(1/1413) Rescue of diabetes-related impairment of angiogenesis by intramuscular gene therapy with adeno-VEGF.
Diabetes is a major risk factor for coronary and peripheral artery diseases. Although diabetic patients often present with advanced forms of these diseases, it is not known whether the compensatory mechanisms to vascular ischemia are affected in this condition. Accordingly, we sought to determine whether diabetes could: 1) impair the development of new collateral vessel formation in response to tissue ischemia and 2) inhibit cytokine-induced therapeutic neovascularization. Hindlimb ischemia was created by femoral artery ligation in nonobese diabetic mice (NOD mice, n = 20) and in control C57 mice (n = 20). Hindlimb perfusion was evaluated by serial laser Doppler studies after the surgery. In NOD mice, measurement of the Doppler flow ratio between the ischemic and the normal limb indicated that restoration of perfusion in the ischemic hindlimb was significantly impaired. At day 14 after surgery, Doppler flow ratio in the NOD mice was 0.49+/-0.04 versus 0.73+/-0.06 for the C57 mice (P< or =0.005). This impairment in blood flow recovery persisted throughout the duration of the study with Doppler flow ratio values at day 35 of 0.50+/-0.05 versus 0.90+/-0.07 in the NOD and C57 mice, respectively (P< or =0.001). CD31 immunostaining confirmed the laser Doppler data by showing a significant reduction in capillary density in the NOD mice at 35 days after surgery (302+/-4 capillaries/mm2 versus 782+/-78 in C57 mice (P< or =0.005). The reduction in neovascularization in the NOD mice was the result of a lower level of vascular endothelial growth factor (VEGF) in the ischemic tissues, as assessed by Northern blot, Western blot and immunohistochemistry. The central role of VEGF was confirmed by showing that normal levels of neovascularization (compared with C57) could be achieved in NOD mice that had been supplemented for this growth factor via intramuscular injection of an adenoviral vector encoding for VEGF. We conclude that 1) diabetes impairs endogenous neovascularization of ischemic tissues; 2) the impairment in new blood vessel formation results from reduced expression of VEGF; and 3) cytokine supplementation achieved by intramuscular adeno-VEGF gene transfer restores neovascularization in a mouse model of diabetes. (+info)
(2/1413) Brightness alters Heidelberg retinal flowmeter measurements in an in vitro model.
PURPOSE: The Heidelberg Retinal Flowmeter (HRF), a laser Doppler flowmetry device, has captured interest as a research and clinical tool for measurement of ocular blood flow. Concerns remain about the range and accuracy of the values that it reports. METHODS: An in vitro blood-flow model was constructed to provide well-controlled laminar flow through a glass capillary for assessment by HRF. A change in material behind the glass capillary was used to simulate changing brightness conditions between eyes. RESULTS: Velocities reported by the HRF correlated linearly to true velocities below 8.8 mm/sec. Beyond 8.8 mm/sec, HRF readings fluctuated randomly. True velocity and HRF reported velocities were highly correlated, with r = 0.967 (P < 0.001) from 0.0 mm/sec to 2.7 mm/sec mean velocity using a light background, and r = 0.900 (P < 0.001) from 2.7 mm/sec to 8.8 mm/sec using a darker background. However, a large change in the y-intercept occurred in the calibration curve with the background change. CONCLUSIONS: The HRF may report velocities inaccurately because of varying brightness in the fundus. In the present experiment, a darker background produced an overreporting of velocities. An offset, possibly introduced by a noise correction routine, apparently contributed to the inaccuracies of the HRF measurements. Such offsets vary with local and global brightness. Therefore, HRF measurements may be error prone when comparing eyes. When used to track perfusion in a single eye over time, meaningful comparison may be possible if meticulous care is taken to align vessels and intensity controls to achieve a similar level of noise correction between measurements. (+info)
(3/1413) Analysis of blood flow in the long posterior ciliary artery of the cat.
