Search PubMed⌕ Search

Biomedical subjects

S Geyer

Publications and source records attributed to S Geyer.

At least 55 records · Page 3Linked to original sources
PubMed1997

[Assessment of AIDS risks: effects of different scale ranges and preventive knowledge].

In a sample of 552 respondents effects of different scale ranges and respondents' knowledge about AIDS for answering questions about AIDS-risks were examined. Knowledge was assessed with 12 items related to risks for HIV infections and preventive measures. AIDS hazards for different groups (prostitutes, fixers, hospital personnel, homosexuals, and haemophiliacs) had to be rated with five items, one for each group. Response variations were assessed in three parallel questionnaire versions with different ranges of risk assignments. Estimations had to be performed in comparison with the average population. Some groups were consistently rated to be at high risk, others were assigned low risks for becoming infected with the HIV-virus. The analysis of response patterns revealed that the three versions of numeric quantifiers determined the risk ratings only to some extent. The distribution patterns suggest that our subjects had an ordinal risk ordering in mind that might better be expressed in verbal terms. The knowledge about AIDS had no systematic effects on response behavior.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Some conceptual considerations on the sense of coherence.

Aaron Antonovsky's sense of coherence (SOC) [(1987) Unraveling the Mystery of Health, How People Manage Stress and Stay Well, Jossey-Bass, San Francisco] ought to explain why some people manage stress and stay well while others break down. According to Antonovsky's formulation, SOC is strongly developed if a person sees the world as comprehensible (i.e. rational, understandable, consistent and predictable), as manageable, and as meaningful (i.e. challenging and that things are worth making commitments for). Sense of coherence has gained widespread attention and has been used as an explanatory variable in many studies. This paper discusses some aspects that have not sufficiently been considered in the SOC literature. First, an outline of the construct is given. Next, overlaps and differences with other concepts in the same domain are discussed. Little empirical evidence concerning the stability of SOC is available. Therefore, findings from experimental social psychological studies on self-esteem are applied to SOC. Third, it can be assumed that SOC is an attitude of people who are well educated, are in rather privileged societal positions, and with opportunities for decision-making. Finally, the empirical basis is reviewed. Statistical relationships between SOC and symptoms/disease are in the predicted direction, but due to the simultaneous assessment of variables it is open to debate whether a low SOC has some effect on the probability of falling ill or whether it is the other way around. Very high negative correlations between SOC and depression/anxiety suggest that the instruments used may assess the same phenomenon, but with inverse signs. Based on these considerations, directions for further research are proposed.

Adaptation, Psychological↗
PubMed1997

[Approaches to explaining social maldistribution of illnesses and mortality].

Socially unequal distribution of illness and mortality rates is nothing new. Studies dealing with this phenomenon date back to at least the past century. Despite this age-old tradition, explanatory patterns in respect of socio-epidemiology. are few and far between. The following article describes the approaches that have been tried to date. Materialistic explanations are the order of the day in British socio-epidemiology. It is assumed that low income results in increasing everyday problems due to lack of resources, funds being no longer sufficient to maintain health. Another series of explanations is based on characteristics of working conditions. According to this theory, cardiovascular risk is increased by combinations such as high demands/low wages and high demands/low level of controlling the work. Characteristic features of job activity also exercise a long-term influence on mental flexibility and problem-solving competence. The characteristic pattern realisations that are considered undesirable, occur more frequently in the lower strata of society. Events resulting in stress bringing about a change in life, as well as lack of basic social support, are also more frequently seen in the lower strata of society. The theory of experience of coherence postulates that a more efficient solution of problems and less subjective stress are associated with perceiving the environment as coherent and manageable. This characteristic, too, is sociostructurally not uniformly distributed.

Causality↗
PubMed1996

Two different areas within the primary motor cortex of man.

The primary motor area (M1) of mammals has long been considered to be structurally and functionally homogeneous. This area corresponds to Brodmann's cytoarchitectural area 4. A few reports showing that arm and hand are doubly represented in M1 of macaque monkeys and perhaps man, and that each subarea has separate connections from somatosensory areas, have, with a few exceptions, gone largely unnoticed. Here we show that area 4 in man can be subdivided into areas '4 anterior' (4a) and '4 posterior' (4p) on the basis of both quantitative cytoarchitecture and quantitative distributions of transmitter-binding sites. We also show by positron emission tomography that two representations of the fingers exist, one in area 4a and one in area 4p. Roughness discrimination activated area 4p significantly more than a control condition of self-generated movements. We therefore suggest that the primary motor area is subdivided on the basis of anatomy, neurochemistry and function.

Autoradiography↗
PubMed1996

Structural asymmetries in the human forebrain and the forebrain of non-human primates and rats.

