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D M Brown

Publications and source records attributed to D M Brown.

At least 145 records · Page 8Linked to original sources
PubMed1993

Abnormal renal hemodynamic response to reduced renal perfusion pressure in diabetic rats: role of NO.

Diabetic rats manifest abnormal renal hemodynamic responses, with persistent renal vasodilation at reduced renal perfusion pressures. We hypothesized that in diabetes, renal hemodynamics are modulated by increased activity of the endogenous vasodilator, NO. In anesthetized Munich-Wistar rats, after 6 wk of streptozotocin-induced, insulin-treated diabetes, and in age-matched, nondiabetic littermates (n = 7-8), basal renal hemodynamics and responses to graded reductions in renal perfusion pressure were determined before and after intrarenal arterial infusion of the NO synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME). An identical protocol was followed in a second cohort of rats pretreated with indomethacin (4 mg/kg iv). Diabetic rats demonstrated hyperglycemia, renal enlargement, hyperfiltration, and increased urinary excretion of the stable NO metabolites, NO2 and NO3. L-NAME eliminated basal hyperfiltration in diabetic rats, and L-NAME, but not indomethacin, also eliminated persistent renal vasodilation at reduced renal perfusion pressure. We conclude that in a rat model of diabetes, increased endogenous NO activity may play a role in basal hyperfiltration and in the persistent renal vasodilatation manifested at reduced renal perfusion pressures.

Amino Acid Oxidoreductases↗
PubMed1993

LFA-1 and ICAM-1 in homotypic aggregation of rat alveolar macrophages: organic dust-mediated aggregation by a non-protein kinase C-dependent pathway.

We have examined the role of cell adhesion molecules in the homotypic aggregation of rat alveolar macrophages after exposure to wool and grain dusts. Molecules such as bacterial lipopolysaccharide (LPS) and phorbol myristate acetate (PMA) can upregulate adhesion molecules, resulting in aggregation of lymphocytes. In rats treated intratracheally with an inspirable sample of wool dust collected from the air of British wool textile mills, and sieved grain dust, aggregates of macrophages were present in the bronchoalveolar lavage (BAL). Our hypothesis was that substances present on the dust surface could activate and upregulate adhesion molecules of the CD11/CD18 complex on the BAL cells and account for the aggregates. Macrophages from untreated rats form aggregates in vitro, which averaged 19 cells/aggregate; when treated with both wool and grain dusts, this rose to 25 and 24 cells/aggregate, respectively. LPS, PMA, and the proinflammatory cytokine tumor necrosis factor (TNF) also caused increases in aggregate size. Staurosporine, an inhibitor of protein kinase C (PKC), reduced the number of cells per aggregate from 35 cells/aggregate in LPS- and PMA-treated macrophages to 18 cells/aggregate, the same as untreated. In contrast, staurosporine had no effect in reducing the size of aggregates produced by the organic dusts. Removal of divalent cations, which are essential for maintaining integrin stability and PKC activity, resulted in complete abolition of aggregate formation. Treatment with monoclonal antibodies to lymphocyte function-associated antigen-1 (LFA-1) alpha and beta and intercellular adhesion molecule-1 (ICAM-1) resulted in the inhibition of aggregate formation in a dose-dependent manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaloids↗
PubMed1993

Children's creative thinking and color discrimination.

60 children in Grades 3 through 6 from two schools were administered the Farnsworth Munsell 100-Hue Test and teachers provided a measure of different aspects of each child's creative thinking on the Williams Scale of Children's Divergent Thinking. Fluency and imagination scores were positively associated with color discrimination. While other dimensions of creative thinking did not correlate with color discrimination, some correlations suggested thematic connections between color discrimination and other manifestations of creative thinking as evaluated by teachers. Color discrimination was also positively associated with age, as older children differentiated between small differences in colors better than younger children. As intelligence or other variables may be relevant, further study is needed.

Age Factors↗
PubMed1993

Closure of complex abdominal wall defects with bilateral rectus femoris flaps with fascial extensions.

