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J Yee

Publications and source records attributed to J Yee.

At least 73 records · Page 4Linked to original sources
PubMed1995

Transient transfection and expression of firefly luciferase in Giardia lamblia.

We have developed a gene transfer system for the protozoan parasite Giardia lamblia. This organism is responsible for many cases of diarrhea worldwide and is considered to be one of the most primitive eukaryotes. Expression of a heterologous gene was detected in this parasite after electroporation with appropriate DNA constructs. We constructed a series of transfection plasmids using flanking sequences of the Giardia glutamate dehydrogenase (GDH) gene to drive expression of the firefly luciferase reporter gene. The optimal construct consisted of a GDH/luciferase fusion gene in which the first 18 codons of the GDH gene immediately preceded the luciferase gene; this fusion gene was flanked by the upstream and downstream sequences of the GDH gene. Electroporation of this construct into Giardia yielded luciferase activity that was 3000- to 50,000-fold above background. Removal of either the 5' or 3' GDH flanking sequences from this construct resulted in significantly reduced luciferase activity, and removal of both flanking sequences reduced luciferase activity to background levels. Luciferase activity was proportional to the amount of DNA electroporated and was maximal at 6 hr after electroporation.

Animals↗
PubMed1995

Passive immunization of rhesus macaques against SIV infection and disease.

To evaluate the role of humoral immunity against simian immunodeficiency virus (SIV), we tested whether passive immunization with plasma from SIVmac251 vaccine-protected or healthy infected animals would protect rhesus monkeys against intravenous infection with ten 50% animal infectious doses of the cell-free homologous virus. The challenge dose of this SIVmac251 virus stock had previously caused persistent infection in all (21 of 21) nonimmunized controls. A plasma pool was obtained from a donor that had been immunized with an inactivated whole SIVmac251 vaccine produced in human T cells. This plasma pool contained low levels of SIVmac binding and neutralizing antibody but had a high titer of antibodies recognizing human cell proteins. Given 4 or 18 hr before intravenous challenge, this plasma completely protected three of eight recipients from infection and delayed virus detection in one recipient. The five unprotected animals had only a transient or undetectable p27 antigenemia and low virus load in their PBMCs, and all survived at least 7 months after infection. By contrast, no protection was observed in 6 monkeys given inactivated, pooled plasma or purified immunoglobulin (Ig) from healthy SIVmac251-infected animals. This plasma pool and the Ig preparation contained high levels of SIV-binding and neutralizing antibody but no reactivity to human cellular components. Five of the six recipients had persistent antigenemia after challenge and four died acutely from simian AIDS in 4-7 months. These studies suggest that passive transfer of antibody to human cellular antigens can confer protection against SIVmac whereas passive transfer of neutralizing antibodies without human cellular antibodies does not protect against the homologous virus and may enhance infection.

Animals↗
PubMed1995

The delayed hypersensitivity response and host resistance in surgical patients. 20 years later.

OBJECTIVE: A 20-year follow-up was conducted on research into the implications of a lack of a delayed-type hypersensitivity (DTH) skin test response among surgical patients. SUMMARY BACKGROUND DATA: The authors' original report showed that a failed DTH response was associated with increased hospital mortality, but the role of specific and nonspecific host defense elements, comorbid factors, nutritional supplementation, and the mechanism for anergy in this adverse outcome was unknown. METHODS: A data base of 4292 patients was analyzed and reported on individual studies designed to answer some of the above questions. RESULTS: Prospective studies showed a strong association between the DTH response and mortality: reactive patients, 2.9% (75/2576); anergic patients, 20.9% (239/1142, chi square = 265, p < 0.0000001). Antibody response to protein antigens was reduced in anergic patients. Antibody response to polysaccharide antigens was normal in all patients. The hallmark of anergy is a lack of T cells in the skin, as measured by mRNA signal (CD3) for T cells. The nonspecific component of host defense, as measured by circulating and exudate polymorphonuclear cell function, showed no statistically significant difference between elective reactive and elective anergic patients. Notwithstanding some mild malnutrition in anergic patients, parental nutrition failed to correct the DTH response or many of the cellular immune functions measured. CONCLUSIONS: Over the last 5 years, because of a reduction in overall patient mortality, the contribution of a reduced DTH response to septic related mortality has lost statistical significance in elective surgical patients. A reduced DTH response maintains its strong association to sepsis-related mortality in intensive care/trauma patients, and this is the group on which future research efforts should be concentrated.

Aged↗
PubMed1995

Developmentally regulated expression of a Giardia lamblia cyst wall protein gene.

