Modulators of transmembrane calcium exchange in myometrium mitochondria change their hydrodynamic diameter

The influence of modulators of calcium exchange in mitochondria--oligomycin, Mg2+ and ruthenium red (RuR)--on the myometrium mitochondria size and granularity was studied in the work. The study of the mitochondria size was carried out using the photon correlation spectroscopy. It was shown that the average hydrodynamic diameter was 655 +/- 14 nm (n = 5; control). The addition of oligomycin (1 microg/ml)--the inhibitor of ATP-synthase F0-component, increases the mitochondria average hydrodynamic diameter to 913 +/- 75 nm (n = 5), that is by 39% more than the control. In the presence of RuR (10 microM) (Ca2(+)-uniporter inhibitor) and Mg2+ (7 mM) the mitochondria average hydrodynamic diameter increases to 788 +/- 28 and 788 +/- 38 nm (n = 5) respectively, that is by 17% more than the control. Using flow cytometry it was shown, that oligomycin (1 microg/ml) causes the increase of side scattering of the mitochondria. Addition of RuR (10 microM) and Mg2+ (7 mM) does not lead to significant changes in side scattering of the mitochondria. So it was shown that oligomycin significantly increases mitochondria granularity, but Mg2+ and RuR have no influence on this parameter     

Disinfecting properties of performic acid against bacteriophage phi X 174 as a model of small envelope--free viruses

Performic acid HCOOH (PFA) is a wide-spectrum disinfectant. It inactivates viruses, bacteria and bacterial spores, mycobacteria as well as microscopic fungi. Its main drawback is its instability, which makes it a logical necessity that it is to be prepared prior to use from its components HCOOH and H2O2. The mixing of 8 ml HCOOH of the concentration 850 ml/l and 17 ml H2O2 of the concentration 300 ml/l in a 100 ml-volume reagent bottle with a ground-in glass stopper gives, after an 1-hour rest at room temperature and after another 1 hour in a refrigerator, a stock solution that contains about 50 ml/l of PFA the actual concentration of which is determined iodometrically. Bacteriophage phi X 174 (host E. coli C) is characterized by cubic ikosahedral-type symmetry of particles free of envelope, has 27 mm in diameter and contains single-strand cyclic DNA; formerly was classed among Parvoviridae. The possibility of plaque assay-based quantitative determination of the number of infectious particles makes if it a feasible model for assessing disinfectant action on small hydrophilic viruses under conditions close to those of practical disinfection procedures. PFA stock solution diluted to 1 X 10(-3) (0.05 ml/l of effective component) inactivates the model virus of a concentration 10(8) pfu/ml aqueous suspension within 5 min so that no virus is detectable; the drop in the number of pfu amounts to 7 log orders of magnitude. In the presence of 400 ml/l of serum, the identical effect is achieved within 5 min by PFA stock solution diluted to 5 X 10(-3). The lowest PFA concentration that reliably inactivates bacteriophage phi X 174 in aqueous suspension is identical with the lowest concentration inactivating Coxsackie B 1 virus in tissue cultures. On textile, glass, plastic, rubber and metal carriers contaminated by swabbing or by a dried drop of bacteriophage suspension containing about 1 X 10(9) pfu/ml, the lowest reliably effective concentrations of PFA range within 0.25-0.025 ml/l, i.e. PFA stock solutions diluted to 5 X 10(-3)-5 X 10(-4), depending on the type of carrier and the type of contamination.     

Blood–Brain Barrier Permeability to Sodium. Modification by Glucose or Insulin?

In order to explore the pathogenetic mechanism underlying the changes in blood-brain barrier sodium transport in experimental diabetes, the effects of hyperglycemia and of hypoinsulinemia were studied in nondiabetic rats. In untreated diabetes, the neocortical blood-brain barrier permeability for sodium decreased by 20% (5.6 +/- 0.7 versus 7.0 +/- 0.8 X 10(5) ml/g/s) as compared to controls. Intravenous infusion of 50% glucose for 2 h was associated with a decrease in the blood-brain barrier permeability to sodium (5.4 +/- 1.2 X 10(5) ml/g/s), whereas rats treated with an inhibitor of insulin-secretion (SMS 201-995, a somatostatin-analogue) had normal sodium permeability (7.3 +/- 2.0 X 10(5) ml/g/s). Acute insulin treatment of diabetic rats normalized the sodium permeability within a few hours as compared to a separate control group (7.7 +/- 1.1 versus 6.9 +/- 1.4 X 10(5) ml/g/s). To elucidate whether the abnormal blood-brain barrier passage is caused by a metabolic effect of glucose or by the concomitant hyperosmolality, rats were made hyperosmolar by intravenous injection of 50% mannitol. Although not statistically significant, blood-brain barrier sodium permeability increased in hyperosmolar rats as compared to the control rats (8.3 +/- 1.0 and 7.0 +/- 1.9 X 10(5) ml/g/s, respectively). It is concluded that either hyperglycemia per se or a glucose metabolite is responsible for the blood-brain barrier abnormality which occurs in diabetes. Further, we suggest that the specific decrease of sodium permeability could be the result of glucose-mediated inhibition of the Na+K+-ATPase localized at the blood-brain barrier.     

