Architecture of the synovial vasculature in rabbit knee joints studied by scanning electron microscopy.
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Adipose Tissue↗
Biomedical subjects
R H Funk
Publications and source records attributed to R H Funk.
Microendoscopy of the synovial vasculature in the rabbit knee joint.
The functional morphology of the synovial vasculature in the rabbit knee joint was investigated using our technique of microendoscopy, which involves an in vivo microscopy via a 1.9-mm endoscope. In the vessels of the fibrous tissue of the joint capsule it was found that after intraarticular administration of epinephrine the blood flow and the vascular diameters decrease for 3-5 min. In the areolar part of the synovial tissue, an external elevation of the intraarticular pressure causes collapse of the capillaries at 10-15 mm Hg, whereas the collapse pressure of the arterioles is 30-40 mm Hg. Intraarticular application of Neuropeptide Y (NPY) leads to a marked vasoconstriction including the arteriovenous anastomoses, whereas after epinephrine the arteriovenous anastomoses remain patent or dilate during the arteriolar constriction phase. It is concluded that the technique of microendoscopy allows a valuable in vivo investigation of the synovial microvasculature.
Animals↗
Nitrergic innervation and nitrergic cells in arteriovenous anastomoses.
Nitrergic innervation and nitrergic epithelioid cells were studied in arteriovenous anastomoses of the tongue, ear, eye, and glomus organ of the finger in different species (rat, rabbit, dog, and man), by means of immunohistochemistry for nitric oxide synthase and enzyme histochemistry utilizing the catalytic activity of this enzyme (the NADPH-diaphorase reaction). Nitrergic perivascular fibers of the tongue were concentrated along the arterial tree and were maximal at the arteriovenous anastomoses in all species. Generally, fewer fibers were located around comparable segments of the episcleral eye vasculature. Only a few nitrergic fibers were found in the canine and rabbit ear, and in the glomus organ of the human finger; however, epithelioid cells in the tunica media of arteriovenous anastomoses of these organs were NADPH-diaphorase-positive and were moderately immunoreactive for nitric oxide synthase. In the epithelioid cells, the reaction product of the NADPH-diaphorase could also be demonstrated by transmission electron microscopy. The epithelioid cells were negative for the panneural and neuroendocrine marker PGP 9.5 confirming the myocytotic nature of these nitrergic cells. Thus, nitric oxide might play a role in mediating the vessel tone of arteriovenous anastomoses via nitrergic nerves or epithelioid cells.
Amino Acid Oxidoreductases↗
A combination of microendoscopy and spectrophotometry allowing real-time analysis of microcirculatory parameters during in vivo observations.
A combination of microendoscopy (which is a modification of endoscopy with fine rigid endoscopes) and spectrophotometry (which analyses on line the remission spectra from the endoscopic picture) is presented. This setup allows the endoscopic in vivo observation of haemodynamics as well as simultaneous on line determination of intravascular haemoglobin oxygenation. Furthermore, the clearance of intravasally applied tracers can be analysed. Application, results and further evaluation of this new technique are demonstrated in the retinal vessels of the albino rabbit.
Animals↗
Innervation of the ciliary process vasculature and epithelium by nerve fibers containing catecholamines and neuropeptide Y.
The ciliary processes (CPs) in the rat were investigated for the presence of neuropeptide Y (NPY)-like immunoreactivity and for histofluorescence indicating catecholamine (CAM)-ergic innervation in the rat, rabbit and cynomolgus monkey. Special attention was paid to those CP vessel segments which in previous studies showed distinct reactions on application of CAM or NPY, and on the respective sections of the CP epithelium. In the rat and cynomolgus monkey most CAM-ergic nerve fibers concentrated along the terminal arterioles and the epithelium of the anteriormost portion of the major CPs. In comparison, the rabbit displayed most intense CAM-ergic innervation along the terminal arterioles and the epithelium of both the iridial processes and the anterior portion of the major CPs. The NPY-ergic nerve fibers built up a dense subepithelial nervous plexus in the anterior portion of the rat CPs, diminishing towards the posterior CPs. Also, many NPY-ergic fibers were found along the terminal arterioles of the anterior CPs. The findings demonstrate that CAM- and NPY-ergic nerve fibers preferentially supply vasculature and epithelium of the anterior ciliary processes, suggesting a crucial function of these structures for the precise regulation of aqueous humor formation.