The protozoan Giardia lamblia is an obligate parasite of the mammalian small intestine. We studied the expression of a gene that encodes a protein component of the cyst wall, a complex structure assembled during the differentiation of trophozoites to cysts and which is critical to survival of the parasite outside its mammalian host. Transcripts from the cyst wall protein gene increase more than 100-fold during encystation, reaching a maximum between 5 and 24 hours after induction. Cyst wall protein expression also increases dramatically during encystation, and, prior to its incorporation into the nascent cyst wall, the protein is contained within the encystation-specific vesicles of encysting trophozoites. The sequence of the cloned gene predicts an acidic, leucine-rich polypeptide of M(r) 26,000 that contains 5.3 tandemly arranged copies of a degenerate 24-amino-acid repeat. A hydrophobic amino-terminal peptide probably serves as the initial signal that targets this protein to a secretory pathway involving vesicular localization during encystation and, ultimately, secretion to form the cyst wall.

Amino Acid Sequence↗
PubMed1995

Gastrointestinal manifestations of AIDS.

As the AIDS epidemic continues to grow, it becomes increasingly important that physicians are aware of the gastrointestinal and abdominal diseases specific to this group of patients. Most AIDS patients exhibit gastrointestinal symptoms at some time during the course of their disease. Clinical AIDS is often determined by identifying an opportunistic infection or neoplasm of the gastrointestinal tract. Radiology often plays a key role in helping to determine the diagnosis as well as in directing the management.

AIDS-Related Opportunistic Infections↗
PubMed1994

CYP1A1 genetic polymorphisms and in situ colorectal cancer.

Numerous studies have associated colorectal adenoma with smoking and large bowel cancer with consumption of foods potentially containing polycyclic aromatic hydrocarbons. Enhanced metabolic activation of polycyclic aromatic hydrocarbons has recently been observed in homozygotes for a MspI mutation in the 3'-end of CYP1A1. We conducted a population-based case-control study to investigate whether CYP1A1 polymorphisms were related to colorectal cancer risk. Using polymerase chain reaction-based methods, we assessed the frequency of the MspI polymorphism in the 3'-end of CYP1A1 and another mutation in exon 7 of the gene (Ile-Val polymorphism) among 43 patients with in situ adenocarcinoma of the large bowel and 129 population controls. Homozygosity for the MspI mutant genotype was found to be positively associated with in situ colorectal cancer in Japanese (P = 0.008) and Hawaiians/part-Hawaiians (P < 0.001), whereas the study lacked power to detect a similar association in Caucasians. The odds ratio for the homozygous variant genotype compared to the heterozygous and wild-type genotypes was 7.9 (95% confidence interval, 1.4-44.4) in Japanese. A similar association was suggested for the exon 7 mutation homozygosity in Japanese, as the two polymorphisms are in genetic disequilibrium. Thus, this study suggests a potentially important role for CYP1A1 and polycyclic aromatic hydrocarbons in the etiology of colorectal cancer in populations with a high gene frequency.

Adult↗
PubMed1994

Exudative neutrophils. Modulation of microbicidal function in the inflammatory microenvironment.

OBJECTIVE: To determine whether the inflammatory microenvironment primes neutrophils for increased microbicidal activity. DESIGN: In vitro studies of host defense were performed on surgical patients. SETTING: A tertiary care, university hospital. PATIENTS: A volunteer sample of hospitalized preoperative, noninfected surgical patients. INTERVENTION: Exudative neutrophils were collected from skin-blister chambers and functionally compared with circulating neutrophils. METHODS: Flow cytometry was used to evaluate directly neutrophil microbicidal activity (using fluoresceinated Candida albicans), formyl-methionyl-leucyl-phenylalanine (fMLP)-induced superoxide production (using 123 dihydrorhodamine), and surface expression of CD11b, CD16, and the fMLP receptor. In vitro tumor necrosis factor alpha was used to determine the possibility and extent of further priming in both circulating and exudative neutrophils. RESULTS: Exudative polymorphonuclear neutrophils have enhanced microbicidal activity, superoxide production, and expression of CD11b, CD16, and the fMLP receptor. Exogenous tumor necrosis factor was able to prime circulating neutrophils but did not further augment superoxide production in exudative neutrophils. CONCLUSION: The microbicidal activity of neutrophils is enhanced after exudation and is associated with neutrophil priming. The inability of exogenous tumor necrosis factor to further augment superoxide production after exudation suggests that this priming has been maximized.

Candida albicans↗
PubMed1994

Reduced tumor necrosis factor alpha production in lipopolysaccharide-treated whole blood from patients in the intensive care unit.

