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Biomedical subjects

J Horne

Publications and source records attributed to J Horne.

At least 19 recordsLinked to original sources
PubMed2006

Proteolysis and microstructure of Piacentinu Ennese cheese made using different farm technologies.

The aim of this study was to provide the biochemical and structural characterization of Piacentinu Ennese cheese and to evaluate the impact of different farm technologies on cheese proteolysis and microstructure. Fifteen cheeses were manufactured according to traditional technology, i.e., from raw milk and farmhouse rennet in the absence of starter culture. Pasteurized milk, commercial rennet, and starter were used for production of 20 nontraditional cheeses. Proteolysis in Piacentinu Ennese cheese was monitored during a 2- to 10-mo ripening time. Low rates of overall proteolysis were observed in cheese, as percentages of total N soluble at pH 4.6 and in 12% trichloroacetic acid were about 11.40 and 8.10%, respectively, after 10 mo of age. Patterns of primary proteolysis by urea-PAGE showed that alpha(s)-caseins were degraded to a larger extent than were beta-caseins, although a considerable amount of both caseins was still intact after 10 mo. Reversed phase-HPLC analysis of the cheese peptide fractions showed a slow decrease in the levels of hydrophobic peptides coupled to increasing levels of hydrophilic compounds as the cheese aged. The structural characteristics of Piacentinu Ennese cheese were evaluated by scanning electron microscopy after 2, 4, and 6 mo of age. The micrographs showed a sponge-like structural network with a well-distributed system of empty spaces, originally occupied by whey and fat. The microstructure changed during cheese ripening to become more compact with cavities of smaller size. Farm technology significantly affected cheese proteolysis and microstructure. Nontraditional cheeses had higher levels of pH 4.6-soluble N and showed a larger hydrolysis of alpha(s)-casein fractions by urea-PAGE analysis than did traditional cheeses. Large differences between cheese-types also concerned the patterns of secondary proteolysis. Nontraditional cheeses had higher levels of 12% trichloroacetic acid-soluble N and showed larger proportions of free amino acids and hydrophilic peptides in the HPLC profiles of the corresponding 70% ethanol-soluble N fraction than traditional cheeses. Nontraditional cheeses also had a more open structure with a coarser and less continuous appearance than did traditional cheeses. A large amount of variability in cheese proteolysis and structure within nontraditional treatment reflected farm-dependent changes in manufacturing conditions related to the use of various types of rennet and starter.

Agriculture↗
PubMed2005

Evaluation of bitterness in Ragusano cheese.

The appearance of undesirable bitter taste in Ragusano cheese was investigated by comparing the composition of 9 bitter cheeses with that of 9 reference cheeses of good quality by means of chemical, electrophoretic, and chromatographic analyses. Rates of proteolysis were significantly affected in cheeses of different quality. Primary proteolysis, as measured by pH 4.6-soluble N, was significantly greater in bitter cheeses compared with reference samples. Urea-PAGE profiles showed an almost complete breakdown of caseins in bitter cheeses and the further degradation of primary peptides into smaller compounds not detectable by this technique. Cheeses with defects had significantly lower levels of secondary proteolysis as reflected by the percentage of pH 4.6-soluble N soluble in 12% trichloroacetic acid and the amounts of total free amino acids. Peptides separated by reversed phase-HPLC revealed that the large and significant differences in peptide profiles of the soluble fractions between bitter and reference cheeses were mainly due to a much higher proportion of hydrophobic peptides in the former. The occurrence of bitterness in Ragusano cheese was therefore attributable to unbalanced levels of proteolysis and peptidolysis. Extensive degradation of caseins and primary peptides by activities of proteases produced large amounts of small- and medium-sized hydrophobic peptides that were not adequately removed by peptidases of microflora and therefore accumulated in cheese potentially contributing to its bitter taste. The presence of these compounds in bitter cheeses was related to high salt-in-moisture and low moisture contents that limited the enzymatic activities of microflora important in secondary proteolysis. Combining salt-in-moisture and the ratio of hydrophobic-to-hydrophilic soluble peptides resulted in the best logistic partial least squares regression model predicting cheese quality. Although bitterness is known to be rarely encountered in cheese at salt-in-moisture levels >5.0, all of the bitter cheeses analyzed in this study had salt-in-moisture levels much greater than this value. According to the logistic model, a risk of bitterness development may exist for cheeses with a midrange (5 to 10%) salt-in-moisture content but with an inadequate level of secondary proteolysis.

