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Biomedical subjects

M Hogan

Publications and source records attributed to M Hogan.

102 records · Page 6Linked to original sources
PubMed1978

B scan detection of pelvic masses: accuracy compared to the barium enema, intravenous pyelogram.

One hundred fifty nine pelvic ultrasonic examinations were performed; 54 were verified. The relative diagnostic accuracy of ultrasound, intravenous pyelograms, and barium enemas in detecting pelvic masses is discussed. Ultrasound is highly accurate except in ascites. While barium enema and intravenous pyelogram are both inaccurate. Ultrasound should be the initial examination for the evaluation of patients with a possible pelvic mass.

Ascites↗
PubMed1978

Transient electric dichroism of rod-like DNA molecules.

We report transient electric dichroism studies on monodisperse rod-like DNA molecules. By using restriction fragments and DNAs of known length, it is shown that the orientation time is accurately predicted by the theoretically calculated rotational diffusion coefficient. The field dependence of the steady-state dichroism values is not consistent with the induced electric dipole orientation mechanism, and the time dependence is not consistent with the presence of a permanent dipole moment. In order to explain the dependence of the dichroism on the electric field, the ionic strength of the medium, and the length of the macromolecule, we propose a new model in which anisotropic ion flow produces an asymmetric ion atmosphere around the polyelectrolyte, resulting in an orienting torque. From the limiting dichroism at high field, we estimate that the DNA bases are inclined at an angle of 73 degrees or less relative to the helix axis, in good agreement with the revised model of B-form DNA suggested by Levitt, in which the base pairs have a propeller-like twist. Our results establish transient electric dichroism measurements as a technique well suited for study of alterations in the length and base pair inclination of rod-like DNA molecules.

Anions↗
PubMed1978

Does irehdiamine kink DNA?

We report equilibrium, relaxation kinetic, and transient electric dichroism studies on the complex of the diamino steroid irehdiamine A with DNA. The results are consistent with a beta-kinked structure for the complex at saturation, with a kink in the DNA structure induced by a bound steroid every second base pair. The results that favor this hypothesis include an apparent length decrease of rod-like bacterial DNA molecules when only a small amount of drug is bound, followed by an apparent length increase at saturation. The limiting dichroism amplitude implies a substantial increase in the tilt of the bases relative to the orientation axis; at saturation the base UV transition moments are tilted about 31 degrees from the plane perpendicular to the orientation axis. Because of the direction of polarization of the 260-nm transition moments, the results indicate that the tilt of the bases must be predominantly in the short rather than the long axis of the base pair. The large hyperchroism of the complex is consistent with loss of base stacking, as required by a kinked structure. The kinetic results imply a bimolecular reaction mechanism, with a temperature-dependent association rate constant of roughly 10(8) M(-1) sec(-1), and a dissociation rate constant of about 5 x 10(3) sec(-1), nearly independent of temperature. The association activation energy and apparent reaction enthalpy vary from 12 to 22 kcal mol(-1); heat is absorbed on complex formation as expected for loss of base-stacking interactions. An anomalous result of the experiments is the larger apparent length increase (13%) exhibited by two eukaryotic DNAs, compared to 6% for three prokaryotic DNAs. Differences were also observed in the kinetic properties of the complexes.

Binding Sites↗
PubMed1978

Effects of hydrogen ion dissociation and concentration of the reactivity of dichromate-fixed tissue components to the PAS procedure: recommendations for reducing undesirable background staining.

The undesirable PAS reactivity of cytoplasmic aldehydes after dichromate fixation can be suppressed without affecting selective staining by lowering the pH of Lillie's Cold Schiff reagent to 1.5. Alternatively, dilution of pH 2.2 Cold Schiff reagent with distilled water (1:2) is recommended. Hydrogen ion concentration and dissociation effect the rate of color formation in various PAS positive sites differentially with respect to the time of incubation in Schiff reagent. Based on the experiments, aldehydes exposed in different tissue components appear to be chemically distinct and separable depending on the rate of color formation and duration of incubation in Schiff reagent.

Aldehydes↗
PubMed1977

Climatic droplet keratopathy in a 16-year-old boy.

Primary climatic droplet degeneration of the cornea that consisted of bandshaped keratopathy and superficial spheroidal golden opacities occurred in a 16-year-old boy. Light microscopy showed proteinaceous deposits in the superficial corneal stroma. Electron microscopy confirmed the colloidal nature of this material.

