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Biomedical subjects

L Lu

Publications and source records attributed to L Lu.

At least 37 records · Page 2Linked to original sources
PubMed2001

Complex trait analysis of the hippocampus: mapping and biometric analysis of two novel gene loci with specific effects on hippocampal structure in mice.

Notable differences in hippocampal structure are associated with intriguing differences in development and behavioral capabilities. We explored genetic and environmental factors that modulate hippocampal size, structure, and cell number using sets of C57BL/6J (B6) and DBA/2J (D2) mice; their F1 and F2 intercrosses (n = 180); and 35 lines of BXD recombinant inbred (RI) strains. Hippocampal weights of the parental strains differ by 20%. Estimates of granule cell number also differ by approximately 20%. Hippocampal weights of RI strains range from 21 to 31 mg, and those of individual F2 mice range from 23 to 36 mg (bilateral weights). Volume and granule cell number are well correlated (r = 0.7-0.8). Significant variation is associated with differences in age and sex. The hippocampus increases in weight by 0.24 mg per month, and those of males are 0.55 mg heavier (bilateral) than those of females. Heritability of variation is approximately 50%, and half of this genetic variation is generated by two quantitative trait loci that map to chromosome 1 (Hipp1a: genome-wide p < 0.005, between 65 and 100 cM) and to chromosome 5 (Hipp5a, p < 0.05, between 15 and 40 cM). These are among the first gene loci known to produce normal variation in forebrain structure. Hipp1a and Hipp5a individually modulate hippocampal weight by 1.0-2.0 mg, an effect size greater than that generated by age or sex. The Hipp gene loci modulate neuron number in the dentate gyrus, collectively shifting the population up or down by as much as 200,000 cells. Candidate genes for the Hipp loci include Rxrg and Fgfr3.

Aging↗
PubMed2001

Il-12 antagonism enhances apoptotic death of T cells within hepatic allografts from Flt3 ligand-treated donors and promotes graft acceptance.

Mouse livers are accepted across MHC barriers and induce donor-specific tolerance without immunosuppressive therapy. By contrast, livers from donors treated with Flt3 ligand, which dramatically increases hepatic interstitial dendritic cells, are rejected acutely (median survival time 5 days). This switch from tolerance to rejection is associated with a marked reduction in apoptotic activity of graft-infiltrating cells. We hypothesized that IL-12 production by enhanced numbers of donor APC might inhibit apoptosis, promote expansion of Th1 cells, and play a key role in liver rejection. Therefore, C3H (H2(k)) recipients of liver grafts from Flt3 ligand-treated B10 donors were given neutralizing anti-IL-12 mAb (200 or 500 microg) on days 0 and 2 after transplant. Graft survival was markedly prolonged at the higher mAb dose, with 50% of grafts surviving >100 days. This effect was associated with reductions in IFN-gamma gene transcripts within the graft-infiltrating cell population and with reductions in circulating IFN-gamma and IL-10 levels, donor-specific CTL and NK cell activities, and circulating alloantibody levels. At the same time, there were marked increases in apoptotic (TUNEL(+)) CD4(+) and especially CD8(+) cells, both within the grafts and in spleens of anti-IL-12 mAb-treated mice. In vitro, exogenous IL-12 inhibited apoptotic death induced in naive allogeneic T cells by liver nonparenchymal cells. These findings suggest that suppression of rejection by IL-12 antagonism, linked to restoration of apoptotic activity within the peripheral alloreactive T cell population, is important for liver allograft survival and tolerance induction.

Adjuvants, Immunologic↗
PubMed2001

Different role of cholecystokinin (CCK)-A and CCK-B receptors in relapse to morphine dependence in rats.

The possible effect of different cholecystokinin (CCK) receptor antagonists (MK-329 and L-365260) on the maintenance and reactivation of morphine conditioned place preference (CPP) were investigated in rats, respectively. The results show that the maintenance of morphine CPP could be induced by injection of morphine (10 mg/kg, s.c.) once for 3 days and this effects were significantly attenuated by pretreatment with 1 but not by 0.1 mg/kg L-365260. Furthermore, following a 28-day extinction, the morphine CPP disappeared and then reactivated again by a single injection of morphine (10 mg/kg). Pretreatment with L-365260 (1 and 0.1 mg/kg) significantly blocked this reactivation of morphine CPP. In contrast, pretreatment of MK-329 (1 and 0.1 mg/kg) failed to do so. The present study demonstrated that CCK-B receptor but not CCK-A receptor is involved in the maintenance and reactivation of morphine CPP. These findings suggest that CCK-B receptor antagonists might be of some value in the treatment and prevention of relapse to drug dependence long after detoxification.

