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Biomedical subjects

A L Kelly

Publications and source records attributed to A L Kelly.

At least 19 recordsLinked to original sources
PubMed2006

Stability of casein micelles cross-linked by transglutaminase.

In this study, caseins micelles were internally cross-linked using the enzyme transglutaminase (TGase). The integrity of the micelles was examined on solubilization of micellar calcium phosphate (MCP) or on disruption of hydrophobic interactions and breakage of hydrogen bonds. The level of monomeric caseins, determined electrophoretically, decreased with increasing time of incubation with TGase at 30 degrees C; after incubation for 24 h, no monomeric beta- or kappa-caseins were detected, whereas only a small level of monomeric alphaS1-casein remained, suggesting near complete intramicellar cross-linking. The ability of casein micelles to maintain structural integrity on disruption of hydrophobic interactions (using urea, sodium dodecyl sulfate, or heating in the presence of ethanol), solubilization of MCP (using the calcium-chelating agent trisodium citrate) or high-pressure treatment was estimated by measurement of the L*-value of milk; i.e., the amount of back-scattered light. The amount of light scattered by casein micelles in noncross-linked milk was reduced by >95% on complete disruption of hydrophobic interactions or complete solubilization of MCP; treatment of milk with TGase increased the stability of casein micelles against disruption by all methods studied and stability increased progressively with incubation time. After 24 h of cross-linking, reductions in the extent of light scattering were still apparent in the presence of high levels of dissociating agents, possibly through citrate-induced removal of MCP nanoclusters from the micelles, or urea- or sodium dodecyl sulfate-induced increases in solvent refractive index, which reduce the extent of light-scattering.

Animals↗
PubMed2005

Sensory characteristics and related volatile flavor compound profiles of different types of whey.

To characterize the flavor of liquid whey, 11 samples of whey representing a wide range of types were sourced from cheese and casein-making procedures, either industrial or from pilot-plant facilities. Whey samples were assessed for flavor by descriptive sensory evaluation and analyzed for headspace volatile composition by proton transfer reaction-mass spectrometry (PTR-MS). The sensory data clearly distinguished between the samples in relation to the processes of manufacture; that is, significant differences were apparent between cheese, rennet, and acid wheys. For Mozzarella and Quarg wheys, in which fermentation progressed to low pH values, the starter cultures used for cheese making had a significant influence on flavor. In comparison, Cheddar and Gouda wheys were described by milk-like flavors, and rennet casein wheys were described by "sweet" (oat-like and "sweet") and thermally induced flavors. The volatile compound data obtained by PTR-MS differentiated the samples as distinctive and reproducible "chemical fingerprints". On applying partial least squares regression to determine relationships between sensory and volatile composition data, sensory characteristics such as "rancid" and cheese-like odors and "caramelized milk," yogurt-like, "sweet," and oat-like flavors were found to be related to the presence and absence of specific volatile compounds.

Caseins↗
PubMed2005

Influence of starter culture on flavor and headspace volatile profiles of fermented whey and whey produced from fermented milk.

Rennet whey and skim milk were compared as media for fermentation by commercial cheese, yogurt, and probiotic starter cultures. Effect of culture, medium, and their interaction on flavor was assessed and compared by sensory descriptive analysis and headspace volatile analysis by proton transfer reaction-mass spectrometry. In general, the aroma of fermented whey was similar to that of whey separated from fermented milk, indicating a favorable possibility of substituting milk with whey in the manufacture of fermented milk-like beverages. Starter culture significantly affected most sensory characteristics of the products. Key volatile compounds for the characteristic flavor of yogurt, such as acetaldehyde and diacetyl, were not significantly affected by medium when fermented with the yogurt culture, and reached similar levels in both systems. Volatile analysis results were consistent with the results of the sensory evaluation, indicating the high reliability of proton transfer reaction-mass spectrometry in detecting important volatile compounds for aroma. Integration of this sensory and chemical information allows a better understanding of how flavor and related compounds are affected by ingredients or processing, which may be useful for the development of value-added whey products.

