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Results for “Capillary Fragility”

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PubMed1999

Pterygium with bulbar conjunctival hemorrhages.

BACKGROUND: This study was carried out to describe the clinical features and electron-microscopic characteristics of the capillaries in pterygium with conjunctival hemorrhage. METHODS: We compared the clinical findings in Japanese and Tunisian primary pterygia and in pterygium with and without bulbar conjunctival hemorrhages. The capillary fine structures of pterygium with bulbar conjunctival hemorrhages were studied by electron microscopy and compared with those without bulbar conjunctival hemorrhages. RESULTS: Conjunctival hemorrhages were noted in 16.4% of Tunisian patients but not in any Japanese patients. The former pterygia were significantly larger, more vascular and more frequently hyperemic than the latter. Pterygia with bulbar conjunctival hemorrhages were more hyperemic than without hemorrhages. Electron microscopy revealed interruptions of the endothelial cells and basement membrane of the capillaries in the pterygia with bulbar conjunctival hemorrhages, with blood cells escaping through the endothelial interruptions. CONCLUSION: Conjunctival hemorrhage in pterygia may be caused by fragility of the endothelial cells and basement membrane in the capillaries, which easily induces hemorrhage when the eyes are irritated by rubbing or by conjunctival foreign bodies. Pterygium with conjunctival hemorrhage is more frequently found in Tunisians than in Japanese.

Adult↗
PubMed1996

[Measuring capillary resistance values in atopic dermatitis].

For over 100 years many different methods have been used to determine capillary resistance as a measure of small vessel fragility. There is still no firm agreement as to the most suitable method; the procedure is not standardized and an objective system for measurement is lacking. We have developed a computerized system that makes it possible to count petechiae and determine their area without the results varying with different examiners. Although we tried to keep the conditions for our examinations constant, we found a wide individual spread. In spite of this, the capillary resistance of atopic subjects was significantly lower than that of healthy persons.

Adult↗
PubMed1984

How do vessels proliferate in the capsule of a chronic subdural hematoma?

An ultrastructural study was performed to define the mechanisms of proliferation of macrocapillaries and capillaries in the capsule of chronic subdural hematoma. Mitotic activities of endothelial cells and vascular sprouts may contribute to the vascular proliferation. Platelets may also play an important role. Endothelial cells of proliferating macrocapillaries were highly attenuated except for the nuclear portion and showed variable electron densities. The adjacent endothelial cells had less intimate cellular junctions than the proliferating capillaries. The proliferating endothelial cell sometimes contacted the opposing endothelial cell across the lumen, separating the latter into two compartments. The pericytes varied remarkably in size, shape, and electron density. Proliferating capillaries had a narrowed vascular lumen and were characterized by cuboidal or thickened endothelial cells with enlarged nuclei, numerous pinocytotic vesicles, and cytoplasmic protrusions into the vascular lumen. They occasionally had intimate cellular junctions with interdigitations and slender pericytes of high electron density. Proliferating vessels occasionally had some clear endothelial cells that contained filamentous material and a few dense bodies. These cells might represent degenerated or swollen endothelial cells. However, they showed no evidence of increased permeability. Postdegranulation platelets were sometimes trapped in the endothelial linings. These data indicate that the most important factor for the development of chronic subdural hematoma exists in the vessels of the capsules, which have a marked proliferation potential and a fragile nature. The possibility of transition from proliferating capillaries to macrocapillaries is discussed.

Blood Platelets↗
PubMed1999

Electron microscopic and immunohistochemical investigation of Reinke's edema.

Examination was made of the vocal fold mucosa of Reinke's edema immunohistochemically and electron microscopically, with special attention to blood vessels in Reinke's space (RS). Ten surgical specimens of Reinke's edema were used, and the results obtained are summarized as follows. There were subepithelial vascularization and many dilated vessels in RS. The vessels had thin endothelium with many fenestrae, many vesicles, and a thickened basement membrane. Plasma exuded from the capillaries into surrounding tissue via fenestrae. These findings demonstrate increased permeability of the vessels. The vascular walls were thin, with few pericytes. The pericytes were situated away from the endothelial cells. Some endothelial cells and pericytes had degenerated, and vessel occlusion was apparent in some cases. These findings indicate the vessels had become fragile. Interstitial cells and/or inflammatory cells in RS showed stained cytoplasm with vascular endothelial growth factor. This growth factor may possibly enhance capillary permeability and form fragile vessels in RS. Fragility and alteration in permeability of the vessels are presumed to cause edema of RS, which may progress to Reinke's edema.

