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D Chow

Publications and source records attributed to D Chow.

At least 37 records · Page 2Linked to original sources
PubMed1994

High-performance liquid chromatographic assay of cefazolin in rat tissues.

A rapid, sensitive and reproducible high-performance liquid chromatographic (HPLC) assay for cefazolin in rat tissues was developed. Tissue samples were homogenized in distilled water, acidified with 8.5% phosphoric acid, and centrifuged. Cefazolin was isolated from the supernatant by solid-phase extraction on C18 cartridges. The eluate containing cefazolin and internal standard, cephalexin, was injected onto a reversed-phase C18 column and eluted with a mobile phase of 23% methanol in 0.02 M sodium phosphate monobasic (pH 5.0) and detected with UV absorbance at 270 nm. Recoveries of cefazolin were 33.7 +/- 2.5%, 45.4 +/- 2.1%, and 42.9 +/- 1.0% from liver, spleen and lung, respectively. The calibration curves for cefazolin were established at 0.5-1500 micrograms/g in spleen, 0.1-250 micrograms/g in liver and 0.1-75 micrograms/g in lung. The assay was reproducible with within-day and between-day variations of 1-2 and 1-4%, respectively. Application of the assay for tissue distribution of cefazolin in liposomal targeting study was demonstrated.

Animals↗
PubMed1993

Monosaccharide and oligosaccharide analysis of proteins transferred to polyvinylidene fluoride membranes after sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

We have developed an intermediate method toward the complete carbohydrate analysis of proteins, which should be universally applicable to all proteins and independent of sample matrix. Using only Coomassie Blue-stained proteins which have been electroblotted onto polyvinylidene fluoride membranes, we report a strategy for: (i) determining unequivocally whether a protein is glycosylated; (ii) obtaining a complete monosaccharide composition; (iii) oligosaccharide mapping which separates most forms according to size, charge and isomerity; and (iv) sequentially releasing and analyzing specific classes of oligosaccharides with endoglycosidases. The method was shown to be applicable to a variety of well characterized soluble glycoproteins and to the membrane-bound protein, the gastric H+, K(+)-ATPase. The monosaccharide composition of the H+,K(+)-ATPase revealed the absence of N-acetylneuraminic or N-glycolylneuraminic acids and a monosaccharide composition which indicated O-linked sugar chains. Oligomannosidic/hybrid and biantennary oligosaccharides were sequentially released and analyzed from one electroblotted band of recombinant tissue plasminogen activator using endo-beta-N-acetylglucosaminidase H and endo-beta-N-acetylglucosaminidase F2, respectively. Sialylated polylactosamine structures were identified and quantified by analyzing high performance liquid chromatography profiles of oligosaccharides first released by peptide-N4-(N-acetyl-beta-D-glucosaminyl)asparagine amidase and then treated with endo-beta-galactosidase, using a single, stained band of recombinant erythropoietin. This recombinant erythropoietin was found to contain eight times more tetrasialylated oligosaccharides than previously reported (Sasaki, H., Bothner, B., Dell, A., and Fukuda, M. (1987) J. Biol. Chem. 262, 12059-12076); 47% of released oligosaccharides were identified as polylactosamine structures.

Animals↗
PubMed1992

Incidence of retinal detachment following Nd:YAG capsulotomy after cataract surgery.

In a retrospective study, we reviewed 218 consecutive Nd:YAG laser posterior capsulotomies performed at the Gimbel Eye Centre between June 1987 and November 1989 for the incidence of retinal detachment (RD) following treatment. Matched controls were found for 198 YAG cases. The median post-surgical follow-up for the YAG cases was 49.5 months; for the controls, 50.0 months. The median time between cataract extraction and YAG laser posterior capsulotomy was 24.8 months. The median follow-up after YAG was 24.2 months. Two of the 198 YAG cases (1.0%) and one of the 198 controls (0.5%) had RD. In the YAG cases, RD occurred 54.8 and 36.5 months after cataract surgery; in the control cases, 51.8 months after cataract surgery. Retinal detachment occurred at 15.0 and 17.0 months after YAG capsulotomy. These rates were lower than those reported in the literature. We feel that the surgical techniques of continuous circular capsulorhexis and in-the-bag IOL placement reduce the risk of RD following Nd:YAG posterior capsulotomy.

