Influence of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors on mitochondrial respiration in rat liver during ischemia

Effects of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, pravastatin and simvastatin, on mitochondrial respiration in ischemic rat liver were examined. Either vehicle, pravastatin (2 or 4 mg/kg per day), or simvastatin (1 or 2 mg/kg per day) was orally administered for 3 weeks. Liver ischemia was induced by cessation of the systemic circulation for 60 min. Liver mitochondria were isolated and the respiration was determined by polarography using glutamate and succinate as substrates. In the vehicle-treated group, ischemia drcreased ZO3, respiratory control index (RCI: QO3/QO4), and ADP/O ratio. Pretreatments with pravastatin and simvastatin enhanced the decreases in QO3 measured with either glutamate or succinate, and in ADP/O ratio measured with succinate. Because of decreasing QO4, HMG-CoA reductase inhibitors did not modify the changes in RCI due to ischemia. There were no significant differences in respiratory indices between pravastatin- and simvastatin-treated groups. In conclusion, HMG-CoA reductase inhibitors may enhance respiratory impairment of liver mitochondria under pathophysiological conditions, such as ischemia.

Pituitary adenylate cyclase-activating polypeptide: effects on pancreatic-adrenal hormone secretion and glucose-lipid metabolism in normal conscious dogs

The effects of pituitary adenylate cyclase-activating polypeptide (PACAP) on plasma insulin, glucagon, catecholamine, cortisol, glucose, triglyceride (TG), free fatty acid (FFA), cholesterol, and cyclic adenosine monophosphate (cAMP) concentrations were examined in unanesthetized normal dogs. A bolus injection of 6 pmol/kg PACAP27 elicited a transient increase in plasma insulin, epinephrine, and norepinephrine concentrations, with a peak value at 2 minutes after injection. Injections of 60 and 600 pmol/kg caused greater increases in these hormone concentrations in a dose-dependent manner. The plasma cortisol concentration was not changed by a bolus injection of 6 pmol/kg PACAP27, and was gradually increased by injections of 60 and 600 pmol/kg. Significant increases were observed from 10 and 5 minutes after the injection of 60 and 600 pmol/kg, respectively. The plasma glucagon concentration was not changed by either 6, 60, or 600 pmol/kg. The plasma glucose concentration decreased with 60 pmol/kg PACAP27 and increased with 600 pmol/kg. The plasma FFA concentration was increased gradually, with a peak value at 10 minutes after the injection, in a dose-dependent manner. The plasma TG concentration was slightly increased with 600 pmol/kg with a peak value at 10 minutes, although plasma cholesterol did not change. The plasma cAMP concentration increased significantly with 600 pmol/kg PACAP27, but not with 6 or 60 pmol/kg. These effects of PACAP27 were observed with a bolus injection of PACAP38 of an equal potency. Infusion of graded doses of PACAP27 (1, 3, and 10 pmol/kg/min every 20 minutes) caused a gradual increase in plasma cortisol, catecholamine, FFA, and cAMP concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

ATP-dependent proteolysis in yeast mitochondria

An ATP-dependent proteolysis system in yeast mitochondria was characterized by examining the hydrolysis of mitochondrial translation products in isolated mitochondria. Degradation of [35S]methionine-labeled polypeptides synthesized in isolated yeast mitochondria was activated by exogenously added ATP. ADP, GTP, and CTP substituted for ATP to some extent, but nonhydrolyzable ATP analogues did not. Adenosine-5'-O-(3'-thio-triphosphate) effectively competed with ATP as activator. Carboxyatractyloside, an inhibitor of adenine nucleotide translocation across the mitochondrial inner membrane, and the metal chelator o-phenanthroline inhibited the ATP-dependent proteolysis. The latter inhibition was abolished by subsequent addition of Mn2+ or Co2+ but not Ca2+ or Zn2+. Hemin inhibited the ATP-dependent proteolysis of mitochondrial translation products with a half-maximum inhibition at 12 microM. Analysis by SDS-polyacrylamide gel electrophoresis showed that [35S]methionine-labeled polypeptides were rapidly degraded into low-molecular-weight species. Submitochondrial particles retained the ATP-dependent proteolytic activity and had the same spectrum of inhibitors as intact mitochondria except for a reduced effect of carboxyatractyloside. These results indicate that yeast mitochondria contain an ATP-dependent and hemin-sensitive proteolysis system which is associated with the inner membrane and can hydrolyze mitochondrial translation products, and that a chelator-sensitive protease is probably involved in this system.

