Functional expression of three P2X(2) receptor splice variants from guinea pig cochlea

ATP has been suggested to act as a neurotransmitter or a neuromodulator in the cochlea. The responses to ATP in different cell types of the cochlea vary in terms of the rate of desensitization and magnitude, suggesting that there may be different subtypes of P2X receptors distributed in the cochlea. Recently three ionotropic P2X(2) receptor splice variants, P2X(2-1), P2X(2-2), and P2X(2-3,) were isolated and sequenced from a guinea pig cochlear cDNA library. To test the hypothesis that these different splice variants could be expressed as functional homomeric receptors, the three P2X(2) receptor variants were individually and transiently expressed in human embryonic kidney cells (HEK293). The biophysical and pharmacological properties of these receptors were characterized using the whole cell patch-clamp technique. Extracellular application of ATP induced an inward current in HEK293 cells containing each of the three splice variants in a dose-dependent manner indicating the expression of homomeric receptors. Current-voltage (I-V) relationships for the ATP-gated current show that the three subtypes of the P2X(2) receptor had a similar reversal potential and an inward rectification index (I(50 mV)/I(-50 mV)). However, the ATP-induced currents in cells expressing P2X(2-1) and P2X(2-2) variants were large and desensitized rapidly whereas the current in those cells expressing the P2X(2-3) variant was much smaller and desensitized slower. The order of potency to ATP agonists was 2-MeSATP > ATP > alpha,beta -MeATP for all three expressed splice variants. The ATP receptor antagonists suramin and PPADS reduced the effects of ATP on all three variants. Results demonstrate that three P2X(2) splice variants from guinea pig cochlea, P2X(2-1), P2X(2-2), and P2X(2-3), can individually form nonselective cation receptor channels when these subunits are expressed in HEK293 cells. The distinct properties of these P2X(2) receptor splice variants may contribute to the differences in the response to ATP observed in native cochlear cells.

Binding sites for human interferon-gamma in protocerebrum and hemolymph of tobacco hornworm (Manduca sexta) larvae differ in sensitivity to polycationic peptides

We have recently characterized specific binding sites for human interferon-gamma on particulates prepared from the protocerebrum and hemolymph of tobacco hornworm larvae, Manduca sexta ¿(Parker, M.S., Ourth, D.D., 1999. Comp. Biochem. Physiol. B 122, 155-163). The sensitivity to sulfated polysaccharides indicated an involvement of oligobasic epitopes of hIFN-gamma in the binding. In the present study, we found that polycationic peptides inhibited the binding of [125I]hIFN-gamma to particulates from either the hemolymph or the protocerebrum of Manduca sexta larvae. With amino acid homopolymers, the rank order of potency was poly-L-lysine > poly-L-arginine >> poly-L-ornithine, while the acidic side chain polymer poly-L-aspartate was not inhibitory. However, the potency of all polycationic peptides was at least three-fold greater at the hemolymph particulates. Also, acidic polysaccharides such as heparin were much more efficacious in the inhibition of hIFN-gamma binding to hemolymph relative to protocerebral particulates. The peptide polycations inhibited the binding of [125I](Leu31,Pro34)human peptide YY, a ligand selective for the Y1 subtype of the neuropeptide Y receptor, to rabbit kidney or to parietal cortex particulates with the expected rank order of poly-L-arginine > poly-L-lysine >> poly-L-ornithine, and with little cross-tissue difference in affinity. The selectivity observed with M. sexta particulates indicates a preferential involvement of oligobasic lysine-rich C-terminal sequences of IFN-gamma, while large insect tissue-related affinity differences point to involvement of diverse oligoacidic sequences in binding to protocerebrum and hemolymph sites. This study provides evidence for the presence of molecules in lepidopteran larvae that are similar in structure to vertebrate co-receptors of IFN-gamma, and adds to the characterization of these binding sites.

