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R Chan

Publications and source records attributed to R Chan.

At least 127 records · Page 7Linked to original sources
PubMed1989

The use of fluorescein-conjugated lectins for visualizing atypical mycobacteria.

We investigated the feasibility of using fluorescein-conjugated lectins for visualizing and differentiating two species of atypical mycobacteria. Pure cultures of Mycobacterium fortuitum and Mycobacterium chelonei were established, as was an experimental model of infectious keratitis involving these two organisms. Samples from the pure cultures and corneal scrapings were placed on glass slides, fixed, and incubated with one of a panel of 22 fluorescein-conjugated lectins. The slides were examined using an epifluorescence microscope. Fluorescein-conjugated concanavalin A brightly stained both species of atypical mycobacteria, in both the pure culture and experimental keratitis samples. Several additional fluorescein-conjugated lectins (wheat germ agglutinin, succinylated wheat germ agglutinin, Phaseolus vulgaris erythroagglutinin, and Psophocarpus tetragonolobus agglutinin) brightly stained M chelonei, but only moderately stained M fortuitum. These staining patterns are consistent with the known carbohydrate compositions of the cell walls of atypical mycobacteria and suggest that fluorescein-conjugated lectins may be useful for the visualization of these organisms in corneal infections.

Abscess↗
PubMed1989

Fluorescein-conjugated lectin visualization of fungi and acanthamoebae in infectious keratitis.

The authors investigated the efficacy of two fluorescein-conjugated lectins (FCLs), concanavalin A (F-ConA) and wheat germ agglutinin (F-WGA), to visualize microorganisms from clinical specimens with documented mycotic and acanthamoebic keratitis. Corneal scrapings from 18 patients with culture-proven keratomycosis and deparaffinized histopathologic specimens from five culture-proven cases of acanthamoebic keratitis were evaluated. The F-ConA provided consistently bright staining of the mycotic structures in each of the corneal scrapings. Both F-ConA and F-WGA stained acanthamoebic trophozoites and cysts in the histopathologic specimens. In both the corneal scrapings and the histopathologic specimens, the microorganisms were easily differentiated from background corneal cells and tissue. These staining patterns correlate well with the results from experimental studies, and with the known cell wall carbohydrate compositions for fungi and acanthamoebae. This study provides further evidence that FCLs (particularly F-ConA) may eventually become effective first-line stains for the visualization of microorganisms in specimens from ocular infections.

Acanthamoeba↗
PubMed1989

Kidneys of chronic alcoholic rats are more vulnerable to ischemic insult.

The effects of chronic ethanol ingestion on the rat kidney were studied. Rats were fed a liquid diet containing ethanol for 5 weeks to induce chronic alcoholism. Renal ischemia was introduced by clamping the renal artery and vein either for 10 or 20 min. The glomerular filtration rate (GFR) and the renal blood flow (RBF) were determined by using I125-iothalamate and I131-iodohippurate. In the absence of renal ischemia, there were no significant differences in the renal function between nonalcoholic rats (n = 5) and alcoholic rats (n = 5): 380 +/- 30 vs. 403 +/- 27 microliters/min/100 g body weight (BW) in GFR, and 3.1 +/- 0.1 vs. 3.1 +/- 0.2 ml/min/100 g BW in RBF. The recovery of GFR measured 2 h following 10-min renal ischemia in both groups was not significantly different; the values returned to 340 +/- 40 microliters/min/100 g BW (nonalcoholic rats) and 246 +/- 22 microliters/min/100 g BW (alcoholic rats), respectively. The changes of RBF following 10 min ischemia were also similar in both groups. However, the effects of alcoholism on the renal function became apparent when animals were subjected to more prolonged renal ischemia. In nonalcoholic rats (n = 5), GFR and RBF measured 2 h following 20 min renal ischemia were 245 +/- 51 microliters/min/100 g BW and 2.5 +/- 0.4 ml/min/100 g BW, whereas in alcoholic rats (n = 5) the GFR and RBF were significantly decreased to 93 +/- 15 microliters/min/100 g BW and 1.1 +/- 0.2 ml/min/100 g BW, respectively (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Alcoholism↗
PubMed1988

Rapid visualization of Acanthamoeba using fluorescein-conjugated lectins.

