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Biomedical subjects

B Schmidt

Publications and source records attributed to B Schmidt.

At least 127 records · Page 7Linked to original sources
PubMed1999

[Long-term follow-up MRI in children with craniocerebral trauma].

PURPOSE: A prospective study was initiated for the correlation of the findings in the initial cranial CT with the long-term follow-up MRI in children with severe head injury. Another aim was the evaluation of frequency and location of lesions, found only in MRI. METHODS: 70 children with severe head injury and initially performed pathological CCT were followed up (mean time 3 years) by MRI. RESULTS: 71% of the children had a pathological MRI. In 43% of the children with subdural bleeding could be found parenchymal lesions in the underlying cortex. All 15 children with epidural bleeding had unsuspicious findings at the former hematoma. All of the contusions were found as parenchymal residual lesions. 44% of the children had evidence of parenchymal lesions in the follow-up MRI initially and retrospectively not revealable. 16 lesions in the corpus callosum were only revealed by MRI. CONCLUSION: This study shows the higher sensitivity of magnetic resonance imaging in non-hemorrhagic parenchymal lesions and in "diffuse axonal injury". A MRI-examination is recommended in children with severe head injury, especially in patients with normal CCT and posttraumatic neurological deficits.

Adolescent↗
PubMed1999

Bone mineral density of the proximal femur after unilateral cementless total hip replacement.

It was the aim of this study to examine bone mineral density changes in the non-operated contralateral femur of patients undergoing total hip replacement. Bone density in the contralateral femur of 45 patients with an average age of 54 years was measured with the aid of the DEXA technique at one week, 3 and 6 months after total hip replacement. Within the first 3 months there was an average reduction of bone density of 3.9% (3.0%-5.9%). After a further 3 months the average difference was 2.5%.

Absorptiometry, Photon↗
PubMed1999

A PC program for estimating organ dose and effective dose values in computed tomography.

Dose values in CT are specified by the manufacturers for all CT systems and operating conditions in phantoms. It is not trivial, however, to derive dose values in patients from this information. Therefore, we have developed a PC-based program which calculates organ dose and effective dose values for arbitrary scan parameters and anatomical ranges. Values for primary radiation are derived from measurements or manufacturer specifications; values for scattered radiation are derived from Monte Carlo calculations tabulated for standard anthropomorphic phantoms. Based on these values, organ doses can be computed by the program for arbitrary scan protocols in conventional and in spiral CT. Effective dose values are also provided, both with ICRP 26 and ICRP 60 tissue-weighting coefficients. Results for several standard CT protocols are presented in tabular form in this paper. In addition, potential for dose reduction is demonstrated, for example, in spiral CT and in quantitative CT. Providing realistic patient dose estimates for arbitrary CT protocols is relevant both for the physician and the patient, and it is particularly useful for educational and training purposes. The program, called WinDose, is now in use at the Erlangen University hospitals (Germany) as an information tool for radiologists and patients. Further extensions are planned.

Dose-Response Relationship, Radiation↗
PubMed1999

Sacrococcygeal teratoma: clinical course and prognosis with a special view to long-term functional results.

From 1976 to 1995, 23 children, 4 boys and 19 girls, were treated at our department for sacrococcygeal teratomas (SCT). Their records were analyzed retrospectively, considering age at operation, histopathology, recurrences, and long-term evolution. One died on the 1st day of life following tumor rupture with hemorrhagic shock without surgical intervention. All others were operated upon at a mean age of 4.2 days for those 19 (= 82%) who were diagnosed in the neonatal period and whose histology proved benign. In the remaining 3 children, in whom tumor manifestation did not occur before 11 months, 13 months, and 10 years of age, respectively, histopathologic evaluation revealed 2 carcinomas and 1 yolk-sac tumor, and all 3 recurred. Overall, 5 patients died, the 1 mentioned above, 1 due to volvulus after laparotomy, and 1 from multiple associated congenital malformations. Two deaths were related to malignancy, whereby only 1 was a malignant teratoma diagnosed at the original operation. Eight children had recurrences, 2 were benign and 6 malignant, with 3 of the latter having been graded benign on histology of the primary tumor. Of the 18 surviving patients, 17 (93.5%) returned for clinical review following a standardized protocol. The average interval from the primary surgery was 12.3 years (range 3.5-22 years). Four had malignant tumors with a recurrence-free period of from 9 to 14 years; 5 (29.4%) had urinary or anorectal functional impairment. One child with a patulous anus presented with fecal soiling. Two reported nocturnal enuresis, 1 associated with perineal anesthesia. One had a neurogenic bladder with overflow voiding and bilateral third-degree vesicoureteral reflux. Second-degree reflux was found in the last patient. We conclude that follow-up after surgery for SCT should not only search for tumor recurrence but include the diagnosis and treatment of possible secondary urinary and/or fecal incontinence.