Ligand association with the rabbit kidney and brain Y1, Y2 and Y5-like neuropeptide Y (NPY) receptors shows large subtype-related differences in sensitivity to chaotropic and alkylating agents

The binding to rabbit kidney or hypothalamic particulates of the subtype-selective neuropeptide Y (NPY) receptor ligands [125I](Leu31,Pro34)hPYY (as Y1 site label at 2 nM human pancreatic polypeptide (hPP)), [125I]-hPYY(3-36) (Y2 label), and [125I]-hPP (Y5 label) displayed great differences in sensitivity to alkylators and chaotropic agents. Sensitivity to a nonionic chaotrope, urea, was much higher for the Y1 binding than for the Y5-like binding or the Y2 binding. The non-selective alkylator N-ethylmaleimide (NEM) and several alkylators selective for aminergic receptors were much more efficacious against the Y1 relative to the Y2 binding. Similar differences could be confirmed with the attachment of Y1 and Y2-selective tracers to CHO cells expressing the cloned guinea-pig Y1 or Y2 receptors. The Y5-like binding was quite insensitive to NEM, but sensitive to chloroethylclonidine (CEC) and prazobind, which were less potent at the Y1, and especially at the Y2 site. The unrestricted-access alkylator 2-aminoethyl methanethiosulfonate inhibited the binding to all subtypes, while the restricted-access agent 2-(trimethylammonium)ethylmethanethiosulfonate poorly inhibited the Y5-like binding, or the guanine nucleotide-insensitive Y2 binding. These results are compatible with an active conformation of the Y5-like site dependent on maintenance of a shared hydrophobic cavity. The Y2 sites resistant to guanosine polyphosphates and restricted-access alkylators were detected mainly in particulates slowly solubilized by cholate at 0-5 degrees C; these sites could be clustered.

FMRFamides exert a unique modulation of rodent pancreatic polypeptide sensitive neuropeptide Y (NPY) receptors

FMRFamide and related peptides (RFamides) were found to inhibit the association binding of iodinated human pancreatic polypeptide ([125I]hPP) to Y5-like neuropeptide Y (NPY) receptor in rodent tissues. An allosteric regulation of the activity of the rodent kidney PP-sensitive neuropeptide Y (NPY) receptor by RFamides was indicated by potency decrease with particle concentration in the inhibition of the association binding of 125I-labeled human pancreatic polypeptide (hPP) by RFamides at rabbit kidney membranes. The competition by C-terminal hexapeptide of hPP (LTRPRY.NH2) did not show such affinity change. The steady-state binding of hPP showed little sensitivity to any of the RFamides tested. The Y1-selective binding of [125I][Leu31,Pro34]hPYY (at 2 nM hPP) was much less sensitive to RFamides than the binding of [125I]hPP, albeit with some differences across tissue or cell types. The binding of Y2-selective agonist 125I-labeled human peptide YY (3-36) was quite insensitive to RFamides. The presence of a unique component in the inhibition of hPP binding by RFamides was further indicated by a degree of antagonism with phospholipase C inhibitor U-73122, and by an only limited cooperation with a N5-amiloride compound, and with alkylator chloroethylclonidine. Change of the chirality of individual residues in the FMRFamide molecule produced a significant reduction of inhibitory potency only with D-Phe in the C-terminal position. Substitution of the (C-3) L-Met by L-Leu greatly increased the inhibitory potency of RFamides relative to otherwise identical congeners. RFamides could act both as ligands of membrane neighbors of the PP receptor, and as competitors of Y5-like NPY receptor epitopes that accommodate the C-terminal aspects of agonist peptides.

Phosphorothioate oligodeoxynucleotides can selectively alter neuronal activity in the cochlea

A growing body of evidence indicates that extracellular adenosine triphosphate (ATP) may have a major role in cochlear function. Antagonists of ionotropic ATP receptors (P2X2) have significant effects on cochlear potentials and distortion product otoacoustic emissions (DPOAEs). We tested whether antisense oligodeoxynucleotides (ODNs) would mimic the functional deficiencies induced by the ATP antagonists through binding to P2X2 ATP receptor mRNA and thereby reduce the number of ATP receptors expressed in the membrane of the cells. Both a phosphorothioate ODN (S-ODN) antisense and a phosphodiester ODN (P-ODN) antisense to the P2X2 sequence and random sense ODNs containing 21 nucleotides were administered chronically (7 days) to the guinea pig cochlea via the perilymph compartment. Sound evoked cochlear potentials (cochlear microphonic; summating potential; compound action potential of the auditory nerve, CAP; latency of the first negative peak in the CAP, N1 latency) and DPOAEs were monitored to assess the effects of the ODNs. Results indicate that the phosphorothioate derivatives of both the antisense and random sense ODNs suppressed the CAP and prolonged the N1 latency with no significant effect on the other parameters. The P-ODNs had no effect. Since both the antisense and random sense S-ODNs had the same effect, we conclude that the S-ODNs affected neuronal function in a manner that did not involve binding to the ATP receptor mRNA.