Possible asymmetries of the following structures were studied: volumes of total human hemispheres, cortex and white matter volumes in post-mortem- (unknown handedness) and living brains (male right-handers); volumes of the rat primary visual cortex, its mon- and binocular subfields, its layer iv and the density of myelinated fibres in layer iv; transmitter receptor densities (NMDA, AMPA, kainate and GABAA receptors) in sensorimotor regions of the rat cortex; volume of the motor cortex and the 3D-extent of the central sulcus in the post-mortem- (unknown handedness) and living human brain (male right-handers); petalia of the hemispheres in human (male right- and left-handers) and chimpanzee brains. Histological, MRI and receptor autoradiographic techniques were used. With the notable exceptions of the transmitter receptors and the total primary visual cortex in rats and the hemispheres in chimpanzees, which do not show any significant directional asymmetry, all other parameters studied are asymmetrically distributed between the right- and left hemispheres. The regional distribution pattern and the degree of asymmetry of frontal and occipital petalia in living human brains differ between right- and left-handers.

Animals↗
PubMed1994

The evaluation of life event data.

Data from three life event studies are compared. The interviews covered events that occurred within a period of 2 years before interview. The same inventory was used in each of the studies. Samples were drawn from depressives, myocardial infarction patients and an industrial worker population. The patient groups were interviewed twice within 4 weeks. Fewer than 50% of the total number of events reported in the retests were recorded twice. For events reported in both interviews the correlations of subjective appraisals were only moderate. There is considerable fall-off for reports of events occurring more than 6 months before interview. It was expected that the severest events would have the lowest, and the least severe ones the highest frequencies. Instead, inappropriate labels of the rating scales led to clusterings of severity ratings at their extreme points. Numbers of events and severity ratings were positively correlated with measures of depression.

Adult↗
PubMed1994

Measles vaccine failures: lack of sustained measles-specific immunoglobulin G responses in revaccinated adolescents and young adults.

The measles-specific antibody responses of seronegative adolescents and young adults were evaluated after revaccination. Of 1650 previously vaccinated healthy volunteers between the ages of 10 and 30 years, 4.4% were found to be seronegative for measles antibodies and 9.9% had equivocal titers. Seronegative volunteers were revaccinated to measles and followed serially for development of measles-specific IgG. Of 43 subjects followed for at least 1 year, only 58% developed and maintained positive antibody titers; 12% never developed positive titers and 30% initially developed titers that fell below positive levels within 1 year. The peak titers achieved by those subjects who responded transiently were lower than those achieved by subjects who developed sustained responses. Thus even after the recommended two dose schedule of the current measles vaccine, some adolescents and young adults lack protective titers of measles-specific antibody.

Adolescent↗
PubMed1993

Life events, chronic difficulties and vulnerability factors preceding breast cancer.

This study deals with the association between life events, family history of mammary carcinoma and breast cancer. It was guided by a model consisting of events, family disposition and age at the side of the independent variables. In addition to these factors 'lack of social support' was introduced. The latter is conceptualized as a vulnerability factor capable of aggravating the impact of events without having an independent effect. There was no hypothesis on chronic difficulties, so this is exploratory. This research was conducted as a so-called 'limited prospective' design. Women with a suspicious breast lump were interviewed before surgery. After having confirmed the outcome of the surgery the sample was divided into a group with cancer and cases with a benign diagnosis. Women with gall stones were introduced as another control group. The interviews were performed along a semi-structured schedule, tape recorded and analyzed by using Brown and Harris' Life Events and Difficulties Scale. The analyses were made with 33 women with cancer, 59 with a benign tumor and 20 with gall stones. In the 'malignant' group the severest events was four times as high as in controls. All other degrees of threat were equally distributed over the groups. Chronic difficulties of the highest degree of severity also occur more often in the cancer group. They are not independent from events so that analyzing them separately is not useful. The rate of family history of breast cancer does not differ between the tumor groups, but is much lower in the gall stone patients. In the cancer group there is an association between this possibly hereditary factor and severe events, in the 'benign' group both are uncorrelated. The life event effect is explained in context of a higher illness susceptibility due to a hereditary disposition. For events occurring without it an explanation remains unclear.

Adult↗
PubMed1993

Inhibition of HIV-1 replication in H9 cells by nystatin-A compared with other antiviral agents.

Nystatin A was compared in vitro with amphotericin B, AZT, or foscarnet for their respective abilities to inhibit the replication of human immunodeficiency virus type 1 (HIV-1) in H9 cells. HIV-1-infected H9 cells were cultured for 7 days in the presence of each of these drugs, at various concentrations. Reverse transcriptase activity and p24 antigen production were quantitated. Untreated, HIV-1-infected H9 cells served as the control. Nystatin A inhibited viral replication most effectively at 10 micrograms/ml, a concentration that did not affect cell viability. Nystatin-A treatment inhibited RT activity by 85% and p24 production by 90%. These levels of inhibition were comparable to that mediated by amphotericin B, AZT, or foscarnet at 10, 25, and 50 micrograms/ml, respectively. Western blot analysis of the HIV-1-infected H9 cells treated with these drugs did not detect any expression of viral proteins. These findings were further corroborated by indirect immunofluorescence studies using monoclonal anti-gp120 FITC-conjugated antibodies and by polymerase chain reaction for proviral DNA analysis, using a 32P-labeled probe. These results suggest that Nystatin A merits attention as an antiviral drug for the treatment of HIV-1 infection. In vivo drug delivery by liposome encapsulation to overcome problems of bioavailability is currently under study.

