Aortic pressure as a determinant of cardiac protein degradation

Titin governs myocardial passive stiffness with major support from microtubules and actin and the extracellular matrix

Myocardial passive stiffness is crucial for the heart's pump function and is determined by mechanical elements, including the extracellular matrix and cytoskeletal filaments; however, their individual contributions are controversially discussed and difficult to quantify. In this study, we targeted the cytoskeletal filaments in a mouse model, which enables the specific, acute and complete cleavage of the sarcomeric titin springs. We show in vitro that each cytoskeletal filament's stiffness contribution varies depending on whether the elastic or the viscous forces are considered and on strain level. Titin governs myocardial elastic forces, with the largest contribution provided at both low and high strain. Viscous force contributions are more uniformly distributed among the microtubules, titin and actin. The extracellular matrix contributes at high strain. The remaining forces after total target element disruption are likely derived from desmin filaments. Our findings answer longstanding questions about cardiac mechanical architecture and allow better targeting of passive myocardial stiffness in heart failure.

The Use of Porcine Proximal Tubular Cells for Studying NephrotoxicityIn Vitro:The Role of Oxidative Stress in Cisplatin-induced Cell Death

The effects of a widely used antitumour drug, cisplatin, on freshly isolated porcine proximal tubular cells (PPTC) in suspension were investigated. Incubation of the PPTC with 5-500μM cisplatin resulted in a decrease in mitochondrial membrane potential (MMP) and in cell death. In addition, the formation of reactive oxygen species (ROS) was observed within 20 minutes. Prevention of ROS formation with the antioxidants diphenyl- p-phenylene-diamine (DPPD) or desferrioxamine had no effect on the cisplatin-induced effects on MMP and cell death, implying that cisplatin-induced ROS formation is not a cause of cell death. In order to investigate whether the ROS formation was related to mitochondrial damage, we determined the effects of cisplatin on the enzymatic activities of NADP:ubiquinone reductase (Complex I) and succinate:ubiquinone reductase (Complex II) of the respiratory chain. Exposure of the PPTC to cisplatin resulted in a time-dependent and dose-dependent inhibition of the activities of both Complex I and Complex II. The inhibition of these activities and the depletion of ATP could not be prevented by the antioxidants, indicating that these effects are not a consequence of ROS formation. We propose that damage to the mitochondria could be a key event in cisplatin-induced cell death.

Methionine Sulfoxide Reductase A Deficiency Exacerbates Cisplatin-Induced Nephrotoxicity via Increased Mitochondrial Damage and Renal Cell Death

AIMS

Methionine sulfoxide reductase A (MsrA), which is abundantly localized in the mitochondria, reduces methionine-S-sulfoxide, scavenging reactive oxygen species (ROS). Cisplatin, an anticancer drug, accumulates at high levels in the mitochondria of renal cells, causing mitochondrial impairment that ultimately leads to nephrotoxicity. Here, we investigated the role of MsrA in cisplatin-induced mitochondrial damage and kidney cell death using MsrA gene-deleted (MsrA^-/-) mice.

RESULTS

Cisplatin injection resulted in increases of ROS production, methionine oxidation, and oxidative damage in the kidneys. This oxidative stress was greater in MsrA^-/- mouse kidneys than in wild-type (MsrA^+/+) mouse kidneys. MsrA gene deletion exacerbated cisplatin-induced reductions in the expression and activity of MsrA and MsrBs, and the expression of thioredoxin 1, glutathione peroxidase 1 and 4, mitochondrial superoxide dismutase, cystathionine-β-synthase, and cystathionine-γ-lyase. Cisplatin induced swelling, cristae loss, and fragmentation of mitochondria with increased lipid peroxidation, more so in MsrA^-/- than in MsrA^+/+ kidneys. The ratio of mitochondrial fission regulator (Fis1) to fusion regulator (Opa1) was higher in MsrA^-/- than MsrA^+/+ mice. MsrA deletion exacerbated cisplatin-induced increases in Bax to Bcl-2 ratio, cleaved caspase-3 level, and apoptosis, whereas MsrA overexpression attenuated cisplatin-induced oxidative stress and apoptosis.

INNOVATION

MsrA gene deletion in mice exacerbates cisplatin-induced renal injury through increases of mitochondrial susceptibility, whereas MsrA overexpression protects cells against cisplatin.

CONCLUSION

This study demonstrates that MsrA protects kidney cells against cisplatin-induced methionine oxidation, oxidative stress, mitochondrial damage, and apoptosis, suggesting that MsrA could be a useful target protein for the treatment of cisplatin-induced nephrotoxicity. Antioxid. Redox Signal. 27, 727-741.

C-phycocyanin prevents cisplatin-induced mitochondrial dysfunction and oxidative stress

The potential of C-phycocyanin (C-PC) to prevent cisplatin (CP)-induced kidney mitochondrial dysfunction was determined in CD-1 male mice. The CP-induced mitochondrial dysfunction was characterized by ultrastructural abnormalities and by decrease in the following parameters in isolated kidney mitochondria: adenosine diphosphate (ADP)-induced oxygen consumption (state 3), respiratory control ratio, ADP/oxygen (ADP/O) ratio, adenosine triphosphate synthesis, membrane potential, calcium retention, glutathione (GSH) content, and activity of respiratory complex I, aconitase, catalase, and GSH peroxidase. These mitochondria also showed increase in hydrogen peroxide production, malondialdehyde, and 3-nitrotyrosine protein adducts content. The above-described changes, as well as CP-induced nephrotoxicity, were attenuated in mice pretreated with a single injection of C-PC. Our data suggest that the attenuation of mitochondrial abnormalities is involved in the protective effect of C-PC against CP-induced nephrotoxicity. This is the first demonstration that C-PC pretreatment prevents CP-induced mitochondrial dysfunction in mice.

Cardiotoxicity in rabbits after a low-level exposure to diazinon, propoxur, and chlorpyrifos

Lethal cardiac complications leading to death and various arrhythmias have been reported after organophosphate and/or carbamate poisonings. The present study focuses on the long-term effects of repeated low-level exposure to diazinon, propoxur, and chlorpyrifos (CPF) on cardiac function in rabbits. The yearly based experimental scheme of exposure consisted of two oral administration periods, lasting 3 months and 1 month each, interrupted by an 8-month washout period (total duration 12 months). At the end of the experimental scheme, the rabbits underwent an echocardiographic evaluation under sedation, after which they were killed and the tissue and serum samples were collected. A mild localized cardiotoxic effect was established by echocardiography for the three pesticides tested. Severe histological alterations were identified, especially in the diazinon-treated animals in agreement with increased persistence of this pesticide established in the cardiac tissue. In addition, all pesticides tested increased the oxidative stress and oxidative modifications in the genomic DNA content of the cardiac tissues, each one following a distinct mechanism.

