Visualization of the intrarenal distribution of capillary blood flow.

This study describes a modified technique to fill the renal vasculature with a silicon rubber (Microfil) compound and obtain morphologic information about the intrarenal distribution of capillary blood flow under a variety of conditions. Kidneys and cremaster muscles of rats were perfused in vivo with Microfil using a perfusion pressure equal to the animal's mean arterial pressure at body temperature. Microfil did not alter arteriolar diameter or the pattern of flow in the microcirculation of the cremaster muscle. The modified protocol reproducibly filled the renal vasculature, including; glomerular, peritubular, and vasa recta capillaries. We compared the filling of the renal circulation in control rats with that seen in animals subjected to maneuvers reported to alter the intrarenal distribution of blood flow. Infusion of angiotensin II, hypotension, volume expansion, and mannitol- or furosemide-induced diuresis redistributed flow between renal cortical and medullary capillaries. The advantage of the current technique is that it provides anatomical information regarding the number, diameter, and branching patterns of capillaries in the postglomerular circulation critical in determining the intrarenal distribution of cortical and medullary blood flow.

Surface changes of nanotopography by carbon ion implantation to enhance the biocompatibility of silicone rubber: an in vitro study of the optimum ion fluence and adsorbed protein.

Lower cellular adhesion and dense fibrous capsule formation around silicone breast implants caused by lower biocompatibility is a serious clinical problem. Preliminary work has shown that ion implantation enhances cell adhesion. Whether the biocompatibility is further enhanced by higher doses of carbon ion implantation and the mechanism by which ion implantation enhances biocompatibility remain unclear. In this study, five doses of carbon ions, which gradually increase, were implanted on the surface of silicone rubber and then the surface characteristics were surveyed. Then, cell adhesion, proliferation and migration were investigated. Furthermore, the vitronectin (VN) protein was used as a model protein to investigate whether the ion implantation affected the adsorbed protein on the surface. The obtained results indicate that enhanced cytocompatibility is dose dependent when the doses of ion implantation are less than 1 × 1016 ions/cm2. However, when the doses of ion implantation are more than 1 × 1016 ions/cm2, enhanced cytocompatibility is not significant. In addition, surface physicochemical changes by ion implantation induced a conformational change of the adsorbed vitronectin protein that enhanced cytocompatibility. Together, these results suggest that the optimum value of carbon ion implantation in silicone rubber to enhance biocompatibility is 1 × 1016 ions/cm2, and ion implantation regulates conformational changes of adsorbed ECM proteins, such as VN, and mediates the expression of intracellular signals that enhance the biocompatibility of silicone rubber. The results herein provide new insights into the surface modification of implant polymer materials to enhance biocompatibility. It has potentially broad applications in the biomedical field.

4'-O-methylhonokiol increases levels of 2-arachidonoyl glycerol in mouse brain via selective inhibition of its COX-2-mediated oxygenation.

BACKGROUND AND PURPOSE: 4'-O-methylhonokiol (MH) is a natural product showing anti-inflammatory, anti-osteoclastogenic, and neuroprotective effects. MH was reported to modulate cannabinoid CB2 receptors as an inverse agonist for cAMP production and an agonist for intracellular [Ca2+]. It was recently shown that MH inhibits cAMP formation via CB2 receptors. In this study, the exact modulation of MH on CB2 receptor activity was elucidated and its endocannabinoid substrate-specific inhibition (SSI) of cyclooxygenase-2 (COX-2) and CNS bioavailability are described for the first time. METHODS: CB2 receptor modulation ([35S]GTPγS, cAMP, and ß-arrestin) by MH was measured in hCB2-transfected CHO-K1 cells and native conditions (HL60 cells and mouse spleen). The COX-2 SSI was investigated in RAW264.7 cells and in Swiss albino mice by targeted metabolomics using LC-MS/MS. RESULTS: MH is a CB2 receptor agonist and a potent COX-2 SSI. It induced partial agonism in both the [35S]GTPγS binding and ß-arrestin recruitment assays while being a full agonist in the cAMP pathway. MH selectively inhibited PGE2 glycerol ester formation (over PGE2) in RAW264.7 cells and significantly increased the levels of 2-AG in mouse brain in a dose-dependent manner (3 to 20 mg kg(-1)) without affecting other metabolites. After 7 h from intraperitoneal (i.p.) injection, MH was quantified in significant amounts in the brain (corresponding to 200 to 300 nM). CONCLUSIONS: LC-MS/MS quantification shows that MH is bioavailable to the brain and under condition of inflammation exerts significant indirect effects on 2-AG levels. The biphenyl scaffold might serve as valuable source of dual CB2 receptor modulators and COX-2 SSIs as demonstrated by additional MH analogs that show similar effects. The combination of CB2 agonism and COX-2 SSI offers a yet unexplored polypharmacology with expected synergistic effects in neuroinflammatory diseases, thus providing a rationale for the diverse neuroprotective effects reported for MH in animal models.

