Synthesis of hyaluronan by normal and wounded rabbit iris.

BACKGROUND: Endogenous hyaluronan has been found in different tissues in the normal and traumatized eye. However, the main source, the biological aspects and the full potential role of hyloronan are still unclear. METHODS: Hyaluronan production was studied both in organ culture and in vivo, using a double-label protocol with [35S]sulfate and [3H]glucosamine. RESULTS: [3H]glucosamine and [35S]sulfate were incorporated into hyaluronan and sulfated glycosaminoglycans in normal and in traumatized iris tissue in organ culture and in vivo. There was low relative hyaluronan synthesis in vivo, only 2% of total incorporated [3H]glucosamine in normal irides. Increased relative incorporation of [3H]glucosamine into hyaluronan was seen after operative trauma to iris tissue both in vivo and in vitro. CONCLUSION: Our findings demonstrate synthesis of hyaluronan by normal and traumatized iris. The iris seems to be the most important source of aqueous hyaluronan.

Endogenous hyaluronan in the normal and traumatized rabbit iris.

PURPOSE: Hyaluronan concentration in the iris tissue after iridectomy was studied in order to establish the influence of trauma on the production of hyaluronan in the anterior chamber of the eye and whether the iris participates in this process or not. METHOD: Hyaluronan was measured with a radiometric assay at different time points after surgery and identified with specific histochemical staining. RESULTS AND CONCLUSIONS: The concentration of hyaluronan in iris tissue peaked two days after surgery, reaching an average of 115.3 (S.E.M.:+/-12.2) microg/g. It then decreased slowly to almost normal values after 3 to 5 weeks. Histochemistry demonstrated the most intense hyaluronan staining in the iris stroma and in iridial processes around the iridectomy two days after the operation. Our findings indicate in situ synthesis of hyaluronan in the iris tissue.

Corticosteroid suppression of trauma-induced hyaluronan in rabbit cornea and aqueous.

BACKGROUND: Corneal and aqueous hyaluronan have recently been shown to react in response to several different types of trauma, including cataract surgery. In order to find ways to influence the reaction, we have evaluated the effect of topical dexamethasone (Isopto-Maxidex, Alcon Universal Ltd, Fort Worth, Tex) or indomethacin (Confortid, Dumex Ltd, Copenhagen, Denmark) on the postoperative hyaluronan concentration in rabbit cornea and aqueous after extracapsular lens extraction. METHODS: The drugs were administered as topical eye drops three times daily. The hyaluronan concentration in rabbit cornea and aqueous after extracapsular lens extraction was measured with a radioligand assay. RESULTS: Dexamethasone treatment (1 mg/mL) significantly suppressed the increase in corneal hyaluronan seen after extracapsular lens extraction, 2 (p < or = 0.0022) and 3 weeks (p < or = 0.0002) after surgery, while indomethacin did not induce any significant difference at 2 weeks. When the dexamethasone concentration was lowered to 0.1 and 0.2 mg/mL, there was still a significant decrease (p < or = 0.009) in hyaluronan concentration, but at lower concentrations of dexamethasone (0.01 and 0.02 mg/mL), no significant decrease was seen. The increase in aqueous hyaluronan concentration seen 2 days after surgery in untreated eyes was significantly lowered by both dexamethasone (p < or = 0.0076) and indomethacin (p < 0.036). CONCLUSIONS: Dexamethasone lowers reactive corneal and aqueous hyaluronan concentration in vivo after extracapsular lens extraction.

Endogenous hyaluronan in corneal disease.

PURPOSE: Hyaluronan (HA) is a disaccharide polymer capable of binding considerable amounts of water. It is present in trace amounts on the cornea endothelium, and it is not normally found in the epithelium or stroma. A specific histochemical stain was used to test for HA in a wide variety of corneal disorders. METHODS. Eighty-six human corneal tissue specimens were examined histochemically for HA. The material consisted of 84 full-thickness corneal buttons, one epithelium scraping, and one pterygium. Cases were analyzed according to the patient's sex, age, diagnosis, and localization of HA staining. RESULTS: The corneal tissue specimens came from 47 women and 39 men, average age 59 years. Fifty-seven percent of the specimens displayed abnormal HA. HA was visualized in Fuch's dystrophy, keratoconus, infections, regrafts, mechanical and chemical trauma, post-excimer ablations, dystrophies, degenerations, pseudophakic bullous keratopathy, congenital opacities, Stevens-Johnson syndrome, and others. Staining was variously seen in the epithelium, stroma, and endothelium, with intensity of staining ranging from trace amounts to extremely heavy. CONCLUSIONS: Endogenous hyaluronan production is seen in virtually the entire spectrum of corneal disorders. The presence of HA was most often associated with dividing, migrating, or fibroblast-like cells and probably represents a nonspecific tissue response to wounding. Its production is biochemically distinct from that of normally present proteoglycans. The abnormal presence of HA may reduce corneal transparency by disrupting the normal spacing between collagen fibrils, creating focal changes in the index of refraction, and altering the normal flow of solutes through the cornea.

Influence of radial keratotomy on endogenous hyaluronan in cornea and aqueous humour.

