Influence of renal perfusion pressure on alpha- and beta-adrenergic stimulation of renin release

Experiments were performed in pentobarbital-anesthetized dogs to 1) determine if neural stimulation of renin release can be mediated by renal alpha-adrenoceptors at renal nerve stimulation (RNS) frequencies that have little or no effect on total renal blood flow (less than or equal to 1.2 Hz) and 2) ascertain whether alpha-adrenergic control of renin release is affected by renal perfusion pressure (RPP). The renal nerves were electrically stimulated both in the absence of RPP control and with RPP controlled near 85 mmHg. Decreased RPP lowered the threshold for neurogenic stimulation of renin release from less than or equal to 1.2 to 0.3 Hz. beta-Adrenoceptor blockade with propranolol blunted the renin secretion rate (RSR) response to graded RNS (0.3-5.0 Hz), but the extent of inhibition during low-frequency RNS was dependent on RPP. Propranolol prevented increased RSR at 0.6-1.2 Hz RNS when RPP was 111-120 mmHg but not when RPP was 85 mmHg. Combined alpha- and beta-blockade with prazosin and propranolol totally prevented increased RSR during 0.6-1.2 Hz RNS at reduced RPP. In summary, both alpha- and beta-adrenoceptors mediate neural stimulation of renin release at RNS frequencies that do not decrease total renal blood flow when RPP is 85 mmHg.

A simple model for estimating the hemolytic rate in patients with sickle cell anemia

The pathophysiologic processes of hemolysis in sickle cell anemia were formulated by a simple mathematical model that assumed a unimodal bone marrow erythrocyte population and a finite probability of random destruction of red blood cells (RBCs) in the circulation. Recognizing that the hemolytic rate of marrow RBCs is likely to be distributed normally around a mean hemolytic rate, we simplified the model by using the mean hemolytic rate as representative of the entire marrow RBC population. The model thus constructed allows an easy estimation of the mean steady-state hemolytic rate simply by measurement of reticulocyte counts and hematocrit levels. When the model was applied to data from 43 patients with sickle cell anemia, the estimated mean hemolytic rates based on the model correlated significantly with the published hemolytic rates obtained by diisopropylphosphofluoridate-RBC survival studies of the peripheral blood, but were generally greater than the published rates. This discrepancy was postulated to be the result of an enrichment of RBCs with smaller hemolytic rate in the circulation. The results of computer simulation studies were consistent with this hypothesis and suggest that the variation in the hemolytic rate for marrow RBCs is on the order of 10%. This simplified model may serve as a close approximation of this pathophysiologic system. The estimates of the steady-state hemolytic rate provided by the model should be clinically useful, especially when repeated estimations are required. The method of calculation is illustrated.

Renal norepinephrine overflow during graded renal nerve stimulation before and after beta-adrenoceptor blockade

These experiments were designed to determine if renal venous norepinephrine (NE) overflow provides a valid index of renal sympathetic nerve activity. In addition, we evaluated the effect of beta-adrenoceptor blockade on renal NE overflow during graded renal nerve stimulation in order to examine the possibility that presynaptic beta-adrenoceptors facilitate neuronal release of NE in the kidney. In 6 pentobarbital-anesthetized dogs, the renal nerves were transected to remove tonic nerve activity and the distal ends were electrically stimulated (8-25 V, 0.5 ms) over the range of 0.3-5.0 Hz for consecutive 4-min periods. NE overflow rate was calculated as the product of the veno-arterial NE concentration difference and renal plasma flow. Control values of NE overflow (-8.7 +/- 1.8 ng/min) demonstrated net clearance of NE from the renal circulation. NE overflow rate rose to -3.1 +/- 2.2, 1.0 +/- 4.0, and 33.2 +/- 15.4 ng/min at 0.3, 0.6, and 1.2 Hz stimulation, respectively, with no accompanying change in renal blood flow. At 2.4 and 5.0 Hz, renal blood flow decreased by 21 +/- 4% and 37 +/- 3%, but there was no further increase in NE overflow rate (38.8 +/- 9.4 and 27.8 +/- 6.5 ng/min). Propranolol (0.5-1.0 mg . kg-1 plus 0.4-0.5 mg . kg-1 i.v., n = 4) did not alter the effect of nerve stimulation on either NE overflow or renal blood flow. Thus we were unable to demonstrate the presence of functional renal presynaptic beta-adrenoceptors. Further, our data indicate that renal norepinephrine overflow rate is not always a reliable index of renal nerve activity, since NE overflow was not proportional to renal nerve stimulation rate at frequencies high enough to cause vasoconstriction.