Adolescent↗
PubMedDate not supplied

Evaluation of a pharmaceutical care education series for chain pharmacists using the focus group method.

OBJECTIVES: (1) Describe a pharmaceutical care education program presented to a group of pharmacists employed by a large pharmacy chain; (2) present the results of a formative evaluation of that program, and show how these can be used to improve subsequent offerings of the program as well as to enhance the efforts of other pharmacies and colleges involved in similar ventures; and (3) describe the focus group method in detail and demonstrate its usefulness as an evaluation tool. DESIGN AND PARTICIPANTS: Two pharmacist focus groups and two patient focus groups. SETTING: Chain pharmacy corporation and two colleges of pharmacy. MAIN OUTCOME MEASURES: Effects on attitudes and practice. RESULTS: The focus group method is useful for this type of evaluation. The educational series had a positive effect on pharmacists' attitudes and reported practice behavior. However, these improvements were not obvious to patients. Small group learning modules that include cases or problem-based exercises are probably effective vehicles for achieving educational goals. CONCLUSION: The chain pharmacy corporation should revise the educational program and expose more pharmacist-employees to it. This company and others should consider providing off-site, in-person education to employee pharmacists that makes use of an interactive, small group format. Although effective, the focus group method could have been improved by a more rigorous patient recruitment process and greater structure to the debriefing sessions for staff.

Adult↗
PubMedDate not supplied

Dependence of DNA helix flexibility on base composition.

We have used triplet anisotropy decay techniques to study the flexibility of synthetic DNA fragments with different base pair compositions. We have found major differences in the torsional and bending stiffness of poly(dG) . poly(dC), poly(dA) . poly(dT) and poly(dA-dC) . poly(dT-dG). Poly(dG) . poly(dC) has a torsional modulus more than 40 times larger than poly(dA-dC) . poly(dT-dG), and approximately 20 times larger than poly(dA) . poly(dT). These differences imply that the torsional stiffness of DNA can vary greatly with base composition. The Young's modulus (bending stiffness) we have measured for poly(dG) . poly(dC) is at least twice that of poly(dA-dC) . poly(dT-dG) or random sequence DNA, and is at least threefold greater than that of poly(dA) . poly(dT). This implies that the bending stiffness of DNA is also strongly dependent on base composition. In light of this dramatic base composition dependence, we suggest here that such stiffness variation may lead to local variations in the stability of chromatin or other protein complexes that require bending or twisting of the DNA helix.

Animals↗
PubMedDate not supplied

Acceleration of nucleic acid hybridization on DNA microarrays driven by pH tunable modifications.

A series of peptides containing histidine residues were designed as potential hybridization rate enhancers within a polymeric matrix of DNA microarrays. The polymeric matrix modified with these peptides showed strong attraction to DNA molecules under conditions of induction. DNA probes on the peptide-modified sites rapidly hybridized to their complementary targets with single base pair mismatch discrimination.

DNA↗
PubMedDate not supplied

Peritoneal washing cytology. Uses and diagnostic criteria in gynecologic neoplasms.

Review of a 20-month experience with 241 peritoneal washes performed on 191 patients showed that the use of these specimens has expanded greatly. Of the 19 patients with neoplastic cells in their peritoneal washing cytology specimens, 12 had primary ovarian neoplasms, 4 had primary uterine cervical neoplasms, 2 had primary endometrial neoplasms, and 1 had mammary carcinoma metastatic to the ovary. Gynecologic oncologists at this institution are now routinely obtaining peritoneal washing cytology specimens whenever there is intraabdominal surgery on patients known to have or suspected of having a pelvic neoplasm. The following criteria were found to be essential to the accurate evaluation of these specimens: (1) cells considered to be malignant should be present both singly and in groups and should be malignant by the usual cytologic criteria, (2) the patients must have or be known to have had a neoplasm whose cells are similar to those in the washing specimen, and (3) the cells considered to be neoplastic must be different from and not confused with reactive mesothelial cells. The last criterion is important because the peritoneal lavage traumatically removes mesothelium, which can appear atypical. These criteria make the cytologic interpretation of most peritoneal washing specimens straightforward; interesting diagnostic problems occur, however, including the evaluation of neoplasms of borderline malignancy, those "spilled" during surgery and second neoplasms found by peritoneal washing cytology.

Ascitic Fluid↗