Caseins↗
PubMed2004

The DNA sequence and comparative analysis of human chromosome 10.

The finished sequence of human chromosome 10 comprises a total of 131,666,441 base pairs. It represents 99.4% of the euchromatic DNA and includes one megabase of heterochromatic sequence within the pericentromeric region of the short and long arm of the chromosome. Sequence annotation revealed 1,357 genes, of which 816 are protein coding, and 430 are pseudogenes. We observed widespread occurrence of overlapping coding genes (either strand) and identified 67 antisense transcripts. Our analysis suggests that both inter- and intrachromosomal segmental duplications have impacted on the gene count on chromosome 10. Multispecies comparative analysis indicated that we can readily annotate the protein-coding genes with current resources. We estimate that over 95% of all coding exons were identified in this study. Assessment of single base changes between the human chromosome 10 and chimpanzee sequence revealed nonsense mutations in only 21 coding genes with respect to the human sequence.

Animals↗
PubMed2004

Contribution of native pasture to the sensory properties of Ragusano cheese.

Ragusano is a Protected Denomination of Origin cheese produced in the Hyblean area of Sicily. Sixteen samples of Ragusano cheese from two different treatments [pasture and total mixed ration (TMR)] were evaluated after 4 and 7 mo of aging. The color of the cheeses produced from milk of cows consuming fresh native pasture plants was much more yellow than cheeses from TMR fed cows (i.e., higher Hunter b value). This was due to transfer of beta-carotene and related compounds from the diet and demonstrated that compounds from native pasture plants changed the sensory characteristics of Ragusano cheese. To avoid a "halo" effect in a trained panel, quantitative descriptive analysis sensory evaluation of these cheeses for odor, taste, consistency, and mouth structure, color differences among cheeses were masked. A unique approach in sensory analysis was developed using sunglasses with lenses designed to block light at the specific wavelengths at which panelists would detect differences in color among samples. Testing was conducted every 2-wk period (15-d increments) with two tests per week using 11 trained panelists. All the panelists tasted all the products. Panelists were able to detect significant differences in the sensory characteristics of cheeses produced from milk of cows consuming native pastures versus TMR even when the color difference was masked.

Animal Feed↗
PubMed2004

Chemometric analysis of proteolysis during ripening of Ragusano cheese.

Chemometric modeling of peptide and free amino acid data was used to study proteolysis in Protected Denomination of Origin Ragusano cheese. Twelve cheeses ripened 3 to 7 mo were selected from local farmers and were analyzed in 4 layers: rind, external, middle, and internal. Proteolysis was significantly affected by cheese layer and age. Significant increases in nitrogen soluble in pH 4.6 acetate buffer and 12% trichloroacetic acid were found from rind to core and throughout ripening. Patterns of proteolysis by urea-PAGE showed that rind-to-core and age-related gradients of moisture and salt contents influenced coagulant and plasmin activities, as reflected in varying rates of hydrolysis of the caseins. Analysis of significant intercorrelations among chemical parameters revealed that moisture, more than salt content, had the largest single influence on rates of proteolysis. Lower levels of 70% ethanol-insoluble peptides coupled to higher levels of 70% ethanol-soluble peptides were found by reversed phase-HPLC in the innermost cheese layers and as the cheeses aged. Non-significant increases of individual free amino acids were found with cheese age and layer. Total free amino acids ranged from 14.3 mg/g (6.2% of total protein) at 3 mo to 22.0 mg/g (8.4% of total protein) after 7 mo. Glutamic acid had the largest concentration in all samples at each time and, jointly with lysine and leucine, accounted for 48% of total free amino acids. Principal components analysis and hierarchical cluster analysis of the data from reversed phase-HPLC chromatograms and free amino acids analysis showed that the peptide profiles were more useful in differentiating Ragusano cheese by age and farm origin than the amino acid data. Combining free amino acid and peptide data resulted in the best partial least squares regression model (R(2) = 0.976; Q(2) = 0.952) predicting cheese age, even though the peptide data alone led to a similarly precise prediction (R(2) = 0.961; Q(2) = 0.923). The most important predictors of age were soluble and insoluble peptides with medium hydrophobicity. The combined peptide data set also resulted in a 100% correct classification by partial least squares discriminant analysis of cheeses according to age and farm origin. Hydrophobic peptides were again discriminatory for distinguishing among sample classes in both cases.