Acetaldehyde↗
PubMed2003

Randomised, double-blind, placebo-controlled parallel group study of P54FP for the treatment of dogs with osteoarthritis.

P54FP is an extract of Indian and Javanese turmeric, Curcuma domestica and Curcuma xanthorrhiza respectively, which contains a mixture of active ingredients including curcuminoids and essential oils. A randomised, double-blind, placebo-controlled, parallel group clinical trial of P54FP as a treatment for osteoarthritis of the canine elbow or hip was conducted to assess its efficacy and safety. Sixty-one client-owned dogs with osteoarthritis were recruited through first-opinion practices and examined at a single centre. After a two-week wash-out period, they were randomly allocated to receive P54FP or a placebo orally twice daily for eight weeks, and were re-examined after four, six and eight weeks of treatment. The effectiveness of the treatment was assessed in terms of the peak vertical force (PVz) and vertical impulse of the affected limbs, as measured with a force platform, by clinical assessments of lameness and joint pain by the investigators, and overall assessments of the response to treatment by the investigators and the owners. The results from 25 P54FP-treated dogs and 29 placebo-treated dogs showed that there was no statistically significant difference between the groups in terms of the PVz of the affected limb. The investigators' overall assessment showed a statistically significant treatment effect in favour of P54FP (P=0.012), but the owners' assessment just failed to reach statistical significance (P=0.063). No serious adverse effects were recorded, but two P54FP-treated dogs and four placebo-treated dogs were withdrawn from the study because their condition deteriorated.

Animals↗
PubMed2002

Influence of transglutaminase treatment on some physico-chemical properties of milk.

Transglutaminase (TGase) is an enzyme that cross-links many proteins, including milk proteins. In this study, the effects of TGase on some physico-chemical properties of milk were studied. TGase-treated milk was not coagulable by rennet, which was due to failure of the primary (enzymic) stage of rennet action rather than the non-enzymic secondary phase. Dissociation of TGase-treated casein micelles by urea or sodium citrate or removal of colloidal calcium phosphate by acidification and dialysis was reduced, presumably due to the formation of cross-links between the caseins. Casein micelles in TGase-treated milks were also resistant to high pressure treatment and to hydrolysis by plasmin. Results of the present study show that milk proteins are fundamentally modified by the action of TGase, which may have applications in the manufacture of functional proteins for use as novel food ingredients.

Animals↗
PubMed2002

Effect of transglutaminase on the heat stability of milk: a possible mechanism.

Treatment of milk with transglutaminase (TGase) affects its heat stability, but the manner in which it does so depends on whether or not the milk had been preheated before incubation and on the temperature of preheating. In raw milk, it appears that cross-link formation between the individual caseins is responsible for preventing the dissociation of kappa-casein from the micelles at pH values in the region of minimum stability. In milks preheated before incubation with TGase, denaturation of whey protein may have allowed the formation of cross-links by TGase between denatured whey proteins and the individual caseins which, in combination with cross-linking of the caseins, contributed to greatly improved heat stability at pH > 6.5. It appears from the results of this study that TGase has potential commercial applications as a food-grade additive capable of improving the heat stability of milk.

Animals↗
PubMed2001

Thermal inactivation kinetics of bovine cathepsin D.

Cathepsin D, the principal indigenous acid proteinase in bovine milk, is a lysosomal proteinase, which exists in milk in four forms, including the inactive zymogen procathepsin D. The thermal inactivation kinetics of bovine cathepsin D, isolated from spleen and milk, were studied under isothermal conditions, using a specific HPLC assay to determine residual activity. Inactivation of the blood enzyme preparation followed first order kinetics, with z-values in phosphate buffer (pH 6.7) and skimmed milk of 6.5 and 7.6 degrees C, respectively, the enzyme being far more stable in the latter environment. Inactivation kinetics of the enzyme purified from milk were more complex, and could be best approximated by a double exponential model. Again, stability was higher in milk than in buffer. The double exponential model may indicate differing heat stabilities of isoforms of the enzyme, or stabilization of the enzyme by some milk constituent. It is clear that the enzyme can survive, at least partially, processes such as heating at 55 degrees C for 30 min during manufacture of high-cook cheese varieties (45% survival), and HTST pasteurization (8% survival), and thus may contribute to proteolysis in a range of dairy products.

