Inhibition of endotoxin-mediated activation of endothelial cells by a perfluorocarbon emulsion

Endothelial cell (EC) activation plays a key role in the inflammatory response by promoting the margination of leukocytes in inflamed loci. Augmented leukocyte margination to activated EC is mediated by the increased display of leukocyte adhesion molecules on EC surface membranes. The biocompatibility of synthetic oxygen-transport fluids is intimately linked to EC function, since one of the first tissues encountered by such fluids is the vascular endothelium. We investigated the effect of one such agent, a phospholipid-based perfluorocarbon emulsion containing 90% w/v perflurooctyl bromide (perflubron, PFOB) on EC activation. Human umbilical vein EC (HUVEC) were activated by 5 U/ml interleukin-1 (IL-1), 20 U/ml tumor necrosis factor (TNF), or 50 ng/ml E coli endotoxin (LPS) in the presence or absence of up to 20%, w/v perflubron. HUVEC activation was monitored by the extent of up-regulation of expression of intercellular adhesion molecule-1 (ICAM) and endothelial-leukocyte adhesion molecule-1 (ELAM). Exposure of HUVEC to perflubron did not alter the up-regulation of ICAM or ELAM in response to IL-1 or TNF (n = 20). However, at 10% perflubron ICAM up-regulation in response to LPS was inhibited by 95 +/- 6% (n = 9; p less than .05). ELAM expression was similarly affected. The concentration of perflubron required to diminish LPS-induced up-regulation by 50% was 6.0 +/- 0.6% (n = 3). The inhibitory effect of 10% perflubron was overcome by greater than 1 ug/ml LPS (n = 3) and the inhibitory effect was attenuated by adding perflubron to the cultures after LPS.(ABSTRACT TRUNCATED AT 250 WORDS)

Ultrastructure of the ciliary process vasculature in cynomolgus monkeys

The ultrastructure of the ciliary process vasculature in cynomolgus monkeys is described with transmission electron microscopy. Special attention is paid to a special segment of the anterior arterioles (afferent segment) and to the end of the marginal venule (efferent segment)-vascular structures which have been described as haemodynamically important. The major arterial circle of iris (MACI), the exclusive blood supply of the ciliary processes, has only a one- or two-layered medium. A short distance after the anterior arterioles of the ciliary processes have branched off, these arterioles develop a characteristic segment of about 100 microns in length and which possesses a two-layered medium where prominent special myocytes lie on the adventitial side (afferent segment). Nerve endings with dense-core and large vesicles are closely associated to the vessel wall of these afferent segments. On the 'venous' side of the ciliary process vasculature, the very thin wall of the marginal ciliary process vessel becomes reinforced by a layer of myocytes in a segment which is located in the zone where the marginal vessel bends into the layer of the pars plana venules (efferent segment). Here, the endothelium is substantially thickened and filled with different-sized granules. Nerve endings with clear- and large dense-core vesicles lie around this segment.

Spectrometric measurements in the anterior eye vasculature of the albino rabbit--a study with the EMPHO I

Intracapillary haemoglobin oxygenation (oxygen saturation) and haemoglobin concentration (corresponding with blood volume) were measured in different regions of the albino rabbit anterior eye segment using the Erlangen micro-lightguide spectrophotometer (EMPHO I). The tip of the microlightguide (active diameter 210 microns, cover diameter 0.5 mm) was placed in the vitreous by a goniometric mounting and controlled by a micromanipulator. After stepwise elevation of intraocular pressure (IOP) the haemoglobin oxygenation decreased slightly in the iris at an IOP-level of 60 mmHg, whereas in the three regions of the ciliary processes and in the peripheral choroid haemoglobin oxygenation did not decrease until values of 80 mmHg were applied. In contrast, haemoglobin concentration decreases when the IOP increases in all regions except in the pars plana where the haemoglobin concentration increased at 40 and 60 mmHg. The most pronounced reactive hyperaemia was found in the major ciliary processes. Quite passive changes of haemoglobin concentration were seen in the peripheral choroid. Effective regulatory mechanisms must exist which result in IOP-independent (20-60 mmHg) haemoglobin oxygenation, whereas pronounced changes in intracapillary haemoglobin concentration were observed. The decay of both parameters at IOP 80 mmHg is indicative of an exhaustion of their regulatory capacity. Epinephrine topically applied onto the conjunctival sac or injected into the common carotid artery led to a short-term decrease of haemoglobin concentration and, later, a hyperaemic response. A short-term haemoglobin deoxygenation was found especially in the major ciliary processes.

