Biomedical subjects

W Bloch

Publications and source records attributed to W Bloch.

At least 55 records · Page 3Linked to original sources

PubMed2000

The angiogenesis inhibitor endostatin impairs blood vessel maturation during wound healing.

Endostatin is a cleavage product of collagen XVIII that strongly inhibits tumor angiogenesis. To determine if endostatin affects other angiogenic processes, we generated full-thickness excisional wounds on the back of mice that were systemically treated with recombinant murine endostatin. No macroscopic abnormalities of the wound healing process were observed. Histological analysis revealed normal wound contraction and re-epithelialization, but a slight reduction in granulation tissue formation and reduced matrix deposition at the wound edge. The blood vessel density in the wounds of endostatin-treated mice was not affected. However, ultrastructural analysis demonstrated severe abnormalities in blood vessel maturation. The wound vessels in the endostatin-treated mice were narrowed or closed with an irregular luminal surface, resulting in a severe reduction in the number of functional vessels and extravasation of erythrocytes. Endostatin treatment did not affect the expression level and localization of collagen XVIII mRNA and protein. Furthermore, the angiogenesis regulators vascular endothelial growth factor, angiopoietin-1, and angiopoietin-2 were normally expressed in the wounds of endostatin-treated mice. However, expression of the major wound matrix proteins fibronectin and collagens I and III was significantly reduced. This reduction is likely to explain the reduced density of the wound matrix. Our results demonstrate that endostatin treatment reduces the number of functional blood vessels and the matrix density in the granulation tissue, but does not significantly affect the overall wound healing process.

Angiogenesis Inhibitors↗

PubMed2000

Expression of inducible nitric oxide synthase (iNOS/NOS II) in the vestibule of guinea pigs after the application of cisplatin.

It is well known that the anti-cancer drug cisplatin has an ototoxic property; however, the details are not yet evident. In this study, the expression of inducible nitric oxide synthase (INOS/NOS II) in the vestibule of guinea pigs after i.p. injections of cisplatin was examined immunohistochemically. Three days after the injection of cisplatin (10 mg/kg) or placebo, animals were sacrificed. Then the temporal bones were removed and subjected to Immunohistochemical studies for iNOS. In the cisplatin group, INOS was detectable, whereas the tissue in the control group was negative for iNOS. The vestibule, the wall of blood vessels and the vestibular ganglion cells showed immunoreactivity for iNOS. It is known that INOS catalyzes an inadequate quantity of NO under pathological conditions. Increased NO levels lead to inner ear dysfunction. Therefore, our results indicate that iNOS could also mediate the vestibulo-toxicity of cisplatin.

Animals↗

PubMed2000

Nitric oxide synthase inhibitor suppresses the ototoxic side effect of cisplatin in guinea pigs.

Cisplatin is known to cause inner ear damage (ototoxicity). The role of inducible nitric oxide synthase (iNOS) in the cochlea of guinea pigs after injections of cisplatin or a combination of cisplatin and NOS inhibitor (NG-nitro-L-arginine methyl ester, L-NAME) i.p. was examined electro-and immunohistochemically. The auditory brain stem responses (ABR) were measured prior to injection and 3 days after the injection. Three days after injection, the cochleas were examined immunohistochemically for iNOS. We found that iNOS was expressed in the cisplatin- and L-NAME/ cisplatin-treated cochlea. The threshold shift of ABR was significant in the cisplatin group, whereas it was decreased in the L-NAME/cisplatin group. iNOS catalyzed high NO levels lead to inner ear dysfunction. Our results indicate that iNOS mediates the ototoxicity of cisplatin.

Animals↗

PubMed2000

Testosterone-propionate impairs the response of the cardiac capillary bed to exercise.

