Bovine liver dihydropyrimidine amidohydrolase: pH dependencies of the steady-state kinetic and proton relaxation rate properties of the Mn(II)-containing enzyme

The essential Zn(II) in bovine liver dihydropyrimidine amidohydrolase (DHPase) was removed by incubation with 2,6-dipicolinic acid and replaced with Mn(II). Electron paramagnetic resonance studies of Mn(II) binding show that there are four binding sites per tetramer, and the dissociation constant at pH 7.5 is 13.5 microM. The substitution of Mn(II) for Zn(II) increases the specific activity of the enzyme approximately sixfold but has only a small effect (twofold increase) on the Km for 5-bromo-5,6-dihydrouracil (BrH2Ura). The pH dependence of the catalytic properties of Mn(II)-DHPase is the same as for the Zn(II) enzyme (Lee, M., Cowling, R., Sander, E., and Pettigrew, D. (1986) Arch. Biochem. Biophys. 248, 368-378). The pH dependence is well described in terms of the ionization of a single group with a pK of about 6 in the free enzyme. The ionization of this group is required for catalytic activity. The substitution of Mn(II) for Zn(II) does not affect the pH dependence of DHPase catalysis and therefore strongly suggests that the ionizable group is an amino acid residue at or near the active site, rather than a metal-bound water molecule. The pH dependence of the enhancement of the paramagnetic effect of the DHPase-Mn complex on the relaxation rate of the solvent water protons also is well described in terms of the ionization of a single group with a pK of about 6. Ionization of the group which is involved in catalysis also perturbs the environment of the bound Mn(II). The ionization of the active site group does not affect the number of exchangeable water molecules but does affect the symmetry of the environment of the bound Mn(II) and its electron relaxation.

Antibody that inhibits human immunodeficiency virus reverse transcriptase and association with inability to isolate virus

Most individuals infected with human immunodeficiency virus (HIV), the causative agent of acquired immune deficiency syndrome, produce an antibody against the viral reverse transcriptase (RT). Our studies show that 67% of HIV-seropositive individuals (33 of 49) produced an antibody that specifically inhibited viral RT enzyme activity. We were able to isolate HIV from only 18% of these individuals (6 of 33). On the other hand, virus was readily isolated from 63% of HIV-seropositive individuals (10 of 16) who did not demonstrate this antibody. Further examination of this RT-inhibiting antibody and its role during virus infection is needed, as it may prove to be of diagnostic, prognostic, or therapeutic value in this study and treatment of acquired immune deficiency syndrome.

Sensitive reverse transcriptase assay to detect and quantitate human immunodeficiency virus

A sensitive biochemical assay of viral reverse transcriptase (RT) was developed that is useful for both the detection and quantitation of human immunodeficiency virus (HIV), the agent responsible for acquired immune deficiency syndrome in humans. This assay gave a 20- to 40-fold increase in enzyme activity over the current method used for RT detection of HIV. The test is based on a previous biochemical study showing the unusual stability of avian oncornavirus RNA-dependent DNA polymerases at 30 degrees C for at least 2 days. Our study shows that the HIV polymerase is stable at 30 to 37 degrees C for up to 3 days. By using this sensitive RT assay, as few as 250 HIV virions can be quantitated directly in tissue culture medium. This assay should prove useful in studies in which the detection of HIV or the quantitation of the number of virions is required.

Clonidine induced variations of plasma norepinephrine and blood pressure in essential hypertension

To assess the contribution of sympathetic outflow to blood pressure in patients with essential hypertension, clonidine induced variations of plasma norepinephrine, mean arterial pressure and the pulse rate three hours after a 300 μg dose of oral clonidine, an antihypertensive agent that decreases central sympathetic outflow, were studied.

Baseline and clonidine suppressed plasma norepinephrine levels were not significantly different between the normal controls and patients with essential hypertension. The average plasma norepinephrine level, mean arterial pressure and pulse rate were significantly decreased from the baseline value in both normal control and essential hypertension (p<.005). The depressor response to sympathetic inhibition after clonidine were exaggerated in significant proportion in patients with essential hypertension compared to normal control group.

