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Biomedical subjects

K Moore

Publications and source records attributed to K Moore.

At least 73 records · Page 4Linked to original sources
PubMed1999

Quantification of the major urinary metabolite of 15-F2t-isoprostane (8-iso-PGF2alpha) by a stable isotope dilution mass spectrometric assay.

The isoprostanes (IsoPs) are a series of novel prostaglandin (PG)-like compounds generated from the free radical-catalyzed peroxidation of arachidonic acid. The first series of IsoPs characterized contained F-type prostane rings analogous to PGF2alpha. One F-ring IsoP, 15-F2t-IsoP (8-iso-PGF2alpha) has been shown to be formed in abundance in vivo and to exert potent biological activity. As a means to assess the endogenous production of this compound, we developed a method to quantify the major urinary metabolite of 15-F2t-IsoP, 2,3-dinor-5,6-dihydro-15-F2t-IsoP (2,3-dinor-5, 6-dihydro-8-iso-PGF2alpha), by gas chromotography/negative ion chemical ionization mass spectrometry. This metabolite was chemically synthesized and converted to an 18O2-labeled derivative for use as an internal standard. After purification, the compound was analyzed as a pentafluorobenzyl ester trimethylsilyl ether. Precision of the assay is +/-4% and accuracy is 97%. The lower limit of sensitivity is approximately 20 pg. Levels of the urinary excretion of this metabolite in 10 normal adults were found to be 0. 39 +/- 0.18 ng/mg creatinine (mean +/- 2 SD). Substantial elevations in the urinary excretion of the metabolite were found in situations in which IsoP generation is increased and antioxidants effectively suppressed metabolite excretion. Levels of 2,3-dinor-5, 6-dihydro-15-F2t-IsoP were not affected by cyclooxygenase inhibitors. Thus, this assay provides a sensitive and accurate method to assess endogenous production of 15-F2t-IsoP as a means to explore the pathophysiological role of this compound in human disease.

Adult↗
PubMed1999

Lipoic acid prevents development of the hyperdynamic circulation in anesthetized rats with biliary cirrhosis.

Chronic bile duct ligation is associated with the development of oxidant injury, biliary cirrhosis, portal hypertension, and a hyperdynamic circulation. We have previously demonstrated that the hyperdynamic circulation in the partial portal vein-ligated rat can be prevented by the administration of N-acetylcysteine. To extend these findings, we have examined the effect of lipoic acid, a thiol-containing antioxidant, on hemodynamics, oxidative stress, and nitric oxide (NO) production in bile duct-ligated (BDL) cirrhotic rats. Lipoic acid was given continuously in drinking water to normal and BDL rats; control rats received ordinary drinking water, and animals were studied at 24 days following surgery. Lipoic acid prevented the development of the hyperdynamic circulation (cardiac index [CI]: 15.7 +/- 2.0 vs. 29.5 +/- 2.1 mL x min-1 x 100 g-1; P <. 05) and significantly attenuated the rise in portal pressure (PP) (12.7 +/- 0.8 vs. 15.2 +/- 0.5 mm Hg; P <.05). Hepatic nitric oxide synthase (NOS) activity and plasma nitrite/nitrate concentration increased significantly following bile duct ligation, and both of these were prevented by lipoic acid. Lipoic acid had no effect on the biochemical or histological parameters of liver function in the cirrhotic group. We conclude that lipoic acid prevents the development of the hyperdynamic circulation in the rat model of biliary cirrhosis, and that this is associated with decreased synthesis of NO.

Animals↗
PubMed1999

Increased sensitivity to endotoxemia in the bile duct-ligated cirrhotic Rat.

