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Biomedical subjects

C Lenz

Publications and source records attributed to C Lenz.

At least 55 records · Page 3Linked to original sources
PubMed1999

The phytoestrogens Genistein and Daidzein, and 17 beta-estradiol inhibit development of neointima in aortas from male and female rabbits in vitro after injury.

BACKGROUND: 17 beta-Estradiol and phytoestrogens are known to have beneficial effects on the cardiovascular systems of women. The exact mechanisms for how estrogens and phytoestrogens influence the cardiovascular system are not yet understood in detail. OBJECTIVE: The objective of this study was to investigate whether 17 beta-estradiol and the phytoestrogens Genistein and Daidzein have an effect on post-injury processes in vessel walls. METHODS: In this in-vitro experiment, the sex-specific effects of 50 micrograms/ml 17 beta-estradiol (equivalent to 180 mumol/l), and of the isoflavones Genistein (5 and 50 micrograms/ml, equivalent to 18.5 and 185 mumol/l), and Daidzein (5 and 50 micrograms/ml, equivalent to 19.7 and 197 mumol/l) on endothelium-denuded aortas from female and male rabbits after vascular injury were studied. Morphometry and immunohistochemistry were performed for quantitative and qualitative analysis. RESULTS: Neointimal cells were in part positive for alpha-actin staining of smooth muscle cells. Staining with 5'-bromo-2'deoxyuridine plus 2'-deoxycytidine showed that proliferative activity in the neointima had significantly decreased after 28 days for groups that had been treated with 50 micrograms/ml Genistein. Immunofluorescence staining for the expression of nuclear estrogen receptor protein in the arterial wall for aortic rings from female and male rabbits was positive. 17 beta-Estradiol, Genistein, and its analog Daidzein (with no protein tyrosine kinase activity) inhibited formation of neointima sex-independently at equivalent concentrations of 50 micrograms/ml. However, a concentration of 5 micrograms/ml Genistein decreased formation of neointima significantly for aortic rings from male rabbits only, whereas 5 micrograms/ml Genistein increased formation of neointima in rings from female rabbits, which corresponded to the increase in proliferative activity detected after 28 days. CONCLUSION: Genistein and Daidzein both inhibited proliferation at certain concentrations, so this effect is supposed to be independent from Genistein's protein tyrosine kinase activity. The antiproliferative properties of all three estrogens were observed in the absence of endothelium and therefore are independent from endothelium-mediated effects.

Actins↗
PubMed1999

Antiproliferative effect of a polysaccharide fraction of a 20% methanolic extract of stinging nettle roots upon epithelial cells of the human prostate (LNCaP).

In Germany, plant extracts are often used in the treatment of early stages of benign prostate hyperplasia (BPH). The effects of different concentrations of the polysaccharide fraction of the 20% methanolic extract of stinging nettle roots (POLY-M) on the cellular proliferation of lymph node carcinoma of the prostate (LNCaP) cells were determined by measurement of the genomic DNA content of the samples. All concentrations of POLY-M showed an inhibitory effect on the growth of the LNCaP cells during 7 days except the two lowest concentrations. The reduced proliferation of POLY-M treated LNCaP cells was significantly (p < 0.05) different from the untreated control. The inhibition was time- and concentration-dependent with the maximum suppression (50%) on day 6 and at concentrations of 1.0E-9 and 1.0E-11 mg/ml. No cytotoxic effect of POLY-M on cell proliferation was observed. The in vitro results show for the first time an antiproliferative effect of Urtica compounds on human prostatic epithelium and confirm our previous in vivo findings.

Antigens, Surface↗
PubMed1998

Improved ternary matrices for the analysis of ferri-pyoverdins by fast atom bombardment mass spectrometry.

The use of explosives as matrices, a principle used previously in plasma desorption mass spectrometry, was applied to fast atom bombardment mass spectrometry (FABMS). Ternary matrices were prepared by the addition of picric acid and related compounds to the binary matrix routinely used for the analysis of peptides, viz. thioglycerol-dithiodiethanol. With the new matrices, the spectra of three ferri-pyoverdins (iron-siderophore complexes which are often difficult to analyse by FABMS with standard matrices) showed a significant increase in both intensity and duration of the ion current. They present a valuable tool for the analysis of problematic analytes and for collision-induced dissociation MS/MS experiments.

