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Biomedical subjects

D Ching

Publications and source records attributed to D Ching.

12 recordsLinked to original sources
PubMed1999

Requirement for Ras and phosphatidylinositol 3-kinase signaling uncouples the glucocorticoid-induced junctional organization and transepithelial electrical resistance in mammary tumor cells.

In Con8 rat mammary epithelial tumor cells, the synthetic glucocorticoid dexamethasone stimulates the remodeling of the apical junction (tight and adherens junctions) and the transepithelial electrical resistance (TER), which reflects tight junction sealing. Indirect immunofluorescence revealed that dexamethasone induced the recruitment of endogenous Ras and the p85 regulatory subunit of phosphatidylinositol (PI) 3-kinase to regions of cell-cell contact, concurrently with the stimulation of TER. Expression of dominant-negative RasN17 abolished the dexamethasone stimulation in TER, whereas, dexamethasone induced the reorganization of tight junction and adherens junction proteins, ZO-1 and beta-catenin, as well as F-actin, to precise regions of cell-cell contact in a Ras-independent manner. Confocal microscopy revealed that RasN17 and the p85 regulatory subunit of PI 3-kinase co-localized with ZO-1 and F-actin at the tight junction and adherens junction, respectively. Treatment with either of the PI 3-kinase inhibitors, wortmannin or LY294002, or the MEK inhibitor PD 098059, which prevents MAPK signaling, attenuated the dexamethasone stimulation of TER without affecting apical junction remodeling. Similar to dominant-negative RasN17, disruption of both Ras effector pathways using a combination of inhibitors abolished the glucocorticoid stimulation of TER. Thus, the glucocorticoiddependent remodeling of the apical junction and tight junction sealing can be uncoupled by their dependence on Ras and/or PI 3-kinase-dependent pathways, implicating a new role for Ras and PI 3-kinase cell signaling events in the steroid control of cell-cell interactions.

Actins↗
PubMed1999

Glucocorticoid down-regulation of fascin protein expression is required for the steroid-induced formation of tight junctions and cell-cell interactions in rat mammary epithelial tumor cells.

Glucocorticoid hormones, which are physiological regulators of mammary epithelium development, induce the formation of tight junctions in rat Con8 mammary epithelial tumor cells. We have discovered that, as part of this process, the synthetic glucocorticoid dexamethasone strongly and reversibly down-regulated the expression of fascin, an actin-bundling protein that also interacts with the adherens junction component beta-catenin. Ectopic constitutive expression of full-length mouse fascin containing a Myc epitope tag (Myc-fascin) in Con8 cells inhibited the dexamethasone stimulation of transepithelial electrical resistance, disrupted the induced localization of the tight junction protein occludin and the adherens junction protein beta-catenin to the cell periphery, and prevented the rearrangement of the actin cytoskeleton. Ectopic expression of either the carboxyl-terminal 213 amino acids of fascin, which includes the actin and beta-catenin-binding sites, or the amino-terminal 313 amino acids of fascin failed to disrupt the glucocorticoid induction of tight junction formation. Mammary tumor cells expressing the full-length Myc-fascin remained generally glucocorticoid responsive and displayed no changes in the levels or protein-protein interactions of junctional proteins or the amount of cytoskeletal associated actin filaments. However, a cell aggregation assay demonstrated that the expression of Myc-fascin abrogated the dexamethasone induction of cell-cell adhesion. Our results implicate the down-regulation of fascin as a key intermediate step that directly links glucocorticoid receptor signaling to the coordinate control of junctional complex formation and cell-cell interactions in mammary tumor epithelial cells.

Actins↗
PubMed1997

Beta2-chimaerin is a high affinity receptor for the phorbol ester tumor promoters.

Beta2-chimaerin, a member of the GTPase-activating proteins for the small GTP-binding protein p21Rac, possesses a single cysteine-rich domain with high homology to those implicated in phorbol ester and diacylglycerol binding in protein kinase C (PKC) isozymes. We have expressed beta2-chimaerin in Sf9 insect cells using the baculovirus expression system and determined that, like PKCs, beta2-chimaerin binds phorbol esters with high affinity in the presence of phosphatidylserine as a cofactor. Scatchard plot analysis using the radioligand [3H]phorbol 12,13-dibutyrate revealed a dissociation constant of 1.9 +/- 0.2 nM for beta2-chimaerin. Likewise, beta2-chimaerin is a high affinity receptor for the bryostatins, a class of atypical PKC activators. A detailed comparison of structure-activity relations using several phorbol ester analogs revealed striking differences in binding recognition between beta2-chimaerin and PKCalpha. Although the diacylglycerol 1-oleoyl-2-acetylglycerol binds with similar potency to both beta2-chimaerin and PKCalpha, the mezerein analog thymeleatoxin has 56-fold less affinity for binding to beta2-chimaerin. To establish whether beta2-chimaerin responds to phorbol esters in cellular systems, we overexpressed beta2-chimaerin in COS-7 cells and monitored its subcellular distribution after phorbol ester treatment. Interestingly, as described previously for PKC isozymes, beta2-chimaerin translocates from cytosolic to particulate fractions as a consequence of phorbol ester treatment. Our results demonstrate that beta2-chimaerin is a novel target for the phorbol ester tumor promoters. The expansion of the family of phorbol ester receptors strongly suggests a potential for the "non-kinase" receptors as cellular mediators of the phorbol ester responses.

