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Biomedical subjects

J Lai

Publications and source records attributed to J Lai.

At least 109 records · Page 6Linked to original sources
PubMed1995

Characterization of the antiallodynic efficacy of morphine in a model of neuropathic pain in rats.

Neuropathic pains have often been classified as opioid resistant. Here, the ability of systemic (i.p.), intracerebroventricular (i.c.v.) and intrathecal (i.th.) morphine to inhibit mechanical allodynia were studied in a nerve ligation (L5, L6 nerve roots) model of neuropathic pain in rats. Morphine administered i.p. or i.c.v. produced dose-dependent antiallodynia which was readily antagonized by naloxone (5 mg kg-1, i.p. at -10 min). In contrast, i.th. morphine at doses up to 100 micrograms was without effect. These data suggest that the failure of i.th. morphine to produce antiallodynic effects may be due, in part, to the lack of available functional spinal opioid mu-receptors which may occur following nerve injury. In contrast, the antiallodynic actions of i.p. or i.c.v. morphine appear to depend on supraspinal activation of opioid (mu?) receptors and subsequent activation of descending modulatory systems. The inconsistent data seen clinically with morphine in neuropathic pains may be related to the lack of supraspinal/spinal synergy that is normally associated with morphine efficacy in conditions of acute pain.

Animals↗
PubMed1995

Opioid peptide receptor studies. 4. Antisense oligodeoxynucleotide to the delta opioid receptor delineates opioid receptor subtypes.

Prior work in our laboratory has identified putative subtypes of delta (delta cx-1, delta cx-2, delta ncx-1, delta ncx-2) and kappa 2 (kappa 2a and kappa 2b) receptors. Previous studies showed that chronic (three day) i.c.v. administration of antisense oligodeoxynucleotide to the cloned delta opioid receptor selectively decreased [3H][D-Ala2,D-Leu5]enkephalin binding to the delta ncx site, not the delta cx-2 site. The present study extends this work by demonstrating that delta antisense DNA selectively affects the delta ncx-2 site sparing the other putative delta receptor subtypes and kappa 2 receptor subtypes. This selectivity is not due to anatomically specific effects of delta antisense DNA since autoradiograms show that delta binding is reduced in all regions of the brain after chronic i.c.v. administration of delta antisense DNA. These data strongly suggest that the delta cx-1, delta cx-2, delta ncx-1, kappa 2a and kappa 2b binding sites are different proteins than the delta ncx-2 binding site, which, based on its sensitivity to delta antisense DNA, is synonymous to the cloned delta opioid receptor. Viewed collectively, these data suggest that administration of delta antisense DNA, and by extension other receptor-selective antisense DNA, is a powerful approach to distinguishing between postulated receptor subtypes.

Animals↗
PubMed1995

Increased expression of opioid delta receptors by deoxy conformation heme proteins in NG108-15 cells.

Adaptations to prolonged hypoxia include an increase in the expression of proteins that may facilitate survival. One mechanism by which hypoxia increases protein expression involves a change of heme proteins from oxygenated to deoxygenated conformations. In the present study, we tested the hypothesis that treatment of NG108-15 cells with metallic cations, which are known to induce a deoxygenated conformation of heme proteins, would increase delta opioid receptor (DOR) expression. Cells were treated with cobalt and nickel, which induce deoxygenated heme protein conformation, or zinc as a control for 48 h prior to quantifying DOR expression. Cobalt and nickel, but not zinc, significantly increased DOR expression. Heme synthesis inhibitors would block the synthesis of cobalt-substituted heme proteins which are locked in a deoxygenated conformation. The cobalt-induced increase in DOR expression was blocked by the heme synthesis inhibitor, 4,6-dioxoheptanoic acid. These experiments indicate that deoxygenated conformation heme proteins, which are thought to partially mimic hypoxia, increase DOR expression. The increase in DOR expression suggests that the DOR gene may be hypoxia-sensitive. Further, the increase in DOR expression suggests a potential adaptation strategy to hypoxia and may represent one of the first findings of physiological regulation of DOR expression.