Sepsis is a common complication of cirrhosis with a high mortality. In this study, we have investigated some of the pathways that may be involved in tissue injury and death. Bile duct-ligated (BDL) cirrhotic and control rats were challenged with lipopolysaccharide (LPS). Sensitivity to LPS was markedly enhanced in the BDL group, and was associated with increased liver injury and mortality. There was a 5-fold constitutive activation of nuclear factor kappa B (NFkappaB) in the liver of BDL rat controls (P <.001), and this was activated further, but to a similar extent, in the liver of both sham and BDL rats after injection of LPS. Plasma tumor necrosis factor alpha (TNF-alpha) increased more markedly in the BDL cirrhotic rats (2,463 +/- 697 pg/mL in BDL rats versus 401 +/- 160 pg/mL in the controls at 3 hours; P <.01). Plasma nitrite/nitrate concentrations were increased in the BDL controls at baseline, and increased further after LPS (P <.05), but did not differ from sham controls at 6 hours. Plasma F(2)-isoprostanes increased 6-fold in the cirrhotic rats and 2-fold in the controls (P <.01) indicative of lipid peroxidation. Esterified F(2)-isoprostanes in the liver increased 2- to 3-fold at 1 hour in control and BDL rats, but returned to baseline levels by 3 hours. Esterified F(2)-isoprostanes in the kidney increased by 2-fold in the BDL rats after LPS administration, but remained unchanged in sham controls. We conclude that there is a marked increase in sensitivity to LPS in BDL cirrhotic rats. This is associated with an enhanced TNF-alpha response and increased lipid peroxidation. These may be directly and causally related to mortality.

Animals↗
PubMed1999

PPAR gamma is required for the differentiation of adipose tissue in vivo and in vitro.

The process of adipogenesis is known to involve the interplay of several transcription factors. Activation of one of these factors, the nuclear hormone receptor PPAR gamma, is known to promote fat cell differentiation in vitro. Whether PPAR gamma is required for this process in vivo has remained an open question because a viable loss-of-function model for PPAR gamma has been lacking. We demonstrate here that mice chimeric for wild-type and PPAR gamma null cells show little or no contribution of null cells to adipose tissue, whereas most other organs examined do not require PPAR gamma for proper development. In vitro, the differentiation of ES cells into fat is shown to be dependent on PPAR gamma gene dosage. These data provide direct evidence that PPAR gamma is essential for the formation of fat.

Adipose Tissue↗
PubMed1999

Codon optimization, genetic insulation, and an rtTA reporter improve performance of the tetracycline switch.

The objective of this work was to further develop a tetracycline repressor (TetR) protein system that allows control of transgene expression. First, to circumvent the need for a binary approach, a single plasmid design was constructed and tested in tissue culture. To indirectly assay integrations that express the synthetic transcription factor (rtTA), a bicistronic gene was built which included an internal ribosome entry site (IRES) and a green fluorescent protein coding region (GFP) on the same expression cassette as the coding region of rtTA (pTetGREEN). This construct did not produce fluorescent colonies when stably integrated and provided minimal expression of GFP in the face of adequate expression of rtTA. The coding region for TetR was then altered by introducing 156 silent point mutations to simulate mammalian genes. Replacement of wild-type TetR gene (tetR) in pTetGREEN with 'mammalianized' tetR provided GFP expression. Adjustment of codon usage in the tetR region of rtTA nearly doubled the expression level of functional rtTA. To increase the number of rtTA expressing lines, the chicken egg-white lysozyme matrix attachment region (MAR) was introduced into the single plasmid design just upstream of the tetracycline operators (tetO). Inclusion of the MAR doubled the number of colonies that expressed rtTA (44% vs 88%). With the modifications described here, the number of lines that express rtTA and provide induction from a single plasmid design can be increased by the inclusion of a MAR and the level of rtTA expression can be further increased by adjusting the base composition of the TetR coding region. The MAR also insulates the inducible gene from the promoter driving rtTA.

Amino Acid Sequence↗
PubMed1999

Acute cholestasis-induced renal failure: effects of antioxidants and ligands for the thromboxane A2 receptor.

