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Biomedical subjects

L Vogt

Publications and source records attributed to L Vogt.

At least 55 records · Page 3Linked to original sources
PubMed1995

The feasibility of Doppler monitoring during EVA.

During extravehicular activities (EVA) outside the spacecraft, astronauts have to work under reduced pressure in a space suit. This pressure reduction induces the risk of decompression sickness (DCS) by the formation of gas bubbles from excess nitrogen dissolved in the organism by breathing air at normal pressure. Under laboratory conditions the gas bubbles moving in the blood stream can be detected by the non-invasive ultrasonic Doppler method. By early detection of excessive bubble formation the development of DCS symptoms may be prevented by early application of preventative measures. The method could also be useful when applied in the space suit in order to compare the results of laboratory tests with operational results, because there is a discrepancy according to the DCS risk of laboratory experiments and actual EVA missions, where no symptoms have been reported yet. A prototype Doppler sensor has been developed and implemented in the Russian Orlan suit. To investigate the feasibility of this method under simulated space conditions, the equipment has been used in a series of 12 thermovacuum chamber tests with suited subjects, where intravenous bubble formation was compared to unsuited control experiments. In more than 50% of the suited tests good Doppler recordings could be achieved. In some cases with unsatisfying results the signal could be improved by breathholding. Although the results do not yet allow any conclusion about a possible difference between suited and unsuited subjects due to the small number of tests performed, the method proved its feasibility for use in EVA suits and should be further developed to enhance the safety of EVA procedures.

Aerospace Medicine↗
PubMed1995

Application of the mechanical oscillator technique to the investigation of EVA decompression.

The ultrasonic bubble detection technique has been used as a versatile tool in the investigation of hypobaric decompression procedures for the last two decades. However, this method can only detect relatively large bubbles > 30-50 micrometers (usually in venous blood) and not the very first stages of bubble formation. Recently, the mechanical oscillator technique has been applied in air diving trials in order to detect small blood density changes due to hypothetical fluid shifts. However, sharp density drops were found in the decompression process, and these have been attributed to gas bubble formation. In this study, this method was applied together with Doppler controls to a series of altitude decompressions to 300 and 500 hPa, which represents the range of EVA operational pressures currently used or planned. Six subjects participated in both series; the oscillator sample tube could be pressurized. By the application of pressure on a blood sample containing questionable gas bubbles, these are reduced in volume, like in recompression therapy, and thus the density of the sample is increased. This effect has been shown in all 6 subjects undergoing decompression to 300 hPa, whereas in the 500 hPa series only 3 out of 6 subjects corresponded with gas phase formation immediately after decompression. Typically, Doppler bubbles appeared only after some latency time between 20 and 60 min; after this time, the density effect had nearly vanished. It is concluded that the mechanical oscillator technique represents a complementary research instrument to the Doppler method, because it is able to deliver a quantitative resolution of the early stage of gas phase formation.

Aerospace Medicine↗
PubMed1995

Locus on chromosome 18 cosegregates with diabetes in the BB/OK rat subline.

The spontaneously diabetic BB rat is a well-established animal model of human insulin-dependent diabetes mellitus. Besides the lymphopenia gene (Iddm 1) and the MHC class-II genes of the RT1u haplotype (Iddm 2), at least one other non-MHC gene (Iddm 3) is considered essential for diabetes development. To investigate the participation of this third gene in the development of diabetes in our BB/OK rat subline, we analysed 119 [(BB/OK x DA)F1 x BB/OK] first backcross hybrids phenotypically and genotypically. Genotyping with 5 classical and 28 polymorphic microsatellite markers indicated that the third gene is located on chromosome 18, about 22 +/- 7 cM distal from the Olf locus (Iod score = 2.33). Significantly more diabetics than Iddm 1 and Iddm 2 homozygous nondiabetic subjects were homozygous for this locus. Interacting genes located on chromosomes X and/or 1 seem to be involved.

Animals↗
PubMed1994

EVA: European plans.

