Truncation of the carboxyl-terminal region of the rat parathyroid hormone (PTH)/PTH-related peptide receptor enhances PTH stimulation of adenylyl cyclase but not phospholipase C

The functional role of the rat parathyroid hormone(PTH)/PTH-related peptide (PTHrP) receptor's carboxyl-terminal region was characterized by comparing the binding and signaling properties of receptors that have 78 and 111 amino acid deletions (R513 and R480, respectively), with those of the 591-amino acid wild-type (WT) receptor. R480 and R513 have 4- and 1.5-fold lower apparent Kd values for rat PTH-(1-34) (rPTH), compared with the WT receptor (WT, 1.81 +/- 0.19 nM; R513, 1.24 +/- 0.12 nM; R480, 0.48 +/- 0.05 nM, mean +/- S.E.). PTH (100 nM)-stimulated cAMP accumulation and polyphosphoinositide hydrolysis both correlated positively with receptor expression. However, whereas PTH-stimulated polyphosphoinositide hydrolysis was indistinguishable among WT and either truncated mutant at comparable levels of expressed receptors, maximal PTH-stimulated cAMP accumulation was 4-6- and 2-3-fold higher in cells expressing R480 and R513, respectively. Furthermore, pretreatment of COS-7 cells with 100 ng/ml of pertussis toxin (PTX) enhanced PTH-stimulated cAMP accumulation in cells expressing the WT receptor, but failed to do so in cells expressing either R480 or R513. Thus, sequences in the PTH/PTHrP receptor's carboxyl-terminal tail lower the affinity of the WT receptor for agonist; directly interact with, or indirectly facilitate the interaction of the receptor with a PTX-sensitive G protein that inhibits adenylyl cyclase; and decrease the efficacy with which the receptor interacts with Gs.

Mechanistically different catalytic antibodies obtained from immunization with a single transition-state analog

The variable-region peptide sequence and steady-state kinetic behavior are compared for a family of catalytic antibodies that arose from the same immune response to a transition-state analog. The crystal structure of the most catalytically active member of the family (17E8) has been solved to 2.5 A resolution and shows that the antibody active site contains a SerH99-HisH35 (H = heavy chain) catalytic dyad analogous to the Ser-His-Asp catalytic triad of serine proteases. The variable-region peptide sequence of the next most active antibody (29G11) differs from that of 17E8 by nine heavy-chain point mutations, and results from computer modeling suggest that the three-dimensional structure of 29G11 is similar to that of 17E8. In addition, 29G11 is an efficient catalytic antibody; it possesses 26% of the hydrolytic activity of 17E8. There is one active-site mutation in 29G11 compared to 17E8; position 99 of the heavy chain of 29G11 contains a glycine residue in place of the nucleophilic serine at this position in 17E8. Consistent with this mutation, results from pH-rate studies and hydroxylamine partitioning experiments indicate that in contrast to the catalytic mechanism of 17E8, the mechanism of 29G11-catalyzed esterolysis does not feature nucleophilic catalysis.

A sustained inward current activated at the diastolic potential range in rabbit sino-atrial node cells

1. After blocking both the hyperpolarization-activated current and the membrane K+ conductance, depolarizations from -80 mV to between -70 and -50 mV induced a sustained current in sino-atrial node cells. We have tentatively designated this current Ist. 2. Ist was blocked by both organic and inorganic Ca2+ channel blockers, but was insensitive to tetrodotoxin (30 microM). Isoprenaline increased Ist. 3. The peak of Ist (at about -50 mV) was increased to 149 +/- 13% (n = 8, P < 0.01) by lowering the external Ca2+ concentration ([Ca2+]o) from 1.8 to 0.1 mM, in contrast to the marked depression of the L-type Ca2+ current. In 0.1 mM [Ca2+]o solution, the nicardipine-sensitive current-voltage relation showed the peak amplitude at about -50 mV and a reversal potential of +37.4 +/- 4.4 mV (n = 5). The isoprenaline-sensitive component also showed a reversal potential of about +30 mV. 4. Reducing [Na+]o from 140 to 70 mM in 0.1 mM [Ca2+]o decreased Ist to 53 +/- 5% (n = 7, P < 0.01). Increasing [Ca2+]o or [Mg2+]o decreased the amplitude of Ist. The half-maximum concentration of Mg2+ inhibition was 2.2 mM. 5. At 1.8 mM [Ca2+]o, Ist was inactivated by clamping for 5s at -10 mV, and gradually recovered after repolarization to -80 mV with a half-time of 1.36 +/- 0.4 s (n = 6). 6. The transitional sino-atrial node cell had minimal amplitude of Ist. 7. These characteristics of Ist are qualitatively comparable to those of the monovalent cation conductance of the L-type Ca2+ channel induced by depleting external divalent cations to the micromolar range. We conclude that Ist is generated by a novel subtype of L-type Ca2+ channel.

