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Biomedical subjects

C Davidson

Publications and source records attributed to C Davidson.

At least 19 recordsLinked to original sources
PubMed1992

Histopathology of spontaneous brain herniations into the middle ear.

Two patients with spontaneous brain herniation into the middle ear have been operated on with a combined otoneurological approach. In case No. 1, two 2 x 3 mm arachnoid tissue herniations were found in the tegmen antri of the left ear. Six years later, a 8 x 9 mm mass consisting of prolapsed brain was removed from the right ear. The histological examination showed normal but disorganized nervous tissue. The surface consisted of middle ear mucosa or modified glial cells. More deeply numerous well preserved neurons and synapses were observed. In case No. 2, a 2 x 1 cm herniation was found in contact with the ossicles and the bony walls of the middle ear. The herniation consisted of partly degenerated nervous tissue which could explain the episode of temporal lobe seizure the patient experienced 8 years before surgery. In the world literature during the last 40 years, 29 cases of spontaneous or idiopathic brain herniation into the middle ear and mastoid have been reported. In 10, the herniations were multiple, as in our case No. 1. Case No. 1 is interesting also because the spontaneous brain herniation was bilateral.

Cerebrospinal Fluid Otorrhea↗
PubMed1992

Very far-advanced otosclerosis.

The term very far-advanced otosclerosis is proposed to indicate otosclerotic patients with both bone and air conduction thresholds nonmeasurable on a standard clinical audiometer (blank audiogram). Three of these patients have undergone stapedotomy with satisfactory results. This confirms that cochlear implantation is not the best treatment for all profoundly deaf patients at least with implants available today. Some of the patients with a blank audiogram are better off with exploratory tympanotomy and stapedotomy.

Adult↗
PubMed1990

Serial evaluation of ventricular function after percutaneous aortic balloon valvuloplasty.

To evaluate the serial changes in right and left ventricular performance after percutaneous aortic balloon valvuloplasty, 15 patients, mean age 75 +/- 18 years, and in New York Heart Association (NYHA) class III, were studied with first-pass radionuclide angiocardiography (RNA) immediately before, then 5 minutes, 2 hours, 4 hours, 6 hours, and 3 days after valvuloplasty. No change was observed in heart rate, aortic root systolic pressure, Fick, or RNA cardiac output, amount of aortic insufficiency measured either angiographically or with the regurgitant fraction determination immediately after valvuloplasty. However, significant changes were observed in the peak-to-peak aortic valve gradient (63 to 35 mm Hg; p less than 0.001), mean aortic valve gradient (54 to 33 mm Hg; p less than 0.001), aortic valve area (0.60 to 0.90 cm2; p less than 0.001), and meridional wall stress (79 to 50 10(3) dynes/cm2; p less than 0.01) immediately following valvuloplasty. In addition, left ventricular end-diastolic volume decreased from 186 to 153 ml (p less than 0.001), end-systolic volume decreased from 114 to 86 ml (p less than 0.001), micromanometric left ventricular end-diastolic pressure decreased from 20 to 14 mm Hg (p less than 0.02), and left ventricular ejection fraction increased from 0.39 to 0.45 (p less than 0.001). Peak positive left ventricular dP/dt and end-systolic pressure-volume ratio did not change after valvuloplasty (1700 to 1550 mm Hg/sec, 2.1 to 2.5 mm Hg/ml, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1990

A semiautomated method for measuring brain infarct volume.

An accurate, reproducible method for determining the infarct volumes of gray matter structures is presented for use with presently available image analysis systems. Areas of stained sections with optical densities above that of a threshold value are automatically recognized and measured. This eliminates the potential error and bias inherent in manually delineating infarcted regions. Moreover, the volume of surviving normal gray matter is determined rather than that of the infarct. This approach minimizes the error that is introduced by edema, which distorts and enlarges the infarcted tissue and surrounding white matter.

Animals↗
PubMed1989

Sexing the human fetus and identification of polyploid nuclei by DNA-DNA in situ hybridisation in interphase nuclei.

Samples of human adult lymphocytes, fetal lymphocytes, amniotic fluid cells, and chorionic villus cells were sexed independently by cytogenetics and DNA-DNA in situ hybridisation to a tritiated Y probe. For the in situ hybridisation analysis, the presence of Y bodies (hybridisation bodies) in 100 interphase nuclei were scored after autoradiography. In all, 82/83 samples were sexed in this way (one technical failure) and 78/82 were sexed by both in situ hybridisation and cytogenetics. There was complete agreement between the two methods. There was a considerable variation (40-100%) in the percentage of interphase nuclei with a hybridisation body among the male samples, but very few nuclei from female samples showed significant hybridisation. In situ hybridisation could be used to sex the conceptus when males but not females are at risk for various X-linked genetic disorders and may also be useful for detecting 45,X/46,XY mosaicism or polyploid/diploid mosaicism. This would be particularly useful for direct preparations of chorionic villus samples, which often prove difficult to analyse cytogenetically but offer the best means of avoiding maternal contamination. Some interphase nuclei had more than one hybridisation body, and this was most commonly found among amniotic fluid cells. Comparison of sizes of nuclei with one or two hybridisation bodies strongly suggested that most of the amniotic fluid cell nuclei with two hybridisation bodies were tetraploid.

