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Biomedical subjects

D Richter

Publications and source records attributed to D Richter.

At least 109 records · Page 6Linked to original sources
PubMed1999

Brillouin and Umklapp scattering in polybutadiene: comparison of neutron and x-ray scattering.

We report a comparison of high resolution inelastic x-ray Brillouin scattering to coherent inelastic neutron scattering for amorphous deuterated polybutadiene, done for one temperature in the glass phase and another one in the melt. The x-ray scattering proves to be by far the better technique for such a polymer within its present resolution bounds. The neutron scattering allows one to extend these measurements to a much better resolution, showing an additional quasielastic signal in the melt. The results suggest x-ray measurements at higher momentum transfer, to see whether they are complementary to neutrons.

Journal Article↗
PubMed1999

Characteristics of garden dormice that contribute to their capacity as reservoirs for lyme disease spirochetes.

To describe the contribution of garden dormice to the epizootiology of Lyme disease, we compared their reservoir capacity for these pathogens to that of other sympatric hosts. Garden dormice are trapped most abundantly during early spring and again during midsummer, when their offspring forage. They are closely associated with moist forests. Garden dormice serve as hosts to nymphal ticks far more frequently than do other small mammals. Spirochetal infection is most prevalent in dormice, and many more larval ticks acquire infection in the course of feeding on these than on other rodents in the study site. Mature dormice appear to contribute more infections to the vector population than juveniles do. Replete larval ticks generally detach while their dormouse hosts remain within their nests. The population of garden dormice contributes five- to sevenfold more infections to the vector population than the mouse population does. Their competence, nymphal feeding density, and preference for a tick-permissive habitat combine to favor garden dormice over other putative reservoir hosts of Lyme disease spirochetes.

Animals↗
PubMed1999

[How significant is the comparison for length of stay in psychiatric hospitals based on diagnosis and age?].

AIM OF THE STUDY: According to German Hospital Financing Regulations hospital comparisons are undertaken to serve as information basis to providers and purchasers concerning budget findings. The current purchasers' hospital comparison includes diagnosis and patients' age to compare costs between hospitals. This study aims at evaluating diagnosis, age and additional variables as predictors of length of stay for psychiatric inpatient treatment. METHODS: Data of one year's admissions of a German state psychiatric hospital (N = 2450) were evaluated by a linear regression analysis. RESULTS: The purchasers' model of diagnosis and age accounts for 10.5% of the variation of length of stay. A second model with additional sociodemographic and clinical variables accounts only for 11.3% of the variation. CONCLUSIONS: Results of this study are confirmed by several international studies on length of stay in psychiatric hospitals. It is concluded that diagnosis and age do not account sufficiently for the variation of length of stay in psychiatry. Meaningful hospital comparisons should include disease specific clinical, biographical and sociodemographic measures.

Age Factors↗
PubMed1999

[Minimally invasive therapeutic concepts in fracture surgery].

Recent publications show a clear tendency towards minimally invasive procedures for fracture care in trauma patients. Intramedullary stabilization has become the first choice in reconstructing axis and length of the diaphyseal fractures of the long bones. Indications for intramedullary nailing have become wider with the development of unreamed or retrograde nailing. Essential modifications of plate osteosynthesis from limited contact implants to percutaneous plating and the development of an internal fixator have made this procedure minimally-invasive as well. Techniques of closed reduction and percutaneous osteosynthesis or arthroscopically-assisted procedures have become more important in the stabilization of metaphyseal fractures. Although long term results of some of the mentioned procedures are unknown by now, minimally-invasive techniques appear to have positive influence on functional outcome in most patients. However problems of intraoperative control of axis and rotation in long-bone fractures as well as the surgeon's high exposure to radiation remain unsolved problems in minimally-invasive traumatology.

Bone Nails↗
PubMed1999

Effects of ischemia on QT dispersion during spontaneous anginal episodes.

Myocardial ischemia induced by pacing, angioplasty, or stress results in a significant increase in QT dispersion (QTd = QT maximum - QT minimum). This study investigated the effects of ischemia on QTd and the rate-corrected QTd (QT(c)d) during spontaneous anginal episodes in patients with coronary artery disease (CAD). Ninety-five patients with CAD and typical angina pectoris and 15 control subjects complaining of anginalike symptoms were studied. QTd and QT(c)d were calculated from 12-lead surface electrocardiograms recorded during and after the relief of pain. QTd and QT(c)d were significantly higher during the anginal episode (84+/-31 ms and 98+/-51 ms) compared to the painless conditions (69+/-24 ms and 71+/-24 ms) (P = .003 and P = .001 for QTd and QT(c)d, respectively) only in the 57 CAD patients who had a history of an old previous myocardial infarction. QTd and QT(c)d are significantly increased during spontaneous angina in patients with documented CAD and history of previous myocardial infarction.

