Hypoxia- or hyperoxia-induced changes in arteriolar vasomotion in skeletal muscle microcirculation.

Arteriolar vasomotion was characterized in the skin muscle of the unanesthetized hamster skinfold window preparation and related to the specific arterioles that give rise to the different types of activity. The arterioles were classified according to the Strahler method: order 0 was assigned to capillaries and order 4 to the largest arterioles. The arterioles showed vasomotion with a specific range of frequencies that varied according to the vessel order; the highest fundamental frequency (9.

Arteriolar vasomotion: implications for tissue ischemia.

Vasomotion, the rhythmical contraction and relaxation of the arterioles, is a natural property of the arteriolar microcirculation. It is observed clinically through related flow variations (flux motion) which are detected by laser Doppler flowmetry. It presents two distinct regimens: slow and fast waves, with frequencies of 1-2 and 10-20 cpm, respectively.

Capillary narrowing in hemorrhagic shock is rectified by hyperosmotic saline-dextran reinfusion.

Previously, we showed that skeletal muscle capillaries narrow during hemorrhagic shock due to swelling of endothelial cells. The present study investigated if these narrowed capillaries affected reflow and compared the effects of fluid reinfusion with iso- and hyperosmotic solutions, in particular 7.5% NaCl/6% dextran 70 (HSD) and Ringer's lactate (RL).

Microvascular responses in rabbit skeletal muscle after fixed volume hemorrhage.

The effect of hemorrhage on the microvascular responses in the tenuissimus muscle was studied by means of intravital microscopy in rabbits anesthetized with urethan. The rabbits were bled 30% of their calculated blood volume within 3 min. Hemorrhage initially caused mean arterial pressure to drop from 70 +/- 7 to 26 +/- 5 mmHg.

Four window differential capillary velocimetry.

A video red blood cell velocimeter was implemented with four photometric windows in such a fashion that the upstream and downstream signals are the difference between spatially separated window pairs. The performance of this system was compared with that of a conventional dual window photometric video velocimeter. Tests were made with artificial patterns of red blood cells that simulated long trains of contiguous cells, or large plasma gaps.

Hemodynamic responses in rabbit tenuissimus muscle arterioles during local reduction in perfusion pressure.

Transverse (TR) and terminal (TE) arteriolar diameters and TR pressure were measured in the rabbit tenuissimus muscle during steady state reductions in perfusion pressure. An inflatable occluder was positioned on the abdominal aorta proximal to the bifurcation to alter perfusion pressure. In the control conditions, TEs exhibited highly regular cyclic activity (20 +/- 4 cpm).

The efficacy of iso- and hyperosmotic fluids as volume expanders in fixed-volume and uncontrolled hemorrhage.

Rapid blood volume expansion is the goal in prehospital hemorrhage resuscitation. A comparison was made for fixed volume and uncontrolled hemorrhage between three fluid regimes: Ringer's lactate (RL), Macrodex (MD), or a small volume of a hyperosmotic solution (HSD, 7.5% NaCl/6% dextran 70) followed by RL.

Confocal laser tomographic analysis of the retina in eyes with macular hole formation and other focal macular diseases.

To study the retinal surface in the human eye in normal and diseased states we used laser scanning tomography. The confocal arrangement of the laser tomographic scanner permits examination of retinal topography in the axis perpendicular to the retinal surface. The eyes examined with the laser tomographic scanner included normal eyes, eyes with macular holes, impending macular holes, radiation retinopathy, macular edema, photocoagulation scars, subfoveal scars, and serous detachment of the fovea associated with subretinal neovascularization.

Lumenal narrowing and endothelial cell swelling in skeletal muscle capillaries during hemorrhagic shock.

Capillary lumenal narrowing in hemorrhagic shock was investigated using intravital microscopy to visualize capillaries directly in the rabbit tenuissimus muscle after a rapid single-withdrawal of 40% of the blood volume. The ensuing 1 hr shock period in the animals was marked by a protracted systemic hypotension and metabolic acidosis. Changes in capillary lumen diameter were inferred by changes in the width and length of red blood cells (RBCs) as they traversed the capillary.

The Prony spectral line estimation (PSLE) method for the analysis of vascular oscillations.

The Prony spectral line estimation (PSLE) technique is implemented and tested on data consisting of sinusoids mixed with Gaussian noise and on recordings of oscillatory diameter changes (vasomotion) of arterioles. It is concluded that the PSLE method is well suited for the spectrum analysis of short oscillatory diameter records.

Volume changes of an endothelial cell monolayer on exposure to anisotonic media.

The osmotic process plays an important role in controlling the distribution of water across cell membranes and thus the cell volume. A system was designed to detect the volume changes of an endothelial cell monolayer when cells were exposed to media with altered osmolalities. Electrodes housed in a flow chamber measured the resistance of ionic media flowing over a cultured cell layer.

Computer assisted leukocyte adhesion measurement in intravital microscopy.

The pathogenetic role of the leukocytes in the development of postischemic injury is not yet understood. Therefore a model was developed which allows for in vivo quantification of leukocyte-endothelium interaction in the awake animal. The velocity of leukocytes was measured by means of intravital microscopy and interactive digital image analysis.

