[A study on uric acid excretion in patients with hypouricemia]

We studied four patients with hypouricemia and almost normal renal function. Two patients are idiopathic renal and familial. The other two cases are secondary to diabetes mellitus. The study of the uricosuric mechanism with pyrazinamide (PZA) and benzbromarone (Bb) test shows that two patients have a defect of pre-secretory reabsorption of urate, the other one a incomplete combined defect of pre-and post-secretory reabsorption, and the other one a enhanced secretion of urate. The fact that two patients have the history of acute renal failure (ARF) suggested that strenuous exercise or dehydration would be responsible for ARF in patients with renal hypouricemia.

Systemic necrotizing vasculitis with renal involvement accompanied by remarkable eosinophilia: a case with overlapping features of polyarteritis nodosa and allergic granulomatous angiitis

A 71-year-old woman was clinically suspected of allergic granulomatous angiitis (AGA) because of preceding allergic diseases including bronchial asthma, remarkable eosinophilia (14,300/mm3), mononeuritis multiplex, positive rheumatoid factor, elevated serum immunoglobulin E, and eosinophilic inflammation of the kidney. Autopsy findings, however, were characterized of polyarteritis nodosa (PAN). Necrotizing angiitis was present in several organs except for the lung; focal and segmental glomerular lesions with crescent formation were observed in the kidney, and granuloma formation was not found. This case may be an intermediate type between PAN and AGA (an overlap syndrome) and provide useful information on the clinical entities of systemic necrotizing vasculitis.

Ruptured chordae tendineae in acromegaly. An autopsy case

A 57-year-old woman with acromegaly associated with mitral chordal rupture is reported. She was noted to have abnormal development in the size of her hands and feet in childhood. She occasionally suffered from shortness of breath on exertion and nocturnal dyspnea for several years, and was diagnosed and treated as having congestive heart failure due to valvular heart disease. On admission to our hospital, chordal rupture was suspected on the basis of M-mode and two-dimensional echocardiography. Seven years after discharge, she died of congestive heart failure. On autopsy, the heart weight and ventricular wall thickness were increased. Rupture of the posterior chordae was confirmed, but evidence of an old myocardial infarction was not found. There was severe interstitial fibrosis in the left ventricular wall. A possible etiology of the chordal rupture in this case was thought to be the excessive stretching caused by the disproportional visceromegaly of the heart.

The primary structure and structural characteristics of Achromobacter lyticus protease I, a lysine-specific serine protease

The complete amino acid sequence of Achromobacter lyticus protease I (EC 3.4.21.50), which specifically hydrolyzes lysyl peptide bonds, has been established. This has been achieved by sequence analysis of the reduced and S-carboxymethylated protease and of peptides obtained by enzymatic digestion with Achromobacter protease I itself and Staphylococcus aureus V8 protease and by chemical cleavage with cyanogen bromide. The protease consists of 268 residues with three disulfide bonds, which have been assigned to Cys6-Cys216, Cys12-Cys80, and Cys36-Cys58. Comparison of the amino acid sequence of Achromobacter protease and other serine proteases of bacterial and mammalian origins has revealed that Achromobacter protease I is a mammalian-type serine protease of which the catalytic triad comprises His57, Asp113, and Ser194. It has also been shown that the protease has 9- and 26-residue extensions of the peptide chain at the N and C termini, respectively, and overall sequence homology is as low as 20% with bovine trypsin. The presence of a disulfide bridge between the N-terminal extension Cys6 and Cys216 close to the putative active site in the C-terminal region is thought to be responsible for the generation of maximal proteolytic function in the pH range 8.5-10.7 and enhanced stability to denaturation.

Waldenström's macroglobulinemia associated with amyloidosis and crescentic glomerulonephritis

An unusual case of Waldenström's macroglobulinemia associated with amyloidosis and crescentic glomerulonephritis is described. At autopsy, crescent formation was present in 80% of the glomeruli, and the breaks in the glomerular basement membranes were found at the same place as the deposition of amyloid.

Single anion-selective channel and its ion selectivity in the vascular smooth muscle cell

The properties of voltage-gated Cl channels of cultured smooth muscle cell prepared from embryonic rat aorta were studied. In the excised patch (inside-out configuration), we observed the activity of channels, opening and closing spontaneously, when the membrane potential was held at around 0 mV. The channels were active at a potential range between +10 and -10 mV. A step change of the membrane potential from the active potential range in either a positive or a negative direction closed the channel to an apparently inactivated state. The time course of this inactivation process became faster as the amplitude of the step change was increased. Returning the membrane potential to 0 mV allowed the channel to recover from the inactivated state. The channel had at least two open conductance states. Ca ions at the cytoplasmic face were not required for the activation of the channel. Adenosine nucleotides at the same side of the membrane had no effect on channel activity. The channels were selective to anions rather than cations, and they had a large single channel conductance of 340.5 +/- 20.4 pS in symmetrical 150 mM TEA-Cl. The reversal potential of the channel was shifted by -15.2 +/- 2.6 and 17.0 +/- 1.7 mV, when the Cl concentration at the intracellular side was changed to 75 mM or 300 mM, respectively. The permeability sequence of halides was I- greater than Br- greater than Cl- greater than F- (1.4:1.3:1.0:0.7), whereas the conductance sequence was Cl- greater than Br- greater than F- greater than I- (1.00:0.89:0.86:0.83).(ABSTRACT TRUNCATED AT 250 WORDS)

