[Structure of venular vessels and cellular composition of hepatic sinusoidal capillaries in newborn infants].

The objective of this study was to identify the structural peculiarities of terminal interlobular venules and to determine the number of endotheliocytes, hepatic fat-storing cells (FSC) and stellate macrophages (SM) in the liver of newborn infants. Liver fragments were obtained from 5 healthy newborn infants during medico-legal autopsies. In the sections stained using Mallory's method, the relation of the connective tissue of terminal portal tracts with the adventitia of interlobular veins was determined. The numbers of endotheliocytes, FSC and CD68+ SM were counted in different zones of the liver acini. It was found that the adventitia of the terminal interlobular venules was completely represented by the connective tissue of the terminal portal tracts. Anastomoses with the sinusoidal capillaries (SC) via the circumlobular venules form the preterminal veins. FSC were concentrated in the central and periportal zones of the liver acinus, endotheliocytes of SC - in the periportal and peripheral zones, while SM were evenly distributed in all parts of the liver acinus. Thus, in newborn infants, liver cells possessing fibrogenic potential were numerous and were accumulated mainly near terminal interlobular venules, their circumlobular branches and within their adventitia.

Microvascular architecture of human epicolic and paracolic lymph nodes located in the vicinity of colon cancer: a SEM study of corrosion casts.

The vascular systems of epicolic and paracolic lymph nodes located in the vicinity of colon tumors resected from three patients were investigated by corrosion casting and scanning electron microscopy. Large vessels entered the nodes either at one site, not always corresponding with the anatomical hilus, or at 2-4 sites located along their perimeters. In the cortical zone of most examined nodes, the location of lymphoid nodules was marked by rosette-like capillary arrays drained by peripheral arcuate venules. The paracortex and medulla showed a dense capillary network with areas of tortuous capillaries, sometimes forming glomerular arrays suggesting nonsprouting angiogenesis by capillary elongation. Venules were abundant, especially in the paracortex and medulla, but high endothelial venules showing characteristic imprints of bulging endothelial cells in the casts were very rarely observed. Focal angiogenesis, abundance of venules and scarcity of high endothelial venules could result from remodeling of blood vessels induced by the tumor.

Retinal vascular caliber and metabolic syndrome in a Chinese population.

BACKGROUND: Microvascular changes have been associated with the metabolic syndrome. METHODS: We included 869 participants aged ≥ 40 years from the High-risk for Diabetes Changfeng Study, who had gradable fundus photographs. On digital photographs sum retinal arteriolar and venular calibers were measured with a semi-automated system. Metabolic syndrome was defined according to the International Diabetes Federation consensus. RESULTS: A total of 286 (32.9%) participants was diagnosed with metabolic syndrome. Participants with narrower retinal arteriolar caliber were more often diagnosed with metabolic syndrome (odds ratio 1.78, 95% confidence interval 1.02 ­ 3.10; lowest vs highest quintile). Additionally adjusting for age, gender, education, smoking and weekly activity, and adding arteriolar and venular caliber simultaneously in the same models did not alter these associations. In the component analyses, participants with narrower retinal arteriolar caliber were more likely to have central obesity, dyslipidaemia or raised blood pressure, and less likely to have raised fasting plasma glucose. The association between wider venular caliber and metabolic syndrome was less pronounced and non-significant (odds ratio 1.34; 95% confidence interval 0.79 ­ 2.38; highest vs lowest quintile). CONCLUSION: Retinal arteriolar narrowing and, to a lesser extent, retinal venular dilatation were associated with metabolic syndrome in this Chinese population. These vascular changes, although small in magnitude, may still be important in the pathophysiological mechanisms involved in the metabolic syndrome.

Microbeam radiation-induced tissue damage depends on the stage of vascular maturation.