Angiogenic microenvironment augments impaired endothelial responses under diabetic conditions

Diabetes-induced cardiomyopathy is characterized by cardiac remodeling, fibrosis, and endothelial dysfunction, with no treatment options currently available. Hyperglycemic memory by endothelial cells may play the key role in microvascular complications in diabetes, providing a potential target for therapeutic approaches. This study tested the hypothesis that a proangiogenic environment can augment diabetes-induced deficiencies in endothelial cell angiogenic and biomechanical responses. Endothelial responses were quantified for two models of diabetic conditions: 1) an in vitro acute and chronic hyperglycemia where normal cardiac endothelial cells were exposed to high-glucose media, and 2) an in vivo chronic diabetes model where the cells were isolated from rats with type I streptozotocin-induced diabetes. Capillary morphogenesis, VEGF and nitric oxide expression, cell morphology, orientation, proliferation, and apoptosis were determined for cells cultured on Matrigel or proangiogenic nanofiber hydrogel. The effects of biomechanical stimulation were assessed following cell exposure to uniaxial strain. The results demonstrate that diabetes alters cardiac endothelium angiogenic response, with differential effects of acute and chronic exposure to high-glucose conditions, consistent with the concept that endothelial cells may have a long-term "hyperglycemic memory" of the physiological environment in the body. Furthermore, endothelial cell exposure to strain significantly diminishes their angiogenic potential following strain application. Both diabetes and strain-associated deficiencies can be augmented in the proangiogenic nanofiber microenvironment. These findings may contribute to the development of novel approaches to reverse hyperglycemic memory of endothelium and enhance vascularization of the diabetic heart, where improved angiogenic and biomechanical responses can be the key factor to successful therapy.

Androgen modulates cardiac fibrosis contributing to gender differences on heart failure

Chronic heart failure (HF) is a major health problem throughout the world. Gender has significant effects on the pathophysiology of HF. Low levels of free testosterone are independently associated with increased chronic HF symptoms and mortality. Cardiac fibrosis plays a pivotal role in structural remodeling in HF. Transforming growth factor (TGF)-β, angiotensin II and oxidative stress contribute to the activity/extent of cardiac fibrosis. Androgen deficiency can up-regulate TGF-β expression under angiotensin II stimulation in vivo. In this review, we summarized the potential mechanisms accounting for the effects of androgen on cardiac fibrosis through regulating fibrocytes activity under TGF, which can explain wound healing and cardiac fibrosis in male with acute myocardial injury and chronic HF.

Features and full reversibility of the renal toxicity of the ruthenium-based drug NAMI-A in mice

The ruthenium-based compound imidazolium trans-imidazoledimethylsulfoxide-tetrachlororuthenate (NAMI-A) is free of cytotoxicity up to 1mM concentration after 1h in vitro exposure of the LLC-PK1 renal tubule cells. In vivo, one cycle of i.p. administrations of 35 mg/kg/day NAMI-A (1 cycle=6 consecutive days), is free of a measurable toxicity on mouse kidneys. After two cycles with a one-week drug-free washout between cycles, mitochondrial membrane potential of the renal cells drops by 37% (p<0.05), serum creatinine increases by 30% (p<0.05) and a significant decrease of body weight of 12% (p<0.05) occurs. These parameters return to normal within 7 days after the end of treatment. A cycle-dependent alteration of glomeruli and a diffused swelling of renal tubules are also evident leading to a significant alteration of these structures after the third cycle. These effects are completely prevented if a 2-week drug free washout is used between two consecutive cycles. These data support the toxic accumulation of NAMI-A or of its products of transformation in the kidneys and stress the need of at least 14 days washout between two treatment cycles when the drug is given daily for 6 consecutive days.

Computational modeling of apoptotic signaling pathways induced by cisplatin

Background

Apoptosis is an essential property of all higher organisms that involves extremely complex signaling pathways. Mathematical modeling provides a rigorous integrative approach for analyzing and understanding such intricate biological systems.

Results

Here, we constructed a large-scale, literature-based model of apoptosis pathways responding to an external stimulus, cisplatin. Our model includes the key elements of three apoptotic pathways induced by cisplatin: death receptor-mediated, mitochondrial, and endoplasmic reticulum-stress pathways. We showed that cisplatin-induced apoptosis had dose- and time-dependent characteristics, and the level of apoptosis was saturated at higher concentrations of cisplatin. Simulated results demonstrated that the effect of the mitochondrial pathway on apoptosis was the strongest of the three pathways. The cross-talk effect among pathways accounted for approximately 25% of the total apoptosis level.

Conclusions

Using this model, we revealed a novel mechanism by which cisplatin induces dose-dependent cell death. Our finding that the level of apoptosis was affected by not only cisplatin concentration, but also by cross talk among pathways provides in silico evidence for a functional impact of system-level characteristics of signaling pathways on apoptosis.

Cisplatin nephrotoxicity involves mitochondrial injury with impaired tubular mitochondrial enzyme activity

Cisplatin is a widely used antineoplastic agent. However, its major limitation is dose-dependent nephrotoxicity whose precise mechanism is poorly understood. Recent studies have suggested that mitochondrial dysfunction in tubular epithelium contributes to cisplatin-induced nephrotoxicity. Here the authors extend those findings by describing the role of an important electron transport chain enzyme, cytochrome c oxidase (COX). Immunohistochemistry for COX 1 protein demonstrated that, in response to cisplatin, expression was mostly maintained in focally damaged tubular epithelium. In contrast, COX enzyme activity in proximal tubules (by light microscopy) was decreased. Ultrastructural analysis of the cortex and outer stripe of the outer medulla showed decreased mitochondrial mass, disruption of cristae, and extensive mitochondrial swelling in proximal tubular epithelium. Functional electron microscopy showed that COX enzyme activity was decreased in the remaining mitochondria in the proximal tubules but maintained in distal tubules. In summary, cisplatin-induced nephrotoxicity is associated with structural and functional damage to the mitochondria. More broadly, using functional electron microscopy to measure mitochondrial enzyme activity may generate mechanistic insights across a spectrum of renal disorders.

Cisplatin-induced nephrotoxicity and targets of nephroprotection: an update

Cisplatin is a highly effective antitumor agent whose clinical application is limited by the inherent nephrotoxicity. The current measures of nephroprotection used in patients receiving cisplatin are not satisfactory, and studies have focused on the investigation of new possible protective strategies. Many pathways involved in cisplatin nephrotoxicity have been delineated and proposed as targets for nephroprotection, and many new potentially protective agents have been reported. The multiple pathways which lead to renal damage and renal cell death have points of convergence and share some common modulators. The most frequent event among all the described pathways is the oxidative stress that acts as both a trigger and a result. The most exploited pathways, the proposed protective strategies, the achievements obtained so far as well as conflicting data are summarized and discussed in this review, providing a general view of the knowledge accumulated with past and recent research on this subject.

