Biomedical subjects

C E Lyon

Publications and source records attributed to C E Lyon.

35 records · Page 2Linked to original sources

PubMed1997

Purification and characterisation of p99, a nuclear modulator of protein phosphatase 1 activity.

We have purified a form of protein phosphatase 1 (PP1) from HeLa cell nuclei, in which the phosphatase is complexed to a regulatory subunit termed p99. We report here the cloning and characterisation of the p99 component. p99 mRNA is widely expressed in human tissues and immunofluorescence analysis with anti-p99 antibodies showed a punctate nucleoplasmic staining with additional accumulations within the nucleolus. The C-terminus of p99 contains seven RGG RNA-binding motifs, followed by eleven decapeptide repeats containing six or more of the following conserved residues (GHRPHEGPGG), and finally a putative zinc finger domain. Recombinant p99 suppresses the phosphorylase phosphatase activity of PP1 by > 90% and the canonical PP1-binding motif on p99 (residues 396-401) is unusual in that the phenylalanine residue is replaced by tryptophan.

Amino Acid Sequence↗

PubMed1997

Inhibition of protein dephosphorylation results in the accumulation of splicing snRNPs and coiled bodies within the nucleolus.

Coiled bodies are conserved subnuclear organelles that contain splicing snRNPs, a subset of nucleolar antigens, and the autoantigen p80 coilin. Most nuclei contain one to five nucleoplasmic coiled bodies, often with one or more located at the nucleolar periphery. Here we show that exposure of mammalian cells to low levels of the specific Ser/Thr protein phosphatase inhibitor, okadaic acid, results in the accumulation of p80 coilin and splicing snRNPs within nucleoli. Mutation of a single serine residue in p80 coilin to aspartate (S202D) also causes coiled bodies and splicing snRNPs to localize within nucleoli when the mutant is transiently transfected and expressed in HeLa cells. Neither okadaic acid nor the S202D coilin mutant causes nucleolar accumulation of serine-arginine-domain proteins. These data indicate that protein dephosphorylation is required to allow normal formation of nucleoplasmic coiled bodies and point to p80 coilin as a substrate whose phosphorylation state may regulate snRNP-nucleolar interactions. The data are consistent with a trafficking mechanism whereby splicing snRNPs cycle through the nucleolus.

Biological Transport, Active↗

PubMed1997

Effect of calcium marination on biochemical and textural properties of peri-rigor chicken breast meat.

The objective of this study was to evaluate effects of marinades containing varying calcium concentrations on the biochemical and texture characteristics of peri-rigor chicken breast fillets. Breast muscles from 200 broiler chickens were excised immediately post-mortem and marinated in 0, 50, 100, 150, or 200 mM CaCl2. The treatments had no effect on meat pH either before or after cooking, but as calcium concentration increased, the normal post-mortem conversion of adenosine triphosphate (ATP) to inosine monophosphate (IMP) increased, according to the IMP:ATP ratios (R-values). Calcium treatment at all levels tested improved meat tenderness, but both marinade absorption and cooking losses increased as the calcium concentration in the marinades increased. It was concluded that although treating peri-rigor breast muscle with calcium might be useful in reducing or eliminating the conditioning period to assure tender chicken, methods must be developed for restoring the moisture binding properties that are damaged by the calcium.

Adenosine Triphosphate↗

PubMed1997

Effect of electrical stimulation in combination with calcium chloride or sodium chloride treatments at constant ionic strength on moisture binding and textural quality of early-harvested breast fillets.