Characterization of indo-1 and quin-2 as spectroscopic probes for Zn2(+)-protein interactions

1-[2-Amino-5-(6-carboxyindol-2-yl)phenoxyl]-2-(2'- amino-5'-methylphenoxy)ethane-N,N,N',N'-tetraacetic acid (indo-1) and 2-[2-(bis(carboxymethyl)amino-5-methylphenoxy) methyl]-6- methyl-8-[bis-(carboxymethyl)amino]quinoline (quin-2) are sensitive, spectral indicators for Zn2+. Additions of subsaturating Zn2+ to 10-80 microM indo-1 or quin-2 at pH 7.0 produce uv difference spectra with isosbestic wavelengths at 342 and 282 nm or at 342, 317, and 252 nm, respectively. Formation of 1:1 Zn2+:indicator complexes at pH 7.0 and 20 degrees C in the absence (presence) of 100 mM KCl gives delta epsilon max = -2.4 +/- 0.2 X 10(4) M-1 cm-1 at 367 nm (-2.1 +/- 0.2 X 10(4) M-1 cm-1 at 365 nm) for indo-1 and delta epsilon max = -2.7 +/- 0.1 X 10(4) M-1 cm-1 at 266 nm (-2.6 +/- 0.1 X 10(4) M-1 cm-1 at 265 nm) for quin-2. Competition experiments at pH 7.0 and 20 degrees C with indo-1 and quin-2 and also 4-(2-pyridylazo)resorcinol (PAR) as the second chelator in the absence (presence) of 100 mM KCl yield apparent affinity constants: K'A = 2.5 +/- 1.0 X 10(10) M-1 (6.2 +/- 0.5 X 10(9) M-1) for indo-1 binding Zn2+ and K'A = 9.4 +/- 3.3 X 10(11) M-1 (2.7 +/- 0.1 X 10(11) M-1) for quin-2 binding Zn2+. The above constants provide the basis for rapid steady-state spectrophotometric determinations of the affinity of a protein for Zn2+ with K'A approximately 10(10) - 10(13) M-1.(ABSTRACT TRUNCATED AT 250 WORDS)     

Diffusion Constant and Dimension of Bacteriophage φX174 as Determined by Self-Beat Laser Light Spectroscopy and Electron Microscopy

The diffusion constant of bacteriophage phiX174 was determined by laser light self-beat spectroscopy. The method allows one to establish the diffusion constant in comparatively short time and with high accuracy. From the diffusion constant D(37) = 1.96 +/- 0.08 x 10(-7) cm(2)/s, the size of the virus particles within their aqueous milieu can be calculated. For phiX174, a diffusional diameter of 31.4 +/- 1.0 nm was found, in good agreement with measurements of diameters of freezeetched (32.3 +/- 1.8 nm) and negatively stained particles (33.8 +/- 2.1 nm), provided that the entire spikes of the virion are included. Other isometric viruses may show a complex interaction of the virion with the surrounding water and its ions.     

Antioxidants attenuate endotoxin-induced microvascular leakage of macromolecules in vivo.

