Hydrogen exchange kinetics of core peptide protons in Streptomyces subtilisin inhibitor

The hydrogen isotope exchange kinetics of the 10 slowest exchanging resonances in the 1H NMR spectrum of Streptomyces subtilisin inhibitor (SSI) have been determined at pH 7-11 and 30-60 degrees C. These resonances are assigned to peptide amide protons in the beta-sheet core that comprises the extensive protein-protein interface of the tightly bound SSI dimer. The core protons are atypical in that their exchange rates are orders of magnitude slower than those for all other SSI protons. When they do exchange at temperatures greater than 50 degrees C, they do so as a set and with a very high temperature coefficient. The pH dependence of the exchange rate constants is also atypical. Exchange rates are approximately first order in hydroxyl ion dependence at pH less than 8.5 and greater than 9.5 and pH independent between pH 8.5 and 9.5. The pH dependence and temperature dependence of the SSI proton exchange rates are interpreted by the two-process model [Woodward, C. K., & Hilton, B. D. (1980) Biophys. J. 32, 561-575]. The results suggest that in the average solution structure of SSI, an unusual mobility of secondary structural elements at the protein surface is, in a sense, compensated by an unusual rigidity and inaccessibility of the beta-sheet core at the dimer interface.

Transhepatic obliteration of esophageal varices using stainless coils combined with hypertonic glucose and gelfoam

A total of 63 patients with variceal bleeding were included in this study. Fifty-six attempts at percutaneous transhepatic variceal obliteration were made using stainless steel coils followed by 50% glucose and Gelfoam in 27 emergency cases, in whom bleeding did not stop by conventional medical treatment; and in 18 elective cases, in whom bleeding did stop by conventional medical treatment. The remaining 18 patients, whose bleeding was controlled by conventional medical treatment, were used as a control for the elective cases (conservative cases). The overall success rate was 93%. In 92% of the 37 acute bleeders, bleeding ceased as soon as the varices were obliterated. In emergency cases, the cumulative variceal rebleeding rate at 1, 2, 3, 6, 9, and 12 months after obliteration was 16%, 29%, 34%, 44%, 56%, and 56%, respectively. Its mortality within 1 month after the first bleeding was only 11%. In elective cases, the rebleeding rate at 1, 2, and 12 months was significantly lower; and the survival rate at 1 and 2 months was significantly higher compared with conservative cases. Follow-up portography in 10 active rebleeders and two nonrebleeders demonstrated new vessel formation in six, and recanalization of previously completely occluded varices in two. Complications included transient hemiparesis and partial stenosis of intrahepatic portal branches, but none was fatal. When compared with a conventional treatment, transhepatic variceal obliteration using steel coils followed by 50% glucose and Gelfoam proved to be an effective, safe emergency treatment for variceal hemorrhage. However, since the rebleeding rate was high, this procedure should be followed by an elective operation or other procedures for a lasting prevention of bleeding.

Effects of cimetidine and ranitidine on splanchnic hemodynamics in patients with chronic liver disease

Effects of two histamine H2 receptor antagonists, cimetidine and ranitidine, on systemic and splanchnic hemodynamics were studied in patients with chronic liver disease by simultaneous catheterization of the portal vein and the right hepatic vein and measurement of portal venous flow using the ultrasound doppler system or cineangiography. Neither infusion of 200 mg of cimetidine nor 50 mg of ranitidine reduced cardiac output, portal venous pressure, the gradient between wedged hepatic venous pressure and free hepatic venous pressure, hepatic blood flow, and portal venous flow. It is unlikely that histamine is an important modulator of flow via the H2 receptor.

