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Biomedical subjects

S Lehr

Publications and source records attributed to S Lehr.

At least 19 recordsLinked to original sources
PubMed2000

MAP kinases Erk1/2 phosphorylate sterol regulatory element-binding protein (SREBP)-1a at serine 117 in vitro.

Sterol regulatory element-binding protein (SREBP)-1a is a transcription factor sensing cellular cholesterol levels and integrating gene regulatory signals mediated by MAP kinase cascades. Here we report the identification of serine 117 in SREBP-1a as the major phosphorylation site of the MAP kinases Erk1/2. This site was identified by nanoelectrospray mass spectrometry and peptide sequencing of recombinant fusion proteins phosphorylated by Erk1/2 in vitro. Serine 117 was verified as the major phosphorylation site by in vitro mutagenesis. Mutation of serine 117 to alanine abolished Erk2-mediated phosphorylation in vitro and the MAP kinase-related transcriptional activation of SREBP-1a by insulin and platelet-derived growth factor in vivo. Our data indicate that the MAP kinase-mediated effects on SREBP-1a-regulated target genes are linked to this phosphorylation site.

Amino Acid Sequence↗
PubMed2000

Identification of major tyrosine phosphorylation sites in the human insulin receptor substrate Gab-1 by insulin receptor kinase in vitro.

Gab-1 (Grb2-associated binder-1), which appears to play a central role in cellular growth response, transformation, and apoptosis, is a member of the insulin receptor substrate (IRS) family. IRS proteins act downstream in the signaling pathways of different receptor tyrosine kinases, including the insulin receptor (IR). In this paper, we characterize the phosphorylation of recombinant human Gab-1 (hGab-1) by IR in vitro. Kinetic phosphorylation data revealed that hGab-1 is a high affinity substrate for the IR (K(M): 12.0 microM for native IR vs 23.3 microM for recombinant IR). To elucidate the IR-specific phosphorylation pattern of hGab-1, we used phosphopeptide mapping by two-dimensional HPLC analysis. Phosphorylated tyrosine residues were subsequently identified by sequencing the separated phosphopeptides by matrix assisted laser desorption ionization mass spectrometry (MALDI-MS) and Edman degradation. Our results demonstrate that hGab-1 was phosphorylated by IR at eight tyrosine residues (Y242, Y285, Y373, Y447, Y472, Y619, Y657, and Y689). Seventy-five percent of the identified radioactivity was incorporated into tyrosine residues Y447, Y472, and Y619 exhibiting features (NYVPM motif) of potential binding sites for the regulatory subunit (p85) of phosphatidylinositol (PI)-3 kinase. Accordingly, pull down assays with human HepG2 cell lysates showed that IR-specific phosphorylation of wild-type hGab-1 strongly enhanced PI-3 kinase binding. This is still the case when a single tyrosine residue in the NYVPM motif was mutated to phenylalanine. In contrast, phosphorylation-dependent binding of PI-3 kinase was completely abolished by changing a second tyrosine residue in a NYVPM motif independent from its location. Recently, we identified a similar cohort of tyrosine phosphorylation sites for the epidermal growth factor receptor (EGFR) with a predominant phosphorylation of tyrosine residue Y657 and binding of Syp [Lehr, S. et al. (1999) Biochemistry 38, 151-159]. These differences in the phosphorylation pattern of hGab-1 may contribute to signaling specificity by different tyrosine kinase receptors engaging distinct SH2 signaling molecules.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Effects of vitamin E on chronic and acute endothelial dysfunction in smokers.

