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K Meyer

Publications and source records attributed to K Meyer.

At least 73 records · Page 4Linked to original sources
PubMed2001

[Liver sonography and ultrasound-guided puncture of the gallbladder in pigs: new possibilities for the diagnosis of mycotoxicosis].

60 pigs representing all age groups (suckling pigs, weaner pigs, hogs, gilts and sows; thereof 37 females, 2 males, 21 castrated males) were examined by ultrasound of the liver and by ultrasound guided gallbladder puncture. The visibility of the liver and gallbladder was strongly influenced by the size of the animals. The thickness of the abdominal and thoracic walls in older animals proved to be a highly ultrasound-absorptive medium, which limited the ability to assess the underlying tissue structures. As a result, gallbladder puncture of these animals was possible only with a certain degree of technical difficulty. The gallbladder puncture procedure itself posed little risk to the animal. The primary risk resulted from the general anesthesia required. Autopsy showed no pathological findings due to gallbladder puncture with the exception of minimal, rapidly healing, local infectious processes. The bile proved to be a suitable medium of the detection of mycotoxins and their metabolites. Selective accumulation of these toxins in bile provide a more reliable diagnostic tool than the standard mycotoxicological tests of feed.

Animals↗
PubMed2001

Historical biogeography of Melastomataceae: the roles of Tertiary migration and long-distance dispersal.

Melastomataceae and Memecylaceae are pantropically distributed sister groups for which an ndhF gene phylogeny for 91 species in 59 genera is here linked with Eurasian and North American fossils in a molecular clock approach to biogeographical reconstruction. Nine species from the eight next-closest families are used to root phylogenetic trees obtained under maximum likelihood criteria. Melastomataceae comprise ∼3000 species in the neotropics, ∼1000 in tropical Asia, 240 in Africa, and 225 in Madagascar in 150-166 genera, and the taxa sampled come from throughout this geographic range. Based on fossils, ranges of closest relatives, tree topology, and calibrated molecular divergences, Melastomataceae initially diversified in Paloecene/Eocene times in tropical forest north of the Tethys. Their earliest (Eocene) fossils are from northeastern North America, and during the Oligocene and Miocene melastomes occurred in North America as well as throughout Eurasia. They also entered South America, with earliest (Oligocene) South American fossils representing Merianieae. One clade (Melastomeae) reached Africa from the neotropics 14-12 million years ago and from there spread to Madagascar, India, and Indochina. Basalmost Melastomataceae (Kibessieae, Astronieae) are species-poor lineages restricted to Southeast Asia. However, a more derived Asian clade (Sonerileae/Dissochaeteae) repeatedly reached Madagascar and Africa during the Miocene and Pliocene. Contradicting earlier hypotheses, the current distribution of Melastomataceae is thus best explained by Neogene long-distance dispersal, not Gondwana fragmentation.

Journal Article↗
PubMed2000

Functional features of hepatitis C virus glycoproteins for pseudotype virus entry into mammalian cells.

We have previously reported the generation of pseudotype virus from chimeric gene constructs encoding the ectodomain of the E1 or E2 glycoprotein of hepatitis C virus (HCV) genotype 1a appended to the trans membrane domain and cytoplasmic tail of the vesicular stomatitis virus (VSV) G protein. Sera derived from chimpanzees immunized with homologous HCV glycoproteins neutralized pseudotype virus infectivity (L. M. Lagging et al., J. Virol. 72, 3539-3546, 1998). We have now extended this study to further understand the role of HCV glycoproteins in pseudotype virus entry. Although a number of mammalian epithelial cells were susceptible to VSV/HCV pseudotype virus infection, plaquing efficiency was different among host cell lines. Pseudotype virus adsorption at low temperature decreased plaque numbers. Treatment of E1 or E2 pseudotype virus in media between pH 5 and 8 before adsorption on cells did not significantly reduce plaque numbers. On the other hand, treatment of cells with lysosomotropic agents or inhibitors of vacuolar H(+) ATPases had an inhibitory role on virus entry. Concanavalin A, a plant lectin, exhibited neutralization of both HCV E1 and E2 pseudotype virus infectivity. However, mannose binding protein, a C-type mammalian lectin, did not neutralize virus in the absence or presence of serum complement. Pseudotype virus infectivity was only partially inhibited by heparin, a highly sulfated glycosaminoglycan, in a saturable manner. Additional studies suggested that low-density lipoprotein receptor related molecules partially inhibit E1 pseudotype virus infectivity, while CD81 related molecules interfere with E2 pseudotype virus infectivity. A further understanding of HCV entry and strategies appropriate for mimicking cell surface molecules may help in the development of new therapeutic modalities against HCV infection.