Aged↗
PubMed1992

Insulin-like growth factor-II overexpression in MCF-7 cells induces phenotypic changes associated with malignant progression.

It has been proposed that the insulin-like growth factors (IGFs) can act as autocrine and/or paracrine growth promoters in breast cancer. To investigate this hypothesis, we infected early passage MCF-7 cells with a retroviral vector containing the coding sequence for the IGF-II preprohormone along with a constitutive cytomegalovirus promoter sequence. These cells do not normally express IGF-I or IGF-II. After infection with the retroviral vector, several single cell clones were analyzed. Seven of nine isolated clones expressed very high levels of IGF-II mRNA. Biologically active IGF-II protein was easily detectable in the medium conditioned by the IGF-II-expressing clones, and IGF receptors were down-regulated in these. All IGF-II-expressing clones showed marked morphological changes in anchorage-dependent culture, growing in large clumps and as free-floating colonies. The cells also cloned in soft agar in the absence of estrogen, while the wild-type MCF-7 cells and control cells infected with an irrelevant DNA sequence showed none of these properties. alpha IR-3, an antibody that blocks the type I IGF receptor, inhibited the growth of IGF-II-expressing clones in serum-free medium. This model demonstrates that IGF-II can serve as an autocrine growth stimulant in breast cancer epithelial cells and that IGF-II overexpression may be capable of mediating malignant progression in human breast cancer.

Breast Neoplasms↗
PubMed1990

Cloning of the H,K-ATPase beta subunit. Tissue-specific expression, chromosomal assignment, and relationship to Na,K-ATPase beta subunits.

We have isolated cDNA clones encoding the bovine and rat gastric H,K-ATPase beta subunit. A bovine abomasum lambda gt11 cDNA library was screened with a monoclonal antibody raised against the rabbit H,K-ATPase beta subunit. A single positive phage clone containing an approximately 900-base pair cDNA insert was identified as reactive with the antibody. The identity of the cDNA was established by comparing the deduced amino acid sequence with sequences of cyanogen bromide fragments of the porcine H,K-ATPase beta subunit. Polymerase chain reaction and rapid amplification of cDNA ends were used to generate a cDNA fragment encoding the carboxyl-terminal portion of the rat gastric H,K-ATPase beta subunit. A rat stomach cDNA library was screened with the polymerase chain reaction product, and several full-length beta subunit cDNA clones were identified. The open reading frame predicts a protein of 294 amino acids with a molecular weight of 33,689. The rat H,K-ATPase beta subunit shows 41% amino acid sequence identity to the rat Na,K-ATPase beta 2 subunit and shares a number of structural similarities with Na,K-ATPase beta subunit isoforms. By analyzing the segregation of restriction fragment length polymorphisms among recombinant inbred strains of mice, we localized the H,K-ATPase beta subunit gene to murine chromosome 8. Northern and Western blot analysis reveals that this gene is expressed exclusively in stomach. Our results suggest that the H,K-ATPase and Na,K-ATPase beta subunits evolved from a common ancestral gene and may play similar functional roles in enzyme activity.

Adenosine Triphosphatases↗
PubMed1990

Simultaneous determination of physostigmine and tetrahydroaminoacridine in a transdermal permeation study by high-performance liquid chromatography.

