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B Lee

Publications and source records attributed to B Lee.

At least 181 records · Page 10Linked to original sources
PubMed1999

Whole genome genetic-typing in yeast using high-density oligonucleotide arrays.

Genome sequence information in combination with new technologies has allowed researchers to approach genetic problems in new ways. High-density oligonucleotide arrays were used to probe the genome content of the yeast Saccharomyces cerevisiae. We show that these arrays, containing oligonucleotides complementary to the sequenced strain of S. cerevisiae, can be used to identify open reading frames that are missing or present in higher or lower copy number in related isolates of S. cerevisiae. We apply this method to the characterization of the genome of a strain derived from a clinical isolate of S. cerevisiae. Our results show that the telomeres are the regions with the most variability between the two strains.

Gene Deletion↗
PubMed1999

Conformational studies of irreversible HIV-1 protease inhibitors containing cis-epoxide as an amide isostere.

We have carried out NMR and molecular modeling studies of peptidomimetic HIV-1 protease inhibitors, LB71116: Qc-Asn-Phepsi[(1R,2S)-cis-epoxide]Gly-NH-CH(isopropyl)2 where Qc stands for quinaldic acid and LB71148: Qc-(SMe)Pen(O)2-Phepsi[(1R,2S)-cis-epoxide]Gly-NH-CH(isoprop yl)2 where (SMe)Pen(O)2 stands for S-methyl-S-dioxo-penicillamine. Through conformational calculations and NMR data analysis, we have obtained preferred conformations of the two inhibitors in solution. To our knowledge, this work is one of the first extensive conformational studies of peptidomimetics containing cis-epoxide amide isostere. The resulting preferred conformations contain extended structures. In these conformations, the psi of Phe(cep) is maintained about 130 degrees and the phi angle of (cep)Gly prefers +/- 150 degrees [where Phe(cep) and (cep)Gly are the residues generated by the replacement of the Phe-Gly peptide bond with cis-epoxide]. Two conformations were commonly observed in the preferred conformations of each inhibitor. Through restrained molecular dynamics simulating the hydrogen bond formation between our inhibitor and a water molecule ('flap water'), one of the conformations is assumed as the conformation which can bind to the enzyme without large conformational changes. Recently, we had the opportunity to compare the selected preferred conformation with the binding conformation of LB71116 observed from the X-ray studies of the complex between LB71116 and HIV-1 protease. These two conformations are surprisingly similar to each other. Thus, we can explain high activity and selectivity of our inhibitors to the HIV-1 protease by the similarity between the preferred conformations in solution and the binding conformation.

Amides↗
PubMed1999

Resurgence of measles in Singapore: profile of hospital cases.

OBJECTIVE: To ascertain the profile of cases of measles seen at a general hospital during a recent outbreak that occurred despite a measles vaccination program. METHODOLOGY: A retrospective study from January 1991 to March 1998. All patients with measles (ICD code 055. 9) seen at the emergency unit or as inpatients were included. RESULTS: There were 87 cases identified. The diagnosis was clinical in all and proven serologically in 71%. Eighty-five per cent of the cases occurred between January 1997 and March 1998. There was a bi-modal age distribution with peaks in the very young (</= 18 months) and those aged 16-20 years. The majority was unvaccinated (58/87). A proportion (11/87) demonstrated vaccine failure, most likely primary failures. CONCLUSION: This changing measles epidemiology suggests lowering of herd immunity. 'Catch up' vaccinations in July- October 1997 given to school children aged 12-18 years (200 000 individuals or 82% of cohort), may have helped contain the outbreak. These results substantiated the need for a two-dose policy and 'catch-up' immunization program.

Adolescent↗
PubMed1999

Gastroprotective mechanism of lafutidine, a novel anti-ulcer drug with histamine H2-receptor antagonistic activity.

Lafutidine (CAS 118288-08-7, FRG-8813) is a novel histamine H2-receptor antagonist with gastroprotective activity. The aim of this study was to investigate the property of the gastro-protective activity of lafutidine by examining the effect on ammonia-induced change in transmucosal potential difference (PD), basal gastric mucosal blood flow (GMBF) and noxious agent-induced cell damage. Intragastrical application of lafutidine accelerated the recovery of the PD reduction after exposure of the mucosa to 0.25% ammonia solution and the accelerating effect was abolished by chemical deafferentation, but not with indometacin, a cyclooxygenase inhibitor. The application of capsaicin, as a reference compound, significantly promoted the recovery of the ammonia-induced PD reduction and this effect was not altered with indometacin. Lafutidine given intragastrically caused a sustained increase in GMBF in a dose-dependent fashion, which was also completely inhibited in the deafferentated rats. In vitro studies revealed that, in contrast to 16,16-dimethyl prostaglandin E2, lafutidine did not protect isolated gastric superficial epithelial cells from ethanol- or ammonia-induced damage. In conclusion, the gastroprotection of lafutidine is induced by promoting the restitution of the damaged mucosa after a noxious agent, not by directly protecting the epithelial cells and this effect may be caused through the mechanism of capsaicin-sensitive afferent nerves.

