Search PubMed⌕ Search

Biomedical subjects

D S Miller

Publications and source records attributed to D S Miller.

At least 73 records · Page 4Linked to original sources
PubMed1998

Mutations in the BRCA1-associated RING domain (BARD1) gene in primary breast, ovarian and uterine cancers.

Germline alterations of BRCA1 result in susceptibility to breast and ovarian cancer. The protein encoded by BRCA1 interacts in vivo with the BRCA1-associated RING domain (BARD1) protein. Accordingly, BARD1 is likely to be a critical factor in BRCA1-mediated tumor suppression and may also serve as a target for tumorigenic lesions in some human cancers. We have now determined the genomic structure of BARD1 and performed a mutational analysis of 58 ovarian tumors, 50 breast tumors and 60 uterine tumors. Seven polymorphisms were detected within the 2.34 kb coding sequence of BARD1 . Somatically acquired missense mutations were observed in one breast carcinoma and one endometrial tumor; in at least one of these cases, tumor formation was accompanied by loss of the wild-type BARD1 allele, following the paradigm for known tumor suppressor genes. In addition, a germline alteration of BARD1 was identified in a clear cell ovarian tumor (Gln564His); again, loss of the wild-type BARD1 allele was observed in the malignant cells of this patient. The Gln564His patient was also diagnosed with two other primary cancers: a synchronous lobular breast carcinoma and a stage IA clear cell endometrioid cancer confined to an endometrial polyp 6 years earlier. These findings suggest an occasional role for BARD1 mutations in the development of sporadic and hereditary tumors.

Adenocarcinoma↗
PubMed1998

Protective efficacy of DNA vaccines against duck hepatitis B virus infection.

The efficacy of DNA vaccines encoding the duck hepatitis B virus (DHBV) pre-S/S and S proteins were tested in Pekin ducks. Plasmid pcDNA I/Amp DNA containing the DHBV pre-S/S or S genes was injected intramuscularly three times, at 3-week intervals. All pre-S/S and S-vaccinated ducks developed total anti-DHBs and specific anti-S antibodies with similar titers reaching 1/10,000 to 1/50,000 and 1/2,500 to 1/4,000, respectively, after the third vaccination. However, following virus challenge, significant differences in the rate of virus removal from the bloodstream and the presence of virus replication in the liver were found between the groups. In three of four S-vaccinated ducks, 90% of the inoculum was removed between <5 and 15 min postchallenge (p.c.) and no virus replication was detected in the liver at 4 days p.c. In contrast, in all four pre-S/S-vaccinated ducks, 90% of the inoculum was removed between 60 and 90 min p.c. and DHBsAg was detected in 10 to 40% of hepatocytes. Anti-S serum abolished virus infectivity when preincubated with DHBV before inoculation into 1-day-old ducklings and primary duck hepatocyte cultures, while anti-pre-S/S serum showed very limited capacity to neutralize virus infectivity in these two systems. Thus, although both DNA vaccines induced high titers of anti-DHBs antibodies, anti-S antibodies induced by the S-DNA construct were highly effective in neutralizing virus infectivity while similar levels of anti-S induced by the pre-S/S-DNA construct conferred only very limited protection. This phenomenon requires further clarification, particularly in light of the development of newer HBV vaccines containing pre-S proteins and a possible discrepancy between anti-HBs titers and protective efficacy.

Animals↗
PubMed1998

Excretory transport of xenobiotics by dogfish shark rectal gland tubules.