Characterization of rabbit kidney and brain pancreatic polypeptide-binding neuropeptide Y receptors: differences with Y1 and Y2 sites in sensitivity to amiloride derivatives affecting sodium transport

Sites sensitive to human and rat pancreatic polypeptides (hPP and rPP) accounted for more than 30% of the specific binding of [125I](Leu31,Pro34) human peptide YY (LP-PYY) in particulates from rabbit kidney cortex, and about 10% of the specific binding in membranes from rabbit hypothalamus. The binding of [125I]hPP or [125I]rPP showed a high-affinity displacement with either hPP, rPP, LP-PYY, neuropeptide Y or peptide YY (Ki below 50 pM for all), while being quite insensitive to Y2-selective ligands. The PP binding had a high sensitivity to alkali cations and inhibitors of phospholipase C, very similar to that of LP-PYY binding 'masked' by excess cold hPP. However, as different from the Y1-like LP-PYY binding, but similar to the binding of the Y2-selective ligand [125I]human peptide YY(3-36) (hPYY(3-36)), the PP binding showed a low sensitivity to guanosine polyphosphates. The PP binding was much more sensitive to N5-substituted amiloride inhibitors of Na+ transport than the binding of LP-PYY, or that of hPYY(3-36). The inhibition of PP binding by N5-substituted amilorides was not enhanced by guanine nucleotides or by phospholipase C blockers. However, pairing of N5-substituted amilorides disproportionately increased the inhibition of hPP binding. Thus, in rabbit kidney or hypothalamus, the high-affinity PP-responding sites share some of the basic properties of the Y1 and Y2 sites, but are distinguished from both by a high sensitivity to compounds affecting sodium transport. These PP/NPY receptors could associate with membrane structures involved in the control of ion balance and osmotic responses.

Specific binding of human interferon-gamma to particulates from hemolymph and protocerebrum of tobacco hornworm (Manduca sexta) larvae

Specific binding sites for human interferon-gamma (hIFN-gamma) were found on particulates prepared from the hemolymph and protocerebrum of fifth-instar larvae of the tobacco hornworm, Manduca sexta. A portion of these sites could be solubilized in an active form by the zwitterionic detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propane sulfonate (CHAPS). A well-defined specific binding was also associated with hemolymph particulate residue after solubilization by CHAPS. About one-half of [125I]hIFN-gamma binding could be displaced by heparin. The bound hIFN-gamma could be covalently cross-linked to the binding sites using disuccinylamide suberate, and the molecular weight range of these complexes was 200-800 kDa as determined by density gradient sedimentation and gel-exclusion chromatography. Only a small fraction of the hemolymph IFN-gamma binding could be competed by another mammalian cytokine, rat prolactin (rPRL), while there was no sensitivity to rat growth hormone. The small specific rPRL binding found in Manduca hemolymph showed an affinity similar to the prolactin sites found in the liver of pregnant rats. The detergent-insoluble Manduca hIFN-gamma binding was bimodal and similar in affinity distribution to the binding found with human platelet membranes (Kdiss range 0.1-2 nM). The detergent-solubilized IFN-gamma sites were homogenous, with a Kdiss of about 1.5 nM. The IFN-gamma binding sites in Manduca tissues may therefore include molecular species similar to the known invertebrate cytokine receptors and proteoglycan co-receptors.

