Biomedical subjects

D R Brown

Publications and source records attributed to D R Brown.

At least 199 records · Page 11Linked to original sources

PubMed1996

Hepatic lipase gene therapy in hepatic lipase-deficient mice. Adenovirus-mediated replacement of a lipolytic enzyme to the vascular endothelium.

Hepatic lipase (HL) is an endothelial-bound lipolytic enzyme which functions as a phospholipase as well as a triacylglycerol hydrolase and is necessary for the metabolism of IDL and HDL. To evaluate the feasibility of replacing an enzyme whose in vivo physiologic function depends on its localization on the vascular endothelium, we have infused recombinant replication-deficient adenovirus vectors expressing either human HL (HL-rAdV; n = 7) or luciferase cDNA (Lucif-rAdV; n = 4) into HL-deficient mice with pretreatment plasma cholesterol, phospholipid, and HDL cholesterol values of 176 +/- 9, 314 +/- 12, and 129 +/- 9, respectively. After infusion of HL-rAdV, HL could be detected in the postheparin plasma of HL-deficient mice by immunoblotting and postheparin plasma HL activities were 25,700 +/- 4,810 and 1,510 +/- 688 nmol/min/ml on days 5 and 15, respectively. Unlike the mouse HL, 97% of the newly synthesized human HL was heparin releasable, indicating that the human enzyme was virtually totally bound to the mouse vascular endothelium. Infusion of HL-rAdV in HL-deficient mice was associated with a 50-80% decrease in total cholesterol, triglyceride, phospholipids, cholesteryl ester, and HDL cholesterol (P < 0.001) as well as normalization of the plasma fast protein liquid chromatography lipoprotein profile by day 8. These studies demonstrate successful expression and delivery of a lipolytic enzyme to the vascular endothelium for ultimate correction of the HL gene defect in HL-deficient mice and indicate that recombinant adenovirus vectors may be useful in the replacement of endothelial-bound lipolytic enzymes in human lipolytic deficiency states.

Adenoviridae↗

PubMed1996

Association of human papillomavirus type 11 DNA with squamous cell carcinoma of the tongue.

A 47-year-old man with a history of a benign papilloma of the tongue 5 years earlier was treated for a squamous cell carcinoma of the tongue with surgical resection. An analysis of the tumor DNA using several methods showed the presence of human papillomavirus (HPV) type 11 sequences that migrated with the high molecular weight cellular DNA, suggesting integration of viral DNA into the cellular genome. A segment of the HPV DNA was cloned from the lesion and shown to be similar to prototype HPV 11 DNA, except for some variability in the viral long control region. The proviral DNA contained part of the L1 region, all of the viral long control region, the entire E6 and E7 open-reading frames, and at least a portion of the E1 region; the E4 region appeared to be deleted. The integration sites of the HPV DNA could not be specifically identified. An analysis of the p53 tumor suppressor gene region of the tumor DNA showed no evidence of mutation. These results suggest that the HPV 11 DNA may have had a role in the origin of the cancer in this patient.

Blotting, Southern↗

PubMed1996

Temporal and histologic relationships of proliferating cell nuclear antigen and human papillomavirus type 11 in the mouse xenograft system.

Proliferating cell nuclear antigen (PCNA) is an accessory protein of DNA polymerase delta. This protein is associated with cell cycle progression and can be detected in the replicating cells of normal tissues. Condylomata acuminata are benign epithelial tumors caused by infection with human papillomaviruses and are characterized by abnormal cell proliferation. The athymic mouse xenograft model of HPV 11 infection was used to test the hypothesis that PCNA is induced early in the course of HPV 11 infection and to study the temporal and histologic relationships between detection of PCNA and HPV DNA. Human foreskin tissue was infected with HPV 11 and implanted under the renal capsules of 10 athymic mice. Pairs of mice were sacrificed every week beginning four weeks after implantation. HPV DNA was detected in sections of foreskin implants by in situ hybridization. PCNA was as or more abundant in implants removed at earlier time points than at later time points, whereas HPV DNA became increasingly more abundant with time. PCNA was detected only in basal cells in areas of histologically normal epithelium that were also negative for HPV DNA. In contrast, PCNA was present throughout the epithelium in regions that were HPV DNA-positive. HPV DNA was detected only in differentiated epithelial cells in implants removed at all five time points, but in HPV DNA-positive regions, PCNA was detected with equal intensity in differentiated and undifferentiated cells. The foci of PCNA-positive cells were well demarcated and were larger than, but included, the foci of HPV DNA-positive cells. PCNA may be induced maximally in differentiated epithelium by HPV 11 prior to significant HPV DNA replication.

