Capillary Patency Research Articles

Uncoupling of Microvascular Blood Flow and Capillary Density in Vascular Cognitive Impairment.

Cerebral small vessel disease (cSVD) plays an important role in dementia and is a major cause for vascular cognitive impairment (VCI). Recent studies hypothesized that capillary dysfunction including reduction of capillary patency, rather than a flow-limiting pathology is crucial in cSVD. As cSVD is considered a systemic microvascular disease, we examined sublingual microvascular blood flow and capillary density in patients with VCI and controls. Fifteen patients with VCI due to cSVD and 15 controls underwent intravital microscopy of the sublingual microvessels. Microvascular blood flow and capillary density in high and low flow areas were determined for each participant. Flow-density coupling was examined by determining the ratio of density changes to flow changes, and the ratio of feed vessel red blood cell (RBC) velocity to capillary RBC velocity. These were compared between VCI and controls. In healthy controls, capillary density increased proportionally with feed vessel blood flow increase. In patients with VCI, no increase of capillary density was observed. Moreover, increase of feed vessel RBC velocity led to significant increase of capillary RBC velocity in VCI, whereas in controls, the capillary RBC increased only slightly. Flow-density coupling differed significantly between VCI and controls, also after correcting for age and hypertension. Our findings suggest uncoupling of microvascular blood flow and capillary density in patients with VCI. This uncoupling may impair oxygen and nutrients exchange when blood flow increases in response to increased metabolic demand, ultimately leading to tissue damage.

Mitigation of Hydrochloric Acid (HCl)-Induced Lung Injury in Mice by Aerosol Therapy of Surface-Active Nanovesicles Containing Antioxidant and Anti-inflammatory Drugs.

Acute lung injury leading to alveolar inflammation and surfactant dysfunction remains a medical challenge. Surface-active lipid nanovesicles of 200-250 nm size with antioxidant D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) and anti-inflammatory drug dexamethasone disodium phosphate (DXP) dual combination (Dual-NV) were developed for delivery as aerosols by nebulization in acid lung injury models. Drug deposition studies showed Dual-NV deposited ∼2.5 times more DXP compared to equivalent DXP solution. Nanovesicles are actively internalized by A549 cells through ATP- and clathrin-dependent pathways. The nanovesicles could be phagocytosed by RAW 264.7 macrophages and were nonimmunogenic and did not elicit overproduction of TNF-α, IL-1β, and IL-6. Dual-NV aerosol therapy at 200 mg/kg body weight, in HCl acid-induced lung injury in mice, markedly reduced pulmonary hemorrhage and protein leakage and improved capillary (airway) patency to ∼96%. Dual-NV aerosol therapy also significantly lowered production of inflammatory cytokine IL-1β, IL-6, and TNF-α and reduced oxidative stress by ∼95% in the injured group. Surface-active Dual-NV aerosol therapy is promising for replenishing the dysfunctional surfactant pool and mitigating inflammation and oxidative stress in lung injuries.

Venous-to-arterial carbon dioxide differences and the microcirculation in sepsis.

Assessment of the microcirculation has been of particular interest in the management of septic shock for over a decade (1,2). It has garnered more attention in light of conflicting data recently on oxygen-derived parameters in patients with sepsis (3). Microcirculatory dysfunction has been linked to organ failure despite adequate macro-hemodynamic stability (4).The microcirculatory perfusion is regulated by the myogenic, metabolic and neurohumoral systems, which in turn affect the arteriolar tone, driving pressure, capillary patency and hemorheology (4). In septic states, perfusion pressure and deformability of cells are reduced, and arteriolar constriction ensues; the end-result is shunting of blood, bypassing essential areas of capillary exchange (5). These changes debilitate the microcirculation and impede tissue oxygenation, resulting in impaired organ functions. Moreover, with stasis in the capillary bed and inflammatory factors released from injured cells that cannot be cleared due to deficient flow, the microcirculation becomes a nidus for continued bacterial growth and persistent insult, sustaining the toxemia and acidemia.

