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Biomedical subjects

R Schmidt

Publications and source records attributed to R Schmidt.

At least 973 records · Page 54Linked to original sources
PubMedDate not supplied

Toxicological investigations in the semiconductor industry: IV. Studies on the subchronic oral toxicity and genotoxicity of vacuum pump oils contaminated by waste products from aluminum plasma etching processes.

Dry etching processes in semiconductor manufacturing use ionized gases in closed reactors at pressures below 1 torr. Vacuum pump systems that service the reaction chambers are potential sources of exposure to complex mixtures of inorganic and organic compounds. These mixtures consist of unused process gases and process by-products that condense and accumulate in the vacuum pump oils. To evaluate potential hazards of dry etch vacuum equipment, a contaminated vacuum pump oil sample from a BCl3/Cl2 etching process was analyzed. The waste oil was administered by gavage for 14 or 28 days to male and female Wistar rats. Neither death nor behavioral changes occurred after subchronic treatment or during a 14-day posttreatment period. Only slight effects on body weights, clinical chemistry, and hematology data were seen in the exposed animals, although the livers of all waste oil-exposed rats of both sexes showed remarkable hypertrophic degenerations. Genotoxicological investigations were performed through the Ames assay (Salmonella assay) and the Micronucleus assay. The contaminated oil sample caused clear genotoxic effects in both test systems.

Administration, Oral↗
PubMedDate not supplied

[Primary stability of 2 acetabulum roof cups and an acetabulum reinforcement cup. Effect of osseous defects].

The aim of this experimental study was to analyse the effects of implant design and bone stock defects on the primary stability of three different acetabular components. Fresh frozen human pelves were employed for the investigation. Müller and Ganz rings and a Burch-Schneider cage (Protek, Münsingen, Switzerland) were fixed with screws in 6 normal acetabula using standard techniques, and in 30 acetabula previously prepared with 5 different segmental bone stock defects. A servohydraulic testing machine (Instron, Canton, USA) was used for the investigation. Three electromagnetic displacement transducers (Micro-Epsilon, Ortenburg, Germany) were placed in the three main quadrants of the acetabular rim to detect implant micromotion, which reflects stability. Displacement was recorded during 20 consecutive cycles under loads of up to 2354 N. All implants were stable (< 150 microns) in all quadrants of normal acetabula and also in those with ectatic, protrusive and ventral defects. There was no statistically significant difference in the results between Müller and Ganz rings. Displacement of more than 150 microns was observed in acetabula with cranial or dorsal defects. The cage was stable under all defect conditions. The reinforcement implants showed low displacement rates in most of the acetabular bony defects. Stability is a function of the area of surface contact between prosthesis and bone.

Acetabulum↗
PubMedDate not supplied

Subtleties of structure-agonist versus antagonist relationships of opioid peptides and peptidomimetics.

The development of novel delta opioid antagonists and delta opioid agonists structurally derived from the prototype delta antagonist TIPP (H-Tyr-Tic-Phe-Phe-OH), is reviewed. Both delta antagonists and delta agonists with extraordinary potency and unprecedented delta receptor selectivity were discovered. Some of them are already widely used as pharmacological tools and are also of interest as potential therapeutic agents for use in analgesia. The results of the performed structure-activity studies revealed that the delta antagonist versus delta agonist behavior of this class of compounds depended on very subtle structural differences in diverse locations of the molecule. These observations can be best explained with a receptor model involving a number of different inactive and active receptor conformations.

Animals↗
PubMedDate not supplied

Multiparametric time course prognoses by means of case-based reasoning and abstractions of data and time.

In this paper we describe an approach to utilize Case-Based Reasoning methods for trend prognoses for medical problems. Since using conventional methods for reasoning over time does not fit for course predictions without medical knowledge of typical course pattern, we have developed abstraction methods suitable for integration into our Case-Based Reasoning system ICONS. These methods combine medical experience with prognoses of multiparametric courses. We have chosen the monitoring of the kidney function in an Intensive Care Unit (ICU) setting as an example for diagnostic problems. On the ICU, the monitoring system NIMON provides a daily report based on current measured and calculated kidney function parameters. We abstract these parameters to a daily kidney function state. Subsequently, we use these states to generate course-characteristic trend descriptions of the renal function over the course of time. Using Case-Based Reasoning retrieval methods, we search in the case base for courses similar to the current trend descriptions. Finally, we present the current course together with similar courses as comparisons and as possible prognoses to the user.

Artificial Intelligence↗
PubMedDate not supplied

Clinical outcome and quantitative evaluation of periprosthetic bone-remodeling of an uncemented femoral component with taper design. A prospective study.

