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Biomedical subjects

M J Miller

Publications and source records attributed to M J Miller.

At least 55 records · Page 3Linked to original sources
PubMed2001

Degradation of cyanobacterial hepatotoxins in batch experiments.

Bank filtration offers a cost effective and low maintenance technique for the removal of cyanobacterial hepatotoxins from drinking water. For bank filtration to be effective, the toxins must be degraded. The broad aim of this research was to determine whether the hepatotoxins, nodularin and microcystin-LR, could be completely removed from the soil/water matrix of three soils by microbial degradation. The results indicated that complete toxin removal was possible within 10-16 d in 2/3 soils that were incubated in the dark at 20 degrees C. The soils with the highest organic carbon content (2.9%) and the highest clay content (16.1%) were the most effective at removing the toxins in batch experiments. However, the sandy soil (98.5% sand) was incapable of degrading either toxin. The half-lives of toxin losses due to adsorption, desorption and degradation were calculated and for all soils. The degradation process had the highest half-life for both toxins. This suggested that degradation was likely to be the rate-limiting step of complete toxin removal. It was concluded that when a bank filtration site was being chosen, the degradation potential and the textural properties of the riverbank soil would be important when considering complete removal of cyanobacterial hepatotoxins.

Adsorption↗
PubMed2001

Preconditioning for cardioprotection against ischemia reperfusion injury: the roles of nitric oxide, reactive oxygen species, heat shock proteins, reactive hyperemia and antioxidants--a mini review.

BACKGROUND: In recent years, extensive studies have expanded the knowledge of the role of preconditioning (PC) for cardiac protection against ischemia reperfusion (I/R) injury. These studies are reviewed, and their relevance to the early and late phases of cardiac protection is discussed. CONCLUSIONS: First, there is strong evidence that the L-arginine-nitric oxide pathway plays a major role in PC. Second, early and late phase protection are probably distinct phenomena with similar effects induced by different mechanisms. Third, nitric oxide appears to be causally involved in both mechanisms. Fourth, nitric oxide produced by endothelial nitric oxide synthase (eNOS) in the early seconds of ischemia induces reactive hyperemia. It is proposed that reactive hyperemia provides the short-lived protection of early phase PC. It is unlikely that heat shock protein 72 (HSP72) or antioxidants have a role in early phase protection--both have a time lag of 12 to 24 h after PC before gene expression occurs. Fifth, late phase PC appears to depend on HSP72 gene expression mediated by the L-arginine-nitric-oxide pathway; during late phase PC, the inducible nitric oxide synthase (iNOS) content is increased while the eNOS content is unchanged. There is good evidence for an obligatory role of iNOS in cardiac protection afforded by the late phase of I/R protection in vivo. Sixth, the results of studies on the role of endogenous antioxidants in late phase protection are contradictory and further study is required. Seventh, studies on the signalling and transduction processes associated with preconditioning provide important information that may be helpful in the development of drugs protective against I/R injury. Finally, until such drugs are developed, PC by heat shock may be an effective alternative. A recent study in a human subject reported that HSP72 is upregulated by induction of hyperthermia within a range of moderate fever levels--oral temperatures between 38.6 degrees C and 39.5 degrees C. If this is confirmed, it seems plausible that inducing hyperthermia 24 h before major cardiac surgery may be an effective therapeutic strategy for protection against I/R.

Antioxidants↗
PubMed2000

Constitutive nitric oxide release modulates neurally-evoked chloride secretion in guinea pig colon.

