Suppression of phase transitions at low temperature by chromium substitution in vanadium spinel Fe(V1-x Cr x )2O4.

Synchrotron powder diffraction, magnetization, and specific heat measurements have been used to investigate the structural and magnetic phase transitions in the spinel-type vanadate Fe(V1-x Cr x )2O4 (0.0 ⩽ x ⩽ 1.0). We observed five different transitions in our polycrystalline samples. The canted-type ferrimagnetic phase transition accompanied by the lattice distortion was suppressed by Cr substitution (x = 0.2). Additionally, high-resolution synchrotron powder diffraction revealed that the low-temperature orthorhombic phase appears in FeV2O4 below 30 K and disappears by subtle Cr doping. In contrast, for x ⩾ 0.7, we observed a different magnetic transition of possibly conical-type ferrimagnetic ordering that did not induce significant lattice distortion at the transition temperature. We performed structural refinements for low-temperature phases and suggest that the crystal system of Fe(V1-x Cr x )2O4 at 15K is an orthorhombic lattice for all x values. In the orthorhombic phase, a unique behaviour was observed, with the lattice constants a and b approaching each other as Cr doping increased. This behaviour can be explained by the change of orbitally ordered states of the Fe(2+) ions.

Beta-blockade prevents ventricular failure following aortic regurgitation in rabbits.

This study investigated the effects of chronic beta-blockade on the pathophysiology of heart failure following induction of aortic regurgitation (AR). Nine rabbits with AR were administered propranolol continuously for 7 days (AR+P), 8 rabbits with AR received vehicle for the same period (AR+C), and 7 rabbits underwent sham operation. Cardiac output was lower and the left-ventricular end-diastolic pressure was higher in AR+C than in sham-operated rabbits, but there was no difference in the right-ventricular end-diastolic pressure between the two groups. Down-regulation of beta-adrenoceptors was observed in the left ventricle, but not in the right ventricle. All of these variables were reversed in AR+P. In left-ventricular failure produced by AR, (1) the augmentation of adrenergic drive occurred selectively in the left ventricle, and (2) propranolol blunted adrenergic drive and played a protective role against myocardial damage.

[Acute retrograde dissection of the aorta is a formidable complication in retrograde perfusion through the femoral artery].

To avoid this complication, we applied a Nelaton catheter (Imamura, Tokyo, Japan: standard type) as a guide to insert an arterial perfusion cannula (Bardic) into the femoral artery. Initially, the Nelaton catheter is accurately placed into the femoral artery through a purse string suture without applying vascular clamps on the artery or its branches. Then the perfusion cannula is advanced using the Nelaton catheter as a guide. We believe this procedure will avoid acute retrograde dissection of the aorta since it protects the femoral artery from injuries caused by the vascular clamps or the tip of the perfusion cannula.

Effect of chronic digoxin on beta-adrenergic receptors in rabbits with heart failure.

This study investigated the effect of chronic digitalis glycoside use on beta-adrenergic sympathetic activities in heart failure. Twenty-two Japanese white rabbits were anesthetized by intravenous injection of chloral hydrate. Aortic regurgitation (AR) was produced by perforating aortic valves in 14 rabbits. Digoxin was given for 1 week to 7 rabbits with AR (AR + Dig) and saline to 7 rabbits with AR (AR + C). Sham operation was performed in the remaining 8 rabbits (S). The left ventricular end-diastolic pressure was higher in AR + C than S (p < 0.05). It was lower in AR + Dig than AR + C (p < 0.05). Cardiac output was lower in AR + C than S (p < 0.05). There was no difference between AR + Dig and S. Both the left ventricular end-diastolic and end-systolic diameters were larger in AR + C (p < 0.05) than S, but they were similar between AR + Dig and S. Plasma norepinephrine level was lower in AR + Dig than AR + C. Myocardial beta-adrenergic receptors number determined by radioligand binding assay using 30-800 pM 125I-iodocyanopindolol was lower in AR + C than S (28.8 +/- 7.9 vs. 69.9 +/- 12.3 fmol/mg protein, p < 0.05). It was higher in AR + Dig (39.9 +/- 9.8) than AR + C (p < 0.05). Myocardial norepinephrine content was lower in both AR + C (p < 0.05) and AR + Dig than S (p < 0.05). Thus, digitalis glycosides exert favorable effects on beta-adrenergic sympathetic activities in addition to the effects on hemodynamic variables in this animal model of heart failure.

Abnormal beta-adrenergic transmembrane signaling in rabbits with adriamycin-induced cardiomyopathy.