Marine elasmobranch rectal gland is a specialized, osmoregulatory organ composed of numerous blind-ended, branched tubules emptying into a central duct. To date, NaCl excretion has been its only described function. Here we use isolated rectal gland tubule fragments from dogfish shark (Squalus acanthias), fluorescent xenobiotics, and confocal microscopy to describe a second function, xenobiotic excretion. Isolated rectal gland tubules rapidly transported the fluorescent organic anion sulforhodamine 101 from bath to lumen. Luminal accumulation was concentrative, saturable, and inhibited by cyclosporin A (CSA), chlorodinitrobenzene, leukotriene C4, and KCN. Inhibitors of renal organic anion transport (probenecid, p-aminohippurate), organic cation transport (tetraethylammonium and verapamil), and P-glycoprotein (verapamil) were without effect. Cellular accumulation of sulforhodamine 101 was not concentrative, saturable, or inhibitable. Rectal gland tubules did not secrete fluorescein, daunomycin, or a fluorescent CSA derivative. Finally, frozen rectal gland sections stained with an antibody to a hepatic canalicular multispecific organic anion transporter (cMOAT or MRP2) showed heavy and specific staining on the luminal membrane of the epithelial cells. We conclude that rectal gland is capable of active and specific excretion of xenobiotics and that such transport is mediated by a shark analog of MRP2, an ATP-driven xenobiotic transporter, but not by P-glycoprotein.

Animals↗
PubMed1998

Protein kinase C regulation of organic anion transport in renal proximal tubule.

Fluorescence microscopy and digital image analysis were used to examine the role of protein kinase C (PKC) in the control of organic anion (fluorescein, FL) transport in killifish renal proximal tubules. Phorbol ester (1-100 nM) reduced cellular and luminal accumulation of FL, and protein kinase inhibitors [staurosporine and 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine, 10-1,000 nM] increased cellular and luminal accumulation. Phorbol ester effects were blocked by staurosporine. The increases in tissue fluorescence caused by staurosporine were blocked by p-aminohippurate, indicating that they represent increased FL transport on the organic anion system. Neither phorbol ester nor staurosporine had any effects on the cell-to-lumen transport of a fluorescent organic anion that was generated intracellularly from a nonfluorescent, uncharged precursor. Finally, studies with a fluorescent PKC inhibitor showed that phorbol ester caused PKC translocation from cytoplasm to the plasma membrane. Together, these findings indicate that renal organic anion transport is negatively correlated with PKC activity and that PKC directly or indirectly controls the basolateral step in transport.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1998

Protein kinase C regulation of p-glycoprotein-mediated xenobiotic secretion in renal proximal tubule.

Fluorescence microscopy, fluorescent substrates [daunomycin and a fluorescent cyclosporin A (CSA) derivative] and digital image analysis were used to examine the role of protein kinase C (PKC) in the control of p-glycoprotein in killifish renal proximal tubules. PKC activators, phorbol ester (phorbol 12-myristate 13-acetate, PMA) and dioctylglycerol, reduced luminal drug accumulation, and protein kinase inhibitors, staurosporine and 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7), increased luminal accumulation; a PMA analog that does not activate PKC was without effect. PMA effects were blocked by staurosporine. The increase in luminal fluorescence caused by staurosporine was blocked by the p-glycoprotein substrate, CSA, indicating that this component of transport was indeed mediated by p-glycoprotein. Neither PMA, dioctylglycerol, nor protein kinase inhibitors altered cellular drug accumulation. Finally, in primary cultures of flounder proximal tubule cells, PMA decreased transepithelial [3H]daunomycin secretion. This pharmacological approach demonstrates that in teleost renal proximal tubule, p-glycoprotein-mediated xenobiotic secretion is negatively correlated with changes in PKC activity, a finding that conflicts with results from studies using mammalian tumor cells that express p-glycoprotein.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1998

The National Breast and Cervical Cancer Early Detection Program: report on the first 4 years of mammography provided to medically underserved women.