Large full-thickness abdominal wall defects present a difficult reconstructive problem. Synthetic mesh has significant drawbacks and should be used only as a temporizing measure. Ideally abdominal wall defects should be resurfaced with well-vascularized autologous fascia and skin. A variety of myofascial, myocutaneous, and myofasciocutaneous flaps have been described. This report describes two cases of near-total abdominal wall reconstruction using bilateral rectus femoris myocutaneous flaps with fasciocutaneous extensions of superficial thigh fascia and skin. In both cases the rectus femoris flaps and fascial extensions healed, and the patients went on to full recovery. In one patient the skin over the fascial extension did not survive and had to be debrided and the underlying vascularized fascia resurfaced with a skin graft. The extended rectus femoris flap is a reliable and versatile flap that leaves negligible functional deficits. The fascial extensions are reliable and well perfused and should be included in the reconstruction of larger abdominal wall defects. The skin overlying the fascial extensions is less reliable, and selective use is recommended.

Abdominal Muscles↗
PubMed1992

Synthesis of oligodeoxyribonucleotides containing degenerate bases and their use as primers in the polymerase chain reaction.

Heptadecaoligodeoxyribonucleotides containing one or more of the bases, 6H,8H-3,4-dihydropyrimido[4,5-c][1,2]oxazin-7-one (P), 2-amino-6-methoxyaminopurine (K), and hypoxanthine (I) and combinations of P with K and I have been synthesised on a DNA synthesiser. The stability of duplexes containing these basemodified oligomers with P/A, P/G, K/C and K/T; P/A, P/G, I/C, I/T and I/A, I/G, I/C, I/T base pairs were compared by measuring their melting transition (Tm) values. Oligomers containing both P and K and P and I were more stable than those with I alone or with mismatches. These oligomers together with one with a P base at the 3'-end were used as primers in polymerase chain reaction (PCR) experiments. They were all effective primers except one with I alone and a triple mismatch. Thus the use of the degenerate bases P and K in primer design is established.

Amides↗
PubMed1992

Procollagen II gene mutation in Stickler syndrome.

Four affected members of a family with Stickler syndrome were found to have a single base-pair deletion resulting in a translational frameshift in exon 40 of the procollagen II (COL2A1) gene on chromosome 12. This mutation was not seen in any of five clinically unaffected family members or in any of 15 unrelated control patients. All affected members had distinctly abnormal vitreous syneresis and all had retinal perivascular pigmentation. Retinal detachments occurred in three of the four affected patients. Three of the four affected patients had peripheral cortical "wedge" cataracts, and the fourth had extensive nuclear sclerosis. Abnormalities of the soft palate were found in all four affected patients. All patients reported severe joint pains, and epiphyseal dysplasia was found radiographically in all patients.

Adolescent↗
PubMed1992

Decreased wound contraction with fibrin glue--treated skin grafts.

Skin grafts can be used effectively to inhibit wound contraction. A critical element of this inhibition is the adherence of the graft to the wound bed. Fibrin glue has been shown to increase the adherence of skin grafts to wound beds. We therefore devised an experiment to determine the effect of fibrin glue on skin graft inhibition of wound contraction. Two 2.5 x 2.5-cm full-thickness defects were created on the dorsa of 15 Sprague-Dawley rats. Thirty partial-thickness grafts were harvested from isogeneric donor animals using a brown dermatome. Prior to grafting, one full-thickness defect, each animal received 0.2 mL of fibrin glue (Immuno AG, Vienna, Austria). The adjacent wound served as the control and received 0.2 mL of normal saline. Grafts were applied, sutured, and protected with an occlusive dressing. The size of graft sites treated with fibrin glue or normal saline was determined at the time of graft application and thereafter at 3-day intervals for 21 days using standardized photographic techniques. The percentage of change from initial wound size at each point was recorded for each group. Graft sites treated with fibrin glue contracted less than the controls from the ninth postgraft day to the completion of the study. The mechanism by which fibrin glue inhibits wound contraction may be related to increased adherence of grafts to the underlying wound bed. As an adjunct in skin grafting, fibrin glue may offer certain advantages that are not achieved by suturing alone.

Animals↗
PubMed1992

Activated human peripheral blood neutrophils produce epithelial injury and fibronectin breakdown in vitro.