Our study suggests that the pressor sensitivity to norepinephrine plays more important role than sympathetic overactivity in some patients with essential hypertension.

Influence of naloxone on electro-acupuncture analgesia using an experimental dental pain test. Review of possible mechanisms of action

The purpose of this study was to examine in man the analgesic effect of non-segmental electroacupuncture (EA) limited to a single point (Hoku hand point) and the influence of naloxone using an original modified electrical dental pain test. Results in the literature are still contradictory as to the degree and specificity of acupuncture analgesia and its opioid nature. Acupuncture techniques as well as experimental pain models are factors accounting for the discrepancies in the results. For this reason, we designed an experimental pain test characterized by a high degree of specificity, validity and reliability. We chose optimal conditions for eliciting specific acupuncture effect, i.e. non-segmental, low frequency and painful intensity range. A cross-over repeated measure experimental design was used. Five normal trained subjects participated in 65 sessions under four conditions (control, EA, EA+naloxone, EA+placebo). Changes in experimental dental pain thresholds served as indices of analgesia. The results indicated a 27% pain threshold increase after 30 minutes of EA stimulation (p less than .0001), with no differential effect between pain detection (mild pain sensation) and pain discomfort (strong pain sensation). This increase was partially blocked by the double blind injection of 0.8 mg naloxone IM (p less than .005). The experiment was designed in such a way as to prevent the occurrence of a stress analgesic effect. The endogenous opioid system was shown to be partially involved in acupuncture analgesia. Other mechanisms of action are discussed in view of the literature findings.

Effects of simultaneous viewing and vaporization of plaques using the steerable, laser-heated metal cap in the atherosclerotic monkey model

A steerable, fiberoptic catheter coupled to a laser light guide tipped with a metal cap was used. Four monkeys fed an atherogenic diet for 7-8 years were angiographed and were found to have extensive mural plaque in the iliac arteries. Plaque sites in these monkeys were vaporized using the laser-heated metal cap. Energies of 1.5-9 Joules were employed. Application of the energy was tangential of perpendicular to the plaque. Lased sites were examined histologically at 24 hr or at 3 months after treatment. No effect was seen at 1.5 Joules. Three to six Joules tangentially produced a superficial lesion that extended into the tunica intima. Six Joules perpendicularly produced a burn into the tunica adventitia, with damage to the vasavasorum. Nine Joules tangentially produced a burn into the tunica media. Three months after treatment, this lased site showed no stenosis or aneurysm formation.

The lipid binding, regulatory domain of protein kinase C. A 32-kDa fragment contains the calcium- and phosphatidylserine-dependent phorbol diester binding activity

Trypsinization of rat brain protein kinase C (80 kDa) into 50- and 32-kDa fragments occurred without inhibition of [3H]phorbol dibutyrate ([3H]PDBu) binding activity. The 50-kDa fragment, the catalytic domain (Inoue, M., Kishimoto, A., Takai, Y., and Nishizuka, Y. (1977) J. Biol. Chem. 252, 7610-7616), was further degraded by trypsin, whereas the 32-kDa fragment was resistant. Protein kinase activity and the [3H]PDBu binding activity were completely separated upon gel filtration of a solution containing Triton X-100/phosphatidylserine mixed micelles and trypsinized protein kinase C. Pooled fractions of the [3H]PDBu binding activity contained a 32-kDa fragment exclusively. The binding of [3H]PDBu to this fragment was dependent on calcium and phosphatidylserine and was of high affinity (Kd = 2.8 nM) and of essentially identical specificity to that of native protein kinase C. It is concluded that the 32-kDa fragment represents a lipid binding, regulatory domain of protein kinase C.

