Phorbol ester does not mimic,but antagonizes the alpha-adrenoceptor-mediated positive inotropic effect in the rabbit papillary muscle

Summary The phorbol ester 12-O-tetradecanoyl phorbol-13-acetate (TPA) was used to examine the hypothesis that phosphoinositide turnover is involved in the regulation of myocardial contractility mediated by stimulation of alpha-adrenoceptors in the mammalian cardiac muscle. Exposure of the isolated rabbit papillary muscle electrically driven at a rate of 1 Hz at a temperature of 37°C to TPA in concentrations of 10–1000 nmol/l for 30 min did not affect the basal force of contraction. The concentration-response curve for the positive inotropic effect of (–)-phenylephrine mediated by stimulation of alpha-adrenoceptors in the presence of (±)-bupranolol (100 nmol/1) was shifted to the right and downward by TPA in concentrations of 30–1000 nmol/l, while the effect of (–)-phenylephrine mediated by stimulation of beta-adrenoceptors in the presence of prazosin (100 nmol/l) was not decreased, but slightly enhanced by exposure of the muscle to relatively low concentrations of TPA (10–100 nmol/l). Incubation of the membrane fraction isolated from the rabbit ventricular muscle with TPA in vitro under the same condition as employed in the physiological experiments decreased the specific binding of [³H]prazosin but not that of [³H]CGP-12177, while the non-tumor promoting phorbol ester, PDD, was ineffective. These results indicate that activation of protein kinase C by TPA does not mimic the positive inotropic effect of catecholamines mediated by activation of myocardial alpha-adrenoceptors. on the other hand, the specific interaction of alpha-adrenoceptor-mediated processes with TPA in the rabbit papillary muscle is in line with the view that the facilitation of phosphoinositide turnover and subsequent activation of protein kinase C may play a certain role in the coupling of alpha-adrenoceptor occupation by agonists to the process leading to the positive inotropic action. Send offprint requests to M. Endoh     

Preponderance of β- over α-adrenoceptors in mediating the positive inotropic effect of phenylephrine in the ferret ventricular myocardium

Summary [³H]prazosin bound to the membrane fraction derived from the ferret ventricular muscle with high affinity in a saturable manner (K _d = 0.25 nmol/l and B _max = 27 fmol/mg protein in the right ventricle). [³H]CGP-12177, a -adrenoceptor ligand, bound to the membrane fraction with a _{K d} value of 0.29 nmol/l and a B _max of 42 fmol/mg protein. In the isolated ferret papillary muscle driven at 1 Hz at 37°C, phenylephrine elicited a concentration-dependent positive intropic effect. The maximal effect of phenylephrine was comparable to that of isoprenaline. Prazosin (0.3 ol/l) shifted the concentration-response curve for phenylephrine slightly but significantly to the right, the maximal response being unaffected. In contrast, bupranolol (0.3 gmol/l) shifted the curve for phenylephrine markedly downwards: the maximal response was depressed significantly to 40% and the curve became less steep. In the presence of prazosin and bupranolol the curve was shifted to the right, being essentially parallel to the control curve. These results indicate that in the ferret ventricular myocardium both - and -adrenoceptors mediate the positive inotropic effect of phenylephrine. The extent of contribution of the two classes of adrenoceptor is quite different from that in other mammalian species. In the ferret heart, -adrenoceptors predominate over -adrenoceptors in mediating the positive inotropic effect of phenylephrine, although the number of -adrenoceptors is not especially high when compared with other species. Send offprint requests to M. Endoh at the above address     

Endotoxin toxicity in rats with 6-sulfanilamidoindazole arthritis.