The purpose of this study was to examine whether antioxidants attenuate endotoxin-induced microvascular hyper-permeability for macromolecules in the hamster cheek pouch. Twenty-two adult male Syrian hamsters were anesthetized, and a removable plastic chamber was placed in the cheek pouch to observe and collect suffusate from the microvasculature. Fluorescent-labeled dextran (FITC-D; mol wt 150,000) was injected intravenously, and changes in the number of microvascular leaky sites and microvascular clearance of FITC-D were measured in five groups: saline control (group 1, n = 4), endotoxin (0.1 mg/ml) suffusion for 120 min (group 2, n = 6), endotoxin plus dimethyl sulfoxide (1.0 g/kg iv; group 3, n = 4), endotoxin plus allopurinol (30 mg/kg ip; group 4, n = 4), and endotoxin plus dimethyl sulfoxide and allopurinol (group 5, n = 4). The number of leaky sites and the FITC-D clearance were significantly higher in group 2 [45 +/- 18 (SD) sites/cm2 and 20 +/- 6 X 10(-6) ml/min, respectively; P less than 0.01] than in group 1 (7 +/- 6 sites/cm2 and 7 +/- 5 X 10(-6) ml/min), group 3 (9 +/- 5 sites/cm2 and 8 +/- 2 X 10(-6) ml/min), group 4 (11 +/- 7 sites/cm2 and 9 +/- 4 X 10(-6) ml/min), and group 5 (11 +/- 6 sites/cm2 and 7 +/- 1 x 10(-6) ml/min). The leaky sites appeared predominantly in postcapillary venules. There was a positive and significant correlation between the number of leaky sites and FITC-D clearance.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of anesthesia on cystometry and leak point pressure of the female rat

Anesthetics operate by different mechanisms and are often used to perform urodynamics in animals. The objective of this study was to compare the effects of ketamine/xylazine and urethane anesthetics on filling, voiding, and leak point pressure (LPP) in female rats. Nineteen rats underwent awake cystometry 2 days after suprapubic bladder catheter implantation. Bladders were filled with saline (5 ml/hr), while bladder pressure was measured. Half the rats were then anesthetized with urethane i.p. and half were anesthetized with ketamine and xylazine i.p. (K/X). All rats then underwent cystometry and LPP testing under anesthesia. Spontaneous nonvoiding contractions were analyzed and capacity was determined by voiding or leakage. Capacity was significantly higher in awake rats (0.55 +/- 0.06 ml) than with either K/X (0.21 +/- 0.06 ml) or urethane (0.30 +/- 0.05 ml). The pressure just prior to voiding in awake cystometry (15.6 +/- 1.7 cm H2O) was not significantly different from that with either anesthetic (K/X: 10.1 +/- 1.0 cm H2O; urethane: 13.3 +/- 2.0 cm H2O). Spontaneous nonvoiding contractions occurred in 4 rats with urethane and 3 rats with K/X. The volume at which the first contraction occurred was significantly lower with K/X (0.05 +/- 0.02 ml) than urethane (0.19 +/- 0.04 ml). There was no significant difference in the frequency of spontaneous nonvoiding contractions between K/X (4.58 +/- 0.30/min) and urethane (5.16 +/- 2.66/min), nor was there a difference in LPP between anesthetics (K/X: 40.4 +/- 2.4 cm H2O; urethane: 36.2 +/- 3.9 cm H2O). The results suggest that urethane is preferable to K/X for anesthetized cystometry studies since it more closely simulates normal physiological responses.     

Rapid spectral scan and stopped-flow studies of carbon monoxide binding to bovine adrenocortical cytochrome P-450scc

Carbon monoxide binding with both cholesterol-free (low-spin) and cholesterol-bound (high-spin) reduced forms of purified cytochrome P-450scc has been investigated by rapid-scan and stopped-flow spectrometry. CO binding occurs within 150 ms at 25 degrees C for both forms of P-450scc, with a typical absorption maximum at 450 nm. Isosbestic points occur at the following wavelengths: between reduced-CO and reduced cholesterol-free P-450scc at 434 and 471 nm; between reduced-CO and reduced cholesterol-bound P-450scc at 433 and 469 nm. Both the 'on' (k1) and 'off' rate constants (k-1) are found to be independent of pH between pH 5 and 9. The mean values of k1 for cholesterol-free (1.8 +/- 0.2) X 10(5) M-1 X s-1) and cholesterol-bound [1.9 +/- 0.1) X 10(5) M-1 X s-1) P-450scc are almost identical, while the mean value of k-1 for the former [2.3 +/- 0.3) X 10 s-1) is about double that of the latter [1.2 +/- 0.1) X 10 s-1). This suggests the instability of the reduced-CO complex in the absence of cholesterol.     