The current status of European EVA (extravehicular activity) plans is reviewed. The major difference to already existing EVA scenarios in U.S.A. and Soviet Union consists in the adoption of a higher suit pressure, namely 500 hPa. The results of a study concerned with the physiological consequences of this adoption are presented, including recommendations for protective procedures and their necessary experimental validation. A certain discrepancy between laboratory experimental decompression data and EVA operational results is discussed, leading to the identification of several items which may influence space decompression. Microgravity and the influence of the space suit itself are most likely factors in the explanation of this discrepancy, and both experimental procedures and technological developments are proposed to clarify their role for the future design of EVA procedures.

Aerospace Medicine↗
PubMed1993

Genetic analysis of frequencies of phenotypes in the spontaneously diabetic BB rat--a main animal model of autoimmune type-I-diabetes.

The incidence of diabetes shows variations of 40 to 80% in different BB rat sublines. Whether genetic or environmental factors are responsible for this observation remains unclear. Little data is available on population-based investigations and no results have been reported about computer-aided simulation of models with regard to the inheritance of spontaneous diabetes in BB rats. On the basis of the finding that diabetes incidence in offspring of diabetic parents is significantly higher than in matings in which one or both parents were non-diabetic we have analysed the frequencies of parental phenotypes in relation to the incidence of diabetes over 25 inbred generations in our BB/OK rat strain. We could ascertain a relation of a high frequency of matings of diabetic parents to high diabetes incidence. This was confirmed by model-based simulations and comparison of simulated and observed diabetes incidence. The study gives strong evidence of segregation of one additional gene in the BB/OK rat subline.

Animals↗
PubMed1993

Epidemiology of insulin-treated diabetes mellitus in the East-German population: differences in long-term trends between incidence and prevalence rates.

In order to evaluate temporal trend variations of incidence and prevalence rates of Type 1 (insulin-treated) diabetes mellitus in the East-German population (19.6 million) 85,904 incidence cases, recorded by the Diabetes Registry between 1960 and 1989, were analyzed by calculating the regression coefficients for defined time intervals. The total incidence trend was characterized by a rise from 18/10(5) in 1960 to 29/10(5) in 1965, a decrease to 14/10(5) in 1975, and a slight increase to 15/10(5) in 1989. This trend was reflected only by patients with insulin treated diabetes mellitus aged > or = 30 yrs. Patients of the age groups 0-9 yrs., 10-19 yrs., and 20-29 yrs. exhibited increasing rates of 0.21/10(5)/year (1960-75), 0.22/10(5)/year, and 0.08/10(5)/year (1960-89), respectively. The rise in the prevalence rate from 187/10(5) (1960) to 658/10(5) (1989) demonstrated temporal trend variations during the periods 1960-71 (+19.3/10(5)/year), 1972-77 (-0.8/10(5)/year), and 1978-89 (+25.6/10(5)/year). The age-specific increasing prevalence trend varied between +0.81/10(5)/year (0-9 yrs.) and +48.89/10(5)/year (60-69 yrs.). The differences observed between incidence and prevalence trends were mainly due to changes in relative mortality rates of patients with insulin treated diabetes and the percentage of secondarily insulinized Type 2 diabetic patients. In summary, the incidence of Type 1 diabetes mellitus in East-Germany increased over the past 3 decades of registration by about 94% in children and adolescents, by 38% in adults aged 20-29 yrs., but not in people aged > or = 30 yrs.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

The frequency of diabetes in children of type 1 diabetic parents.