Indicators and Reagents↗
PubMed1998

Induction of protein inhibitor of neuronal nitric oxide synthase/cytoplasmic dynein light chain following cerebral ischemia.

Administration of inhibitors of neuronal nitric oxide synthase or deletion of the encoding gene in rodents provided evidence that neuronal nitric oxide synthase activity may contribute to neuronal cell death following global and focal cerebral ischemia. In the present study, we investigated by in situ hybridization the expression of an endogenous inhibitor of neuronal nitric oxide synthase activity, designated protein inhibitor of neuronal nitric oxide synthase and homologous to cytoplasmic dynein light chain, in the post-ischemic rat brain. Following global ischemia induced by cardiac arrest, messenger RNA expression of protein inhibitor of neuronal nitric oxide synthase was rapidly induced in pyramidal neurons of the hippocampal CA3 region and granule cell of the dentate gyrus which are resistant to ischemic damage. In vulnerable CA1 pyramidal neurons however, protein inhibitor of neuronal nitric oxide synthase expression remained at basal level after global ischemia and was associated with an increase in nicotinamide adenine dinucleotide phosphate-diaphorase activity and subsequent DNA fragmentation indicating ischemia-mediated neuronal cell death. Following focal cerebral ischemia induced by permanent occlusion of the middle cerebral artery, transcripts of protein inhibitor of neuronal nitric oxide synthase progressively accumulated in cortical neurons bordering the infarct area. After transient middle cerebral artery occlusion however, messenger RNA levels of protein inhibitor of neuronal nitric oxide synthase increased in the reperfused neocortex. Our findings indicate that cerebral ischemia leads to an increase in neuronal expression of protein inhibitor of neuronal nitric oxide synthase in brain regions where sustained or "uncoupled" nitric oxide synthase activity may be detrimental to neurons. Lack of post-ischemic induction of protein inhibitor of neuronal nitric oxide synthase in CA1 pyramidal neurons may result in high nitric oxide synthase activity after global ischemia and could contribute to delayed neuronal cell death.

Animals↗
PubMed1998

Artificial oxygen carriers.

The clinical availability of artificial oxygen carriers (AOCs) would result in profound alterations in transfusion medical practice. Rapid progress in the scientific and technological development of AOCs has advanced to a critical stage at which safe and effective alternatives to the transfusion of red blood cells are emerging. Haemoglobin- and perfluorocarbon-based oxygen carriers are under current clinical investigation. Artificial oxygen-carrying solutions, by virtue of their acellular structure, can be used to transport oxygen to ischaemic tissues that cannot otherwise be reached by cellular blood components. Organs awaiting transplantation can be preserved for a long time after perfusion with AOCs and tumour susceptibility to chemo- and radiotherapy is increased. The use of AOCs is therefore not confined to their use as red blood cell substitutes, but may find a wide spectrum of interdisciplinary applications.

Blood Substitutes↗
PubMed1998

Local cerebral blood flow, local cerebral glucose utilization, and flow-metabolism coupling during sevoflurane versus isoflurane anesthesia in rats.

