Sven Österlin

Posterior vitreous detachment

Sixty-one postmortem eyes were examined with clinical methods (slit lamp) and later sectioned for measurement of the liquid and gel vitreous. The amount of liquid vitreous was found to be progressively greater with increasing posterior vitreous detachment (PVD), and it was concluded that slit-lamp examination is a reliable method of evaluating the rheological state of the vitreous in the living eye. The total content of sodium hyaluronate (NaHA) in the vitreous was measured. Eyes proven to have no PVD had a higher concentration of NaHA than eyes with total PVD. Also, females had a lower concentration than males. There was no significant difference in NaHA concentration between the gel and liquid vitreous. The role played by different structural elements for the stability of the vitreous gel is discussed.

The synthesis of hyaluronic acid in vitreous: I. Soluble and particulate transferases in hyalocytes

The cortical tissue layer of the vitreous, which is contiguous to the retina and ciliary body, contains a uniform population of cells called hyalocytes. Homogenates of hyalocytes isolated from the posterior vitreous were separated into soluble and particulate fractions by ultra-centrifugation, and both fractions were found to contain nucleotide sugar transferase activity. The soluble hyalocyte extract contains endogenous hyaluronic acid, which acts as acceptor of radioactivity from UDP-[ 14 ]C]GlcUA and UDP-[ 14 C]GlcNAc. When endogenous hyaluronic acid is removed and no exogenous acceptor added, the soluble enzyme is able to synthesize oligosaccharide from the added nucleotide sugars, both of which are required for optimal incorporation of radioactivity. The particulate transferase is also able to catalyze the incorporation of radioactivity from UDP-[ 14 C]GlcUA into chromatographically immobile material. Although the soluble transferase showed the same activity whether synthesizing new oligosaccharide or transferring sugar residues to polymeric hyaluronic acid, the particulate transferase evidenced a greater capacity for oligosaccharide synthesis than for catalyzing transfer to polymer.

Autonomic neuropathy in non‐insulin dependent (type II) diabetes mellitus. Possible influence of obesity

Abstract. To assess the prevalence of autonomic neuropathy (AN) in non‐insulin dependent diabetes mellitus (NIDDM) and its relationships with other diabetic complications, duration of diabetes, and obesity, we evaluated 51 NIDDM patients (age 41–59 years, mean 49 years, duration of diabetes 0–15 years, mean 6.9 years). AN tests included a deep breathing test (E/I ratio) and an orthostatic tilt table test (acceleration and brake indices). AN was prevalent: almost half of the patients showed signs of AN (25 of 51, 49%) and the most frequent disturbance was an impaired E/I ratio (18 of 25; 72%). There were no obvious correlations between AN indices and the duration of diabetes, symptoms of AN, peripheral neuropathy or retinopathy. However, an influence of obesity on AN was suggested. Patients with AN showed a significantly higher BMI than patients without AN (31.0±0.9 vs. 27.5±0.8; P<0.01).

Glucose concentration in the vitreous of nondiabetic and diabetic human eyes

Glycation (nonenzymatic glucosylation) of collagen may play a role in the primary pathology of the vitreous in diabetes. The extent of glycation is determined by the glucose concentration in the tissue. In this study glucose concentration was assayed in blood and vitreous samples obtained from three patient groups undergoing vitrectomy: nondiabetic patients (ND), diabetic patients with insulin-dependent diabetes mellitus (IDDM) and diabetic patients with non-insulin-dependent diabetes mellitus (NIDDM). In the ND group the glucose concentration in the vitreous (3.5 +- 1.8 mM/1) was always lower than in the blood (9.1 +- 3.5 mM/1). In the diabetic groups the vitreous glucose concentration was, with a few exceptions, generally lower than the blood glucose concentration. The vitreous glucose concentration in these groups was generally higher (IDDM 9.4+-3.3 mM/1, NIDDM 7.2+-3.9 mM/1) than in the ND group, and in 15 specimens exceeded 11 mM/1, a level increasing the probability of collagen glycation in the vitreous of diabetic patients.

Macromolecular composition of the vitreous in the aphakic owl monkey eye

Abstract The concentration of different macromolecular components of the owl monkey vitreous was investigated after surgical procedures equivalent to intracapsular and extracapsular cataract extraction. Following intracapsular extraction the concentration of hyaluronic acid decreased markedly during the early postoperative period, whereas in eyes subjected to extracapsular extraction, hyaluronic acid concentration was virtually unchanged. The molecular parameters of hyaluronic acid might change as reflected on the gel chromatographic profile. Both surgical methods were accompanied by increased concentrations of protein in the vitreous.