Capillaries↗
PubMed1977

Fluid absorption and capillarity of suture materials.

The fluid absorption and capillarity of different suture materials commonly used were investigated in saline and blood plasma. Linen and silk have high fluid absorption in plasma (92.2 +/- 1.3%, 65.2 +/- 0.7% of dry weight), and polyamide twisted with cover together with polyester considerably lower absorption (27.0 +/- 0.8%, 16.0 +/- 0.3%). Monofilament polyamide has fluid absorption ability in spite of its homogeneous structure (10.1 +/- 0.2%). Capillary properties were demonstrated in all multifilament synthetic and natural materials but were effectively eliminated by waxing treatment. The fluid transport rate constant varied considerably between different materials and was highest for polyamide with cover. Fluid absorption and capillary properties are presumed to be of significance for the impact of contaminating bacteria.

Absorption↗
PubMed1995

Dermal angiopathy in hemodialysis patients: the effect of time.

We studied skin biopsies from 14 patients after 6 months to 18 years on hemodialysis (HD) to discern any effect of duration of treatment on skin and dermal capillaries. Patients selected for biopsy were without evidence of other diseases known to affect vasculature such as diabetes mellitus. Pathological changes compared with duration of HD were: capillary wall thickening, endothelial proliferation and new capillary formation, lipid content, and epidermal atrophy. Severity of morphologic changes were graded from 0 to 4+ by a pathologist who had no knowledge of HD duration. The earliest change observed was reduplication of the capillary basement membrane. Narrowing of capillary lumina due to endothelial cell proliferation and new capillary formation were noted after five years of HD; lipid droplets were noted in capillaries by five years; and epidermal atrophy by 10 years. Progressive severity of each finding was associated with length of time on HD. Neither amyloid nor Ca++ deposits were observed in any specimens. By clinical observation, easy bruisability and increased skin fragility were worse the longer the patient was on HD. Capillary occlusion inducing tissue ischemia could be a cause of the atrophic skin changes noted. However, no patient manifested dermal necrosis. While pathogenesis of the capillary changes in uremic skin is unknown, the changes have been shown to stabilize following successful kidney transplantation.

Adult↗
PubMed1994

The transitional region of the eighth nerve in elderly humans: light and electron microscopic study.

To investigate the central-peripheral transitional region (TR) of the eighth nerve in elderly humans and to determine the reasons for its fragility, the eighth nerve root was studied by light and electron microscopy and by immunohistochemistry. Central and peripheral nervous tissue showed complex interdigitations at the TR. Slight proliferation of central glial tissue accompanied with disarranged course of the nerve fibers was also seen in this region. These findings were though to be age-related changes of the eight nerve. The capillaries ran in various directions at the TR and formed anastomoses with capillaries in the peripheral portion of the nerve. The density of capillaries in the peripheral nervous tissue was twice as high as that in the central nervous tissue. These findings indicated that the capillaries at the TR provide a connection between the blood supply to the central and peripheral portions of the eighth nerve. The occurrence of the age-related changes and complex course of the capillaries at the eighth nerve TR appeared to be related with the fragility of this region.

Adult↗
PubMed2006

New polyurethane-based material for vascular corrosion casting with improved physical and imaging characteristics.