OBJECTIVES: The aims of this study were to determine whether chronic or acute impairment of flow mediated vasodilation (FMD) in the brachial artery of smokers can be restored or preserved by the antioxidant vitamin E. BACKGROUND: Transient impairment of endothelial function after heavy cigarette smoking and chronic endothelial dysfunction in smokers result at least in part from increased oxidative stress. METHODS: We studied 22 healthy male smokers (mean +/- SD, 23 +/- 9 cigarettes per day) randomly assigned to receive either 600 IU vitamin E per day (n = 11, age 28 +/- 6 years) or placebo (n = 11, age 27 +/- 6 years) for four weeks and 11 age-matched healthy male nonsmokers. Flow mediated vasodilation and endothelium-independent, nitroglycerin-induced dilation were assessed in the brachial artery using high resolution ultrasound (7.5 MHz) at baseline and after therapy. Subjects stopped smoking 2 h before the ultrasound examinations. At the end of the treatment period, a third scan was obtained 20 min after smoking a cigarette (0.6 mg nicotine, 7 mg tar) to estimate transient impairment of FMD. RESULTS: Flow mediated vasodilation at baseline was abnormal in the vitamin E (5.3 +/- 3.8, p < 0.01) and in the placebo group (6.4 +/- 3.5, p < 0.05) compared with nonsmoking controls (11.6 +/- 4.7). Using a two-way repeated measures analysis of variance (ANOVA) to examine the effects of vitamin E on FMD, we found no effect for the grouping factor (p = 0.5834) in the ANOVA over time but a highly significant difference with respect to time (p = 0.0065). The interaction of the time factor and the grouping factor also proved to be significant (p = 0.0318). Flow mediated vasodilation values remained similar after treatment for four weeks in both groups but declined faster after smoking a cigarette in subjects taking placebo compared with those receiving vitamin E (p values from successive differences for the time/group factor: 0.0001/0.0017). The transient attenuation of FMD (calculated as the percent change in FMD) was related to the improvement of the antioxidant status, estimated as percent changes in thiobarbituric acid-reactive substances (r = -0.67, p = 0.0024). Nitroglycerin-induced dilation did not differ between study groups at baseline or after therapy. CONCLUSIONS: These results demonstrate that oral supplementation of vitamin E can attenuate transient impairment of endothelial function after heavy smoking due to an improvement of the oxidative status but cannot restore chronic endothelial dysfunction within four weeks in healthy male smokers.

Adult↗
PubMed2000

Correlates of safer sex communication among college students.

Correlates of safer sex communication among college students The purpose of this study was to examine factors that are thought to promote communication about safer sex and HIV among college students in the United States of America and to determine the extent to which communication about safer sex is important in the use of condoms. A better understanding of factors associated with safer sex communication can be helpful in developing HIV and STD prevention programmes for college students. Following approval from the institutional review boards of the six participating colleges and universities, researchers collected data from a random sample of students. The study included participant responses if participants were 18-25 years of age, single and sexually active. For the sample of 1349 participants, the mean age was 20.6 years. Sixty-three per cent of the sample was female, 50.5% white, 42.3% African-American, and the remainder of other ethnic groups. Over 50% of respondents reported frequent condom use, with 28% noting that they used a condom every time and 30.6% reporting condom use almost every time they had sex. Only 9.6% indicated that they never used a condom. The results of hierarchical multiple regression analysis revealed that the perception of quality of general communication with parents, the perception of a partner's attitude towards communication, communication self-efficacy, and communication outcome expectancies, were associated with safer sex communication. However, the association between safer sex communication and condom use was weak, suggesting that other factors excluded from this study are important in determining condom use for this sample of respondents. The findings provide some implications for HIV interventions. Interventions that enhance self-efficacy and positive outcome expectancies related to communication about safer sex are likely to foster discussion with a sexual partner. However, they might not lead to actual condom use.

Adolescent↗
PubMed2000

Risk of injury through snowboarding.

OBJECTIVE: Survey of a group of snowboarders and study of their injuries, as well as analysis of the risk of injury considering the time spent on the snowboard. MATERIALS AND METHODS: Of 7,221 students participating in winter sport programs organized by Austrian schools, 2,745 of those riding snowboards were asked to fill out questionnaires pertaining to demographics, their experience level, equipment, snowboard riding habits, and associated injuries. RESULTS: A total of 2,579 snowboarders (94%), who spent a total of 10,119 days snowboarding, filled out a questionnaire which could be evaluated. A total of 152 snowboarders had suffered a mean of 10.6 injuries per 1,000 days of snowboarding, which required medical care; 5.4/1,000 injuries were moderate or severe. The most common injuries were to the wrist (32%), the hand (20%), and the head (11%). The rate of injury was especially high during the first half-day (roughly 3 hours). Use of wrist protection devices reduced injuries to the wrist from 2 to 0.5% (p = 0.048). CONCLUSION: Risk of snowboard related injury was highest in beginners. Through the use of wrist protection devices, the incidence of the most common injuries was dramatically reduced.