The objective of this study was to assess the effects of a CaCl2 or NaCl treatment combined with electrical stimulation (ES) on textural and moisture binding of early-harvested chicken breast fillets. During exsanguination, half the birds were subjected to ES, and then all carcasses were aged for 30, 60, 90, or 120 min before excising both Pectoralis major muscles. Half the muscles were chilled with a NaCl solution and half with a CaCl2 solution. Effects of ES and chill medium composition on meat pH, moisture absorption, cooking loss, and shear value of the fillets were assessed. The ES reduced meat pH for the NaCl-treated muscles, but had no effect on those treated with CaCl2 of on moisture absorbed during chilling. Cooking loss was greater for the CaCl2-treated than NaCl-treated muscles and for muscles from stimulated birds that were excised more than 30 min post-mortem. Shear values were unaffected by chilling medium composition. However, even though shear values for both ES and unstimulated birds declined as aging time increased, the rate of decline was greater, and ultimate shear value lower, for muscles from ES birds. Results indicate that, although ES might offer some advantage in improving the tenderness of early-harvested breast fillets, combining ES with CaCl2 treatment offers no real advantage. Moreover, reductions in moisture binding properties by these technologies might limit applicability in some commercial environments.

Absorption↗

PubMed1997

Effect of postchill aging and sodium tripolyphosphate on moisture binding properties, color, and Warner-Bratzler shear values of chicken breast meat.

The objective of this study was to assess the effects of treating chicken breast forequarters with sodium tripolyphosphate (STPP) after various postchill storage times on meat quality. Sixty-four commercially reared broilers (two replicates of 32 birds each) were slaughtered and chilled, and then the forequarters (split breasts with spine and ribs) were harvested and aged for 0, 120, 180, or 240 min postchill. After each aging period, one forequarter from each of 16 birds was marinated with a NaCl solution and the opposite forequarter was marinated with the same NaCl solution containing STPP. The quarters were then cooked and the following traits measured: marinade absorption, cooking loss, objective color values, and Warner-Bratzler shear values. As aging time prior to marination increased, cooking loss and redness of the cooked meat decreased, but marinade absorption and the color values were unaffected. The STPP treatment increased marinade absorption, decreased cooking losses, and decreased cooked meat redness (P < 0.05). Shear values decreased with aging time for both the control and STPP-treated breast meat. When the STPP treatment was applied immediately after carcass chilling, the STPP-treated meat exhibited shear values more than 60% greater than those of the controls (9.14 and 5.69 kg, respectively). Results indicate that time postchill at which further processed products are treated with STPP can have a significant effect on quality, especially cooked product texture.

Animals↗

PubMed1997

Effect of muscle opposition during rigor on development of broiler breast meat tenderness.

Two experiments were conducted to determine the effect of mutual opposition of breast muscles during rigor development on ultimate tenderness of the cooked meat. In each experiment, 32 broilers were conventionally processed. Immediately after evisceration, the supracoracoideus tendon was cut at the humeral insertion on one wing (treatment) and the opposite wing was sham-operated with the tendon exposed but not cut (control). The tendon of insertion for the Pectoralis minor muscle was cut to prevent the opposition of breast muscles during rigor, while avoiding confounding effects caused by making cuts on the muscles, as would occur during typical deboning. Cutting the tendon significantly (P < 0.05) increased Warner-Bratzler shear values after cooking for both the Pectoralis major and P. minor. Deboning at 2 h post-mortem resulted in shear values for the P. major of 7.22 kg for controls and 9.08 kg for treated carcasses; P. minor shear values were 2.98 kg for controls and 4.04 kg for treated carcasses. Deboning at 24 h post-mortem produced P. major shear values of 4.68 kg for controls and 5.68 kg for treated carcasses. On whole carcasses, breast muscle opposition during rigor contributes to the tenderness of the cooked meat.

Animals↗

PubMed1996

Effect of stunning time and polyphosphates on quality of cooked chicken breast meat.