Characterization of Y1, Y2 and Y5 subtypes of the neuropeptide Y (NPY) receptor in rabbit kidney. Sensitivity of ligand binding to guanine nucleotides and phospholipase C inhibitors

The binding of two peptide YY/neuropeptide Y analogues selective for major subtypes of neuropeptide Y (NPY) receptors was compared in particulates from rabbit kidney cortex employing modulators of activity of G-proteins, phospholipase enzymes, and ion channels. The binding of (Leu31,Pro34)human peptide YY resembled the patterns observed previously for the brain tissue Y1 receptor, exhibiting a high sensitivity to monovalent cations, disulfide disruptors, guanosine polyphosphates and phospholipase C inhibitors. However, this binding was bimodal in response to human pancreatic polypeptide and to peptides selective for the Y2 subtype of the NPY receptor, displaying a large component pharmacologically similar to the brain Y5 receptor. This kidney Y5-like binding largely shared the sensitivity to monovalent cations, guanine nucleotides and phospholipase C inhibitors found for either the kidney or the brain Y1 receptor, and also was activated by Ca2+ ion. Both Y1- and Y5-like binding in the kidney displayed a uniformly low reactivity to a nonpeptidic Y1 antagonist, BIBP-3226, and to a receptor peptide mimetic, mastoparan analogue MAS-7. The kidney Y2 binding shared the low sensitivity to ionic environment observed for the brain Y2 subtype, and was only partially sensitive to guanine nucleotides or to MAS-7. The Y2 liganding had a sensitivity to phospholipase C inhibitors similar to the Y1/Y5 binding. This reactivity was retained in the fraction of the Y2 receptor persisting detergent solubilization in a high-affinity form, which, however, was activated rather than inhibited by G-protein agonists.

Novel variant of the P2X2 ATP receptor from the guinea pig organ of Corti

ATP functions as a neurotransmitter and a neuromodulator in various tissues by acting on metabotropic (P2Y) and ionotropic (P2X) receptors. Evidence suggests that ATP activates P2X receptors on several cell types in the organ of Corti of guinea pig including outer hair cells (OHCs), Deiters' cells, Hensen's cells, pillar cells and inner hair cells (IHCs). Determining the sequence and structure of P2X receptors in guinea pig organ of Corti is important for understanding the function of ATP in the cochlea. We screened a guinea pig organ of Corti cDNA library for P2X2 ATP receptors using rat P2X2 cDNA as a probe. We sequenced three P2X2 variants which were found to be abundant in this library. One is a novel P2X2 isoform (P2X2-3) created by a retained intron coding for an additional 27 amino acids (81 bp) in the putative extracellular domain. We have also sequenced a variant (P2X2-2) that lacks both the 81-bp sequence and a 192-bp sequence in the 3' intracellular domain. A third variant (P2X2-1) contains the intracellular 192-bp sequence but not the extracellular 81-bp sequence found in P2X2-3. The multiple transcripts arise from alternative intron and exon splicing events. In situ hybridization with a probe common to the three variants localized P2X2 to many of the cells of the organ of Corti.

Characterization of G protein and phospholipase C-coupled agonist binding to the Y1 neuropeptide Y receptor in rat brain: sensitivity to G protein activators and inhibitors and to inhibitors of phospholipase C

Binding of a Y1-subtype-selective agonist of neuropeptide Y (NPY) receptor, (Leu31,Pro34)human peptide YY (LP-PYY), to particulates from four rat brain areas (parietal cortex area 1, piriform cortex, anterior hypothalamus and hippocampus) showed a distinct response to LP-PYY and PYY, a uniformly low sensitivity to ligands selective for the Y2, Y4 and Y5 NPY receptor subtypes and high sensitivity to a Y1 site-selective antagonist, BIBP-3226. The Y1 binding was sensitive to guanine nucleotide-binding protein (G protein) agonist and antagonist nucleotides, with the rank order of guanosine 5'-O-(thiotriphosphate) (GTP gamma S) > GTP > GDP > guanosine 5'-O-(thiodiphosphate). However, guanine nucleotides did not affect about one third of the specific Y1 binding. Most of Y1 binding could be inhibited by a G protein nucleotide site/docking site receptor mimic, mastoparan analog MAS-7. In all areas examined, the Y1 binding of LP-PYY was little affected by up to 100 microM of the antagonists of K+, Na+ and Ca++ channels, protein kinase C, phospholipase A2, phospholipase D and phosphatidylinositol 3-kinase, phospholipase substrate phospholipids, steroids or detergents. However, the binding was potently inhibited by phospholipase C inhibitors (especially the aminosteroid U-73122), which also dissociated the bound Y1 ligand in steady-state conditions. U-73122 also displaced the Y1 binding insensitive to GTP gamma S. Ligand association with the brain Y1 NPY receptor thus strongly depends on activity of both G proteins and phospholipase C, implying specific interactions of these transducers/effectors with the receptor molecule in ligand binding. A portion of brain Y1 sites could be directly coupled to phospholipase(s) C.

