Distinct pathways for constitutive endocytosis of fully conformed and non-conformed L(d) molecules

PROBLEM: To characterize the constitutive internalization of major histocompatibility complex (MHC) class I molecules, we have studied the expression of completely conformed (full) and unconformed (empty) L(d) molecules on non-polarized murine P815 cells. METHODS OF STUDY: Spontaneous endocytosis of L(d) molecules was induced by cycloheximide, an inhibitor of protein synthesis, and their disappearance from the cell surface was determined by flow cytometry. In order to investigate the mechanism of internalization, a palette of inhibitors of endocytosis and vesicular transport was used. RESULTS: Inhibitors of clathrine endocytosis did not influence the internalization of L(d) molecules. Inhibitors of caveolar endocytosis and inhibitors of endolysosomal degradation prevented down-regulation of empty, but not of full L(d) molecules. CONCLUSIONS: Empty L(d) molecules are internalized mostly by caveolar endocytosis and full L(d) molecules use a different pathway, neither clathrine-mediated nor caveolar. After internalization, full L(d) molecules are probably degraded and empty L(d) molecules recycle between endosomal compartment and the cell surface before they enter into the degradation compartment.     

Pathologic calcification in patients with chronic kidney failure

Pathologic, extraskeletal calcifications are frequently seen in chronic renal failure patients. According to pathogenesis, they can be classified to dystrophic and metastatic, and according to localization to visceral and non-visceral. As to physicochemical composition, two major types have been characterized: hydroxyapatite and amorphous calcium magnesium phosphate. The pathogenesis is not completely understood. Today, there are convincing data showing that calcification is an active, regulated process rather than a passive accumulation of calcium and phosphate. Control of calcium, phosphate and parathormone level, correction of metabolic acidosis and adequate dialysis are important in the prevention and treatment of pathologic calcification.     

Ageing is associated with a decrease in the number of sarcolemmal ATP-sensitive K+ channels in a gender-dependent manner

The opening of sarcolemmal K(ATP) channels is considered to be an important endogenous cardioprotective mechanism. On the other hand, age-dependent changes in the myocardial susceptibility to ischemia and hypoxia have been observed in different species, including humans. Here, we have hypothesized that aging might be associated with the changes in sarcolemmal K(ATP) channels. Therefore, the main objective of the present study was to establish whether aging changes expression of cardiac sarcolemmal ATP-sensitive K+ (K(ATP)) channels. RT-PCR using primers specific for K(ATP) channel subunits, Kir6.2, Kir6.1 and SUR2A subunits was performed using total RNA from guinea-pig ventricular tissue. Whole cell electrophysiology was done on isolated guinea-pig ventricular cardiomyocytes. Western blotting using anti-Kir6.2 and anti-SUR2A antibodies was performed on cardiac membrane fraction. Tissue and cells were harvested from young and old, male and female guinea-pigs. RT-PCR analysis did not reveal significant age-related changes in levels of Kir6.1 or Kir6.2 mRNAs. However, levels of SUR2A were significantly lower in old than in young females. Such age-differences were not observed with cardiac tissue from male animals. In both old and young males, pinacidil (100 microM) induced outward currents. The difference between current density of pinacidil-sensitive component in females, but not males, was statistically significant. Western blotting analysis revealed higher levels of Kir6.2 and SUR2A proteins in cardiac membrane fraction from young than old females. The present study demonstrates that in females, but not males, aging is associated with decrease in number of cardiac K(ATP) channels which is due to decrease in levels of the SUR2A subunit.     

Toxoplasmosis--morphologic diagnosis options for the ever topical disease

It has been estimated that 60 percent of people in Croatia will be infected with Toxoplasma gondii until the age of 40. The infection is most frequently asymptomatic, or presented with an lymphadenitis, acute infection during pregnancy that can cause serious damage to the fetus in 10-30 percent, depending on the gestation phase. After acute infection Toxoplasma gondii resides in the body for life, being controlled by cellular immunity. In case of the immune system compromise, reactivation of the infection and serious inflammatory changes, mostly in the central nervous system, occur. Prenatal infection and serious clinical picture in immunocompromised patients classify toxoplasmosis among ever topical infections, thus all research toward better understanding of its pathogenesis in immunocompetent patients is of utmost importance. The aim of the study was to systematically analyze the morphology and changes in cytologic smears of lymph nodes from patients acutely infected with Toxoplasma gondii, and to morphologically visualize Toxoplasma gondii in the lymph nodes by use of specific monoclonal antibodies. For this purpose, 30 aspirates of lymph nodes of patients who had definite serologic evidence for and clinical picture of acute toxoplasma infection were analyzed by use of classic cytology and immunocytochemistry methods. Results confirmed a recognizable cytologic picture of reactive hyperplasia of follicular center cells and granulomatous inflammation, with a unique finding of Toxoplasma gondii tachyzoite in lymphatic cells.     

Sarcolemmal K(ATP) channels in ageing

This review highlights some recent research addressing sarcolemmal K(ATP) channels in ageing. These channels are abundant in cardiac myocytes where they are essential in coupling the cellular metabolic state with membrane excitability. The opening of sarcolemmal ATP-sensitive K+ (K(ATP)) channels occurs during ischaemia and protect the heart against injury. Age-dependent changes in the myocardial susceptibility to ischemia have been observed in different species, including humans. Recent research has demonstrated that ageing is associated with decrease in numbers of sarcolemmal K(ATP) in hearts from females, but not males. This phenomenon seems to be associated with age-dependent decrease in concentration of circulating estrogens. In the heart, SUR2A, a regulatory subunit of K(ATP) channels, is present in excess over Kir6.2, a pore-forming K(ATP) channel subunit. The consequence of this is that SUR2A is a subunit that controls the number of sarcolemmal K(ATP) channels. Estrogens specifically up-regulate SUR2A and, thereby, control the number of sarcolemmal K(ATP) channels. Age-dependent loss of sarcolemmal K(ATP) channels creates a cardiac phenotype more sensitive to ischaemia, which may explain, at least in part, an ageing-associated decrease of myocardial tolerance to stress that occurs in elderly women.     

Plunging ranula

Saliva extravasation from the sublingual gland causes ductal lesion or obstruction and results in the formation of a ranula. It spreads through or behind the mylohyoid muscle situated on the neck. Most frequently it is located in the submandibular or submental region. The diagnosis of plunging ranula is simple if the signs of ranula are present in the intraoral cavity, whereas in case of a ranula localized on the neck definite diagnosis is made by histologic analysis of the pseudocyst that has been surgically excised in toto. Cases are presented of both types of plunging ranula treated by various surgical approaches. Plunging ranula in the submental region was treated by transoral approach, marsupialization and aspiration of the content, whereas the ranula in the submandibular region was treated by exterior cervical approach. In both cases, sublingual gland was removed. During the 3.5-year follow-up, neither recurrence of the disease in the neck area nor the occurrence of simple ranula in the intraoral region was observed.