OBJECTIVE: Experimental application of anabolic-androgenic steroids and exercise training induce cardiac hypertrophy. This study quantifies for the first time, on microscopical level, the adaptation of the cardiac capillaries and myocytes to the concomitant application of testosterone-propionate and exercise training. METHODS: Female SPF-NMRI mice were studied over 3 and 6 wk. Experimental groups: (i) sedentary control (C); (ii) exercise (treadmill running, E); (iii) testosterone-propionate (TP); and (iv) testosterone-propionate+exercise (TPE). Morphometric parameters: 1) papillary muscles: capillary density, intercapillary distance, number of capillaries around a myocyte, and minimal myocyte diameter; and 2) left ventricular wall: capillary density and intercapillary distance. RESULTS: Papillary muscle: A striking suppression of the exercise-induced improvement in capillary supply occurs in the testosterone-propionate+exercise groups over 3 and 6 wk. Exercise without drugs increases significantly (P < 0.05) the capillary density, shortens significantly (P < 0.05) the intercapillary distance, whereas it increases the number of capillaries around a myocyte. These alterations are not observed in the testosterone-propionate treated sedentary animals; e.g., capillary density after 6 wk (mean values +/- standard deviation, capillaries x mm(-2)): C: 4272 +/- 287, E: 5411 +/- 758, TP: 4221 +/- 364, and TPE: 3997 +/- 397. Moreover, only in the testosterone-propionate+exercise groups occurs a mild myocyte hypertrophy after both time periods: there is a trend toward hypertrophy (P < 0.1) in comparison with the C groups and a significant hypertrophy (P < 0.05) in comparison with the E groups. CONCLUSIONS: Testosterone-propionate profoundly inhibits the exercise-induced augmented capillarization, whereas (under training conditions) it leads to a mild myocyte hypertrophy. The microvascular impairment could trigger an imbalance between the myocardial oxygen supply and demand, especially during physical exercise.

Animals↗

PubMed2000

SERCA2a activity correlates with the force-frequency relationship in human myocardium.

The present investigation addresses whether protein expression and function of sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA2a) and phospholamban (PLB) correlate in failing and nonfailing human myocardium. SERCA2a activity and protein expression, PLB phosphorylation, and the force-frequency relationship (FFR) have been determined in right atrium (RA) and left ventricle (LV) from nonfailing (NF, n = 12) and terminally failing [dilated cardiomyopathy (DCM), n = 12] human hearts. Only in LV of DCM hearts was SERCA2a activity significantly decreased [maximal turnover rate (V(max)) = 196 +/- 11 and 396 +/- 30 nmol. mg(-1). min(-1) in LV and RA, respectively], whereas protein expression of SERCA2a in the different chambers was unchanged in NF (3.9 +/- 0.3 and 3.2 +/- 0.4 densitometric units in LV and RA, respectively) and DCM hearts (4.8 +/- 0.8 and 3.4 +/- 0.1 densitometric units in LV and RA, respectively). Phosphorylation of PLB was higher in LV than in RA in NF (Ser(16): 180.5 +/- 19.0 vs. 56.8 +/- 6.0 densitometric units; Thr(17): 174.6 +/- 11.2 vs. 37.4 +/- 8.9 densitometric units) and DCM hearts (Ser(16): 132.0 +/- 5.4 vs. 22.4 +/- 3.5 densitometric units; Thr(17): 131.2 +/- 10.9 vs. 9.2 +/- 2.4 densitometric units). SERCA2a function, but not protein expression, correlated well with the functional parameters of the FFR in DCM and NF human hearts. Regulation of SERCA2a function depends on the phosphorylation of PLB at Ser(16) and Thr(17). However, direct SERCA2a regulation might also be affected by an unknown mechanism.

Adult↗

PubMed2000

Different effect of the Ca(2+) sensitizers EMD 57033 and CGP 48506 on cross-bridge cycling in human myocardium.