Diffusible suppressor factor from splenic macrophages in murine plasmacytoma

The immunosuppressive effect of splenic macrophages (M phi) in mice bearing plasmacytoma was previously shown to be mediated by a diffusible factor. This diffusible suppressor factor (DSF) was found to be non-dialysable and sensitive to heating to 56 degrees C and to the proteolytic action of trypsin. The suppressor factor could be removed from culture supernatants by binding to ligands that specifically bind to corresponding myeloma proteins. DSF from splenic suppressor M phi of mice bearing MOPC 315 was capable of binding dinitrophenyl L-lysine, and that from mice bearing MOPC 104E, dextran S. The suppressor factor apparently cross-reacted with anti-idiotypic antibody to the corresponding myeloma protein, but did not interact with anti-isotypic antibody to mouse immunoglobulins (Ig). A higher concentration of mouse Ig than that found in DSF preparations did not have a suppressive effect. Metabolic inhibitors for RNA and protein, but not DNA synthesis effectively blocked the production of DSF. These findings suggest that DSF is a non-Ig protein that may have a structural similarity to myeloma idiotype. Continuous RNA and protein synthesis is required for the elaboration of DSF by splenic suppressor M phi in cultures.

Biphasic effect on platelet aggregation by phospholipase a purified from Vipera russellii snake venom

A basic phospholipase A was isolated from Vipera russellii snake venom. It induced a biphasic effect on washed rabbit platelets suspended in Tyrode's solution. The first phase was a reversible aggregation which was dependent on stirring and extracellular calcium. The second phase was an inhibitory effect on platelet aggregation, occurring 5 min after the addition of the venom phospholipase A without stirring or after a recovery from the reversible aggregation. The aggregating phase could be inhibited by indomethacin, tetracaine, papaverine, creatine phosphate/creatine phosphokinase, mepacrine, verapamil, sodium nitroprusside, prostaglandin E1 or bovine serum albumin. The venom phospholipase A released free fatty acids from synthetic phosphatidylcholine and intact platelets. p-Bromophenacyl bromide-modified venom phospholipase A lost its phospholipase A enzymatic and platelet-aggregating activities, but protected platelets from the aggregation induced by the native enzyme. The second phase of the venom phospholipase A action showed a different degree of inhibition on platelet aggregation induced by some activators in following order: arachidonic acid greater than collagen greater than thrombin greater than ionophore A23187. The longer the incubation time or the higher the concentration of the venom phospholipase A, the more pronounced was the inhibitory effect. The venom phospholipase A did not affect the thrombin-induced release reaction which was caused by intracellular Ca2+ mobilization in the presence of EDTA, but inhibited collagen-induced release reaction which was caused by Ca2+ influx from extracellular medium. The inhibitory effect of the venom phospholipase A and also lysophosphatidylcholine or arachidonic acid could be antagonized or reversed by bovine serum albumin. It was concluded that the first stimulatory phase of the venom phospholipase A action might be due to arachidonate liberation from platelet membrane. The second phase of inhibition of platelet aggregation and the release of ATP might be due to the inhibitory action of the split products produced by this venom phospholipase A.