Animals↗
Effect of epinephrine on local partial pressure of oxygen in the ciliary processes.
Local pO2 was measured close to the ciliary process of the rabbit eye using polarographic microelectrodes under microendoscopic observation. The experiments were performed in 5 anaesthetized New Zealand rabbits. Changes in local pO2, intraocular pressure (IOP) and blood flow velocity (BFV) were investigated after intra-arterial and topical application of epinephrine. After intra-arterial epinephrine, a simultaneous decrease in BFV, IOP and local pO2 was found. pO2 decrease was more pronounced in the anterior part of the ciliary processes than in the posterior part. Topical epinephrine lead to similar changes of all parameters mentioned above, the time constants being 10-20 times longer. In these topical experiments, no recovery of local pO2 was found over a period of at least 30 min despite an increase in BFV. Our results indicate that in the hyperemic phase after epinephrine the activity of the ciliary epithelium (and probably the total aqueous formation) is higher than normal. Thus, the decrease in IOP in this phase must be due to an increased outflow facility.
Administration, Topical↗
The vessel architecture of the pars plana in the cynomolgus monkey, rat and rabbit eye. A scanning electron microscopic study of plastic corrosion casts.
In the cynomolgus monkey, rabbit and rat the architecture of the pars plana vasculature was investigated using scanning electron micrographs of resin casts. The most complex vessel architecture was found in the cynomolgus monkey. Here, the pars plana venules have affluxes from the ciliary processes, ciliary muscle and iris. Numerous interconnections between these venules exist in the central portion of the pars plana. Arterial affluxes reach the pars plana not until the choriocapillaries. The variations of this architecture in the rat and rabbit are not only caused by the different size of the ciliary muscle and its vascularization. In the rat the most peripheral part of the uveal supply of the retina represents a transition form between pars plana venules and the choriocapillaries. In the rabbit, two vascular layers exist in the pars plana while in the cynomolgus monkey and rat the pars plana vessels spread out in one plane. The functional significance of the vessel architecture and the species differences are discussed.
Animals↗
The effect of epinephrine on ciliary process vasculature and IOP studied by intraocular microendoscopy in the albino rabbit.
The effect of epinephrine on intraocular pressure (IOP) and the hemodynamics of the ciliary process vasculature in albino rabbits was studied by intraocular microendoscopy. Intraarterial application of epinephrine (15, 50, 250 ng/kg bw) lead to an immediate vasoconstriction and a reduction in blood flow velocity (BFV) in the iridial and major ciliary processes lasting from 30 to 120 sec. This anemic phase was followed by a hyperemic phase of about 60 to 240 sec. showing a vasodilation up to 150% of the initial diameters and an increase in BFV. The hyperemic phase can be prevented by pretreatment with indomethacin. Simultaneously measured IOP decreases in the anemic and increases in the hyperemic phase parallel with the changes in vascular diameter. After topical administration of epinephrine (25-50 micrograms/kg bw) a marked vasoconstriction followed by a vasodilatory phase was similarly found. However, the reactive changes of the ciliary process vasculature lasted considerably longer. The anemic phase lasted 15 minutes, the hyperemic phase 40 to 60 min. Again, this hyperemia can be prevented by indomethacin-pretreatment. In the iridial processes the anemic phase persisted till 70 minutes. No hyperemia and no substantial influence of indomethacin-pretreatment was found in this territory. In the anemic phase the IOP decreased in average from 20 mmHg to 15 mmHg. However, in contrast to the reactive changes of the IOP after intraarterial epinephrine application, the IOP did not increase again in the hyperemic phase, but decreased further to about 12 mmHg. After pretreatment with indomethacin the IOP remained at the level of 15 mmHg. The short-term IOP-changes after i.a. application of epinephrine, mirror the vasoconstrictory and vasodilatory reactions in the ciliary processes and might be due to volume changes in the eye (plethysmographic effect). However, the long lasting IOP reduction after topical epinephrine in the hyperemic phase can not be due to vascular reactions in the ciliary processes. There must be other factors responsible for the long lasting pressure reducing effect of epinephrine.
