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Biomedical subjects

H Summers

Publications and source records attributed to H Summers.

6 recordsLinked to original sources
PubMed2001

Endoscopic prosthesis augmentation of the lower esophageal sphincter in swine.

HYPOTHESIS: Endoscopically delivered prostheses are safe, durable, and may augment a defective lower esophageal sphincter (LES). METHODS: Pigs were studied as normal-LES or LES-weakened animals. A novel endoscopic delivery system was developed in order to place multiple hydrogel prostheses into the LES submucosa. Histopathology sections evaluated ultimate durability and the relationship of the prostheses to esophageal anatomy. RESULTS: Overall, 97% of 179 prosthesis delivery attempts were successful. LES-weakened animals had LES pressures return to normal or supranormal values at 2 weeks and 2 months after prosthesis augmentation. Weakened gastric yield pressures improved to normal values at 2 weeks after prosthesis augmentation. The thickness of the muscular layers and the mucosal integrity of the esophagus was unaffected by the retained prostheses. CONCLUSIONS: Endoscopically delivered hydrogel prostheses are safe and durable. These prostheses can successfully augment a defective sphincter without recognizable damage to the esophagus.

Animals↗
PubMed1999

Effect of aerobic fitness on the physiological stress response in women.

Stress reactivity was assessed in aerobically fit (n = 14) and unfit (n = 8) females during the follicular phase of the menstrual cycle. Participants completed the Spielberger State-Trait Anxiety Inventory and provided a urine sample for catecholamine analysis before and after mental stress testing, Stroop Color-Word Test. Blood pressure, heart rate, muscle tension, and skin conductance were measured during mental stress testing. Fit and unfit participants differed significantly in baseline heart rate but not in stress reactivity or in state or trait anxiety. These data suggest that aerobic fitness does not attenuate the stress response in women prior to menopause.

Adult↗
PubMed1997

Requirements for Epstein-Barr nuclear antigen 1 (EBNA1)-induced permanganate sensitivity of the epstein-barr virus latent origin of DNA replication.

Epstein-Barr nuclear antigen 1 (EBNA1) activates DNA replication from the Epstein-Barr virus latent origin of DNA replication, oriP. EBNA1 binds cooperatively to four recognition sites in the dyad symmetry (DS) element of oriP, causing alterations in the origin DNA structure, which can be detected by the increased sensitivity of one Thy residue in two of the binding sites to permanganate oxidation. To better understand the significance of this EBNA1-induced origin distortion, we have investigated the DNA sequence and EBNA1 amino acid requirements for permanganate sensitivity. We have shown that the EBNA1 DNA binding and dimerization domains are sufficient to induce permanganate sensitivity and that amino acids 463-467, which form an extended chain that travels along the minor groove of the EBNA1 recognition site, play an important role in generating the DNA distortion. The EBNA1-induced permanganate sensitivity is independent of cooperative interactions between EBNA1 molecules on the origin and requires a specific sequence within the EBNA1 binding site. Using synthetic EBNA1 binding sites, we found that the inversion of a single AT base pair in the EBNA1 recognition sequence is sufficient to confer EBNA1-induced permanganate sensitivity. These studies indicate that permanganate oxidation can detect very minor alterations in DNA structure.

Binding Sites↗
PubMed1996

Cooperative assembly of EBNA1 on the Epstein-Barr virus latent origin of replication.

The EBNA1 protein of Epstein-Barr virus (EBV) activates DNA replication by binding to multiple copies of its 18-bp recognition sequence present in the Epstein-Barr virus latent origin of DNA replication, oriP. Using electrophoretic mobility shift assays, we have localized the minimal DNA binding domain of EBNA1 to between amino acids 470 and 607. We have also demonstrated that EBNA1 assembles cooperatively on the dyad symmetry subelement of oriP and that this cooperative interaction is mediated by residues within the minimal DNA binding and dimerization domain of EBNA1.

Antigens, Viral↗