Biomedical subjects

P H Cooke

Publications and source records attributed to P H Cooke.

At least 19 recordsLinked to original sources

PubMed2006

The management of failed ankle replacement.

Advances in the design of the components for total ankle replacement have led to a resurgence of interest in this procedure. Between January 1999 and December 2004, 16 patients with a failed total ankle replacement were referred to our unit. In the presence of infection, a two-stage salvage procedure was planned. The first involved the removal of the components and the insertion of a cement spacer. Definitive treatment options included hindfoot fusion with a circular frame or amputation. When there was no infection, a one-stage salvage procedure was planned. Options included hindfoot fusion with an intramedullary nail or revision total ankle replacement. When there was suspicion of infection, a percutaneous biopsy was performed. The patients were followed up for a minimum of 12 months. Of the 16 patients, 14 had aseptic loosening, five of whom underwent a revision total ankle replacement and nine a hindfoot fusion. Of the two with infection, one underwent fusion and the other a below-knee amputation. There were no cases of wound breakdown, nonunion or malunion. Management of the failed total ankle replacement should be performed by experienced surgeons and ideally in units where multidisciplinary support is available. Currently, a hindfoot fusion appears to be preferable to a revision total ankle replacement.

Aged↗

PubMed2006

Properties of whey protein isolates extruded under acidic and alkaline conditions.

Whey proteins have wide acceptance and use in many products due to their beneficial nutritional properties. To further increase the amount of whey protein isolates (WPI) that may be added to products such as extruded snacks and meats, texturization of WPI is necessary. Texturization changes the folding of globular proteins to improve interaction with other ingredients and create new functional ingredients. In this study, WPI pastes (60% solids) were extruded in a twin-screw extruder at 100 degrees C with 4 pH-adjusted water streams: acidic (pH 2.0 +/- 0.2) and alkaline (pH 12.4 +/- 0.4) streams from 2 N HCl and 2 N NaOH, respectively, and acidic (pH 2.5 +/- 0.2) and alkaline (pH 11.5 +/- 0.4) electrolyzed water streams; these were compared with WPI extruded with deionized water. The effects of water acidity on WPI solubility at pH 7, color, microstructure, Rapid Visco Analyzer pasting properties, and physical structure were determined. Alkaline conditions increased insolubility caused yellowing and increased pasting properties significantly. Acidic conditions increased solubility and decreased WPI pasting properties. Subtle structural changes occurred under acidic conditions, but were more pronounced under alkaline conditions. Overall, alkaline conditions increased denaturation in the extruded WPI resulting in stringy texturized WPI products, which could be used in meat applications.

Buffers↗

PubMed2003

Functionality of extrusion--texturized whey proteins.

Whey, a byproduct of the cheesemaking process, is concentrated by processors to make whey protein concentrates (WPC) and isolates (WPI). Only 50% of whey proteins are used in foods. In order to increase their usage, texturizing WPC, WPI, and whey albumin is proposed to create ingredients with new functionality. Extrusion processing texturizes globular proteins by shearing and stretching them into aligned or entangled fibrous bundles. In this study, WPC, WPI, and whey albumin were extruded in a twin screw extruder at approximately 38% moisture content (15.2 ml/min, feed rate 25 g/min) and, at different extrusion cook temperatures, at the same temperature for the last four zones before the die (35, 50, 75, and 100 degrees C, respectively). Protein solubility, gelation, foaming, and digestibility were determined in extrudates. Degree of extrusion-induced insolubility (denaturation) or texturization, determined by lack of solubility at pH 7 for WPI, increased from 30 to 60, 85, and 95% for the four temperature conditions 35, 50, 75, and 100 degrees C, respectively. Gel strength of extruded isolates increased initially 115% (35 degrees C) and 145% (50 degrees C), but gel strength was lost at 75 and 100 degrees C. Denaturation at these melt temperatures had minimal effect on foaming and digestibility. Varying extrusion cook temperature allowed a new controlled rate of denaturation, indicating that a texturized ingredient with a predetermined functionality based on degree of denaturation can be created.

Animals↗

PubMed2002

Giant-cell tumour of the tendon sheath in the foot and ankle.

Giant-cell tumour of the tendon sheath (GCT-TS) is a benign solitary tumour which usually arises in the limbs. It occurs most often in the hand where local recurrence after excision has been reported in up to 45% of cases. It is less common in the foot where the biological behaviour and risk of local recurrence have not been defined. We have studied 17 cases of GCT-TS of the foot and ankle in which treatment was by excision. Fifteen presented as a solitary, painless, slow-growing soft-tissue swelling. One lesion was associated with sensory deficit of a digital nerve and one with pain on walking. Thirteen cases originated from the periarticular tendon-sheath complex of the small joints of the toes and four from the capsule or long tendons of the ankle. A correct preoperative diagnosis was made in only three cases. MRI proved to be the most useful preoperative investigation as GCT-TS has a characteristic appearance which allows planned local excision to be carried out. None of the patients with histologically confirmed GCT-TS required further surgery. There was no local recurrence in 15 patients who were available for follow-up at a mean of 85 months.