Hydrodynamic Events in the Vitreous Space Accompanying Eye Movements

The powers elicited in the vitreous body by eye movements have hardly been subjected to examinations, and the same goes for currents in the vitreous. Model experiments have demonstrated that intra-ocular currents are not elicited by translatory, but so much more by rotatory movements. Furthermore, it is demonstrated that a thin perforated membrane fitted on the inside of the wall of a glass cylinder filled with water, will detach, with rotatory movements. Even minimal rotational movements cause a flow through the hole. It is discussed whether these findings apply to the eye in vivo.

The synthesis of hyaluronic acid in vitreous *: III. In vivo metabolism in the owl monkey

The incorporation of [1- 14 C]glucosamine into the hyaluronic acid of the owl monkey vitreous was studied. The precursor administered intramuscularly appeared in the vitreous within 2 hr and was incorporated into non-dialyzable hyaluronic acid molecules within 24 hr. The incorporation took place exclusively in the hexosamine moiety of the hyaluronic acid. The labeled hyaluronic acid did not show significant turnover during the 72-day experimental period. The specific activity of the hyaluronic acid during the first few days was highest in those parts of the vitreous that are contiguous to the retina and the ciliary body, indicating that the vitreous cells are involved in the synthetic process.

The synthesis of hyaluronic acid in vitreous *: II. The presence of soluble transferase and nucleotide sugar in the acellular vitreous gel

The acellular portion of bovine vitreous has been found to contain a transferase that catalyzes the incorporation of radioactivity from UDP-[ 14 C]GlcUA into endogenous hyaluronic acid and oligosaccharide. The transferase was prepared by ammonium sulfate precipitation of protein from the vitreous gel. The gel preparations were isolated by two methods that would preclude contamination of the gel by enzymes resulting from broken cells. A nucleotide pyrophosphatase activity also was identified. Injection of [1- 14 C]glucosamine into the anterior chamber of calf eyes led to the isolation of labeled UDP- N -acetylhexosamine from the acellular central vitreous. Analysis indicated the radioactive hexosamine to be glucosamine rather than galactosamine. The large excess of unlabeled glucosamine found, over and above that added as chromatographic standard, indicates that UDP- N -acetylglucosamine is endogenous to the vitreous gel. In contrast, no galactosamine over and above the amount added as standard was found. Oligosaccharides labeled in the glucosamine and glucuronoic moieties were isolated from the central vitreous 1 hr and 25 min after injection of [ 14 C]glucose and [ 14 C]glucosamine into the anterior chamber of the eye. Radioactive polysaccharide was not found in this preparation. The experimental results may be interpreted to indicate the initiation of hyaluronic acid synthesis by the intracellular production of low molecular weight material, followed by the continuation of this process in the extracellular matrix.

Retinal vessels in the ora region. Possible role in the vitreo-retinal pathology in aphakia.

During intracapsular lens extraction the extreme retinal periphery is subjected to zonula‐mediated traction and possible damage to the retinal vessels. The vascular pattern at the ora serrata was studied with special reference to the frequency and distribution of vessels positioned adjacent to the ora structures. The possible role of leakage from such vessels in vitreo‐retinal pathology of the aphakic eye is discussed.

Pilocarpine-induced lysosomal enzyme secretion, from bovine trabecular meshwork cells

It has long been held that pilocarpine-induced ciliary muscle contraction causes a mechanical change in the configuration of the trabecular meshwork, thereby increasing its fluid conductance. Though the results of many studies are consistent with this theory, other findings suggest a direct action of pilocarpine on the meshwork. We used cultured bovine trabecular meshwork (BTM) cells to study the cell biological effects of pilocarpine, chemically a weak base, and demonstrated increased vacuolization of the BTM cells after incubation with pilocarpine, reflecting a trapping of the protonated base inside the lysosomes. We also showed that pilocarpine enhanced the release of lysosomal hydrolases into the medium. We hypothesize that this is clinically relevant and that the pilocarpine-induced release of hydrolases modifies the extracellular matrix of the trabecular meshwork, thereby increasing its fluid conductance.