Animals↗

PubMed1996

Human papillomavirus detection by hybrid capture in paired cervicovaginal lavage and cervical biopsy specimens.

Infection of the uterine cervix with human papillomavirus (HPV) is associated with dysplastic lesions that may progress to malignancy. Certain HPV types are associated with higher risk of cervical cancer than other genital HPVs. The goal of this study was to determine if cells obtained by cervicovaginal lavage contain similar HPV types as paired cervical biopsy in women referred because of abnormal cervical cytology. Thirty-four paired lavage and biopsy samples were analyzed for HPV DNA by hybrid capture, using "low risk" (HPV types 6. 11, and related types and "high risk" group (HPV types 16, 18, and related types) HPV. HPV was detected in 24 lavage samples and 18 biopsies. High risk types were predominant. In 14 of 18 HPV-positive biopsies, the paired lavage was also positive for the same HPV group. Four biopsies were HPV-positive at low levels, and the paired lavage was HPV-negative. The mean viral copy numbers of the biopsies from patients with positive and negative lavage samples were 2.7 and 0.1, respectively (P = .02). Ten low level HPV infections were detected by lavage that were not detected by biopsy. HPV detection by hybrid capture in cells obtained by cervicovaginal lavage reflects the results of HPV testing in cervical biopsies.

Cell Biology↗

PubMed1996

A neurotoxic prion protein fragment enhances proliferation of microglia but not astrocytes in culture.

The scrapie isoform of the prion protein (PrPSc) induces pathological changes in the central nervous system including neurodegeneration and gliosis. A synthetic prion protein (PrP) peptide corresponding to amino acid residues 106-126 has been shown to be toxic to neurons that express PrPC, the cellular isoform of PrP. Here we show that in mixed glial cultures PrP106-126 induces astroglial proliferation that is dependent on cellular PrPc expression. In purified cultures of glial subtypes only microglia proliferated in response to PrP106-126. This effect was independent of PrP expression. Destruction of microglia in mixed glial cultures by L-leucine methyl ester (LLME) treatment abolished enhanced proliferation caused by PrP106-126. This proliferative effect can be restored by co-culturing LLME-treated astrocytes with microglia. Microglia therefore seem to mediate the proliferative effect exerted by PrP106-126 on astrocytes.

Amino Acid Sequence↗

PubMed1996

Presence of immunocytes and sulfidopeptide leukotrienes in the inflamed guinea pig distal colon.

This study examined whether the immunocyte recruitment associated with a mild inflammatory state induced by acetic acid would produce detectable sulfidopeptide leukotriene (LT) levels from colonic tissues or in dialysates. Histological examination and measurements of peroxidase activities of inflamed tissues indicated edema, hyperplasia and neutrophil infiltration. Significant elevated LTB4 and prostaglandin E2(PGE2) levels were found but only slight elevations in sulfidopeptide LTs occurred. A slight elevation in eosinophil peroxidase indicated that eosinophil infiltration also occurred. The increase in sulfidopeptide LT levels appeared insufficient by itself to alter secretory responses in the distal colon. However, combined with other immunocyte products such as PGs, the sulfidopeptide LTs may influence the symptomology of inflammatory bowel disease.

Acetic Acid↗

PubMed1996

A case study of the natural attenuation of gas condensate hydrocarbons in soil and groundwater.

Condensate liquids have been found to contaminate soil and groundwater at two gas production sites in the Denver Basin operated by Amoco Production Co. These sites have been closely monitored since July 1993 to determine whether intrinsic aerobic or anaerobic bioremediation of hydrocarbons occurs at a sufficient rate and to an adequate end point to support a no-intervention decision. Groundwater monitoring and analysis of soil cores suggest that intrinsic bioremediation is occurring at these sites by multiple pathways, including aerobic oxidation, Fe(III) reduction, and sulfate reduction.

