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  • fluid secretion  (8)
  • Louisiana  (7)
  • Insulin  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Evidence for a Na+/K+/Cl− cotransport system in basolateral membrane vesicles from the rabbit parotid (1986)
    Springer
    The journal of membrane biology 94 (1986), S. 143-152 
    Details
    ISSN: 1432-1424
    Keywords: fluid secretion ; exocrine gland ; chloride transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Sodium (22Na) transport was studied in a basolateral membrane vesicle preparation from rabbit parotid. Sodium uptake was markedly dependent on the presence of both K+ and Cl− in the extravesicular medium, being reduced 5 times when K+ was replaced by a nonphysiologic cation and 10 times when Cl− was replaced by a nonphysiologic anion. Sodium uptake was stimulated by gradients of either K+ or Cl− (relative to nongradient conditions) and could be driven against a sodium concentration gradient by a KCl gradient. No effect of membrane potentials on KCl-dependent sodium flux could be detected, indicating that this is an electroneutral process. A KCl-dependent component of sodium flux could also be demonstrated under equuilibrium exchange conditions, indicating a direct effect of K+ and Cl− on the sodium transport pathway. KCl-dependent sodium uptake exhibited a hyperbolic dependence on sodium concentration consistent with the existence of a single-transport system withK m =3.2mm at 80mm KCl and 23°C. Furosemide inhibited this transporter withK 0.5=2×10−4 m (23°C). When sodium uptake was measured as a function of potassium and chloride concentrations a hyperbolic dependence on [K] (Hill coefficient =1.31±0.07) were observed, consistent with a Na/K/Cl stoichiometry of 1∶1∶2. Taken together these data provide strong evidence for the electroneutral coupling of sodium and KCl movements in this preparation and strongly support the hypothesis that a Na+/K+/Cl− cotransport system thought to be associated with transepithelial chloride and water movements in many exocrine glands is present in the parotid acinar basolateral membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01871194
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  • 2
    Electronic Resource
    Electronic Resource
    Control of pulsatile insulin secretion in man (1983)
    Springer
    Diabetologia 24 (1983), S. 231-237 
    Details
    ISSN: 1432-0428
    Keywords: Insulin ; Type 2 diabetes ; oscillations ; pulsations ; man ; vagotomy ; pacemaker ; atropine ; naloxone ; phentolamine ; propranolol ; glucose ; tolbutamide ; sodium salicylate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Plasma insulin and glucose concentrations were examined in man in a basal state from central venous samples taken at 1-min intervals for up to 2.5 h. Normal subjects have insulin oscillations of mean period 14 min (significant autocorrelation, p 〈 0.0001) with changes in concentration of 40% over 7 min. The pulsation frequency was stable through cholinergic, endorphin, α-adrenergic or β-adrenergic blockade, or small pertubations with glucose or insulin. Stimulation of insulin secretion by intravenous glucose, tolbutamide or sodium salicylate increased the amplitude of the insulin oscillations while the frequency remained stable. Patients with a truncal vagotomy or after Whipple's operation had longer-term oscillations of 33 and 37 min periodicity (autocorrelation: p 〈 0.0001), with insulin-associated glucose swings four times larger than those of normal subjects. Type 2 (non-insulin-dependent) diabetic patients had a similarly increased insulin-associated glucose swing of six times that seen in normal subjects. The hypothesis is proposed that the 14-min cycle of insulin production is controlled by a ‘pacemaker’ which assists glucose homeostasis. The longer 33–37-min oscillations, seen in those with denervation, may arise from a limit-cycle of the feedback loop between insulin from the B cells and glucose from the liver. The vagus may provide hierarchical control of insulin release.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00282705
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  • 3
    Electronic Resource
    Electronic Resource
    No glucotoxicity after 53 hours of 6.0 mmol/l hyperglycaemia in normal man (1991)
    Springer
    Diabetologia 34 (1991), S. 570-575 
    Details
    ISSN: 1432-0428
    Keywords: Insulin ; glucose ; insulin resistance ; man ; glucotoxicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In vitro and in vivo studies have suggested that metabolic deterioration can be induced by hyperglycaemia per se. The effect of 53 h of 2.2 mg glucose · kg ideal body weight−1· min−1 was examined in four normal male subjects. This produced overnight hyperglycaemia of 6.0 mmol/l on the two nights of the study compared with 4.7 mmol/l on the control night (p〈0.05). In response there was a sustained, two-fold increase in basal plasma insulin (p〈0.005) and C-peptide (p〈0.05) levels. After two days of hyperglycaemia an increased Beta-cell response was demonstrated in response to an additional glucose infusion stimulus (estimated Beta-cell function median of 84% on the control day to 100% after two days glucose infusion). Plasma insulin and C-peptide responses to a 10.0 mmol/l hyperglycaemic clamp increased over the two days of the study (insulin from median 48 mU/l to 73 mU/l and C-peptide from median 2.0 pmol/ml to 2.6 pmol/ml). Glucose tolerance to the additional glucose infusion stimulus improved, suggesting that the increased insulin response during hyperglycaemia was enhancing peripheral glucose uptake. The calculated peripheral insulin sensitivity was unchanged during the hyperglycaemic clamp. Thus, in response to the two days of basal hyperglycaemia, both the basal and stimulated Beta-cell responses were enhanced and there was no evidence for ‘glucose toxicity’ to the Beta-cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00400275