The rationale of uncemented taper stems is based on fixation in the proximal portion of the femoral diaphysis, a self-locking principle, and a low modulus of elasticity. The aim of this study was to evaluate a collarless femoral component designed to be a three-dimensional taper for press-fit insertion with regard to clinical outcome, efficacy of fixation, incidence of osteolysis, and periprosthetic bone-remodeling. The first 48 consecutive patients (50 hips) with osteoarthritis who had had primary total hip arthroplasty using the Cerafit Multicone stem and the Cerafit Triradius-M press-fit cup with alumina-alumina pairing (Ceraver Osteal, Paris, France) were followed-up for a mean of 2.3 years (2 to 2.5 years). The mean age of patients at index operations was 52.5 years. Current criteria were used for clinical and radiological assessment. Quantitative evaluation of periprosthetic bone-remodeling was prospectively assessed using computed tomography. Clinical and radiological follow-up was obtained in all hips. Forty-nine hips (98%) were clinically rated good or excellent, one hip (2%) was rated fair, owing to a persisting limp. The mean preoperative Harris Hip Score was rated 62, and it has improved to 93.5 at the time of follow-up. One hip (2%) had marked postoperative thigh pain. This pain had disappeared at 3-month follow-up. All stems showed radiological signs of stable fixation by bone ingrowth. No stem required revision. Thirty-four hips (68%) had either no change in femoral bone density or only patchy loss of bone density isolated to Gruen zones 1 and 7. Sixteen hips (32%) had some reduction of bone density isolated to zone 1. Radiolucencies without progression were found in zones 1 and 7 in 3 hips (6%), and in zone 1 alone in 3 other hips (6%). A slight cortical hypertrophy was seen in 3 hips (6%). Twenty-three hips (46%) developed radiographic appearance of bone apposition at the stem tip as partial pedestal (19 hips) and as complete pedestal (4 hips). No signs of cup loosening were detected at follow-up. Twenty-four patients (25 hips) were eligible for computed tomography. The mean decrease of the overall bone mineral density in the metaphyseal portion of the femur one year after insertion of the stem was rated 15.4%, and the mean decrease of the cortical bone mineral density was rated 17.2%. On the other hand, a mean decrease of the cortical bone mineral density of less than 5% was observed in the diaphyseal portion of the femur around the implant. The clinical and radiological results of the Cerafit Multicone stem at a mean follow-up of 2.3 years are very promising and do not contrast with those achieved using other uncemented stems with tapered design. Furthermore, results of quantitative evaluation of periprosthetic bone-remodeling were considered satisfactory favourably with others reported in the literature using stems inserted without cemented.

Adult↗
PubMedDate not supplied

[Surgical treatment of lung cancer: therapy or palliative?].

In spite of the revolutionary innovations concerning diagnostic and intensive care techniques as well as better understanding of tumor biology during the last decade, rates of resection and long-term survival in bronchogenic carcinoma could not be improved. All efforts are to be done in investigation on practicable, suitable, and supportable screening programs for early recognition of tumors in the first stages.

Carcinoma, Non-Small-Cell Lung↗
PubMedDate not supplied

The morphologic correlate of incidental punctate white matter hyperintensities on MR images.

Postmortem examinations were made of the brains of six patients, 52-63 years old, who exhibited incidental punctate white matter hyperintensities on MR images before death. Our aim was to unravel the morphologic correlate of such lesions. By repeating the MR study after fixation on four specimens, cutting the brain parallel to the MR imaging plane, and examining whole-hemisphere microscopic sections, we optimized lesion identification. The white matter signal abnormalities were better delineated on pre- than postmortem scans, and visual inspection of the brain slices was normal in all but one location. Histologically, we found areas of reduced myelination with atrophy of the neuropil around fibrohyalinotic arteries as well as different stages of perivenous damage. The latter ranged from spongiform transformation of the neuropil and scattered foci of demyelination to large perivenous areas with marked rarefaction of myelinated fibers. Edematous glial swelling in foci of ganglion cell heterotopia caused subcortical white matter hyperintensities in one case. Our results suggest minor perivascular damage but not infarction as the most likely substrate of punctate MR white matter hyperintensities in elderly brains. Histologic correlations with MR images obtained during life or with studies of unfixed material are necessary to analyze such small lesions.

Brain↗
PubMedDate not supplied

[Effect of co-medication with magnesium sulfate in beta-mimetic tocolysis on parameters of water-electrolyte balance].

With 2 groups of 10 patients the influence of an additional therapy with 1 g magnesium sulfate/h during i.v. tocolysis with the betamimetic fenoterol (2 micrograms/min) upon parameters of water and electrolyte balance has been investigated. The whole of the magnesium administered during the 24 hours investigational period has been eliminated via the kidneys. Most probably due to a competition within the distal tubulus hypermagnesemia was associated with hypocalcemia and hypercalciuria, followed by a rise in parathyroid hormone. As PTH is able to compensate hypocalcemia not only by means of bone mobilisation but also by an increase in enteral Ca absorption, estimated losses of calcium are minimal. These may be neglected, as additional therapy with magnesium sulfate--besides the advantages yet known (cardioprotection, saving of betamimetic dosage, reduction of drug tolerance development)--reduces betamimetic induced water retention, thus significantly diminishing lung edema hazard during tocolytic therapy.

