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Biomedical subjects

R D Brown

Publications and source records attributed to R D Brown.

At least 127 records · Page 7Linked to original sources
PubMed1997

Immunocytochemical localization of the alpha-1B adrenergic receptor and the contribution of this and the other subtypes to vascular smooth muscle contraction: analysis with selective ligands and antisense oligonucleotides.

The contribution of the alpha-1B adrenergic receptor (AR) to vascular smooth muscle contraction has been assessed using a combination of immunological, molecular biological and pharmacological approaches. A subtype-selective antibody detected alpha-1B immunoreactivity in the medial layer of the aorta, caudal, femoral, iliac, mesenteric resistance, renal and superior mesenteric arteries. Receptor protection assays and antisense oligonucleotides were used to assess the contribution of the alpha-1B AR to contraction. The alpha-1B AR was implicated in mediating the phenylephrine-induced contraction of the mesenteric resistance artery. The alpha-1D AR was implicated in mediating the contraction of the aorta, femoral, iliac and superior mesenteric arteries. Similarly, the alpha-1A AR was implicated in mediating contraction of the caudal and renal arteries. In vivo application of antisense oligonucleotides targeted to the translational start site of the alpha-1B AR had no effect on the phenylephrine-induced contraction of the femoral or renal arteries. In contrast, antisense oligonucleotides directed against the alpha-1D AR significantly inhibited the phenylephrine response in the femoral artery but had no effect on the renal artery. Application of alpha-1A AR antisense oligonucleotides inhibited the contraction of the renal artery without effect on the femoral artery. These data show that (1) alpha-1B AR immunoreactivity is widely distributed in the same peripheral arteries in which previous studies detected its mRNA, and (2) despite this distribution, receptor protection and antisense oligonucleotide studies indicate that the alpha-1B AR mediates the contraction of only the mesenteric resistance artery.

Animals↗
PubMed1996

Pharmacokinetics of kanamycin in the developing rat.

The developing rat is hypersensitive to aminoglycoside ototoxicity during the period of anatomical and functional development of the cochlea. Toxicity is expressed only after a few days of treatment when kanamycin is given during the most sensitive period for production of ototoxicity (postnatal days 11-20). In contrast, when the drug is administered after the 20th postnatal day, the same dose and duration of treatment do not produce an ototoxic effect. Only after prolonged treatment (e.g., > or = 20 days) is there an observed effect. We characterized the pharmacokinetics of kanamycin in the serum of 12- and 25-day-old rats and observed a greater than 2.5-fold increase in elimination half-life in the 12- versus 25-day-old rat. The longer duration half-life of kanamycin in younger rats may explain the hypersensitivity of immature mammals to aminoglycoside ototoxicity.

Analysis of Variance↗
PubMed1996

Brush cytology for pancreatic carcinoma: an analysis of factors influencing results.

BACKGROUND: Despite recent advances in cytology brush design, yield of endoscopic brush cytology in suspected pancreatic carcinoma remains low. METHODS: We prospectively evaluated 32 such patients by ERCP to analyze differences in yield based on anatomic location of the pancreatic stricture, and the role of concurrent biliary stricture brush cytology, in improving the overall yield. Endoscopic brush cytology was performed on all strictures following ERCP. A final diagnosis of pancreatic carcinoma was confirmed in all patients. RESULTS: Twenty-three of the 32 patients had positive cytology for pancreatic malignancy (71.9%). Eight patients had positive brushings from biliary strictures alone (25%) and 15 had positive brushings obtained from pancreatic strictures (46.9%). The yield varied widely depending on the anatomic location of the stricture; ampullary, genu, and tail regions had low rates of positive cytology, in part due to technical factors and brush design (1 of 8, 2 of 6, and 1 of 4, respectively). Strictures of the head and body yielded high rates of positive cytology (7 of 8 and 4 of 6, respectively). CONCLUSIONS: The yield of endopancreatic brush cytology is related to the location of malignancy, with overall yield enhanced by concurrent brushing of bile duct strictures.