Fecal Incontinence↗
PubMed1999

Temporary tracheobronchial stenting in malignant lymphoma.

BACKGROUND: Temporary stenting is a new strategy in the treatment of malignant airway stenoses. Patients receive stents as primary palliation followed by tumor-specific therapy in order to reduce the stenosis and subsequently remove the stent. METHODS: We investigated this strategy of temporary airway stenting in 5 consecutive patients with malignant lymphoma (Non-Hodgkin's lymphoma, n = 3; Hodgkin's lymphoma, n = 2) who presented with severe dyspnoea. Nine stents (six Strecker, three Dumon stents) were implanted into the trachea or main bronchi. After stenting, patients underwent tumor-specific therapy (chemotherapy, n = 4; percutaneous radiotherapy, n = 1). RESULTS: Clinical improvement of dyspnoea and stridor was observed in each patient after stent implantation. In 4 patients (80%), stents could easily be removed after successful tumor-specific therapy, which led to reduction of stenosis after a mean interval of 26 days (14 to 52 days). One patient died during chemotherapy 6 days after stenting. CONCLUSIONS: The results show that temporary stenting is a valuable strategy in chemo- and radiosensitive malignancies, as it ameliorates the patients' respiratory condition until tumor-specific therapy is effective, and prevents poststenotic complications. It integrates stent implantation in a multi-therapy concept.

Adolescent↗
PubMed1999

Do sick newborn infants benefit from participation in a randomized clinical trial?

BACKGROUND: Adult participants in randomized controlled trials often have better outcomes than patients who are eligible but not enrolled. OBJECTIVE: To examine whether newborn infants who were allocated to placebo in an investigational drug trial had better outcomes than infants who were eligible but not randomized (eligible NR). STUDY DESIGN: During a randomized controlled trial of antithrombin therapy in premature infants with respiratory distress syndrome, data were collected prospectively on all 76 infants in the eligible NR group. Study outcomes were compared with those of all 61 infants who were randomized to placebo. The same exogenous surfactant was used in all patients. RESULTS: In the placebo group the mean (SD) birth weight was 1201 (314) g, mean (SD) gestational age was 28.8 (2.3) weeks, and 51% were male. In infants in the eligible NR group, mean (SD) birth weight was 1141 (262) g, mean (SD) gestational age was 28.3 (2. 3) weeks, and 58% were male; 57% of infants in both groups had been exposed to steroids before birth. The median duration of mechanical ventilation was reduced from 6.2 days in the eligible NR group to 4. 8 days in the placebo group (P =.008). There was also a trend toward less frequent and less severe intraventricular hemorrhage in trial participants. CONCLUSIONS: These data are consistent with the hypothesis that sick newborn infants may benefit from participation in a randomized controlled trial.

Antithrombins↗
PubMed1999

Placement of endosseous implants in children and adolescents with hereditary ectodermal dysplasia.

OBJECTIVE: The purposes of this investigation were to study the feasibility of placing endosseous implants in children and adolescents with ectodermal dysplasia and to assess the position and stability of such implants during growth. This article reports on 6 subjects with long-term follow-up. Study design. A prospective study was commenced in 1991. Patients with hereditary ectodermal dysplasia who were over the age of 5 years and who presented to the University of California San Francisco Ectodermal Dysplasia Clinic for dental treatment were included and maintained in the study. In each case, clinical and radiographic records were obtained before treatment, immediately after implant placement, at delivery of the prosthesis, and subsequently at yearly intervals. Six subjects are reported, 4 as members of the prospective study group and 2 who had been treated before the study began. RESULTS: A total of 41 implants (19 maxillary, 22 mandibular) were placed. The average follow-up after implant placement was 7.8 years (range, 6-11 years), and the average time since restoration was 6 years (range, 5-10 years). Forty implants successfully integrated and have been restored. There was no evidence that implant placement or prosthetic rehabilitation resulted in restriction of transverse or sagittal growth. One mandibular implant, placed in a partially dentate 5-year-old, became submerged because of adjacent alveolar development and required placement of a longer abutment. Four maxillary implants placed in a partially dentate 7-year-old also became submerged and required prosthetic revision and the placement of longer abutments. CONCLUSIONS: This preliminary report suggests that endosseous implants can be successfully placed and can provide support for prosthetic restoration in patients with hereditary ectodermal dysplasia. However, vertical dentoalveolar growth results in submergence of the implant relative to the adjacent natural dentition when implants are placed adjacent to erupting permanent teeth.

