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Biomedical subjects

R Chung

Publications and source records attributed to R Chung.

At least 37 records · Page 2Linked to original sources
PubMed1995

Increases in intra-abdominal pressure affect pulmonary compliance.

OBJECTIVES: To determine the effect of increased intra-abdominal pressure (IAP) on pulmonary compliance and to determine an effective means to measure IAP. DESIGN: A prospective study. SETTING: An urban tertiary care hospital. PATIENTS: Twenty-six adult patients undergoing laparoscopic cholecystectomy. INTERVENTIONS: Intra-operative management of laparoscopic cholecystectomy requiring endotracheal intubation with general anesthesia, nasogastric and urinary bladder catheters, and position changes. Additional interventions included use of a rectal manometer and a respiratory pressure module inserted within the ventilator circuit. MAIN OUTCOME MEASURES: Correlation of changes in IAP with changes in dynamic pulmonary compliance, measured as tidal volume/(end inspiratory pressure--end expiratory pressure) and comparison of three different measurement techniques (bladder, rectal, and gastric) with a standard technique (insufflation pressure) in three different positions (supine, Trendelenburg's, and reverse Trendelenburg's). RESULTS: Compliance was significantly related to insufflation pressure (P < .001) by analysis of variance. In the gas insufflation model, the mean increment in bladder pressure reflected most closely the IAP increment in the supine position (5.7 vs 6 mm Hg) but not in the Trendelenburg (2.1 vs 6 mm Hg) and reverse Trendelenburg positions (3.4 vs 6 mm Hg). Rectal and gastric pressures were also position dependent and technically less reliable. CONCLUSIONS: Increased IAP has a major influence on pulmonary compliance (50% decrease at 16 mm Hg). Measurements of IAP by intraorgan manometry are position dependent and may not accurately reflect the intraperitoneal pressure.

Abdomen↗
PubMed1995

Reduction in tissue blood flow in J-shaped pelvic ileal reservoirs.

PURPOSE: This study sought to evaluate tissue blood flow during J-shaped ileal reservoir construction. METHODS: Using laser Doppler flowmetry, tissue blood flow was measured at various locations in J-shaped ileal reservoirs constructed in 10 dogs before pouch-anal anastomosis. For 12 weeks postoperatively, animals were assessed for clinical complications. In another five dogs, tissue blood flow was measured at various stages of J-pouch construction. RESULTS: Tissue blood flow in the reservoir was reduced and was lowest at the "apex" of the "J", the site of clinical stricture in one animal. During reservoir construction, longitudinal enterotomy was associated with the greatest reduction in tissue blood flow. Lowest blood flow in the reservoir was at the site of the intended pouch-anal anastomosis (11.5 +/- 1.6 ml/100 g/min vs. 43.4 +/- 3.4 ml/100 g/min (controls); P < 0.05). CONCLUSIONS: Operative maneuvers of J-shaped ileal reservoir construction, particularly longitudinal enterotomy, significantly reduce tissue perfusion in the involved bowel segment. Tissue blood flow in the pouch is lowest at the site of intended pouch-anal anastomosis, and this may contribute to development of complications seen clinically.

Anal Canal↗
PubMed1995

The effect of managed care on the treatment outcome of substance use disorders.

This study examined the effect of managed care and other reimbursement mechanisms on the outcome of substance abuse treatment at a single treatment facility. A retrospective review of 1594 patient records yielded treatment utilization, diagnostic, and demographic data. Recidivism rates for intensive managed care, traditional managed care, private pay, and state-funded groups of patients were compared. Results showed that, contrary to expectations, recidivism rates were not different for managed vs nonmanaged care patients. In addition, recidivist patients had significantly more ICD-9 diagnoses than nonrecidivist patients. A discussion of future research suggests that other outcome measures need to be examined in addition to recidivism rate, such as psychosocial functioning following treatment and indicator(s) of severity of illness, to better determine the effect of managed care and other reimbursement mechanisms on treatment outcome.

Adult↗
PubMed1995

Rates of p24 antigenemia and viral isolation in comparable white and black HIV-infected subjects. Military Medical Consortium for Applied Retroviral Research.