We investigated the efficacy of fluorescein-conjugated lectins (FCLs) for the rapid visualization of Acanthamoeba species. Cultures of Acanthamoeba castellani, Acanthamoeba culbertsoni, and Acanthamoeba polyphaga were established on nonnutrient agar plates supplemented with Escherichia coli. Maximal trophozoite populations were established four to five days after initial subculturing; mature cysts were routinely noted three to six days later. At various time points, trophozoites and/or cysts were harvested and suspended in Page's saline. Following a previously described protocol, samples of the suspensions were placed on glass slides and incubated with one of a panel of 14 FCLs. At the end of the incubation period, the slides were examined using an epifluorescence microscope. Concanavalin A brightly stained both cysts and trophozoites. Wheat germ agglutinin brightly stained cysts but only minimally stained trophozoites. These results suggest that FCLs may be useful for rapid visualization of Acanthamoeba organisms in corneal infections.

Acanthamoeba↗
PubMed1988

Characterization of urinary keratin number 18 using a new assay.

The levels of the low-molecular weight keratin 18 appearing in the voided urine of 130 healthy volunteers was studied using a new immunoradiometric assay for keratin 18 (IRMAK-18). Keratin 18 was detected in 79 urines with an average level of 2.5 +/- 4.7 ng./ml. The assay does not detect complex epidermal keratins or non-keratin intermediate filaments. Only 50% of the purified keratin added to urine could be recovered. The recovered keratin had the same molecular weight as the input molecules, implying that substances in the urine physically inhibited the assay rather than destroyed the keratin. The independent variables of cell count, dead cells, and protein concentration were not found to be important in evaluating the results. However, the urine concentration, as measured by creatinine, might be an important consideration for assessing the levels of keratin detected.

Adult↗
PubMed1988

Radioimmunoassay of detirelix ([ N-Ac-D-Nal(2)1,D-p-Cl-Phe2,D-Trp3, D-hArg(Et)6(2),D-Ala10]-luteinizing hormone-releasing hormone) in plasma or serum.

A procedure for the radioimmunoassay (RIA) of detirelix in plasma or serum at concentrations as low as 0.15 ng/ml is described. Antiserum was produced by deacetylation of the N-terminus amino groups of detirelix and coupling this analog to bovine serum albumin with a carbodiimide and immunizing rabbits with the resultant conjugate. For RIA, 125I-labeled detirelix was used as the tracer and a double antibody procedure was used to separate the free and bound fractions. No purification of samples was required prior to RIA. Accuracy of the method was assessed by adding known quantities of detirelix to detirelix-free plasma and determining the ratio of measured to added analyte. Linear regression analysis for the concentration range 0.15-150.0 ng/ml yielded a regression equation of y = 0.88 X +1.46 and a correlation coefficient of 0.996. Additional validation was obtained from an in vivo study in which [14C]detirelix was administered to monkeys and plasma clearance profiles were determined by RIA and an HPLC-radiochemical method. The RIA results were in good agreement with those obtained by the HPLC method.

Animals↗
PubMed1988

Characterization of two monoclonal antibodies in an immunohistochemical study of keratin 8 and 18 expression.

Two monoclonal antibodies, UCD/AB 6.11 and UCD/PR 10.11, were evaluated for their patterns of immunohistochemical reactivity in a survey of paraffin-embedded human tissues by the avidin-biotin-immunoperoxidase technique. By two-dimensional immunoblotting, UCD/AB 6.11 reacts with keratin number 18 and UCD/PR 10.11 identifies both keratin numbers 8 and 18, the major keratins found in human simple epithelial cells. Both antibodies have excellent signal-to-noise ratios, and specifically react with simple epithelia, transitional epithelia, mesothelia and tumors derived from such tissues, making them superior immunological reagents. They do not react with neural, muscle, hematopoietic, connective or most epidermal tissues. However, within a given tissue or cell type, differences in the distributions of the antigens recognized by these two antibodies can be observed, raising the possibility of differential expression, modification, or masking of the keratin epitopes revealed by UCD/AB 6.11 and UCD/PR 10.11.

Antibodies, Monoclonal↗
PubMed1988

Cefoperazone compared with ampicillin plus tobramycin for severe biliary tract infections.