Adolescent↗
PubMed2000

Anatomy of commitment: an in vivo study.

A self-evaluation of one small but innovative agency providing supported living and other community supports to individuals with developmental disabilities is presented. Key elements that appear to perpetuate a culture of commitment among direct support and supervisory staff are described. Agency staff people have achieved the capacity to listen and respond to individuals and honor their choices. In order to assure that individuals get what they need, staff members take appropriate initiative, work outside of their assigned hours, and support one another. Whereas most human service organizations function within the parameters of well-defined policies and procedures, the agency described here operates more flexibly. The observed pattern of organizational dynamism and reflexivity is compared to that of a living organism.

Adult↗
PubMed1999

Identification of tyrosine phosphorylation sites in human Gab-1 protein by EGF receptor kinase in vitro.

Grb2-associated binder-1 (Gab-1) has been identified recently in a cDNA library of glioblastoma tumors and appears to play a central role in cellular growth response, transformation, and apoptosis. Structural and functional features indicate that Gab-1 is a multisubstrate docking protein downstream in the signaling pathways of different receptor tyrosine kinases, including the epidermal growth factor receptor (EGFR). Therefore, the aim of the study was to characterize the phosphorylation of recombinant human Gab-1 (hGab-1) protein by EGFR in vitro. Using the pGEX system to express the entire protein and different domains of hGab-1 as glutathione S-transferase proteins, kinetic data for phosphorylation of these proteins by wheat germ agglutinine-purified EGFR and the recombinant EGFR (rEGFR) receptor kinase domain were determined. Our data revealed similar affinities of hGab-1-C for both receptor preparations (KM = 2.7 microM for rEGFR vs 3.2 microM for WGA EGFR) as well as for the different recombinant hGab-1 domains. To identify the specific EGFR phosphorylation sites, hGab-1-C was sequenced by Edman degradation and mass spectrometry. The entire protein was phosphorylated by rEGFR at eight tyrosine residues (Y285, Y373, Y406, Y447, Y472, Y619, Y657, and Y689). Fifty percent of the identified radioactivity was incorporated in tyrosine Y657 as the predominant peak in HPLC analysis, a site exhibiting features of a potential Syp (PTP1D) binding site. Accordingly, GST-pull down assays with A431 and HepG2 cell lysates showed that phosphorylated intact hGab-1 was able to bind Syp. This binding appears to be specific, because it was abolished by changing the Y657 of hGab-1 to F657. These results demonstrate that hGab-1 is a high-affinity substrate for the EGFR and the major tyrosine phosphorylation site Y657 in the C terminus is a specific binding site for the tyrosine phosphatase Syp.

Adaptor Proteins, Signal Transducing↗
PubMed1997

Adrenaline inhibits depolarization-induced increases in capacitance the presence of elevated [Ca2+]i in insulin secreting cells.

Cell capacitance (Cm), cell conductance (Gm), access conductance (Ga) and membrane voltage (Vm) were measured simultaneously in insulin secreting cells using the dual frequency method. Depolarization and stimulation of the cells with secretagogues increased Cm. EGTA abolished the increase in [Ca2+]i and prevented the rise of Cm. Adrenaline inhibited the augmentation of Cm without lowering [Ca2+]i. In pertussis toxin pretreated cells adrenaline had no effect. Thus, stimulation of insulin secretion is accompanied by an increase in Cm. Inhibition of exocytosis by adrenaline occurs even in the presence of elevated [Ca2+]i, i.e. at a more distal step of exocytosis.

1-Methyl-3-isobutylxanthine↗
PubMed1997

Reemployment of patients with surgical salvage of open, high-energy tibial fractures: an outcome study.

