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Biomedical subjects

D Richter

Publications and source records attributed to D Richter.

At least 181 records · Page 10Linked to original sources
PubMed1995

Hydration dependence of chain dynamics and local diffusion in L-alpha-dipalmitoylphosphtidylcholine multilayers studied by incoherent quasi-elastic neutron scattering.

Incoherent quasi-elastic neutron scattering is applied to study the local diffusion and chain dynamics of L-alpha-diplamiotylphosphatidylcholine molecules in oriented model membranes. Different motions are distinguished by changing the hydration of the multilayers as well as by measuring below and above the gel-to-liquid crystalline phase transition. The time range of the utilized time-of-flight spectrometer permits to observe two types of motion to be observed more closely: chain defect motions and the local diffusion of the whole molecule in its solvation cage. Oriented lipid membranes are a useful system for the observation of chain defects, as they can be macroscopically oriented, in contrast to most polymers. As a representative model for a chain defect a kink is chosen and the corresponding scattering functions are derived. The kink motion can explain the entire dynamics seen in the gel phase, and the lifetime of such a defect was found to be 10-15 ps, in good agreement with theoretical predictions. On the other hand the dynamics in the liquid crystalline phase cannot be explained even by a superposition of several kinks and thus requires the consideration of an additional motion: the local diffusion of the molecule in its solvation cage. The size of the solvation cage is increasing with multilayer hydration and reduced temperature. Particularly interesting in view of recent discussions about the origin of the short-range repulsive forces between membranes is the experimental finding of an out-of-plane motion with an amplitude of 1-1.5 A, which cannot be explained by the undulation of the whole membrane.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1995

Aspartic acid residue 124 in the third transmembrane domain of the somatostatin receptor subtype 3 is essential for somatostatin-14 binding.

A highly conserved aspartic acid residue present in the third membrane-spanning region of adrenergic and muscarinic receptors is directly involved in ligand binding. The five cloned somatostatin receptor subtypes also contain this residue at the same relative position. To test whether Asp-124 of the rat somatostatin receptor subtype 3 (SSTR3) is responsible for the binding of somatostain-14 (SST-14), this amino acid residue was replaced by an asparagine or a glutamic acid by polymerase chain reaction (PCR)-mediated site-directed mutagenesis. Expression and binding activity of the wild-type and mutant receptor constructs were studied in COS and HEK cells by ligand binding, UV cross-linking, Western blot, and immunocytochemical analysis. The Asn or Glu mutations result in a significant loss of SST-14 binding, although the mutant receptors are correctly transferred to the cell surface, demonstrating that Asp-124 is directly involved in binding of SST-14.

Amino Acid Sequence↗
PubMed1995

Electrocardiographic changes during desipramine and clomipramine treatment in children and adolescents.

OBJECTIVE: With the increased use of tricyclic antidepressants in children, and several reports of several sudden deaths associated with desipramine (DMI) treatment, systematic study of their cardiac effects is indicated. In the present study, DMI's and clomipramine's (CMI) short-term effects on the electrocardiogram (ECG) were compared, as well as the long-term effects of CMI. METHOD: The ECGs of 47 children and adolescents in treatment trials were examined at baseline, after 5 weeks of CMI and of DMI treatment, and during CMI maintenance (mean duration 24.6 months). RESULTS: At 5 weeks of CMI and of DMI treatment, the heart rate, PR, QRS, and QT-corrected (QTc) intervals on ECG were significantly increased from baseline (p < .05); DMI increased PR and QRS intervals more than CMI (p < .05), and CMI increased QTc more (p < .05). Tachycardia was the most common change (36%). More patients experienced an incomplete intraventricular conduction delay during DMI treatment (23%, 9/39) than during CMI (2%, 1/47) (p < .05). Four patients (9%) acutely developed a prolonged QTc during either DMI or CMI. Long-term maintenance ECGs during CMI treatment (n = 25) were not significantly different from that at week 5, although some individuals developed or resolved specific ECG changes. CONCLUSION: CMI and DMI both produced ECG changes typically reported for tricyclic antidepressants, and they differed on specific ECG changes. Changes in ECG measures for individuals from short to long term suggest that continued monitoring is required.

Adolescent↗
PubMed1995

Distribution of somatostatin receptor subtype 1 mRNA in the developing cerebral hemispheres of the rat.