Cell Line↗
PubMed1995

Expression of cDNA fragment encoding sperm membrane peptide in E. coli.

A secretory high-level expression cloning vector designated as pSBC-20 was constructed by inserting a DNA fragment encoding the signal peptide of ompA protein into pBV 220 vector. Any foreign DNA fragment can be inserted into the polylinker cloning sites located after the secretion signal sequence. The cloned foreign gene is under the control of the PR-PL promoter while the expression of the gene is regulated by the cI-gene product. The products are secreted into the periplasmic space of bacteria or into the medium. A recombinant plasmid (pRSD-220) was constructed by inserting the 210 bp from RSD-2, a cDNA encoding a peptide fragment of human sperm protein, into the EcoRI site of pSBC-20. The E. coli cells transformed with pRSD-220 were propagated at 30 degrees C, then incubated at 42 degrees C for several hrs. The cloned gene product was secreted into the culture medium at a high rate. The yield was about 60 mg of gene product per liter of cultured medium.

Base Sequence↗
PubMed1995

Opioid peptide receptor studies. 1. Identification of a novel delta-opioid receptor binding site in rat brain membranes.

Our laboratory was among the first to propose the existence of delta receptor subtypes: a delta site thought to be associated with a mu-delta-opioid receptor complex termed the delta cx binding site and delta site not associated with the mu-delta-opioid receptor complex, termed the delta ncx site. In previous studies, we assayed the delta cx site with [3H][D-Ala2,D-Leu5]enkephalin using rat brain membranes depleted of delta ncx sites by pretreatment with the site-directed acylating agent, (+)-trans-SUPERFIT. In the present study, we investigated, using (+)-trans-SUPERFIT-pretreated membranes, the possibility of heterogeneity of the delta cx binding site. Two sites were resolved: the delta cx-1 site at which mu ligands are potent noncompetitive inhibitors and delta ligands are weak competitive inhibitors, and the delta cx-2 site where delta ligands are potent and mu ligands are weak, mixed competitive-noncompetitive inhibitors. Although the delta cx-2 site has a delta-like ligand-selectivity profile, several experiments distinguished it from the delta ncx site. Two lines of evidence suggest that the delta ncx site corresponds to the cloned delta receptor. One, the delta receptor was cloned from the NG108-15 cell line, and this receptor, like the delta ncx binding site, irreversibly binds SUPERFIT and (+)-trans-SUPERFIT. Secondly, administration of delta-antisense DNA selectively decreases delta ncx binding. Viewed collectively, the major finding of this study is the discovery of a novel SUPERFIT-insensitive and delta-antisense-insensitive delta cx-2 binding site.

Analgesics↗
PubMed1995

Umbilical cord haematoma: a serious pregnancy complication.

The 2 cases presented show the potential morbidity and mortality which may be associated with umbilical cord haematoma. That timely diagnoses and delivery can save such an affected fetus is seen in Case 1. If fetal movements are absent, both a nonstress cardiotocograph and ultrasound scan may lead to the correct management.

Adult↗
PubMed1995

Regulation of airway muscarinic cholinergic receptor subtypes by chronic anticholinergic treatment.

Anticholinergic agents are commonly used as bronchodilators for patients with airway obstructive diseases. The effects of chronic anticholinergic therapy on airway function and bronchial responsiveness are not known, but data from clinical studies suggest the possibility of adverse effects. We demonstrated in rabbits that, after atropine treatment for 4 weeks, the efficacy (maximum contraction) of in vitro methacholine-induced contraction of mainstem bronchi was increased [control (untreated), 1.0 +/- 0.1 g; atropine-treated, 1.6 g +/- 0.2 g; p = 0.04]. However, there was no significant change in the potency (EC50) of methacholine-induced contraction. Chronic atropine treatment increased the maximum density (Bmax) of muscarinic receptors in the airways, as determined by radioligand binding studies with tritiated quinuclidinyl benzilate. Individual muscarinic receptor subtypes were measured using antibodies selective for the m1-m5 subtypes. Of the subtypes detected in rabbit tracheal smooth muscle (m2, m3, and m4), only the m2 and m3 muscarinic receptor subtypes were significantly up-regulated compared with control, after chronic atropine treatment. Because cholinergic agent-mediated contraction of smooth muscle has been shown to be mediated by m3 muscarinic receptors, the atropine-induced increase in the methacholine response in airway smooth muscle appears to be the result of the up-regulation of m3 muscarinic cholinergic receptors. Such a mechanism may explain the clinical observations that chronic anticholinergic therapy for asthmatic patients is associated with an increase in bronchial responsiveness and that continuous versus "on demand" anticholinergic bronchodilator therapy may cause an accelerated decline in ventilatory function.

