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PubMedDate not supplied

Efficiency of white cell filtration and a freeze-thaw procedure for removal of HIV-infected cells from blood.

Strategies for diminishing the risk of blood transfusion-associated transmission of HIV-1 were evaluated. HIV-1-infected peripheral blood mononuclear cells were added to blood that was subsequently filtered by using different white cell (WBC) filters (cellulose acetate and polyester). The average log reduction of infected cells with polyester filters was at least 2.5 as measured by ID50 titration and polymerase chain reaction. In two WBC filtration experiments with blood from seropositive donors diluted 1:4 with seronegative blood, log reductions of 2.4 and greater than 2.5 were observed. No cell-free virus was retained by the filter used. A freeze-thaw procedure applied to HIV-1-contaminated blood resulted in a minimal log reduction. These results indicate that the reduction of HIV-1 infectivity as a result of filtration is mainly due to the removal of HIV-1-infected WBCs, and that complete removal of infected WBCs cannot be achieved by the current filtration or freeze-thaw procedures. However, the development of filters with enhanced ability to remove (possibly infected) WBCs may have the added benefit of improving the safety of donor blood, especially in multiply transfused patients.

Blood↗

PubMed1993

The mechanism of white cell reduction by synthetic fiber cell filters.

The mechanism of white cell (WBC) retention by synthetic fiber-based WBC filters was studied. Filters were made of nonwoven fleece prepared from polyester, surface-modified polyester, or polypropylene fibers. Human platelet concentrates were filtered through experimental filters consisting of 8 to 54 layers of nonwoven fleece with mean pore sizes from 7.3 to 14.2 microns. Filters made of fleece of smaller pore size removed WBCs less effectively than filters with larger-pore fleece. Retention of lymphocytes and granulocytes gradually dropped to 0 percent as increasing loads were applied to the filters. The maximal retention capacity for these cell types (i.e., the number of cells retained when "saturating" numbers of WBCs were applied) was proportional to the number of layers of filter material used. Platelet retention did not correlate with WBC retention. Depth filtration, rather than mechanical sieving, seems to be the principal means of WBC removal by nonwoven fiber filters. A low initial number of WBCs in the component to be filtered is important for successful WBC filtration.

Blood Banks↗

PubMed1999

Frame dislocation of body middle rings in endovascular stent tube grafts.

OBJECTIVES: To understand the cause, and propose a mechanism for frame dislocation in endovascular grafts. MATERIALS AND METHODS: Five tube grafts were explanted due to secondary distal leakage 15-21 months after operation. One bifurcated graft was removed during emergency operation after aortic rupture caused by secondary leakage. A second bifurcated graft was harvested from a patient with thrombotic occlusion of one limb, who died after transurethral prostatic resection. The inside of the grafts were examined endoscopically. The stent was inspected after removal of the fabric, broken ligatures were counted and examined by scanning electron microscopy. The fabric strength was tested by probe puncture. RESULTS: We found 17-44% of the stent ligatures of the body middle rings to be loose. The knots were intact. Degradation of the polyester textile was not observed. CONCLUSIONS: Continuous movements in the grafted aorta and blood pressure impose permanent stress to the stent frame and the polyester fabric resulting in morphological changes in the body middle ring of grafts. The clinical implications of the suture breakages are unknown although they may be related to distal secondary leakage in tube grafts.

Aortic Aneurysm, Abdominal↗

PubMed2002

What can we learn from explanted endovascular devices?

OBJECTIVE: To examine the durability of the Stentor and Vanguard endovascular devices in human implants. METHODS: The textile covering, the polypropylene ligatures and the stent metal of 34 devices (25 Stentor, 9 Vanguard) with a mean duration of implantation of 28.8 +/- 16 months was examined by means of stereomicroscopy and scanning electron microscopy. RESULTS: The polyester textile covering showed gaps along the sutured seam and isolated holes in the fabric. All of the examined polypropylene ligatures were worn, some ruptured. Four different types of stent corrosion were classified--pits (100%), bizarre craters (68%), large deficiencies (14%) and fractures (32%). CONCLUSION: Holes in the polyester fabric and frame dislocations are specific for the design of Stentor and Vanguard grafts. The early corrosion of the stent metal Nitinol in these devices is surprising. Until more experience is gained with other devices, we have to be reminded, that the "gold standard" for the long-term durability of artificial vascular grafts is still "today's" conventional graft.

