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Biomedical subjects

A Chu

Publications and source records attributed to A Chu.

At least 37 records · Page 2Linked to original sources
PubMed1999

Tissue specificity of E- and P-selectin ligands in Th1-mediated chronic inflammation.

The demonstrated role of E- and P-selectin ligands in the recruitment of Th1 cells raises the question of tissue specificity determination by pathogenic T cells. We took advantage of the fact that chronic Th1-mediated inflammation in the scid/scid CD4+CD45RBhigh T cell transfer model can occur at multiple tissue sites, resembling inflammatory bowel disease in the colon and psoriasis in the skin. We show that the majority of infiltrating effector T cells from psoriatic skin expresses high levels of functional P-selectin ligand (87 +/- 3%), detected by P-selectin-Ig (PIg), while a significantly smaller subset of T cells from colitic lesions expresses this ligand (24 +/- 2%). Similarly, E-selectin ligand is preferentially expressed on CD4+ T cells infiltrating the skin (24 +/- 2%), but only on very few CD4+ T cells infiltrating the colon (CIT; 1.3 +/- 0.8%). In contrast, CD4+ T cells infiltrating the skin express alpha4beta7 at a significantly lower level than CIT (mean fluorescence intensity, 28 vs 61, respectively), although, interestingly, alphaEbeta7 was expressed at high levels on both populations. Analysis of the disease-inducing potential of PIg+ and PIg- CD4+ CIT cells revealed that both populations not only express similar levels of the gut-homing molecule alpha4beta7 (mean fluorescence intensity, 50 vs 56, respectively), but do not differ in their capacity to express IFN-gamma. Furthermore, CIT depleted of cells expressing functional P-selectin ligand were able to induce colitis upon transfer, suggesting that induction of colitis in this model may be independent of E- and P-selectin. These results indicate that adhesion molecule expression and the homing pattern of inflammatory T cells are regulated by the local environment independently of their inflammatory capacity.

Adoptive Transfer↗
PubMed1999

Independent and overlapping effects of corticosterone and testosterone on corticotropin-releasing hormone and arginine vasopressin mRNA expression in the paraventricular nucleus of the hypothalamus and stress-induced adrenocorticotropic hormone release.

Adrenocorticotropin (ACTH) release is regulated by both glucocorticoids and androgens; however, the precise interactions are unclear. We have controlled circulating corticosterone (B) and testosterone (T) by adrenalectomy (ADX) +/- B replacement and gonadectomy (GDX) +/- T replacement, comparing these to sham-operated groups. We hoped to reveal how and where these neuroendocrine systems interact to affect resting and stress-induced ACTH secretion. ADX responses. In gonadal-intact rats, ADX increased corticotropin-releasing factor (CRH) and vasopressin (AVP) mRNA in hypothalamic parvocellular paraventricular nuclei (PVN) and ACTH in pituitary and plasma. B restored these toward normal. GDX blocked the increase in AVP but not CRH mRNA and reduced plasma, but not pituitary ACTH in ADX rats. GDX+T restored increased AVP mRNA in ADX rats, although plasma ACTH remained decreased. Stress responses. Restraint-induced ACTH responses were elevated in ADX gonadally intact rats, and B reduced these toward normal. GDX in adrenal-intact and ADX+B rats increased ACTH responses. Without B, T did not affect ACTH; together with B, T restored ACTH responses to normal. The magnitude of ACTH responses to stress was paralleled by similar effects on the number of c-fos staining neurons in the hypophysiotropic PVN. We conclude that gonadal regulation of ACTH responses to ADX is determined by T dependent effects on AVP biosynthesis, whereas CRH biosynthesis is B-dependent. Stress-induced ACTH release is not explained by B and T interactions at the PVN, but is determined by B- and T-dependent changes in drive to PVN motorneurons.

Adrenalectomy↗
PubMed1999

IL-12, independently of IFN-gamma, plays a crucial role in the pathogenesis of a murine psoriasis-like skin disorder.