Contrast-Enhanced Ultrasound Detects Differences in Microvascular Blood Flow in Adults with Sickle Cell Disease Administered Regadenoson

Background: Outcome measures for therapeutic studies in patients with sickle cell disease (SCD) are poor.Abnormal microvascular blood flow (MBF), the basis for tissue ischemia and injury associated with vaso-occlusion, would be an optimal outcome measure for SCD studies. Ideally, a modality to measure blood flow in SCD would non-invasively quantify microvascular tissue perfusion rather than assess conduit arterial flow through large vessels. Limitations of existing techniques to measure blood flow prevent their widespread use in clinical trials of patients with SCD. Contrast-enhanced ultrasound (CEU) is a non-invasive and portable technique that uses standard ultrasound equipment to measure microvascular perfusion and functional capillary patency. The primary objective of this study was to determine whether CEU is able to detect differences in the MBF of skeletal muscle: 1) before and after infusion with the adenosine A2A receptor (A2AR) agonist regadenoson, and 2) between steady state and vaso-occlusive crisis (VOC).Methods: CEU measurements were obtained in forearm skeletal muscle in adult HbSS patients. Two measures are used to calculate MBF: 1) velocity of RBCs through capillaries and 2) volume of blood perfused in an area of tissue. MBF is the product of RBC velocity and volume of blood. In one study cohort, MBF was measured in steady-state patients during a 24-hour infusion of regadenoson (1.44 µg/kg/hour). CEU perfusion imaging was obtained at baseline, 6 and 24 hours after initiation of regadenoson. In the second study cohort, CEU measurements were obtained within the same patient during a hospital admission for VOC and at steady state. MBF was expressed in terms of a ratio to baseline flow (pre-regadenoson) in cohort 1 and as a ratio of VOC to steady-state flow for cohort 2.Results: CEU measurements were obtained in13 patients administered regadenoson, and 7 patients at steady state and during VOC. Median age (range) of all patients studied was 24 years (20-45) and 55% were female. During regadenoson infusion, there was a median increase in skeletal muscle MBF of 29% at 6 hours (ratio 1.29, IQR 0.81) and 9% at 24 hours (ratio 1.09, IQR 1.40). Increase in MBF during regadenoson administration was largely due to higher RBC velocity (6 hours ratio: 1.24, IQR 0.88; 24 hours: ratio 1.12 IQR 0.85). There was a median decrease of 40% in skeletal muscle blood flow during VOC compared to steady state (ratio 0.60, IQR 0.27). Similarly, a decrease in RBC velocity accounted for most of the reduction in MBF in VOC compared to steady state (ratio 0.63, IQR 0.35).Conclusion: CEU measures of skeletal muscle MBF increased during a 24-hour infusion of regadenoson and decreased in VOC compared to steady state. Changes in RBC velocity, as opposed to the volume of blood perfused, accounted for most of the differences in MBF seen during regadenoson infusion and VOC. Alterations in rheology or vascular tone could explain these changes. These data provide additional evidence for the A2AR agonist regadenoson as a therapeutic modality for patients with SCD and suggest that CEU is a valid measure of blood flow in VOC. Taken together, the findings of this preliminary study demonstrate that CEU, a non-invasive, portable technique to measure MBF, could be used as an objective outcome measure for therapeutic studies in SCD. DisclosuresField:NKTT: Consultancy, Research Funding. Off Label Use: IND for regadenoson for treatment of VOC in sickle cell disease.

How to use capillary refill time

Capillary refill time (CRT) is defined as the time taken for colour to return to an external capillary bed after pressure is applied to cause blanching.1 It was first described...

