Loop diuretics and in vitro relaxation of human fetal and newborn mouse airways

This study was designed to test the hypotheses that furosemide directly causes relaxation in human fetal airway and that delivery of loop diuretics to either the adventitial or epithelial surface of newborn mouse airway results in equivalent relaxation. Isometric tension changes were measured in human fetal (11-16 wk) trachea and mainstem bronchus rings exposed to furosemide (300 microM) or saline after acetylcholine or leukotriene D(4) constriction. Significant decreases in isometric tension to furosemide were demonstrated after constriction with acetylcholine or leukotriene D(4). To examine the site of effect and mimic aerosolized and systemic administration, furosemide (3-300 microM) and bumetanide (0.3-30 microM) were applied separately to epithelial and adventitial surfaces of newborn mouse airways. No differences in airway diameter changes to epithelial or adventitial furosemide or bumetanide were observed, but a 10-fold difference in potency was found. In summary, human fetal airway relaxed to furosemide when constricted with either neurotransmitter or inflammatory mediator in vitro. Further, no differences in relaxation to equimolar epithelial and adventitial furosemide were observed in isolated newborn mouse airway. Taken together, this provides evidence that furosemide has a direct, nonepithelial-dependent effect on airway smooth muscle tone.

The mechanism of aubstrate eecognition of pyroglutamyl-peptidase I from Bacillus amyloliquefaciens as determined by X-ray crystallography and site-directed mutagenesis

Pyroglutamyl-peptidase is able to specifically remove the amino-terminal pyroglutamyl residue protecting proteins or peptides from aminopeptidases. To clarify the mechanism of substrate recognition for the unique structure of the pyrrolidone ring, x-ray crystallography and site-directed mutagenesis were applied. The crystal structure of pyroglutamyl-peptidase bound to a transition state analog inhibitor (Inh), pyroglutaminal, was determined. Two hydrogen bonds were located between the main chain of the enzyme and the inhibitor (71:O.H-N:Inh and Gln71:N-H.OE:Inh), and the pyrrolidone ring of the inhibitor was inserted into the hydrophobic pocket composed of Phe-10, Phe-13, Thr-45, Ile-92, Phe-142, and Val-143. To study in detail the hydrophobic pocket, Phe-10, Phe-13, and Phe-142 were selected for mutation experiments. The k(cat) value of the F10Y mutant decreased, but the two phenylalanine mutants F13Y and F142Y did not exhibit significant changes in kinetic parameters compared with the wild-type enzyme. The catalytic efficiencies (k(cat)/K(m)) for the F13A and F142A mutants were less than 1000-fold that of the wild-type enzyme. The x-ray crystallographic study of the F142A mutant showed no significant change except for a minor one in the hydrophobic pocket compared with the wild type. These findings indicate that the molecular recognition of pyroglutamic acid is achieved through two hydrogen bonds and an insertion in the hydrophobic pocket. In the pocket, Phe-10 is more important to the hydrophobic interaction than is Phe-142, and furthermore Phe-13 serves as an "induced fit" mechanism.

Differential effects of inhaled nitric oxide and hyperoxia on pulmonary dysfunction in newborn guinea pigs

This study tested the hypothesis that inhaled nitric oxide (NO) and combined NO and hyperoxia will result in less pulmonary dysfunction and delay onset of respiratory signs compared with hyperoxia-exposed newborn guinea pigs (GPs). GPs were exposed to room air (n = 14), 95% O(2) (n = 36), 20 parts per million (ppm) NO (n = 14), or combined 20 ppm NO and 95% O(2) (NO/O(2), n = 13) for up to 5 days. Data evaluated included latency interval for onset of respiratory distress, pressure volume curves, lung histology, and bronchoalveolar lavage (BAL) polymorphonuclear cells (PMNs), proteolytic activity, and total protein. NO-exposed GPs did not develop respiratory distress and had no evidence of pulmonary dysfunction. O(2)-exposed GPs developed respiratory distress after 1-5 days (median 4.0) vs. 3-5 days (median 5.0) for NO/O(2) exposure (P < 0.05). BAL from O(2)-exposed GPs showed increased PMNs compared with NO/O(2)-exposed GPs. O(2)- and NO/O(2)-exposed GPs had comparable reduced lung volumes, lung histology, and increased BAL proteinase activity and total protein. In summary 1) O(2) exposure resulted in multiple measures of pulmonary dysfunction in newborn GPs, 2) 5-day exposure to NO produced no noticeable respiratory effects and pulmonary dysfunction, and 3) short-term exposure (</=5 days) to NO/O(2) delayed onset of respiratory distress and neither exacerbated nor attenuated pulmonary dysfunction compared with O(2) exposure alone.

Synthesis of oligonucleotides containing the oxidatively modified kappaB site: unique binding affinity to the NFkappaB p50 homodimer

Synthesis of oligonucleotide 26-mers including single 5-formyl-2'-deoxyuridine (1) or 5-formyl-2'-O-methyluridine (2) in place of thymidine at the kappaB site has been accomplished. One of the 26-mers with 1 was critically discriminated by the NFkappaB p50 homodimer in binding.

