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Biomedical subjects

N Becker

Publications and source records attributed to N Becker.

At least 127 records · Page 7Linked to original sources
PubMed1977

Estimation for discrete time branching processes with application to epidemics.

Certain estimators for the mean of the offspring distribution of a Galton-Watson process are considered. The asymptotic behaviour of each of these estimators is studied when the true underlying model is in fact a multitype branching process or a branching process with a random environment. It is revealed which of the estimators remain consistent indicators of whether or not the process is subcritical, under these alternative underlying models. It is then indicated how this "robustness" result might influence the choice of an estimator by considering the problem of estimating the level of immunity required in a community in order to prevent major epidemics. The application is illustrated with references to smallpox using data from an outbreak in São Paulo, Brazil.

Disease Outbreaks↗
PubMed1976

Estimation for an epidemic model.

In many epidemic models the initial infection rate, suitably defined, plays a fundamental role in determining the probability of a major epidemic. An estimate for this rate is suggested on the basis of least squares and maximum likelihood methods. The model used to arrive at the estimate is a Galton-Watson process modified by letting the offspring distribution change from generation to generation in a way as to approximate to an epidemic process. The estimates of the parameter and its associated variance are easily computed and compare well with other computationally tedious methods in an application to smallpox data.

Disease Outbreaks↗
PubMed1976

Effects of manganese on carcinogenicity and metabolism of nickel subsulfide.

Nickel subsulfide, Ni3S2, alone or combined with manganese or chromium dusts, was administered i.m. to Fischer rats to study the effects of the metals upon Ni3S2 induction of sarcomas at the injection site. The incidence of sarcomas within 2 years after injection of Ni3S2 (1.2 mg) plus manganese (1.0 mg) was 7%, versus 77% in rats that received only Ni3S2 (1.2 mg), and 80% in rats that received Ni3S2 (1.2 mg) plus chromium (1.0 mg) (p less than 0.005). No local sarcomas occurred in rats that received the injection vehicle, or in rats that received manganese or chromium without Ni3S2. Admixture of manganese diminished the solubility of 63Ni3S2 in rat serum, serum ultrafiltrate, or water, in vitro. Admixture of manganese with 63Ni3S2 did not affect the mobilization or excretion of 63Ni in vivo, nor did it alter the acute pathological reactions to Ni3S2. 63Ni concentrations in ultrafiltrates of supernatant fractions of homogenates of injection sites averaged 2.8 (S. D. +/- 0.7) ng/ml at 5 to 6 months after injection of 63Ni3S2 (1.2 mg) plus manganese (1.0 mg), versus 5.4 +/- 2.0 ng/ml after injection of only 63Ni3S2 (1.2 mg) (p less than 0.02). This study demonstrates that admixture of manganese dust and Ni3S2 inhibits Ni3S2 tumorigenesis in rats, and reveals that manganese dust affects the subcellular distribution of 63Ni derived from 63Ni3S2, without influencing 63Ni kinetics as estimated by compartmental analysis.

Animals↗
PubMed1975

Total pancreatectomy with primary mesenteric vascular reconstruction.

Total pancreaticoduodenectomy with resection of the superior mesenteric artery and vein was performed in a sixty-two year old man with islet cell carcinoma of the pancreas. Arterial reconstruction was accomplished with an aortomesenteric interposition Dacron graft. The venous system was reanastomosed primarily, the infrapancreatic superior mesenteric vein to the portal vein in the hepatic hilum. This procedure, although it did not result in long-term survival, demonstrates the technical feasibility of wide regional resection for tumors of the pancreas impinging upon the mesenteric vasculature in the region of the neck and uncinate process.

Adenoma, Islet Cell↗
PubMed1975

Altered hypothalamic-pituitary-adrenal responsiveness to dexamethasone-insulin tolerance test in active acromegaly.

Eight acromegalic patients showed a plasma cortisol (11-OHCS) rise after insulin hypoglycemia which was similar to that seen in control patients, with mean peak values (+/-SEM) of 23.2 +/- 3.5 mug/100 ml and 27.2 +/- 3.3 mug/100 ml, respectively. One mg of dexamethasone was given the evening prior to repeat insulin hypoglycemia (DEX-ITT). After dexamethasone, the control subjects showed a mean post hypoglycemic plasma 11-OHCS rise to 18.3 +/- 2.3 mug/100 ml. In contrast, acromegalic patients had a negligible rise is plasma 11-OHCS, despite a comparable degree of hypoglycemia. These data indicate that, in active acromegaly, abnormal hypothalamic-pituitary-adrenal suppressibility can be induced to insulin hypoglycemia after dexamethasone.

