Pharmacologic targeting of Cdc42 GTPase by a small molecule Cdc42 activity-specific inhibitor prevents platelet activation and thrombosis.

Gene targeting of Cdc42 GTPase has been shown to inhibit platelet activation. In this study, we investigated a hypothesis that inhibition of Cdc42 activity by CASIN, a small molecule Cdc42 Activity-Specific INhibitor, may down regulate platelet activation and thrombus formation. We investigated the effects of CASIN on platelet activation in vitro and thrombosis in vivo. In human platelets, CASIN, but not its inactive analog Pirl7, blocked collagen induced activation of Cdc42 and inhibited phosphorylation of its downstream effector, PAK1/2. Moreover, addition of CASIN to washed human platelets inhibited platelet spreading on immobilized fibrinogen. Treatment of human platelets with CASIN inhibited collagen or thrombin induced: (a) ATP secretion and platelet aggregation; and (b) phosphorylation of Akt, ERK and p38-MAPK. Pre-incubation of platelets with Pirl7, an inactive analog of CASIN, failed to inhibit collagen induced aggregation. Washing of human platelets after incubation with CASIN eliminated its inhibitory effect on collagen induced aggregation. Intraperitoneal administration of CASIN to wild type mice inhibited ex vivo aggregation induced by collagen but did not affect the murine tail bleeding times. CASIN administration, prior to laser-induced injury in murine cremaster muscle arterioles, resulted in formation of smaller and unstable thrombi compared to control mice without CASIN treatment. These data suggest that pharmacologic targeting of Cdc42 by specific and reversible inhibitors may lead to the discovery of novel antithrombotic agents.

Diazoxide ameliorates microcirculatory disturbances through PKC-dependent pathway in I/R-injured rat cremaster muscles.

Diazoxide is a selective mitochondria ATP-sensitive potassium (K(ATP)) channel opener, which has been reported to preserve the microvascular integrity of ischemia-reperfusion (I/R)-injured tissues. Our study aimed to assess diazoxide's effects on I/R-injured cremaster muscles and to further elucidate its underlying mechanisms. Male Sprague Dawley (SD) rats were randomized (n = 8 per group) into four groups: sham-operated control group, I/R group (4 h of pudic epigastic artery ischemia followed by 2 h of reperfusion), diazoxide + I/R group, and chelerythrine (PKC inhibitor)+diazoxide+I/R group. Microscopically, we observed that I/R markedly increased the number of rolling, adhering, and transmigrating leukocytes. I/R also markedly decreased the number of functional capillaries. Biochemically, we found that I/R significantly increased TNF-alpha, E-selectin,L-selectin and P-selectin expressions. However, I/R did not cause significant changes in ICAM-1 and PECAM-1 expressions. On the other hand, in I/R + diazoxide group, we found that diazoxide reduced the number of rolling, adhering, and transmigrating leukocytes. Furthermore, biochemical study revealed that diazoxide caused only a decrease in L-selectin expression but had no effect on TNF-alpha, E-selectin, P-selectin, ICAM-1, and PECAM-1 expressions. Finally, in chelerythrine + diazoxide + I/R group, we observed that diazoxide's protective effects were blocked by the addition of chelerythrine. Diazoxide's ability to protect against I/R injury was confirmed by the observation that it reduced the number of rolling, adhering, and transmigrating leukocytes, and increased the number of functional capillaries. Our results indicated that diazoxide operated via a PKC-dependent pathway to achieve protection against I/R injury.

Muscle infarction involving muscles of abdominal and thoracic walls in diabetes.

AIMS: This paper presents two cases of muscle infarction involving four major muscles of the anterior abdominal wall (case 1) and pectoralis major (case 2) in individuals with diabetes. METHODS: Erythrocyte sedimentation rate (ESR) and creatine kinase (CK) were measured and Doppler ultrasound, an open muscle biopsy (case 1) and magnetic resonance imaging (MRI) (case 2) were performed. RESULT: The diagnosis of muscle infarction was made by histological findings and MRI images with hyper-intensive signals on a gadolinium-enhanced T2-weighted sequence, respectively. Both patients were treated with bed rest, immobilization of the involved extremities, analgesia and intensive insulin therapy. In addition, anticoagulant drugs such as low molecular weight heparin sodium and cilostazol, and some traditional Chinese medicines such as ligustrazine and salvia miltiorrhiza were administered. The symptoms of both patients resolved gradually after 3 weeks. However, muscle infarction reoccurred in case 1 on the opposite side of the abdomen and recovered after 40 days. CONCLUSIONS: This is the first report of muscle infarction involving the muscles of anterior abdominal walls and pectoralis major in diabetes. MRI is the best non-invasive technique and T2-weighted imaging is the most valuable method for the diagnosis. In addition to supportive therapy, administration of anticoagulant agents and some Chinese traditional medicine may be useful in symptom relief.

Circulatory alterations induced by intra-arterial injection of iodized oil and emulsions of iodized oil and doxorubicin: experimental study.

PURPOSE: To evaluate circulatory alterations induced by intra-arterial injection of iodized oil and emulsions of iodized oil with an anticancer drug. MATERIALS AND METHODS: The viscosities and stability were evaluated in arterial flow of iodized oil and the emulsions. Doppler ultrasound was used to quantify the embolic effect in the arteries of rabbits. The behavior of doxorubicin and iodized oil in the rat cremaster muscle was studied with videomicroscopy. RESULTS: The emulsions did not break up after injection, and the size of discontinuous-phase droplets did not change. The embolic effect did not correlate with viscosity. The thinnest water-in-oil emulsion had the lowest embolic effect and induced homogeneous distribution of iodized oil droplets in the arterial tree. CONCLUSION: Changes in the formulation of emulsions obtained with the same proportions of drug and iodized oil change the distribution of iodized oil in the arterial tree, the location at which the drug is released, and the embolic effect.