Cisplatin-induced renal salt wasting syndrome

Cisplatin was the first platinum compound to be introduced as a chemotherapeutic agent with antineoplastic activity against a wide variety of solid tumors. Renal impairment with a decline in glomerular filtration has been the classical nephrotoxicity of cisplatin. Renal salt wasting syndrome is yet another, though it is not common. Previous studies were identified by searching the Pubmed database using the following keywords: cisplatin, cisplatin nephrotoxicity, renal salt wasting, and salt loosing nephropathy. Renal salt wasting syndrome has been described in 17 case reports since 1984. It is a rare side effect of cisplatin that manifests with polyuria, hypovolemia, and hyponatremia, and, because of similarities in clinical settings and laboratory values, it is frequently misdiagnosed as a syndrome of inappropriate antidiuretic hormone. Other causes of polyuria and hyponatremia should be excluded. Treatment aims at restoring the lost water and salt. Substituting cisplatin with carboplatin depends on individual clinical settings. Prognosis is excellent, as recovery was the rule in all the reported cases.

Impaired fasting glycaemia vs impaired glucose tolerance: similar impairment of pancreatic alpha and beta cell function but differential roles of incretin hormones and insulin action

AIMS/HYPOTHESIS

The impact of strategies for prevention of type 2 diabetes in isolated impaired fasting glycaemia (i-IFG) vs isolated impaired glucose tolerance (i-IGT) may differ depending on the underlying pathophysiology. We examined insulin secretion during OGTTs and IVGTTs, hepatic and peripheral insulin action, and glucagon and incretin hormone secretion in individuals with i-IFG (n = 18), i-IGT (n = 28) and normal glucose tolerance (NGT, n = 20).

METHODS

Glucose tolerance status was confirmed by a repeated OGTT, during which circulating insulin, glucagon, glucose-dependent insulinotrophic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) levels were measured. A euglycaemic-hyperinsulinaemic clamp with [3-3H]glucose preceded by an IVGTT was performed.

RESULTS

Absolute first-phase insulin secretion during IVGTT was decreased in i-IFG (p = 0.026), but not in i-IGT (p = 0.892) compared with NGT. Hepatic insulin sensitivity was normal in i-IFG and i-IGT individuals (p > or = 0.179). Individuals with i-IGT had peripheral insulin resistance (p = 0.003 vs NGT), and consequently the disposition index (DI; insulin secretion x insulin sensitivity) during IVGTT (DI(IVGTT))) was reduced in both i-IFG and i-IGT (p < 0.005 vs NGT). In contrast, the DI during OGTT (DI(OGTT)) was decreased only in i-IGT (p < 0.001), but not in i-IFG (p = 0.143) compared with NGT. Decreased levels of GIP in i-IGT (p = 0.045 vs NGT) vs increased levels of GLP-1 in i-IFG (p = 0.013 vs NGT) during the OGTT may partially explain these discrepancies. Basal and post-load glucagon levels were significantly increased in both i-IFG and i-IGT individuals (p < or = 0.001 vs NGT).

CONCLUSIONS/INTERPRETATION

We propose that differentiated preventive initiatives in prediabetic individuals should be tested, targeting the specific underlying metabolic defects.

ECM remodeling in hypertensive heart disease

Hypertensive heart disease (HHD) occurs in patients that clinically have both diastolic and systolic heart failure and will soon become the most common cause of heart failure. Two key aspects of heart failure secondary to HHD are the relatively highly prevalent LV hypertrophy and cardiac fibrosis, caused by changes in the local and systemic neurohormonal environment. The fibrotic state is marked by changes in the balance between MMPs and their inhibitors, which alter the composition of the ECM. Importantly, the fibrotic ECM impairs cardiomyocyte function. Recent research suggests that therapies targeting the expression, synthesis, or activation of the enzymes responsible for ECM homeostasis might represent novel opportunities to modify the natural progression of HHD.

Renoprotective effect of Spirulina fusiformis on cisplatin-induced oxidative stress and renal dysfunction in rats

Cisplatin is an effective chemotherapeutic agent used in the treatment of a wide array of both pediatric and adult malignancies. Dose-dependent and cumulative nephrotoxicity is the major toxicity of this compound, sometimes requiring a reduction in dose or discontinuation of treatment. Recent evidences have implicated oxidative and nitrosative stress in cisplatin-induced nephrotoxicity. Spirulina fusiformis, blue-green algae, is claimed to be a potential antioxidant. The present study was designed to explore the renoprotective potential of Spirulina fusiformis against cisplatin-induced oxidative stress and renal dysfunction. Spirulina fusiformis (500,1000,1500 mg/kg(-1) p.o.) was administered 2 days before and until 3 days after cisplatin challenge (5 mg/kg(-1) i.p.). Renal injury was assessed by measuring serum creatinine, blood urea nitrogen, creatinine and urea clearance, and serum nitrite levels. Renal oxidative stress was determined by renal TBARS levels, reduced glutathione levels, and by enzymatic activity of superoxide dismutase and catalase. A single dose of cisplatin produced marked renal oxidative and nitrosative stress and significantly deranged renal functions. Chronic Spirulina fusiformis treatment significantly and dose-dependently restored renal functions, reduced lipid peroxidation, and enhanced reduced glutathione levels, superoxide dismutase, and catalase activities. The results of the present study clearly demonstrate the pivotal role of reactive oxygen species and their relation to renal dysfunction and point to the therapeutic potential of Spirulina fusiformis in cisplatin-induced nephrotoxicity.

Role of ERK activation in cisplatin-induced apoptosis in OK renal epithelial cells

Cisplatin induces apoptosis in a variety of cell types. However, the signaling pathway of cisplatin-induced apoptosis in renal epithelial cells is poorly understood. The present study was undertaken to determine the role of the extracellular signal-regulated kinase (ERK) in cisplatin-induced apoptosis of renal epithelial cells using opossum kidney cells. Cisplatin at 50 microM induced apoptosis in a time-dependent manner. Cisplatin treatment caused sustained activation of ERK1/2, which was prevented by PD98059 and U0126, inhibitors of ERK1/2 upstream kinase MEK1/2. Transient transfection of cells with constitutive active MEK1 increased the cisplatin-induced apoptosis, whereas that with a dominant-negative mutant of MEK1 decreased it. Cisplatin induced an increase in Bax expression, mitochondrial membrane depolarization, mitochondrial cytochrome c release and caspase-3 activation, and these changes were prevented by the MEK inhibitor. These results suggested that (1) the ERK1/2 activation is required for the cisplatin-induced apoptosis of renal epithelial cells; and (2) ERK1/2 mediates the mitochondria-dependent apoptotic signaling by acting upstream of Bax expression.

p53-dependent caspase-2 activation in mitochondrial release of apoptosis-inducing factor and its role in renal tubular epithelial cell injury