Animals↗
PubMed1995

Regulation of morphine antiallodynic efficacy by cholecystokinin in a model of neuropathic pain in rats.

Neuropathic pains have often been classified as opioid-resistant. Here, spinal (intrathecal) actions of morphine and nonmorphine opioids have been studied in a nerve ligation model of neuropathic pain in rats. Mechanical allodynia was evaluated using von Frey filaments. Nerve-injured animals exhibited allodynia that was stable for up to 6 weeks after the surgery. Morphine did not alter allodynia at doses up to 300 nmol (100 micrograms). In contrast, [D-Ala2, NMPhe4, Gly-ol]enkephalin (DAMGO), a high-efficacy mu opioid agonist, produced a significant, dose-related antiallodynic action. [D-Ala2, Glu4]deltorphin (delta agonist) produced a significant antiallodynic effect only at 300 nmol, reaching approximately 70% of the maximum. Coadministration of morphine with a dose of [D-Ala2, Glu4]deltorphin, which was inactive alone, produced a significant and long-lasting antiallodynic action that was antagonized by NTI (delta receptor antagonist); NTI alone had no effect. Although blockade of cholecystokinin-B (CCKB) receptors with L365,260 did not produce effects alone, a significant antiallodynic action was observed when coadministered with morphine; this elevation of nociceptive threshold was abolished by NTI. The finding that DAMGO, but not very large doses of morphine, produced antiallodynic actions suggests that the ability of mu opioids to alleviate the allodynia is related, in part, to efficacy at postsynaptic mu receptors. At an inactive dose, a delta agonist or a CCKB antagonist enhanced morphine antiallodynic efficacy in an NTI-sensitive fashion. CCKB receptor blockade may enhance endogenous enkephalin actions, resulting in enhancement of morphine efficacy through a mu-delta receptor interaction.

Analgesics, Opioid↗
PubMed1995

Analysis of K-ras gene mutations in periampullary cancers, gallbladder cancers and cholangiocarcinomas from paraffin-embedded tissue sections.

Point mutations of the K-ras gene were analyzed in 25 periampullary cancers (21 ampulla vater cancers, two common bile duct cancers and two duodenal cancers), two gallbladder cancers and six cholangiocarcinomas. DNA extracted from the paraffin-embedded tissues was amplified with the polymerase chain reaction and subsequently analyzed by direct cycle sequencing at codons 12, 13 and 18 of the K-ras gene. Codon 61 was first screened with single strand conformation polymorphism and then sequenced by direct cycle sequencing. No point mutation was found in any of the 25 periampullary cancers or the two gallbladder cancers. These results are similar to previous reports. Mutation of the K-ras gene seems not to play an important role in tumorigenesis of periampullary cancer. In two of six (33%) cholangiocarcinoma patients, point mutations were found. Both mutations were transitions, GGT to GAT at codon 12. The incidence of mutation was greater than that in Thailand (about 8%) but less than that in Japan (about 60%). Mutation of the K-ras gene may play varied roles in the tumorigenesis of cholangiocarcinoma, depending on geographic area.

Adult↗
PubMed1994

Antisense oligodeoxynucleotide to the CCKB receptor produces naltrindole- and [Leu5]enkephalin antiserum-sensitive enhancement of morphine antinociception.

