Proteolysis in skeletal muscle and whole body in response to euglycemic hyperinsulinemia in normal adults

To simultaneously assess the relative antiproteolytic effect of insulin on both skeletal muscle and in the whole body, phenylalanine rates of appearance (Ra; reflecting proteolysis) were measured across the leg (reflecting skeletal muscle) and in the whole body, utilizing a constant tracer infusion of [2H5]phenylalanine in the basal state and during euglycemic hyperinsulinemia (2,600 microU/ml) in seven normal adults. Phenylalanine Ra in the leg was significantly decreased during hyperinsulinemia (6.11 +/- 0.83 vs 3.59 +/- 0.70 mumol/min, P less than 0.001). In contrast, leg phenylalanine rate of utilization (Rd) was not significantly changed (4.88 +/- 0.77 vs. 3.86 +/- 0.92 mumol/min). Phenylalanine Ra in the whole body was significantly decreased during hyperinsulinemia (49.4 +/- 2.2 vs. 41.9 +/- 2.3 mumol/min, P less than 0.001). However, phenylalanine release was suppressed to a significantly greater degree in release was suppressed to a significantly greater degree in the leg than in the whole body during hyperinsulinemia (43 +/- 7 vs. 15 +/- 2%, P less than 0.01). These results suggest that insulin suppresses proteolysis in the whole body and in skeletal muscle, even in the face of hypoaminoacidemia. In addition, the substantially greater degree of suppression of proteolysis by insulin in skeletal muscle compared with the whole body suggests that, at least under these conditions, insulin may have a greater antiproteolytic effect on skeletal muscle compared with other tissues.

Gating of L-type Ca2+ channels in embryonic chick ventricle cells: dependence on voltage, current and channel density

1. L-type calcium channels in embryonic chick heart ventricle have voltage-dependent, time-variant kinetics when they conduct inward currents carried by 20 mM-Ba2+. Depolarizing the membrane from -20 to 20 mV increases mean open time from 1.4 to 4.2 ms. Mean open time increases monotonically with voltage. The single-channel conductance, 18 +/- 2 pS, is approximately linear over this voltage range, and the extrapolated reversal potential is 38 +/- 5 mV. 2. In cell-attached patches with five or more L-type Ca2+ channels in the patch, the currents elicited by 500 ms depolarizing steps, from a -80 mV holding potential, inactivate rapidly and have large tail currents. In the same patch, currents from a -40 mV holding potential are smaller, inactivate more slowly, and have practically no tail currents. 3. In cell-attached patches containing one of two L-type Ca2+ channels, currents from -80 or -40 mV are virtually identical, and they are similar to the currents from multichannel patches held at -40 mV. 4. The voltage-dependent, time-variant kinetics of individual L-type Ca2+ channels are unaltered if the patch is removed from the cell and forms an inside-out configuration. In these experiments the internal membrane was bathed with an artificial, intracellular-like solution containing no phosphorylating enzymes or substrates. 5. Cells bathed in 20 mM-Ba2+ solutions and held at -80 mV have currents with an early phase that inactivates in tens of milliseconds, a late phase that inactivates in hundreds of milliseconds, and a large, slow tail current. Currents from -40 mV have only the late phase and practically no tails. However, if the maximum current is less than 0.1 pA pF-1, records from either -80 or -40 mV are virtually identical, and they are similar to currents from cells with higher channel density held at -40 mV. Furthermore, if cells are stimulated before full recovery from inactivation, the reduced current is accompanied by slower inactivation. 6. Whole-cell currents in 1.5 mM-Ca2+ solutions are entirely abolished by addition of 20 microM-nifedipine, and they are enhanced 2-3 times by addition of 30 microM-cyclic AMP and 3 mM-ATP to the whole-cell recording electrode. The whole-cell currents in 20 mM-Ba2+ solutions are also completely blocked by 20 microM-nifedipine, regardless of kinetics or holding potential. Thus, by definition, the cells we are studying contain only L-type channels.(ABSTRACT TRUNCATED AT 400 WORDS)