Adolescent↗
PubMed1999

Rapid, phenotypic HIV-1 drug sensitivity assay for protease and reverse transcriptase inhibitors.

BACKGROUND: Development of drug resistance is one of the major reasons for the failure of antiretroviral therapy of HIV-1 infection. Knowing the drug sensitivity-resistance profile of viruses present in a patient prior to treatment or change in treatment could help to optimize therapy. OBJECTIVE: Development of a rapid standardized phenotypic HIV-1 drug sensitivity assay for protease (PR) and reverse transcriptase (RT) inhibitors. DESIGN: The PR gene (codons 1-99) and the 5' part of the RT gene (codons 1-300) of HIV-1 is amplified from the plasma of infected individuals by RT-PCR and ligated into a proviral clone of HIV-1 containing a deletion of the PR gene and the 5' part of the RT gene. Bacteria are transformed with the ligation product and plasmid DNA is prepared from a library of transformed bacteria. The plasmid DNA is transfected into 293 T cells and recombinant virus is harvested from the supernatant of the transfected cells 2 days after transfection. The sensitivity of the recombinant virus is determined with the help of a sensitive indicator cell line. RESULTS: Recombinant viruses were generated with high efficiency. Determination of the drug sensitivity of the recombinant viruses with an indicator cell line was highly reproducible. The recombinant viruses accurately reflected the sensitivity-resistance profile of the parental viruses. The phenotypic drug sensitivity determined by this assay correlated well with the treatment history of patients. CONCLUSION: This assay system should allow rapid, high-throughput analyses of phenotypic HIV-1 drug sensitivity for PR and RT inhibitors. Due to the efficient generation of recombinant viruses, propagation of the recombinant viruses in cell culture is not required prior to the determination of the sensitivity of the recombinant viruses. The risk of selecting fitter non-resistant viruses due to culture conditions is minimized.

Anti-HIV Agents↗
PubMed1999

Platelet-leukocyte aggregates during hemodialysis: effect of membrane type.

Hemodialysis is associated with the formation of platelet-leukocyte aggregates. Whether this phenomenon is hemodialysis (HD) membrane dependent is unclear. To evaluate this process, we examined respectively platelet activation (anti-CD41, anti-CD62, and antifibrinogen monoclonal antibodies [MoAb] binding), leukocyte activation (CD11b expression), and the appearance of platelet specific antigens on leukocytes as an index of platelet-leukocyte aggregation during HD using 3 different membrane materials, Cuprophan, Hemophan, and polysulfone. Flow cytometric techniques and specific MoAb were used. All parameters were assayed 5 min after initiation of HD to avoid the confounding variable of leukopenia and resultant cell subpopulation analysis. Platelet activation (anti-CD62 and antifibrinogen binding) occurred only with Cuprophan. All 3 membranes induced equivalent increases in CD11b expression on neutrophils and similarly increased the binding of anti-CD41 to neutrophils, reflecting an increment in the formation of platelet neutrophil aggregates. However, only Cuprophan induced an increase in anti-CD62 binding to neutrophils, suggesting that the aggregated platelets linked to neutrophils were activated. Increased anti-CD41 binding by monocytes was similarly observed with all 3 membranes. However, only polysulfone induced an increase in CD11b expression and fibrinogen binding to monocytes. We conclude that while the formation of platelet leukocyte aggregates appears to be a universal phenomenon in HD occurring with a variety of membrane types, subtypes of this phenomenon consisting of activated platelets and fibrinogen binding may be membrane dependent. This phenomenon may serve as a new biocompatibility parameter and may shed light on some of the biologic consequences of hemodialysis.

Antibodies, Monoclonal↗
PubMed1999

Cerebral vasodilatation causing acute intracranial hypertension: a method for noninvasive assessment.

