Prostanoid receptors: ontogeny and implications in vascular physiology

Prostanoids exert significant effects on circulatory beds. They play a role in the response of the vasculature to adjustments in perfusion pressure and oxygen and carbon dioxide tension, and they mediate the actions of numerous factors. The role of prostanoids in governing circulation of the perinate is suggested to surpass that in the adult. Prostanoids are abundantly generated in the perinate. They have been implicated in autoregulation of blood flow as studied in brain and eyes. Prostaglandins are also dominant regulators of ductus arteriosus tone. The effects of these autacoids are mediated through specific G protein-coupled receptors. In addition to the pharmacological characterization of the prostanoid receptors, important advances in understanding the biology of these receptors have been made in the last decade. Their cloning and the development of animals with disrupted genes of these receptors have been very informative. The involvement of prostanoid receptors in the developing subject, especially on brain and ocular vasculature and on ductus arteriosus, has also begun to be investigated; the expression of these receptors changes with development. Some but not all of the ontogenic changes in these receptors are attributed to homologous regulation. Interestingly, in the process of elucidating their effects, functional perinuclear prostaglandin E2 receptors have been uncovered. This article reviews prostanoid receptors and addresses implications on the developing subject with attention to vascular physiology.

Protection of translation initiation factor eIF2 phosphorylation correlates with eIF2-associated glycoprotein p67 levels and requires the lysine-rich domain I of p67

The rate of protein synthesis in mammals is largely regulated by phosphorylation of the alpha-subunit of eukaryotic initiation factor 2 (eIF2) that is modulated by the cellular glycoprotein, p67, due to its protection of eIF2alpha phosphorylation (POEP) activity. At the N-terminus of p67, there are three unique domains, and at the C-terminus there is a conserved amino acid sequence. To analyze the importance of these domains, C-terminal deletion mutants of rat p67 were expressed constitutively in KRC-7 cells. In these cells, the phosphorylation level of the alpha-subunit of eIF2 was determined, and it was found that expression of the 1-97 amino acid segment of rat p67 increases POEP activity in vivo, and induces the endogenous levels of p67. These cells also show increased growth rate, and efficient translation of chloramphenicol acetyltransferase and beta-galactosidase reporter genes. At the N-terminus of p67, there are two unique domains: a lysine-rich domain I with the sequence (36)KKKRRKKKK(44), and an acidic residue-rich domain with the sequence (77)EEKEKDDDDEDGDGD(91). Substitution of lysine-rich domain I with (36)NMKSGNKTQ(44) in rat recombinant p67 resulted in the inhibition of its POEP activity, and substitution of the acidic residue-rich domain with (77)QNIQKALEPEAGDGA(91), resulted in no inhibition of POEP activity in KRC-7 cells. Taken together, our data suggest that protection of translation initiation factor eIF2 phosphorylation correlates with eIF2-associated glycoprotein p67 levels and requires the lysine-rich domain I of p67.

Spatial-temporal patterning of metabotropic glutamate receptor-mediated inositol 1,4,5-triphosphate, calcium, and protein kinase C oscillations: protein kinase C-dependent receptor phosphorylation is not required

The metabotropic glutamate receptors (mGluR), mGluR1a and mGluR5a, are G protein-coupled receptors that couple via G(q) to the hydrolysis of phosphoinositides, the release of Ca(2+) from intracellular stores, and the activation of protein kinase C (PKC). We show here that mGluR1/5 activation results in oscillatory G protein coupling to phospholipase C thereby stimulating oscillations in both inositol 1,4,5-triphosphate formation and intracellular Ca(2+) concentrations. The mGluR1/5-stimulated Ca(2+) oscillations are translated into the synchronized repetitive redistribution of PKCbetaII between the cytosol and plasma membrane. The frequency at which mGluR1a and mGluR5a subtypes stimulate inositol 1,4,5-triphosphate, Ca(2+), and PKCbetaII oscillations is regulated by the charge of a single amino acid residue localized within their G protein-coupling domains. However, oscillatory mGluR signaling does not involve the repetitive feedback phosphorylation and desensitization of mGluR activity, since mutation of the putative PKC consensus sites within the first and second intracellular loops as well as the carboxyl-terminal tail does not prevent mGluR1a-stimulated PKCbetaII oscillations. Furthermore, oscillations in Ca(2+) continued in the presence of PKC inhibitors, which blocked PKCbetaII redistribution from the plasma membrane back into the cytosol. We conclude that oscillatory mGluR signaling represents an intrinsic receptor/G protein coupling property that does not involve PKC feedback phosphorylation.