Vascular corrosion casting has been established as a method to reconstruct the three-dimensional (3D) structure of blood vessels of organs and tissues. After replacing the blood volume with a low viscosity resin, the surrounding tissue is removed to replicate the vascular architecture, typically using scanning electron microscopy (SEM). To date available casting resins have had significant limitations such as lack of viscosity, leading to insufficient perfusion of smallest capillaries in organs and tissues of smaller species, interaction with surrounding tissue or fragility of resulting casts. We have reported here about a new polyurethane-based casting resin (PU4ii) with superior physical and imaging characteristics. Low viscosity, timely polymerization, and minimal shrinking of PU4ii produces high quality casts, including the finest capillaries. These casts are highly elastic while retaining their original structure to facilitate postcasting tissue dissection and pruning of casts. SEM images illustrate the high reproduction quality, including endothelial cell imprints, features that allow one to discern arterial and veinal vessels. For quantitative analysis, casts from PU4ii can be imaged using micro-computed tomography to produce digital 3D reconstructions. The inherent fluorescence of PU4ii is sufficient to reproduce casts with or without tissue using confocal microscopy (CM). Because of the simplified casting procedure, the high reproducibility and the superior reproduction quality, a combination of vascular corrosion casting using PU4ii with advanced imaging technologies has great potential to support the description of vascular defects and drug effects in disease models using mutant mice.

Animals↗
PubMed2005

Microfluidic motion for a direct investigation of the structural dynamics of glass-forming liquids.

Glass-forming liquids, polymer solutions, and biofluids have additional inertial and elastic macroscopic degrees of freedom that are related to the elasticity of the molecular coils and affect the determination of the structural dynamical parameters. In this work, we propose a new approach for the direct evaluation of the fundamental material parameters (viscosity, fragility, glass transition temperature) of a viscoelastic liquid in a capillary flow inside a microfluidic device. The proposed technique substantially reduces the complexity of the theoretical analysis and provides an evaluation of the most relevant functional parameters of the fluid dynamics. Moreover, the approach allows the investigation of localization phenomena in geometrical confined systems, such as those required in miniaturized devices.

Microfluidic Analytical Techniques↗
PubMed1996

Endometrial vasculature in Norplant users: preliminary results from a hysteroscopic study.

Long-acting progestogenic contraceptives are frequently associated with disturbances of menstrual bleeding patterns. In particular, irregular, frequent and prolonged bleeding are commonly seen. The mechanism of this irregular bleeding is unknown, but changes in the endometrial vasculature are thought to be of importance. In endometrial biopsies from Norplant users, an increase in endometrial microvascular density has been observed after 3-12 months. Morphological changes in endometrial capillaries following progestogen exposure have suggested an increase in vascular fragility. Little is known about the structure and function of the endometrial vasculature in vivo following exposure to exogenous contraceptive steroids. This study has developed techniques for the assessment of vascular fragility by imposing a mechanical stress on the endometrium and observing subsequent bleeding under direct vision. The techniques were used in a preliminary examination between 1 and 9 months after Norplant insertion, and the study identified a number of morphological and functional characteristics of Norplant-exposed endometrium.

Adolescent↗
PubMed2002

MALC, a novel microinjection method for loading of macromolecules into cultured neurons.

Microinjection is one of the most useful and important methods in cellular neurobiology. However, direct insertion and retraction of a capillary produce physical stresses inside cells that make it difficult to apply on small and fragile cells, especially the central nervous system (CNS) neurons. In this study, we developed a novel method called MALC (microinjection method assisted with laser activated chromophore) to avoid this disadvantage of the conventional method. In MALC, a capillary is just attached on cell surface, and combination of a newly developed photosensitizer with a laser pointing system makes the plasma membrane permeable to molecules. This novel method can expand the application of the microinjection method and realize molecular manipulations inside CNS neurons.

Animals↗
PubMed1997

Hydroxyurea in the treatment of sickle-cell anemia.