PURPOSE: To explore the effects of microbeam radiation (MR) on vascular biology, we used the chick chorioallantoic membrane (CAM) model of an almost pure vascular system with immature vessels (lacking periendothelial coverage) at Day 8 and mature vessels (with coverage) at Day 12 of development. METHODS AND MATERIALS: CAMs were irradiated with microplanar beams (width, ∼25 µm; interbeam spacing, ∼200 µm) at entrance doses of 200 or 300 Gy and, for comparison, with a broad beam (seamless radiation [SLR]), with entrance doses of 5 to 40 Gy. RESULTS: In vivo monitoring of Day-8 CAM vasculature 6 h after 200 Gy MR revealed a near total destruction of the immature capillary plexus. Conversely, 200 Gy MR barely affected Day-12 CAM mature microvasculature. Morphological evaluation of Day-12 CAMs after the dose was increased to 300 Gy revealed opened interendothelial junctions, which could explain the transient mesenchymal edema immediately after irradiation. Electron micrographs revealed cytoplasmic vacuolization of endothelial cells in the beam path, with disrupted luminal surfaces; often the lumen was engorged with erythrocytes and leukocytes. After 30 min, the capillary plexus adopted a striated metronomic pattern, with alternating destroyed and intact zones, corresponding to the beam and the interbeam paths within the array. SLR at a dose of 10 Gy caused growth retardation, resulting in a remarkable reduction in the vascular endpoint density 24 h postirradiation. A dose of 40 Gy damaged the entire CAM vasculature. CONCLUSIONS: The effects of MR are mediated by capillary damage, with tissue injury caused by insufficient blood supply. Vascular toxicity and physiological effects of MR depend on the stage of capillary maturation and appear in the first 15 to 60 min after irradiation. Conversely, the effects of SLR, due to the arrest of cell proliferation, persist for a longer time.

The morphological basis of proestrus endometrial bleeding in canines.

Endometrial bleeding during proestrus is a well-known phenomenon in the bitch. However, the exact events on the cellular level have not been studied. In the present investigation, immunohistochemical methods and transmission electron microscopy were employed to obtain more information about this cyclic event in canines. Long, stretched blood vessels were seen in H&E stained sections during proestrus. These vessels showed mitotic activity, as evidenced by Ki67 immunostaining. Although the endothelial lining and basement membrane of endometrial blood vessels seemed continuous, as indicated by immunohistochemical staining for laminin and Von Willebrand factor, transmission electron microscopy showed an extreme thinning and even interruption of the vascular wall in endometrial venules. Platelets were frequently seen in those areas, and also detected by immunohistochemistry. Interestingly, all endometrial capillaries examined by electron microscopy had an intact wall. We therefore postulate the endometrial venules to be the blood vessels that are mainly responsible for proestrus endometrial bleeding, rather than subepithelial capillaries.

LFA-1 and Mac-1 define characteristically different intralumenal crawling and emigration patterns for monocytes and neutrophils in situ.

To exit blood vessels, most (∼80%) of the lumenally adhered monocytes and neutrophils crawl toward locations that support transmigration. Using intravital confocal microscopy of anesthetized mouse cremaster muscle, we separately examined the crawling and emigration patterns of monocytes and neutrophils in blood-perfused unstimulated or TNF-α-activated venules. Most of the interacting cells in microvessels are neutrophils; however, in unstimulated venules, a greater percentage of the total monocyte population is adherent compared with neutrophils (58.2 ± 6.1% versus 13.6 ± 0.9%, adhered/total interacting), and they crawl for significantly longer distances (147.3 ± 13.4 versus 61.8 ± 5.4 µm). Intriguingly, after TNF-α activation, monocytes crawled for significantly shorter distances (67.4 ± 9.6 µm), resembling neutrophil crawling. Using function-blocking Abs, we show that these different crawling patterns were due to CD11a/CD18 (LFA-1)- versus CD11b/CD18 (Mac-1)-mediated crawling. Blockade of either Mac-1 or LFA-1 revealed that both LFA-1 and Mac-1 contribute to monocyte crawling; however, the LFA-1-dependent crawling in unstimulated venules becomes Mac-1 dependent upon inflammation, likely due to increased expression of Mac-1. Mac-1 alone was responsible for neutrophil crawling in both unstimulated and TNF-α-activated venules. Consistent with the role of Mac-1 in crawling, Mac-1 block (compared with LFA-1) was also significantly more efficient in blocking TNF-α-induced extravasation of both monocytes and neutrophils in cremaster tissue and the peritoneal cavity. Thus, mechanisms underlying leukocyte crawling are important in regulating the inflammatory responses by regulating the numbers of leukocytes that transmigrate.

