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Biomedical subjects

S Sugano

Publications and source records attributed to S Sugano.

At least 181 records · Page 10Linked to original sources
PubMed1992

Effect of hyperlipidemia on cardiovascular responses to adrenergic stimulation in piglets.

This study was designed to assess the effect of hyperlipidemia on cardiovascular responses to adrenergic stimulation in a porcine model. Four-week-old piglets (n = 10) were divided into two groups; one fed a control diet and the other was fed an atherogenic diet for 8 weeks. Cardiovascular responses were evaluated to both norepinephrine (NE; 0.5 and 2.5 micrograms/kg) and isoproterenol (ISO; 0.1 and 0.5 microgram/kg) from simultaneous recordings of femoral arterial pressure, heart rate, left intraventricular pressure and left intraventricular dP/dt. It was found that no significant difference in the baseline values of cardiovascular function was observed between the control and hyperlipidemic groups. However, in the hyperlipidemic group as compared with the control group: 1) arterial blood pressure responses to NE were significantly increased (P less than 0.05), 2) cardiac contractile responses to NE and ISO were significantly potentiated (P less than 0.05), and 3) reflex bradycardia in response to increasing arterial blood pressure did not occur. These findings indicate that hyperlipidemia can potentiate the cardiovascular responses to adrenergic stimulation, whereas reflex cardiovascular regulation is somewhat altered by hyperlipidemia. Conceivably, these observations may have relevance to the possible role of the mechanism of the interaction of hyperlipidemia and hypertension in atherogenesis.

Analysis of Variance↗
PubMed1992

Characteristics of ventricular activation and recovery patterns in the rat.

Bipolar or unipolar epicardial and intraseptum electrograms were recorded from the in situ rat hearts with spontaneous sinus rhythm or myocardial electrical stimulation of 400 bpm in order to investigate the sequence and duration of cardiac activation in the rat. The ventricular epicardial isochronous maps in the rat showed the activation sequence comparable to those in humans and dogs, although the activation time (6 to 13 msec) of epicardium was approximately one-third of those of such species. The delay of activation between septum and ventricular surface in the rat was 5 to 8 msec, which was also shorter as compared with those in humans and dogs. However, the conduction velocity of the ventricular epicardium in the rat was approximately 40 cm/sec, mostly equal to that of humans. These findings might be accounted for by the possible presence of the bundle branch-purkinje system, at least functionally, similar to humans. The local QT interval in the septum were relatively longer (69 to 123 msec), compared with that of the ventricular surface (50 to 98 msec), and such durations of ventricular epicardium and septum were considerably less than those of dogs and humans. These results are consistent with the configuration of QRS-T on the limb lead ECG.

Animals↗
PubMed1992

Vagal afferent activities and respiratory reflexes during drug-induced bronchoconstriction in the guinea pig.

Vagal afferent activities and respiratory reflexes during drug-induced bronchoconstriction were studied in 31 anesthetized, spontaneously breathing or artificially ventilated guinea pigs. Histamine (5, 10, 20 micrograms/kg), ACh (10, 20, 40 micrograms/kg) and endothelin-1 (2 micrograms/kg) were intravenously injected to the animals in order to induce the bronchoconstriction. In spontaneously breathing and vagi intact animals, a considerable respiratory change characterized by rapid-shallow breathing was elicited by histamine. Such respiratory change was abolished by bilateral vagotomy, indicating that the vagal pathway fairly participated in the respiratory change during bronchoconstriction. Indeed, recordings of electrical activities of single vagal afferent nerve fibers from pulmonary stretch and irritant receptors elucidated that the bronchoconstriction by the three drugs markedly influenced these receptor activities. The response of stretch receptors to bronchoconstriction was grouped into four types: two of those types showed a marked increase in their activities and the other two a decrease or no change. Such uneven response was assumed to be derived from heterogenous contraction and aeration among the intrapulmonary small airway. On the other hand, irritant receptors were invariably stimulated by increased transmural pressure during bronchoconstriction. Administration of isoproterenol (20 micrograms/kg) which inhibited the smooth muscle contraction abolished stimulatory effect of the drugs to irritant receptors, suggesting that the effect was due to indirect action through the muscle contraction rather than their direct action to the nerve endings.