Amino Acids↗
PubMed2000

Contrast and range effects for category, magnitude and labeled magnitude scales in judgements of sweetness intensity.

The labeled magnitude scale (LMS) is a verbally anchored quasi-logarithmically spaced response scale with properties similar to magnitude estimation. Three experiments examined whether the LMS showed context effects similar to those found with magnitude estimation and category scales. Two versions of the LMS were used, one anchored at the high end to the strongest imaginable sweetness and the other to the strongest imaginable oral sensation. In a simple contrast experiment, subjects judged the sweetness of a 10% sucrose fruit beverage in the context of a less sweet (5%) beverage or a more sweet (20%) beverage. Consistent with previous literature, the sweetness was judged more intense in the low context and less intense in the high context, for all scaling methods. In a second experiment, this effect persisted (although was smaller) when the contextual item preceded the to-be-rated item, a so-called 'reversed-pair' design. Once again, the effect was highly significant for all scaling methods. In a third experiment, a range effect was examined using wide and narrow ranges of concentration. Psychophysical functions were flatter in a wide context and steeper in a narrow context, consistent with previous observations on range-mapping bias. This result was obtained for all scales. In three common contextual effects, the labeled magnitude scale behaved similarly to other scaling procedures. Its application to comparisons across individuals may be limited if those individuals have different experiential contexts within which they make their judgements.

Female↗
PubMed1999

Turn up the HEAT.

The recently determined crystal structure of the PR65/A subunit of protein phosphatase 2A reveals the architecture of proteins containing HEAT repeats. The structural properties of this solenoid protein explain many functional characteristics and account for the involvement of solenoids as scaffold, anchoring and adaptor proteins.

Phosphoprotein Phosphatases↗
PubMed1999

Vehicle accidents related to sleep: a review.

UNLABELLED: Falling asleep while driving accounts for a considerable proportion of vehicle accidents under monotonous driving conditions. Many of these accidents are related to work--for example, drivers of lorries, goods vehicles, and company cars. Time of day (circadian) effects are profound, with sleepiness being particularly evident during night shift work, and driving home afterwards. Circadian factors are as important in determining driver sleepiness as is the duration of the drive, but only duration of the drive is built into legislation protecting professional drivers. Older drivers are also vulnerable to sleepiness in the mid-afternoon. Possible pathological causes of driver sleepiness are discussed, but there is little evidence that this factor contributes greatly to the accident statistics. Sleep does not occur spontaneously without warning. Drivers falling asleep are unlikely to recollect having done so, but will be aware of the precursory state of increasing sleepiness; probably reaching a state of fighting off sleep before an accident. Self awareness of sleepiness is a better method for alerting the driver than automatic sleepiness detectors in the vehicle. None of these have been proved to be reliable and most have shortcomings. Putative counter measures to sleepiness, adopted during continued driving (cold air, use of car radio) are only effective for a short time. The only safe counter measure to driver sleepiness, particularly when the driver reaches the stage of fighting sleep, is to stop driving, and--for example, take a 30 minute break encompassing a short (< 15 minute) nap or coffee (about 150 mg caffeine), which are very effective particularly if taken together. Exercise is of little use. CONCLUSIONS: More education of employers and employees is needed about planning journeys, the dangers of driving while sleepy, and driving at vulnerable times of the day.

Accidents, Occupational↗
PubMed1996

Astringency of organic acids is related to pH.

Astringency and sourness of lactic, acetic and citric acids, each adjusted to pH 3, 5 and 7, were evaluated in two experiments, one starting at equal concentrations in wt/vol before neutralization and the second starting at equal molarity. Astringency and sourness decreased with increasing pH. However, acids were differentially sour at equal pH, consistent with previous findings. In contrast, the tactile attributes associated with astringency (drying, roughing of oral tissues and puckery/tightening sensations) were similar across acids; pH was the major influence on astringency. Strong dependence on pH suggests that astringency of these acids is a direct result of their acidic properties, and not solely due to the hydrogen bonding mechanisms previously suggested as an explanation of astringency in tannin interactions with salivary proteins.