The onset of acute psoriasis and the exacerbation of chronic psoriasis are often associated with a history of bacterial infection. We demonstrate that while only few scid/scid mice develop disease when CD4+CD45Rbhigh T cells are transferred alone, coadministration of LPS plus IL-12 or staphylococcal enterotoxin B into scid/scid mice 1 day after CD4+CD45Rbhigh T cell transfer greatly enhances disease penetrance and severity. Most importantly, the skin lesions induced by this method exhibit many of the histologic hallmarks observed in human psoriasis. Skin infiltrating CD4+ T cells were predominantly memory/effector cells (CD45Rblow) and exhibited a highly polarized Th1 phenotype. To test whether the development of pathogenic T cells was dependent on their production of IFN-gamma, we transferred IFN-gamma-/- CD4+CD45Rbhigh T cells into scid/scid or into T, B and NK cell-deficient scid/beige mice. Surprisingly, the incidence of psoriasis was similar to scid/scid animals that received IFN-gamma+/+ T cells, although acanthosis of the skin was attenuated. In contrast, the development of psoriasis was abolished if anti-IL-12 mAb was administered on day 7 and 35 after T cell transfer. Skin-derived IFN-gamma-/- inflammatory cells, but not cells from anti-IL-12-treated animals, secreted substantial amounts of TNF-alpha, suggesting that the inflammatory effect of IFN-gamma-/- T cells may be partly exerted by TNF-alpha and that the therapeutic effect of anti-IL-12 may depend on its ability to down-regulate both TNF-alpha and IFN-gamma. Overall, these results suggest that IL-12, independently of IFN-gamma, is able to induce pathogenic, inflammatory T cells that are able to induce psoriasiform lesions in mice.

Adoptive Transfer↗
PubMed1999

Starvation: early signals, sensors, and sequelae.

To identify the sequences of changes in putative signals, reception of these and responses to starvation, we sampled fed and starved rats at 2- to 6-h intervals after removal of food 2 h before dark. Metabolites, hormones, hypothalamic neuropeptide expression, fat depots, and leptin expression were measured. At 2 h, insulin decreased, and FFA and corticosterone (B) increased; by 4 h, leptin and glucose levels decreased. Neuropeptide Y messenger RNA (mRNA) increased 6 h after food removal and thereafter. Adrenal and plasma B did not follow ACTH and were elevated throughout, with a nadir at the dark-light transition. Leptin correlated inversely with adrenal B. Fat stores decreased during the last 12 h. Leptin mRNA in perirenal and sc fat peaked during the dark period, resembling plasma leptin in fed rats. We conclude that 1) within the first 4 h, hormonal and metabolic signals relay starvation-induced information to the hypothalamus; 2) hypothalamic neuropeptide synthesis responds rapidly to the altered metabolic signals; 3) catabolic activity quickly predominates, reinforced by elevated B, not driven by ACTH, but possibly to a minor extent by leptin, and more by adrenal neural activity; and 4) leptin secretion decreases before leptin mRNA or fat depot weight, showing synthesis-independent regulation.

Adipose Tissue↗
PubMed1999

Warning! Nearby construction can profoundly affect your experiments.

This is meant to alert people to potentially major effects of construction projects on research results. Because we study the effects of stress on regulation of ACTH and corticosterone secretion and of serotonin receptors and stress on energy balance, we serve as an early warning system when things go awry. Most of our experiments include taking daily, or twice daily, measurements of rat or mouse weights and food intake as well as stress hormone levels. We are highly sensitized to environmental disruption and we've shown previously the effects of construction on stress hormones (1). However, we did not anticipate the change and disruption in energy balance that may occur in response to environmental perturbation. We provide two examples of these, below.

Animals↗
PubMed1999

Quantitative MR imaging of carpal tunnel syndrome.