Mode of regulation of the ACh-sensitive K-channel by the muscarinic receptor in rabbit atrial cells

The mechanism underlying the regulation of the K-channel by the muscarinic receptor was examined with patch-clamp experiments in atrial cells isolated enzymatically from the rabbit heart. The patch-electrode and the recording chamber were perfused with various solutions while the activity of the K-channels in the membrane-patch was recorded continuously. In the absence of muscarinic agonists, opening of K-channels occurred at a low frequency (basal activity). Application of ACh to the bath did not affect the basal activity, but perfusion of the patch electrode with ACh markedly increased the channel activity in the "cell-attached" patch. Application of oxotremorine, i.e. a specific muscarinic agonist, via the pipette also opened K-channels. When the membrane patch was isolated from the cell body ("inside-out" patch), ACh-induced single K-channel currents were still observed, but the frequency was reduced. Perfusion of atropine or scopolamine, two muscarinic antagonists, through the patch-electrode depressed the basal activity. In the case of scopolamine, channel-activity recovered after washing out the drug. The current voltage relationship determined from the basal activity was similar to that of ACh-induced single K-channel currents. The mean open time was 0.49 ms at basal activity and 1.35 ms during the application of 0.1 microM ACh via the patch electrode. Application of oxotremorine via the pipette hardly affected the open-time, it remained at 99 +/- 4% (n = 7) of the control.(ABSTRACT TRUNCATED AT 250 WORDS)

Single channel analysis of the inward rectifier K current in the rabbit ventricular cells

The inward rectifier K channel in rabbit ventricular cells was studied by the patch-clamp method. Single channel currents were recorded in giga-sealed cell-attached patches with 150 mM K+ in the pipette. The slope conductance in the membrane potential range from -140 to -40 mV was 46.6 +/- 6.7 pS (mean +/- S.D., n = 16), and was reduced by decreasing [K+] in the pipette (20 or 50 mM). The channel was blocked by an application of Cs+ or Ba2+ (0.04-1 mM) in the pipette. Outwardly directed current, recorded with 50 mM K+ in the pipette, revealed the inward rectification of the single channel current. The probability of the channel being open was 0.33 +/- 0.05 (n = 10) at the resting potential (RP=-81.7 +/- 1.7 mV, n = 16) with 150 mM K+ in the pipette, and it decreased with hyperpolarization. The mean open time of the channel was 178 +/- 25 msec (n = 6) at RP. The closed time of the channel seemed to have two exponential components, with time constants of 11.0 +/- 2.0 msec and 1.92 +/- 0.52 sec (n = 6) at RP. The slower time constant was increased with hyperpolarization. The averaged patch current recorded upon hyperpolarizing pulses demonstrated a time-dependent current decay as expected from the single channel kinetics. The results indicated that the inward rectifier K+ current has time- and voltage-dependent kinetics.

Studies on a new proteolytic enzyme from Achromobacter lyticus M497-1. II. specificity and inhibition studies of Achromobacter protease I

The unique specificity of Achromobacter protease I for lysine residue was investigated using synthetic and natural substrates, i.e., lysine derivatives, arginine derivatives, lysine vasopressin, substance P, ACTH and insulin. The enzyme cleaved only the -Lys-X- bonds in the above substrates. The binding affinity of alkylamines as determined by Ki was much stronger than that of the corresponding alkylguanidines.

Studies on a new proteolytic enzyme from A chromobacter lyticus M497-1. I. Purification and some enzymatic properties

Achromobacter lyticus M497-1 produces three kinds of alkaline proteases (protease I, II and III) in culture medium along with the bacteriolytic enzyme (Masaki, T., Nakamura, K., Isono, M. and Soejima, M. (1978) Agric. Biol. Chem. 42, 1443--1445). Among these three proteases, Achromobacter protease I (EC 3.4.21.-) shows strict splitting for lysine residues at the carboxyl side of the splitting point. This enzyme was purified through a sequence of benzalkonium chloride treatment, acetone fractionation, CM-cellulose and DEAE-cellulose treatment chromatography on AH-Sepharose 4B and isoelectric focusing method. This form was shown to be homogeneous by polyacrylamide gel electrophoresis and ultracentrifugation analysis. The physicochemical properties of the enzyme were: Mr 30 500; partial specific volume (v), 0.717 ml/g; intrinsic viscosity (nu), 0.0385) dl/g; isoelectric point (pI) 6.9; and E1%1cm at 280 nm, 18.77. The enzyme was composed of 294 residues of amino acid per molecule, with glycine as NH2-terminal and lysine as COOH-terminal amino acids. The optimum pH values with casein, Bz-lys-pNA and Tos-Lys-OMe were 8.5--10.7, 9.0--9.5 and 7.8--8.2, respectively. The enzyme was inhibited by iPr2P-F, PhCH2SO2F and Tos-LysCH2Cl but not by Tos-ArgCH2Cl, EDTA, o-phenanthroline and PCMB.