Fallot's tetralogy presenting with variceal bleed

The erythrocytosis of Fallot's tetralogy may lead to spontaneous thrombosis at any site, but splenic vein thrombosis and variceal bleed is rarely a presentation of Fallot's tetralogy. A case of a 48 years old female with undiagnosed Fallot's tetralogy, presenting with variceal bleed due to splenic vein thrombosis, is reported. It is also interesting to note that the patient survived till this age without any medical or surgical treatment.

Characterization of PGE2 receptors in fetal and newborn ductus arteriosus in the pig

We compared the total density and the relative expression of EP receptor (EP) subtypes in ductus arteriosus (DA) of the newborn with that of the fetal piglet. Saturation binding experiments showed 3-fold less PGE2 receptors in the newborn than in the fetus because of loss of EP3 and EP4 receptors thus explaining, at least partly, the reduced responsiveness to PGE2 of the newborn DA. Displacement experiments showed that the relative proportions of EP2, EP3, and EP4 were similar in the fetal DA but only EP2 was detected in the DA of the newborn pig. Hence, PGE2 effects in the newborn DA seem to be exclusively mediated by EP2 receptors both in vitro and in vivo. These findings may help to propose more specific therapies for regulation of DA's tone in certain newborns for whom conventional therapy is contraindicated.

Antibiotic- and metal-resistant strains of Vibrio parahaemolyticus isolated from shrimps

Enteropathogenic strains of Vibrio parahaemolyticus were isolated from shrimps, Penaeus monodon collected from the region of the Deltaic Sundarbans (West Bengal, India). About 63% of the isolated strains were resistant to ampicillin, cephalexin, and kanamycin. However, all these strains were sensitive to nitrofurantoin, nalidixic acid, tetracycline, and norfloxacin. The isolated strains were resistant to Ni2+] (75%), Cu2+ (87%), and Co2+ (37%), but all the strains were resistant against Cd2+, Zn2+, and Pb2+ at 10 mM concentration.

G protein-coupled receptor kinase-mediated desensitization of metabotropic glutamate receptor 1A protects against cell death

Metabotropic glutamate receptors (mGluRs) constitute a unique subclass of G protein-coupled receptors (GPCRs) that bear little sequence homology to other members of the GPCR superfamily. The mGluR subtypes that are coupled to the hydrolysis of phosphoinositide contribute to both synaptic plasticity and glutamate-mediated excitotoxicity in neurons. In the present study, the expression of mGluR1a in HEK 293 cells led to agonist-independent cell death. Since G protein-coupled receptor kinases (GRKs) desensitize a diverse variety of GPCRs, we explored whether GRKs contributed to the regulation of both constitutive and agonist-stimulated mGluR1a activity and thereby may prevent mGluR1a-mediated excitotoxicity associated with mGluR1a overactivation. We find that the co-expression of mGluR1a with GRK2 and GRK5, but not GRK4 and GRK6, reduced both constitutive and agonist-stimulated mGluR1a activity. Agonist-stimulated mGluR1a phosphorylation was enhanced by the co-expression of GRK2 and was blocked by two different GRK2 dominant-negative mutants. Furthermore, GRK2-dependent mGluR1a desensitization protected against mGluR1a-mediated cell death, at least in part by blocking mGluR1a-stimulated apoptosis. Our data indicate that as with other members of the GPCR superfamily, a member of the structurally distinct mGluR family (mGluR1a) serves as a substrate for GRK-mediated phosphorylation and that GRK-dependent "feedback" modulation of mGluR1a responsiveness protects against pathophysiological mGluR1a signaling.

Measurement of gamow-teller strength for 176Yb --> 176Lu and the efficiency of a solar neutrino detector

We report a 0 degrees 176Yb(p,n)176Lu measurement at IUCF where we used 120 and 160 MeV protons and the energy dependence method to determine Gamow-Teller (GT) matrix elements relative to the model independent Fermi matrix element. The data show that there is an isolated concentration of GT strength in the low-lying 1(+) states making the proposed Low Energy Neutrino Spectroscopy detector (based on neutrino captures on 176Yb) sensitive to pp and 7Be neutrinos and a promising detector to resolve the solar neutrino problem.