Crystal structure of a plant ribonuclease, RNase LE

Ribonuclease LE (RNase LE) from cultured tomato (Lycopersicon esculentum) cells is a member of the RNase T(2) family showing broad base specificity. The crystal structure of RNase LE has been determined at 1.65 A resolution. The structure consists of seven alpha-helices and seven beta-strands, belonging to an alpha+beta type structure. Comparison of the structure of RNase LE with that of RNase Rh, a microbial RNase belonging to the RNase T(2) family, reveals that while the overall folding topologies are similar to each other, major insertions and deletions are found at the N-terminal regions. The structural comparison, an amino acid sequence alignment of the RNase T(2) enzymes, and comparison of the disulfide-bonding pattern of these enzymes show that the structure of RNase LE shown here is the basic framework of the animal/plant subfamily of RNase T(2) enzymes (including a self-incompatibility protein called S-RNase), and the structure of RNase Rh is that of the fungal subfamily of RNase T(2) enzymes (including RNase T(2)). Subsequently, we superposed the active-site of the RNase LE with that of RNase Rh and found that (1) His39, Trp42, His92, Glu93, Lys96, and His97 of RNase LE coincided exactly with His46, Trp49, His104, Glu105, Lys108, and His109, respectively, of RNase Rh, and (2) two conserved water molecules were found at the putative P(1) sites of both enzymes. These facts suggest that plant RNase LE has a very similar hydrolysis mechanism to that of fungal RNase Rh, and almost all the RNase T(2) enzymes widely distributed in various species share a common catalytic mechanism. A cluster of hydrophobic residues was found on the active-site face of the RNase LE molecule and two large hydrophobic pockets exist. These hydrophobic pockets appear to be base binding sites mainly by hydrophobic interactions and are responsible for the base non-specificity of RNase LE.

m-hydroxy benzoylecgonine recovery in fetal guinea pigs

Recently, meta-hydroxybenzoylecgonine (m-OH BE) was identified by gas chromatography-mass spectroscopy during quantitative analysis for cocaine. Identification of m-OH BE in addition to the routinely identified benzoylecgonine by gas chromatography-mass spectroscopy confirmatory assays may increase detection of cocaine-exposed infants and decrease false negative results. However, it is not known whether m-OH BE is derived directly from benzoylecgonine or from hydroxylated cocaine, or whether this metabolite is produced in the fetus or transferred across the placenta from the maternal circulation. We quantitated the recovery of cocaine, benzoylecgonine, and m-OH BE from amniotic fluid, fetal meconium, fetal intestine, and maternal urine for up to 4 days after single dose administration of either cocaine or benzoylecgonine to pregnant time-bred guinea pigs. m-OH BE was recovered from meconium after maternal injections of cocaine and benzoylecgonine. There was no significant detection of m-OH BE from amniotic fluid or intestine and minimal recovery from maternal urine after either cocaine or benzoylecgonine administration. Detection of m-OH BE in meconium increased the identification of in utero exposed guinea pigs, and the greatest yield of m-OH BE from meconium occurred later than that observed for cocaine or benzoylecgonine.

Crystallization and Preliminary X-ray Crystallographic Studies of Ribonuclease LE from Lycopersicon esculentum

Abstract:

The ribonuclease LE, a plant ribonuclease from lycopersicon esculentum, has been crystallized by the hanging-drop vapour diffusion method using polyethylene glycol 1,540 as the precipitating agent. The crystals belong to an orthorhombic space group P2,2,2, with cell dimensions of a = 74.10 A, b = 78.72 A, and c = 33.00 A. There is one molecule per asymmetric unit. The crystals diffract to at least 2.0 A resolution and are suitable for X-ray structure analysis at high resolution.

Crystal structure of prolyl aminopeptidase from Serratia marcescens

Prolyl aminopeptidase from Serratia marcescens specifically catalyzes the removal of N-terminal proline residues from peptides. We have solved its three-dimensional structure at 2.3 A resolution by the multiple isomorphous replacement method. The enzyme consists of two contiguous domains. The larger domain shows the general topology of the alpha/beta hydrolase fold, with a central eight-stranded beta-sheet and six helices. The smaller domain consists of six helices. The catalytic triad (Ser113, His296, and Asp268) is located near the large cavity at the interface between the two domains. Cys271, which is sensitive to SH reagents, is located near the catalytic residues, in spite of the fact that the enzyme is a serine peptidase. The specific residues which make up the hydrophobic pocket line the smaller domain, and the specificity of the exo-type enzyme originates from this smaller domain, which blocks the N-terminal of P1 proline.

Cross-desensitization to furosemide and salbutamol in isolated neonatal guinea pig airways

Airway hyperresponsiveness in neonatal chronic lung disease is treated with both furosemide, a diurectic that inhibits the Na-K-2Cl cotrasporter, and salbutamol, a beta2-adrenoceptor agonist. Tachyphylaxis to both drugs in vitro has been described. This study was conducted to determine if the relaxation response in newborn guinea pig airways to furosemide and salbutamol can be cross-desensitized in vitro. Tracheal ring segments from 4- to 7-day-old guinea pigs were suspended in HEPES buffer for measurement of isometric tension. Segments were pre-treated with either furosemide (300 microM, 1 h) or salbutamol (10 microM, 30 min). After constriction with 3 microM acetylcholine, relaxation response to salbutamol or furosemide, respectively, was measured. Pretreatment with furosemide diminished relaxation response to salbutamol [87 +/- 3% (n = 11) vs. 117 +/- 8% (n = 10), p < 0.05], as compared to saline-treated controls. In addition, pretreatment with salbutamol diminished relaxation response to furosemide [53 +/- 2% (n = 11) vs. saline-treated (83 +/- 7%, n = 7, p < 0.05) and DMSO-treated controls (69 +/- 5%, n = 5, p < 0.05)]. Measurements of 86Rb uptake, cyclic AMP levels and responses in the presence of charybdotoxin make it unlikely that Na-K-2Cl cotransporter activity, stimulation of cAMP, or opening of maxi-K+ channels are mechanisms involved in the cross-desensitization to furosemide and salbutamol in vitro.