Angina Pectoris↗
PubMed1998

The lymnaea cardioexcitatory peptide (LyCEP) receptor: a G-protein-coupled receptor for a novel member of the RFamide neuropeptide family.

A novel G-protein-coupled receptor (GRL106) resembling neuropeptide Y and tachykinin receptors was cloned from the mollusc Lymnaea stagnalis. Application of a peptide extract from the Lymnaea brain to Xenopus oocytes expressing GRL106 activated a calcium-dependent chloride channel. Using this response as a bioassay, we purified the ligand for GRL106, Lymnaea cardioexcitatory peptide (LyCEP), an RFamide-type decapeptide (TPHWRPQGRF-NH2) displaying significant similarity to the Achatina cardioexcitatory peptide (ACEP-1) as well as to the recently identified family of mammalian prolactin-releasing peptides. In the Lymnaea brain, the cells that produce egg-laying hormone are the predominant site of GRL106 gene expression and appear to be innervated by LyCEP-containing fibers. Indeed, LyCEP application transiently hyperpolarizes isolated egg-laying hormone cells. In the Lymnaea pericardium, LyCEP-containing fibers end blindly at the pericardial lumen, and the heart is stimulated by LyCEP in vitro. These data confirm that LyCEP is an RFamide ligand for GRL106.

Action Potentials↗
PubMed1998

Characterization of the 5'-flanking promoter region of the rat somatostatin receptor subtype 3 gene.

We investigated the 5'-flanking promoter region of the rat somatostatin receptor subtype 3 (rSSTR3). Using a cDNA probe, genomic clones containing the 5'-flanking promoter region of the rSSTR3 gene were isolated. A sequence of 5.4 kb directly upstream from the start codon was analyzed and two introns were found in the 5' untranslated region (UTR) of the cDNA sequence. The transcriptional initiation site was determined by 5' rapid amplification of cDNA ends (RACE), primer extension and RNase protection analysis with cerebellar RNA. Two major transcriptional initiation sites were found at position 1040 (tsp1) and -856 (tsp2) relative to the translational initiation site. Like a number of other promoters of G-protein-coupled receptors, the rSSTR3 gene lacks TATA and CAAT motifs and includes G+C-rich regions. Functional analysis of the promoter region by transfecting rSSTR3 luciferase-reporter gene constructs into rat pituitary GH3 cells and HEK 293 cells indicated that a 107-bp region upstream of tsp2 was sufficient to drive transcription. Furthermore a 562-bp region at position -1304 to -1865 upstream of the ATG start codon exerted a negative regulatory effect on transcriptional activity.

5' Untranslated Regions↗
PubMed1998

Investigation of the Dielectric beta-Process in Polyisobutylene by Incoherent Quasielastic Neutron Scattering.

Recently by dielectric spectroscopy a new secondary relaxation process in polyisobutylene (PIB) was detected showing all the signatures of a Johari-Goldstein relaxation [Richter, D; Arbe, A.; Colmenero, J.; Monkenbusch, M.; Farago, B.; Faust, R. Macromolecules 1998, 31, 1133]. Using high resolution neutron backscattering, we investigated the quasielastic neutron spectra from protonated PIB which are related to this process as a function of momentum transfer and temperature. In addition we studied the elastically scattered intensity over a wide temperature range. After multiple scattering corrections all results can be described consistently in terms of a local jump process with the distribution parameters from the dielectric beta-relaxation. The spatial extent of the associated protonic motion was determined to be d = 2.7 Å. A comparison with the existing body of data for PIB leads to the conclusion that the dielectric beta-process and the earlier found delta-process must be identical, thereby revising the assignment of the delta-process as due to methyl group rotation. Finally, we remark on aspects of the relation between quasielastic coherent and incoherent scattering and address the seemingly contradictory result of different length scales revealed for the same process with the two techniques.

Journal Article↗
PubMed1998

[Ankle para-articular tibial fracture. Is osteosynthesis with the unreamed intramedullary nail adequate?].