Animals↗
PubMed2001

A spontaneous recurrent seizure-related Rattus NSF gene identified by linker capture subtraction.

Spontaneous recurrent seizures (SRS) are the major clinical characteristic of epilepsy. In this study, using a SRS-behavior test combined with linker capture subtraction (LCS) to identify genes altered in their expression in response to a single kainic acid (KA)-induced SRS at 3 weeks in the rat hippocampal formation. Dot blot analysis of the differentially expressed cDNA fragments with LCS showed the down-regulation of one cDNA related to SRS, which was designated epilepsy-related gene 1 (ERG1). Northern blot analysis showed that ERG1 mRNA was reduced by KA administration with and without SRS, but more so with SRS. This differential expression had also been confirmed by in situ hybridization, which showed that ERG1 mRNA was down-regulated in the dorsal dentate granule cells (dDGCs) of the hippocampal formation, but remarkable up-regulated in the amygdalohippocampal area (AHi), posteromedial cortical amygdaloid nucleus (PMCo) and perirhinal cortex (PRh). The complete cDNA of ERG1 was cloned, sequenced (AF142097). It encodes a Rattus homologue of N-ethylmaleimide-sensitive fusion protein (NSF), which is an ATPase that plays a key role in mediating docking and/or fusion of transport vesicles in the multi-step pathways of vesicular transport. Sequence analysis revealed that ERG1 has high sequence similarity with the cDNA of the Mus musculus suppressor of K(+) transport growth defect (SKD2), N-ethylmaleimide(NEM)-sensitive fusion protein of Chinese hamster and human NEM-sensitive factor (HSU03985).

Animals↗
PubMed2001

A cyclopentenone prostaglandin activates mesangial MAP kinase independently of PPARgamma.

The mitogen-activated protein (MAP) kinases mediate the response of renal glomerular mesangial cells to a variety of physiologic and pathologic stimuli. This investigation examines the effect of the cyclopentenone prostaglandin 15-deoxy-delta(12,14)-prostaglandin J2 (15d-PGJ2) on MAP kinases in human mesangial cells. We show that 15d-PGJ2 dose-dependently increases the extracellular signal-regulated kinase (ERK) activity of human mesangial cells, but has no effect on Jun-NH2-terminal kinase or p38 MAP kinase. Despite the fact that 15d-PGJ2 is a peroxisome proliferator-activated receptor (PPAR) ligand, and PPARgamma is shown to be expressed by mesangial cells, the thiazolidinedione PPARgamma agonist ciglitazone does not activate ERK. Additionally, a synthetic PPARgamma antagonist does not attenuate the activation of ERK by 15d-PGJ2. 15d-PGJ2-mediated ERK activation is however blocked by the MEK inhibitor PD 098059, appears to require phosphatidylinositol-3 kinase, but is independent of protein kinase C activation. These results demonstrate a novel effect of 15d-PGJ2 to induce ERK in human mesangial cells independently of PPARgamma.

Cells, Cultured↗
PubMed2001

Isolation and characterization of senescence-induced cDNAs encoding deoxyhypusine synthase and eucaryotic translation initiation factor 5A from tomato.

Full-length cDNA clones encoding deoxyhypusine synthase (DHS) and eucaryotic initiation factor 5A (eIF-5A) have been isolated from a cDNA expression library prepared from tomato leaves (Lycopersicon esculentum, cv. Match) exposed to environmental stress. DHS mediates the first of two enzymatic reactions that activate eIF-5A by converting a conserved lysine to the unusual amino acid, deoxyhypusine. Recombinant protein obtained by expressing tomato DHS cDNA in Escherichia coli proved capable of carrying out the deoxyhypusine synthase reaction in vitro in the presence of eIF-5A. Of particular interest is the finding that DHS mRNA and eIF-5A mRNA show a parallel increase in abundance in senescing tomato flowers, senescing tomato fruit, and environmentally stressed tomato leaves exhibiting programmed cell death. Western blot analyses indicated that DHS protein also increases at the onset of senescence. It is apparent from previous studies with yeast and mammalian cells that hypusine-modified eIF-5A facilitates the translation of a subset of mRNAs mediating cell division. The present study provides evidence for senescence-induced DHS and eIF-5A in tomato tissues that may facilitate the translation of mRNA species required for programmed cell death.