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  • 4
    Electronic Resource
    Electronic Resource
    Haemolysis affects insulin but not C-peptide immunoassay (1987)
    Springer
    Diabetologia 30 (1987), S. 394-396 
    Details
    ISSN: 1432-0428
    Keywords: Insulin ; C-peptide ; radio-immunoassay ; haemolysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Venous blood was taken at the end of a glucose infusion test in 19 individuals and divided into four aliquots, 3 of which were variably haemolysed by repeated passage through a 23-gauge needle to simulate traumatic venepuncture. Plasma insulin (measured by both a charcoal separation and a double-antibody method), C-peptide, and haemoglobin were measured in each aliquot, and haemolysis was also assessed visibly. A significant loss of immuno-assayable plasma insulin was found in samples with only a trace of visible haemolysis, with up to 90% lost in severely haemolysed samples. Plasma C-peptide was unaffected by haemolysis. This represents an additional advantage for the use of plasma C-peptide in assessing insulin secretion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00292540
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  • 5
    Electronic Resource
    Electronic Resource
    Backfilling canals to mitigate Wetland dredging in Louisiana coastal marshes (1987)
    Springer
    Environmental management 11 (1987), S. 823-836 
    Details
    ISSN: 1432-1009
    Keywords: Backfilling ; Mitigation ; Wetlands ; Louisiana ; Dredging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Returning canal spoil banks into canals, or backfilling, is used in Louisiana marshes to mitigate damage caused by dredging for oil and gas extraction. We evaluated 33 canals backfilled through July 1984 to assess the success of habitat restoration. We determined restoration success by examining canal depth, vegetation recolonization, and regraded spoil bank soils after backfilling. Restoration success depended on: marsh type, canal location, canal age, marsh soil characteristics, the presence or absence of a plug at the canal mouth, whether mitigation was on- or off-site, and dredge operator performance. Backfilling reduced median canal depth from 2.4 to 1.1 m, restored marsh vegetation on the backfilled spoil bank, but did not restore emergent marsh vegetation in the canal because of the lack of sufficient spoil material to fill the canal and time. Median percentage of cover of marsh vegetation on the canal spoil banks was 51.6%. Median percentage of cover in the canal was 0.7%. The organic matter and water content of spoil bank soils were restored to values intermediate between spoil bank levels and predredging marsh conditions. The average percentage of cover of marsh vegetation on backfilled spoil banks was highest in intermediate marshes (68.6%) and lowest in fresh (34.7%) and salt marshes (33.9%). Average canal depth was greatest in intermediate marshes (1.50 m) and least in fresh marshes (0.85 m). Canals backfilled in the Chenier Plain of western Louisiana were shallower (average depth = 0.61 m) than in the eastern Deltaic Plain (mean depth range = 1.08 to 1.30 m), probably because of differences in sediment type, lower subsidence rate, and lower tidal exchange in the Chenier Plain. Canals backfilled in marshes with more organic soils were deeper, probably as a result of greater loss of spoil volume caused by oxidation of soil organic matter. Canals ten or more years old at the time of backfilling had shallower depths after backfilling. Depths varied widely among canals backfilled within ten years of dredging. Canal size showed no relationship to canal depth or amount of vegetation reestablished. Plugged canals contained more marsh reestablished in the canal and much greater chance of colonization by submerged aquatic vegetation compared with unplugged canals. Dredge operator skill was important in leveling spoil banks to allow vegetation reestablishment. Wide variation in dredge performance led to differing success of vegetation restoration. Complete reestablishment of the vegetation was not a necessary condition for successful restoration. In addition to providing vegetation reestablishment, backfilling canals resulted in shallow water areas with higher habitat value for benthos, fish, and waterfowl than unfilled canals. Spoil bank removal also may help restore water flow patterns over the marsh surface. Increased backfilling for wetland mitigation and restoration is recommended.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01867248