Administration, Topical↗
Microendoscopic observations of the hemodynamics in the rabbit ciliary processes.
The in vivo hemodynamics of the ciliary process vasculature in the albino rabbit were studied with an improved technique of intraocular microendoscopy. The spreading pattern and velocity of the dye front has been observed in defined vessel segments following intracarotid injection of Evans Blue. In the anterior portion of the ciliary processes a "thoroughfare channel" (bypass) was found leading from the arteriolar tree directly into the marginal venule bypassing the capillary network of the ciliary processes. This bypass is characterized by a higher blood flow velocity (1.5-3mm/sec) than was found for the capillary network (0.8-1mm/sec). A stoppage of blood flow was observed in the capillary network at 45-50mmHg after step-wise elevation of intraocular pressure (IOP): blood flow was not stopped in the thoroughfare channel until IOP values of 55-60mmHg were reached. Intraarterial administration of vasoconstrictive agents could lead to a complete stoppage of blood flow in the capillary net whereas the marginal route often remained patent.
Animals↗
Immunoelectron microscopical characterization of the epithelioid type of smooth muscle cells in human glomus organs.
The wall structure of arterio-venous anastomoses in human glomus organs was studied by immunohistochemistry and immunoelectron microscopy. Smooth muscle cells of the epithelioid type I and of the dense type II could be found in the media. The immunohistochemical study confirmed the immunopositivity of both smooth muscle cell types for alpha-smooth muscle actin, vimentin, and smooth muscle myosin. All smooth muscle cells also stained positively for caveolin, a recently described structural protein of microvesicles present in selected epithelial and nonepithelial cells. The immunoreactivity for cathepsin D, however, was much higher in the type I cells than in the type II cells. Immunoelectron microscopy revealed that type I cells contain loose arrays of alpha smooth muscle actin positive microfilaments, sometimes arranged in small bundles, whereas the dense medial smooth muscle cells of the type II have tightly packed actin filaments. Only type I cells contained cathepsin D positive lysosomes. The data suggest that two types of phenotypic variants of vascular smooth muscle cells in the human arterio-venous anastomosis exist: a more "synthetic" type I cell and a more contractile type II cell.
Actins↗
Limitations of erbium:YAG laser photorefractive keratectomy.
PURPOSE: The erbium:YAG laser (lambda = 2.94 microm) has been considered promising as an alternative to the ArF excimer laser in photorefractive keratectomy (PRK). However, corneal application of this mid-infrared solid state laser is still plagued with various disadvantages compared to that of the ArF excimer laser (lambda = 193 nm). We discuss the limitations of PRK with the erbium:YAG laser. METHODS: Measurements of ablation threshold, ablation efficiency, and thermal damage were done to compare the process of erbium:YAG laser photoevaporization to the ArF excimer laser. PRK procedures were performed on fresh enucleated pig corneas to investigate the morphology and surface roughness of the cornea after scanning-spot and fundamental mode photoablation. Surface roughness was measured by using a tactile surface reprofiling system. RESULTS: The ablation threshold and the ablation efficiencies for the erbium:YAG laser are significantly higher compared to the ArF excimer laser. Collateral thermal damage decreases with a reduction of laser pulse duration to a minimum of approximately 5 microm. Scanning electron microscopy and surface roughness measurements of the corneal surface after erbium:YAG laser treatment demonstrated higher surface roughness compared to ArF excimer laser treatments. CONCLUSIONS: The erbium:YAG laser is not at present an alternative to the ArF excimer laser for photorefractive keratectomy.
Animals↗