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Biomedical subjects

L Phillips

Publications and source records attributed to L Phillips.

At least 145 records · Page 8Linked to original sources
PubMed1992

A mathematical model for estimation of broiler egg weight loss from physical dimensions and air cell size during incubation.

A formula was derived that will enable hatcheries to estimate percentage weight loss using the width, length, and air cell diameter of the egg. The formula was derived by fitting an equation to the shape of the egg and using this shape equation to obtain estimates of air cell volume and egg volume. These estimates were coupled with the principle that weight = density x volume to give the final formula as a function of air cell diameter divided by egg width. The formula was tested by comparing its estimated values with measured values from eggs set at two different incubation conditions chosen to cover the range of conditions found in commercial hatcheries. As the day of transfer approached, embryo size and distortion of the air cell caused inaccuracies to develop in the results of this equation. However, data suggest that the equation can be used to calculate percentage weight loss until approximately the 16th day of incubation.

Animals↗
PubMed1992

The distribution of DNA sequences hybridizing with antibiotic production and resistance gene probes within type strains and wild isolates of Streptomyces species.

Total DNA preparations from 74 antibiotic-producing type strains and 102 natural Streptomyces isolates were examined by dot blots for homology to 6 antibiotic production and resistance genes. Pattern diversity of hybridizations decreased as stringency increased from 65% to 85%. There were 146 unique profiles at 65% stringency with 13 repeated patterns, whilst there were only 14 unique and 11 repeated profiles at 85% stringency. Most of the strains which hybridized at 85% reacted with one or two probes although a few strains showed multiple homologies. This data was used to cluster strains and the groups defined were examined for phenotypic antibiotic resistance. Producers of certain classes of antibiotics clustered to specific groups and some gene homologies were more common amongst strains which produced similar antibiotics.

Anti-Bacterial Agents↗
PubMed1991

Amino acid residues in the T cell receptor CDR3 determine the antigenic reactivity patterns of insulin-reactive hybridomas.

We examined TCR gene usage in a panel of beef insulin/I-Ad-restricted T cell hybrids obtained from BALB/c mice. These hybrids demonstrated several distinct patterns of reactivity defined by their ability to respond to species variants of insulin. Correlation of TCR-alpha and -beta-gene usage with these patterns of reactivity demonstrated that TCR gene usage was restricted within Ag reactivity groups. In particular, V-J junctional regions (CDR3 equivalent) were restricted with conserved junctional amino acid motifs present in both TCR-alpha- and -beta-chains. Comparison of TCR gene usage in hybrids expressing identical V alpha and V beta gene segments but demonstrating different patterns of reactivity revealed that changes in either J alpha and/or J beta gene segment usage could alter antigenic reactivity. Indeed, single or limited amino acid differences within the CDR3 region were sufficient to markedly alter fine specificity. These data demonstrate the critical role for CDR3 in determining antigenic reactivity in beef insulin-reactive hybrids and are compatible with the current model of TCR/peptide/MHC interaction.

Amino Acid Sequence↗
PubMed1991

Actin dynamics studied by solid-state NMR spectroscopy.

Solid-state nuclear magnetic resonance spectroscopy was used to study the motion of 2H and 19F probes attached to the skeletal muscle actin residues Cys-10, Lys-61 and Cys-374. The probe resonances were observed in dried and hydrated G-actin, F-actin and F-actin-myosin subfragment-1 complexes. Restricted motion was exhibited by 19F probes attached to Cys-10 and Cys-374 on actin. The dynamics of probes attached to dry cysteine powder or F-actin were very similar and the binding of myosin had little effect indicating that the local probe environment imposes the major influence on motion in the solid state. Correlation times determined for the solid state probes indicated that they were undergoing some rapid internal motion in both G-actin and F-actin such as domain twisting. The probe size influenced the motion in G-actin and appeared to sense monomer rotation but not in F-actin where segmental mobility and intramonomer co-ordination appeared to dominate.