Rosuvastatin in experimental brain trauma: Improved capillary patency but no effect on edema or cerebral blood flow

BackgroundMicrovascular dysfunction, characterized by edema formation secondary to increased blood–brain barrier (BBB) permeability and decreased blood flow, contributes to poor outcome following brain trauma. Recent studies have indicated that statins may counteract edema formation following brain trauma but little is known about other circulatory effects of statins in this setting. The objective of this study was to investigate whether statin treatment improves brain microcirculation early after traumatic brain injury, and whether microvascular effects are associated with altered production of nitric oxide and prostacyclin. MethodsAfter fluid percussion injury, rats were randomized to intravenous treatment with 20mg/kg of rosuvastatin or vehicle. Brain edema (wet/dry weight), BBB integrity (51Cr-EDTA blood to brain transfer), cerebral blood flow (14C-iodoantipyrine autoradiography), and number of perfused cortical capillaries (FITC-albumin fluorescence microscopy), were measured at 4 and 24h. NO and prostacyclin production was estimated from plasma concentration of the degradation products NO2− and NO3− (NOx) and 6-keto-PGF1-alpha, respectively. Sham injured animals were treated with vehicle and analyzed at 4h. ResultsTrauma resulted in brain edema, BBB dysfunction, and reduced cortical blood flow, with no effect of statin treatment. Trauma also induced a reduction in the number of perfused capillaries, which was improved by statin treatment. Statin treatment led to increased NOx levels and reduced mean arterial blood pressure. 6-Keto-PGF1-alpha levels tended to increase after trauma, and were significantly reduced by rosuvastatin. ConclusionsRosuvastatin treatment may improve microcirculation after traumatic brain injury by preserved patency of cerebral capillaries. This effect is associated with increased NO and reduced prostacyclin production. No effect on brain edema or BBB integrity was found.

Development and evaluation of anti-oxidant and anti-inflammatory drugs loaded lung surfactants

Surface active liposomes containing, D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) and dexamethasone disodium phosphate (DXP) were developed and evaluated for potential use as lung surfactant replacement. 1,2-dipalmitoyl-sn-glycerol-3-phosphatidylcholine (DPPC) + TPGS (1 : 0.25 w/w) surfactant system (S1) and binary mixture of DPPC with 1-palmitoyl-2-oleoyl-sn-glycerol-3-phosphoglycerol ammonium salt (DPPC : POPG 9 : 1 w/w) + TPGS (1 : 0.25 w/w) surfactant system (S2) containing incremental amount of DXP in the range of 1 : 0.1–1 : 1 w/w were evaluated. S1:DXP and S2:DXP (1 : 0.1 to 1 : 1 w/w) mixed films reached 1–2 mN m−1 minimum surface tension (MST) indicating surfactant functions even on concomitant addition of TPGS and DXP. Liposomal S1:DXP (1 : 0.1 to 1 : 1 w/w) attained significantly lower surface tension on adsorption, 35–29 mN m−1 in one second, in comparison to 46 mN m−1 attained by DPPC liposomes. Similarly, liposomes of S2:DXP (1 : 0.1–0.125 w/w) lowered surface tension on adsorption to 27–29 mN m−1 in 1 second. Capillary surfactometer studies showed S1:DXP and S2:DXP (1 : 0.1–1 : 1 w/w) liposomes maintained >98% capillary patency. Rheological studies revealed that liposomal S2:DXP 1 : 0.1 and 1 : 0.125 w/w formulations (25 mg ml−1) exhibited shear thinning properties and had significantly lower shear viscosities of ∼2.5 and 6.3 mPa s respectively at shear rate of 70 s−1 in comparison to ∼29 mPa s for Survanta™ (25 mg ml−1). S2:DXP 1 : 0.1 and 1 : 0.125 w/w liposomes were unilamellar with diameter of 200–250 and 250–350 nm respectively. Twin impinger drug deposition studies showed that on nebulization, S2:DXP 1 : 0.1 and 1 : 0.125 w/w liposomes system showed significantly higher deposition in the lower impingement chamber in comparison to that of free drug. Lipid peroxidation of Curosurf™ was reduced by 21–24% upon addition of S2:DXP liposomal formulation. The TPGS and DXP added DPPC : POPG liposomes may thus serve dual purposes of acting as a surfactant replacement and efficiently delivering antioxidant and anti-inflammatory drugs in inflammatory respiratory diseases.

Review Article: Comparison of perfusion modes on microcirculation during acute and chronic cardiac support: is there a difference?