Respective roles of hypoxia and halothane metabolism in halothane-induced liver injury in rats

To evaluate the respective roles of halothane metabolism and hypoxia in rats with halothane hepatotoxicity, experiments were designed with special reference to blood gas. After pretreatment with phenobarbital (80 mg per kg., i.p.) for four consecutive days, rats were exposed to 1.0% halothane under a mildly hypoxic condition (FiO2 = 14%) for 2 hr. Since halothane anesthesia caused significant decrease in PaO2 levels, rats exposed to a highly hypoxic atmosphere (FiO2 = 10%) in which PaO2 levels were comparable to those in the halothane group, served as the control. In the halothane group, marked centrilobular necrosis and elevation of SGPT activity were observed; neither significant histological lesions nor elevation of transaminase activity occurred in the highly hypoxic group. Although phenobarbital treatment did not decrease PaO2 levels during halothane anesthesia, the serum fluoride level, which appears to reflect quantitatively the reductive pathway of halothane metabolism, increased. These results strongly indicate that halothane metabolism rather than hypoxia, per se, plays a major role in development of halothane-induced liver injury in rats.

Microbore packed-column anion-exchange liquid chromatography of nucleobases, nucleosides and nucleotides

Low-capacity anion-exchange resin was packed into a 45 cm X 0.19 mm I.D. fused-silica tubing and applied to micro-column liquid chromatography of nucleobases, nucleosides and isomers of nucleotides. The effects of the chromatographic conditions on the elution behaviour of these compounds were studied. The efficiency of the microbore packed column was comparable with that of the conventional size column.

Effects of propranolol on portal hemodynamics in patients with chronic liver disease

To elucidate the mechanism by which propranolol reportedly affects portal hemodynamics, we investigated the effect of propranolol on systemic and splanchnic hemodynamics in 15 patients with portal hypertension and esophageal varices by simultaneous catheterization of the portal vein and the right hepatic vein and measurement of portal venous flow using an ultrasound doppler system. Infusion of 5 mg of propranolol significantly decreased pulse rate (-12.6%), cardiac output (-24.5%), portal venous flow (-22.3%), portal venous pressure (-13.3%), and gradient between portal venous pressure and free hepatic venous pressure (-24.8%). Thus, propranolol seems to decrease portal venous pressure by reducing portal venous flow, at least in part, as a result of reduction of cardiac output due to its beta 1 adrenergic receptor blocking action.

An unusual portal-systemic shunt, most likely through a patent ductus venosus. A case report

A 46-yr-old man with cirrhosis presented with mental confusion, headache, and nausea. Colloid liver scintigraphy showed a defect in the hilar area, and portograms after superior mesenteric arteriography demonstrated varicose veins in the same area. Computed tomography revealed a sausage-shaped low-density channel connecting the hepatic hilum and the inferior vena cava, and bolus injection contrast enhancement demonstrated transit of contrast medium from the portal vein directly into the inferior vena cava through this channel. Real-time ultrasound demonstrated a large conduit contiguous from the portal vein to the inferior vena cava through and behind the liver. The catheter introduced into the inferior vena cava opacified a large opening of this shunt below the right and left hepatic vein openings. Measurements of blood pressure, ammonia, and PaO2 clearly indicated that portal vein blood was being shunted through this channel. These findings are highly suggestive of a portosystemic shunt through a patent ductus venosus.

Dynamic states of the three methionyl residues of Streptomyces subtilisin inhibitor. 1H NMR studies

High resolution 1H NMR spectroscopy at 360 and 400 MHZ was used to study the dynamic states of the three methionyl residues (Met 70, 73, and 103) of Streptomyces subtilisin inhibitor (SSI) in a neutral aqueous (2H2O) solution. Chemical modification and nuclear Overhauser effect studies show that one of the methyl groups exists in the interior of the protein and is surrounded by phenylalanyl residues. With reference to the crystal structure, this methyl group is assignable to that of Met 103 in the hydrophobic core. The other two methionyl residues (Met 70 and 73) are equally susceptible to chemical modifications, but their methyl signals are affected in a different manner by the alpha-chymotrypsin-cleavage of the peptide bond between Met 73 and Val 74 at the reactive site. The observed linewidths of the methyl groups are consistent with the assumption that the whole side-chain of both Met 70 and 73 are already undergoing rapid internal motions at 20 degrees C, whereas for Met 103 only the rotation of the methyl group is allowed, even above approximately 40 degrees C. The high-field shift of the methyl proton resonance of Met 103 by about 0.3 ppm is attributable to the ring current effect from the surrounding phenylalanyl residues. This shift is invariant in the temperature range of 40-90 degrees C, showing that the native environment of the methyl group of Met 103 persists up to 90 degrees C at neutral pH. Destruction of the native methionyl environments occurs only above 90 degrees C, and the rate of conversion between the native and the denatured conformations is slower than 10 s-1. When SSI is mixed with subtilisin BPN' in a one-to-one molar ratio, at least one of the methyl signals of Met 70 and 73 is completely broadened, showing that the side-chain of this methionine is directly involved in the interaction with the enzyme.

