Endogenous prostaglandin E2 mediates inhibition of rat thick ascending limb Cl reabsorption in chronic hypercalcemia

The hypothesis that endogenous PGE2 mediates defective thick ascending limb (TAL) Cl reabsorption (percent delivered load: FRCl%) in rats with vitamin D-induced chronic hypercalcemia (HC) was tested by measuring FRCl% in loop segments microperfused in vivo in HC and control rats treated acutely with indomethacin (Indo) or its vehicle, and obtaining the corresponding outer medullary [PGE2]. Microperfusion conditions were developed in which FRCl% was exclusively furosemide sensitive. To determine the cellular mechanism, tubules were perfused acutely with forskolin (FSK), cAMP, or the protein kinase C inhibitor staurosporine (SSP). Outer medullary [PGE2] in HC rats was 9 to 10 times greater than control and could be normalized by Indo. FRCl% was 20% lower in HC rats infused with vehicle, and Indo, FSK, and cAMP returned FRCl% to normal despite sustained HC. Indo or FSK had no effect on FRCl% in control rats and Indo did not prevent inhibition of FRCl% by luminal PGE2 (1 microM). Luminal SSP (10(-7), 10(-8) M) in HC did not return FRCl% to control values. We conclude that impaired TAL FRCl% in HC occurs at a pre-cAMP site and is due to endogenous PGE2 and not to HC.     

The relationship of the theophylline concentration in the saliva and the blood serum in patients with a broncho-obstructive syndrome

Theophylline salivary and serum concentrations (Tser and Tsal) were quantified after a single dose administration of theophylline drugs: euphylline (2.4% solution, 10 ml i.v. jet and 0.15 orally), theo-dur, retaphil, theopek, theobilong (0.3 g orally). The drugs were given to patients with broncho-obstructive syndrome. The samples were obtained within 6 and 24 hours upon administration for euphylline and other drugs, respectively. Tser and Tsal were determined at high-performance liquid chromatography. The authors revealed a linear relationship between Tser and Tsal in different time intervals. The percentage factors and formulas of Tser calculation by its Tsal values have been estimated.     

Endovascular stents in congenital heart disease

Acquired or de novo vascular obstructions can adversely affect the outcomes of management algorithms for children with congenital heart lesions. Although surgical repair is frequently feasible, some acquired or congenital obstructions are difficult to address in the operating theater. Presented is the recent experience with endovascular stents to relieve such stenoses, and their impact on patient care.     

Design of inhibitors of glycogen phosphorylase: a study of alpha- and beta-C-glucosides and 1-thio-beta-D-glucose compounds

alpha-D-Glucose is a weak inhibitor of glycogen phosphorylase b (Ki = 1.7 mM) and acts as a physiological regulator of hepatic glycogen metabolism. Glucose binds to phosphorylase at the catalytic site and results in a conformational change that stabilizes the inactive T state of the enzyme, promoting the action of protein phosphatase 1 and stimulating glycogen synthase. It has been suggested that, in the liver, glucose analogues with greater affinity for glycogen phosphorylase may result in a more effective regulatory agent. Several alpha- and beta-anhydroglucoheptonic acid derivatives and 1-deoxy-1-thio-beta-D-glucose analogues have been synthesized and tested in a series of crystallographic and kinetic binding studies with glycogen phosphorylase. The structural results of the bound enzyme-ligand complexes have been analyzed, together with the resulting affinities, in an effort to understand and exploit the molecular interactions that might give rise to a better inhibitor. This work has shown the following: (i) Similar affinities may be obtained through different sets of interactions. Specifically, in the case of the alpha- and beta-glucose-C-amides, similar Ki's (0.37 and 0.44 mM, respectively) are obtained with the alpha-anomer through interactions from the ligand via water molecules to the protein and with the beta-anomer through direct interaction from the ligand to the protein. Thus, hydrogen bonds through water can contribute binding energy similar to that of hydrogen bonds directly to the protein. (ii) Attempts to improve the inhibition by additional groups did not always lead to the expected result. The addition of nonpolar groups to the alpha-carboxamide resulted in a change in conformation of the pyranose ring from a chair to a skew boat and the consequent loss of favorable hydrogen bonds and increase in the Ki. (iii) The addition of polar groups to the alpha-carboxamide led to compounds with the chair conformation, and in the examples studied, it appears that hydration by a water molecule may provide sufficient stabilization to retain the chair conformation. (iv) The best inhibitor was N-methyl-beta-glucose-C-carboxamide (Ki = 0.16 mM), which showed a 46-fold improvement in Ki from the parent beta-D-glucose. The decrease in Ki may be accounted for by a single hydrogen bond from the amide nitrogen to a main-chain carbonyl oxygen, an increase in entropy through displacement of a water molecule, and favorable van der Waals contacts between the methyl substituent and nonpolar protein residues.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cardiovascular system related peptides and hypothalamic neurons

The hypothalamus is known to be an integrative site of cardiovascular, endocrine and autonomic functions. Our previous studies, using extracellular, intracellular and/or whole cell patch-clamp recordings in rat hypothalamic slice preparations, revealed that cardiovascular related peptides such as atrial natriuretic polypeptides (ANP), B-type polypeptides (BNP), endothelin (ET), angiotensin II (AII) and interleukin-1 beta (IL-1 beta) influence the hypothalamic neurons. ANP modulated the firing rates in the supraoptic nucleus (SON). BNP inhibited the SON neurons and these effects were mediated through cGMP and cGMP-dependent protein kinase. ET also inhibited approximately 60% of SON neurons. By using slice patch-clamp techniques, AII inhibited the transient outward potassium current in the SON neurons. IL-1 beta increased the firing rate and depolarized the membrane of the most SON neurons. A new type of transmitter, nitric oxide (NO), identified as an endothelial-derived relaxing factor (EDRF), modulated the glutaminergic inputs of the SON neurons. The results suggest that cardiovascular related peptides and NO modulate the neuronal activity of neurosecretory cells in the SON.