Identification of regions in which positive selection may operate in S-RNase of Rosaceae: implication for S-allele-specific recognition sites in S-RNase

A stylar S-RNase is associated with gametophytic self-incompatibility in the Rosaceae, Solanaceae, and Scrophulariaceae. This S-RNase is responsible for S-allele-specific recognition in the self-incompatible reaction, but how it functions in specific discrimination is not clear. Window analysis of the numbers of synonymous (dS) and non-synonymous (dN) substitutions in rosaceous S-RNases detected four regions with an excess of dN over dS in which positive selection may operate (PS regions). The topology of the secondary structure of the S-RNases predicted by the PHD method is very similar to that of fungal RNase Rh whose tertiary structure is known. When the sequences of S-RNases are aligned with the sequence of RNase Rh based on the predicted secondary structures, the four PS regions correspond to two surface sites on the tertiary structure of RNase Rh. These findings suggest that in S-RNases the PS regions also form two sites and are candidates for the recognition sites for S-allele-specific discrimination.

Stereocontrolled cyclization at the anomeric position of 6-(hydroxyalkyl)uridines using hypoiodite reaction

Hypoiodite reaction of 6-(hydroxyalkyl)-2',3'-O-isopropylideneuridines (1-3) was found to yield a new class of spiro nucleosides having an anomeric orthoester structure. It appeared that the 6-hydroxyalkyl substituent and the 2',3'-O-isopropylidene group are working cooperatively to control the anomeric stereochemistry (beta/alpha = 35/1-2/1) of the cyclization.

Structural analysis and molecular model of a self-incompatibility RNase from wild tomato

Self-incompatibility RNases (S-RNases) are an allelic series of style glycoproteins associated with rejection of self-pollen in solanaceous plants. The nucleotide sequences of S-RNase alleles from several genera have been determined, but the structure of the gene products has only been described for those from Nicotiana alata. We report on the N-glycan structures and the disulfide bonding of the S3-RNase from wild tomato (Lycopersicon peruvianum) and use this and other information to construct a model of this molecule. The S3-RNase has a single N-glycosylation site (Asn-28) to which one of three N-glycans is attached. S3-RNase has seven Cys residues; six are involved in disulfide linkages (Cys-16-Cys-21, Cys-46-Cys-91, and Cys-166-Cys-177), and one has a free thiol group (Cys-150). The disulfide-bonding pattern is consistent with that observed in RNase Rh, a related RNase for which radiographic-crystallographic information is available. A molecular model of the S3-RNase shows that four of the most variable regions of the S-RNases are clustered on one surface of the molecule. This is discussed in the context of recent experiments that set out to determine the regions of the S-RNase important for recognition during the self-incompatibility response.

Amiloride-induced contraction of isolated guinea pig, mouse, and human fetal airways

Nebulized amiloride has been proposed as therapy in cystic fibrosis to block Na+ hyperabsorption in airway epithelium and prevent dehydration of secretions. Patients with cystic fibrosis often have reaction airways. Bovine and canine trachea relax to amiloride in vitro, suggesting another benefit as a bronchodilator, whereas guinea pig trachea, a useful model of human airways, does not. We hypothesized that human airways would respond like guinea pig airways. Airway ring segments from guinea pigs, mice, and human fetuses were constricted with the concentration of acetylcholine producing 50-75% maximum contraction. Subsequent changes in isometric tension to cumulative additions of amiloride (10(-8)-10(-4) M) were measured. Guinea pig airways contracted 29 +/- 5%, mouse airways contracted 23 +/- 6%, and human fetal airways contracted 30 +/- 8%. Contraction to amiloride was mimicked by dimethylamiloride, a more selective inhibitor of the Na+/H+ antiporter, and was attenuated by protein kinase C (PKC) inhibition with GF109203X and staurosporine. The present study indicates that amiloride-induced airway contraction in guinea pigs and mice closely parallels the response in isolated human airways and that the mechanism may involve the Na+/H+ antiporter and PKC.

Furosemide-induced airway relaxation in guinea pigs: relation to Na-K-2Cl cotransporter function

This study tested the hypothesis that airway relaxation to furosemide is mediated via the Na-K-2Cl cotransporter. If this mechanism exists in airway smooth muscle like in vascular smooth muscle, changes in airway relaxation should be associated with changes in Na-K-2Cl cotransporter function, and both should be substrate dependent. Tracheal rings from newborn guinea pigs were bathed in standard (STD) or varying low Cl- concentration ([Cl-]) N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES). Isometric relaxation to 300 microM furosemide or 10(-8) to 10(-5) M salbutamol was measured. Airway segments were incubated with rubidium-86 (86Rb) in STD or varying low [Cl-] HEPES, with and without 300 microM furosemide or 25 microM salbutamol. Furosemide was unable to reduce 86Rb uptake at 10 mM [Cl-], although relaxation was still observed in 10 mM [Cl-]. Salbutamol did not affect 86Rb uptake. This study demonstrated that there is a furosemide-sensitive Na-K-2Cl cotransporter in newborn guinea pig trachea. However, the effect of furosemide on cotransporter function did not always directly correspond to differences in relaxation, suggesting that the Na-K-2Cl cotransporter may play a major, but not exclusive, role in furosemide-induced airway relaxation.

Heliquinomycin, a new inhibitor of DNA helicase, produced by Streptomyces sp. MJ929-SF2 II. Structure determination of heliquinomycin

The structure of heliquinomycin which was isolated from the culture broth of Streptomyces sp. MJ929-SF2 was studied by NMR spectroscopies, X-ray crystallographic analysis and degradation experiments. Heliquinomycin is the first member of glycosylated rubromycins and griseorhodins group antibiotics.