Limited protective effects of etomidate during brainstem ischemia in dogs

To evaluate etomidate as a neuroprotective agent in the brain stem, 33 dogs were divided into seven groups and were exposed to isolated, reversible brainstem ischemia in the presence or absence of etomidate using a newly developed canine model of brainstem ischemia. Brainstem auditory evoked potentials (BAEP) and regional cerebral blood flow were measured during ischemia and for 5 hours after reperfusion. This model provides a potential physiological environment in which to test the efficacy of putative brainstem ischemic protective strategies. During ischemia, BAEP were abolished in all animals. Without etomidate 10 minutes of ischemia was of short enough duration to allow complete recovery of BAEP. Ischemia of 20 or 30 minutes' duration resulted in minimal recovery. The dose of etomidate administered did not suppress BAEP or brainstem cardiovascular response to ischemia. In animals receiving etomidate and rendered ischemic for 20 minutes, a significant but only temporary recovery in BAEP was seen. Etomidate failed to have a significant effect in animals rendered ischemic for 30 minutes. The minimal effect of etomidate on the current measures of brainstem function is in contrast to etomidate's known suppressive effect on cortical electroencephalogram and predicts that etomidate does little to alter brainstem metabolism. Etomidate's failure to provide for permanent recovery of BAEP suggests that the drug does not give sufficient protection from ischemia to the brainstem neurons in the auditory pathway. If these auditory neurons reflect brainstem function as a whole, etomidate may not be the protective agent of choice during temporary arterial occlusion of posterior circulation.

Intravenous perflubron emulsion administration improves the recovery of auditory evoked potentials after temporary brain stem ischemia in dogs

Oxygent, a second-generation perfluorocarbon (Perflubron) emulsion (Alliance Pharmaceutical Corporation, San Diego, CA) with superior oxygen delivery characteristics and greater stability than previous perfluorocarbon emulsions, was evaluated as a cerebroprotective agent in a dog model of partial brain stem ischemia. Six dogs were exposed to 20 minutes of isolated brain stem ischemia after receiving an intravenous bolus of Oxygent at a dose of 1.5 ml/kg. Brain stem auditory evoked potentials (BAEP) and regional cerebral blood flow were measured before and during the ischemia and for 5 hours after reperfusion. Changes in BAEP in this group were compared with those in four control dogs that experienced an identical ischemic period but that did not receive Oxygent. During the ischemic period, both control and Oxygent-treated animals experienced a dramatic decline in BAEP to under 10% of the baseline value. After reperfusion, the BAEP increased in both groups to between 50 and 70% of the baseline. In the Oxygent-treated group, the BAEP continued to recover to a final sustained level of over 80% of baseline. In contrast, the control animals suffered a drop in BAEP to 23% of baseline after the brief postischemic peak. The continued improvement in the BAEP in the Oxygent-treated group compared with the control groups suggests that Oxygent may be of some value as a protective agent to the brain stem during ischemia. This effect may be the result of improved oxygen delivery to the brain stem or may be related to other effects of Oxygent, such as reduction of reperfusion injury. Results suggest that Oxygent may be useful as a cerebroprotectant during cerebrovascular surgeries that require temporarily reducing blood flow to the brain stem.

[Double embolization of bronchial artery to control massive hemoptysis]

Bronchial arteriography and double embolization is to block the peripheral bronches of the bronchial artery with micro-gelatin particles and then the trunk of the artery with sponge gelatin. The blood flow from the artery trunk and from the rich arterial bronches which forms B-P bypass is blocked. By this way the embolization is more complete. Clinical observation of 93 cases shows that the success rate reached 91% which indicate that the massive hemoptysis could stopped by this method.

