Glycosylation and secretion of acid phosphatase in Schizosaccharomyces pombe

We have purified secreted acid phosphatase of Schizosaccharomyces pombe. The enzyme is N-glycosylated, the associated carbohydrate accounts for 90% of the total molecular mass and the protein moiety has a molecular mass of 54 kDa. The deglycosylated enzyme still exhibits enzymatic activity. Using antibodies recognizing the protein moiety of the enzyme we have identified two intracellular precursors of acid phosphatase: an unglycosylated membrane-bound 54-kDa form that accumulates in the presence of tunicamycin and a partially glycosylated 72-kDa form that accumulates mostly in membranes of cells grown in rich medium. We further showed that the conversion of the 54-kDa and 72-kDa forms to partially glycosylated and fully glycosylated acid phosphatase is a regulated process. Growth conditions determine how much of translated 54-kDa acid phosphatase is glycosylated to the 72-kDa form and how much remains unglycosylated in membranes. When cells are grown in a rich medium, 5% of the total acid phosphatase protein remains as unglycosylated enzyme and 8% as partially glycosylated 72-kDa form. In cells grown in the minimal medium, however, all of the 54-kDa and 72-kDa forms of acid phosphatase are rapidly processed to fully glycosylated enzyme. The 72-kDa form and the unglycosylated form of acid phosphatase are not secreted or transported to the plasma membrane.

Elastase-type activity, elastase inhibitory capacity, lipids and lipoproteins in the sera of patients with ischemic vascular disease

Elastase-type activity and elastase inhibitory capacity were determined in the sera of 130 atherosclerotic patients, suffering from ischemic vascular disease (IVD) localized at various sites, and of 60 control subjects. The concentrations of serum lipoprotein constituents (triglycerides, total cholesterol, HDL cholesterol, apo-A, apo-B) have also been investigated. HDL cholesterol and apo-A levels were decreased at every site on IVD. Plasma HDL concentration in men was lower than that in women. There was a sex-related difference in the elastase-type activity of the sera: within every atherosclerotic group, elastase-type activity in women was significantly higher than in men. Elastase-type activity did not appear to vary with age and did not show any correlation with the concentration of serum lipoprotein constituents. Pancreatic elastase inhibitory capacity of sera was significantly elevated in the sera of atherosclerotic patients. There was a significant negative correlation between the inhibitory capacity and the HDL cholesterol and apo-A content of sera, respectively. Inhibitory capacity did not show sex-, or age-related variation. There was a significant positive correlation between elastase-type activity and elastase inhibitory capacity measured in control sera. In the sera of atherosclerotic patients this correlation could not be established.

Waste-related cadmium cycle in Switzerland

The anthropogenic contribution to the global cadmium flux exceeds natural sources by a factor of three. The most important pathway is the atmosphere; therefore, high cadmium concentrations can be found even in remote areas. On a local level, the increase in cadmium consumption can be observed in increasing concentrations in the soil, plants, and food. The question arises as to what extent the soil-plant-man-waste-soil cycle can be loaded with cadmium in order to function without negative impact on the environment. In Switzerland, 120 tons (t) of cadmium are consumed per year. Of this amount, 25 t end up in municipal solid waste, 3 t in wastewater, and 19 t in precipitation and dry fallout. As a consequence of today's waste management practice (75% incineration, 20% sanitary landfill, 5% composting; 75% of all sewage is purified), the annual input to the soil is 40 t: 18 t concentrated in landfills, 19 t dissipated via the atmosphere, and 3 t directly spread via sewage sludge, compost, and fertilizer on agricultural land. If even distribution were possible, the cadmium content of the soil would theoretically double in 150 years. The accumulation in the soil will increase the cadmium content of plants grown on such a soil. According to a simple model, the level of 3 ppm cadmium in soils should not be surpassed. At such concentrations, plants are likely to contain greater than 0.4 mg Cd/kg, a concentration which can cause toxic effects in long-term experiments. The safe level in food might be even lower. In reality, cadmium is not evenly distributed over Switzerland. According to today's practice, it must be assumed that in only 14 years the use of compost will have enriched soils to such an extent that its cadmium content will prohibit the production of food for human consumption. For sewage sludge, this timespan is 130 years. If heavy metal limits in food are to be observed, the input of such metals to the soil has to be limited. In a steady state, the cadmium input to the soil should be equal to its output via plants, leachate, and erosion. This implies that today's dissipative use of cadmium must be stopped.

Generalized dermal melanocytosis

A female infant was born with generalized blue-gray discoloration of the skin. Light microscopy demonstrated the diffuse distribution of dihydroxyphenylalanine-positive, dermal melanocytes. Electron microscopy confirmed the identification of the pigment-bearing cells as melanocytes and demonstrated individual melanocytes to be invested with a filamentous extracellular sheath. To our knowledge, comparable, generalized, dermal melanocytosis has not previously been reported in a newborn.

Diffuse neonatal hemangiomatosis. A case with heart failure and thrombocytopenia

An examination of the skin in a nine day old infant revealed multiple cherry-red superficial hemangiomas, which progressively increased in size and number. At the age of three weeks these skin lesions involved the scalp, trunk, extremities, palms, soles, and buccal mucous membranes. In addition, similar lesions of the liver and gastrointestinal tract were found. Steroids and irradiation were tried with limited success. Finally, hepatic artery ligation was successful in eliminating the heart failure.