We investigated alterations in the beta-adrenergic receptor-adenylate cyclase system in rabbits with congestive heart failure induced by adriamycin cardiotoxicity. A dose of 24 mg/kg adriamycin was administered over 16 weeks in 16 rabbits. Five of them died and 4 of them could not tolerate the full dose of adriamycin. Complete data were obtained in the remaining 7 rabbits. Another 7 rabbits received physiological saline for the same period and served as controls. Plasma norepinephrine concentration increased in adriamycin-treated rabbits, but not in the control rabbits. Cardiac output was lower in the adriamycin-treated group than in the control group. Both the left and right ventricular end-diastolic pressure were higher in the adriamycin-treated group. The density of myocardial beta-adrenergic receptors and the norepinephrine content were reduced in both ventricles in the adriamycin-treated group. Basal and isoproterenol-, sodium fluoride- and forskolin-stimulated adenylate cyclase activities were lower in the adriamycin-treated group. Thus, alterations in beta-adrenergic signaling occurred in both ventricles in animals with chronic biventricular failure induced by adriamycin. These may be the result of post-receptor abnormalities, including abnormalities of guanine nucleotide-binding proteins or of the catalytic unit of adenylate cyclase.

Effects of methylprednisolone on hemodynamics and beta-adrenergic receptor signaling in rabbits with acute left ventricular failure.

Studies suggest that corticosteroids may restore the responsiveness to catecholamines in hypotensive patients. Since the significance of this promising intervention in congestive heart failure remains to be explored, we determined the effects of methylprednisolone, a potent activator of beta-adrenergic receptor signaling, on hemodynamics and beta-adrenergic receptor regulation in an animal model of heart failure. Acute left ventricular overloading was produced by aortic regurgitation (AR) in 22 Japanese white rabbits. Eleven animals received an intravenous administration of methylprednisolone (AR + PSL), while 11 received saline (AR + C) for 1 week. A sham operation was performed on 10 other rabbits (S). There was no difference between the AR + C and AR + PSL groups in the decrease in aortic diastolic pressure immediately after the production of AR. The aortic diastolic pressure and regurgitant fractions were also similar in the two groups. The left ventricular end-diastolic and end-systolic dimensions were both larger, and the left ventricular end-diastolic pressure was higher in AR + C or AR + PSL than in S rabbits. Between the AR + C and AR + PSL, there were no differences in any of these variables. Cardiac output was lower in AR + C, but not in AR + PSL, than in S. Cardiac output in AR + PSL was significantly higher than in AR + C. The myocardial concentration of norepinephrine and the number of beta-adrenergic receptors were both lower in the AR + C and AR + PSL than in the S groups. The number of receptors in AR + PSL was higher than in AR + C. Maximal isoproterenol-stimulated adenylyl cyclase activity was similar in the AR + C and AR + PSL groups. Results suggest methylprednisolone yielded some benefits, including an increase in cardiac output and in total beta-adrenergic receptor number, in this animal model of heart failure.

Myocardial sympathetic denervation prevents chamber-specific alteration of beta-adrenergic transmembrane signaling in rabbits with heart failure.

OBJECTIVES: The purpose of this study was to assess the effect of myocardial sympathetic denervation on the chamber-specific alteration of beta-adrenergic signaling in left ventricular failure in rabbits. BACKGROUND: Local abnormalities in sympathetic nerve terminals, including the neuronal reuptake of norepinephrine, are thought to be responsible for the chamber-specific regulation of beta-adrenergic signaling in heart failure. METHODS: Sixteen rabbits were given 6-hydroxydopamine, 25 mg/kg body weight intravenously on days 1 and 2 and 50 mg/kg intravenously on days 7 and 8. Another 16 rabbits received vehicle. Aortic regurgitation was induced in eight of the 6-hydroxydopamine-treated and eight of the vehicle-treated rabbits on day 14. Another eight of the 6-hydroxydopamine-treated and eight of the vehicle-treated rabbits underwent a sham operation. The hearts were excised for biochemical analysis on day 21. RESULTS: Hemodynamic characteristics on day 21 showed left ventricular failure in both the aortic regurgitation groups. The plasma norepinephrine concentration on day 21 was higher in both the aortic regurgitation groups than in the sham groups. The beta-adrenoceptor densities and isoproterenol plus 5'-guanylylimidodiphosphate-, 5'-guanylylimidodiphosphate- and sodium fluoride-stimulated adenylyl cyclase activities were decreased only in the failing left ventricle of the vehicle-pretreated aortic regurgitation group, but in both ventricles of the 6-hydroxydopamine-pretreated aortic regurgitation group. The basal and forskolin-stimulated adenylyl cyclase activities were similar in both the aortic regurgitation groups and in the sham groups. CONCLUSIONS: Sympathetic denervation prevented chamber-specific alterations in beta-adrenergic signaling in acute left ventricular failure. Local loss of sympathetic nerve endings, and especially the defective neuronal norepinephrine reuptake, are likely to be responsible for the chamber-specific alteration of the beta-adrenoceptor-G protein-adenylyl cyclase system in heart failure in rabbits.

