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Biomedical subjects

C L Chou

Publications and source records attributed to C L Chou.

At least 19 recordsLinked to original sources
PubMed2004

Distribution of contaminants in biota and sediments in the Musquash Estuary, Atlantic Canada, marine protected area site initiative and contaminant exclusion zone.

The Musquash Estuary, one of the last ecologically intact estuaries in New Brunswick, has been designated an area of interest for a marine protected area (MPA) under the Oceans Act. The area has been assessed for contaminant background levels as required for establishing MPA environmental quality. American lobster (Homarus americanus), blue mussel (Mytilus edulis) and sediments were collected for assessing contaminant levels and distribution in the harbour. Levels of contaminants from the indicator species and the abiotic component have shown: (1) two extremes of high and low Cu and Ag in lobster from the area; and (2) lower metal levels in inner Musquash Harbour sediments and mussels than in those from the harbour mouth. These suggest that deposition of contaminants into the Musquash MPA site was due to transport of contaminants by coastal currents from upstream coastal industrial activities. This reverse trend with higher contaminant levels in the biotic and abiotic components in the outer harbour than in the inner harbour differs from a contaminated harbour and suggests that a contaminant exclusion zone should be considered for controlling contamination from nearby coastal and estuarine industrial sites to protect the sensitive habitats within the marine protected area.

Animals↗
PubMed2004

A regression model using sediment chemistry for the evaluation of marine environmental impacts associated with salmon aquaculture cage wastes.

This study was undertaken to develop an approach for modelling changes of sediment chemistry related to the accumulation of aquaculture waste. Metal composition of sediment Al, Cu, Fe, Li, Mn, and Zn; organic carbon and < 63 microm particles were used to determine the extent of detectable effects around the cage. This study showed marked differences in the sediment chemistry between aquaculture sites and the natural background: (1) negative correlations between sediment Cu and Zn with Al, (2) poor correlations between metals and Li, and (3) concentrations of Fe and Mn decreased with increased accumulation of organic carbon. There is a trend among normalised metals, organic carbon and particles related to normal, hypoxic and anoxic sediment conditions. The trends are useful for detecting and assessing the cumulative effects from aquaculture wastes to the marine environment. Lithium is less interactive with other metals in aquaculture sediments compared with the natural background sediments. Principal components analysis (PCA) was carried out on the metals, organic carbon, and particles to cluster the similarities of the variables so as to establish the predicted or adjusted environmental monitoring program (EMP) ratings. This approach, using the adjusted EMP rating based on sediment chemistry, yields a regression model with R2 = 0.945 compared to R2= 0.653 for the regression model using unadjusted EMP for assessing the environmental conditions.

Animals↗
PubMed2003

Selection of bioindicators for monitoring marine environmental quality in the Bay of Fundy, Atlantic Canada.

Distribution of metals, PAH's and PCB's in lobsters, mussels, and sediments were used to assess marine environmental quality of the Bay of Fundy. This study demonstrates that the lobster (Homarus americanus) is a better bioindicator for monitoring contaminants in the marine environment and has a greater capacity for the uptake and accumulation of contaminants than the mussel (Mytilus edulis) and sediments. A definite pattern in the spatial distribution of lobster Cu, Cd, and Ag was evident. The distribution of organic contaminants for both mussels and lobsters in the Bay of Fundy lacked a spatial trend, and organic contaminants were undetectable in sediments from all sites. The Gulf Watch Programme, which monitors chemicals in mussels in the Bay of Fundy, did not indicate a problem with high levels of Cu, Cd, and Zn in the ecosystem. Analytes below the detection limit, such as in mussels and sediments, increase the difficulties of chemical analysis and detection for environmental monitoring. Deficiencies of mussels in monitoring the Bay of Fundy were discussed.

Animals↗
PubMed2002

Metal contaminants for modelling lobster (Homarus americanus) migration patterns in the Inner Bay of Fundy, Atlantic Canada.

