Biomedical subjects

H Hoeger

Publications and source records attributed to H Hoeger.

34 records · Page 2Linked to original sources

PubMed1998

Mitochondrial oxygen consumption, lipid peroxidation and antioxidant enzyme systems in skeletal muscle of senile dystrophic mice.

To evaluate age-dependent abnormalities in mitochondrial redox metabolism specifically in dystrophic skeletal muscle, oxygen consumption, thiobarbituric acid reactivity (TBARS), free-radical scavengers and oxidative marker enzymes were measured in the skeletal muscle from adult and senile control (C57BL/10) and dystrophic (mdx/+) mice. Mitochondrial oxygen consumption in state 3 was significantly lowered with age in the senile dystrophic (-52%) and less markedly in the senile control (-30%) skeletal muscle. Compared with adult muscle, mitochondrial concentration of TBARS and cellular concentration of lipofuscin were significantly increased in senile control and dystrophic muscle. Enzymatic activity of glutathione peroxidase (GSH-Px) and concentration of alpha-tocopherol were significantly increased in the senile control (GSH-Px 43+/-5.7 vs 53+/-8.7 U/g protein, alpha-tocopherol 0.19+/-0. 09 vs 0.29+/-0.14 micromol/g total lipids), but significantly decreased in the senile dystrophic (GSH-Px 80+/-8.0 vs 53+/-12 U/g protein, alpha-tocopherol 0.45+/-0.13 vs 0.19+/-0.03 micromol/g total lipids) muscle. Selenium content was significantly decreased only in senile dystrophic muscle (1.37+/-0.42 vs 0.78+/-0.21 nmol/g wet muscle). In conclusion, the enzymatic adaptation to reactive oxygen species was limited in the dystrophic skeletal muscle, suggesting a higher need for antioxidants, especially alpha-tocopherol.

Aging↗

PubMed1998

Deficient transcription of subunit RPA 40 of RNA polymerase I and III in heart of rats with neonatal asphyxia.

RNA polymerases transcribe nuclear genes for ribosomal RNA thus representing ribosomal biogenesis. RNA polymerase I transcribes class I genes, coding for large ribosomal RNA and is located in the nucleolus. RNA polymerase III transcribes class III genes, those that encode a number of small ribosomal RNA molecules. Both RNA polymerases form ribosomal biogenesis in a concerted action and have a common subunit, RPA40, essential for function and integrity. The aim of our study was to study the influence of hypoxia/asphyxia on transcription of this subunit as deterioration of ribosomal biogenesis may not be compatible with life. To test this hypothesis we used a nonsophisticated model of neonatal asphyxia. Rat pups were exposed to various asphyctic periods up to twenty minutes and heart tissue was taken for the evaluation of mRNA RPA40 levels, pH measurements and histological evaluation of the nucleolus by silver staining. mRNA RPA40 levels gradually decreased with the length of the asphyctic period paralleling the decrease of pH. Silver staining was remarkably decreased at the asphyctic period of 20 minutes. Our findings of decreased transcription of this essential RNA polymerase subunit indicate impairment of the ribosomal RNA synthetizing machinery and the histological findings suggest its structural relevance. This is the first in vivo observation of deteriorated RNA polymerase in asphyxia/hypoxia.

Actins↗

PubMed1998

Oral administration of methylglyoxal leads to kidney collagen accumulation in the mouse.