Scanning electron microscopic study on the vasculature of the human anterior eye segment, especially with respect to the ciliary processes

The architecture of the vasculature of the human anterior eye segment was studied by scanning electron microscopy of vascular resin casts. Regarding the major vessels it was found that the perforating branches of the anterior ciliary arteries (ACA) form an anastomozing circle which lies in the posterior portion of the ciliary muscle (intramuscular circle). The ACAs supply the outer and posterior parts of the ciliary muscle, partly the iris, and the peripheral choroid by recurrent ACA branches. The major arterial circle of iris (MACI) which lies more anteriorly is formed mainly by the long posterior ciliary arteries and supplies the inner and anterior portion of the ciliary muscle, the iris and the ciliary processes. The ciliary process vasculature consists of three different vascular territories with discrete arterioles and venules. The first vascular territory which is located at the anterior end of the major processes, is drained posteriorly by venules which pass the ciliary body without greater connections to the venules of the major ciliary processes. The second and third territories comprise the vasculature of the major and minor ciliary processes drained posteriorly by venules which are located at the margin of the ciliary processes. In supravital experiments with human autopsy eyes, a characteristic segment of arterioles supplying the first and second territory was found to be constricted after immersion with epinephrine in a similar way as in cynomolgus monkeys in vivo. Although the general arrangement of the ciliary process vessels is similar to that of the cynomolgus monkey, there are characteristic differences in the size of the territories and in the pattern of the capillary networks. The division of the ciliary process vasculature into three vascular territories may reflect a functional differentiation in the process of aqueous humour production.

SEM studies on age related changes in the surface structures of rat hairs

In albino rats of four age groups (male and female; 1, 6, 12 and 36 months) telogen hairs of the back were investigated in scanning electron microscopy at defined locations. The length of the cuticular 'scales' as well as the thickness of the hair shaft decreased significantly in the 36 month group of both sexes. In addition the scales of this group had irregular contours, cracks and spindle shaped inclusions.

Oxygen delivery to the anterior chamber of the eye--a novel function of the anterior iris surface

By means of pO2-needle electrodes the oxygen tension in the anterior chamber of rabbit and cynomolgus monkey eyes was measured and correlated with the topography. It can be clearly shown that the pO2 in front of the pupil is substantially lower than in front of the anterior iris surface. It is evident that the O2-supply of the anterior chamber is provided by the iris vasculature. This result was confirmed by measurements after partial or total iridectomy. A brief recapitulation of the morphology of the iris showed that the abundance of iris vasculature is well understandable in view of these pO2 measurements.

Long-lasting effects of naltrexone, an opioid receptor antagonist, on cell proliferation in developing rat forebrain

Several studies have demonstrated in the past that endogenous opioid peptides and opioid receptors may be involved as mediators of brain tissue growth and function in the neonate. Applying histological and autoradiographic methods, we have examined the effect of the mu-receptor-specific antagonist, naltrexone, on the proliferation of the 4-12-week-old rat forebrain subependymal layer. We found that naltrexone, when given daily throughout the weaning period, evoked a long-lasting increase of the mitotic rate and the [3H]thymidine labelling index. This effect was most significant about 8-10 weeks after ending the naltrexone treatment. Although a direct influence of naltrexone on long-term subependymal cell proliferation cannot be excluded, we are discussing evidence of an indirect effect via suppression of noradrenergic activity in the forebrain.

Microendoscopy of the anterior segment vasculature in the rabbit eye

Intraocular microendoscopy is introduced as a new method which allows a direct in vivo observation of the microvasculature of the eye. Using video equipment, a quantitative evaluation of changes in vessel diameters, e.g. after administration of vasoactive agents, and an estimation of blood oxygenation are possible. Experimental studies with fluorescent dyes can also be performed using special filters. In albino rabbits, no apparent vascular disturbances were observed under certain experimental conditions. Touching a ciliary process with the tip of the endoscope immediately resulted in a vasodilation and stoppage of blood flow, surprisingly in the affected area only. After epinephrine, the locally traumatized ciliary processes remained unchanged while the vessels of the neighboring ciliary processes constricted intensely. After reduction of the intraocular pressure the major ciliary processes began to swell. A leakage of fluorescein-dextran was only found in the iridial ciliary processes.

Functional morphology of rabbit iridial ciliary processes

Using scanning electron microscopy of vascular resin casts, it was found that the capillary network of the iridial ciliary processes is supplied by arterioles of its own and drained posteriorly by long isolated venules. These venules pass the ciliary body without greater connection to the venules of the major ciliary processes (shunt-system). Transmission electron microscopy showed that in contrast to the pigment epithelium (PE) of the major ciliary processes, the PE of the iridial processes develops elongated finger-like cytoplasmic processes which protrude into the stroma, often in the direction of the vessels, forming a 'basolateral labyrinth', like the kidney tubule epithelium. After paracentesis, an enlargement and leakage of the iridial ciliary process capillaries was found, resulting in resin leakage at various sites; no leakage was found in the vasculature of the major ciliary processes. Electron microscopically, the basolateral labyrinth of the PE appeared enormously enlarged, forming wide protein-containing intercellular spaces. These findings suggest that the function of the iridial ciliary processes in rabbits has a dual nature. Under normal circumstances, the main function of the iridial processes may be fluid reabsorption rather than aqueous humor secretion. In cases of paracentesis, for example, the very sensitive blood aqueous barrier of this area breaks down with resulting protein exudation.