11-Hydroxycorticosteroids↗
PubMedDate not supplied

Lymphoma of the maxillary sinus in a patient infected with human immunodeficiency virus type 1.

A 27-year-old woman with a history of intravenous drug abuse presented with a stage IE, diffuse, large cell lymphoma of the right maxillary sinus. A test for antibodies to the human immunodeficiency virus was positive. The patient was treated with systemic chemotherapy and local maxillary sinus irradiation which resulted in complete regression of the disease. Therapy was complicated by mucositis, neutropenia, and opportunistic infections. This is the first case report to discuss the presentation and treatment of acquired immunodeficiency syndrome (AIDS)-related lymphoma of the maxillary sinus.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Geographical clusters and common patterns in cancer mortality of the Federal Republic of Germany.

This paper quantitatively analyzes the maps of the Cancer Atlas of the Federal Republic of Germany with respect to regional clustering in the patterns of rates and relations between the patterns for different localizations. Indices of clustering and association are introduced and compared with those values resulting from computer simulations assuming random distributions. For most localizations, the clusterings could not be considered random, even though they were more or less marked, a finding which, in some cases, is neither evident nor generally known. The clusterings and correlations found offer a wealth of material for generating etiological hypotheses.

Epidemiologic Methods↗
PubMedDate not supplied

Cumulative damage models in cancer epidemiology: application to human incidence and mortality data.

Cumulative damage models are a special class of mathematical models within reliability theory that describe the probability of failure of a given system under the impact of a damaging environment. Though originally introduced to handle wear and tear processes, their concepts can easily be interpreted in terms of the epidemiologic aspects of human carcinogenesis. This paper introduces the new approach and demonstrates its applicability to human cancer incidence and mortality data from Denmark and the Federal Republic of Germany. A slight simplification of the originally stochastic model provides an explicit formula for the relative risk between different populations, which predicts that this basic measure used in cancer epidemiology may have to be considered age-dependent in contrast to a widely used practice which, for convenience, postulates age-independent relative risks. A comparison with empirical data reveals that the concept of age-dependent relative risks is not inconsistent with real world examples of cancer incidence. Thus, some basic assumptions and concepts of epidemiology concerning carcinogenesis and strategies for data analysis may require reconsideration.

Cohort Studies↗
PubMedDate not supplied

Cumulative damage models of additional exposures and host factors.

Cumulative damage models represent a mathematically accurate conceptualized approach for the consideration of various problems of descriptive and analytical epidemiology. This study demonstrates the application of these models to situations where additional exposures, e.g., occupational exposures or smoking, overlay an always existing background exposure. Moreover, a way to incorporate host responses into the model is outlined, which is straightforward within this new approach, but has not been achieved by existing models to date. Based on empirical data, it is shown that some effects, which arise from additional exposures, can be understood as a kind of host response. This result contrasts with interpretations given by existing models and promises to open interesting discussion regarding which biological processes can be observed by epidemiological data.

Carcinogens↗
PubMedDate not supplied

Frequency of common colds and serum levels of sICAM-1 (CD54), sLFA-3 (CD58) and sIL-2R (CD25).

Epidemiologic case-control studies have suggested an inverse relationship between past medical history of frequency of common colds and subsequent cancer risk for various sites. One hypothetical explanation for this finding may be that there are unknown differences in immune responsiveness between patients developing cancer and healthy individuals. The present study examines the relationship between the frequency of common colds and a) plasma levels of sICAM-1/CD54, sLFA-3/CD58 and sIL-2R/CD25 which are believed to modulate activation of immune responses, and b) cell-mediated immunity in vivo as determined by Multitest Mérieux. The investigation was conducted as a correlation study amongst a healthy group of individuals from the general population in Germany. We found a statistically significant inverse relationship between frequency of common colds and levels of sCD58 and, partially, sCD54. No association was found between levels of sCD25 and results of Multitest Mérieux.

Aged↗