Although heart-lung machines and cardiac assist devices have been used successfully for acute and chronic cardiac support for decades, controversies still remain concerning the benefits of pulsatile and non-pulsatile perfusion. The core of the debate is whether enough energy is generated by the artificial pulse to keep capillary beds open and cell metabolism stabilized during acute or chronic cardiac support. In other words, does artificial pulsatility exist in the microcirculation: small vessels of less than 100 microm in diameter? Many investigators have tried to use different tools and biomarkers to reflect directly or indirectly the state of the microcirculation when comparing the two different perfusion modes during acute and chronic cardiac support. However, the results are controversial. First, direct observation of the state of the microcirculation during acute and chronic cardiac support is limited; and reports concerning direct observation of the microcirculation with different perfusion modes in contemporary literature are rare. Secondly, different investigators have used their own criteria to define pulsatile flow. Therefore, it is necessary to develop more efficient methodologies, enabling direct observation of the microcirculation during acute and chronic cardiac support and also establish common criteria that will precisely quantify the pulsatile flow in terms of energy equivalent pressure (EEP) and surplus hemodynamic energy (SHE) levels. Using these critical parameters may explain how excess energy is created by pulsatile flow and maintains perfusion through the microcirculation by ensuring capillary patency.

Altered pericyte–endothelial relations in the rat retina during aging: Implications for vessel stability

Mural cells (smooth muscle cells and pericytes) regulate blood flow and contribute to vessel stability. We examined whether mural cell changes accompany age-related alterations in the microvasculature of the central nervous system. The retinas of young adult and aged Wistar rats were subjected to immunohistofluorescence analysis of α-smooth muscle actin (SMA), caldesmon, calponin, desmin, and NG2 to identify mural cells. The vasculature was visualized by lectin histochemistry or perfusion of horse-radish peroxidase, and vessel walls were examined by electron microscopy. The early stage of aging was characterized by changes in peripheral retinal capillaries, including vessel broadening, thickening of the basement membrane, an altered length and orientation of desmin filaments in pericytes, a more widespread SMA distribution and changes in a subset of pre-arteriolar sphincters. In the later stages of aging, loss of capillary patency, aneurysms, distorted vessels, and foci of angiogenesis were apparent, especially in the peripheral deep vascular plexus. The capillary changes are consistent with impaired vascular autoregulation and may result in reduced pericyte–endothelial cell contact, destabilizing the capillaries and rendering them susceptible to angiogenic stimuli and endothelial cell loss as well as impairing the exchange of metabolites required for optimal neuronal function. This metabolic uncoupling leads to reactivation of “physiological hypoxia” and angiogenesis in CNS aging.

Retinal Microvascular Patency in the Diabetic Rat

To study whether the patency to erythrocytes in retinal microvessels of diabetic rats is reduced or blocked before the vessels lose their patency to plasma flow. We used recognized techniques to induce diabetic and galactose related microvascular retinal lesions in rats: (1) alloxan induction (2) streptozotocin induction (3) galactose-containing diet. The rats were followed up to 17 months. We used our vascular trichrome technique to observe the effects of the ongoing diabetes on the retinal microcirculation. A focal leakage of a plasma-borne fluorescent dye was noted around the junction of the deep retinal capillaries and the ascending venules to the superficial retinal circulation in the streptozotocin and alloxan diabetic rats by the 14th month, and, by the 16th month, retinal capillary non-perfusion and retinal vascular malformations were present. The affected vessels showed patency to microspheres (0.2 microm in diameter) but no perfusion of erythrocytes. No such changes were seen in the galactose-fed rats. (1) The location between the deep retinal capillary net and the ascending venules may be the site of early vascular leakage in the diabetic rat model, (2) the erythrocytes' passage in the affected retinal microcirculation was blocked before the development of complete blockage to plasma in diabetic rats. The logical assumption that during the development stage of retinal capillary occlusion there may be a transient stage of microvascular insufficiency was examined. The lathyrogen, imino-diproprionitrile (IDPN), had previously been effective for creating a fast-developing model of retinal vasculopathy. Using that model, we demonstrated a stage in which the retinal microvasculature was blocked to erythrocytes but not to plasma [1]. However, we questioned the applicability of our findings to more slowly developing microvasculopathies, such as diabetic retinopathy. We designed the current study to examine the presence of such stage in slowly developing microvasculopathy. Animal models that are known to induce "diabetic retinopathy-like" changes used [2-4]. The diabetic animals were followed for a period of 17 months. Starting at the 12th month, a few animals of each group were killed and the retains were examined with our trichrome method [1] for relative capillary patency to erythrocytes and plasma, for functionality of endothelial cells, and for disturbances in the blood-retinal barrier. The results of this study support the hypothesis that retinal microvascular insufficiency does exist as a temporary stage that precedes the development of complete capillary blockage in long-term developing rat models of diabetic retinopathy.