Clinical laser recanalization of coronary obstruction. Angioscopic and angiographic documentation

Coronary angioscopy was used to assess the configuration and cross-sectional luminal area of atherosclerotic obstruction prior to and following laser recanalization in a patient at the time of bypass surgery. Angioscopy served as a useful adjunct to angiography by providing documentation of immediate improvement and patency of the laser-recanalized site.

Sympathetic effects of manual and electrical acupuncture of the Tsusanli knee point: comparison with the Hoku hand point sympathetic effects

Sympathetic effects of manual and electrical acupuncture of the Tsusanli knee point were evaluated by thermography in 19 normal subjects under the same procedure used in a previous study using the Hoku hand point. A generalized long-lasting warming (sympathetic inhibition) effect was observed under manual and electrical acupuncture of the Tsusanli point. In addition, a segmentally related short-lasting cooling (sympathetic activation) effect occurred with Tsusanli electrical acupuncture only. The warming effect is consistent with the results of the Hoku study and appears to be a central sympathetic inhibition evoked by acupuncture. The cooling effect was segmentally related to the acupuncture site in both studies. This cooling effect most likely reflects a segmental activation of vasomotor spinal reflexes and not a general emotional arousal. These sympathetic mechanisms may be functionally correlated with central and peripheral mechanisms of acupuncture analgesia.

Cloning and expression of multiple protein kinase C cDNAs

Three different protein kinase C related cDNA clones were isolated from a rat brain cDNA library and designated PKC-I, PKC-II, and PKC-III. These each encode very similar, but distinct, polypeptides that contain a region homologous with other protein kinases. COS cells transfected with either PKC-I or PKC-II specifically bind at least 5-fold more 3H-PDBu (phorbol ester) than control cells. An increase in Ca2+, phosphatidylserine, and diacylglycerol/phorbol-ester-dependent protein kinase activity is also observed in COS cells transfected with either PKC-I or PKC-II. The physiological implications of the discovery of three protein-kinase-C-related cDNAs are discussed.

Malignant lymphoma of the heart in acquired immune deficiency syndrome

Malignant lymphoma of the heart was found at autopsy of two homosexual men with acquired immune deficiency syndrome (AIDS). Both patients had symptoms and signs of cardiac dysfunction, and it is likely that the immediate cause of their deaths was related to the cardiac tumors. In both cases, there was lymphomatous involvement of other organs, but the heart was the predominant site of disease. There was prominent endocardial and myocardial involvement, and both tumors were high grade large cell lymphomas with plasmacytoid features. In both instances, the lymphomas were diagnosed only at the autopsy, despite extensive antemortem cardiac evaluation in one patient. The clinicopathologic correlation, gross pathologic and histologic findings of the tumor, and their pattern and distribution suggest a de novo origin of the lymphoma in the heart in these two patients. Lymphomatous infiltration of the heart should be suspected in patients with AIDS who have cardiac symptoms.

Aluminum induced reversible change in permeability of the blood-brain barrier to [14C]sucrose

To determine whether aluminum alters the permeability of the blood-brain barrier (BBB), 4 groups of rats were given an intraperitoneal injection of aluminum chloride, aluminum lactate, aluminum hydroxide or physiological saline. Two hours later, [14C]sucrose was injected, and brain radioactivity was measured from 5 different brain regions. The permeability capillary surface area (PA) was calculated by the dual compartment model (plasma-brain) proposed by Rapoport et al. The PAs for [14C]sucrose were significantly elevated in all brain regions of the animals injected with the aluminum chloride or aluminum lactate. However, the aluminum hydroxide group showed no BBB permeability change. In the second experiment, the reversibility of the aluminum induced BBB change was examined. PA was determined at 2, 4 or 24 h after exposure to aluminum lactate. Significant permeability changes were observed at 2 and 4 h after aluminum. However, the difference disappeared by 24 h. These findings indicate that exposure to a high level of aluminum alters the function of BBB in the rat and the aluminum induced BBB change is reversible. An increase in the blood aluminum level and time after exposure appear to be important factors associated with the BBB permeability change. Implications of the results are discussed in terms of aluminum's potential action on the endothelial cells.