A method, which uses metal compositions in lobster digestive glands as natural environmental tags, has been developed to trace lobster movements. Lobsters were collected from three selected sites, Minas Channel, Minas Basin, and Cobequid Bay, Inner Bay of Fundy, New Brunswick, Canada, that were known to be contaminated with Cu. Five metal variables (Ag, Cd, Cu, Mn and Zn) were processed for principal component analysis (PCA). Metal concentration and burden models were investigated and PCA was able to differentiate lobsters from the respective catch sites. The method was applied to investigate the May and June lobsters collected at the three sites to determine the migration rate during this period of the fishing season. The results show a high level of mixing at Minas Basin and Cobequid Bay in June, and lobster movement inward toward the inner reaches of the bay, with very limited movement outward from the inner bay.

Animals↗
PubMed2002

Aquaculture-related trace metals in sediments and lobsters and relevance to environmental monitoring program ratings for near-field effects.

The study was undertaken to assess the marine environmental effects from feed and waste associated with aquaculture activities. Metal compositions of sediment, lobster, and feed were used to evaluate the extent of detectable effects at 0 m (under the cage) and 50 m distance. Sediments that were collected under the cages and were characterised as hypoxic or anoxic, showed elevated levels of Cu, Zn, organic carbon, and % <63 microm particles, and low Mn and Fe. At 50 m there was a major reduction in waste chemical impact. Using lobster, a bioindicator species, as a tool for detecting near-field impacts, showed accumulations of high Cu associated with active aquaculture sites. Chemical compositions and metal ratios normalised with organic carbon, were used to assess the sediment conditions associated with environmental monitoring program ratings (EMP--normal, hypoxic, and anoxic). Principal component analysis (PCA) was used to explore chemical data at all sites for differentiating normal, hypoxic and anoxic sediment conditions. Selected variables (Cu, Zn, Fe, Mn, organic carbon, and particles <63 microm) were sufficient for the PCA approach with >90% explainable variance of first two components. The groupings based on PCA and cluster analysis were similar to EMP classifications with some exceptions of mis-identification by EMP. The sediment chemistry components were valid indicators for evaluating marine environmental conditions and for assessing aquaculture operating sites. The developed techniques, using chemical variables in combination with EMP and the statistical approach should be useful to predict the effects of aquaculture practices and the suitability of aquaculture operations.

Animal Feed↗
PubMed2001

97- and 117-kDa forms of collecting duct urea transporter UT-A1 are due to different states of glycosylation.

UT-A1 is an extremely hydrophobic 929-amino acid integral membrane protein, expressed in the renal inner medullary collecting duct, with a central role in the urinary concentrating mechanism. Previous immunoblotting studies in rats have revealed that UT-A1 is present in kidney in 97- and 117-kDa monomeric forms and that the relative abundance of the two forms is altered by vasopressin treatment and other treatments that altered urinary inner medullary urea concentration. The present studies were carried out using protein chemistry techniques to determine the origin of the two forms. Peptide-directed polyclonal antibodies targeted to five sites along the polypeptide sequence from the NH2 to the COOH terminus labeled both forms, thus failing to demonstrate a significant deletion in the primary amino acid chain. The 97- and 117-kDa monomeric forms were both reduced to 88 kDa by deglycosylation with N-glycosidase F, indicating that a single polypeptide chain is glycosylated to two different extents. Studies using nonionic detergents for membrane solubilization or using homobifunctional cross-linkers demonstrated that UT-A1 exists as a 206-kDa protein complex in native kidney membranes. The mobility of this complex was also increased by deglycosylation. Both the 97- and 117-kDa proteins, as well as the 206-kDa complex, were immunoprecipitated with UT-A1 antibodies. We conclude that UT-A1 is a glycoprotein and that the two monomeric forms (97 and 117 kDa) in inner medullary collecting duct are the consequence of different states of glycosylation.

Animals↗
PubMed2000

HLA-DM recognizes the flexible conformation of major histocompatibility complex class II.