The objective of this research was to determine effects of stunning duration and polyphosphates on color, pH, and texture of chicken breast meat. Sixty broiler chickens were electrically stunned for 2 to 10 s in 2-s intervals and then slaughtered. Left and right Pectoralis major muscles were excised 1 h post-mortem. The left muscles (treated) were treated with a sodium tripolyphosphate salt solution, and the right muscles (controls) were treated with a salt solution alone. All muscles were cooked to an endpoint temperature of 72 C in a 95 C water bath. Measurements of muscle pH were taken on the meat 1 h post-mortem, after treating, and after cooking. Color values and Warner-Bratzler shear values were evaluated on each cooked meat sample. As stunning time increased, pH increased at 1 h post-mortem but treating with either of the solutions eliminated this trend. Muscle pH also increased upon cooking except in the polyphosphate-treated muscles, because the latter muscles achieved maximum pH prior to cooking. Stunning had no apparent effect on color values of the cooked meat; however, polyphosphate treatment resulted in meat that was darker and less red than controls. Longer stunning times resulted in greater shear values but polyphosphates did not affect Warner-Bratzler results. Taken together, these data suggest that processing variables that affect muscle pH also affect quality attributes.

Animals↗

PubMed1996

The word-detection effect: sophisticated guessing or perceptual enhancement?

Subjects discriminate letters in words better than letters in nonwords. The sophisticated guessing hypothesis attributes this word advantage to a guessing strategy. In words, the possible letters at each letter position are constrained by letters at other positions, whereas letters in nonwords are not restricted in this manner. A critical test of this hypothesis is that if subjects are given explicit knowledge of the letters in nonwords before the trial, the word advantage would disappear. We investigated the effect of preknowledge of the alternatives in the word-detection effect. In the word-detection effect, subjects decide which of two character strings contains letters and which contains pseudoletters. In four experiments, subjects were more accurate with words than with nonwords, and subjects were more accurate when they were told the word or nonword before the trial. However, even with foreknowledge of the alternatives, subjects were more accurate with words than with nonwords.

Humans↗

PubMed1996

Texture evaluations of cooked, diced broiler breast samples by sensory and mechanical methods.

The texture of cooked chicken breast is usually determined on intact pieces or strips that are representative of the muscle. Researchers emphasize the importance of uniformity of sample size and orientation of fibers to the shearing blades to ensure consistent data from instruments such as shear devices. For sensory evaluations, sample pieces of chicken breasts presented to panelists are often sized as single 2-cm2 or several 1-cm2 pieces. In this study, two sensory and two mechanical procedures were evaluated for efficacy in discerning texture differences in 1-cm2 pieces of cooked chicken. Three postmortem deboning times (2, 6, and 24 h) provided a texture quality spectrum. Sensory characteristics were evaluated by descriptive analysis trained panel (DA-TP) and by category scales-untrained panel (CS-UP). Twenty-gram breast portions of 1-cm2 pieces were evaluated using a multi-blade Allo-Kramer (AK) shear blade. Warner-Bratzler (WB) shear values of intact 1.9-cm-wide strips were also recorded. Discriminant analysis classification based on CS-UP gave higher error rates (probabilities of misclassification) than classification based on DA-TP. The CS-UP error rates were 0.36 (tender) and 0.65 (juiciness). The error rate of classification by DA-TP was 0.21. Error rates for classification by mechanical devices were 0.30 for WB and 0.21 for AK. Sample size is a consideration in texture evaluation protocols. Smaller sample pieces appear to mask differences in initial chew characteristics and in juiciness that are due to deboning time.

Adult↗

PubMed1994

The effect of an acetic acid dip on carcass appearance, microbiological quality, and cooked breast meat texture and flavor.

In Experiment 1, broiler carcasses were subjected to a 10-min prechill treatment with and without a food grade vinegar at a concentration of .6% acetic acid. After treatment the carcasses were monitored for visual appearance and microbiological quality. Color change and skin appearance were subjectively monitored. Microbiological quality was determined using the low volume whole carcass rinse. Shear values of cooked muscle were determined using a Warner-Bratzler attachment to an Instron. In a second experiment using the same treatment protocol, treated carcasses were chilled in an ice slush for 30 min and held overnight at 2 C. The breast muscles were removed and cooked by two methods. Triangle tests to determine sensory differences due to acetic acid were conducted. The skin color of treated carcasses turned a light yellow, and the feather follicles were protruded or puckered. Total aerobic counts were not affected by any of the treatments, but Enterobacteriaceae (ENT) counts of treated carcasses were significantly lower than the counts for the water control carcasses. Log10 ENT counts ranged from 4.51 for the control to 3.80 for the carcasses treated with acetic acid. Based on sensory triangle tests using a trained panel, there were no significant differences in the samples from either cooking method.