Animals↗
PubMed2001

Ethanol-dependent heat-induced dissociation of casein micelles.

The dissociation of casein micelles when heated to approximately 65 degrees C in the presence of ethanol [1:1 mixture (v/v) of milk and 65% (w/w) aqueous ethanol] was investigated using L* values and transmission measurements. Mixtures of milk and ethanol became transparent on heating, which suggests dissociation of casein micelles. Results of experiments using confocal laser scanning microscopy, light scattering (static and dynamic), and dialysis to examine the changes of milk during heating in the presence of ethanol supported the assertion that such treatments result in dissociation of casein micelles, as did studies of model beta-casein micellar systems.

Animals↗
PubMed2001

Mechanism for the ethanol-dependent heat-induced dissociation of casein micelles.

An explanation as to how casein micelles dissociate when heated in the presence of ethanol is presented. Dissociation of casein micelles in milk-ethanol mixtures was studied using (1)H NMR, and the effects of addition of CaCl(2), NaCl, or EDTA or alteration of milk pH on this dissociation were studied. It is proposed that at low temperatures, ethanol reduces the solvent quality of milk serum, but above a critical temperature (approximately 30 degrees C in a 35% ethanol solution), ethanol enhances solvent quality and dissociates the casein micelles. Ethanol reduced protein hydrophobicity and increased the pK(a) value of phosphoserine, effects that are likely to be significant in the dissociating effect of ethanol at elevated temperatures.

Animals↗
PubMed2001

Classification and genetic features of neonatal haemochromatosis: a study of 27 affected pedigrees and molecular analysis of genes implicated in iron metabolism.

Neonatal haemochromatosis (NH) is a severe and newly recognised syndrome of uncertain aetiology, characterised by congenital cirrhosis or fulminant hepatitis and widespread tissue iron deposition. NH occurs in the context of maternal disease including viral infection, as a complication of metabolic disease in the fetus, and sporadically or recurrently, without overt cause, in sibs. Although an underlying genetic basis for NH has been suspected, no test is available for predictive analysis in at risk pregnancies. As a first step towards an understanding of the putative genetic basis for neonatal haemochromatosis, we have conducted a systematic study of the mode of transmission of this disorder in a total of 40 infants born to 27 families. We have moreover carried out a molecular analysis of candidate genes (beta(2)-microglobulin, HFE, and haem oxygenases 1 and 2) implicated in iron metabolism. No pathogenic mutations in these genes were identified that segregate consistently with the disease phenotype in multiplex pedigrees. However, excluding four pedigrees with clear evidence of maternal infection associated with NH, a pedigree showing transmission of maternal antinuclear factor and ribonucleoprotein antibodies to the affected infants, and two families with possible matrilineal inheritance of disease in maternal half sibs, a large subgroup of the affected pedigrees point to the inheritance of an autosomal recessive trait. This included 14 pedigrees with affected and unaffected infants and a single pedigree where all four affected infants were the sole offspring of consanguineous but otherwise healthy parents. We thus report three distinct patterns of disease transmission in neonatal haemochromatosis. In the differentiation of a large subgroup showing transmission of disease in a manner suggesting autosomal recessive inheritance, we also provide the basis for further genome wide studies to define chromosomal determinants of iron storage disease in the newborn.

Adolescent↗
PubMed2001

Short communication: influence of transglutaminase on the heat stability of milk.

Skim milk powders were prepared from control and transglutaminase-treated skimmed milk. The heat stability of reconstituted transglutaminase-treated skimmed milk (9.0% total solids) was markedly increased in the pH region of minimum stability (pH 6.8 to 7.1) compared with control milk, while the heat stability of reconstituted concentrated transglutaminase-treated skimmed milk (22.5% total solids) increased progressively as a function of pH relative to control milk. The effect of transglutaminase treatment on the heat stability of skimmed milk may have commercial applications, but extensive research is necessary to gain a better understanding of the mechanism by which transglutaminase improves heat stability.