The ability of peripheral blood neutrophils to injure elements of the alveolar septum was assessed. Experiments consisted of activating previously isolated neutrophils (PMNs) with a soluble (phorbol myristate acetate, PMA) and a particulate (zymosan) trigger, and measuring detachment of 51Cr-labeled epithelial cells. In addition, the mechanisms of epithelial injury were investigated by including anti-proteinase and antioxidants in the system. Untriggered PMNs produced only slight detachment injury to epithelial cells at two effector-target cell ratios, this effect being dramatically increased after triggering with PMA; zymosan caused triggering but less than was produced by PMA. Alpha-1-protease inhibitor produced a decrease in detachment when both PMA- and zymosan-triggered cells were the effectors; superoxide dismutase did not significantly reduce detachment. The ability of triggered PMNs to cause proteolysis of fibronectin, as measured in a radiolabeled fibronectin matrix degradation assay, was related to their triggerability in the detachment assay, zymosan being largely ineffective in triggering enhanced proteolysis. These findings suggest that fibronectin is important in maintaining the integrity of the alveolar epithelial surfaces. Furthermore, in inflamed alveoli, activated PMNs can release proteinases, which cause degradation of this matrix component leading to compromise of the alveolar epithelial barrier.

Cell Adhesion↗
PubMed1992

Prostaglandin E2 induces apoptosis in immature normal and malignant B lymphocytes.

The purpose of this research was to determine whether prostaglandin E2 (PGE2), a major product of macrophages which can kill certain murine B cell lymphomas, induces death by a necrotic mechanism or by an alternate pathway called apoptosis. CH31 is a phenotypically "immature" B cell lymphoma which resembles immature neonatal B cells in its susceptibility to killing by reagents which cross-link surface immunoglobulin (sIg). In the present study we first show that PGE2, but not the closely related prostanoid, PGF2 alpha, kills CH31 lymphoma cells. In contrast, CH12, a phenotypically "mature" lymphoma which is not negatively affected by sIg cross-linking, is not induced to die after exposure to PGE2. Agarose gel electrophoresis demonstrated that the DNA of PGE2-treated CH31, but not CH12 cells, is cleaved into characteristic 200 base pair oligonucleosomal fragments indicative of an apoptotic mechanism of death. However, a necrotic form of death, indicated by random DNA cleavage which produces a smear following electrophoresis, could be induced by treatment of CH12 or CH31 with anti-class II MHC antibodies and complement. The apoptotic mechanism of CH31 cell killing by PGE2 was confirmed using scanning electron microscopy which demonstrated the unique membrane blebbing and bubbling pathognomonic of this form of death. Finally, using a recently devised flow cytometric method to study apoptosis in heterogeneous cell populations, we compared the ability of anti-IgM, PGE2, or PGF2 alpha to induce apoptosis in B lymphocytes from neonatal or adult mice. Anti-IgM, and to a lesser extent PGE2, but not PGF2 alpha, induces apoptosis in a fraction of neonatal B cells. None of these treatments induced cell death in B lymphocytes from mature mice. Overall, these observations suggest that PGE-secreting cells such as macrophages, which inhabit the B cell microenvironments of lymphoid organs, may eliminate a subset of immature B lymphocytes and may be important in controlling the spread of PGE-sensitive malignant B lymphoma cells.

Animals↗
PubMed1992

The effect of intralesional 5-fluorouracil therapeutic implant (MPI 5003) for treatment of basal cell carcinoma.

BACKGROUND: Basal cell carcinomas (BCCs) are usually treated with ablative procedures. A nonsurgical treatment alternative would be of value in selected patients. OBJECTIVE: We evaluated the safety and efficacy of a new preparation for intralesional sustained-release chemotherapy with MPI 5003, 5-Fluorouracil Therapeutic Implant, for treatment of BCCs. METHODS: Two doses of intralesional MPI 5003 (0.25 and 0.5 ml) were compared in a double-blind study of 20 patients with biopsy-proven BCC. One BCC per patient was treated weekly for up to 6 weeks and followed up monthly for 3 months until excisional biopsy for histologic examination. Before excision the cosmetic appearance of the test site was graded. RESULTS: Eighty percent of 10 BCCs treated with 0.5 ml of MPI 5003 had histologically confirmed cures as compared with 60% of 10 tumors treated with the lower dose (0.25 ml). Cosmetic assessments before excision were typically good to excellent. No systemic side effects occurred. CONCLUSION: Results indicate the potential of MPI 5003 for targeted local chemotherapy for BCC.

