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Biomedical subjects

M Herr

Publications and source records attributed to M Herr.

14 recordsLinked to original sources
PubMed2002

Deconvolution of surface topology for quantification of initial wear in highly cross-linked acetabular components for THA.

Evaluation of the surface morphology of short-term retrieved cross-linked acetabular components requires differentiation between the features generated during machining and the smaller-scale morphologies generated during the in vivo wear process. Previously, the distinction between the waviness of machining and the roughness of wear has been related to the grain size of the UHMWPE. Here a low-frequency cutoff is proposed, based on the maximum spectral frequency of machining marks, rather than on the grain size of the bulk UHMWPE material, as a reliable method for deconvolving machining marks from in vivo wear following short-term implantation. To this end, as-machined articulating surfaces of conventional (GUR 1050) and two groups of highly cross-linked UHMWPE acetabular components were examined to determine whether they exhibited a periodic surface morphology with a well-defined spatial frequency. The surface frequency spectra revealed low-frequency peaks associated with the machining marks, which were unique to each type of implant. Furthermore, the surface frequency spectra appeared uniform within a single group of implants. Statistically significant differences in the surface roughness and waviness were observed between the three groups of new implants. Our research suggests that machining marks can be effectively deconvolved from the articulating surface with the use of a Fourier transform algorithm with a single cutoff frequency of 0.08 1/microm, corresponding to a wavelength of 12.5 microm. The results of this study provide a unified conceptual framework for discriminating between waviness and roughness of the articulating surface for machined orthopedic components. The distinction between waviness and roughness is expected to be crucial for the comprehensive evaluation of wear surfaces after short-term implantation, when machining marks may be partially worn away or plastically deformed in vivo.

Acetabulum↗
PubMed2001

Low frequency of HLA DRB1*03 - DQB1*02 and DQB1*0302 haplotypes in Romania is consistent with the country's low incidence of Type I diabetes.

AIMS/HYPOTHESIS: Our study aimed to determine the association of HLA class II HLA-DQB1 alleles with Type I (insulin-dependent) diabetes mellitus and the frequencies of these alleles in the Romanian population, which has one of the lowest incidences of Type I diabetes in children aged 0-14 years in Europe at 3-4 cases per 100,000 person-years. METHODS: We used the sequence specific primer-polymerase chain reaction (PCR-SSP) technique to type HLA-DQB1 alleles, the HLA-DRB1alleles DRB1*03 and one single nucleotide polymorphism (SNP) in the insulin gene (INS). We studied 204 Type I diabetic Romanian families, 196 of which were simplex with 70.3 % of subjects diagnosed under 14 years of age. Data was analysed using a modified version of the Transmission Disequilibrium Test, the Transmission Disequilibrium Test itself, and the affected family-based control method. RESULTS: We found, as expected, the strong positive DQB1*02-DRB1*03 and DQB1*0302, and negative DQB1*0602, HLA class II allele associations with Type I diabetes in these Romanian families. However, using the affected family-based control method, we found relatively low population frequencies of DQB1*02-DRB1*03 and DQB1*0302 alleles in Romania (15.8%) compared with Sardinia (31.3%), a high incidence European region (35 cases per 100,000 person-years in children aged 0-14years). The INS locus had a strong effect in this data set with 80.5 % transmission of the susceptible INS allele from parents to affected siblings (relative risk = 4.1). CONCLUSION/INTERPRETATION: Part of the explanation for the low incidence of Type I diabetes in Romania could be the lower frequency of the DRB1*03 DQB1*02 and DQBI*0302 susceptibility haplotypes in this country.

Child↗
PubMed2000

Data mining applied to linkage disequilibrium mapping.

We introduce a new method for linkage disequilibrium mapping: haplotype pattern mining (HPM). The method, inspired by data mining methods, is based on discovery of recurrent patterns. We define a class of useful haplotype patterns in genetic case-control data and use the algorithm for finding disease-associated haplotypes. The haplotypes are ordered by their strength of association with the phenotype, and all haplotypes exceeding a given threshold level are used for prediction of disease susceptibility-gene location. The method is model-free, in the sense that it does not require (and is unable to utilize) any assumptions about the inheritance model of the disease. The statistical model is nonparametric. The haplotypes are allowed to contain gaps, which improves the method's robustness to mutations and to missing and erroneous data. Experimental studies with simulated microsatellite and SNP data show that the method has good localization power in data sets with large degrees of phenocopies and with lots of missing and erroneous data. The power of HPM is roughly identical for marker maps at a density of 3 single-nucleotide polymorphisms/cM or 1 microsatellite/cM. The capacity to handle high proportions of phenocopies makes the method promising for complex disease mapping. An example of correct disease susceptibility-gene localization with HPM is given with real marker data from families from the United Kingdom affected by type 1 diabetes. The method is extendable to include environmental covariates or phenotype measurements or to find several genes simultaneously.