A selective and stability-indicating high-performance liquid chromatographic assay with diazepam as the internal standard was developed for simultaneously analyzing physostigmine and tetrahydroaminoacridine in skin samples, permeation diffusates and dosage form. Baseline resolution was achieved with an octadecyl column for physostigmine, its two degradation products and tetrahydroaminoacridine. Peak homogeneity of physostigmine and tetrahydroaminoacridine was confirmed. The calibration curves for both drugs in skin samples were established at 1-50 micrograms per 200 mg skin. Those for diffusate samples were at 10-50 ng per 50 microliters for physostigmine and 30-150 ng per 50 microliters for tetrahydroaminoacridine. The assay was reproducible with within-day and between-day variations of 5-6 and 4-10%, respectively. Application of the assay for in vitro transdermal permeation study was demonstrated.

Aged↗
PubMed1990

Membrane and protein recycling associated with gastric HCl secretion.

Stimulation of the gastric parietal cell requires massive membrane transformations as H(+)-pumps from the domain of cytoplasmic tubulovesicles are recruited into the apical plasma membrane domain. The recycling of membrane pools, through fusion and fission processes that accompany stimulation and inhibition of HCl secretion, also involves highly selective events of protein incorporation and segregation. This manuscript describes several proteins that have been identified with the apical plasma membrane from maximally stimulated parietal cells, and broadly characterizes them either as permanent resident proteins of the apical membrane, or transient proteins that move into and out of the apical membrane as the cell progresses through the secretory cycle. A typical example of transient association with the apical membrane concerns the pump proteins, including the 94 kDa catalytic alpha-subunit of the H+K(+)-ATPase and its newly discovered beta-subunit glycoprotein, which move between tubulovesicles. Proteins that remain associated with the apical plasma membrane during rest and secretion include actin, and an 80-kDa phosphoprotein, which has been variously called 80 K, ezrin, p81 and cytovillin, and whose phosphorylation is increased by the histamine/cAMP pathway of parietal cell stimulation. An example of a cytosolic protein that becomes associated with the apical plasma membrane after stimulation is a 120-kDa protein, which appears to have protein kinase activity. Note that the identification, localization and characterization of the K+ and Cl- transport proteins, which participate in net HCl secretion, are of immediate importance.

Actins↗
PubMed1989

Preformulation study of etoposide: identification of physicochemical characteristics responsible for the low and erratic oral bioavailability of etoposide.

Preformulation studies of etoposide, including pH-solubility profile, partition coefficient, pH-stability profile, and in vitro dissolution kinetics, were conducted to identify the responsible factor(s) for the low and erratic oral bioavailability of etoposide. A stability-indicating high-performance liquid chromatographic (HPLC) assay was used for drug monitoring. The equilibrium aqueous solubility of etoposide at 37 degrees C was low, 148.5-167.25 micrograms/ml, and did not vary over the pH range of 2 to 6. The pH-stability profile indicated rapid degradation of etoposide at pH 1.3 and 10, with degradation half-lives of 2.88 and 3.83 hr, respectively, at 25 degrees C. The half-life at pH 7.30 was 27.72 days. Maximum stability at 25 degrees C was reached at pH 5 to 6.15, with half-lives of 63 and 49.5 days, respectively. The intrinsic dissolution rate, determined on a Wood's apparatus, was slow, 0.0094 mg/min/cm2, while the etoposide partition coefficient between n-octanol and water was 9.94. Therefore, etoposide absorption appears to be dissolution rate limited rather than permeation rate limited. The low equilibrium aqueous solubility, slow intrinsic dissolution rate, and chemical instability at pH 1.3 could account for the low oral bioavailability.

Biological Availability↗
PubMed1988

Adrenal response in children receiving high doses of ketoconazole for systemic coccidioidomycosis.