Ultrastructural and Morphometric Comparison of Retinal and Myocardial Capillaries Following Acute Ischaemia

The recovery of any tissue following a period of ischaemia is dependent on a patent microvasculature to restore blood flow. In the ischaemic myocardium, a reduction in capillary cross-sectional dimensions occurs, which is likely to contribute to “no-reflow” injury. Clinical and experimental evidence indicates that the retina is able to tolerate moderate periods of ischaemia without significant loss of function. The aim of the present study is to test the hypothesis that, as an end-arterial system, the retina possesses compensatory processes to maintain a functional microcirculation following acute ischaemia. Thirty minutes of no-flow global ischaemia was induced in isolated hearts of Wistar rats without reperfusion. The retina was also made ischaemic for 30 min using two experimental models: microsphere embolization and anoxic superfusion. Changes in capillary dimensions were assessed by ultrastructural morphometry. Following 30 min of myocardial ischaemia capillaries appeared swollen with a significant reduction in total capillary and luminal cross-sectional area. By contrast, ischaemic retinal capillaries showed minimal morphological changes and no significant alteration in dimensions. We have demonstrated notable differences in the response of retinal and myocardial microvessels to acute ischaemia. It is likely that the maintenance of capillary patency following short periods ischaemia in the retina is part of an adaptive mechanism to protect visual function.

Intravital videomicroscopy of peritubular capillaries in renal ischemia.

The recent refinement and computerization of intravital microscopy have permitted us to monitor microcirculation in vivo with minimal invasion. Here, we report on the first findings made with the use of a pencil-lens intravital microscope as applied to the ischemic rat kidney. Peritubular capillary and glomerular blood flow were monitored under basal conditions, during renal artery occlusion, and immediately after release of the clamp. Erythrocyte velocity was calculated as an angle in consecutive spatiotemporal images. Intravital videomicroscopy during the reperfusion period showed intermittent cessation and partial recovery of blood flow in both peritubular and glomerular capillaries. Blood flow was uniformly orthograde under control conditions; however, the retrograde flow occurred on reperfusion. The patency of peritubular capillaries was partially compromised during the early reperfusion period but rapidly recovered. The recovery of glomerular microcirculation occurred faster than that of peritubular capillaries. We suggest that a functional vasculopathy develops very early in the course of ischemia-reperfusion in superficial cortical microvasculature and is more pronounced in peritubular capillaries, thus accounting for the development of patchy injury of tubular epithelia.

Dynamic changes in three-dimensional architecture and vascular volume of transmural coronary microvasculature between diastolic- and systolic-arrested rat hearts.