Aging↗
PubMed2001

Functionally distinct, sequence-specific replicator and origin elements are required for Drosophila chorion gene amplification.

To meet the demand for the rapid synthesis of chorion (eggshell) proteins, Drosophila ovarian follicle cells amplify the chromosomal loci containing the chorion gene clusters up to 60-fold. Amplification occurs by repeated firing of one or more origins located within each gene cluster. Deletion analyses of transgenic constructs derived from the third chromosome cluster have identified a 320-bp amplification control element (ACE3) required for amplification, as well as several stimulatory amplification enhancing regions (AERs). Two-dimensional (2D) gel analyses have identified multiple DNA replication initiation sites (origins) that partially overlap in location with ACE3 and the AERs. To further study sequence requirements for amplification, a vector was used in which transgenic constructs are protected from chromosomal position effects by flanking insulator elements, the suppressor Hairy-wing protein binding site (SHWBS). Using the buffered vector, the 320-bp ACE3 and an 884-bp element designated ori-beta were found to be necessary and sufficient for amplification. Two-dimensional gels revealed that ori-beta was acting as the origin. In contrast, origin activity could not be detected for ACE3. An insulator placed between ACE3 and ori-beta inhibited amplification, indicating that ACE3 activates ori-beta in cis. The results suggest that ACE3 acts as a replicator and support and extend the replicator model for the organization of metazoan chromosomal replicons.

Animals↗
PubMed2001

Viral IL-10 gene transfer inhibits DTH responses to soluble antigens: evidence for involvement of genetically modified dendritic cells and macrophages.

Expression of the viral interleukin-10 (vIL-10) gene within one joint of an animal with polyarticular, inflammatory arthritis suppresses disease in both treated and untreated joints (the "contralateral effect"). We used a mouse delayed-type hypersensitivity (DTH) model to investigate this phenomenon. Adenoviral delivery of the vIL-10 gene suppressed DTH reactions in injected and contralateral paws. T lymphocytes recovered from immunized mice injected with the adenoviral vector (ad-vIL-10) were unable to transfer the DTH response, but were not inhibitory. Peritoneal exudate cells recovered from mice injected intraperitoneally with ad-vIL-10 inhibited DTH reactions in recipient mice, but only when the donor mice had been sensitized to the antigen used to incite the DTH response. Dendritic cells (DCs) recovered from the draining lymph nodes of mice injected with ad-vIL-10 behaved similarly. Bone-marrow-derived DCs cultured ex vivo with ad-vIL-10 or recombinant mouse IL-10 also suppressed DTH reactions by adoptive transfer when pulsed with the inciting antigen. Collectively, these data suggest a mechanism for the contralateral effect in which genetically modified macrophages and DCs present antigen in the context of high, local concentrations of vIL-10, thereby generating unresponsive T lymphocytes. These findings suggest new ways in which to treat immune-driven diseases by gene and cell therapy.

Adenoviridae↗
PubMed2001

Expression of the amino-terminal domain of platelet glycoprotein Ib alpha: exploitation of a calmodulin tag for determination of its functional activity.

Platelet glycoprotein (GP) Ibalpha is a component of the GPIb-IX receptor complex, which is involved in multiple physiological and pathological processes, including platelet adhesion at sites of vascular injury, thrombin binding, Bernard-Soulier syndrome, platelet-type von Willebrand disease, and immune-mediated thrombocytopenias. The amino-terminal domain of approximately 300 residues of GPIbalpha mediates both normal biological function (by providing the sites for direct ligand interaction) and aberrant function (through amino acid substitutions). To investigate the molecular interactions mediated by this region of GPIbalpha, we have developed a recombinant baculovirus to facilitate its expression as a calmodulin fusion protein from insect cells. By employing the calmodulin tag, the fusion protein could be obtained at >90% purity after a single isolation step at yields of 8 mg/L of insect cell medium (purified fusion protein). The recombinant GPIbalpha fragment was shown to be posttranslationally sulfated and glycosylated, although its glycosylation differed from that of the equivalent GPIbalpha fragment isolated from human platelets. The differential glycosylation, however, did not affect the function of the recombinant GPIbalpha fragment in either von Willebrand factor (vWf) or thrombin binding as these were both found to be identical to those of the same-length GPIbalpha fragment derived from human platelets. The calmodulin tag was also exploited in the development of assays to measure directly vWf and thrombin binding, since it did not interfere with either, demonstrating the feasibility for the use of this soluble receptor fusion protein in detailed biophysical assays to investigate the molecular mode of binding of platelet glycoprotein Ibalpha to these ligands.