Acetone↗
PubMed1990

Characterization of the specificity of peptide binding to four DR haplotypes.

This study describes the establishment of a peptide-binding assay for purified, detergent-solubilized DR molecules. For each of the DR specificities and peptides studied, a unique pattern of interaction was observed. Excellent correlation was detected between the DR1-, 2-, 5-, and 52a-binding capacities and the known DR restrictions of a panel of synthetic peptides. This supports the immunologic relevance of the binding assay, and emphasizes the importance of determinant selection in defining the immune response of individuals. We have also examined the capacity of a panel of DR-restricted peptides to compete with one another for binding to DR1. The results obtained are compatible with a single peptide-binding site on DR molecules. The peptide-binding capacity of the four different DR types (DR1, DR2, DR5, and DR52a) has been further examined by testing a collection of 133 different peptides. This collection is unbiased with respect to previously known DR binding and restrictions, and includes peptides of eukaryotic, bacterial, and viral origins. It was found that: 1) approximately 15 to 35% of the peptides tested bound any given DR type; 2) DR-binding capacities appeared to correlate with each other, suggesting that different alleles of the DR isotype may recognize related structures on an Ag molecule; and 3) despite the statistical correlation between binding capacity of different DR types, approximately 50% of the peptides that were positive binders still were specific in that they could bind only one of the four DR molecules tested. Degenerate binding (i.e., binding to most or all the DR molecules tested) was detected in only a minority of the cases analyzed (approximately 25%).

Amino Acid Sequence↗
PubMed1990

19F NMR study of the myosin and tropomyosin binding sites on actin.

Actin was labeled with pentafluorophenyl isothiocyanate at Lys-61. The label was sufficiently small not to affect the rate or extent of actin polymerization unlike the much larger fluorescein 5-isothiocyanate which completely inhibits actin polymerization [Burtnick, L. D. (1984) Biochim. Biophys. Acta 791, 57-62]. Furthermore, the label resonances in the 376.3-MHz 19F NMR spectrum were unaffected by actin polymerization. However, the binding of the relaxing protein tropomyosin resulted in the fluorinated Lys-61 resonances broadening out beyond detection due to a substantial increase in the effective correlation time of the label. Similarly, the binding of myosin subfragment 1 to F-actin resulted in the dramatic broadening of the labeled Lys-61 resonances. Thus, Lys-61 on actin appears to be closely associated with the binding sites for both tropomyosin and myosin, suggesting that both these proteins can compete for the same site on actin. The other region of actin known to be involved in myosin binding, Cys-10, was found to be more remote from the actin-actin interfaces than Lys-61. Labels on Cys-10 exhibited substantially greater mobility than fluorescein 5-isothiocyanate attached to Lys-61 which appeared to be held down on the surface of the actin monomer. This may sterically hinder the actin-actin interaction about 1 nm from the tropomyosin/myosin binding site.

Actins↗
PubMed1990

Comparison of three related methods to select T cell-presented sequences of protein antigens.

A comparison of three methods to predict T cell-presented sequences within antigenic proteins led to the view that recurrent hydrophobic residues might nucleate excised peptides as alpha-helices against hydrophobic surfaces. Such helices could be protease-protected structures on their way to desetope binding. The compared methods were: the amphipathicity algorithm of DeLisi and Berzofsky [Proc. natn. Acad. Sci. U.S.A. 82, 7048-7052. (1985)] as modified by Margalit et al. [J. Immun. 138, 2213-2229. (1987)] the strip of-helix hydrophobicity algorithm (SOHHA) of Stille et al. [Molec. Immun. 24, 1021-1027. (1987)] and the motifs algorithm of Rothbard and Taylor [EMBO J. 7, 93-100. (1988)]. Correct prediction was defined at two levels of stringency: (1) the predicted sequence overlapped the experimentally reported sequence when the ratio of the intersection of both to the union of both greater than or equal to 0.5 or (2) the sequences touched when there was a non-empty intersection of both sequences. We determined the sensitivity (correct predictions/number of reported T cell-presented sequences) and efficiency (correct predictions/number of predictions) at each level of stringency. In terms of overlap, the SOHHA was more sensitive (0.43) than the amphipathicity (0.29) (not significant) and motifs (0.0, 0.0) (p less than 0.05) predictions and more efficient (0.35) than the amphipathicity (0.14) and motifs (0.0, 0.0) predictions. At the less stringent criterion touching, the amphipathicity method (0.71) was as sensitive as motif Rothbard-4 (0.79) and more sensitive than SOHHA (0.57) and motif Rothbard-5 (0.43). At that criterion, the SOHHA was more efficient (0.47) than the amphipathicity (0.36) and motifs (0.25, 0.40) methods. We hypothesize that the comparability of these approaches reflected the common, predominant influence of recurrent hydrophobicity in their predictions.

