Raf-1 is a potential substrate for mitogen-activated protein kinase in vivo

MAP (mitogen-activated protein) kinase is shown to phosphorylate baculovirally expressed Raf-1 in vitro, generating one major tryptic phosphopeptide which co-migrated with a peptide from Raf-1 32P-labelled in situ. This peptide also undergoes an insulin-dependent increase in labelling. Thus the serine/threonine kinase Raf-1 may be a substrate for MAP kinase in vivo.

A second, expressed thrombospondin gene (Thbs2) exists in the mouse genome

The diverse and occasionally conflicting properties described for the extracellular, cell surface-associated protein thrombospondin (TSP) have raised the possibility that functionally distinct forms of the protein exist in the same organism. We have isolated and characterized a partial cDNA clone for mouse TSP that is clearly homologous to, but distinct from, the coding sequence for mouse TSP deduced from a mouse genomic clone (Bornstein, P., Alfi, D., Devarayalu, L., Framson, P., and Li, P. (1990) J. Biol. Chem. 265, 16691-16698). This second TSP, which we term thrombospondin 2, is the product of a separate gene (Thbs2) and is expressed in a variety of mouse tissues in a pattern that differs from that for TSP1. Based on their translated amino acid sequences, it seems likely that TSP1 and TSP2 will be found to have both common and unique properties and that the functional consequences of TSP production will reflect the ratio of the levels of these two related proteins.

Left ventricular dysfunction induced by chronic alcohol ingestion in rats

To determine whether moderate ingestion of alcohol for protracted periods of time affects normal cardiac performance and produces myocyte damage, male Fischer 344 rats at 4 mo of age were given 30% ethanol in their drinking water every day for a period of 8 mo. Experimental animals and age-matched controls were examined hemodynamically and morphometrically at 12 mo of age. Body and cardiac growth were depressed in alcoholic animals by 15 and 12%, respectively. Although left ventricular (LV) weight was reduced by 14% in alcoholic rats, no difference in right ventricular (RV) weight was noted, and consequently the ratio of RV weight to body weight increased by 12%. Systemic arterial pressures as well as LV peak systolic pressure decreased in alcoholic rats despite an unchanged heart rate. Myocardial contractility in alcoholic rats was further depressed as revealed by a significant decrease in the peak rate of ventricular pressure decay. Importantly, end-diastolic pressure was elevated 5.2-fold in the left ventricle and 2.9-fold in the right ventricle after 8 mo of ethanol consumption. LV diastolic chamber volume increased through myocardial remodeling as the longitudinal axis and transverse diameters from the base to the apex increased in experimental animals while the thickness of the LV diminished. Structural and hemodynamic alterations resulted in a 571% increase in the volume of diastolic circumferential wall stress on the left ventricle. Damage to the myocardium was increased in alcoholic animals with the volume percent of myocardial lesions increasing 342% in the wall of the left ventricle.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of an active, non-myristylated, cytoplasmic form of the lymphoid protein tyrosine kinase pp56lck

pp56lck is a member of the src family of tyrosine kinases mainly expressed in T lymphocytes. Src tyrosine kinases have been implicated in the control of cell growth and differentiation in different cell types, but the mechanism of regulation of these enzymes is poorly understood. In order to characterize the distinct species of pp56lck, we have produced high yields of enzymatically active wild type pp56lck using the eukaryotic baculovirus expression system in Spodoptera frugiperda insect cells (Sf9). We find that the various species of baculoviral pp56lck are not only differentially phosphorylated (on serine and tyrosine residues) but also heterogeneously myristylated. Surprisingly a non-myristylated, very active form of bv-pp56lck is found in the cytoplasm of Sf9 cells. Fractionation of T cells reveals that cytoplasmic pp56lck exists in T lymphocytes as well.

A polymer carrier system for taste masking of macrolide antibiotics

A polymer carrier system was developed to reduce the bitterness of erythromycin and its 6-O-methyl derivative, clarithromycin, by absorption to Carbopol. The mechanism involves ionic bonding of the amine macrolide to the high molecular weight polyacrylic acid, thereby removing the drug from the solution phase in an ion-free suspension. After ingestion, endogenous cations displace the drug from the polymer in the gastrointestinal tract to achieve bioavailability. The macrolide-Carbopol complexes were prepared by dissolving or slurrying predetermined ratios of drug and polymer in water or hydroalcoholic mixtures. A series of in vitro equilibrium studies, taste screening, and bioavailability studies in dogs established the characteristics for the various drug-polymer ratios. Taste protection was further improved by encapsulating the adsorbate particles with polymer coatings. Hydroxypropyl methylcellulose phthalate (HP-55) provided the best combination of suspension stability, taste protection and bioavailability. Human bioavailability studies demonstrated that the microencapsulated Carbopol absorbates of erythromycin and clarithromycin gave blood levels comparable to those obtained from conventional solid formulations.