Adolescent↗
PubMed2000

Evaluation of fine mapping strategies for a multifactorial disease locus: systematic linkage and association analysis of IDDM1 in the HLA region on chromosome 6p21.

The positional cloning of multifactorial disease genes is a major challenge in human genetics. We have therefore empirically tested the utility of the available polymorphic microsatellite map to locate the already identified type 1 diabetes locus IDDM1 (sibling risk/population prevalence ratio lambda(s)= 2.7) within a 14 Mb region of chromosome 6p21 linked to disease. In a two-stage approach to fine mapping, linkage was evaluated in 385 affected sib-pair families using 13 evenly spaced polymorphic microsatellite markers. The whole 14 Mb showed strong linkage. Then, each marker was analysed for evidence of allelic association, revealing evidence of disease association at one marker located within the 95% confidence interval of 1.7 cM obtained by linkage. Analysis of an additional 12 markers flanking this marker revealed a highly specific region of 570 kb associated with disease ( P = 7.5 x 10(-35)), which included the HLA class II genes, known to be the primary determinants of IDDM1. The peak of association was as close as 85 kb centromeric of the disease-predisposing class II gene HLA-DQB1. We investigated the importance of the underlying inter-marker linkage disequilibrium, marker informativity and recombination for fine mapping and demonstrate that the majority of disease association in the region can be explained by linkage disequilibrium with the class II susceptibility genes. Recombination within the major histocompatibility complex was rare and nearly absent in the class III region. We demonstrate that fine mapping of a multifactorial disease gene is possible with high accuracy even in a region with extraordinary linkage disequilibrium across distances of several Mb. The results will be applicable to association studies of disease loci with lambda(s)values <2.7 except that much larger data sets will be required.

Adolescent↗
PubMed2000

Migratory activity of human glioma cell lines in vitro assessed by continuous single cell observation.

A new migration assay, the time-lapse individual cell migration assay (TIM-assay), was developed, which allows the observation of cells over 24 h under controlled conditions. Using this technique, the migratory behavior of 8 human glioblastoma cell lines in vitro was studied. Special features are simultaneous documentation of migratory parameters of individual cells, i.e., migration velocities and migration paths of individual cells. Migration velocity for cell populations of the same cell line ranged from 0 to 24 microm/h. The migration paths were examined for being directional. Two thirds of all cells showed directional migration. Migration paths were further classified according to visual judgements for being linear, oscillating or mixed. The migration index had a mean of 91%. The presented TIM-assay allows the assessment of several new parameters. that may be useful to identify subgroups of gliomas with different biological characteristics.

Adult↗
PubMed2000

Human immunodeficiency virus infection in rural areas and small cities of the southeast: contributions of migration and behavior.

The design of education and prevention strategies to stem the spread of human immunodeficiency virus (HIV) and acquired immune deficiency syndrome (AIDS) in rural areas depends on having accurate patterns of risk behavior and transmission in local areas. Interviews were conducted with people in rural areas and small cities in Delaware, Florida, Georgia and South Carolina who were at least 18 years old and infected with HIV in order to describe demographic characteristics, migration patterns and risk behaviors. Interviews were conducted with 608 people. Most respondents were male (66 percent), black (63 percent of men, 85 percent of women) and had been infected through sexual contact (67 percent of men, 66 percent of women). Most (65 percent) had lived away from a rural area or small city for at least one month; of those, 71 percent had moved from an urban area. Twenty-seven percent of respondents indicated they had been infected locally. People with a history of injection drug use were less likely to have been infected locally than those who had no history of injection drug use (6 percent vs. 26 percent among men, 3 percent vs. 40 percent among women, P < 0.001). Further understanding of the role of socioeconomic factors in HIV transmission in rural areas and small cities is needed. Programs designed to prevent HIV acquisition among people living in rural areas and small cities in the Southeast should focus on sexual behavior.