Methylglyoxal (MG) is a physiological substrate of the glyoxalase system which is impaired in the diabetic state and implicated in the development of diabetic complications. Like other reactive aldehydes in diabetes mellitus (DM) this carbonyl can bind to and modify proteins which may lead to changes of biochemical and biophysical properties of connective tissue proteins, a hallmark of diabetes mellitus. As previous studies on MG effects were confounded by other aldehydes found in DM, we decided to administer MG to 10 healthy, female OF-1 mice for a period of five months, at a level of 50 mg/kg body weight per day using 10 healthy untreated litter mates as controls. The left kidneys were taken for the determination of total kidney collagen, fluorescence, acid solubility of collagen and the right kidneys were used for the determination of glomerular basement membrane thickness. Total kidney collagen was significantly higher in the MG treated mice compared to control mice. Only about half the amount of collagen could be extracted from kidneys of MG treated animals indicating reduced solubility. Fluorescence in proteins from extracted kidneys of MG treated animals was about twice that of untreated animals. Glomerular basement membrane thickness was significantly higher in MG treated animals. Our findings indicate that MG can increase glomerular basement membrane thickness and the suggested underlying mechanism may be decreased solubility by increased cross linking as reflected by elevated protein fluorescence and decreased acid salt extraction. The involvement of MG in the development of diabetic complications postulated by others is herewith clearly supported by our findings.

Administration, Oral↗

PubMed1998

mRNA levels of the hypoxia inducible factor (HIF-1) and DNA repair genes in perinatal asphyxia of the rat.

Hypoxia inducible factor 1 (HIF-1) is a transcription factor which is expressed, when mammalian cells are subjected to hypoxia, activating the transcription of genes encoding proteins thought important for maintaining oxygen hemostasis. The aim of the study was to evaluate HIF-1 mRNA levels in a non-invasive model of perinatal asphyxia (PA). Brain was taken for studies on HIF-1 alpha and beta 10 min following the asphyctic period. To rule out influences by the redox status we also determined antioxidant enzyme mRNA levels for superoxide dismutase, catalase, glutathion peroxidase and performed electron spin resonance studies. To study the link to protein phosphorylation as previously proposed, we evaluated mRNA levels for protein kinase C. As DNA breaks were reported to occur in PA, we determined mRNA levels of two genes representing DNA nucleotide excision repair, ERCC2 and ERCC3, and a DNA repair gene involved in the repair of oxidation mediated DNA damage, XRCC1. mRNAs for HIF-1 were not detectable following 5-20 minutes of asphyxia. The antioxidant enzymes did not show any changes during the asphyctic periods either and electron spin resonance failed to detect the presence of the hydroxyl radical. PKC significantly decreased with the length of the asphyctic period. ERCC2 and XRCC1 mRNAs were inducible during the acute phase of asphyxia indicating early repair phenomena. HIF-1 may not be relevant for periods of PA up to 20 minutes, the maximal survival time in our model. Neonatal factors may be responsible for that phenomenon although we cannot rule out that HIF-1 changes may occur at the protein level.

Animals↗

PubMed1998

Aromatic hydroxylation in animal models of diabetes mellitus.

Although the involvement of oxidative stress is well documented in the diabetic state, the individual active oxygen species generated have not been demonstrated in animal models of diabetes currently used. Since streptozotocin-induced diabetes mellitus in animals still serves as an animal model of diabetes mellitus, but streptozotocin induces diabetes and generates oxidative stress per se, we decided to study whether aromatic hydroxylation reflecting hydroxyl radical attack was found in three animal models of diabetes mellitus without streptozotocin induction or in streptozotocin-induced diabetes only. For this purpose, we compared lipid peroxidation, aromatic hydroxylation of phenylalanine, glycoxidation in genetically determined diabetic mouse strains db/db and kk, and the diabetic BB rat to these parameters in the streptozotocin-treated rat. Kidney malondialdehyde concentrations, reflecting lipid peroxidation, pentosidine, and Nepsilon-caboxymethyllysine concentrations, reflecting glycoxidation, were significantly elevated in all diabetic groups as compared to their nondiabetic mates. Aromatic hydroxylation was significantly elevated in the streptozotocin-induced diabetic state exclusively. We conclude that biochemical, pathophysiological, and treatment studies in the streptozotocin model of diabetes mellitus may be confounded by the presence of products, reactions, and tissue damage generated by aromatic hydroxylation reflecting hydroxyl radical attack. We suggest it is not the diabetic state but streptozotocin that generates the hydroxyl radical, as reflected by aromatic hydroxylation in this model.