Acetylcholine↗
PubMed1992

Effects of atherogenic diet on young farm pigs.

This study was designed to assess the usefulness of young farm pigs as an experimental model for hypercholesterolemia. In order to test this, we investigated both serologic and electrocardiographic effects of atherogenic diet. Four-week-old pigs were fed an atherogenic diet for 8 weeks. No arrhythmia was observed on ECG in all animals. There were no significant difference between control and atherogenic diet group on the values of ECG parameters. However, plasma lipids values of atherogenic diet group were significantly (p less than 0.05) higher than those of control diet group. Thus, hypercholesterolemia was induced in young farm pigs by feeding atherogenic diet in a relatively short time. This fact suggests that young farm pigs may be an useful model for further studies of the effect of hypercholesterolemia on cardiovascular function and the early pathogenesis of atherosclerosis.

Animals↗
PubMed1991

Incidence of ultrasound-detected intrahepatic hematomas due to Tru-cut needle liver biopsy.

This is a prospective study in which 120 patients with diffuse liver disease undergoing liver biopsy were followed by serial ultrasounds to determine the incidence of postbiopsy intrahepatic hematoma formation. Forty-five of the patients had a blind biopsy, while the remaining 75 patients had a biopsy performed during laparoscopy. In both groups a 2.0-mm Tru-cut needle was employed. The overall incidence of postbiopsy hematoma formation was 18.3%, with approximately the same results occurring in blind biopsy patients (20%) and laparoscopy-guided biopsy patients (17%). Only two patients had significant pain associated with the hematoma formation (one from each group), one of whom had evidence of intraperitoneal bleed and rebleed. Our results suggest that postbiopsy asymptomatic hematomas occur more frequently than had been generally thought and that laparoscopy-guided biopsy is not safer than blind biopsy.

Biopsy, Needle↗
PubMed1991

A rodent model of cirrhosis, ascites, and bacterial peritonitis.

We sought to develop a rodent model of spontaneous bacterial peritonitis and report here the preliminary results of carbon tetrachloride-induced cirrhosis in which ascites and bacterial peritonitis predictably develop. Of 41 rats that survived the initial carbon tetrachloride toxicity, 38 (92.7%) developed cirrhosis with ascites. Of these 38, 21 (55.3%) developed 24 episodes of ascitic fluid infection without iatrogenic colonization. No surgically treatable source of infection was identified at autopsy in any rat; therefore, the infections were presumed to be "spontaneous." Eight (50%) of the 16 rats with culture-positive ascitic fluid at postmortem examination also had spontaneous pleural fluid infection with the same organism. Escherichia coli and Proteus sp. were the organisms most commonly isolated. This rodent model of cirrhosis with ascites appears to be the first high-yield animal model of spontaneous bacterial peritonitis. Ascitic fluid infection in these rats resembles ascitic fluid infection in humans. This model will allow further investigation of the mechanisms of pathogenesis of ascitic fluid infection and provide insight into the prevention and treatment of spontaneous bacterial peritonitis and pleural fluid infection in patients with cirrhosis.

Animals↗
PubMed1991

Comparison of the multiple molecular forms of bovine adrenocortical P450scc with those of corpus luteum P450scc.