Adolescent↗

PubMed2002

Molten globule structures in milk proteins: implications for potential new structure-function relationships.

Recent advances in the field of protein chemistry have significantly enhanced our understanding of the possible intermediates that may occur during protein folding and unfolding. In particular, studies on alpha-lactalbumin have led to the theory that the molten globule state may be a possible intermediate in the folding of many proteins. The molten globule state is characterized by a somewhat compact structure, a higher degree of hydration and side chain flexibility, a significant amount of native secondary structure but little tertiary folds, and the ability to react with chaperones. Purified alpha(s1)- and kappa-caseins share many of these same properties; these caseins may thus occur naturally in a molten globule-like state with defined, persistent structures. The caseins appear to have defined secondary structures and to proceed to quaternary structures without tertiary folds. This process may be explained, in part, by comparison with the architectural concepts of tensegrity. By taking advantage of this "new view" of protein folding, and applying these concepts to dairy proteins, it may be possible to generate new and useful forms of proteins for the food ingredient market.

Animals↗

PubMed2001

Effects of chilling on sampling of bacteria attached to swine carcasses.

Two microbiological sampling techniques, excision and sponge swabbing, were compared by determining counts of aerobic bacteria, coliforms and injured coliforms from 20 de-haired swine carcasses before and after chilling. Excised jowl skin produced significantly greater counts of the three types of bacteria than sponge swabs. Aerobic bacteria, coliforms and injured coliforms recovered by sponge swabbing carcasses before chilling were 11.6%, 0.9% and 11.0% of excised samples, respectively; the corresponding percentages recovered after chilling were 23.9%, 11.1% and 5.0%. Numbers of all bacteria present on the post-chill carcasses were substantially lower than on the pre-chill carcasses. Excision usually produced more countable plates for coliforms and injured coliforms on chilled carcasses than sponge swabbing and therefore, is more suitable in estimating low numbers of faecal bacteria on chilled carcasses. To explore the possible structural bases for these findings, skin samples were inoculated with 10(2)-10(7) cfu cm(-2) faecal bacteria and examined by scanning electron microscopy. Chilled samples showed bacteria and biofilm embedded in superficial crevices, which underlies a possible reason for the lower recovery of bacterial cells by the sponge swabbing. The study indicates that the differences between sampling techniques may be a result of the chilling process of swine carcasses.

Animals↗

PubMed2001

Response to trisodium phosphate treatment of Salmonella Chester attached to fresh-cut green pepper slices.

A laboratory model using green pepper disks was developed to investigate the attachment of Salmonella Chester on plant tissue and to evaluate the effectiveness of sanitizer agents in inactivating attached bacteria on fruits. Pepper disks (14 mm in diam, and 3-4 mm in thickness) were immersed in a bacterial suspension containing 1.5 x 107 cfu x mL(-1) of S. Chester for 30 s and subsequently air-dried at room temperature for 10 min. Approximately 30% of the bacteria retained on the disk after immersion were firmly attached and could not be removed by two washes and agitation. A positive correlation was observed between the number of bacteria attached and the concentration of bacteria in the suspension. Population studies and scanning electron microscopic examinations revealed that attachment of S. Chester on pepper disks occurred mainly on the surfaces of injured (cut) tissue but rarely on the unbroken skin. When inoculated disks were treated with 3% to 12% (w/v) of trisodium phosphate (TSP) at pH 12.3 for 5 min, the population of bacteria on the disk was reduced by 10- to 100-fold. A small portion (0.7% to 7.1%) of bacteria attached to the disk were either resistant to or protected from the TSP treatment. When the pH of TSP solution was reduced from 12.3 to 4.5, the effectiveness of TSP in inactivating S. Chester on pepper disks was reduced by 26%. This study shows that surfaces of injured fruit tissue are the principal sites for bacterial attachment, and a small portion of the bacteria attached to the tissue are resistant to the sanitizer treatment. Avoiding mechanical injuries to fresh fruits during and after harvest would reduce the chance of pathogen attachment and contamination on green pepper and fruits of similar nature.

Bacterial Adhesion↗

PubMed2000

Enzymatic hydrolysis, grease permeation, and water barrier properties of zein isolate coated paper.