Blood Vessel Prosthesis↗

PubMed2002

Direct measurement of bacterial penetration through surgical gowns: a new method.

There is a paucity of data on the penetration of bacteria through surgical gowns during operations. A simple new method was developed, using Petri dishes filled with horse blood agar that were attached to the outside of the gown material. This was used to assess bacterial penetration through disposable spun-bonded polyester gowns and re-usable woven polyester gowns during normal use. There was a significant difference between the two gown types when tested in the axilla (P = 0.02), the groin (P = 0.02) and the peri-anal region (P < 0.01), with the disposable gowns performing to a higher standard. Re-usable gowns demonstrated variation in penetrability, and for this reason, may be unsuitable for use in orthopaedic implant surgery.

Bacteria↗

PubMed2001

Effect of absorbable polydioxanone flexor tendon repair and restricted active mobilization in a canine model.

We performed an experimental study to evaluate the mechanical and histologic healing process of flexor tendon repair using absorbable polydioxanone monofilament followed by active mobilization. Sixty-four canine flexor digitorum profundus tendons were repaired using polydioxanone monofilament or control braided polyester. Animals were evaluated 7, 14, 28, and 42 days after surgery with 12 day 0 control tendons. All repaired tendons healed without rupture or gap formation. Mechanically, all specimens had adequate tensile strength enabling active mobilization. The tendons that were repaired using braided polyester healed without initial tensile depression; however, the ultimate tensile strength values of polydioxanone specimens showed a significant decrease at day 14. Histologically, an inflammatory response was observed around the polydioxanone monofilament; this reaction increased from day 14 to day 42. However, the inflammatory response did not cause large adhesions or large tendon callus formation. This method of using absorbable suture material for tendon repair has the potential for use in the clinical setting.

Animals↗

PubMed2001

Bone suture anchors versus the pullout button for repair of distal profundus tendon injuries: a comparison of strength in human cadaveric hands.

Avulsion or distal tendon laceration of flexor digitorum profundus (FDP) is classically repaired to the base of the distal phalanx via a pullout suture over a button. Bone suture anchors, used extensively in other surgical areas, have recently been proposed for reattachment of the FDP to the distal phalanx. The FDP tendons of the index, long, and ring fingers in 9 fresh frozen cadeveric hands were randomized to 1 of 3 repair techniques after simulated distal avulsion injuries. These were the pullout button using 3-0 monofilament nylon in a 2-strand Bunnell suture pattern, the 1.8 mm Mini QuickAnchor (Mitek Products, Norwood, MA) using 3-0 braided polyester in a 2-strand Bunnell suture pattern, and the Mitek micro anchor using 3-0 braided polyester with a modified 4-strand Becker suture pattern. Nine specimens were loaded to failure, noting maximum load and mode of failure. The 1.3 mm Micro QuickAnchor (Mitek) technique (69.6 +/- 10.8 N) was significantly stronger than the pullout button (43.3 +/- 4.8 N) or the Mini anchor technique (44.6 +/- 12.7 N). The Micro bone suture anchor provides a stronger tendon to bone repair than the pullout button or the Mini anchor. Given the disadvantages of the pullout button, the Micro bone suture anchor with the modified Becker technique is worth consideration as an alternative method to repair distal FDP avulsions.

Aged↗

PubMed1998

Exclusion of lumbar arteries by aortic endovascular grafts: can angiography demonstrate sealing characteristics?