OBJECTIVE: Previous MR imaging studies have produced evidence of changes to structures within the wrist believed to be associated with carpal tunnel syndrome. In an attempt to resolve the conflicting and inconclusive results of these studies, we report here the results of an MR imaging study at a field strength of 3.0 T, which is higher than that previously reported. SUBJECTS AND METHODS: Patients with carpal tunnel syndrome and control groups of asymptomatic subjects were studied using MR imaging. We evaluated electrophysiologically the median nerve function of the affected wrists of all patients. A gradient-recalled echo pulse sequence was used to study 13 3-mm-thick slices within the wrist of each patient or asymptomatic subject. Spatial resolution was approximately 0.3 x 0.3 mm2. The median nerve and other structures associated with the carpal tunnel, which were clearly shown on the MR images, were analyzed to yield structural data. RESULTS: Analysis revealed that the cross-sectional area of the nerve within and proximal to the carpal tunnel was approximately 50% larger in patients with carpal tunnel syndrome than in asymptomatic subjects. We found no significant difference in the area of the nerve within the carpal tunnel compartment compared with the area of the nerve proximal to the carpal tunnel either in patients or in asymptomatic subjects. Also, flattening of the nerve on entering the carpal tunnel was not significantly different in patients than in asymptomatic subjects. In patients an increase in the palmar bowing of the flexor retinaculum was found only at the level of the hamate compared with that found in asymptomatic subjects. The cross-sectional area of the carpal tunnel was of a similar size in patients and in asymptomatic subjects. Comparison of electrodiagnostic results indicated no correlations between the MR parameters and electrophysiologic dysfunction of the median nerve for patients. CONCLUSION: The only statistically significant differences found between patients with carpal tunnel syndrome and asymptomatic subjects were that the median nerve was approximately 50% larger within and proximal to the carpal tunnel in patients with carpal tunnel syndrome and palmar bowing of the flexor retinaculum occurred in patients only at the level of the hamate.

Adult↗
PubMed1999

Zinc modulates antagonist interactions with D2-like dopamine receptors through distinct molecular mechanisms.

Recently, zinc has been shown to modulate antagonist drug interactions with the D1 dopamine receptor (Schetz and Sibley, 1997) and the dopamine transporter (Norregaard et al., 1998). We now demonstrate that zinc also reversibly and dose-dependently modulates the specific binding of the butyrophenone antagonist [3H]methylspiperone to all D2-like dopamine receptors: D2L, D3, and D4. The molecular mechanisms of zinc regulation of these D2-like receptor subtypes are distinct because zinc inhibition of [3H]methylspiperone binding to the D4 receptor is noncompetitive by both equilibrium and kinetic measures (lower Bmax and essentially no change in koff), whereas the corresponding inhibition of zinc at D2L and D3 receptors is primarily characterized by competitive allosterism (increases in KD and koff). Interestingly, thermodynamic measurements reveal that the macroscopic properties of zinc binding are entropy-driven for all receptor subtypes, despite their having distinct molecular mechanisms. Zinc also reduces the binding affinity of the D2L receptor for [3H]raclopride, a structurally different antagonist of the substituted benzamide class. Sodium ions negatively modulate zinc inhibition of both sodium-insensitive [3H]methylspiperone binding and sodium-sensitive [3H]raclopride binding. In addition to its demonstrated effects on antagonist binding in membrane preparations, zinc also retards the functional effects of antagonist at the D2L receptor in intact cells. These findings suggest that synaptic zinc may be a factor influencing the effectiveness of therapies that rely on dopamine receptor antagonists.

Algorithms↗
PubMed1998

Velcro in the nuclear envelope: LBR and LAPs.

The nuclear envelope is crucial for the functional organization of the nucleus. Lamin B receptor (LBR) and several lamina-associated proteins (LAPs), residing in the inner membrane, provide attachment sites for chromatin and the nuclear lamina. LAPs and LAP-related proteins are members of a growing family of proteins, whose genes are expressed in a tissue and development specific manner, opening the opportunity for a complex regulation of membrane-chromatin and membrane-lamina interactions. Post-translational modifications of LBR and LAPs are likely to modulate their binding to lamins and chromatin, interactions that need to be dynamic to accommodate nuclear growth in interphase and nuclear envelope disassembly in mitosis. Accumulation of proteins in the inner nuclear membrane is believed to depend on their retention mediated by the interaction with nuclear components such as chromatin and lamins.