Ca(2+) sensitizers may be advantageous for treatment in human heart failure by increasing cardiac force without increasing the Ca(2+) transient or energy consumption. To study the mode of action of the Ca(2+) sensitizers EMD 57033 (EMD) and CGP 48506 (CGP), their influence on butanedione monoxime (BDM)-mediated depression of cross-bridge cycling was analyzed in human myocardium (explanted hearts, dilated cardiomyopathy, n = 19). In Triton X (1%)-skinned fiber preparations of left ventricular myocardium from patients suffering from dilated cardiomyopathy, troponin I was extracted by vanadate (10 mM) treatment, resulting in a Ca(2+)-independent contraction. In troponin I-depleted fibers BDM (5-50 mM) was applied in the absence and presence of EMD (10 microM) or CGP (10 microM). To analyze the influence on cross-bridge kinetics, tension cost (ratio of ATPase activity and tension development) was studied. BDM exerted a dose-dependent force inhibition in troponin I-depleted fibers (IC(50) = 7.22 mM), which was antagonized by EMD (IC(50) of BDM + EMD = 19.97 mM) and CGP (IC(50) of BDM + CGP = 15.30 mM). EMD increased Ca(2+) sensitivity of force and maximal force in Triton X-skinned fibers. The Ca(2+)-sensitizing effect of CGP was accompanied by an increased Ca(2+) sensitivity of myosin-ATPase activity, an increased slope of the Ca(2+) force and Ca(2+) ATPase curve, as well as a reduced maximal myosin ATPase activity. CGP and EMD reduced tension cost. In conclusion, EMD and CGP antagonize the BDM-mediated relaxation in troponin I-depleted cardiac muscle fibers. The Ca(2+)-sensitizing effect of CGP seems to be dependent on an improvement of the myofilament cooperativity, whereas EMD seems to operate by increasing the force per cross-bridge.

Adult↗

PubMed1999

Perlecan maintains the integrity of cartilage and some basement membranes.

Perlecan is a heparan sulfate proteoglycan that is expressed in all basement membranes (BMs), in cartilage, and several other mesenchymal tissues during development. Perlecan binds growth factors and interacts with various extracellular matrix proteins and cell adhesion molecules. Homozygous mice with a null mutation in the perlecan gene exhibit normal formation of BMs. However, BMs deteriorate in regions with increased mechanical stress such as the contracting myocardium and the expanding brain vesicles showing that perlecan is crucial for maintaining BM integrity. As a consequence, small clefts are formed in the cardiac muscle leading to blood leakage into the pericardial cavity and an arrest of heart function. The defects in the BM separating the brain from the adjacent mesenchyme caused invasion of brain tissue into the overlaying ectoderm leading to abnormal expansion of neuroepithelium, neuronal ectopias, and exencephaly. Finally, homozygotes developed a severe defect in cartilage, a tissue that lacks BMs. The chondrodysplasia is characterized by a reduction of the fibrillar collagen network, shortened collagen fibers, and elevated expression of cartilage extracellular matrix genes, suggesting that perlecan protects cartilage extracellular matrix from degradation.

Animals↗

PubMed1999

Nitric oxide synthase expression and role during cardiomyogenesis.

OBJECTIVE: The aim of the present study was the investigation of the expression of NOS during cardiomyogenesis and its functional role. DESIGN: The qualitative and quantitative expression of NOS isoforms during different stages of cardiac development was evaluated using immunocytochemistry and dot blots, respectively. The functional relevance of NOS expression during cardiomyogenesis was investigated using the in vitro ES cell-differentiation model and selective pharmacological agents. RESULTS: On day 7.5 of embryonic development (E7.5) none of the NOS isoforms were expressed in the embryo, whereas the inducible (iNOS), as well as the endothelial (eNOS) isoforms were detected in the extraembryonic parts. In contrast, starting from E9.5 rat and murine embryos displayed prominent iNOS and eNOS expression. This was correlated with high expression of soluble guanylylcyclase (sGC) as well as high cyclic GMP (cGMP) content. During further development after E14.5 both, iNOS as well as eNOS, started to be downregulated and shortly prior to birth reduced staining for eNOS was found, whereas iNOS was hardly detectable. We further investigated whether NO plays a role for cardiomyogenesis, using in vitro ES cell-derived cardiomyocytes differentiating within embryoid bodies (EBs). The NOS expression pattern in these cells paralleled the one detected in vivo. We demonstrate that continuous incubation of EBs with the NOS inhibitors L-NMMA (2-10 mM) or L-NA (2-10 mM) for 4 to 9 days after plating resulted in a pronounced differentiation arrest of cardiomyocytes, whereas this effect could be reversed by coapplication of the NO-donor spermine-NONOate (10 microM). CONCLUSIONS: Both, iNOS and eNOS isoforms are prominently expressed during early stages of cardiomyogenesis. Around E14.5 NOS expression starts to decline. Moreover, the NO-generation is required for cardiomyogenesis since NOS inhibitors prevent the maturation of terminally differentiated cardiomyocytes using the ES cell system.