OBJECTIVE: To determine the relative frequencies of HIV-1 p24 antigen and culture positivity in white and black patients. DESIGN: Volunteers in the US military's HIV natural history study were 46% white, 44% black, 7% Hispanic and 3% other. Focusing on the comparable groups of whites and blacks, a retrospective analysis was performed of the results of virologic assays collected over a 2-year period. METHODS: p24 antigen was quantitated in sera with and without immune complex dissociation (ICD); viral isolation was performed by coculture of peripheral blood mononuclear cells. RESULTS: Results of the two virologic assays were very similar in the two racial groups, both overall and after stratification by CD4 cell count. As reported previously, the concentration of serum immunoglobulin G was found to be greater in black than white subjects. In contrast to results with ICD, sera tested without ICD resulted in differing (higher) rates of antigenemia in whites than blacks (P = 0.002). CONCLUSIONS: The frequencies of p24 antigen and culture positivity were found to be independent of race. Previously observed racial differences in antigen positivity were likely to be due to more extensive antibody binding in blacks than in whites.

Adult↗
PubMed1994

Cycles in the two-sex problem: an investigation of a nonlinear demographic model.

"A fundamental shortcoming of classic stable population theory is its failure to handle populations differentiated by sex. The classic theory is linear while the two-sex problem is inherently nonlinear. Previous two-sex investigations have focused on equilibrium conditions rather than dynamics, and ignored competition between age groups for marriage partners. This study makes a start at analyzing dynamics and models that incorporate competition, which can play an important role in any realistic marriage model and can turn a model with a stable equilibrium sex ratio into one with a cycling equilibrium." This is a revised version of a paper originally presented at the 1990 Annual Meeting of the Population Association of America. (SUMMARY IN FRE)

Demography↗
PubMed1994

The in vitro effects of stem cell factor, interleukin 3 and granulocyte-macrophage colony stimulating factor on haemopoietic progenitor cells from premature infants.

Circulating haemopoietic progenitor cells from premature infants were assessed for their ability to respond to interleukin 3, granulocyte-macrophage colony stimulating factor and stem cell factor (SCF) in vitro. All three cytokines increased the number of colonies derived from burst forming units erythroid (BFU-E), colony forming units granulocyte-macrophage (CFU-GM) and multi-lineage progenitors (CFU-Mix) grown in the presence of erythropoietin (Epo). The size and haemoglobin content of BFU-E derived colonies also increased in the presence of the cytokines. Of those tested, SCF was found to be the most potent additive to Epo for the enhanced growth of BFU-E and CFU-Mix. In short-term liquid cultures without Epo, SCF alone induced globin synthesizing cells. Progenitors from premature infants were at least as responsive to all three cytokines as those from healthy adults. The use of SCF in combination with Epo in the prevention or treatment of anaemia in premature infants warrants further investigation.

Cells, Cultured↗
PubMed1994

Dideoxynucleoside resistance emerges with prolonged zidovudine monotherapy. The RV43 Study Group.

Human immunodeficiency virus type 1 (HIV-1) isolates resistant to zidovudine (ZDV) have previously been demonstrated to exhibit in vitro cross-resistance to other similar dideoxynucleoside agents which contain a 3'-azido group. However, cross-resistance to didanosine (ddI) or dideoxycytidine (ddC) has been less well documented. ZDV, ddI, and ddC susceptibility data have been collected from clinical HIV-1 isolates obtained by five clinical centers and their respective retrovirology laboratories. All subjects were treated only with ZDV. Clinical HIV-1 isolates were isolated, amplified, and assayed for drug susceptibility in standardized cultures of phytohemagglutinin-stimulated donor peripheral blood mononuclear cells obtained from healthy seronegative donors. All five cohorts showed a correlation between decreased in vitro susceptibility to ZDV and decreased susceptibility to ddI and ddC. For each 10-fold decrease in ZDV susceptibility, an average corresponding decrease of 2.2-fold in ddI susceptibility was observed (129 isolates studied; P < 0.001, Fisher's test of combined significance). Similarly, susceptibility to ddC decreased 2.0-fold for each 10-fold decrease in ZDV susceptibility (82 isolates studied; P < 0.001, Fisher's test of combined significance). These data indicate that a correlation exists between HIV-1 susceptibilities to ZDV and ddI or ddC for clinical HIV-1 isolates.