Cholecystokinin (CCK) has been shown to attenuate, while CCK antagonists enhance, the antinociceptive activity of morphine, suggesting that this peptide may act as an endogenous modulator of the opioid system. Here, we have investigated the effects of administration of a synthetic oligodeoxynucleotide (oligo) complementary to the 5' coding region of the cloned mouse CCKB receptor (antisense), or a mismatch oligo, on the antinociceptive effects of morphine. Intracerebroventricular (i.c.v.) treatment of mice with CCKB antisense, but not mismatch, oligo for 3 days resulted in an enhancement of the antinociceptive potency of i.c.v. morphine, as indicated by an approximately 6-fold leftward shift of the dose-effect curve. The antinociceptive effects of morphine in control and CCKB antisense-treated animals were investigated in the presence or absence of naltrindole, an opioid delta receptor antagonist, as well as in the presence or absence of antisera directed against either [Leu5]- or [Met5]enkephalin. The enhanced potency of morphine in mice pretreated with CCKB antisense oligo was blocked by a delta-selective dose of naltrindole and antisera to [Leu5]enkephalin, but not [Met5]enkephalin; naltrindole, or antisera towards [Leu5]enkephalin or [Met5]enkephalin did not produce antinociceptive effects when given alone and did not alter the antinociceptive actions of morphine in control mice. These data suggest that CCK may act via CCKB receptors to tonically inhibit the release of [Leu5]enkephalin, or a [Leu5]enkephalin-like peptide. The enhancement of morphine antinociception seen in the presence of blockade of the CCKB receptor may be the result of the well-known enhancement of morphine antinociception by opioid delta agonists.

Animals↗
PubMed1994

Pharmacological characterization of the cloned kappa opioid receptor as a kappa 1b subtype.

Substantial pharmacological evidence in vitro and in vivo has suggested the existence of subtypes of the kappa opioid receptor. Quantitative radioligand binding techniques resolved the presence of two high affinity binding sites for the kappa 1 ligand [3H]U69,593 in mouse brain membranes, termed kappa 1a and kappa 1b, respectively. Whereas the kappa 1a site has high affinity for fedotozine and oxymorphindole and low affinity for bremazocine and alpha-neoendorphin, site kappa 1b has high affinity for bremazocine and alpha-neoendorphin and low affinity for fedotozine and oxymorphindole. CI-977 and U69,593 bind equally well at both sites. To determine the relationship between these kappa 1 receptor subtypes and the recently cloned mouse kappa 1 receptor (KOR), we examined [3H]U69,593 binding to the KOR in stably transfected cells (KORCHN-8). Competition of [3H]U69,593 binding to the KOR by bremazocine, alpha-neoendorphin, fedotozine and oxymorphindole resolved a single class of binding sites at which these agents had binding affinities similar to that of the kappa 1b site present in mouse brain. These results suggest that the cloned KOR corresponds to the kappa 1 site in mouse brain defined as kappa 1b.

Animals↗
PubMed1994

Treatment with antisense oligodeoxynucleotide to the opioid delta receptor selectively inhibits delta 2-agonist antinociception.

Using approaches emphasizing differential antagonism of receptor selective agonists and cross-tolerance paradigms, evidence in vivo has suggested the existence of subtypes of opioid delta receptors, which have been termed delta 1 and delta 2. Recent work has elucidated the structure of an opioid delta receptor. The present investigation attempted to continue to test the hypothesis of subtypes of delta receptors and to correlate the cloned delta receptor with the existing pharmacological classification. Synthetic oligodeoxynucleotides (oligos) complementary to the 5' end of the cloned delta receptor coding region (antisense) or its corresponding sequence (sense) were given by intracerebroventricular (i.c.v.) administration to mice, twice-daily for 3 days and antinociceptive responses to selective agonists at putative delta 1 and delta 2 receptors were subsequently determined. Treatment with antisense, but not sense, oligo significantly inhibited the response to [D-Ala2,Glu4]deltorphin (delta 2 agonist), but not to [D-Pen2,D-Pen5]enkephalin (DPDPE, delta 1 agonist). Further, subsequent administration of DPDPE elicited a full antinociceptive response in the same antisense oligo treated mice which did not show a significant response to [D-Ala2,Glu4]deltorphin while antisense oligo treated mice which responded to DPDPE did not show antinociception when tested subsequently with [D-Ala2,Glu4]deltorphin. The data suggest that the cloned delta receptor corresponds to that pharmacologically classified as delta 2 and continue to support the concept of subtypes of opioid delta receptors.