Animals↗

PubMed1999

Expression of inducible nitric oxide synthase (iNOS/NOS II) in the cochlea of guinea pigs after intratympanical endotoxin-treatment.

Since NO is believed to be involved in cochlear physiology, presence of the constitutive isoforms of nitric oxide synthase (NOS), and the target enzyme of NO, soluble guanylyl cyclase (sGC) in structures of the mammalian cochlea have been demonstrated. To date, no reports have been published regarding the detection of the inducible isoform (NOS II) in the cochlea. In order to show the capability of iNOS expression in cochlear tissue, a mixture of proinflammatory bacterial lipopolysaccharides (LPS) and tumor necrosis factor alpha (TNF-alpha) was injected into the tympanic cavity of guinea pigs, vs. saline-solution as control. Paraffin sections of LPS/TNF-alpha treated and saline-treated cochleae (6 h) were examined immunohistochemically with specific antibodies to neuronal, endothelial and inducible NOS and to sGC. Initiated expression of iNOS in the cochlea was observed in the wall of blood vessels of the spiral ligament (SL) and the modiolus, in supporting cells of the organ of Corti, in the limbus, in nerve fibers and in a part of the perikarya of the spiral ganglion after LPS/TNFalpha-treatment. iNOS was not detected in saline-treated control tissue. Expression of both constitutive NOS-isoforms (endothelial and neuronal NOS) and of sGC showed no significant differences in both experimental groups. Endothelial eNOS and neuronal bNOS were detected co-localized in ganglion cells, in nerve fibers, in cells of the SL and in supporting cells of the organ of Corti, but not in sensory cells. Strong labeling for bNOS became evident in the endosteum of the cochlea, while in the endothelium of blood vessels and in the epithelium of the limbus only eNOS could be labeled. sGC could be detected in SL, in supporting and sensory cells of the organ of Corti, in nerve fibers, ganglion cells, in the wall of blood vessels and in the limbus-epithelium. While small amounts of NO, generated by bNOS and eNOS, seem to support the cochlear blood flow and auditory function as well as neurotransmission, high amounts of iNOS-generated NO could have dysregulative and neurotoxic effects on the inner ear during bacterial and viral infections of the middle and inner ear.

Animals↗

PubMed1999

Expression of inducible nitric oxide-synthase in the vestibular system of hydropic guinea pigs.

Immunohistochemical investigations of the guinea pig vestibular system, using a specific antibody to the inducible isoform of NO-synthase (iNOS/NOS II), have been performed 3 weeks after surgical closure of the right endolymphatic duct (n = 7). Endolymphatic hydrops (ELH) of the right temporal bone became evident by excavation of the Reissner's membrane in all seven animals. Those animals revealed iNOS-expression in ganglion cells, in the wall of blood vessels and in nerve fibers of the right vestibular system, while the corresponding left temporal bones and temporal bones of non-operated controls (n = 6) as well as of sham-operated animals (n = 3) did not show any iNOS-positive structures. iNOS-generated NO could be involved in the pathophysiology of vestibular dysfunction in Meniere's disease.

Animals↗

PubMed1999

Inhibition of phosphatidylinositol-3-kinase blocks development of functional embryonic cardiomyocytes.

