The instilled fluid dynamics and surface chemistry of polymers in the preocular tear film. (17/220)

Using slit lamp fluorophotometry it was demonstrated that the rate of drainage of a vehicle placed in the eye increased with increasing volume and that polymer solutions increased the thickness of the precorneal tear film (PTF). By increasing the viscosity of the delivery vehicle, (e.g., a hydroxypropylmethylcellulose polymer solutions), the PTF retention of fluorescein could be increased. The increased retention was shown to be due to an increase in the tear reservoir volume provided by the more viscous solutions. The PTF retention of fluorescein in a polyvinyl alcohol (PVA) vehicle was not as viscosity dependent, although PVA did seem to produce greater initial PTF fluorescence. This suggested that PVA initially produced a thicker PTF. The PTF retention of fluorescein by five commercial solutions did not have any relation to their wetting properties. The only good correlation with fluorescein retention in the PTF measured, seemed to be the ability of different polymer solutions to stabilize a thick layer of water as measured by the spontaneous spreading of polymer molecules at the air/liquid interface on wet glass surfaces. This model was designed to simulate tear film spreading in vivo. The results suggest that different polymer solutions may produce thicker PTF's than normal by virtue of their ability to drag water with them as they spread over the ocular surface with each blink. Mechanisms by which polymer solutions may increase the thickness of the PTF are discussed.  (+info)

The effect of tear substitutes on tear film break-up time. (18/220)

Twelve commercial artificial tear solutions and a newly developed one were evaluated as to their effect on tear film breakup time (BUT) in ten normal subjects. Instillation of one drop of these solutions altered the BUT in such a way that serial BUT measurements could be used as an index of retention time. Results demonstrated significantly longer retention time for three related products (Adapt, Adapette, and Adsorbotear) and a newly developed product (Alcon 0413) [Tears Naturale (Alcon TM)]. This method appears to be an accurate nonirritative way of assessing retention time of tear substitute/vehicles and demonstrate values much longer than previously reported by other methods.  (+info)

Effects of culture system and protein supplementation on mRNA expression in pre-implantation bovine embryos. (19/220)

Assisted reproduction technologies have made great progress during the last 15 years in most mammalian species, including humans. Growing evidence indicates that bovine pre-implantation development is a superior model for investigating early human development than the mouse. The purpose of this study was to investigate the effects of two basic culture systems [tissue culture medium (TCM) with 5% CO(2) in air or synthetic oviduct fluid (SOF) with 7% O(2), 88% N(2,) 5% CO(2)] and various protein supplements (serum, bovine serum albumin or polyvinyl alcohol) on the relative abundance of a set of developmentally important gene transcripts in bovine morulae and blastocysts and to compare the results with those for their in-vivo-derived counterparts. The basic culture system including the basic medium composition and oxygen tension had profound effects on the amounts of specific transcripts in bovine embryos, whereas the 'protein source' had only weak effects. Significant differences (P < or = 0.05) in the relative abundance of specific gene transcripts were detected between in-vivo and in-vitro-derived embryos, especially at the morula stage. More differences were found between embryos produced in the TCM system and in-vivo-derived embryos than between SOF-generated embryos and their in-vivo counterparts. No differences were found in the relative abundance of gene transcripts in embryos generated under chemically defined conditions in the two different laboratories. It is concluded that the SOF system provides an environment in which pre-implantation development of bovine embryos is more similar to that occurring in vivo than in the TCM system.  (+info)

Spinal metastases from renal cell carcinoma: effect of preoperative particle embolization on intraoperative blood loss. (20/220)

BACKGROUND AND PURPOSE: Surgical repair of spinal metastases from renal origin is often complicated by excessive bleeding. The purpose of this study was to assess the effect of preoperative particulate embolization on intraoperative blood loss. METHODS: Twenty spinal metastases from renal origin (17 patients) treated by preoperative embolization with polyvinyl alcohol particles were analyzed retrospectively. Surgical decompression was performed within 2 days after embolization. A control group of 10 patients with 11 spinal metastases of renal origin underwent surgery without embolization. The effect of preoperative embolization, of completeness of embolization, and of particle size on the estimated intraoperative blood loss was analyzed using nonparametric statistical tests. RESULTS: Complete embolization was achieved in 10 cases and partial embolization in the other 10. The estimated blood loss of 19 embolized and 11 control cases was available from the surgical report. Median intraoperative blood loss in 19 embolized lesions was 1500 mL (range, 300-8000 mL), compared with 5000 mL (range, 1440-15000 mL) in the control group. Even after partial embolization, blood loss (median, 2000 mL) was significantly lower than in the control group. No significant differences in estimated blood loss were noted between the use of particles smaller than 250 microm and those larger than 250 microm. No embolization-related permanent neurologic deficit or skin or muscle necrosis occurred. CONCLUSION: Preoperative embolization of spinal metastases of renal origin with polyvinyl alcohol particles is safe and might reduce intraoperative blood loss significantly. Even partial embolization seems to be effective.  (+info)

Man-made respirable-sized organic fibers: what do we know about their toxicological profiles? (21/220)