Cholangiopancreatography, Endoscopic Retrograde↗
PubMed1996

Saline injection needle-knife sphincterotomy: a preliminary report.

BACKGROUND AND STUDY AIMS: Needle-knife sphincterotomy is an established technique in the management of some patients with biliary tract obstruction. However, the technique can be technically difficult in patients with very small papillae, specially when associated with distorted ampullary and duodenal anatomy. We present here a technique that may enhance successful needle-knife sphincterotomy in this situation. PATIENTS AND METHODS: Eight patients with biliary tract obstruction who had small papillae and distorted ampullary or duodenal anatomy were evaluated. All patients had undergone one or more unsuccessful cannulations prior to referral. All eight patients underwent saline injection of their papillae, creating a bulging papilla, prior to needle-knife sphincterotomy. RESULTS: Seven of the eight patients had successful needle-knife sphincterotomy following saline injection, and endoscopic therapy during the first attempt. In one patient, the procedure was successful at a second attempt 48 hours later. There were no instances of significant complications. CONCLUSION: Saline injection into the papilla prior to needle-knife sphincterotomy may improve success rates in patients with unusually small papillae and distorted ampullary or duodenal anatomy. However, at present this technique should only be attempted by experienced endoscopists. Further studies with larger numbers of patients are required before the safety of this technique can be fully evaluated.

Ampulla of Vater↗
PubMed1996

The effect of number of histogram events on reproducibility and variation of flow cytometric proliferation measurement.

Sources of variation in synthesis phase fraction (SPF) calculation were studied, and the number of histogram events was found to be an important quality control consideration. Six cell cycle models (CCMs) for histograms composed of 1,000 to 20,000 events were compared. All CCMs were cytometer based, or available in Multicycle (MC) software. The experiment consisted of five consecutive acquisitions, on the same day, of the same propidium iodide (PI) stained sample of T24 human cell line, at each of nine "landmarks" between 1,000 and 20,000 events. The authors found (1) all CCMs evaluated required > or = 5,000 events for accurate, reproducible SPF; and (2) in the 5,000-20,000 event range the MC models provided the most accurate, reproducible SPF values. Therefore, histogram-dependent curve fitting models may enhance clinical applications of FCM proliferation measurements. The authors conclude that histogram rejection criteria for S-phase analysis should be established, and that two-color multiparametric DNA analysis "live" gating with tissue specific markers may assure acquisition of sufficient events for accurate SPF.

Carcinoma, Transitional Cell↗
PubMed1996

Regulation of protein synthesis by alpha 1-adrenergic receptor subtypes in cultured rabbit aortic vascular smooth muscle cells.

To investigate the role of the sympathetic nervous system in maintenance and remodeling of vascular smooth muscle, we have examined regulation of protein synthesis by alpha 1-adrenergic receptors (alpha 1-AR) in cultured rabbit aortic vascular smooth muscle cells (VSMC). Stimulation of postconfluent cultures (passages 2-6) in serum-free growth medium with the alpha-AR agonist phenylephrine (PE, 30 microM) increases protein synthesis, measured as [3H]leucine incorporation into protein (146 +/- 5%, p < or = 0.001) and total protein content (117 +/- 2%, p < or = 0.001). PE treatment does not affect cellular proliferation or [3H]thymidine incorporation into DNA. PE-stimulated protein synthesis is evident within 24 h, sustained over 96 h, concentration-dependent, and saturable. PE-elicited responses are completely inhibited by the alpha 1-AR antagonist prazosin but not by the alpha 2-AR antagonist yohimbine or the beta-AR antagonists propranolol and atenolol; the beta-AR agonist isoproterenol is ineffective. Competition with [3H]prazosin occupancy of alpha 1-AR and agonist-elicited [3H]leucine incorporation by subtype-selective receptor antagonists (WB4101 and 5-methylurapidil, alpha 1A; chloroethylclonidine, alpha 1B) demonstrates that these cells express a majority of alpha 1B-AR (75%) relative to alpha 1A-AR (25%), which elicit protein metabolism in proportion to their relative abundances. These results indicate that alpha 1B-AR predominate in coupling to metabolic responses, in contrast to previous reports that contractile responses in this tissue are preferentially mediated by alpha 1A-AR.