Acetates↗

PubMed1993

Effect of two stunning voltages on blood loss and objective texture of meat deboned at various post-mortem times.

Two experiments were conducted to determine the effect of different stunning voltages on the objective texture of the Pectoralis major muscles deboned at various post-mortem times. Broilers were stunned at either 50 or 200 V alternating current (VAC) for 10 s in a brine stunner. The artery and vein on one side of the neck were severed, blood collected for 90 s, and blood loss calculated as percentage of live weight. Carcasses were then processed under simulated commercial conditions. In the first experiment, the right and left Pectoralis major muscles were excised at 1 and 2 h post-mortem respectively, weighed, vacuum-sealed in plastic bags, and held overnight at 2 C. In the second experiment, the Pectoralis major muscles were excised at 4 h post-mortem and held overnight at 2 C. The muscles were then heated at 85 C for 30 min, equilibrated to room temperature, and prepared for Warner-Bratzler shear analysis. The stunning treatments did not significantly affect blood loss, which averaged 2.86 and 2.64% for 50 and 200 VAC, respectively. Birds subjected to the 50 VAC treatment had a mean shear value of 7.3 kg, which was significantly lower (P < .05) than the mean shear value of 10 kg for birds subjected to the 200 VAC treatment for muscles excised 2 h post-mortem. The use of 200 VAC for stunning could be used without any detrimental effect on the cooked meat as long as the standard deboning time of 4 h was maintained.

Animals↗

PubMed1990

Comparison of microscopic and laser diffraction methods for measuring sarcomere lengths of contracted muscle fibers of chicken pectoralis major muscle.

The objective of the present study was to compare the effectiveness of a microscopy method with a laser diffraction method for measuring sarcomere lengths of chicken pectoralis major (p. major) muscle fibers exhibiting various contraction states. Chicken p. major muscles were excised from the animals at death. Samples of each muscle were treated with pH-buffered (5.0 and 7.5) isoionic CaCl2, KCl, or ethylene glycol bis-(b-aminoethyl ether) N,N,N',N'-tetraacetic acid (EGTA) solutions in order to produce variability in the degree of fiber contraction. Sarcomere lengths (SL) of the fibers were observed using light microscopy and a laser diffraction method. The methods gave comparable results for sarcomere lengths greater than 1.6 microns. However, for SL less than 1.6 microns, sarcomere contraction was not accurately assessed by the laser diffraction method.

Animals↗

PubMed1989

Physical degradation of lignified stem tissues by ruminal fungi.

Ruminal bacteria or fungi were selected by the addition of cycloheximide or streptomycin and penicillin, respectively, to ruminal fluid, and the weakening and degradation of lignified tissues in alfalfa and Bermuda grass stems by these treatments and whole ruminal fluid were evaluated in vitro. Dry weight loss in alfalfa was similar for whole ruminal fluid and streptomycin-penicillin treatment, whereas that with streptomycin-penicillin treatment was significantly higher (P </= 0.05) than that with cycloheximide treatment. In Bermuda grass, dry weight loss was significantly higher with streptomycin-penicillin than that with whole ruminal fluid and cycloheximide treatment, which were equal. Both peak load (Newtons) and peak stress were less (P </= 0.05) for streptomycin-penicillin treatment than with other treatments in both forages. Fungi colonized the lignified ring in alfalfa and tended to reduce the width of cell walls in this tissue, but a large number of fungal penetrations through cell walls was not observed. In contrast, fungal rhizoids frequently penetrated into and through cell walls in the lignified ring of Bermuda grass, often expanding the pit fields between the cells. Ruminal fungi disrupt lignified tissues in stems, and their activity results in a weakened residue more amendable to physical degradation. This weakening may allow plant digesta to be more easily broken apart during animal's rumination and thus facilitate digesta flow and fiber utilization.