Acetic Acid↗
PubMed1995

Night-shift work in Antarctica: sleep characteristics and bright light treatment.

Changes in sleep parameters during and after night-shift and the effects of bright white (2500-3000 1x) and dim red (> 500 1x) light treatment on re adaptation after night-shift during winter were studied in 14 men on the British Antarctic Survey Base of Halley (75 degrees south). Subjects kept daily sleep diaries and mood ratings from one week before to three weeks after night-shift and received either full-spectrum white or dim red light treatment from 1100 to 1300 h daily during the first week after night-shift. Plasma melatonin (for 24 h at the end of weeks 1, 2 and 4), and urinary 6-sulfatoxymelatonin (aMT6s, for 48 h weekly) were measured. A significant (MANOVA; p < 0.05) improvement in sleep was seen during night shift (latency and duration) and with bright light treatment (latency). Melatonin and aMT6s rhythms delayed by 7-8 h during night-shift. The white light group readapted slowly, apparently by phase delay, as assessed by aMT6s measurement. The red light group readapted slightly, but significantly (ANOVA, p < 0.01) faster than the white light group.

Adaptation, Psychological↗
PubMed1993

Determination of the solution structure of neuropeptide K by high-resolution nuclear magnetic resonance spectroscopy.

1H NMR chemical shift assignments for neuropeptide K (NPK) and neurokinin A (NKA) have been determined at 600 MHz in 28% trifluoroethanol/water solution. Two-dimensional NMR techniques were used to assign proton resonances, and interproton distances were estimated from the observed nuclear Overhauser effects (NOEs). These distances were used as constraints in a simulated annealing protocol within the program XPLOR to generate structures consistent with experimental data. NPK forms a regular amphipathic alpha-helical structure from Asp 3, terminating at Gly 18. Slowly exchanging amide protons identified in this region are likely to be involved in hydrogen bonds to stabilize the helix. The remainder of the molecule displays many sequential NOEs, with some i-(i + 2) contacts, but little further evidence of defined secondary conformation. NKA displays strong sequential connectivities between amide protons from Thr 3 to Met 10, and some i-(i + 2) connectivities suggestive of a series of dynamic turns in equilibrium. A comparison of the tail region of NPK with the related peptide homologue, neurokinin A, in the same solvent system, indicates that both show increasing order when trifluoroethanol is titrated into water solution, with the appearance of sequential NOEs between backbone amide protons. Differences between the corresponding spans of primary sequence appear to be minimal. The clear finding that NPK adopts a well-defined helix in its N-terminal half and is relatively disordered in the C-terminal half, which includes the entire NKA sequence, may have important implications for understanding the increased selectivity of NPK over NKA for one class of neurokinin receptor.

Amino Acid Sequence↗
PubMed1992

Human slow wave sleep: a review and appraisal of recent findings, with implications for sleep functions, and psychiatric illness.

Recent findings concerning human slow wave sleep (hSWS-stages 3 + 4; delta EEG activity) are critically reviewed. Areas covered include the significance of the first hSWS cycle; hSWS in extended sleep; relationship between hSWS, prior wakefulness and sleep loss; hSWS influence on sleep length; problems with hSWS deprivation; influence of the circadian rhythm; individual differences in hSWS, especially, age, gender and constitutional variables such as physical fitness and body composition. Transient increases in hSWS can be produced by increasing both the quality and quantity of prior wakefulness, with an underlying mechanism perhaps relating to the waking level of brain metabolism. Whilst there may also be thermoregulatory influences on hSWS, hypotheses that energy conservation and brain cooling are major roles for hSWS are debatable. hSWS seems to offer some form of cerebral recovery, with the prefrontal cortex being particularly implicated. The hSWS characteristics of certain forms of major psychiatric disorders may well endorse this prefrontal link.

Adult↗
PubMed1992

Human slow-wave sleep and the cerebral cortex.

Recent hypotheses about the roles of human slow-wave sleep (hSWS-delta EEG activity) are appraised. The possible linkage between hSWS and the functions of the prefrontal cortex (PFC) are explored with respect to normal subjects and to disorders involving PFC deficits.

Journal Article↗