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Biomedical subjects

S Mayfield

Publications and source records attributed to S Mayfield.

9 recordsLinked to original sources
PubMed2002

Lateral digital photography with computer-aided goniometry versus standard goniometry for recording finger joint angles.

This study compares the accuracy of computer-aided goniometry with standard goniometry. 109 finger joint angles at the extremes of flexion and extension were measured by a senior hand therapist using standard goniometry. Lateral digital photographs were then taken of the hands and the same angles were read from these by computer. There was good correlation (r(2)=0.975) between the results. Computer goniometry averaged 1 degrees (95%Cl=0 degrees -+2 degrees ) more than the standard goniometry. We feel that computer goniometry of finger joints is accurate and compares well with standard goniometry.

Cluster Analysis↗
PubMed2001

DNA strand breaks and cell cycle perturbation in herceptin treated breast cancer cell lines.

BACKGROUND: Herceptin is a humanized antibody that binds to the product of the HER-2 oncogene. Clinical studies have indicated that treatment with Herceptin may slow disease progression in tumors expressing high levels of the HER-2 antigen. However, the mechanism of this action is not known. METHODS: Four different cell lines were used that had different levels of HER-2 expression. Treated and nontreated cells were analyzed for DNA strand breaks and cell cycle perturbation using standard flow cytometry methods. RESULTS: In this study we found that cell lines expressing high levels of HER-2, when treated with Herceptin, exhibited marked increases in DNA strand breaks as measured by the TUNEL assay, and that these cells also exhibited slowed growth. BT-474 and SKBR-3 cell lines, both of which express high levels of the HER-2 antigen, had significant increases in labeled nucleotide expression at 3 and 6 day time points following exposure to Herceptin at a concentration of 10 microg/ml. Similar treatment of MCF-7 and MDA-231 cell lines, both of which express low levels of HER-2, had little effect on the level of labeled nucleotide expression at either the 3 or 6 day time points. Following 4 days of Herceptin treatment, BT-474 and SKBR-3 cell lines had significant decreases in the percentage of cells in the S phase of growth. This effect was not seen in either the MCF-7 or MDA-231 cell lines. CONCLUSION: Herceptin has a biological effect only on cells that contain high levels of HER-2. This effect is a decrease in cell proliferation that is coincident with, and may be caused by an increase frequency of DNA strand breaks.

Antibodies, Monoclonal↗
PubMed2000

A note on a possible influence of traps on assessment of the diet of Jasus lalandii (H. Milne-Edwards).

Dietary analyses are important components of ecological studies. However, some methods of collecting organisms may expose them to exceptionally high densities of prey items, leading to inaccurate dietary assessments. These methods include the use of baited traps. We hypothesised that such a "trap effect" occurred during work on the diet of the rock lobster Jasus lalandii, because baited traps attracted isopods, which were then eaten opportunistically by trapped J. lalandii. To test this hypothesis, rock lobsters were collected at two sites using both baited-traps and Scuba diving. Results showed that large numbers of isopods were attracted to, and consumed, the trap-bait. Analyses of the stomach contents of trap-caught J. lalandii from both localities reflected a larger occurrence and significantly greater abundance of isopods in stomach samples from trap- rather than Scuba-caught rock lobsters. For probably similar reasons, small fish were significantly over-represented in the gut contents of trap-caught rock lobsters, although the evidence is less clear-cut and there may be other explanations for the high proportions of fish in the diet. Although isopods and fish may be naturally consumed at a low rate, predation on them is greatly inflated in traps, and the dietary analyses of trap-caught J. lalandii. All assessments of the diets of animals traditionally caught with traps should consider and account for such "trap effects", by calibrating the data for trap-caught animals against an alternative sampling method.

Journal Article↗
PubMed1996

Double agent: translational regulation by a transcription factor.

