Coir fibre toxicity: In vivo and in vitro studies

The biological activity of coir fibre, coir ash and their components were investigated in vitro by measuring the haemolytic activity and macrophage cytotoxicity. In vivo studies carried out by injecting guinea pigs intratracheally with coir fibres resulted in resolving granulomas. The observed haemolytic activity and macrophage cytotoxicity was more marked with coir ash compared with coir fibres. Chemical analysis of coir ash revealed the presence of toxic chemical constituents in appreciable amounts.     

Inhibition of increased permeability of the blood-aqueous barrier by non-steroidal anti-inflammatory compounds as demonstrated by fluorescein angiography.

Inhibitory effects of non-steroidal anti-inflammatory compounds such as indomethacin, indoxole and pirprofen on breakdown of the blood-aqueous barrier by paracentesis and sodium arachidonate were studied, using fluorescein angiographic technique.Sodium arachidonate (1%) administered topically affected the vascular integrity of the iris and, to a lesser extent, of the ciliary processes, whereas the effects of paracentesis were predominantly on the ciliary processes. Indomethacin, indoxole and pirprofen (0·125%) administered topically prevented the breakdown of the blood-aqueous barrier after arachidonate much more effectively than that caused by paracentesis.     

Increased prostaglandin synthetase activity in inflamed tissues of the rabbit eye.

Tissues from normal and inflamed rabbit eyes were examined for prostaglandin synthetase activity using homogenates and microsomal preparation. Ocular inflammation was induced with 10 microgram Shigella endotoxin injected into the vitreous body. Homogenates of iris-ciliary processes of normal and inflamed eyes synthesized 2.3 and 5.6 microgram respectively of prostaglandins per g wet weight of tissues from endogenous substrate. Intact tissues from normal and inflamed eyes produced similar amounts of prostaglandins (2.2 and 5.3 microgram/g wet wt. respectively). Microsomes obtained from inflamed tissues produced 565 ng of prostaglandins per mg of protein per 30 min compared with 190 ng synthetized by normal microsomes. The apparent Km for the substrate of prostaglandin synthetase from inflamed tissues compared with that from normal was found to be lower. It is suggested that prostaglandin synthetase activity in the ocular tissues is modified during Shigella endotoxin-induced inflammation.     

The influence of 12(R)-hydroxyeicosatetraenoic acid on ciliary epithelial sodium, potassium-adenosine triphosphatase activity and intraocular pressure in the rabbit.

Ciliary epithelium was isolated from the rabbit eye and used as a source of plasma membrane material for sodium, potassium-adenosine triphosphatase (Na,K-ATPase) measurements. In the presence of 12(R)-hydroxyeicosatetraenoic acid [12(R)HETE], Na,K-ATPase (ouabain-sensitive ATPase) activity was reduced from 22.5 to 16.3 microM phosphate released/mg protein/hr. Ouabain-insensitive ATPase activity was not altered by 12(R)HETE. No changes in ciliary epithelium ATPase activity were observed in the presence of 12(S)HETE. In parallel studies with conscious rabbits, 12(R)HETE applied topically to the eye was found to lower intraocular pressure (IOP). It is possible that the IOP-lowering effect of 12(R)HETE may be, in part, associated with its ability to suppress the Na,K-ATPase activity of the ciliary epithelium.     

Calibration of the Alcon applanation pneumatonograph and Perkins tonometer for use in rabbits and cats

The Alcon pneumatonograph (PTG) and Perkins tonometer were calibrated for use on rabbits and cats by connecting the eyes of the anaesthetised animal to a pressure manometer and performing tonometry at varying known pressures. The slope of the calibration graph obtained for the PTG was steeper when the stopcock was closed just before tonometry, whereas open and closed stopcock curves were identical using the Perkins tonometer. When using the PTG on rabbits it was found that tonometer readings could exaggerate changes in intraocular pressure unless converted to mmHg using a relevant calibration curve.     

Effect of cadmium and zinc on microbial adherence

A study has been made of the effect of cadmium chloride and zinc acetate on the adherence of Streptococcus faecalis, Escherichia coli and Candida albicans to buccal cells from man. Cadmium led to a significant decrease in the adherence of the three microorganisms tested. Zinc increased the adherence of S. faecalis and E. coli. These alterations in adherence were suppressed by chelating agents. S. faecalis grown in the presence of zinc or cadmium exhibited a decrease in adhesiveness. Pre-incubation of organisms with zinc interfered with the inhibitory effect of cadmium.