PURPOSE: Experiments were undertaken to use a new technique for direct on-line measurement of blood flow in the long posterior ciliary artery (LPCA) in cats and to evaluate possible physiological mechanisms controlling blood flow in the vascular beds perfused by this artery. METHODS: Blood flow in the temporal LPCA was measured on a continuous basis using ultrasonic flowmetry in anesthetized cats. Effects of acute sectioning of the sympathetic nerve and changes in LPCA and cerebral blood flows in response to altered levels of inspired CO2 and O2 were tested in some animals. In others, the presence of vascular autoregulatory mechanisms in response to stepwise elevations of intraocular pressure was studied. RESULTS: Blood flow in the temporal LPCA averaged 0.58+/-0.03 ml/min in 45 cats anesthetized with pentobarbital. Basal LPCA blood flow was not altered by acute sectioning of the sympathetic nerve or by changes in low levels of inspired CO2 and O2, although 10% CO2 caused a modest increase. Stepwise elevations of intraocular pressure resulted in comparable stepwise decreases of LPCA blood flow, with perfusion pressure declining in a linear manner throughout the perfusion-pressure range. CONCLUSIONS: Ultrasonic flowmetry seems to be a useful tool for continuous on-line measurement of LPCA blood flow in the cat eye. Blood flow to vascular beds perfused by this artery does not seem to be under sympathetic neural control and is refractory to modest alterations of blood gas levels of CO2 and O2. Blood vessels perfused by the LPCA show no clear autoregulatory mechanisms. (+info)
(4/1413) Perfusion of the human finger during cold-induced vasodilatation.
We have investigated the effect of severe local cooling on the vasomotor activity of the arteriovenous anastomoses (AVAs) and other finger vessels. The right third finger was subjected to local cooling (3 degrees C) for 30-45 min in 21 healthy, thermoneutral subjects. Blood velocity in the third finger arteries of both hands was simultaneously recorded using ultrasound Doppler, and skin temperature and laser-Doppler flux from the pulp of the cooled finger were also recorded. The results demonstrate that the initial cold-induced vasoconstriction during severe local cooling involves constriction of the AVAs as well as the two main arteries supplying this finger. During cold-induced vasodilatation (CIVD), the maximum velocity values were not significantly different from those before cooling. Furthermore, the velocity fluctuations in the cooled finger were in most subjects found to be synchronous with the velocity fluctuations in the control finger. This indicates that the large blood flow to the finger and the high skin temperature during CIVD are caused by relaxation of the smooth muscle cells of the AVAs. (+info)
(5/1413) Analysis of optical signals evoked by peripheral nerve stimulation in rat somatosensory cortex: dynamic changes in hemoglobin concentration and oxygenation.
The origins of reflected light changes associated with neuronal activity (optical signals) were investigated in rat somatosensory cortex with optical imaging, microspectrophotometry, and laser-Doppler flowmetry, and dynamic changes in local hemoglobin concentration and oxygenation were focused on. Functional activation was carried out by 2-second, 5-Hz electrical stimulation of the hind limb under chloralose anesthesia. These measurements were performed at the contralateral parietal cortex through a thinned skull. Regional cortical blood flow (rCBF) started to rise 1.5 seconds after the stimulus onset, peaked at 3.5 seconds (26.7% +/- 9.7% increase over baseline), and returned to near baseline by 10 seconds. Optical signal responses at 577, 586, and 805 nm showed a monophasic increase in absorbance coincident with the increase in rCBF; however, the signal responses at 605 and 760 nm were biphasic (an early increase and late decrease in absorbance) and microanatomically heterogeneous. The spectral changes of absorbance indicated that the concentrations of both total hemoglobin and oxyhemoglobin increased together with rCBF; deoxyhemoglobin, increased slightly but distinctly (P = 0.016 at 1.0 seconds, P = 0.00038 at 1.5 seconds) just before rCBF increases, then decreased. The authors conclude that activity-related optical signals are greatly associated with a moment-to-moment adjustment of rCBF and metabolism to neuronal activity. (+info)
(6/1413) Role of nitric oxide in the regulation of microvascular perfusion in human skin in vivo.