Seven oral administrations of 6-sulfanilamidoindazole (6-SAI) to 10- to 12-month-old rats sensitized the animals to endotoxin, with dosages as small as 2.5 microgram causing death in 80% of animals. Endotoxin in a dosage of 3,000 microgram was not lethal for nonmedicated control animals. 6-SAI-treated 1-month-old rats were not as sensitive to endotoxin as aged animals. The sulfonamide-induced sensitivity to endotoxin could not be passively transferred and could not be explained by blockade of the reticuloendothelial system or impairment of endotoxin detoxification. 6-SAI administration was associated with both depletion of liver glycogen and lowering of blood glucose concentration without changes in blood lactic acid concentration. Disseminated intravascular coagulation is believed to be involved in the pathogenesis of shock and death as evidenced by: (i) concomitant decreases in plasma fibrinogen concentration and elevations in fibrin degradation products after endotoxin challenge; (ii) protection against lethal actions of endotoxin by pretreatment with heparin. Treatment of 6-SAI-medicated rats with glucocorticoids before endotoxin challenge protected the animals against lethal doses of endotoxin and prevented deposition of fibrin thrombi in the glomerular capillaries.     

Active matrix metalloproteinases in the tear fluid of individuals with vernal keratoconjunctivitis

Corneal epithelial lesions distinguish vernal keratoconjunctivitis (VKC) from other ocular allergic diseases. Such lesions result from degradation of the corneal epithelial basement membrane, which comprises mostly type IV collagen and laminin. Matrix metalloproteinase 2 (MMP-2) and MMP-9 catalyze the degradation of these 2 extracellular matrix proteins. The possible role of MMP-2 and MMP-9 in the pathogenesis of corneal lesions associated with VKC was investigated by assaying tear fluid for the presence of these enzymes. Tear fluid was collected from 6 eyes of 6 patients with active VKC, 14 eyes of 14 patients with active allergic conjunctivitis, and 6 eyes of 6 nonallergic healthy volunteers. Gelatin zymography revealed that the tear fluid of healthy volunteers contained inactive proforms of both MMP-2 and MMP-9 but not the active forms of these enzymes. Active forms of MMP-2 or MMP-9 were detected in a minority of patients with allergic conjunctivitis. However, with the exception of one individual for whom active MMP-9 was not detected, tear fluid from all patients with VKC contained both proforms and active forms of MMP-2 and MMP-9. These results implicate MMP-2 and MMP-9 in the pathogenesis of corneal epithelial disorders associated with VKC.     

Photography of precipitin bands developed with fluorescent antibodies

A procedure demonstrating the usefulness of combining fluorescence with agar diffusion is presented. A minor obstacle to its use is the means of permanently recording the colours that are obtained. The method described gives the conditions under which photographs can be taken. However, since the degree of fluorescence may vary from specimen to specimen exposure times, f-openings and conditions of lighting must be varied for optimum results.     

Morpho-metrical features of the pelvis in standing posture

The morpho-metrical features of the human pelvis differ according to gender, particularly with regard to size and shape, and bipedal standing posture appears to have been a major determinant of pelvic structure. In standing posture, the three points of the right and left superior anterior iliac spines and pubic tubercle are in contact with the vertical frontal plane. In this situation, the superior anterior iliac spine is lower than the superior posterior iliac spine. From a lateral view, the vertical line from the body's center of gravity passes through the center of the hip joint or acetabulum. The anatomical or biomechanical problem has been whether the line of gravity passes through the promontory or the center of auricular surface. To clarify this point, the three points of the acetabular center, promontory and auricular center were examined as to how they are positioned in relation to each other and the distance of each on the vertical frontal plane. Those measurements are as followed: A) distance between vertical frontal plane and promontory, B) distance between vertical frontal plane and anterior margin of auricular surface, C) distance between vertical frontal plane and mid-point of auricular surface computed from (B + D)/2, D) distance between vertical frontal plane and posterior margin of auricular surface, E) distance between vertical frontal plane and mid-point of acetabulum, F) inclination angle of the pelvis. From the results, the acetabular center and promontory are in alignment with the vertical line. The auricular center is positioned further back than the acetabular center or promontory. In this situation, the mean angle of inclination of the pelvis was found to be 63 degrees in 16 Japanese male specimens. The means of the other Japanese populations are into range of 63 degrees to 66 degrees in the males. If the auricular center coincides with the acetabular center, it is possible the angle of inclination of the pelvis would exceed 63 degrees. The frontal plane in contact with the right and left superior anterior iliac spines and pubic tubercle is not vertical. The morphological features clarified in the present study are that the promontory and acetabular center are in vertical alignment when viewed laterally and that the angle of inclination of the pelvis is 63 degrees.