Properties of the lymphatic cerebrospinal fluid transport system in the rat: impact of elevated intracranial pressure.

Previous studies suggested that a major portion of cerebrospinal fluid (CSF) is absorbed by extracranial lymphatics located in the olfactory turbinates. The objective of this study was to determine the impact of elevated intracranial pressure (ICP) on downstream cervical lymphatic pressures in the rat. Pressures were measured in the deep cervical lymph nodes using a servo-null micropressure system. A catheter was placed in a lateral ventricle and fluid was infused from a reservoir at defined ICPs. When Ringer's solution was infused, elevations of ICP from 10 to 50 cm H2O resulted on average in a reduction of diastolic cervical node pressures. In contrast, when a diluted plasma solution (80% plasma in Ringer's) was infused, downstream diastolic lymphatic pressures increased as ICP was elevated to 50 cm H2O. These data are consistent with the view that much of the CSF-derived water that convects into the lymphatics is absorbed into the ethmoidal or nodal blood vessels. This study supports the concept of fluid continuity between the subarachnoid space and extracranial lymphatics and suggests that this loss of CSF-derived water may act as a safety mechanism to reduce the volume load to the downstream lymphatic vessels.

Reassessment of the pathways responsible for cerebrospinal fluid absorption in the neonate.

OBJECTIVE: In neonatal lambs, the quantitative evidence suggests that a significant volume of cranial CSF drainage is associated with transport along olfactory nerves with absorption primarily into extracranial lymphatics in the paranasal region. Arachnoid granulations appear to be poorly developed at this level of development and their function is unknown. In this report, we tested whether a CSF protein tracer ((131)I-human serum albumin) could transport directly into the superior sagittal sinus of newborn lambs. METHODS AND RESULTS: The concentration of the tracer administered into the CSF compartment was measured in the confluence of the intracranial venous sinuses (torcula) and in the peripheral blood (inferior vena cava). Enrichment of the CSF tracer in the cranial venous system was most evident when the CSF-venous sinus pressure gradients approached 20-30 cm H(2)O. CONCLUSION: The data suggests that neonatal CSF can be absorbed directly into the cranial venous system. However, contrary to the classical view, this route may represent an auxiliary system that is recruited to compliment lymphatic transport when intracranial pressures are very high.

Influence of silicone elastomer solubility and diffusivity on the in vitro release of drugs from intravaginal rings.

The in vitro release characteristics of eight low-molecular-weight drugs (clindamycin, 17beta-estradiol, 17beta-estradiol-3-acetate, 17beta-estradiol diacetate, metronidazole, norethisterone, norethisterone acetate and oxybutynin) from silicone matrix-type intravaginal rings of various drug loadings have been evaluated under sink conditions. Through modelling of the release data using the Higuchi equation, and determination of the silicone solubility of the drugs, the apparent silicone elastomer diffusion coefficients of the drugs have been calculated. Furthermore, in an attempt to develop a quantitative model for predicting release rates of new drug substances from these vaginal ring devices, it has been observed that linear relationships exist between the log of the silicone solubility of the drug (mg x ml(-1)) and the reciprocal of its melting point (K(-1)) (y=3.558x-9.620, R=0.77), and also between the log of the diffusion coefficient (cm(2) s(-1)) and the molecular weight of the drug molecule (g x mol(-1)) (y=-0.0068x-4.0738, R=0.95). Given that the silicone solubility and silicone diffusion coefficient are the major parameters influencing the permeation of drugs through silicone elastomers, it is now possible to predict through use of the appropriate mathematical equations both matrix-type and reservoir-type intravaginal ring release rates simply from a knowledge of drug melting temperature and molecular weight.

Water-activated, pH-controlled patch in transdermal administration of timolol. I. Preclinical tests.

Previously, transdermal patches with internal pH-controlled release were described. The aim of this study was to test the suitability of the patch design in transdermal delivery and, further, to select such transdermal patch formulations to a clinical study with timolol. In vitro release of timolol from the patches was determined as well as timolol permeation across the human cadaver skin. The effect of the skin on drug release were evaluated in vitro. In vitro data and pharmacokinetic parameters from the literature were used to construct a pharmacokinetic model for the prediction of in vivo performance of the devices. With water-activated, pH-controlled silicone reservoir devices, both the rate of drug release and the duration of constant release were controlled. The rate of timolol release was decreased when the devices were placed on human cadaver skin, and thus, the skin partly controls the rate and extent of timolol delivery to the systemic circulation in vivo. On the basis of in vitro data and kinetic simulations, devices of 10-cm(2) volume releasing timolol in vitro at the rates of 119 and 10 microgh(-1)cm(-2) were selected for human tests.

Water-activated, pH-controlled patch in transdermal administration of timolol. II. Drug absorption and skin irritation.

