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Biomedical subjects

K Dietz

Publications and source records attributed to K Dietz.

At least 127 records · Page 7Linked to original sources
PubMed1988

Infection with human T-cell leukemia virus type I in patients with leukemia.

Among 211 adults with leukemia who received multiple transfusions, 6 were found to be seropositive for human T-cell leukemia virus Type I (HTLV-I). Before the positive serum specimens were obtained, these patients received a mean of 14 units of red cells and 78 units of platelets. Seroconversion could be documented in three patients. None of the 6 patients seropositive for HTLV-I had a T-cell leukemia, other illnesses attributable to HTLV-I infection, or risk factors for HTLV-I infection other than transfusion: none were seropositive for human immunodeficiency virus. Patients with leukemia who receive multiple transfusions appear to be at risk for HTLV-I infection.

Antibodies, Viral↗
PubMed1988

Epidemiological models for sexually transmitted diseases.

The classical models for sexually transmitted infections assume homogeneous mixing either between all males and females or between certain subgroups of males and females with heterogeneous contact rates. This implies that everybody is all the time at risk of acquiring an infection. These models ignore the fact that the formation of a pair of two susceptibles renders them in a sense temporarily immune to infection as long as the partners do not separate and have no contacts with other partners. The present paper takes into account the phenomenon of pair formation by introducing explicitly a pairing rate and a separation rate. The infection transmission dynamics depends on the contact rate within a pair and the duration of a partnership. It turns out that endemic equilibria can only exist if the separation rate is sufficiently large in order to ensure the necessary number of sexual partners. The classical models are recovered if one lets the separation rate tend to infinity.

Epidemiologic Methods↗
PubMed1988

Reply.

Explore the source record for details and available documents.

Letter↗
PubMed1988

Density-dependence in parasite transmission dynamics.

The transmission of vector-borne parasites is complex, yet to a large extent this complexity can be unravelled through the insights gained from simple mathematical models of the transmission system. The principle is simple because the key question is merely "what is the rate of increase in numbers of hosts affected?" Clearly, if this rate of increase is greater than unity then the infection can spread, while if it is less than unity it will decline. Ronald Ross in 1911 was the first to formulate this idea for malarial(1) and malaria transmission has since attracted most attention from modellers of parasitic diseases(2-4). But although it is implicitly recognized that nothing- not even parasitic transmission - can increase indefinitely, the importance of some degree of density-dependence in regulating the system tends to be neglected (see Box 1). In this article, Klaus Dietz explores some classical ideas of modelling parasitic disease transmission, emphasizing not only the importance of density dependence but also the importance of knowing exactly where such effects operate in the system.

Journal Article↗
PubMed1988

Emergence of Onchocerca volvulus microfilariae from skin snips before and after treatment of patients with ivermectin.

As ivermectin is supposed to have a paralyzing effect, the emergence of Onchocerca volvulus microfilariae from skin snips before and after treatment was examined. Before treatment 79.8% of the microfilariae emerged from the skin snips. Three days after treatment the microfilarial skin density had dropped to 83% (placebo), 28% (100 microgram/kg ivermectin), 19% (150 micrograms/kg) and 14% (200 micrograms/kg) of the pretreatment values but the microfilarial emergence was not altered distinctly. The majority of the remaining microfilariae were mobile and able to leave the biopsy. Only a slight, but significant, dose-dependent trend of reduced emergence could be shown. From our results no direct support is derived for the hypothesis that O. volvulus microfilariae are paralyzed or immobilized by ivermectin.

Analysis of Variance↗
PubMed1988

Human immunodeficiency virus infection in patients with leukemia.

Eighteen human immunodeficiency virus (HIV)-seropositive patients were found among 211 previously treated adult patients with a variety of leukemias who had been multiply transfused before April 1985. Patients known to be homosexual or intravenous drug users were excluded from this study. The spouse of one HIV-seropositive patient became HIV infected and subsequently developed the acquired immune deficiency syndrome. Patients with leukemia who were multiply transfused before the availability of screening of blood products for HIV antibody should be counseled regarding their individual risks of HIV infection and the risk to sexual contacts.

Female↗
PubMed1987

Common respiratory and gastrointestinal illness in paediatric student nurses and medical technology students.

The aim of this study was to establish the risk of acquiring common respiratory and gastrointestinal illness for paediatric nurses. Using self-administered questionnaires, student nurses at two children's hospitals and students at one school of medical technology reported biweekly the number of minor illnesses, symptoms, and indicators of severity of infection over a 3-year period (1975-8). Although a systematic bias was evident with some symptoms, others appeared to be quite reliable. The following four syndromes were defined to estimate the risk: upper respiratory syndrome (URS), lower respiratory syndrome (LRS), respiratory and gastrointestinal syndrome (RGS), and gastrointestinal syndrome (GS). Surveillance days were allocated to groups with high- or low-intensity contact with children. The incidence of all illnesses was 2.9 per person-year in the low-intensity contact group and 4.4 per person-year in the high-intensity contact group. The reported incidence of LRS and RGS in the high-intensity contact group was 1.55 times higher than in the low-intensity group (P less than 0.001). LRS and RGS incidence was similar in nurses at both schools. During low contact periods it corresponded to that of the medical technologists.

Adolescent↗
PubMed1987

Seroepidemiological studies on the occurrence of common respiratory infections in paediatric student nurses and medical technology students.