Combinatorial mutagenesis of the reactive site region in plasminogen activator inhibitor I

Plasminogen activator inhibitor (PAI-I) rapidly inactivates tissue plasminogen activator (t-PA) and urokinase (UK) with nearly identical association rate constants. The contributions of Ser344, Ala345, and Arg346 (P3, P2, and P1 residues, respectively) in PAI-I to inhibition of UK and t-PA were evaluated using combinatorial mutagenesis of the human PAI-I cDNA. A bacteriophage lambda expression library potentially encoding the 8000 unique PAI-I species were screened for inhibitory activity against UK using a fibrin indicator gel. 390 plaques demarcated by zones of retarded fibrinolysis were analyzed to determine the DNA sequences of their associated active PAI-1 species. We found 134 unique PAI-1 variants that retained inhibitory activity towards UK; they contained a variety of amino acids in their P3 and P2 positions but only Arg or, infrequently, Lys in their P1 position. Each of the unique active PAI-1 were assayed for inhibitory activity towards UK or t-PA; many substitutions differentially affected the ability of the inhibitor to inactivate UK and t-PA. For example, replacement of Ser344 and Ala344 with Val and Pro, respectively, yielded a PAI-1 variant exhibiting an association rate constant that was unchanged for t-PA but decreased 23-fold for UK, relative to native PAI-1. In general, the PAI-1 variants were more potent inhibitors of t-PA than UK. Hence, t-PA appears more tolerant than UK of structural diversity present in the P3 and P2 positions of the PAI-1 variants.

Convergent inputs to neurones in the nucleus paragigantocellularis lateralis in the cat

Extracellular recordings were made in the nucleus paragigantocellularis (PGL) of the cat in response to stimulation of the hypothalamic perifornical defence area (HPDA), dorsal periaqueductal grey matter (PAG), nucleus raphe obscurus (Rob), deep peroneal nerve (DPN), and superficial peroneal nerve (SPN). Stimulation of the HPDA, dorsal PAG and SPN evoked excitatory responses whilst the prevalent response to stimulation of Rob was inhibition. However, most of the defence-reaction-related neurones showed little response to stimulation of DPN. Of 53 cells tested 48 (91%) received convergent inputs from two or more sites of stimulation. These findings are discussed in relation to the integrative function of PGL in cardiovascular control.

Modulatory Effect of Somatic Inputs on Medullary Cardiovascular Neuronal Function

Inhibition of somatic inputs on pressor response and arrhythmia is due to activating opiate receptors in the rostral ventrolateral medulla (rVLM), while its pressor response and blocking effect on bradycardia are due to activating cholinergic receptor in rVLM.

[Electrophysiological properties of atrial fibrillation with WPW syndrome and the role of procainamide in conversion]

Fifty one patients with recurrent episodes of atrial fibrillation associated with WPW syndrome were studied by pre-operative clinical electrophysiogical testing. The results showed that: these patients had an markedly prolonged intra-atrial conduction time (PA intervals: 42.22 +/- 10.93 ms) than the patients only with attack of atrioventricular reentry tachycardia (AVRT) (PA intervals: 17.21 +/- 9.68ms, P less than 0.001). The attack of atrial fibrillation related to an markedly prolonged atrial vulnerable phase and the retrograde conduction of accessory pathway (AP). The clinical results of atrial fibrillation were decided by the antegrade effective refractory period (AERP) of AP. When the shortest R-R (V-V) intervals during attack of atrial fibrillation was shorter than 180ms, the atrial fibrillation spontaneously turned to the ventricular fibrillation. The conversion of atrial fibrillation to sinus rhythm showed that procainamide not only prolonged AERP of AP, which were 248.57 +/- 15.74ms and 388.57 +/- 63.9 ms (P less than 0.001) respectively before and after intravenous procainamide infusion, but also prolonged intra-atrial conduction time significantly, the PA interval before and after intravenous procainamide infusion were 42.22 +/- 10.93 ms and 57.14 +/- 11.12 ms (P less than 0.025) respectively.