Outbreak of nosocomial infections due to extended-spectrum beta-lactamase-producing strains of enteric group 137, a new member of the family Enterobacteriaceae closely related to Citrobacter farmeri and Citrobacter amalonaticus

A member of the Enterobacteriaceae initially identified as Kluyvera cryocrescens by the MicroScan Gram-Negative Combo 13 panel caused an outbreak of nosocomial infections in four patients (pneumonia, n = 2; urinary tract infection, n = 1; wound infection, n = 1) and urinary tract colonization in one patient. When the strains were tested by the Enteric Reference Laboratory of the Centers for Disease Control and Prevention, biochemical results were most compatible with Yersinia intermedia, Kluyvera cryocrescens, and Citrobacter farmeri but identification scores were low and test results were discrepant. However, when the biochemical test profile was placed in the computer database as a new organism, all strains were identified as the organism with high identification scores (0. 999968 to 0.999997) and no discrepant test results. By 16S rRNA sequence analysis the organism clustered most closely with, but was distinct from, Citrobacter farmeri and Citrobacter amalonaticus. Based on its unique biochemical profile and rRNA sequence, this organism is designated Enteric Group 137. Restriction endonuclease analysis and taxonomic antibiograms of strains causing the outbreak demonstrated a single clone of Enteric Group 137, and antibiotic susceptibility testing revealed the presence of extended-spectrum beta-lactamase (ESBL) resistance. Enteric Group 137 appears to be a new opportunistic pathogen that can serve as a source of ESBL resistance in the hospital.

Shape of the 8B alpha and neutrino spectra

The beta-delayed alpha spectrum from the decay of 8B has been measured with a setup that minimized systematic uncertainties that affected previous measurements. Consequently the deduced neutrino spectrum presents much smaller uncertainties than the previous recommendation [J. N. Bahcall et al., Phys. Rev. C 54, 411 (1996)]. The 8B nu spectrum is found to be harder than previously recommended with about (10-20)% more neutrinos at energies between 12-14 MeV. The integrated cross sections of the 37Cl, 71Ga, 40Ar, and Super-Kamiokande detectors are, respectively, 3.6%, 1.4%, 5.7%, and 2.1% larger than previously thought.

Lichen planus: a clinical and epidemiological study

Clinical and epidemiological data from 232 patients with lichen planus is presented. Lichen planus constituted 0.38% of the total dermatology, outpatients diagnosed. The patient ages ranged from 8 to 76 years, most being in the age range from 20 to 49 years. Duration of disease varied from 1 month to 7 years. Both sexes were equally affected. The majority of the patients (47.4%) had classical lesions followed by hypertrophic and actinic lichen planus next in frequency. Itching was the predominant symptom in 79.3%. Limbs were the most frequent initial site of onset (55.6%). Mucosal involvement along with cutaneous lesions were observed in 16.8% and genital involvement in only 5.2%. Nail changes were observed in 15.1% of patients. A history of recurrence of the disease was obtained from 10.3% of patients. Liver disease was found to be associated in 2.2% of patients. No malignant changes were observed in any of the lesions of lichen planus.

Oxidants, nitric oxide and prostanoids in the developing ocular vasculature: a basis for ischemic retinopathy

The choroid is the main source of oxygen to the retina. In contrast to the adult, the absence of autoregulation of choroidal blood flow in the newborn leads to hyperoxygenation of the retina. In the immature retina which contains relatively low levels of antioxidants this hyperoxygenation favors peroxidation including the generation of biologically active isoprostanes, and results in vasoconstriction and vascular cytotoxicity leading to ischemia, which predisposes to the development of a vasoproliferative retinopathy, commonly termed retinopathy of prematurity. During frequently encountered oxidative stress to the perinate, the combined absence of vascular autoregulation and excessive oxygen delivery to the eyes of the developing subject is largely the result of a complex epigenetic and genetic interplay between prostanoids and nitric oxide (NO) systems on vasomotor regulation. The effects of certain prostaglandins are NO-dependent; conversely, those of NO have also been found to be largely prostaglandin I(2)-mediated in the eye; and NO synthase expression seems to be significantly regulated by other prostaglandins apparently through activation of functional perinuclear prostanoid receptors which affect gene transcription. The increased production of both prostaglandins and NO in the perinate augment ocular blood flow and as a result oxygen delivery to an immature retina partly devoid of antioxidant defenses. The ensuing peroxidation results in impaired circulation (partly thromboxane A(2)-dependent) and vascular integrity, leading to ischemia which predisposes to abnormal preretinal neovascularization, a major feature of ischemic retinopathy. Because tissue oxygenation is largely dependent upon circulation and critical in the generation of reactive oxygen species, and since the latter exert a major contribution in the pathogenesis of retinopathy of prematurity, it is important to understand the mechanisms that govern ocular blood flow. In this review we focus on the important and complex interaction between prostanoid, NO and peroxidation products on circulatory control of the immature retina.