Analyses of sister-chromatid exchange and cell-cycle kinetics in mouse T- and B-lymphocytes from peripheral blood cultures

A reliable mouse peripheral blood lymphocyte culture assay has been developed for sister-chromatid exchange analysis. Crucial aspects for optimal mitogenesis include: (1) the addition of 5 X 10(5) leucocytes/ml culture; (2) the use of animals with leucocyte counts from 5 to 7 X 10(6)/ml; and (3) the addition of 6% mouse plasma for the first 24 h of a total 54-h incubation. When 7 micrograms phytohemagglutinin/ml were used to stimulate T-lymphocytes, the mitotic index was 3.4 +/- 0.3%, 28 +/- 2.3% of the metaphases were in first-division, and the SCE frequency/metaphase was 7.3 +/- 0.2 (n = 14 mice). When B-lymphocytes were stimulated with 60 micrograms lipopolysaccharide/ml, the mitotic index was 4.5 +/- 0.3%, 64 +/- 3.3% of the metaphases were in first-division, and the SCE frequency/metaphase was 4.6 +/- 0.1 (n = 7 mice). This culture method consistently yields sufficient numbers of metaphases from both B- and T-lymphocytes for SCE and chromosome-breakage studies.     

Structure and mass of mammalian respiratory ciliary outer arm 19S dynein

Mammalian respiratory ciliary outer arm dyneins isolated as the major ATPase peak migrating at 19S on sucrose density gradients were examined by transmission electron microscopy of negatively stained samples and scanning transmission electron microscopy of unstained samples. The predominant discrete particle structure observed was composed of two globular heads apparently connected by amorphous or indistinct material. The heads were either circular or slightly elliptical of mean 13 +/- 1 X 10 +/- 2 nm dimensions. The mass of this structure averaged 1.22 +/- 0.34 million daltons with the individual globular heads averaging 310 +/- 77 kilodaltons (kD). Negative staining revealed that one or both of the globular heads often contained a central accumulation of stain measuring 2.5 +/- 1 nm across. A second type of structure, appearing with lesser frequency in the 19S fraction than in the unfractionated dynein preparation loaded onto the sucrose gradient, was a single globular head of 13 +/- 1 X 10 +/- 2 nm often with 2 +/- 1 nm centrally accumulated stain and with or without an appendage. This one-headed particle thus resembled one-half of the two-headed particle. Mass measurements were lower, however, for isolated, single globular heads, averaging 220 +/- 111 kD. A third type of particle observed was a ring-like structure with 4 +/- 1 nm centrally accumulated stain and without appendages. The ring structure was slightly larger in diameter, 14 +/- 1 nm, and had a greater peripheral accumulation of negative stain than either of the one- or two-headed particles, suggesting that it was not derived therefrom.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparative study on the inactivation of MS2 and M13 bacteriophages using energetic femtosecond lasers

Femtosecond (fs) laser irradiation techniques are emerging tools for inactivating viruses that do not involve ionizing radiation. In this work, the inactivation of two bacteriophages representing protective capsids with different geometric constraints, that is, the near‐spherical MS2 (with a diameter of 27 nm) and the filamentous M13 (with a length of 880 nm) is compared using energetic visible and near‐infrared fs laser pulses with various energies, pulse durations, and exposure times. Intriguingly, the results show that inactivation using 400 nm lasers is substantially more efficient for MS2 compared to M13. In contrast, using 800 nm lasers, M13 was slightly more efficiently inactivated. For both viruses, the genome was exposed to a harmful environment upon fs‐laser irradiation. However, in addition to the protection of the genome, the metastable capsids differ in many properties required for stepwise cell entry that may explain their dissimilar behavior after (partial) disassembly. For MS2, the dominant mechanism of fs‐laser inactivation was the aggregation of the viral capsid proteins, whereas aggregation did not affect M13 inactivation, suggesting that the dominant mechanism of M13 inactivation was related to breaking of secondary protein links.     

Total and free testosterone in plasma of hypo- and agonadal men.