Antigens, CD↗
PubMed2000

Selective regulatory effects of purine and pyrimidine nucleotides on vacuolar transport of amino acids.

The release of amino acids from their vacuolar store was studied in situ, i.e. in cells with selectively permeabilized plasma membrane and functionally intact vacuoles. As we previously described [Roos et al., J. Biol. Chem. 272 (1997) 15849-15855], this transport process is regulated by extravacuolar adenylates at their physiological concentrations. We now show, using our test object Penicillium cyclopium, that not only purine but also pyrimidine nucleotides are involved in the control of efflux of vacuolar phenylalanine. At 0.1 mM adenosine or guanosine phosphates inhibit, whereas cytidine or uridine phosphates stimulate the rate of efflux. At 1 mM the same nucleotides have no measurable impact on efflux but abolish the effects of other nucleotides present at 0.1 mM. This argues for at least two interacting binding sites with different nucleotide affinities. The minimum structural requirement for any of the observed effects is a non-cyclic ribonucleoside monophosphate. In intact cells, cytosolic concentrations of ATP (representing purine nucleotides) and CTP (representing pyrimidine nucleotides) are 1-2 mM and 0.05-0.2 mM, respectively. ATP is therefore assumed to dominate transport control and allow optimum efflux (and uptake) rates. Short-time starvation of carbon and nitrogen adjusts CTP and ATP at levels that cause declining efflux rates. During prolonged starvation both nucleotides fall below their transport-controlling concentrations and thus allow increasing rates of efflux from the still maintained vacuolar pool. Hence, efflux control under nutrient limitation includes an interplay of purine and pyrimidine nucleotides which precisely regulates the release of vacuolar amino acids and enables flexible adjustment to either amino acid saving or cell survival.

Amino Acid Transport Systems↗
PubMed2000

Hepatitis C virus core protein promotes immortalization of primary human hepatocytes.

Hepatitis C virus (HCV) core protein has many intriguing properties as a viral factor and is implicated in cell growth regulation. In this study, the cell growth regulation potential of HCV core protein was investigated by introduction of the core genomic region into primary human hepatocytes, a natural host for virus replication and tropism. Core-transfected primary human hepatocytes displayed altered cell morphology resembling that of low-differentiated epithelial cells. Those cells retained an immortalized phenotype and exhibited continuous growth after more than 50 passages over 2 years. Stable hepatocyte transfectants exhibited albumin secretion and HCV core protein expression. Telomerase activity, a characteristic of immortalized or transformed cells, was evident in the transfected hepatocytes immediately after senescence. Anchorage-independent growth of the immortalized hepatocytes provided further evidence for a transformed phenotype. Results from these studies suggest that the HCV core protein promotes primary human hepatocytes to an immortalized phenotype, which may predispose cells over an extended period of time to undergo a transforming event. Thus, HCV core protein appears to contribute to virus-mediated pathogenesis in a persistently infected host.

Adult↗
PubMed2000

[Hematopoietic stem cells II. Diagnostic and therapeutic aspects].