Analgesics↗
PubMed1994

A faster-acting and more potent form of tissue plasminogen activator.

Current treatment with tissue plasminogen activator (tPA) requires an intravenous infusion (1.5-3 h) because the clearance of tPA from the circulation is rapid (t 1/2 approximately 6 min). We have developed a tPA variant, T103N,N117Q, KHRR(296-299)AAAA (TNK-tPA) that has substantially slower in vivo clearance (1.9 vs. 16.1 ml per min per kg for tPA in rabbits) and near-normal fibrin binding and plasma clot lysis activity (87% and 82% compared with wild-type tPA). TNK-tPA exhibits 80-fold higher resistance to plasminogen activator inhibitor 1 than tPA and 14-fold enhanced relative fibrin specificity. In vitro, TNK-tPA is 10-fold more effective at conserving fibrinogen in plasma compared to tPA. Arterial venous shunt models of fibrinolysis in rabbits indicate that TNK-tPA (by bolus) induces 50% lysis in one-third the time required by tPA (by infusion). TNK-tPA is 8- and 13-fold more potent in rabbits than tPA toward whole blood clots and platelet-enriched clots, respectively. TNK-tPA conserves fibrinogen and, because of its slower clearance and normal clot lysis activity, is effective as a thrombolytic agent when given as a bolus at a relatively low dose.

Animals↗
PubMed1994

Selective inhibition of [D-Ala2, Glu4]deltorphin antinociception by supraspinal, but not spinal, administration of an antisense oligodeoxynucleotide to an opioid delta receptor.

Evidence in vivo has suggested the existence of subtypes of the delta opioid receptor (DOR), which have been termed delta 1 and delta 2. These proposed DOR subtypes are thought to be activated by [D-Pen2, D-Pen5]enkephalin (DPDPE, delta 1) and [D-Ala2, Glu4]deltorphin (delta 2). Recent work in which an antisense oligodeoxynucleotide (oligo) to a cloned DOR was administered by the intrathecal (i.th.) route has demonstrated a reduction in the antinociceptive actions of both i.th. DPDPE and [D-Ala2, Glu4]deltorphin, but not of [D-Ala2, NMPhe4, Gly-ol]enkephalin (DAMGO, mu agonist) in mice. The present investigation has extended these observations by administering the same DOR antisense oligo sequence by the intracerebroventricular (i.c.v.) route and evaluating the antinociceptive actions of i.c.v. agonists selective for delta, mu and kappa receptors. I.th. treatment with DOR antisense oligo, but not mismatch oligo, significantly inhibited the antinociceptive actions of both i.th. DPDPE and [D-Ala2, Glu4]deltorphin but not of i.th. DAMGO or U69,593 (kappa agonist), confirming previous data. In contrast, i.c.v. DOR antisense oligo, but not mismatch oligo, selectively inhibited the antinociceptive response to i.c.v. [D-Ala2, Glu4]deltorphin without altering the antinociceptive actions of i.c.v. DPDPE, DAMGO or U69,593. The data suggest that the cloned DOR corresponds to that pharmacologically classified as delta 2 and further, suggest that this delta receptor subtype may play a major role in eliciting spinal delta-mediated antinociception.

Analgesics↗
PubMed1994

Doppler sonography of adnexal masses: the predictive value of the pulsatility index in benign and malignant disease.