The role of constitutive nitric oxide (NO) release in enteric neural pathways regulating ion transport was examined in guinea pig distal colon, in vitro and ex vivo. In in vitro studies, 43% of colonic preparations exhibited oscillations in baseline short-circuit current (Isc), which were reduced by tetrodotoxin (TTX). The NO chelator, hemoglobin (Hb), and neuronal NO synthase inhibitor, 7-nitroindazole (7-NI), significantly increased the baseline Isc in these tissues, which was reduced by TTX. In tissues without oscillations in baseline Isc, Hb reduced the Isc, while 7-NI had little effect. In all tissues, electrical field stimulation (EFS; 15 V/10 Hz) caused a biphasic increase in the Isc which was enhanced by both Hb and 7-NI. In the ex vivo studies, basal release of nitric oxide was significantly lower in colonic segments isolated from guinea pigs administered N omega-nitro-L-arginine methyl ester (L-NAME) i.p. compared to control tissues. Moreover, carbachol, caused a 10-fold increase in NO release in control tissues, but had no effect in tissues isolated from the L-NAME group. L-NAME increased tissue conductance and EFS-induced changes in Isc, which were reversed by L-arginine. However, carbachol-induced ion secretion was unaltered in the L-NAME group compared to control animals. The results suggest that, in guinea pig colon, constitutive enteric NO release tonically suppresses submucous neural activity and it is involved in the maintenance of basal epithelial chloride secretion and mucosal permeability. Hence, constitutive NO promotes a delicate balance between pro-absorptive and pro-secretory processes in guinea pig colon.

Animals↗
PubMed2000

Up-regulation of the IKCa1 potassium channel during T-cell activation. Molecular mechanism and functional consequences.

We used whole cell recording to evaluate functional expression of the intermediate conductance Ca(2+)-activated K(+) channel, IKCa1, in response to various mitogenic stimuli. One to two days following engagement of T-cell receptors to trigger both PKC- and Ca(2+)-dependent events, IKCa1 expression increased from an average of 8 to 300-800 channels/cell. Selective stimulation of the PKC pathway resulted in equivalent up-regulation, whereas a calcium ionophore was relatively ineffective. Enhancement in IKCa1 mRNA levels paralleled the increased channel number. The genomic organization of IKCa1, SKCa2, and SKCa3 were defined, and IK(Ca) and SK(Ca) genes were found to have a remarkably similar intron-exon structure. Mitogens enhanced IKCa1 promoter activity proportional to the increase in IKCa1 mRNA, suggesting that transcriptional mechanisms underlie channel up-regulation. Mutation of motifs for AP1 and Ikaros-2 in the promoter abolished this induction. Selective Kv1.3 inhibitors ShK-Dap(22), margatoxin, and correolide suppressed mitogenesis of resting T-cells but not preactivated T-cells with up-regulated IKCa1 channel expression. Selectively blocking IKCa1 channels with clotrimazole or TRAM-34 suppressed mitogenesis of preactivated lymphocytes, whereas resting T-cells were less sensitive. Thus, Kv1.3 channels are essential for activation of quiescent cells, but signaling through the PKC pathway enhances expression of IKCa1 channels that are required for continued proliferation.

Calcium Channel Blockers↗
PubMed2000

Cellular dissociation of NF-kappaB and inducible nitric oxide synthase in Helicobacter pylori infection.

The transcription factor nuclear factor kappaB (NF-kappaB) regulates the expression of inducible nitric oxide synthase (iNOS). We hypothesized that induction of iNOS in Helicobacter pylori gastritis may be due to NF-kappaB activation. Antral biopsy specimens from Helicobacter pylori-infected gastritis patients were collected before (n = 30) and after antimicrobial therapy to clear the infection (n = 22). Biopsies were assessed for NF-kappaB by immunohistochemistry (p65). The mRNA and protein of iNOS were localized by in situ RT-PCR and immunohistochemistry. Both of iNOS protein and mRNA were evident in stromal inflammatory cells, but absent in epithelia. Antimicrobial therapy resulted in a 73% reduction in iNOS levels (protein, p <.002). Nuclear staining for NF-kappaB p65 was evident in epithelial cells, especially in the neck region of gastric glands, and inflammatory cells. Treatment to clear H. pylori infection resulted in a 74% reduction in the epithelial staining for NF-kappaB p65 (p =.0001), whereas the lamina propria staining was unaltered. In conclusion, H. pylori infection activates NF-kappaB and iNOS expression. However, as the changes in NF-kappaB and iNOS with H. pylori clearance occurred in different cell types (epithelial vs. inflammatory), it appears that a NF-kappaB-dependent epithelial-derived mediator may be responsible for the induction of iNOS expression.