An inexpensive zein-lipid mixture was isolated from yellow dent, dry-milled corn. Grease permeation through zein isolate applied to brown Kraft paper was found to be independent of loading levels at zein isolate levels above 30 mg/16 in.(2). The data shows that water vapor transmission rates depended on the amount of coating applied. Triacylglycerols were the most abundant lipid in milled corn but were absent in the zein isolate (perhaps due to hydrolysis by lipases). Zein from the paper was hydrolyzed enzymatically and the hydrolysis monitored by SDS-capillary electrophoresis. At an E:S ratio of 1:100 no further increase in the hydrolysate peak occurred after 10 and 30 min for alpha-chymotrypsin and pancreatin 8 x; however, zein and lipid were still present 1 h after hydrolysis by pancreatin 1 x.

Chromatography, High Pressure Liquid↗

PubMed1999

Characterization of the particles of purified kappa-casein: trypsin as a probe of surface-accessible residues.

kappa-Casein as purified from bovine milk exhibits a rather unique disulfide bonding pattern as revealed by SDS-PAGE. The disulfide-bonded caseins present range from dimer to octamer and above and preparations contain about 10% monomer. All of these heterogeneous polymers, however, self-associate into nearly spherical particles with an average diameter of 13 nm at pH 8.0, as revealed by negatively stained transmission electron micrographs and dynamic light scattering. The weight-average molecular weight of the aggregates at pH 8.0, as judged by analytical ultracentrifugation, is 648,000. Trypsin digestion at pH 8.0 was used to probe the surface groups of the kappa-casein A polymers. The reaction with trypsin was rapid and the peptides liberated were identified by separation with reverse-phase HPLC, amino acid analysis, and protein sequencing. The most rapidly released peptides (t1/2 < 30 sec) were from cleavage at Arg 97 and Lys residues 111 and 112. These results suggest a surface orientation for these residues, and the data are in accord with earlier proposed 3D predictive models for kappa-casein. It is speculated that Arg 97, together with adjacent His residues (98 and 100) and Lys residues 111 and 112, form two positively charged clusters on the surface of the otherwise negatively charged casein. These clusters bracket the neutral chymosin cleavage site (whose hydrolysis triggers a well-known digestive process) and so these clusters may facilitate docking of the substrate caseins with chymosin.

Amino Acid Sequence↗

PubMed1999

Divot sign: a new observation in anterior impingement of the ankle.

Anterior impingement of the ankle results from osteophyte formation on the anterior edge of the distal tibia. Classically, subsequent degeneration results in an osteophyte forming on the anterior neck of the talus. This results in limited dorsiflexion and impingement seen in the ankles of athletes. Recent clinical observation in high performance soccer players has revealed a previously unrecognized pattern of a localized divot forming in the talar neck in place of the osteophyte. This accepts the tibial osteophyte during dorsiflexion, which is therefore not limited in these patients.

Adaptation, Physiological↗

PubMed1996

Particle sizes of purified kappa-casein: metal effect and correspondence with predicted three-dimensional molecular models.

Amino Acids↗

PubMed1995

Electron-density patterns in low-fat mozzarella cheeses during refrigerated storage.

Explore the source record for details and available documents.

Animals↗

PubMed1995

Streptococcus bovis-infected total hip arthroplasty.

The case of a 51-year-old man who underwent a total hip arthroplasty following failed AO screw fixation of a subcapital femoral neck fracture is reported. Infection of the prosthesis with Streptococcus bovis type 1 followed a febrile illness. Further investigation revealed an occult premalignant polyp in the proximal colon. Colonic neoplasia and S. bovis bacteremia are associated with endocarditis; however, S. bovis is a rare pathogen infecting joint prostheses and should raise the possibility of a gastrointestinal lesion.

Colonic Polyps↗

PubMed1995

In situ characterization of Clostridium botulinum neurotoxin synthesis and export.

A monoclonal antitoxin/colloidal gold probe and sequential centrifugation were used to study synthesis, translocation and export of Clostridium botulinum strain 62A neurotoxin (NT). Exponential growth occurred after 5 h of anaerobic incubation of spores and continued for 15-16 h. NT was detected at 15 h using the probe and transmission electron microscopy (TEM), 2 h earlier than the first detection by the mouse bioassay. During exponential growth, the probe localized NT primarily in the cytoplasm, on the inner side of the cytoplasmic membrane and in the cell wall. During stationary and death phases, the NT was located within the cytoplasm, cell wall and extracellularly. NT was released from the cell during cell wall exfoliation. Cells retained NT after repeated gelatin-phosphate washes and sequential centrifugations, consistent with the TEM observation that the NT is bound to the cell wall. These observations indicate that the process of Cl. botulinum type A NT production follows a sequence of synthesis, translocation across the cytoplasmic membrane and export through the cell wall.

Animals↗

PubMed1993

Developmental regulation of sterol carrier protein 2 in chicken intestine and liver at time of hatching.