BACKGROUND: Compared to isoflurane, knowledge of local cerebral glucose utilization (LCGU) and local cerebral blood flow (LCBF) during sevoflurane anesthesia is limited. METHODS: LCGU, LCBF, and their overall means were measured in Sprague-Dawley rats (8 groups, n=6 each) during sevoflurane and isoflurane anesthesia, 1 and 2 MAC, and in conscious control animals (2 groups, n=6 each) using the autoradiographic 2-[14C]deoxy-D-glucose and 4-iodo-N-methyl-[14C]antipyrine methods. RESULTS: During anesthesia, mean cerebral glucose utilization was decreased: control, 56+/-5 micronmol x 100 g(-1) x min(-1); 1 MAC isoflurane, 32+/-4 micromol x 100 g(-1) x min(-1) (-43%); 1 MAC sevoflurane, 37+/-5 micromol x 100 g(-1) x min(-1) (-34%); 2 MAC isoflurane, 23+/-3 micromol x 100 g(-1) x min(-1) (-58%); 2 MAC sevoflurane, 23+/-5 micromol x 100 g(-1) x min(-1) (-59%). Local analysis showed a reduction in LCGU in the majority of the 40 brain regions analyzed. Mean cerebral blood flow was increased as follows: control 93+/-8 ml x 100 g(-1) x min(-1); 1 MAC isofurane, 119+/-19 ml x 100 g(-1) x min(-1) (+28%); 1 MAC sevoflurane, 104+/-15 ml x 100 g(-1) x min(-1) (+12%); 2 MAC isoflurane, 149+/-17 ml x 100 g(-1) x min(-1) (+60%); 2 MAC sevoflurane, 118+/-21 ml x 100 g(-1) min(-1) (+27%). LCBF was increased in most brain structures investigated. Correlation coefficients obtained for the relationship between LCGU and LCBF were as follows: control 0.93; 1 MAC isoflurane, 0.89; 2 MAC isoflurane, 0.71; 1 MAC sevoflurane, 0.83; 2 MAC sevoflurane, 0.59). CONCLUSION: Mean and local cerebral blood flows were lower during sevoflurane than during isoflurane anesthesia. This difference cannot be explained by differing changes in glucose utilization because glucose utilization was decreased to the same extent in both groups.

Anesthesia↗
PubMed1998

Effect of the antioxidant Nicanartine on the proliferative and inflammatory response after experimental balloon angioplasty.

BACKGROUND: Antioxidant treatment seems to reduce the development of restenosis after percutaneous transluminal angioplasty. In this study, the effect of Nicanartine, a new antioxidant drug with both antiproliferative and lipid-lowering properties, on the proliferative and inflammatory response after balloon angioplasty was investigated in a rabbit model of restenosis. METHODS: To induce pre-interventional plaques in the common carotid artery of 48 New Zealand White rabbits, electrostimulation was carried out for 28 days. After a break of 7 days, balloon angioplasty was performed in 36 animals, of which 18 received Nicanartine at a dose of 120 mg/kg body weight; the other 18 served as a control group. The vessels were excised by day 7 and 28 after balloon angioplasty and examined for intimal plaque size, macrophage content and proliferative activity. Bromodeoxyuridine labeling was used to determine proliferating cells in the dilated segment; macrophages were detected using the RAM-11 antibody. RESULTS: In the Nicanartine-treated group, immunohistological quantification 7 days after intervention showed a statistically significant (P< 0.05) reduction of both cells undergoing DNA synthesis (1.6+/-1.4% versus 3.7+/-2.2%) and intimal macrophages (0.7+/-1.2% versus 1.3+/-0.6%). Twenty-eight days after balloon angioplasty, proliferative activity in both groups was decreased to a level comparable to the non-dilated control groups. A clear trend towards smaller plaques could be seen in the Nicanartine group (0.146+/-0.077 mm2 versus 0.255+/-0.174 mm2). Total cholesterol levels did not differ significantly between the groups. CONCLUSION: Under treatment with Nicanartine a clear reduction in the proliferative and inflammatory response after balloon angioplasty was observed. Antioxidant treatment, especially with compounds having antiproliferative and lipid-lowering properties, appears to be an effective secondary preventive strategy after interventional treatment in patients with coronary artery disease.

Angioplasty, Balloon↗
PubMed1998

Does anti-atherogenic estradiol valerate treatment cause adverse effects on liver and uterus in NZW rabbits?

