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Biomedical subjects

K Richter

Publications and source records attributed to K Richter.

At least 217 records · Page 12Linked to original sources
PubMed1991

The influence of food on the absorption of diclofenac as a pure substance.

The interaction of diclofenac as a pure substance was investigated without and with concomitant administration of food in 8 healthy, male volunteers (age: 23-29 years, body weight: 60-87 kg). Diclofenac was given as a pure substance by means of a rapid dissolving capsule in a dose of 50 mg. Paracetamol (1.5 g), a marker of gastric emptying rate, was administered simultaneously with diclofenac in order to elucidate the influence of gastric emptying rate on diclofenac absorption. The bioavailability was determined according to the time (tmax) of the concentration maximum in plasma (Cmax) and the area under the curve (AUC). Food significantly delays tmax of diclofenac (without food: [mean +/- SD] 0.8 +/- 0.5 h, range: 0.5 +/- 2 h; with food: 2.4 +/- 0.9 h, range: 1.5-4 h) and diminishes Cmax (without food: 1,125 +/- 765 ng/ml, range: 95-2,100 ng/ml; with food: 434 +/- 151 ng/ml, range: 250-555 ng/ml). The AUC is not influenced (without food: 1,217 +/- 368 ng/ml x h; with food: 1,037 +/- 267 ng/ml x h). The bioavailability of paracetamol is unchanged. It is concluded that the diminishing of Cmax and the delay of tmax of diclofenac are possibly the consequence of an interaction with food and not of the delayed gastric emptying per se.

Acetaminophen↗
PubMed1991

Localization of a nervous system-specific class II beta-tubulin gene in Xenopus laevis embryos by whole-mount in situ hybridization.

A neural-specific beta-tubulin mRNA is expressed in the developing central nervous system shown by whole-mount in situ hybridization experiments. Of special interest is the fact that from the late blastula (stage 9; Nieuwkoop and Faber, 1967; Hausen and Ribesell, 1991) until the early neurula (stage 13) the signal can be found not only in the presumptive neural plate but also in the presumptive epidermis. Later in development (from stage 13) the specific mRNA becomes restricted to the presumptive brain and spinal cord area. The results are discussed in the context of predisposition and (pre)determination.

Animals↗
PubMed1991

Freezing: facts and hypothesis.

Hexagonal ice crystals formed in frozen biological specimens are large and branched. They can produce severe structural damage by solute segregation but there are also cases where they seem to cause only minor damage. When cooling is more rapid, cubic ice crystals can be formed. These are small and in general, they cause little damage. These observations can be readily explained with the hypothesis that large hexagonal ice crystals can originate from the rewarming induced transformation of a large number of cubic ice crystals. This transformation would take place without significant solute displacement.

Animals↗
PubMed1991

[Merkel cell tumor (neuroendocrine carcinoma of the skin) in an unusual location. Immunohistochemical and lectin histochemical findings].

Neuroendocrine carcinoma of the skin usually occurs in elderly individuals. Head and neck are the most common primary sites followed by the extremities and trunk. As this tumor represents a remarkable rarity in younger people, we report the case of a 33-year-old woman with a neuroendocrine carcinoma in an unusual localization. Diagnosis was based on the results of the examination of a metastasis in the inguinal lymph nodes. The lesion at the Labium minus pudendi which is to be considered the primary tumor was detected several months later. Diagnosis of Merkel cell tumor until recently had depended on ultrastructural demonstration of dense-core membrane-bound granules. Today, diagnosis can be secured also by optical light microscopy, on the basis of a certain constellation of immunohistochemical and lectin histochemical findings.

Adult↗
PubMed1990

Two precursors of thyrotropin-releasing hormone from skin of Xenopus laevis. Each contains seven copies of the end product.

From the skin of Xenopus laevis, the cloned cDNAs of two precursors of thyrotropin-releasing hormone have been isolated and sequenced. These encode almost identical precursor polypeptides each containing seven copies of the end product flanked by typical prohormones processing signals. Northern blot analysis has corroborated the existence of two thyrotropin-releasing hormone precursor mRNAs of similar size as the cloned cDNA and demonstrated the existence of a third smaller species as well. Two or more mRNAs for this precursor are also present in the brain and eyes of X. laevis adults and tadpoles.

Amino Acid Sequence↗
PubMed1990

Molecular cloning of a cDNA encoding the bombesin precursor in skin of Bombina variegata.

