Search PubMed⌕ Search

Biomedical subjects

J H Walker

Publications and source records attributed to J H Walker.

At least 19 recordsLinked to original sources
PubMed2006

Sensory, functional, and analytical comparisons of whey butter with other butters.

The objective of this work was to characterize the sensory attributes of whey (WB), cultured (CB), and regular sweet cream (SB) unsalted butters produced at the Dairy Products Technology Center (experimental; n = 3) or obtained from commercial sources (n = 6). Nine judges were trained for nine 1-h sessions; they then rated samples on a 15-cm line scale in triplicate using descriptive analysis. Data obtained were analyzed using SAS statistical software. Significant differences between the 3 types of butters were obtained on yellow, shiny, acidic odor, melt rate, porous, hard, spreadable, cheese odor, mouthcoating, nutty, cardboard odors, acidic, nutty, diacetyl, and grassy flavors. Cultured butter and SB were significantly shinier than WB. Whey butter was more yellow than CB, which in turn was more yellow than SB. Whey butter was more porous, and had higher scores on nutty flavor and cardboard odor than SB and CB. Sweet cream butter was significantly harder than CB but not WB. Cultured butter had more mouthcoating, acidic odor and flavor, and grassy flavor than SB and WB. The commercial samples were more porous, crumbly, and had significantly more artificial butter odor, rancid odor, and flavor. Results from principal component analysis indicated that experimental WB and SB were similar and were characterized by a sweet taste. Whey butter's characteristics compared favorably with commercial CB and were very similar to sweet cream butter. No major significant differences were obtained for triangle tests, with the exception of that for WB and CB in pound cake. No significant differences were obtained for the acceptability of the different versions of any of the 3 foods.

Butter↗
PubMed2006

Sensory evaluation of whey and sweet cream buttermilk.

The objective of this work was to characterize the sensory attributes of sweet cream buttermilk (CBM) and a nontraditional product, whey buttermilk (WBM). Whey buttermilk results from processing whey cream into butter. The products were evaluated as fresh liquid buttermilk obtained directly from the butter churn, and as reconstituted buttermilk or whey buttermilk powders. Sweet cream buttermilk and WBM were produced either at the Dairy Products Technology Center (experimental samples, n = 2) or provided by the industry (n = 2 from 2 different commercial sources). Nine panelists were trained for twenty-four 1-h sessions; they then rated samples on a 15-cm line scale in triplicate using descriptive analysis. Data obtained were analyzed using SAS statistical software. Results indicated that WBM had similar sensory characteristics as regular CBM; however, there was a marked color difference between them. Liquid buttermilk was not significantly different from reconstituted buttermilk powder on many attributes. However, WBM was significantly more yellow, more sour, and more astringent than the CBM samples, and it had more cardboard flavor than the commercially produced CBM. Liquid buttermilk was not significantly different from reconstituted buttermilk powder on many attributes. However, some buttermilk types had more cardboard aroma and flavor in their powdered form than in liquid form. Most attributes showed no significant differences across replicates, indicating consistency of rating. Principal component analysis showed that attributes were separated on the 2 principal components based on production site and processing form (fresh vs. reconstituted).

Adult↗
PubMed2005

Cytosolic phospholipase A2-alpha mediates endothelial cell proliferation and is inactivated by association with the Golgi apparatus.

Arachidonic acid and its metabolites are implicated in regulating endothelial cell proliferation. Cytosolic phospholipase A2-alpha (cPLA2alpha) is responsible for receptor-mediated arachidonic acid evolution. We tested the hypothesis that cPLA2alpha activity is linked to endothelial cell proliferation. The specific cPLA2alpha inhibitor, pyrrolidine-1, inhibited umbilical vein endothelial cell (HUVEC) proliferation in a dose-dependent manner. Exogenous arachidonic acid addition reversed this inhibitory effect. Inhibition of sPLA2 did not affect HUVEC proliferation. The levels of cPLA2alpha did not differ between subconfluent and confluent cultures of cells. However, using fluorescence microscopy we observed a novel, confluence-dependent redistribution of cPLA2alpha to the distal Golgi apparatus in HUVECs. Association of cPLA2alpha with the Golgi was linked to the proliferative status of HUVECs. When associated with the Golgi apparatus, cPLA2alpha activity was seen to be 87% inhibited. Relocation of cPLA2alpha to the cytoplasm and nucleus, and cPLA2alpha enzyme activity were required for cell cycle entry upon mechanical wounding of confluent monolayers. Thus, cPLA2alpha activity and function in controlling endothelial cell proliferation is regulated by reversible association with the Golgi apparatus.

