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Biomedical subjects

M Bauer

Publications and source records attributed to M Bauer.

At least 145 records · Page 8Linked to original sources
PubMed1999

Dichotomous regulation of myosin phosphorylation and shape change by Rho-kinase and calcium in intact human platelets.

Both Rho-kinase and the Ca(2+)/calmodulin-dependent myosin light chain (MLC) kinase increase the phosphorylation of MLC. We show that upon thrombin receptor stimulation by low-dose thrombin or the peptide ligand YFLLRNP, or upon thromboxane receptor activation by U46619, shape change and MLC phosphorylation in human platelets proceed through a pathway that does not involve an increase in cytosolic Ca(2+). Under these conditions, Y-27632, a specific Rho-kinase inhibitor, prevented shape change and reduced the stimulation of MLC-phosphorylation. In contrast, Y-27632 barely affected shape change and MLC-phosphorylation by adenosine diphosphate (ADP), collagen-related peptide, and ionomycin that were associated with an increase in cytosolic Ca(2+) and inhibited by BAPTA-AM/EGTA treatment. Furthermore, C3 exoenzyme, which inactivates Rho, inhibited preferentially the shape change induced by YFLLRNP compared with ADP and ionomycin. The results indicate that the Rho/Rho-kinase pathway is pivotal in mediating the MLC phosphorylation and platelet shape change by low concentrations of certain G protein-coupled platelet receptors, independent of an increase in cytosolic Ca(2+). Our study defines 2 alternate pathways, Rho/Rho-kinase and Ca(2+)/calmodulin-regulated MLC-kinase, that lead independently of each other through stimulation of MLC-phosphorylation to the same physiological response in human platelets (ie, shape change).

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1999

Lysophosphatidic acid mediates the rapid activation of platelets and endothelial cells by mildly oxidized low density lipoprotein and accumulates in human atherosclerotic lesions.

Oxidized low density lipoprotein (LDL) is a key factor in the pathogenesis of atherosclerosis and its thrombotic complications, such as stroke and myocardial infarction. It activates endothelial cells and platelets through mechanisms that are largely unknown. Here, we show that lysophosphatidic acid (LPA) was formed during mild oxidation of LDL and was the active compound in mildly oxidized LDL and minimally modified LDL, initiating platelet activation and stimulating endothelial cell stress-fiber and gap formation. Antagonists of the LPA receptor prevented platelet and endothelial cell activation by mildly oxidized LDL. We also found that LPA accumulated in and was the primary platelet-activating lipid of atherosclerotic plaques. Notably, the amount of LPA within the human carotid atherosclerotic lesion was highest in the lipid-rich core, the region most thrombogenic and most prone to rupture. Given the potent biological activity of LPA on platelets and on cells of the vessel wall, our study identifies LPA as an atherothrombogenic molecule and suggests a possible strategy to prevent and treat atherosclerosis and cardiocerebrovascular diseases.

Arteriosclerosis↗
PubMed1999

Increased adhesion and aggregation of platelets lacking cyclic guanosine 3',5'-monophosphate kinase I.

Atherosclerotic vascular lesions are considered to be a major cause of ischemic diseases, including myocardial infarction and stroke. Platelet adhesion and aggregation during ischemia-reperfusion are thought to be the initial steps leading to remodeling and reocclusion of the postischemic vasculature. Nitric oxide (NO) inhibits platelet aggregation and smooth muscle proliferation. A major downstream target of NO is cyclic guanosine 3', 5'-monophosphate kinase I (cGKI). To test the intravascular significance of the NO/cGKI signaling pathway in vivo, we have studied platelet-endothelial cell and platelet-platelet interactions during ischemia/reperfusion using cGKI-deficient (cGKI-/-) mice. Platelet cGKI but not endothelial or smooth muscle cGKI is essential to prevent intravascular adhesion and aggregation of platelets after ischemia. The defect in platelet cGKI is not compensated by the cAMP/cAMP kinase pathway supporting the essential role of cGKI in prevention of ischemia-induced platelet adhesion and aggregation.

Animals↗
PubMed1999

Kinetic studies on the enzyme (S)-hydroxynitrile lyase from hevea brasiliensis using initial rate methods and progress curve analysis

(S)-Hydroxynitrile lyase (EC 4.1.2.39) from Hevea brasiliensis(rubber tree) catalyzes the reversible cleavage of cyanohydrins to aldehydes or ketones and prussic acid (HCN). Enzyme kinetics in both directions was studied on a model system with mandelonitrile, benzaldehyde, and HCN using two different methods-initial rate measurements and progress curve analysis. To discriminate between possible mechanisms with the initial rate method, product inhibition was studied. Benzaldehyde acts as a linear competitive inhibitor against mandelonitrile whereas HCN shows S-linear I-parabolic mixed-type inhibition. These results indicate an Ordered Uni Bi mechanism with the formation of a dead-end complex of enzyme, (S)-mandelonitrile and HCN. Prussic acid is the first product released from the enzyme followed by benzaldehyde. For progress curve analysis, a kinetic model of an Ordered Uni Bi mechanism including a dead-end complex, enzyme inactivation, and the chemical parallel reaction was set up, which described the experimental values very well. From the reaction rates obtained the kinetic constants were calculated and compared with the ones obtained from the initial rate method. Good agreement could be achieved between the two methods supporting the suggested mechanism. Copyright 1999 John Wiley & Sons, Inc.