SEM studies of the functional morphology of the ciliary process vasculature in the cynomolgus monkey: reactions after application of epinephrine

In the ciliary processes of the cynomolgus monkey three vascular territories with discrete arterioles and venules were found by means of scanning electron micrographs of vascular resin casts. The first vascular territory, which is located at the anterior end of the major processes, is drained posteriorly by long isolated venules, which pass the ciliary body without greater connections to the venules of the major ciliary processes, whereas the second and third territories comprise the vasculature of the major and minor ciliary processes drained posteriorly by veins which are located at the internal edge of the ciliary processes. With the functional resin casting method it could be demonstrated that 15 min after application of 20 micrograms of epinephrine into the conjunctival sac the terminal arterioles supplying the first vascular territory constricted most intensely, whereas the terminal arterioles related to the middle and posterior vascular territory of the ciliary processes constricted to a lesser extent. Twenty-five minutes after topical application of epinephrine only the posterior vascular territory and the capillaries of the ciliary muscle appeared filled in the resin casts. The vasculature of the anterior territories remained empty because of strong vasoconstriction of the supplying arterioles. The three morphologically different vascular territories with their different sensitivities to epinephrine may reflect a functional differentiation in respect to aqueous humour formation and resorption.

Reactions of efferent venous segments in the ciliary process vasculature of albino rabbits

In albino rabbits, the reactions of a defined venous segment of the ciliary process vasculature to vasoactive agents were studied using our new technique of in vivo microendoscopy and using supravital specimens of the anterior eye. This segment is situated in the pars plana of the ciliary body and is the continuation of the venules at the inner edge of the minor and major ciliary processes which posteriorly drain the blood in the veins of the peripheral choroid. Three- to 4 min after administration of carbachol, a constriction of this efferent venous segment was seen in the in vivo microendoscopy as well as in supravital specimens. The adjacent vessel segments remained relatively unchanged. Two- to 3 min after intra-arterial administration of atriopeptin (ANP), an intense constriction of the efferent venous segment, followed by a reactive hyperaemia, was found by in vivo microendoscopy. The iris veins which collect the blood from the iris and the iridial ciliary processes pass the pars plana without touching the ciliary process vasculature. No reactions to the vasoactive agents tested were observed in these vessels. It has been concluded that the efferent venous segment of the ciliary process may play a role in the regulation of perfusion pressure within the ciliary process capillaries.

Intraocular microendoscopy of the ciliary-process vasculature in albino rabbits: effects of vasoactive agents

The reactions of the ciliary-process microvasculature following administration of various vasoactive substances were studied in the albino rabbit using a new method of intraocular microendoscopy. This technique allows an in vivo observation of arterioles, capillaries and venules of the ciliary body and iris. As long as these tissues are not traumatized, the newly described method of intraocular microendoscopy produces no reactive changes in the vasculature. The video images of microendoscopy were also evaluated quantitatively. Administration of substance P caused a short-term ischemic phase in the ciliary-process vasculature which preceded a long-term hyperaemia. After topical administration of epinephrine as well as intra-arterial administration of epinephrine, phenylephrine and isoproterenol, rapid and intense vasoconstrictory or vasodilatory reactions were seen in the terminal arterioles of the vascular territories in the ciliary processes. The terminal arterioles of the iridial ciliary processes responded faster and more intensely than those of the major ciliary processes. It is concluded that the terminal arterioles play an important role in blood-flow regulation of the ciliary processes and function as special afferent vessel segments which control the circulation within the ciliary-process capillaries.

SEM studies on the functional morphology of the rabbit ciliary process vasculature

Architecture and functional reactions of the blood vessels of the rabbit ciliary processes were studied after administration of epinephrine and isoproterenol. A new corrosion cast technique was applied which allows the analysis of different functional stages in the vascular system by scanning electron microscopy. The ciliary process vasculature is divided into three different vascular territories, each supplied by individual arterioles: (1) the iridial ciliary processes; (2) the anterior (pre-lenticular) portion of the major ciliary processes; and (3) the minor ciliary processes localized post-lenticularly between the major processes. The three vascular territories differ not only in form and architecture of the capillaries but also in their reactions on vasoactive agents. After epinephrine, the earliest reactions were seen in the first vascular territory followed by the second, the third vascular territory being least sensitive. The most intense vasoconstrictory changes were found in the terminal arterioles which supply each vascular territory separately. This afferent vascular segment might therefore be considered to be the most important structure for regulation of blood flow through the ciliary processes.