A minimum 5.0 ml of sputum improves the sensitivity of acid-fast smear for Mycobacterium tuberculosis

Detection of acid-fast bacilli (AFB) by sputum smear supports treatment decisions with pulmonary tuberculosis (TB), but smear sensitivity for Mycobacterium tuberculosis is only approximately 45 to 75%. In an effort to increase sensitivity, smears were prepared using a minimum sputum volume of 5.0 ml. Sensitivity of smears during a 39-mo period (n = 1,849) using >/= 5.0 ml of sputum was 92. 0%, significantly greater (p < 0.001) than a sensitivity of 72.5% in a previous 24-mo period (n = 3,486) when all specimens were processed regardless of volume. All new cases of TB (n = 18) were smear-positive with >/= 5.0 ml of sputum before treatment, and all were receiving antituberculosis drugs at hospital discharge. In contrast, significantly fewer new cases of TB (14 of 26, p = 0.002) were positive before treatment when smears were prepared using sputum of any volume, and significantly fewer of these new TB cases (18 of 26, p = 0.03) were receiving treatment at hospital discharge. The eight cases without treatment were smear-negative. These results indicate that acid-fast smear using >/= 5.0 ml of sputum increases sensitivity for M. tuberculosis and accelerates treatment of TB.

Effect of Mg(2+) ion in protein secretion by magnesium-resistant strains of Pseudomonas aeruginosa and Vibrio parahaemolyticus isolated from the coastal water of Haldia port

A rapidly growing industrial complex including oil refineries and chemical industries has developed around the coastal area of Haldia port in the district of Midnapore, West Bengal, India. The coastal water is highly polluted with industrial wastes along with petroleum hydrocarbons. The bacteria isolated from the different sites of the coastal waters were Escherichia coli, Alcaligenes, Acinetobacter, Klebsiella spp., Micrococcus spp., Vibrio spp., Pseudomonas aeruginosa and Vibrio parahaemolyticus. The salinity of the water during the time of collection of samples around the port area was 8. 2 ppt. Among the isolated organisms, only two isolates, P. aeruginosa and V. parahaemolyticus, showed growth at 300 mM Mg(2+) ion concentration. However, a 3 mM Mg(2+) concentration was detected in the coastal water whereas other metal ion concentrations were less than 3x10(-5) mM. Resistance to Mg(2+) (300 mM) was determined by a 5.5-kb plasmid. A large amount of a 40-kDa outer membrane protein, which was highly soluble in 1 M MgCl(2), was isolated from both V. parahaemolyticus and P. aeruginosa. The secretion of proteins in the culture supernatant of V. parahaemolyticus was highly increased when the cells were grown in the presence of 300 mM Mg(2+), whereas very low secretion was observed in the same concentration of Mg(2+) in the case of P. aeruginosa. Mg(2+) may act as a specific release factor in protein secretion by V. parahaemolyticus strains.

Upregulation of mRNA for the melanocortin-1 receptor but not for melanogenic proteins in macrophage x melanoma fusion hybrids exhibiting increased melanogenic and metastatic potential