Environmental Monitoring↗

PubMed1996

Increased delayed type hypersensitivity in rats subjected to unilateral mononeuropathy is mediated by neurokinin-1 receptors.

An animal model or peripheral mononeuropathy was utilized in the present study to investigate the potential role of substance P (SP) in modifying immune responses associated with chronic pain conditions. Animals subjected to unilateral sciatic ligation and sham-operated animals were sensitized with keyhole limpet hemocyanin (KLH) and subsequently challenged in the ipsilateral or contralateral hind paw to produce a delayed-type hypersensitivity (DTH) response. Subcutaneous microdialysis and radioimmunoassay were used to measure interstitial fluid SP levels in the challenged tissue prior to and following immune challenge in control and neuropathic animals. Following immune challenge, there was a significant increase in the concentration of SP in tissue dialysate samples from the challenged paw of both sham-operated and neuropathic animals. However, tissue SP levels in neuropathic animals were more than two-fold higher than those obtained from sham-operated controls following challenge. SP concentration remained elevated for 2.5 h following immune challenge in neuropathic animals compared to 90 min in sham-operated animals. Compared with controls, neuropathic animals also exhibited an increased DTH response that was reversed, in a dose-related fashion, by the non-peptide NK-1 receptor blocker L-703,606. The same antagonist had no effect in sham-operated animals. These data suggest that the increased DTH response in animals subjected to unilateral mononeuropathy involves SP and NK-1 receptors present in the challenged tissue.

Animals↗

PubMed1996

Mucosal protection through active intestinal secretion: neural and paracrine modulation by 5-hydroxytryptamine.

5-Hydroxytryptamine (5-HT) is widely distributed within enteroendocrine cells and neurons of the digestive tract. It stimulates active anion secretion in the intestinal epithelium, an effect which promotes the dilution and elimination of luminal pathogens. The intestinal secretory effects of 5-HT appear to be mediated in part by epithelial 5-HT2 like receptors that are linked to phosphatidylinositol turnover. In addition, 5-HT appears to interact with 5-HT3 or 5-HT4 receptors on submucosal neurons to elicit neuronal depolarization and an associated increase in intestinal secretion. Although the precise cellular mechanisms by which 5-HT modulates mucosal ion transport are incompletely understood, it is clear that 5-HT plays an important role as a intestinal secretagogue in certain diarrheal states, in laxation, and in intestinal hypersensitivity reactions.

Animals↗

PubMed1996

Cancer-associated human papillomavirus types are selectively increased in the cervix of women in the first trimester of pregnancy.

OBJECTIVE: Because of incomplete data in the current literature, we sought to determine whether pregnancy is an independent risk for the detection of human papillomavirus infection. STUDY DESIGN: Pregnant patients in their first trimester who are seen for routine care at an obstetrics clinic and nonpregnant patients receiving routine care at a sexually transmitted diseases clinic and a gynecology clinic were recruited. Cervical cells were collected by saline solution lavage, and deoxyribonucleic acid was extracted and tested for the presence of human papillomavirus deoxyribonucleic acid with the hybrid capture assay. This assay detects the deoxyribonucleic acid of five "low cancer risk" and nine "high cancer risk" human papillomavirus types with two separate pools of deoxyribonucleic acid probes. RESULTS: Results from 245 pregnant women, 248 patients from the sexually transmitted diseases clinics, and 246 gynecology clinic patients were analyzed. Human papillomavirus deoxyribonucleic acid was detected in samples from 31% of the pregnant patients compared with 17.7% and 18.6% of the sexually transmitted diseases clinic and gynecology clinic patients, respectively. There was no significant difference in positivity for the "low-risk" human papillomavirus types among the three groups (positivity rates from 8.9% to 12.7%), but the pregnant patients had a significantly higher positivity rate for the "high-risk" human papillomavirus types (24.9% compared with 13.3% and 11.4% for the sexually transmitted diseases and gynecology clinic patients, respectively; p < 0.001). A multiple logistic regression analysis showed that pregnancy was an independent predictor of a positive test result for a "high-risk" human papillomavirus type (odds ratio 1.79, 95% confidence interval 1.11 to 2.89) but not a positive test result for a "low-risk" type. CONCLUSIONS: Because sexual activity was not greater among the pregnant patients, we propose that the increased detection of "high-risk" human papillomavirus types among the pregnant patients represents a selective activation of these viruses by hormonal or immunologic factors associated with pregnancy.