Cell Proliferation↗
PubMed2005

Nuclear actin is partially associated with Cajal bodies in human cells in culture and relocates to the nuclear periphery after infection of cells by adenovirus 5.

Cajal bodies are intra-nuclear structures enriched in proteins involved in transcription and mRNA processing. In this study, immunofluorescence microscopy experiments using a highly specific antibody to actin revealed nuclear actin spots that colocalized in part with p80 coilin-positive Cajal bodies. Actin remained associated with Cajal bodies in cells extracted to reveal the nuclear matrix. Adenovirus infection, which is known to disassemble Cajal bodies, resulted in loss of actin from these structures late in infection. In infected cells, nuclear actin was observed to relocate to structures at the periphery of the nucleus, inside the nuclear envelope. Based on these findings, it is suggested that actin may play an important role in the organization or function of the Cajal body.

Actins↗
PubMed2005

Cost-minimization analysis of treprostinil vs. epoprostenol as an alternate to oral therapy non-responders for the treatment of pulmonary arterial hypertension.

INTRODUCTION: Idiopathic pulmonary arterial hypertension (IPAH) is associated with substantial morbidity and mortality. Treprostinil was compared to epoprostenol for the economic impact of treating IPAH patients who failed or were not candidates for bosentan. METHODS: The model was a cost-minimization analysis, assuming clinical equivalence was achieved by proper dosing of both drugs, in terms of survival and surrogate measures. Two theoretical cohorts of 270 patients were treated with subcutaneous treprostinil and intravenous epoprostenol, and were evaluated over 3 years using a spreadsheet model. Annual survival rates were estimated for the cohorts so that at endpoint 114 (42%) patients survived in both groups. The model utilized resource valuation data for medication and supply costs from Medicare; hospital, consultation, surgical, and diagnostic procedural fees from North Carolina hospitals; and costs to treat adverse events from published sources. Costs were obtained from standard lists and were presented as 2003 US dollars, discounted at 3%. Sensitivity analyses were performed testing all model uncertainties. RESULTS: In the base case analysis, treprostinil demonstrated savings of 22,701 US dollars and 37,433 US dollars per patient over 1- and 3-year time horizons, respectively. The greatest savings came from reduced or minimal hospitalizations attributed to the dose titration and treatment of adverse events, such as sepsis, associated with epoprostenol and its delivery system. Probabilistic sensitivity analyses resulted in average 3-year cost-savings of 41,051 US dollars (Standard Deviation = 13,902 US dollars) per patient. CONCLUSIONS: By initiating and continuing treatment with treprostinil over a 3-year period, the economic burden associated with IPAH may be reduced compared to treatment with epoprostenol. The greatest saving with treprostinil was attributed to decreased sepsis.

Administration, Oral↗
PubMed2003

Invertebrate responses to the management of genetically modified herbicide-tolerant and conventional spring crops. I. Soil-surface-active invertebrates.