Journal Article↗
PubMed1999

Urokinase gene expression indicates early invasive growth in squamous cell lesions of the uterine cervix.

The plasminogen activating system plays a key role in the cascade of tumour-associated proteolysis leading to extracellular matrix degradation and stromal invasion. Changes in the expression of this system, consisting of urokinase- and tissue-type plasminogen activators (uPA and tPA, respectively), plasminogen activator inhibitors (PAI-1, PAI-2) and uPA receptor, have been associated with tumour aggressiveness in a variety of solid malignant tumours. This paper describes a study of squamous intraepithelial lesions (SILs, n=36), squamous cell carcinomas (SCCs, n=42), and normal mucosa (n=5) of the uterine cervix by in situ hybridization with (35)S-labelled RNA probes. uPA transcripts were absent from normal mucosa and non-invasive lesions, but present in atypical epithelial cells of all microinvasive carcinomas ( n=19) and in some of the more advanced invasive carcinomas (n=11). PAI-1 transcripts were found in stromal cells of most tissue samples with, however, significantly increased levels in invasive SCC compared with SIL, microinvasive SCC, and normal mucosa. uPA-positive invasive carcinomas often displayed additional PAI-1 expression by tumour cells. At variance with uPA, tPA transcripts were found in atypical epithelial cells of low- and high-grade SILs. In the majority of SCCs tested (27/29 cases), the HPV 16 E6/E7 oncogene and uPA transcription were correlated. uPA and PAI-1 expression indicates invasive growth when expressed by atypical epithelial cells of squamous cervical lesions. Moreover, the presence of uPA transcripts is indicative of early invasive growth. uPA and tPA seem to have different functions in the development of invasive properties in uterine cervical squamous epithelium.

Carcinoma, Squamous Cell↗
PubMed1999

Differential effects of angiotensin II receptor blockade on pressure-induced left ventricular hypertrophy and fibrosis in rats.

The effects of the angiotensin II receptor type 1 (AT1) antagonist losartan on pressure overload-induced left ventricular (LV) hypertrophy were studied in female Sprague-Dawley rats. Starting on the day of surgery, losartan (L, 12 mg/kg/day) was administered as continuous intraperitoneal infusion for 2 weeks by using alzet mini-osmotic-pumps (model 2002). This dose of losartan shifted the in vivo dose-response curve of the angiotensin II-induced elevation of left ventricular systolic pressure (LVSP) to the right. Pressure overload was achieved by placing a band around the aortic arch. This caused an aortic stenosis (AS) with an outer diameter of 1.0 mm. The hemodynamic effects were measured in the intact, anesthetized rats (n = 15). The hearts were excised, and the weights of the left (LV) and right ventricle (RV) were determined. Some of these hearts (n = 7) were perfused with collagenase to obtain isolated cardiac myocytes for the measurement of cell volume. Other hearts (n = 8) were examined for morphological changes. In the animals with AS, LVSP was markedly elevated. Furthermore, LV weight and LV myocyte cell volume were increased in this group, while RV weight and RV myocyte cell volume remained stable in all the groups. L had no significant effect on the AS-induced increase in LVSP and cell size parameters, nor on the weight gain of the LV. Histological analysis revealed that the AS-induced enlargement of the mean myocyte diameter was not affected by L. The interstitial collagen fraction was increased in the AS rats and became normalized by L. These data suggest that the renin-angiotensin system might not be involved in the development of pressure-induced cardiac hypertrophy within the time-frame of these experiments, but that it does play a major role in the genesis of the interstitial fibrosis which is a typical feature of this pathophysiological condition.

Angiotensin Receptor Antagonists↗
PubMed1999

Somatic gene therapy in animal models of Parkinson's disease.

Gene therapy in Parkinson's disease (PD) emerged about 10 years ago but until now, no clinical trials are under way, because most approaches have failed to show long-term therapeutic effects in PD animal models and because safety concerns precluded the use in humans so far. This review tries to give an overview on the development of different strategies in gene therapy in PD animal models and point out new and possibly more successful directions, including the transplantation of neural precursor cells and pig tissue.