BACKGROUND: Acute biliary obstruction is associated with the development of renal impairment and oxidative stress. The F2-isoprostanes, formed during oxidant injury, are renal vasoconstrictors acting via thromboxane (TX)-like receptors. We determined whether the formation of F2-isoprostanes is increased in experimental cholestasis and whether thiol containing antioxidants or ligands for the TXA2 receptor could improve renal function. METHODS: The effects on renal function of acute bile duct ligation (BDL) in the rat were studied for two days. The consequences of administration of N-acetylcysteine (NAC), alpha-lipoic acid (LA), the TX receptor antagonist (TXRA) BAYu3405, or placebo were then examined. RESULTS: BDL caused a reduction in creatinine clearance from 1.10 +/- 0.05 to 0.55 +/- 0.05 ml/min and sodium excretion from 52 +/- 3 to 17 +/- 3 micromol/hr. Urinary F2-isoprostanes increased from 14 +/- 2 to 197 +/- 22 pg/ml following BDL. Renal functional changes were ameliorated by NAC (creatinine clearance 0.73 +/- 0.05 ml/min), LA (0.64 +/- 0.03 ml/min), and a TXRA (0.90 +/- 0.15 ml/min); P < 0.05. Similarly, sodium excretion was increased from 17 +/- 3 micromol/hr (placebo) to 34 +/- 3 micromol/hr (NAC), 29 +/- 3 micromol/hr (LA), and 38 +/- 5 micromol/hr (TXRA); P < 0.005. Hepatic glutathione concentrations increased from 6.5 +/- 0.3 micromol/g (normal liver) to 8.8 +/- 0.5 micromol/g (NAC) and 7.7 +/- 0.3 micromol/g (LA), P < 0.01. However, only LA markedly inhibited F2-isoprostane formation (197 +/- 22 to 36 +/- 11 pg/ml creatinine clearance; P < 0.05). Urinary TXB2 excretion was elevated after BDL (2.2 +/- 0.5 to 111.1 +/- 20.3 pg/min) but was unaffected by NAC and LA. CONCLUSION: NAC, LA, and TXRA can partially prevent renal dysfunction in experimental cholestasis. The effects of the antioxidants are independent of their ability to inhibit lipid peroxidation or TX synthesis.

Acetylcysteine↗
PubMed1999

Cloning and characterization of a secreted frizzled-related protein that is expressed by the retinal pigment epithelium.

The Wnt/frizzled cell signaling pathway has been implicated in the determination of polarity in a number of systems, including the Drosophila retina. The vertebrate retina develops from an undifferentiated neuroepithelium into an organized and laminated structure that demonstrates a high degree of polarity at both the tissue and cellular levels. In the process of searching for molecules that are preferentially expressed by the vertebrate retinal pigment epithelium (RPE), we identified secreted frizzled-related protein 5 (SFRP5), a member of the SFRP family that appears to act by modulating Wnt signal transduction. SFRP5 is highly expressed by RPE cells, and is also expressed in the pancreas. Within the retina, the related molecule SFRP2 is expressed specifically by cells of the inner nuclear layer. Thus, photoreceptors are likely to be bathed by two opposing gradients of SFRP molecules. Consistent with SFRP5 's postulated role in modulating Wnt signaling in the retina, it inhibits the ability of Xwnt-8 mRNA to induce axis duplication in Xenopus embryos. The human SFRP5 gene consists of three coding exons and it maps to chromosome 10q24.1; human SFRP2 maps to 4q31.3. Based on the biology and complementary expression patterns of SFRP2 and SFRP5, we suggest that they may be involved in determining the polarity of photoreceptor, and perhaps other, cells in the retina.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Implementation of the ANA report card.

A major challenge in healthcare today is measuring the quality of care. To explore nursing's contribution to patients in acute care settings, the American Nurses Association commissioned the development of the "Nursing Report Card." This study explored whether these report card indicators capture quality care. The convenience sample comprised 1,500 patients and 300 nurses from 16 units at an academic medical center. Using regression analysis, the most consistent predictor of outcome indicators was the percentage of RNs of the total staff.

Adult↗
PubMed1999

Renal failure in acute liver failure.

Renal failure develops in approximately 55% of all patients referred to specialized centres with acute liver failure. The renal failure may be secondary to the liver failure itself (and is termed the hepatorenal syndrome) or the renal failure may be a secondary insult that directly affects both liver and kidney alike (for example paracetamol overdose). The pathogenesis of the hepatorenal syndrome involves the development of a hyperdynamic circulation, with a lowering of renal perfusion pressure, the activation of the sympathetic nervous system, which renders the kidneys more susceptible to modest decreases in perfusion pressure, and increased synthesis of a variety of vasoactive mediators. These mediators can cause renal vasoconstriction, but more importantly they can also decrease the glomerular capillary ultrafiltration coefficient (Kf), thus causing a decline of glomerular filtration rate over and above that caused by renal vasoconstriction alone. The treatment of the renal failure in acute liver failure involves the optimization of renal haemodynamics and haemofiltration. Renal failure will always recover when there is recovery of liver function, and in the absence of a spontaneous hepatic recovery, liver transplantation will reverse the hepatorenal syndrome.

Acute Kidney Injury↗
PubMed1999

Subthalamic stimulation-induced synaptic responses in substantia nigra pars compacta dopaminergic neurons in vitro.

