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Biomedical subjects

M Carlson

Publications and source records attributed to M Carlson.

At least 37 records · Page 2Linked to original sources
PubMed2000

Analyte loss due to membrane filter adsorption as determined by high-performance liquid chromatography.

The phenomenon of membrane filter adsorption in high-performance liquid chromatography (HPLC) is investigated utilizing 16 brands of filters representing 3 polymeric materials: cellulose acetate (CA), nylon, and polyvinylidene difluoride in a variety of diameters (3, 4, 7, 13, and 25 mm). Sixteen compounds commonly encountered in drug preparations are selected as sample analytes and classified as acidic, basic, and neutral in chemical behavior. Six mobile phase/sample solvent mixtures are included: 3 with methanol-water and 3 with acetonitrile-water as major constituents. When using methanol as the mobile phase organic component, CA, nylon, and polyvinylidene difluoride (PVDF) filters exhibit negligible to moderate adsorption levels with regard to the neutral and basic drug compounds. The acidic drug test compounds are adsorbed by 50% of all 3 filter materials tested in methanol-water. In acetonitrile, neutral compounds are affected by 31.4%, basic compounds are affected by 47.0%, and acidic compounds are affected by 53.6% of the nylon and PVDF filters. CA is incompatible with acetonitrile and is excluded from the study with this solvent.

Absorption↗
PubMed2000

Sip5 interacts with both the Reg1/Glc7 protein phosphatase and the Snf1 protein kinase of Saccharomyces cerevisiae.

The Snf1 protein kinase is an essential component of the glucose starvation signalling pathway in Saccharomyces cerevisiae. We have used the two-hybrid system to identify a new protein, Sip5, that interacts with the Snf1 kinase complex in response to glucose limitation. Coimmunoprecipitation studies confirmed the association of Sip5 and Snf1 in cell extracts. We found that Sip5 also interacts strongly with Reg1, the regulatory subunit of the Reg1/Glc7 protein phosphatase 1 complex, in both two-hybrid and coimmunoprecipitation assays. Previous work showed that Reg1/Glc7 interacts with the Snf1 kinase under glucose-limiting conditions and negatively regulates its activity. Sip5 is the first protein that has been shown to interact with both Snf1 and Reg1/Glc7. Genetic analysis showed that the two-hybrid interaction between Reg1 and Snf1 is reduced threefold in a sip5Delta mutant. These findings suggest that Sip5 facilitates the interaction between the Reg1/Glc7 phosphatase and the Snf1 kinase.

Base Sequence↗
PubMed2000

A glucose transporter chimera confers a dominant negative glucose starvation phenotype in Saccharomyces cerevisiae.

A family of glucose transporters mediates glucose uptake in Saccharomyces cerevisiae. We show that the dominant mutation GSF4-1, which impairs glucose repression of SUC2, results in a nonfunctional chimera of the transporters Hxt1p and Hxt4p. Hxt1/4p inhibits the function of wild-type glucose transporters. Similar mutations may facilitate analysis of the major facilitator superfamily.

Base Sequence↗
PubMed2000

Selective digestive tract decontamination and vancomycin-resistant enterococcus isolation in the surgical intensive care unit.

Vancomycin-resistant Enterococcus (VRE) has emerged as a significant nosocomial pathogen in the surgical intensive care unit (SICU). We wished to test the hypothesis that the use of selective digestive tract decontamination (SDD) in the SICU affects the frequency of VRE isolation. A retrospective review of hospital records and the SICU database was performed using patients admitted to the SICU service for three or more days from January 1, 1996 to December 31, 1999 at our large tertiary-care teaching hospital. During this time use of SDD in selected patient populations decreased due to physician preference. Information gathered included length of SICU stay, presence of VRE infection or colonization, and use and duration of SDD protocol, vancomycin, and ceftazidime. There were 110 newly diagnosed VRE cases in the SICU during this time period. During the same time period 54 patients received SDD. Eight patients who received SDD had positive VRE cultures and seven had the initial positive culture after receiving SDD. Overall, 9.1% of eligible SICU patients received SDD, 18.5% of patients in the SICU for over 3 days had VRE, 7.3% of VRE patients received SDD, and 13.0% of the SICU patients who received SDD subsequently developed VRE. SDD use was not associated with VRE in univariate analysis. Logistic regression analysis showed higher odds ratios for SDD use in combination with vancomycin than for vancomycin use alone (OR=4.3 vs. 10.9). Odds ratios were over three times higher for SDD plus vancomycin plus ceftazidime use when compared to vancomycin plus ceftazidime use alone (OR=70.5 vs. 19.8). We conclude that administration of SDD alone did not correlate with increased VRE isolation, but that SDD use in conjunction with vancomycin and ceftazidime was associated with VRE isolation.

Antibiotic Prophylaxis↗
PubMed2000

Regulatory interactions between the Reg1-Glc7 protein phosphatase and the Snf1 protein kinase.