Tachyphylaxis to furosemide in isolated airways of guinea pigs

This in vitro study was conducted to determine whether tachyphylaxis of guinea pig airway to furosemide occurs under conditions that produce tachyphylaxis to the beta 2-adrenoceptor agonist, salbutamol. Isometric tension was measured in tracheal rings bathed in HEPES buffer from 4-6 d newborn guinea pigs of either sex, and 6 wk old males. Paired rings were first incubated with furosemide, 30 or 300 microM, or control for 60 min, washed, then constricted with 3 microM acetylcholine. At stable contraction, relaxation to furosemide (30 microM-1 mM) was measured. For comparison, similar experiments were performed with 10 microM salbutamol incubation for 30 min. 86Rb uptake, a marker for K+ transport and Na-K-Cl cotransport activity, was also measured in these airway segments. Pre-exposure to these airway relaxants did not affect contractile force generation by acetylcholine. Tracheal desensitization to both salbutamol and furosemide was observed. Partial recovery of furosemide induced relaxation was seen one hour after desensitization. Pre-exposure to 300 microM furosemide did not inhibit the decrease in 86Rb uptake normally observed with furosemide. In summary, we found that: 1) tachyphylaxis of guinea pig airway relaxation occurred with both salbutamol and furosemide under similar experimental conditions; however 2) inhibition of 86Rb uptake by furosemide was not affected by prior exposure. Taken together, these results suggest that furosemide induced airway relaxation could be affected by repeated or prolonged exposure, but this response may not be associated with changes in furosemide-sensitive Na-K-Cl cotransporter activity.

The crystal structure of ribonuclease Rh from Rhizopus niveus at 2.0 A resolution

The three-dimensional structure of ribonuclease Rh (RNase Rh), a new class of microbial ribonuclease from Rhizopus niveus, has been determined at 2.0 A resolution. The overall structure of RNase Rh is completely different from those of other previously studied RNases, such as RNase A from bovine pancreas and RNase T1 from Aspergillus oryzae. In the structure of RNase Rh, two histidine residues (His46 and His109) and one glutamic acid residue (Glu105), which were predicted to be critical to the activity from the chemical modification and mutagenesis experiments, are found to be located close together, constructing the active site. The indole ring of Trp49 plays an important role in preserving the active site structure by its stacking interactions with the imidazole ring of His 109, and by hydrogen bonding with the carboxyl group of Glu105. There exists a hydrophobic pocket around the active site, which contains the aromatic side-chain of Trp49 and Tyr57. The results of mutagenesis studies suggest that this pocket is the base binding site of the substrate.

Derivatives of tetrodecamycin

The derivatives of tetrodecamycin (1), being introduced acyl, carbamoyl and alkyl groups at 14-hydroxyl group and modified at exo-methylene group, were synthesized and evaluated on their antibacterial activities. Although 14-O-substituted tetrodecamycins (3 approximately 19) showed weak activity against Pasteurella piscicida, they were more active against Gram-positive bacteria than 1. Among them, 15 showed approximately 10-fold higher activity than 1. The derivatives (20 approximately 23) modified at 4 or 5 positions had moderate antibacterial activity. The absolute structure of 4(R),5-dibromotetrodecamycin (23) was determined by X-ray crystallographic analysis.

Tetrodecamycin and dihydrotetrodecamycin, new antimicrobial antibiotics against Pasteurella piscicida produced by Streptomyces nashvillensis MJ885-mF8. II. Structure determination

Novel antimicrobial antibiotics against Pasteurella piscicida, tetrodecamycin (1) and weakly active dihydrotetrodecamycin (2) were isolated from a culture broth of Streptomyces nashvillensis MJ885-mF8. The planar structure of 1 was determined to be 2-acyl-4-ylidene tetronic acid alkyl ether containing decaline ring by various NMR spectral data of 1 and its acetyl derivative (3). The structure of 2 was elucidated by comparison with the spectral data of 1 and confirmed by catalytic reduction of 1 into 2. The X-ray crystallography of 2 showed the relative stereochemistry. Their absolute configurations were determined by using modified Mosher's method.

Acute hyperoxic injury attenuates the relaxing effects of "loop" diuretics and salbutamol on large airways of newborn guinea pigs

We have previously found an age-dependent relaxing effect of furosemide in normal fetal, newborn, and adult guinea pig airways with fetal trachea exhibiting the greatest relaxation and adult tissue the least. This study was designed to expand upon this finding by determining if in vivo hyperoxic exposure would influence in vitro airway relaxation mediated by the loop diuretics, furosemide and ethacrynic acid, and the beta 2-adrenoceptor agonist, salbutamol. Newborn guinea pigs were raised in > 95% FiO2 until ill; controls in room air. Isometric relaxation to 3 x 10(-5) M furosemide, 3 x 10(-6) M ethacrynic acid, or 10(-8)-10(-6) M salbutamol was recorded in 3 x 10(-6) M histamine-constricted airway rings. Ethacrynic acid, like furosemide, relaxed newborn guinea pig airways. Hyperoxia did not alter the contractile effect of 3 x 10(-6) M histamine but did significantly decrease the relaxing effect of furosemide, ethacrynic acid, and salbutamol. Loop diuretic mediated airway relaxation was accentuated in HEPES buffer when compared with Krebs, whereas salbutamol-mediated relaxation was unaffected. These results suggest that hyperoxia nonspecifically decreases airway responsiveness to the relaxing agents studied.

Ultrastructure and x-ray microanalytical study of human pineal concretions

We examined human pineal concretions and found them to exhibit a multi-layered concentric structure consisting of irregularly spaced dense and sparse zones containing fine crystals. The hydroxyapatite crystallites were shown to be irregularly outlined plate forms (measuring 11-70 nm in their longest dimension and 2-10 nm in thickness). At the center of each crystallite a central dark line was observed by means of high resolution electron microscopy. The structure and size of the crystals were similar to those of dentin and bone. The ground surface of the concretions was observed metallurgically by means of an electron probe microanalyzer (EPMA). The surface zones of the concretions contained a higher concentration of zinc, which seems to play an important role during the mineralization process, whereas calcium and phosphorus exhibited higher concentrations at the center.