Adolescent↗
PubMed1998

Head-down-tilt bed rest alters forearm vasodilator and vasoconstrictor responses.

To test the hypothesis that head-down-tilt bed rest (HDBR) for 14 days alters vascular reactivity to vasodilatory and vasoconstrictor stimuli, the reactive hyperemic forearm blood flow (RHBF, measured by venous occlusion plethysmography) and mean arterial pressure (MAP, measured by Finapres) responses after 10 min of circulatory arrest were measured in a control trial (n = 20) and when sympathetic discharge was increased by a cold pressor test (RHBF + cold pressor test; n = 10). Vascular conductance (VC) was calculated (VC = RHBF/MAP). In the control trial, peak RHBF at 5 s after circulatory arrest (34.1 +/- 2.5 vs. 48.9 +/- 4.3 ml . 100 ml-1 . min-1) and VC (0.34 +/- 0.02 vs. 0.53 +/- 0.05 ml . 100 ml-1 . min-1 . mmHg-1) were reduced in the post- compared with the pre-HDBR tests (P < 0. 05). Total excess RHBF over 3 min was diminished in the post- compared with the pre-HDBR trial (84.8 vs. 117 ml/100 ml, P < 0.002). The ability of the cold pressor test to lower forearm blood flow was less in the post- than in the pre-HDBR test (P < 0.05), despite similar increases in MAP. These data suggest that regulation of vascular dilation and the interaction between dilatory and constrictor influences were altered with bed rest.

Adult↗
PubMed1995

Differences in participation in experimental drug trials among persons with AIDS.

To measure participation in experimental drug trials among persons with acquired immunodeficiency syndrome (AIDS), we interviewed 4,604 persons at least 18 years of age who were reported to have AIDS to 11 state and city health departments in the United States. Ten percent reported that they were currently in a trial. Current enrollment differed significantly (p < 0.05) by race/ethnicity (blacks, 5%; whites, 14%; Hispanics, 15%), gender (women, 7%; men, 11%), exposure mode (injection drug use, 5%, men who have sex with men, 14%), annual household income (< $10,000, 8%, > or = $10,000, 14%), education (< 12 years, 6%; > or = 12 years, 12%), health care (no regular care, 1%, public care, 8%; private care, 17%), and time since AIDS diagnosis (< or = 6 months, 9%; > 6 months, 12%). Adjusting for all factors and time since AIDS diagnosis, blacks (adjusted odds ratio [AOR] = 0.35, 95% confidence interval [CI] 0.26, 0.47), persons with less than 12 years of education (AOR = 0.71, CI 0.53, 0.96), and those without regular health care (AOR = 0.24, CI 0.10, 0.61) remained less likely to be in a trial. Blacks, those with less than 12 years of education, and persons without regular health care were less likely than other persons with AIDS to be currently enrolled in AIDS trials. To increase enrollment of these persons, researchers must address barriers to participation for these groups.

Acquired Immunodeficiency Syndrome↗
PubMed1995

HIV testing patterns: where, why, and when were persons with AIDS tested for HIV?

OBJECTIVE: To describe the location of, primary reason for, and time between the first positive HIV test and AIDS diagnosis in a sample of persons with newly diagnosed AIDS. DESIGN: Interviews supplementing information routinely collected through AIDS case reporting. SETTING: Eleven US states and cities. PATIENTS: Persons with AIDS (2441) diagnosed between January 1990 and December 1992. MAIN OUTCOME MEASURES: Location of first positive HIV test, primary reason for testing, and time interval between first positive HIV test and AIDS diagnosis. RESULTS: Overall, persons were tested late in their course of HIV infection: 36% were tested for HIV within 2 months and 51% within 1 year of their AIDS diagnosis. Sixty-five per cent were HIV-tested in acute health-care settings: 33% in hospitals, 28% in physicians' offices, and 4% in emergency departments. Testing during hospitalization was most common among injecting drug users (43%) and persons infected through heterosexual contact (50%). Persons primarily sought HIV testing because of illness (58%); other reasons included being in a known risk group (13%) and having had a known HIV-infected sex partner (8%). Testing because of being in a known risk group was least common among persons infected through heterosexual contact (1%). Among persons in these exposure categories, testing differed by race/ethnicity. CONCLUSION: Most persons with AIDS were tested relatively late in their course of HIV infection, in acute health-care settings, and because of illness. Not knowing one's serostatus precludes early medical intervention and may increase transmission.