Adult↗
PubMedDate not supplied

Bilateral giant cyst of the shoulder.

The case of a 61 year old white female with a rapidly progressive rheumatoid arthritis who developed bilateral giant cyst of the shoulder is described here. Arthrographic investigation indicated that these giant cysts were true synovial cysts rather than "pseudocysts".

Arthritis, Rheumatoid↗
PubMedDate not supplied

Clinical results with fast neutrons (DT, 14 MeV).

In Hamburg, the therapy with DT-neutrons had the best curative effect on highly differentiated tumors. With the standard dose of 15.6 Gy in four weeks with fast neutrons only or--in treating tumors in radiosensitive organs such as brain and intestine--with a photon-neutron schedule, we have seen no necroses in normal tissues. The rate of medium or slight subcutaneous fibroses has been no more than 10%. The local effect on tumors in our pilot study has been better than with megavoltage therapy in invasive thyroid cancer, prostate cancer stage C, soft tissue sarcoma, and rectal carcinoma. The best results have been achieved with neutrons only, but a photon-neutron schedule may be more effective as megavoltage therapy only. With our DT-neutrons we find some indications for better results than with megavoltage therapy if we use sophisticated treatment planning and if we strictly observe the tolerance dose of the different tissues and organs. The therapeutic index of our DT-neutrons is higher than with cyclotron-produced neutrons.

Fast Neutrons↗
PubMedDate not supplied

[Group specific improvements in activities of daily living in elderly stroke patients in the rehabilitation phase. A report from the study, "Rehabilitation in geriatrics--analysis and evaluation of rehabilitation procedures in over-60 stroke patients with reference to its epidemiologic aspects")].

Significant as well as non-significant but still distinct improvements in the average functional status of Activities of Daily Living (ADL), according to the Barthel Index and Rüstigkeitsskala as shown by the total patient group of two rehabilitation clinics are presented. The initial status and the time elapsed between stroke and rehabilitation are of great importance for the changes which can be attained. Patient groups which differ in factors such as age, sex, and family status also show clear differences in the average improvement of their functional status.

Activities of Daily Living↗
PubMedDate not supplied

["Released" employees of the 6th decade--a new retirement generation. Report on central results of a meeting of experts on the topic].

More and more workers and employees leave their working places and renumerated employment for good from the age of 50 onwards - by way of acknowledged incapacity to continue work due to health reasons, unemployment, forced retirement after production plants have closed down and early retirement schemes. How retirement is experienced very much depends on the living conditions encountered and on the process of transition to retirement. Acceptancy of premature retirement is of central importance - as are the opportunities of influencing by one's own decisions the age of retirement, the predictability of this event and the chances of transition through a phase of gradual re-orientation. Differentiation between those with good and very good income levels and those with only minimal financial means is imperative. Negative outcomes of the latter situation may be a feeling of total hopelessness, frictions within the family, reduction of social contacts and of out-of-door activities--a tendency to hide away in shame. To be labelled as old in too early a phase in life is not acceptable. The social status attained tends to be unclearly defined with accompanying negative effects on the self-concept as well as on the image held by others.

Aged↗
PubMedDate not supplied

Tick-borne meningopolyneuritis (Garin-Bujadoux, Bannwarth).

We studied 100 patients with tick-borne meningopolyneuritis (Garin-Bujadoux, Bannwarth), the neurologic component of European erythema chronicum migrans disease. They had intensive radicular pain, asymmetric polyneuritis combined often with uni- or bilateral facial palsy, lymphocytic meningitis without or with only slight meningismus, and a course lasting three to five months. Neurologic abnormalities were preceded by the bite of a tick or an insect in 37 percent of patients or by an erythema in 41 percent. In addition, many patients had extraneural involvement, such as fever or fatigue. The outcome was favorable in all cases, and occurred faster with antibiotic treatment, but a few patients had slight residual peripheral nervous system deficits.

Adolescent↗
PubMedDate not supplied

Effects of 13-CIS retinoids on premalignant and malignant cells of lung origin.

Deficiency of vitamin A has been shown to cause squamous metaplasia of the epithelium of the tracheobronchial tree. Vitamin A analogues, such as retinoid acid, have been shown to be effective in the treatment of various skin disorders in humans; these compounds have also caused a reduction in the incidence of carcinogen-induced tumors in experimental animals. For these reasons, a clinical trial with orally administered 13-CIS retinoic acid was conducted in 26 patients with varying degrees of cytologic abnormalities in sputum, ranging from moderately atypical metaplasia to overt carcinoma. The drug was administered in daily doses from 1 to 2.5 mg/kg or until toxicity was observed. The cytologic effects of the drug were monitored in sputum. The treatment did not affect the quantitative aspects of sputum cytology. However, degenerative alterations were observed in many of the abnormal cells. Although the experience with 13-CIS retinoic acid reported in this paper is too small for statistical analysis, the cytotoxic effects observed are sufficiently intriguing to suggest further studies in humans and experimental animals.

Adult↗