OBJECTIVE: We describe results from 284,503 mammographic examinations and associated diagnostic workups provided to medically underserved women in an ongoing nationwide breast cancer early detection program. MATERIALS AND METHODS: We report the results of mammographic examinations and diagnostic workups on 230,143 medically underserved women 40 years old or older who underwent at least one mammographic examination from July 1991 through June 1995. Mammograms were obtained in hundreds of mammography and clinical facilities throughout the United States, including community health centers, health department clinics, private practitioners' offices, university based facilities, and mobile mammography units. Our analysis included rates of mammograms with abnormal findings (reported according to the categories of the American College of Radiology Breast Imaging Reporting and Data System), breast cancer detection rates, numbers of diagnostic procedures performed, stage and size distribution of breast cancers, and positive predictive value of mammograms and biopsies with abnormal findings--all presented according to screening round and 10-year age intervals. RESULTS: Mammograms with abnormal findings constituted 5% of mammograms in the first round and 4% in subsequent rounds, both proportions declining by approximately one third from the youngest (40-49 years) to the oldest (70 years and older) age group. Breast cancer detection rates per 1000 mammographic examinations were 5.1 for the first round and 2.0 for subsequent rounds; from the youngest to the oldest age group, the first-round rates doubled and the subsequent-round rates tripled. Early-stage cancers accounted for 54% of first-round cancers and 81% of subsequent-round cancers. Percentage of invasive cancers at least 2 cm in size declined from 51% in the first round to 33% in subsequent rounds: however, we found little change in the proportion of lesions smaller than 1 cm. Positive predictive values declined from 9.5 cancers per 100 mammograms with abnormal findings in the first round to 5.6 cancers per 100 mammograms with abnormal findings in the subsequent rounds. CONCLUSION: A large nationwide breast cancer early detection program conducted through hundreds of diverse facilities has provided results that, although not a statistically representative sample of mammography services, are probably the best available characterization of the current state of breast cancer screening practices as they actually occur in the 1990s in the United States. These results should be useful to clinicians, researchers, and public health personnel in counseling patients, planning new studies, and improving efforts to control breast cancer.

Adult↗
PubMed1998

Adaptation to pregnancy in three different ethnic groups: Latin-American, African-American, and Anglo-American.

Interview assessments on adaptation to pregnancy were made of Latin-American (N = 30), African-American (N = 34), and Anglo-American (N = 30) women in the latter half of their pregnancy. Most subjects were 18-27 years old, single, had 12 years or less education, and had a parity of 0 or 1. Psychosocial measures of adaptation to pregnancy included Acceptance of Pregnancy, Identification with Motherhood Role, Relationship with Mother and with Husband/Partner, and Preparation for Labour. Data were analyzed using chi-square for group differences. The results indicate that in all 3 groups pregnancy was unplanned but wanted. African Americans least often anticipated life changes as a result of pregnancy, cited fewest aspects of pregnancy that were gratifying to them, and least often chose to stay home with their infant. Most women in all ethnic groups reflected on their role as mother, but Latin Americans most often indicated that they wanted to be like their own mother and that they consulted with their mother about pregnancy and parenting. African Americans least often anticipated domestic help from their partner and most often expected help from other family members. Regarding intimate relationships with husband/partner, for all groups sexual intercourse decreased during pregnancy. Anglo-Americans reported the least number of problems/discomforts with intercourse, Latin Americans the most. Anglo-Americans most often found alternative methods of sexually satisfying their partner, African Americans least often. The results of this exploratory study have significance for differences in the delivery of health care to the 3 ethnic groups and warrant further research.

Adaptation, Psychological↗
PubMed1997

Dual pathways for organic anion secretion in renal proximal tubule.

Transport on the "classical" organic anion system in renal proximal tubule is specific, active, Na-dependent, and ouabain sensitive. Here we review recent studies using intact teleost proximal tubules and laser scanning confocal microscopy which show that the secretion of large organic anions, such as, fluorescein-methotrexate (FL-MTX, Mw 923 Da) is handled by a separate and distinct organic anion transport system. In contrast to the classical system, FL-MTX uptake into cells and secretion into the tubular lumen was ouabain insensitive and largely Na-independent. KCN did not affect cellular uptake but abolished secretion into the lumen. PAH and probenecid, potent inhibitors of transport on the classical system, were weak inhibitors of FL-MTX transport. Uptake and secretion of FL-MTX were inhibited by micromolar concentrations of other organic anions (MTX, folate, bromocresol green, bromosulfonphthalein). FL-MTX secretion into the lumen was inhibited by leukotriene C4 and cyclosporine A, neither of which affected transport of the model substrate for the classical system, fluorescein. Thus, FL-MTX secretion is specific, but largely Na-independent and ouabain-insensitive. Both the basolateral and luminal steps in FL-MTX transport differ from those associated with fluorescein and P-aminohippurate secretion.