BACKGROUND: This study evaluates sealing characteristics of two designs of endovascular grafts by angiographic demonstration of exclusion of porcine lumbar arteries. METHODS: 6 endovascular grafts (3 self-expandable with integrated polyurethane wall versus 3 nitinol structures covered with polyester fabric) were implanted in 6 porcine aortae. Perfusion of lumbar arteries was assessed by angiography after implantation and by angiography and dissection at graft explantation after 4 +/- 2 months. Tissue healing was evaluated by light and scanning electron microscopy. RESULTS: Immediate exclusion of the lumbar arteries was achieved in 14/31 vessels (12 by polyurethane grafts and 2 by polyester grafts, p < 0.001). Follow-up angiography and dissection at explantation revealed perfusion of 30/31 lumbar arteries with a collateral network in most cases. Another reason for reperfusion of initially excluded branches was distention of the polyurethane grafts with resulting shortening allowing reperfusion of 8 of the 31 originally covered branches. Histological examination revealed a complete neointimal lining and a tight contact between endovascular grafts and aorta. CONCLUSIONS: The immediate angiographic demonstration of exclusion of lumbar arteries predicts sealing characteristics of endovascular grafts. Later angiographic reappearance is due to development of a collateral network and possible shortening of self-expandable devices.

Animals↗

PubMed2000

Filtration of activated granulocytes during cardiopulmonary bypass surgery: a morphologic and immunologic study to characterize the trapped leukocytes.

Cardiopulmonary bypass surgery induces an inflammatory reaction among others by activation of granulocytes. Leukocyte filtration has been shown to reduce the postoperative morbidity mediated by activated granulocytes. However, little is known about the mechanism of filter-leukocyte interaction. This study examines whether a leukocyte filter removes activated granulocytes or a general leukocyte population. Eleven patients undergoing cardiopulmonary bypass surgery were included in this study. Leukocyte filtration was achieved before the reperfusion phase with a Pall non-woven polyester filter located at the venous side of the heart-lung machine. After filtration, the trapped granulocytes inside the filter were examined morphologically with light and scanning electron microscopy and immunologically by CD45RO antigen binding to the filter material. Furthermore, leukocyte release markers were measured to determine whether cells were activated during filtration. Microscopic evaluation revealed 84% granulocytes and 14% lymphocytes trapped in the filter, compared with 78% granulocytes and 22% lymphocytes in the blood before filtration. Granulocytes were trapped significantly more in the first blood contact layer of the filter material than in the middle layer and last layer, whereas lymphocytes trapped slightly more in the middle layer. The near maximum level of CD45RO expression was measured on granulocytes trapped inside the filter material, whereas CD2 and CD19 measured on lymphocytes were bound to a minor extent. Beta-glucuronidase concentration did not increase after filtration, suggesting the absence of activation of granulocytes by filtration. A leukocyte filter made of non-woven polyester material removes the activated granulocytes rather than leukocytes at random. This implies that this particular type of leukocyte removal filter is suitable for use in cardiopulmonary bypass patients whose granulocytes in the circulation are activated. Furthermore, measurement of activated granulocytes instead of total leukocyte count is likely preferable for functional assessment of leukocyte removal devices.

Aged↗

PubMed1993

Comparative in vivo study on the healing qualities of four different presealed vascular prostheses.

PURPOSE: The purpose of this article is to assess the healing qualities of presealed knitted polyester prostheses. METHODS: Thoracic aortic replacement was performed with grafts with four different coating materials-collagen (CP), albumin (AP), and two with gelatin (GP1/GP2)-in four groups of 15 pigs each. Two weeks, 6 weeks, and 6 months after operation, five pigs of each group were killed. Healing quality was assessed by morphometric analysis of the remaining coating, the extent of tissue ingrowth, and the thickness of the inner layer. RESULTS: The sealant was rapidly absorbed in all prostheses except for the AP (remaining coating at 2 weeks: GP1 22.1%, GP2 34.7%, and CP 68.0% vs AP 97.1% [p < 0.05]), remaining coating at 6 weeks: GP1/GP2 0% and CP 2.5% vs AP 76.7% (p < .01). At 6 months, remaining coating was only detectable in AP (21.5%). At 2 weeks the extent of tissue ingrowth ranged from 65.7% in GP1 and 75.3% in CP to 80% in GP2 versus 8.9% in AP (p < 0.05). There was a slow increase of tissue ingrowth until the sixth postoperative week (GP1 74.4%, GP2 85.0%, and CP 91.3% versus AP 19.6% [p < 0.01]). Thickness of the internal layer varied from 0.11 to 0.21 mm at 2 weeks in all grafts studied and from 1.02 mm (AP) and 1.28 mm (GP2) to 1.39 mm (GP1), versus 0.41 mm in the CP (p < 0.01) after 6 months of implantation. CONCLUSIONS: The type of coating significantly influences the healing properties of knitted polyester prostheses. When used for thoracic aortic replacement in pigs, AP coating clearly results in inferior healing compared with GP1/GP2 or CP impregnation, with digestion of the coating material and tissue ingrowth used as parameters. The thinnest internal layer was found in the CP prostheses, reflecting superior healing properties of this coating in the model studied.