Animals↗
PubMed1999

[Olanzapine in the treatment of depressive disorders with psychotic symptoms].

We report on the successful treatment of two female patients with psychotic depression with the new atypical neuroleptic drug olanzapine. A 75-year-old female inpatient suffering from recurrent endogenous depression with tactile hallucinations and coenesthesia was refractory to a systematic sequential antidepressant treatment strategy during a 39-week period. After addition of the new atypical neuroleptic olanzapine to the SSRI citalopram, she showed immediate and ongoing symptom relief. In the second case of a 57-year-old female inpatient suffering from delusional depression, we observed marked symptom relief and correction of the delusions of impoverishment. Olanzapine is discussed with regard to its receptor-binding profile (antagonism to 5-HT2A- and D1-D4 receptors) as a potential neuroleptic drug in the treatment of affective disorders with psychotic symptoms.

Affective Disorders, Psychotic↗
PubMed1999

[Therapeutic strategies in refractory bipolar disorder].

Lithium is still regarded as the first choice substance in the prophylactic treatment of bipolar disorder. However, approximately one third of patients with a "classic" course of bipolar affective disorder do not adequately respond to lithium prophylaxis. The introduction of carbamazepine and valproic acid allowed a more differential syndrome- and course-orientated approach to the prophylactic treatment of bipolar disorder for the first time. However, about 10 to 20 percent of patients still remain refractory to standard regimes. Therefore, criteria for resistance to prophylactic treatment have to be further established. It has been suggested that at least two adequate trials of more than 12 months duration with sufficient drug blood levels have to be performed before refractoriness should be assumed. A severe subtype of affective disorder with poor response to lithium and other treatment approaches is a rapid cycling course which is characterised by at least four affective episodes per year. Here we present an overview of the currently available alternatives for prophylactic treatment, i.e. anticonvulsants, combination treatment, adjunctive thyroxine, calcium channel blockers, and more experimental approaches for treating refractory bipolar disorder patients. Suggestions for optimizing the prophylactic treatment of bipolar disorder are summarized in an algorithm.

Algorithms↗
PubMed1999

Mixed agonistic-antagonistic cytokine response in whole blood from patients undergoing abdominal aortic aneurysm repair.

OBJECTIVE: To characterize the impact of abdominal aortic aneurysm repair (AAAR) on spontaneous as well as lipopolysaccharide (LPS)-induced gene expression of pro- and anti-inflammatory cytokines. DESIGN: Prospective, controlled in vivo/ex vivo study. SETTING: University hospital. PATIENTS AND INTERVENTIONS: Whole blood from 14 consecutive patients undergoing AAAR withdrawn prior to surgery (T1), at the end of ischemia (T2), 90 min after declamping (T3) and on the first postoperative day (T4) was cultured in the absence or presence of LPS. Five patients undergoing elective inguinal hernia repair served as controls. MEASUREMENTS AND RESULTS: While tumor necrosis factor (TNF), Interleukin (IL)-1 and IL-10 plasma concentrations did not increase significantly, IL-6 was elevated at each time point, as compared with T1. Despite the spontaneous release of trace amounts of IL-6, the ability of cultured whole blood to mount a cytokine response in vitro to LPS was impaired for all cytokines studied at T2 (TNF-62%, IL-1-51%, IL-6 -20%, IL-10-51%). The stimulated IL-6 response was restored early after declamping (T3: +56 %) and enhanced 1 day after operation (T4: +144%). In contrast, stimulated TNF and IL-1 responses remained depressed at T3 (TNF -48%, IL-1-64%) and T4 (TNF-40%, IL-1-24%). A biphasic pattern was observed for IL-10 with initial depression at T3 (-51%) and restoration at T4 (+40%). Among the different cytokines monitored, only impaired TNF responsiveness at early reperfusion (T3) correlated with the postoperative course, as reflected by APACHE II. Cytokine response to LPS was maintained or even increased during and after surgery in the whole blood from patients undergoing hernia repair. CONCLUSIONS: Despite consistent development of clinical signs of systemic inflammatory response syndrome (SIRS) and spontaneous release of IL-6 abdominal aortic aneurysm repair produces a state of impaired pro-inflammatory cytokine response upon a subsequent in vitro Gram-negative stimulus. This early impairment of TNF responsiveness seems to correlate with an unfavorable postoperative course.

Aged↗
PubMed1999

Nerve cell loss in the thalamic mediodorsal nucleus in Huntington's disease.