Culturing murine embryonic stem (ES) cells within embryoid bodies (EBs) has been reported to reproduce cardiomyocyte development from primitive precursor cells to highly specialized phenotypes of cardiac tissue. We show here that the specific inhibitor of phosphatidylinositol-3-kinase (PI-3-kinase), LY294002, blocks the growth and induces apoptosis as well as necrosis of D3 ES cells within early EBs. Treatment of EBs from day 3 to day 7 with 50 microM LY294002 resulted in a massive loss of alpha-actinin-stained cardiomyocytes after plating the EBs for additional 7 days. In parallel we observed a strong decrease in the number of EBs containing area(s) with beating cardiomyocytes. The specific action of the PI-3-kinase inhibitor on development of cardiomyocytes was demonstrated by the observation that formation of endothelial cells was not affected in the same EBs. Our results provide the first evidence that signal transduction via the PI-3-kinase pathway is essential for mammalian early cardiomyocyte development.

Animals↗

PubMed1999

Immunolocalization of inducible and constitutive nitric oxide synthases in human bladder cancer.

OBJECTIVES: Nitric oxide (NO) is synthesized by the enzyme family of NO synthases (NOS) and plays an important role in tumor growth and angiogenesis. NO generation by inducible NOS (iNOS) also influences the cytotoxicity of macrophages and tumor-induced immunosuppression. Before now, the expression of iNOS and constitutive NOS in bladder carcinoma tissue had not been determined. METHODS: Bladder carcinoma tissue specimens were procured from 18 patients (mean age 69.7 years) undergoing transurethral resection. In every patient, tumor biopsies were compared with biopsies of benign bladder regions. Histochemical NADPH-diaphorase staining and NOS immunohistochemistry were performed on all tissue specimens. RESULTS: Positive NADPH-diaphorase staining was detected in all sections from bladder carcinoma tissue. NOS immunohistochemistry showed a different pattern. The malignant epithelial cells were highly iNOS positive. Specimens of bladder mucosa outside of the malignant regions showed only a weak positive iNOS immunostaining. The endothelial cells of abundant precapillary vessels in the stroma of bladder tumors showed a highly positive endothelial NOS (eNOS) immunostaining compared with the stroma of nonmalignant bladder tissue. Neuronal NOS immunoreactivity was only found in nitrinergic fibers in the fibromuscular stroma. CONCLUSIONS: Bladder carcinoma tissue had a high iNOS content; benign tissue did not. NO generation from iNOS in the malignant epithelium and from eNOS in tumor stroma may play different roles in tumor angiogenesis and tumor-induced immunosuppression.

Aged↗

PubMed1999

Localization of the NO/cGMP-pathway in the cochlea of guinea pigs.

The presence of nitric oxide synthase (NOS) in substructures of the cochlea of guinea pigs is an issue of current focus. Moreover, information concerning the localization of cells effected by the NO/cGMP-pathway are rare. Paraffin sections of guinea pig cochlea were incubated with specific antibodies to the three known NOS isoforms, soluble guanylyl cyclase (sGC) and cyclic guanosine-monophosphate (cGMP), the second messenger system of NO. While detection of inducible iNOS failed in all cochlear structures, expression of endothelial eNOS was found in the spiral ligament, in the stria vascularis, in cells of the organ of Corti, in nerve fibers and in some perikaryia of the spiral ganglion. The cochlear nerve showed an accentuated affinity for immunostaining in distal, basal segments of the cochlea. Neuronal bNOS was found predominantly in the endosteum of the modiolus and cochlea and was less intensively present in all perikaryia of the spiral ganglion and in the spiral ligament. Supporting cells of the organ of Corti and cells in the limbus spiralis displayed only modest immunostaining, while bNOS was not found in outer and inner hair cells. NOS detection was accompanied by immunoreactivity to sGC and to cGMP. The presence of NOS and its second messenger system gives evidence for a possible involvement in neurotransmission, regulation of the cochlear amplifier and in homeostasis.

Animals↗

PubMed1999

Nitric oxide based influence of nitrates on micturition in patients with benign prostatic hyperplasia.