The subthalamic nucleus (STN) is one of the principal sources of excitatory glutamatergic input to dopaminergic neurons of the substantia nigra, yet stimulation of the STN produces both excitatory and inhibitory effects on nigral dopaminergic neurons recorded extracellularly in vivo. The present experiments were designed to determine the sources of the excitatory and inhibitory effects. Synaptic potentials were recorded intracellularly from substantia nigra pars compacta dopaminergic neurons in parasagittal slices in response to stimulation of the STN. Synaptic potentials were analyzed for onset latency, amplitude, duration, and reversal potential in the presence and absence of GABA and glutamate receptor antagonists. STN-evoked depolarizing synaptic responses in dopaminergic neurons reversed at approximately -31 mV, intermediate between the expected reversal potential for an excitatory and an inhibitory postsynaptic potential (EPSP and IPSP). Blockade of GABA(A) receptors with bicuculline caused a positive shift in the reversal potential to near 0 mV, suggesting that STN stimulation evoked a near simultaneous EPSP and IPSP. Both synaptic responses were blocked by application of the glutamate receptor antagonist, 6-cyano-7-nitroquinoxalene-2,3-dione. The confounding influence of inhibitory fibers of passage from globus pallidus and/or striatum by STN stimulation was eliminated by unilaterally transecting striatonigral and pallidonigral fibers 3 days before recording. The reversal potential of STN-evoked synaptic responses in dopaminergic neurons in slices from transected animals was approximately -30 mV. Bath application of bicuculline shifted the reversal potential to approximately 5 mV as it did in intact animals, suggesting that the source of the IPSP was within substantia nigra. These data indicate that electrical stimulation of the STN elicits a mixed EPSP-IPSP in nigral dopaminergic neurons due to the coactivation of an excitatory monosynaptic and an inhibitory polysynaptic connection between the STN and the dopaminergic neurons of substantia nigra pars compacta. The EPSP arises from a direct monosynaptic excitatory glutamatergic input from the STN. The IPSP arises polysynaptically, most likely through STN-evoked excitation of GABAergic neurons in substantia nigra pars reticulata, which produces feed-forward GABA(A)-mediated inhibition of dopaminergic neurons through inhibitory intranigral axon collaterals.

Animals↗
PubMed1999

Stereotactic posterioventral pallidotomy improves balance control as assessed by computerized posturography.

Postural instability is arguably the most debilitating symptom of Parkinson's disease (PD). Recently, posterioventral pallidotomy/pallidoansotomy (PVP) has been advocated to improve a multitude of symptoms associated with PD. Dyskinesias, rigidity and bradykinesia are the most talked about improved symptoms, but posture and gait are also affected after PVP. To analyze the effect of PVP on postural control, 14 patients with PD were prospectively studied using a computerized dynamic posturography machine. Seven males and 7 females underwent a total of 18 procedures, 6 left PVP, 6 right PVP, 2 bilateral and 2 had Vim thalamotomies in addition to PVP. Data were collected pre- and postoperatively after a 12-hour drug-free interval ('off' period) and 1-2 h after medications ('on' period). Postoperative analyses were performed between 1 and 3 months postoperatively. As a group, patients' balance, in the off period, improved after surgery in a dynamic setting. Prior to surgery, patients' anterior-posterior sway exceeded their stability limits (patient fell) on 31% of the trials. After surgery, the fall rate decreased to 23%. Anterior-posterior sway decreased significantly (p < 0.05) postoperatively when the platform was sway referenced. In comparing the effect of surgery in decreasing sway with that of medication preoperatively, improvement after surgery (off period) was better than the preoperative on period (p < 0.05). Patients also improved in ostoperative off state when compared to preoperative off state with the platform sway referenced (p < 0.05), controlling for improvement in dyskinesia-induced imbalance. In conclusion, PVP improves standing balance performance better than that achieved with medications preoperatively. Since central input parameters were improved, the mechanism of PVP may be centralized.

Aged↗
PubMed1999

The structure and composition of chronic wound eschar.