The effects of herbicide management of genetically modified herbicide-tolerant (GMHT) beet, maize and spring oilseed rape on the abundance and diversity of soil-surface-active invertebrates were assessed. Most effects did not differ between years, environmental zones or initial seedbanks or between sugar and fodder beet. This suggests that the results may be treated as generally applicable to agricultural situations throughout the UK for these crops. The direction of the effects was evenly balanced between increases and decreases in counts in the GMHT compared with the conventional treatment. Most effects involving a greater capture in the GMHT treatments occurred in maize, whereas most effects involving a smaller capture were in beet and spring oilseed rape. Differences between GMHT and conventional crop herbicide management had a significant effect on the capture of most surface-active invertebrate species and higher taxa tested in at least one crop, and these differences reflected the phenology and ecology of the invertebrates. Counts of carabids that feed on weed seeds were smaller in GMHT beet and spring oilseed rape but larger in GMHT maize. In contrast, collembolan detritivore counts were significantly larger under GMHT crop management.

Agriculture↗
PubMed2003

Invertebrate responses to the management of genetically modified herbicide-tolerant and conventional spring crops. II. Within-field epigeal and aerial arthropods.

The effects of the management of genetically modified herbicide-tolerant (GMHT) crops on the abundances of aerial and epigeal arthropods were assessed in 66 beet, 68 maize and 67 spring oilseed rape sites as part of the Farm Scale Evaluations of GMHT crops. Most higher taxa were insensitive to differences between GMHT and conventional weed management, but significant effects were found on the abundance of at least one group within each taxon studied. Numbers of butterflies in beet and spring oilseed rape and of Heteroptera and bees in beet were smaller under the relevant GMHT crop management, whereas the abundance of Collembola was consistently greater in all GMHT crops. Generally, these effects were specific to each crop type, reflected the phenology and ecology of the arthropod taxa, were indirect and related to herbicide management. These results apply generally to agriculture across Britain, and could be used in mathematical models to predict the possible long-term effects of the widespread adoption of GMHT technology. The results for bees and butterflies relate to foraging preferences and might or might not translate into effects on population densities, depending on whether adoption leads to forage reductions over large areas. These species, and the detritivore Collembola, may be useful indicator species for future studies of GMHT management.

Agriculture↗
PubMed2001

Overexpression of the myristoylated alanine-rich C kinase substrate decreases uptake and K(+)-evoked release of noradrenaline in the human neuroblastoma SH-SY5Y.

The aim of this study was to investigate a possible role of the myristoylated alanine-rich C kinase substrate (MARCKS) in the mechanism of noradrenaline uptake and release in the human neuroblastoma cell line SH-SY5Y. A stable cell line showing a twofold overexpression of MARCKS was prepared by transfecting SH-SY5Y with pCEP4 containing MARCKS cDNA in the sense orientation. This cell line showed no changes in the expression of neurofilaments or markers of noradrenergic large dense-cored vesicles compared with both untransfected SH-SY5Y and SH-SY5Y transfected with pCEP4 only (mock transfected). Similarly, no differences in the rate of cell growth could be detected between these three cell lines. In contrast, specific uptake and depolarization-evoked (100 mM K(+)) release of noradrenaline from the cell line overexpressing MARCKS was inhibited by approximately 50% compared with mock-transfected SH-SY5Y. K(+)-evoked noradrenaline release enhanced by pretreatment with 12-O-tetradecanoylphorbol 13-acetate (100 nM) was also inhibited by 50%. In contrast, carbachol-evoked noradrenaline release was unaffected. Thus, in SH-SY5Y cells, overexpression of MARCKS leads to a decrease in the K(+)-evoked noradrenaline release possibly by increased actin cross-linking preventing the movement of noradrenaline containing large dense-cored vesicles to the plasma membrane in response to depolarization.

Carrier Proteins↗
PubMed2000

Investigation of the relocation of cytosolic phospholipase A2 and annexin V in activated platelets.