Somatostatin (SST) is one of the major peptide transmitters in the mammalian central nervous system and also seems to exert specific functions during brain development. In contrast to ligand binding experiments, by which two pharmacologically different binding sites were characterized, molecular cloning techniques have led to the identification of at least five different receptor subtypes (SSTR1-5), which according to RNA blot analyses seem to be differentially distributed and regulated in the developing brain. In order to provide more precise data on the distribution of SSTR1 during ontogenesis, we have performed an in situ hybridization analysis, using a 35S-labelled RNA probe, in the developing rat cortex between embryonic day (E)12 and adulthood. Within the cortical plate, expression of SSTR1 gene was first detected in parallel with the establishment of the deep laminae V/VI at E16, thereby following the characteristic morphogenetic gradients of cortical plate construction. Thus, with the subsequent addition of cells along the radial dimension, e.g. the deposition of the supragranular neurons beyond E18, the hybridization signal spreads as an uniform homogenous band through the entire cortical plate, whereby silver grains reach their peak density around birth. Similar developmental gradients were observed along the lateromedial and frontooccipital dimension, whereby SSTR1 transcripts were detected near the frontal pole and the lateral cortical areas roughly 2 days before they appeared in the occipital and medial cortical anlage, respectively. From the initially homogenous distribution, two distinct SSTR1 mRNA-positive bands coextensive with laminae V/VI and II/III, respectively, and sparing lamina IV evolved during the first postnatal week, the grain density of which decreased during further postnatal development. Within the hippocampal formation, SSTR1 transcripts were initially observed at E18 in the subicular complex, and after birth also extending into the neighboring CA1 region. During the 1st and 2nd postnatal week, silver grains were observed over the pyramidal cell layer of CA2 and CA3 and as a faint supragranular band in the dentate gyrus. Similar to the isocortex, grain density decreased thereafter. Hypothetically, the pronounced temporospatial regulation of SSTR1 gene expression during brain development can be correlated with (1) the establishment and eventual reduction of transient cortical SSTergic neuron populations described for late pregnancy and early postnatal development and (2) a receptor subtype exchange during maturation as evidenced by the late (from postnatal day 7 onward) appearance of e.g. SSTR3.

Animals↗
PubMed1995

Molecular and pharmacological characterization of somatostatin receptor subtypes in adrenal, extraadrenal, and malignant pheochromocytomas.

SRIH receptors were quantified by radioautography in 33 pheochromocytomas and 5 normal adrenals. Binding was evenly distributed over the tumors, whereas it was more intense in adrenal medulla than cortex. Binding levels were significantly higher in tumoral than in normal tissue, but did not differ among tumors. At 100 nmol/L, SRIH-14 and octreotide (or BIM23014 in cross-linking experiments to a 57-kilodalton component) comparably displaced SRIH binding, BIM23042 and BIM23052 were less potent, and BIM23056 was inefficient. In increasing doses, the rank order of potency was SRIH-14 > SRIH-28 > octreotide > BIM23052 >> BIM23042 >> > BIM23056. All five species of SRIH receptor (SSTR1-5) messenger ribonucleic acids (mRNAs) were measurable in pheochromocytomas and normal adrenals, SSTR2 and SSTR4 mRNA were the most expressed moieties. The proportion of SSTR5 mRNA species was higher in normal adrenals (21%) than in pheochromocytomas (6%). In the presence of guanylylimidodiphosphate, SRIH binding was reduced by 83%. However, SRIH did not alter basal or forskolin-stimulated adenylyl cyclase activity. Taken together, these pharmacological and molecular data indicate that SRIH binding on pheochromocytomas depends on a mixed population of receptors, mainly of the SSTR2 and SSTR4 subtypes, efficiently coupled to G proteins, but not to adenylyl cyclase inhibition.

3-Iodobenzylguanidine↗
PubMed1995

[Extracorporeal shock wave therapy--an alternative concept for the treatment of epicondylitis of the humerus and radius?].