Sickle-cell anemia is a congenital hemolytic anemia characterized by sickle-shaped RBCs. The deformed RBCs become distorted and rigid and may occlude small arterioles and capillaries leading to tissue ischemia and infarction. Sickled RBCs are too fragile to withstand the trauma of circulation, and hemolysis occurs after they enter the circulation. RBCs with a high level of Hb F are resistant to sickling. Hydroxyurea has been shown to stimulate Hb F synthesis, leading to a reduction in the incidence of hemolytic and vaso-occlusive manifestations; however, hydroxyurea has no role in the treatment of crises already in progress. The National Heart, Lung, and Blood Institute announced in January 1995 that treatment with hydroxyurea leads to an increase in Hb F production within RBCs and a reduction in the frequency of painful crises in patients with sickle-cell anemia. Although the mechanism by which hydroxyurea increases Hb F is not known, one possible explanation is that hydroxyurea is cytotoxic to the more rapidly dividing late erythroid precursors, leading to the recruitment of early erythroid precursors that have demonstrated increased capacities to produce Hb F. Clinical trials have demonstrated that hydroxyurea results in an increase in Hb F concentrations; however, this increase may not dramatically affect the progressive vascular changes associated with sickle-cell anemia; thus, patients may still experience complications related to sickle-cell anemia. At North Carolina Baptist Hospital in Winston-Salem, NC, compliant patients with sickle-cell anemia are started on hydroxyurea. There are no specific criteria for patient selection or monitoring. The dosage is started at 10-15 mg/kg/d. Platelet count, complete blood count, and Hb F are monitored and hydroxyurea dosages are adjusted accordingly. Although hydroxyurea has been effective in the treatment of sickle-cell anemia, large double-blind, placebo-controlled clinical trials are needed to determine whether the risks of long-term administration outweight the risk of vaso-occlusive disease in untreated patients.

Anemia, Sickle Cell↗
PubMed2000

The pathophysiology of the collateral circulation (arteriogenesis).

Since the mid 1980s a new strategy is coming from bench to bedside termed angiogenesis. This process involves sprouting of capillaries and finally results in newly developed microvessels which belong to the capillary level. Importantly these newly formed capillary tubes lack vascular smooth muscle cells, they are not surrounded by mural cells and are fragile and prone to rupture. Therefore these networks remain susceptible to hypoxic regulation, fail to become remodelled and are unable to sustain proper circulation: they cannot adapt to changes in physiological demands of blood supply. Since atherosclerosis affects large conductance arteries, capillary sprouting from compromised vessels cannot provide an adequate supply of blood flow to the endangered tissue. However, the body provides a natural system of pre-existing collateral arteries, which may bypass sites of arterial occlusion. These vessels can dramatically increase their lumen by growth so as to provide enhanced perfusion to the jeopardized ischaemic regions. This process - termed arteriogenesis - finally results in fully functional and structurally normal arteries which can ameliorate the ensuing detrimental effects of vessel obstruction in many regions of the body. Hallmarks of arteriogenesis are increased levels of shear forces (rather than ischaemia), the invasion of circulating monocytes (and their pluripotent precursors), and the substrates of arteriogenesis are pre-existing collateral arterioles.

Angiogenesis Inducing Agents↗
PubMed2000

Comparing cardiac action potentials recorded with metal and glass microelectrodes.

Machine-pulled high-impedance glass capillary microelectrode is standard for transmembrane potential (TMP) recordings. However, it is fragile and difficult to impale, especially in beating myocardial tissues. We hypothesize that a high-impedance pure iridium metal electrode can be used as an alternative to the glass microelectrode for TMP recording. The TMPs were simultaneously recorded from isolated perfused swine right ventricles with a metal microelectrode and a standard glass microelectrode during pacing and during ventricular fibrillation. The basic morphology of TMP recorded with these electrodes was comparable. The action potential duration (APD) at 90% repolarization was 241 +/- 29 ms for the metal microelectrode and 236 +/- 31 ms for the glass microelectrode with a good correlation (r = 0.99, P < 0.0001). The maximum slope value of the APD restitution curves during pacing was also significantly correlated. One metal microelectrode and >20 glass microelectrodes were needed per study. We conclude that, in isolated perfused swine right ventricles, the TMP recorded by the metal microelectrode is comparable with that recorded by the glass microelectrode. Because the metal microelectrode is more durable than the glass microelectrode, it can serve as an alternative for APD recording and for restitution analyses.

Action Potentials↗