There is little information in the literature about the actual diabetes risk of children of Type 1 diabetic parents. In a follow-up study of 48 children born from 35 Type 1 diabetic parents between 1955 and 1989, we have recorded all data relating to the incidence of Type 1 diabetes and of appearance of signs of subclinical diabetes by June, 1992. Information about the state of health was obtained during repeated stays of the patients in our hospital or by interviewing them by letter. In 21 children aged between 4 and 29 years who had not developed diabetes, we were able to investigate oral glucose tolerance, first phase insulin secretion, islet cell antibodies and insulin autoantibodies. HLA-typing was performed in 69 of the 118 study subjects (children and their parents). Type 1 diabetes developed in 19 out of 48 offspring of Type 1 diabetic parents. Frequency is also 25% in those 24 offspring born before 1972. The children developed the disease significantly earlier than the parents (8.2 +/- 6.0 versus 15.9 +/- 8.3, p < 0.01). Diabetes became manifest in 4 single children, in 2 HLA-identical pairs of siblings, and in 4 children with non-diabetic siblings. In 5 out of 21 non-diabetic offspring investigated we found impaired glucose tolerance, diminished first-phase insulin secretion, and/or Islet Cell Antibodies between 5 and 80 JDF units. The frequency of diabetes in the offsprings of Type 1 diabetic parents was lower than expected, but in addition 24% of the non-diabetic children displayed signs of subclinical diabetes.

Adolescent↗
PubMed1993

Influence of sex and phenotype of parents on the incidence of diabetes in BB/OK rat litters.

Because diabetes incidence (in the context of animal diabetes defined as percentage of animals developing diabetes until the age of 200 days) in BB rats is largely the same in males and females, a sex-influenced or sex-linked inheritance of diabetes has been excluded. However, in crossing studies using diabetic rats of the BB/OK rat subline and different diabetes-resistant rat strains, an excess of females was frequently observed, generally connected with an excess of diabetic males. Therefore the incidence of diabetes in 12 litters of [(dBB x DA)F1 x dBB] first backcross hybrids (BC1) and in 331 litters of BB/OK rats was analyzed according to sex ratio of litters and phenotype of parents (d-diabetic, nd-nondiabetic). In BC1 hybrids and BB/OK rats, about 50% of litters with an excess of females were observed, but an excess of diabetic males was established only in BC1 hybrids. However, in BB/OK rats correlations were found between diabetes incidence and litters with 1:1 proportion of diabetic males to females (r = -0.42 p < 0.05), phenotype of parents d x d (r = 0.73 p < 0.01) and nd x nd (r = -0.69 p < 0.01). Furthermore, an indirect influence is observable from correlations between the phenotype of parents d x d and litters with an excess of males (r = -0.40 p < 0.05) and diabetic females (r = -0.42 p < 0.05) as well as litters with a 1:1 proportion of diabetic males and females (r = -0.42 p < 0.05). It is concluded that diabetes in BB/OK rats is most probably incompatible with a "biologically normal" sex proportion in litters and that a sex-related inheritance appears to exist.

Animals↗
PubMed1993

Model-based prediction of diabetes incidence in BB/OK rats.

In the BB/OK rat strain, the incidence of diabetes (in the context of animal diabetes defined as the percentage of animals developing diabetes up to the age of 200 days) is related to the sex distribution within litters and to the phenotype of the parents. On the basis of these observations, an algorithm was developed to predict the incidence of diabetes of an inbred generation as the percentage of diabetic animals of a given inbred generation. Thus, the incidence of diabetes was analysed in 25 inbred generations of our BB/OK colony according to sex ratio and the phenotype of parents, which is thought to be an important genetic factor for diabetes onset in the offspring. On the basis of a single gene model, the Maximum-Likelihood method was used to predict the incidence of diabetes (average and standard deviation). The practicability of this approach was checked by a retrospective calculation of Maximum-Likelihood estimates and their comparison with the diabetes incidence as observed in the individual inbred generation. The average difference between the estimated and observed values was 5.4% which shows the practicability of the proposed algorithm and confirms the dominance of genetic factors in the development of diabetes in this BB rat subline.

Algorithms↗
PubMed1993

Primary health care of diabetic patients in a specialized outpatient setting: a DIABCARE-based analysis.