AIDS-Related Complex↗
PubMed1993

Protease nexin-2/amyloid beta protein precursor. A tight-binding inhibitor of coagulation factor IXa.

Protease nexin-2/amyloid beta protein precursor (PN-2/A beta PP) is an abundant, secreted platelet protein which is a potent inhibitor of coagulation Factor XIa. We examined other potential anticoagulant activities of PN-2/A beta PP. Purified Kunitz protease inhibitor domain of PN-2/A beta PP and PN-2/A beta PP itself were found to prolong the coagulation time of plasma and pure Factor IXa. The Kunitz protease inhibitor domain also inhibited the ability of Factor IXa to activate Factor X. PN-2/A beta PP inhibited Factor IXa with a Ki of 7.9 to 3.9 x 10(-11) M in the absence and presence of heparin, respectively. When the second-order rate constant of PN-2/A beta PP's inhibition of Factor IXa (2.7 x 10(8) M-1min-1) was compared to that of antithrombin III (3.8 x 10(6) M-1min-1), PN-2/A beta PP was at least a 71-fold more potent inhibitor of Factor IXa than antithrombin III. PN-2/A beta PP formed a complex with Factor IXa as detected by gel filtration and ELISA. The finding that PN-2/A beta PP is a potent inhibitor of Factor IXa could help to explain the spontaneous intracerebral hemorrhages seen in patients with hereditary cerebral hemorrhage with amyloidosis Dutch-type where there is an extensive accumulation of PN-2/A beta PP in their cerebral blood vessels.

Amyloid beta-Protein Precursor↗
PubMed1992

Purification and characterization of wheat and pine small basic protein substrates for plant calcium-dependent protein kinase.

A wheat basic protein (WBP) was purified to homogeneity from wheat germ by a protocol involving extraction, centrifugation, batchwise elution from carboxymethylcellulose (CM-52), acidification with trifluoroacetic acid, neutralization and HPLC on a SP5PW cation exchange column. WBP is a 10 kDa protein and is phosphorylated on serine residues by wheat germ Ca(2+)-dependent protein kinase (CDPK). [32P]phosphoWBP exactly comigrates with WBP on SDS-PAGE. WBP does not inhibit either wheat germ CDPK or calmodulin-dependent myosin light chain kinase. Apart from histone H1, WBP is the best endogenous substrate yet found for wheat embryo CDPK. A 12 kDa pine basic protein (PBP) was purified to homogeneity from seeds of stone pine (Pinus pinea L.) by a simple procedure involving batchwise elution from carboxymethylcellulose and cation exchange HPLC. PBP is also a good substrate for CDPK and is phosphorylated on Ser residues. N-terminal sequencing of WBP and PBP revealed that these proteins are homologous to a family of small basic plant proteins having a phospholipid transfer function.

Amino Acid Sequence↗
PubMed1992

Pre-oxygenation: the Hudson mask as an alternative technique.

The use of a simple oxygen facemask (Hudson) with high oxygen inflow (48 l.min-1) was investigated as a technique for pre-oxygenation, comparing it with the Magill system (oxygen flow: 100 ml.kg-1.min-1). One hundred and thirty-eight patients scheduled for elective gynaecological and orthopaedic surgery were studied: group 1, Hudson mask and group 2, Magill system (ASA 1-2, n = 107); group 3, Hudson mask and group 4, Magill system (ASA 3, n = 30). Pre-oxygenation was assessed by measuring the times to 97%, 95% and 93% arterial desaturation (finger pulse oximetry) following 3 min of pre-oxygenation. The times taken to achieve these end-points in all the study groups suggest that the Hudson mask offers an alternative technique for pre-oxygenation.

Adult↗
PubMed1992

Iontophoresis of vinblastine into normal skin and for treatment of Kaposi's sarcoma in human immunodeficiency virus-positive patients. The Military Medical Consortium for Applied Retroviral Research.

