WR-2721 inhibits parathyroid adenylate cyclase.

WR-2721 [S-2-(3-aminopropylamino)ethylphosphorothioic acid] is a chemoprotective and radioprotective agent that has been shown to lower serum calcium in dogs and in humans. This is secondary both to impaired release of Ca2+ from bone and diminished secretion of parathyroid hormone (PTH) from parathyroid glands. Because cAMP plays a role in the regulation of PTH secretion and WR-2721 has been shown to lower cAMP levels in radiated mouse spleen, we investigated the effects of WR-2721 on cAMP production in dispersed bovine parathyroid cells. Additionally, we studied the adenylate cyclase in plasma membranes from normal bovine parathyroid glands after exposure to WR-2721. With parathyroid cells incubated at 0.5 mM Ca2+, addition of WR-2721 in concentrations ranging from 0.02 to 2.0 mM resulted in a progressive decrease in intracellular cAMP (42-50%, respectively). In plasma membranes of bovine parathyroid cells a dose-dependent decrease in adenylate cyclase activity was noted. Inhibition of the cyclase was seen over a wide range of Mg2+ concentrations (2.5-40 mM). WR-2721 inhibited both basal and NaF, Gpp(NH)p, forskolin, and pertussin toxin-stimulated adenylate cyclase. These data suggest that WR-2721 inhibits the activity of parathyroid adenylate cyclase.

A quantitative study of the anatomy and distribution of coronary arteries in swine in comparison with other animals and man.

The coronary circulation of swine was studied to establish adequate baseline information for using swine in cardiovascular research. Of 65 hearts from domestic and miniature pigs, 45 were injected with a methacrylate plastic and prepared as coronary artery casts whose branches were described and measured, and 20 were injected with different coloured dyes in the right, left anterior descending, and circumflex coronary arteries so that horizontal sections of the heart showed the distribution of each artery and the source of blood supply to particular areas or structures of the heart. Like man, the swine had a left coronary artery that was larger in diameter and longer than the right coronary artery. The right coronary artery was almost always dominant (78%), supplying the posterior septum and atrioventricular node via the posterior descending coronary artery. Eight (17%) of the hearts possessed a balanced blood supply. Two (5%) hearts had a left dominant supply. The intracoronary artery dye injections showed that 72.4% of the right ventricular mass was supplied by the right coronary artery and 27.6% by the left anterior descending coronary artery. In the left ventricle 49% of the mass was supplied by the left anterior descending coronary artery, 25.5% by the right coronary artery, and 25.5% by the circumflex coronary artery. The left anterior descending coronary artery supplied 58% of the interventricular septal mass, while the posterior descending coronary artery supplied 42%. The distribution of the left anterior descending coronary artery branches to the ventricular wall varied inversely in number and size of its diagonal branches (2-9) with the obtuse marginal branches of the circumflex coronary artery which were occasionally more numerous or extended to the apex. The blood supply to the sinoatrial node was always by a branch of the right coronary artery. This analysis shows that not only the coronary anatomy but also the distribution of blood supply to particular areas or structures of the swine heart are very similar to that of humans.

A cadaver workshop to teach medical procedures.

A seminar and workshop were conducted to train students in the indications, techniques and hazards of common diagnostic and therapeutic procedures in general medicine. Cadavers were utilized to teach the techniques of thoracentesis, pleural biopsy, chest-tube insertion, bone marrow biopsy and aspiration, paracentesis, percutaneous liver biopsy and arthrocentesis. The use of cadavers was realistic and provided standardized instruction to each student. The method gave students an opportunity to become familiar with equipment, techniques, indications and hazards of each procedure prior to actual performance. It is readily adapted to a wide variety of additional procedures.

Penetration of trimethoprim and sulfamethoxazole into cysts in a patient with autosomal-dominant polycystic kidney disease.

