Melatonin-induced glycosaminoglycans augmentation in myocardium remote to infarction.

Elevated levels of collagen as well as transient increases of glycosaminoglycans (GAG) have been shown in the myocardium remote to the infarction. The aim of the study is to observe the effect of melatonin on the accumulation of collagen and GAG in the left ventricle wall, remote to the infarction. A second aim is to determine whether the effect of the pineal indole is mediated by the membrane melatonin receptors of heart fibroblasts. Rats with myocardial infarction induced by ligation of the left coronary artery were treated with melatonin at a dose of 60 µg/100 g b.w. or vehicle (2% ethanol in 0.9% NaCl). The results were compared with an untreated control. In the second part of the study, the fibroblasts from the non-infarcted part of myocardium were isolated and cultured. Melatonin at a range of concentrations from 10(-8) M to 10(-6) M was applied to the fibroblast cultures. In the final part of the study, the influence of luzindole (10(-6) M), the melatonin membrane receptor inhibitor, on melatonin-induced GAG augmentation was investigated. Both collagen and GAG content were measured in the experiment. Melatonin elevated GAG content in the myocardium remote to the infarcted heart. Collagen level was not changed by pineal indoleamine. Fibroblasts isolated from the myocardium varied in shape from fusiform to spindle-shaped. Moreover, the pineal hormone (10(-7)M and 10(-6)M) increased GAG accumulation in the fibroblast culture. Luzindole inhibited melatonin-induced elevation of GAG content at 10(-6)M. Melatonin increased GAG content in the myocardium remote to infarction. This effect was dependent on the direct influence of the pineal indole on the heart fibroblasts. The melatonin-induced GAG elevation is blocked by luzindole, the melatonin membrane receptors inhibitor, indicating a direct effect of this indole.

Pharmacological doses of melatonin reduce the glycosaminoglycan level within the infarcted heart scar.

The aim of the study was to define the effect of pharmacological doses of melatonin, an agent known to be a scavenger of reactive oxygen species, on the extracellular matrix composition (glycosaminoglycans and collagen) in the infarcted heart scar. Rats were administered with melatonin at doses of 300 µg/100 g b.w. or 3 mg/100 g b.w. once daily (between 5:00 and 6:00 in the afternoon) or with 1.5 mg/100 g b.w. twice daily (between 8:00 and 9:00 in the morning and additionally between 5:00 and 6:00 in the afternoon). The levels of collagen, glycosaminoglycans (GAG) and some oxidative stress markers (lipid oxidation, the content of sulphydryl groups in proteins and glutathione) were evaluated. In the second part of the experiment, cells were isolated from the scar, identified as myofibroblasts, cultured and treated with melatonin at concentrations ranging from 10⁻7 M to 10⁻¹° M. The pineal indoleamine was seen to reduce the GAG content of the scar, while the collagen content of the scar remained unchanged. A 10⁻7 M concentration of melatonin caused an increase in the GAG level in the myofibroblast cultures, while lower concentrations (10⁻8 M-10⁻¹° M) of pineal indoleamine were not effective. Melatonin decreased lipid oxidation and increased the sulphydryl groups of total proteins and glutathione, which suggests its antioxidative activity in the applied doses. The present study shows that pharmacological doses of melatonin reduce the GAG level in an infarcted heart scar. Since the mechanism of GAG content reduction cannot be explained by direct action of the pineal indoleamine on myofibroblasts in the myocardial infarction scar, we hypothesise that changes in GAG content could be indirectly induced by melatonin, that is caused by changes in regulatory systems or reduction of the inflammatory reaction in the area of the infarction. In addition, this paper shows that long-term treatment with melatonin of rats affected by myocardial infarction may reduce oxidative stress in the infarction area.

Experimental hypothyroidism increases content of collagen and glycosaminoglycans in the heart.

The connective tissue matrix of the heart remains under regulatory influence of the thyroid hormones. Some conflicting data describe the connective tissue changes in subjects with thyroid gland disorders. The aim of the study was to assess the changes of the connective tissue accumulation in the heart of rats in the state of hypothyroidism and to answer the question whether TSH is involved in mechanism of the observed phenomena. Hypothyroidism in rats was induced by methylotiouracil treatment or by thyreoidectomy. The thyroid hormones [freeT3 (fT3), freeT4 (fT4)] and pituitary TSH were measured in plasma with radioimmunological method. The glycosaminoglycans (GAG) and total collagen were measured in heart muscle of both left and right ventricles. Cells from the rat's heart were isolated and cultured. The cells were identified as myofibroblasts by electron microscopy method. The effects of TSH in concentrations ranging from 0.002 to 20 mIU/ml, on connective tissue accumulation in heart myofibroblasts cultures were tested. The primary hypothyroidism was developed both in groups with thyroidectomy and with methylthiouracil. The levels of fT3 and fT4 both in rats with thyreoidectomy and animals treated with methylthiouracil were decreased and TSH level in these two experimental groups was elevated. In the heart of the rats with experimental hypothyroidism increased content of both GAG and collagen was found. Myofibroblast number in culture was increased by TSH. Regardless of the method of its induction, hypothyroidism increased collagen and GAG contents in the heart. TSH is not involved in regulation of collagen and glycosaminoglycans accumulation in the heart of rats affected with primary hypothyroidism.