Absorption↗

PubMed2000

An evaluation of the costs to health care institutions of endovascular aortic aneurysm repair.

BACKGROUND: Endovascular graft techniques hold great potential as a less invasive means for the repair of aortic aneurysms, yet the impact of these new modalities remains poorly elucidated. METHODS: Over a 10-month period at a single institution, 139 patients underwent infrarenal aortic aneurysm repair through a traditional open surgical technique (OS group, 94 patients) or an endovascular approach (ES group, 45 patients). Coated polyester prostheses (Hemashield; Boston Scientific Corporation, Boston, Mass) were used in the OS patients, whereas a modular nitinol polyester device (AneuRx; Medtronic, Sunnyvale, Calif) was used in the ES group. The hospital costs exclusive of professional charges were tabulated for the two groups using the hospital cost accounting system. Outliers were included in the data analysis. RESULTS: The mean operating room time was longer in the OS group than in the ES group (285 minutes vs 166 minutes). The average length of stay was also longer in the OS group (9.7 days vs 3.2 days). Hospital costs related to the length of stay were higher in the OS group, including laboratory costs ($327 higher), pharmacy costs ($688 higher), and nursing costs ($780 higher). Anesthesia costs were also higher in the OS group ($493 higher). Despite these marked differences, the total hospital cost averaged $7205 more in the ES group, a finding that was driven by the cost of the implantable devices themselves ($8976 in the ES group vs $597 in the OS group). CONCLUSIONS: Despite reductions in the length of hospitalization, the cost of care was substantially greater in patients undergoing endovascular aneurysm repair than in patients in whom an open surgical technique was used. These differences are driven by the cost of the endograft device itself, a cost that must not exceed $6000 if the economic impact of endovascular repair is to be in parity with traditional methods. Unless these economic disparities can be ameliorated, the economic impact of endovascular aneurysm repair may limit the widespread application of this technology.

Aged↗

PubMed2002

Biochemical characterization of the Pseudomonas putida 3-hydroxyacyl ACP:CoA transacylase, which diverts intermediates of fatty acid de novo biosynthesis.

The 3-hydroxyacyl ACP:CoA transacylase (PhaG) was recently identified in various Pseudomonas species and catalyzes the diversion of ACP thioester intermediates of fatty acid de novo biosynthesis toward the respective CoA thioesters, which serve as precursors for polyester and rhamnolipid biosynthesis. PhaG from Pseudomonas putida was overproduced in Escherichia coli as a C-terminal hexahistidine-tagged (His(6)) fusion protein in high yield. The His(6)-PhaG was purified to homogeneity by refolding of PhaG obtained from inclusion bodies, and a new enzyme assay was established. Kinetic analysis of the 3-hydroxyacyl transfer to ACP, catalyzed by His(6)-PhaG, gave K(0.5) values of 28 microm (ACP) and 65 microm (3-hydroxyacyl-CoA) considering V(max) values of 11.7 milliunits/mg and 12.4 milliunits/mg, respectively. A Hill coefficient of 1.38 (ACP) and 1.32 (3-hydroxyacyl-CoA) indicated a positive substrate cooperativity. Subcellular localization studies showed that PhaG is not attached to polyester granules and resides in the cytosol. Gel filtration chromatography analysis in combination with light scattering analysis indicated substrate-induced dimerization of the transacylase. A threading model of PhaG was developed based on the homology to an epoxide hydrolase (1cqz). In addition, the alignment with the alpha/beta-hydrolase fold region indicated that PhaG belongs to alpha/beta-hydrolase superfamily. Accordingly, CD analysis suggested a secondary structure composition of 29% alpha-helix, 22% beta-sheet, 18% beta-turn, and 31% random coil. Site-specific mutagenesis of seven highly conserved amino acid residues (Asp-60, Ser-102, His-177, Asp-182, His-192, Asp-223, His-251) was used to validate the protein model and to investigate organization of the transacylase active site. Only the D182(A/E) mutation was permissive with about 30% specific activity of the wild type enzyme. Furthermore, this mutation caused a change in substrate specificity, indicating a functional role in substrate binding. The serine-specific agent phenylmethylsulfonyl fluoride (PMSF) or the histidine-specific agent diethylpyrocarbonate (DEPC) caused inhibition of 3-hydroxyacyl transfer to holo-ACP, and the S102(A/T) or H251(A/R) PhaG mutant was incapable of catalyzing 3-hydroxyacyl transfer, suggesting that these residues are part of a catalytic triad.