Animals↗
PubMed1994

Gowning does not affect colonization or infection rates in a neonatal intensive care unit.

OBJECTIVE: To study the effect of gowning in a neonatal intensive care unit on colonization patterns, necrotizing enterocolitis, respiratory syncytial virus and other infections, mortality, and traffic and handwashing patterns. METHODS: Alternate 2-month gowning and no-gowning cycles were established in a 24-bed level III neonatal intensive care unit for 8 months, with respiratory site, umbilical, and stool surveillance cultures done weekly on all patients. Traffic flow and handwashing compliance were evaluated by direct observation. RESULTS: Demographic data did not differ between periods. There were no significant differences between the gowning and no-gowning periods in the rates of bacterial colonization, any type of infection, or mortality. There was no effect on traffic flow or handwashing compliance. CONCLUSION: Gowning in the neonatal intensive care unit is an unnecessary custom without benefit in neonatal colonization, infection rates, mortality, traffic patterns, and handwashing behavior.

Bacteria↗
PubMed1991

Septic bursitis: experience in a community practice.

We reviewed 47 episodes of septic bursitis occurring in a private community medical practice. Most patients were male (85%), and roughly half (49%) the cases were related to recreational or occupational trauma. About 72% of cases were located in the olecranon bursa, while the remaining cases were prepatellar. Prepatellar bursitis patients were more likely to be hospitalized. Staphylococcus aureus was isolated from 70% of bursal fluid aspirations; other etiologic organisms included gram negative bacteria and Mycobacterium marinum. The majority of patients were able to be treated as outpatients with oral antibiotics. All patients were eventually cured without serious complications.

Adolescent↗
PubMed1990

Epstein-Barr virus and other herpesvirus infections in Kawasaki syndrome.

Epstein-Barr virus (EBV), a possible cause of Kawasaki syndrome (KS), is not pathenogenically associated with KS in Hawaii. The prevalence of EBV capsid antibody in KS patients was found not to differ significantly from that in controls, and the antibody response in those infected with EBV was the same as that in other children similarly infected. No EBV was isolated from acute-phase patients. All patients with capsid antibody at the onset of KS also had Epstein-Barr nuclear antigen antibody: 36 patients developed antibody within 3 months after onset of KS; in 10, EBV infection could have been coincidental with the disease. Cytomegalovirus (CMV) was isolated from 9 patients with KS and 10 controls. A similar number of controls and patients had antibody to human herpesvirus 6 (HHV6); one patient seroconverted. None of the herpes viruses (EBV, CMV, HHV6, varicella-zoster virus, or herpes simplex virus) plays a unique or dominant role in the etiology or pathogenesis of KS in Hawaii.

Age Factors↗
PubMed1989

Absence of significant RNA-dependent DNA polymerase activity in lymphocytes from patients with Kawasaki syndrome.

Kawasaki syndrome, an acute febrile multisystem illness of young children, is a panvasculitis with prominent rheumatic features. Arthritis and pancarditis are frequent during the acute stage; coronary artery aneurysms occur in 20% of cases and the disease is now the leading cause of acquired heart disease in childhood. A microbial aetiology is suggested by the acute febrile self-limited character of the disease, the regular occurrence of epidemic outbreaks at intervals of 2-3 years, and the virtual restriction to young children, consistent with the early acquisition of immunity. Reports of elevated DNA polymerase activity (assumed to be RNA-dependent reverse transcriptase) in cultured lymphocytes from patients with acute Kawasaki syndrome suggest that a retrovirus might be the causative agent. We have measured supernatant DNA polymerase activity in lymphocyte cultures from 49 Hawaiian patients in acute and convalescent stages of Kawasaki syndrome and have been unable to demonstrate significant reverse transcriptase activity or other evidence of involvement of a retrovirus in the aetiology of the disease.

Acute Disease↗
PubMedDate not supplied

Storage and microencapsulation of islets for transplantation.

Microencapsulation is an effective means of immunoisolation for pancreatic islet transplants. However, the process of isolating, purifying, encapsulating, and transplanting islets in a single day is labor intensive and difficult for routine use. There is an apparent need for reliable methods of islet storage, and cryopreservation has emerged as an attractive system of islet banking. While studies have shown that cryopreserved islets are viable when tested unencapsulated after thawing, it is not clear if the combination of freezing and encapsulation would affect islet function. The purpose of the present study was to determine the in vitro function of cryopreserved islets following thawing and microencapsulation. Islets were isolated from the pancreata of Sprague-Dawley rats and cryopreserved under liquid nitrogen for either 1 week or 1 month, following an overnight culture at 37 degrees C. Upon thawing, the islets were tested either unencapsulated or after encapsulation in polylysine-alginate membrane. In all experiments islets were preperifused for 1 h at 37 degrees C with a modified Krebs-Ringer bicarbonate buffer containing 3.3 mM (60 mg/dl) glucose and maintained at pH 7.4 by continuous gassing with 95% air/5% CO2. Following basal effluent sample collection on ice, the glucose concentration was raised to 16.7 mM (300 mg/dl). It was found that, within 10 min of high glucose stimulation, an average of twofold increase in insulin secretion (p < 0.01) was obtained in islets within or without microcapsules. We conclude that islets cryopreserved for 1 month prior to thawing and microencapsulation retained functional viability as determined in in vitro experiments.

Animals↗