A cDNA library was constructed using poly(A)-rich RNA isolated from skin of the frog Bombina variegata. This library was screened with two oligo-nucleotides complementary to parts of the sequence of bombesin. The nucleotide sequence of one of the cloned cDNAs encoding a bombesin precursor is presented. The predicted polypeptide contains a single copy of the end-product. The bombesin sequence is preceded by a leucine residue suggesting an unusual type of precursor processing.

Amino Acid Sequence↗
PubMed1990

High-affinity glutamine uptake of the rat hippocampus during postnatal development: a quantitative autoradiographic study.

Glutamine uptake into hippocampal slices of the rat was investigated autoradiographically. The characteristics of registered [14C]glutamine uptake such as the incubation with the radiolabelled amino acid at a concentration of 3.5 mumol/l, sodium dependency, the distribution pattern of radioactive material, and the postnatal development of uptake capacity are comparable with those of high-affinity uptake of glutamate. Densitometric evaluation of grain density over hippocampal layers exhibited a marked enhancement of uptake capacity in the neuropil areas during the first postnatal weeks. In the strata oriens and radiatum (CA1) radiolabelling increased from day 2 to 25 by about 390 and 410%, in the strata oriens and lacunosum-moleculare of CA3 by about 350 and 375%, respectively. In contrast, the rise in the accumulation rate in cell body layers was negligible. The temporal and topographical profiles of glutamine uptake in the hippocampal neuropil correlated with those of the activity of phosphate-activated glutaminase and parameters of maturation of the glutamatergic transmission system which have fairly similar time characteristics, suggesting a mutually causative relationship of all these factors.

Aging↗
PubMed1990

cDNAs encoding [D-Ala2]deltorphin precursors from skin of Phyllomedusa bicolor also contain genetic information for three dermorphin-related opioid peptides.

We present the structure of four precursors for [D-Ala2]deltorphins I and II as deduced from cDNAs cloned from skin of the frog Phyllomedusa bicolor. These contain the genetic information for one copy of [D-Ala2]deltorphin II and zero, one, or three copies of [D-Ala2]deltorphin I. In each case, the D-alanine of the end product is encoded by a normal GCG codon for L-alanine. In addition, the existence of three peptides related to dermorphin was predicted from the amino acid sequence of the precursors. These peptides were synthesized with a D-alanine in position 2 and their pharmacological properties were tested. Two of them, [Lys7]dermorphin-OH and [Trp4,Asn7]dermorphin-OH, were found to have roughly the same affinity and selectivity for mu-type opioid receptors as dermorphin.

Amino Acid Sequence↗
PubMed1990

A nervous system-specific isotype of the beta subunit of Na+,K(+)-ATPase expressed during early development of Xenopus laevis.

We have previously described the isolation of several genes expressed exclusively in the nervous system of adult Xenopus laevis and activated in the embryo shortly after neural induction. The sequence of one of these cDNAs, 24-15, identifies the corresponding protein as an isotype of the beta subunit of Na+,K(+)-ATPase [ATP phosphohydrolase (Na+/K(+)-transporting); EC 3.6.1.37]. This form is distinct from the previously described beta 1 subunit of Xenopus, and the protein sequence comparison suggests that it is not the frog homolog of the mammalian beta 2 subunit; therefore, we refer to the 24-15 protein as the beta 3 subunit of Na+,K(+)-ATPase of Xenopus. Antisera directed against beta 3-subunit fusion protein detected a protein in adult brain extracts with the size and properties expected for a Na+,K(+)-ATPase beta subunit. In Xenopus the beta 1 and beta 3 subunits are expressed as maternal mRNAs at similar levels; during embryogenesis rapid accumulation of beta 3 mRNA begins at stage 14 (early neurula), and the rapid accumulation of beta 1 mRNA begins at stage 23/24. In situ hybridization of antisense RNA probes to tadpole brain sections indicates that beta 3 subunit is expressed throughout the developing brain. We suggest that beta 3 is a major Na+,K(+)-ATPase beta subunit present during early nervous system development in the frog.

Amino Acid Sequence↗
PubMed1990

[HIV study of the German Red Cross of West Germany 1985-1989: prevalence/incidence and mode of infection, retrospective studies].