Algorithms↗
PubMed1990

Inhibition of collagen II-induced arthritis in mice--a comparison of the effects of Sch 24937, immunosuppressants and nonsteroidal antiinflammatory drugs on the clinical expression of disease.

Previous studies from this laboratory have described Sch 24937 as a potent immunosuppressive agent that is particularly effective in suppressing humoral immune responses in mice. These findings prompted an evaluation of the effects of Sch 24937 in type II collagen-induced arthritis in mice where disease manifestations include the development of a strong humoral response to the collagen antigen. Sch 24937 reduced the incidence and severity of arthritis in collagen sensitized mice which appeared to be directly related to the immunosuppressive properties of the drug. However in contrast to the steroid betamethasone which also exhibited immunosuppressive activity, Sch 24937 did not prevent the changes occurring in the lymphocyte population of the draining lymph nodes of mice immunized with type II collagen. While the exact mechanism of the immunosuppressive activity of Sch 24937 remains to be elucidated, its mode of action in suppressing arthritis differs at least to some extent from that of a steroid.

Animals↗
PubMed1990

Ethical reasoning associated with the feeding of terminally ill elderly cancer patients. An international perspective.

An international nursing research study examined the ethical decision-making of "good and experienced" registered nurses in eight countries. The subjects were asked about their decision to feed or not to feed a hypothetical terminally ill, mentally alert, elderly cancer patient who refuses to eat. Cultural variations were demonstrated in the decisions as well as differences in ethical justification. The majority of nurses who would not feed appeared to use the principle of autonomy, whereas nurses who would feed the patient used beneficence as justification. Conditions under which nurses would change their decision to either feed or not feed the patient against her will included doctor's orders and lack of peer support for the decision. The majority of nurses clearly experienced a dilemma.

Adult↗
PubMed1989

Surgical correction of concomitant cranioventral abdominal wall, caudal sternal, diaphragmatic, and pericardial defects in young dogs.

Seven puppies with concomitant congenital cranioventral abdominal wall, caudal sternal, diaphragmatic, and pericardial defects were treated surgically when they were between 10 and 12 weeks old. Three pups had ventricular septal defects that were not corrected. Diaphragmatic herniorrhaphy without extension of the diaphragmatic defect was performed in 6 pups. In one pup, paracostal extension of the diaphragmatic defect was necessary to decrease tension on the diaphragmatic closure. All pups were healthy at 6-month follow-up examinations, but 2 of 3 pups with ventricular septal defects had moderate generalized cardiomegaly evident on thoracic radiography. Early surgical correction of the congenital defects in these pups was usually simple because there were few or no thoracic adhesions, the dogs were small, the defects were small in 6 of 7 dogs, and the costal arch was pliable in each dog.

Abdominal Muscles↗
PubMed1989

Prediction of protein helices with a derivative of the strip-of-helix hydrophobicity algorithm.