Plasma total testosterone (T), apparently free T and testosterone binding globulin (TeBG) capacity determined in 14 normal men aged 30-40 years were 461 +/- 100 ng/100 ml, 9.4 +/- 3.0 ng/100 ml and 5.7 +/- 1.9 X 10(-8) M, respectively, whereas in 16 hypogonadal men the corresponding values were 38.6 +/- 27.2 ng/100 ml, 0.47 +/- 0.41 ng/100 ml and 10.4 +/- 3.4 X 10(-8) M showing the TeBG capacity significantly higher (p less than 0.001) in hypogonadal than in normal men. Treatment of 5 hypogonadal subjects with 250 mg testosterone enanthate plus 50 mg testosterone propionate decreased (p less than 0.001) the TeBG level from 14.7 +/- 2.5 X 10(-8YM to 8.3 +/- 1.4 X 10(-8) M on day 8 after a single injection. According to this difference in TeBG, the free T fraction in plasma rose from 0.94% to 1.9% of the total T concentration. These results suggest that alteration of total plasma T affected the TeBG capacity. Decreased T levels raised and increased T concentrations suppressed TeBG, but with a delayed response to the changed T concentrations. The initial mean values in 12 patients with prostatic cancer aged 60-74 years were 397 +/- 165 ng/100 ml, 4.05 +/- 1.8 ng/100 ml and 11.9 +/- 3.3 X 10(-8) M, respectively. The TeBG capacity in these patients was significantly higher and the free T concentration significantly lower (p less than 0.001) than those of the younger normal males. After treatment with 12 g diethylstilbestrol diphosphate and orchidectomy, the TeBG increased to 33.3 +/- 13.1 X 10(-8) M and the plasma free T concentration decreased to the minimal value of 0.053 +/- 0.04 ng/100 ml.     

Characterization of two lipoproteins containing apolipoproteins B and E from lesion-free human aortic intima

Lesion-free areas of aortic intimas from seven men, 30 to 49 years old, were extracted with aqueous buffer within a few hours after an accidental or sudden death. Two lipoprotein fractions could be isolated by density gradient ultracentrifugation from all cases. The mean composition of fraction I (d less than 1.012 g/ml) resembled that reported for the cholesteryl ester-rich, beta-migrating very low density lipoprotein (beta-VLDL); the composition of fraction II (d 1.021-1.046 g/ml) resembled that of plasma low density lipoprotein (LDL). Mean diameter of the particles was 35 +/- 8 nm in fraction I and 25 +/- 5 nm in fraction II (22 +/- 2 nm in plasma LDL). Both fractions contained apolipoproteins B (apoB) and E (apoE), and had increased electrophoretic mobilities and reduced contents of linoleic acid. The immunoreactivity of apoB to a polyclonal and two monoclonal antibodies in both fractions was not different from that of plasma lipoproteins. The apoE isoform patterns in both fractions were similar to those obtained from the respective postmortem plasmas. When incubated with mouse peritoneal macrophages, fractions I and II enhanced the incorporation of radioactive oleate into cholesteryl esters by 10- to 20-fold and 3- to 4-fold, respectively, in comparison to plasma LDL. In conclusion, our results indicate that lesion-free human aortic intima contains two types of apoB- and apoE-containing lipoprotein particles, both of which might be potentially atherogenic.     

Shape and quaternary structure of alpha-globulin from sesame (Sesamum indicum L.) seed as revealed by small angle x-ray scattering and quasi-elastic light scattering

The alpha-globulin from sesame seed has a molar mass of 2.7 X 10(5) g mol-1, determined by x-ray scattering, and (2.8 +/- 0.3) 10(5) g mol-1, determined by quasi-elastic light scattering. The radius of gyration RG amounts to (4.1 +/- 0.1) nm and (3.9 +/- 0.2) nm as determined by Guinier approximation and from the distribution function D(x), respectively. The molecule has a Stokes radius Rs of (5.4 +/- 0.15) nm and a maximum dimension L of (11 less than L less than 15) nm. The translational diffusion coefficient D0(20),w and the ratio of fractional coefficients f/fmin amount to (3.95 +/- 0.12) X 10(-7) cm2 s-1 and 1.25, respectively. The quaternary structure of the protein molecule is approximated by a model consisting of six spherical subunits situated at the vertices of an octahedron having the symmetry 32.     