Animals↗

PubMed1997

Transcription and activity of antioxidant enzymes after ionizing irradiation in radiation-resistant and radiation-sensitive mice.

The involvement of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase in radiobiological processes has been described at the enzyme activity level. We irradiated radiation-resistant (RR) and radiation-sensitive (RS) mice and studied antioxidant enzymes at the transcriptional and activity level. In addition, aromatic hydroxylation and lipid peroxidation parameters were determined to study radiation resistance at the oxidation level. RS BALB/c/J Him mice and RR C3H He/Him mice were whole-body-irradiated with x-rays at 2, 4, and 6 Gy and killed 5, 15, and 30 min after irradiation. mRNA was isolated from liver and hybridized with probes for antioxidant enzymes and beta-actin as a housekeeping gene control. Antioxidant enzyme activities were determined by standard assays. Parameters for aromatic hydroxylation (o-tyrosine) and lipid peroxidation (malondialdehyde) were determined by HPLC methods. Antioxidant transcription was unchanged in contrast to antioxidant activities; SOD and CAT activities were elevated within 15 min in RR animals but not in RS mice, at all doses studied. Glutathione peroxidase activity was not different between RR and RS mice and was only moderately elevated after irradiation. No significant differences were found between RR and RS animals at the oxidation level, although a radiation dose-dependent increase of oxidation products was detected in both groups. We found that ionizing irradiation led to increased antioxidant activity only minutes after irradiation in the absence of increased transcription of these antioxidant enzymes. RR animals show higher antioxidant enzyme activities than do RS mice, but oxidation products are comparable in RS and RR mice. As unchanged transcription of antioxidant enzymes could not have been responsible for the increased antioxidant enzyme activities, preformed antioxidant enzymes should have been released by the irradiation process. This would be in agreement with previous studies of preformed, stored SOD. The finding of higher SOD and CAT activities in RR than in RS animals could point to a role for these antioxidant enzymes for the process of radiation sensitivity.

Animals↗

PubMed1997

Decrease of heart protein kinase C and cyclin-dependent kinase precedes death in perinatal asphyxia of the rat.

Acidosis, energy depletion, overstimulation by excitatory amino acids, and free radical-mediated reactions are the major current concepts for the explanation of damage and death resulting from asphyxia. Impaired phosphorylation by protein kinase C (PKC) represents another mechanism incriminated for cell death. We used an unsophisticated perinatal asphyxia model to study heart protein kinases PKC and cyclin dependent kinase (CDK). Tissue pH, ATP, the antioxidant enzymes superoxide dismutase, catalase, and glutathion peroxidase, lipid peroxidation products, carbonyls, and aromatic hydroxylation were also tested. Electron spin resonance was applied to demonstrate the possible presence of radical adducts. An ELISA method was used to determine cell death. PKC activity and mRNA decreased with the length of the asphyctic periods and were paralleled by CDK and pH, whereas cell death gradually increased. No evidence was found for the involvement of active oxygen species or a radical adduct, and no energy depletion was observed. We conclude that impaired protein phosphorylation and/or acidosis may play a role in the pathobiochemistry of death from perinatal asphyxia in the rat.

Animals↗

PubMed1997

The transcription of liver thioredoxin following the ionizing irradiation of radioresistant and radiosensitive mice.