Cytosolic phospholipase A(2) is a Ca(2+)-dependent enzyme that acts on membrane phospholipids to release arachidonic acid, which in platelets is converted to thromboxane A(2). Annexin V is a Ca(2+)-dependent, phospholipid-binding protein, which is proposed to regulate inflammation by inhibiting cytosolic phospholipase A(2). Here, we have studied the association of cytosolic phospholipase A(2) and annexin V with platelet membranes after thrombin stimulation. In a time-dependent manner, an exact correlation was found between the membrane association of cytosolic phospholipase A(2) and annexin V. Calcium from the intracellular stores was sufficient for the relocation of intracellular annexin V and cytosolic phospholipase A(2) to platelet membranes. Activation in the presence of arginyl-glycyl-aspartyl-serine (RGDS), which inhibits binding of fibrinogen to its adhesive ligand, does not alter the amount of cytosolic phospholipase A(2) or annexin V that binds to membranes. When activation-induced actin polymerisation was prevented by cytochalasin E, the recovery of both annexin V and cytosolic phospholipase A(2) remained unchanged. However, complete depolymerisation of the cytoskeleton with DNase I almost abolished the association of cytosolic phospholipase A(2) with the membranes, and it completely abolished the relocation of annexin V to platelet membranes. Finally, we show that cytosolic phospholipase A(2) can be specifically purified from platelet membranes by affinity chromatography on GST-annexin V and that immunoprecipitation using antibodies against cytosolic phospholipase A(2) copurify annexin V and cytosolic phospholipase A(2) from activated platelets. These findings suggest that following platelet activation with thrombin, both cytosolic phospholipase A(2) and annexin V, relocate to platelet membranes where they interact. An intact cytoskeleton seems to be a prerequisite for the interaction of cytosolic phospholipase A(2) and annexin V with platelet membranes. The incorporation of cytosolic phospholipase A(2) into the membrane fraction of thrombin-activated platelets parallels that of annexin V, which suggests an interaction between the two proteins.

Annexin A5↗
PubMed2000

Annexin V relocates to the platelet cytoskeleton upon activation and binds to a specific isoform of actin.

We have previously reported that stimulation of platelets causes a relocation of annexin V to the cytoplasmic side of the plasma membrane where it associates with actin. This study examined the association of annexin V with the platelet cytoskeleton and its binding to actin, following both physiological activation with thrombin and Ca2+ -ionophore activation. The time-dependence of annexin V incorporation into the detergent-extracted cytoskeleton following activation with thrombin was also measured. Although calcium from the intracellular stores was enough to relocate intracellular annexin V to the cytoskeleton, this relocation was further enhanced by influx of extracellular calcium. The association of annexin V with the cytoskeleton was found to be unaffected by the action of cytochalasin E, however, annexin V was solubilized when DNase I was used to depolymerize the membrane cytoskeleton, and spontaneously re-associated with the actin filaments when re-polymerization was induced in vitro. Using a bifunctional crosslinking reagent we have identified an 85-kDa complex in both membrane and cytoskeleton fractions containing annexin V and actin. Direct binding to actin filaments was only observed in high [Ca2+], however, inclusion of an extract from thrombin-stimulated platelets lowered the [Ca2+] requirement for the binding of annexin V to F-actin to physiological levels. We also show that GST-annexin V mimics the physiological binding of annexin V to membranes, and that this GST-annexin V binds directly to a specific isoform of actin. Immunoprecipitation using antibodies against annexin V copurify annexin V and gamma- but not beta-actin from activated platelets. This is the first report of a possible preferential binding of annexin V to a specific isoform of actin, namely gamma-actin. The results of this study suggest a model in which annexin V that relocates to the plasma membrane and binds to gamma-actin in an activation-dependent manner forms a strong association with the platelet cytoskeleton.

Actins↗
PubMed2000

Platelet annexin V: the ins and outs.

One of the most important signals accompanying platelet activation is the increase in intracellular calcium, and it is known that calcium-binding proteins play an important role in linking this calcium signal to the final platelet responses. Annexins are highly conserved calcium-binding proteins, of which annexin V is the major annexin in human platelets. The last few years have seen an accumulation of information on and speculations about the roles of annexins in both intracellular and extracellular locations. Additionally, annexin V has proven very useful as a marker for apoptosis and platelet activation. It also has potential for the delivery of thrombolytic agents to thrombi and for imaging thrombi as they form in the human body. This review distinguishes between the potential intracellular role of annexin V in platelet activation, and the uses of annexin V in particular to detect apoptosis.