Base Sequence↗
PubMed2000

Total synthesis of the siderophore danoxamine.

The total synthesis of the linear trihydroxamate siderophore, Danoxamine, is described. Danoxamine is a siderophore component of the naturally occurring siderophore-drug conjugates Salmycin A-D. The synthesis of Danoxamine features a series of coupling reactions involving N-(5-benzyloxypentyl)-O-benzylhydroxylamine being linked by a succinoyl linker to N-(benzyloxy)-1,5-pentanediamine. Two more succinoyl linkers and another N-(benzyloxy)-1,5-pentanediamine were used in coupling reactions to afford the fully protected siderophore. The linear tetrabenzyl-protected trihydroxamate was deprotected to afford the natural product Danoxamine.

Hydroxamic Acids↗
PubMed2000

Design of a potent and selective inhibitor of the intermediate-conductance Ca2+-activated K+ channel, IKCa1: a potential immunosuppressant.

The antimycotic clotrimazole, a potent inhibitor of the intermediate-conductance calcium-activated K(+) channel, IKCa1, is in clinical trials for the treatment of sickle cell disease and diarrhea and is effective in ameliorating the symptoms of rheumatoid arthritis. However, inhibition of cytochrome P450 enzymes by clotrimazole limits its therapeutic value. We have used a rational design strategy to develop a clotrimazole analog that selectively inhibits IKCa1 without blocking cytochrome P450 enzymes. A screen of 83 triarylmethanes revealed the pharmacophore for channel block to be different from that required for cytochrome P450 inhibition. The "IKCa1-pharmacophore" consists of a (2-halogenophenyl)diphenylmethane moiety substituted by an unsubstituted polar pi-electron-rich heterocycle (pyrazole or tetrazole) or a -C≡N group, whereas cytochrome P450 inhibition absolutely requires the imidazole ring. A series of pyrazoles, acetonitriles, and tetrazoles were synthesized and found to selectively block IKCa1. TRAM-34 (1-[(2-chlorophenyl)diphenylmethyl]-1H-pyrazole) inhibits the cloned and the native IKCa1 channel in human T lymphocytes with a K(d) of 20-25 nM and is 200- to 1,500-fold selective over other ion channels. Using TRAM-34, we show that blocking IKCa1 in human lymphocytes, in the absence of P450-inhibition, results in suppression of mitogen-stimulated [(3)H]thymidine incorporation of preactivated lymphocytes with EC(50)-values of 100 nM-1 microM depending on the donor. Combinations of TRAM-34 and cyclosporin A are more effective in suppressing lymphocyte mitogenesis than either compound alone. Our studies suggest that TRAM-34 and related compounds may hold therapeutic promise as immunosuppressants.

Calcium Channel Blockers↗
PubMed2000

Cat's claw inhibits TNFalpha production and scavenges free radicals: role in cytoprotection.

Cat's claw (Uncaria tomentosa) is a medicinal plant from the Amazon River basin that is widely used for inflammatory disorders and was previously described as an inhibitor of NF-kappaB. Cat's claw was prepared as a decoction (water extraction) of micropulverized bark with and without concentration by freeze-drying. Murine macrophages (RAW 264.7 cells) were used in cytotoxicity assays (trypan blue exclusion) in response to the free radical 1, 1-diphenyl-2-picrilhydrazyl (DPPH, 0.3 microM) and ultraviolet light (UV) light. TNFalpha production was induced by lipopolysaccharide (LPS 0.5 microg/ml). Cat's claw was an effective scavenger of DPPH; the EC(50) value for freeze-dried concentrates was significantly less than micropulverized (18 vs. 150 microg/ml, p <.05). Cat's claw (10 microg/ml freeze-dried) was fully protective against DPPH and UV irradiation-induced cytotoxicity. LPS increased TNFalpha media levels from 3 to 97 ng/ml. Cat's claw suppressed TNFalpha production by approximately 65-85% (p <.01) but at concentrations considerably lower than its antioxidant activity: freeze-dried EC(50) = 1.2 ng/ml, micropulverized EC(50) = 28 ng/ml. In conclusion, cat's claw is an effective antioxidant, but perhaps more importantly a remarkably potent inhibitor of TNFalpha production. The primary mechanism for cat's claw anti-inflammatory actions appears to be immunomodulation via suppression of TNFalpha synthesis.