[Effects of noradrenaline and acetylcholine on transient inward current in sheep cardiac Purkinje fibers]

By using two-microelectrode voltage clamp technique, the effect of noradrenaline and acetylcholine on transient inward current (ITi) induced by acetylstrophanthidin was observed in sheep cardiac Purkinje fibers. In the presence of acetyl strophanthidin (4.5 X 10(-8) mol/L), the stability of ITi could be maintained for about 1.5 h. Noradrenaline (1.5 X 10(-6) mol/L) increased the ITi from 11.4 +/- 2.5 nA to 14.5 +/- 4.1 nA (n = 11, P less than 0.01) and shortened the ITi duration from 688 +/- 278 ms to 556 +/- 237 ms (n = 11, P less than 0.05). Acetylcholine (2.5 X 10(-6) mol/L) decreased the ITi amplitude from 13.4 +/- 3.8 nA to 10.6 +/- 3.2 nA (n = 8, P less than 0.01) and prolonged the ITi duration from 653 +/- 193 ms to 741 +/- 222 ms (n = 8, P less than 0.05). Acetylcholine (2.5 X 10(-6) mol/L) also decreased the ITi amplitude in the preparation pretreated with noradrenaline (2 X 10(-6) mol/L) from 14.8 +/- 7.7 nA to 10.0 +/- 6.7 nA (n = 6, P less than 0.01). In addition, the mechanism of noradrenaline effect was also studied. When the slow inward current (Isi) was blocked by Mn2+ (0.75 mmol/L), noradrenaline still increased the ITi amplitude from 2.2 +/- 0.2 nA to 4.9 +/- 1.1 nA (n = 6, P less than 0.01) but had no effect on Isi, suggesting that noradrenaline has a direct effect on ITi.

Gigantecin: a novel antimitotic and cytotoxic acetogenin, with nonadjacent tetrahydrofuran rings, from Goniothalamus giganteus (Annonaceae)

Gigantecin (I), a novel tetrahydroxy-di-tetrahydrofuran fatty acid gamma-lactone (acetogenin), was isolated from an ethanolic extract of the stem bark of Goniothalamus giganteus Hook. f., Thomas (Annonaceae), by means of activity-directed fractionation (brine shrimp lethality test). This new compound is extremely cytotoxic to human tumor cells, inhibits crown gall tumors on potato discs, and is active in an assay designed to detect antimitotic agents (9 ASK).

Sylvaticin: a new cytotoxic and insecticidal acetogenin from Rollinia sylvatica (Annonaceae)

Sylvaticin (I), a new tetrahydroxy annonaceous acetogenin with nonadjacent tetrahydrofuran rings, has been isolated from the dried fruits of Rollinia sylvatica St. Hil. (Annonaceae). This compound is extremely cytotoxic to human tumor cells and shows promising insect control properties.

Inhibition of rabbit platelet aggregation by 1,4-naphthoquinones

The effects of four 1,4-naphthoquinone derivatives on the aggregation of rabbit platelets were examined. All the four 1,4-naphthoquinone derivatives inhibited the platelet aggregation of washed rabbit platelets induced by thrombin (0.1 U/ml) and the IC50 is: 2-chloro-3-methyl-1,4-naphthoquinone (CMN), 5 micrograms/ml; 3-methyl-5,8-dihydroxy-1,4-naphthoquinone, 13 micrograms/ml; 5,8-dihydroxy-1,4-naphthoquinone, 18 micrograms/ml; 3-methyl-1,4-naphthoquinone (vitamin K3), 53 micrograms/ml. CMN was the most potent in inhibiting the aggregation and release reaction induced by ADP, arachidonic acid, PAF, ionophore A23187, collagen and thrombin in a dose-dependent manner in washed platelets, platelet-rich-plasma and whole blood. The thromboxane B2 formation caused by collagen and ionophore A23187 was inhibited by CMN. However, the thromboxane B2 formation by arachidonic acid was markedly increased. The platelet inhibitory effect of CMN could not be antagonized either by raising the concentrations of extracellular Ca++ or by wash out. The phosphoinositides breakdown induced by thrombin was inhibited by CMN. Phospholipids (PE, PC, PI) could slightly antagonize the antiplatelet effect of CMN. It is concluded that the inhibitory effect of CMN on rabbit platelet aggregation may be due to the inhibition of phosphoinositides breakdown caused by the inducers.