Animals↗
PubMed2000

Localization of iron transport and regulatory proteins in human cells.

The recent discovery of HFE, the MHC-Class-I-like gene mutated in up to 90% of patients with hereditary haemochromatosis, and the gene encoding the Nramp2/divalent metal transporter-1 (DMT-1) implicated in ferrous iron transport holds promise for a greater understanding of human iron metabolism. Since the HFE protein can be crystallized as a ternary complex with the transferrin receptor and iron-saturated transferrin, and DMT-1 expression is up-regulated in hereditary haemochromatosis, these proteins are likely to interact in a common pathway for human iron homeostasis. To investigate the cellular interactions between the cognate proteins encoded by these genes, we generated a panel of rabbit and avian antisera from human HFE and DMT-1 derived peptides. The antibodies were characterized by ELISA reactions and Western immunoblotting. Immunohistochemical staining showed that DMT-1 protein localized to the brush border of human duodenum where it is predicted to serve as the principal transporter of ferrous iron from the intestinal lumen. In the human cell lines, Caco-2 (small intestinal phenotype upon differentiation) and K562 (erythroleukaemic) HFE, in the presence of iron-saturated transferrin, co-localized with transferrin receptors in an early endosome compartment using confocal immunofluorescence microscopy. This interaction may be critical in small-intestinal crypt cells which express HFE, where it may function to modulate their intrinsic iron status thereby programming iron absorption by DMT-1 in the mature enterocyte. In undifferentiated Caco-2 cells, DMT-1 localized to a discrete late endosome compartment distinct from that occupied by HFE where, in addition to brush-border iron uptake, it may function to regulate the availability of iron delivery to intracellular iron pools. Disruption of the HFE gene as a result of mutations associated with hereditary haemochromatosis may thus impair homeostatic mechanisms controlling iron absorption within the small-intestine epithelium by a direct interaction with transferrin receptors and by subsequent alteration of DMT-1 expression. Identification of the molecular interactions of HFE with DMT-1 and other key components of the iron transport pathway has implications for a mechanistic understanding of the pathophysiology of human iron storage diseases as well as the regulation of normal iron balance.

Animals↗
PubMed2000

Use of hydrostatic pressure for inactivation of microbial contaminants in cheese.

The objective of this study was to determine the effect of high pressure (HP) on the inactivation of microbial contaminants in Cheddar cheese (Escherichia coli K-12, Staphylococcus aureus ATCC 6538, and Penicillium roqueforti IMI 297987). Initially, cheese slurries inoculated with E. coli, S. aureus, and P. roqueforti were used as a convenient means to define the effects of a range of pressures and temperatures on the viability of these microorganisms. Cheese slurries were subjected to pressures of 50 to 800 MPa for 20 min at temperatures of 10, 20, and 30 degrees C. At 400 MPa, the viability of P. roqueforti in cheese slurry decreased by >2-log-unit cycles at 10 degrees C and by 6-log-unit cycles at temperatures of 20 and 30 degrees C. S. aureus and E. coli were not detected after HP treatments in cheese slurry of >600 MPa at 20 degrees C and >400 MPa at 30 degrees C, respectively. In addition to cell death, the presence of sublethally injured cells in HP-treated slurries was demonstrated by differential plating using nonselective agar incorporating salt or glucose. Kinetic experiments of HP inactivation demonstrated that increasing the pressure from 300 to 400 MPa resulted in a higher degree of inactivation than increasing the pressurization time from 0 to 60 min, indicating a greater antimicrobial impact of pressure. Selected conditions were subsequently tested on Cheddar cheese by adding the isolates to cheese milk and pressure treating the resultant cheeses at 100 to 500 MPa for 20 min at 20 degrees C. The relative sensitivities of the isolates to HP in Cheddar cheese were similar to those observed in the cheese slurry, i.e., P. roqueforti was more sensitive than E. coli, which was more sensitive than S. aureus. The organisms were more sensitive to pressure in cheese than slurry, especially with E. coli. On comparison of the sensitivities of the microorganisms in a pH 5.3 phosphate buffer, cheese slurry, and Cheddar cheese, greatest sensitivity to HP was shown in the pH 5.3 phosphate buffer by S. aureus and P. roqueforti while greatest sensitivity to HP by E. coli was exhibited in Cheddar cheese. Therefore, the medium in which the microorganisms are treated is an important determinant of the level of inactivation observed.