Nonischemic myocardial damage induced by nonocclusive constriction of coronary artery in rats

To determine whether reduction in coronary vessel diameter leads to alterations in cardiac function, coronary perfusion, and tissue integrity, the left coronary artery of rats was narrowed and ventricular hemodynamics measured at 3 and 5 days after surgery. Coronary artery narrowing averaged 62% and end-diastolic pressure was increased, whereas peak systolic pressure, positive change in pressure over time, stroke volume, and total peripheral resistance were decreased. However, this impairment of function was accompanied by a preservation of resting coronary blood flow (CBF), although a 43% decrease in maximal CBF was detected. Foci of reparative fibrosis and myocytolytic necrosis were found primarily in the endomyocardium and midmyocardium. These lesions were temporally distinct, corresponding to 5 days and 12- to 24-h-old forms of myocardial damage, respectively. The changes in maximal CBF correlated with the degree of stenosis, whereas the volume fraction, average cross-sectional area, and number of foci of reparative fibrosis lesions per unit area of myocardium correlated exclusively with end-diastolic pressure. In conclusion, reductions in luminal diameter of a major coronary artery not affecting resting coronary perfusion have a profound detrimental impact on cardiac performance and initiate immediate myocyte cell loss that is ongoing. Thus tissue and cellular damage may not be ischemic in nature but rather mediated by other mechanisms such as unbearable mechanical stress.

Enzymatic diagnosis of Morquio A syndrome with a new fluorimetric substrate

We synthesized a new fluorimetric substrate for the enzymatic assay of galactose 6-sulphate sulphatase (Gal-6S), an enzyme which is deficient in Morquio A syndrome. Our synthetic 4-methylumbelliferyl-galactoside 6-sulphate (4Mu-Gal-6S) proved highly effective and sensitive in the postnatal, prenatal and retrospective diagnosis of Morquio A syndrome as compared to the commonly used radiolabelled substrate. With 4Mu-Gal-6S as substrate and dialyzed supernatant as the enzyme source, we defined the optimal assay conditions for Gal-6S, determined the normal control values for all available materials, and successfully performed postnatal and prenatal diagnosis of Morquio A syndrome.

Studies on the preparative capability of the horizontal flow-through coil planet centrifuge and high-performance liquid chromatography in the separation of polar compounds from Oxytropis ochrocephala Bunge

Horizontal flow-through coil planet centrifuge (CPC) and high-performance liquid chromatography (HPLC) techniques were used for separation of polar compounds from a crude ethanol extract of Oxytropis ochrocephala Bunge, a poisonous legume plant widely distributed in northwestern China. The performance of these two chromatographic methods was compared in terms of column efficiency, peak resolution, separation time, sample loading capacity, etc. The results indicated that two polar compounds in the crude extract were equally well separated by these two methods. HPLC gave comparable peak resolution in shorter separation time while its sample loading capacity was limited to the mg range. The CPC method required a long separation time, but yielded a higher purity of fractions with a much greater capacity.

Large-volume paracentesis versus dialytic ultrafiltration in the treatment of cirrhotic ascites

We compared the clinical efficacy and safety of large-volume paracentesis and dialytic ultrafiltration in the treatment of refractory ascites in cirrhotic patients. A group of cirrhotic subjects (age 49-80 years) were randomly allocated to either continuous paracentesis (1-1.5 l/hour) or dialytic ultrafiltration until disappearance of ascites. Each patient was maintained on bed rest, fluid restriction (1 l/day) and a low (25 mmol/day) sodium diet for 14 days. Five patients (three in the paracentesis group and two in dialytic ultrafiltration group) developed massive ascites 3-5 months later, and received the crossover treatment. The average volume of fluid removed was similar in the two groups (4.70 +/- 1.47 l for dialytic ultrafiltration versus 4.69 +/- 1.84 l for paracentesis), but the treatment period was significantly shorter with dialytic ultrafiltration. The plasma creatinine significantly increased three days after paracentesis but did not increase in patients treated with dialytic ultrafiltration. There was an initial fall in mean arterial pressure during the first two hours of either treatment; a further fall in blood pressure was observed with paracentesis but not with dialytic ultrafiltration. Pretreatment plasma renin activity was elevated, but was not altered by either treatment. Plasma atrial natriuretic peptide levels were in the high-normal range before treatment. Paracentesis was associated with a delayed fall in plasma atrial natriuretic peptide, while dialytic ultrafiltration induced a modest but significant rise. No complication was experienced with dialytic ultrafiltration in the two weeks following treatment, but four of the eight patients who underwent paracentesis had developed severe complications.(ABSTRACT TRUNCATED AT 250 WORDS)

Rostral medullary cholinergic mechanisms and chronic stress-induced hypertension

This work was designed to study the relationship between the cholinergic mechanisms in the rostral ventrolateral medulla (rVLM) and the incidence of hypertension induced by chronic stress. Under anaesthetized conditions, bilateral microinjection of scopolamine (1.18 nmol/site) into the rVLM produced a much greater depressor response in chronic stress-induced hypertensive rats than in normotensive rats. Similar bradycardic effects were observed in both the normotensive and the hypertensive rats when scopolamine was injected into the rVLM. Acetylcholine (Ach) content and choline acetyltransferase (ChAT) activity in rostral medulla were determined by radioimmunoassay both in the normotensive and the hypertensive rats. Ach content and ChAT activity increased significantly in the hypertensive rats, and such increase mainly occurred within the ventral part of the rostral medulla. These results suggest that the cholinergic mechanisms in the rVLM may be activated during chronic stress and such activation may be involved in the pathogenesis of the hypertension induced by chronic stress.