Bovine liver dihydropyrimidine amidohydrolase: pH dependencies of inactivation by chelators and steady-state kinetic properties

Dihydropyrimidine amidohydrolase (EC 3.5.2.2) catalyzes the reversible hydrolysis of 5,6-dihydropyrimidines to the corresponding beta-ureido acids. Previous work has shown that incubation of this Zn2+ metalloenzyme with 2,6-dipicolinic acid, 8-hydroxyquinoline-5-sulfonic acid, or o-phenanthroline results in inactivation by Zn2+ removal by a reaction pathway involving formation of a ternary enzyme-Zn2+-chelator complex which subsequently dissociates to yield apoenzyme and the Zn2+-chelate (K. P. Brooks, E. A. Jones, B. D. Kim, and E. G. Sander, (1983) Arch. Biochem. Biophys. 226, 469-483). In the present work, the pH dependence of chelator inactivation is studied. The equilibrium constant for formation of the ternary complex is strongly pH dependent and increases with decreasing pH for all three chelators. There is a positive correlation between the value of the equilibrium constant observed for each chelator and the value of its stability constant for formation of Zn2+-chelate. The affinity of the chelators for the enzyme increases in the order 8-hydroxyquinoline-5-sulfonic acid greater than o-phenanthroline greater than 2,6-dipicolinic acid. The first-order rate constant for breakdown of the ternary complex to yield apoenzyme and Zn2+-chelate is invariant with pH for a given chelator but is different for each chelator, increasing in the reverse order. The pH dependence of the inactivation shows that two ionizable groups on the enzyme are involved in the inactivation. On the other hand, the steady-state kinetic behavior of the enzyme is well-described by ionization of a single group with a pK of 6.0 in the free enzyme. The basic form of the group is required for catalysis; protonation of the group decreases both Vmax and the apparent affinity for substrate. Conversely, binding of substrate decreases the pK of this group to about 5. L-Dihydroorotic acid is shown to be a competitive inhibitor of dihydropyrimidine amidohydrolase. Binding of L-dihydroorotic acid increases the pK of the ionizable group to 6.5. The agreement between the pK in the enzyme-L-dihydroorotic acid complex and the higher pK observed in the pH dependence of inactivation by chelators suggests that the same group is involved in the binding of acid, and chelators. The different effects of substrate and L-dihydroorotic acid on the pK suggest that the binding modes of these two ligands may be different and suggest a structural basis for the mutally exclusive substrate specificities of dihydropyrimidine amidohydrolase and dihydroorotase.

Plasma apolipoproteins and lipids in normal persons and patients with hypertension

We measured apolipoprotein A (ApoA), apolipoprotein B (ApoB), and lipid levels in 115 hypertensive patients and 100 normal subjects in order to evaluate the risk of atherosclerotic heart disease in hypertensive patients. The hypertensive patients were divided into the following subgroups: blood pressure controlled (A) and uncontrolled hypertensive subgroup (B), and without complication (C) and with complication (D).

In the hypertensive group, the mean plasma ApoA, ApoB, total cholesterol, triglyceride and beta-lipoprotein (LpB) levels were significantly higher than in the normal control group. The plasma high density lipoprotein cholesterol (HDL-cholesterol) level was not significantly different between the hypertensive group and the normal control group. ApoB/A ratio in the hypertensive group was higher than in the normal control group, but the difference was not significant statistically.

In the hypertensive subgroups, plasma Apo A was higher in all the hypertensive subgroups compared to normal control group, but these differences were not statistically significant. In subgroup B, C and D, the plasma ApoB level increased significantly as compared to the normal control group, but not so in the subgroup A. All of the subgroups had significantly higher levels of triglyceride and LpB level than the normal control group. HLD cholesteol level of all of the subgroups did not show any significant difference as compared to the normal control group. In subgroup B, C and D, the ApoB/A ratio was not significantly different from the normal control group. In the subgroup A, ApoB/A ratio was lower than in the normal control group, this was not significant statistically. Between subgroup A and B, and subgroup C and D, all of the plasma lipids and apolipoproteins did not show significant differences.