Laminin↗
PubMed1998

Oxazolone colitis: A murine model of T helper cell type 2 colitis treatable with antibodies to interleukin 4.

In this study we describe oxazolone colitis, a new form of experimental colitis. This model is induced in SJL/J mice by the rectal instillation of the haptenating agent, oxazolone, and is characterized by a rapidly developing colitis confined to the distal half of the colon; it consists of a mixed neutrophil/lymphocyte infiltration limited to the superficial layer of the mucosa which is associated with ulceration. Oxazolone colitis is a T helper cell type 2 (Th2)-mediated process since stimulated T cells from lesional tissue produce markedly increased amounts of interleukin (IL)-4 and IL-5; in addition, anti-IL-4 administration leads to a striking amelioration of disease, whereas anti-IL-12 administration either has no effect or exacerbates disease. Finally, this proinflammatory Th2 cytokine response is counterbalanced by a massive transforming growth factor-beta (TGF-beta) response which limits both the extent and duration of disease: lesional (distal) T cells manifest a 20-30-fold increase in TGF-beta production, whereas nonlesional (proximal) T cells manifest an even greater 40-50-fold increase. In addition, anti-TGF-beta administration leads to more severe inflammation which now involves the entire colon. The histologic features and distribution of oxazolone colitis have characteristics that resemble ulcerative colitis (UC) and thus sharply distinguish this model from most other models, which usually resemble Crohn's disease. This feature of oxazolone colitis as well as its cytokine profile have important implications to the pathogenesis and treatment of UC.

Administration, Rectal↗
PubMed1998

Electromagnetic field-induced stimulation of Bruton's tyrosine kinase.

Here we present evidence that exposure of DT40 lymphoma B-cells to low energy electromagnetic fields (EMF) results in activation of phospholipase C-gamma 2 (PLC-gamma2), leading to increased inositol phospholipid turnover. PLC-gamma2 activation in EMF-stimulated cells is mediated by stimulation of the Bruton's tyrosine kinase (BTK), a member of the Src-related TEC family of protein tyrosine kinases, which acts downstream of LYN kinase and upstream of PLC-gamma2. B-cells rendered BTK-deficient by targeted disruption of the btk gene did not show enhanced PLC-gamma2 activation in response to EMF exposure. Introduction of the wild-type (but not a kinase domain mutant) human btk gene into BTK-deficient B-cells restored their EMF responsiveness. Thus, BTK exerts a pivotal and mandatory function in initiation of EMF-induced signaling cascades in B-cells.

Agammaglobulinaemia Tyrosine Kinase↗
PubMed1998

Stimulation of Src family protein-tyrosine kinases as a proximal and mandatory step for SYK kinase-dependent phospholipase Cgamma2 activation in lymphoma B cells exposed to low energy electromagnetic fields.

Here, we present evidence that exposure of DT40 lymphoma B cells to low energy electromagnetic field (EMF) results in a tyrosine kinase-dependent activation of phospholipase Cgamma2 (PLC-gamma2) leading to increased inositol phospholipid turnover. B cells rendered PLC-gamma2-deficient by targeted disruption of the PLC-gamma2 gene as well as PLC-gamma2-deficient cells reconstituted with Src homology domain 2 (SH2) domain mutant PLC-gamma2 did not show any increase in inositol-1,4,5-trisphosphate levels after EMF exposure, providing direct evidence that PLC-gamma2 is responsible for EMF-induced stimulation of inositol phospholipid turnover, and its SH2 domains are essential for this function. B cells rendered SYK-deficient by targeted disruption of the syk gene did not show PLC-gamma2 activation in response to EMF exposure. The C-terminal SH2 domain of SYK kinase is essential for its ability to activate PLC-gamma2. SYK-deficient cells reconstituted with a C-terminal SH2 domain mutant syk gene failed to elicit increased inositol phospholipid turnover after EMF exposure, whereas SYK-deficient cells reconstituted with an N-terminal SH2 domain mutant syk gene showed a normal EMF response. LYN kinase is essential for the initiation of this biochemical signaling cascade. Lymphoma B cells rendered LYN-deficient through targeted disruption of the lyn gene did not elicit enhanced inositol phospholipid turnover after EMF exposure. Introduction of the wild-type (but not a kinase domain mutant) mouse fyn gene into LYN-deficient B cells restored their EMF responsiveness. B cells reconstituted with a SH2 domain mutant fyn gene showed a normal EMF response, whereas no increase in inositol phospholipid turnover in response to EMF was noticed in LYN-deficient cells reconstituted with a SH3 domain mutant fyn gene. Taken together, these results indicate that EMF-induced PLC-gamma2 activation is mediated by LYN-regulated stimulation of SYK, which acts downstream of LYN kinase and upstream of PLC-gamma2.