All German Red Cross Blood Banks in the FRG cooperate in a study on prevalence and epidemiology of HIV-antibodies in blood donors. The prevalences of 1 to 2 Western blot positive donors per 100,000 donors/donations quarterly since 1987 are constantly low. The measures undertaken to defer persons at risk seem to be effective. The "look back" data confirm the "rest risk" of HIV-infections by blood products in the FRG which is estimated to be about 1:1 million on the basis of the epidemiologic data. More than 90% of the donors infected are members of risk groups of heterosexual partners to persons at risk. Until today, in blood donors there is no indication of an increasing number of unaware heterosexually acquired HIV-infections.

Blood Banks↗
PubMed1990

A developmentally regulated, nervous system-specific gene in Xenopus encodes a putative RNA-binding protein.

A gene from Xenopus laevis that is expressed specifically in the nervous system beginning at the stage of neural plate formation has been isolated and several cDNAs have been sequenced. The sequence of the predicted protein contains two copies of a presumed RNA-binding domain, each of which includes two short conserved motifs characteristic for ribonucleoproteins (RNPs), called the RNP-1 and RNP-2 consensus sequences. We name this gene Xenopus nrp-1, for nervous system-specific RNP protein-1. Sequence comparisons suggest that the nrp-1 protein is a heterogeneous nuclear RNP protein, but it is clearly distinct from previously reported hnRNP proteins such as the A1, A2/B1, and C1 proteins. nrp-1 RNA undergoes an alternative splicing event giving rise to two predicted protein isoforms that differ from each other by seven amino acids. In situ hybridization to tadpole brain shows that the nrp-1 gene is expressed in the ventricular zone where cell proliferation takes place. The occurrence of an RNP protein with nervous system-limited expression suggests that it may be involved in the tissue-specific control of RNA processing.

Alleles↗
PubMed1990

[Individually-adjusted dosages of aminophylline in children with bronchial asthma].

Theophylline concentrations in serum between 10 to 20 micrograms/ml cannot be obtained with usual dosage of theophylline in children with individual very short elimination half time of theophylline. Multiple corrections of dosage and repeated controls of theophylline concentrations in serum are necessary for empirical adjustment of individual optimal dosage. Pharmacokinetic investigations were made to shorten this management. 12 patients with bronchial asthma, 6 to 18 years of age, received 1.5 to 3 tablets of Aminophyllin under conditions of steady state. Blood samples were taken up to 6 hours after oral application. As a result of statistical analysis we found that the biological half time of theophylline could be determined from 2 to 3 blood samples. Estimation of optimal individual dosage is possible by simple mathematical pharmacokinetic formulas.

Adolescent↗
PubMed1990

Significant X-ray patterns in cardiomyopathy--an approach improving noninvasive diagnosis.

To identify their characteristic patterns, the X-ray dorso-ventral chest images of 118 patients with cardiomyopathy (63--dilated cardiomyopathy, 25--hypertrophic obstructive cardiomyopathy, 30--hypertrophic nonobstructive cardiomyopathy) were analyzed and compared with those of 22 patients without cardiac abnormalities. All 140 patients underwent comprehensive invasive cardiac examinations. In dilated and hypertrophic nonobstructive cardiomyopathy transvasal endomyocardial biopsy was performed. Irrespective of the type and the aetiology of cardiomyopathy, 4 characteristic patterns of X-ray findings could be identified: a class of left heart abnormality (class L) and 3 types of bilateral cardiac abnormalities with various stages of left heart failure (class L + R). An association between the image patterns and haemodynamic parameters (left ventricular end-diastolic pressure, wall mass index, pulmonary mean pressure) was demonstrated which was most obvious in dilated and less evident in hypertrophic obstructive cardiomyopathy. Mitral insufficiency in all types and classes frequently corresponded with the X-ray findings of left atrial enlargement. The X-ray classification method proved to be an efficient approach and superior to the heart-to-lung ratio.

Adult↗
PubMed1990

[Current data on the prevalence and epidemiology of HIV from the HIV study by the German Red Cross of West Germany].

From the multicenter study of the Red Cross Blood Banks in the FRG HIV-antibody prevalences and incidences are documented since July 1985. Constantly low prevalences and incidences since 1987 of less than 2 Western blot (Wb)-positive donors and less than 1 Wb-positive donor per 100,000 donors respectively confirm our estimate of the rest risk of an HIV-infection by blood products of 1:500,000 to 1:3 million donations. In the epidemiologic details there seems to be a trend to an increase of the incidence in male repeat blood donors. The modes of HIV-infection in blood donors have changed to an increasing number of infections acquired in heterosexual contacts to persons at risk.

AIDS Serodiagnosis↗