C-peptide secretion during the remission phase of juvenile diabetes

C-peptide secretion was studied in eight juvenile diabetics during the remission phase of the disease. The release of C-peptide was measured after a (1) normal intravenous glucose tolerance test, (2) a double glucose tolerance test, (3) an arginine infusion, and (4) after an intravenous glucose tolerance test followed by an arginine infusion. Under all conditions the intravenous glucose load had only a minimal effect on the secretion of C-peptide, while arginine alone or after the intravenous glucose tolerance test stimulated the release of the peptide in all patients. Pretreatment with glucose did not augment the effect of arginine on C-peptide release. The results indicate that during the remission phase of juvenile-onset diabetes the endocrine pancreas does not recognize glucose as and appropriate signal for C-peptide release and cannot transform the amplifying effect of glucose into a higher hormonal secretion rate.

Insulin therapy in relation to circulating C-peptide levels

Part 1. Beta-cell secretion was stimulated maximally by an intravenous glibenclamide-glucose load in four groups of 10 adultonset diabetics divided according to their therapy, which was determined by clinical criteria. Under the standardized conditions of this test, the 20 patients requiring insulin had a mean fasting blood glucose (BG) of 255 mg./100 ml. and showed no stimulation of immunoassayable C-peptide (IMCP) by glibenclamide-glucose. In contrast, the mean fasting BG was 160 mg./100 ml., but the IMCP rose in patients who were able to be managed with sulfonylurea tablets. These differences in IMCP proved to be of value for the clinician in predicting the efficacy of diabetes therapy with either insulin or sulfonylurea tablets.

Part 2. Twenty-four-hour profiles of BG and IMCP were per performed in 28 insulin-requiring diabetics (age range: 14 to 74 years) who were 66 to 111 per cent of normal weight and had had diabetes for 0.2 to 31 years. These patients were divided into diabetics with IMCP (n = 14) and without IMCP (n = 14); the mean age and weight were similar in the two groups. The mean IMCP value and its standard deviation correlated inversely with the mean blood glucose (MBG) in all diabetics and healthy subjects. According to clinical criteria, diabetes control was better in the patients with IMCP. Analysis of variance showed that the mean BG concentrations for diabetics with and without IMCP were statistically different (p<0.02). Patients with IMCP were found to inject less insulin daily, and six of them were adequately treated with only one daily injection.

Human C-peptide. Part I: Radioimmunoassay

Synthetic human C-peptide bearing a Tyrosine group at its amino end is labelled with 125iodine using chloramin T or hydrogen peroxide and lactoperoxidase. The results are compared applying both methods. Antiserum to synthetic human C-peptide (without Tyrosine) which was partially compared to rabbit albumin, is raised in guinea pigs and goats. Goats show to be superior to guinea pigs concerning antibody production. The so-called "hook effect" phenomenon is observed in setting up the standard curves for the radioimmunoassay. Monotonically decreasing standard curves are obtained on dilution of antiserum with a high antibody titer which was produced by repeated immunization in goats. Free C-peptide and C-peptide bound to antiserum are separated with the anxion exchange resin Amberlite. Using this separation technique we excluded unspecific binding of labelled C-peptide to protein fractions in serum of diabetics. The sensitivity of our radioimmunoassay is approx. 0.3 ng C-peptide/ml serum. Intra- and interassay variability are below 10%. Human proinsulin is the only substance found to crossreact with the antiserum.

Human C-peptide. Part II: Clinical studies

Human C-peptide is determined by radioimmunoassay. On gel filtration of serum from a healthy subject and from a patient with islet cell carcinoma, C-peptide (MW 3025) appears ahead of insulin (MW 5808) and shows much higher molar concentrations than the hormone. Human proinsulin cross-reacts with our antiserum to synthetic human C-peptide. On direct determination of immunomeasurable C-peptide (IMCP) in fasting serum of 25 healthy subjects we find an average of 1.8 (+/- 0.4) ng/ml, corresponding to 60.4 X 10(-11) Mol/l. The molar concentration is about five-fold as compared to IMI (immuno-measurable insulin). IMCP and IMI patterns are not identical on stimulation of beta-cell secretion in healthy subjects by i.v. glucose or glucose-glibenclamide. This is probably due to differences in peripheral metabolism of both compounds. We conclude from our results that C-peptide determined in peripheral venous serum is a better indicator of beta-cell secretion than is insulin. Among 26 insulin-treated juvenile diabetics 15 show not measurable and 11 subnormal IMCP levels in fasting serum. No rise in IMCP is found 1-2 h following breakfast. Four juvenile patients receiving no insulin in a phase of total diabetes remission have normal or raised fasting IMCP concentrations. Only 2 out of 24 adult diabetics (16 treated with insulin and 8 with tablets) show non-measurable fasting IMCP concentrations, in another 4 patients values are below and in the remaining 18 cases above 1 ng/ml serum. Stimulation of beta-cell secretion through glucose-glibenclamide is more or less impaired in all adult diabetics compared to the healthy subjects.

High-molecular IRI (big, big insulin) in islet cell adenoma

In agreement with data previously reported (Yalow and Berson 1973), after gel filtration of acid-ethanol extracts of islet cell adenomas (performed in 3 M acetic acid) 1.4% to 1.8% of total immunoreactive insulin (IRI) eluted ahead of proinsulin. The high-molecular IRI (HM-IRI) was, however, found to be heterogenous in size and consisted of at least three components, the major one having an estimated molecular weight of about 50,000. Under certain conditions, HM-IRI was partially dissociated into proinsulin- and insulin-like components. We conclude that HM-IRI does not represent a precursor of proinsulin and insulin, but probably a self-association product of the peptides or an association of insulin and proinsulin to other proteins extracted from tumor tissue.