The rabbit has been a widely accepted animal model for atherosclerosis research since Anitschkow first used this animal in 1913 in identifying dietary-induced hypercholesterolemia as a major risk factor for atherogenesis. Experiments with cholesterol-fed rabbits have demonstrated the beneficial effects of estrogen treatment on the development of atheroma for more than 50 y. Clinical trials have found a reduction in cardiovascular events of up to 50% in postmenopausal women receiving estrogen replacement therapy. However, metabolic conditions in rabbits, as well as physiological estrogen serum levels, differ in some aspects from those in humans. In rabbits, experimentally-induced hormone levels are about 5- to 10-fold higher than those found in untreated animals. Normal physiological estrogen levels in rabbits are not cardioprotective under dietary-induced hypercholesterolemia. We investigated whether replacement induced "hyperestrogenemia" causes adverse effects on organs other than the cardiovascular system. Twenty-nine female rabbits were divided into 4 different groups, 2 without and 2 with estrogen treatment (1 mg estradiol valerate/kg body weight/w over 12 w). Organ weights, transaminases and uterine histology were examined. In rabbits treated with estrogen, we did not see relevant adverse effects on heart, kidney and liver weights, or on liver enzymes. But there was a significant increase in spleen weights, as well as notable changes in the endometrium with moderate inflammation. These findings indicate that the dosage of estrogen commonly used for atherosclerosis research does not cause serious disorders in the major organs of cholesterol-fed rabbits.

Animals↗
PubMed1997

Focal cerebral ischemia enhances glial expression of ecto-5'-nucleotidase.

The effect of ischemia on the reactive expression of ecto-5'-nucleotidase in rat brain was studied 6 h and 1, 2 and 7 days after permanent middle cerebral artery occlusion (MCAO). The distribution of 5'-nucleotidase in the infarcted brain was compared to markers for astrocytes (glial fibrillary acidic protein (GFAP)) and microglia (complement receptor type 3, antibody OX42) using histological staining or immunohistochemistry. 5'-Nucleotidase could be associated with reactive astrocytes by immunohistochemistry and with reactive microglia by enzyme histochemistry. In the untreated control 5'-nucleotidase was associated with astrocytes only in the hippocampus and the submeningeal space. After ischemia the enzyme was expressed on reactive astrocytes in the tissue surrounding the volume of infarction. Individual reactive astrocytes were observed 6 h after MCAO and the astrocytic expression became continuously enhanced during the following days. An enzyme histochemical analysis of 5'-nucleotidase activity revealed a postischemic increase in reaction product around the infarcted tissue. Seven days after MCAO a discrete band (0.2-0.4 mm) of reaction product characterized the rim of the infarcted area. This band of activity of 5'-nucleotidase colocalized with a band of immunoreactivity for OX42, indicative of an intense accumulation of 5'-nucleotidase expressing microglia. Our results suggest that ischemia following permanent MCAO results in an upregulation of the capacity for the hydrolysis of nucleotides within the tissue adjacent to the infarcted volume. Nucleotides released from the damaged cells can be hydrolyzed and the adenosine eventually formed may exert neuroprotective functions limiting the extent of damage.

5'-Nucleotidase↗
PubMed1997

Exon 1 leader sequences downstream of U5 are important for efficient human immunodeficiency virus type 1 gene expression.

In previous studies, little attention has been paid to maintaining the native HIV-1 leader sequence in reporter constructs analyzing the human immunodeficiency virus type 1 (HIV-1) promoter activity. To investigate a possible influence of the leader sequence on HIV-1-driven gene expression in the presence as well as in the absence of Tat, an expression vector was designed for transcripts consisting of the native HIV-1 tat 1.4 mRNA leader followed by the open reading frame for the bacterial chloramphenicol acetyltransferase (CAT). Deletion mutants with mutations within the leader sequence downstream of U5 (lsdU5) were constructed, as well as a mutant containing a mutation with a reverse orientation of this region. Quantification of CAT protein in HeLa-T4+ cells transiently transfected with wild-type and mutant leader constructs showed that the exon 1-derived lsdU5 region has an influence on basal as well as Tat-induced protein expression. The dramatic decrease in the level of CAT protein upon deletion of lsdU5 was paralleled by a drop in the steady-state level of CAT mRNA. Deletion of the exon 1-derived lsdU5 region also decreased the expression of mRNAs containing authentic HIV-1 sequences instead of CAT. The effect observed with the reporter constructs was not due to the loss of binding sites for nuclear factors, as could be shown with DBF1 and Sp1 mutant constructs. Nuclear run-on transcription assays showed that the presence or absence of lsdU5 did not influence the rate of transcription. This indicates that the exon 1 lsdU5 element functions at the posttranscriptional level in the processing, nucleocytoplasmic export, or stabilization of HIV-1 transcripts.