17beta-estradiol mediated protection against vascular leak after hemorrhagic shock: role of estrogen receptors and apoptotic signaling.

Vascular hyperpermeability is a clinical complication associated with hemorrhagic shock (HS) and occurs mainly because of the disruption of the adherens junctional complex. The objective of this study was to understand the role of 17beta-estradiol in HS-induced hyperpermeability particularly focusing on estrogen receptors. In male Sprague-Dawley rats, HS was induced by withdrawing blood to reduce the mean arterial pressure to 40 mmHg for 1 hour followed by 1 hour of resuscitation to 90 mmHg. The study groups were 17beta-estradiol, tamoxifen, fulvestrant plus 17beta-estradiol, propyl pyrazole triol plus 17beta-estradiol, and diarylpropionitrile plus 17beta-estradiol. Intravital microscopy was used to study changes in mesenteric postcapillary venules. Mitochondrial reactive oxygen species formation was studied in vivo using dihydrorhodamine 123. The mitochondrial transmembrane potential was studied using the fluorescent cationic probe 5,5',6,6'tetrachloro-1,1',3,3'tetraethylbenzimidazolyl carbocyanine iodide (JC-1). The mesenteric microvasculature was analyzed for cytochrome c levels by enzyme-linked immunosorbent assay and caspase-3 activity by a fluorometric assay. Our results demonstrated that 17beta-estradiol attenuated HS-induced hyperpermeability. Fulvestrant reversed this protective effect (P < 0.05). Tamoxifen 5 mg/kg attenuated HS-induced hyperpermeability, whereas 10 mg/kg induced permeability (P < 0.05). Both alpha and beta estrogen receptor agonists inhibited HS-induced hyperpermeability (P < 0.05). 17beta-Estradiol decreased HS-induced reactive oxygen species formation and restored mitochondrial transmembrane potential. 17beta-Estradiol decreased both cytosolic cytochrome c level and activation of caspase-3 (P < 0.05). These findings suggest that 17beta-estradiol protects the microvasculature after HS, and that this protection may be mediated through the alpha and beta estrogen receptors.

Congruence between NOTCH3 mutations and GOM in 131 CADASIL patients.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is the most common hereditary subcortical vascular dementia. It is caused by mutations in NOTCH3 gene, which encodes a large transmembrane receptor Notch3. The key pathological finding is the accumulation of granular osmiophilic material (GOM), which contains extracellular domains of Notch3, on degenerating vascular smooth muscle cells (VSMCs). GOM has been considered specifically diagnostic for CADASIL, but the reports on the sensitivity of detecting GOM in patients' skin biopsy have been contradictory. To solve this contradiction, we performed a retrospective investigation of 131 Finnish, Swedish and French CADASIL patients, who had been adequately examined for both NOTCH3 mutation and presence of GOM. The patients were examined according to the diagnostic practice in each country. NOTCH3 mutations were assessed by restriction enzyme analysis of specific mutations or by sequence analysis. Presence of GOM was examined by electron microscopy (EM) in skin biopsies. Biopsies of 26 mutation-negative relatives from CADASIL families served as the controls. GOM was detected in all 131 mutation positive patients. Altogether our patients had 34 different pathogenic mutations which included three novel point mutations (p.Cys67Ser, p.Cys251Tyr and p.Tyr1069Cys) and a novel duplication (p.Glu434_Leu436dup). The detection of GOM by EM in skin biopsies was a highly reliable diagnostic method: in this cohort the congruence between NOTCH3 mutations and presence of GOM was 100%. However, due to the retrospective nature of this study, exact figure for sensitivity cannot be determined, but it would require a prospective study to exclude possible selection bias. The identification of a pathogenic NOTCH3 mutation is an indisputable evidence for CADASIL, but demonstration of GOM provides a cost-effective guide for estimating how far one should proceed with the extensive search for a new or an uncommon mutations among the presently known over 170 different NOTCH3 gene defects. The diagnostic skin biopsy should include the border zone between deep dermis and upper subcutis, where small arterial vessels of correct size are located. Detection of GOM requires technically adequate biopsies and distinction of true GOM from fallacious deposits. If GOM is not found in the first vessel or biopsy, other vessels or additional biopsies should be examined.