Adrenergic alpha-1 Receptor Agonists↗
PubMed1996

Nucleoside transporters, bcl-2 and apoptosis in CLL cells exposed to nucleoside analogues in vitro.

The purine nucleoside analogues fludarabine (F1) and chlorodeoxyadenosine (2-CdA) are considered to be cell cycle specific agents which require DNA synthesis for cytotoxicity. However, their efficacy in the treatment of CLL, an indolent lymphoid malignancy suggests additional mechanisms of action. Like cytosine arabinoside (AraC), F1 and 2-CdA gain access to the cell via a specific nucleoside transporter (NST) protein. To investigate the mode of action of these drugs in CLL, we used a fluorescent ligand for the NST (5'-(SAENTA- x8)-fluorescein) and 3-colour flow cytometry to determine NST expression on CD5+/CD19+ B-cells from the peripheral blood (PB) of patients with CLL. NST levels on these cells was found to be not significantly different from normal control lymphocytes (mean = 485 +/- 425) vs. (mean = 553 +/- 178). Exposure to varying concentrations (0, 3 microM and 30 microM) of F1 and 2-CdA, however, resulted in an upregulation of NST (mean = 1552 +/- 775 with 30 microM FL; mean = 3392 +/- 2197 with 30 microM 2-CdA) after 48. "Large" lymphoid cells (not present in normal PB) were found to express significantly more NST (mean = 2540 +/- 2861) and have a higher proliferative capacity than "small" cells (mean = 357 +/- 517 NST/cell). Incubation of CLL cells with F1 (n = 6) and 2-CdA (n = 8) in vitro over 48 h also resulted in an increase in the proportion of cells in S-phase (0 microM = 0.2 + 2 - 0.1; 30 microM FL = 2.4 +/- 2.0; 30 microM 2-CdA = 3.3 +/- 1.3) and a significant increase in morphologically identifiable apoptosis. Apoptosis was confirmed by flow cytometric DNA analysis (0 microM = 13 +/- 8%; 30 microM FL = 40 +/- 20%; 30 microM 2-CdA = 48 +/- 11%). In situ hybridization using a biotinylated cDNA bcl-2 probe demonstrated that bcl-2 mRNA expression was markedly decreased in treated cells after 24 h. These studies have demonstrated that: (1) NST expression on CLL lymphocytes is low; (2) in vitro exposure to the analogues increases both the level of NST expression and the % cells in S-phase; (3) exposure to the analogues downregulates bcl-2 expression and increases apoptosis.

Antigens, CD19↗
PubMed1996

Incidence and prevalence of intracranial vascular malformations in Olmsted County, Minnesota, 1965 to 1992.

We used the Mayo Clinic medical records linkage system to detect all cases of intracranial vascular malformation (IVM) among residents of Olmsted County, Minnesota from 1965 to 1992 and found 48 IVMs over the 27-year period, including four patients with IVM detected at autopsy, without prior symptoms. Twenty-nine of 48 patients were symptomatic at presentation. From 1985 to 1992, the age- and sex-adjusted detection rate for IVMs excluding asymptomatic autopsy cases was 2.75 in 100,000 person-years (P-Y) (95% CI, 1.6 to 3.9). From 1965 to 1992, the detection rate was 1.84 in 100,000 P-Y (95% CI, 1.3 to 2.4). On January 1, 1990, the age- and sex-adjusted prevalence rate of identified IVMs was 19.0 in 100,000 P-Y (95% CI, 10.5 to 27.5). Detection rates increased from 1965 to 1992, probably due to increased identification of cases because of advances in imaging technology. This study provides unique data on incidence rates of detection and prevalence of IVMs on a population basis.