Acyltransferases↗

PubMed1984

The effect of formaldehyde or glutaraldehyde application to lucerne before ensiling on silage fermentation and silage N digestion in sheep.

The primary growth of lucerne (Medicago sativa) was ensiled after treatment with either formic acid alone (4.1 litres/t; silage F) or with formic acid and either formaldehyde (30.5 g/kg crude protein (nitrogen X 6.25; CP); silage FF), glutaraldehyde (44.2 g/kg CP; silage FG) or a mixture of the two aldehydes at approximately half their individual application rates (silage FFG). Compared with formic acid alone, both formaldehyde and glutaraldehyde reduced protein breakdown and carbohydrate fermentation during ensiling. The extent of protein protection afforded within the silo was similar for the two aldehydes, whereas formaldehyde was more effective in restricting carbohydrate fermentation. The effect of treatment FFG on silage fermentation was confounded by the silo bag bursting and the development of a clostridial-type fermentation. All aldehyde treatments reduced silage soluble-N content but N disappearance when the silages were incubated in polyester bags in the rumen was high for all silages and reductions due to the aldehydes were small. Silage digestion was studied in four mature sheep each fitted with a rumen cannula and re-entrant cannulas in the proximal duodenum and distal ileum. The apparent digestibility of organic matter (OM) in the whole tract was reduced (P less than 0.05) to a similar extent by both aldehydes, whereas rumen OM digestion was reduced (P less than 0.05) more by glutaraldehyde than by formaldehyde. The effects on digestion appeared to be due to the action of the aldehydes on the foods rather than to any adverse influences of the aldehydes on the metabolism of the rumen microbes because, although rumen ammonia levels were lower (P less than 0.05) when the aldehyde-treated silages were given, rumen casein-degrading activity, the degradation of different feedstuffs when incubated in polyester bags in the rumen and microbial N flow at the duodenum did not differ (P greater than 0.05) between silages. All aldehyde treatments decreased (P less than 0.05) the apparent digestibility of N in the whole tract. Silage N degradability in the rumen was also decreased (P less than 0.05) from 0.82 for silage F to 0.67, 0.60 and 0.62 for silages FF, FG and FFG respectively, and consequently non-ammonia-N (NAN) flow at the duodenum increased (P less than 0.05). The aldehydes did not adversely affect the apparent digestibility of NAN in the small intestine, and net NAN absorption from the small intestine increased from 8.8 g/d with silage F to 11.4, 15.3 and 14.2 g/d with silages FF, FG and FFG respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

Aldehydes↗

PubMed1985

Estimation of the degradability of dietary protein in the sheep rumen by in vivo and in vitro procedures.