Amphotericin B↗
PubMed1993

[Situational effects in reporting life change events? A comparison of two assessment techniques].

Studies on the role of life events in the development of malignant diseases (particularly breast cancer) often rely on so-called limited prospective designs: Women with a suspicious breast lump are interviewed prior to surgery. After having learnt the final diagnosis, the sample is divided into a group having cancer and a control group. Research using this approach was criticised for producing artifacts: knowledge of diagnosis should cause reevaluations of past events and lead to overreporting of stressful experiences. Two limited prospective studies using different assessment methodologies are compared for possible artifacts due to knowledge of diagnosis. When considering less severe events, the application of a checklist technique leads to marked memory bias as assumed above. When leaving the respondents time to reconstruct their events at length, no artifacts are present. Reporting of the severest event categories remains unaffected under both methods.

Adult↗
PubMed1992

Artifacts in "limited prospective" designs? Testing confounding effects on response behaviour of women prior to breast surgery.

Data from a 'limited prospective' study on life events and breast cancer were tested whether they were biased by knowledge of the prospective diagnosis or by related mood states. Data were gathered by semi-structured and tape-recorded interviews. Event classifications were made according to Brown and Harris' Life Events and Difficulties Scale, an interviewer-based rating method. Ratings were performed before the interviewer learned the final diagnosis. Among the women coming to hospital with a suspicious breast lump, 33 had a malignant and 59 had a benign diagnosis. For comparison for mood effects two more control groups (women prior to gall stone surgery and healthy women interviewed at home) were included. Although artifacts may in general play a role for reporting events in 'limited prospective' designs, the present study could not document a sizeable effect of presumed confounding variables on response behaviour.

Adult↗
PubMed1991

Life events prior to manifestation of breast cancer: a limited prospective study covering eight years before diagnosis.

The role of life events in breast cancer was conceptualized within two models differing by vulnerability factors, 'social support' and 'early loss of mother'. The eight years prior to manifestation of the lump were covered by semi-structured interviews. Event ratings were performed according to Brown and Harris' Life Events and Difficulties Scale, an interviewer-based rating method. Data were collected within a so-called limited prospective design. This setting was subject to critical evaluation to control possible artifacts. Interviews were tape-recorded and rated before learning the final diagnosis. In the tumor groups, 97 women with a suspicious breast lump were interviewed immediately after hospital admission. In 33 cases, the diagnosis turned out to be malign, 59 had a benign result. Data analysis revealed that life events in the severest categories were reported most often in the cancer group. Path analyses showed that effects do not disappear when control variables are taken into account.

Adaptation, Psychological↗
PubMed1991

Bioreactor and process design for large-scale mammalian cell culture manufacturing.

Good Manufacturing Practice for pharmaceuticals requires that the manufacturing processes be controlled and reproducible. The biological nature of cell culture-based processes lends them an inherently higher variability than is generally found for processes involving production of defined chemical entities. As one regulatory body has pointed out, this places a greater emphasis on in-process controls and adherence to GMPs in the manufacture of cell culture products. Design of bioreactors and associated process control systems is a key element in the successful implementation of a commercial-scale cell culture manufacturing process capable of meeting such high standards. It should be noted that reactor and control system designs for animal cell culture are still very much in a state of evolution from the modified bacterial fermentation systems that currently predominate, and it is difficult to predict how design strategies may change in the coming years. Having said this, however, it should be clear from the information presented here that satisfactory processes can be devised today using proven equipment configurations such as the stirred-tank reactor.

Animals↗
PubMed1991

The preparation and validation of stock cultures of mammalian cells.

The utilization of continuous cell substrates is now widely accepted for the production of biologics. As part of the evaluation and licensing process of these products, the regulatory agencies are requiring extensive validation of the production system. That production system begins with the validation or qualification of a defined cell bank. This includes the validation of the stability cells at both the genetic and biochemical levels during cell culture production. Process validation plus cell bank validation provide the necessary assurance that the final product will be free of contaminating viruses and other adventitious agents. A combination of cell bank characterization and product characterization (peptide mapping or amino acid sequencing, or a combination thereof) will also demonstrate the stability of the production process. The validation of a cell bank for adventitious agents and cell line stability will not, in itself, ensure that the product is sterile and stable. However, cell bank validation is critical for demonstrating the safety of a product when combined with both process validation and end-product testing.

Animals↗
PubMed1984

Social and psychological differences between cancer and noncancer patients: cause or consequence of the disease?

83 female patients with breast tumors were interviewed prior to biopsy. The interview contained a psychological instrument measuring action control as an indicator for the patients' reaction to stress together with questions about the expected diagnosis. Using multiple-regression analysis we estimated the explained variance of the variables relating to the histological result of the biopsy. Since most of the patients gave a correct prognosis of the nature of their disease-this variable proved to be very important-most of the social psychological findings have to be interpreted as consequences rather than causes of cancer.

Adaptation, Psychological↗