The three-dimensional microvascular architecture of the human Kaposi sarcoma implanted in nude mice: a SEM corrosion casting study.

The human Kaposi sarcoma represents one of the most common skin lesions associated with AIDS. Its clinical presentation and anatomopathological structure seem to demonstrate a particularly rich vascularity. The latest therapies aim to limit its intrinsic angiogenic activity in an attempt to reduce vascular density and the formation of new vessels. For these reasons, we decided to study the microvascular architecture of Kaposi sarcoma in three dimensions. We used a corrosion casting technique applied to nude mice previously transplanted subcutaneously with human modified neoplastic Kaposi sarcoma cells. The cooption of host vessels made by the tumor was demonstrated by three-dimensional scanning electron microscopy (SEM) images. At high magnification several angiogenic patterns were observed in the form of potato-shaped vessels, sprouts, intussusceptions and mouse tailed end tipped capillaries along with some ultrastructural features such as intercellular extravasations and endothelial cell modifications. Our investigation allowed us to build a detailed map of tumor vasculature in human Kaposi sarcoma. Furthermore, this study want to shed light on the sharp morphological three-dimensional conformation of angiogenic sprouts so to be able to better understand their modifications occurred during time and after antiangiogenic experimental therapies, by now observed only by immunohistochemical or immunofluorescent assays.

Functional photoacoustic microscopy for high-resolution and noninvasive in vivo imaging.

Although optical absorption is strongly associated with the physiological status of biological tissue, existing high-resolution optical imaging modalities, including confocal microscopy, two-photon microscopy and optical coherence tomography, do not sense optical absorption directly. Furthermore, optical scattering prevents these methods from imaging deeper than approximately 1 mm below the tissue surface. Here we report functional photoacoustic microscopy (fPAM), which provides multiwavelength imaging of optical absorption and permits high spatial resolution beyond this depth limit with a ratio of maximum imaging depth to depth resolution greater than 100. Reflection mode, rather than orthogonal or transmission mode, is adopted because it is applicable to more anatomical sites than the others. fPAM is demonstrated with in vivo imaging of angiogenesis, melanoma, hemoglobin oxygen saturation (sO2) of single vessels in animals and total hemoglobin concentration in humans.

Microvascular adaptation to growth in rat humeral head.

The aim of this work is to investigate the growth of the vasculature in the rat humeral head cartilage after the initial development of the secondary ossification centre until the adult organization. Rats aging from 5 weeks to 12 months were used. Histological observations on humeral heads were implemented with morphometrical analysis. Subsequently, vascular corrosion cast, that permits a three-dimensional observation of the vasculature, were prepared and observed by scanning electron microscopy. In young animals the epiphysis contains thin bone trabeculae and most of the epiphysis is occupied by bone marrow spaces. With age, the bone trabeculae progressively enlarge up to double their thickness. The percentage of bone tissue increases from 33.6 to 58.6% of the entire epiphysis, while the bone marrow spaces tend to increase very little in their mean dimension. Vascular corrosion casts show that the epiphyseal microcirculation is well distinguished from that of the diaphysis, and arises from the vessels present in the capsule and the periosteal networks. In young animals the only capillaries are bone marrow sinusoids and few subchondral capillaries. In adult animals small vessels run between the clusters of sinusoids forming the trabecular circulation. Capillary sprouts from sinusoids are always observed both in the young and adult animals. Thus, in adult rats different proper microcirculatory districts can be distinguished in the epiphysis: (a) the sinusoidal network, that supplies the hematopoiesis of the bone marrow and the adjacent osteogenic tissue; (b) the bone tissue microcirculation, limited to small vessels that supply the metabolism and the remodelling of the bone tissue. The reported microvascular organization and its adaptation to the epiphyseal growth represent the morphological basis for understanding the reciprocal interaction among the different tissues in developing and adult rat epiphysis.

