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Biomedical subjects

K M Weiss

Publications and source records attributed to K M Weiss.

100 records · Page 6Linked to original sources
PubMed1968

Some effects of the conditioned suppression paradigm on operant discrimination performance.

Three experiments were conducted with rats to determine the effects of electric shock on responding during an operant discrimination. In two of these experiments, a conditioned suppression procedure was superimposed upon a stimulus signalling the availability of food reinforcement (S(D)). Response rates were greatly suppressed, not only in the warning signal periods which preceded each shock, but in the presence of S(D), and the stimulus signalling the unavailability of reinforcement (S(Delta)) as well. A third experiment, in which a very mild shock was used without a warning signal, demonstrated an increased response rate in S(D) and S(Delta), although this effect was rather unsystematic. In a similar study, Hearst (1965) found an increased rate in S(Delta) independent of any change in the S(D) rate. The present study failed to obtain Hearst's effect but illustrated a suppressive effect with a similar procedure.

Animals↗
PubMedDate not supplied

Relative risks of diseases in the presence of incomplete penetrance and sporadics.

In most diseases of contemporary interest to epidemiology, the importance of familial risk factors is often assessed by relative risk measures computed from family history data. In this paper, we examine the efficiency of relative risk measures in discerning the genetic background of a disease. It is shown that even for a simple (one locus, two alleles) genetic disease, incomplete penetrance of the disease allele and/or occurrence of sporadics (i.e. non-heritable cases caused by environmental risk factors) often yields a rather small value of relative risk. This means that a small value of relative risk need not necessarily imply that genetic factors are unimportant in the aetiology of the disease. Furthermore, it is shown that the relative risk measures are complicated functions of disease gene frequency, the penetrance parameter and the sporadic rate. A rejection of genetic involvement for a disease on the basis of a single relative risk estimate may, therefore, be erroneous.

Genetic Diseases, Inborn↗
PubMedDate not supplied

Information overload disrupts digit recall performance in schizophrenics.

The effect of auditory information overload on schizophrenics was examined by using a modified forward digit recall task. When memory capacity was exceeded, schizophrenics, but not controls, showed severe disruptions in performance on individual trials. Theories to account for the disruptions are discussed. A combination of factors, rather than simply limited information handling capacity, appears best able to account for the phenomenon. It is emphasized that further understanding of active cognitive process requires examination of trial by trial individual subject data.

Adult↗
PubMedDate not supplied

Colour-blindness in Colombia.

The frequency of defective colour vision was studied in two neighbouring villages in the Andes Mountains of Colombia using AO H-R-R Pseudoisochromatic plates. The frequency of the red-green colour-blindness in males is almost the same in both villages (2.36-2.53%), being similar to frequencies reported for other mestizo' populations in Latin America. In one of the communities, families in which colour-blindness occurred were wealthier (P is less than 0.05) than non-colour-blind families, but there were no significant differences by colour vision class in numbers of surviving children nor mother's marriage age. These findings are consistent with the idea that in societies at the agricultural level, colour-blindness is selectively neutral. The association of colour-blindness with higher socio-economic status is expected given the history of European conquest in the New World, and suggests that the major cause of varying rates of the defect in Latin American populations is socio-economic heterogeneity and by inference different degrees of European-Amerindian admixture.

Age Factors↗
PubMedDate not supplied

Infant mortality in a Mexican-American community: Laredo, Texas, 1950-1977.

Published infant mortality rates (IMR's) for Mexican-American populations frequently are lower than expected given the socioeconomic status (SES) of these populations. It has been speculated that this is due to bias or incompleteness in Mexican-American vital statistics. In this paper an extensive genealogical data base constructed from Catholic church records and civil records for the border city of Laredo, Texas is used to study this problem. The infant mortality probabilities (IMP's) since 1950 are compared to conventional IMR's, both based strictly on the population at risk defined by baptisms, in which the deaths are a proper subset of the denominator, and these are compared with IMR's calculated in the usual way from aggregate civil records of births and infant deaths for Laredo. We find that when these data are used, the IMR's for the most recent years are about twice the conventional rates computed from registered vital statistics.

Bias↗
PubMedDate not supplied

Human papillomavirus infection and neoplasia of the cervix and anogenital region in women with Hodgkin's disease.

Immunosuppression has been associated with an increased incidence of condyloma and neoplasia of the cervix and anogenital region, lesions associated with human papillomavirus (HPV) infection. The role of immunosuppression as a risk factor for the development of these lesions in patients with Hodgkin's disease was studied in a series of 666 consecutive women seen at the University of Texas M. D. Anderson Hospital between 1963 and 1982. Thirty-nine patients (5.9%) of the entire series and 45.9% of the 85 women with Hodgkin's disease who had a gynecologic examination showed evidence of condyloma, dysplasia or carcinoma of the cervix or anogenital region. This is a significantly greater percentage of affected women than would be expected based on published results from Papanicolaou screening services. The evidence is compatible with immunosuppression from Hodgkin's disease or its treatment rendering a woman susceptible to persistent HPV infection and its consequences.

Adenocarcinoma↗