[Changes in nurses' knowledge and attitudes regarding AIDS in Mie Prefecture, Japan].

In 1990, we conducted a questionnaire survey showing that many nurses had incorrect knowledge of AIDS resulting in inappropriate attitudes toward AIDS patients. Following the first survey conducted in 1990, nurses were given various forms of AIDS education. The effectiveness of the AIDS education requires assessment. Therefore a second questionnaire survey was performed in 1993 to assess changes in nurses' knowledge and attitudes regarding AIDS. The same questionnaire as used in the first survey was sent to a random sample of nurses working at general hospitals in Mie Prefecture, Japan. The questionnaire covered knowledge of AIDS, psychological responses, attitudes and conduct around infected persons and measures against AIDS. Results of both questionnaire surveys showed that the majority of nurses acquired their knowledge predominantly from the mass media, and a large number of nurses worried that AIDS would spread in Japan. Almost half of the nurses were worried that they might be infected with AIDS. The second survey showed that nurses who acquired knowledge of AIDS from printed material, pamphlets and other educational resources, including lectures had increased. In 1993, many more nurses had accurate knowledge compared to the number in the first survey. In 1993 the number of nurses who discriminated against AIDS patients and HIV-infected persons had decreased.

Experimental methods for immunization and challenge in antigenicity studies in guinea pigs.

Optimal experimental methods for antigenicity studies in guinea pigs were investigated on: (1) the effects of different immunizing methods using complete or incomplete Freund's adjuvants (CFA or IFA), and various injection sites, the number of immunizations, the immunizing doses, and the immunizing periods, (2) the relationship between the severity of active systemic anaphylaxis (ASA) reactions and passive cutaneous anaphylaxis (PCA) titers, (3) positive control for oral administration, and (4) the effects of incubation mixture of drug and serum protein as the challenge for the ASA assay. The following results provided useful information for designing more appropriate methods for antigenicity studies: (1) The optimal immunization method for benzylpenicillin (PcG), cephaloridine, 2,4,6-trinitrobenzene sulfonic acid and adriamycin, which were selected as positive controls for low molecular medicines in this experiment, involved subcutaneous administration of 1 ml of a test substance in CFA (1st immunization) or IFA (2nd and 3rd immunizations) at two doses, 1 and 10 mg/animal, 3 times at 2-week intervals on the back of a guinea pig. Blood collection for PCA assay was needed 2 weeks after the last immunization, and ASA assay, 1 or 2 days after the blood collection. (2) The insensitivity of ASA reactions in bovine serum albumin-immunized animals with very high PCA titers was overcome by increasing the challenge antigen dose from 1 to 10 mg/animal. (3) Most animals administered lysozyme at 0.1, 1 or 10 mg/animal by gavage for 2 weeks or more showed ASA and PCA reactions. (4) Incubation of a mixture of 20 mg/ml of PcG and 2 mg/ml of guinea pig serum albumin for 4 hr was the most effective as challenge for the induction of ASA reaction in PcG-immunized guinea pigs.

Effect of the angiotensin-converting enzyme inhibitor alacepril on ventricular function and beta-adrenoceptor number in rabbits with aortic regurgitation.

This study was performed to determine the effects of the angiotensin-converting enzyme inhibitor alacepril on hemodynamic variables and beta-adrenoceptor number in rabbits with heart failure induced by aortic regurgitation. Aortic regurgitation was induced by perforation of the aortic valve in 12 rabbits. Sixty mg/kg of alacepril was administered by gastric tube for 7 days after manifestation of aortic regurgitation to 6 rabbits (group AR + A). The other 6 rabbits with aortic regurgitation were administered vehicle in the same fashion (group AR + C). Seven rabbits underwent sham operation (group S). One week after induction of aortic regurgitation left ventricular end-diastolic pressure was higher and cardiac output was lower in AR + C than in S. End-diastolic and end-systolic left ventricular diameter were larger and left ventricular weight was also higher in AR + C than in S. For each of these parameters, the opposite findings were obtained from a comparison of AR + A and S. Myocardial beta-adrenoceptor density and norepinephrine content were reduced in AR + C, but were restored in AR + A. These findings indicate that alacepril has beneficial effects on ventricular remodeling and function, and on sympatho-neuronal regulation in the volume-overloaded myocardium.