[Efficacy of combination therapy against MRSA in Ibaraki Prefecture]

Clinical efficacies of fosfomycin (FOM) or arbekacin (ABK) plus beta-lactam combination therapies against methicillin-resistant Staphylococcus aureus (MRSA) infections were examined in 15 major hospitals in Ibaraki Prefecture. The subjects were 54 inpatients from January 1991 to April 1993, and most of them showed moderate to severe infections with underlying diseases. MRSA alone was isolated from 23 patients and the other 31 patients had polymicobes including MRSA. Pseudomonas aeruginosa was the most frequent among the co-isolated strains. The number of patients treated with FOM and cefmetazole (CMZ) was 22 (Group C) and that with FOM and flomoxef (FMOX) was 25 (Group F). CMZ or FMOX was administrated 60 minutes after FOM administration. To 8 nonresponding patients in Groups C and F and 7 nonresponders to the other therapies, ABK and ceftazidime (CAZ) or ABK and piperacillin (PIPC) were treated simultaneously (Group A). The clinical efficacies of Groups C and F were 63.6% and 64%, respectively. The bacteriological efficacies (eradication rates) of both groups including microbial substitutions were 42.9% in the former and 56.5% in the latter. No statistical differences were observed in the clinical and the bacteriological efficacies between Groups C and F. The clinical and bacteriological efficacies in Group A were 66.7% and 46.2%, respectively. No side effects were observed in any cases. Mild disturbances of hepatic functions were observed in 2 cases of Groups C and F, and there were no abnormal laboratory test results in Group A.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of diazoxide on KCl- and norepinephrine-induced contraction in isolated rat aorta

Diazoxide produced endothelium-independent relaxations of the rat aorta contracted by either low concentrations of KCl or norepinephrine (NE). However, contraction with a high concentration of KCl was not altered by diazoxide. Hydrochlorothiazide did not affect the contraction induced by either KCI or NE. Tetraethylammonium and glibenclamide inhibited the relaxations of the aorta induced by diazoxide. Diazoxide significantly reduced the phasic and tonic contractions under Ca2+-free conditions induced by NE and CaCl2 following NE addition, respectively. These results suggest that diazoxide dilates vascular smooth muscle by opening the ATP-sensitive K+ channels and inhibiting receptor-operated Ca2+ movements from either the intracellular store sites or extracellular space to the cytoplasm, but not antagonizing voltage-dependent Ca2+ channels directly.

Aminopeptidase Y, a new aminopeptidase from Saccharomyces cerevisiae. Purification, properties, localization, and processing by protease B

A novel aminopeptidase, termed aminopeptidase Y, was purified from yeast, Saccharomyces cerevisiae, as two molecular forms of 70 and 75 kDa, which were identical immunologically, catalytically and in N-terminal sequence up to 14 residues. They contained 0.81 and 0.84 mol of zinc atom/mol of protein, respectively. N-Gly-canase generated a single 53-kDa species from both forms, and endoglycosidase H gave a 54-kDa species. Immunoblotting after subcellular fractionation showed that aminopeptidase Y is localized in the vacuole/lysosome-soluble compartment as the 70-kDa form. Aminopeptidase Y hydrolyzed all amino acid-4-methylcoumaryl-7-amides (MCA) examined, especially Lys- and Arg-MCA. Dipeptidyl-MCAs were far more rapidly hydrolyzed (Lys-Ala-MCA/Lys-MCA = 350-fold, Arg-Arg-MCA/Arg-MCA = 150-fold). Hydrolysis of amino acid-MCAs or dipeptides was markedly enhanced by Co2+, whereas that of dipeptidyl-MCAs, tripeptides, and larger peptides was inhibited. Rabbit anti-aminopeptidase Y antiserum adsorbed over half the aminopeptidase activities in vacuolar extract from wild-type yeast cells. ABYS1 mutant cells from which the genes of four vacuolar proteases had been deleted contained aminopeptidase Y as a 74-kDa proform. This was converted to the mature form (70 kDa) by vacuolar extract of wild-type cells and by purified yeast vacuolar protease B.