The feasibility of the water-activated, pH-controlled silicone reservoir devices for transdermal administration was investigated using timolol maleate as a model drug. Timolol patches were applied to the arm of 12 volunteers for 81 h, two patches per subject. Timolol absorption from patches was compared to that from a peroral timolol tablet formulation (Blocanol((R)) 10 mg). Furthermore, in vivo plasma levels of timolol were compared with those predicted by kinetic simulations. Skin irritation induced by timolol patches was assessed by visual scoring and color reflectance measurements. With water-activated, pH-controlled patches both steady-state concentrations of timolol in plasma and its duration could be controlled. However, a considerable, inter-individual variability in the transdermal absorption of timolol was observed. This is due to the high fractional skin control in timolol delivery. Timolol patches were well tolerated by subjects. Skin irritation induced by the combination of timolol with long-term occlusion was mild, and after removal of the patches, skin changes were practically reversed in 24 h. Simulation model was useful in prediction of timolol levels in plasma after transdermal administration.

Dynamic study of iodized oil in the liver and blood supply to hepatic tumors. An experimental investigation in several animal species.

A better understanding of the biologic behavior of embolic agents in the liver and the blood supply to hepatic tumors is of utmost importance in embolization and chemoembolization. In vivo microscopy, which allows observation of live hepatic circulation, was used in this study along with angiography, vascular cast technique, and light and electron microscopy. Iodized oil injected into the hepatic artery passed through the peribiliary plexus to enter the portal vein, and subsequently traversed the hepatic sinusoids. The time required for clearance of the oil from the liver and recovery of the microcirculation depended largely on the patency of the hepatic artery. Kupffer cells actively captured and phagocytosed iodized oil droplets in hepatic sinusoids. The hepatic tumors were confirmed to have a dual blood supply from the hepatic artery and the portal vein. Embolization of either the hepatic artery or the portal vein alone did not completely stop the blood circulation in the tumors. A reciprocal relationship between the hepatic artery and the portal vein in the blood supply to hepatic tumors was demonstrated dynamically and intrahepatic arterioloportal communications, especially the peribiliary plexus, play an important role in the tumor circulation. The current trans-catheter intraarterial management of hepatic tumors is insufficient in that it deals only with the hepatic arterial blood supply and ignores that from the portal vein. Iodized oil creates the potential for dual embolization of the hepatic tumor through a single hepatic arterial catheterization.

Peribiliary plexa--important pathways for shunting of iodized oil and silicon rubber solution from the hepatic artery to the portal vein. An experimental study in rats.

OBJECTIVES: Iodized oil is commonly used in chemoembolization of hepatic tumors, and silicon rubber solution is used for casting studies of hepatic tumor vasculature. Understanding the distribution patterns of iodized oil and silicon rubber solution is of significance in the refinement of iodized oil techniques and proper interpretation of hepatic tumor vascular studies. In this study, the location for iodized oil and silicon rubber solution shunting from the hepatic artery to the portal vein was identified. METHODS: Iodized oil and silicone rubber solution were injected into the hepatic artery in rats. The porta hepatis and the liver periphery were examined using in vivo microscopy. RESULTS: Iodized oil and silicone rubber solution had identical distribution patterns in the hepatic circulation. Both were shunted in large quantities from the hepatic artery into the portal vein through the peribiliary plexa. Other potential shunting sites did not contribute to the shunting. CONCLUSIONS: Though of different chemical natures, iodized oil and silicon rubber solution share similar distribution patterns in the liver. Hepatic arterioportal shunting of these substances occurs via the peribiliary plexa.

Silicone shedding from artificial urinary sphincter in children.

Silicone is an inert material used in all genitourinary prosthetic devices. Silicone particle shedding has been documented in adults with penile prostheses and artificial urinary sphincters. We searched prospectively for silicone particles in the peri-prosthetic tissue and regional lymph nodes in 6 children who underwent removal or exchange of an artificial urinary sphincter. The peri-prosthetic fibrous capsule was biopsied and examined by light and polarizing microscopy. Regional lymph nodes were biopsied if clinically enlarged and evaluated in a similar manner. Lymph nodes from 2 children without an artificial urinary sphincter served as controls. An artificial urinary sphincter was in place from 3 to 10 years (mean 4.3 years) and none of the sphincters demonstrated infection or erosion. Silicone particles were found in the peri-sphincteric tissue of 3 patients, which induced foreign body giant cell reaction in 2 and eosinophilic infiltrate in 1. Focal histiocytic proliferation around the cuff was seen in another case without silicone migration. There was fibrosis around the sphincter in all cases. No silicone was found in the regional lymph nodes. Silicone shedding was documented in 50% of our patients. X-ray energy dispersive spectroscopy was not performed, raising the possibility that it was under-detected. Long-term effects of silicone in children with an artificial urinary sphincter are unknown and warrant further study.