Animals↗
PubMed1997

Identification of an element required for acetylcholine receptor-inducing activity (ARIA)-induced expression of the acetylcholine receptor epsilon subunit gene.

Acetylcholine Receptor (AChR)-inducing activity (ARIA) is believed to be the trophic factor utilized by motoneurons to stimulate AChR synthesis in the subsynaptic area. Among the four AChR subunit genes, the epsilon subunit gene is strictly expressed in nuclei localized to the synaptic region of the muscle. To understand mechanisms of the regulation of synapse-specific transcription, we studied the promoter activity of the 5'-flanking region of the AChR epsilon subunit gene in response to ARIA. Transgenes containing the wild type or mutant 5'-flanking regions upstream of a luciferase gene were transfected in C2C12 muscle cells. The promoter activity of these transgenes was determined by assaying activity of expressed luciferase. Analyzing a combination of 5' deletion and site-directed mutants, we identified a 10-nucleotide element (position -55/-46), which was crucial for ARIA-induced expression from the epsilon subunit promoter. This element was named ARE for ARIA-responsive element. Mutation of ARE greatly diminished ARIA-induced transgene expression and deletion of ARE abolished completely the ARIA response. Electrophoretic mobility shift analyses revealed a DNA binding activity in muscle nuclear extract that interacted with ARE. Such interaction was enhanced by ARIA stimulation of muscle cells and appeared to be dependent on nuclear protein phosphorylation.

Animals↗
PubMed1997

Protection against methoxyacetic-acid-induced spermatocyte apoptosis with calcium channel blockers in cultured rat seminiferous tubules: possible mechanisms.

A calcium-mediated mechanism underlying spermatocyte apoptosis induced by 2-methoxyethanol (2-ME) has been previously proposed. This hypothesis was tested in vitro in the present study using cultured juvenile (25 days old) and adult rat seminiferous tubules (JRST and ARST, respectively) with methoxyacetic acid (MAA, the active metabolite of 2-ME). In JRST, spermatocyte degeneration was morphologically obvious 19 hr after a 5-hr exposure to 5 mM MAA. The lesion was unaffected by the presence or absence of extratubular Ca2+. However, MAA-induced cell death was significantly prevented by cotreatment with the dihydropyridines (DHP) nifedipine (50 microM) and nicardipine (20 microM), as well as verapamil (50 microM) and TMB-8 (50 microM), all of which are able to inhibit calcium movement through plasma membranes. However, neither ryanodine, dantrolene, nor cyclosporin A and ruthenium red, which inhibit Ca2+ mobilization from intracellular stores (endoplasmic reticulum and mitochondria), affected the MAA-induced cell death. Inhibition of calcium mobilization through IP3-sensitive pathways by blocking the product of IP3 with manoalide, neomycin, and U73122 did not block the MAA-induced lesion. The protective effects of 50 microM nifedipine and 50 microM TMB-8 were also observed in ARSTs treated with 10 mM MAA for 5 hr. However, when rat testicular sections were immunohistochemically stained with monoclonal antibodies specific for the alpha 1 (the DHP receptor) or the alpha 2 subunits of DHP-sensitive calcium channels, no positive staining was found. Finally, in an attempt to see whether the intracellular free calcium concentrations ([Ca2+]i) in germ cells were increased after the MAA treatment, intact seminiferous tubules were loaded with indo-1 and were measured using laser-scanning confocal microscopy. No detectable increase in the signal in MA A-sensitive spermatocytes was observed, while a 34-54% increase in the signal could be detected in the same cell types when tubules were exposed to 10 microM of the calcium ionophore 4-bromo-A23187 for 5 min. Collectively, these data suggest that the protective effect of calcium channel blockers against the MAA-induced spermatocyte apoptosis is probably not through their blocking effect on DHP-sensitive calcium channels. We postulate alternate mechanisms based on stabilization of cells membranes, or interactions with calmodulin or protein kinase C.

