Beta-hexosaminidase activities in tears and plasma, diphosphoglycerate in blood of diabetic patients

Molecular mechanisms of lacrimal acinar secretory vesicle exocytosis

The acinar epithelial cells of the lacrimal gland are responsible for the production, packaging and regulated exocytosis of tear proteins into ocular surface fluid. This review summarizes new findings on the mechanisms of exocytosis in these cells. Participating proteins are discussed within the context of different categories of trafficking effectors including targeting and specificity factors (rabs, SNAREs) and transport factors (microtubules, actin filaments and motor proteins). Recent information describing fundamental changes in basic exocytotic mechanisms in the NOD mouse, an animal model of Sjögren's syndrome, is presented.

Recovery of protein from tear fluid stored in cellulose sponges

Human tear fluid collected in glass capillaries was absorbed in cellulose sponges. After various time intervals the recovery was measured for total protein, amylase (AMY), lysozyme (LZM), immunoglobulin A (IgA) and lactoferrin (LF). After one day storage at 4 degrees C of moistened sponges of at least 92% recovery was observed. Storage for longer periods at 4 degrees C up to seven days showed a decreasing recovery for total protein, AMY and IgA. Tear collection with sponges and storage of wet sponges for maximally one day at 4 degrees C followed by centrifugation or storage of the fluid at -20 degrees C are reliable ways of sample treatment.

Serum albumin, serum antiproteases and polymorphonuclear leucocyte neutral collagenolytic protease in the tear fluid of normal healthy persons

Using a micro-electroimmune assay and a 'non-reflex stimulating' method to collect normal tear fluid, the concentration of the serum proteins albumin (S-A), alfa-1-antitrypsin (alpha 1A), alfa-1-antichymotrypsin (alpha 1X) and alfa-2-macroglobulin (alpha 1M) was determined in the tear fluid of 53 normal persons. In addition, the tear fluid was tested for the content of polymorphonuclear leucocyte neutral collagenolytic protease (PML-c-ase). PML-c-ase and alpha 1X could not be detected in any tear samples. The concentrations of S-A, alpha 1A and alpha 1M were constant over time, and showed no variation with sex, age or between the right and left eyes. There was no correlation between the concentration levels of the detected proteins in the tear fluid and correlation between tear fluid levels and corresponding serum concentration levels of the proteins could not be shown.

Plasma and urinary beta-hexosaminidase in juvenile diabetes mellitus

The activity of beta-hexosaminidase (E C 3.2.1.30) in plasma and urine was determined in 99 patients with juvenile diabetes mellitus and in 40 age-matched controls. Plasma enzyme activities were above normal in plasma from diabetics and showed significant correlations with blood glucose and glycosylated HbA1 (GHbA1) but not with the presence of retinopathy. The urinary excretion of beta-hexosaminidase, which is a sensitive indicator of renal injury, was also excessive in the diabetics and showed a significant correlation with blood GHbA1. The results show that plasma and urinary beta-hexosaminidase correlate with parameters of diabetic control and that urinary beta-hexosaminidase may be more sensitive than urinary albumin as an indicator of early renal damage.

N-Acetyl-beta-D-glucosaminidase levels and the onset of diabetic microangiopathy

N-Acetyl-beta-D-glucosaminidase (NAG) levels in serum and urine from diabetics have been measured over a three-year period to assess their potential as indicators of the onset of retinopathy and nephropathy. The presence of retinopathy and nephropathy was confirmed by fluorescein angiography performed at the end of the study and by proteinuria, respectively. Three groups of diabetics were investigated, those on insulin, on oral hypoglycaemics, or on diet only. There was no apparent correlation between total NAG activity in serum with the development of retinopathy, nor were serum isoenzyme variations useful in this context. However, urine total NAG activity demonstrated a striking difference between diabetics of all groups and normals. In particular the B isoenzyme doubled in diabetics. The potential use of this finding in relation to prediction of the onset of microangiopathy is discussed.

Clinical biochemistry of tears

The composition of tear fluid as it exists in the conjunctival fornix and in the precorneal tear film is of a complicated nature. The precorneal tear film is a physically inhomogenous system, produced by the lacrimal glands, the accessory lacrimal glands and the goblet cells of the conjunctiva and the Meibomian glands of the lid margin. The method of collection is crucial for the quantity and concentration of a great number of different compounds that have been demonstrated in tears. A survey is given of the literature concerning tears as they are composed of proteins, enzymes, lipids, metabolites, electrolytes and drugs, the latter secreted during therapy. Clinical applications of the determination of several compounds for diagnosis or for monitoring drug therapy are summarized.

The effect of indomethacin on the anterior segment of the eye after paracentesis

The prostaglandin-inhibiting effect of Indomethacin (IN) was studied in rabbits, using paracentesis as a stimulus and rise in aqueous protein and fluorescein concentration after intravenous fluorescein injection as parameters. In eye pre-treated with IN eyedrops the rise in fluorescein and protein concentration in the secondary aqueous was less than the control eyes; the rise in the control eyes was less than in the eye of rabbits not treated with IN. There was good correlation between the rise in protein and the rise in fluorescein concentration in the secondary aqueous. The four different 0.5% IN suspensions used showed different PG-inhibiting activity, attributed to the difference in physiochemical composition.

Increased serum alpha-L-fucosidase and beta-N-acetylglucosaminidase activities in diabetic, cirrhotic and gastric cancer patients

The activities of several glycosidases (alpha-L-fucosidase, alpha-D-mannosidase, alpha-D-galactosidase, beta-D-galactosidase, beta-N-acetylglucosaminidase and beta-D-glucuronidase) were determined in human sera from 10 normal subjects and in three groups each of 10 patients with diabetes mellitus, hepatic cirrhosis and gastric carcinoma. The results show significantly higher activities in the patients for alpha-L-fucosidase (p less than 0.001) and for beta-N-acetylglucosaminidase (p less than 0.1, p less than 0.001 and p less than 0.05, respectively), and smaller or not significantly greater values for the other glycosidases.

N-Acetyl-beta-D-glucosaminidase levels and diabetic microangiopathy

N-Acetyl-beta-D-glucosaminidase (NAG) activity has been measured in the serum and urine of primary and secondary diabetics and in primary diabetics with microangiopathy. NAG activity has also been measured in the tears of diabetics with ocular complications and diabetics with no ocular changes. Results have shown significantly higher levels of urinary NAG in diabetics with proteinuria (p less than 0.001) and proteinuria and retinopathy (p less than 0.001). There was no correlation between urinary NAG activity and serum creatinine (r = 0.28) or urinary NAG and the degree of proteinuria (r = 0.24). Increased urinary NAG levels were also observed in secondary diabetes associated with haemochromatosis and acromegaly. Significantly higher serum NAG levels were found in newly diagnosed diabetics (p less than 0.01) and significantly lower levels in chemical diabetics (p less than 0.01). Compared to non-diabetic controls tear NAG levels were significantly higher in the diabetic controls (p less than 0.01), in diabetics with retinopathy (p less than 0.01), and in diabetics with cataract formation (p less than 0.05). An assessment of this enzyme is made in relation to the development of diabetic microangiopathy.