Molecular cloning of the aminopeptidase Y gene of Saccharomyces cerevisiae. Sequence analysis and gene disruption of a new aminopeptidase

A yeast genomic DNA encoding a new vacuolar aminopeptidase, aminopeptidase Y, was isolated by using a cDNA fragment obtained by screening the lambda gt11 yeast cDNA library with anti-aminopeptidase Y antibody. The DNA sequence encodes 537 amino acids. The "mature" protein, whose NH2-terminal sequence was determined previously by analysis of the purified enzyme, consists of 481 amino acids, and the calculated molecular weight (52,900) coincides with the value obtained by SDS-polyacrylamide gel electrophoresis of the enzyme after removal of sugar chains, 53 kDa. The 56-residue preprosequence was divided into two parts by putative processing sites for signal peptidase and conversion to the mature form; the 21-residue presequence has a hydrophobic stretch which may function as the signal sequence for transit through the endoplasmic reticulum, and the 35-residue prosequence (4013 Da) accounts for the 4-kDa difference between proaminopeptidase Y in the vacuolar proteases-deleted ABYS1 mutant and wild-type mature enzyme. The aminopeptidase Y gene was localized on chromosome II by genetic mapping. A deletion mutant was constructed by disrupting the aminopeptidase Y gene. Vacuolar aminopeptidase activities toward Ala-4-methylcoumaryl-7-amide (MCA) and Lys-MCA were 13 and 20% of wild-type, and those in the presence of Co2+ were 2.2 and 2.8%, respectively. Mutant cells showed no ability to hydrolyze Lys-Ala-MCA to Lys and Ala-MCA, although vacuolar carboxypeptidase Y activity was similar to that in wild-type cells.

Effect of diazoxide on serum and tissue electrolyte levels in rats with deoxycorticosterone acetate-induced hypertension

Effects of diazoxide, a benzothiadiazine derivative, on the blood pressure, excretion of Na+, K+, and Ca2+, and the levels of these electrolytes in serum, kidney, and aorta were studied in rats with deoxycorticosterone acetate (DOCA)-induced hypertension in comparison with rats treated with hydrochlorothiazide. After a lateral nephrectomy, 5 mg kg-1 of DOCA was injected subcutaneously three times a week. Drinking water for the rats injected with DOCA contained 1% NaCl. Systolic blood pressure in the DOCA-induced hypertensive rats became about 170 mmHg, with associated elevation of serum level of Na+ 7 weeks after the treatment, whereas that in the normotensive rats was about 100 mmHg. In the DOCA-hypertensive rats, urinary output, and renal excretion of Na+ and Ca2+ increased, and aortic tissue level of Ca2+ decreased as compared with those in the normotensive rats. After 7 weeks of the treatment, diazoxide (10 mg kg-1) or hydrochlorothiazide (10 mg kg-1) was injected intravenously. Diazoxide decreased the blood pressure in both DOCA-hypertensive and normotensive rats, whereas hydrochlorothiazide decreased it only in the DOCA-hypertensive rats. Diazoxide recovered the tissue aortic Ca2+ level that had been decreased by hypertension to that in the normotensive rats. Diazoxide may improve Ca2+ perturbation in the vascular smooth muscle due to DOCA-induced hypertension.

[Effects of inhaled furosemide after indomethacin premedication on bronchial hyperresponsiveness in patients with chronic congestive heart failure]

We studied the effects of inhaled furosemide (40 mg) on bronchial responsiveness to acetylcholine (ACh) in patients with chronic congestive heart failure who had been premedicated with indomethacin (75 mg/day) for five days. The measurement of bronchial responsiveness was performed by inhaling doses of ACh and calculating the provocative concentration of ACh needed to cause a 20% fall in FEV1.0 (PC20-ACh). Inhaled furosemide (N = 11) had no effect on resting pulmonary function but did cause a significant increase in the median value of PC20-ACh, from 7.58 to 11.9 mg/ml (p < 0.01). Irrespective of premedication with indomethacin, inhaled furosemide reduces bronchial hyperresponsiveness to ACh in patients with chronic congestive heart failure. Therefore, we speculate that the mechanism of bronchial hyperresponsiveness noticed in our patients is not related to prostaglandins such as PGE2 or PGI2.