4-Aminopyridine↗
PubMed1997

Preinvasive and invasive breast and cervical cancer prior to or during pregnancy.

In conclusion, cervical and breast cancer are the two most frequently encountered malignancies during pregnancy. Although cervical cancer generally is diagnosed in its early stages, breast cancer tends to be discovered in more advanced stages. Therefore, the physician must have a high index of suspicion and must aggressively pursue the diagnosis of breast masses in pregnant women to try to detect the disease as early as possible. Premalignant lesions of the cervix also must be evaluated thoroughly. Therapy for these two cancers is similar to the treatment of nonpregnant women, with some modifications made due to fetal considerations and informed maternal desires. Pregnancy does not affect the progression or prognosis of either disease significantly. Pregnancy following the treatment for cervical cancer is unlikely, if not impossible, because current standard therapies will render these women infertile. There have, however, been some recent reports describing trachelectomy followed by laparoscopic lymph-node dissection for the treatment of early-stage cervical cancer in an attempt to preserve future fertility. Successful pregnancies are possible following the treatment of breast cancer and do not influence recurrence.

Breast Neoplasms↗
PubMed1997

Multicystic ovarian tumor weighing 156 lbs: the second largest tumor in Texas.

A woman's lifetime risk of developing an ovarian neoplasm is approximately 7%. A small subset of these neoplasms comprises the gigantic ovarian tumors (> 25 lbs) that often present challenging and difficult problems. We present a case of a 156-lb ovarian tumor with emphasis on the diagnostic and therapeutic approaches to successful management.

Cystadenoma, Mucinous↗
PubMed1997

p-Glycoprotein-mediated transport of a fluorescent rapamycin derivative in renal proximal tubule.

The transport of a fluorescent rapamycin derivative was measured in killifish (Fundulus heteroclitus) renal proximal tubules by means of confocal microscopy and image analysis. Renal cells and tubular lumens rapidly accumulated the rapamycin analog from the medium and attained steady state within 60 min. At steady state, luminal fluorescence intensity was two to four times higher than cellular fluorescence. Cellular fluorescence intensity was a linear function of medium substrate concentration and was not affected by any treatment used. In contrast, luminal fluorescence exhibited a saturable component as the medium concentration of the rapamycin derivative was increased. Secretion into the lumen was blocked by KCN, rapamycin, cyclosporin A and substrates for p-glycoprotein (verapamil, PSC-833 and FK506), but not by substrates for the renal organic anion or organic cation transport systems, such as p-aminohippurate, leukotriene C4 or tetraethylammonium. Finally, rapamycin blocked p-glycoprotein-mediated secretion of a fluorescent cyclosporin A derivative. The data are consistent with the fluorescent rapamycin analog entering proximal tubule cells by simple diffusion and then being pumped into the tubular lumen by p-glycoprotein. They suggest that the parent compound, rapamycin, would be handled similarly.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

Multicultural issues in organ transplantation: the influence of patients' cultural perspectives on compliance with treatment.

The potential influence of racially or ethnically diverse cultural perspectives on patient compliance with post-transplant treatments is discussed. Domains of competency regarding culturally sensitive clinical practice are outlined to assist providers in better understanding the perspectives that may influence the views and behavior of culturally diverse patients.

Communication↗
PubMed1997

Topotecan in the treatment of gynecologic cancer.

Topotecan (Hycamtin; SmithKline Beecham Pharmaceuticals, Philadelphia, PA), a derivative of the topoisomerase I inhibitor camptothecin, was approved by the Food and Drug Administration in May 1996 for the salvage treatment of ovarian cancer. It has shown promising clinical activity in a variety of solid tumors, including cervical cancer. Phase II and III trials in patients with cisplatin-resistant ovarian cancer have been conducted using a regimen of a single 30-minute intravenous topotecan infusion (1.5 mg/m2/d) for 5 days, repeated every 21 days. Significant responses, both partial and complete, have been observed in 14% to 21% of patients, with stable disease achieved in as many as 61%. In advanced or recurrent cervical cancer, partial response or stable disease was achieved in 59% of phase II trial patients. Myelosuppression is the major dose-limiting toxicity associated with topotecan. In general, the severity of myelosuppression shows a positive correlation to the magnitude of exposure to topotecan. Support with granulocyte colony-stimulating factor may partially ameliorate myelosuppressive effects.