The phase difference of coronary arterial and venous flows indicates the importance of intramyocardial capacitance vessels in storing diastolic flow and in discharging volume in systole. However, the anatomic and functional characteristics of the capacitance vessels are unclear. We aimed to clarify those characteristics with their transmural difference by 3D visualization of transmural microvessels under diastole and systole. We performed complete intracoronary filling of a contrast medium into Langendorff's Wistar rat hearts under (1) St Thomas-perfused diastolic arrest (D-mode) and (2) BaCl(2)-induced systolic arrest (S-mode). Precise transmural 3D architectures of capillaries and of pre- and post-capillary microvessels (ie, microvessels larger than capillaries) were visualized clearly with a confocal laser scanning microscope and x-ray microcomputed tomography (microCT), respectively. Vascular volume fraction (VF) and systolic-induced VF reduction rate from D- to S-mode were analyzed. The net capillary VF in D-mode (20.4 +/- 0.9%) was 10 times that of larger microvessels and was reduced in S-mode by 32% without capillary collapse. Systolic-induced VF reduction rate was smaller in capillaries than in larger microvessels (48%; P<0.05). The larger microvessel VF in D-mode (2.2 +/-0.2%) was reduced in S-mode, accompanied by complicated 3D deformation. Capillaries were relatively resistant to the systolic extravascular compression compared with pre- and post-capillary microvessels, conveniently beneficial for the myocardial oxygen delivery throughout a cardiac cycle. Nevertheless, a larger change in the absolute volume of capillaries may function as effective capacitance. On one hand, the pre- and post-capillary microvessels showed a larger phasic change in resistance, which may function to maintain the capillary patency during systole.

Experimental rupture of atherosclerotic lesions increases distal vascular resistance: a limiting factor to the success of infarct angioplasty.

Rupture of atherosclerotic lesions, resulting in localized thrombi and marked falls in distal blood flow, is a pivotal event in unstable coronary syndromes. We tested the hypothesis that after lesion rupture, vasoconstrictor mechanisms are major contributors to a marked rise in distal microvascular resistance, which is responsible for much of the interruption in blood flow. Cholesterol-fed rabbits underwent endothelial denudation of their left iliac arteries to induce angiographically severe, fatty, American Heart Association type IV-like atherosclerotic lesions. After lesion disruption with a stiff wire, we measured distal blood flow and pressure, capillary patency in the distal vascular bed, and the response to the vasodilators adenosine, nitroprusside, and glyceryl trinitrate. Morphology of the lesions and of the associated thrombi was also examined to assess lumen restriction at the site of rupture. Disruption of atherosclerotic lesions reduced mean flow from 5.04+/-1.21 to 1.23+/-0.37 mL/min (P<0.005), and calculated distal vascular resistance rose rapidly, from 17.5+/-2.9 to 37.9+/-6.4 mm Hg. min/mL (P<0.005). Lesion rupture did not significantly affect capillary patency in the distal muscle vascular bed, and although nonocclusive thrombi were present at the site of nearly all ruptured lesions, embolized thrombi were rare in capillaries (<1%). The early rise in distal microvascular resistance could be normalized with intra-arterially administered adenosine or the NO donor nitroprusside, but not glyceryl trinitrate, an organonitrate possessing large muscular artery-selective vasodilator characteristics. Thus, rupture of atherosclerotic lesions induces rapid and marked increases in distal vascular resistance, which is the consequence of severe microvascular vasoconstriction. Therapeutic targeting of the microvasculature should improve reperfusion in acute coronary syndromes.

Matrix metalloproteinases in pathophysiology and treatment of heart failure

The structural integrity of the heart is dependent on an extensive network of fibrillar collagens. First recognised in skeletal muscle by Holmgren in 1907, 1 Holmgren E Ueber die Trophospongien der quergestreiften Muskelfasern, nebst Bemerkungen uber den allgemeinen Bau dieser Fasern. Arch Mikrosk Anat. 1907; 71: 165-201 Crossref Scopus (21) Google Scholar these collagen fibres are grouped in weaves that surround myocytes, struts that interconnect adjacent myocytes, small fibrils that attach the plasma membrane to the encircling basal lamina, long tendon-like bundles that link adjacent weaves, and collagen struts that connect the myocytes to adjacent capillaries. 2 Borg TK Caulfield JB The collagen matrix of the heart. Fed Proc. 1981; 40: 2037-2041 PubMed Google Scholar This complex scaffolding facilitates the transmission of force between neighbouring myocytes, maintains capillary patency during ventricular contractions, maintains lateral cell-to-cell alignment, and precludes cell slippage and ventricular-cavity dilatation during diastole. 3 Weber KT Cardiac interstitium in health and disease: the Fibrillar Collagen Network. J Am Coll Cardiol. 1989; 13: 1637-1652 Summary Full Text PDF PubMed Scopus (841) Google Scholar In addition, collagen cross-linking is an important determinant of systolic and diastolic performance. In the cardiac extracellular matrix, collagens are produced by fibroblasts, the most common collagen subtypes in the myocardium being types I and III. 3 Weber KT Cardiac interstitium in health and disease: the Fibrillar Collagen Network. J Am Coll Cardiol. 1989; 13: 1637-1652 Summary Full Text PDF PubMed Scopus (841) Google Scholar Type I, which predominates in the heart, has a higher tensile strength than type III, which provides greater distensibility. To what extent is research into their metabolism contributing to the development of therapies for heart failure?

