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Biomedical subjects

D E Jackson

Publications and source records attributed to D E Jackson.

At least 37 records · Page 2Linked to original sources
PubMed1994

Prewatering and haloperidol have similar effects on rats' response rate and duration.

Haloperidol (0.1 mg/kg) and 5-min prewatering were given to 12 rats on three occasions each to determine effects on fixed ratio 15 (FR 15) responding for water. Compared to baseline, both treatments significantly reduced rate (prewatering slightly more) and both significantly increased duration. Though similar, drug and prewatering effects showed enough differences to suggest that there are both anhedonic and motoric deficit components to haloperidol's effects on rats' lever-pressing behavior for water.

Animals↗
PubMed1994

Atomic force microscopy and scanning tunnelling microscopy: refining techniques for studying biomolecules.

The scanning tunnelling microscope and the atomic force microscope offer the prospect of real-time, nanometre-scale imaging of biomolecules and biosurfaces under physiological environments. Much effort is therefore being made to establish these techniques as routine biophysical tools. The considerable recent progress that has been made in biotechnological applications is reviewed, highlighting specific examples of the applications of this new and exciting method of analysis.

Biological Products↗
PubMed1994

Protein C is responsible for the rapid inactivation of factor Va following blood clotting in vitro.

When whole blood is allowed to clot in vitro, factor V is rapidly activated to factor Va which is subsequently inactivated. We developed two monoclonal anti-protein C antibodies, one of which inhibits protein C activation and the other inhibits protein C activity. The addition of either antibody to blood before clotting in vitro significantly inhibited the inactivation of factor Va, confirming the essential role of protein C in mediating the rapid inactivation of factor Va.

Antibodies, Monoclonal↗
PubMed1992

Structural and computational investigations of the conformation of antigenic peptide fragments of human polymorphic epithelial mucin.

Human polymorphic epithelial mucins (PEM) are complex glycoproteins that are associated with breast and ovarian carcinomas. The PEM core protein consists of variable numbers of a tandem repeat sequence which contains a short antigenic hydrophilic region (Pro1-Asp-Thr-Arg-Pro-Ala-Pro7). High-field n.m.r. studies undertaken on antigenic 20- and 11-amino acid fragments of the PEM core protein in dimethyl sulphoxide have identified a type-I beta-turn to be present in the region Pro1-Asp-Thr-Arg4. This region includes and overlaps the identified type-I (Asp2-Thr-Arg4) and type-II (Arg4-Pro-Ala6) epitopes of anti-PEM monoclonal antibodies. The studies indicate that the beta-turn is stabilized by the presence of a salt-bridge interaction between Asp-2 and Arg-4. In order to probe the conformations accessible to the PEM peptides a computational study was undertaken independently on the peptide Pro-Asp-Thr-Arg-Pro using a modified Metropolis Monte Carlo algorithm. This study identified the n.m.r.-observed salt-bridge type-I beta-turn as the major low-energy conformer. These results suggest that this structural motif may be involved in the immune recognition of PEM.

Amino Acid Sequence↗
PubMed1992

Topographical investigations of human ovarian-carcinoma polymorphic epithelial mucin by scanning tunnelling microscopy.

Human polymorphic epithelial mucin is a high-molecular-mass glycoprotein that associates to provide protection to the epithelial-cell surface and may afford the malignant cell a selective advantage for growth. The scanning-tunnelling-microscopy micrographs obtained in the present study identify the purified human ovarian-carcinoma polymorphic epithelial mucin glycoproteins as rod-shaped molecules of mixed length. The dimensions of the individual molecules range from 25 to 45 nm in length and are 3-4 nm in width. The images further suggest that lateral association of the rods occurs.

Animals↗
PubMed1992

Traumatic lesions of the suprasellar region: MR imaging.

The authors studied nine patients with injuries to the suprasellar region with 1.5-T magnetic resonance (MR) imaging. Five patients had chiasmal injuries diagnosed by means of clinical examination. MR imaging demonstrated complete transection in two of these five patients, contusion of the chiasm by inferior herniation of the gyrus rectus in one, and a normal chiasm in two. Two patients had large tears of the floor of the third ventricle resulting in wide communication between the third ventricle and the prepontine cistern. One of these patients also had an avulsed third nerve. Transection of the pituitary stalk was seen in two patients. MR imaging can demonstrate injuries to the suprasellar structures. The MR imaging appearance of optic chiasm correlates with different types of injury to the chiasm described in the clinical literature and may alleviate the need for additional diagnostic studies to help explain the patient's symptoms.

Adult↗
PubMed1991

Resectable gastric carcinoma. An evaluation of preoperative and postoperative chemotherapy.

