Biomedical subjects

F Mohamed

Publications and source records attributed to F Mohamed.

41 records · Page 3Linked to original sources

PubMed1983

Scanning electron microscopy of terminal airways of guinea pigs chronically inhaling diesel exhaust.

The structural physiology of airways from 80 guinea pigs was examined for changes induced by diesel exhaust (DE) exposure. Acute, subacute and chronic studies contrasted inhalation effects of 250, 750, 1500 and 6000 micrograms DE/m3 with "clean air" breathing of age-matched controls. Nonciliated epithelial (Clara) cells, epithelial type 2 cells and alveolar macrophages were increased in a DE dose dependent fashion. Also, eosinophils, were recruited. Epithelial type 1 cells of the distal airways internalized DEP. The relative dustiness (particulate density) of airways was assessed from coded specimens. Some 86% of DE exposed animals were correctly identified. Scanning Electron Microscopy (SEM) resolved surface located DE particulates (DEP). Single particles, loose clusters, low density agglomerates occurred. While SEM visual clues are insufficient for absolute identification of DE particles, there was supporting evidence from transmission electron microscopy (TEM) and from SEM studies comparing vascular with intratracheally fixed specimens. Presumptive DEP were notable on bifurcation bridges in respiratory bronchioles and alveolar ducts while alveolar outpockets had heavy dust burdens. Clumps of macrophages in such alveoli almost occluded the airspace. We conclude that normal guinea pigs appear to adapt to a chronic DE stress environment. But, the ultrastructural basis (cellular protrusions, DEP agglomerates and secretional debris) exists in peripheral airways for airflow instability and increased airflow resistance.

Animals↗

PubMed1978

A comparison of methods for measurement of rectal potential difference in man: effects of rectal infusion of amiloride.

1. Two methods for measurement of rectal potential difference in man were compared. A saline-filled catheter technique gave more reproducible results and was better tolerated by patients than the solid probe technique. 2. Infusion of amiloride at a concentration of 4 x 10(-6) mol/l in saline produced a variable fall of potential difference in six normal subjects. Dose-response curves in two subjects showed that complete inhibition of rectal difference occurred at 4 x 10(-5) mol/l and 4 x 10(-6) mol/l respectively. 3. This finding provides additional evidence that rectal potential difference in man results from electrogenic ion transport across the mucosal epithelial cell.

Adult↗

PubMedDate not supplied

In vivo validation of tissue segmentation based on a 3D feature map using both a hamster brain tumor model and stereotactically guided biopsy of brain tumors in man.

The purpose of this study was to validate our MR tissue segmentation technique using a hamster brain tumor model and malignant brain tumors in man. We used a multispectral tissue segmentation analysis. Three sets of MRI data were included: proton density, T2-weighted fast spin echo, and T1-weighted spin echo, as inputs. Three image preprocessing steps included correcting image nonuniformity, application of an anisotropic diffusion type filter, and data point selection by a qualified observer. We used the k-Nearest Neighbor segmentation algorithm, which does not require prior knowledge of the sample distribution. This choice allowed us to optimize the different tissue clusters present in three-dimensional (3D) feature space. In vivo validation of the technique was performed in hamsters harboring tumors induced with JC virus-transformed HJC-15 cells, as compared to three control animals. Human brain tumors obtained by stereotactically guided biopsy in six patients were also included in the study. Finally, brain tumors were removed from two patients who underwent conventional craniotomy using segmentation-derived images as a guide. In the hamsters, 10 tissues were correctly identified by segmentation and were confirmed histologically (P < .02). In the patients, there was also a strong correlation between our segmentation results and the tissue obtained by stereotactic biopsy (P < .01). In one of the two patients who underwent open craniotomy, segmentation images were useful in revealing tumor spread into vital areas of the brain (motor area). In conclusion, the results of segmentation correlate well with the tissues in vivo and thus warrant further clinical utilization and evaluation.

Adult↗

PubMedDate not supplied

Seasonal variations of gonadotropins in the pars distalis male viscacha pituitary. Effect of chronic melatonin treatment.

The gonadotropes, LH and FSH cells, were immunohistochemically identified in the pituitary pars distalis of the adult male viscacha (Lagostomus maximus maximus) using specific antibodies against hLHbeta and hFSHbeta with the streptavidin-biotin-peroxidase complex. The distribution, size and percentage immunopositive area of these cells were analyzed by image analysis in viscachas captured during the annual reproductive cycle and after the chronic administration of melatonin. The LHbeta and FSHbeta cells showed seasonal changes in the distribution, size and percentage immunopositive area. The LHbeta cells were found widely distributed throughout the pars distalis during the reproductive period, and they were found in the ventro-medial region in the pars distalis during the gonadal regression and gonadal recovery periods. The LHbeta cells reached the largest size and immunopositive area during the reproductive period and the smallest size and immunopositive area during the gonadal regression period. The FSHbeta cells were found in the ventro-medial region during reproductive and gonadal regression periods. The FSHbeta cells were found widely distributed throughout the pars distalis during the gonadal recovery period when they showed the maximum percentage immunopositive area. A decrease in the size of LHbeta and FSHbeta cells was observed after the chronic administration of melatonin. Moreover, it produces a decrease in the immunopositive area occupied by the LHbeta cells but not in the immunopositive area occupied by the FSHbeta cells. Our results show great activity of LHbeta and FSHbeta cells in different moments of the annual reproductive cycle demonstrating that these cells do not secrete in parallel. Moreover, melatonin acts differentially on the activity of the gonadotrope cells.

Animals↗

PubMedDate not supplied

Adenosine enhances left ventricular flow during 24-hour hypothermic perfusion of isolated cardiac allografts.

Left ventricular flow progressively decreases during preservation of ex vivo hearts by continuous hypothermic perfusion, according to previous studies. This study was done to determine whether left ventricular flow could be maintained during 24-hour hypothermic perfusion by the addition of adenosine to the perfusate. Isolated canine hearts were perfused with either a modified Krebs-Henseleit solution or with the control solution containing adenosine (20 mumol/L) for either 4 or 24 hours. On completion of the perfusion period, radioactive microspheres were injected into the arterial inflow of the hearts. Myocardial samples were then taken from the endocardial, midcardial, and epicardial portions of the free wall and papillary muscles of the right and left ventricles, as well as the interventricular septum. Concentrations of radioactivity were determined for each sample, summed, and averaged for each ventricle. The ratio of average concentrations (L/R ratio) was significantly increased in the 24-hour adenosine hearts compared with 24-hour controls (1.10 +/- 0.15 vs 0.64 +/- 0.21, p less than 0.005). The L/R ratio of 4-hour controls (1.30 +/- 0.48) was also greater than that of 24-hour controls (p less than 0.005). These results suggest that left ventricular flow decreases during continuous hypothermic perfusion. The tendency toward diminished left ventricular perfusion after 24 hours is reduced when adenosine is added to the perfusate. Adenosine may be beneficial in ex vivo heart preservation with hypothermic perfusion by improving left ventricular flow.

Adenosine↗