Capillary patency after transient middle cerebral artery occlusion of 2 h duration

Reperfusion after transient focal ischemia of 2 h duration is followed by secondary bioenergetic failure after 4 h of reperfusion. The objective of the present study was to explore whether or not this secondary deterioration is due to secondary microcirculatory compromise. Normal fasted rats were subjected to 2 h of MCA occlusion and allowed reperfusion for 2, 4, 6 and 8 h. At predetermined reperfusion times, rats were injected with Evans blue and decapitated. Capillary patency was determined using a fluorescent double-staining technique. No capillary perfusion deficits were detected in the ischemic neocortical penumbra, neocortical focus or striatal focus. We concluded that the secondary deterioration of bioenergetic state is not due to microcirculatory compromise. Since hyperglycemic animals show pan-necrotic lesions, a hyperglycemic group was added at 8 h of reperfusion to test if the adverse effect of hyperglycemia on ischemic damage is related to capillary compromise. The results showed that, in hyperglycemic rats, capillary perfusion in the striatal focus was compromised after 8 h of recirculation following 2 h of MCA occlusion. It is concluded that when normoglycemic rats are subjected to 2 h of MCA occlusion, capillary patency is not affected during the first 4–6 h of reflow. At 8 h of reflow, though, particularly in hyperglycemic rats, microcirculation is compromised in the caudoputamenal focus, probably reflecting infarction.

Hyperglycemia-exaggerated ischemic brain damage following 30 min of middle cerebral artery occlusion is not due to capillary obstruction

Transient focal ischemia of brief duration (15–30 min) gives rise to brain damage. In normoglycemic animals this damage usually consists of selective neuronal necrosis (SNN), and is largely confined to the lateral caudoputamen. In hyperglycemic subjects damage occurs more rapidly, involves also neocortical areas, and is often of the pan-necrotic type (`infarction'). Since experiments on forebrain ischemia of 30 min duration suggest that microcirculatory compromise develops during recirculation, we studied whether focal ischemia of the same duration, followed by reperfusion for 1, 2 or 4 h, leads to microcirculatory dysfunction. To test this possibility, we fixed the tissue by perfusion and counted the number of formed elements (leukocytes, macrophages and erythrocytes) in capillaries and postcapillary venules. Furthermore, capillary patency was evaluated following in vivo injection of Evan's blue. Histopathological examination of tissue fixed by perfusion after 1, 2 and 4 h of recirculation showed an increasing density of SNN in the caudoputamen of normoglycemic animals. Hyperglycemic, but not normoglycemic, animals showed pan-necrotic lesions (`infarction') after 4 h of recirculation. As a result, the total volume of tissue damage (SNN plus infarction) was larger in hyper- than in normoglycemic animals at 2 and 4 h of recirculation. In addition, hyperglycemic animals showed involvement of neocortex which increased with the time of reperfusion. In the ischemic hemisphere, between 5 and 10% of counted capillaries contained formed elements. However, since hyperglycemic animals contained an equal (or smaller) amount of cells the results did not suggest that capillary `plugging' could explain the aggravated damage. Moreover, both normo- and hyperglycemic animals showed close to 100% capillary patency. The results thus fail to support the notion that the aggravation of focal ischemic damage by hyperglycemia is due to obstruction of microvessel by swelling or leukocyte adherence.