AIDS-related bronchogenic carcinoma: fact or fiction?

OBJECTIVE

Case reviews and retrospective analyses have raised the possibility of an increased frequency of primary lung carcinoma in HIV- and AIDS-infected patients. Conclusions have often been controversial and conflicting. We conducted a population-based epidemiologic study to assess the incidence of lung neoplasms in an HIV/AIDS cohort.

MATERIALS AND METHODS

The Texas Department of Health generated descriptive data on lung neoplasms in HIV-AIDS patients whose conditions were diagnosed between 1990 and 1995. The cancer registry matched against all patients whose conditions were diagnosed during the same time interval. Relative risk was measured through standardized incidence ratios of lung neoplasms in the HIV-AIDS population as compared with that of the US population.

RESULTS

The HIV-AIDS data file included 26,181 cases. A total of 76 lung cancer cases were identified, of which 36 (47.4%) were primary lung cancers. All major histologies were represented. The observed (36)/expected (5.6) ratio (standard incidence ratio) for primary lung cancer compared to the US population was 6.5 (4.5 to 8.9, 95% confidence interval).

CONCLUSIONS

Our data indicate a 6.5-fold increased incidence of primary lung cancer in HIV- and AIDS-infected patients. We present the results of our study, a review of the work of other investigators, and address a potentially even greater public health problem in the HIV/AIDS population than previously realized.

The Hermansky-Pudlak syndrome

Hermansky-Pudlak Syndrome (HPS) is a rare, inheritable disorder characterized by the classic triad of oculo-cutaneous albinism, platelet dysfunction, and ceroid deposition. An associated complication is pulmonary fibrosis with progressive restrictive lung disease. This report discusses the lung involvement often seen in this condition correlated with radiography, computed tomography, high-resolution computed tomography, and the underlying pathology, by means of two such afflicted siblings. The elder died of respiratory failure while awaiting lung transplantation. The younger sibling is currently undergoing evaluation for transplantation.

Differences in cation sensitivity of ligand binding to Y1 and Y2 subtype of neuropeptide Y receptor of rat brain

The binding of selective ligands to the Y1 subtype of neuropeptide Y receptor in rat brain particulates was promoted by Ca2+ and also stimulated by Sr2+, but reversibly reduced by Ba2+, Mg2+, Mn2+, by the organic polycations neomycin and spermidine, and by chelating agents. The alkali monovalent cations inhibited the Ca(2+)-enabled Y1 subtype binding with some selectivity (Cs+ > or = NH4+ > Li+ > Na+, K+), with half-inhibition between 70-120 mM. The specific Y2 subtype binding was enhanced by all alkaline-earth divalent cations, Mn2+, neomycin and spermidine in the range of 0.1-10 mM, and by alkali cations at up to 100 mM, and also by Na+ salts of the chelators EGTA and EDTA. The large disparity in cation sensitivity indicates substantial differences in the structure of the binding sites of the Y1 and Y2 receptors, predictable from known distinct features of ligand epitopes and of primary structure of the receptors.

Abdominal aortic injury associated with transverse lumbar spine fracture--imaging findings

The association of abdominal aortic injury with transverse fractures of the lumbar spine is not well recognized. Three cases are presented with description of a mechanism common to both injuries that may explain this association--that of distraction and hyperflexion, such as occurs in seat-belt injuries. Whenever a transverse lumbar spine fracture following such a mechanism of injury is recognized, the co-existence of an injury to the abdominal aorta should be excluded by aortography if there is any doubt concerning the integrity of the peripheral pulses. This is best performed prior to laparotomy for any associated intraperitoneal injuries. Repeated clinical examination may detect deterioration in those cases with initially normal pulses. Ultimately, detection of the aortic injury rests on a high index of suspicion.