Animals↗
PubMed2000

Factors predictive of response to cyclosporin treatment for severe, steroid-resistant ulcerative colitis.

OBJECTIVE: Cyclosporin-A (CSA) has been demonstrated to be effective for treatment of severe, steroid-resistant ulcerative colitis (UC). Use of CSA has been limited, however, because of low 1-yr response rates and the potential for complications. The aim of this study is to define clinical and laboratory factors predictive of response in severe, steroid-resistant UC. METHODS: A retrospective review of 36 cases of severe, steroid-resistant UC treated with CSA was performed. Intravenous (i.v.) CSA was administered at an initial dose of 2.5 mg/kg, and oral (p.o.) CSA was given as twice the i.v. dose. Clinical response was recorded and logistic regression analysis was performed on clinical and laboratory factors for prediction of response to CSA. RESULTS: Of 36 patients, 25 responded to i.v. CSA and were switched to p.o. CSA. Of the 25, 13 required colectomy by 9 months. The other 12 patients had a sustained response to CSA and avoided colectomy at 9 months. Overall, 24 of 36 patients treated with CSA required colectomy by 9 months. A high percentage of band neutrophils (bands) on admission was found to be a significant predictor of response to CSA. CONCLUSIONS: Bands on admission are predictive of response to CSA and ultimately, the requirement for surgery in steroid-resistant UC.

Administration, Oral↗
PubMed1999

Annexin V binds to the actin-based cytoskeleton at the plasma membrane of activated platelets.

Immunocytochemical studies demonstrate that annexin V relocates to the plasma membranes of intact stimulated blood platelets. Anti-annexin V antibodies label the cytoplasmic side of the substrate-adherent plasma membrane of mechanically unroofed, glass-activated platelets and colocalize with actin. In addition, crosslinking experiments using detergent-solubilized membranes of activated platelets have identified an 85-kDa complex containing annexin V. The 85-kDa complex is also recognized by antibodies against actin, suggesting that annexin V interacts with actin. In addition, annexin V was found to associate with filamentous actin in the presence of millimolar Ca(2+). Annexin V was also shown by immunofluorescence microscopy to be associated with platelet cytoskeletons, colocalizing with actin in the presence of micromolar Ca(2+). These findings provide the first evidence for annexin V binding to the plasma membrane and to the actin-based cytoskeleton in activated platelets and indicate that annexin V may function in both cytoskeletal and membrane domains.

Actin Cytoskeleton↗
PubMed1999

Redistribution of F-actin and large dense-cored vesicles in the human neuroblastoma SH-SY5Y in response to secretagogues and protein kinase Calpha activation.

Our previous studies have shown that noradrenaline release is enhanced by activation of protein kinase Calpha in SH-SY5Y cells. In the present study, we report that activation of protein kinase Calpha leads to (a) partial redistribution of the F-actin cytoskeleton and (b) a 2.5-fold increase in the number of large dense-cored vesicles within 100 nm of the plasma membrane. This redistribution can be prevented by down-regulation of protein kinase Calpha by up to 48 h exposure to phorbol dibutyrate. Treatment with the secretagogues 100 mM KCl, the Ca2+ ionophore A23187 (20 microM) and 1 mM carbachol also leads to a partial disassembly of the F-actin cytoskeleton. This is accompanied by an increase in the number of large dense cored vesicles at the plasma membrane following exposure to KCl and A23187 but not following exposure to carbachol. These results are discussed in relation to the hypothesis that a key step in the enhancement of noradrenaline release following activation of protein kinase Calpha and elevation of intracellular calcium is the movement of large dense cored vesicles to the plasma membrane following partial disassembly of the F-actin cytoskeleton.

Actins↗
PubMed1999

Annexin V relocates to the periphery of activated platelets following thrombin activation: an ultrastructural immunohistochemical approach.