16,16-Dimethylprostaglandin E2↗
PubMed1999

Microsurgical reconstruction of extensive scalp defects.

Large, full-thickness scalp defects represent a reconstructive challenge that has benefitted greatly from the introduction of microsurgical techniques. The authors review their experience with 16 patients with acquired defects of the scalp for which local or regional reconstructive options were unavailable. The mean age at the time of operation was 44.8 years. Nine patients underwent resection of malignant scalp lesions, followed immediately by free-flap coverage. Six patients required revision procedures for unstable scar as a result of prior trauma (2), old scalp avulsions (2), and multiple intracranial procedures (2). The remaining patient underwent replantation of an acutely avulsed scalp. The free-flap donor sites utilized included latissimus (6), scapular (3), radial forearm (2), rectus abdomnis (2), and omentum (2). Vein grafts were required in four cases. All flaps survived, although one required anastomotic revision and skin grafting for superficial loss. Additional complications were limited to seromas at two latissimus donor sites. Tumor control rates were poor, with all malignancy-associated defects having persistent disease or recurring soon after surgery. All patients eventually achieved full defect coverage. The authors conclude that microsurgical reconstruction is a reliable option for providing stable coverage of large, complex, scalp defects.

Adolescent↗
PubMed1999

Aftereffects and the representation of stereoscopic surfaces.

The structure of human disparity representation is examined through (i) adaptation experiments and (ii) model simulations of the data. Section 3 presents results of adaptation experiments designed to illuminate the structure of human disparity representation. Section 4 presents model simulations of three different disparity representation schemes. In the experiments, participants adapted to a 0.133 cycle deg-1 sinusoidally corrugated surface with 10 min of arc peak-to-trough disparity. A flat test surface was briefly presented, in which the aftereffect surface was perceived. Adapt and test surfaces were placed on disparity pedestals and thus presented in front of or behind the plane of fixation. The adapt surface could be offset from the fixation plane by +/- 8 to 24 min of arc. The test surface could be offset from the fixation plane by +/- 8 to 48 min of arc. The depth aftereffect was measured in different disparity planes by a nulling method and 'topping-up' procedure. Aftereffect tuning functions were obtained whose bandwidths, magnitudes, and tuning depended on the disparity planes of both the adapt and test surfaces. These parameters were used to constrain the models tested in section 4. On the basis of the two studies, it is argued that the human stereoscopic system encodes spatial changes of disparity using channels localised within disparity planes. A localised disparity-gradient model of the human representation of disparity is proposed.

Adaptation, Psychological↗
PubMed1999

Effect of wheat bran on serum lipids: influence of particle size and wheat protein.

OBJECTIVE: Wheat fiber appears to protect from cardiovascular disease despite its lack of consistent effect on serum lipids. We therefore wished to determine whether reported inconsistencies in the effect of wheat bran resulted from differences in particle size or its high gluten content. METHODS: Two studies were conducted. In one-month metabolic diets, 24 hyperlipidemic subjects consumed breads providing an additional 19 g/d dietary fiber as medium or ultra-fine wheat bran and extra protein (10% of energy as wheat gluten). In two-week ad libitum diets, 24 predominantly normolipidemic subjects consumed breakfast cereals providing an additional 19 g/d of dietary fiber as coarse or a mixture of ultra-fine and coarse wheat bran with no change in gluten intake. Both studies followed a randomized crossover design with control periods when subjects ate low-fiber breads and cereals respectively with no added gluten. Fasting blood lipids were measured on day zero and at the end of each phase. RESULTS: Wheat bran had no effect on total, LDL or HDL cholesterol irrespective of particle size or level of gluten in the diet. However, consumption of increased gluten in the metabolic study was associated with a 13+/-4% reduction in serum triglycerides (p = 0.005) which was not seen in the normal-gluten ad libitum study. CONCLUSIONS: The protective effect of wheat fiber in cardiovascular disease cannot be explained by an effect of wheat bran in reducing serum cholesterol although in hyperlipidemic subjects displacement of carbohydrate by gluten on the high-fiber phases was associated with lower serum triglycerides.