Studies on the functional morphology of rat ocular vessels with scanning electron microscopy

Tests are still lacking about the suitability of scanning electron microscopy (SEM) of vascular resin casts to show different functional states of peripheral blood vessels. With the aid of a vitalmicroscopic device, we tried to elaborate a vascular casting method using the model of the albino rat iris vasculature. Functional variations of the vasculature were induced by local application of epinephrine to one eye using the untreated fellow eye as a control. It was found that if our modification of Araldite plastic is injected via a systemic access and without preceding rinsing with fixatives or salt solutions there is a good correlation between the vessel diameters seen in SEM of resin casts and the vessel diameters found in the vitalmicroscopic observations. Thus, this method appears also suitable for studying the effect of vasoactive substances.

Intraocular pressure and systemic blood pressure after administration of vasoactive substances in hypertensive and normal rats

Intraocular pressure (IOP) and arterial blood pressure (BP) were recorded manometrically in normotensive Wistar Kyoto rats (NR) and stroke-prone spontaneously hypertensive rats (SHR). IOP was significantly lower in SHR (7.8 +/- 0.2 mm Hg) compared to NR (15.9 +/- 0.4 mm Hg). In NR, administration of vasoactive substances (kallikrein, bradykinin, angiotensin I and II) or bloodletting resulted in significant IOP reactions, which ran nearly parallel to the acute BP changes. In SHR, however, IOP showed little reaction after comparable changes in BP. The cause of the low IOP in SHR is unknown. It is assumed that in SHR rarefaction of arterioles and capillaries and a decrease in the compliance of eye vessels, in combination with an increase in the distensibility of the bulbus at this low IOP level, contribute to the lack of IOP response after administration of vasoactive drugs.

Comparative morphological studies on blood vessels in eyes of normotensive and spontaneously hypertensive rats

The spontaneously hypertensive rats (SHR) show a lower intraocular pressure--despite high arterial blood pressure--than the normotensive Wistar Kyoto rats (NR). In SHR the quantitative evaluation of resin casts and flat-mount preparations of the blood vessels of the ciliary body and choroid showed a significant dilation of the vessels when compared to NR. In the capillaries of the ciliary processes, as well as in the choriocapillaries, a vascular rarefaction was seen. In all regions of the ciliary body the number of fenestrations found in the endothelium of the capillaries was reduced by about half in SHR. In addition, hyalinization of the connective tissue--particularly around the vessels at the base of ciliary processes--was seen in SHR. The morphological changes of the vasculature and connective tissue described here may be considered the cause of the reduced aqueous formation and low intraocular pressure found in SHR.

Possible role of cyclic GMP in stimulus-secretion coupling by salt gland of the duck

Stimulation of salt galnd secretion in domestic ducks in vivo increased the cyclic GMP concentration of the tissue, but had no effect on cyclic AMP levels. Methacholine, which is known to stimulate sodium transport by the glands both in vivo and in vitro, stimulated ouabain-sensitive respiration in salt gland slices. Cyclic GMP stimulated ouabain-sensitive respiration to the same extent as methacholine. Guanylate cyclase stimulators, hydroxylamine and sodium azide, also stimulated ouabain-sensitive respiration. The stimulation of ouabain-sensitive respiration by methacholine was blocked either by atropine or by removal of calcium from the incubation medium. The stimulation of ouabain-sensitive respiration by cyclic GMP still occurred in the absence of calcium. The above observations seem to indicate that cyclic GMP acts as a tertiary link in the process of stimulus-secretion coupling in the tissue.

Endotoxin stimulated nitroblue-tetrazolium (NBT)-test in patients with hypoparathyroidism, pseudohypoparathyroidism and other forms of hypocalcemia

Endotoxin-stimulated NBT-tests were carried out in 15 patients with hypocalcemia of varying etiology and in 14 normocalcemic children free of infection. In the control group the formazan cell percentage (FCP) was 73.8 +/- 1.6% (range 63% to 83%). In 5 patients with hypoparathyroidism or pseudohypoparathyroidism the FCP before treatment was lower than normal. Vitamin D3 therapy produced a rapid increase of serum calcium but normalisation of NBT-test was only achieved after a latent period of one or more months. Patients with hypocalcemic rickets and children with an acute relapse of the nephrotic syndrome also showed abnormal results. The clinical significance of the NBT-test in hypocalcemic conditions is discussed.