Antineoplastic Agents↗
PubMed1996

Kinetics of duck hepatitis B virus infection following low dose virus inoculation: one virus DNA genome is infectious in neonatal ducks.

Using pooled serum from congenitally duck hepatitis B virus (DHBV)-infected ducks as inoculum, we examined the effect of virus dose on the incubation period of infection and on the patterns of spread of virus infection in the liver. The pooled serum inoculum contained 9.5 x 10(9) DHBV genomes per milliliter and had an infectivity titre (ID50) in newly hatched ducks of 1.5 x 10(10) per milliliter with a 95% confidence interval of 3.0 x 10(9) to 6.3 x 10(10) ID50/ml, indicating the equivalence between one DHBV genome and one infectious unit within the limits of the assays. The incubation period of infection was inversely related to the dose of inoculum and the onset of viraemia ranged from Day 6 with the highest dose to Day 14 or 29 with the lowest dose inoculum. To study the spread of virus infection from a low percentage of initially infected cells we inoculated newly hatched ducks intravenously with sufficient DHBV (1.5 x 10(3) ID50) to infect only approximately 0.0001% of total liver cells. DHBV infection first reached detectable levels on Day 4 postinoculation (p.i.) and was detected in approximately 0.035% of hepatocytes, most of which occurred as single cells or pairs of cells, indicating that a number of rounds of infection had occurred with the spread of virus both to adjoining cells, i.e., by cell-to-cell spread, and to cells located in other parts of the liver lobule. Despite some bird-to-bird variation in timing, the percentage of infected hepatocytes increased exponentially with a mean doubling time of 16 hr from Day 4 to Day 14 p.i., by which time replication was seen in > 95% of hepatocytes. This rapid dissemination from a small number of infected hepatocytes suggests that, in neonatal ducks, there are no major delays in virus replication within the liver, that any innate and adaptive defence mechanisms operating during the first 10 to 14 days of infection are insufficient to contain virus spread, and that even a small number of infected hepatocytes produce enough progeny to rapidly infect the remaining hepatocytes.

Age Factors↗
PubMed1996

Potential role of membrane internalization and vesicle fusion in adhesion of neutrophils in response to lipopolysaccharide and TNF.

Human polymorphonuclear leukocytes (PMN) respond to LPS with strongly increased integrin-mediated adhesion. While the first step of this process has been identified as the interaction of LPS with CD14 on the cell surface, subsequent steps remain to be elucidated. The experiments presented here suggest that monomeric LPS is internalized in vesicles, and uptake may be required for signaling. Fluorescently labeled LPS presented as monomeric complexes with soluble CD14 appeared in the plasma membrane of PMN by 5 min and was concentrated in cytoplasmic vesicles by 20 min. Adhesion in response to LPS/soluble CD14 occurred only after a 15- to 20-min lag period, consistent with endocytosis occurring before signal generation. In contrast, there was no time lag for adhesion in response to the formyl peptide formyl-norleucyl-leucyl-phenylalanine (fNLLP). Adhesion in response to LPS, but not fNLLP, was completely blocked by lowering the temperature to 19 degrees C, a procedure that prevents vesicle fusion. These studies indicated that an event with the time and temperature dependence of endocytosis precedes signaling by LPS. Cytochalasin D, an inhibitor of phagocytosis, and wortmannin, an inhibitor of phosphatidylinositol 3-kinase that blocks vesicle fusion and phagocytosis, both completely blocked adhesion in response to LPS but not in response to fNLLP. These results support the idea that LPS internalization and early endosomal fusion may be required for signal transduction. Parallel studies showed that the adhesion response to TNF had time, temperature, and inhibitor sensitivities nearly identical with those of LPS, suggesting that responses to TNF may also include an obligate vesicle fusion step.

Cell Adhesion↗