1. Bovine adrenocortical P450scc was resolved into several fractions by chromatography on AH-Sepharose 4B followed by gel filtration on Toyopearl HW55S. All fractions contained P450scc of the same molecular size and the P450scc could be resolved into 3-4 major and more than 10 minor isoelectric point forms by isoelectric focusing on polyacrylamide gel in the presence of Emulgen 913. 2. Both the AH-Sepharose chromatography profile and the isoelectric focusing pattern of the adrenocortical P450scc were more complex than those of the corpus luteum P450scc. The corpus luteum P450scc was practically devoid of the neutral to acidic isoelectric point forms. 3. Three to four P450scc subfractions with different isoelectric focusing pattern were obtained from a purified preparation of adrenocortical P450scc by ion-exchange chromatography on DEAE-Toyopearl 650S or DEAE-Sephadex A25. These P450scc subfractions showed essentially the same spectral properties, catalytic activity, molecular weight and N-terminal amino acid sequence. 4. The most acidic (the latest eluting) subfraction was composed mostly of the neutral to acidic isoelectric point forms. The sedimentation characteristics of this subfraction was also studied. 5. The structural basis of the multiple molecular forms was discussed.

Adrenal Cortex↗
PubMed1991

Characterization of Bacillus subtilis glutamine synthetase by limited proteolysis.

The inactivation of native glutamine synthetase (GS) from Bacillus subtilis by trypsin, chymotrypsin, or subtilisin followed pseudo-fast order kinetics. Trypsin cleaved the polypeptide chain of GS into two principal fragments, one of about 43,000 (Mr) and the other of smaller than 10,000. Chymotrypsin and subtilisin caused similar cleavage of GS. A large fragment (Mr 35,000) and one smaller than 10,000 were detected on SDS-PAGE. The nicked protein remained dodecameric, as observed on gel filtration, electrophoresis, and electron micrography. In the presence of glutamate, ATP, and Mn2+, the digestion of GS by each of the three proteases was retarded completely; however, the presence of one substrate, L-glutamate, ATP+Mn2+, or ATP+Mg2+ led to partial protection. The product, L-glutamine, did not retard but altered the susceptibility of the protease sensitive sites. Amino acid sequence analysis of the two smaller polypeptide fragments showed that the nicked region was around serine 375 and serine 311, respectively, and that both large fragments (43,000 and 35,000) were N-terminal polypeptides of GS. The serine 311 region was involved in the formation of the enzyme-substrate complex. Tyrosine 372 near serine 375 corresponded to tyrosine 397 which was adenylylated by adenyltransferase in Escherichia coli GS.

Amino Acid Sequence↗
PubMed1991

Characteristics of electrocardiographic changes with some representative antiarrhythmic drugs in adult rats.

The characteristics of ECG changes with representative antiarrhythmic drugs; procainamide (PA) (class Ia), lidocaine (LC) (class Ib), propranolol (PN) (class II), and verapamil (VP) (class IV) were investigated in adult rats. Action potential (AP) was also recorded from myocardial cells during electrical stimuli with frequencies of 1-5 Hz. All the four drugs produced ECG abnormalities which contained AV and SA blocks at middle and high dose levels. Three drugs except VP induced a prolongation of QRS complex and notched QRS at low or middle dose level. As compared such effects with those in dogs and humans, some differences were noted as follows: (1) a dose-dependent prolongation of QT interval by LC and PN, and (2) a shortening of RR interval by VP at the dose of 0.6 mg/kg or less. LC and PN elongated the QT interval in the unipolar precordial chest lead ECGs at right anterior chest positions. These two drugs did not affect the duration of AP (APD90), whereas maximum upstroke velocity (Vmax) decreased. These results suggest that the prolongation of QT interval with LC and PN was due to a delay in local ventricular conduction time, especially on the right ventricle. The shortening of RR interval by VP was clearly blocked by the pretreatment with PN, indicating that this shortening reflected the sympathetic nervous reflex presumably due to the peripheral vasodilation effect of VP.

Action Potentials↗
PubMed1991

Reflex activities of the upper airway muscles during experimental nasal occlusion in anesthetized dogs.