OBJECTIVE: To determine the cytokine response to lipopolysaccharide in patients in the intensive care unit. PATIENTS: Patients in a mixed medical/surgical intensive care unit with fever and a de novo clinical dysfunction of at least one organ system. METHODS: Whole blood from patients and from laboratory controls was stimulated with 8 ng/mL of lipopolysaccharide (Escherichia coli 0111:B4) at 37 degrees C, and tumor necrosis factor alpha (TNF-alpha) was measured using enzyme linked immunosorbent assay at 4, 8, and 24 hours. The same subjects' purified monocytes were cultured with 8 ng/mL of lipopolysaccharide in the presence of autologous or pooled control plasma or cocultured with purified autologous polymorphonuclear leukocytes at a polymorphonuclear leukocyte-monocyte ratio of 10:1, and TNF-alpha was measured at 24 hours using the enzyme linked immunosorbent assay. RESULTS: We detected high (n = 5) and low (n = 5) TNF-alpha responders in whole blood producing a mean (+/- SEM) of 27.2 +/- 6.3 pg/mL per 1000 monocytes vs 0.0 +/- 2.4 pg/mL per 1000 monocytes, respectively (controls, 58.0 +/- 13.0 pg/mL per 1000 monocytes). The kinetics of TNF-alpha production in both groups were comparable. Purified monocytes from both groups of patients cultured with lipopolysaccharide alone produced equivalent TNF-alpha values (42.4 +/- 10.5 vs 40.8 +/- 12.5 pg/mL per 1000 monocytes). Assayable TNF-alpha was not different with autologous vs control serum but was markedly diminished by the presence of polymorphonuclear leukocytes in patients as well as in controls; the two groups of patients did not differ in this polymorphonuclear leukocyte effect. CONCLUSION: Lipopolysaccharide stimulation of monocytes in the whole blood results in marked variation of TNF-alpha production. This phenomenon may account for the variable septic response to infection in patients in the intensive care unit.

Adult↗
PubMed1994

The local role of tumor necrosis factor alpha in the modulation of neutrophil function at sites of inflammation.

OBJECTIVE: To examine the hypothesis that tumor necrosis factor alpha (TNF-alpha) is an important local modulator of neutrophil function in the inflammatory microenvironment. DESIGN: In vitro studies of host defense. PATIENTS: A volunteer sample of healthy subjects. INTERVENTION: Exudative neutrophils were collected from skin-blister chambers and functionally compared with blood neutrophils. METHODS: Tumor necrosis factor alpha levels at sites of inflammation and neutrophil exudation were determined and compared with serum concentrations. Flow cytometry was used to evaluate neutrophil microbicidal activity and N-formyl-methionyl-leucyl-phenylalanine-induced changes in intracellular calcium and superoxide production. In vitro TNF-alpha was used to evaluate the nature and dose response of TNF-alpha-induced changes in neutrophil function. RESULTS: Exudative neutrophils have an increased responsiveness to subsequent N-formyl-methionyl-leucyl-phenylalanine stimulation, as determined by changes in intracellular calcium. Microbicidal activity and superoxide production are also up-regulated compared with circulating neutrophils. The exudative microenvironment contains TNF-alpha at local levels that are capable of significantly enhancing neutrophil host defense. CONCLUSIONS: Tumor necrosis factor alpha may serve to enhance neutrophil function at sites of inflammation. Neutrophils become more cytotoxic and have an enhanced ability to respond to weak environmental signals.

Blood Bactericidal Activity↗
PubMed1994

A yeast artificial chromosome clone map of the Drosophila genome.

We describe the mapping of 979 randomly selected large yeast artificial chromosome (YAC) clones of Drosophila DNA by in situ hybridization to polytene chromosomes. Eight hundred and fifty-five of the clones are euchromatic and have primary hybridization sites in the banded portions of the polytene chromosomes, whereas 124 are heterochromatic and label the chromocenter. The average euchromatic clone contains about 211 kb and, at its primary site, labels eight or nine contiguous polytene bands. Thus, the extent as well as chromosomal position of each clone has been determined. By direct band counts, we estimate our clones provide about 76% coverage of the euchromatin of the major autosomes, and 63% coverage of the X. When previously reported YAC mapping data are combined with ours, euchromatic coverage is extended to about 90% for the autosomes and 82% for the X. The distribution of gap sizes in our map and the coverage achieved are in good agreement with expectations based on the assumption of random coverage, indicating that euchromatic clones are essentially randomly distributed. However, certain gaps in coverage, including the entire fourth chromosome euchromatin, may be significant. Heterochromatic sequences are underrepresented among the YAC clones by two to three fold. This may result, at least in part, from underrepresentation of heterochromatic sequences in adult DNA (the source of most of the clones analyzed), or from clone instability.

Animals↗