In a prospective study, 16 patients with chronic, painful epicondylitis humeri radialis were treated with extracorporal high-energy shock waves. A complaint-free period of 3 months was achieved in 13 patients. In 2 of them complete release from pain was achieved for more than 3 months. We conclude that release from the symptoms is achieved by local hyperemia in the area of tendinitis. In contrast to the encouraging observations of other authors, our results suggest that a critical view of extracorporal shock waves for the treatment of chronic epicondylitis radialis of the elbow is reasonable.

Adult↗
PubMed1995

[Ventral hyperostosis of the cervical spine--a rare differential diagnosis of dysphagia].

A case of dysphagia and hoarseness due to external compression by anterior hyperostosis between the third and fourth cervical vertebra is reported. Immediate relief of the symptoms was accomplished by surgical excision of the hyperostosis through an antero-lateral approach. The pathogenesis of the symptoms with reference to literature is discussed.

Cervical Vertebrae↗
PubMed1995

Sequence analysis of a cDNA encoding an isotocin precursor and localization of the corresponding mRNA in the brain of the cartilaginous fish Torpedo marmorata.

The nucleotide sequence of a cDNA encoding an isotocin hormone precursor has been elucidated by analyzing a lambda ZAPII library constructed using poly(A)+ RNA from the brain of the cartilaginous fish Torpedo marmorata. The sequence predicts a precursor of 126 amino acid residues that consists of a signal peptide, the isotocin moiety, and a neurophysin carrier protein. In contrast to other known fish isotocin precursor sequences, the Torpedo neurophysin moiety is not extended at its carboxy-terminus by a copeptin-like sequence. The T. marmorata isotocin precursor exhibits highest amino acid sequence identity (61%) to the toad mesotocin precursor. As demonstrated by in situ hybridization, the isotocin mRNA is present in neurons of the preoptic area of the Torpedo brain.

Amino Acid Sequence↗
PubMed1995

[Classification, therapy and complications of pediatric femoral neck fractures].

Femoral neck fractures in children are rare injuries (less than 1 percent). The fracture pattern consists of transepiphyseal, transcervical, cervicotrochanteric and intertrochanteric fractures. Main problems with this type of injury are avascular necrosis, varus deformity, nonunion and premature epiphyseal closure. Varus and nonunion are affected by the treatment, vascular compromise with necrosis or growth problems are not related to therapy and hardly to control. Primary dislocated fractures are emergencies and need immediate operative management. Stabilization is achieved with K-wires or cancellous screws dependent on the child's age. In children below 3 years a pelvis cast is necessary post-operatively. Partial weight bearing is started 6 weeks post trauma and is rapidly increased to full weight bearing. One year post-operation the metal is removed, K-wires directly after bony healing.

Adolescent↗
PubMed1995

[Causal attributions and coping with illness by breast cancer patients: results of a longitudinal study].

The present 3-year longitudinal study investigated the relationship between causal attribution and coping mechanism. Data were collected in a group of 66 breast cancer patients by self-report questionnaires. Three issues were addressed: 1. How do the patients explain the cause of their illness? 2. Do the subjective causes change over the course of three years? 3. What kind of relationship can be found between the causal attributions and the coping mechanism of the patients? Results showed a predominance of psychological attribution. Only little statistical prove could be found for changes between the four ratings. Analysing the individual data of the patients however revealed changing perceptions for about half the patients. A relationship between psychological attribution and depressive coping and problem solving as well were found.

Adaptation, Psychological↗
PubMed1995

[Nursing science and sociology: in what way can sociological expertise support nursing research?].

Nursing science is currently orientated towards theories and methods from the social sciences. The article asks in which exact fields nursing science can use experiences of sociologists. Central topics are methodological aspects as well as concrete research contents. The following aspects are dealt with in greater detail: In the methodological field the relation of theory and practice is analyzed. Secondly, the relation of empirical and theoretical methods is described. Concerning the concrete research contents it is suggested that the topics nursing and society, nursing and hospital organisation, and the patient-nurse-interaction by sociological means should be analyzed. Several examples relevant to nursing illustrate the argument.

Humans↗
PubMed1995

[Injury pattern after fall from great height. An analysis of 101 cases].