To assure health care quality requires a tool for establishing the feedback between parameters of patient management and related standards. To assess the current situation and to evaluate the DIABCARE system as a potential monitoring instrument, a retrospective study was performed in 85 randomly assigned insulin-treated patients (72% type 2) who were regularly attending the diabetes outpatient unit (total of 3,595 patients) in a township of approximately 90,000 inhabitants. 1,195 records of sequential medical visits during the years 1987 and 1990 were analyzed. -Selected results (averages in 1987 vs. 1990): (1) Visits per year 6.9 vs 7.1; (2) intensified insulin treatment in 14 vs. 27% of all patients, they were on 4.0 vs. 4.5 injections per day applying doses of 0.8 vs. 0.6 IU kg-1 d-1; (3) glycaemic control: random blood glucose 6.0 vs. 5.8 mmol/l on conventional and 6.4 vs. 5.7 mmol/l on intensified regimes, HbA1 regular measurements in 2 vs. 21% of the patients; (4) body mass index 26.4 vs. 26.6 (conventional) and 24.7 vs. 25.9 (intensified) kg/(m)2; (5) retinopathy prevalence 30 vs. 29%, in 4 vs. 29% of the patients no information; (6) nephropathy prevalence 7 vs. 11%, in 75 vs. 68% of the patients no information; (7) foot complications prevalence 6 vs. 9%, in 91 vs. 84% of the patients no pathological findings. -The DIABCARE monitor proved appropriate but too laborious. The general level of care showed a tendency towards improvement between the two investigated periods but dit not yet meet the standards which must be attained to attain the St. Vincent Declaration.

Adult↗
PubMed1992

Different frequencies of diabetic complications in insulin-treated patients with diabetes of comparable duration, in relation to age at onset of diabetes.

Diabetic complications such as retinopathy and nephropathy affect the quality of life of diabetic patients. The aim of this study was to find out whether there are differences in the development of these complications associated with the age at onset of diabetes and the different effects of diabetes onset before, during or after puberty. Therefore, we tested the hypothesis whether onset of insulin dependent diabetes in puberty was connected with an increased risk of developing diabetic microangiopathy. We found a significantly increased risk in patients with diabetes onset in puberty up to a diabetes duration of 20 years if compared with diabetes onset before but not with that after puberty. It seems that diabetes onset before puberty delays the development of early diabetic complications and that changes of the hormonal status during puberty may be responsible for an earlier development of retinopathy. After about 20 years of diabetes there are no significant differences between the groups. Our results emphasize the necessity of early ophthalmological diagnosis and adequate metabolic control, especially in patients with diabetes onset during or after puberty, in order to prevent or delay the development of diabetic complications.

Adolescent↗
PubMed1992

BB_RADABA: a computer program as a tool for breeding and management of laboratory animals.

The use of well characterized laboratory animals in biomedical research is of importance for quality securing and reproducibility of animal experiments. Therefore, breeders should not only have in mind the reproduction of their animal stocks, but they should also be interested to achieve an optimal resemblance of the animals in the main traits characterizing them as a model of human diseases. Specific software applications which helps the breeders in monitoring the main breeding parameters, selecting suitable breeding pairs and data processing are practically not available. This prompted us to develop a computer program for management of breeding and experimental data, which we called BB_RADABA. In this report we want to give a short survey on this computer program.

Animals↗
PubMed1992

[Electrocardiographic diagnosis of acute graft rejection after heart transplantation].

In order to evaluate the diagnostic value of standard-ECG (ST-ECG) and precordial mapping-ECG with 63 unipolar leads (PM-ECG) for detection of acute cardiac allograft rejection, 15 patients (12 male, 3 female; age range 24-64 years) were studied. ST-ECG and PM-ECG were recorded along with 94 endomyocardial biopsies. Twenty-four acute rejections were detected histologically. Using the ST-ECG, a reduction of the QRS-amplitude-sum (lead I, II, III, V1 and V6) greater than or equal to 5% in comparison with the ECG obtained 1 week before was found to be the best diagnostic criterion (sensitivity 63%, specificity 74%, positive predictive value 48%, negative predictive value 85%). By analysing the PM-ECG a drop of the QRS-amplitude greater than or equal to 12% in greater than or equal to 14/63 precordial leads was determined to be the most reliable parameter (sensitivity 79%, specificity 71%, positive predictive value 49%, negative predictive value 91%). In contrast to the high sensitivity of PM-ECG, ST-ECG was less suitable for detection of acute rejection. However, taking into account the high negative predictive value of PM-ECG, acute rejection could be excluded with high probability, if the QRS-amplitudes of the PM-ECG remained stable. This may lead to a lower frequency of routinely performed endomyocardial biopsies.

