Biomedical subjects

R Summers

Publications and source records attributed to R Summers.

75 records · Page 5Linked to original sources

PubMedDate not supplied

Effects of methyldopa metabolites on amine transmitters and adrenergic receptors in rat brain.

Studies of catecholamine concentrations in defined nuclei from the anterior hypothalamic-preoptic regions and the medulla oblongata, known to contribute to cardiovascular control, were measured following acute or chronic methyldopa administration. These studies indicated that methyldopa was enzymatically converted to methyldopamine and methylnorepinephrine, and in some areas to methylepinephrine which replaced endogenous epinephrine. The predominant metabolite was methylnorepinephrine, which accumulated in concentrations higher than endogenous norepinephrine levels. (-)Methylnorepinephrine was found to be 6 times more potent and 75 times more selective for alpha 2-adrenergic receptors than (-) norepinephrine, and it is suggested that this alpha 2-adrenergic receptor action, particularly in the nucleus tractus solitarius, contributes to a major part of the antihypertensive effect of methyldopa.

Animals↗

PubMedDate not supplied

The bone-added osteotome sinus floor elevation technique: multicenter retrospective report of consecutively treated patients.

A retrospective clinical evaluation of patients consecutively treated from multiple centers was performed. The treatment of these patients utilized the bone-added osteotome sinus floor elevation (BAOSFE) procedure with immediate implant fixation. The BAOSFE method employs a specific set of osteotome instruments to tent the sinus membrane with bone graft material placed through the osteotomy site. A total of 174 implants was placed in 101 patients. Implants were of both screw and cylinder shapes with machined, titanium plasma-sprayed, and hydroxyapatite surfaces from various manufacturers. The 9 participating clinicians used autografts, allografts, and xenografts alone or in various combinations, and the type of graft was selected by the individual clinicians. The choice of graft material did not appear to influence survival rates. Loading periods varied from 6 to 66 months. The survival rate was 96% or higher when pretreatment bone height was 5 mm or more and dropped to 85.7% when pretreatment bone height was 4 mm or less. The most important factor influencing implant survival with the BAOSFE was the preexisting bone height between the sinus floor and crest. This short-term retrospective investigation suggests that the BAOSFE can be a successful procedure with a wide variety of implant types and grafting procedures.

Adult↗

PubMedDate not supplied

Epidemiological use of rectal proliferation measures.

Measures of rectal mucosal proliferation have been developed and used in research clinical settings, but their utility for larger-scale epidemiological studies remains uncertain. We assessed the suitability of bromodeoxyuridine (BrdUrd) and proliferating cell nuclear antigen (PCNA)-labeling indices (LIs) in the setting of a multicenter clinical trial of adenoma recurrence. Subjects at participating practices were asked to permit biopsy of normal rectal mucosa during a colonoscopy scheduled for other reasons. PCNA and BrdUrd labeling was performed, and corresponding LIs were computed. In general, subjects were willing to undergo biopsy during their scheduled procedures; less than 10% refused. Specimen preparation for PCNA was acceptable; the mean number of scorable crypts (+/- SE) was 12.99 +/- 0.37. Preparation for BrdUrd labeling was less successful, with a higher proportion of unscorable specimens and a lower mean number of scorable crypts. Among the 54 specimens with both LIs computed, the LI for PCNA was modestly higher than that for BrdUrd LI (4.1 +/- 0.2 and 3.7 +/- 0.2 respectively; P = 0.03). The rank order correlation between the two indices was 0.38). There was variation across centers in the PCNA LIs but few differences according to number of crypts scored. Measurement of rectal mucosal proliferation is feasible among endoscopy patients in large studies if PCNA is used; BrdUrd seems more difficult. The relationship between these two labels requires further study.

Adenoma↗