DM facilitates formation of high affinity complexes of peptide-major histocompatibility complex (MHC) by release of class II MHC-associated invariant chain peptide (CLIP). This has been proposed to occur through discrimination of complex stability. By probing kinetic and conformational intermediates of the wild-type and mutant human histocompatibility leukocyte antigen (HLA)-DR1-peptide complexes, and examining their reactivities with DM, we propose that DM interacts with the flexible hydrophobic pocket 1 of DR1 and converts the molecule into a conformation that is highly peptide receptive. A more rigid conformation, generated upon filling of pocket 1, is less susceptible to DM effects. Thus, DM edits peptide-MHC by recognition of the flexibility rather than stability of the complex.

Antigens, Differentiation, B-Lymphocyte↗
PubMed2000

Regulation of aquaporin-2 trafficking by vasopressin in the renal collecting duct. Roles of ryanodine-sensitive Ca2+ stores and calmodulin.

In the renal collecting duct, vasopressin increases osmotic water permeability (P(f)) by triggering trafficking of aquaporin-2 vesicles to the apical plasma membrane. We investigated the role of vasopressin-induced intracellular Ca(2+) mobilization in this process. In isolated inner medullary collecting ducts (IMCDs), vasopressin (0.1 nm) and 8-(4-chlorophenylthio)-cAMP (0.1 mm) elicited marked increases in [Ca(2+)](i) (fluo-4). Vasopressin-induced Ca(2+) mobilization was completely blocked by preloading with the Ca(2+) chelator BAPTA. In parallel experiments, BAPTA completely blocked the vasopressin-induced increase in P(f) without affecting adenosine 3',5'-cyclic monophosphate (cAMP) production. Previously, we demonstrated the lack of activation of the phosphoinositide-signaling pathway by vasopressin in IMCD, suggesting an inositol 1,4,5-trisphosphate-independent mechanism of Ca(2+) release. Evidence for expression of the type 1 ryanodine receptor (RyR1) in IMCD was obtained by immunofluorescence, immunoblotting, and reverse transcription-polymerase chain reaction. Ryanodine (100 microm), a ryanodine receptor antagonist, blocked the arginine vasopressin-mediated increase in P(f) and blocked vasopressin-stimulated redistribution of aquaporin-2 to the plasma membrane domain in primary cultures of IMCD cells, as assessed by immunofluorescence immunocytochemistry. Calmodulin inhibitors (W7 and trifluoperazine) blocked the P(f) response to vasopressin and the vasopressin-stimulated redistribution of aquaporin-2. The results suggest that Ca(2+) release from ryanodine-sensitive stores plays an essential role in vasopressin-mediated aquaporin-2 trafficking via a calmodulin-dependent mechanism.

Animals↗
PubMed2000

A simple co-precipitation inductively coupled plasma mass spectrometric method for the determination of uranium in seawater.

Inductively coupled plasma mass spectrometry (ICP-MS) was used in the determination of 238uranium in seawater after concentration by a simplified co-precipitation with iron hydroxide. Ocean water and reference seawater were used in the study. The co-precipitation method required a smaller sample volume (10 fold less), and less column separation to recover the uranium from the seawater matrix, compared to the original iron hydroxide method. The direct seawater dilution technique requires only a small seawater volume (0.5 mL) and offers a rapid, reliable method for uranium analysis in seawater compared to traditional methods. Comparison of the results for simple co-precipitation, direct dilution of seawater, and theoretical uranium values based on salinity concentrations, yielded negligible differences. Data from this work show that the certified value for NASS-4 is low.

Journal Article↗
PubMed2000

Use of an orientation clinic to reduce failed new patient appointments in primary care.