Precore and X region mutants in hepatitis B virus infections among renal dialysis patients

Hepatitis B virus (HBV) variants containing mutations within the X and the precore regions of the viral genome were demonstrated by polymerase chain reaction (PCR) amplification and DNA sequencing in renal dialysis patients with different serological patterns of HBV infection. Among carriers, X region deletion mutants predominated in patients who lost hepatitis B e antigen (HBeAg), or developed anti-HBe, but not in persistently HBeAg-positive patients. The precore region remained wild type in all carriers whether or not they seroconverted from HBeAg to anti-HBe. The frequency of precore and X region mutants was greatest among non-carrier patients with viral antibodies as the only indication of infection and among patients with non-A, non-B hepatitis (NANBH), suggesting an inverse relationship between the presence of wild type HBV markers and the presence of HBV mutants. Furthermore, the detection of one but not the other mutation in many serum samples suggests that these mutations are independently selected for during infection. Finally, the absence of HBV DNA in 21 'uninfected' dialysis patients with normal transaminases and no viral serology, suggests that replication of these mutants is associated with hepatitis. These results have important implications for HBV screening and treatment, as well as for the pathogenesis of chronic infection.

Enhancement of NGF gene expression in rat brain by the memory-enhancing peptide AVP(4-8)

Northern blot analysis of nerve growth factor (NGF) was used to evaluate the effect of exogenous AVP(4-8) on the transcription of NGF gene in rat brain. NGF expression was found to be significantly enhanced by exogenous AVP(4-8) in the hippocampus as well as in the cerebral cortex in a time period of 12 h. This effect was inhibited by an antagonist to AVP(4-8). In addition, gel mobility shift assay was also used to observe the in vitro expression of c-fos gene in rat hippocampal slices. Our results suggest that NGF gene is one of the target genes responsible for memory-enhancing responses induced by AVP(4-8) and that the enhancement of NGF gene expression may share the signaling pathway mediated by AVP(4-8) receptor and c-fos gene expression.

Clinical biochemical and pathologic correlations in Bietti's crystalline dystrophy

We examined three affected members of a Chinese-American family with Bietti's crystalline retinopathy. The clinical characteristics of a 24-year-old proband are contrasted to the clinical findings of her grandmother, for whom we have 26 years of follow-up data. Lymphocytes and fibroblasts from a skin biopsy of the grandmother contained crystalline lysosomal material, which supports the diagnosis. Biochemical studies of the crystalline lysosomal material failed to identify the stored compounds but did not show them to be cholesterol or cholesterol ester. Finally, histopathologic studies performed for this condition demonstrated advanced panchorioretinal atrophy, with crystals and complex lipid inclusions seen in choroidal fibroblasts.

Abnormal class I assembly and peptide presentation in the nonobese diabetic mouse

Presentation of self-antigens by major histocompatibility complex (MHC) class I molecules requires the function of the MHC class II-linked genes Tap-1 and Tap-2. Evidence suggests that interruption of self-peptide presentation results in reduced cell surface expression of MHC class I molecules and the interruption correlates with progression to diabetic autoimmunity in nonobese diabetic (NOD) mice and humans. NOD mice possess a rare Tap-1 allele (Tap-1b); this is associated with reduced Tap-1 mRNA abundance in lymphocytes from diabetes-prone females and decreased conformationally correct class I molecules on the cell surface. In this study, we demonstrate that, similar to lymphoma cell lines with mutations in Tap-1 or Tap-2, the reduced expression of class I molecules on the surface of lymphocytes from diabetes-prone female NOD mice was normalized by incubation at low temperatures or by exposure to class I allele-specific peptides. As would be expected for cells that express surface class I molecules not associated with peptide, female NOD lymphocytes were resistant to lysis by class I-restricted, peptide-specific cytotoxic T lymphocytes. Furthermore, the rate of class I exit from the endoplasmic reticulum of lymphocytes from female NOD mice was delayed as demonstrated by delayed glycosylation. Male NOD mice, which are not prone to diabetes, lacked these functional defects in class I assembly and had near-normal levels of Tap-1 mRNA and exhibited normal density of class I epitopes that were peptide filled. These results are consistent with the possibility that the rare Tap-1b allele is associated with a quantitative defect in Tap-1 expression that influences disease course.