1. Nitric oxide (NO) concentrations were measured in dialysate from healthy human skin, in vivo, both at rest and during the inflammatory response to intradermal histamine or bradykinin. Changes in dialysate NO concentration, measured by electrochemical detection, were related to changes in dermal vascular perfusion, measured using scanning laser Doppler imaging. 2. Basal NO concentration in dermal microdialysate was 0.60 +/- 0.14 microM (mean +/- s.e.m.). Following the intradermal injection of histamine, a transient, time-dependent increase in NO concentration was measured in areas of skin incorporating the weal and in others incorporating the flare. The increase in NO concentration was associated with an increase in dialysate cGMP concentration in both the weal and flare areas. 3. Addition of N G-nitro-l-arginine-methyl ester (L-NAME, 5 mM) to the probe perfusate resulted in an inhibition of the histamine-induced increase in NO and cGMP. Moreover, the reduction in dialysate NO concentration was associated with a reduction in dermal vascular flux, both under basal conditions and within the weal and flare response. 4. These results demonstrate, by the use of microdialysis, that vasoactive mediators can be measured in healthy human skin in vivo. They provide direct evidence that endogenous concentration of NO increases during the inflammatory weal and flare response to histamine and that the increase in dermal NO concentration is associated with increases in cGMP concentration and dermal vascular perfusion, thus confirming a role for NO in vasoregulation in human skin. (+info)
(7/1413) The association between laser Doppler reactive hyperaemia curves and the distribution of peripheral arterial disease.
OBJECTIVES: To determine whether postocclusive laser Doppler fluxmetry (LDF) curves can be related to the arteriographic distribution of disease. DESIGN: Prospective study. MATERIALS: Sixty-nine patients with symptomatic peripheral ischaemia and 15 healthy subjects. METHODS: Laser Doppler fluxmetry (LDF) was monitored on the dorsum of the symptomatic foot following 2 min of arterial occlusion at the ankle. During reperfusion three patterns of LDF were identified (types I-III). All patients subsequently underwent arteriography which was reported independent of LDF results. The distribution of disease, particularly patency of below-knee vessels, was related to the type of LDF curve observed during reactive hyperaemia. RESULTS: Type I curves were observed in all healthy subjects and 75% of patients with a single arterial lesion. Type II curves were found in 78% of patients with multiple lesions above the knee. The presence of either a type I or II curve was associated with a continuous vessel from knee to ankle (positive predictive value 83%, p < 0.01), whilst type III curve was associated with discontinuous infrapopliteal run-off (positive predictive value 86%, p < 0.01). CONCLUSIONS: This pilot study suggests that post-occlusive LDF curves may identify the distribution of arterial disease and may be useful in the non-invasive management of peripheral ischaemia. (+info)
(8/1413) Detection of autonomic sympathetic dysfunction in diabetic patients. A study using laser Doppler imaging.
OBJECTIVE: To study signs of the disturbed reflex autonomic sympathetic nerve function in type 1 and type 2 diabetic patients. RESEARCH DESIGN AND METHODS: Measurements were made on 15 type 1 (duration 13-32 years) and on 50 recently diagnosed type 2 diabetic patients (duration 3-4 years). The vasoconstrictor responses in the distal phalanx of the middle finger (locally heated to 40 degrees C) to the cooling of the contralateral arm were measured using Laser Doppler Imaging (LDI). A vasoconstriction index (VAC) was calculated taking age into account and was compared with reference values obtained in 80 control subjects. The diabetic patients were also studied with deep-breathing tests (i.e., the heart-rate variation expressed as the expiration-to-inspiration [E/I] ratio, a test of parasympathetic nerve function). RESULTS: The vasoconstrictor responses to indirect cooling (VAC) were significantly reduced in the fingers of the diabetic patients, both type 2 (0.77 +/- 0.02 V; P < 0.01) and type 1 (0.83 +/- 0.04 V; P < 0.001), compared with the healthy control subjects (0.65 +/- 0.01); the age-corrected VAC (VACz) was slightly more impaired in type 1 than in type 2 diabetic patients. The frequency of an abnormal VACz corresponded well to the frequency of an abnormal E/I ratio in type 1 diabetic patients (approximately 50%), whereas the frequency of an abnormal VACz was significantly higher than an abnormal E/I ratio among type 2 diabetic patients (11/50 vs. 4/50; P < 0.05). CONCLUSIONS: Both type 1 and type 2 diabetic patients have impaired cutaneous blood flow regulation. The VAC index seems to be a promising tool for detection of subclinical changes in autonomic sympathetic function. (+info)