Adult↗

PubMed1996

Adenoviral delivery of low-density lipoprotein receptors to hyperlipidemic rabbits: receptor expression modulates high-density lipoproteins.

Plasma concentrations of low-density lipoproteins (LDLs) and high-density lipoproteins (HDLs) are inversely related in several dyslipoproteinemias. To elucidate the interactions between these lipoproteins, we used a recombinant adenovirus (hLDLR-rAdV) to express human LDL receptors (hLDLRs) in LDL receptor-deficient rabbits. hLDLR-rAdV administration resulted in hepatocyte expression and a reduction of total, intermediate-density lipoprotein (IDL), and LDL cholesterol. In addition, we found that hLDLR-rAdV treatment induced (1) increased very-low-density lipoprotein (VLDL) cholesterol, (2) increased VLDL, IDL and LDL triglycerides, (3) decreased alpha- and pre-beta-migrating apolipoprotein E (apo E) and decreased pre-beta-migrating apo A-I at 2 to 4 days posttreatment, and (4) increased total plasma apo A-I and pre-beta-migrating apo A-I beginning 8 to 10 days posttreatment. Virtually all plasma apo A-I was present on alpha- and pre-beta-HDL. Pre-beta-HDL particles with size and electrophoretic properties consistent with nascent HDL demonstrated the greatest relative apo A-I enrichment following hLDLR-rAdV treatment. In summary, enhanced expression of hepatocyte LDLRs by hLDLR-rAdV treatment markedly altered apo A-I-containing lipoproteins and IDL and LDL. The use of recombinant viruses to express physiologically relevant genes in intact animals, analogous to transfection of cells in culture, provides a new strategy for the evaluation of effects of specific gene products on metabolic systems in vivo.

Adenoviridae↗

PubMed1996

Evaluation of smoking on the physical activity and depressive symptoms relationship.

Physical activity is inversely associated with depressive symptoms, and cigarette smoking is positively associated with depressive symptoms. Data from the first National Health and Nutrition Examination Survey (NHANES I) and the NHANES I Epidemiologic Follow-up study were analyzed to determine whether the relationship between physical activity and self-reported distress (depressive symptoms as measured by the Center for Epidemiologic Studies Depression Scale) was different for cigarette smokers and nonsmokers. Logistic regression was used to calculate odds ratios (adjusted for age, race, sex, education, alcohol use, and perceived health status) for depressive symptoms (> or = 16) associated with physical activity and smoking status among 2,054 respondents. At baseline, the odds ratio for depressive symptoms was about 2 times higher for moderately active smokers and nonsmokers, and 3 times higher for low active smokers and nonsmokers, compared with highly active nonsmokers. For 1,132 persons with a low number of depressive symptoms (< 16) at baseline, the incidence of depressive symptoms after 7-9 yr of follow-up was about 2 times higher for low/moderately active smokers and nonsmokers than for highly active nonsmokers. The association between physical activity and the prevalence and incidence of depressive symptoms is not significantly modified by smoking status.

Adult↗

PubMed1996

Sequence conservation within the major capsid protein of human papillomavirus (HPV) type 18 and formation of HPV-18 virus-like particles in Saccharomyces cerevisiae.

The major capsid protein L1 of human papillomaviruses (HPVs) has been identified as a promising candidate antigen for a prophylactic HPV vaccine. Since amino acid sequence heterogeneity has been demonstrated for the L1 genes within individual HPV types, nucleotide sequences of L1 were determined from six HPV-18 clinical isolates and the cervical carcinoma cell line SW756 and compared to the published HPV-18 prototype sequence. The sequences were almost identical between the clinical isolates and SW756 but differed markedly from the published prototype sequence. Resequencing the prototype HPV-18 revealed that these differences were due to sequencing artifacts of the prototype HPV-18 sequence archived in GenBank. Thus, the HPV-18 L1 genes seem to display a very high level of sequence conservation. The HPV-18 L1 gene derived from SW756 was expressed in Saccharomyces cerevisiae and self-assembly of the L1 protein into virus-like particles was demonstrated.