Acute abdominal symptoms caused by hemorrhagic necrosis of a pheochromocytoma: report of a case

The diagnosis of pheochromocytoma is often difficult in a patient presenting with acute illness but without the classical constitutional symptoms. We report herein the case of a woman who developed acute abdominal symptoms following hemorrhagic necrosis of a previously unsuspected pheochromocytoma. This patient underwent successful emergency resuscitation followed later by elective surgical resection of a right adrenal pheochromocytoma. A review of 27 other cases indicates that a fatal outcome is likely to result without the initiation of prompt and appropriate emergency treatment, followed later by removal of the tumor. Thus, early diagnosis is important not only for controlling hypertension, but also because performing a laparotomy on a patient with unrecognized hemorrhagic necrosis of pheochromocytoma can create a potentially lethal situation.

Solution structure of a de novo helical protein by 2D-NMR spectroscopy

The de novo design of proteins represents a critical test for our knowledge of protein structure. However, no structure of a successfully designed protein has yet been reported. This paper reports the design and the tertiary structure of a de novo 35-residue helix-loop-helix protein (ALIN), with helices arranged in an anti-parallel manner. For the helical region, we designed sequences that have high helicities even as isolated peptides. A flexible loop containing glycine residues was used to connect the two helices and the interhelical hydrophobic interaction was stabilized by the introduction of an SS-bridge. This arrangement of two consecutive helices bridged by a disulfide bond is not observed in any natural proteins. The protein is highly soluble and monomeric in aqueous solution. The structure of ALIN, determined by 1H-NMR and distance geometry calculation, agrees well with the design. In addition, the exchange rates of amide protons indicate the presence of stable hydrogen bonds in the helical region. ALIN is the first de novo designed protein with a stable tertiary fold confirmed by NMR.

The cell envelope structure of the lipopolysaccharide-lacking gram-negative bacterium Sphingomonas paucimobilis

From the cell envelope preparation of Sphingomonas paucimobilis two membrane fractions with different densities were separated by sucrose density gradient ultracentrifugation. The high-density fraction contained several major proteins, phospholipids, and glycosphingolipids, which are the only glycolipids of this lipopolysaccharide-lacking gram-negative bacterium. The low-density fraction showed many minor bands of proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and NADH oxidase activity was localized in this fraction. Combined with morphological data of vesicles formed by these membrane fractions, the high-density and low-density fractions were proposed to be an outer membrane and a cytoplasmic membrane, respectively. The localization of the glycosphingolipid was investigated also by means of immunoelectron microscopic analysis using a glycosphingolipid-specific antibody. The glycosphingolipid was shown to localize at the cell envelope, and the antigenic sugar portion was exposed to the bacterial cell surface. From these results the glycosphingolipid was assumed to have a function similar to that of the lipopolysaccharide of other gram-negative bacteria.

[The effects of short and long duration of hypothyroidism on prolactin secretion in rats]

The aim of the present study was to evaluate the time-dependent effect of an experimentally induced hypothyroid state on prolactin (PRL) secretion in rats. Treatment with radioactive iodine and propylthiouracil (PTU) resulted in reduced serum concentrations of total thyroxine and triiodothyronine, and increased serum TSH concentrations in rats one week after the start of the treatment. Basal serum PRL concentrations were not significantly altered in 1-, 2- and 4-week hypothyroid rats, whereas in 8-week hypothyroid rats, serum PRL concentrations were significantly reduced and remained depressed throughout 24 weeks of PTU ingestion. The PRL response to i.p. administration of haloperidol (0.5mg/kg) was significantly reduced after one week of PTU ingestion. When the duration of hypothyroidism was increased, there was a progressive fall in the PRL response to haloperidol that reached the lowest value after 12 weeks of PTU ingestion. The PRL response to an i.v. bolus injection of vasoactive intestinal peptide (VIP, 150 mu g/kg) was markedly reduced in hypothyroid rats after one week of PTU ingestion and reached the lowest value after two weeks. The PRL response to VIP was progressively recovered after treatment for 4 weeks with PTU, and reached the highest value in 24-week hypothyroid rats. However, the PRL response to VIP in 24-week hypothyroid rats was significantly lower than that in euthyroid rats. Serum PRL response to an i.v. bolus injection of beta -endorphin (450 mu g/kg) was significantly reduced in 8-week hypothyroid rats. Dopamine (DA) concentrations in the pituitary and the hypothalamus were not significantly altered in 2-week hypothyroid rats. In contrast, DA concentrations were significantly increased in both the pituitary and hypothalamus in 8- and 24-week hypothyroid rats. These findings observed in hypothyroid rats were reversed by the administration of thyroxine and triiodothyronine for 9 days. The present results support a modulatory role for thyroid status in regulating the concentration of DA in the pituitary and the hypothalamus, and consequently on PRL secretion by the pituitary. This suggests that PRL releasing factors do not appear to play a major role in PRL secretion in hypothyroid rats. These data also indicate that alterations in PRL secretion and DA concentrations in the pituitary and the hypothalamus in the hypothyroid state become more prominent as the duration of hypothyroidism increases.