In situ complement activation in porcine membranoproliferative glomerulonephritis type II

Pigs genetically deficient in complement factor H all develop lethal membranoproliferative glomerulonephritis (MPGN) type II characterized by massive glomerular deposits of complement, intramembranous dense deposits, and mesangial hypercellularity. To elucidate the chronological relationship between these glomerular changes, and to precisely determine the localization of glomerular complement deposits, we studied kidney specimens from factor H-deficient piglets at different ages from fetal life until terminal kidney failure had developed. Deposits of C3 and the terminal complement complex localized within the glomerular basement membrane (GBM) were present already in factor H-deficient fetuses, without concurrent intramembranous dense deposits or mesangial hypercellularity. Incipient subendothelial dense deposits containing complement appeared no earlier than four days after birth, and intramembranous dense deposits in older piglets with established MPGN type II also contained large amounts of complement as detected by immune electron microscopy. Onset of kidney failure coincided with pronounced mesangial hypercellularity and expansion, compromising glomerular capillary patency. Formation of glomerular capillary wall double contours coincided with electron microscopic evidence of laminar disintegration of intramembranous dense deposits. Complement was also deposited in the mesangial matrix, but not on glomerular cells. We conclude that all components of the alternative and terminal pathways of complement have access into the GBM and the mesangial matrix. In the absence of factor H, complement is spontaneously activated and deposited in situ in these locations resulting in dense deposit formation. It is proposed that factor H dysfunction may play an essential role even in human MPGN type II.

Preischemic hyperglycemia leads to rapidly developing brain damage with no change in capillary patency

The present experiments were undertaken to explore whether exaggeration of ischemic brain damage by preischemic hyperglycemia is due to lack of capillary patency in the postischemic period. Normo- and hyperglycemic rats were exposed to 10 min of forebrain ischemia. Histopathological changes were evaluated after 6 and 16–18 h of recovery by light microscopy, and capillary patency was assessed at the same time points by a double-staining technique, depicting perfused and morphologically identifiable capillaries. The results demonstrate that some neuronal damage was detectable after 6 h of recirculation which was aggravated after 16–18 h of recirculation in hyperglycemic rats. In contrast, the degree of capillary patency was similar in normo- and hyperglycemic rats. In both groups the perfusion marker, Evans blue, perfused about 95% of all capillaries when injected 10 s before decapitation. Since preischemic hyperglycemia exaggerates brain damage without cessation of capillary perfusion the primary targets of hyperglycemic brain damage may not be capillaries but neurons or glial cells.

Morphologic variations of dense deposit disease: Light and electron microscopic, immunohistochemical and clinical findings in 10 patients

Twenty-one renal biopsy specimens obtained from 10 patients with dense deposit disease (DDD) were investigated using light microscopy, electron microscopy and immunohistochemistry. The patients included four females and six males aged 6 to 35 years (mean 16.1 years). A morphological diagnosis of DDD was made following the ultrastructural detection of continuous intramembranous dense deposits (CIMDD) in some capillary loops of at least one of the series of the repeated biopsies from each patient. With light microscopy, six patients showed membranoproliferative glomerulonephritis (MPGN). The other four patients showed diffuse proliferative glomerulonephritis (DPGN) with acute lesions showing intraglomerular neutrophilic infiltration, hump formation and endothelial swelling in three and minor glomerular abnormalities in one. Follow-up biopsies were obtained in six patients. Two patients progressed from DPGN to MPGN within 7 months, whereas three patients with MPGN showed morphologic improvement that featured increased capillary patency and regional disappearance of dense deposits along with the reduction of proteinuria. Dense deposit disease did not always feature typical amorphous and osmiophilic CIMDD spreading across the whole width of the lamina densa. This classical ultrastructural manifestation was mainly found in the patients with histologic non-MPGN and a linear peripheral pattern of complement component (C3) deposition. The MPGN patients with a granular peripheral pattern of C3 deposition also had CIMDD, but also additionally featured less dense subepithelial deposits superimposed on the CIMDD to produce an appearance simulating membranous transformation.(ABSTRACT TRUNCATED AT 250 WORDS)