Estimates of degradability of nitrogen in the sheep rumen for a basal hay diet and for soya-bean meal (SBM), groundnut meal (GNM) and fish meal (FM), when given together with the hay, were determined from measurements of duodenal N flow, ammonia kinetics and rumen N disappearance from polyester bags and rumen outflow rate. The ability of various in vitro procedures to predict in vivo N degradability was also examined. Four sheep were given a basal hay diet (800 g dry matter (DM) and 19 g N/d) either alone or supplemented with isonitrogenous amounts (15 g N/d) of SBM, GNM or FM. Duodenal non-ammonia-N flow (g/d) was increased more by FM (8.0) than by GNM (5.9) and SBM (5.8), whilst microbial N flow (g/d) was increased more by SBM (3.9) than by GNM (2.3) and FM (1.6). N degradability values calculated from these results were 0.88, 0.76 and 0.57 for the SBM, GNM and FM respectively. The corresponding value for hay was calculated to be 0.76. The irreversible loss of ammonia in the forestomachs (g N/d) was increased more by SBM (11.9) than by GNM (7.2) and FM (5.8), whilst ammonia outflow from the rumen (g N/d) was increased to a similar extent by all supplements (1.1, 0.9 and 0.8 respectively), as was the amount of microbial N (g/d) synthesized from sources other than rumen ammonia (1.8, 2.0 and 1.9 respectively). N degradability values calculated from these results were 0.84, 0.54 and 0.45 for the SBM, GNM and FM respectively. The fractional rate of N disappearance (/h) when the feedstuffs were incubated in polyester bags in the rumen of sheep receiving the basal hay diet (800 g DM/d) was the highest for SBM (0.145) and lowest for FM (0.037), with the hay (0.082) and GNM (0.071) intermediate, whilst the fractional outflow rates from the rumen (/h) of the three supplements were similar (0.034, 0.038 and 0.030 for SBM, GNM and FM respectively). N degradability values calculated from these results were 0.82, 0.67 and 0.60 for the SBM, GNM and FM respectively; the value for the hay was 0.73. Of a number of in vitro procedures tested, only N solubility in sodium hydroxide and ammonia or total non-protein-N (NPN) production during incubation with rumen fluid in the absence of hydrazine sulphate ranked the supplements, although not the hay, in the same order as in the vivo degradability procedures.(ABSTRACT TRUNCATED AT 400 WORDS)

Ammonia↗

PubMed1996

The effect of condensed tannins in Lotus pedunculatus on the solubilization and degradation of ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39; Rubisco) protein in the rumen and the sites of Rubisco digestion.

Three experiments were undertaken to determine the effect of condensed tannin (CT) in Lotus pedunculatus (45-55 g extractable CT/kg DM) on the digestion of the principal leaf protein, ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39; Rubisco; fraction 1 leaf protein). In two of the experiments Lotus pedunculatus was fed to sheep, with one group receiving a continuous intraruminal infusion (per fistulum) of PEG (molecular weight 3500) to bind and inactivate the CT (PEG group). The other group, which did not receive PEG, was termed the control sheep (CT acting). Expt 3 involved in vitro incubations of Lotus pedunculatus in buffered rumen fluid, with and without PEG added. In all experiments the results have been interpreted in terms of the effects of CT on Rubisco solubilization and degradation. Disappearance of N and Rubisco from Lotus pedunculatus suspended in polyester bags in the rumen was used as a measure of solubilization. Degradation was defined as the disappearance of Rubisco from in vitro incubations of Lotus pedunculatus in rumen fluid. In Expt 1, CT reduced the digestion of Rubisco in the rumen from 0.96 to 0.72 of intake (P < 0.01). Rubisco digestion in the small intestine was 0.27 of intake in control sheep and 0.04 of intake in PEG sheep. In Expt 2, PEG had no effect on the loss of Rubisco from Lotus pedunculatus contained in polyester bags which were incubated in the rumen, hence CT did not affect the solubilization of Rubisco. Observations in Expt 1 were confirmed by in vitro incubations in Expt 3, where PEG addition substantially increased the rate of degradation of plant protein to NH3. Addition of PEG decreased the period of time taken to degrade 50% of the Rubisco from about 13.8 h to about 3.0 h. It was concluded that the action of CT reduced the digestion of Rubisco in the rumen of sheep fed on fresh Lotus pedunculatus, and that this was primarily due to the ability of CT to slow its degradation by rumen micro-organisms, without affecting its solubilization. Both fresh-minced, and freeze-dried and ground lotus were used for in sacco and in vitro incubations; however, fresh-minced lotus was more suitable for the evaluation of protein solubilization and degradation in fresh forages.