We demonstrate the role of p53-mediated caspase-2 activation in the mitochondrial release of apoptosis-inducing factor (AIF) in cisplatin-treated renal tubular epithelial cells. Gene silencing of AIF with its small interfering RNA (siRNA) suppressed cisplatin-induced AIF expression and provided a marked protection against cell death. Subcellular fractionation and immunofluorescence studies revealed cisplatin-induced translocation of AIF from the mitochondria to the nuclei. Pancaspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone or p53 inhibitor pifithrin-alpha markedly prevented mitochondrial release of AIF, suggesting that caspases and p53 are involved in this release. Caspase-2 and -3 that were predominantly activated in response to cisplatin provided a unique model to study the role of these caspases in AIF release. Cisplatin-treated caspase-3 (+/+) and caspase-3 (-/-) cells exhibited similar AIF translocation to the nuclei, suggesting that caspase-3 does not affect AIF translocation, and thus, caspase-2 may be involved in the translocation. Caspase-2 inhibitor benzyloxycarbonyl-Val-Asp-Val-Ala-Asp-fluoromethylketone or down-regulation of caspase-2 by its siRNA significantly prevented translocation of AIF. Caspase-2 activation was a critical response from p53, which was markedly induced and phosphorylated in cisplatin-treated cells. Overexpression of p53 not only resulted in caspase-2 activation but also mitochondrial release of AIF. The p53 inhibitor pifithrin-alpha or p53 siRNA prevented both cisplatin-induced caspase-2 activation and mitochondrial release of AIF. Caspase-2 activation was dependent on the p53-responsive gene, PIDD, a death domain-containing protein that was induced by cisplatin in a p53-dependent manner. These results suggest that caspase-2 activation mediated by p53 is an important pathway involved in the mitochondrial release of AIF in response to cisplatin injury.

Saline, mannitol, and furosemide hydration in acute cisplatin nephrotoxicity: a randomized trial

OBJECTIVE

To determine which hydration (saline, saline + mannitol, or saline + furosemide) is associated with least cisplatin nephrotoxicity.

METHODS

We randomized 49 women who received cisplatin (75 mg/m(2) every 3 weeks) into one of the three hydration arms. The 24-h creatinine clearance was measured before and on day 6 after cisplatin infusion. The patients of each arm received 2 l of saline hydration. In the saline + furosemide arm, 40 mg of furosemide was given after hydration. In the saline + mannitol arm, 50 g of mannitol was mixed with the cisplatin.

RESULTS

For the first cycle of chemotherapy, 15 women were randomized to saline, 17 to saline + furosemide, and 17 to saline + mannitol. For each group, the creatinine clearances before cisplatin infusion were (means+/-SD, milliliters per minute) 84.5+/-26.8, 82.5+/-24.0 and 87.4+/-25.6, and after cisplatin infusion were 79.1+/-31.9, 68.7+/-21.5, and 56.4+/-22.9, respectively. The decreases in creatinine clearance were similar between the saline group and the saline + furosemide group ( P=0.66), but different between the saline + mannitol group and the saline group ( P=0.02) or the saline + furosemide group ( P=0.02). As each woman received multiple courses of cisplatin, 15 who received saline contributed 41 paired datasets, 17 who received saline + furosemide contributed 49 paired datasets, and 17 who received saline + mannitol contributed 36 paired datasets showed similar patterns.

CONCLUSIONS

Hydration with saline or saline + furosemide appears to be associated with less cisplatin nephrotoxicity than saline + mannitol.

Tumour-inhibiting platinum complexes--state of the art and future perspectives

Thirty years after the onset of the first clinical studies with cisplatin, the development of antineoplastic platinum drugs continues to be a productive field of research. This article reviews the current preclinical and clinical status, including a discussion of the molecular basis for the activity of the parent drug cisplatin and platinum drugs of the second and third generation, in particular their interaction with DNA. Further emphasis is laid on the development of third generation platinum drugs with activity in cisplatin-resistant tumours, particularly on chelates containing 1,2-diaminocyclohexane (DACH) and on the promising and more recently evolving field of non-classic ( trans- and multinuclear) platinum complexes. The development of oral platinum drugs and drug targeting strategies using liposomes, polymers or low-molecular-weight carriers in order to improve the therapeutic index of platinum chemotherapy are also covered.

Protective effect of procaine hydrochloride on cisplatin-induced alterations in rat kidney

Efforts have been made to reduce the undesirable side effects of cisplatin, mainly nephro- and neurotoxicity, but their reduction is usually accompanied by a concomitant inhibition of antitumor activity. The local anesthetic procaine hydrochloride (P.HCl) improves the therapeutic index of cisplatin not only by the reduction of its nephro- and hemotoxicity, but also by an increase of its antitumor activity. We therefore investigated the effects of a combined treatment of cisplatin and P.HCl on rat kidneys and compared this to kidneys from rats treated with a toxic dose of cisplatin or P.HCl alone. Treatment with a saline solution was used as control. Dehydrogenase activities [succinate dehydrogenase (SDH) and NADPH diaphorase reaction demonstrating nitric oxide synthase (NOS/NADPHd)] and phosphatase activities [K -nitrophenyl phosphatase (K pNPPase), alkaline phosphatase (AlPase) and acid phosphatase (AcPase)] were studied on cryostatic sections of kidneys from controls and treated rats. Evidence of heavy morphological damage and altered AlPase and AcPase activities induced by cisplatin were observed in the S3 segment of the proximal tubules. In addition, SDH and K pNPPase activities showed some changes in the distal tubule cells. The NOS/NADPHd activity in macula densa was drastically reduced. Combined treatment of cisplatin and P.HCl greatly attenuated morphological alterations of the rat kidney and reduced the changes in enzyme activities, except for NOS/NADPHd activity, compared to the cisplatin-treated group of animals. The study indicates that, in cisplatin-induced nephrotoxicity, a significant role is played by enzyme activities, in particular K pNPPase and NOS/NADPHd, and that P.HCl can mitigate the nephrotoxicity of cisplatin, possibly by influencing some enzyme activities involved in important renal metabolic pathways.

Design and construction of a uniaxial cell stretcher

In vitro mechanical cell stimulators are used for the study of the effect of mechanical stimulation on anchorage-dependent cells. We developed a new mechanical cell stimulator, which uses stepper motor technology and computer control to achieve a high degree of accuracy and repeatability. This device also uses high-performance plastic components that have been shown to be noncytotoxic, dimensionally stable, and resistant to chemical degradation from common culture laboratory chemicals. We show that treatment with glow discharge for 25 s at 20 mA is sufficient to modify the surface of the rubber to allow proper adhesion for polymerization of aligned collagen. We show through finite element analysis that the middle area of the membrane, away from the clamped ends, is predictable, homogeneous, and has negligible shear strain. To test the efficacy of the mechanical stretch, we examined the effect of mechanical stimulation on the production of beta(1)-integrin by neonatal rat cardiac fibroblasts. Mechanical stimulation was tested in the range of 0-12% stretch and 0-10-cycles/min stretch frequency. The fibroblasts respond with an increase in beta(1)-integrin at 3% stretch and a decrease at 6 and 12% stretch. Stretch frequency was found to not significantly effect the concentration of beta(1)-integrin. These studies yield a new and improved mechanical cell stimulator and demonstrate that mechanical stimulation has an effect on the expression of beta(1)-integrin.