A new approach for predicting the enhancement in the effective conductivity of perfused muscle tissue due to hyperthermia.

This study attempts to measure the hyperthermic response of individual microvessels in skeletal muscle tissue subject to local heating and then to predict the enhancement in thermal conductivity that results from the observed changes in vascular diameter and flow. In contrast to existing studies, which have tried to relate changes in tissue thermal conductivity to local blood perfusion using thermal clearance and self-heated thermistor techniques, we have developed a two-dimensional muscle tissue preparation in which the hyperemic response has been quantified by measuring the in vivo changes in diameter and blood flow of 1A to 4A generation vessels of rat cremaster muscle when the temperature was raised in 2 degrees increments from 34 to 42 degrees C. Only 3A and 4A vessels showed vasodilation when subject to hyperthermia, indicating that the measured increase in flow in the 1A and 2A vessels was the result of a decrease in downstream resistance. Our cremaster muscle preparations have also been used to obtain the first detailed anatomic measurements of the number density and length of countercurrent vessel pairs between 50-200 microns diameter. These combined measurements have been used to establish the limits of validity of the Weinbaum-Jiji theory. Our experimental data indicate that the Weinbaum-Jiji expression for keff is valid in cremaster muscle and cat mesentery tissue for both normal and hyperthermic conditions provided the largest vessels are < 200 microns in diameter. The theory predicts that significant enhancements in keff start to occur for vessels that are 70 microns in diameter or larger, that a 2.5-fold increase in keff can be achieved for a maximally dilated 200 microns diameter 1A vessel pair in cremaster muscle of larger rats, and a 6-fold increase is predicted for maximally dilated 200 microns diameter vessels in the cat mesentery. The experiments also show that maximally dilated 1A to 4A vessels in the microcirculation closely satisfy the condition Q(flow)/(2a)3 = constant, which is consistent with the hypothesis that there is an adaptive regulation of vessel diameter which keeps the wall shear stress nearly constant during temporal changes in flow.

The effect of hyperbaric oxygen treatment on a compromised axial pattern flap in the cat.

A pedicle skin flap based on the caudal superficial epigastric artery was created in 12 cats. The artery was ligated and the vein left intact. Six cats were treated with hyperbaric oxygen at 2 atm absolute for 90 minutes daily for 14 days, starting the day after surgery. Skin flap color was significantly better in the treated cats on days 1, 2, and 3. The amount of exudate was significantly less in the treated cats on day 3. There was no difference in the amount of swelling between treated and nontreated control cats. Although five of six of the treated cats had 100% skin flap survival, there was no significant difference in total flap survival between treated and nontreated control cats.

The effect of skeletal muscle ventricle pouch pressure on muscle blood flow.

Skeletal muscle powered assist ventricles (SMV) are being investigated in animal studies as a treatment for heart failure. Muscle fatigue is almost always dependent upon muscle capillary blood flow. This study examined the relationship between SMV intrapouch pressure and blood flow to the circumferential muscle in a working SMV with a mock circulation. The unconditioned rectus abdominis muscle was used to create an in situ SMV in five dogs. Muscle blood flow was measured by both the radioactive microsphere and the electromagnetic flow probe method as the pouch pressure was varied between 10 and 70 mmHg and as the SMV was stimulated to contract at a rate of 20 min-1. The correlation coefficient for the two methods was 0.908. At pouch pressures of 10, 40, and 70 mmHg, the respective blood flow values were 22.60 +/- 2.50 (1 SEM), 12.20 +/- 2.10, and 4.40 +/- 0.74 ml min-1 (p less than 0.05). When they were corrected for muscle weight, the mean blood flow values at these same pouch pressures were 0.28 +/- 0.03, 0.15 +/- 0.03, and 0.05 +/- 0.01 ml min-1 g-1, respectively (p less than 0.05). SMV output was measured for each pouch pressure that was tested. Pouch output, expressed as ml min-1, was 458 +/- 20 (1 SEM) at an SMV diastolic pouch pressure of 10 mmHg, 309 +/- 22 at a pouch pressure of 40 mmHg, and 103 +/- 6 at a pouch pressure of 70 mmHg.(ABSTRACT TRUNCATED AT 250 WORDS)

[Electric stimulation of skeletal muscles as the optimal method of left-ventricular bypass]. / Elektrostimuliatsiia skeletnykh myshts kak sredstvo optimizatsii levozheludochkovogo obkhoda.

Experiments were performed on 15 mongrel dogs to evaluate the influence of electrostimulated contractions of the hind limb and abdominal skeletal muscles on the efficacy of assisted circulation (AC). The influence of massage of the abdomen on AC efficacy was studied in 10 experiments. In electrostimulation of the hind limb muscles the drainage along the femoral vein, measured by the direct method, increased threefold: from 58 +/- 9 to 162 +/- 7 ml/min under conditions of an intact heart and from 5.8 +/- 0.8 to 15 +/- 1.2 ml/min in cardiac insufficiency. The efficacy of AC by the method of left-ventricular bypass by means of the Module artificial heart ventricle (AHV) increased through the flow of blood to the heart, which was manifested by greater AHV performance with rise of systolic and diastolic pressure to 7-8 mm Hg. In cardiovascular insufficiency the influence of electrostimulation on AC efficacy was weaker, the systolic and diastolic pressure increased only by 2-4 mm Hg, in massage of the abdomen both indices increased by 8-10 mm Hg.