[The effect of early decompression on the extent of changes in spinal cord microcirculation in experimental traumatic injury to the cord in rabbits]. / Wplyw wczesnego odbarczenia na dynamike zmian w mikrokrazeniu rdzeniowym w doswiadczalnym, urazowym uszkodzeniu rdzenia kregowego u królika.

The purpose of the study was the assessment of the effect of compression of the spinal cord after traumatic injury on spinal microcirculation disturbances and the evaluation in what degree early decompression of the cord reduces the degree of these changes. The experimental study was carried out on 20 rabbits. The injury to the cord was produced at the Th9-Th10 level with simultaneous compression causing vertebral canal narrowing by 1/3 of its width. The assessment was based on the results of microangiographic qualitative and quantitative studies. The animals were divided into 4 groups depending on the duration of cord compression 2, 4, 6 and 12 hours. In each group microcirculation studies were done 12 hours after decompression. Prolonged compression was found to increase the extent of microcirculation disturbances, which were most pronounced after 6 hours of compression. In the group of 12-hour compression microcirculation improvement was observed near the focal lesion. It is concluded that possibly early decompression up to 6 hours after trauma can reduce the degree of secondary damage caused by ischaemia.

Morphometric studies of the hepatocyte mitochondria and endoplasmic reticulum after acute ethylene glycol poisoning.

The stereology work on the hepatocyte smooth endoplasmic reticulum (SER) and mitochondria was performed in order to bring evidence of changes in the hepatocyte ultrastructure during acute ethylene glycol poisoning. Hepatocytes of Wistar rats were examined 1, 5, and 14 days after acute intoxication. On the ground of measurements made with a computer image analysis system, the following stereological parameters, which characterize the examined organelles, were calculated: volume density of the SER cisterns, surface density of the SER membranes, numerical density of the mitochondria and volume density of mitochondria. It has been stated that on the first day after intoxication proliferation of SER takes place, and this shows active participation of smooth reticulum enzymes in the metabolism of ethylene glycol. The decrease of SER quantity on 5th and 14th day after intoxication may probably be the result of synthesis handicap of structural proteins. The decrease of mitochondria indexes during the 1st day can be the result of considerable sensibility of those organelles to toxic action of ethylene glycol metabolites and metabolite acidosis being the result of intoxication. The progressive increase of mitochondria quantity on the 5th and 14th day shows that gradually the compensatory mechanisms are initiated.

Electron microscopic study of association between coccoid forms of Helicobacter pylori and gastric epithelial cells.

OBJECTIVE: To investigate the relationship between helical and coccoid forms of Helicobacter pylori and gastric epithelial cells. METHODS: Gastric antral and body biopsies were obtained from eight children, aged 10-17 yr, who underwent diagnostic gastroscopy. Specimens were processed for electron microscopy. The location of organisms and ultrastructural features were assessed with a transmission electron microscope. RESULTS: We observed two morphological forms of bacteria in three of eight H. pylori-positive patients. Helical forms were localized only in the proximity to unchanged or variously damaged mucous cells, but coccoid forms were present only above strongly damaged epithelial cells. CONCLUSION: Coccoid forms of H. pylori are closely associated with damaged gastric mucous cells. Possible explanations for this phenomenon are discussed.

Colloidal gold-RNase labeling of RNA in regenerating rat liver hepatocytes.

During the early liver regeneration following partial hepatectomy, distinct changes of the transcriptional activity of hepatocyte nuclei are observed. Changes in the proportion of dense fibrillar component (DFC) and granular component (GC) of nucleoli are related to pre-rRNA synthesis. The RNase-gold ultracytochemical method was applied to localize RNA molecules in thin sections of regenerating rat liver hepatocyte nuclei. The method allowed for the detection of pre-rRNA molecules at the periphery of fibrillar centers (FC). The distribution of colloidal gold-RNase complexes in combination with quantification of labeling density demonstrated the highest transcriptional activity of nucleoli 18 hours following partial hepatectomy.