[Changes of Isi and Ix in sheep cardiac Purkinje fibers during alpha- and beta- adrenoceptor excitation]

When alpha- and beta- adrenoceptors were activated respectively in sheep cardiac Purkinje fibers, changes of the slow inward current (Isi) and delayed rectifier current (Ix) were studied by using two-microelectrode voltage clamp technique. When beta-receptor was blocked by propranolol, phenylephrine 5.0 x 10(-6) mol/L increased the peak value of Isi from 17.5 to 26 nA (n = 6, P less than 0.05) and prolonged the ms recovery time of Isi from inactivation from 293 +/- 51 ms to 441 +/- 190 (n = 4, P less than 0.05). Phenylephrine had no effect on the delayed rectifier current (Ix). When alpha-adrenoceptor was blocked by phentolamine, isoprenaline of 4 x 10(-7) mol/L increased the peak value of Isi from 27.7 to 40.8 nA (n = 7, P less than 0.05) and had no effect on the kinetics of Isi, but it did increase the tail current (Ix) peak value from 6.7 to 14.4 nA (n = 6, P less than 0.05). The results suggest that alpha- and beta-adrenoceptor agonists differ in their effects on delay rectifier current.

Discrimination between sheep antibodies to Brucella melitensis and to Brucella ovis

When preparations containing smooth Brucella abortus lipopolysaccharide (LPS) were used as antigen in an ELISA, strong positive reactions were obtained with sera from sheep infected with Brucella melitensis or with Brucella ovis. Oxidation of the LPS with sodium metaperiodate greatly reduced the extent of the cross-reactions with antisera to B. ovis, with little effect on the reactions with antisera to smooth B. melitensis. Periodate oxidation of hot saline extract (HSX) antigen of B. ovis markedly reduced its reactivity in ELISA with anti-B. ovis sera and eliminated cross-reactivity with anti-B. melitensis sera. The reactivity of HSX was maintained after treatment with proteinase K. A simple ELISA system, in which replicate samples from a single serum dilution were tested in parallel against both B. ovis HSX antigen and periodate-oxidised smooth phase B. abortus LPS, was evaluated. It was found to discriminate well between antibodies induced by vaccination or virulent infection with B. melitensis strains and those induced by infection with B. ovis.

Absorption of calcium and magnesium from fortified human milk by very low birth weight infants

Absorption of calcium and magnesium endogenous to human milk, as well as calcium and magnesium added as an exogenous supplement to human milk, was determined in 9 very low birth wt infants. Human milk, intrinsically labeled with stable isotopic tracers of calcium and magnesium, was prepared by administering isotopic tracers intravenously to a lactating woman. Different isotopic tracers, which were representative of calcium and magnesium in the supplement (Enfamil Human Milk Fortifier, Mead Johnson Nutritional Div.), were added to the intrinsically labeled milk. The fortified milk, which was labeled with two calcium tracers and two magnesium tracers, was given orally to the test subjects in a single feeding. True absorption of calcium and magnesium was determined from differences between the doses of tracer ingested and the quantities of tracer excreted in the feces. Stable isotopic tracers were quantified by fast atom bombardment mass spectrometry. These results demonstrate that the fractional absorptions of calcium in the human milk and the added mineral supplement are 80 and 82%, respectively. A total of 89% magnesium endogenous to human milk and 86% of magnesium derived from the mineral supplement was absorbed by the VLBW infants.