The effect of ketoconazole on adrenal cortical function was studied in 10 prepubertal children receiving long-term (3 to 52 months) high-dose (10 to 23 mg/kg/d) orally administered ketoconazole treatment because of systemic coccidioidomycosis. Four hours after the once daily morning dose of ketoconazole, the patients had significantly elevated baseline desoxycorticosterone (DOC) and precursor/product ratios, and blunted cortisol and aldosterone responses to ACTH stimulation. Twenty-four hours after ketoconazole ingestion, both DOC and DOC/corticosterone ratio were approaching normal; the cortisol response to ACTH was normal in all but two of the 10 study patients, and these two had significantly improved response compared with their own 4-hour values. There appeared to be no differential adrenal response related to either duration of treatment (greater than 12 vs less than 12 months) or dose of medication per kilogram (greater than 18 or less than 18 mg/kg/d). Our data suggest that ketoconazole impairs production of cortisol and aldosterone by imposing a partial and temporary block at the 11-beta-hydroxylase step of steroid hormone synthesis. None of the patients required adrenal steroid replacement therapy in times of acute illness or surgery, and none had clinical evidence of adrenal insufficiency.

Adrenal Cortex↗
PubMed1988

Clinical and immunological studies of cadaveric renal transplant recipients given total-lymphoid irradiation and maintained on low-dose prednisone.

Twenty-five recipients of cadaveric renal transplants were given total lymphoid irradiation (TLI), perioperative antithymocyte globulin, and low-dose prednisone as the sole maintenance immunosuppressive drug. Nine patients were diabetic, and follow-up was between 19 and 37 months. One-year graft and patient survival was 76% and 87%, respectively, Serious complications included four deaths from cardiovascular disorders, and two deaths from viral infections. Studies of peripheral blood T cell subsets showed a prolonged reduction in the absolute number of helper (Leu-3+) cells, and a rapid recovery of cytotoxic/suppressor (Leu-2+) cells. Analysis of the latter subset, using the monoclonal antibody 9.3, showed that the ratio of suppressor/cytotoxic cells was approximately 10:1. The normal ratio is 1:1. The mean mixed leukocyte reaction remained below 30% of the pre-TLI value for 6 months, and approached 80% at two years. Similar kinetics were observed in the proliferative response to mitogens. The results show that maintenance immunosuppressive drug therapy can be reduced after TLI as compared with conventional drug regimens that use prednisone in combination with cyclosporine and/or azathioprine.

Adult↗
PubMed1987

Stability-indicating high-performance liquid chromatography of etoposide at various pH conditions using a reversed-phase octyl column.

A stability-indicating reversed-phase high-performance liquid chromatographic assay of etoposide is described. Baseline resolution was achieved with an octyl column for etoposide and its four degradation products, including picrolactone. Peak homogeneity of etoposide was confirmed by quantitating etoposide in degraded samples at 230, 254 and 286 nm, respectively. The assay was reproducible with low within-day and between-day variations. Application of the assay for stability kinetic study was demonstrated. Etoposide in 0.1 M hydrochloric acid (pH 1.29) degraded with a half-life of 2.85 h, which may be responsible for the low oral bioavailability of etoposide.

Chromatography, High Pressure Liquid↗
PubMed1987

Renal transplant patients treated with total lymphoid irradiation show specific unresponsiveness to donor antigens the mixed leukocyte reaction (MLR).

A group of 25 cadaveric renal transplant recipients received total lymphoid irradiation (TLI) before transplantation, rabbit anti-thymocyte globulin on alternate days for 10 days after transplantation, and low dose prednisone (5 to 10 mg/day) as the sole maintenance immunosuppressive therapy. Allograft function and the mixed leukocyte reaction (MLR) were monitored serially. After 18 to 30 mo, nine patients were selected on the basis of a return of the MLR such that the mean stimulation index to a panel of normal stimulator cells was greater than or equal to 5, a stable serum creatinine level which was less than or equal to 2 mg/dl, and a history of no more than one rejection episode. The MLR of these patients' post-transplant peripheral blood mononuclear leukocytes (PBML) against cryopreserved donor cells was compared with that against cryopreserved normal third-party cells. In control experiments, the MLR of cryopreserved pre-TLI recipient PBML or fresh normal PBML were tested against the same panel of donor and third-party stimulator cells. Seven of the nine recipients showed a pattern of specific unresponsiveness to the donor cells more than 18 mo after transplantation. Preliminary attempts to identify antigen specific suppressor cells were unsuccessful. The pattern of unresponsiveness may indicate a state of specific immune tolerance to the allogeneic graft.