Adolescent↗
PubMed1996

Frequency of intracranial hemorrhage as a presenting symptom and subtype analysis: a population-based study of intracranial vascular malformations in Olmsted Country, Minnesota.

The purpose of this study was to determine the symptoms at presentation and the incidence of intracranial hemorrhage (ICrH) caused by intracranial vascular malformations (IVMs) in a defined population. The authors used the Mayo Clinic medical records linkage system to detect all cases of IVM among residents of Olmsted County, Minnesota, during the period 1965 through 1992. Forty-eight IVMs were detected over the 27-year period. Twenty-nine of the 48 patients were symptomatic at presentation. The most common presenting symptom was ICrH, which was present in 20 patients, 69% of all symptomatic cases. Sixty-five percent of arteriovenous malformations (AVMs) presented with ICrH. The most common subtype of ICrH was intracerebral hemorrhage, which was found in nine of 20 patients; the second most common subtype was subarachnoid hemorrhage. The peak occurrence of hemorrhage was during the fifth decade of life. The age- and gender-adjusted occurrence of a first ICrH from an IVM among residents of Olmsted County, Minnesota was 0.82 per 100,000 person years (95% confidence interval 0.46-1.19). There was no increase in the detection of IVM-related ICrH throughout the study period. The 30-day mortality rate following ICrH was 17.6% for patients with an AVM and 25% for all patients with IVMs. This study provides unique data on symptoms at presentation and the incidence of ICrH and hemorrhage subtypes from IVMs on a population basis.

Adolescent↗
PubMed1996

Stroke incidence, prevalence, and survival: secular trends in Rochester, Minnesota, through 1989.

BACKGROUND AND PURPOSE: Trends in stroke incidence and mortality are available from few sites worldwide. The unique nature of the medical care in patients from Rochester, Minn, has allowed the ascertainment of virtually all cases of stroke for community residents for the period dating from 1955. This study updates incidence rates, stroke mortality, radiological imaging availability, and prevalence for stroke and subtypes of stroke though 1989 and evaluates trends since 1955. METHODS: Medical records of all residents of Rochester with potential diagnosis of stroke during the 5-year period through December 31, 1989 were screened to determine whether the case met the criteria for stroke. The type of stroke was determined with the use of all available data. Average annual age- and sex-adjusted incidence rates for stroke and various types of stroke were calculated for 5-year periods from 1955 to 1989. Prevalence of stroke was also determined. Poisson regression was used to better clarify the dependence of stroke incidence on multiple variables. Cox proportional hazards modeling evaluated trends in short-term and long-term stroke survival. RESULTS: We found that 496 incidence cases of stroke occurred among Rochester residents during 1985 to 1989. The annual age- and sex-adjusted stroke incidence rates was 145 per 100 000 population, which was virtually unchanged from 1980 to 1984 and 13% higher than the rate determined in 1975 to 1979. Increasing incidence rates compared with the 1970s were noted in all groups aged older than 54 years and in both sexes. Survival after cerebral infarction was dependent on age and calendar year when trends dating from 1955 were evaluated. The annual incidence rate of intraparenchymal hemorrhage was twice that of subarachnoid hemorrhage. CONCLUSIONS: Incidence rates for stroke have remained at a high rate than those determined in the 1970s. Although the occurrence of untreated hypertension has been reported to be stable or decreasing, the incidence rate of stroke is higher than those noted during the decline in stroke incidence during the 1960s and 1970s. In addition to the impact of radiological imaging, increased contribution of patients with ischemic heart disease, and the possible detection of milder cases of stroke, other factors, which are undefined, may be contributing to the increased stroke incidence rates detected over the last 10 years.

Adult↗
PubMed1996

Utilization of acute care services in the year before and after first stroke: A population-based study.