Protein phosphatase 1, comprising the regulatory subunit Reg1 and the catalytic subunit Glc7, has a role in glucose repression in Saccharomyces cerevisiae. Previous studies showed that Reg1 regulates the Snf1 protein kinase in response to glucose. Here, we explore the functional relationships between Reg1, Glc7, and Snf1. We show that different sequences of Reg1 interact with Glc7 and Snf1. We use a mutant Reg1 altered in the Glc7-binding motif to demonstrate that Reg1 facilitates the return of the activated Snf1 kinase complex to the autoinhibited state by targeting Glc7 to the complex. Genetic evidence indicated that the catalytic activity of Snf1 negatively regulates its interaction with Reg1. We show that Reg1 is phosphorylated in response to glucose limitation and that this phosphorylation requires Snf1; moreover, Reg1 is dephosphorylated by Glc7 when glucose is added. Finally, we show that hexokinase PII (Hxk2) has a role in regulating the phosphorylation state of Reg1, which may account for the effect of Hxk2 on Snf1 function. These findings suggest that the phosphorylation of Reg1 by Snf1 is required for the release of Reg1-Glc7 from the kinase complex and also stimulates the activity of Glc7 in promoting closure of the complex.

Base Sequence↗
PubMed2000

Derivation and pilot assessment of a health promotion program for Mandarin-speaking Chinese older adults.

As the percentage of older adults of diverse ethnicities increases in the United States, the call for culturally sensitive health care service strategies that target the special needs of older people grows. The present report describes methods used to adapt a health care program so that it would better meet the needs of a group of well, older Mandarin-speaking Chinese residents of Los Angeles. The specific qualitative research procedures that we used to adapt the treatment program are described, along with the particular adaptations that emerged. Additionally, outcomes from a randomized pilot experiment are presented that are consistent with the notion that the adapted program was effective in reducing health-related declines among older Mandarin-speaking men and women. The overall outcome of this project is in agreement with other reports in the health care literature that address the importance of providing culturally sensitive health care service for elders.

Aged↗
PubMed1999

Gal83 mediates the interaction of the Snf1 kinase complex with the transcription activator Sip4.

The Snf1/AMPK protein kinase family is widely conserved in eukaryotes. In Saccharomyces cerevisiae, the Snf1 kinase is an essential element of the glucose response pathway and has diverse regulatory roles. The Snf1 complex contains one of the related proteins Sip1, Sip2 and Gal83, which are also conserved in higher eukaryotes. Previous studies showed that the Sip1/Sip2/Gal83 component plays a structural role in the complex. We present evidence that this component also mediates the interaction of the Snf1 kinase complex with specific targets. We show that Gal83 mediates the association of the kinase with Sip4, a Snf1-regulated transcription activator of gluconeogenic genes. Gal83 interacts with Sip4 in two-hybrid assays in vivo, and bacterially expressed proteins bind in vitro. Moreover, Gal83 is required for the two-hybrid interaction of Sip4 with the Snf1 kinase. Gal83 also facilitates the rapid Snf1-dependent phosphorylation and activation of Sip4 in response to glucose limitation, indicating that Gal83 mediates the functional interaction of Snf1 with Sip4. Evidence indicates that Sip1 and Sip2 do not interact with Sip4. We propose that members of the Sip1/Sip2/Gal83 family confer specificity to the kinase complex in its interactions with target proteins.

Basic-Leucine Zipper Transcription Factors↗
PubMed1999

Reg1p targets protein phosphatase 1 to dephosphorylate hexokinase II in Saccharomyces cerevisiae: characterizing the effects of a phosphatase subunit on the yeast proteome.

Protein phosphatase 1 (Glc7p) and its binding protein Reg1p are essential for the regulation of glucose repression pathways in Saccharomyces cerevisiae. In order to identify physiological substrates for the Glc7p-Reg1p complex, we examined the effects of deletion of the REG1 gene on the yeast phosphoproteome. Analysis by two-dimensional phosphoprotein mapping identified two distinct proteins that were greatly increased in phosphate content in reg1Delta mutants. Mixed peptide sequencing identified these proteins as hexokinase II (Hxk2p) and the E1alpha subunit of pyruvate dehydrogenase. Consistent with increased phosphorylation of Hxk2p in response to REG1 deletion, fractionation of yeast extracts by anion-exchange chromatography identified Hxk2p phosphatase activity in wild-type strains that was selectively lost in the reg1Delta mutant. The phosphorylation state of Hxk2p and Hxk2p phosphatase activity was restored to wild-type levels in the reg1Delta mutant by expression of a LexA-Reg1p fusion protein. In contrast, expression of LexA-Reg1p containing mutations at phenylalanine in the putative PP-1C-binding site motif (K/R)(X)(I/V)XF was unable to rescue Hxk2p dephosphorylation in intact yeast or restore Hxk2p phosphatase activity. These results demonstrate that Reg1p targets PP-1C to dephosphorylate Hxk2p in vivo and that the motif (K/R)(X) (I/V)XF is necessary for its PP-1 targeting function.

Amino Acid Sequence↗
PubMed1999

Efficient export of the glucose transporter Hxt1p from the endoplasmic reticulum requires Gsf2p.