Cisplatin DNA adduct detection and depurination measured by 32P DNA radiolabeling and two-dimensional thin-layer chromatography: a time and concentration study

Platinum-based chemotherapies cause the formation of DNA adducts and have profound effects on DNA. This study measured cis-diamminedichloroplatinum II (cisplatin) DNA adducts by 32P-radiolabeling DNA, enzymatically digesting radiolabeled DNA, separating the formed adducts on two-dimensional thin-layer chromatography, and quantitating the adducts with autoradiography and densitometry. HeLa DNA was incubated with cisplatin at varying concentrations (6.25-325 nM) and times (0 min to 72 hr). Cisplatin rapidly depurinated dGMP and dAMP (90%, 15-min incubation with 325 nM cisplatin). Partial depurination of dGMP (15%) and dAMP (25%) occurred with lower cisplatin concentrations at equal incubation times. A minimum of four new adducts, with relatively rapid migratory patterns, were detected at high cisplatin concentrations with short incubation times. These results indicate that the depurination of DNA correlates with DNA adduct formation and that the quantification of these adducts may be applicable to monitoring tumor and host cell response to cisplatin chemotherapy.

Nitric oxide-dependent guanylyl cyclase participates in the glutamatergic neurotransmission within the rostral ventrolateral medulla of awake rats

A well-known action of nitric oxide (NO) is to stimulate the soluble form of guanylyl cyclase, evoking an accumulation of cyclic GMP in target cells. The aim of the present study was to examine the effects of inhibition of guanylyl cyclase dependent on NO during cardiovascular responses induced by L-glutamate and S-nitrosoglutathione (SNOG) microinjected into the rostral ventrolateral medulla (RVLM) of awake rats. Three days before the experiments, adult male Wistar rats (280 to 320 g) were anesthetized for implantation of guide cannulas to the desired stereotaxic position (AP=-2.5 mm, L=1.8 mm) in relation to lambda. The cannulas were fixed to the skull with acrylic cement. Twenty-four hours before the experiments, a femoral artery and vein were cannulated for recording arterial pressure (AP) and heart rate (HR) and injection of anesthetic. Unilateral microinjections (100 nL) of L-glutamate (5 nmol/L) and SNOG (2.5 nmol/L) were made into the histologically confirmed RVLM. The cardiovascular responses to these drugs were evaluated before and after microinjection (3 nmol/L, 200 nL) of either methylene blue or oxodiazoloquinoxaline (ODQ). The hypertensive effect of L-glutamate was attenuated by 74% after methylene blue (DeltaAP=49+/-8 to 13+/-4 mm Hg) and by 80.5% after ODQ (DeltaAP=30+/-2 to 6+/-2 mm Hg). The increase in AP produced by SNOG was fully blocked by ODQ (DeltaAP=39+/-8 to 1+/-2 mm Hg). These data indicate that cyclic GMP mechanisms have a key role in glutamatergic neurotransmission in the RVLM of awake rats, and it is most probable that NO participates in this response.

Intrinsic vasomotor innervation of blood vessels in human ventrolateral medulla

Medullae were obtained at autopsy from seven patients with no neurologic disease, and sections were processed for tyrosine hydroxylase (TH), nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d), or both. Both TH- and NADPH-d reactive neurons had close anatomical relationship with penetrating blood vessels in the ventrolateral medulla (VLM). Three patterns were identified: 1) processes arising from a neighboring neuron reaching the blood vessel; 2) direct appositions of cell bodies to blood vessels; and 3) fibers coursing parallel to the blood vessels. This intrinsic innervation may provide a mechanism of coupling among local metabolism, sympathetic activity, and blood flow in the VLM.

Pressure-induced expression of heat shock protein 70 mRNA in adult rat heart is coupled both to protein kinase A-dependent and protein kinase C-dependent systems

BACKGROUND

Production of heat shock protein 70 (HSP70) in the heart is induced by hemodynamic stress, but its intracellular signal transduction system has not been elucidated well.

OBJECTIVE

To investigate the hypothesis that protein kinase A (PKA)-dependent and protein kinase C (PKC)dependent systems are involved in the pressure-induced expression of HSP70 mRNA in perfused adult rat heart

METHODS

Isolated tetrodotoxin-arrested Sprague-Dawley rat hearts were perfused as Langendorff preparations at a constant aortic pressure of 60 mmHg. Aortic pressure in rats of the pressure-overloaded group was elevated from 60 to 120 mmHg for 2-120 min. cAMP contents and rates of synthesis of protein were measured by radioimmunoassay and the incorporation of [14C]-phenylalanine into total heart protein, respectively. Expression of HSP70 mRNA was determined by Northern blot analysis.

RESULTS

Elevation of aortic pressure significantly increased cAMP content after 2 min of perfusion (by 41%), significantly increased rates of synthesis of protein during the second hour of perfusion (by 41%), and induced expression of HSP70 mRNA maximally after 60 min of perfusion (2.7-fold the control value). Exposure to glucagon, forskolin or 1 -methyl-3-isobutylxanthine mimicked increases in these parameters caused by elevation of aortic pressure. Administration of a selective PKA inhibitor, H-89, significantly prevented induction of increases in expression of HSP70 mRNA and rates of synthesis of protein by a high pressure overload and exposure to agents that increase cAMP content. Furthermore, administration of phorbol ester induced expression of HSP70 mRNA. Administration of a PKC inhibitor, calphostin C, significantly prevented induction of increases in expression of HSP70 mRNA by a pressure overload and by exposure to phorbol ester.

CONCLUSIONS

These results suggest that the pressure-induced induction of production of HSP70 is regulated both by PKA-dependent and by PKC-dependent systems during periods of active synthesis of protein in adult rat heart.

Involvement of transcriptional and posttranscriptional mechanisms in cardiac overload-induced increase of B-type natriuretic peptide gene expression

The induction of atrial and ventricular B-type natriuretic peptide (BNP) gene expression is one of the earliest events occurring during hemodynamic overload. To examine the molecular mechanisms for increased BNP gene expression during cardiac overload, we studied the induction of the BNP gene expression compared with that of atrial natriuretic peptide (ANP) in a modified perfused rat heart preparation. An increase in right atrial pressure of 5 mm Hg resulted in a 1.4-fold (P < .05) and 2.2-fold (P < .01) increase in BNP mRNA levels after 1 and 2 hours, respectively, whereas ANP mRNA levels remained unchanged. Stretching for up to 2 hours also significantly increased right atrial immunoreactive BNP (ir-BNP) levels (from 15.8 +/- 2.2 to 20.1 +/- 1.2 ng/mg, P < .05). Actinomycin D (10 micrograms/mL), a transcriptional inhibitor, completely inhibited the stretch-induced increase in atrial BNP mRNA levels at 1 hour (P < .05) and 2 hours (P < .001), whereas a protein synthesis inhibitor, cycloheximide (90 micrograms/mL), had no effect on basal or direct mechanical stretch-induced increase in right atrial BNP mRNA levels. Furthermore, we examined the role of tyrosine kinase and protein kinase C activities in acute mechanical stretch-induced increase in BNP synthesis. Tyrosine kinase inhibitors lavendustin A (1 mumol/L) and tyrphostin A25 (3 mumol/L) and protein kinase C inhibitors staurosporine (30 nmol/L) and chelerythrine (1 mumol/L) prevented the stretch-induced increase in right atrial ir-BNP concentrations at 2 hours. In addition, chelerythrine inhibited the increase of right atrial BNP mRNA levels stimulated by cardiac overload. These resuls demonstrate that the early increase of BNP mRNA levels by mechanical stretch results from increased transcriptional activation and is independent of protein synthesis. Our results also suggest that protein kinase C and tyrosine kinases activities may be involved in coupling cardiac overload to alterations in atrial BNP synthesis.