Vascular resistance vs. perfusate osmolarity: the short term microvascular effect of hypotonic and hypertonic perfusion in the isolated kidney.

Vascular resistance changes were measured in response to alteration in perfusate osmolarity in isolated rabbit kidneys perfused at 10 degrees C. The data obtained were found to fit a simple mathematical model of the vascular resistance of the microcirculation in which it was assumed that variation in this parameter depended solely upon osmotic alterations in the size of the cells within and around the blood vessel walls. The model predicts that the volumetric changes due to the different osmolarities are produced in a tissue layer whose thickness is 30% relative to a fixed outer radius.

Capillary fluxmeter: the simultaneous measurement of hematocrit, velocity and flux.

An automated technique was developed for the measurement of capillary hematocrit in vivo. The method is based on the photometric detection of the passage of the red blood cells (RBC) through video photometric windows. Red blood cell flux is derived from the primary measurement of opacity and velocity, as opposed to frequency of cell passage and cell transit time.

Local tissue oxygenation during constant red blood cell flux: a discrete source analysis of velocity and hematocrit changes.

Tissue oxygenation in the proximity of single capillaries was investigated mathematically, with the red blood cells (RBC) modeled as discrete oxygen sources separated by plasma gaps. The variables studied are the simultaneous change of capillary RBC flow velocity, and hematocrit (Hct), during constant flux (e.g.

Changes of activated partial thromboplastin time during constant intravenous and fixed intermittent subcutaneous administration of heparin.

Marked circadian variations in the activated partial thromboplastin time (APTt) during continuous heparin infusions for thromboembolic episodes have been reported in a French study. The aim of the present study was to test if these variations could be reproduced in a Swedish population. The frequency spectrum variations in APTt values were analysed with the Prony and the statistical Pearson product momentum correlation coefficient methods.

Shunting of leukocytes in rabbit tenuissimus muscle.

Leukocyte distribution was studied in 58 arterioles and capillaries constituting eight networks in the fascia adjacent to the rabbit tenuissimus muscle. Fluorescence video microscopy (acridine red) and digital image processing were used to visualize the leukocytes. Leukocyte concentration in the transverse arterioles leaving the muscle proper to irrigate the fascia was significantly elevated to 143 +/- 13% (mean +/- SE) of the systemic count.

Central effects of angiotensin II in conscious hamsters: drinking, pressor response, and release of vasopressin.

The effects of intracerebroventricular (icv) injections of angiotensin II (ANG II) on water intake, blood pressure, heart rate, and plasma arginine-vasopressin (AVP) concentration were studied in chronically instrumented adult male Syrian golden hamsters (Mesocricetus auratus). Furthermore, the effects of pharmacological ganglionic blockade, and of vascular AVP receptor blockade, on central ANG II-induced cardiovascular responses were investigated. ANG II (1, 10, and 100 ng, icv) elicited dose-dependent increases in water intake and arterial blood pressure.

Central angiotensin II stimulates arteriolar vasomotion in conscious hamsters.

The effects of intracerebroventricular (icv) injections of 10 ng angiotensin II (ANG II) on mean arteriolar diameter and spontaneous arteriolar vasomotion were studied in subcutaneous tissue of conscious, restrained hamsters, using the skin fold window chamber preparation. Angiotensin II caused a significant decrease in mean arteriolar diameter which was associated with a significant elevation in the amplitude of vasomotion. The frequency of vasomotion did not change significantly.

Increase in capillary blood flow and relative haematocrit in rabbit skeletal muscle following acute normovolaemic anaemia.

The effect of acute normovolaemic haemodilution on microvascular red blood cell flow was studied by intravital microscopy in the tenuissimus muscle of the rabbit. Blood was substituted isovolaemically with equal volumes of a 6% solution of dextran 70 (MW 70,000). The systemic haematocrit (Hsys) decreased from 36 +/- 4% (mean +/- SD) to 17 +/- 2%.

Dynamic fluid redistribution in hyperosmotic resuscitation of hypovolemic hemorrhage.

A mathematical description of blood volume restoration after hemorrhage with resuscitative fluids, particularly hyperosmotic solutions, is presented. It is based on irreversible thermodynamic transport equations and known physiological data. The model shows that after a 20% hemorrhage, the rapid addition of a hypertonic (7.

Contrast enhancement amplifier for television microscopy.

A video amplifier is described for the purpose of enhancing the contrast of televised scene features. The system operates by amplifying the video signals bracketed by selectable gray levels, in such a fashion that the features of interest take up the whole dynamic range of the video display. The system operates and can be used directly in conjunction with on line video processors such as automated microvessel diameter measuring systems and video blood cell velocimeters.

Beta-adrenergic control of resistance in individual vessels in rabbit tenuissimus muscle.

The microvascular responses to topically applied isoproterenol and to epinephrine in the intact and beta-adrenoceptor-blocked microcirculation were studied in the rabbit tenuissimus muscle by direct intravital microscopy. The main feeding arterioles in this muscle supply two vascular areas, the muscle capillaries and the adjacent connective tissue. beta-Adrenergic stimulation with isoproterenol and epinephrine dilated the transverse arterioles that supply muscle and connective tissues, whereas their first-order side branches (terminal arterioles), which only supply the muscle capillaries, were little affected.