Active leukocyte crawling in microvessels assessed by digital time-lapse intravital microscopy.

OBJECTIVE: The ability of active movement is an important feature of leukocytes. Here, we used a hybrid technique that combines intravital microscopy and digital time-lapse video microscopy to investigate the physiology and molecular mechanisms of intravascular leukocyte movement. METHODS: Intravital microscopy of mesenteric venules was performed in male, Wistar rats using digital video recording and time-lapse image compression. The leukocyte movement and extravasation were analyzed after local application of TNF-alpha, after blockade of endothelial (anti-ICAM-1 antibody) and leukocyte (anti-CD18 antibody) adhesion molecules. Additionally, the migratory activity of isolated leukocytes in collagen gel was analyzed and compared with their intravascular locomotion. RESULTS: Adherent leukocytes showed an active intraluminal crawling along the endothelial lining. Most permanent stickers (84 +/- 13%) crawled actively on the intraluminal site of venules. Baseline measurement of leukocyte crawling velocity yielded an average 9.0 +/- 1.8 mum/min that was not significantly different from crawling velocity of extravascular leukocytes (8.9 +/- 4.5 mum/min). The maximum distance of leukocyte crawling observed was 150 microm. The maximum time of crawling was 15 min. Intraluminal crawlers traveled over a mean distance of 35 +/- 17 mum with the average duration of 5.4 +/- 1.4 min. Under unstimulated conditions, almost all crawling leukocytes detached from the endothelium and did not migrate through the vascular wall. TNF-alpha induced a significant increase of leukocyte extravasation. Anti-ICAM-1 and anti-CD18 antibodies significantly reduced leukocyte crawling. The proportion of isolated migrating leukocytes in collagen gel (87% +/- 6%) was not significantly different from the percentage of intravascular crawling leukocytes in vivo. CONCLUSIONS: The method of digital time-lapse intravital microscopy represents an advantageous technology for the investigation of intravascular, transendothelial, and extravascular migration of leukocytes. Using this technology, we showed that leukocyte-endothelial-interactions are an active and dynamic process. This process involves long-time (several minutes) crawling of leukocytes along the endothelium and, finally, detachment from the endothelium. Intravascular leukocyte crawling reflects the migratory potential of circulating leukocytes and strongly depends on the expression of adhesion molecules. For extravasation, an additional pro-inflammatory stimulus is required.

Bone marrow microvessel density and its prognostic significance in AML.

Microvessel density reportedly is increased in various hematologic disorders including acute lymphatic and myeloid leukemias. In these patients the bone marrow microvessel density (BM-MVD) appears to be associated with an unfavorable prognosis. In the present study, we have retrospectively analyzed the BM-MVD (at diagnosis) in 31 patients with acute myeloid leukemia (AML) (median age: 38 years; range: 21-53 years; f:m-ratio: 1:1,4) who underwent conventional chemotherapy and consecutive allogeneic bone marrow transplantation (BMT). The median BM-MVD at diagnosis was 30/mm2 (range: 17-48/mm2) and thus was significantly higher compared to controls (n = 9; BM-MVD: median 7/mm2, range 2-11/mm2; P < 0.05). In patients who failed to achieve a complete remission (CR) in response to induction chemotherapy, the BM-MVD was significantly higher (median: 41.5/mm2) at diagnosis than in patients who entered CR (median: 28.5/mm2, P < 0.05). In addition, patients with high BM-MVD ( > 30 mm2) had a significantly shorter overall survival compared to patients with a lower BM-MVD ( < 30 mm2, P < 0.05). Moreover, patients with a high BM-MVD ( > 30 mm2) were found to have a significantly higher risk of relapse (P < 0.05). In 4 patients in whom a continuous complete remission was documented after BMT, the BM-MVD levels were analyzed at diagnosis as well as between day + 80 and day + 100 after BMT. In all 4 patients, the BM-MVD was found to decrease in response to BMT until day 100 (P < 0.05). Together, our data suggest that the BM-MVD could be a prognostic parameter concerning survival in patients with AML undergoing allogeneic BMT.