Study of natural diamonds by dynamic nuclear polarization-enhanced 13C nuclear magnetic resonance spectroscopy

The results of a study of two types of natural-diamond crystals by dynamic nuclear polarization (DNP)-enhanced high-resolution solid-state 13C nuclear magnetic resonance (NMR) are reported. The home-built DNP magic-angle spinning (MAS) 13C NMR spectrometer operates at 54 GHz for electrons and 20.2 MHz for carbons. The power of the microwave source was about 30 W and the highest DNP enhancement factor came near to 10(3). It was shown that in the MAS spectra the 13C NMR linewidths of the Ib-type diamond were broader than those of IaB3-type diamond. From the hyperfine structure of the DNP enhancement as a function of frequency, four kinds of nitrogen-centred and one kind of carbon-centred free radicals could be identified in the Ib-type diamond. The hyperfine structures of the DNP enhancement curve that originated from the anisotropic hyperfine interaction between electron and nuclei could be partially averaged out by MAS. The 13C polarization time of DNP was rather long, i.e. 1500 s, and the spin-lattice relaxation time (without microwave irradiation) was about 300 s, which was somewhat shorter than anticipated. Discussions on these experimental results have been made in this report.

Transmission of the human polyomavirus JC virus occurs both within the family and outside the family

JC polyomavirus (JCV) is a ubiquitous symbiote in the human population, infecting children asymptomatically and then persisting in renal tissue. We reevaluated the urinary excretion of JCV in subjects in various age groups using PCR. The detection rate for urinary JCV DNA was 9 to 17% until the age of 20 years; this rate increased dramatically to about 46% at the ages of 20 to 29 years and then increased gradually with age. Therefore, it appears that in most people excretion of JCV begins at the age of 20 to 29 years, which is earlier than suggested previously. Next, we studied the way in which JCV is spread in the human population. We selected eight Japanese families in which both parents and children excreted JCV in their urine. Their JCV subtypes were determined by PCR amplification of a JCV DNA fragment; this was followed by restriction enzyme analysis. JCV species in all JCV-positive family members were classified into either of the two subtypes, subtypes CY and MY, which are prevalent in the Japanese population. The following features of JCV subtype distribution were seen in the families: (i) both subtypes were detected in children of five of the eight families, and (ii) of 21 children who excreted JCV, 14 children excreted the same subtypes excreted by their mothers or fathers, while the remainder (7 children) excreted subtypes different from those excreted by their parents. These features suggest that JCV is transmitted both within the family and outside the family. The data also indicate that vertical transmission is not common in the spread of JCV.

HS-142-1, a potent antagonist of natriuretic peptides in vitro and in vivo

To determine whether HS-142-1 (HS), a potent atrial natriuretic peptide (ANP) receptor antagonist, also inhibits the effects of brain natriuretic peptide (BNP), urodilatin (URO), and C-type natriuretic peptide, in vitro studies were carried out, demonstrating that HS inhibited production of cGMP by rat fetal lung fibroblast cells induced by ANP, BNP, URO, and C-type natriuretic peptide. Acute clearance studies were conducted in euvolemic Munich-Wistar rats under inactin anesthesia to characterize the effects of HS in vivo. In response to ANP, BNP, or URO (4 micrograms/kg priming dose plus 0.5 micrograms/kg per minute for 20 min), urine flow, absolute sodium excretion rates, and fractional sodium excretion exhibited similar increases (four- to fivefold) in vehicle-treated rats; these responses were, however, completely abolished by prior HS treatment. The tendency for GFR to rise during the infusion of natriuretic peptides (NP) was also blocked after HS. By contrast, HS did not block the renal effects of L-arginine, a precursor of nitric oxide, or of furosemide. Furthermore, the inhibition of endogenous NP by HS was associated with small but significant reductions in GFR and absolute and fractional sodium excretion in normal rats under euvolemic but not hydropenic conditions. These studies provide evidence that the observed effects of HS in vivo and in vitro are mediated exclusively by receptors of NP. Together, these data support the view that HS is a highly specific ligand for NP receptors, capable of antagonizing the renal effects not only of exogenous ANP, but also those of BNP and URO.