Aldecalmycin, a new antimicrobial antibiotic from Streptomyces. III. Determination of absolute configuration

The planar structure of aldecalmycin (1) had been determined in the previous paper, together with the conformations of the substituted trans decalin ring having one double bond and the sugar: beta-glucopyranoside type. The absolute configuration of 1 was a following problem to be solved. X-Ray crystallographic analysis of crystalline 4'-6'-O-benzylidenedihydroaldecalmycin (4) revealed the relative configuration. On the other hand, the stereoisomerism of the sugar was determined to be D by the optical rotation value of tetra-O-acetyl-alpha-methylglucopyranoside derived from 1. These results established the absolute configuration of 1.

Ontogenic changes in renal response to alpha 1-adrenoceptor stimulation in sheep

The present study was designed to examine the effect of direct intrarenal infusion of the alpha 1-adrenoceptor agonist, phenylephrine, on urinary flow rate (UFR) and on renal Na and Cl excretion in conscious and chronically instrumented fetal (128-133 days gestation, term 145 days), newborn (6-12 days), and adult sheep. Five different renal concentrations of phenylephrine, varying from 5 +/- 1 to 72 +/- 2 ng/ml, were studied. Low renal phenylephrine concentration (< or = 12 +/- 1 ng/ml) induced a significant renal vasoconstrictor response in fetuses but not in newborn and adult sheep. The effects of intrarenal phenylephrine infusion on UFR and fractional excretion of Na (FENa) was greater (P < 0.05) in newborn lambs than in fetal and adult sheep. At a renal concentration of phenylephrine between 9 +/- 1 and 12 +/- 1 ng/ml, the percent decrease in UFR was greater (P < 0.05) in newborn lambs (-19.1 +/- 4.7%) than in fetal (9.8 +/- 8.9%) and adult sheep (-3.3 +/- 3.9). The percent decrease in FENa at renal concentration of phenylephrine between 18 +/- 1 and 24 +/- 1 ng/ml was also significantly (P < 0.05) larger in newborn lambs (-20.2 +/- 2.8%) than in fetal (-8.0 +/- 3.1%) and adult sheep (-11.2 +/- 2.6%). In summary, the present results indicate that the fetal kidney has a limited ability to increase sodium reabsorption in response to stimulation of alpha-adrenoceptors and that the effect of renal alpha-adrenoceptor stimulation on urinary volume and urinary sodium excretion increases during the newborn period.

Unexpected preterm delivery in tourists: implications for long-distance travel during pregnancy

From 1984 to 1989, 33 pregnant tourists were delivered of preterm infants requiring neonatal intensive care. We retrospectively reviewed medical records of all high-risk infants delivered to tourists during this period and compared these results with those of a previous review from 1978 to 1984. Thirty-seven infants were admitted during this later period compared with 27 previously observed. Of recent mothers, 30% had identifiable high-risk factors compared with 50% previously studied. Infant demographic and outcome data were similar, except for fewer recent intraventricular hemorrhages. Outcome was adversely affected by maternal high-risk factors during both periods. Pregnant tourists, many with identifiable high-risk factors, continue to be delivered of premature infants who may require prolonged hospitalization. Because of this, and the potential for serious psychosocial and economic consequences of preterm delivery, we recommend that long-distance travel in pregnant women with identified high-risk factors be restricted about the time when viability of the fetus is possible.

pH profile of kinetic constants of RNase Rh from Rhizopus niveus and its mutant enzymes towards UpU, and possible mechanisms of RNase Rh

In order to elucidate the mechanism of action of Rhizopus niveus RNase Rh, we investigated the pH profiles of the kinetic parameters of RNase RNAP Rh, a derivative of RNase Rh, and its mutant enzymes, i.e., RNase RNAP Rh H104F, RNase RNAP Rh E105Q, and RNase RNAP Rh D51N. Based on comparisons of their profiles we concluded that protonation of His104 is indispensable for the enzymatic activity and Glu105 accelerates the enzymatic activity, especially at acid pH centered at pH 3.5. Based on these data and the previous data on the chemical modification and enzymatic properties of other mutant enzymes, we propose the following as a possible mechanisms of RNase Rh action. (i) His109 participates in enzymatic action as a general base catalyst which removes the hydrogen of the 2'-OH of the ribose moiety. (ii) His46 participates in the reaction as a general acid catalyst which interacts with the 5'-oxygen atom of the scissile phosphodiester bond and becomes a proton donor to the departing nucleoside or nucleotide. (iii) His104 interacts with phosphate anion and its protonation is favorable for the enzymatic activity. (iv) Since the protonated form of Glu105 is more favorable for activity, we postulate two possible roles for Glu105: (a) its stabilizes the intermediate, and (b) it interacts with the oxygen atom of P = O and polarizes the phosphorus atom.