Adult↗
PubMed1999

The effect of wheat bran particle size on laxation and colonic fermentation.

OBJECTIVE: Due to perceived inferior fecal bulking ability, finely ground wheat bran is not recommended for treatment of colonic disorders, despite possible short chain fatty acid generation with potential benefits for colonic mucosal health. We therefore tested the effects of very fine particle size wheat bran on colonic function. METHODS: Two studies, each with three phases, were undertaken in healthy subjects in a randomized crossover design. In one study (metabolic, n=23) subjects took three diets containing either an additional 19 g/d dietary fiber with mean particle size (MPS) 50 microm or 758 microm in bread or a control low fiber bread. In the other study where the supplement was provided as a breakfast cereal (ad libitum, n=24) the respective wheat bran MPS were 692 microm and 1158 microm and the control was low fiber. Fecal collections were obtained during the last week of each diet. In the metabolic study, fecal short chain fatty acids were measured and 12-hour breath gas collections obtained. RESULTS: In both studies, wheat bran supplements significantly increased fecal bulk compared to the control (p<0.004), with no significant differences between brans of different particle size and no differences in fecal water content. However, higher fecal butyrate concentrations (p<0.007), butyrate output and breath CH4 levels (p=0.025) were seen on the low MPS wheat bran compared to the other two treatments, suggesting increased bacterial fermentation. CONCLUSIONS: Fine MPS wheat bran is an effective fecal bulking agent and may have added advantages if increased butyrate concentrations promote colonic mucosal integrity.

Adult↗
PubMed1999

CBFA1 mutation analysis and functional correlation with phenotypic variability in cleidocranial dysplasia.

Cleidocranial dysplasia (CCD) is a dominantly inherited skeletal dysplasia caused by mutations in the osteoblast-specific transcription factor CBFA1. To correlate CBFA1 mutations in different functional domains with the CCD clinical spectrum, we studied 26 independent cases of CCD and a total of 16 new mutations were identified in 17 families. The majority of mutations were de novo missense mutations that affected conserved residues in the runt domain and completely abolished both DNA binding and transactivation of a reporter gene. These, and mutations which result in premature termination in the runt domain, produced a classic CCD phenotype by abolishing transactivation of the mutant protein with consequent haploinsufficiency. We further identified three putative hypomorphic mutations (R391X, T200A and 90insC) which result in a clinical spectrum including classic and mild CCD, as well as an isolated dental phenotype characterized by delayed eruption of permanent teeth. Functional studies show that two of the three mutations were hypomorphic in nature and two were associated with significant intrafamilial variable expressivity, including isolated dental anomalies without the skeletal features of CCD. Together these data show that variable loss of function due to alterations in the runt and PST domains of CBFA1 may give rise to clinical variability, including classic CCD, mild CCD and isolated primary dental anomalies.

Animals↗
PubMed1999

Scanning electron microscopy and comparative morphometrics of eggs from six bot fly species (Diptera: Oestridae).

Scanning electron microscope comparisons were made of the eggs of Cuterebra austeni Sabrosky, C. fontinella Coquillet, C. jellisoni Curran, C. lepusculi Townsend, C. ruficrus (Austen), and Alouattamyia baeri (Shannon & Greene). Larvae of these flies parasitize rodents, lagomorphs, and monkeys. Image analysis of the egg length (maximum projection) and width (minimum projection), egg area (in dorsal view), operculum area (in dorsal view), and operculum area as a percentage of egg area revealed differences among species. The chorion of these eggs is sculptured with a distinct pattern of "cells" covering the dorsal, lateral, and opercular surfaces. The chorion of A. baeri eggs was distinct with deeply sculpted, large, highly polymorphic "cells." C. jellisoni eggs also had large, highly polymorphic cells, but the sculpturing was not deep. The chorion of the 4 remaining species was quite similar. Image analysis of the chorionic sculpturing patterns revealed significant differences in the area, perimeter, maximum projection, minimum projection and aspect ratio of chorionic "cells" among the species examined. The chorionic "cell" parameters of A. baeri and C. jellisoni were different from 1 another and from the other species in all parameters. The "cell" parameters of C. lepusculi and C. ruficrus were similar. A combination of overall egg features in combination with cell features allow the eggs to be differentiated from one another. There was no strong association among structural features of the eggs and the habitat in which they were found. However, the deep sculpturing of the A. baeri eggs might help to prevent drowning in tropical rain forests.

Animals↗
PubMed1999

Pain relief using smart technology: an overview of a new patient-controlled analgesia device.