Between January 1, 1988, and December 31, 1990, 36 patients with 37 type III high-energy open tibial shaft fractures were treated at Lehigh Valley Hospital. Patients with primary amputations were excluded. All patients with high-energy open tibial fractures with an intact posterior tibial nerve, protective sensations of the plantar surface of the foot, and warm ischemia time of less than 6 hours were considered salvageable. A retrospective review of the charts was completed. Twenty-eight patients with 29 fractures were interviewed for work status, an average of 39 months after treatment. Twenty-five patients with 25 fractures were working at the time of the accident. Three patients with four fractures were not working at the time of the accident. Nineteen of 25 patients (76%) returned to work. Sixteen of 25 patients (64%) returned to work at a similar level of manual labor. The average delay between injury and return to work was 11 months (range, 3-18 months). Two of the 36 patients (5.5%) required secondary amputations. Twenty-five of 28 patients (89%) interviewed reported one or more subjective complaints. The two amputees reported no subjective complaints.

Adolescent↗
PubMed1996

Adrenaline-, not somatostatin-induced hyperpolarization is accompanied by a sustained inhibition of insulin secretion in INS-1 cells. Activation of sulphonylurea K+ATP channels is not involved.

Adrenaline and somatostatin inhibit insulin secretion via pertussis toxin (PTX)-sensitive mechanisms. Since glucose-stimulated release involves inhibition of ATP-sensitive K+ (K+ATP) channels and activation of Ca2+ influx, we took advantage of the glucose-sensitive, insulin-secreting cell line INS-1 to investigate whether inhibitors of insulin release modulate membrane voltage and K+ATP channel activity in cell-attached patch-clamp experiments. We found that adrenaline, through alpha2-adrenoceptors, and somatostatin counteracted glucose-induced depolarization and action potentials. As expected, these effects were mediated via PTX-sensitive G proteins since PTX pretreatment of the cells eliminated the effects of adrenaline and somatostatin on membrane voltage. When INS-1 cells were activated by adding both the K+ATP channel inhibitor tolbutamide and the adenylyl cyclase activator forskolin, adrenaline and somatostatin still repolarized the plasma membrane. Single-channel measurements in the cell-attached mode revealed that tolbutamide closed a 40 to 70 pS K+ channel which was neither reopened by adrenaline nor by somatostatin. In parallel cell preparations, insulin secretion was measured by radioimmunoassay. Insulin release induced by glucose, forskolin and tolbutamide was abolished by adrenaline. In contrast, somatostatin attenuated insulin secretion by only 30%. After comparing the potency of adrenaline and somatostatin on membrane voltage and on insulin secretion, it is concluded that the repolarizing effect of adrenaline on membrane voltage is not sufficient to explain its potent inhibitory effect on insulin secretion.

Adenosine Triphosphate↗
PubMed1996

Effects of glucose, forskolin and tolbutamide on membrane potential and insulin secretion in the insulin-secreting cell line INS-1.

Membrane voltages (Vm) of INS-1 cells, an insulin-secreting cell line, were measured mostly using the cell-attached mode of the patch-clamp method. The cell-attached configuration allowed the cell to be kept intact. Measurement of Vm was possible because seal resistances were very high and because the membrane obviously had a sufficiently high conductance (probably via K+ channels). Resting Vm was -80 +/- 1 mV (n = 42) and was mainly determined by sulphonylurea-sensitive K+ATP channels since tolbutamide depolarized the plasma membrane in a concentration-dependent manner and generated action potentials at 50 and 100 micromol/l. D-Glucose, tested between 0.5 and 16.7 mmol/l, also depolarized the plasma membrane in a concentration-dependent manner and induced action potentials at concentrations higher than 5.6 mmol/l. Similarly, forskolin (5 micromol/l) depolarized the cells and increased the frequency of Ca2+-mediated action potentials. Insulin secretion was measured from cells growing in culture dishes, by radioimmunoassay. Glucose doubled secretion in INS-1 cells, whereas tolbutamide had no significant effect on secretion in the presence of 0.5 mmol/l and 16. 7 mmol/l glucose. At 3 mmol/l glucose, tolbutamide increased insulin release slightly. Forskolin elevated secretion twofold at a low glucose concentration. In contrast, when glucose or tolbutamide were added together with forskolin secretion was potentiated five- to tenfold. These results show that glucose induces membrane activation in INS-1 cells. Furthermore, the potent effect of tolbutamide, i.e. to depolarize the plasma membrane without inducing insulin release, leads to the conclusion that effects distal to depolarization are pivotal for secretion in INS-1 cells.