Reflex responses of the upper airway muscles during experimental nasal and tracheal occlusions were studied in 21 anesthetized dogs breathing through the nose or a tracheostomy (tracheal cannula). Out of them, five animals were examined for maintained negative and positive pressures applied to the isolated upper airway. When the nose was occluded at end-expiration during three consecutive breathings, the electromyographic (EMG) activity of alae nasi (AN) and posterior cricoarytenoid (PCA) muscle markedly increased. The upper airway was subjected to negative pressure, -2.41 approximately -3.04 kPa (n = 34) by these nasal occlusions. The activity of upper airway muscles was also increased by tracheal occlusions. However, such augmentation of PCA activity was much less in tracheal occlusions than nasal occlusions, whereas there was the smaller difference in AN activity between both occlusions. During nasal occlusions, a prolongation of the inspiratory time (TI) was observed. Furthermore, maintained negative pressure applied to the isolated upper airway provoked an augmentation of PCA activity. Such an augmented EMG activity of PCA and the prolongation of TI were largely diminished by sectioning the superior laryngeal nerves. These results proves that the upper airway muscles play an important role to protect the upper airway from collapsing by nasal occlusions. In addition, it is suggested that a lack of lung volume feedback is substantially concerned with the activation of AN, while negative pressure in the upper airway is essential to stimulate PCA.

Airway Obstruction↗
PubMed1991

Evaluation of a new tail-cuff method for blood pressure measurements in rats with special reference to the effects of ambient temperature.

We evaluated a recently developed tail-cuff apparatus for the indirect blood pressure measurement in rats with special reference to the effects of ambient temperature. For this purpose, we designed two preparations 1) an intact preparation to determine the effect of ambient temperature on blood pressure measurements and 2) an anesthetized and catheterized preparation for comparison of the values of blood pressure obtained by the indirect and by the direct method. This apparatus also required enough pulse volume oscillations to measure the accurate value of blood pressure. Sufficient pulse volume oscillations were obtained within 20 min at 30 and 40 degrees C. At 40 degrees C, the values of blood pressure, pulse rate and rectal temperature were significantly higher than those at 30 degrees C. Correlation between blood pressure and rectal temperature was significant, and blood pressure increased with rectal temperature dependently. The values of the indirect measurement were close to the values measured directly, and these correlations were highly significant. Thus, we showed the effects of temperature for indirect blood pressure measurement. This tail-cuff apparatus could measure the accurate value of indirect blood pressure without thermal stress at 30 degrees C.

Animals↗
PubMed1990

Use of the human elongation factor 1 alpha promoter as a versatile and efficient expression system.

We have characterized the promoter region of the human elongation factor 1 alpha-encoding gene (EF-1 alpha) and developed a versatile expression system which has a wide host range and a high efficiency of gene expression. To identify the promoter region of the EF-1 alpha gene necessary for efficient gene expression, we constructed four pEF-CAT plasmids that have the bacterial cat gene fused to four different sites of the human EF-1 alpha gene: (i) ligated to the end of the TATA box (pEF220-CAT); (ii) ligated in exon 1 (pEF204-CAT and pEF233-CAT), and (iii) ligated in exon 2 (pEF321-CAT). All the pEF-CAT plasmids were highly expressed in all the cell types tested, including fibroblasts and lymphoid cells. Plasmid pEF321-CAT, which contains the first exon and the first intron, gave the highest level of cat expression. Plasmids pEF204- and pEF233-CAT, which contain part of the first exon but do not contain the first intron, were less efficient in cat expression than was pEF321-CAT. Plasmid pEF220-CAT, which lacks both the first exon and the first intron, was the least efficient. Plasmid pEF321-CAT was several- to 100-fold more efficient in cat expression than plasmid pSV2-CAT depending on the recipient cell types. The promoter of pEF321 plasmid also directed the stable expression of the bacterial neo gene more efficiently than the promoter of the simian virus 40 (SV40) early gene or the long terminal repeat of Rous sarcoma virus. Using this system, the SV40 early gene and the cDNA encoding human CD4 were also expressed efficiently.

Animals↗
PubMed1990

Cytochrome P-450scc-catalyzed production of progesterone from 22R-hydroxycholest-4-en-3-one by way of 20,22-dihydroxycholest-4-en-3-one.