Characterization and isolation of haematopoietic stem cells (HSC) have resulted in their clinical application in patients with malignant disorders and--through gene therapeutic initiatives--also in the treatment of inherited diseases. Autologous stem cell transplantation (ASCT), which was introduced because of the high number of relapses in cancer patients in remission, involves dose-intensification (conditioning), which induces myeloablation. In this setting, reinfusion of HSC is performed to restore haematopoiesis. Flow cytometric determination of CD34+ cells and clonogenic assays for committed myeloid HSC (CFU-GM) are vehicles for quality control of the harvested HSC material and are integrated into the ASCT programs. Moreover, harvest of HSC and purification of CD34+ cells enables new treatment options such as removal of cancer cells from grafts, optimization of gene transduction as well as ex vivo expansion of HSC before reinfusion. In conclusion, the expanding insights into HSC in the 1990's have already been translated into valuable diagnostic and therapeutic modalities.

Antigens, CD34↗
PubMed2000

Serum androgen levels in adolescents with type 1 diabetes: relationship to pubertal stage and metabolic control.

Delayed sexual maturation is still frequently seen in adolescents with type 1 diabetes. A close relationship between insulin and androgen metabolism has been found in a number of studies. Our study was designed to investigate whether or not abnormalities in androgen secretion could play a role in the onset of sexual maturation in adolescents with type 1 diabetes. We have asked whether or not there was a correlation between daily insulin dosage, duration of diabetes, metabolic control, age, pubertal stage, and body mass index (BMI) versus serum androgen concentrations. Basal total and free testosterone, dehydroepiandrosterone-sulfate (DHEA-S), dihydrotestosterone (DHT), sex hormone binding globulin (SHBG) and 3alpha-androstanediol glucuronide (3alpha diol-G) plasma concentrations were measured in 36 pubertal boys and 31 pubertal girls with type 1 diabetes and in 59 sex- and pubertal stage-matched control subjects without diabetes. Significantly higher serum total testosterone (p<0.01) and free testosterone (p<0.05) levels were found in females and males with type 1 diabetes than in controls at pubertal stage 5. DHEA-S, SHBG, DHT and 3alpha diol G concentrations in patients with diabetes were not significantly different from those in controls. There was no correlation between daily insulin requirements and serum androgen levels. These data suggest that adolescents with diabetes have similar serum levels of DHEA-S, SHBG, DHT and 3alpha diol G as healthy subjects at all stages of puberty. However, there are significant differences in serum testosterone and free testosterone levels in adolescents with diabetes when compared to healthy, sex- and pubertal stage-matched controls in late puberty. We hypothesize that the increased testosterone levels in patients with diabetes could relate to reduced fertility in females, disorders of sexual maturation and an increased risk for cardiovascular complications later in life.

Adolescent↗
PubMed2000

Hepatitis C virus NS5A protein protects against TNF-alpha mediated apoptotic cell death.

Hepatitis C virus (HCV) often causes a prolonged and persistent infection which may lead to hepatocellular carcinoma. We have previously reported that the nonstructural 5A (NS5A) protein of HCV promotes cell growth [Ghosh, A.K., Steele, R., Meyer, K., Ray, R., Ray, R.B., 1999. Hepatitis C virus NS5A protein modulates cell cycle regulatory genes and promotes cell growth. J. Gen. Virol. 80, 1179-1183]. In this study, we investigated the role of HCV NS5A (genotype 1a, strain H) in TNF-alpha induced apoptotic cell death. HepG2 cells expressing NS5A exhibited an inhibitory role in relation to TNF-alpha mediated apoptotic cell death. The NS5A protein blocked the activation of caspase-3 and inhibited proteolytic cleavage of the death substrate poly (ADP-ribose) polymerase in TNF-alpha induced cells. Together, these results suggest that HCV NS5A protein protects against TNF-alpha mediated apoptotic cell death.

Blotting, Western↗
PubMed2000

Modified lignin in tobacco and poplar plants over-expressing the Arabidopsis gene encoding ferulate 5-hydroxylase.