Animals↗
PubMed1997

Interaction between the adhesion receptor, CD44, and the oncogene product, p185HER2, promotes human ovarian tumor cell activation.

In this study we have examined the interaction between CD44s (the standard form) and the p185(HER2) proto-oncogene in the ovarian carcinoma cell line. Surface biotinylation followed by wheat germ agglutinin column chromatography and anti-CD44-mediated immunoprecipitation indicate that both CD44s and p185(HER2) are expressed on the cell surface and most importantly, that these two molecules are physically linked to each other via interchain disulfide bonds. We have also determined that hyaluronic acid stimulates CD44s-associated p185(HER2) tyrosine kinase activity, leading to an increase in the ovarian carcinoma cell growth. After transfection of the ovarian carcinoma cell line with the adenovirus 5 E1A gene, which is known to repress p185(HER2) expression, we observed that both surface CD44s expression and CD44s-mediated cell adhesion to hyaluronic acid are significantly reduced in the transfectant cells compared with the control cells. These data suggest that down-regulation of p185(HER2) blocks CD44s expression and subsequent adhesion function. Our findings also indicate that the CD44s-p185(HER2) interaction is both functionally coupled and biosynthetically regulated. We believe that direct "cross-talk" between these two surface molecules (i.e. CD44s and the p185(HER2)) may be one of the most important signaling events in human ovarian carcinoma development.

Adenovirus E1A Proteins↗
PubMed1997

Effects of coat protein mutations and reduced movement protein expression on infection spread by cowpea chlorotic mottle virus and its hybrid derivatives.

Previously we have reported that the essential 3a movement gene of icosahedral cowpea chlorotic mottle virus (CCMV) can be functionally replaced by the 30-kDa movement gene of rod-shaped sunn-hemp mosaic virus (SHMV). Because plant RNA viruses differ in requiring or not requiring coat protein for systemic infection, we have now investigated whether systemic spread by this CCMV/SHMV hybrid is dependent on its CCMV coat protein as well as its SHMV movement protein. We find that either deletion or frameshift mutations in the coat protein gene block systemic spread. Thus, like wild-type CCMV, systemic infection by the hybrid is dependent on both movement protein and coat protein. These results further support the conclusion that the required functions of the coat and movement proteins in CCMV spread do not depend on sequence-specific interaction between these proteins. Additional features of the hybrid also motivated testing the effects of modulating movement protein expression. Creating an extra, out-of-frame translational start codon (AUG) shortly upstream of the 3a movement protein gene in CCMV downregulated its expression 18-fold. Nevertheless, for CCMV derivatives bearing either the CCMV 3a gene or the SHMV 30-kDa gene, the extra AUG resulted in only a minor delay in the onset of viral spread and little or no effect on the subsequent rate of cell-to-cell spread. Thus, under normal circumstances, the rate of CCMV cell-to-cell spread in cowpea plants appears to be limited primarily by factors other than movement protein synthesis.

Amino Acid Sequence↗
PubMed1997

Validation of a new UNIX-based quantitative coronary angiographic system for the measurement of coronary artery lesions.