Crystal structure of ribonuclease Ms (as a ribonuclease T1 homologue) complexed with a guanylyl-3',5'-cytidine analogue

A ribonuclease T1 homologue, ribonuclease Ms (RNase Ms) from Aspergillus saitoi, has been crystallized as a complex with a substrate analogue GfpC where the 2'-hydroxyl (2'-OH) group of guanosine in guanylyl-3',5'-cytidine (GpC) is replaced by the 2'-fluorine (2'-F) atom to prevent transesterification. The crystal structure of the complex was solved at 1.8-A resolution to a final R-factor of 0.204. The role of His92 (RNase T1 numbering) as the general acid catalyst was confirmed. Of the two alternative candidates for a general base to abstract a proton from the 2'-OH group, His40 and Glu58 were found close to the 2'-F atom, making the decision between the two groups difficult. We then superposed the active site of the RNase Ms/GfpC complex with that of pancreatic ribonuclease S (RNase S) complexed with a substrate analogue UpcA, a phosphonate analogue of uridylyl-3',5'-adenosine (UpA), and found that His12 and His119 of RNase A almost exactly coincided with Glu58 and His92, respectively, of RNase Ms. Similar superposition with a prokaryotic microbial ribonuclease, RNase St [Nakamura, K. T., Iwahashi, K., Yamamoto, Y., Iitaka, Y., Yoshida, N., & Mitsui, Y. (1982) Nature 299, 564-566], also indicated Glu58 as a general base. Thus the present comparative geometrical studies consistently favor, albeit indirectly, the traditional as well as the most recent notion [Steyaert, J., Hallenga, K., Wyns, L., & Stanssens, P. (1990) Biochemistry 29, 9064-9072] that Glu58, rather than His40, must be the general base catalyst in the intact enzymes of the RNase T1 family.

Hyperoxic exposure enhances airway reactivity of newborn guinea pigs

To determine whether altered airway smooth muscle contractility contributes to airway hyperreactivity resulting from hyperoxic exposure, in vitro contractile responses of airways to two physiological constrictors, acetylcholine (10(-9) to 10(-4) M) and histamine (10(-8) to 10(-4) M), were examined. Extrathoracic trachea, intrathoracic trachea, and bronchus from 1- to 2-day-old (newborn) guinea pigs exposed to 85% oxygen for 84 h were compared with tissues obtained from newborns reared in room air. Responses in the presence and absence of aspirin (ASA; 10(-3) M) were compared. Hyperoxic exposure did not affect the histology of the airway epithelia. Contractile responses to acetylcholine and histamine were similar. Without ASA, maximal tensions generated were higher in both extrathoracic and intrathoracic trachea obtained from hyperoxia-exposed neonates than in trachea from newborns reared in room air. ASA caused maximal tensions of trachea from newborns reared in room air to increase but did not affect the already increased contractility of trachea from hyperoxia-exposed animals; the tensions achieved in hyperoxic tissues with and without ASA were similar to the hyperactive responses induced by ASA in tissues from animals reared in room air. Bronchi showed responses similar to those seen in tracheal segments. Thus, despite no apparent histological effect on the airway epithelium, hyperoxic exposure seems to increase airway smooth muscle contractility, is nonspecific for different constricting agents, and shows no regional differences in airway reactivity.

Effect of calcium agonists, BAY K 8644 and CGP 28392, on guinea pig airway smooth muscle function during development

Dihydropyridine calcium agonists affect airway smooth muscle function by modulating the voltage-dependent calcium channel. Two such agonists, BAY K 8644 and CGP 28392 increase airway smooth muscle tone in adult guinea pigs but their actions during ontogeny are unknown. We compared contractile responses of airway tissue from fetal, newborn and young adult guinea pigs to cumulative doses of both BAY K 8644 and CGP 28392 under isometric conditions in vitro. Responses were examined in the presence and absence of aspirin to determine if endogenous cyclooxygenase products modulated these effects. BAY K 8644 generated a contractile response in 85 of 86 tissues. Maximum contraction was greater in extrathoracic tracheas from newborns when compared to adults (P < .05). In fetuses and newborns, contraction overall was greater in the presence of aspirin; however, in adult airways cyclooxygenase blockade did not appear to have any effect (P < .05). In contrast, CGP 28392 produced no contraction in 14 of 19 tracheas (all ages combined) in the presence of aspirin; whereas, all 18 tracheas in the absence of aspirin contracted. Also, there were no significant differences in maximum response among these age groups or tissue types to CGP 28392. Increased sensitivity of tracheas in immature guinea pigs was observed for both drugs in the absence of aspirin.(ABSTRACT TRUNCATED AT 250 WORDS)

Ontogeny of epithelial modulation of airway smooth muscle function in the guinea pig

The purpose of this study was to investigate the ontogeny of guinea pig airway smooth muscle (ASM) responses and the epithelial modulation of these responses. Paired tracheal rings from fetal, newborn, and adult guinea pigs were studied. One of each pair was denuded of airway epithelium (AE) by gentle rubbing. Isometric tension was measured in rings mounted in organ baths filled with Krebs' solution. Cumulative dose-response curves were generated by adding either acetylcholine (ACh) or histamine over a concentration range of 10(-8)-10(-4) M. Significant agent-specific, age-related differences in maximal contraction were seen for both ACh and histamine in intact tissues (Ach: for fetus 66.7 +/- 6.2 x 10(-2) g/mg wet wt, for newborn 51.4 +/- 6.2, for adult 29.3 +/- 2.6; histamine: for fetus 46.1 +/- 5.1, for newborn 72.9 +/- 6.0, for adult 25.3 +/- 3.2). Similar differences in sensitivity to both agents were observed (EC50 with ACh: for fetus 0.80 +/- 0.11 x 10(-6) M; for newborn 0.85 +/- 0.26 x 10(-6) M; for adult 1.7 +/- 0.20 x 10(-6) M; EC50 with histamine; for fetus 1.88 +/- 0.50 x 10(-6) M; for newborn 1.34 +/- 0.16 x 10(-6) M; for adult 3.78 +/- 0.75 x 10(-6) M). Removal of AE caused a significant decrease in maximal responses to ACh in fetal tissue, a smaller, insignificant one for newborn and a nonsignificant alteration for adult tissues. Age-related sensitivity difference was abolished with removal of AE to ACh but not to histamine.(ABSTRACT TRUNCATED AT 250 WORDS)