Journal Article↗

PubMed1989

Effects of electrical stimulation on the post-mortem biochemical changes and texture of broiler pectoralis muscle.

A study was conducted to determine the influence of electrical stimulation (50,200, or 350 V ac) on biochemical and textural changes in broiler breast muscle. Sixty-four broilers were stunned (50 V ac) prior to kill, and all but a control group were pulse stimulated during bleeding. After processing, carcasses were held in 10-C water for 1 h, then in 2-C ice/water slush for 1 h prior to muscle removal at 2 h post-mortem (PM). Bagged samples were held at 2 C for 24 h, then cooked. The pH, R value (ratio of adenine nucleotides to inosine nucleotides), cook yield, fluids and solids lost (F&S), and objective texture were measured. In addition, 16 broilers processed in the same manner were used in producing a profile of sarcoplasmic protein/enzyme changes in the breast muscle by cation exchange fast protein-liquid chromatography at 10 min, 2, and 24 h PM. The R values and soluble protein were also determined. Stimulation at 200 and 350 V accelerated the onset of rigor noted by lower pH values at 10 min and 1 h PM, and higher R values at 2 h PM. Muscle stimulated at 350 V exhibited the lowest cook yield and highest percentage of F&S lost, suggesting both the loss of functional properties and muscle integrity due to this treatment. All control and stimulated samples exhibited shear values in excess of what would be considered tender. Hardness and chewiness values increased as stimulation voltage levels increased. Only one of the seven principal chromatographic peaks decreased in response to increased electrical stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenine Nucleotides↗

PubMed1987

Scleral buckling with intraocular air injection complicated by arcuate retinal folds.

Three cases of bullous superior rhegmatogenous retinal detachment were surgically repaired by circumferential scleral buckling and intravitreal air injection. Unusual retinal folds were found postoperatively. Unlike the well-recognized radial retinal folds classically associated with circumferential buckling of bullous retinal detachments, the folds reported herein originated from the "end" of a hard silicone exoplant and traversed an arcuate course corresponding to the lower meniscus of the intravitreal air bubble. Although the macula was involved in all three cases, the retinal break was unaffected.

Air↗

PubMed1986

Detection of blood (hemoglobin) contamination in poultry muscle tissue.

Incidence of blood spots in fresh marketed poultry and batter or breaded frozen fried chicken may be related to certain processing parameters (i.e., stunning, bleed-out time). Spectrophotometric and cation exchange high performance liquid chromatography (HPLC) procedures were evaluated as potential methods to test for hemoglobin (Hb) contamination in poultry tissue. Muscle tissue was blended with TRIS-ethylenediaminetetraacetate buffer, pH 7.4, centrifuged and the extract scanned for absorbance at 540 and 580 nm. Tests with model systems gave a linear regression coefficient of r + .98 for detection of 0 to 1% blood in experimentally contaminated tissue. Analyses of extracts by cation exchange HPLC (545 nm) showed three separation peaks characteristic of hemoglobin. Isoelectrofocusing of the extracts on thin-layer polyacrylamide gels (pI 3 to 10) was also evaluated. These procedures could prove useful in subsequent studies to determine the cause of blood spotting in muscle tissue.

Animals↗

PubMed1985

Clinicopathological correlation of a solitary choroidal tuberculoma.

In a 34-year-old black man with pulmonary tuberculosis, a rapidly enlarging choroidal tuberculoma progressed to larger size, despite appropriate systemic anti-tuberculous therapy. The eye harboring the tuberculoma became blind and painful, and was subsequently enucleated. Conventional staining of tissue sections revealed a choroidal granuloma without evidence of organisms, but tubercle bacilli were demonstrated by fluorescence microscopy.

Adult↗