Exercise responses in pregnant sheep: oxygen consumption, uterine blood flow, and blood volume

In an attempt to explore the acute maternal responses to exercise we measured oxygen consumption, uterine blood flow, and blood volume in 13 chronically catheterized pregnant sheep at rest and while exercising on a treadmill. With maximal exercise O2 consumption increased 5.6 times, from a resting value of 5.8 +/- 0.3 (SE) to 32.1 +/- 2.8 ml X min -1 X kg -1, cardiac output increased 2.7 times, from 149 +/- 8 to 404 +/- 32 ml X min -1 X kg -1, and arteriovenous oxygen content difference increased 2.1 times, from 3.9 +/- 0.2 to 8.0 +/- 0.4 ml X dl -1. Total uterine blood flow decreased from a mean resting value of 292 +/- 6 to 222 +/- 19 ml X min -1 X kg fetus -1 near exhaustion during prolonged (40 min) exercise at 70% maximal oxygen consumption. Maternal blood volume decreased 14% (P less than 0.01) from 67.5 +/- 3.7 to 57.8 +/- 3.6 ml X kg -1 during this exercise period, with a 20% decrease in plasma volume without a change in red cell volume. We conclude that uterine blood flow decreases during maternal exercise. However, hemoconcentration helps to maintain a relatively constant oxygen delivery to the uterus.     

Coupling between the bacteriorhodopsin photocycle and the protonmotive force in Halobacterium halobium cell envelope vesicles. III. Time-resolved increase in the transmembrane electric potential and modeling of the associated ion fluxes.

Bacteriorhodopsin functions as an electrogenic, light-driven proton pump in Halobacterium halobium. In cell envelope vesicles, its photocycle kinetics can be correlated with membrane potential. The initial decay rate of the M photocycle intermediate(s) decreases with increasing membrane potential, allowing the construction of a calibration curve. The laser (592.5 nm) was flashed at various time delays following the start of background illumination (592 +/- 25 nm) and transient absorbance changes at 418 nm monitored in cell envelope vesicles. The vesicles were loaded with and suspended in either 3 M NaCl or 3 M KCl buffered with 50 mM HEPES at pH 7.5 and the membrane permeability to protons modified by pretreatment with N,N'-dicyclohexylcarbodiimide. In each case the membrane potential rose with a halftime of approximately 75 ms. The steady-state potential achieved depends on the cation present and the proton permeability of the membrane, i.e., higher potentials are developed in dicyclohexylcarbodiimide treated vesicles or in NaCl media as compared with KCl media. The results are modeled using an irreversible thermodynamics formulation, which assumes a constant driving reaction affinity (Ach) and a variable reaction rate (Jr) for the proton-pumping cycle of bacteriorhodopsin. Additionally, the model includes a voltage-gated, electrogenic Na+/H+ antiporter that is active when vesicles are suspended in NaCl. Estimates for the linear phenomenological coefficients describing the overall proton-pumping cycle (Lr = 3.5 X 10(-11)/mol2/J X g X s), passive cation permeabilities (LHu = 2 X 10(-10), LKu = 2.2 X 10(-10), LNau = 1 X 10(-11)), and the Na+/H+ exchange via the antiporter (Lex = 5 X 10(-11)) have been obtained.     

Effect of ethmozine on action potentials and myocardial contraction in guinea pigs

Ethmozine decreased the maximum rate of action potential rise (Vmax) in a dose-dependent manner. Using the Scatchard plot the apparent dissociation constant was calculated to be 1.52 X 10(-5) g/ml. Ethmozine also decreased the force of contraction in the concentration range between 1 X 10(-6) and 1 X 10(-4) g/ml with the apparent dissociation constant obtained from the Scatchard plot being equal to 1.48 X 10(-5) g/ml. The linear correlation coefficient between the decrease in Vmax and the decrease in the force of contraction was found to be equal to 0.998. Negative inotropic action of ethmozine was less pronounced when the stimulation frequency had been switched from 0.8 to 0.1 Hz. The decrease in Vmax under the action of ethmozine (3 X 10(-5) g/ml) was diminished from 56 +/- 7% (0.8 Hz) to only 3 +/- 8% (0.1 Hz). This was accompanied by the decrease in the negative inotropic effect: from 58 +/- 9% (0.8 Hz) to 16 +/- 15% (0.1 Hz). It was assumed that the negative inotropic action of ethmozine was mediated by the Na--Ca exchange, which was inhibited by the decrease of the intracellular Na+ concentration due to the blockade of sodium channels by ethmozine.     