Furosemide differentially relaxes airway and vascular smooth muscle in fetal, newborn, and adult guinea pigs

Furosemide, an inhibitor of Cl-dependent Na+,K+ cotransport, is the most frequently used diuretic in newborns. Recently, furosemide was also demonstrated to decrease bronchial hyper-responsiveness in adults, although little is known about the direct effect of furosemide on smooth muscle of immature animals. This in vitro study was designed to determine the action of furosemide on airway and vascular smooth muscle during ontogeny. Extrathoracic trachea (ET), main stem bronchi, main pulmonary artery, and thoracic aorta ring segments from fetal, newborn, and adult Hartley albino guinea pigs were suspended in HEPES solution for measurement of isometric tension. Furosemide (30 or 300 microM) was administered after preconstriction with an ED35-70 concentration of histamine or acetylcholine for airway and ED40-100 concentration of norepinephrine for vessels. Furosemide (30 microM) caused significant relaxation of airway smooth muscle at all ages. After histamine-induced preconstriction, fetal airway segments exhibited greatest relaxation (183 +/- 28%), with newborn airway demonstrating 123 +/- 15% relaxation and modest relaxation seen in adults (40 +/- 4%). This pattern was similar for both ET and bronchus and appeared greater for histamine compared with ACh preconstriction. Epithelial removal slightly enhanced relaxation. Furosemide also relaxed pulmonary artery segments, but at a 10-fold higher concentration. In striking contrast to the pattern seen in airway, adult pulmonary artery relaxed more than newborn and newborn, more than fetus. Cyclooxygenase blockade and endothelium removal did not change pulmonary artery relaxation. Furosemide did not significantly relax aorta after NE preconstriction. Taken together, these results suggest that furosemide may be more effective in relaxing airway compared with vascular smooth muscle, and the ontogeny of these responses indicates a greater efficacy and selectivity in airways of immature animals.

Three-dimensional crystal structure of recombinant murine interferon-beta

The crystal structure of recombinant murine interferon-beta (IFN-beta) has been solved by the multiple isomorphous replacement method and refined to an R-factor of 20.5% against 2.6 A X-ray diffraction data. The structure shows a variant of the alpha-helix bundle with a new chain-folding topology, which seems to represent a basic structural framework of all the IFN-alpha and IFN-beta molecules belonging to the type I family. Functionally important segments of the polypeptide chain, as implied through numerous gene manipulation studies carried out so far, are spatially clustered indicating the binding site(s) to the receptor(s). Comparison of the present structure with those of other alpha-helical cytokine proteins, including porcine growth hormone, interleukin 2 and interferon gamma, indicated either a topological similarity in chain folding or a similar spatial arrangement of the alpha-helices.

Exosurf treatment investigational new drug phase: effect of an individualized third dose in infants with respiratory distress syndrome

Of 95 infants treated with the synthetic surfactant, Exosurf, under a Treatment Investigational New Drug protocol, 17 received one dose, 40 received two, and 38 received three doses. Seventy-six (80%) of the infants were treated by rescue protocol. We retrospectively reviewed the clinical course of the 67 surviving rescue infants. We found that, compared to one- and two-dose infants, those treated with three doses of Exosurf were more premature, smaller, required a longer ventilator course, and had more frequent complications, including patent ductus arteriosus (PDA), intraventricular hemorrhage, nosocomial pneumonia, and apnea. They required higher oxygen concentrations starting 8 hr after their first dose and higher mean airway pressure (MAP) from the time of their second dose. These trends continued during all subsequent time points, as compared to infants treated with two doses. The third dose was administered an average of 17 hr after the second, resulting in little change of MAP, but some reduction in oxygen requirements. By 24 hr after the last dose, only 4% of three-dose infants were extubated compared with 30% of the two-dose and 71% of one-dose infants. In conclusion, repeated administration of Exosurf is not equally effective in every treated infant with respiratory distress syndrome (RDS) and complications of prematurity may affect or accompany poor response.(ABSTRACT TRUNCATED AT 250 WORDS)

Crystal and molecular structure of RNase Rh, a new class of microbial ribonuclease from Rhizopus niveus

The crystal structure of RNase Rh, a new class of microbial ribonuclease from Rhizopus niveus, has been determined at 2.5 A resolution by the multiple isomorphous replacement method. The crystal structure was refined by simulated annealing with molecular dynamics. The current crystallographic R-factor is 0.200 in the 10-2.5 A resolution range. The molecular structure which is completely different from the known structures of RNase A and RNase T1 consists of six alpha-helices and seven beta-strands, belonging to the alpha+beta type structure. Two histidine and one glutamic acid residues which were predicted as the most probably functional residues by chemical modification studies are found to be clustered. The steric nature of the active site taken together with the relevant site-directed mutagenesis experiments (Irie et al.) indicates that: (i) the two histidine residues are the general acid and base; and (ii) an aspartic acid residue plays a role of recognizing adenine moiety of the substrate.