In a prospective, randomized, multicenter study, the efficacy and safety of cefoperazone and the combination ampicillin-tobramycin as initial therapy for patients with severe acute biliary tract infections were compared. Of 77 patients initially entered in the study, definite severe biliary tract infection was confirmed in 67. Sixty-four patients completed treatment. At the end of treatment, 35 of 36 (97%) patients given cefoperazone and 23 of 28 (82%) given ampicillin-tobramycin were cured of their infection (P = 0.07). Pathogens were recovered from the bile in 32 patients; microbiological cures were observed in 18 of 19 (94%) patients receiving cefoperazone and 8 of 13 (62%) receiving ampicillin-tobramycin (P = 0.03). Thirteen patients had septicemia. None (0%) of the eight septicemic patients from the cefoperazone group, but two of five (40%) from the ampicillin-tobramycin group, were clinical failures. Of the isolated pathogens, 51% were resistant to ampicillin, while the resistance rate was 4% for tobramycin and 1% for cefoperazone (P less than 0.001). Biliary concentrations of cefoperazone were maintained at high levels--236 +/- 87 micrograms/ml up to 12 h after administration. Even in the presence of severe obstruction, cefoperazone levels in the bile and gallbladder wall were above MICs for most pathogens. Cefoperazone may be considered as an excellent alternative in the therapy of severe biliary tract infections.

Acute Disease↗
PubMed1987

Ischemic heart disease risk factors in middle-aged Seventh-day Adventist men and their neighbors.

Seventh-day Adventists in California have much lower mortality from ischemic heart disease than do other Californians, but the risk factors have not been well documented previously for a representative sample. This study, conducted in 1982, chose a random sample of 160 Californian non-Hispanic white middle-aged Adventist men, 160 of their similar-aged male neighbors, and documented traditional ischemic heart disease risk factors. Results show major dietary differences between the two groups as expected, this being reflected in significant differences in consumption of total fat, saturated fat, dietary cholesterol, and crude fiber. Questionnaire data suggested that the Adventists also exercised 50% more, rarely smoked, but had identical Framingham Type A/B scores. There were no differences in obesity or blood pressure levels, but serum total cholesterol was significantly lower in the Adventists (190.1 vs. 203.5 mg/dl, p less than 0.001), as was low density lipoprotein cholesterol (125 vs. 134.0 mg/dl, p less than 0.03) and high density lipoprotein (HDL) cholesterol (42.3 vs. 46.0 mg/dl, p less than 0.005). Consequently, the ratio of total cholesterol/HDL cholesterol was virtually identical between the two groups. Possible explanations for some of these findings are discussed.

Adult↗
PubMed1987

Ultrasound measurement of endometrial thickness on different ovarian stimulation regimens during in-vitro fertilization.

Endometrial thickness was measured ultrasonographically in three groups of patients undergoing in-vitro fertilization (IVF) on three different ovulation induction regimens. The endometrial thickness was comparable on all three regimens and similar to that observed in a group of spontaneously ovulating, normal, fertile controls. These patterns of endometrial thickness were observed despite significantly higher levels of serum oestradiol-17 beta in all of the hyperstimulated cycles, suggesting that in the normal cycle a maximum response in terms of endometrial development may be achieved. In the three conception cycles endometrial thickness continued to increase throughout the luteal phase, whilst in non-conception cycles plateauing of thickness increase occurred in the mid-luteal phase and reduction in late luteal phase. Whether ultrasonographic evaluation of endometrium during IVF stimulation cycles has any prognostic value regarding prediction of conception has yet to be determined.

Clomiphene↗
PubMed1987

Rapid diagnosis of intravascular catheter-related sepsis.

The use of Gram-stained "impression smears" of the external surface of intravascular catheters for rapid detection of catheter-associated infection was studied. Gram's stain results of 322 catheters were correlated with clinical episodes of systemic sepsis and semiquantitative cultures of the catheters. Organisms were seen on Gram's stain of 82 catheters, 37 of which were positive on semiquantitative cultures (greater than or equal to 15 colonies per plate). Catheter-related bacteremia occurred on three occasions. All three catheters showed numerous organisms on Gram's stain, although one was negative on semiquantitative culture. All five catheters, in place during bacteremic episodes that were unrelated to catheter infection, were negative on Gram's stain. If the presence of any organisms on Gram's stain was taken as a positive test result, the sensitivity of Gram's stain in predicting the result of semiquantitative culture was 83%, the specificity was 81%, and the predictive value of a positive and negative culture was 44% and 96%, respectively. Slides took two to five minutes to examine microscopically. Gram-stained impression smears of intravenous catheters can be made by a simple, inexpensive, and rapid technique that is accurate in diagnosing catheter-related infection. However, in this study in which a relatively low prevalence of catheter-related bacteremia occurred, the positive predictive value of the Gram's stain result in the diagnosis of catheter-related bacteremia, in contrast to catheter colonization, was low. Only in a patient group with a high prevalence of catheter-related bacteremia would the test be likely to have a high positive predictive value. Thus, selectivity should be exercised in the application of this method.