Modification of the cutaneous vascular response to exercise by local skin temperature

This study examined how local forearm temperature (Tloc) affects the responsiveness of the cutaneous vasculature to a reflex drive for vasoconstriction. We observed responses in forearm blood flow (FBF) and arterial blood pressure to a 5-min bout of supine leg exercise of moderate intensity (125-175 W) after the forearm had been locally warmed to 36, 38, 40, or 42 degrees C for 48 min. With exercise, FBF fell by 1.82 +/- 0.23, 4.06 +/- 0.58, and 3.64 +/- 1.48 ml X 100 ml-1 X min-1 at 36, 38, and 40 degrees C, respectively, and rose by 2.16 +/- 0.57 ml X 100 ml X min-1 at a Tloc of 42 degrees C (mean +/- SE). Forearm vascular conductance (FVC) fell with the onset of exercise by averages of 2.77 +/- 0.57, 7.02 +/- 0.51, 5.36 +/- 0.85, and 4.17 +/- 0.79 ml X 100 ml-1 X min-1 X 100 mmHg-1 at 36, 38, 40, and 42 degrees C, respectively. Second-order polynomial regression analysis indicated that the reductions in FVC were greatest near a Tloc of 39 degrees C and that at a Tloc of 40 or 42 degrees C the cutaneous vasoconstrictor response to the onset of exercise is attenuated. Although elevated Tloc can be used to increase base-line FBF levels to make cutaneous vasoconstrictor responses more obvious, the direct effects of Tloc on this response must also be considered. We conclude that the optimum Tloc for observing reflex cutaneous vasoconstriction is near 39 degrees C.     

Identification of receptors in a system of functionally heterogeneous proteins specifically bound to androgens in rat liver cytosol

The methods of androgen receptor (RA) isolation and identification in rat liver cytosol were studied. It was shown that male rat liver contains a system of specific androgen (A)-binding proteins consisting of at least three main components: RA, delta 4-androstendione (delta 4-A)-binding component and an unusual estrogen-binding protein interacting also with A and the first two components in females. The identity of one of A-binding components to RA was proved by cumulative properties of this component which are similar to those of RA from other tissues. These properties are as follows: 1) high values of apparent association constant, Ka, for 3H-R1881 (2.8 +/- 0.3 X 10(8) M-1) and 3H-5 alpha-dihydrotestosterone (3H-DHT) (5.0 +/- 0.4 X 10(8) M-1); 2) low binding capacity--approximately 10 fmol/mg of protein of nonfractionated cytosol; 3) pronounced specificity of affinity for active A (DHT, R1881, testosterone); 4) large size of the protein molecule (6.5 +/- 0.25 nm); 5) ability to decrease this size to 3.2 +/- 0.08 nm in a high ionic strength buffer; 6) precipitation at low concentrations of ammonium sulfate: 7) strong interaction with heparin-Sepharose. The properties of the delta 4-A-binding component do not coincide with those of RA: it has a low Ka for 3H-delta 4-A (1.15 +/- 0.5 X 10(6) M-1), a high binding capacity (1.22 +/- 0,12 pmol/mg of protein of nonfractionated cytosol) and can bind various delta 4-3-ketosteroids irrespective of the degree and nature of their biological activity. It was concluded that preliminary isolation of rat liver RA on heparin-Sepharose can be used for differential identification and characterization of this protein.     

Three-dimensional reconstruction of alveoli in the rat lung for pressure-volume relationships

To determine alveolar pressure-volume relationships, alveolar three-dimensional reconstructions were prepared from lungs fixed by vascular perfusion at various points on the pressure-volume curve. Lungs from male Sprague-Dawley rats were fixed by perfusion through the pulmonary artery following a pressure-volume maneuver to the desired pressure point on either the inflation or deflation curve. Tissue samples from lungs were serially sectioned for determination of the volume fraction of alveoli and alveolar ducts and reconstruction of alveoli. Alveoli from lungs fixed at 5 cmH2O on the deflation curve (approximating functional residual volume) had a volume of 173 X 10(3) microns3, a surface area of 11,529 microns2, a mouth opening diameter of 72.7 microns, and a mean caliper diameter of 91.8 micron (SE). Alveolar shape changes during deflation from total lung capacity to residual volume was first (30 to 10 cmH2O) associated with little change in the diameter of the alveoli (102.7 +/- 2.4 to 100.3 +/- 3.3 microns). In the range overlapping normal breathing (10 to 0 cmH2O) there was a substantial decrease in diameter (100.3 +/- 3.3 to 43.3 +/- 2.3 microns). These measurements and others made on the relative changes in the dimensions of the alveolus suggest that the elastic network, particularly around the alveolar ducts, are predominant in determining lung behavior near the volume expansion limits of the lung while the elastic and surface tension properties of the alveoli are predominant in the volume range around functional residual capacity.