Methamphetamine Detection from Meconium and Amniotic Fluid in Guinea Pigs Depends on Gestational Age and Metabolism

Significant adverse perinatal effects of maternal methamphetamine use have been reported, but little is known about factors influencing methamphetamine screening test results during the perinatal period. We tested the hypothesis that gestational age would affect quantitative recovery of methamphetamine in meconium and amniotic fluid. Time-bred guinea pigs received an intraperitoneal (i.p.) injection of 1 mg/kg methamphetamine at either 44 days (0.65 of term, n = 5), 50 days (0.74, n = 8), 56 days (0.82, n = 9) or 63 days (0.93, n = 4) gestation. At 1 or 7 days after i.p. methamphetamine, meconium and amniotic fluid were collected for quantitative methamphetamine assay by gas chromatography-mass spectrometry. Recovery from amniotic fluid and meconium 1 day after injection was influenced by gestational age. Greater values in amniotic fluid and meconium and a higher percentage of positive samples were seen in older fetuses. Collectively at all gestational ages, combined testing of amniotic fluid and meconium yielded detectable methamphetamine or its metabolites in 87% of guinea pigs 1 day after injection. However, methamphetamine was not detectable 1 week after injection in any sample (n = 63) at either 0.74 or 0.82 of term except for one positive amniotic fluid sample. Finally, demethylation of methamphetamine to amphetamine was higher in older fetuses.(ABSTRACT TRUNCATED AT 250 WORDS)

Crystal structure of an engineered subtilisin inhibitor complexed with bovine trypsin

Proteinase specificity of a proteinaceous inhibitor of subtilisin (SSI; Streptomyces subtilisin inhibitor) can be altered so as to strongly inhibit trypsin simply by replacing P1 methionine with lysine (with or without concomitant change of the P4 residue) through site-directed mutagenesis. Now the crystal structure of one such engineered SSI (P1 methionine converted to lysine and P4 methionine converted to glycine) complexed with bovine trypsin has been solved at 2.6 A resolution and refined to a crystallographic R factor of 0.173. Comparing this structure with the previously established structure of the native SSI complexed with subtilisin BPN', it was found that (i) P1 lysine of the mutant SSI is accommodated in the S1 pocket of trypsin as usual, and (ii) upon complex formation, considerable conformation change occurs to the reactive site loop of the mutant SSI. Thus, in this case, flexibility of the reactive site loop seems important for successfully changing the proteinase specificity through mere replacement of the P1 residue.

Refined crystal structure of the complex of subtilisin BPN' and Streptomyces subtilisin inhibitor at 1.8 A resolution

The crystal structure of subtilisin BPN' complexed with a proteinaceous inhibitor SSI (Streptomyces subtilisin inhibitor) was refined at 1.8 A resolution to an R-factor of 0.177 with a root-mean-square deviation from ideal bond lengths of 0.014 A. The work finally established that the SSI-subtilisin complex is a Michaelis complex with a distance between the O gamma of active Ser221 and the carbonyl carbon of the scissile peptide bond being an intermediate value between a covalent bond and a van der Waals' contact, 2.7 A. This feature, as well as the geometry of the catalytic triad and the oxyanion hole, is coincident with that found in other highly refined crystal structures of the complex of subtilisin Novo, subtilisin Carlsberg, bovine trypsin or Streptomyces griseus protease B with their proteinaceous inhibitors. The enzyme-inhibitor beta-sheet interaction is composed of two separate parts: that between the P1-P3 residues of SSI and the 125-127 chain segment (the "S1-3 site") of subtilisin and that between the P4-P6 residues of SSI and th 102-104 chain segment (the "S4-6 site") of subtilisin. The latter beta-interaction is unique to subtilisin. In contrast, the beta-sheet interaction previously found in the complex of subtilisin Novo and chymotrypsin inhibitor 2 or in the complex of subtilisin Carlsberg and Eglin C is distinct from the present complex in that the two types of beta-interactions are not separate. As for the flexibility of the molecules comprising the present complex, the following observations were made by comparing the B-factors for free and complexed SSI and comparing those for free and complexed subtilisin BPN'. The rigidification of the component molecules upon complex formation occurs in a very localized region: in SSI, the "primary" and "secondary" contact regions and the flanking region; in subtilisin BPN', the S1-3 and S4-6 sites and the flanking region.

Three-dimensional structure of ribonuclease Ms*3'-guanylic acid complex at 2.5 A resolution

The crystal structure of ribonuclease Ms*3'-guanylic acid complex has been determined by molecular replacement methods based on the known structure of ribonuclease T1. The pattern of hydrogen-bonds between the enzyme and the guanine base is similar to that discovered by Arni et al. [( 1988) J. Biol. Chem. 263, 15358-15368] in the crystal structure of ribonuclease T1*2'-guanylic acid complex. As for the possible general base in the trans-phosphorylation step of the catalysis, 0 epsilon 1 of Glu57 is within the hydrogen-bond distance (2.7 A) of the 2'-0 of the nucleotide while N epsilon 2 of His39 is significantly more distant (3.4 A) from the 2'-0.

Molecular recognition at the active site of subtilisin BPN': crystallographic studies using genetically engineered proteinaceous inhibitor SSI (Streptomyces subtilisin inhibitor)

Unlike trypsin-like serine proteases having only one conspicuous binding pocket in the active site, subtilisin BPN' has two such pockets, the S1 and S4 pockets, which accommodate the P1 and P4 residues of ligands (after Schechter and Berger notation) respectively. Using computer graphics, the geometrical nature of the two pockets was carefully examined and strategies for site-directed mutagenesis studies were set up against a protein SSI (Streptomyces subtilisin inhibitor), which is a strong proteinaceous inhibitor (or a substrate analogue) of subtilisin BPN'. It was decided to convert the P1 residue, methionine 73, into lysine (M73K) with or without additional conversion of the P4 residue, methionine 70, into glycine (M70G). The crystal structures of the two complexes of subtilisin BPN', one with the single mutant SSI (M73K) and the other with the double mutant SSI (M73K, M70G) were solved showing that (i) small 'electrostatic induced-fit movement' occurs in the S1 pocket upon introducing the terminal plus charge of the lysine side chain, and (ii) large 'mechanical induced-fit movement' occurs in the S4 pocket upon reducing the size of the P4 side chain from methionine to glycine. In both (i) and (ii), the induced-fit movement occurred in a concerted fashion involving both the enzyme and 'substrate' amino acid residues. The term 'substrate-assisted stabilization' was coined to stress the cooperative nature of the induced-fit movements.