Ferulate 5-hydroxylase (F5H) is a cytochrome P450-dependent monooxygenase that catalyses the hydroxylation of ferulic acid, coniferaldehyde and coniferyl alcohol in the pathways leading to sinapic acid and syringyl lignin biosynthesis. Earlier studies in Arabidopsis have demonstrated that F5H over-expression increases lignin syringyl monomer content and abolishes the tissue-specificity of its deposition. To determine whether this enzyme has a similar regulatory role in plants that undergo secondary growth, we over-expressed the F5H gene in tobacco and poplar. In tobacco, over-expression of F5H under the control of the cauliflower mosaic virus 35S promoter increased lignin syringyl monomer content in petioles, but had no detectable effect on lignification in stems. By contrast, when the cinnamate 4-hydroxylase (C4H) promoter was used to drive F5H expression, there was a significant increase in stem lignin syringyl monomer content. Yields of thioglycolic acid and Klason lignin in C4H-F5H lines were lower than in the wild-type, suggesting that F5H over-expression leads to a reduced deposition or an altered extractability of lignin in the transgenic plants. Histochemical analysis suggested that the novel lignin in C4H-F5H transgenic lines was altered in its content of hydroxycinnamyl aldehydes. Transgenic poplar trees carrying the C4H-F5H transgene also displayed enhanced lignin syringyl monomer content. Taken together, these data show that hydroxylation of guaiacyl-substituted lignin precursors controls lignin monomer composition in woody plants, and that F5H over-expression is a viable metabolic engineering strategy for modifying lignin biosynthesis in forest species.

Arabidopsis↗
PubMed2000

Differential ability of heparan sulfate proteoglycans to assemble the fibroblast growth factor receptor complex in situ.

Fibroblast growth factors (FGFs) require heparan sulfate proteoglycans (HSPGs) as cofactors for signaling. The heparan sulfate chains (HS) mediate stable high affinity binding of FGFs to their receptor tyrosine kinases (FR) and may specifically regulate FGF activity. A novel in situ binding assay was developed to examine the ability of HSPGs to promote FGF/FR binding using a soluble FR fusion construct (FR1-AP). This fusion protein probe forms a dimer in solution, simulating the dimerization or oligomerization that is thought to occur at the cell surface physiologically. In frozen sections of human skin, FGF-2 binds to keratinocytes and basement membranes of epidermis and dermal blood vessels. In contrast, in skin preincubated with FGF-2, FR1-AP binds avidly to FGF-2 immobilized on keratinocyte cell surfaces, but fails to bind to basement membranes at the dermo-epidermal junction or dermal microvessels despite the fact that these structures bind large amounts of FGF-2. Apparently, basement membrane and cell surface HSPGs differ in their ability to mediate the assembly of a FGF/FR signaling complex presumably due to structural differences of the heparan sulfate chains.

Animals↗
PubMed2000

Cloning of the SNG1 gene of Arabidopsis reveals a role for a serine carboxypeptidase-like protein as an acyltransferase in secondary metabolism.

Serine carboxypeptidases contain a conserved catalytic triad of serine, histidine, and aspartic acid active-site residues. These enzymes cleave the peptide bond between the penultimate and C-terminal amino acid residues of their protein or peptide substrates. The Arabidopsis Genome Initiative has revealed that the Arabidopsis genome encodes numerous proteins with homology to serine carboxypeptidases. Although many of these proteins may be involved in protein turnover or processing, the role of virtually all of these serine carboxypeptidase-like (SCPL) proteins in plant metabolism is unknown. We previously identified an Arabidopsis mutant, sng1 (sinapoylglucose accumulator 1), that is defective in synthesis of sinapoylmalate, one of the major phenylpropanoid secondary metabolites accumulated by Arabidopsis and some other members of the Brassicaceae. We have cloned the gene that is defective in sng1 and have found that it encodes a SCPL protein. Expression of SNG1 in Escherichia coli demonstrates that it encodes sinapoylglucose:malate sinapoyltransferase, an enzyme that catalyzes a transesterification instead of functioning like a hydrolase, as do the other carboxypeptidases. This finding suggests that SCPL proteins have acquired novel functions in plant metabolism and provides an insight into the evolution of secondary metabolic pathways in plants.