Thus our results showed that ApoB, LpB and triglyceride, which are closely related to atherosclerotic heart disease, were significantly increased in any of hypertensive subgroups compared to the normal control group.

Primary malignant lymphoma of the anorectum in homosexual men

Two homosexual men presented with primary malignant lymphomas of the anorectum. Each patient presented with a painful mass, diagnosed by biopsy and immunologic cell marker studies. One patient, who had a reversed T4/T8 cell ratio, developed a local relapse of the tumor 11 months after radiotherapy, and Pneumocystis carinii pneumonia. The other patient, with a normal T4/T8 ratio, remained lymphoma-free and without evidence of opportunistic infection 25 months after combined chemotherapy and radiotherapy. Anorectal pathologic findings in homosexual men includes proctitis, inflammatory stricture, fissure, or anal warts. Malignant anorectal diseases, such as Kaposi's sarcoma, and cloacogenic or squamous cell carcinomas have been described in homosexual men. Primary malignant lymphoma of the anorectum is rare in both the homosexual and general populations.

Analysis of a scan conversion algorithm for a real-time sector scanner

In a conventional digital ultrasound sector scanner, the sampling space is in polar coordinates while the display space is in Cartesian coordinates, which necessitates a coordinate transformation process. As a result, a number of artifacts appear in the displayed image. In this paper, we propose a new data space, to be called the uniform-ladder space, in which the sampling space is the same as the display space. In this new approach, sampled points are uniformly distributed in each horizontal line as well as in each radial ray so that the data are displayed as they are acquired without any interpolation process required. To implement the new real-time sector scanner, two frequency synthesizers with very high-speed switching time and a low-pass filter are required. The former determines the precise location of the data points in the new data space, and the latter fills the gap between pixels in the horizontal direction. Mathematical models of various interpolation schemes are devised to compare their performance.

Guanosine thiophosphate derivatives as substrate analogues for phosphoenolpyruvate carboxykinase

The interactions of nucleotides with phosphoenolpyruvate carboxykinase were studied by using the stereospecific thiophosphate analogues of GDP and GTP. The metal ion dependent stereoselectivity of these analogues was determined by using steady-state kinetics. The RP and SP isomers of guanosine 5'-O-(1-thiodiphosphate) (GDP alpha S) were substrates with low turnover, and a small preference for the RP isomer was observed. Neither the enzyme-metal nor the nucleotide-metal complex elicited any substantial change in the selectivity. Guanosine 5'-O-(2-thiodiphosphate) (GDP beta S) exhibited no substrate activity for the enzyme, regardless of the cations. This nucleotide was a competitive inhibitor against GDP, however. Both RP and SP diastereomers of guanosine 5'-O-(1-thiotriphosphate) (GTP alpha S) were good substrates for phosphoenolpyruvate carboxykinase; in several cases, depending upon the cation, kcat and/or Vm/Km for the RP isomer is greater than for the substrate GTP. The enzyme-metal complex but not the nucleotide-metal complex affects the relative Km and the Vmax values. In contrast, guanosine 5'-O-(2-thiotriphosphate) (GTP beta S) (SP) is a much better substrate (greater than 50 times) than is GTP beta S (RP). The metal ions have little effect on the selectivity. These results suggest a specific interaction of the beta-phosphate of the nucleotide with the protein. The analogue guanosine 5'-O-(3-thiotriphosphate) (GPT gamma S) serves as a substrate to yield GDP and thiophosphoenolpyruvate. The latter was detected by 31P NMR and was shown to slowly hydrolyze to form phosphoenolpyruvate.(ABSTRACT TRUNCATED AT 250 WORDS)