Near-infrared spectrophotoscopy of finger venules in assessment of autonomic dysfunction.

The authors evaluated morphologic changes in the venules of the finger using near-infrared spectrophotoscopy in patients with autonomic dysfunction, such as familial amyloidotic polyneuropathy and multiple-system atrophy. Abnormalities of the venules, such as tortuosity, irregular venous caliber, and microaneurysm-like change, and a linear negative correlation between the degree of orthostatic hypotension and the degree of vasoconstriction of the venules were observed.

Age-related changes in vascular endothelial growth factor dependency and angiopoietin-1-induced plasticity of adult blood vessels.

Vascular endothelial growth factor (VEGF) and angiopoietin-1 (Ang1) are essential for vascular development, but this dependency has been assumed not to persist into adult life. In this study, we report that after 10 days of systemic treatment of 4-, 8-, and 16-week-old mice with VEGF-Trap, an inhibitor of VEGF, the number of capillaries in the tracheal mucosa was reduced by 39%, 28%, and 14%, respectively. The magnitude of the reduction decreased with age (r2=0.6, P<0.001), but was still significant at 16 weeks. A corresponding age-related decrease in vascular endothelial growth factor receptor-2 (VEGFR-2) immunoreactivity suggests that diminished VEGFR-2 expression may contribute to resistance to VEGF signaling inhibition. VEGF-Trap further reduced VEGFR-2 expression in tracheal capillaries. By comparison, systemic treatment with adenovirus encoding Ang1 led to a significant enlargement of tracheal venules with little age effect (64%, 56%, and 49% increase in diameter at 10 days). When Ang1 was given in combination with VEGF-Trap, tracheal vessels presented the typical response to each factor, showing that the Ang1 effect was not VEGF-mediated, yet Ang1 seems to have a protective effect, as judged by prevention of VEGF-Trap-induced reduction in tracheal capillaries in the oldest group. Together, these findings indicate that VEGF and Ang1 participate in blood vessel survival and plasticity in adult life.

[Angioarchitecture of the endometrial venous system of human myomatous uteri--scanning electron microscopy study]. / Angioarchitektonika naczyn zylnych endometrium miesniakowatej macicy ludzkiej--badania w mikroskopii skaningowej.

OBJECTIVES: The venous system of endometrium of myomatous uteri was examined. MATERIAL AND METHODS: The studies were carried out on 20 uteri obtained from autopsies. Corrosion casts were studied using scanning electron microscopy. RESULTS: The specimens revealed a chaotic network of tortuous and distended veins, venules and venous capillaries. The so-called venous lakes were observable in the whole length of the functional layer of the endometrium. CONCLUSIONS: Veins of the endometrium do not go in a company with arteries. No arterio-venous anastomoses were found.

Retinal microvascular changes and MRI signs of cerebral atrophy in healthy, middle-aged people.

OBJECTIVE: To examine the relation of retinal microvascular abnormalities and MRI signs of cerebral atrophy in healthy middle-aged people. METHODS: A population-based, cross-sectional study involved 1,684 persons aged 51 to 72 years who had cerebral MRI and retinal photography in 1993 to 1995. Sulcal and ventricular size were quantified from the MRI scans and coded as grades 0 to 9, with sulcal widening (SW) and ventricular enlargement (VE) defined as grades 3 or higher. The presence or absence of retinopathy, microaneurysms, hemorrhages, and other characteristics were defined from retinal photographs using a standardized protocol. Generalized arteriolar narrowing was defined from a computer-assisted measurement of arteriolar diameters from digitized photographs. RESULTS: Persons with retinopathy had higher sulcal (p = 0.001) and ventricular (p = 0.03) grades than persons without retinopathy. After adjusting for age, gender, race, mean arterial blood pressure, diabetes, cigarette smoking, common carotid artery intima-media thickness, and other vascular risk factors, retinopathy was significantly associated with SW (odds ratio [OR], 1.9; 95% CI, 1.2, 3.0) and VE (OR, 1.5; 95% CI, 1.0, 2.3). These associations persisted even in people without diabetes or hypertension (OR 1.9, 95% CI, 0.8, 4.4 for SW; OR 2.7, 95% CI, 1.2, 6.5 for VE). Other retinal arteriolar characteristics (arteriovenous nicking, focal and generalized arteriolar narrowing) were not related to sulcal or ventricular grade. CONCLUSIONS: In healthy, middle-aged people, retinopathy is independently associated with sulcal and ventricular enlargement on MRI. This finding is compatible with the hypothesis that microvascular characteristics may influence the development of cerebral atrophic changes.