Base Sequence↗

PubMed1996

Transcriptional activation of the human epidermal growth factor receptor promoter by human p53.

The human epidermal growth factor receptor (EGFR) promoter is activated by both wild-type and tumor-derived mutant p53. In this communication, we demonstrate that EGFR promoter sequence requirements for transactivation by wild-type and mutant p53 are different. Transient-expression assays with EGFR promoter deletions identified a wild-type human p53 response element, 5'-AGCTAGACGTCCGGGCAGCCCCCGGCG -3', from positions --265 to --239. Electrophoretic mobility shift analysis and DNase I footprinting assays indicated that wild-type p53 binds sequence specifically to the response element. Using circularly permuted DNA fragments containing the p53-binding site, we show that wild-type p53 binding induces DNA bending at this site. We further show that the EGFR promoter is also activated by tumor-derived p53 mutants p53-143A, p53-175H, p53-248W, p53-273H, and p53-281G. However, the transactivation by mutant p53 does not require the wild-type p53-binding site. The minimal EGFR promoter from positions --104 to --20 which does not contain the wild-type p53-binding site is transactivated by the p53 mutants but not by the wild-type protein, showing a difference in the mechanism of transactivation by wild-type and mutant p53. Transactivation of the EGFR promoter by p53 may represent a novel mechanism of cell growth regulation.

Amino Acid Sequence↗

PubMed1996

Collagen crosslinks in longissimus muscle from lambs expressing the callipyge gene.

The objective of this study was to determine whether increased amounts of collagen and (or) hydroxylysylpyridinoline crosslinks in longissimus muscle are partially responsible for decreased tenderness when callipyge lambs are compared to normal lambs. The longissimus muscle was used because we believe tenderness is a greater problem in loin chops of callipyge lambs than it is in other cuts. Ten normal and 10 half-sibling lambs expressing the callipyge gene were compared. Lambs were slaughtered at approximately 8 mo of age when they reached a target weight of 59 kg. Dressing percentages were higher for the leaner callipyge lambs that exhibited larger longissimus muscle areas and heavier leg weights (P < .01). Warner-Bratzler shear values for longissimus muscle from callipyge lambs were higher (P < .01) than those from normal lambs. The higher shear values were not explained by amount of muscle collagen or by hydroxylysylpyridinoline crosslink concentration because both collagen percentage (P < .09) and crosslink concentration (P < .04) were lower in callipyge lambs. Therefore, attempts to modify shear values and make loin chops from callipyge lambs more acceptable to consumers should focus on the myofibrillar fraction of muscle.

Amino Acids↗

PubMed1996

Blood-brain barrier breach following cortical contusion in the rat.

Adult Fisher 344 rats were subjected to a unilateral impact to the dorsal cortex above the hippocampus at 3.5 m/second, resulting in a 2-mm cortical depression. This caused severe cortical damage and neuronal loss in hippocampus subfields CA1, CA3, and hilus. Breakdown of the blood-brain barrier (BBB) was assessed by injecting the protein horseradish peroxidase (HRP) 5 minutes prior to or at various times after injury (5 minutes, 1, 3, 6, and 12 hours, 1, 2, 5, and 10 days). Animals were killed 1 hour after HRP injection and brain sections were reacted with diaminobenzidine to visualize extravascular accumulation of the protein. Maximum staining occurred in animals injected with HRP 5 minutes prior to or 5 minutes after cortical contusion. Staining at these time points was observed in the ipsilateral cortex of the impact area and areas adjacent to it, as well as in the ipsilateral hippocampus. Some modest staining occurred in the dorsal contralateral cortex near the superior sagittal sinus. Cortical HRP staining gradually decreased at increasing time intervals postinjury. By 10 days, no HRP staining was observed in any area of the brain. In the ipsilateral hippocampus, HRP staining was absent by 3 hours postinjury and remained so at the 6- and 12-hour time points. Surprisingly, HRP staining was again observed in the ipsilateral hippocampus 1 and 2 days after cortical contusion, indicating a biphasic opening of the BBB following head trauma and a possible second wave of secondary brain damage days after the contusion injury. These data indicate that regions not initially destroyed by cortical impact, but evidencing BBB breach, may be accessible to neurotrophic factors administered intravenously both immediately and days after brain trauma.