Endourethral urethroplasty with prepuce graft for long posterior urethral stricture

Twenty patients underwent endourethral urethroplasty with free prepuce graft in combination with transurethral resection of scar for posterior urethral stricture. Two-year follow-up showed that they had good continent and free voiding results. Problems about surgical technique were detailed. We conclude that a free full-thickness prepuce evenly patched by means of the tube balloon to the freshly prepared wound derived from the stricture is the key to surgical success.

Subaperture testing of aspheres with annular zones

A subaperture configuration to test aspheric optical components or systems has been developed. The aperture is divided into annular subaperture regions, and an interferometer is refocused for each region to reduce the fringe density. The method is suited to phase-measuring interferometry and may be used with standard interferogram reduction software. The theoretical basis for the method, requirements for the number of annular zones, sensitivity to the selection of the number of polynomials, and tolerances for centration and radius are described. Numerical and experimental validations of the algorithm are described. The method may eliminate the need to use null lenses for measuring some aspheres at the center of curvature.

Suppression of cone-driven responses by rods in the isolated frog retina

The sensitivity of rod- and cone-driven responses was studied in the isolated frog retina during the period of rapid dark adaptation following a conditioning flash which bleached a negligible amount of visual pigment. Following a conditioning flash, cone-driven b-wave responses were first enhanced and then depressed. The time courses of the enhancement and subsequent depression of cone-drive responses varies greatly with the intensity and wavelength of the conditioning flash, but were identical when the conditioning flashes were matched for equal excitation of 502 nm rods. These changes in cone-driven response sensitivity were correlated with the desensitization and recovery of rods following the conditioning flash. When signal transmission from rods to second-order cells was interrupted by the addition of L-glutamate, the conditioning flash did not produce the above-described enhancement and subsequent depression of long-wavelength receptor potential responses. The suppression of cone-driven response therefore appears to be due to a synaptically mediated influence from 502 nm rods which is maximal when the rods are in the dark-adapted state, with little or no contribution from 433 nm rods, and no involvement of the pigment epithelium.

Adaptation of the left ventricle to exercise-induced hypertrophy

Cardiac functional and structural adaptations to exercise-induced hypertrophy were studied in 68 pigs. Pigs were exercise trained on a treadmill for 10 wk. Sequential measurements were made of cardiac dimensions, [left ventricular end-diastolic diameter (EDD), changes in diameter (delta D%), wall thickness (WTh), wall thickening (WTh%), left ventricular pressure (LVP), time derivative of pressure (dP/dt), stroke volume, total body O2 consumption (VO2), blood gases, and systemic hemodynamics] at rest and during moderate and severe exercise. Postmortem studies included morphometric measurements of capillary density, arteriolar density, mitochondria, and myofibrils. All of the exercise-trained pigs showed significant increases in aerobic capacity. Maximum O2 consumption (VO2 max) increased by 37.5% in group 1 (moderate exercise training) and 34% in group 3 (heavy exercise training). Cardiac hypertrophy ranged from less than 15% in a group (n = 8) subjected to moderate exercise training to greater than 30% in a group (n = 11) subjected to heavy exercise training. Before training, exercise was characterized by a decreasing EDD during progressive exercise; this was reversed after exercise training. Stroke volume and end-diastolic volumes during exercise showed a highly significant increase after exercise training and hypertrophy. Morphometric measurements showed that mitochondria and cell membranes increased with increasing myocyte growth in all exercise groups, but there was only a partially compensated adaptation of capillary proliferation. Arteriolar number and length increased in all exercise groups. Intrinsic contractility as measured by delta D%, WTh%, or left ventricular dP/dt did not increase with exercise training and in some instances decreased. Therefore, left ventricular adaptation to strenuous exercise in the pig heart is primarily one of changes in left ventricular dimensions and a compensated hypertrophy. Exercise-induced increases in EDD and stroke volume can be accounted for by decreases in peripheral resistance and increased cardiac dimensions.