Purification and properties of the main coagulant and anticoagulant principles of Vipera russellii snake venom

Vipera russellii venom was separated into thirteen fractions by means of DEAE-Sephadex A-50 column chromatography. Fraction III possessed anticoagulant and phospholipase A activities and Fraction XI possessed procoagulant and caseinolytic activities, both were further purified by gel filtration on Sephacryl S-200 column. Purified procoagulant (Component II) was a two-chain protein with molecular weight of 86 000 consisting of A-chain (Mr 66 000) and B-chain (Mr 20 000). It was a glycoprotein containing 7.8% neutral sugar and 715 amino-acid residues. The procoagulant activity was 10-times that of the crude venom. It was an acidic proteinase with isoelectric point of pH 4.2. Upon heat treatment at 60 degrees C, Component II was stable at pH 5.5 and 7.2 for 3 h, but was destroyed completely after 30 min at pH 8.9. It was devoid of esterase or amidase activity. Purified anticoagulant (Component I) was a single peptide chain with molecular weight of 16 000. It was carbohydrate free and contained 136 amino-acid residues. It was a basic protein with an isoelectric point of larger than pH 10. It was a potent phospholipase A with an enzymatic activity of 510 +/- 30 mumol/min per mg using phosphatidylcholine as substrate, and 1 microgram/ml was sufficient to cause 100% hemolysis by the indirect hemolytic method. Upon heat treatment at 90 degrees C, Component I was heat stable at pH 5.5 for more than 3 h, but was destroyed completely after 2 h at pH 7.2 and 8.9. The anticoagulant activity of Component I could be neutralized by platelet factor 3, tissue thromboplastin and cephalin.

Optical activity and conformation of beta-bungarotoxin in solution

beta-Bungarotoxin, which consists of two polypeptide chains (A- and B-chain), in the venom of Formosan banded krait is stable in 7.5 M urea but can be denatured in 6.0 M guanidine hydrochloride. Its conformation remains virtually the same in solvents of lower polarity than water such as a mixture of 1,2-ethanediol-water (4:1 by volume). The circular dichroism spectrum in water shows a double minima at 222 and 209 nm, which is characteristic of the helical structure. The ellipticities at these two wavelengths indicate that the helical content of this toxin is not high. Comparing how guanidine hydrochloride effects the helix-coil transition of the toxin with that of phospholipase A2's which are structurally homologous to A-chain implicates that the two polypeptide chains should be coexisted and interacted with each other in order to maintain the active conformation of beta-bungarotoxin. Removal of eight amino acid residues from the N-terminus of the A-chain by action of CNBr on beta-bungarotoxin does not disrupt the polypeptide folding but abolishes the neurotoxicity.

Separation of isoenzymes of glucose-6-phosphate dehydrogenase from human erythrocytes by two-dimensional gel electrophoresis

Isoelectric focusing performed in 6.0% polyacrylamide gel in the presence of 1.0 M urea separates well the various molecular forms of glucose-6-phosphate dehydrogenase from human erythrocytes. At least seven sharp bands appear in the gel pattern, which vary both in isoelectric points and in the relative intensity. Their isoelectric points are at pH 6.88 for band 1, pH 6.79 for band 2, pH 6.64 for band 3, pH 6.50 for band 4, pH 6.39 for band 5, pH 6.19 for band 6, and pH 6.10 for band 7. A second-dimensional disc electrophoresis performed in a polyacrylamide gel slab resolves each band into two components, a slow and a fast component defined according to their mobilities in the disc gel. The slow component constitutes the major portion of each band. All the seven slow components appear to be dimer having a molecular weight between 98,000-94,000. They belong to "change isomers" having identical molecular size but containing different net changes. The molecular weight of the fast components is between 66,800-50,600. These fast components might be monomer or the digested products of slow components.

Membrane disintegration and hemolysis of human erythrocytes by snake venom cardiotoxin (a membrane-disruptive polypeptide)

The action of 7.2 microM cardiotoxin on 0.25% (v/v) human erythrocytes in plasma extender solution was studied by osmotic fragility and hemolysis. The toxin loosened the membrane rigidity without lysis for about 25 min and then the cells hemolyzed for about 6 h at 37 degrees. The membrane was not perturbed at 15 degrees. The hemolysis of cells was optimal at 37 degrees and virtually stopped below 20 degrees. Both events could be suppressed by adding inorganic salts or toxin antibody. Once the membrane was loosened, the addition of phospholipase A2 would potentiate the disintegration of erythrocytes. In contrast, hemolysis of erythrocytes by (Lys)n lacked a non-lytic period and was temperature independent and insensitive towards salts and phospholipase A2.