The effect of influenza C virus on the Purkinje cells of chick embryo cerebellum

Intra-amniotic inoculation of influenza C virus resulted in observable and quantitatively measurable changes in the Purkinje cells of chick embryo cerebellum. Purkinje cells were visualized by the Golgi-Cox procedure and prepared for statistical and computer evaluation from camera lucida drawings. Four computer-generated measurements (the area of the dendritic arbor, the perimeter of the dendritic tree, and the height and width of the cell's arborization) and two manually counted measurements (total number of branches and the number of first order branches) were made. Analysis of Purkinje cells from influenza C virus-infected embryos showed disturbances in dendritic arborization patterns and misalignment in the arrangement of the cells in the Purkinje cell layer compared to control cells. Statistical evaluation of Purkinje cell arborization showed significant decreases in all measured parameters for the influenza C virus-infected members when compared with the members of the uninfected control group.

Influence of gamma radiation on the gel rigidity index and binding capability of gelatin

Changes in the rigidity indices of gelatin gel before and after gamma irradiation were characterized by dynamic mechanical testing, and the significance of these changes on the strength of granules was evaluated. Results illustrate the difficulty of obtaining reproducible values for gels containing less than 20% gelatin. However, rigidity indices for gels with a gelatin content of 20% and higher are consistent and may provide a useful controlling factor for preparation of gelatins of more precise specifications. The data indicate that rigidity degradation kinetics of several concentrations of gelatin gel at different radiation doses are complex, showing both increasing and decreasing rates. These findings strongly suggest that doses of less than 2.0 Mrad of gamma radiation should be used in order to obtain gelatins of acceptable quality for pharmaceutical applications. The crushing strength of granules of lactose powder granulated with irradiated gelatin reveals that the binding capability of such gelatin is significantly reduced. The results obtained for various size fractions and granule hardnesses containing different binder concentrations also suggest that particle size influences the granule strength to a lesser extent than does binder concentration and its consistency.

Prospective intellectual testing in children with brain tumors

Sixteen children with brain tumors received prospective intellectual evaluations with a follow-up of 2 to 5 years. All patients were treated with surgery and radiation and 5 received chemotherapy. Most of the children remained within the normal range of intelligence, but intelligence quotient (IQ) scores declined over time. Learning disabilities were present in 15 of 16 children after radiation, and 11 required special educational services. Risk factors associated with decline in IQ appear to be young age at time of radiation and adjuvant chemotherapy.

Inimical effects of compaction speed on microorganisms in powder systems with dissimilar compaction mechanisms

Tablets were prepared from powders that were consolidated by plastic deformation and fragmentation mechanisms. Cells of Staphylococcus aureus and spores of Bacillus subtilis were incorporated in the tablets by compaction at various pressures and compression speeds. The extent of inactivation of organisms was dependent on the compression behavior of the powders, on the speed of compaction, and on the degree of densification of compacts. Scanning electron micrographs of fractured compacts revealed that particle rearrangement, fragmentation, and deformation significantly influence the "survivor". The "pressure-survivor plots" showed a linear relationship with greater inactivation in brittle material, while the extent in inactivation was reduced, and followed a nonlinear pattern in those powders exhibiting plastic deformation.

In vitro prostaglandin E2 stimulation of 45Ca mobilization from chick bone

The ability of prostaglandin E2 (PGE2) to mobilize 45Ca from chick embryo long bones was assayed in an in vitro bone culture system. Concentrations of PGE2 tested ranged from 10(-9) to 10(-5) M. The PGE2 was effective in stimulating release of 45Ca from prelabelled bones at all concentrations tested except at 10(-9) M. In addition, stimulation of 45Ca release could be produced daily for 4 consecutive days of PGE2 culture-pulsing at what appeared to be the optimal PGE2 concentration, 10(-7) M. We conclude, as in mammals, PGE2 is a potent stimulator of calcium mobilization from avian bone. The potential involvement of prostaglandins in eggshell formation is discussed.

Hypercalcemia in coccidioidomycosis

Two patients with disseminated coccidioidomycosis and hypercalcemia are presented. One patient studied showed normal levels of 25-hydroxyvitamin D with depressed levels of 1 alpha,25-dihydroxyvitamin D. The serum calcitonin level was appropriate for the level of serum calcium, and the serum parathyroid hormone level was suppressed with elevation of the nephrogenous cAMP level. Intestinal absorption of calcium was elevated at 63 percent. Hypercalcemia and hypercalciuria persisted despite a 300 mg calcium diet. An osteotropic substance similar to the humoral hypercalcemia of malignancy is postulated.