We describe a method of validation of computerized quantitative coronary arteriography and report the results of a new UNIX-based quantitative coronary arteriography software program developed for rapid on-line (digital) and off-line (digital or cinefilm) analysis. The UNIX operating system is widely available in computer systems using very fast processors and has excellent graphics capabilities. The system is potentially compatible with any cardiac digital x-ray system for on-line analysis and has been designed to incorporate an integrated database, have on-line and immediate recall capabilities, and provide digital access to all data. The accuracy (mean signed differences of the observed minus the true dimensions) and precision (pooled standard deviations of the measurements) of the program were determined x-ray vessel phantoms. Intra- and interobserver variabilities were assessed from in vivo studies during routine clinical coronary arteriography. Precision from the x-ray phantom studies (6-In. field of view) for digital images was 0.066 mm and for digitized cine images was 0.060 mm. Accuracy was 0.076 mm (overestimation) for digital images compared to 0.008 mm for digitized cine images. Diagnostic coronary catheters were also used for calibration; accuracy.varied according to size of catheter and whether or not they were filled with iodinated contrast. Intra- and interobserver variabilities were excellent and indicated that coronary lesion measurements were relatively user-independent. Thus, this easy to use and very fast UNIX based program appears to be robust with optimal accuracy and precision for clinical and research applications.

Algorithms↗
PubMed1997

Stable expression of CD1a molecule in human epithelial cell lines shows temperature-dependent expression and affects cell morphology and growth.

The human CD1a molecule is a transmembrane protein which shares structural similarities with HLA class I molecules. It has restricted tissue distribution in normal individuals, and is a useful diagnostic marker for certain disease states such as Langerhans cell histiocytosis. In order to investigate the function of this molecule, a cDNA fragment encoding the CD1a molecule was cloned into several EUKARYOTIC expression vectors which were then used to establish human epithelial cell lines stably expressing the membrane-bound CD1a molecule. Human keratinocytes (HaCaT) and epithelial cells (HeLa) stably expressing CD1a were established by retroviral-mediated gene transfer and DNA transfection, respectively. Expression and localization of the CD1A molecule were then confirmed by Northern blot analysis and immunofluorescence methods. CD1a expression appears to have profound effects on cellular growth and morphology. Both stably CD1a-expressing HeLa and HaCaT cells showed increased doubling times, and up to 20% of CD1a-expressing cells showed altered cell morphology. Clonogenicity experiments demonstrated a reduction in colony size and plating efficiency was augmented in CD1a-positive cells when compared with vector-transfected/infected controls. Our findings suggest that CD1A expression may act as a negative growth regulator in these cells in vitro. Furthermore, lower temperatures greatly enhanced the expression of CD1a at both the protein and mRNA levels in a time-dependent fashion. Since the physiological skin temperatures lie well below the core temperature, this observation may have important implications in the study of Langerhans cells in vitro.

Antigens, CD1↗
PubMed1997

An STS-based radiation hybrid map of the human genome.

We have constructed a physical map of the human genome by using a panel of 83 whole genome radiation hybrids (the Stanford G3 panel) in conjunction with 10,478 sequence-tagged sites (STSs) derived from random genomic DNA sequences, previously mapped genetic markers, and expressed sequences. Of these STSs, 5049 are framework markers that fall into 1766 high-confidence bins. An additional 945 STSs are indistinguishable in their map location from one or more of the framework markers. These 5994 mapped STSs have an average spacing of 500 kb. An additional 4484 STSs are positioned with respect to the framework markers. Comparison of the orders of markers on this map with orders derived from independent meiotic and YAC STS-content maps indicates that the error rate in defining high-confidence bins is < 5%. Analysis of 322 random cDNAs indicates that the map covers the vast majority of the human genome. This STS-based radiation hybrid map of the human genome brings us one step closer to the goal of a physical map containing 30,000 unique ordered landmarks with an average marker spacing of 100 kb.

Animals↗