Deep spontaneous vasodilatatory events are frequently recorded in various cerebral diseases, causing dramatic increases (A-waves) in intracranial pressure (ICP) and subsequently provoking ischemic brain insults. The relationship between fluctuations in CBF, ICP, and arterial blood pressure (ABP) is influenced by properties of cerebrovascular control mechanisms and the cerebrospinal pressure-volume compensation. The goal of this study was to construct a mathematical model of this relationship and to assess its ability to predict the occurrence and time course of A-waves. A group of 17 severely head-injured patients were included in the study. In our model ICP was derived from the ABP waveform using a linear signal transformation. The transformation was modified during the simulation by a relationship between ABP and flow velocity, i.e., by the characterization of the cerebrovascular bed. In this way the ICP could be calculated from the ABP waveform. This model was verified by comparison of simulated and directly measured ICP during A-waves recorded in seven of the patients. In all simulations, plateau elevations of ICP were well replicated. The mean absolute error between real and simulated ICP was 8.3 +/- 5.4 mm Hg at the baseline and 7.9 +/- 4.3 mm Hg at the top of plateau waves. The correlation coefficient between real and simulated increase in ICP was R = 0.98; P < .001. Similarly, correlation between real and simulated increase in pulse amplitude of ICP was highly significant (R = 0.94; P < .001). The mathematical model of the relationship between ABP, flow velocity, and ICP is of potential clinical use for the noninvasive detection of A-waves in patients in whom invasive ICP assessment is not conducted.

Adolescent↗
PubMed1999

Experimental determination of the thermal neutron flux around two different types of high intensity 252Cf sources.

The application of neutron emitting radioisotopes in brachytherapy facilitates the use of the higher biological effectiveness of neutrons compared to photons in treating some cancers. Different types of high intensity 252Cf sources are in use for the treatment of different cancers. To improve the therapy of bulky tumors the dose can be augmented by the additional use of the boron capture reaction of thermal neutrons. This requires information about the thermal neutron dose component around the Cf source. In this work, a Mg/Ar-ionization chamber internally coated with 10B was used to measure the thermal neutrons. These measurements were performed on two different 252Cf sources, one in use in the Gershenson Radiation Oncology Center at Harper Hospital in Detroit, MI, and one at the University Hospital of Chiang Mai in Chiang Mai, Thailand. The results of these measurements are compared and indicate that the differences in the construction of the sources influence the thermal dose component.

Argon↗
PubMed1999

Psychosocial care by general practitioners--where are the problems? Results of a demonstration project on quality management in psychosocial primary care.

OBJECTIVE: Since 1987, psychosocial services have been a part of the primary care setting in Germany. In the framework of an eight-center national demonstration program, problems in the diagnosis and therapy of psychosocial problems and psychosomatic disorders were assessed. Methods to improve quality were also implemented. METHOD: General practitioners (n = 191) from six regions participated in the study. One thousand three hundred and forty-one treatment episodes of patients with predominantly psychosocial symptoms were documented. Differences between psychosocial strain, treatment, and outcome were determined by analyses of variance. RESULTS: Anxiety (62%), depression (51%), and marital/family conflicts (44%) were the most frequent symptoms. Psychosocial treatment was offered more often to those patients who had the highest level of anxiety and depression. Patients with pain and without a psychological attribution to their illnesses were offered less psychosocial treatment and suffered worse results. Partners and family members were rarely integrated into therapy. The procedures employed to improve outcome were quality circles, family-oriented case conferences, consultation services, and collaborative groups. CONCLUSIONS: These initial results are promising. A process of internal quality management has been initiated. Some of the physicians still resist documenting the data. Patients with somatic symptoms without psychological attribution may need special psychosocial interventions to improve their outcomes.

Adolescent↗
PubMed1999

[Secondary prevention: an approach to improve the German drug abuse prevention system].

Drug prevention in Germany traditionally focuses on primary prevention programmes for children without any drug experience. Only a few programmes have been specifically developed for drug-taking youth, although especially children and adolescents at high risk for drug problems need intervention services which provide helpful support to reduce drug misuse. Empirical studies in two German cities show that prevention services are not available for the high-risk population of drug-taking youth. On an international level several projects are testing out new approaches for drug use prevention for at-risk youth. The primary goal of such secondary prevention programmes is to reduce the incidence and prevalence of drug use and abuse through early detection and intervention strategies. These programmes aim at preventing adolescents who are experimenting with drugs from progressing to misuse or addiction. Testing new prevention strategies to support drug-taking youth in Germany is likely to produce a valuable contribution to our knowledge of effective drug prevention.