Man-made organic fibers (MMOFs) have been manufactured for over 50 years. Until recently, there have been few concerns raised regarding the safety of organic fiber dusts. This is due, in large part, to the perception that the dimensions of most, if not all, of these products were too large to be inhaled into the distal lungs of workers, i.e., were considered to be nonrespirable. A brief review of some of the issues related to organic fiber toxicology is presented herein. Some of the organic fiber-types used in commerce are identified and some fundamental tenets of fiber toxicology are discussed. In addition, the European Union, in their recent consideration for banning chrysotile asbestos fibers, evaluated some organic fiber substitutes and compared them to the hazards of asbestos. A brief review of their conclusions is described below. Finally, the results of some recent studies assessing the mechanisms of biodegradability of para-aramid respirable-sized, fiber-shaped particulates (RFP) are presented. Para-aramid (p-aramid) RFP are the most extensively-studied respirable organic fiber-type and RFP is the new term which describes respirable-sized organic fibers (ECETOC, 1996) (1). The results of these studies provide clues regarding the mechanism(s) of p-aramid RFP shortening in the lungs of exposed animals, and may be relevant for humans.  (+info)

Influence of vitamin A on wound healing in rats with femoral fracture. (22/220)

Groups of healthy wounded rats with and without comminuted femoral fractures, and maintained on nutritionally complete commercial rat chow with and without supplemental vitamin A, were studied. The test wounds were standard dorsal skin incisions and s.c. polyvinyl alcohol sponge implants. In some experiments the rats were pair-fed; the rats with femoral fracture not receiving supplemental vitamin A were the lead group for determining food allowanced. In other experiments, the rats were allowed food ad libitum. We found that wound healing of rats with femoral fracture was increased when supplemental vitamin A was given, but the supplemental vitamin A did not completely obviate the adverse effects of fracture. The ratio of the breaking strengths of the skin incisions after formalin fixation to the breaking strengths of the incisions in the fresh state was higher in the unsupplemented rats, supporting the results of our earlier experiments that vitamin A increases the rate of collagen cross-linking.  (+info)

Lipid and fatty acid analysis of fresh and frozen-thawed immature and in vitro matured bovine oocytes. (23/220)

The lipid content and fatty acid composition of fresh immature and in vitro matured bovine oocytes cultured in media with or without serum, and also those of frozen-thawed immature oocytes were analysed. All oocytes were ranked (A or B) on the basis of their cytoplasmic quality. Fatty acid composition (mol %; w/w) in the total lipid fraction was analysed by gas chromatography. Triglyceride, total cholesterol, phospholipid (phosphocholine-containing phospholipid) and non-esterified fatty acid contents of immature and in vitro matured oocytes were determined using lipid analysis kits. Phosphocholine-containing phospholipid and non-esterified fatty acid contents were determined in frozen-thawed immature bovine oocytes. Palmitic acid was the most abundant fatty acid in immature oocytes (A: 35%, B: 36%), and in in vitro matured oocytes cultured in the medium containing serum (A: 36%, B: 35%) or polyvinyl alcohol (A: 33%, B: 36%). Oleic acid was the second most abundant fatty acid in all A ranked oocytes, whereas stearic acid was the second most abundant fatty acid in all B ranked oocytes. There were significant differences (P < 0.05) in linoleic and arachidonic acid fractions between A and B ranked immature oocytes. In vitro matured oocytes had significantly (P < 0.05) lower proportions of linoleic and arachidonic acids, and significantly (P < 0.01) lower contents of triglyceride and total cholesterol compared with those of immature oocytes. The fatty acid composition of in vitro matured oocytes cultured in medium containing fetal calf serum or polyvinyl alcohol was similar, but significant differences (P < 0.01) in triglyceride and the total cholesterol content were observed. There was a significant decrease (P < 0.05) in the arachidonic acid proportion in frozen-thawed immature oocytes compared with that in fresh immature oocytes. In addition, significant (P < 0.05) decreases in both phospholipid (15.8--10.6 pmol) and non-esterified fatty acid (11.0--4.1 pmol) were found in frozen--thawed immature oocytes. The results indicate that lipids are available for use as an energy source for maturation and that serum lipids are incorporated into the oocyte cytoplasm during in vitro maturation. The changes in the lipid content (mainly phospholipid) and fatty acid composition were also observed in frozen--thawed immature oocytes. The study indicates that the alteration of fatty acid composition in bovine oocytes might improve maturation and cryopreservation.  (+info)

Passive targeting of doxorubicin with polymer coated liposomes in tumor bearing rats. (24/220)

The purpose of this study was to reveal the effectiveness of the polymer coated liposomes as a carrier of the anticancer drug doxorubicin in intravenous administration. The size controlled doxorubicin-loaded liposomes (egg phosphatidylcholine : cholesterol = 1:1 in molar ratio) were coated with hydrophilic polymers (polyvinyl alcohol; PVA and hydroxypropylmethylcellulose; HPMC) having a hydrophobic moiety in the molecules (PVA-R, HPMC-R). The existence of a thick polymer layer on the surface of the polymer coated liposomes was confirmed by measuring the change in particle size and the amount of polymer on the liposomal surface. The polymer coating effects on the tumor accumulation of the drug encapsulated in the liposomes were evaluated in Walker rat carcinoma 256 cell bearing rats. The doxorubicin-loaded liposomes coated with PVA-R and HPMC-R showed higher drug accumulation into the tumor site by prolonging the systemic circulation in tumor-bearing rats. The targeting efficiency of the polymer coated liposomes calculated with the total and tumorous clearance of the drug was ca. 5 times larger than that of non-coated liposomes. We ascertained that polymers having a hydrophobic moiety in the molecule such as PVA-R and HPMC-R are suitable materials for modifying the surfaces of the doxorubicin-loaded liposome to improve its targeting properties.  (+info)