Fusion of mouse peritoneal macrophages or human blood monocytes with weakly metastatic mouse Cloudman S91 melanoma cells resulted in hybrids with enhanced metastatic potential (Rachkovsky et al., 1998. Clin. Exp. Metastasis, 16: 299-312). With few exceptions, such hybrids also showed increased basal- and MSH-induced pigmentation, at least in part through increased N-glycosylation of melanogenic proteins (Sodi et al., 1998. Pigment Cell Res., 11: 299-309). Here we report analyses regarding expression of the melanocyte-stimulating hormone (MSH) receptor (melanocortin-1 receptor, MC1-R) and the melanogenic proteins, tyrosinase (E.C. 1.14.18.1), tyrosinase-related protein 1 (TRP-1), and the tyrosinase-related protein 2 (TRP-2, E.C. 5.3.2.3), by a panel of cell lines consisting of parental Cloudman S91 melanoma cells, macrophages from DBA/2J mice, artificially derived macrophage x melanoma hybrids of high and low metastatic potential, and a naturally occurring highly metastatic hybrid between a Cloudman S91 tumor cell and a DBA/2J tumor-infiltrating cell. We show that incubation of cells with MSH/isobutylmethylxanthine (IBMX) resulted in strong melanogenic and morphologic responses in high metastatic hybrids compared to parental cells and the low metastatic hybrid, and that high metastatic hybrids exhibit increased mRNA expression for MC1-R accompanied by increased 125I-alphaMSH binding. Although tyrosinase activity and the protein level for tyrosinase and TRP-2, but not for TRP-1, were increased in the high metastatic hybrids versus the other cells, no significant changes in mRNA either for tyrosinase or for TRPs were observed in them. Furthermore, unlike tyrosinase, the abundance and gel mobility pattern of TRP-2 did not correlate with changes in activity in all hybrids and parental melanoma cells. The results suggest that although the activity MC1-R and tyrosinase correlate with enhanced basal as well as MSH-induced melanogenesis in metastatic/melanotic hybrids, their expression is differentially regulated, i.e., regulation of MC1-R while at transcriptional level, the TRPs are primarily regulated via post-transcriptional mechanisms in high metastatic hybrids.

Developmental changes in prostaglandin E(2) receptor subtypes in porcine ductus arteriosus. Possible contribution in altered responsiveness to prostaglandin E(2)

BACKGROUND

Prostaglandin E(2) (PGE(2)) is important in ductus arteriosus (DA) patency, but the types of functional PGE(2) receptors (EP) in the developing DA are not known. We postulated that age-dependent alterations in EP and/or their subtypes may possibly contribute to the reduced responsiveness of the newborn DA to PGE(2).

METHODS AND RESULTS

We determined PGE(2) receptor subtypes by competition binding and immunoblot studies on the DA of fetal ( approximately 75% and 90% gestation) and newborn (<45 minutes old) pigs. We studied the effects of EP receptor stimulation on cAMP signaling in vitro and on term newborn (<3 hours old) DA patency in vivo. Fetal pig DA expressed EP(2), EP(3), and EP(4) receptors equivalently, but not EP(1). In neonatal DA, EP(1), EP(3), and EP(4) were undetectable, whereas EP(2) density was similar in fetus and newborn. Prostaglandin-induced changes in cAMP mirrored binding data. 16,16-Dimethyl PGE(2) and 11-deoxy PGE(1) (EP(2)/EP(3)/EP(4) agonist) produced more cAMP in fetus than newborn, but butaprost (selective EP(2) agonist) caused similar cAMP increases in both; EP(3) and EP(4) ligands (M&B28767 and AH23848B, respectively) affected cAMP production only in fetus. After birth, administration of butaprost alone was as effective as 11-deoxy PGE(1) and 16,16-dimethyl PGE(2) in dilating DA in vivo.

CONCLUSIONS

The data reveal fewer PGE(2) receptors in the DA of the newborn than in that of the fetus; this may contribute to the decreased responsiveness of the DA to PGE(2) in newborn. Because EP(2) receptors seem to mediate the effects of PGE(2) on the newborn DA, one may propose that a selective EP(2) agonist may be preferred as a pharmacological agent to maintain DA patency in infants with certain congenital heart diseases.

Time-dependent changes in dough color in hexaploid wheat landraces differing in polyphenol oxidase activity

Time-dependent changes in the color of noodle sheets (using 2% NaCl or 1% alkaline salts in the formulation) made from 43 Iranian hexaploid wheat landrace accessions were measured. Pekar slick tests in water and in alkaline conditions were also carried out. A wide variation in color characteristics of the landraces was found, with L values of salted noodle sheets at 2 h ranging from 80.9 to 89.2 and b values of alkaline noodle sheets at 2 h ranging from 19.1 to 27.4, showing potential application in noodle wheat improvement programs. For initial rapid screening of samples it was observed that a single reading of the dough sheet after 2 h was adequate. The dough sheets should be kept at 5 degrees C during storage, to prevent microbiological activity in the dough, which would give erroneous results. The Pekar slick test results were not highly correlated to color measurements on the dough, so this test is not recommended for screening for noodle color potential in landraces.

An Efficient Method for the Reduction of N-Protected Amino Acids and Peptides to the Corresponding Alcohols

Reduction of pentachlorophenyl esters of Boc protected amino acids and peptides to the corresponding alcohols is described.