Adult↗
PubMed1992

On the influence of metabolic state of parents at conception and pregnancy on incidence and age at onset of diabetes in the progeny of BB/OK rats.

Thirty first and second litters of same parents of the BB/OK rat population were observed for diabetes occurrence up to an age of 200 days. The parents were nondiabetic at conception and pregnancy of their first litter (nd x nd) and either they remained nondiabetic up to an age of 200 days (nd x nd-->nd x nd) or the father (nd x nd-->d x nd) and the mother (nd x nd-->nd x d), respectively, were diabetic at conception of their second litter. There were no significant differences between first and second litters in incidence and age at onset of diabetes in the progeny, so that the genetic constitution of parents and not their metabolic state determines both traits. But, an influence of the maternal age on diabetes incidence of offspring was found. This influence, however, was not related to the metabolic state of mothers. This finding suggests that the age of mothers per se and not the metabolic state of mothers determines the diabetic disposition of the offspring in BB/OK rats.

Aging↗
PubMed1991

European EVA decompression sickness risks.

For the first manned flight of Hermes there will be a capability of performing EVA. The European EVA Space Suit will be an anthropomorphic system with an internal pressure of 500 hPa of pure oxygen. The pressure reduction from the Hermes cabin pressure of 1013 hPa will induce a risk for Decompression Sickness (DCS) for the EVA crewmember if no adequate protective procedures are implemented. Specific decompression procedures have to be developed. From a critical review of the literature and by using knowledge gained from research conducted in the past in the fields of diving and aerospace medicine safe protective procedures are proposed for the European EVA scenario. An R factor of 1.2 and a tissue half-time (t1/2) of 360 minutes in a single-tissue model have been identified as appropriate operational values. On the basis of an acceptable risk level of approximately 1%, oxygen prebreathing times are proposed for (a) direct pressure reduction from 1013 hPa to a suit pressure of 500 hPa, and (b) staged decompression using a 700 hPa intermediate stage in the spacecraft cabin. In addition, factors which influence individual susceptibility to DCS are identified. Recommendations are also given in the areas of crew selection and medical monitoring requirements together with therapeutic measures that can be implemented in the Hermes scenario. A method for demonstration of the validity of proposed risks and procedures is proposed.

Aerospace Medicine↗
PubMed1991

Importance of morphological findings in the progress and treatment of chest wall deformities with special reference to the value of computed tomography, echocardiography and stereophotogrammetry.

Patients with chest wall deformities have many particular anatomical, physiological, genetic, biomechanical and psychological characteristics. It is generally recognized that surgical correction of funnel chest and pigeon breast may be done for psychosocial reasons alone. Morphological and dynamic investigations are done to identify the function of the deformed chest wall and to permit objective assessment of the cosmetic and functional outcomes of the operation. There is no universally agreed standard for the diagnosis of funnel chest and pigeon breast. Non-invasive investigations, such as computed tomography (CT), echocardiography (ECG) and stereophotogrammetry (SP), improve the quality of the diagnostic assessment, including evaluation of its functional aspects, without directly influencing the decision to operate, which is still made mainly on subjective grounds. The value of these techniques in the diagnosis of chest wall deformities is assessed and the results of our personal experience are presented.

Adolescent↗
PubMed1991

Breeding and management of BB rats by the aid of the computer program BB RADABA.

In the process of breeding laboratory animals for experimental research a host of data will be produced. Our computer program BB RADABA permits the management of breeding and experimental data as well as planning of experiments and evaluation of experimental results. More than one year of practical work with this program has shown that BB RADABA provides a better survey over the data, moreover it is able to supply objective recommendations of suitable breeding pairs and had the advantage of graphic and statistic data presentation.

Animal Husbandry↗