Patients who fail to attend initial appointments reduce clinic efficiency. To maximize attendance by newly referred outpatients, we introduced a mandatory group orientation clinic for all new patients and determined its effects on no-show rates. Orientation clinic also provided health care screening and opportunities for patient feedback. The new patient no-show rate for initial provider visits decreased significantly from 45% before institution of orientation clinic to 18% afterwards (P<.0001). The total no-show (patients who failed to attend orientation clinic or an initial provider visit) rate of the postintervention group was 51% (P = .28, compared with before the intervention). This intervention improved the efficiency and minimized the wasted time of our clinicians.

Appointments and Schedules↗
PubMed1999

Vasopressin regulates apical targeting of aquaporin-2 but not of UT1 urea transporter in renal collecting duct.

In the renal inner medullary collecting duct (IMCD), vasopressin regulates two key transporters, namely aquaporin-2 (AQP2) and the vasopressin-regulated urea transporter (VRUT). Both are present in intracellular vesicles as well as the apical plasma membrane. Short-term regulation of AQP2 has been demonstrated to occur by vasopressin-induced trafficking of AQP2-containing vesicles to the apical plasma membrane. Here, we have carried out studies to determine whether short-term regulation of VRUT occurs by a similar process. Cell surface labeling with NHS-LC-biotin in rat IMCD suspensions revealed that vasopressin causes a dose-dependent increase in the amount of AQP2 labeled at the cell surface, whereas VRUT labeled at the cell surface did not increase in response to vasopressin. Immunoperoxidase labeling of inner medullary thin sections from Brattleboro rats treated with 1-desamino-8-D-arginine vasopressin (DDAVP) for 20 min revealed dramatic translocation of AQP2 to the apical region of the cell, with no change in the cellular distribution of VRUT. In addition, differential centrifugation of inner medullary homogenates from Brattleboro rats treated with DDAVP for 60 min revealed a marked depletion of AQP2 from the low-density membrane fraction (enriched in intracellular vesicles) but did not alter the quantity of VRUT in this fraction. Finally, AQP2-containing vesicles immunoisolated from a low-density membrane fraction from renal inner medulla did not contain immunoreactive VRUT. Thus vasopressin-mediated regulation of AQP2, but not of VRUT, depends on regulated vesicular trafficking to the plasma membrane.

Animals↗
PubMed1999

Reduced water permeability and altered ultrastructure in thin descending limb of Henle in aquaporin-1 null mice.

It has been controversial whether high water permeability in the thin descending limb of Henle (TDLH) is required for formation of a concentrated urine by the kidney. Freeze-fracture electron microscopy (FFEM) of rat TDLH has shown an exceptionally high density of intramembrane particles (IMPs), which were proposed to consist of tetramers of aquaporin-1 (AQP1) water channels. In this study, transepithelial osmotic water permeability (Pf) was measured in isolated perfused segments (0.5-1 mm) of TDLH in wild-type (+/+), AQP1 heterozygous (+/-), and AQP1 null (-/-) mice. Pf was measured at 37 degrees C using a 100 mM bath-to-lumen osmotic gradient of raffinose, and fluorescein isothiocyanate (FITC)-dextran as the luminal volume marker. Pf was (in cm/s): 0.26 +/- 0.02 ([+/+]; SE, n = 9 tubules), 0.21 +/- 0.01 ([+/-]; n = 12), and 0.031 +/- 0.007 ([-/-]; n = 6) (P < 0.02, [+/+] vs. [+/-]; P < 0.0001, [+/+] vs. [-/-]). FFEM of kidney medulla showed remarkably fewer IMPs in TDLH from (-/-) vs. (+/+) and (+/-) mice. IMP densities were (in microm-2, SD, 5-12 micrographs): 5,880 +/- 238 (+/+); 5,780 +/- 450 (+/-); and 877 +/- 420 (-/-). IMP size distribution analysis revealed mean IMP diameters of 8.4 nm ([+/+] and [+/-]) and 5.2 nm ([-/-]). These results demonstrate that AQP1 is the principal water channel in TDLH and support the view that osmotic equilibration along TDLH by water transport plays a key role in the renal countercurrent concentrating mechanism. The similar Pf and AQP1 expression in TDLH of (+/+) and (+/-) mice was an unexpected finding that probably accounts for the unimpaired urinary concentrating ability in (+/-) mice.