Catheterization↗
PubMed1987

Experience with I-131-metaiodobenzylguanidine (MIBG): a retrospective study.

We report a retrospective study of two years experience with I-131-metaiodobenzylguanidine (MIBG). I-131 MIBG was prepared locally and was found to have decreased background activity as compared with other available commercial preparations from Great Britain and the United States. Fifty-nine patients were studied with a total of 65 scans. The study included 11 members of a family with multiple endocrine adenomatosis (MEA) type II syndrome. Of 16 patients found to have abnormal scans, 12 had disease confirmed surgically. These cases consisted of nine pheochromocytomas, one paraganglioma, one neurilemmoma, and one neuroblastoma. MIBG scans for pheochromocytoma detection had an accuracy of 94.5%, a sensitivity of 100%, and a specificity of 93.5% in this study of patients with a high prior probability of the disease.

3-Iodobenzylguanidine↗
PubMed1987

Attempts to stimulate multiple follicular growth for IVF by administration of pulsatile LHRH.

Administration of pulsatile LHRH (14.4 microgram/pulse per 90 min) from day 5 to 9, or day 7 to 11 of the cycle following clomiphene pretreatment on days 2-6 induced multiple follicular growth for oocyte recovery for in vitro fertilisation. Administration of LHRH without clomiphene pretreatment failed to induce multiple follicular development. The same group of patients treated with clomiphene alone had fewer numbers of mature follicles, fewer oocytes recovered and less pre-embryos for transfer than when treated with clomiphene and LHRH in combination. Peak gonadotrophin release following commencement of LHRH was seen within the first 24 h of administration with a gradual fall in both LH and FSH toward baseline pretreatment values by the fourth day of administration. A discernible LH increment to LHRH was still present on the fourth day of LHRH treatment, but in many individuals no FSH increment was observed. The preovulatory oocytes recovered were predominantly mature with fertilisation rates of 70% and 85.7% for the two regimens. No pregnancy occurred in the six patients who underwent pre-embryo transfer.

Adult↗
PubMed1986

Stimulation of multiple follicular growth for in vitro fertilization by administration of pulsatile luteinizing hormone-releasing hormone during the midfollicular phase.

Pulsatile subcutaneous administration of LH-RH (14.4 micrograms/pulse/90 minutes) during the midfollicular phase (days 7 to 11) of the cycle induced significant increases in circulating LH, FSH, and E2 in all eight women treated. When CC (150 mg/day on days 2 to 6) was administered prior to the LH-RH, multiple follicular development occurred, five to seven mature follicles (greater than 16 mm) being found on day 12 of the cycle. The administration of pulsatile LH-RH in this manner may prove to be an additional regimen for use in IVF programs.

Adult↗
PubMed1986

Evaluation of lysis filtration as an adjunct to conventional blood culture.

A lysis filtration system was used in conjunction with conventional broth culture for 1112 blood cultures. The system, which entailed collection of 5 ml of blood into bottles containing 50 ml isotonic phosphate buffer, Tween 20, and Rhozyme with subsequent filtration using a 0.45 micron Millipore field monitor, was simple and economical to use. Positive results were obtained earlier than those obtained with conventional broth cultures, and almost twice as many fungi and yeasts were isolated. Some fastidious organisms such as Haemophilus influenzae and Streptococcus pneumoniae however, were not recovered from the lysis system, and contaminants in lysis cultures were three times as common as in conventional culture. The number of positive cultures was also adversely influenced by incubation of the blood lysis mixture overnight before filtration. We conclude that this lysis filtration system is useful as an adjunct to conventional broth culture in selected patients in cases in which filtration can be carried out soon after collection.

Bacteria↗
PubMed1986

Presence of proteolytically processed keratins in the culture medium of MCF-7 cells.

MCF-7 human mammary epithelial cells are known to express three distinct cytoskeletal intermediate filament proteins designated numbers 8 (Mr 52,000), 18 (Mr 45,000), and 19 (Mr 40,000) keratin. Using a panel of monoclonal antibodies and peptide mapping, we have determined that MCF-7 cells release proteolytic derivatives of keratins 18 and 19 into the culture medium. These extracellular keratins consist of multiple isoforms (Mr 38,000-45,000, isoelectric point 5.0-5.2) on two-dimensional gels, many of which are smaller and more acidic than the predominant intracellular forms and appear to be associated together as a soluble, large molecular weight complex. These results may potentially be correlated with observations of keratin-like antigens in body fluids of cancer patients and the presence of antikeratin antibodies in individuals with certain autoimmune diseases and acute viral infections.

Amino Acids↗