This study examines the causes for the therapeutic failure of trimethoprim-sulfamethoxazole in a patient with infected cysts caused by a sensitive strain of Escherichia coli. We determined the concentration of trimethoprim and sulfamethoxazole in eight cysts (four proximal, four distal) following therapeutic nephrectomy in a patient treated eight days with trimethoprim-sulfamethoxazole in appropriate doses. In four proximal cysts, mean trimethoprim level was 16.1 +/- 0.8 micrograms/mL with mean sulfamethoxazole level of 94.7 +/- 13.0 micrograms/mL. In distal cysts, mean trimethoprim level was 227.8 +/- 16.8 micrograms/mL with mean sulfamethoxazole level of 9.7 +/- 3.6 micrograms/mL. Serum peak and trough trimethoprim concentrations were 9.8 micrograms/mL and 5.4 micrograms/mL with peak and trough sulfamethoxazole concentrations of 136.0 micrograms/mL and 65.0 micrograms/mL. Significant WBC counts were present in seven cysts, three proximal and four distal. All three proximal cysts were sterile; in contrast, the four distal cysts grew the same strain of E coli isolated from the blood and urine of this patient. The infection resolved following nephrectomy. We conclude that the failure of trimethoprim-sulfamethoxazole to eradicate the infection was caused by the inability of sulfamethoxazole to enter distal cysts in sufficient concentration for the synergistic effect commonly seen with trimethoprim and sulfamethoxazole in combination. Treatment of cyst infections with trimethoprim-sulfamethoxazole should probably be avoided in instances when the organism is resistant to trimethoprim alone.

Effects of aluminum on bovine parathyroid adenylate cyclase.

It is known that the secretion of PTH is often impaired in association with aluminum (Al3+) accumulation in patients with renal failure. The mechanisms involved remain ill defined. Since adenylate cyclase plays a role in the regulation of PTH secretion, these studies examine the effects of Al3+ on parathyroid adenylate cyclase. In membranes from normal bovine parathyroid glands, basal adenylate cyclase activity, in the presence of 0.2 mM ATP and 20 mM Mg2+, increased by 22% as Al3+ was raised from 0-10 microM. Higher Al3+ concentrations caused a progressive decrease in adenylate cyclase activity, reaching 68% inhibition of control activity at 2 mM Al3+. Since adenylate cyclase activation is influenced by the interaction of multiple sites within the adenylate cyclase complex, the nature of the inhibition by Al3+ was explored by examining the interaction of Al3+ with substrate ATP and with Mg2+, an allosteric activating metal ion. In the presence of 20 mM Mg2+, Al3+ concentrations of 1-2 mM resulted in noncompetitive inhibition with respect to ATP [decrease in maximum velocity (Vmax) from 4176 in the absence of Al3+ to 1106 pmol cAMP/mg protein X 15 min; Michaelis Menten constant (Km) for ATP was unchanged]. In contrast, at fixed ATP (0.2 mM), 0.5 mM resulted in competitive inhibition of adenylate cyclase with respect to Mg2+, whereas at higher Al3+ concentrations the inhibition was noncompetitive. When Mg2+ was replaced by Mn2+ (enzyme activity reflects the activity of the catalytic unit), the inhibitory effect of Al3+ on adenylate cyclase activity was abolished. These data suggest that the inhibition of parathyroid adenylate cyclase by Al3+ occurs at the level of the allosteric metal activating site. These data provide a potential mechanism for the inhibition of PTH secretion by Al3+.

Graves' ophthalmopathy. An unusual course.

A patient with an unusual course of Graves' ophthalmopathy is presented; serial computed tomographic scanning of the orbits was used to follow the course of the eye disease. Right-sided unilateral ophthalmopathy first developed two years after thyroid ablation with radioactive iodine and was followed by complete resolution two years later. The remission of this patient's eye disease was short-lived; within eight months, unilateral ophthalmopathy affected the left eye, and ophthalmopathy recurred in the right eye a few months later. Current hypotheses do not readily explain the course of this patient's ophthalmopathy.

Fibril diameters in the extracellular matrix of the periodontal connective tissues of the rat.

The diameters of collagen fibrils were measured in three varieties of periodontal connective tissue in the rat mandible (incisor periodontal ligament, incisor enamel-related connective tissue and molar periodontal ligament). Despite structural and functional differences between the tissues, a similar range of collagen fibril diameters was seen in each (average 45 nm). Variation between animals and between adjacent fiber bundles in any given tissue was observed. Even within any single fiber bundle, the fibrils had a variety of diameters. Although it has been claimed that collagen fibrils have diameters which are multiples of 8 nm, such a relationship could not be discerned for periodontal collagen fibrils. It was estimated that about 65 per cent of a periodontal collagen fiber bundle or sheet is composed of ground substance. Despite reports of abundant oxytalan fibers in periodontal tissues at the light microscope level, only one fiber having characteristics of oxytalan was observed in this electron microscopic study. Some aspects of the functional significance of the findings are discussed.