The occupational risk of acquiring minor respiratory infections for paediatric student nurses was estimated by performing serological examinations with influenza A, B, C, parainfluenza, mumps, respiratory syncytial virus, adenovirus and Mycoplasma pneumoniae at 6-month intervals over a period of 4 years in paediatric student nurses at two schools of nursing and students at one school of medical technology. Titre increases against all tested agents occurred 1.86 times more often in the student nurses than in the medical technology students, the most frequent agents in both groups being influenza A and B. No difference in the relative distribution of the agents could be verified in the two occupational groups. Data on the protective value of pre-infectious antibody levels for influenza A, B, and coronavirus OC43 and on the importance of the spread of single agents among classmates are presented.

Adolescent↗
PubMed1987

[Causes of inadequate vision in drivers and their significance in traffic].

From an analysis of the data of 462 automobile drivers with inadequate visual acuity it was established that the frequency of visits to the ophthalmologist by drivers with inadequate vision is determined less by age than by the cause of the visual deficiency. Here, considerable differences appear in the duration of inadequate vision before it is detected by the ophthalmologist and in the frequency of visits to the ophthalmologist. These have the effect that the refractive error, the most common visual deficiency among younger drivers, is considerably more important as an accident risk in road traffic than one might assume from the number of those affected. A precautionary elimination of visual deficiencies as cause of accidents therefore necessitates an examination of visual acuity which includes all age groups. In order to eliminate visual deficiencies in road traffic as a cause of accidents as a precaution, the officials responsible must find a practicable way of detecting and eliminating these deficiencies so early as possible. On the other hand, ophthalmologists must make it clear to their visually unsuited patients that in their own and the general interest they should give up driving.

Adolescent↗
PubMed1986

[The incidence of visually impaired drivers seen in ophthalmologic consultation].

On the basis of a critical review by Dr. rer. nat. Bresser the calculation contained in the paper "Ophthalmological Experiences with Automobile Drivers with Inadequate Visual Acuity" is corrected. From the information on visits to the ophthalmologist contained in the study data, the average frequency of repeated visits can be worked out to 1.56. As a consequence, the average duration of unsuitable vision is 22.1 months. This results in a prevalence P = 360750. However, this figure can only apply to drivers who visit an ophthalmologist. According to a recent study based on a random sample of the population, the true number of drivers with unsuitable vision seems to be more than 4 times the figure quoted.

Automobile Driving↗
PubMed1985

Proportionate mixing models for age-dependent infection transmission.

We present explicit formulas for the transmission potential of an immunizing infection where the contact rates and the vaccination rates depend on the chronological age of an individual, and the infectivity and the recovery rate depend on the duration of an infection.

Age Factors↗
PubMed1985

[Initial experiences with a new stereo roentgen technic in general radiology].

A new stereo X-ray technic, which is simple, easy to handle, universally applicable and without intrinsic disadvantages for the patient, is demonstrated. The two attributes of stereo X-ray, exact spatial representation of the relationship between structures and the addition of the two stereo pictures to give better signal/noise ratio are explained. The efficiency of this method is presented with investigations of the G.I. tract, abdominal angiography and the knee arthrography.

Digestive System↗
PubMed1984

Population dynamics of killing parasites which reproduce in the host.

For a parasitic infection in human hosts a model is derived from basic assumptions on the population structure of the host, in particular mortality depending on age and parasite load, and on the reproduction and transmission of parasites. The model assumes the form of a system of partial differential equations. The paper contains proofs of local and global existence and existence and uniqueness of nontrivial stationary states, and a discussion of the relation to birth and death processes and other models for parasitic infections.

Age Factors↗
PubMed1984

Evaluation of age-specific vaccination strategies.

Under the assumption that maternal antibodies and vaccine immunity decay exponentially the proportions of susceptibles in the total population for given age-specific vaccination strategies and zero infection incidence are determined explicitly. The reciprocal value of such a proportion determines the maximum reproductive rate of an infection which could be eradicated by the corresponding strategy. For a single vaccination during life the optimum age is determined, for which the proportion of susceptibles reaches a minimum. The effect of one revaccination during school age is explored.

Age Factors↗
PubMed1984

[Improved clinical course of herpes zoster in immunosuppressed patients treated with fibroblast interferon].

In a randomized study with patients suffering from herpes zoster spread of eruptions was inhibited and segmental pain was reduced rapidly by continuous infusion of daily 0.5 X 10(6) IE fibroblast interferon/kg body weight for 3-5 days. Postherpetic neuralgia was observed more rarely and interferon healing of eruptions was accelerated by interferon compared to the controls.

Adult↗
PubMed1983

Inhibition of male fertility by STS 557.

To ascertain the effects of STS 557 (17 alpha-cyanomethyl-17 beta-hydroxy-estra-4, 9-dien-3-one) on the reproductive and endocrine functions, male rabbits were given the substance orally daily over 8 weeks. In doses of 10 and 20 mg STS 557 per animal per day fertility inhibition was accompanied by a decrease of spermatogenesis and sexual activity. At the chosen dose of 5 mg per day, STS 557 caused a decrease of sperm motility, semen fructose content and sterility of the bucks. On the other hand, libido, semen volume, sperm number, sialic acid content in semen, serum LH and testosterone remained unaffected. Concomitant injection of testosterone did not reverse the suppressive effect of STS 557 on fertility. Motility of human sperm was lowered markedly by STS 557 in vitro. The human sperm penetration and pronuclear formation were significantly reduced in the vitro fertilization assay with zona-free hamster eggs. Findings are discussed in view of the development of male contraceptives.

Animals↗