[Adult case of bronchial asthma induced by chironomid midges]

A 48-year-old woman who was diagnosed to have bronchial asthma induced by chironomid midges is reported. In spring of 1985, massive growth of chironomid midges occurred in the river beside her house. Since then, moderate growth has occurred in every spring or summer. She had wheezing attacks every May or June since June 1986. On May 2, 1991, she was hospitalized because of exacerbation of wheezing and dyspnea. Wheezing attacks were improved by appropriate medical treatment during hospitalization. Examination was performed during the state of stable clinical symptoms. RAST scores to Chironomus thummi thummi (CTT) and Chironomus plumosus (CP) were 4 and 3, respectively. Allergic skin reaction showed the threshold dilution of CP of 10(-6). CP skin test concomitantly provoked a mild acute asthma attack. The midges found swarming around her house were identified as Chironomus nippodorsalis. According to her clinical history and allergic skin reactions followed by acute asthmatic attack, this patient was diagnosed to have bronchial asthma induced by chironomid midges. Chironomid midge can be one of the inhalant allergens in adults.

[Resuscitation from experimentally induced hemorrhagic shock with hypertonic saline (effects on thoracic duct lymph flow and tissue oxygen tension)]

We compared the effect of hypertonic salt solution (7.2%, HS) with that of normal saline (NS) and lactated Ringer's solution (LR) for the treatment of hemorrhagic shock. We monitored hemodynamic parameters, thoracic duct lymph flow, and tissue oxygen tension over 3 hours after hemorrhage. Twenty-seven anesthetized mongrel dogs (0.5% halothane) were bled to an aortic pressure of 60 mmHg for 90 min following 40 mmHg for 30 min and then they were resuscitated with each solution. In NS group, the volume transfused was twice the bled volume, and in other two groups, each solution was transfused providing equal amounts of sodium as NS group. We found that hemodynamics were restored in HS group as well as in other two groups. On the other hand, thoracic duct lymph flow and tissue oxygen tension of renal cortex and liver increased significantly over other two groups. We conclude that small volume resuscitation with 7.2% NaCl may be effective in the initial treatment of hemorrhagic shock from the view of tissue circulation in vital organs.

Limitation of stunning in dog myocardium by nucleoside and nucleotide mixture, OG-VI

BACKGROUND

OG-VI is a nucleoside-nucleotide solution composed of 30 mM inosine, 30 mM cytidine, 30 mM sodium 5'-guanylate, 22.5 mM uridine, and 7.4 mM thymidine. It is expected to enhance the efficacy of intravenous hyperalimentation in surgically stressed patients. One of the main causes of ischemic myocardial damage is loss of adenine nucleotides from heart cells. The aim of the present study, therefore, was to examine the effect of OG-VI on myocardial mechanical function and energy metabolism in stunned myocardium.

METHODS

Pentobarbital-anesthetized dogs were subjected to 20 min ligation of the left anterior descending (LAD) coronary artery, followed by reperfusion for 30 min. OG-VI at 0.1 or 0.2 ml/kg/min or saline was infused from the left femoral vein throughout the experiment. The tissue levels of high-energy phosphates in the hearts were determined after 30 min reperfusion.

RESULTS

LAD flow, first derivative of left ventricular pressure (LVdp/dt), and segment function were increased by OG-VI in a dose-dependent manner. OG-VI infusion resulted in a significant improvement in LVdP/dt and segment shortening in the ischemic/reperfused myocardium compared with saline infusion. The levels of segment shortening with saline, 0.1, and 0.2 ml/kg/min OG-VI after reperfusion for 30 min were -0.3, 75, and 82% of the preligation levels, respectively. The tissue level of adenosine triphosphate (ATP) after reperfusion in OG-VI-infused animals was significantly higher than that in saline-infused animals.

CONCLUSION

OG-VI has a positive inotropic action, and its infusion results in a marked cardioprotective effect in stunned myocardium associated with the restoration of tissue ATP level.