Sterol Carrier Protein 2, a protein thought to be involved in various aspects of intracellular sterol transport and metabolism, was studied in the small intestine and liver of chickens near hatching. In the intestine, a sudden shift in molecular mass, from 12 kDa to 64 kDa was noted by Western blotting on the day of hatching. Immediately post-hatching, the molecular mass returned to 12 kDa but the protein was several fold more abundant than prior to hatching. In the liver, several molecular mass forms were present at all ages examined but total shift to the 64 kDa form was not seen. Following hatching, however, the 12 kDa form became more abundant. Regardless of age of bird or molecular mass, the protein was found mainly in peroxisomes.

Animals↗

PubMed1993

The myosin molecule--charge response to nucleotide binding.

A decrease in the net fixed electric charge in the A-bands of cross-striated muscle was observed by Bartels and Elliott [2,10] when the muscle went from the rigor to the relaxed condition. The current work localises the source of the charge decrease by following the net charge on myosin (in the form of concentrated gels) and also myosin rod and light meromyosin gels when the gels are exposed to different concentrations of ATP. The work includes a study of muscle A-bands when the muscle is exposed to the same variations in ATP concentrations as the protein gels. The work shows that (i) Only 100-200 microns ATP is needed to initiate the charge decrease between the rigor and relaxed conditions; (ii) the effect of ATP is seen in the muscle A-band and the myosin and myosin rod gels, but not in LMM gels; (iii) pyrophosphate (PPi) shows a similar charge effect to ATP. ADP does not affect the charge on myosin gels, on the other hand. The results suggest that the charge decrease caused by ATP or PPi is due to ligand interaction with one or more sites on the myosin molecule. This interaction causes a disseminated effect in the protein, and a consequent loss in net negative charge either by a decrease in the absorption, of anions to Saroff sites on the protein, or, less probably, by an increase in the absorption of cations at those sites.

Adenosine Diphosphate↗

PubMed1993

Virulence of an Escherichia coli O157:H7 sorbitol-positive mutant.

Virulence and pathogenicity of an Escherichia coli O157:H7 sorbitol-positive mutant were investigated with an infant rabbit animal model as well as a battery of in vitro assays. Total cell lysate protein profiles, outer membrane protein profiles, plasmid profiles, and levels of cytotoxic activity against Vero cells were similar in the wild-type and mutant strains. Both adhered to intestinal epithelial cells in culture and reacted with fluorescein isothiocyanate-labeled antiserum against E. coli O157:H7. The mutant appeared to be similar to the wild type in all respects except in its ability to ferment sorbitol. [14C]sorbitol uptake and sorbitol-6-phosphate dehydrogenase activities were notably increased in the mutant strain. Diarrhea developed in rabbits administered the wild-type strain and in those fed the sorbitol-positive mutant. There was greater bacterial attachment and mucosal damage in the cecum and large intestine than in the small intestine. Scanning electron microscopy revealed bacteria adhering as single cells and as aggregates closely associated with mucus. Mucosal lesions consisted of areas of tissue necrosis with sloughing of epithelial cells. By transmission electron microscopy, electron-dense necrotic epithelial cells were visible in areas where bacteria were present, and epithelial cell debris containing bacteria was observed between the villar luminal surfaces. Light microscopy of epithelial cells of intestinal sections of infected rabbits revealed noticeable vacuolation and spherical, pyknotic nuclei. These data indicate that the sorbitol-negative phenotype is not associated with the pathogenicity of E. coli O157:H7.

Animals↗

PubMed1991

Synchrotron x-ray diffraction studies of the cornea, with implications for stromal hydration.

The intermolecular and interfibrillar spacings of collagen in bovine corneal stroma have been measured as a function of tissue hydration. Data were recorded from low- and high-angle x-ray diffraction patterns obtained using a high intensity synchrotron source. The most frequently occurring interfibrillar spacing varied from 34 nm in dry corneas to 76 nm at H = 5 (the hydration, H, is defined as the ratio of the weight of water to the dry weight). The most frequently occurring intermolecular Bragg spacing increased from 1.15 nm (dry) to approximately 1.60 nm at normal hydration (H approximately 3.2) and continued to increase only slowly above normal hydration. Most of the increase in the intermolecular spacing occurred between H = O and H = 1. Over this hydration range the interfibrillar and intermolecular spacings moved in tandem, which suggests that the initial water goes equally within and between the fibrils. Above H = 1 water goes preferentially between the fibrils. The results suggest that, even at normal hydration, water does not fill the interfibrillar space uniformly, and a proportion is located in another space or compartment. In dried-then-rehydrated corneas, a larger proportion of the water goes into this other compartment. In both cases, it is possible to postulate a second set or population of fibrils that are more widely and irregularly separated and therefore do not contribute significantly to the diffraction pattern.

Animals↗