Animals↗
PubMed2001

Identification of quantitative trait loci controlling activation of TRBV4 CD8+ T cells during murine gamma-herpesvirus-induced infectious mononucleosis.

The murine gamma-herpesvirus, MHV-68, shares important biological and genetic features with the human gamma-herpesvirus, Epstein-Barr virus. Following intranasal infection, mice develop an infectious mononucleosis-like syndrome accompanied by increased numbers of activated CD8+ T cells in the blood. A consistent feature of the CD8+ T-cell activation is a marked increase in the frequency of cells expressing a TRBV4+ T-cell receptor. Previous studies suggested that the magnitude of TRBV4 expansion varied significantly among mouse strains, and was influenced by both MHC and non-MHC genes. Detailed analysis of strains with high (C57BL/6) or low (DBA/2) TRBV4 CD8+ T-cell expansion showed that differences in the degree of expansion were not a consequence of variation in genetic susceptibility to the viral infection. Rather, the magnitude of the TRBV4 CD8+ T-cell expansion correlated with differences in expression of the unidentified stimulatory ligand on activated, latently infected B cells. In the present study, analysis of TRBV4 expansion in C57BL/6, DBA/2, B6D2 F1 mice, BXD recombinant inbred strains, and the progeny of C57BL/6xDBA/2 F1 hybrids backcrossed to C57BL/6 demonstrated strong cumulative dominance of the low DBA/2 trait and moderately high heritability (h2 approximately 0.5). Two quantitative trait loci (QTLs) strongly associated with variance in TRBV4 expansion were identified using simple and composite mapping procedures. The first QTL is located on Chromosome (Chr) 17, near or proximal to H2. The second QTL is located on Chr 6 in a region spanning the Tcrb and Cd8a loci.

Animals↗
PubMed2001

Corticotropin-releasing factor receptor type 1 mediates stress-induced relapse to cocaine-conditioned place preference in rats.

Corticotropin-releasing factor (CRF) has been suggested to play an important role in the development of drug dependence and withdrawal. Based on the recent finding that CRF receptor antagonists inhibit the stress-induced relapse to opiate dependence and attenuate anxiety-like responses related to cocaine withdrawal, the present experiment was performed to examine the possible effect of different CRF receptor antagonists on reactivation of cocaine-conditioned place preference induced by cocaine and stress in rats. The results show that a single injection of cocaine (10 mg/kg, i.p.) could reactivate cocaine-conditioned place preference following a 28-day extinction, and pretreatment with i.c.v. 10 microg alpha-helical CRF, a nonspecific CRF receptor antagonist, significantly attenuated this reactivation of conditioned place preference. However, pretreatment with i.p. 1 or 10 mg/kg CP-154,526 (butyl-[2,5-dimethyl-7-(2,4,6-trimethylphenyl)-7H-pyrrolo[2,3-d]pyrimidin-4-yl]-ethylamine), a specific CRF receptor subtype 1 antagonist, and i.c.v. 1 or 10 microg AS-30 ([D-Phe(11),His(12)]Svg-(11-40)), a specific CRF receptor subtype 2 antagonist, failed to show the same effects. In addition, a single footshock stress also elicited the reactivation of cocaine-conditioned place preference following a 28-day extinction and pretreatment with alpha-helical CRF (10 microg, i.c.v.) and CP-154,526 (1 or 10 mg/kg, i.p.) significantly blocked this effect. In contrast, pretreatment with AS-30 at a dose of 1 or 10 microg (i.c.v.) did not affect the stress-induced reactivation of cocaine-conditioned place preference. The present study demonstrated that CRF receptor type 1, but not CRF receptor type 2, mediates the stress-induced reactivation of cocaine-conditioned place preference. These findings suggest that CRF receptor subtype 1 antagonists might be of some value in the treatment and prevention of stress-induced relapse to drug dependence long after detoxification.

