carboxylate (0.35%) for 3 wk and compared with age-matched animals receiving the sulfur amino acid-deficient diet alone. Rats fed the sulfur amino acid-deficient diet had lower glutathione concentrations in bronchoalveolar lining fluid, lung, lymphocytes, and liver than rats fed a sulfur amino acid-deficient diet supplemented with L-2-oxothiazolidine-4-carboxylate. Rats fed the supplemented diet had normal tissue and bronchoalveolar lining fluid glutathione levels. Central venous plasma glutathione concentrations, mostly reflecting liver excretion, were less affected by L-2-oxothiazolidine-4-carboxylate supplementation. Rats fed L-2-oxothiazolidine-4-carboxylate supplementation had normal weight gain compared with a much lower weight gain in animals fed the sulfur amino acid-deficient diet alone. Thus, L-2-oxothiazolidine-4-carboxylate increased tissue glutathione concentrations and stimulated growth in rats. The lung glutathione status of the rats was reflected by glutathione concentrations in lymphocytes and the bronchoalveolar lining fluid, but not by the central venous plasma glutathione concentrations.

Amino Acids, Sulfur↗
PubMed1995

Current status of tumour markers.

Tumour markers are defined as substances, measured by laboratory techniques, which are useful in the management of the patient with cancer. In this review the current clinical use and abuse of tumour markers is discussed with a view to outline the status of quality assurance in their performance and to establish the significance of single marker versus multiple marker analysis. The problems of screening are considered. It is emphasized that in order for tumour markers to take their appropriate place in cancer management the following are needed: high throughput automated equipment; new markers and new assays for old markers; reference materials and standards; nomenclature standardization and the introduction and evaluation of quality assurance programs which include proficiency studies. These needs can only be achieved by close cooperation of clinicians, laboratory professionals and the diagnostic industry.

Biomarkers, Tumor↗
PubMed1995

Automated approaches to rapid-response testing. A comparative evaluation of point-of-care and centralized laboratory testing.

This study evaluates the premise that point-of-care or near-patient testing provides more effective medical care because laboratory turnaround time is reduced and, therefore, presumably the time before therapy begins is reduced. An accurate evaluation of this premise must compare the operation of a point-of-care laboratory and an alternative dedicated, centralized laboratory. Assessment of both laboratory operations with respect to turnaround time, costs and benefits, regulatory factors, and finally patient care outcome are all essential in reaching a conclusion. In this study, laboratory operations in a centralized urgent care laboratory were compared with those of a point-of-care satellite laboratory. Turn-around time analysis for whole blood (heparinized specimens requiring no centrifugation) and serum analytes were measured during a representative time period. Analysis of turnaround time considered both the preanalytic time, defined as collection to receipt of the specimen in the laboratory, and the analytic time component that accounts for receipt, processing, analysis, and reporting of the final data into the laboratory information system. The preanalytic component of the point-of-care satellite laboratory was also compared with the urgent care laboratory equipped with a rapid-transport specimen system. Turnaround time in the point-of-care satellite laboratory and urgent care laboratory equipped with a rapid-transport specimen system. Turnaround time in the point-of-care satellite laboratory and urgent care laboratory equipped with a rapid-transport system were comparable. In this analysis, staff requirements, ability to comply with regulatory requirement, and the increasing demand for a larger selection of tests needed urgently were considered. In a tertiary care medical center, such as the authors', a dedicated, centralized laboratory equipped with a rapid-transport specimen system provides better comprehensive laboratory service than does a point-of-care facility with limited capability.

Automation↗
PubMed1994

Post-doctoral training of the non-physician doctoral scientist.

Postgraduate training of the non-MD clinical chemist (clinical biochemist) is for the most part 'on the job training'. There are few formally structured programs to achieve the necessary skills and understanding needed by individuals before he or she can assume the directorship of a modern clinical laboratory. The experience and training must include management, laboratory performance, medical interface, research and education.

Chemistry, Clinical↗
PubMed1994

Breast cancer marker Ca549. A multicenter study.

A multicenter study of CA549, a marker for breast cancer, was conducted using sera from 1721 patients with benign and malignant conditions by an immunoradiometric assay, BRESMARQ. Acceptable assay performance was demonstrated by studies of intra-assay (2.2% to 12% coefficient of variation [CV]), interassay (4.1% to 11.8% CV), and interlaboratory (4.8% to 8.7% CV) precision; sensitivity (.3 kU/L); linearity; recovery; high-dose hook effect (up to 10,000 kU/L); and interferences (human antimouse antibodies; protein, bilirubin, hemoglobin levels; lipid and cancer therapeutic agents). A reference interval of 0-12.5 kU/L (women) and 0-11.9 kU/L (men) was established from 746 healthy persons. The distribution of values exceeding the reference range for benign conditions was as follows: pregnant and lactating women (2%); benign breast disease (5%); and seven other benign diseases, including liver (24%), lung (19%), prostate (14%), colon, endometrial, gastric, and ovarian (< 10%). For nonbreast cancers, the distribution was Hodgkin's (7%), colon (10%), endometrial (15%), gastric (15%), lymphoma (15%), prostate (20%), ovarian (39%), and liver (45%). For breast cancer, the distribution was stage I (5%), stage II (14%), stage III (32%), and stage IV (74%). The receiver-operating characteristic analysis demonstrated the usefulness of CA549 as a marker in stage IV breast cancer.

Antibodies, Monoclonal↗
PubMed1993

Effect of tamoxifen on serum cholesterol and lipoproteins during chemohormonal therapy.

The effect of tamoxifen on serum cholesterol, high density lipoprotein cholesterol (HDL-cholesterol), low density lipoprotein cholesterol (LDL-cholesterol) and the ratio of LDL-cholesterol to HDL-cholesterol (LDL-C/HDL-C) was investigated in breast cancer patients undergoing therapy for advanced disease. Longitudinal studies in 24 patients treated with tamoxifen (10 mg, twice daily) indicated average decreases in total serum cholesterol (17%) and LDL-cholesterol (27%), whereas the effect of tamoxifen on HDL-cholesterol varied with the individual patient. There was a significant decrease in the LDL-C/HDL-C ratio (33%) consistent with a decreased risk for coronary artery disease. This beneficial influence of tamoxifen on risk factors associated with cardiovascular disease was evident in both premenopausal and postmenopausal patients whether tamoxifen was administered alone or in combination with cytotoxic chemotherapy.

Antineoplastic Combined Chemotherapy Protocols↗