The radiation protective effect of thioredoxin (TRX) in a bacterial system has been reported and based upon this observation we were interested to examine TRX transcription in the mammalian system following ionizing irradiation. In order to answer the question whether radiation sensitive mice (BALB/c) showed TRX transcription different from radiation resistant mice (C3H), we exposed these strains to X-ray doses of 2 Gy, 4 Gy and 6 Gy. Groups consisting of 6 mice were sacrificed 5, 15 and 30 minutes after irradiation and livers were immediately taken into liquid nitrogen. Total RNA was isolated from the organs by the use of a commercially available kit and used for Northern blots and slot blots with a chemiluminescence technique. Northern blots revealed a single band at 538 bp for TRX and at 1.8 kb for beta-actin. Quantification of mRNA TRX by densitometry of slot blots revealed that C3H transcribed TRX significantly higher at an earlier time point (5 min) than BALB/c. This delayed transcription of TRX in the radiosensitive mouse strain showed a comparable pattern at three different radiation doses and may well be responsible for radioresistance although no quantitative differences of TRX transcription between BALB/c and C3H mice were detectable.

Actins↗

PubMed1996

Homocysteine increases cyclin-dependent kinase in aortic rat tissue.

BACKGROUND: Hyperhomocyst(e)inemia is strongly associated with occlusive arterial disease. A direct effect of homocysteine on the proliferation of smooth muscle cells was proposed recently. This observation led us to examine the effect of homocysteine on cyclin-dependent kinase, the starter of mitosis and reflecting proliferation. METHODS AND RESULTS: Seventy Him:OFA rats were divided into seven groups. For 12 weeks, 10 rats were fed homocysteine 25 mg/kg body weight per day, 10 were fed 50 mg/kg body wt per day, and 10 were fed 100 mg/kg body weight per day; 10 were given homocysteic acid 100 mg/kg body weight per day, 10 were administered cysteine 100 mg/kg body weight per day, and 10 were given ascorbic acid 270 mg/kg body weight per day. Ten remained untreated and served as controls. Aortic cyclin-dependent kinase was determined at the transcriptional (mRNA) and protein levels. Phosphokinase C and aortic homocyst(e)ine also were evaluated in aortic tissue. Aortic cyclin-dependent kinase protein was significantly (P = .0001) elevated in the three homocysteine-treated groups, and mRNA cyclin-dependent kinase levels were significantly elevated in the rats given the 50 and 100 mg/kg body weight per day protocol. Endothelial damage was shown at higher homocysteine doses as reflected by circulating ACE and von Willebrand factor changes. Proliferation of cells of the aortic wall by bromodeoxyuridine incorporation could be shown in the high-dose homocysteine group only. CONCLUSIONS: Our findings indicate that homocysteine specifically stimulates aortic cyclin-dependent kinase at the transcriptional level, with the possible consequence of proliferation of aortic cells as revealed by incorporation of bromodeoxyuridine in the aortic wall.

Animals↗

PubMed1996

Decreased tumor incidence and increased survival by one year oral low dose arginine supplementation in the mouse.

The effects of arginine on tumor growth, antitumor mechanisms and a potential therapeutic role have been reviewed recently. In these studies, however controversial they were, high dose protocols for arginine treatment have been applied. Based upon own recent findings that low dose arginine stimulates the immune system and blocks lipid peroxidation, we performed preventive treatment with low dose (50 mg/kg body weight per day, orally administered) L-arginine in 150 mice for a period of one year. We compared survival and total number of tumors at the end of the feeding period to that found in 150 mice given taurine in the same dosage and in 150 mice without treatment. Survival of the arginine treated group was statistically significant as compared to that of the control group without treatment (p < 0.05): 116 mice were alive in the control group, 122 in the group administered taurine and 132 in the arginine treated group. The total number of tumors was significantly lower in the arginine treated group vs. the control group (p < 0.01). The total number of malign and benign tumors was significantly lower in the arginine treated group, whereas taurine significantly reduced the number of benign tumors only (p < 0.05). Arginine and taurine stimulate the immune system at the lymphocyte level. Arginine also acts at the macrophage level, inducing nitric oxide mediated cytotoxicity against tumor cells. Both compounds are known to block the formation of lipid peroxidation products. We therefore suggest that these two mechanisms are responsible for the decreased total number of tumors and the concomitant increase in survival.

Animals↗

PubMed1996

Increased cyclin dependent kinase in aortic tissue of rats fed homocysteine.