Cheese↗
PubMed2000

Correlation between bovine milk somatic cell count and polymorphonuclear leukocyte level for samples of bulk milk and milk from individual cows.

The influence of various factors on the concentrations of polymorphonuclear neutrophilic leukocytes (PMN) in milk samples from bulk tanks and individual cows was investigated. While somatic cell counts (SCC) and PMN level were in both cases significantly correlated, lower correlation coefficients were found between SCC and PMN for samples of bulk tank milks than for milk samples from individual cows. Furthermore, plots of PMN concentrations versus SCC showed great variability in PMN in milk samples of similar total SCC. One factor that may lead to variability in bulk tank PMN levels was shown to be increased proportions of high SCC milk in the bulk tank mixture, which result in relatively high PMN levels without excessive elevation of total SCC. In milk samples from individual cows, it was found that there was also a significant seasonal influence on milk PMN content, with milk from cows calving in the spring having, at SCC > 160,000 cells/ ml, higher proportions of PMN in the total milk SCC than milk from autumn calving cows. The results of this study suggest that the concentration of PMN may be a useful indicator of herd status in bulk tank monitoring schemes.

Animals↗
PubMed1999

Inherited disorders of iron storage and transport.

Diverse hereditary disorders associated with iron accumulation cause widespread organ damage. New insights into cellular pathways of iron transport have emerged from the identification of molecules implicated in heritable defects of iron metabolism. Unravelling the genetic basis of rare variants of haemochromatosis should provide vital functional information to further our mechanistic understanding of iron homeostasis.

Adult↗
PubMed1999

Juvenile hemochromatosis locus maps to chromosome 1q.

Juvenile hemochromatosis (JH) is an autosomal recessive disorder that leads to severe iron loading in the 2d to 3d decade of life. Affected members in families with JH do not show linkage to chromosome 6p and do not have mutations in the HFE gene that lead to the common hereditary hemochromatosis. In this study we performed a genomewide search to map the JH locus in nine families: six consanguineous and three with multiple affected patients. This strategy allowed us to identify the JH locus on the long arm of chromosome 1. A maximum LOD score of 5.75 at a recombination fraction of 0 was detected with marker D1S498, and a LOD score of 5. 16 at a recombination fraction of 0 was detected for marker D1S2344. Homozygosity mapping in consanguineous families defined the limits of the candidate region in an approximately 4-cM interval between markers D1S442 and D1S2347. Analysis of genes mapped in this interval excluded obvious candidates. The JH locus does not correspond to the chromosomal localization of any known gene involved in iron metabolism. These findings provide a means to recognize, at an early age, patients in affected families. They also provide a starting point for the identification of the affected gene by positional cloning.

Adolescent↗
PubMed1998

Haemochromatosis: an inherited metal and toxicity syndrome.

A newly-identified major histocompatibility Class I-like gene, HFE (originally HLA-H) located approximately 3.5 Mb telomeric to the Class I cluster on chromosome 6p 21.3 harbours mutations in haemochromatosis. Two of these, Cys282Tyr (C282Y) and His63Asp (H63D, a minor determinant) have diagnostic utility as approximately 90% of adults are homozygous or compound heterozygotes for these alleles. The pathophysiological role of HFE is unclear: it is expressed as a surface molecule on many cells and the C282Y mutation disrupts interactions with beta 2-microglobulin, thus preventing surface expression. Lately, there has been experimental evidence that HFE protein interacts with the transferrin-receptor, affecting receptor turnover or its affinity for ligand.

Animals↗