Adult↗
PubMed1992

Acute promyelocytic infiltration of the optic nerve treated by oral trans-retinoic acid.

BACKGROUND: Oral trans-retinoic acid has recently been shown to be an effective treatment modality for acute promyelocytic leukemia. This type of drug differs from traditional tumoricidal agents by promoting differentiation of the malignant, immature cells. METHODS: The authors describe a patient with optic nerve infiltration by acute promyelocytic leukemia documented ophthalmoscopically and confirmed by standardized echography and magnetic resonance imaging. High-resolution chromosome banding revealed the patient had a 15;17 chromosomal translocation known to be associated with acute promyelocytic leukemia. Treatment was instituted with oral all trans-retinoic acid without adjuvant radiotherapy or intrathecal chemotherapy. RESULTS: Results of serial bone marrow examination showed progressive differentiation of malignant cells with complete bone marrow remission. Results of serial ophthalmic examinations showed complete resolution of the leukemic optic nerve head infiltration. CONCLUSION: All trans-retinoic acid alone can be an effective treatment for optic nerve head infiltration in acute promyelocytic leukemia. This case suggests that radiation therapy may not be necessary in acute promyelocytic leukemia with optic nerve infiltration.

Administration, Oral↗
PubMed1992

An overview of renal pathology in insulin-dependent diabetes mellitus in relationship to altered glomerular hemodynamics.

Clinical diabetic nephropathy in man is the consequence of the development of a specific constellation of glomerular, tubular, vascular, and interstitial structural abnormalities accompanied by highly characteristic immunohistochemical alterations that, together, are unique to diabetes. Because changes resembling the specific pathology of diabetes do not develop in patients with conditions that lead to long-standing glomerular hyperfunction (such as unilateral nephrectomy), it is unlikely that glomerular hemodynamic abnormalities per se can be the cause of diabetic nephropathy. Whether hemodynamic abnormalities represent a risk factor that, in the presence of the diabetic state, can accelerate the rate of development of the basic lesions of diabetic nephropathy is currently unclear. However, there is considerable evidence that when the renal lesions of diabetes are far advanced, factors such as systemic hypertension can determine the rate of renal functional deterioration in diabetes as in other disorders. Although the diabetic rat may be a useful model for the study of aspects of the pathogenesis of diabetic nephropathy, much confusion has resulted from the inclusion of focal segmental glomerular sclerosis as a diabetic lesion. Similarly, the acceptance of all increases in urinary protein excretions in this model as resulting from or reflecting of diabetic nephropathology can be misleading. It is concluded that treatment aimed at manipulating renal hemodynamics in diabetic patients without evidence of renal disease should remain in the realm of clinical research.

Animals↗
PubMed1992

Epithelial and extracellular matrix injury in quartz-inflamed lung: role of the alveolar macrophage.

The bronchoalveolar leukocytes from quartz-inflamed lung were separated into macrophage-enriched and neutrophil-enriched populations on density gradients. Neutrophil-enriched populations showed the greatest activity in causing injury to epithelial cells and fibronectin in vitro. Inflammatory macrophage-enriched populations from quartz-exposed lung had the ability to cause fibronectin degradation but could not cause detachment injury to epithelial cells over and above that caused by control alveolar macrophages. Fibronectin damage in vivo could be an important factor in disordering the connective tissue scaffold of the lung, thereby favoring fibrosis. In vitro quartz stimulated more production of cytokines by alveolar macrophages than the inert particulate titanium dioxide. Cytokines could be important in upregulating adhesion molecules in the membranes of lung cells in vivo; this process could aid leukocyte/lung cell contact, allowing epithelial injury to be expressed, and could also be a factor leading to pathological change.

Animals↗
PubMed1992

Persistent inflammation and impaired chemotaxis of alveolar macrophages on cessation of dust exposure.