BACKGROUND: Hyperhomocyst(e)inemia is strongly associated with occlusive arterial disease. Several mechanisms for the development of vascular lesions have been described. A direct effect of homocysteine on proliferation of smooth muscle cells and collagen expression was proposed recently. These observations led us to examine the effect of homocysteine on cyclin dependent kinase, the starter of mitosis and reflecting proliferation. METHODS AND RESULTS: Thirty Him: OFA rats were divided into three groups. Ten animals were fed for a period of six weeks 50 mg/kg body wt per day homocysteine, ten the same dose of homocysteic acid and ten remained untreated controls. At the end of the experiment we determined aortic cyclin dependent kinase, phosphokinases A and C, aortic homocyst(e)ine and aortic hydroxyproline. Aortic cyclin dependent kinase was significantly (p = 0.0001) elevated in the homocysteine treated group (mean 120 +/- 15) compared with the homocysteic acid treated group (mean 71 +/- 11) or the untreated group (mean 72 +/- 10 fmol/mg aortic tissue). Aortic homocyst(e)ine was significantly higher in homocysteine treated animals (p = 0.0002) strongly correlating with cyclin dependent kinase (r squared = 0.85, p = 0.0001) and with aortic hydroxyproline (r squared = 0.66, p = 0.0001), which in turn was significantly (p = 0.0001) increased in the homocysteine treated group. Phosphokinases A and C determined to rule out nonspecific effects on kinases were not increased by administered homocysteine. CONCLUSIONS: Our findings indicate that homocysteine stimulates aortic cyclin dependent kinase with the possible consequence of proliferation of aortic cells. Aortic collagen accumulation could be explained by either the homocysteine-effect on collagen synthesis described in literature, or secondarily, by increased proliferation of collagen produced aortic cells.

Animals↗

PubMed1995

Oral administration of homocysteine leads to increased plasma triglycerides and homocysteic acid-additional mechanisms in homocysteine induced endothelial damage?

Increased plasma homocyst(e)ine is strongly correlated with occlusive arterial diseases. A series of different hypotheses have been reported including involvement of free oxygen radicals and therefore oxidative stress. We determined plasma homocyst(e)ine and homocysteic acid levels after oral low dose homocysteine thiolactone administration to rats for a period of six weeks. Plasma levels of homocyst(e)ine and triglycerides were significantly elevated in the group fed homocysteine thiolactone. GC/MS determination of ketone body formation showed that the underlying mechanism for the increase of triglycerides seems to be inhibition of fatty acid oxidation. Homocysteic acid was detected in the experimental group exclusively. The present study showing a homocyst(e)ine correlated increase of plasma triglycerides by the inhibition of fatty acid oxidation may well propose an additional role of triglycerides for vascular pathology. The presence of homocysteic acid in the experimental group only would support the free oxygen radical hypothesis for the development of vascular changes but homocysteic acid as a potent neurotransmitter could play an independent role in the pathogenesis.

Administration, Oral↗

PubMed1995

Alpha-methyl-proline restores normal levels of bone collagen Type I synthesis in ovariectomized rats.

Collagen type I is the major protein of bone matrix and significantly reduced in osteoporosis. We tested the effect of alpha - methyl - proline on collagen synthesis in the model of the ovariectomized rat. Collagen synthesis was studied at the transcriptional level using Northern and dot blotting and at the protein level using hydroxyproline determination and a specific dye binding collagen assay. Alpha - methyl- proline treatment significantly increased collagen synthesis as compared to untreated ovariectomized and estradiol treated ovariectomized rats and restored collagen synthesis to levels of sham operated rats. Proline analogues were described to stimulate procollagen synthesis at the transcriptional level, however, if incorporated, lead to negative collagen production due to rapid intracellular degradation of the deficient collagen. Our synthesized analogue is not being incorporated, thus not interfering with collagen conformation and can therefore induce collagen production.