Mutations in the GSF2 gene cause glucose starvation phenotypes in Saccharomyces cerevisiae. We have isolated the HXT1 gene, which encodes a low-affinity, high-capacity glucose transporter, as a multicopy suppressor of a gsf2 mutation. We show that gsf2 mutants accumulate Hxt1p in the endoplasmic reticulum (ER) and that Gsf2p is a 46-kDa integral membrane protein localized to the ER. gsf2 mutants also display a galactose growth defect and abnormal localization of the galactose transporter Gal2p but are not defective in function or localization of the high-affinity glucose transporter Hxt2p. These findings suggest that Gsf2p functions in the ER to promote the secretion of certain hexose transporters.

Biological Transport↗
PubMed1999

Catheter ablation of accessory pathways, atrioventricular nodal reentrant tachycardia, and the atrioventricular junction: final results of a prospective, multicenter clinical trial. The Atakr Multicenter Investigators Group.

BACKGROUND: The purpose of this study was to evaluate the safety and efficacy of a temperature-controlled radiofrequency catheter ablation system. METHODS AND RESULTS: The patient population included 1050 patients who had undergone ablation of atrioventricular nodal reentrant tachycardia (AVNRT), an accessory pathway (AP), or the atrioventricular junction (AVJ). Ablation was successful in 996 patients. The probability of success was highest among patients who had undergone ablation of the AVJ, lowest in patients who had undergone ablation of an AP, and in between for patients who had undergone ablation of AVNRT. A major complication occurred in 32 patients. Four variables predicted ablation success (AVJ, AVNRT, or left free wall AP ablation and an experienced center). Four factors predicted arrhythmia recurrence (right free wall, posteroseptal, septal, and multiple APs). Two variables predicted development of a complication (structural heart disease and the presence of multiple targets), and 3 variables predicted an increased risk of death (heart disease, lower ejection fraction, and AVJ ablation). CONCLUSIONS: These findings may serve as a guide to clinicians considering therapeutic options in patients who are candidates for ablation.

Adolescent↗
PubMed1999

Glucose repression in yeast.

The Snf1 protein kinase is a central component of the signaling pathway for glucose repression in yeast. Recent studies have addressed the regulation of Snf1 kinase activity and elucidated mechanisms by which Snf1 controls repression and activation of glucose-repressed genes. Important advances include evidence that Snf1 regulates the localization of the Mig1 repressor and that Snf1 functions at multiple points to control Cat8 and Sip4, the activators of gluconeogenic genes.

Gene Expression Regulation, Enzymologic↗
PubMed1999

Increased intraluminal release of eosinophil granule proteins EPO, ECP, EPX, and cytokines in ulcerative colitis and proctitis in segmental perfusion.

OBJECTIVE: The role of the eosinophil granulocyte in bowel mucosa in inflammatory bowel disease still remains obscure. The present study was performed in order to elucidate the local eosinophil activity and activating cytokines in the inflamed lesions of colon and rectum in patients with ulcerative colitis and proctitis. METHODS: The activity of intestinal eosinophils with respect to the release of granule proteins was studied in 18 patients (10 with colitis and 8 with isolated proctitis) and 18 healthy controls, using intraluminal segmental perfusion of the sigmoid colon and rectum. The released amounts of eosinophil granule proteins: eosinophil cationic protein (ECP), eosinophil peroxidase (EPO), and eosinophil protein X (EPX) to perfusion fluid were determined by radioimmunoassays. The intraluminal release of possible eosinophil priming cytokines granulocyte/macrophage-colony stimulating factor (GM-CSF) and interleukin 8 (IL-8), were analyzed by immunoassays. RESULTS: The mucosal release of ECP, EPO, and EPX was increased 10- to 20-fold in patients with colitis and proctitis compared with controls. The intraluminal release of GM-CSF and IL-8, was several-fold enhanced in patients with colitis and proctitis. We also found a correlation between all three eosinophil granule proteins and the levels of IL-8/GM-CSF in the sigmoidal segments of patients with colitis. CONCLUSIONS: We conclude that the increased release of ECP, EPO, and EPX to colorectal perfusion fluid indicate eosinophil involvement in the local disease in patients with colitis and proctitis. IL-8 and GM-CSF may play a role in eosinophil accumulation and priming in colitis.

Adult↗
PubMed1999

Psychometric properties of a Chinese translation of the SF-36 health survey questionnaire in the Well Elderly Study.

OBJECTIVES: To evaluate the psychometric properties of a Chinese translation of the 36-item Short Form Health Survey (SF-36) in the Well Elderly Study--a randomized clinical trial designed to evaluate the effectiveness of preventive occupational therapy services specifically tailored for multiethnic, independent-living, older adults. METHODS: Translation and back-translation procedures were used to obtain appropriate meanings for the SF-36 survey questions and to ensure face, functional, and conceptual equivalence. RESULTS: Statistical analyses demonstrated satisfactory reliability and validity, with the results generally similar to those reported for older Anglo adults. DISCUSSION: As the percentage of older adults of diverse ethnicity increases, the need for health care research and service strategies that can effectively include multiple ethnicities becomes paramount. The results of this study suggest that a Chinese-translated SF-36 can be used to assess multiple dimensions of health in a Mandarin-speaking population of older adults.

Aged↗