BACKGROUND: Hyaluronan is known to appear in corneal wound tissue and is probably involved in the healing process. We measured the changes of endogenous hyaluronan in rabbit cornea and aqueous after radial keratotomy. METHODS: Corneal and aqueous hyaluronan concentrations were measured at different time intervals after radial keratotomies. Hyaluronan was extracted from corneal tissue with two methods employing either pronase or NaCl and measured with a radioimmunoassay. Histochemical staining for hyaluronan was done on the operated eyes. RESULTS: Changes in corneal hyaluronan showed a similar time course with either extraction method. Maximal concentration was reached after 7 to 14 days with a return to normal values in 60 days. Aqueous hyaluronan and proteins were not significantly altered after surgery. Histochemical staining of the corneas demonstrated hyaluronan around the incisions along their entire extent. Blood vessels were absent in the wounds. An increase in elongated fibroblast-like cells was seen in the wound area. CONCLUSIONS: Both quantitatively and histochemically, there is a pronounced increase of corneal hyaluronan in avascular, radial keratomy wounds in the rabbit. The findings suggest a role of hyaluronan in corneal wound healing.

Histochemical identification of hyaluronan in the rabbit anterior segment during the healing period after extracapsular lens extraction.

Extracapsular lens extractions were performed in rabbits. The eyes were examined at different time intervals after surgery with a histochemical method visualizing hyaluronan. There was positive staining for hyaluronan in the wound region from 2 to 90 days postoperatively. The staining was most intense and widespread between 7 and 14 days after surgery. A hyaluronan staining in the corneal stroma extended from the wound towards the central cornea 4 to 14 days postoperatively. The iris showed increased staining on the second postoperative day, but much less so at the other times studied. Cells on the posterior lens capsule were surrounded by hyaluronan from the seventh postoperative day throughout the observation time up to 90 days postoperatively. It is concluded that hyaluronan reacts during corneal wound healing.

Evidence of hyaluronic acid and hyaluronic acid binding sites on human corneal endothelium.

A highly specific hyaluronic acid (HA) recognizing protein (HABR) was used to study whether the human corneal endothelium is covered by HA and to quantify the amount. Tritiated high molecular weight HA was used to determine the capacity of the human endothelium to bind exogenous HA. Human corneas were obtained from keratoconus patients having corneal transplantation and from postmortem eyes. The corneas were immersed in a 4% formaldehyde solution containing 1% cetylpyridine chloride for histochemistry, frozen for biochemistry, or used for 3H-HA (Mr 3 x 10(6) binding. For the biochemical determinations, 125I-labeled HABR was used. Tritiated HA was used for the binding experiment. A specific layer of HA covering the endothelial cells of the corneal buttons was demonstrated. The biochemical analysis also revealed the presence of HA. Finally, the human endothelial cells had specific hyaluronic acid binding sites.

"Delayed" sudden infant death syndrome.

Four cases of "delayed" sudden infant death are described in infants, who were found lifeless and were resuscitated, but did not regain consciousness. Circulatory failure occurred 20-48 hours later. In these cases, one could expect an accentuation of such lesions which might have caused the collapse. Among the cases there were bronchopneumonia, areas of coagulative myocardial necrosis without cellular reaction, and gliosis of the cerebral white matter and the brain stem of focal as well as diffuse type. The CNS changes were of hypoxic type and might have been caused at delivery or shortly after delivery. They seem too insignificant to have caused the collapse, but could have been an auxiliary factor. It cannot be determined whether the bronchopneumonia caused the collapse or if it developed as a consequence of the unconsciousness. Interestingly, no other pathological changes of significance were found.

Sudden natural death in later childhood and adolescence.

During a 6-year period 389 children and adolescents aged between 1 and 20 years died violently and 31 died suddenly, naturally, and unexpectedly in an area of southern Sweden. In about half of these 31 cases, death was caused by common infectious diseases--for example broncho-pneumonia, myocarditis, or acute epiglottiditis. In one group death was certainly sudden, but was caused by a known chronic disease--such as epilepsy or bronchial asthma. Three young men died from chronic heart disease, and one died from adrenal failure during or immediately after physical exertion. There were 4 cases of sudden, natural death for which the cause was unknown--that is 0.007 per 1000 live births. This figure is extremely low compared with the incidence of sudden unexplained infant death--that is deaths of infants aged between one week and one year.

Effect of acute and chronic ethanol intake on metastasis formation in rat liver.

The effect of acute ethanol intoxication and prolonged intake of ethanol on metastasis formation in the liver was studied in the rat. The tumour cells used were derived from a pharmacologically induced colon carcinoma (NGW 1) and were injected intraportally. Acute ethanol intoxication at the time of injection was associated with a liver weight of 13.29 +/- 0.89 gm two weeks later, compared to 8.43 +/- 0.51 gm in controls. Daily intake of ethanol for eight weeks resulted in a mild reduction of platelets. The liver weight in two groups was 7.31 +/- 0.50 gm and 12.19 +/- 1.40 gm three weeks after intraportal injection of cancer cells as compared to 9.53 +/- 1.11 gm and 19.63 +/- 1.67 gm in controls. The results indirectly supported the hypothesis that acute ethanol intoxication causes increased platelet activity and confirmed earlier results showing the importance of platelets for metastasis formation.