We estimated the total neurone number, glial number, and glial index (ratio glial cells/neurone) in the thalamic mediodorsal nucleus (MD) in seven patients suffering from Huntington's disease (HD; four males, three females, mean age 52.4 +/- 13.6 years) and age- and sex-matched controls (four males, three females, mean age 53.6 +/- 12.1 years) by means of a stereological protocol. The mean total neurone number (N(T)) in the MD of controls was 2,985,188 +/- 174,710, the mean glial number (G(T); astrocytes, oligodendrocytes) 21,785,008 +/- 2,986,678, and the glial index 7.29 +/- 0.88. In HD, the average neurone number was decreased by 23.8% to 2,275,321 +/- 247,162 (Mann-Whitney U-test P < 0.05), the mean glial number by 29.7% to 15,318,895 +/- 1,722,524 (Mann-Whitney U-test P < 0.05), the glial index was slightly reduced to 6.81 +/- 1.06. Gallyas' impregnation for the demonstration of fibrous astroglia gave strongly positive results in all cases with HD and negative results in the controls. The morpho-functional correlation of the results is complicated because individual variability, presence of segregated and parallel neuronal circuits, and plasticity of the adult human CNS must be considered.

Adult↗
PubMed1999

Differential gene expression of CINC, NOS II, and ICAM-1 in endotoxemic liver cells by rG-CSF.

INTRODUCTION: We have recently demonstrated that recombinant granulocyte colony-stimulating factor (rG-CSF) modulates lipopolysaccharide (LPS)-induced Kupffer cell activation with subsequent reduction in hepatic leukocyte-endothelial cell interaction, thereby achieving protection against microcirculatory perfusion failure and hepatic dysfunction. To further clarify the underlying mechanisms, rG-CSF treated liver cells were tested for the LPS-induced gene expression of cytokine-induced neutrophil chemoattractant (CINC) and intercellular adhesion molecule-1 (ICAM-1) as potential chemotactic and leukocyte-recruiting factors and for the gene expression of inducible nitric oxide synthase (NOS II) as potential modulator of leukocyte adherence. METHODS: Using a collagenase, DNAse/pronase digestion technique, hepatic parenchymal and nonparenchymal cell fractions were obtained from livers of in vivo rG-CSF pretreated Sprague-Dawley rats 2 h after LPS exposure. mRNA transcripts were assessed using northern blot analysis. RESULTS: In control livers only ICAM-1 mRNA was found constitutively expressed in hepatic nonparenchymal cells. rG-CSF per se did not affect NOS II, CINC, or ICAM-1 expression in hepatic liver cells, while LPS induced a marked expression of NOS II, CINC, and ICAM-1 in nonparenchymal cells and, to a lesser extent, in hepatocytes. Administration of rG-CSF prior to LPS exposure tended to increase NOS II, CINC, and ICAM-1 mRNA transcripts in hepatocytes. In nonparenchymal cells, however, NOS II and CINC were found reduced in rG-CSF pretreated animals upon LPS exposure. CONCLUSIONS: The present data show a strikingly different cell type specific pattern of inflammatory response genes in rG-CSF-modulated hepatic endotoxemia. Reduced expression of NOS II, in particular of CINC, in the nonparenchymal cell fraction may contribute to the reduced leukocyte adherence and thus attenuation of cell-dependent tissue injury in rG-CSF pretreated endotoxemic animals.

Animals↗
PubMed1999

Fibrogenesis and fibrolysis in collagenous colitis. Patterns of procollagen types I and IV, matrix-metalloproteinase-1 and -13, and TIMP-1 gene expression.

Collagenous colitis is characterized by the deposition of a superficial subepithelial collagenous layer, the pathogenesis of which is unknown. Because the excess matrix deposition is potentially reversible, a labile imbalance between fibrogenesis and fibrolysis may be suspected. Expression of procollagen alpha1(I) and alpha1(IV), matrix-metalloproteinase (MMP)-1 and -13, and tissue inhibitor of metalloproteinase (TIMP)-1 genes was semiquantitated by in situ hybridization on serial biopsies of 12 patients with collagenous colitis and compared to controls. Collagen types I, III, IV, and VI, tenascin, undulin/collagen XIV, and alpha-actin were localized by immunohistology. The superficial collagen layer stained strongly for collagen types I, III, and VI, and particularly for tenascin, but not for undulin. Elevated procollagen alpha1(I), procollagen alpha1(IV), and TIMP-1 transcript levels were found in alpha-actin-positive cells with linear distribution underneath the superficial collagenous layer, whereas MMP-1 RNA expression was variable and restricted to cell clusters. MMP-13 expression was undetectable. The patterns of procollagen alpha1(I)- and alpha1(IV)-specific labeling, combined with an intense tenascin- but absent undulin-specific staining, indicate deposition of an immature interstitial matrix that may be susceptible to degradation. The restricted MMP-1 RNA expression, counteracted by increased TIMP-1 expression, suggests locally impaired fibrolysis as a relevant factor in the pathogenesis of collagenous colitis.

Adult↗