BACKGROUND: Nitric oxide (NO) is involved in the physiologic regulation of smooth muscle relaxation in the prostate. Organic nitrates act as NO donors. In this prospective open study we prove the influence of orally given nitrates on micturition. METHODS: Thirty-two patients underwent a urological medical check-up prior to starting nitrate medication for cardiovascular disease. We examined peak flow rates, residual urine, IPS-score, PSA level and prostate volume. Exact inclusion and exclusion criteria were defined. Fifteen patients suffered from obstructive symptoms, 17 patients reported no subjective micturition problems. Urological re-evaluation was performed two weeks and three months after nitrate medication. RESULTS: A significant improvement of peak urinary flow rates (+3.1 ml/s; p<0.05), IPS score and significant decrease of residual urine volume (-22 ml; p<0.05) were found in the symptomatic patients. No significant changes of micturition parameters were found in asymptomatic patients. PSA levels and prostate volumes did not change in either groups. CONCLUSIONS: Organic nitrates influence micturition parameters in patients with obstructive benign prostatic hyperplasia. This might be explained by the known mechanism of NO donation (smooth muscle relaxation) of nitrates. More functional controlled studies are necessary to describe the grade of influence of nitrates on the prostate. Concomitant oral medication with nitrates must be considered as a relevant bias factor on BPH in future clinical studies.

Aged↗

PubMed1999

Selective expression of the NOS II isoform during mouse vestibulocochlear receptorgenesis.

Based on in vitro studies, nitric oxide (NO) is reported to be involved in initial neuronal differentiation. In order to compare this finding with the situation in vivo, we have looked for the expression of the three NO synthase isoforms in the developing mouse vestibulocochlear system. From these isoforms only the inducible NOS II is expressed during inner ear development. Examination of a series of embryonic and early postnatal animals, up to postnatal day 6, reveals a maturation-dependent, monophasic expression of this isoform. Initial expression is observed by day 10 of gestation in nerve cells of the vestibolocochlear ganglion and on their fibres. By day 14 of gestation, these afferent fibres penetrate the epithelium of the prospective receptor fields making contact with early, differentiating immunoreactive cochlear hair cells and receptor cells of the macula and crista ampullaris. This receptor-cell-derived immunoreactivity vanished in differentiated sensory hair cells by postnatal day 6, when both the constitutive isoforms and subsequent activated members of the down stream second messenger cascade (guanylate cyclase/cGMP) of the adult mouse were not then detectable. The strict phasic expression of NOS-II, independent of the second messenger system mentioned above, implies that there is a unique role for the inducible NOS isoform in nerve cell differentiation, independent of the NO/guanylate cyclase/cGMP pathway.

Aging↗

PubMed1999

Expression of nicotinic acetylcholine receptor subunits in the cerebral cortex in Alzheimer's disease: histotopographical correlation with amyloid plaques and hyperphosphorylated-tau protein.

Impairment of cholinergic transmission and decreased numbers of nicotinic binding sites are well-known features accompanying the cognitive dysfunction seen in Alzheimer's disease (AD). In order to elucidate the underlying cause of this cholinoceptive dysfunction, the expression of two pharmacologically different nicotinic acetylcholine receptor (nAChR) subunits (alpha4, alpha7) was studied in the cerebral cortex of Alzheimer patients as compared to controls. Patch-clamp recordings of 14 dissociated neurons of control cortices showed responses suggesting the existence of alpha4- and alpha7-containing functional nAChRs in the human cortex. In cortices of Alzheimer patients and controls, the pattern of distribution and the number of alpha4 and alpha7 mRNA-expressing neurons were similar, whereas at the protein level a decrease in the density of alpha4- and alpha7-expressing neurons of approximately 30% was observed in Alzheimer patients. The histotopographical correlation of nAChR expression with accompanying pathological changes, e.g. accumulation of hyperphosphorylated-tau (HP-tau) protein and beta-amyloid showed that neurons in the vicinity of beta-amyloid plaques bore both nAChR transcripts. Neurons heavily labelled for HP-tau, however, expressed little or no alpha4 and alpha7 mRNA. These results point to an impaired synthesis of nAChRs on the protein level as a possible cause of the cholinoceptive deficit in AD. Further investigations need to elucidate whether interactions of HP-tau with nAChR mRNA, or alterations in the quality of alpha4 and alpha7 transcripts give rise to decreased protein expression at the level of individual neurons.

