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Biomedical subjects

K Dietz

Publications and source records attributed to K Dietz.

At least 145 records · Page 8Linked to original sources
PubMed1982

[Stereo magnification angiography--its application in neuroradiology (author's transl)].

The article discusses the stereo magnification technique using the Stereolix system and explains its clinical application in neuroradiology. The special advantage of the Stereolix tube is that it can be used in routine procedure, since it is suitable both for normal serial angiography and--by pressing a button--for stereo magnification angiography. The emphasis of trials was on the applicability for spinal angiography and in the diagnosis of cerebral aneurysms and arteriovenous angiomas.

Angiography↗
PubMed1980

[Tomoscopy].

UNLABELLED: Report on initial clinical experience with a new form of tomography with fluoroscopy, called 'tomoscopy'. PRINCIPLE: Several grid controlled x-ray tubes firmly mounted (stationary) in circular fashion -- with the foci in equidistance -- are fired in sequential fashion for a short exposure, which creates the impression of tube movement mandatory in conventional tomography, by this sequential firing of several tubes (in 1/50 second total), the mechanical tube motion of conventional tomography can be avoided. In the image intensifier, there is synchronous electromagnetic deflection of the image between input- and output screen; and a tomographic image can be seen at the output screen. This can also be recorded on camera. This new technique allows quick fluoroscopic determination of the ideal 'cut' and thus provides efficient tomography without slowing down the ongoing examination; and it is a useful addition to modern radiographic equipment with image intensification, especially when used with contrast material. Its full future impact on diagnostic radiology can yet not be estimated.

Fluoroscopy↗
PubMed1979

Epidemiologic interference of virus populations.

There are a few simulation studies for interference models in the literature but the present paper discusses an analytical model for the competition of two interfering virus populations in a community. The mathematical model consist of eight coupled differential equations which have up to four equilibrium points. Criteria for local stability are given.

Disease Outbreaks↗
PubMed1979

Antibody against hepatitis A in seven European countries. II. Statistical analysis of cross-sectional surveys.

The age-specific prevalence of hepatitis A antibodies has been analyzed using a catalytic epidemic model for populations in seven European countries: West Germany, Norway, Greece, Switzerland, Holland, France and Sweden. The results indicate a significant decline in the force of infection in recent decades. However, there are substantial differences between the countries, especially between the Scandinavian countries and Greece. The incidence of hepatitis A in Norway and Sweden has declined since 1930, while a downward trend in incidence in Greece may have started only recently.

Adolescent↗
PubMed1978

Further epidemiological evaluation of a malaria model.

The malaria model previously fitted to 1 year of baseline data from the Garki District in the Sudan savanna of northern Nigeria was tested against data collected in the same area over a period of 3 years, including 1(1/2) years during which the insides of houses in certain villages were sprayed with propoxur. It was also tested against data collected in Kisumu, Kenya, also over a period of 3 years, including 20 months during which the insides of houses in part of the area were sprayed with fenitrothion. The test consisted in using the vectorial capacity, calculated from the entomological observations made in the above places and periods, as input in the Garki model while keeping the other parameters as fitted to the Garki baseline data, and in comparing the prevalence of Plasmodium falciparum parasitaemia as estimated by the model to that actually observed. There was relatively good agreement and the model is considered epidemiologically satisfactory and fit for use in planning malaria control operations.

Adolescent↗
PubMed1977

[Frequency of hepatitis A antibodies in populations of various European countries].

Using a solid phase radioimmunoassay, prevalence of anti-HA was determined in sera of 661 German patients treated following accidents, 70 persons born in Mediterranean countries and 175 persons from Lillehammer, Norway. In Germany (55% positive) an increase in prevalence of anti-HA from 13% in the group below 20 years of age to 92% in persons over 49 was noted. This and further data suggest that after infection anti-HA is detectable for life. Persons from Norway (17% positive) aged below 40 years had a low prevalence of anti-HA (4-10%), whereas even young persons from Mediterranean countries (81% positive) hat antibody in about 80% of cases. Prevalence rates in different age groups suggest a remarkable decrease in incidence of hepatitis A infection over the last three decades in Germany. This results in a rise in the mean age at which hepatitis A infection is acquired and high morbidity during travel abroad. Only one of 10 hepatitis A infections appears to produce clinical disease. Young anti-HA positive individuals exhibit higher titers on average than older ones.