Animals↗
PubMed2000

Effects of transforming growth factor beta1 released from biodegradable polymer microparticles on marrow stromal osteoblasts cultured on poly(propylene fumarate) substrates.

Recombinant human transforming growth factor beta1 (TGF-beta1) was incorporated into microparticles of blends of poly(DL-lactic-co-glycolic acid) (PLGA) and poly(ethylene glycol) (PEG) to create a delivery vehicle for the growth factor. The entrapment efficiency of TGF-beta1 in the microparticles containing 5% PEG was 40.3 +/- 1.2% for a TGF-beta1 loading density of 6.0 ng/1 mg of microparticles. For the same loading, 17.9 +/- 0.6 and 32.1 +/- 2.5% of the loaded TGF-beta1 was released after 1 and 8 days, respectively, followed by a plateau for the remaining 3 weeks. Rat marrow stromal cells showed a dose response to TGF-beta1 released from the microparticles similar to that of added TGF-beta1, indicating the activity of TGF-beta1 was retained during microparticle fabrication and after TGF-beta1 release. An optimal TGF-beta1 dosage of 1.0 ng/mL was determined through a 3-day dose response study for maximal alkaline phosphatase (ALP) activity. The TGF-beta1 released from the microparticles loaded with 6.0 ng TGF-beta1/1 mg of microparticles for the optimal dosage of TGF-beta1 enhanced the proliferation and osteoblastic differentiation of marrow stromal cells cultured on poly(propylene fumarate) substrates. The cells showed significantly increased total cell number, ALP activity, and osteocalcin production with values reaching 138,700 +/- 3300 cells/cm(2), 22.8 +/- 1.5 x 10(-7) micromol/min/cell, and 15.9 +/- 1.5 x 10(-6) ng/cell, respectively, after 21 days as compared to cells cultured under control conditions without TGF-beta1. These results suggest that controlled release of TGF-beta1 from the PLGA/PEG blend microparticles may find applications in modulating cellular response during bone healing at a skeletal defect site.

Animals↗
PubMed2000

Structure and localization of mouse Pmscl1 and Pmscl2 genes.

Sera from some patients with polymyositis-scleoderma overlap syndrome (PM-SCL) recognize two antigenically unrelated proteins, PMSCL1 and PMSCL2. Complete mouse Pmscl1 and Pmscl2 cDNA sequences, chromosomal localizations, exon/intron structure, and promoter region sequences of the mouse Pmscl2 gene are presented. The PMSCL1 gene was found to overlap significantly with cyclin A2 in both human and mouse. As such, it may be deduced that PMSCL1 sequences map to human chromosome 4q27 and the proximal portion of mouse chromosome (Chr) 3 where human and mouse cyclin A2 genes reside. Analysis of human and mouse PMSCL1 cDNA sequences provides evidence that the PMSCL1 protein is 68 amino acids longer than previously thought. A BAC containing mouse Pmscl2 was localized to distal mouse Chr 4 by FISH. This BAC contains the microsatellite D4Mit310. D4Mit310 colocalizes with a number of genes that map to human 1p36. In fact, a STS (G25404) located 54.6 cR from the top of human chromosome 1 was found to contain PMSCL2 sequence upon BLAST search.

5' Untranslated Regions↗
PubMed2000

Melatonin suppression by light in euthymic bipolar and unipolar patients.