Abnormalities in sympathoneuronal regulation are localized to failing myocardium in rabbit heart.

OBJECTIVES: This study investigated the differences in sympathoneuronal regulation between acute left ventricular failure and chronic biventricular failure to determine whether an increase in plasma norepinephrine concentration plays a primary role in the genesis of the desensitization phenomenon in heart failure. BACKGROUND: It remains to be determined whether plasma norepinephrine plays a primary role in the pathogenesis of sympathetic desensitization in heart failure in vivo. METHODS: Acute left ventricular failure was induced by aortic regurgitation in seven rabbits. Chronic heart failure was induced by adriamycin treatment in another seven rabbits. RESULTS: Cardiac output was lower in rabbits with aortic regurgitation than in seven sham-operated rabbits. Left ventricular end-diastolic pressure was higher in rabbits with aortic regurgitation, but no significant difference in right ventricular end-diastolic pressure was observed. Beta-adrenoceptor density and norepinephrine concentration in the left ventricular myocardium were lower in rabbits with aortic regurgitation; no such differences were observed for the right ventricular myocardium. Cardiac output was lower in adriamycin-treated rabbits than in seven control rabbits. Both left and right ventricular end-diastolic pressures were higher in experimental rabbits than in control rabbits. Myocardial beta-adrenoceptor density and norepinephrine content were reduced in both ventricles. CONCLUSIONS: In chronic heart failure induced by adriamycin, sympathoneuronal activity was altered in both ventricles, whereas in acute left ventricular failure induced by aortic regurgitation, sympathoneuronal activity was affected only in the left ventricle despite a similar increase in plasma norepinephrine concentration in both animal models. Local abnormalities in sympathoneuronal regulation in failing myocardium therefore appear to be responsible for these phenomena.

Sequential changes in sympatho-neuronal regulation and contractile function following aortic regurgitation in rabbit heart.

This study was designed to determine the sequential changes in sympatho-neuronal regulation and contractile function of hearts exposed to volume overloading. Aortic regurgitation was produced by perforation of the aortic valve in 20 rabbits. Another 20 rabbits underwent sham operation. They were randomly assigned to a 1-day group, a 1-week group, and a 4-week group. Haemodynamics, myocardial beta-adrenoceptor binding number and catecholamines were measured in each period after production of aortic regurgitation. Left ventricular end-diastolic pressure increased and cardiac output decreased progressively over the week following production of aortic regurgitation, but they returned towards normal during the subsequent 3 weeks. Left ventricular free wall thickness increased 4 weeks after production of aortic regurgitation, and plasma norepinephrine increased 1 day after the procedure. Maximal binding sites of myocardial beta-adrenoceptors (125I-iodocyanopindolol) were decreased 1 day and 1 week after production of aortic regurgitation. Myocardial norepinephrine was also reduced. After 4 weeks, both beta-adrenoceptor binding sites and myocardial norepinephrine content were restored. Alterations in sympatho-neuronal regulation are related to the compensatory processes in volume overloaded hearts.

In vitro cytotoxicity test for estimating non-ocular irritation dose of ophthalmic solutions.

The in vitro cytotoxicity test for estimating the non-ocular irritation dose of ophthalmic solutions was investigated. In the in vitro test, normal human epidermal keratinocytes (NHEK) in a confluent monolayer were incubated for 48 hr in a medium with test compounds. The concentration of a test compound which causes a 50% reduction in NHEK viability was determined as IC50 by MTT colorimetric assay. For comparison, the in vivo rabbit ocular irritation tests were carried out by the standard Draize method. The maximum concentration, which did not show any ocular irritation, was determined as DS0. The results showed the correlation coefficient between the IC50 values and the DS0 values for 19 test compounds to be 0.82. However, the correlation coefficients for 10 compounds, which have IC50 values of less than 300 micrograms/ml, and for 7 alcohols were 0.99. The IC50-DS0 correlation curves obtained could be utilized as the critical concentrations for ocular irritation. These results suggest that our in vitro/in vivo test can estimate non-ocular irritation dose of the ophthalmic preparations in advance of the in vivo tests.

Three distinctive activities of human triceps surae muscle during the stance phase in treadmill walking and running.