Acyltransferases↗
PubMed2000

Mycophenolic acid in silage.

We examined 233 silage samples and found that molds were present in 206 samples with counts between 1 x 10(3) and 8.9 x 10(7) (mean, 4.7 x 10(6)) CFU/g. Mycophenolic acid, a metabolite of Penicillium roqueforti, was detected by liquid chromatography-mass spectrometry in 74 (32%) of these samples at levels ranging from 20 to 35,000 (mean, 1,400) microg/kg. This compound has well-known immunosuppressive properties, so feeding with contaminated silage may promote the development of infectious diseases in livestock.

Chromatography, Liquid↗
PubMed2000

Cortisol and 17-hydroxyprogesterone levels in saliva of healthy neonates: normative data and relation to body mass index, arterial cord blood ph and time of sampling after birth.

The measurement of cortisol and 17-hydroxyprogesterone (17-OHP) in saliva has become a reliable tool for both the scientist and the clinician for studying adrenal cortical function in the adult and the older child. We have now established in parallel normative data for salivary cortisol and 17-OHP levels in healthy neonates. We have asked whether or not there is a circadian rhythm of cortisol and 17-OHP saliva levels in neonates. Furthermore, we have asked whether salivary hormone levels correlated with auxologic and clinical data and time of sampling. Cortisol and 17-OHP levels in saliva samples from 119 healthy neonates (55 girls, 64 boys) were measured using in-house time-resolved fluorescent immunoassays. Saliva samples were obtained using a saliva collecting tube three times a day on the first or second day of life. Gender and gestational age did not influence salivary cortisol and 17-OHP levels. No significant circadian rhythm of salivary hormone levels was detected in this group of newborns. However, body mass index, arterial cord blood pH and time of saliva sampling significantly influenced salivary hormone levels. In conclusion, measurement of cortisol and 17-OHP in saliva is feasible in healthy neonates. The existence of normative data forms the basis for future studies on pathophysiologic states in the newborn period.

17-alpha-Hydroxyprogesterone↗
PubMed2000

Single photon emission computed tomographic evaluation of brainstem release phenomenon and seizure in neonates.

We report the ictal brain single photon emission computed tomographic (SPECT) findings in two neonates. One neonate had hypoxic-ischemic encephalopathy, a disorganized discontinuous electroencephalogram (EEG) background, lethargy, seizures, and brainstem release phenomena. A brain SPECT was performed during a brainstem release phenomenon characterized by a 34-second sustained tonic posture of the right arm and chewing. It did not reveal focal cerebral hemisphere hyperfusion. The second neonate had hemimegalencephaly, low-voltage irregular EEG background, and seizures. A brain SPECT was performed during a seizure characterized by a 32-second sustained tonic posture of the right arm. It revealed focal hyperperfusion in the posterior region of the left hemisphere. The brain SPECT findings in these patients indicate that despite clinically similar events, brainstem release phenomena and seizures have different perfusion characteristics, and refute the theory that brainstem release phenomena are due to epileptic foci in the cerebral hemispheres undetectable by EEG.

Brain↗
PubMed2000

[Flupenthixol--a partial atypical neuroleptic?].

There is no really clear-cut definition for "atypical" neuroleptics. The most convincing definition is draft by characterization of the receptor-binding profile. Most important are: the combined antagonism of D2 and 5-HT2 receptors, the preferential binding to D4 and D3 receptors and a balanced relation of D2 to D1 antagonism. Flupentixol fits into this description as well as some modern neuroleptics widely considered as "atypical" neuroleptics. Clinical criteria--like the absence of EPMS and the improvement of negative symptoms--offer no clear-cut distinction between "typical" and "atypical" neuroleptics, too, because some modern "atypical" neuroleptics lead--dose-dependent--to EPMS, and there is no proven efficacy for some atypical neuroleptics in the treatment of negative symptoms. So, neuroleptics are labelled "atypical" if there is a favourable relation between antipsychotic activity and the degree of EPMS, and if there is at least some efficacy in the treatment of negative symptoms. In this regard, Flupentixol has to be labelled at least a "partial atypical neuroleptic".