BACKGROUND: Patients who test positive for human immunodeficiency virus type 1 (HIV-1) and who have disfiguring and/or painful cutaneous lesions of Kaposi's sarcoma (KS) may not be candidates for systemic chemotherapy and/or immunotherapy. Intralesional vinblastine sulfate, as a single-agent chemotherapeutic drug, has been used with some success to treat KS in patients who are HIV-1 positive. However, some patients may not tolerate the pain associated with injection of vinblastine. Transcutaneous iontophoresis of vinblastine was evaluated for therapy of KS in HIV-1-infected patients. Prior to therapy of patients, we iontophoresed vinblastine into the normal skin of volunteers who were not infected with HIV-1 to document the clinical and histologic features that occurred. OBSERVATIONS: Iontophoresis produced a localized erythematous papular eruption in non-HIV-infected volunteers but not in HIV-1-infected patients. Histologic changes in the biopsy specimens taken from non-HIV-infected volunteers consisted primarily of scattered necrotic keratinocytes and a mild to moderate superficial lymphohistiocytic infiltrate. Thirty-one lesions of KS were treated with partial to complete clearing and symptomatic improvement. CONCLUSION: Clinical and histologic features of iontophoresed normal skin suggest an immunologic mechanism of action. Iontophoresis of vinblastine for KS is well tolerated and results in symptomatic improvement as well as varying degrees of clearing of the lesions.

Adult↗
PubMed1991

TP53 gene mutations and 17p deletions in human astrocytomas.

Astrocytomas, including the most malignant form, glioblastoma multiforme, are the most frequent and deadly primary tumors of the human nervous system. Recent molecular genetic analyses of astrocytomas have demonstrated frequent chromosome 17 deletions involving the telomeric region of the short arm (17p12-pter). This region contains a candidate tumor suppressor gene, TP53, which has recently been implicated in the etiology of a broad array of human cancers. To study the possible role of TP53 in astrocytoma development, 24 randomly chosen human astrocytic tumors were examined for genomic TP53 sequence aberrations using primer-directed DNA amplification in conjunction with direct sequencing. Five of the 11 grade III astrocytomas (glioblastoma multiforme), but only one of seven grade II astrocytomas (anaplastic astrocytoma) and none of either the grade I astrocytomas or oligodendrogliomas demonstrated distinct point mutations involving the TP53 gene. These data suggest that TP53 mutations may play a role in astrocytoma development and are predominantly associated with higher grade tumors.

Adult↗
PubMed1986

Wound closure in obese patients.

A five year randomized prospective study was carried out to compare subcutaneous drains versus a type of stay suture closure in morbidly obese patients. While acceptable wound infection rates were found, no statistical superiority was established between these types of closures.

Adult↗
PubMed1984

Safety and antigenicity of typhoid-Shigella sonnei vaccine (strain 5076-1C).

The form-1 antigen of Shigella sonnei was transferred to the avirulent Salmonella typhi strain 21a and the resulting 5076-1C transconjugate strain was tested for safety and immunogenicity as a candidate oral vaccine. The transconjugant strain was shown to be well tolerated and safe in 19 human volunteers who were fed from 1 X 10(7) to 1 X 10(10) organisms. Only two of 10 volunteers tested had developed a rise in antibody titer to the lipopolysaccharide of the hybrid 5076-1C strain.

Administration, Oral↗
PubMed1984

Oral vaccination of monkeys with an invasive Escherichia coli K-12 hybrid expressing Shigella flexneri 2a somatic antigen.

A living oral vaccine, designed to protect against Shigella flexneri 2a infections, was constructed by using Escherichia coli K-12 as a carrier strain. The hybrid strain, designated EC104, contained both chromosomal and plasmid genes from S. flexneri donor strains. In addition to expressing the S. flexneri 2a somatic antigen, it had inherited the property of epithelial-cell invasion. After the oral administration to rhesus monkeys, EC104 was isolated from the feces for up to 3 days, but by day 4 all stool cultures were negative. The serum antibody response against S. flexneri 2a somatic antigen was variable, but the vaccine conferred significant protection against an oral challenge with virulent S. flexneri 2a.

Administration, Oral↗