We have previously shown biochemically that the physiological agonist thrombin can cause translocation of endogenous annexin V to a fraction containing all platelet membranes. This paper reports ultrastructural immunohistochemical data revealing that annexin V molecules localize with plasma membranes of blood platelets following thrombin activation. When ultrathin sections of resting platelets were examined by immunogold staining, annexin V was found to be cytosolic, having a generalized distribution throughout the platelet. After thrombin activation, annexin V became peripheral in location and plasmalemma association increased. Morphometric analysis of gold particles shows that annexin V relocates specifically to the plasma membrane and its underlying cytoskeleton following treatment with thrombin. In control platelets 6.1% +/- 0.78 of annexin V is present at the plasma membrane and 15.0% +/- 0.82 in the region corresponding to the membrane cytoskeleton (10-80 nm); after stimulation with 0.5 unit/ml thrombin for 2 min this increased to 16.7% +/- 0.22 and 40.4% +/- 0.53, respectively.

Annexin A5↗
PubMed1998

Activated protein kinase C alpha associates with annexin VI from skeletal muscle.

We have previously detected a number of protein kinase C (PKC) alpha-binding proteins in skeletal muscle cytosol by blot overlay assay, and now identify the major, 69 kDa binding protein as annexin VI by immunoblotting and overlay assay of hydroxyapatite chromatography fractions. Annexin VI was also detected in immunoprecipitates of PKC alpha. Annexin VI and PKC alpha are both calcium-dependent phospholipid-binding proteins, and detection of the interaction was dependent on the presence of calcium and phosphatidylserine (PS). The association probably involves specific protein-protein interactions rather than mere bridging by lipid molecules: firstly, detection of PKC alpha-annexin VI complexes by overlay assay was not diminished when PS concentrations were increased over a 10-fold range, while that of other PKC alpha-binding protein complexes was reduced or abolished; secondly, the presence in the overlay assay of a PKC pseudosubstrate peptide, analogous to a PKC sequence previously found to be involved in PKC binding activity, reduced complex formation; thirdly, we were also able to detect annexin VI interaction with PKC beta by overlay of skeletal muscle cytosol, but not with PKC theta, the major novel PKC in this tissue, suggesting sequences specific to calcium-dependent PKC isoenzymes are involved. While other annexin isoforms may be PKC substrates or inhibitors, annexin VI phosphorylation by PKC alpha could not be detected after co-purification, while phosphorylation of subsequently-added histone IIIS was readily observed. Annexin VI is a major skeletal muscle protein and our data are consistent with a role for this isoform in the control of calcium-dependent PKC.

Animals↗
PubMed1998

Localization of annexin VI in the adult and neonatal heart.

Annexins are a major family of intracellular Ca(2+)-binding proteins which have been implicated in a variety of cellular functions. In this paper the authors have used confocal microscopy to compare the distribution of annexin VI in vibratome sections of the rat adult left ventricle and striated muscle of the rat oesophagus. It is shown that in rat cardiac myocytes annexin VI is associated with only the sarcolemma and intercalated discs. In contrast, it is demonstrated that in rat skeletal muscle annexin VI is associated with the sarcoplasmic reticulum, in addition to the plasma membrane, suggesting that annexin VI is regulating different processes in these tissues. Also shown is that in vibratome sections of the neonatal rat left ventricle, annexin VI has a different subcellular location to that observed in the terminally differentiated adult myocyte. In these differentiating neonatal cells annexins VI is also associated with specific subcellular structures. Furthermore, using confocal microscopy of isolated myocytes the authors demonstrate that the association of annexin VI with the sarcolemma is stable even after cells are treated with the intracellular calcium chelator BAPTA-AM, to greatly deplete cytosolic calcium levels. This demonstrates that annexin VI associates tightly with the sarcolemma, and suggests that components in addition to phospholipid are involved in binding annexin VI to the membrane. These results demonstrate that the subcellular location of annexin VI is differentially regulated, and suggest that annexin VI is required for a process or processes characteristic of the sarcolemma, and of the sarcoplasmic reticulum of skeletal but not of heart muscle.

Aging↗