The homeodomain protein bicoid activates transcription of several target genes by binding to target sequences in DNA. It has recently been shown that bicoid is also an RNA-binding protein that regulates the translation of caudal mRNA. Several ways for a protein to acquire dual functions can be imagined.

Drosophila Proteins↗
PubMed1989

Nuclear and chloroplast mutations affect the synthesis or stability of the chloroplast psbC gene product in Chlamydomonas reinhardtii.

The psbC gene of Chlamydomonas reinhardtii encodes P6, the 43 kd photosystem II core polypeptide. The sequence of P6 is highly homologous to the corresponding protein in higher plants with the exception of the N-terminal region where the first 12 amino acids are missing. Translation of P6 is initiated at GUG in C. reinhardtii. The chloroplast mutant MA16 produces a highly unstable P6 protein. The mutation in this strain maps near the middle of the psbC gene and consists of a 6 bp duplication that creates a Ser-Leu repeat at the end of one transmembrane domain. Two nuclear mutants, F34 and F64, and one chloroplast mutant, FuD34, are unable to synthesize P6. All of these mutants accumulate wild-type levels of psbC mRNA. The FuD34 mutation has been localized near the middle of the 550 bp 5' untranslated region of psbC where the RNA can be folded into a stem-loop structure. A chloroplast suppressor of F34 has been isolated that partially restores synthesis of the 43 kd protein. The mutation of this suppressor is near that of FuD34, in the same stem-loop region. These chloroplast mutations appear to define the target site of a nuclear factor that is involved in P6 translation.

Amino Acid Sequence↗
PubMed1989

Neurologic and developmental status related to the evolution of visual-motor abnormalities from birth to 2 years of age in preterm infants with intraventricular hemorrhage.

We prospectively and longitudinally evaluated neurologic status, cognitive status, and visual-evoked responses in 63 premature infants with cerebral intraventricular hemorrhage, 27 premature infants without hemorrhage, and 22 full-term normal infants. We hypothesized that severe intraventricular hemorrhage (grades III and IV) is associated with impaired visual-motor function, in part because of compression-related injury of the periventricular white matter by ventricular dilation. Infants with grade III or IV hemorrhage had significantly more neurologic sequelae at term and at 3, 7, 12, and 24 months; lower Bayley mental and motor scores at 3, 7, and 12 months; more abnormality on Kohen-Raz subscales for eye-hand coordination, object manipulation, and object relations at 3, 7, and 12 months; and lower Mullen vision-receptive and vision-expressive coordination scores at 24 months. The 12-month visual-evoked response correlated with the 24-month vision-receptive and vision-expressive organization scores for infants with grade III or IV intraventricular hemorrhage (r = -0.49, p less than 0.01, and r = -0.40, p less than 0.05, respectively). The data confirm our hypotheses of increased cognitive and neurologic sequelae, and increased abnormality of visual-motor coordination, during the first 2 years of life in infants with severe (grade III or IV) intraventricular hemorrhage.

Cerebral Hemorrhage↗
PubMed1984

Isolation and Characterization of a Light-Harvesting Chlorophyll a/b Protein Complex Associated with Photosystem I.

A chlorophyll a/b protein complex has been isolated from a resolved native photosystem I complex by mildly dissociating sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The chlorophyll a/b protein contains a single polypeptide of molecular weight 20 kilodaltons, and has a chlorophyll a/b ratio of 3.5 to 4.0. The visible absorbance spectrum of the chlorophyll a/b protein complex showed a maximum at 667 nanometers in the red region and a 77 K fluorescence emission maximum at 681 nanometers. Alternatively, by treatment of the native photosystem I complex with lithium dodecyl sulfate and Triton, the chlorophyll a/b protein complex could be isolated by chromatography on Sephadex G-75. Immunological assays using antibodies to the P(700)-chlorophyll a-protein and the photosystem II light-harvesting chlorophyll a/b protein show no cross-reaction between the photosystem I chlorophyll a/b protein and the other two chlorophyll-containing protein complexes.

Journal Article↗