There is a need for accurate population-based data on the utilization of medical resources after stroke. The present study used the Rochester Stroke Registry to identify all Rochester, Minnesota residents with confirmed first stroke (hospitalized and nonhospitalized) during the period of 1987 to 1989 (n=292). Events were categorized by type of stroke and assigned Rankin severity. Inpatient and outpatient acute care activity for the 12 months before and after stroke for each individual were obtained from billing tapes provided by Mayo Clinic, Olmstead Medical Group, and affiliated hospitals. These providers account for >95% of acute care received by Rochester residents. The results showed that despite high poststroke mortality, total charges in the year after stroke were 3.4 times those for the previous year. Although greater than 50% of utilization in the year poststroke occurred within the first 30 days, mean monthly charges for acute care remained significantly above prestroke levels for up to 5 months after the event. Poststroke charges per person-day of follow-up were significantly higher for individuals who were hospitalized for the event, who had subarachnoid hemorrhage, whose stroke occurred after admission to the hospital for another reason, and who died within 7 days. Significantly lower poststroke charges were evident for persons with mild cerebral infarctions and persons whose stroke occurred in a nursing home. Neither prestroke utilization, age category, nor sex were predictive of poststroke charges. The unique population-based data presented here have important implications for efforts toward stroke prevention, intervention, and cost containment.

Aged↗
PubMed1995

Agonist regulation of alpha 1B-adrenergic receptor subcellular distribution and function.

We have monitored agonist-induced alpha 1B-adrenergic receptor (alpha 1BAR) redistribution by immunocytochemical procedures in concert with functional measurements of agonist-elicited [3H]inositol phosphate (InsP) production in human embryonal kidney 293 cells stably expressing alpha 1BAR cDNA (HEK293/alpha 1B). Anti-peptide antibodies directed against the carboxyl-terminal decapeptide of the alpha 1BAR were prepared and shown to react specifically with alpha 1BAR on immunoblots and in situ in HEK293/alpha 1B transfectants. Treatment of HEK293/alpha 1B cells with norepinephrine (10 microM) results in a rapid (5-15 min) and striking internalization of cell surface receptor as visualized by confocal immunofluorescence microscopy. Receptor redistribution is sustained in the presence of agonist, rapidly reversed upon agonist removal, and prevented by the alpha 1 antagonist prazosin. Receptor internalizes to endosomes, as shown by colocalization with transferrin receptor, an endosomal marker. Activation of protein kinase C (PKC) with phorbol 12-myristate 13-acetate (50 nM) causes receptor endocytosis similar to agonist; agonist-induced internalization is blocked by the PKC inhibitor staurosporine (0.5 microM). In parallel experiments, agonist-induced [3H]InsP production is abolished by phorbol 12-myristate 13-acetate but potentiated by staurosporine. Inhibition of receptor internalization with hypertonic sucrose attenuates agonist-induced [3H]InsP formation; this effect is reversed by concomitant inhibition of PKC with staurosporine. These results suggest that PKC-dependent phosphorylation occurring as a consequence of alpha 1AR stimulation induces receptor desensitization and internalization. Internalized receptor is reactivated and continuously recycled to the cell surface during agonist exposure.

Adrenergic alpha-1 Receptor Agonists↗
PubMed1995

Characterization of FP21, a cytosolic glycoprotein from Dictyostelium.