Patients with locoregional gastric carcinoma often die because of the low rates of curative resection and frequent appearance of distant metastases (mainly peritoneal and hepatic). To evaluate the feasibility of preoperative and postoperative chemotherapy, 25 consecutive previously untreated patients with potentially resectable locoregional gastric carcinoma received two preoperative and three postoperative courses of etoposide, 5-fluorouracil, and cisplatin (EFP). Ninety-eight courses (median, five courses; range, two to five courses) were administered. Six patients had major responses to EFP. Eighteen patients (72%) had curative resections, and three specimens (12%) contained only microscopic carcinoma. At a median follow-up of 25 months, the median survival of 25 patients was 15 months (range, 4 to 32+ months). Peritoneal carcinomatosis was the most common indication of failure. One patient died of postoperative complications, but there were no deaths due to chemotherapy. EFP-induced toxic reactions were moderate. Preoperative and postoperative chemotherapy for locoregional gastric carcinoma is feasible, and additional studies to develop regimens that could result in 5% to 10% complete pathologic responses may be warranted.

Adenocarcinoma↗
PubMed1991

Current strategies in the management of locoregional and metastatic gastric carcinoma.

Gastric carcinoma remains a significant cause of death worldwide. A patient's prognosis depends on the degree of gastric wall penetration, presence of lymph node metastases, and location of the primary site. Metastatic gastric carcinoma is currently incurable. However, chemotherapy continues to evolve at a rapid pace. Active agents include 5-fluorouracil (5-FU), doxorubicin, cisplatin, methotrexate, mitomycin, and etoposide. Combination etoposide, doxorubicin, and cisplatin (EAP) has been reported to result in encouragingly high response rates, including a 10% complete response rate in patients with metastatic gastric carcinoma. Trials are now under way to confirm these results. Similarly, another etoposide-based combination, etoposide, leucovorin, and 5-FU (ELF), has resulted in an equally good response rate but less toxicity than EAP. The 5-FU, doxorubicin, and methotrexate (FAMTX) regimen, previously reported to have an excellent response rate, is also being investigated further. For patients with locoregional carcinoma, curative resection rate is often unsatisfactorily low; however, curative resection is consistently associated with improved survival (between 23 and 26 months). In patients with potentially resectable carcinoma, two significant problems must be recognized: (1) a low rate of curative resection and (2) the development of widespread carcinoma despite curative resection. Despite many attempts, the postoperative strategies of adjuvant chemotherapy have been ineffective. New strategies must be investigated aggressively. Combination etoposide, 5-FU, and cisplatin (EFP) has been administered preoperatively and postoperatively to patients with resectable gastric carcinoma, resulting in an encouraging curative resection rate (greater than 70%) and manageable toxicity. Based on promising results reported with EAP in patients with unresectable locoregional carcinoma of the stomach, a trial of preoperative and postoperative EAP in potentially resectable carcinoma of the stomach is now under way.

Antineoplastic Agents↗
PubMed1991

COSMIC(90): an improved molecular mechanics treatment of hydrocarbons and conjugated systems.

Four modifications to the COSMIC molecular mechanics force field are described, which greatly increase both its versatility and the accuracy of calculated conformational energies. The Hill non-bonded van der Waals potential function has been replaced by a two-parameter Morse curve and a new H-H potential, similar to that in MM3, incorporated. Hydrocarbon energies in particular are much improved. A simple iterative Hückel pi-electron molecular orbital calculation allows modelling of conjugated systems. Calculated bond lengths and rotational barriers for a series of conjugated hydrocarbons and nitrogen heterocycles are shown to be as accurate as those determined by the MM2 SCF method. Explicit hydrogen-bonding potentials for H-bond acceptor-donor atom pairs have been included to give better hydrogen bond energies and lengths. The van der Waals radii of protonic hydrogens are reduced to 0.5 A and the energy well depth is increased to 1.0 kcal mol-1. Two new general atom types, N+sp2 and O-sp3, have been introduced which allow a wide variety of charged conjugated systems to be studied. A minimum of parameterisation is required, as the new types are easily included in the Hückel scheme which automatically adjusts bond and torsional parameters according to the defined bond-order relationships.

Computer Simulation↗
PubMed1990

Scanning tunneling microscopy imaging of the tumour associated antigenic 20 amino acid human polymorphic epithelial mucin core peptide fragment.

Human polymorphic epithelial mucins (PEM) are high molecular weight glycoproteins that are associated with breast cancer. Recent structural studies have identified that the protein core of PEM contains a 20 amino acid tandem repeat that has elements of secondary structure which coincide with the epitopes for a number of tumour reactive antibodies. In our continuing structural studies we have now investigated the use of the scanning tunneling microscope (STM) to directly image the conformation of the twenty amino acid PEM core peptide. High resolution STM images reveal that the peptide has an overall topography similar to that predicted by molecular modelling. The images identify directly that the free peptide is conformationally non-restricted and can adopt a number of discrete conformations in the solid state.

Amino Acid Sequence↗
PubMed1990

Evaluation of continuous-infusion alpha-difluoromethylornithine therapy for colorectal carcinoma.

