Search PubMed⌕ Search

Biomedical subjects

A Martin

Publications and source records attributed to A Martin.

At least 847 records · Page 47Linked to original sources
PubMed1978

Rheology of pharmaceutical systems: oscillatory and steady shear of non-Newtonian viscoelastic liquids.

A comparative analysis of oscillatory and steady shear rate measurements was made on carboxymethylcellulose solutions of two concentrations and two viscosity grades. In the oscillatory methods, the material is examined under nearly quiescent equilibrium conditions. Steady shear, conversely, produces large deformations and may yield false results, often interpreted as thixotropy, if the shear rate experiment is not conducted properly. Solutions of carboxymethylcellulose at concentrations ordinarily used in drug product formulations were examined by oscillatory and steady shear methods at low shear. Viscoelastic properties of pharmaceutical materials were measured using a newly developed oscillometric instrument. Mathematical expressions, formulated on the basis of a generalized Maxwell model for viscoelasticity and viscosity in steady shear, were correlated using these two rheological test methods. The results showed large increases in viscosity and relaxation time with increasing carboxymethylcellulose concentrations as well as with increasing molecular weights of the polymeric solute. The behavior of carboxymethylcellulose under both oscillatory and steady shear agreed with theory, linking the two methods of testing. Applications in pharmacy to this rheological analysis are presented. The present investigation attempted to bridge the gap between oscillatory and steady shear methods, demonstrating how both can find appropriate use in the analysis of non-Newtonian materials of pharmaceutical importance.

Carboxymethylcellulose Sodium↗
PubMed1978

Influence of the antigenicity of Brucella preparations on modulation of the immune response to sheep erythrocytes.

The relationship between the expression of surface antigenicity of inactivated Brucella and the immunostimulant properties on the sheep erythrocyte response was studied in mice. The agglutinogenic Brucella abortus B19S preparation was compared to two non-agglutinogenic preparations (B19R and PB), using the plaque-forming and rosette-forming cell tests. When Brucella and antigen were injected together, only non-agglutinogenic preparations, even used at low doses, were able to increase the plaque-forming and rosette-forming cell responses measured 4 days after immunization. When the interval between the previous injection of non-agglutinogenic preparations and that of the antigen increased or when they were injected 24 h after the antigen, the modification of those two responses was no longer observed. After day 4, for the simultaneous injection of Brucella and antigen, B19S and PB preparations induced the best responses; this effect was dose dependent. Thus, in the present experimental situation, the modification of the day 4 response appeared independent of those of the ensuing days.

Agglutination↗
PubMed1978

Modulation of immune response by killed Brucella abortus organisms: comparison of the effects of smooth and rough strains on T-dependent responses.

Inactivated Brucella abortus organisms of the smooth (S) or rough (R) strain were tested comparatively on two T-dependent immune responses: mixed-lymphocyte reaction and delayed-type hypersensitivity. The intravenous injection of S organisms depressed the two tests, whereas R organisms increased mixed-lymphocyte reaction and did not alter delayed-type hypersensitivity significantly. This observation may be helpful in understanding the differences in adjuvant properties of S and R brucellae.

Brucella abortus↗
PubMed1978

Serum complement components in Henoch-Schönlein purpura.

Serum levels of C1q, C4, C3, C5, factor B, and properdin were measured in patients with Henoch-Schönlein purpura (HSP). In the cases of acute HSP, 9 of 23 (39%) had a low CH50, and 5 of 17 (30%) a low properdin; C1q, C4, and C3 levels were not depressed. In 10 cases with chronic nephritis following HSP, complement components were normal except for 2 with reduced C4 and one with low properdin. These findings confirm that complement activation occurs in HSP; the low serum levels of properdin in the acute group indicate that there is activation of the alternative pathway in these patients.

Acute Disease↗
PubMed1978

Correlations between variations of electrical field at the body surface and contractions of the stomach in guinea pig.

1. The slow potentiel changes of the base line of the electrocardiogram recorded by cutaneous electrodes, here called EGEG (electrogastroenterogram) have been recorded simultaneously with the electromyogram and pressure variations of the stomach antrum. 2. Periodic fluctuations of EGEG, 400 microV amplitude, were correlated with activities of the antrum EMG consisting of 3 to 6 mV spikes superimposed on slow wave of depolarization, and with gastric intraluminal pressure of 5 to 7 cm of water. 3. An anticholinergic drug abolished all those activities. A gastric contracture flattened the EGEG. 4. Rhythmic distensions of the antrum induced a synchronous modulation of EGEG, the magnitude of which was correlated with the amplitude of distension. These result suggest that the origin of EGEG is essentially the movements of stomach.

Animals↗
PubMed1978

Somatostatin in mucosa of stomach and duodenum in gastroduodenal disease.

In order to study the distribution of somatostatin in the upper digestive tract in man, biopsies were taken through endoscopy or at surgery from the fundus, antrum, and duodenal bulb in 15 subjects with no gastroduodenal lesion, 12 patients with severe antral and/or fundic atrophy in the sampling area, 28 patients with an active duodenal ulcer, and 14 patients with a nonmalignant gastric ulcer. The specimens were extracted in 2 N acetic acid and tested for somatostatin content with a specific radioimmunoassay. In the control subjects, the somatostatin concentration (nanograms per milligram of wet weight) was 0.60 +/- 0.12 in the fundus, 1.68 +/- 0.33 in the antrum, and 1.35 +/- 0.30 in the duodenal bulb. Atrophy of the gastric mucosa was associated with a reduction of the somatostatin concentration in the fundus and the antrum. No significant variation was observed in the present series of patients with gastric ulcer. Duodenal ulcer was associated with a reduction of the somatostatin concentration in the antrum (P less than 0.02). These results indicate that somatostatin is widely distributed from fundus to duodenal bulb in adult human subjects, and that lower antral concentrations are observed in patients with duodenal ulcer.

Adult↗