Animals↗
PubMed2000

[Diagnosis and therapy of leg and pelvic deep vein thrombosis in pregnancy].

OBJECTIVE: To establish differences in the management of acute thrombosis in the deep venous system associated with pregnancy in patients undergoing thrombectomy and in patients receiving heparin therapy. MATERIALS AND METHODS: From 1984 to 1995 the course of pregnancy was assessed retrospectively in 26 patients with acute deep vein thrombosis. Thirteen patients underwent thrombectomy with establishment of an arteriovenous fistula and 13 patients received conservative treatment with heparin therapy. In addition to the assessment of clinical symptoms, signs of thrombosis, diagnoses established with imaging techniques and of laboratory parameters, early complications and obstetric data obtained in surgically and conservatively treated patients were compared. RESULTS: The incidence of deep vein thrombosis in the 26 patients (median age 28 years) was 0.21%. In 53.8% of the cases the occurrence of thrombosis was observed in the second trimester (median: 27.5 weeks of gestation). The presence of risk factors was demonstrated in 58% of cases. The most frequently reported symptoms were swelling of the affected leg (88.5%) and pain (61.5%). A marked predilection for the left leg was recorded in 88% of cases. In contrast to phlebography, twice the number of sonographic studies were performed. The comparison of both therapeutic regimes showed a three-fold increase in the rate of early complications in patients after thrombectomy. The rate of recurrent thrombosis in these patients was 58.3% compared to a recurrence rate of 15.4% in patients undergoing heparin therapy. CONCLUSIONS: Recurrent thrombosis and pulmonary embolism represent the most frequent complications associated with thrombosis in the deep venous system during pregnancy. Although currently there is a lack of conclusive data on the development of postthrombotic syndrome, heparin therapy appears to be associated with fewer maternal risks. Interdisciplinary cooperation is urgently needed.

Adult↗
PubMed2000

[Occurrence of zearalenone, alpha- and beta-zearalenol in bile of breeding sows in relation to reproductive performance].

Although zearalenone-induced reproductive disorders and the clinical appearance of hyperestrogenism were reproduced and documented quite often the role of zearalenone-contaminated fodder as a cause for fertility problems in sow breeding is still discussed controversial. Therefore the correlation of zearalenone and zearalenone-derivatives in bile (n = 794) and feed (n = 158) with fertility problems of unknown origin was investigated in this study. For the analysis of zearalenone and its derivatives in bile a HPLC/EIA combination was used. On the one hand, this procedure guaranteed the quantitatively reproducible detection, on the other hand, the investigation expenditure could be kept small with regard to a later effort in the routine diagnostics. The detection limits for zearalenone, alpha- and beta-zearalenol in bile were at 1.0 ng/ml, 1.0 ng/ml, and 3.0 ng/ml, respectively. Results were confirmed by GC-MS. Zearalenone and zearalenone-derivatives were detected in almost every bile analysed. The contamination rate was 96.2%. In opposition to recent investigations beta-zearalenol was perceived as a relevant metabolite in swine. The contamination rate of feeding stuffs was 25.9%. Incubation of samples with beta-glucosidase did not elevate the detected amounts of zearalenone. As the measurable concentrations in bile and fodder were only slightly correlated the analysis of bile represents a reasonable alternative for fodder investigation. However, a correlation between the occurrence of zearalenone, alpha- and beta-zearalenol in bile of sows and non-infectious reproductive disorders could not be established at the loading level found. These results are in line with those statements obtained in feeding experiments regarding the risk evaluation of zearalenone in sow reproduction.

Animal Feed↗