Action Potentials↗
PubMed1993

Factors associated with use of safer sex practices among college freshmen.

The purpose of this exploratory study was to examine the relationship of knowledge of AIDS, misconceptions about AIDS, knowledge of safer sex practices, perceived susceptibility, and future time perspective to the practice of safer sex behaviors in 352 single, sexually active, college freshmen. Data were analyzed using stepwise multiple regression analysis and discriminant analysis. There were too few black females for analysis. Future time perspective explained the most variance in safer sex practices for black males. Knowledge of AIDS, perceived susceptibility, misconceptions about AIDS, knowledge of safer sex practices, and future time perspective did not explain a significant amount of variance in use of safer sex practices for either white males or females. However, perceived susceptibility and future time perspective differentiated sexually active from nonsexually active white males and females.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Knowledge of AIDS and safer sex practices among college freshmen.

We assessed knowledge of the acquired immunodeficiency syndrome (AIDS) and of safer sex practices among college freshmen. A second purpose of the study was to assess this knowledge among black as well as white students. Students attending classes at three private colleges in a large southern city were asked to participate in the study. Respondents completed the modified AIDS information survey, the knowledge of safe sex practices questionnaire, and a demographic data sheet. A total of 689 questionnaires were received from single college freshmen. The results indicated that respondents were knowledgeable about the cause and transmission of AIDS but were less knowledgeable about medical aspects. Most knew that condoms are effective in preventing the spread of AIDS, but fewer could differentiate between the effectiveness of latex and nonlatex condoms. These findings are useful to health educators in improving AIDS education programs.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Impact of minimal injuries on a level I trauma center.

Overtriage (i.e.; transport of patients with minimal injuries to a trauma center) has been accepted as necessary to avoid missing clinically significant injuries. We reviewed our experience with 344 patients (ISS less than or equal to 4) who were admitted to a level I trauma center during a 2-year period. The trauma team was activated for 209 patients (TA), and emergency department referrals accounted for 135 (ED). One hundred seventy-three patients (TA = 64%, ED = 36%) met American College of Surgeons' Committee on Trauma (ACSCOT) field triage criteria (FTC). Mechanism of injury, especially ejection from a motor vehicle, was the most frequently utilized FTC indicator. We found no differences between the TA and ED groups relative to Trauma Score, Glasgow Coma Scale score, Injury Severity Score, length of stay, or ICU days. Mean total costs were higher for the TA group than for the ED group. The TA group had a higher nursing acuity level than the ED group. Compliance with FTC yields an inherent overtriage of minimally injured patients; however, noncompliance with FTC compounds the overtriage rate. Failure to comply with FTC is costly, labor intensive, and may represent misuse of the trauma system. We propose continual re-education of prehospital personnel, increased responsibility of all hospitals in the trauma center catchment area, and protocols for "downstaging" trauma resuscitation in minimally injured patients.

Adult↗
PubMedDate not supplied

Group dynamics within long-term continuing education programs.

Nursing educators have responded to the need for continuing education by developing a variety of programs ranging in length from half-day seminars to several months of intensive study. Although books and articles have been written about nurses returning to school for baccalaureate degrees and the ensuing expectations, changes, and needs involved in this process, the literature revealed little information on how students, families, and faculty "live" a long-term continuing education (CE) experience. This article will examine the evolution of students into well-defined groups. The stages of group process, development of norms, assumption of roles within the groups, and factors related to conflicts are discussed. Methods used to reduce conflict and facilitate the movement of the groups to the resolution stage are presented in order to assist instructors involved in long-term CE programs.

Adult↗