Activity of human triceps surae muscle (TS) during locomotion was investigated in relation to the muscle shortening and lengthening contractions. Length changes in the TS were presumed from its girth recorded using a mercury-in-silastic gauge wrapped around the muscle belly. The muscle girth during the stance phase resulted in three peaks corresponding to the actions of heel contact, weight support and toe kick. These peak heights were apparently larger than the girth level in the perpendicular standing posture. Three girth increases in running appeared in the process of ankle dorsiflexion. During walking, girth increases on weight support and toe kick were seen in the same phase. The TS through the stance phase is considered to always contract into a shortening state less than the muscle length in the perpendicular standing posture. These muscle activities are probably imposed to resist the muscle stretching. Therefore, it was suggested that the TS contracts eccentrically, with no lengthening contraction.

Blood flow changes following brief concentric contractions of human calf muscles.

The present study was designed to clarify the venous return, filling velocity (Maximum Inflow Rate: MIR), and post-contraction hyperemia following brief concentric contractions of human calf muscles, using a double-stranded mercury-in-silastic gauge. The subject, in a prone position, extended the right ankle joint to 5, 10, 15, and 20 degrees at 20 degrees.sec-1 with a load of 20% of maximum voluntary contraction in ankle extensors. There was a significant relation between increase in calf girth at contraction and the amount of decrease, increase, total change (decrease plus increase), and MIR in calf volume after relaxation, and also between the MIR and amount of decrease, increase and total change in calf volume. The amplitude of the volume pulse wave apparently increased immediately after muscle relaxation, then progressively decreased. The maximum value appeared with the greatest increase in ankle extension. It was found that with increased muscle contraction, there was accelerated venous return, filling velocity of blood, and post-contraction hyperemia. Pulsatile blood flow into muscle tissue after brief muscle contractions might be qualitatively measured by the amplitude of the volume pulse wave.

Excess venous return immediately after brief contraction of human calf muscles.

Venous return immediately after brief contraction of human calf muscles was measured. The subject extended his ankle joint in the range of 20 degrees for one second against loads of 10, 20, 30, and 40% of the maximum voluntary contraction in the ankle extensors. Venous return was determined by the difference between the increase in calf volume with (calf blood flow: CBF) and without (maximum inflow rate: MIR) thigh venous occlusion immediately after muscle relaxation. CBF and MIR progressively increased with the loads, and CBF was significantly greater than MIR. The level of venous return was correlated with the increase in the load. Transient increase in venous return was not associated with muscle pumping. Excess venous return should counteract arterial inflow and contribute to maintenance of equilibrium of the transmural pressure between muscle tissue and the capillaries.

The effects of detergent on the contractility and ultrastructure of frog skeletal muscle.

The contractility of detergent-treated frog skeletal muscle and its ultrastructure were studied. Triton X-100 and Brij-58 were used as nonionic surface active substances. The concentrations of the detergent solutions were adjusted so that the trains of the twitch tensions would continue for about 10 min. The duration of the twitch tensions was about 10 min when the muscles were soaked in 0.1 mM (0.006%) Triton or in 2.5 mM (0.280%) Brij solution. The twitch tensions did not recover upon returning the muscles to the normal Ringer solution after treatment of the detergents. Rapid cooling of muscle that had been soaked in a 1.0 mM caffeine Ringer solution for 10 min provoked a marked contracture (RCC) in 0.1-0.2 mM Triton-treated preparation. No such contracture was obtained in 1.0-2.5 mM Brij-treated preparation. In ultrastructural findings of the Triton-treated muscle, some structural changes were observed in the transverse tubule and the junctional gap, but not in the terminal cisternae. Brij-treated muscle showed damage of each of these membranes, including the terminal cisternae. These findings suggest that the two detergents have different surface activities on the internal membrane system of the skeletal muscle. The biological activities of the membrane remained even after the treatment of Triton with a suitable concentration.

Myofibrils and transverse tubules in glycerol-treated frog skeletal muscle.

Effects of glycerol (400 mM) on the structure of frog skeletal muscle were reported based on measurements of the diameters of myofibrils and transverse tubules (T-tubules). The diameter of the myofibrils decreased to about 0.58 micron from the normal size of 0.79 micron during glycerol treatment, but the spacing between the myofibrils became wider. The size did not recover to the initial value even after return of the muscle to the Ringer solution. T-tubule diameters increased to 35-55 nm from the normal size of about 30 nm in glycerol-treated muscle, and the size was maintained after return of the muscle to the Ringer solution.