Endothelial injury of capillaries in the stria vascularis of guinea pigs treated with cisplatin and gentamicin

The drugs cisplatin and gentamicin are used for treatment of various cancer patients suffering from infection. The authors report a detailed electron microscopic study of blood vessels in stria vascularis of guinea pigs after treatment with cisplatin alone and in combination with gentamicin. The most distinctive features expressing endothelial cellular injury were mitochondrial, including occasional paracrystalline inclusions; electron-lucent foci with depleted organelles; intracytoplasmic vacuole formations; lipid bodies; cytoplasmic extrusions located on the luminal surface; and severe luminal constriction of part of the vessels from animals treated with the combined drugs. The study suggests that the damage to strial capillaries due to treatment with cisplatin alone and in combination with gentamicin may contribute to the injurious effects of these drugs on the strial tissue. Furthermore, the results of this study may enlarge the awareness of the potential vascular damage and vascular complications in additional body systems after medical use of cisplatin alone or in combination with gentamicin.

Effect of long-term cyclic mechanical load on protein synthesis and morphological changes in cultured myocardial cells from neonatal rat

We studied the effect of prolonged cyclic mechanical stimulation on protein synthesis and morphological changes in cultured cardiac myocytes isolated from 3-day-old neonatal rats to develop an in vitro model for cardiac hypertrophy induced by a mechanical load. Myocardial cells were cultured on deformative culture plates with M-199 culture medium in the presence or absence of fetal calf serum (FCS), and a cyclic mechanical load was applied for 2 hours up to 15 days. Mechanical stimulation for 2 hours increased the 14C-phenylalanine incorporation rate of myocardial cells, both in the absence and presence of FCS or when the myocardial cells were either beating or arrested with tetrodotoxin. The incorporation rate always increased by mechanical stimulation during 15 days of cell culture as compared to cells that sustained no mechanical stress. The cell size and protein content, which increased gradually with mechanical stimulation and reached a maximum at 10 days, were even greater in the presence of FCS. Within 10 days myocardial cells had aligned in the direction of the maximal cyclic mechanical load. In these cells electron microscopy revealed an increase in the number of myofilaments associated with the development of mitochondria as recognized in the adult myocardial cells. These results indicate that long-term cyclic mechanical loading of cultured myocardial cells may be a good in vitro model for the study of cardiac hypertrophy.

Ultrastructural localization and afferent sources of corticotropin-releasing factor in the rat rostral ventrolateral medulla: implications for central cardiovascular regulation

We investigated the ultrastructural localization, afferent sources, and arterial pressure effects of corticotropin-releasing factor (CRF) in the nucleus reticularis rostroventrolateralis (RVL), a region of the ventrolateral medulla containing C1 adrenergic neurons and sympatho-excitatory reticulospinal afferents to sympathetic preganglionic neurons. A polyclonal antibody to CRF was localized in acrolein-fixed sections through the rat RVL by the peroxidase-antiperoxidase (PAP) method. Light microscopy showed that 1-7 perikarya/30 micron section and numerous varicose processes contained CRF-like immunoreactivity (CRF-LI). By electron microscopy, CRF-LI was most intensely localized to large (80-100 nm) dense-core vesicles within numerous terminals and a few perikarya and large dendrites. Approximately half of the terminals containing CRF-LI were in direct contact with unlabeled perikarya or dendrites; the remainder were in apposition to either unlabeled terminals or astrocytes. Most synaptic specializations were asymmetric synapses on small, unlabeled dendrites. To examine potential extrinsic sources of CRF-containing terminals in the C1 area of the RVL, PAP immunocytochemical localization of CRF was combined with retrograde transport of wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP). In all cases examined, a number of dually labeled neurons were found in the paraventricular nucleus (PVN) of the hypothalamus and a few dually labeled neurons were observed in the nuclei of the solitary tract; these labeled neurons were ipsilateral to the unilateral injection of WGA-HRP into the C1 area. Fewer dually labeled perikarya were detected in the lateral hypothalamic area and the lateral parabrachial nuclei, ipsilateral to the WGA-HRP injection. Additional physiological studies showed that bilateral microinjections of CRF into the C1 area of the RVL of urethane-anesthetized rats elicited a dose-related increase in arterial pressure. The results suggest that within the C1 area of the RVL, CRF released from terminals, arising predominantly from the PVN of the hypothalamus and probably from local neurons as well, may excite sympathoexcitatory reticulospinal neurons.

Platinum complex-induced dysfunction of cultured renal proximal tubule cells. A comparative study of carboplatin and transplatin with cisplatin

Platinum coordination complexes (PtCx) are potent against several types of cancer but are often nephrotoxic. With a view to developing a PtCx nephrotoxicity model, the toxicity of cisplatin (cDDP), transplatin (tDDP) and carboplatin (CBDCA) was studied in primary cultures of rabbit proximal tubule (RPT) cells and in the renal epithelial OK cell line. The cytotoxicity of these PtCx (10-3000 microM) was assessed after 24 h exposure of confluent monolayers in terms of LDH release; their effects at non-cytotoxic concentrations (1-1000 microM) on DNA and protein synthesis, glucose transport, marker enzymes and the total glutathione concentration were also determined, together with cellular platinum uptakes. The cytotoxicity ranking of the studied compounds differed for OK and RPT cells (cDDP > tDDP; cDDP > CBDCA and tDDP > cDDP; cDDP > CBDCA, respectively). Only results which were obtained in RPT cells corresponded to reported nephrotoxicity in vivo, making OK cells inappropriate for the study of PtCx nephrotoxicity in vitro. cDDP was about 10 times less cytotoxic for OK cells than for RPT cells because of lower cellular uptake. tDDP was unable markedly to inhibit biochemical and functional parameters in RPT cells below cytotoxic concentrations. At non-cytotoxic concentrations, cDDP and CBDCA depressed synthetic activity (mainly DNA) and, to a lesser extent, Na(+)-K(+)-ATPase activity and glucose transport in RPT cells. Total glutathione levels in RPT cells steadily increased during exposure to cDDP, tDDP and CBDCA, before the onset of cell death, arguing against an early role of glutathione depletion in PtCx toxicity.(ABSTRACT TRUNCATED AT 250 WORDS)