Animals↗

PubMed1996

Influence of adrenergic and cholinergic mediators on the equine jejunum in vitro.

OBJECTIVE: To characterize the response of equine jejunal smooth muscle to adrenergic and cholinergic mediators. DESIGN: Evaluation of myogenic responses, using an in vitro model. SAMPLE POPULATION: Intestinal tissues were obtained from horses without gastrointestinal tract disorders or systemic disease. PROCEDURE: Baseline myogenic tone and amplitude and frequency of contraction were determined for suspended jejunal muscle strips. The level of adrenergic and cholinergic regulation was assessed, using atropine and adrenoceptor antagonists. The response of the muscles to norepinephrine was characterized, using adrenergic blockade and alpha- and beta-agonists. RESULTS: Adrenergic and cholinergic blockade had minimal effect on baseline myogenic activity. However, alpha 1- and beta 2-agonists induced significant (P < 0.05) decreases in the amplitude and frequency of contraction. Surprisingly, alpha 2-agonists caused an increase in the contraction amplitude of longitudinal muscle fibers (neurogenic in origin). Change in circular muscle activity was not induced by alpha 2-agonists. Norepinephrine induced a similar selective response and was inhibited by yohimbine. CONCLUSIONS: Baseline jejunal activity appears to be myogenic in origin and can function independently of sympathetic and parasympathetic input. However, intestinal smooth muscle can be affected by adrenergic agonists and potentially by increased concentrations of circulating catecholamines. Norepinephrine may act by altering the activity of other neurotransmitters. Differing responses between circular and longitudinal muscle fibers indicates a need to evaluate both components. CLINICAL RELEVANCE: Selective alpha 2-agonists may be potentially useful for motility modification of the equine jejunum. Therapeutic use of adrenergic blockade will be effective only in cases of increased adrenergic stimulation.

Acetylcholine↗

PubMed1995

Human papillomavirus type 11 E1--E4 and L1 proteins colocalize in the mouse xenograft system at multiple time points.

The most abundant viral mRNA species in HPV 11-infected tissue consists of two exons, joining a segment of open reading frame (ORF) E1 to ORF E4, potentially encoding the E1--E4 protein. The L1 ORF encodes the major capsid protein of HPV. Our previous studies demonstrated colocalization of the HPV 11 E1--E4 and L1 proteins within the same cells of HPV 11-infected human foreskin implants grown in athymic mice (the mouse xenograft system) and removed 12 weeks after implantation. Prior studies have demonstrated E1--E4 transcripts early in infection and throughout the HPV 11-infected epithelium, while L1 transcripts are detected later, and in a subset of E1--E4 mRNA-positive differentiated epithelial cells. Therefore, E1--E4 protein may be produced at an earlier time point or in less differentiated cells than the L1 protein. To study these questions, athymic mice were implanted with HPV 11-infected human foreskin fragments. Mice were sacrificed at 1-week intervals beginning 2 weeks after implantation of tissue. The E1--E4 and L1 proteins colocalized to the same differentiated epithelial cells or to tight clusters of cells in differentiated epithelial layers of HPV 11-infected implants. The E1--E4 and L1 proteins were first detected 4 weeks after implantation. E1--E4 protein was detected in the region of the cell membrane and cytoplasm, and never in the nucleus. L1 protein was only detected in the nucleus. Both proteins were detected in implants containing high viral copy numbers. No specific histologic changes were uniformly associated with detection of these proteins. The tight coupling of the E1-E4 and L1 proteins at multiple time points suggests that expression of both proteins is necessary to complete the virus life cycle.

Animals↗