Wounds with a covering of eschar require debridement before optimal wound healing can proceed. There are several different methods available but these have been derived empirically with no direct evidence of the structure or composition of the tissue they are designed to remove, or of the potential autolytic mechanisms which are the targets for some of these treatments. The aim of this study therefore was to determine the composition of chronic wound eschar and hence identify potential targets for the induction of autolytic debridement. Chronic wound eschar was removed by surgical debridement and analysed using immunohistochemistry, polyacrylamide gel electrophoresis (PAGE) and gelatin zymography. Immunohistochemistry using antibodies specific for extracellular matrix (ECM) proteins revealed a definite tissue structure, consisting of many fibrous regions and fine fibrillar elements separated by areas of tissue which were of a more irregular and amorphous nature. An antibody specific for all leucocytes revealed the presence of leucocytes in the region of tissue closest to the wound bed. The presence of this leucocyte population correlated to elevated levels of gelatinase activity as identified by gelatin zymography. PAGE analysis identified various protein species in the range 3.5-60 kDa molecular weight. These data indicate that wound debridement is likely to require multiple enzyme specificities to degrade the eschar and that these enzymes may be supplied by inflammatory leucocytes infiltrating the eschar from the wound bed. The various protein species demonstrated by PAGE may represent ECM proteins, those with lower molecular weight possibly representing the degradation products of autolytic debridement.

Chronic Disease↗
PubMed1999

Residents' exposure to aboriginal health issues. Survey of family medicine programs in Canada.

OBJECTIVE: To determine whether Canadian family medicine residency programs currently have objectives, staff, and clinical experiences for adequately exposing residents to aboriginal health issues. DESIGN: A one-page questionnaire was developed to survey the details of teaching about and exposure to aboriginal health issues. SETTING: Family medicine programs in Canada. PARTICIPANTS: All Canadian family medicine program directors in the 18 programs (16 at universities and two satellite programs) were surveyed between October 1997 and March 1998. MAIN OUTCOME MEASURES: Whether programs had teaching objectives for exposing residents to aboriginal health issues, whether they had resource people available, what elective and core experiences in aboriginal health were offered, and what types of experiences were available. RESULTS: Response rate was 100%. No programs had formal, written curriculum objectives for residency training in aboriginal health issues, although some were considering them. Some programs, however, had objectives for specific weekend or day sessions. No programs had a strategy for encouraging enrollment of residents of aboriginal origin. Eleven programs had at least one resource person with experience in aboriginal health issues, and 12 had access to community-based aboriginal groups. Core experiences were all weekend seminars or retreats. Elective experiences in aboriginal health were available in 16 programs, and 11 programs were active on reserves. CONCLUSIONS: Many Canadian family medicine programs give residents some exposure to aboriginal health issues, but most need more expertise and direction on these issues. Some programs have unique approaches to teaching aboriginal health care that could be shared. Formalized objectives derived in collaboration with other family medicine programs and aboriginal groups could substantially improve the quality of education in aboriginal health care in Canada.

Adult↗
PubMed1999

Clinical efficacy and safety of tolterodine compared to placebo in detrusor overactivity.

PURPOSE: We evaluated the efficacy, patient acceptability and side effect profile of tolterodine, a new antimuscarinic agent for treating bladder overactivity. MATERIALS AND METHODS: In our randomized, placebo controlled, parallel group study 123, 129 and 64 patients 18 years old or older with proved detrusor overactivity (idiopathic detrusor instability or detrusor hyperreflexia) were randomized to receive 1 or 2 mg. tolterodine, or placebo, respectively, twice daily for 12 weeks. Main outcome measures were number of voids per 24 hours, urine volume per void and episodes of urge incontinence per 24 hours on a frequency-volume chart with detailed recording of side effects. RESULTS: After 12 weeks of treatment mean number of voids per 24 hours plus or minus standard deviation decreased from 11.2 +/- 3.1 to 9.0 +/- 2.6 with the 2 mg. dosage (p = 0.0045 versus placebo). At this dose mean urine volume per void increased from 155 +/- 52 to 190 +/- 70 ml. (p <0.0001 versus placebo), while mean number of incontinence episodes per 24 hours decreased from 3.6 +/- 4.0 to 1.8 +/- 3.1 (p = 0.19 versus placebo). Similar efficacy was observed in patients receiving the 1 mg. dose. Severe dry mouth was reported by only 2, 1 and 2% of patients given the 1 and 2 mg. dose, and placebo, respectively. There was no clinical or electrocardiographic evidence of significant cardiac adverse events. CONCLUSIONS: Tolterodine administration resulted in a significant decrease in the frequency of voiding and improved voided volume but it was seldom associated with troublesome or severe side effects.

Adult↗