WR2721 as a modulator of cisplatin- and carboplatin-induced side effects in comparison with other chemoprotective agents: a molecular approach

Cisplatin is an active cytostatic that became successful in the treatment of several types of solid tumours after its nephrotoxic potential was controlled by hydration and diuresis. Thiol compounds were tested to reduce further cisplatin-induced nephrotoxicity. Thiosulphate is rapidly excreted by the kidneys and protects against cisplatin-induced nephrotoxicity by inactivating reactive platinum species in the kidney. Due to inactivation of cisplatin in the circulation, thiosulphate also interferes with its antitumour activity. Therefore, it is mainly used in two-route schedules, whereby cisplatin is delivered locally to the tumour (i.p. or i.a.) while systemic (i.v.) thiosulphate protects the kidneys. Diethyldithiocarbamate was shown to protect against cisplatin-induced nephrotoxicity in several animal models by reversing cellular damage. However, in the clinic it has been less successful, partly due to its central nervous system toxicity. The endogenous thiol compounds glutathione and metallothionein have been shown to reduce cisplatin-induced toxicity both in animal models and in clinical trials. However, the results are rather preliminary and a reduction in therapeutic efficacy may be expected, for both glutathione and metallothionein have been reported to be involved in platinum resistance. The thioether methionine has been shown to reduce cisplatin-induced nephrotoxicity in animal models but it has not yet been tested in the clinic. Cisplatin-induced acute emesis can be sufficiently controlled with a new class of 5-hydroxytryptamine-3 (5HT3)-receptor blockers, but delayed emesis remains a problem. High-dose cisplatin regimens with protection of the kidneys induces ototoxicity, peripheral neuropathy and myelotoxicity, which become dose-limiting. Neurotoxicity was partly reversed by the neurogenerative agent ORG2766, but this agent does not reduce other cisplatin-induced toxicities. Therefore, an agent capable of protecting multiple non-tumour tissues is needed. Carboplatin is a second-generation analogue of cisplatin with less nephro-, neuro- and ototoxicity. Carboplatin is at least as active as cisplatin at its maximum tolerated dose, which is defined by its myelotoxicity. Protection from carboplatin-induced myelotoxicity may be controlled by autologous bone marrow transplantation and/or hematopoietic growth factor infusions. High-dose carboplatin schedules may cause nephrotoxicity, neurotoxicity and ototoxicity. Again, the protection of multiple non-tumour tissues is needed. WR2721 appears to be such a modulating agent capable of protecting multiple non-tumour tissues. It was shown to be preferentially metabolized and taken up as the thiol metabolite WR1065 by non-tumour tissues as compared with (hypoxic) solid tumours. It was shown to protect mice from cisplatin-induced nephrotoxicity and from cisplatin- and carboplatin-induced myelotoxicity without interfering with the antitumour activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Fiber optic surface fluorometry-reflectometry technique in the renal physiology of rats

Most current knowledge on events in the mitochondria leading to acute renal failure originates from studies in which indirect methods were used. The disadvantage of these methods is that they cannot measure the turnover rate of various metabolites, and only one result per animal can be obtained. Chance et al. /9/ developed a method using optical techniques for continuously monitoring the fluorescence of intramitochondrial NADH, which has been applied mainly to the brain. This optical method has not yet been examined quantitatively in the kidney and no attempt has been made to adapt this method for routine measurement in kidney tissue. The purpose of this study was to adapt the surface fluorometry method for monitoring renal NADH redox state in situ, and to determine whether the hemodynamic artifacts involved in fluorometric studies of the renal surface in situ could be eliminated by using a correction factor. Another purpose was to understand the relationship between the changes in reflectance and blood volume in the rat kidney. This was achieved by measuring the reflectance after: a) blood exchange by FC-43 emulsion; b) intrarenal saline flush; c) occlusion of the renal vein, renal artery and reopening of the renal vein; d) calculation of the correlation between changes in kidney weight after renal artery occlusion, and the reflectance. Our results suggest that in the rat kidney, as opposed to the brain, a correction factor of 1:1 is not always applicable. This factor may vary between animals, and it is therefore necessary to adjust it electronically for each rat kidney. This observation contradicts the view suggesting a constant correction factor of 1:1 in the kidney. The results reported herein indicate that changes in the reflectance in the ischemic rat kidney are due to changes in blood volume. In conclusion, it seems that optical techniques for monitoring fluorescence are suitable for localized, continuous and non-invasive recording of tissue mitochondrial NADH redox states under various conditions in the rat kidney.

Quantitative analysis of bulbospinal projections from the rostral ventrolateral medulla: contribution of C1-adrenergic and nonadrenergic neurons

The contribution of C1-adrenergic and nonadrenergic neurons to the spinal projection from the rostral ventrolateral medulla (RVLM) and their relative innervation density throughout thoracic spinal segments were examined by combining the Fluorogold (FG) retrograde tracing technique with immunofluorescent labeling for the epinephrine-synthesis enzyme phenylethanolamine N-methyltransferase (PNMT). The results indicate that the RVLM-spinal projection is comprised of both PNMT-positive and PNMT-negative neurons located in the subretrofacial area of the RVLM, approximately 1 to 1.7 mm rostral to obex. The bulbospinal projection from the RVLM is predominantly ipsilateral, and bulbospinal neurons do not appear to be organized within the RVLM in a manner indicating their segmental termination site. Eighty-one percent (+/- 4%, n = 2) of the PNMT-positive cells in the ipsilateral subretrofacial RVLM were retrogradely labeled after unilateral FG injections into multiple thoracic levels of the intermediolateral cell column (IML). Following single level FG injections, the number of retrogradely labeled PNMT-positive neurons in the subretrofacial RVLM decreased with injections in more caudal thoracic segments, indicating a heavier innervation of the upper thoracic IML by C1 neurons. PNMT-negative neurons were the main component of the RVLM-spinal population with 63 +/- 8% (n = 7) of the non-PNMT-containing neurons within the ipsilateral subretrofacial RVLM innervating all thoracic levels of the IML. The results indicate that both C1-adrenergic and nonadrenergic neurons in the RVLM make a substantial contribution to the innervation of the IML.