Adult↗
PubMed1986

Exogenous ochronosis resulting from quinine injections.

An 86-year-old woman presented with bluish black macules on each buttock. Skin biopsy revealed ochronotic pigment in the dermis. On the basis of negative results of a urine test for alkaptonuria and a history of having received quinine injections for malaria 70 years ago, the patient was diagnosed as having localized exogenous ochronosis resulting from quinine injections. Exogenous ochronosis has been reported following the topical use of phenol in leg ulcers, the topical use of hydroquinone bleaching creams in black persons, and the oral administration of antimalarials for malaria and connective tissue diseases, but we could find no reports in the literature of exogenous ochronosis following intramuscular injections of antimalarials.

Aged↗
PubMed1982

Progressive adrenal failure in polyglandular autoimmune disease.

We describe the clinical course of a boy who developed progressive adrenal failure, beginning with failure of the zona glomerulosa, as part of polyglandular autoimmune disease. Initially the patient presented with hypoparathyroidism and mucocutaneous candidiasis. ACTH tests at ages 8 and 11 yr resulted in a normal response of both mineralo- and glucocorticoids. The constellation of hyponatremia , hyperkalemia, and growth failure at age 14 yr prompted a reevaluation. A repeat ACTH test, assessing individual contributions of zone fasciculata and glomerulosa, showed normal plasma cortisol, desoxycorticosterone, and corticosterone responses and a normal urinary response of 18-hydroxydeoxycorticosterone and tetrahydrodeoxycorticosterone. Urinary 18-hydroxycorticosterone and urinary as well as plasma aldosterone were undetectable. PRA was markedly elevated. The ACTH response of adrenal androgens, presumably metabolic products of the zona reticularis, was also deficient. Antiadrenal antibodies against all three layers of the adrenal cortex were present. Mineralocorticoid therapy resulted not only in normalization of electrolytes and PRA but also in catch-up growth. Repeat testing of fasciculata function at age 19 yr now shows that the patient's cortisol response to ACTH response in abnormal. The course of this patient suggest that in addition to monitoring the electrolyte status, periodic tests for both mineralo- and glucocorticoid synthesis should be performed in children with polyglandular autoimmune disease because progressive adrenal insufficiency may go unrecognized.

Adrenal Glands↗
PubMed1981

Clinical response to metyrapone as indicated by measurement of mineralocorticoids and glucocorticoids in normal children.

The effect of 24-h metyrapone administration on adrenal mineralocorticoid and glucocorticoid pathways has been studied in normal children. Urine and serum steroid concentrations were evaluated. Simultaneous determinations of deoxycorticosterone (DOC), corticosterone (B), cortisol (F), and aldosterone (aldo), in both urine and serum, were carried out by celite column chromatography and radioimmunoassay. 11-deoxycortisol (Compound S) in serum and urine, urinary free 18-hydroxydeoxycorticosterone (18-OH-DOC), urinary free 18-hydroxycorticosterone (18-OH-B), and urinary aldosterone-18-glucuronide (pH 1 aldo) were measured separately by specific methods. Conclusions drawn were that (1) Useful indices of metyrapone effect were the marked rise of 11-deoxysteroids (DOC and S), and the fall of aldo and 18-OH-B; no changes occurred in 18-OH-DOC and the 11-hydroxylated steroids (B, F); (2) Serum and urine values were significantly correlated, indicating that both were equally reliable in the evaluation of the metyrapone test; (3) Hormonal ratios indicate that metyrapone inhibition affected the 11-hydroxylation of DOC and Compound S, and the 18-hydroxylation of DOC and B; and (4) The correlation between DOC/B and S/F ratios was highly significant (r = 0.86; P less than 0.0001), showing the same degree of inhibition of 11-hydroxylase functions for both 17-hydroxy (17-OHS) and 17-deoxysteroids.

Adolescent↗