There are few references discussing the typical injury patterns of adults after a fall from a height. We present the pattern of injury in 101 adult patients who were treated between 1987 and 1990 at our trauma center after falling from an average height of 7.2 m. In 62 patients the fall was accidental; 39 patients tried to commit suicide by jumping from a height. The most common injuries were fractures of the thoracic and lumbar spine (83.0%) with a preference for the thoracolumbar junction. Fracture of the lower limbs occurred in 45%. The most frequent injuries were fractures of the os calcis (64.4%) and the ankle joint (26.6%). Twenty-five percent of all patients suffered from fractures in the upper limbs with a preference for the distal radius (56.6%) and the elbow (44.0%). There were no differences between the injury patterns after a fall from a height of more than 7 m or less than 7 m. The incidence of thoracic and pelvic injuries (30.0%) increased after falls from more than 7 m. The neurological complications of injuries to the spine corresponded to increasing height. According to our analysis blunt abdominal trauma is an uncommon injury after falling from a great height. Head injuries, which would be expected to be the most common cause of death in all non-survivors in the literature, only occurred in 27% of our patients who all survived their transport to hospital.

Accidental Falls↗
PubMed1995

Production of hybrid oxytocin/vasopressin precursors and accumulation of oxytocin precursors in the rough endoplasmic reticulum of rat magnocellular neurons.

Most magnocellular hypothalamic neurons synthesize the precursor for either vasopressin (AVP) or oxytocin (OT). The AVP precursor is cleaved to give AVP, AVP-associated neurophysin (AVP-NP) and a glycopeptide (GP), whereas the OT precursor gives OT and OT-NP. In Brattleboro rats a frame-shift mutation in the AVP-NP-encoding region of the gene prevents the secretion of AVP by the cells and, in most AVP neurons, AVP itself is virtually undetectable. A small number of magnocellular neurons in homozygous Brattleboro rats contain very large accumulations of peptide in distended saccules of rough endoplasmic reticulum (RER), and this peptide is immunoreactive for AVP and C-terminal OT-NP, but not for OT, AVP-NP or GP (Pow et al., 1992). We have now shown that this results from somatic non-homologous crossing over of the AVP and OT genes, resulting in the production of hybrid mRNA molecules with the 5'end of the AVP sequence and the 3' end of the OT sequence (AVP/OT transcripts). In most cases, the crossing over occurs within the highly homologous B exons (Mohr et al., 1994). In addition to the production of AVP/OT hybrid transcripts, polymerase chain reaction (PCR) amplification of mRNA from the hypothalami of homozygous rats also reveals OT/AVP hybrid transcripts, with 5' OT sequences and 3' AVP sequences. Furthermore, both types of hybrid transcript are not restricted to homozygous Brattleboro rats but can also be found in normal Long Evans animals. To date, we have not been able to locate cells in which the OT/AVP hybrids are produced; all the magnocellular neurons with hybrid peptide accumulations in the RER so far studied have been shown by immunocytochemistry to be of the AVP/OT type. In both normal and homozygous Brattleboro rats large accumulations of peptide do occur in the RER of OT-producing neurons but the peptide is immunoreactive for OT and OT-NP but not for AVP, AVP-NP or GP. Such cells increase in number 10-fold after injection of 20 micrograms estradiol daily for 7 days (Pow et al., 1991). Why this apparently normal gene product accumulates within the RER remains to be determined.

Aging↗
PubMed1994

Somatic nonhomologous crossing-over between neuropeptide genes in rat hypothalamic neurons.

Molecular biological and immunocytochemical data demonstrate nonhomologous crossing-over between the closely linked vasopressin (VP) and oxytocin (OT) genes in rat hypothalamic neuroendocrine neurons. Reverse transcription of hypothalamic total RNA from wild-type or homozygous Brattleboro aged rats combined with polymerase chain reaction (PCR) amplifications in the presence of appropriate 5' forward and 3' reverse primers deduced from the VP and OT cDNA sequences yielded PCR products that, upon cloning and sequencing, revealed several hybrid transcripts. They encode the N-terminal part of the VP precursor fused to the C-terminal part of the OT precursor (VP/OT transcripts) and vice versa (OT/VP transcripts). VP/OT hybrid precursor proteins have been identified immunocytochemically in enlarged cisternae of the rough endoplasmic reticulum, yet there is no evidence that the products can be secreted from affected cells. Recombination appears to be a rather frequent genetic event affecting about 0.06-0.1% of the rat vasopressinergic magnocellular neurons in aged rats.

Amino Acid Sequence↗