Aged↗

PubMed1999

Regulation of the L-type Ca2+ channel during cardiomyogenesis: switch from NO to adenylyl cyclase-mediated inhibition.

In adult mammalian cardiomyocytes, stimulation of muscarinic receptors counterbalances the beta-adrenoceptor-mediated increase in myocardial contractility and heart rate by decreasing the L-type Ca2+ current (ICa) (1, 2). This effect is mediated via inhibition of adenylyl cyclase and subsequent reduction of cAMP-dependent phosphorylation of voltage-dependent L-type Ca2+ channels (3). Little is known, however, about the nature and origin of this pivotal inhibitory pathway. Using embryonic stem cells as an in vitro model of cardiomyogenesis, we found that muscarinic agonists depress ICa by 58 +/-3% (n=34) in early stage cardiomyocytes lacking functional beta-adrenoceptors. The cholinergic inhibition is mediated by the nitric oxide (NO)/cGMP system since it was abolished by application of NOS inhibitors (L-NMA, L-NAME), an inhibitor of the soluble guanylyl cyclase (ODQ), and a selective phosphodiesterase type II antagonist (EHNA). The NO/cGMP-mediated ICa depression was dependent on a reduction of cAMP/protein kinase A (PKA) levels since application of the catalytic subunit of PKA or of the PKA inhibitor PK) prevented the carbachol effect. In late development stage cells, as reported for ventricular cardiomyocytes (2, 4), muscarinic agonists had no effect on basal ICa but antagonized beta-adrenoceptor-stimulated ICa by 43 +/-4% (n=16). This switch in signaling pathways during development is associated with distinct changes in expression of the two NO-producing isoenzymes, eNOS and iNOS, respectively. These findings indicate a fundamental role for NO as a signaling molecule during early embryonic development and demonstrate a switch in the signaling cascades governing ICa regulation.

Adenine↗

PubMed1999

Nitric oxide decreases microvascular permeability in bradykinin stimulated and nonstimulated conditions.

This study examined the occurrence of endothelial nitric oxide (NO)-synthase (NOS-III) in terminal mesenteric vessels and the involvement of NO in microvascular permeability. Possible effects were studied in bradykinin (BK)-induced and basal conditions. NOS expression was investigated by using NOS-III immunohistochemistry and nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase histochemistry on the light- and electron-microscopic levels. Permeability was examined in dissected mesenteries of male rats weighing 250-300 g. Tissue treatment was performed with BK (100 nM), sodium nitroprusside (SNP, 1 and 10 microM), L-nitroarginine (L-NA, 300 microM), BK and L-NA, BK and SNP, L-NA and SNP, as well as with BK, SNP (10 microM), and the guanylylcyclase inhibitor ODQ (10 microM), and BK and ODQ alone. Pharmacologically induced permeability changes were studied with fluorescein isothiocyanate (FITC)-dextran 70 kDa as a tracer for macromolecular transport. Video images were analyzed with computer determination of integrated optical density (IOI). Results were statistically verified by analysis of variance and t test. Microvascular permeability was increased by 168% after BK treatment and was enhanced by NO-synthesis inhibition with L-NA by 607%. However, the NO donor SNP led to a reduced tracer extravasation to 105 and 58%, respectively, an effect blocked by ODQ. Under basal conditions without prior BK induction, L-NA also causes an increase of IOI by 25%, whereas coapplication with SNP resulted in only a 10% increase of permeability. These results point out that NO has a modulatory role for microvascular permeability by supporting the barrier function of the endothelial lining in stimulated and nonstimulated conditions.

Animals↗