A new adaptive patient-controlled analgesia (PCA) system designed to improve PCA through the use of a variable bolus dose and a variable background infusion is outlined here. The handset allows patients to rate their pain on a scale of 1-10. Data derived from the handset signals are used by an expert algorithm to repeatedly adapt the drug dosage of the bolus and the background infusion according to both pain intensity and patient response to previous dosages. A feasibility study of the system consisted of a small number of randomized, double-blind, crossover clinical trials. The new system was alternated with a conventional system every 12 h. When the new system was active, 12-h questionnaire pain scores were significantly lower and a trend toward fewer bolus requests was found in alternating intervals. In addition, when the new system was used to commence trials, the number of bolus requests were significantly lower and there was a trend toward lower handset scores, lower questionnaire pain scores, and lower verbal pain scores over the entire trial period. The new adaptive PCA system was well accepted by both patients and clinical staff. The trials successfully established the feasibility of the new system. Further development is being carried out as a result.

Analgesia, Patient-Controlled↗
PubMed1999

Microglia express CCR5, CXCR4, and CCR3, but of these, CCR5 is the principal coreceptor for human immunodeficiency virus type 1 dementia isolates.

Microglia are the main human immunodeficiency virus (HIV) reservoir in the central nervous system and most likely play a major role in the development of HIV dementia (HIVD). To characterize human adult microglial chemokine receptors, we analyzed the expression and calcium signaling of CCR5, CCR3, and CXCR4 and their roles in HIV entry. Microglia expressed higher levels of CCR5 than of either CCR3 or CXCR4. Of these three chemokine receptors, only CCR5 and CXCR4 were able to transduce a signal in microglia in response to their respective ligands, MIP-1beta and SDF-1alpha, as recorded by single-cell calcium flux experiments. We also found that CCR5 is the predominant coreceptor used for infection of human adult microglia by the HIV type 1 dementia isolates HIV-1DS-br, HIV-1RC-br, and HIV-1YU-2, since the anti-CCR5 antibody 2D7 was able to dramatically inhibit microglial infection by both wild-type and single-round luciferase pseudotype reporter viruses. Anti-CCR3 (7B11) and anti-CXCR4 (12G5) antibodies had little or no effect on infection. Last, we found that virus pseudotyped with the DS-br and RC-br envelopes can infect cells transfected with CD4 in conjunction with the G-protein-coupled receptors APJ, CCR8, and GPR15, which have been previously implicated in HIV entry.

AIDS Dementia Complex↗
PubMed1999

Bone marrow CD34(+) cells and megakaryoblasts secrete beta-chemokines that block infection of hematopoietic cells by M-tropic R5 HIV.

CD34(+) cells are nonpermissive to infection by HIV strains X4 and R5, despite the fact that many CD34(+) cells express high levels of the viral receptor protein CD4 and the coreceptor CXCR4 on their surface. In these cells, the co-receptor CCR5 protein, which, like CXCR4, is a chemokine receptor, is detected mainly intracellularly. We hypothesized that CD34(+) cells secrete CCR5-binding chemokines and that these factors interfere with HIV R5 interactions with these cells, possibly by binding CCR5 or by inducing its internalization. We found that human CD34(+) cells and CD34(+)KIT(+) cells, which are enriched in myeloid progenitor cells, expressed and secreted the CCR5 ligands RANTES, MIP-1alpha, and MIP-1beta and that IFN-gamma stimulated expression of these chemokines. In contrast, SDF-1, a CXCR4 ligand, was not detectable in the CD34(+)KIT(+) cells, even by RT-PCR. Conditioned media from CD34(+) cell culture significantly protected the T lymphocyte cell line PB-1 from infection by R5 but not X4 strains of HIV. Interestingly, the secretion of endogenous chemokines decreased with the maturation of CD34(+) cells, although ex vivo, expanded megakaryoblasts still secreted a significant amount of RANTES. Synthesis of CCR5-binding chemokines by human CD34(+) cells and megakaryoblasts therefore largely determines the susceptibility of these cells to infection by R5 HIV strains. We postulate that therapeutic agents that induce the endogenous synthesis of chemokines in human hematopoietic cells may protect these cells from HIV infection.

Antigens, CD34↗
PubMed1999

Effects of the respiratory stimulant almitrine on breathing and FOS expression in the brain of fetal and newborn sheep.