Adult↗
PubMed1988

Determination of the molecular size distribution of immunoglobulin G (IgG) in intravenous IgG-albumin formulations by high-performance liquid chromatography.

Recent reports have expressed concern about the safety of intravenous human immunoglobulin G (IgG) preparations. Evidence seems to indicate that aggregates in these formulations are responsible for several adverse reactions in some patients, including anaphylaxis and dyspnea. Therefore, monitoring the molecular size distribution of IgG in these products is essential for ensuring their safety. This paper describes a sensitive and precise two-stage high-performance liquid chromatographic method for determining the molecular size distribution profile of IgG in an intravenous formulation stabilized with albumin. In the first step, all molecular forms of IgG are separated from all molecular forms of albumin by anion-exchange chromatography. In the second stage, a portion of the collected IgG fraction is re-chromatographed by size-exclusion chromatography and separated into its aggregate, dimer, and monomer components. Although some minor losses of aggregate do occur in the procedure, the overall molecular size distribution is not significantly affected. The method described is both time-efficient and accurate, and represents an improvement over existing methods.

Albumins↗
PubMed1986

General medicine in the 'eighties.

The general physician with or without an interest is directly responsible for the initial and continuing care in most acute medicine. Specialty interests cover the whole range of medicine but in most instances are subordinate to the claims of general medicine. Consultants in district general hospitals carry a bigger caseload in acute medicine than their colleagues in teaching hospitals, and this has implications for undergraduate and postgraduate training. The management of patients in intensive care units remains very much the task of the general physician. The general physician will continue to be an essential member of the hospital service in the foreseeable future.

Emergencies↗
PubMed1986

Enalapril in moderate to severe hypertension: a comparison with atenolol.

Patients with moderate to severe essential hypertension (mean untreated supine blood pressure 190/112 mm Hg) received once daily enalapril 20-40 mg or atenolol 50-100 mg, supplemented if required by hydrochlorothiazide 25-100 mg, in a randomized observer-blind trial. Both regimens produced a highly significant reduction in supine and standing blood pressure. There was no significant difference in the antihypertensive effects of enalapril and atenolol when they were used as monotherapy. After hydrochlorothiazide was added to patients not achieving 'target' blood pressure, the fall in systolic pressure was significantly greater in the enalapril group than in the atenolol group, despite similar dosage of hydrochlorothiazide in the two groups. At the end of 6 months' treatment, a supine diastolic blood pressure of 90 mm Hg or below was achieved in 74% of patients on enalapril plus hydrochlorothiazide and 56% of patients on atenolol plus hydrochlorothiazide. This difference was not statistically significant. A small rise in plasma urea and creatinine was observed in the enalapril group and a small rise of urea only in the atenolol group. These changes were statistically significant but of uncertain clinical importance. This study confirms that once daily enalapril and atenolol, both alone and in combination with hydrochlorothiazide, are effective drugs in the management of moderate to severe hypertension.

Adolescent↗
PubMed1979

Comparison of the immediate effects of five beta-adrenoreceptor-blocking drugs with different ancillary properties in angina pectoris.

We compared the immediate effects of five beta-adrenoreceptor-blocking agents in 16 patients with stable angina pectoris. Acute dose-response studies showed that all five drugs improved exercise tolerance and reduced ST-segment depression, heart rate and blood pressure by a similar degree in comparison with a placebo (P less than 0.01). Near maximum improvement in exercise tolerance occurred when the acute cumulative oral dose had reached 160 mg for propranolol and oxprenolol, 200 mg for metoprolol and tolamolol and 400 mg for practolol. When these drugs were administered as a single doses, increase in walking time before the development of angina and reduction in ST-segment depression, heart rate and systolic blood pressure all occurred within one hour and persisted for eight hours--effects markedly different from the response to a placebo (P less than 0.01). These data show that non-cardioselective agents (propranolol and oxprenolol), cardioselective agents (practolol, metoprolol and tolamolol), as well as drugs with intrinsic sympathomimetic activity (oxprenolol and practolol), were equally effective in the treatment of angina pectoris.

Adult↗
PubMed1978

Potassium depletion in heart failure and its relation to long-term treatment with diuretics: a review of the literature.

There have been many studies which suggest that patients with heart failure were potassium depleted. This depletion has been attributed to the use of potent diuretics, and these are now given with either potassium supplements or potassium-retaining diuretics. A detailed examination of the studies suggests that the reported decrease in body potassium compared with the results in healthy persons is not due to the diuretics. It can be partly explained by a failure to match patients and controls in terms of age, and the remaining difference can be explained by muscle wasting. There is therefore no evidence of a potassium depletion in these patients with heart failure.

Adult↗
PubMed1978

The effects of potassium supplements, spironolactone of amiloride on the potassium status of patients with heart failure.

Extra potassium supplements, spironolactone or amiloride were given for 5 months to forty-nine patients with heart failure who were taking furosemide and were in a steady state. Plasma potassium increased with all three treatments but there was no significant increase in total body potassium or red cell potassium. These findings together with other studies suggest that patients with heart failure taking diuretics do not have a significant depletion of body potassium.

Adult↗