BACKGROUND: Previous studies have suggested that bipolar patients are supersensitive to light suppression of melatonin and that this may be a trait marker for genetic vulnerability. The present study was an attempt to replicate and extend this observation. Propranolol hydrochloride effects were compared with light effects because of the documented influence of beta-adrenergic receptors on melatonin production. Nighttime levels of corticotropin and cortisol were also examined as potential trait vulnerability markers. METHODS: Melatonin levels in euthymic bipolar patients (n= 29) were tested before and after 500-lux light was administered between 2 and 4 AM and on a separate night in the dark. Results were compared with those of a group of patients with unipolar depression (n= 24) and with those of a group of non-psychiatrically ill control subjects (n= 50). Lithium effects and propranolol effects were tested in subgroups. RESULTS: No group differences were seen in light suppression among bipolar patients, unipolar patients, and controls; an analysis of the whole group did not reveal differences in propranolol effect, differences in corticotropin or cortisol levels, or evidence for a lithium effect. However, patients with bipolar I affective disorder showed the following: (1) significantly lower melatonin levels on the light night, at baseline and following light exposure; and (2) a later peak time for melatonin on the dark night. CONCLUSIONS: The general hypothesis of increased light sensitivity in bipolar patients was not supported. However, melatonin secretion abnormalities were confirmed in the subgroup with bipolar I disorder. Further assessments of circadian rhythm disruption as a vulnerability marker in bipolar illness are indicated.

Adrenocorticotropic Hormone↗
PubMed2000

Acute excitotoxic injury induces expression of monocyte chemoattractant protein-1 and its receptor, CCR2, in neonatal rat brain.

Chemokines are a family of structurally related cytokines that activate and recruit leukocytes into areas of inflammation. The "CC" chemokine, monocyte chemoattractant protein (MCP)-1 may regulate the microglia/monocyte response to acute brain injury. Recent studies have documented increased expression of MCP-1 in diverse acute and chronic experimental brain injury models; in contrast, there is little information regarding expression of the MCP-1 receptor, CCR2, in the brain. In the neonatal rat brain, acute excitotoxic injury elicits a rapid and intense microglial response. To determine if MCP-1 could be a regulator of this response, we evaluated the impact of excitotoxic injury on MCP-1 and CCR2 expression in the neonatal rat brain. We used a reproducible model of focal excitotoxic brain injury elicited by intrahippocampal injection of NMDA (10 nmol) in 7-day-old rats, to examine injury-induced alterations in MCP-1 and CCR2 expression. RT-PCR assays demonstrated rapid stimulation of both MCP-1 and CCR2 mRNA expression. MCP-1 protein content, measured by ELISA in tissue extracts, increased >30-fold in lesioned tissue 8-12 h after lesioning. CCR2 protein was also detectable in tissue extracts. Double-immunofluorescent labeling enabled localization of CCR2 both to activated microglia/monocytes in the corpus callosum adjacent to the lesioned hippocampus and subsequently in microglia/monocytes infiltrating the pyramidal cell layer of the lesioned hippocampus. These results demonstrate that in the neonatal brain, acute excitotoxic injury stimulates expression of both MCP-1 and its receptor, CCR2, and suggests that MCP-1 regulates the microglial/monocyte response to acute brain injury.

Animals↗
PubMed2000

Reduced thrombus burden with abciximab delivered locally before percutaneous intervention in saphenous vein grafts.