Physiological hyperinsulinemia inhibits myocardial protein degradation in vivo in the canine heart

Myocardial protein turnover in vivo was examined in anesthetized dogs following a 16- or 36-hour fast and again during a hyperinsulinemic (2 mU/kg per minute) euglycemic clamp with or without amino acid replacement or during saline infusion. We measured myocardial phenylalanine balance and rates of protein synthesis and degradation, using the extraction of intravenously infused L-[ring-2,6-3H]phenylalanine and the dilution of its specific activity across the heart at isotopic steady state. After both a 16-hour (n = 19) and 36-hour fast (n = 10), there was net myocardial release of phenylalanine indicated by the negative balances for phenylalanine of -52 +/- 9 (p less than 0.001) and -38 +/- 9 (p less than 0.005) nmol/min, respectively. Overall, the basal rate of myocardial protein degradation was lower in the 36-hour-fasted animals (81 +/- 13 versus 121 +/- 12 nmol/min, p less than 0.05). Myocardial phenylalanine balance and rates of protein synthesis and degradation did not change during insulin and glucose infusion in the 36-hour-fasted animals (n = 10). In these animals, there was a 30-40% decline in plasma amino acid concentrations, including branched chain (p less than 0.001) and essential amino acids (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Essential hypertension associated with neurovascular compression: angiographic findings

According to the hypothesis of Jannetta, an arterial compression of the left root entry zone (REZ) of cranial nerves IX and X by looping arteries could play an important role in the pathogenesis of essential hypertension. In an initial anatomical study, the positions of the left vagus and glossopharyngeal nerves in the skull were radiographically determined in 10 cadavers. By using a pattern of REZ topography developed from this information, the angiographic findings in 107 hypertensive and 100 normotensive patients were then compared retrospectively. In 80% of the angiograms of the hypertensive patients that could be evaluated, an artery crossed the left REZ of cranial nerves IX and X. Most frequently, this was the posterior inferior cerebellar artery (35.3% of cases), followed by the vertebral artery (29.4% of cases) and the anterior inferior artery (19.1% of cases). In 9 cases (13%), both the posterior inferior cerebellar artery and the vertebral artery appeared in the REZ. Frequently, a larger diameter of the left vertebral artery was found. The angiograms of normotensive patients that could be evaluated revealed an artery in the REZ in only 34.5% of cases. Our results support the hypothesis that essential hypertension may be associated with neurovascular compression of the left REZ of cranial nerves IX and X.

Titin, a huge, elastic sarcomeric protein with a probable role in morphogenesis

Titin, the largest protein identified to date (over 1 micron long, almost 3 million daltons in mass) is the third most abundant component of the sarcomere. In the mature myofibril, titin molecules span from M line to Z line, forming a third filament system which provides sarcomeric alignment and elastic recoil. In the developing sarcomere, accumulating evidence from studies both in vivo and in vitro implicates titin as part of a morphogenetic scaffolding, upon which critical events in myofibrillogenesis are coordinated in a time- and space-dependent manner.

Neurovascular compression and essential hypertension. An angiographic study

The pathogenesis of essential hypertension still remains unclear. Recently, it has been supposed, that an arterial compression of the left root entry zone (REZ) of the cranial nerves IX and X by looping arteries may play a pathogenetic role. In this report we verified this hypothesis retrospectively by vertebral angiographies in 99 hypertensive and 57 normotensive patients. The angiographic findings were compared with the results obtained from an anatomic study, in which the positions of 10 left vagus/glossopharyngeal nerves in the skull were radiographically determined in 10 cadavers. By using a pattern of REZ topography developed from this information we obtained the following results: In 81% of the evaluable angiographies of hypertensive patients we found an artery in the left REZ of cranial nerves IX and X. The normotensive patients showed an artery in the REZ only in 41.7% of cases. Our results support the hypothesis that essential hypertension may be combined with neurovascular compression of the left REZ of cranial nerves IX/X.

Transmitter interactions in the central cholinergic control of blood pressure regulation

There are at least five mechanisms by which the central nervous system regulates neural and humoral systems that control the blood pressure (BP). Particular attention has been paid to central cholinergic-adrenergic interactions in the regulation of BP. Physostigmine and other anticholinesterases which penetrate the blood-brain barrier, both carbamates and organophosphates, produce an increase of BP. This effect can be abolished by atropine, but not by methylatropine. The available evidence indicates that physostigmine and other AChE inhibitors initially produce an activation of central muscarinic receptors, which subsequently leads to an increase of the peripheral adrenergic activity. The hypertensive response to physostigmine is possible only if a functionally competent ChE is present in the brain. This effect of physostigmine is regularly associated with a dose-related increase in the neural activity in the preganglionic fibers of the cervical sympathetic nerve. BP rise after physostigmine is significantly less in immunosympathectomized animals and almost completely abolished after chemical sympathectomy. Physostigmine significantly increased the plasma concentration of catecholamines. After electrocoagulation of the locus coeruleus, not only did a significant decrease occur in the basic level of noradrenaline in plasma, but there was also a strong depression of the noradrenaline plasma response to physostigmine and immobilization. Physostigmine increased lipolysis and glycogenolysis, whereas neostigmine did not produce any change. Several directly acting cholinergic agonists alter the functions of the cardiovascular system when injected directly into the cerebral ventricular system, or directly into various brain regions. The most probable sites of action of AChE inhibitors and directly acting cholinergic agonists are the locus coeruleus, the nucleus tractus solitarii and the rostral ventrolateral medulla (RVLM). The primary activation of the cholinergic synapse is believed to take place in RVLM. Met-enkephalin, Leu-enkephalin and beta-endorphin, when applied exogenously, depress or even abolish the hypertensive effect of physostigmine. The same type of response was obtained after application of substances which inhibit the enkephalin-degrading enzymes (bestatin, phosphoramidon). Thus, the exogenous or endogenous enkephalins activate the opioid receptors in the brain and at the same time produce a depression of the cholinergic-adrenergic interaction in the central nervous system, which is a prerequisite for the hypertensive response to physostigmine. The functional role of the central cholinergic mechanisms in BP control under physiological conditions has not been established with certainty. These mechanisms might have a more significant role under pathological or homeostatic disturbances. For example, physostigmine showed a life-saving effect in acute hypovolemic shock in rabbits.

Glucose utilization, blood flow and capillary density in the ventrolateral medulla of the rat

A specific population of neurons in the ventrolateral medulla (VLM) acts as the main integration center for the regulation of the sympathetic outflow to the cardiovascular system. In order to investigate whether this nucleus can be distinguished from its surroundings in the reticular formation of the medulla with respect to functional and morphological variables, the present study investigates several of such variables in this area on a quantitative basis. Local medullary glucose utilization was measured by the 2-[14C]deoxyglucose method; local medullary blood flow was quantified using iodo[14C]-antipyrine, and the local density of perfused capillaries was calculated by counting the number of intravascular fluorescent spots in brain sections after i.v. infusion of a globulin-coupled fluorescent dye. The values obtained from the VLM were compared with the respective values found in a reference area of the same brain section (gigantocellular nucleus). The values for glucose utilization, blood flow and capillary density were significantly (P less than 0.05) higher in the VLM than in the reference area (gigantocellular nucleus). This difference was 44.7% for glucose utilization, 34.1% for blood flow and 19.7% for capillary density. These data support the hypothesis that neurons in the VLM are specifically well supplied for being directly regulated in their activity by the PCO2 and pH in the arterial blood.