Transient accumulation of a dihydroxylated steroid was found when 22R-hydroxycholest-4-en-3-one was used as the substrate for a reconstituted cholesterol side-chain cleavage system derived from bovine adrenocortical mitochondria. The indications were that the accumulated steroid was an intermediate in the cytochrome P-450scc-catalyzed reaction. The retention time of the accumulated intermediate was identical with that of authentic 20,22-dihydroxycholest-4-en-3-one on HPLC. When 22R-hydroxycholesterol and 22R-hydroxycholest-4-en-3-one were incubated simultaneously, the total amount of reaction products was essentially the same as that observed with 22R-hydroxycholest-4-en-3-one alone. Under the conditions employed, the apparent turnover number of cytochrome P-450scc for 22R-hydroxycholesterol was calculated to be 77 nmol/min/nmol P-450 from the amount of pregnenolone formed, whereas the apparent turnover number for 22R-hydroxycholest-4-en-3-one was 64 nmol/min/nmol P-450 with respect to the intermediate formation and 77 nmol/min/nmol P-450 with respect to the progesterone formation. The apparent turnover number for 20,22-dihydroxycholest-4-en-3-one was about 125 nmol/min/nmol P-450, which was not significantly different from that of 20,22-dihydroxycholesterol. The apparent Km for 22R-hydroxycholesterol was about 20 microM and those for 22R-hydroxycholest-4-en-3-one and 20,22-dihydroxycholest-4-en-3-one were 50 and 40 microM, respectively. Thus, 22R-hydroxycholest-4-en-3-one was efficiently metabolized to progesterone by way of 20,22-dihydroxycholest-4-en-3-one by cytochrome P-450scc.

Adrenal Glands↗
PubMed1990

Electrocardiographical findings of WBN/Kob rats.

Electrocardiographical (ECG) investigations were carried out on 4 and 12 week old WBN/Kob and Wistar male rats. In comparison with Wistar rats which showed ECG findings typical of those of normal rats, WBN/Kob rats showed significantly larger QRS complex amplitude, smaller T wave amplitude, longer QRS duration, and longer QT interval at 4 weeks of age. This tendency became clearer at 12 weeks of age. There were no changes in serum inorganic ion concentrations or cardiac histopathology suggestive of these ECG changes in WBN/Kob rats. These ECG findings in WBN/Kob rats are considered to be a hereditary characteristic of the strain.

Age Factors↗
PubMed1990

Antihypertensive effect of tryptic hydrolysate of milk casein in spontaneously hypertensive rats.

1. Repeated oral administrations of tryptic hydrolysate of bovine milk casein (CEI) showed antihypertensive effect in spontaneously hypertensive rats. 2. Single oral administration of CEI antagonized the pressor response to angiotensin I. 3. Bovine milk casein hydrolysate inhibited the angiotensin I-converting enzyme (ACE) activity. Three peptides with ACE-inhibiting activity were isolated from CEI. 4. It is suggested that ACE-inhibiting peptides in the tryptic hydrolysate milk casein are absorbed from the intestinal tract and produce an antihypertensive effect.

Administration, Oral↗
PubMed1989

Sensitive assay of cytochrome P450scc activity by high-performance liquid chromatography.

We have developed a simple procedure for analyzing the reaction intermediates and product of the cholesterol side-chain cleavage system by high-performance liquid chromatography with uv absorption monitoring. After the cholesterol side-chain cleavage system had been incubated and the reaction then halted by heat treatment, the product was converted into 3-one-4-en steroid showing intense absorption at 240 nm upon reaction with cholesterol oxidase. The converted steroids were then analyzed by normal-phase HPLC. In consequence, the catalytic activity of the reconstituted adrenocortical cytochrome P450scc system was readily assayed with a sensitivity more than 10-fold higher by this conversion. Also, it was shown that 22R-hydroxy-cholest-4-en-3-one could serve as a good substrate for cytochrome P450scc and that the 20R,22R-dihydroxy derivative could be clearly detected as a reaction intermediate in the reconstituted system.

Animals↗