Adult↗
PubMed1976

Comparative field cage tests of the population suppressing efficiency of three genetic control systems for Aedes Aegypti.

Cycling populations of Aedes aegypti were set up in cages and managed in such a way that the populations had a maximum of threefold recovery potential in response to control measures. Into three such populations daily releases were made of males which had been chemosterilised, or were double translocation heterozygotes (T1T3) or T1T3 with sex ration distortion (DT1T3). Eradication of the populations was achieved with all cases, but the rate of suppression was markedly slower with T1T3 than the other two systems, with which the rates were similar. T1T3 and DT1T3 releases introduced considerable inherited genetic loads into the target populations. The results were in general agreement with computer predictions.

Aedes↗
PubMed1976

The impact of propoxur on Anopheles gambiae s.1. and some other anopheline populations, and its relationship with some pre-spraying variables.

A significant and stable difference in the residual night-biting collection (NBC, observed/expected) of A. gambiae s.l. was observed among different villages of the West African savannah when sprayed for 2 years with propoxur. The residual mosquito density of a given village was positively associated with some of its pre-spraying characteristics: the NBC/PSC (pyrethrum spray collections) ratio, the median biting hour, and possibly the proportion of species B. It was not significantly associated with several other pre-spraying characteristics (absolute mosquito density, the ratios between NBC indoors and NBC outdoors, between ETC (exit-trap collections) and PSC, between fed and gravid in the PSC or ETC, between males and females in the PSC), and was not associated with variations in recorded coverage, with latitude, or with distance from unsprayed villages.In a comparison between A. gambiae s.l., A. funestus, and A. pharoensis, the residual NBC (observed/expected) was positively associated with the pre-spraying NBC/PSC ratio, and was negatively associated with the median biting hour.The pre-spraying NBC/PSC ratio thus appears to be a predictor of the variation, between villages or species, in the reduction of the NBC by residual spraying, and may assist in forecasting the effect of a residual insecticide. The limitations of any absolute prediction must, however, be kept in mind.

Animals↗
PubMed1976

Characteristics of the spread of a wildlife rabies epidemic in Europe.

The control of rabies in wildlife by reducing the fox population has led in Europe to inconsistent results, since little was known of the dynamics of the fox population and the interaction between rabies epidemics, host populations, and control measures. As part of the WHO/FAO Coordinated Research Programme on Wildlife Rabies in Europe, data on epidemics and persisting reservoirs of the disease were processed by computer. The results led to a better understanding of the mechanism of spread of the epidemic and to proposals for the improvement of rabies control in animals and the protection of man.

Animals↗
PubMed1974

A malaria model tested in the African savannah.

A new mathematical model of malaria has been developed for comparing the effects of alternative control measures. It describes both the temporal changes of the P. falciparum infection rate and the immunity level of the population as a function of the dynamics and characteristics of the vector populations, which are summarized in the concept of vectorial capacity. A critical vectorial capacity is specified, below which malaria cannot maintain itself at an endemic level. The model has been tested with epidemiological data collected in a WHO research project in the African Savannah, Kano State, Northern Nigeria, since October 1970. The estimates of the model parameters were obtained by minimizing the chi(2) function that measures the discrepancy between the observed and expected age-specific parasite rates in the two villages with the highest and the lowest vectorial capacity, respectively, at five surveys during one year of baseline data collection and between the observed and expected infant inoculation rates, in the main transmission seasons, in the same two villages. The model describes three aspects of immunity: loss of infectivity, loss of detectability, and increase of recovery rate. It is assumed that loss of infectivity precedes loss of detectability and increase of recovery rate. Superinfections are slowing down the recovery for high inoculation rates but do not reduce them to zero. They do not increase infectivity.

Adolescent↗