Animals↗

PubMed2005

Evidence in support of a role for plant-mediated proteolysis in the rumens of grazing animals.

The present work aimed to differentiate between proteolytic activities of plants and micro-organisms during the incubation of grass in cattle rumens. Freshly cut ryegrass was placed in bags of varying permeability and incubated for 16 h in the rumens of dairy cows that had previously grazed a ryegrass sward, supplemented with 4 kg dairy concentrate daily. Woven polyester bags (50 microm pore size) permitted direct access of the micro-organisms and rumen fluid enzymes to the plant material. The polythene was impermeable even to small molecules such as NH(3). Dialysis tubing excluded micro-organisms and rumen enzymes/metabolites larger than 10 kDa. DM loss was 46.3 % in polyester, 36.2 % in polythene and 38.1 % in dialysis treatments. It is possible that the DM loss within polythene bags occurred due to a solubilisation of plant constituents (e.g. water-soluble carbohydrates) rather than microbial attachment/degradation processes. The final protein content of the herbage residues was not significantly different between treatments. Regardless of bag permeability, over 97 % of the initial protein content was lost during incubations in situ. Electrophoretic separation showed that Rubisco was extensively degraded in herbage residues whereas the membrane-associated, light-harvesting protein remained relatively undegraded. Protease activity was detected in herbage residues and bathing liquids after all incubation in situ treatments. Although rumen fluid contains proteases (possibly of plant and microbial origin), our results suggest that, owing to cell compartmentation, their activity against the proteins of intact plant cells is limited, supporting the view that plant proteases are involved in the degradation of proteins in freshly ingested herbage.

Animal Nutritional Physiological Phenomena↗

PubMed2005

Long-term stability of salivary cortisol.

The measurement of salivary cortisol provides a simple, non-invasive, and stress-free measure frequently used in studies of the hypothalamic-pituitary-adrenal axis activity. In research projects, samples are often required to be stored for longer periods of time either because of the protocol of the project or because of lack of funding for analysis. The aim of the present study was to explore the effects of long-term storage of samples on the amounts of measurable cortisol. Ten pools of saliva were collected on polyester Salivette tampons from five subjects. After centrifugation the samples were either stored in small vials or spiked to polyester Salivette tampons before analysis for cortisol using Spectria RIA kits. The effects of storage were evaluated by a linear regression model (mixed procedure) on a logarithmic scale. No effects on cortisol concentrations were found after storage of saliva at 5 degrees C for up to 3 months or at -20 degrees C and -80 degrees C for up to one year. In contrast, concentrations of cortisol were found to decrease by 9.2% (95% confidence interval (CI): 3.8%; 14.3%) per month in samples stored at room temperature. Repeated freezing and thawing of samples up to four times before analysis did not affect the measured concentrations of cortisol. The coefficient of residual variation (CVresid) for samples stored on Salivette tampons were twice the CVresid for samples stored in separate vials after centrifugation. In conclusion, centrifuged saliva samples for analysis of cortisol may be stored at 5 degrees C for up to 3 months or at -20 degrees C or -80 degrees C for at least one year. However, long-term storage at room temperature cannot be recommended. Repeated cycles of freezing and thawing did not appear to affect the concentrations of cortisol.

Freezing↗

PubMedDate not supplied

Identification of potential migrants from samples of dual-ovenable plastics.

The analysis of samples of dual-ovenable cookware articles has identified chemicals with the potential to migrate into food. Samples were analysed by dynamic headspace analysis at 200 degrees C using a Tenax TA trap cooled in ice, and/or solvent extraction, followed by gas chromatography/mass spectrometry. Plastics analysed were crystalline poly(ethyleneterephthlalate) (cPET), thermoset polyester, poly(ethersulphone) and poly (4-methyl-pent-1-ene) (TPX). The greatest number and quantity of chemicals with the potential to migrate were found in thermoset polyester.

Chromatography, Gel↗