[Epidemiology of connective tissue diseases of the skin (scleroderma, dermatomyositis and polymyositis) in Japan]

An epidemiologic study of connective tissue diseases (scleroderma, dermatomyositis, and polymyositis) performed from 1973 to 1976 in Japanese university hospitals is reported. Data from 32 of 48 university hospitals revealed that a total of 659 cases were collected. There were 396 cases of progressive systemic sclerosis, 178 cases of dermatomyositis, and 85 cases of polymyositis. The following points were analyzed: relationship of regional incidence, sex, initial symptoms, laboratory findings, and statistical analysis of autopsies.

Distribution of macromolecular components in human dermal connective tissue

Normal human skin was sliced into five horizontal layers and distribution of type I and type III collagens, glycosaminoglycans, and non-collagenous glycoprotein(s) among the five layers was analyzed. No remarkable differences in the relative contents of type I and type III collagens and noncollagenous glycoprotein(s) were detected among the five layers. However, glycosaminoglycan content was higher in the upper layers than in the lower and the ratio of hyaluronic acid to dermatan sulfate was also higher in the upper layers. These results are compared and discussed with our previous data on calf skin.

Experimental acantholysis by complement-fixing intercellular antibodies

Complement-fixing intercellular antibodies were detected in 10 of 17 sera from untreated pemphigus patients. The role of complement in the organ culture system was investigated using these sera. Ten sera possessing complement-fixing intercellular antibodies showed IgG binding to the intercellular substance in the organ-cultured skin and acantholysis-like changes were observed in eight cases. C3 deposition was not seen in any case. However, after treatment of the sections of cultured skin with fresh normal human serum, complement fixation of the intercellular substance by bound IgG was revealed in all the ten cases. No significant differences in the grade of acantholysis-like changes between the complement-depleted system and the complement-supplied system were observed. Complement does not appear to be necessary in the acantholytic process in the in vitro organ culture system, even though we considered the presence of complement-fixing intercellular antibodies.

Proton magnetic resonance study of Streptomyces subtilisin inhibitor. pH titration and assignments of individual tyrosyl resonances

This paper reports the pH titration at 25 degrees C and the assignment of aromatic proton resonances of three tyrosyl residues of each identical subunit of Streptomyces subtilisin inhibitor (Mr 23000) by high-resolution 1H NMR spectroscopy. The complete assignments of the specific tyrosyl resonances were made based on the results of the differential chemical modification of the tyrosyl residues with tetranitromethane followed by peptide analysis, independently of the knowledge of the crystal structure. pKa values of Tyr-7, -75, and -93 were determined in a 2H2O solution to be 10.95, 11.8, and greater than or equal to 12.6, respectively, at 25 degrees C, whereas pKa values of nitrated Tyr-7 and -75 were determined to be 7.3 and 7.9, respectively. Tyr-93 was not nitratable under normal conditions. The strong resistance to nitration, together with the extremely high pKa value and the high-field shifted positions of the ring proton resonances of Tyr-93 at neutral pH, strongly suggests that Tyr-93 takes part in a hydrogen bonding as a proton donor. Tyr-7 is more easily modified with tetranitromethane than Tyr-75, although in the crystal Tyr-75 is more exposed than Tyr-7. The result, together with the pKa value of Tyr-75 significantly higher than that of a normal tyrosine, indicates that the microenvironment of Tyr-75 is more restricted in solution than in solid. These results imply that structural details of a protein may be quite similar in solution to those in the crystal in the rigid hydrophobic region of the protein but that in the surface region of the protein local structures may well differ between the solution and the crystal.