In a prospective study, 53 fractures of the distal fifth of the tibia were stabilized by unreamed nailing. Additional involvement of the ankle joint occurred in 18 patients. 50 patients returned for follow-up. In 30 patients tibia and fibula were fractured at the same (distal) level; in 20 patients the fracture of the fibula was located more proximally. In 12 patients the fractures extended into the tibial pilon. Severe soft tissue damage was seen in 24 fractures (18 open, 6 closed). Ninety percent of all fractures healed uneventfully without further surgical intervention after unreamed nailing. In two patients the unreamed nail had to be exchanged for a reamed tibial nail. Bone grafting and secondary dynamization of the nail by removal of a proximal interlocking bolt were performed in one case each. Thirty-one fractures healed in anatomical position. Valgus or varsus angulation of less than 5 degrees occurred in 18 patients. One fracture healed with rotatory angulation of 15 degrees. The highest rate of complications (22%) was seen in patients with distal fractures of the fibula without additional plating (of the fibula). There was no deep infection. Tibial fractures close to the ankle joint can be managed by unreamed nailing. Distal fractures of the fibula should be stabilized by additional plating. Because of the unreamed technique of implantation this procedure can also be used in grade II or III open fractures.

Adult↗
PubMed1998

Prevention of necrotizing enterocolitis in extremely low birth weight infants by IgG feeding?

UNLABELLED: Oral immunoglobulin has been described as preventing necrotizing enterocolitis(NEC) in preterm infants. To prevent NEC in extremely low birth weight infants (ELBW), we have carried out oral IgG prophylaxis since April 1991. The efficacy of this prophylaxis was examined in a study comparing historical cohorts. ELBW infants delivered in the Department of Obstetrics and Gynaecology of the University of Ulm and treated until day 28 in the level III intensive care nursery, Division of Neonatology, University of Ulm were included. Cohort 1, born between 1.1.1988 and 31.3.1991, received no oral IgG and served as a control [n = 84, gestational age: median 26 weeks, range 24-34; birth weight: 811 g, 490-990], cohort 2, born between 1.4.1991 and 31.12.1995 [n= 137, gestational age: 26 weeks, 22-32; birth weight: 760 g, 362-995], received 6 x 100 mg/kg human IgG (Beriglobin) orally on days 1-28. NEC, stage 2a and higher according to the modified classification of Bell, was observed in 9 of 84 (10.7%) infants of cohort 1 and in 11 of 137 (8%) infants of cohort 2 until day 28. The difference did not reach statistical significance (P = 0.63 Fisher's exact test). CONCLUSION: In this historical cohort study, ELBW infants were not protected against NEC by oral IgG. The present published evidence does not allow recommendation of oral human IgG administration in preterm infants as a prophylactic measure against NEC.

Enterocolitis, Necrotizing↗
PubMed1998

Rat somatostatin receptor subtype 4 can be made sensitive to agonist-induced internalization by mutation of a single threonine (residue 331).

A sequence motif of 20 amino acid residues within the C-terminal portion of the rat somatostatin receptor subtype 4 (SSTR4) has been shown to prevent rapid agonist-dependent receptor internalization in transfected human embryonic kidney (HEK) cells. Molecular dissection of this motif by biochemical ligand-binding assays revealed that the block was released by mutating a single residue (threonine 331) to an alanine. These data are in line with confocal microscopic analysis of cultured primary neurons microinjected with cDNA constructs encoding either SSTR4 or the mutant T331A. Immunocytochemical analysis showed that the mutant receptor, but not SSTR4, was internalized. However, internalized T331A was not recycled to the cell surface, suggesting that it lacks sequence elements that determine intracellular sorting after endocytosis. Neither wildtype SSTR nor the mutant T331A exhibited functional desensitization when assayed for their ability to inhibit adenylate cyclase. In agreement with this, the wt receptor and its mutant were not phosphorylated in response to agonist treatment. Lack of desensitization of SSTR4 has been electrophysiologically verified by coexpressing the receptor with a G-protein-gated, inwardly rectifying potassium channel in Xenopus oocytes. A strong somatostatin 14 (SST14)-activated inward potassium current was observed that was long-lasting and which decayed only slowly after washout of the agonist. This is in contrast to another somatostatin receptor subtype, SSTR3, which mediates rapidly desensitizing currents. Binding experiments on HEK cells transfected with either SSTR3 or 4 indicated that this difference is not attributable to slow dissociation of the agonist from the receptor, suggesting that SSTR4 mediates long-lasting signalling, a property which may be relevant for clinical therapy.