OBJECTIVE: The purpose of this study was to determine whether pulsed Doppler sonography can be used to distinguish between benign and malignant adnexal masses on the basis of pulsatility index. SUBJECTS AND METHODS: In an 18-month period, all patients in whom an adnexal mass was detected at sonography had further evaluation of the mass by color and pulsed Doppler sonography. Ninety-nine patients with 102 masses that were surgically removed were included in the study. The pulsatility indexes were calculated from the reproducible spectral waveforms generated from flow centrally or peripherally within or immediately adjacent to the mass. Each lesion was categorized on the basis of its gray scale morphologic features as typically benign or indeterminate/malignant in appearance. RESULTS: Of the 102 adnexal masses, 89 were benign and 13 were malignant. In seven of the 89 benign lesions, no flow could be detected, and these were excluded from analysis. Of the remaining 82 benign lesions, 65 showed pulsatility indexes consistently equal to or greater than 1.0, and 17 showed pulsatility indexes of less than 1.0. Ten of the 13 malignant lesions had pulsatility indexes consistently less than 1.0, and three primary malignant tumors had their lowest pulsatility indexes ranging between 1.1 and 1.8. Sixty-five of the 68 masses with pulsatility indexes equal to or greater than 1.0 were benign, for a positive predictive value of 96% for benign disease. Ten of the 27 masses with pulsatility indexes of less than 1.0 were malignant, for a positive predictive value of 37% for malignant disease. Forty-five masses were detected in perimenopausal and postmenopausal patients. In this group, the pulsatility index had a positive predictive value of 88% for benign disease and 47% for malignant disease. In this study, 45 of 49 masses that had a typically benign sonographic appearance had pulsatility indexes equal to or greater than 1.0. All 49 masses had benign histology. In the remaining 46 masses with an indeterminate/malignant sonographic appearance, 20 of 23 with pulsatility indexes equal to or greater than 1.0 were benign, and 10 of 23 with pulsatility indexes of less than 1.0 were malignant. CONCLUSION: Our results show a high positive predictive value of high-impedance flow in benign adnexal disease and a predominance of low-impedance flow in malignant adnexal disease. However, the pulsatility indexes showed considerable overlap between benign and malignant lesions, indicating that Doppler sonography has severe limitations in the differentiation of benign from malignant adnexal disease on the basis of low-impedance flow (pulsatility index < 1.0).

Adenofibroma↗
PubMed1994

[Analysis of misdiagnostic acoustic neuroma].

72 cases (74 tumors) of acoustic neuroma pathologically confirmed after operation were analysed with special regard to the misdiagnosis made in their initial seeking for medical advice from ENT doctors. The average period of misdiagnosis was 5.48 years. The disease entities that the acoustic neuroma had been mistaken for were sensorineural hearing loss of unknown origin, idiopathic sudden deafness, tinnitus of unknown origin, cervical osteophytosis, nasopharyngeal carcinoma, etc. Emphasis was placed on the discussion of various causes of misdiagnosis.

Adolescent↗
PubMed1993

Simplification of high-energy collision spectra of peptides by amino-terminal derivatization.

Four-sector tandem mass spectrometry proves extremely useful for providing sequence information for peptides. The complexity of ion fragmentations, however, makes data interpretation difficult and time consuming. Attachment of a fixed positive charge to the peptide amino terminus forces production of only N-terminal fragment ions to yield simplified, predictable fragmentation. Reaction of a peptide at pH 6 with iodoacetic anhydride selectively modifies the N-terminus by exploiting the pK(a) differences between the alpha-amino group and any lysine side-chain epsilon-amino groups. The iodoacetyl peptide can react with many reagents to form a fixed positive charge. We find reaction with dimethyloctylamine forms a quaternary ammonium derivative with good surface activity properties and concomitant increased sensitivity. The high-energy CAD fragment ion spectra of the N-terminally derivatized peptides show predominantly a(n) and d(n) ions. The abundant d(n) ions permit ready distinction of leucine and isoleucine. Fewer fragment ions make data interpretation simpler and lead to more intense peaks since the ion intensity is spread among fewer peaks. The method is particularly useful for peptides which do not otherwise yield sufficient fragmentation to provide either the complete sequence or the locations of modified amino acids.

Amino Acid Sequence↗