Animals↗

PubMed1995

Agmatine and spermidine reduce collagen accumulation in kidneys of diabetic db/db mice.

In the present study, we tested the hypothesis whether agmatine and spermidine, metabolites of arginine metabolism, share the pharmacological activities of arginine reducing collagen accumulation in the diabetic kidney. Eleven db/db mice were administered agmatine and 12 db/db mice spermidine (50 mg/kg body weight). Ten db/db mice received no treatment as negative controls and 10 db/db mice were treated with aminoguanidine (50 mg/kg body weight) as positive controls. Mean kidney OH-proline content reflecting kidney collagen content and mean CML concentration were significantly higher but acid solubility of collagen significantly lower in the untreated group than in the treated groups. Agmatine, although missing the alpha-amino group and the carboxyl group, and spermidine, although missing the guanidino group, thus still revealed the arginine activity. We hypothesize that the strongly nucleophilic structure of polyamines common to all active compounds is able to block reactive carbonyls.

Agmatine↗

PubMed1994

Creatine reduces collagen accumulation in the kidneys of diabetic db/db mice.

In the present study, we tested the hypothesis whether creatine, a metabolite of arginine metabolism, shares the pharmacological activities of arginine reducing collagen accumulation in the diabetic kidney. Ten db/db mice were given, for 3 months, a solution containing a daily dosage of creatine of 50 mg/kg body weight. Eleven db/db mice served as controls. At the end of the 3-month study period, the mean N-carboxymethyllysine concentration in the untreated group was significantly higher than in the treated group (0.163 +/- 0.18 versus 0.096 +/- 0.017 nmol/mumol hydroxyproline, p < 0.001). Collagen accumulation was also significantly higher in the untreated than in the treated group (2.21 +/- 0.24 versus 1.68 +/- 0.22 mumol hydroxyproline/100 mg kidney weight, p < 0.001). We conclude that creatine led to a significant reduction in collagen type IV accumulation resembling arginine or aminoguanidine action. We do suggest that the guanidino group common to both compounds is able to block reactive carbonyls.

Animals↗

PubMedDate not supplied

L-arginine reduces kidney lipid peroxidation, glycoxidation and collagen accumulation in the aging NMRI mouse.

Collagen accumulation in organs is a main feature of the physiological aging process. There are two main theories for the responsible mechanisms, the free oxygen radical and the glycoxidation theory. Both lead to carbonyle-induced protein modification, increased collagen cross-linking and subsequently to the collagen accumulation. In previous studies we provided evidence for the blocking of reactive carbonyles by L-arginine in the diabetic state and present here data for this effect in the aging NMRI mouse. NMRI mice were fed L-arginine in tap water for a period of 6 months and compared to an untreated control group. Kidney collagen content of the treated group was significantly reduced (treated: 8.83 +/- 0.72 mg collagen/100 mg kidney weight; untreated: 11.95 +/- 0.98 mg collagen (100 mg kidney weight; p < 0.05). Using a colorimetric assay for lipid peroxidation products we found significantly reduced lipid peroxidation-derived aldehydes in the treated group (treated: 0.25 +/- 0.03 extinction; untreated: 0.36 +/- 0.04 extinction; p < 0.05). The parameter for glycoxidation, N-epsilon-carboxymethyllysine (CML) was significantly lower in the experimental group as well (treated: 2.3 +/- 0.5 nM CML/microM hydroxyproline; untreated: 4.3 +/- 0.52 nM CML/microM hydroxyproline; p < 0.05). No differences were observed for the biomarker of hydroxyradical attack, o-tyrosine. L-Arginine could have reduced collagen accumulation by blocking collagen glyc(oxidation) which is known to lead to increased collagen cross-linking, solubility and degradation as a strong correlation between both CML and collagen content (r2 = 0.654, p < 0.05) as well as between lipid peroxidation products and collagen content (r2 = 0.539, p < 0.05) was observed.

Aging↗