Animals↗
PubMed2001

Retinal pigment epithelial cell adhesion on novel micropatterned surfaces fabricated from synthetic biodegradable polymers.

Novel synthetic biodegradable polymer substrates with specific chemical micropatterns were fabricated from poly(DL-lactic-coglycolic acid) (PLGA) and diblock copolymers of poly(ethylene glycol) and poly(DL-lactic acid) (PEG/PLA). Thin films of PLGA and PEG/PLA supported and inhibited, respectively, retinal pigment epithelial (RPE) cell proliferation, with a corresponding cell density of 352,900 and 850 cells/cm2 after 7 days (from an initial seeding density of 15,000 cells/cm2). A microcontact printing technique was used to define arrays of circular (diameter of 50 microm) PLGA domains surrounded and separated by regions (width of 50 microm) of PEG/PLA. Reversed patterns composed of PEG/PLA circular domains surrounded by PLGA regions were also fabricated. Both micropatterned surfaces were shown to affect initial RPE cell attachment, limit cell spreading, and promote the characteristic cuboidal cell morphology during the 8-h period of the experiments. In contrast, RPE cells on plain PLGA (control films) were elongated and appeared fibroblast-like. The reversed patterns had continuous PLGA regions that allowed cell-cell interactions and thus higher cell adhesion. These results demonstrate the feasibility of fabricating micropatterned synthetic biodegradable polymer surfaces to control RPE cell morphology.

Biodegradation, Environmental↗
PubMed2001

Retinal pigment epithelium engineering using synthetic biodegradable polymers.

Retinal pigment epithelium (RPE) plays a key role in the maintenance of the normal functions of the retina, especially photoreceptors. Alteration in RPE structure and function is implicated in a variety of ocular disorders. Tissue engineering strategies using synthetic biodegradable polymers as temporary substrates for RPE cell culture and subsequent transplantation may provide a promising new therapy. In this review article, the manufacture of thin biodegradable poly(DL-lactic-co-glycolic acid) (PLGA) films and their degradation behavior in vitro are discussed. RPE cell proliferation and differentiation on these PLGA films are reviewed. The fabrication of model substrates with desired chemical micropatterns in the micrometer scale is discussed and the effects of surface patterning on RPE morphology and function are assessed. Finally. the preparation of biodegradable micropatterns with adhesive PLGA and non-adhesive poly(ethylene glycol)/PLA domains to modulate RPE cell adhesion is presented.

Animals↗
PubMed2001

Detection and genotyping of GBV-C/HGV variants in China.

We detected GBV-C/HGV sequences in the sera from 64 out of a total of 324 subjects in the south of China. In agreement with findings of others, we noted an especially high rate of infection among intravenous drug addicts and patients with chronic hepatitis C virus infection. The detection was achieved by nested PCR to amplify the 5' noncoding region (5'NCR) of the viral genome. Sequence analysis of the resulting 234 bp product revealed a total of 26 different sequences of which 25 were found to belong to the genotype G3, which is the most prevalent genotypes among Asian isolates, and one belonged to genotype G1, common among African isolates. The sequence divergence between the genotypes was largely clustered in a short variable region (V2) within the 5'NCR, and we showed that genotyping may be achieved equally well by analysis of this variable region as by the more detail analysis of the entire 5'NCR or of the entire viral genome.

5' Untranslated Regions↗
PubMed2001

Regulation of cell survival during B lymphopoiesis in mouse bone marrow: enhanced pre-B-cell apoptosis in CSF-1-deficient op/op mutant mice.