Adolescent↗
PubMed1999

[Subjective assessment of self health and subjective morbidity in Germany. Results of a representative demographic survey].

This study presents selected results from the poll of a representative cross-section of the German population during the Spring of 1996 was subjective data on health and illness investigated, inter alia. The majority of the questioned subjects stated good health with low impairment of their general condition by their general conditions by their health. Compared with data from 1975, people have the impression that their health is in a better state, but, on the other hand, more significantly inparied by their health. East Germans claim a somewhat lower state of health and more impairment than West Germans; the same results were found for women in comparison with men and elderly persons compared with younger subjects. There is no difference between East and West Germans with respect the frequency of disease, but there were more illnesses with a clear morphological correlation reported by East-Germans. West Germans report more functional infirmities or troubles. One of the most striking results was the high frequency of cardiovascular disorders in East Germany. The influence of social support and social status on the subjective assessment of one's own health and subjective morbidity is of only low importance.

Adolescent↗
PubMed1999

[Sex-specific drug abuse prevention in adolescence].

Several studies are discovering differences in how boys and girls use tobacco, alcohol, and other drugs. In general, boys and girls differ in the intensity and the quality of drug use. Male adolescents report higher usage of drugs than female adolescents do (exception: medication). However, there are only few prevention programmes with integrated sex-specific strategies. The few existing girl-specific and boy-specific prevention programmes focus on strain and deficits. Drug consumption is considered a result of inadequate socialisation and development of boys and girls. New preventive strategies are therefore based on interactional and functional concepts. In this perspective health-related behaviour can be regarded in respect of its differential functionality for girls and boys. Drug use is considered to be a sex-specific attempt to express femininity or masculinity. Sex-specific drug prevention develops different strategies for same-sex and opposite-sex groups in order to meet varying needs and to take the differential functionality of drug consumption into account.

Adolescent↗
PubMed1998

Residues critical for formylglycine formation and/or catalytic activity of arylsulfatase A.

Sulfatases contain a unique posttranslational modification in their active site, a formylglycine residue generated from a cysteine or a serine residue. The formylglycine residue is part of a sequence that is highly conserved among sulfatases, suggesting that it might direct the generation of this unique amino acid derivative. In the present study residues 68-86 flanking formylglycine 69 in arylsulfatase A were subjected to an alanine/glycine scanning mutagenesis. The mutants were analyzed for the conversion of cysteine 69 to formylglycine and their kinetic properties. Only cysteine 69 turned out to be essential for formation of the formylglycine residue, while substitution of leucine 68, proline 71, and alanine 74 within the heptapeptide LCTPSRA reduced the formylglycine formation to about 30-50%. Several residues that are part of or directly adjacent to an alpha-helix presenting the formylglycine 69 at the bottom of the active site pocket were found to be critical for catalysis. A surprising outcome of this study was that a number of residues fully or highly conserved between all known eukaryotic and prokaryotic sulfatases turned out to be essential neither for generation of formylglycine nor for catalysis.

Alanine↗
PubMed1998

Posttranslational formation of formylglycine in prokaryotic sulfatases by modification of either cysteine or serine.

Eukaryotic sulfatases carry an alpha-formylglycine residue that is essential for activity and is located within the catalytic site. This formylglycine is generated by posttranslational modification of a conserved cysteine residue. The arylsulfatase gene of Pseudomonas aeruginosa also encodes a cysteine at the critical position. This protein could be expressed in active form in a sulfatase-deficient strain of P. aeruginosa, thereby restoring growth on aromatic sulfates as sole sulfur source, and in Escherichia coli. Analysis of the mature protein expressed in E. coli revealed the presence of formylglycine at the expected position, showing that the cysteine is also converted to formylglycine in a prokaryotic sulfatase. Substituting the relevant cysteine by a serine codon in the P. aeruginosa gene led to expression of inactive sulfatase protein, lacking the formylglycine. The machinery catalyzing the modification of the Pseudomonas sulfatase in E. coli therefore resembles the eukaryotic machinery, accepting cysteine but not serine as a modification substrate. By contrast, in the arylsulfatase of Klebsiella pneumoniae a formylglycine is found generated by modification of a serine residue. The expression of both the Klebsiella and the Pseudomonas sulfatases as active enzymes in E. coli suggests that two modification systems are present, or that a common modification system is modulated by a cofactor.

Alanine↗