Crystal structure of a catalytic antibody with a serine protease active site

The three-dimensional structure of an unusually active hydrolytic antibody with a phosphonate transition state analog (hapten) bound to the active site has been solved to 2.5 A resolution. The antibody (17E8) catalyzes the hydrolysis of norleucine and methionine phenyl esters and is selective for amino acid esters that have the natural alpha-carbon L configuration. A plot of the pH-dependence of the antibody-catalyzed reaction is bell-shaped with an activity maximum at pH 9.5; experiments on mechanism lend support to the formation of a covalent acyl-antibody intermediate. The structural and kinetic data are complementary and support a hydrolytic mechanism for the antibody that is remarkably similar to that of the serine proteases. The antibody active site contains a Ser-His dyad structure proximal to the phosphorous atom of the bound hapten that resembles two of the three components of the Ser-His-Asp catalytic triad of serine proteases. The antibody active site also contains a Lys residue to stabilize oxyanion formation, and a hydrophobic binding pocket for specific substrate recognition of norleucine and methionine side chains. The structure identifies active site residues that mediate catalysis and suggests specific mutations that may improve the catalytic efficiency of the antibody. This high resolution structure of a catalytic antibody-hapten complex shows that antibodies can converge on active site structures that have arisen through natural enzyme evolution.

Radiofrequency current catheter ablation of the left atrioventricular accessory pathways with paroxysmal supraventricular tachycardia

Seventy patients with left atrioventricular accessory pathways and paroxysmal supraventricular tachycardia (PSVT) underwent radiofrequency catheter ablation (RFCA). The success rate was 94.3%. Among these patients, 26 had manifest preexcitation syndrome, and 44 had concealed preexcitation. Eighteen patients with concealed preexcitation underwent coronary sinus (CS) pacing, and delta wave appeared in 15. The keys to successful RFCA were correct positioning of the radiofrequency (RF) catheter tip, A/V amplitude ratio, AV interval (in sinus rhythm) and VA interval (during SVT or ventricular pacing). After 1-14 months of follow-up, two patients had supraventricular tachycardia (SVT) recurrence.

Phylogenetic comparison between archetypal and disease-associated JC virus isolates in Japan

We examined the phylogenetical correlation between two types of JC virus (JCV) isolates, archetypes derived from the urine of nonimmunocompromised individuals and PML-types derived from the brain of patients with progressive multifocal leukoencephalopathy (PML) in Japan. A phylogenetic tree was constructed for eight JCV isolates, five PML-types obtained in this and previous studies and three representative archetypes, from DNA sequence data on the VP1 (major capsid protein) gene. The eight isolates were divided into two major groups, named subtypes MY and CY after the representative archetypal isolates. Four of five PML-type isolates belonged to subtype MY, and the other one to subtype CY. Isolates belonging to subtype MY were further divided into two groups; one group containing archetype MY and three PML-types and the other one containing archetype YI and a PML-type. These findings, together with those in our previous study that correlated various JCV isolates in the world provide evidence for the hypothesis that JCVs associated with PML may have been generated from archetypal JCVs persisting in the patients.

[The inhibitory effect and its mechanism of transferrin on FSH-induced differentiation of granulosa cells]

Transferrins are a class of related metal-binding transport glycoproteins for transporting iron to various organs and tissues of the body. In recent years, it has been reported that the transferrin can play an important role in the local regulation of ovarian function, apart from its iron-binding characteristic. Transferrin could attenuate FSH-induced differentiation of rat and human granulosa cells and its mechanisms were considered as follows: (1) Transferrins partially blocked the binding of FSH with its receptors on granulosa cells and reduced the formation of intracellular cAMP, and therefore inhibited the expression of FSH receptors. (2) Acting sites beyond cAMP formation also existed for the inhibitory effect of transferrin on inhibin and estradiol production. (3) The inhibitory effect of transferrin seemed not to be involved in the changes of protein kinase C activity, the calcium release and "proliferation-differentiation reversed mechanism" in granulosa cells.