Adenylyl Cyclases↗
PubMed1998

Effect of prior exposure to noninfected ticks on susceptibility of mice to Lyme disease spirochetes.

To determine whether prior exposure to Nearctic Ixodes vector ticks protects native reservoir mice from tick-borne infection by Lyme disease spirochetes, we compared their infectivities for white-footed mice and laboratory mice that had been repeatedly infested by noninfected deer ticks. Nymphal ticks readily engorged on tick-exposed laboratory mice, but their feeding success on white-footed mice progressively declined. Tick-borne spirochetes readily infected previously tick-infested mice. Thus, prior infestation by Nearctic ticks does not protect sympatric reservoir mice or Palearctic laboratory mice from infection by sympatric tick-borne spirochetes.

Animals↗
PubMed1998

Diversity of European Lyme disease spirochetes at the southern margin of their range.

We determined whether the genospecies diversity of Lyme disease spirochetes in vector ticks questing on a subtropical island is as broad as that in Central Europe. Although spirochetes infected < 1% of the ticks sampled on Madeira Island, these infections included all three genospecies implicated in human disease. Therefore, spirochetal diversity is as great at the southern margin as it is in the center of this pathogen's range.

Animals↗
PubMed1998

Failure of Ixodes ticks to inherit Borrelia afzelii infection.

To define conditions promoting inherited infection by Lyme disease spirochetes in Ixodes ticks, we variously infected ticks with Borrelia afzelii and examined their progenies by dark-field microscopy, immunofluorescence, PCR, and serial passage. No episode of inherited infection was evident, regardless of instar or gender infected or frequency of exposure. We suggest that these spirochetes rarely, if ever, are inherited by vector ticks.

Animals↗
PubMed1998

[Incidence of arthrosis in the results of the treatment of coxarthrosis in the young adult with Chiari's osteotomy. Retrospective study of 52 hips with 10.5 years of follow-up].

PURPOSE OF THE STUDY: Fifty two of 53 Chiari pelvic osteotomies performed between 1974 and 1991 were reviewed clinically and radiographically with an average follow-up of 10.5 years. MATERIAL AND METHODS: In more than 46 per cent of cases, the osteotomy was performed on a dysplastic painful hip with severe osteoarthritis. Major complications were rare. The Chiari's osteotomy fixation screw was removed in 16 cases. Technically, the average displacement was 22 mm. A ascending osteotomy, related to the level of the osteotomy (p = 0.001), provided good displacement. RESULTS: The functional results were very good or good in 65 per cent of the patients and lasted more than 10 years. Seventy five per cent of the hips were pain free. Radiographically, the center edge angle and the femoral head covering were corrected by the procedure. Degenerative changes of the hip joint were improved or stabilized in 63.5 per cent of the cases. Fifteen hips had undergone secondary total hip replacement, seven during the first five years and 8 after 13 years. DISCUSSION: Factors associated with a positive outcome included: age under 30 at the time of surgery (80 per cent of survivorship up to 15 years of follow up), low stage (I or II) of osteoarthritis, and a technically perfect Chiari osteotomy. The outcome of initial stage III or IV initial osteoarthritis were not as long lasting. Chiari osteotomy functional results were good for the initial 10 years, after this time they deteriorated quickly. CONCLUSION: Chiari pelvic osteotomy is an alternative procedure to early total hip replacement for severe painful dysplastic hips with low stage of osteoarthritis in young patients.

Adolescent↗
PubMed1998

[Holistic nursing--do nurses take on too much?].

The idea of holism is a central topic of contemporary nursing. This article at first reconstructs the historical background of holistic scientific thinking. For the recent nursing science and practice four divergent holistic concepts are identified: 1. the theory of the unitary human being by Martha Rogers; 2. the holistic therapeutical practice of nurses in the United States; 3. the biopsychosocial model many conceptual models of nursing are based on; 4. the holistic organization of nursing. By analysing the interaction between nurse and patient and by comparing the professional and the domestic organization of care it is argued that holistic nursing is theoretically as well as practically impossible. In order to prevent overtaxing due to holistic claims of nursing theory the limits of nursing practice have to be shown unambiguously.

Holistic Nursing↗