OBJECTIVE: Osteopetrotic (op/op) mice are deficient in macrophages and osteoclasts due to a CSF-1 gene mutation. The aim of this study was to evaluate the effect of these deficiencies and of CSF-1-dependent mechanisms on B lymphopoiesis in bone marrow, with special reference to the apoptotic activity of precursor B cells. MATERIALS AND METHODS: B-cell development and apoptosis were examined in the bone marrow of op/op mice using immunofluorescence labeling and flow cytometry. Short-term cultures of bone marrow were used to evaluate the effect of recombinant CSF-1 on the rate of B-cell apoptosis. RESULTS: Bone marrow cellularity was greatly reduced in op/op mice compared with normal littermates. However, precursor B cells were disproportionately decreased, most markedly at the pre-B-cell stage. Precursor B cells, particularly pre-B cells, displayed elevated apoptotic incidences both ex vivo and in short-term culture. Addition of recombinant CSF-1 reduced the incidence of apoptosis among precursor B cells in short-term cultures of whole bone marrow suspensions from normal mice but not in cultures of sorted B220+ B-lineage cells. CONCLUSIONS: The finding of increased pre-B-cell apoptosis in op/op mice provides evidence that CSF-1-dependent mechanisms can strongly influence the survival of precursor B cells in mouse bone marrow, particularly at the pro-B/pre-B cell transition. It is proposed that the local or systemic levels of CSF-1 during ontogeny may thus play a role in regulating B-cell production within the bone marrow microenvironment.

Animals↗
PubMed2001

Demographic and psychosocial correlates of physical activity in late life.

INTRODUCTION: According to the Centers for Disease Control and Prevention and the World Health Organization, increasing physical activity may help prolong health and preserve the quality of life in late adulthood. Physical activity has taken center stage as the behavior most likely to alter health. However, there is little recent population-wide information about the demographic and psychosocial correlates of physical activity in the elderly population. The purpose of the study was to identify the factors associated with older adults' frequency of physical activity. The study may have implications for preventive interventions. METHODS: Data for 12,611 community-dwelling people aged > or = 65 from the 1996-1997 Canadian National Population Health Survey were examined. Predictors of frequent versus infrequent self-reported physical activity lasting > 15 minutes were examined using logistic regression analyses. The predictor variables included geographic location, psychological distress (Generalized Distress Scale), demographic factors (age, gender, educational level, and marital status), perceived social support, chronic medical conditions, physical limitations due to injury, functional limitations, smoking behavior, and body mass index (BMI). RESULTS: Gender (male); younger age; higher levels of education; being unmarried; absence of chronic conditions, injuries, and functional limitations; lower BMI; social support (females); nonsmoking; region; and lower levels of psychological distress were associated with frequent physical activity in late life. Older adults in western Canadian provinces were more active than those in eastern provinces. CONCLUSIONS: The results will be useful for the design of interventions aimed at improving older adults' health behavior and other health and functional outcomes, especially for subgroups in particular need. Recommendations for further longitudinal research are presented.

Aged↗
PubMed2001

Genetic dissection of the olfactory bulbs of mice: QTLs on four chromosomes modulate bulb size.

Olfaction is influenced by a complex mix of environmental and genetic factors that modulate the production, migration, and maturation of cells in the olfactory bulbs. In this study we analyzed effects of sex, age, body weight, and brain weight on olfactory bulb size in sexually mature mice. We then used regression corrected values (residuals) to map quantitative trait loci (QTLs) that selectively modulate bulb weight. This biometric analysis has relied on an F2 intercross between C57BL/6J (B6) and DBA/2J (D2) inbred strains and a large sample of 35 BXD recombinant inbred (RI) strains. Bilateral bulb weight in adult mice ranges from 10 to 30 mg. Half of this remarkable variation can be predicted from differences in brain weight, sex, body weight, and age. A 100-mg difference in brain weight is associated with a 4.4-mg difference in bulb weight. Bulbs gain in weight by 0.2 mg/week--a 1% increase that continues until at least 300 days of age. Males tend to have slightly larger bulbs than females. By combining data from both related crosses (F2 and RI) we identified four QTLs with selective effects on bulb size (genomewide p < .05). Bulb4a is located on chromosome 4 (Chr 4) and Bulb6a is located on Chr 6. Alleles inherited from B6 at both of these loci increase bulb weight by 0.5-1.0 mg. Bulb11a is located on proximal Chr 11 and Bulb17a is located on the proximal part of Chr 17. In contrast to the first two QTLs, B6 alleles at these two loci decrease bulb weight by 0.5-1.0 mg. Collectively, the four loci account for 20% of the phenotypic variance in bulb weight.

Alleles↗