Binding Sites↗
PubMed1996

Altered expression of Bcl-2, Bcl-X, Bax, and c-Fos colocalizes with DNA fragmentation and ischemic cell damage following middle cerebral artery occlusion in rats.

Permanent occlusion of the middle cerebral artery in rats was used to assess the effects of focal ischemia on the expression of members of the bcl-2 family which have been implicated in the regulation of programmed cell death. Intraluminal occlusion of one middle cerebral artery for 6 h resulted in histologically detectable brain damage within the ipsilateral caudate putamen, basolateral cortex and parts of the thalamus. In the infarcted basolateral cortex and thalamus fragmentation of DNA was detected in many nuclei using in-situ end-labeling of DNA breaks by terminal transferase, whereas only scattered labeled nuclei were visible in the infarcted caudate putamen. Immunohistochemical analysis revealed activation of c-Fos in the infarcted cortex and thalamus and in the non-infarcted cingulate cortex as has been shown by others. A decrease in immunoreactivity for Bcl-2, and Bcl-X and an increase in immunostaining for Bax was observed exclusively in neurons within the ischemic cortex and thalamus. Within the infarcted caudate putamen, however, protein levels of all bcl-2 family members declined and c-Fos remained absent. By reverse transcription and polymerase chain reaction it was demonstrated that levels of bcl-2 mRNA markedly decreased in the ipsilateral hemisphere, whereas the amount of bax mRNA was elevated. These findings suggest that a shift in the ratio of cell death repressor Bcl-2 to cell death effector Bax and a concomitant activation of c-Fos may contribute to neuronal apoptosis in the infarcted thalamus and cortex.

Animals↗
PubMed1996

Evidence for apoptotic cell death in the choroid plexus following focal cerebral ischemia.

Focal cerebral ischemia in rats subjected to middle cerebral artery (MCA) occlusion results in apoptotic DNA fragmentation and activation of putative cell death effector genes in neurons and functional impairment of the plexus choroideus. In the present study we investigated whether cerebral ischemia may induce apoptotic cell death in the choroid plexus. Using in situ end-labeling by terminal transferase and fluorescein-dUTP, nuclear DNA breaks were detected in the choroid plexus of the lateral ventricle of the ischemic hemisphere after 6 h but not after 1.5 h of MCA occlusion. Intense cytoplasmic immunostaining for pro-apoptotic Bax protein and moderate immunolabeling for Bcl-X was observed in the epithelium of the choroid plexus of the lateral and third ventricles. However, constitutive expression of Bax and Bcl-X proteins in the plexus choroideus did not change significantly following focal ischemia. Thus, cells of the choroid plexus may die by apoptosis after several hours of cerebral ischemia. Modulation of cell death effector genes of the bcl-2 family however, may not be required for apoptotic cell death to occur.

Animals↗
PubMed1996

A program for the user-independent computation of the correlation dimension and the largest Lyapunov exponent of heart rate dynamics from small data sets.

We propose a specially optimized computer program for the user-independent calculation of the correlation dimension D and the largest Lyapunov exponent L of heart rate dynamics on the basis of only 1024 electrocardiographically recorded RR intervals (heartbeat intervals). The validity of our program was established by analyzing a set of artificial standard signals. Our norm values of the correlation dimension (D = 5.37 +/- 0.62) and the largest Lyapunov exponent (L = 0.561 +/- 0.037 bits/beat) of RR dynamics, obtained from 79 healthy adults aged 26.3 +/- 4.8 years, were independent of gender and age; D and L correlated slightly with each other (Pearson correlation coefficient r = 0.26). Short-term reliability, tested for 25 of our subjects by two successive recordings, was fair: the intraclass correlation coefficients (ICCs) were 0.45 and 0.41 for D and L of RR dynamics, respectively. However, long-term reliability, tested for eight of our subjects by ten weekly recordings, was acceptable for L (ICC = 0.40) but not for D (ICC = 0.01). These results permit group comparisons on the basis of single measurements of L of RR dynamics. A reliable differentiation between young healthy individuals requires four measurements of L.

Adult↗