The strip-of-helix hydrophobicity algorithm was devised to identify protein sequences which, when coiled as alpha or 3(10) helices, had one axial, hydrophobic strip and otherwise variably hydrophilic residues. The strip-of-helix hydrophobicity algorithm also ranked such sequences according to an index, the mean hydrophobicity of amino acids in the axial strip. This algorithm well predicted T cell-presented fragments of antigenic proteins. A derivative of this algorithm (the structural helices algorithm (SHA] was tested for the prediction of helices in crystallographically defined proteins. For the SHA, eight amino acid sequences, 2 cycles plus one amino acid in an alpha helix, with strip-of-helix hydrophobicity indices greater than 2.5, were selected with overlapping segments joined. These selections were terminated according to simple "capping rules," which took into account the roles of N-terminal Asn or Pro and C-terminal Gly in the stability of helices. In analyses of 35 crystallographically defined proteins with known alpha and 3(10) helices, the predictions with the SHA overlapped (had overlap indices x greater than or equal to 0.5) with 34% of known helices, touched (had overlap indices 0.5 greater than x greater than 0) or overlapped with 66% of known helices, or were neighboring (came within 6 residues) or touched or overlapped with 82% of known helices. At each level of judging the quality of prediction, the SHA was usually less sensitive (correct predictions/total number of known helices) and more efficient (correct predictions/total number of predictions) than the Chou-Fasman and Garnier-Robson methods. It was simpler in design and calculation. The chemical mechanisms underlying these algorithms appear to apply both to protein folding and to selection of T cell-presented antigenic sequences.

Algorithms↗
PubMed1988

Idiopathic pleural effusion in a dog.

Idiopathic pleural effusion was diagnosed in a 4-year-old female Poodle. Treatment included giving low doses of furosemide for 5 months and giving low doses of prednisone that eventually were given on alternate days and discontinued 16 months after initial evaluation. Idiopathic pleural effusion in this dog was eosinophilic. The clinical importance and diagnostic value of this finding were not determined. In man, idiopathic pleural effusions have a high correlation with eosinophilic pleural effusions.

Animals↗
PubMed1988

Growth allometry of craniomandibular muscles, tendons, and bones in the laboratory rat (Rattus norvegicus): relationships to oromotor maturation and biomechanics of feeding.

This study addressed the problem of how growth of craniomandibular muscles, tendons, and bones influences the acquisition of oromotor skills and biomechanics of feeding in the laboratory rat (Rattus norvegicus). Rats representing a 6.6-fold size range were dissected, and muscles, tendons, and mandibles were weighed. Cross-sectional areas of tendons and bones providing attachment surfaces for muscles were estimated. Ontogenetic scaling of craniomandibular muscles, tendons, and bones was described by using linear regression models, and departures from size-required compensations were used to characterize changes in oromotor function. A two-dimensional model was developed which permitted calculation of mechanical advantages of four masticatory muscles; the model was used to show how mandibular growth and tooth eruption influence the biomechanics of rat feeding. Relative to mandible weight, most jaw muscles scaled either isometrically or positively, tendon cross-sectional areas scaled isometrically or negatively, and bone surfaces scaled negatively. With the exception of the superficial masseter and internal pterygoid muscles, mechanical advantages did not change significantly during mandible growth. Growth patterns of craniomandibular muscles, tendons, and bones contribute significantly to changes in morphology and oromotor function.

Animals↗
PubMed1988

The immunohistochemical demonstration of early perineurial change in the development of localized hypertrophic neuropathy.

A case of localized hypertrophic mononeuropathy was studied by electron microscopy and immunohistochemistry for S100 protein, epitopes recognized by the Leu-7 monoclonal antibody, 200 kD neurofilament polypeptide, and the epithelial membrane antigen (EMA). The primary role of perineurial cell proliferation without the participation of Schwann cells in this process was directly demonstrated by EMA immunohistochemistry. Focal delamination of the EMA-positive perineurium, increased fibrosis between its layers, and compartmentalization of the fascicles by EMA-positive septae were the first recognizable changes. In practice, recognition of these early changes by EMA immunocytochemistry may be important for the clear definition of functionally unimpaired segmental margins for excision and graft implantation, and also for the future study of the process responsible for aberrant perineurial proliferation.

Adolescent↗