Suppressor activity of splenic macrophages in murine plasmacytoma (PC) is inhibited by PC specific ligands

Spleens of BALB/c mice with plasmacytoma contain macrophages (M phi) which were found to suppress the in vitro immune function of normal splenic cells through a diffusible factor. The suppressor activity of these macrophages was reversibly inhibited by ligands specific for the corresponding PC globulin, but not by anti-idiotypic antibody. Anti-idiotypic antibody with complement, however, abrogated the suppressor function, presumably by cytotoxicity. Anti-isotype with complement was ineffective. These findings suggest binding of ligand to a surface receptor of the suppressor M phi that although clearly not PC globulin, may be structurally similar to the PC idiotype. These receptors are retained in 3 day cultures of macrophages and are not removed by intensive washing. Ligand binding appears to modulate the suppressor function of M phi through blocking of the production of diffusible suppressor factor.

Role of aromatic residues in the structure-function relationship of alpha-bungarotoxin

The conformation of alpha-bungarotoxin and its cyanogen bromide cleaved and nitrated derivatives was studied by circular dichroism (CD). Native toxin contains no helices but some beta forms and possibly beta turns. Its ordered conformation is little affected when the peptide bond between Met-27 and Trp-28 is cleaved; however, the CD due to Trp-28 is abolished. The CNBr-cleaved derivative retains its immunoaffinity toward anti-toxin sera but loses its neurotoxicity toward the acetylcholine receptor. On the basis of both CD and fluorescence spectra, Trp-28 is probably stabilized by a short-range interaction with the carboxylate group of Asp-30. The ordered conformation of the toxin is also unaltered when one of the two tyrosine residues, identified as Tyr-54, is nitrated with tetranitromethane. This Tyr(NO2)-54 derivative possesses both immunoaffinity and neurotoxicity. However, the toxin is denatured and loses its activities when the other tyrosine residue, Tyr-24, is also nitrated in 6 M guanidine hydrochloride, even after the denaturant is removed. Spectrophotometric titration of the toxin indicates that Tyr-54 has a normal apparent dissociation constant (pKa = 9.7) and Tyr-24 ionizes at pH above 11.2. Both tyrosine residues are in a polar environment, but Tyr-24 is not readily accessible to reagents and is stabilized by long-range interactions, probably involving Glu-41.

Correlations between computerized tomography of the head and motor developmental disturbances of children with cerebral palsy

Two hundred and eight-two children with cerebral palsy (C.P.) and thirty-seven normal children were studied by computerized tomography (C.T.) of the head for finding out the correlations between the organic damage of the brain and the motor developmental disturbance. The abnormal findings of C.T. were: enlargement of the ventricular system, high density area, low density area and porencephalus, enlargement of the sulcus and anomaly of the medial structure. Enlargement of the ventricular system seemed to have correlation with spasticity; the portion and the extent of the enlargement corresponded to the affected extremities and the severity of the spasticity. Children of other types also showed various abnormal C.T. findings but, in general, less than that of spastic types. The prognosis of the motor development of C.P. children cannot be predicted by serial C.T. examinations strictly, because early treatment could cause improvement to that of these children. However, it is of worthy notice that C.T. is an effective method of helping to diagnose the motor developmental disturbance in earlier childhood.

Prolonged and concurrent lactic acidosis and hypoglycemia in a patient with monocytic leukemia

Lactic acidosis or hypoglycemia occasionally occurs in patients with neoplastic diseases. We have described a patient with monocytic leukemia who had both, apparently as a result of marked leukemic infiltration of the liver. These metabolic anomalies were greatly ameliorated by chemotherapy. Thus, in leukemia and other malignant disorders in which significant liver infiltration is present, these metabolic derangements should be looked for, as their presence may call for a prompt and intensive treatment.