Almitrine is a piperazine derivative known to stimulate breathing in the adult but cause apnea in fetal sheep. In fetal sheep (127-133 d gestation; term = 147 d) we confirmed this finding, but found that almitrine (4 mg/kg, i.v. or intra-arterial) had a biphasic effect, briefly stimulating and then suppressing breathing movements for at least 3 h. In 2- to 3-d-old (n = 4) and 7- to 14-d-old (n = 4) lambs almitrine increased both tidal volume and breath frequency, increased arterial partial pressure of oxygen and pH, and decreased partial pressure of carbon dioxide. The changes of tidal volume, partial pressure of oxygen and partial pressure of carbon dioxide were less in the 2- to 3-d-old compared with the 7- to 14-d-old lambs. The distribution of the nuclear phosphoprotein FOS, a marker of neuronal activation was examined in fetal and newborn brains. FOS protein was increased in cardiorespiratory areas of the medulla and pons, in the periaqueductal region of the midbrain, and in the supraoptic and paraventricular regions of the hypothalamus. In the pons, FOS protein was increased in the medial parabrachial and subcoeruleus nuclei in the fetuses but not in the 2- to 3- or 7- to 14-d-old lambs. These observations are similar to those reported for hypoxia, and consistent with the hypothesis that both almitrine and hypoxia inhibit fetal breathing movements by an action on a select group of pontine neurons. Whether these neurons respond directly to these stimuli or receive input from the other centers is yet to be elucidated. The mechanisms that change the almitrine (and hypoxia) response from inhibition to excitation at birth have not been identified, but may be important in preventing apnea in the newborn.

Almitrine↗
PubMed1999

Glucose regulates expression of inositol 1,4,5-trisphosphate receptor isoforms in isolated rat pancreatic islets.

Isolated rat pancreatic islets were studied to determine the dynamic regulatory effects of glucose stimulation on the expression of messenger RNA (mRNA) and protein levels for inositol 1,4,5-trisphosphate (IP3) receptor (IP3R) isoforms I, II, and III. The relative isoform abundance was: IP3R-III > IP3R-II approximately IP3R-I. Culture of islets with glucose (G; 20 mM) or alpha-ketoisocaproic acid for 30 min increased only IP3R-III mRNA expression above control (5.5 mM glucose). 2-Deoxyglucose was without effect. Islet culture for 2 h with G (20 mM) or alpha-ketoisocaproic acid reduced IP3R-III mRNA expression levels below control, and cycloheximide blocked the response. Culturing islets for 1 day or 7 days with G (11 mM) reduced the expression of IP3R-III mRNA but increased the expression of IP3R-II mRNA in a time-dependent manner. Cytosine arabinoside lowered cultured islet IP3R-II and -III mRNA levels, but glucose effects remained evident. IP3R-II mRNA levels were also significantly higher in islets from hyperglycemic 90% partial pancreatectomized rats, compared with sham animals. Islet IP3R mRNA expression also showed osmotic sensitivity. Islet IP3R-III protein levels increased after 2 h islet culture at 20 mM G, were unchanged after 1 day culture at 11 mM G, and were lower than control after 7 days culture at 11 mM G. In contrast, IP3R-II levels increased after 1 day and 7 days culture at 11 mM G, whereas IP3R-I protein levels remained unchanged. Thus, G stimulation rapidly increases transcription and expression of IP3R-III mRNA and protein levels in rat islets. However, chronic G stimulation up-regulates IP3R-II mRNA in cultured islets and in islets from partial pancreatectomized rats. Metabolic regulation of IP3R-II and III expression may mediate beta-cell IP3-responsive Ca2+ mobilization and insulin secretion.

Animals↗
PubMed1999

Identification of LMX1B gene point mutations in italian patients affected with Nail-Patella syndrome.

Nail-Patella syndrome, or osteo-onychodysplasia, is an autosomal dominant disorder characterized by nail dysplasia, absent or hypoplastic patellae, iliac horns and nephropathy. Previous studies have demonstrated linkage of the Nail-Patella locus with polymorphic markers on human chromosome 9q34. Recently, point mutations in the LMX1B gene have been identified in Nail-Patella patients and in families with recurrence of Nail-Patella syndrome and open-angle glaucoma. We describe here the identification of additional point mutations in the LMX1B gene in a set of Italian patients affected with Nail-Patella syndrome: two deletions of 1 and 2 bp causing a frameshift in two sporadic patients and nonsense mutations in two familial and one sporadic cases have been identified. All the mutations affect the homeodomain of the LMX1B protein and could cause the Nail-Patella syndrome through a loss of function as well as a dominant negative effect. Haplotype analysis in the two familial cases carrying the same stop codon mutation suggests the presence of a founder effect. Finally, analysis of cDNA clones obtained from human fetal kidney has revealed the existence of two different transcripts of LMX1B gene likely due to an alternative splicing.

Alternative Splicing↗