PAF- and bradykinin-induced hyperpermeability of rat venules is independent of actin-myosin contraction.

We tested the hypothesis that acutely induced hyperpermeability is dependent on actin-myosin contractility by using individually perfused mesentery venules of pentobarbital-anesthetized rats. Venule hydraulic conductivity (Lp) was measured to monitor hyperpermeability response to the platelet-activating factor (PAF) 1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine or bradykinin. Perfusion with PAF (10 nM) induced a robust transient high Lp [24.3 +/- 1.7 x 10-7 cm/(s.cmH2O)] that peaked in 8.9 +/- 0.5 min and then returned toward control Lp [1.6 +/- 0.1 x 10-7 cm/(s.cmH2O)]. Reconstruction of venular segments with the use of transmission electron microscopy of serial sections confirmed that PAF induces paracellular inflammatory gaps. Specific inhibition of myosin light chain kinase (MLCK) with 1-10 microM 1-(5-iodonaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine hydrochloride (ML-7) failed to block the PAF Lp response or change the time-to-peak Lp. ML-7 reduced baseline Lp 50% at 40 min of pretreatment. ML-7 also increased the rate of recovery from PAF hyperpermeability measured as the decrease of half-time of recovery from 4.8 +/- 0.7 to 3.2 +/- 0.3 min. Inhibition of myosin ATPase with 5-20 mM 2,3-butanedione 2-monoxime also failed to alter the hyperpermeability response to PAF. Similar results were found using ML-7 to modulate responses. These experiments indicate that an actin-myosin contractile mechanism modulated by MLCK does not contribute significantly to the robust initial increase in permeability of rat venular microvessels exposed to two common inflammatory mediators. The results are consistent with paracellular gap formation by local release of endothelial-endothelial cell adhesion structures in the absence of contraction by the actin-myosin network.

Cerebral vascular abnormalities in a murine model of hereditary hemorrhagic telangiectasia.

BACKGROUND AND PURPOSE: Hereditary hemorrhagic telangiectasia type 1 (HHT1) is an autosomal dominant vascular dysplasia caused by mutations in the endoglin gene and characterized by dilated vessels and arteriovenous malformations (AVMs). To understand the etiology of this disorder, we evaluated the cerebral vasculature of endoglin heterozygous (Eng+/-) mice, which represent the only animal model of HHT1. METHODS: The cerebral vasculature of Eng+/- and Eng+/+ mice from C57BL/6 (B6) and 129/Ola (129) strains with a differential susceptibility to HHT1 was studied with corrosion casting. Casts were observed by scanning electron microscopy to detect malformations and evaluate arterial diameters and orientation of endothelial nuclei. Measurements were taken to assess relative constriction at arteriolar branching points and downstream relative dilatation. RESULTS: Three of 10 Eng+/- mice demonstrated abnormal vascular findings including AVMs, while none of 15 Eng+/+ mice did. The incidence of relative constriction at arteriolar branching points was significantly less in both Eng+/- groups than in their Eng+/+ counterparts. The occurrence of relative dilatation was significantly greater in B6-Eng+/- than in B6-Eng+/+ mice. Endothelial nuclei were significantly rounder and deviated more from the direction of blood flow in Eng+/- than in Eng+/+ mice. CONCLUSIONS: Eng+/- mice showed significant structural alterations in cerebral blood vessels, indicating that the level of endoglin on endothelium is critical for maintenance of normal vasculature. Since endoglin haploinsufficiency is associated with HHT1, such changes in arteriolar structures might occur in HHT1 patients and predispose them to AVMs and their sequelae.