Animals↗
PubMed1999

Upregulation of IL-5 receptor expression on bone marrow-derived CD34+ cells from patients with asthma.

BACKGROUND: Interleukin-5 (IL-5) is a potent eosinophilopoietic factor implicated in the chronic inflammatory cell accumulation accompanying bronchial asthma. We studied the expression of the IL-5 receptor alpha-subunit (IL-5R alpha) on bone marrow-derived cluster of differentiation molecule 34 positive (CD34+) progenitor cells in asthmatics to prove the ability of progenitor cells to respond to IL-5 more readily. METHODS: Non-adherent non-T cells (NANT) were separated from heparinized bone marrow blood from 6 asthmatics and 3 normal subjects, loaded with CD34+ and IL-5R alpha monoclonal antibodies conjugated with immunofluorescence and then analyzed by flow cytometry. Colonies grown from progenitor cells cultured in methylcellulose were determined for 14 days in the presence or absence of growth factors, including granulocyte-monocyte colony stimulating factor, stem cell factor, and interleukin-3. RESULTS: The proportion of IL-5R alpha expression on the CD34+ cell surface was significantly increased in asthmatics (12.9 +/- 3.3%, n = 6, p = 0.0163) compared to normal subjects (1.8 +/- 0.6%, n = 3). A significantly greater number of colonies committed to eosinophilic differentiation were found in the asthmatic subjects. CONCLUSION: We demonstrated an increased expression of IL-5R alpha on bone marrow-derived progenitor cells in asthmatics. This supports the concept that bone marrow-derived progenitor cells are ready for eosinophilopoiesis.

Adolescent↗
PubMed1998

Defective proximal tubular fluid reabsorption in transgenic aquaporin-1 null mice.

To investigate the role of aquaporin-1 (AQP1) water channels in proximal tubule function, in vitro proximal tubule microperfusion and in vivo micropuncture measurements were done on AQP1 knockout mice. The knockout mice were generated by targeted gene disruption and found previously to be unable to concentrate their urine in response to water deprivation. Unanesthetized knockout mice consumed 2.8-fold more fluid than wild-type mice and had lower urine osmolality (505 +/- 40 vs. 1081 +/- 68 milliosmolar). Transepithelial osmotic water permeability (Pf) in isolated microperfused S2 segments of proximal tubule from AQP1 knockout [-/-] mice was 0.033 +/- 0.005 cm/s (SE, n = 6 mice, 37 degreesC), much lower than that of 0.15 +/- 0.03 cm/s (n = 8) in tubules from wild-type [+/+] mice (P < 0.01). In the presence of isosmolar luminal perfusate and bath solutions, spontaneous fluid absorption rates (nl/min/mm tubule length) were 0.31 +/- 0.12 (-/-, n = 5) and 0.64 +/- 0.15 (+/+, n = 8). As determined by free-flow micropuncture, the ratios of tubular fluid-to-plasma concentrations of an impermeant marker TF/P in end proximal tubule fluid were 1.36 +/- 0. 05 (-/-, n = 8 mice [53 tubules]) and 1.95 +/- 0.09 (+/+, n = 7 mice [40 tubules]) (P < 0.001), corresponding to 26 +/- 3% [-/-] and 48 +/- 2% [+/+] absorption of the filtered fluid load. In collections of distal tubule fluid, TF/P were 2.8 +/- 0.3 [-/-] and 4.4 +/- 0.5 [+/+], corresponding to 62 +/- 4% [-/-] and 76 +/- 3% [+/+] absorption (P < 0.02). These data indicate that AQP1 deletion in mice results in decreased transepithelial proximal tubule water permeability and defective fluid absorption. Thus, the high water permeability in proximal tubule of wild-type mice is primarily transcellular, mediated by AQP1 water channels, and required for efficient near-isosmolar fluid absorption.

Animals↗