Rats were exposed by inhalation to coal mine dust, titanium dioxide, or quartz. The magnitude of the consequent inflammatory response was assessed by counting numbers and types of leukocytes in the bronchoalveolar lavage fluid. The magnitude of the inflammatory response reflected the toxicity of the dusts, with quartz eliciting the greatest recruitment of inflammatory leukocytes, coal mine dust less than quartz, and titanium dioxide eliciting no inflammation. To assess the persistence of the inflammation, groups of rats were maintained in room air for 30 or 60 days after cessation of dust exposure and then numbers of leukocytes were assessed. Bronchoalveolar leukocytes in rats exposed to coal mine dust were reduced after exposure, but in the quartz-exposed rats the numbers increased with time after exposure. The chemotactic responses of bronchoalveolar leukocytes from rats inhaling coal mine dust and quartz were reduced and remained so after a 30-day recovery period. Their reduced ability to chemotact did not fully prevent macrophages from leaving the bronchoalveolar region of dust-exposed rats. However, it is likely that the delayed removal of inflammatory leukocytes with the potential to injure the lung tissue may contribute to septal damage and so contribute to the pathogenesis of pneumoconiosis.

Animals↗
PubMed1991

Molecular basis for methoxyamine initiated mutagenesis. 1H nuclear magnetic resonance studies of base-modified oligodeoxynucleotides.

In order to reach a more detailed understanding of the mechanism of the mutagenic action of methoxyamine and of N4-methoxycytidine and its 2'-deoxyribo-analogue, the solution structures of the self-complementary octanucleotide, d(CGAATTCG) and its analogues, d(CGAATCCG), d(CGAATMCG) and d(CGAATPCG) (designated 8mer-AT, 8mer-AC, 8mer-AM, and 8mer-AP, respectively), were investigated by 1H nuclear magnetic resonance spectroscopy; M is N4-methoxycytosine (mo4C) and P is an analogue, the bicyclic dihydropyrimido[4,5-c][1,2]oxazin-7-one, in which the N-O bond is held in the anti configuration with respect to N3 of the cytosine ring. Correlated spectroscopy and nuclear Overhauser spectroscopy allowed assignment of the base, anomeric and H2'/H2" protons in 8mers-AT, -AM and -AP, and showed that all three had features consistent with a regular B-DNA duplex structure. Duplex-to-coil transition temperatures were determined to be 52(+/- 2) degrees C (8mer-AT), 51(+/- 2) degrees C (8mer-AP), 32(+/- 2) degrees C (8mer-AM); on the chemical shift timescale, the melting transition was fast for 8mer-AT and 8mer-AP, but slow for 8mer-AM. Imino proton spectra were indicative of Watson-Crick base-pairing in 8mers-AT, -AP and -AM. The 8mer-AP duplex had a structure and melting characteristics virtually identical with those of the 8mer-AT duplex. The preferred syn configuration of the methoxyl group in M had a destabilising effect on the 8mer-AM duplex. At low temperatures, the A.M base-pair was in fast equilibrium between Watson-Crick and wobble configurations, with the methoxyl function anti-oriented, but the melting transition was accompanied by isomerization of the methoxyl group to the syn conformation. This syn-anti isomerization was the rate-determining step in the duplex-to-coil transition. The 8mer-AC oligomer did not form a stable duplex.

Cytidine↗
PubMed1991

Synthesis and duplex stability of oligonucleotides containing adenine-guanine analogues.

The nucleosides N6-methoxy-2'-deoxyadenosine (dZ) and 2-amino-9-(2-deoxy-beta-ribofuranosyl)-6-methoxyaminopurine (dK) have been synthesised and converted into 5'-O-dimethoxytrityl 3'-(2-cyanoethyl N,N-diisopropylphosphoramidites). These monomers have been used in machine DNA synthesis to give a set of heptadecanucleotides containing up to three analogue nucleotides. The melting transitions (Tm) show that the 17-mer duplexes containing Z.T and Z.C base-pairs have closely similar stabilities, as have those containing K.T and K.C pairs. They are less stable than the corresponding fully complementary duplexes, but more stable than those containing mismatched pairs. This, in the case of dZ, is in accord with the amino-imino tautomeric ratio of approximately 1:4 observed for the nucleoside in methyl sulfoxide. The application of oligomers containing such "degenerate" bases in oligonucleotide probes and primers is discussed.

Adenine↗
PubMed1991

A multilens case.

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Contact Lenses↗