AIDS Serodiagnosis↗
PubMed1994

Health insurance coverage among persons with AIDS: results from a multistate surveillance project.

To determine factors associated with health insurance coverage among persons with acquired immunodeficiency syndrome (AIDS), we interviewed 1958 persons 18 years of age or older who were reported to have AIDS in 11 states and cities. Overall, 25% had no insurance, 55% had public insurance, and 20% had private insurance. Factors associated with lack of insurance varied by current employment status. Employed persons with an annual household income of less than $10,000 were 3.6 times more likely to lack insurance than employed persons with a higher income. Unemployed persons diagnosed with AIDS for less than 1 year were two times more likely to lack health insurance than unemployed persons diagnosed for a longer time. Making insurance available to persons identified as most likely to lack insurance should improve access to care for persons with AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Sociodemographics and HIV risk behaviors of bisexual men with AIDS: results from a multistate interview project.

OBJECTIVE: To describe the sociodemographic characteristics and sexual and drug use behaviors of men with AIDS who engage in bisexual activity. METHODS: We interviewed 2120 men aged > or = 18 years who were reported with AIDS in 11 states and cities. Men were considered bisexual if they reported having had sex with a man and a woman in the previous 5 years. RESULTS: Of the 2020 men with AIDS who reported being sexually active in the previous 5 years, 1150 (57%) had had male partners only, 522 (26%) had had female partners only and 348 (17%) had had both. White men were least likely to report bisexual behavior (15%; 161 out of 1071). Men of Latin American descent were most likely to report bisexual behavior (24%; 37 out of 155), especially those born outside the United States who had lived there for < or = 10 years (38%; 11 out of 29). Bisexual Latin American men, regardless of birthplace, were more likely to be currently married than all other bisexual men (22 versus 7%; P < 0.05). HIV risk behaviors differed between men reporting bisexual and those reporting exclusively homosexual or heterosexual activity. Injecting drug use in the previous 5 years was more common among bisexual than homosexual men (12 versus 6%; P < 0.05). Bisexual men were more likely (P < 0.05) to have received money for sex (11%) than homosexual (4%) or heterosexual men (4%). This difference was even greater among injecting drug users receiving money for sex: bisexual (29%), homosexual (13%), heterosexual (3%). CONCLUSIONS: Demographics and HIV risk behaviors of bisexual men with AIDS differ from those of homosexual and heterosexual men with AIDS. These findings indicate that special efforts are needed to prevent sexual transmission of HIV among bisexual men.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

[The effect of coupled cardiovascular and respiratory afferent signals on the central processes of human information processing].

On the basis of contemporary knowledge on close functional connections between respiratory and cardiovascular afferents a computerized experimental device was developed by means of which central information processing can be studied in dependence on respiration phase and the level of baroreceptor activity. In all the examined parameters (time of motor reaction of two hands, latency of eye-lid reflex) the greatest changes were observed at maximum baroreceptor activity. These changes were clearly distinguished by direction during the phases of inhalation and exhalation. Such effect is probably based on the fact that the influence of cardiovascular afferents on the level of central activity is modulated in respiration rhythm through the mechanism of breath "gating" of postsynaptic STN structures.

Acoustic Stimulation↗
PubMedDate not supplied

Socioeconomic differences among people with AIDS: results from a Multistate Surveillance Project.

To characterize the socioeconomic status of persons with acquired immunodeficiency syndrome (AIDS), 11 U.S. state and city health departments interviewed 2,898 persons > or = 18 years of age reported with AIDS between June 1, 1990, and January 31, 1993. Among men who have sex with men, white men reported the lowest percentage (9%), and Central/South American (50%) and Mexican men (40%) reported the highest percentages not completing 12 years of school. Among intravenous drug users (IDUs), 35% of white men, 64% of black men, 67% of Puerto Rican men, 29% of white women, and 63% of black women had not completed 12 years of school. Overall, 77% of the men and 90% of the women were unemployed; we also found racial/ethnic differences by employment but to a lesser degree than differences in education. Among women, but not among men, differences in household income by race and ethnicity were marked; 76% of white and 91% of black female IDUs reported a household income of $10,000. Human immunodeficiency virus (HIV) prevention programs must be targeted toward the educational level of the populations served, and HIV services must adapt to the financial circumstances of their clientele.

Acquired Immunodeficiency Syndrome↗