FP21 is a glycoprotein which, when tracked by radioactivity in its fucosyl moiety, was previously detected in the cytosol of Dictyostelium cells after cell fractionation. This compartmentalization is confirmed by SDS-polyacrylamide gel electrophoresis/Western blotting of cell fractions using three different antibodies. Although a substantial fraction of FP21 is also detected in the particulate fraction using these new antibodies, particulate FP21 is released by disrupting protein-protein interactions, but not membrane disruption. Since purified FP21 is susceptible to aggregation, and purified nuclei do not contain FP21, particulate FP21 is also part of the cytosol. Additional compositional and structural information provides strong evidence that FP21 does not at any time traverse the rough endoplasmic reticulum. First, cDNAs spanning the entire coding region of the FP21 gene predict no hydrophobic motifs expected to promote membrane insertion, but do predict an NH2-terminal coiled coil domain which could explain aggregation. Second, monosaccharide composition analysis of the predominant glycoform of FP21 yields 2 mol of galactose, 1 mol of xylose, and 1 mol of fucose/mol of polypeptide; FP21 from a fucosylation-defective mutant contains 1 additional mol of xylose in place of fucose. Thus the N-glycosylation sequon present in FP21 is not utilized by oligosaccharyl transferase, which resides in the rough endoplasmic reticulum. These findings indicate that nascent FP21 remains in the cytosol after synthesis and is therefore glycosylated by unusual cytosolic xylosyl-, galactosyl-, and fucosyltransferases.

Amino Acid Sequence↗
PubMed1995

Allelic imbalance in gastric cancer: an affected site on chromosome arm 3p.

In order to detect regions of DNA containing tumor suppressor genes involved in the development of gastric cancer, we performed an allelotype study on 78 gastric adenocarcinomas from a population composed largely of Texan Hispanics and Anglos, two ethnic groups that have a ratio of incidence rates of gastric cancer of approximately 2:1. In total, 42 microsatellite markers were employed, which detected at least one site per arm of each autosome in the human genome. These included several markers linked to known tumor suppressor genes (TP53, APC, DCC, RB1, and BRCA1). Sites showing quantitative allelic imbalance (AI) greater than 30% were located on 3p (36%), 11q (31%), 12q (38%), 13q (33%), 17p near TP53 (74%), and 17q near BRCAI (32%). Among the 22% of cases showing microsatellite instability (MI), a subset (4 of 17) showed instability at 59% or more of sites tested. No ethnic bias was detected in cases showing MI or in cases with AI at sites with rates of AI above 30%. Tumors of the intestinal subtype were significantly more likely than diffuse tumors to show AI at DI3S170 (P = 0.01). A deletion map of chromosome arm 3p was prepared for tumors with AI at D3S1478. These data indicate that a tumor suppressor gene on chromosome arm 3p is involved in the development of a subset of gastric cancers.

Adenocarcinoma↗
PubMed1995

The effect of methadone on the immune status of B6C3F1 mice.

Previously, morphine has been shown to elevate corticosterone via the hypothalamic-pituitary-adrenal axis and to suppress the immune system. The present investigation sought to determine if the mu-opiate receptor agonist methadone incurred a similar immune suppression in B6C3F1 mice. Serum methadone and corticosterone levels peaked 1 hr following a single subcutaneous injection of 20 mg/kg methadone HCl. Indeed, the rise in corticosterone levels paralleled that of methadone. After a single injection with 20 mg/kg methadone a pharmacokinetic analysis revealed a serum half-life of approximately 2 hr. Following five injections of methadone over a 24-hr period (every 6 hr), methadone levels were elevated as would be expected; however, corticosterone levels did not become elevated. This suggests that the ability of methadone to elevate corticosterone becomes uncoupled following repeated dosing, indicative of either a tolerance or an increased catabolic mechanism. Moreover, dosing every 6 hr for 5 days induced an increase in the catabolism of methadone itself. Therefore, all assays were begun 1 hr after subcutaneous administration of methadone HCl, a time at which both methadone and corticosterone serum levels were elevated. The primary IgM antibody response to sheep red blood cells (sRBC) was suppressed when splenocytes were immunized in vitro. In contrast, animals immunized with sRBC and assayed for the primary IgM antibody response 4 days later were not suppressed. The activity of the resident macrophages of the liver and spleen as measured by the uptake of 51Cr-sRBC was suppressed in a dose-dependent manner. Previously, it has been demonstrated that morphine suppresses hepatic and splenic phagocytic activity through an opiate receptor-mediated pathway that involves the release of corticosterone. It would appear that methadone plays a similar role in the suppression of hepatic and splenic phagocytosis.

Animals↗