A total of 32 evaluable patients with measurable advanced colorectal carcinoma were treated with continuous-infusion alpha-difluoromethylornithine (DFMO) at a median daily dose of 8 g/m2 (range, 6-14 g/m2). DFMO was infused over 24 h daily for 28 days, followed by a rest period of 7 days. Of the 32 patients, 14 had received no prior chemotherapy. A total of 65 courses was given, with the median being 2 (range, 1-9 courses). None of the patients achieved a partial or complete response; however, 3 patients achieved a minor response and 14 had stable disease. The frequent toxic effects of DFMO included thrombocytopenia (which was dose-limiting), malaise, nausea, vomiting, reversible hearing loss, and diarrhea. Our data suggest that continuous-infusion DFMO therapy is feasible and results in only mild gastrointestinal toxicity. Although DFMO proved to be ineffective as a single agent in this trial, it could probably best be used in combination with cytotoxic agents known to enhance its antitumor activity in a preclinical setting.

Carcinoma↗
PubMed1990

Making video presentations from the Evans and Sutherland PS390.

The presentation of 3-dimensional and dynamic molecular information is often impaired by the use of conventional static display media. This paper explains a simple procedure for the direct capture onto video of graphical output from the Evans and Sutherland PS390 display. A technique for the integration of molecular images with supplementary textual and graphical information provided by commercial video titling software is also explained. We have found such presentation techniques to be of particular value in both the presentation of research results and in the preparation of material for use in a teaching environment.

Computer Graphics↗
PubMed1990

Evaluation of pre- and postoperative chemotherapy for resectable adenocarcinoma of the esophagus or gastroesophageal junction.

Thirty-five consecutive patients with resectable adenocarcinoma of the esophagus or gastroesophageal junction were treated with two preoperative and three or four postoperative chemotherapy courses consisting of etoposide, fluorouracil, and cisplatin (EFP) to evaluate the rate of curative resection, clinical and pathologic response, toxic effects, and survival. One hundred thirty-seven courses with a median number of five courses (range, one to six) were administered. Preoperative EFP resulted in 17 (49%) major responses, including six patients who did not have carcinoma cells in the repeat endoscopic biopsy specimens and cytologic brushings. Among 32 patients who had surgery, 25 (78%) had curative resection, one patient had a complete pathologic response, and one had microscopic carcinoma in the resected specimen. Six patients had microscopic carcinoma at the resection margins and received postoperative radiotherapy. At a median follow-up of 20 months, the projected survival of 35 patients is 23 months (range, 6 to 33+). Fifteen patients died of their carcinomas, and 15 patients were alive (median follow-up, 20+ months; range, 15+ to 33+ months) with no evidence of relapse. There were no deaths related to chemotherapy, surgery, or radiotherapy. EFP-induced toxic reactions were moderate. Our data suggest that multiple courses of EFP are feasible. Future strategies for this disease should consider prolonged chemotherapy with regimens that result frequently in pathologic complete responses.

Adenocarcinoma↗
PubMed1990

A phase II study of trimetrexate therapy for metastatic colorectal carcinoma.

Thirty patients with measurable metastatic colorectal carcinoma who had not received prior systemic therapy for advanced disease were treated with trimetrexate, a methotrexate analog. Trimetrexate was administered at a median daily dose of 15 mg/m2 (range, 6-22 mg/m2) intravenously for five days every three weeks. No patient achieved a complete or partial response, although minor responses of brief duration occurred in eight patients. The drug was generally well tolerated, thus permitting frequent dose escalations. Common toxic effects included mucositis, dermatitis, and myelosuppression. Our data suggest that trimetrexate given at these doses and in this schedule is not active against colorectal carcinoma.

Adult↗
PubMed1989

Topoisomerase II: a potential target for novel antifungal agents.

Several podophyllotoxin-related lignans have been shown to possess significant antifungal activity against a number of filamentous fungi. Initial structure-activity studies indicate this action is sensitive to change at the 4 and 4' positions of the podophyllotoxin skeleton. Good correlation has been observed between antifungal action and the ability to inhibit the relaxation of supercoiled plasmid DNA by a topoisomerase II preparation from Saccharomyces cerevisiae. Etoposide, an inhibitor of mammalian topoisomerase II, is inactive against this yeast enzyme, although good inhibition is shown by amiloride, 4'-(9-acridinylamino)-methanesulphon-m-anisidide (m-AMSA) and novobiocin, known inhibitors of the mammalian enzyme.

Amiloride↗
PubMed1989

Crystallographic studies and semi-empirical MNDO calculations on quisqualic acid and its analogues: systems containing unusual pyramidal heterocyclic ring nitrogens.

X-ray crystallographic studies on synthetic DL-quisqualic acid and the corresponding carbon analogue have revealed pyramidal and almost planar geometries respectively for the ring nitrogen atoms carrying the alkyl side chain. Semi-empirical molecular orbital calculations on methyl-substituted model systems predict ring geometries in close agreement with experimentally observed data. The calculated energy barriers between the two enantiomeric forms (invertomers) of the oxadiazolidine systems along with some physical data would suggest that such forms are rapidly interconverting.

Computer Simulation↗