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  • 6
    Electronic Resource
    Electronic Resource
    Marsh management plans in practice: Do they work in coastal Louisiana, USA? (1988)
    Springer
    Environmental management 12 (1988), S. 37-53 
    Details
    ISSN: 1432-1009
    Keywords: Wetlands ; Marsh management ; Louisiana ; Impoundment ; Water control structures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Louisiana's coastal wetlands represent about 41% of the nation's total and are extensively managed for fish, fur, and waterfowl. Marsh management plans (MMPs) are currently used to avoid potential user conflicts and are believed to be a best management practice for specific management goals. In this article, we define MMPs and examine their variety, history, impacts, and future. A MMP is an organized written plan submitted to state and federal permitting agencies for approval and whose purpose is to regulate wetland habitat quantity and quality (control land loss and enhance productivity). MMPs are usually implemented by making structural modifications in the marsh, primarily by using a variety of water control structures in levees to impound or semi-impound managed areas. It appears that MMPs using impoundments are only marginally successful in achieving and often contradict management goals. Although 20% of coastal Louisiana may be in MMPs by the year 2000, conflict resolution of public and private goals is compromised by a surfeit of opinion and dearth of data and experience. Based on interpretation of these results, we believe the next phase of management should include scientific studies of actual impacts, utilization of post-construction monitoring data, inventory of existing MMPs, development of new techniques, and determination of cumulative impacts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01867376
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  • 7
    Electronic Resource
    Electronic Resource
    Modeling wetland loss in coastal Louisiana: Geology, geography, and human modifications (1988)
    Springer
    Environmental management 12 (1988), S. 827-838 
    Details
    ISSN: 1432-1009
    Keywords: Wetland loss ; Geology ; Coast ; Models ; Louisiana
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Habitat change in coastal Louisiana from 1955/6 to 1978 was analyzed to determine the influence of geological and man-made changes on landscape patterns within 7.5 min quadrangle maps. Three quantitative analyses were used: principal components anlaysis, multiple regression analysis, and cluster analysis. Regional differences in land loss rates reflect variations in geology and the deltaic growth/decay cycles, man-induced chages in hydrology (principally canal dredging and spoil banking), and land-use changes (principally urbanization and agricultural expansion). The coastal zone is not homogeneous with respect to these variables and the interaction between causal factors leading to wetland loss is therefore locally variable and complex. The relationship between wetland loss, hydrologic changes, and geology can be described with statistically meaningful results, even though these data are insufficient to precisely quantify the relationship. However, these data support the hypothesis that the indirect impacts of man-induced changes (hydrologic and land use) may be as influential as the direct impacts resulting in converting wetlands to open water (canals) or modified (impounded) habitat. Three regions within the Louisiana coastal zone can be defined, based on the potential causal factors used in the analyses. The moderate (mean = 22%) wetland loss rates in region 1 are a result of relatively high canal density and developed area in marshes which overlie sediments of moderate age and depth; local geology acts, in this case, to lessen indirect impacts. On the other hand, wetland loss rates in region 2 are high (mean = 36%), despite fewer man-induced impacts; the potential for increased wetland loss due to both direct and indirect effects of man's activity in these areas is high. Conversely, wetland loss (mean = 20%) in region 3 is apparently least influenced by man's activity in the coastal zone because of sedimentary geology (old, thin sediments), even though these areas have already experienced significant direct habitat alteration and wetland loss.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01867610
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  • 8
    Electronic Resource
    Electronic Resource
    A rationale for coastal wetland restoration through spoil bank management in Louisiana, USA (1994)
    Springer
    Environmental management 18 (1994), S. 271-282 
    Details
    ISSN: 1432-1009
    Keywords: Wetland ; Restoration ; Dredging ; Spoil ; Louisiana