BACKGROUND: Existing thrombus can complicate percutaneous saphenous vein graft (SVG) intervention. Local delivery of thrombolytics has been used to reduce the thrombus burden often associated with these interventions. We sought to determine whether local delivery of a platelet glycoprotein IIb/IIIa inhibitor is feasible and can reduce thrombus burden before percutaneous SVG intervention. METHODS: We performed a multicenter pilot study of abciximab (0.25 mg/kg) given by local delivery catheter before percutaneous intervention for de novo SVG stenoses followed by intravenous infusion. All patients (n = 58) had >/=60% stenosis and Thrombolysis In Myocardial Infarction (TIMI) grade >0 flow in an SVG of 3 to 4 mm in diameter. Percent diameter stenosis, TIMI thrombus grade, and TIMI flow grade were measured before and after delivery of abciximab and after intervention. RESULTS: Median percent diameter stenosis improved from 69% to 45% (P =.0001) after local delivery, and TIMI thrombus grade >/=1 incidence reduced from 68% to 34% (P =.0001). TIMI flow grade was not significantly affected (P =.12). All patients had a successful intervention (</=50% residual stenosis). CONCLUSIONS: Local abciximab delivery before percutaneous SVG intervention is associated with significantly reduced thrombus burden, significantly improved percent diameter stenosis, and excellent acute procedural results. Further studies of this approach are warranted to define its clinical utility.

Abciximab↗
PubMed2000

Recurrent hypoxic exposure and reflex responses during development in the piglet.

The effects of recurrent hypoxia on cardiorespiratory reflexes were characterized in anesthetized piglets at 2-10 d (n=15), 2-3 weeks (n=11) and 8-10 weeks (n=8). Responses of phrenic and hypoglossal electroneurograms (ENG(phr) and ENG (hyp)) to hypoxia (8% 0(2), bal N(2), 5 min), hypercapnia (7% CO(2) bal O(2), 5 min) and intravenous capsaicin were tested before and after recurrent exposure to 11 episodes of hypoxia (8% O(2) bal N(2), 5 min). In piglets 2-10 d, ENG(phr) response to hypoxia declined in proportion to the number of hypoxic exposures; however, ENG (hyp) response to hypoxia was unchanged. In piglets at 2-10 d, intracisternal injection of bicuculline (GABA(A) receptor antagonist) reversed effects of recurrent hypoxia on ENG(phr) hypoxic response, eliminated apnea during hypoxia, as well as the delay in appearance of ENG(phr) after hypoxia. The ENG(phr) response to 7% CO(2) inhalation also decreased after recurrent hypoxia; however, the ENG(phr) response to C-fiber stimulation by capsaicin was unaltered. Piglets at 2-3 and 8-10 weeks were resistant to the depressive effects of recurrent hypoxia on respiratory reflex responses. We conclude that the response of the anesthetized newborn piglet to recurrent hypoxia is dominated by increasing inhibition of phrenic neuroelectrical output during successive hypoxic exposures. Central GABAergic inhibition may contribute significantly to the cumulative effects of repeated hypoxia in the newborn piglet experimental model.

Animals↗
PubMed2000

Detection of Loxosceles venom in lesional hair shafts and skin: application of a specific immunoassay to identify dermonecrotic arachnidism.

Loxosceles spiders, of which the brown recluse is the best known, are indigenous to southcentral and southwestern regions of the United States. Loxosceles spider envenomation frequently results in painful, centrally necrotic, erythematous skin lesions that evolve over 24 to 48 hours and may take several weeks to completely heal. The diagnosis of loxoscelism is typically is based on the presence of the characteristic dermal lesion, because no definitive clinical diagnostic assay exists, and the spider is generally not available for identification. We used a rapid Loxosceles-specific enzyme immunoassay to detect spider venom in a dermal biopsy and hairs plucked from a suspicious skin lesion on the lower extremity of a 52-year-old man. This report indicates that in using a novel Loxosceles-specific immunoassay, venom can be detected in dermonecrotic skin and hair specimens for up to 4 days after envenomation.

Biopsy↗
PubMed2000

Nitric oxide in mucosal defense: a little goes a long way.

Nitric oxide (NO) is now recognized as an important modulator of an enormous number of physiological processes, ranging from blood pressure regulation to neuronal transmission to penile erectile function. In the gastrointestinal tract, NO also participates in many physiological and pathophysiological processes. In this review, we summarize the contribution made by NO to the ability of the gastrointestinal mucosa to resist injury induced by luminal toxins and to defend against microbial invasion. We also review some of the main features of NO chemistry and the potential of NO as a target for new drugs to treat gastrointestinal disorders.

Enteritis↗