Hormonal mechanism of sodium oleate-stimulated pancreatic secretion in rats

We have investigated the role of two intestinal hormones, secretin and cholecystokinin (CCK), on the pancreatic exocrine secretion stimulated by sodium oleate in anesthetized rats. Each rat was prepared with a polyethylene tube in the proximal duodenum and ligation of the pylorus. To collect pancreatic juice, the common bile-pancreatic duct was cannulated near the duodenal wall while bile was diverted to the exterior. Intraduodenal infusion of sodium oleate at doses of 0.03, 0.06, 0.12, and 0.24 mmol/h resulted in significant increases in pancreatic secretion including fluid, bicarbonate, and protein output. The increases of the three parameters were dose dependent and were correlated well with the increases in plasma secretin and CCK concentrations. To further clarify their hormonal roles, we have repeated identical experiments under intravenous administration of a rabbit anti-secretin serum (0.1 ml) or CR 1409 (4 mg.kg-1.h-1), a CCK-receptor antagonist, or a combination of both the antiserum and CR 1409. The antiserum significantly suppressed volume flow and bicarbonate secretion with a minor inhibitory effect on protein secretion, whereas a normal rabbit serum did not. CR 1409 significantly suppressed all three parameters. The combined treatment with both the antiserum and CR 1409 almost completely abolished the pancreatic secretion. Atropine given intravenously significantly inhibited the protein output but did not influence volume flow or bicarbonate output in response to sodium oleate. We thus conclude that, in rats, fat-stimulated pancreatic secretion of volume flow and bicarbonate depends entirely on the circulating endogenous secretin and CCK but that the protein output appears to be under control of both hormonal and cholinergic controls.

Mechanism of acid-induced release of secretin in rats. Presence of a secretin-releasing peptide

In fasting rats, intraduodenal infusion of dilute hydrochloric acid results in significant increases in both pancreatic exocrine secretion and plasma concentration of secretin. To test the hypothesis that acid-induced release of secretin is mediated by a secretin-releasing factor (S-RF), anesthetized rats were prepared with pyloric ligation, duodenal and jejunal cannulas, and pancreatic duct cannulas. Donor rats were infused intraduodenally with 0.01 N HCl, 0.15 M NaCl, or a combination of 0.01 N HCl and 0.05 N NaHCO3 at 0.3 ml/min for 1.5 h, and the perfusates were collected via jejunal cannulas. The perfusates with pH adjusted to 6.0 were concentrated threefold and infused into the duodena of recipient rats. The concentrate of acid perfusate (CAP) significantly increased both pancreatic volume flow and bicarbonate output and plasma concentration of secretin, whereas concentrates of the saline perfusate (CSP) or the perfusate of a combination of 0.01 N HCl and 0.05 N NaHCO3 (CABP) did not influence pancreatic secretion or plasma concentration of secretin. The increased pancreatic secretion by CAP was attributed to increased circulating secretin because when secretin was immunoneutralized by a rabbit antisecretin serum, CAP-stimulated pancreatic secretion was abolished. The bioactivity of CAP was trypsin-sensitive and heat stable. The active substance in CAP had a molecular weight of less than 5,000 and greater than 1,000, as determined by ultrafiltration and bioassay. In conclusion, dilute HCl releases an S-RF into the upper small intestinal lumen to stimulate release of secretin. This substance, with molecular weight of less than 5,000, is heat stable and trypsin sensitive. Thus, the acid-stimulated release of secretin is mediated by a secretin-releasing peptide in the upper small intestinal lumen.

Spinal cord substance P mediates carbachol-induced cardiovascular responses from the rostral ventrolateral medulla

Intrathecal (i.t.) infusion of substance P (SP) antagonist, (D-Pro2, D-Trp7,9)-substance P (20 micrograms), lowered blood pressure profoundly without any significant change of heart rate. The hypertensive and tachycardic responses elicited by microinjection of carbachol (25 ng/site) into the bilateral rostral ventrolateral medulla (rVLM) were blocked by i.t. infusion of SP antagonist. These data provided evidence that an excitatory cardiovascular effect induced by cholinergic system in rVLM may be mediated mainly by the SP receptors in spinal cord.