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The rationale and outline of an implementation plan for restoring coastal wetlands in Louisiana is presented. The rationale for the plan is based on reversing the consequences of documented cause-and-effect relationships between wetland loss and hydrologic change. The main feature is to modify the extensive interlocking network of dredged spoil deposits, or spoil banks, by reestablishing a more natural water flow at moderate flow velocity (〈5 cm/sec). Guidelines for site selection from thousands of potential sites are proposed. Examples of suitable sites are given for intermediate marshes. These sites exhibit rapid deterioration following partial or complete hydrologic impoundment, implying a strong hydrologic, rather than sedimentological, cause of wetland deterioration. We used an exploratory hydrologic model to guide determination of the amount of spoil bank to be removed. The results from an economic model indicated a very effective cost-benefit ratio. Both models and practical experience with other types of restoration plans, in Louisiana and elsewhere, exhibit an economy of scale, wherein larger projects are more cost effective than smaller projects. However, in contrast to these other projects, spoil bank management may be 100 to 1000 times more cost effective and useful in wetland tracts 〈1000 ha in size. Modest spoil bank management at numerous small wetland sites appears to offer substantial positive attributes compared to alternative and more intensive management at a few larger wetland sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02393768
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  • 9
    Electronic Resource
    Electronic Resource
    Coastal Louisiana recent land loss and canal impacts (1983)
    Springer
    Environmental management 7 (1983), S. 433-442 
    Details
    ISSN: 1432-1009
    Keywords: Coastal zone management ; Wetlands ; Canals ; Marshes ; Louisiana
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Annual coastal land loss in the sedimentary deltaic plain of southern Louisiana is 102 km2, which is correlated with man-made canal surface area. The relationships between land loss and canals are both direct and indirect and are modified by the deltaic substrate, distance to the coast, and availability of new sediments. Loss rates are highest in the youngest of the former deltas nearest the coast; they are lowest in the more consolidated sediments far from the coast. The average estimate for land loss at zero canal density in the six regression equations developed was 0.09%±0.13% annually, the present land loss rates approach 0 8% annually Although additional analyses are needed, we conclude that canals are causally related to a significant portion of the total coastal land loss rates The relation probably involves an interruption of local and regional hydrologic regimes. Reduction of the present acceleration in land loss rates is possible by managing present canals more effectively, by not permitting new ones, and by changing the design of new canals to allow more natural water flow
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01867123
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  • 10
    Electronic Resource
    Electronic Resource
    Land loss in coastal Louisiana (U.S.A.) (1979)
    Springer
    Environmental management 3 (1979), S. 133-144 
    Details
    ISSN: 1432-1009
    Keywords: Coastal zone Management ; Fisheries ; Marshes ; Wetlands ; Louisiana
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This paper examines causes and consequences of wetland losses in coastal Louisiana. Land loss is a cumulative impact, the result of many impacts both natural and artificial. Natural losses are caused by subsidence, decay of abandoned river deltas, waves, and storms. Artificial losses result from flood-control practices, impoundments, and dredging and subsequent erosion of artificial channels. Wetland loss also results from spoil disposal upon wetlands and land reclamation projects. Total land loss in Louisiana's coastal zone is at least 4,300 ha/year. Some wetlands are converted to spoil banks and other eco-systems so that wetland losses are probably two to three times higher. Annual wetland losses in the Barataria Bay basin are 2.6% of the wetland area. Human activities are the principal determinants of land loss. The present total wetland area directly lost because of canals may be close to 10% if spoil area is included. The interrelationship between hydrology, land, vegetation, substrate, subsidence, and sediment supply are complicated; however, hydrologic units with high canal density are generally associated with higher rates of land loss and the rate may be accelerating. Some cumulative impacts of land loss are increased saltwater intrusion, loss of capacity to buffer the impact of storms, and large additions of nutrients. One measure of the impact is that roughly $8–17 × 106 (U.S.A.) of fisheries products and services are lost annually in Louisiana. Viewed at the level of the hydrologic unit, land loss transcends differences in local vegetation, substrate, geology, and hydrology. Land management should therefore focus at that level of organization. Proper guideline recommendations require an appreciation of the long-term interrelations of the wetland estuarine system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01867025
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