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M Simionescu

Publications and source records attributed to M Simionescu.

90 records · Page 5Linked to original sources
PubMed1974

Morphometric data on the endothelium of blood capillaries.

Local differentiations within the endothelium of both muscular (diaphragm, myocardium) and visceral (pancreas, jejunal villi) capillaries have been studied in rats on sectioned and freeze-cleaved preparations. Four distinct parts have been recognized in the endothelial cells of all these vessels on the basis of subcellular components present in each part and on the basis of variations in the local frequency of plasmalemmal vesicles: (a) the parajunctional zone, (b) the peripheral zone, (c) the organelle region, and (d) the nuclear region. Our data indicate that approximately 16, approximately 7.0, and 8.5% of the endothelial cytoplasmic volume (in the peripheral zone) is accounted for by vesicles, their content, and their membranes, respectively. The average density of vesicular openings per microm(2) is 78 in diaphragm, 89 in myocardium, 25 in pancreas, and 10 in jejunal mucosa capillaries. The frequency of fenestrae is 1.7 times as high in jejunal (26/microm(2)) as in pancreatic capillaries (15/microm(2)), the corresponding fractional areas being approximately 9.5 and approximately 6%, respectively, of the endothelial surface. Intercellular spaces occupy a relatively small area ( approximately 0.08 to 0.2%) of the inner endothelial surface.

Animals↗
PubMed1973

Permeability of muscle capillaries to exogenous myoglobin.

Whale skeletal muscle myoglobin (mol wt 17,800; molecular dimensions 25 x 34 x 42 A) was used as a probe molecule for the pore systems of muscle capillaries. Diaphragms of Wistar-Furth rats were fixed in situ at intervals up to 4 h after the intravenous injection of the tracer, and myoglobin was localized in the tissue by a peroxidase reaction. Gel filtration of plasma samples proved that myoglobin molecules remained in circulation in native monomeric form. At 30-35 s postinjection, the tracer marked approximately 75% of the plasmalemmal vesicles on the blood front of the endothelium, 15% of those located inside and none of those on the tissue front. At 45 s, the labeling of vesicles in the inner group reached 60% but remained nil for those on the tissue front. Marked vesicles appeared on the latter past 45 s and their frequency increased to approximately 80% by 60-75 s, concomitantly with the appearance of myoglobin in the pericapillary spaces. Significant regional heterogeneity in initial labeling was found in the different segments of the endothelium (i.e., perinuclear cytoplasm, organelle region, cell periphery, and parajunctional zone). Up to 60 s, the intercellular junctions and spaces of the endothelium were free of myoglobin reaction product; thereafter, the latter was detected in the distal part of the intercellular spaces in concentration generally equal to or lower than that prevailing in the adjacent pericapillary space. The findings indicate that myoglobin molecules cross the endothelium of muscle capillaries primarily via plasmalemmal vesicles. Since a molecule of this size is supposed to exit through both pore systems, our results confirm the earlier conclusion that the plasmalemmal vesicles represent the large pore system; in addition, they suggest that the same structures are, at least in part, the structural equivalent of the small pore system of this type of capillaries.

Animals↗
PubMed1972

Permeability of intestinal capillaries. Pathway followed by dextrans and glycogens.

The pathway followed by macromolecules across the wall of visceral capillaries has been studied by using a set of tracers of graded sizes, ranging in diameter from 100 A (ferritin) to 300 A (glycogen). Polysaccharide particles, i.e. dextran 75 (mol wt approximately 75,000; diam approximately 125 A), dextran 250 (mol wt 250,000; diam approximately 225 A), shellfish glycogen (diam approximately 200 A) and rabbit liver glycogen (diam approximately 300 A), are well tolerated by Wistar-Furth rats and give no vascular reactions ascribable to histamine release. Good definition and high contrast of the tracer particles were obtained in a one-step fixation-in block staining of the tissues by a mixture containing aldehydes, OsO(4) and lead citrate in phosphate or arsenate buffer, pH 7.4, followed by lead staining of sections. The glycogens and dextrans used move out of the plasma through the fenestrae and channels of the endothelium relatively fast (3-7 min) and create in the pericapillary spaces transient (2-5 min) concentration gradients centered on the fenestrated sectors of the capillary walls. The tracers also gained access to the plasmalemmal vesicles, first on the blood front and subsequently on the tissue front of the endothelium. The particles are temporarily retained by the basement membrane. No probe moved through the intercellular junctions. It is concluded that, in visceral capillaries, the fenestrae, channels, and plasmalemmal vesicles, viewed as related parts in a system of dynamic structures, are the structural equivalent of the large pore system.

Animals↗
PubMedDate not supplied

[The effect of a plant mixture on the metabolic equilibrium in patients with type-2 diabetes mellitus].

The present paper analyses the results obtained in 82 patients with diabetes mellitus of the 2nd type: 59 women and 23 men, between 41 and 74 years old (average +/- DS, 58 +/- 9 years), of which 58 had an index of the body weight higher than 26. The diabetes duration ranged between newly discovered and 11 years. Each patient was given, 3 times a day, a 150 ml cup containing an infusion of the following mixture of plants previously cut into small pieces: Phaseolus vulgaris (pod), Morus alba (leaf), and Vaccinum myrtillus (leaves). The approximate dose used was of about 15 g/day. The treatment lasted for two months. Before and after treatment, the following parameters were determined: Hb Al (Bio-Rex method) in 31 cases; the average of 3 consequent glycemias; the value of glycemia and insulinemia recorded after a standard lunch, consisting of about 40 g glucides, 14 g proteins and 6 g lipids (50 g bread, a boiled egg and a boiled apple of 100 g). Analysis of the results obtained enabled the following temporary conclusions (1). In 74 out of the 82 cases studied, the average values of glycemia, after the treatment with plants, were lower than those recorded before the treatment (the average values of the whole lot: 219 +/- 82 mg/dl before treatment and 166 +/- 76 mg/dl after treatment (2). The overall decrease recorded, of 53 mg/dl, represents 24.3% of the initial value (3).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Comparative study of insulin antibodies in diabetic patients with primary insulin-dependence (type I) and secondary insulin-dependence (type II).

Insulin antibodies (% binding) were determined by RIA method in 404 insulin-treated diabetic patients divided into two groups: (A) primary insulin-dependent patients (Type I diabetes): 300 cases, 170 M, 130 F, mean age +/- SD 29.2 +/- 7.5 yrs, disease and insulin treatment duration 7.7 +/- 6 yrs: (B) Type II diabetic patients needing insulin (secondary insulin-dependence): 104 cases, 47 M, 57 F, aged 53.4 +/- 9.2 yrs, duration of diabetes 13.1 +/- 8.3 yrs, and of insulin treatment 3.1 +/- 2.1 yrs. Both groups of patients were with the same types of insulin preparations. In 297 cases, all belonging to group (A), fasting C-peptide was also determined. The titre of insulin antibodies was significantly (p less than 0.001) higher in patients with secondary insulin dependence than in those with primary insulin dependence (22.96 +/- 15.1% vs 10.25 +/- 9.89) in spite of the longer duration of insulin treatment in the later group; the mean C-peptide value found in 58 Type I diabetic patients with a binding capacity less than 10% was significantly lower (p less than 0.001) than that found in 11 Type I diabetic cases with a binding capacity greater than 20% (0.091 +/- 0.57 vs 0.273 +/- 0.37 pmol/ml); no correlation was found between insulin antibodies and metabolic control, insulin requirements or chronic complications.

C-Peptide↗