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Biomedical subjects

M M Lee

Publications and source records attributed to M M Lee.

At least 163 records · Page 9Linked to original sources
PubMed1983

Fetal circulation of the placenta: a comparative study of human and baboon placenta by scanning electron microscopy of vascular casts.

This study was undertaken to compare the ultrastructural appearance of the fetal microvasculature of the baboon and human placenta by the latex injection corrosion-cast technique. The general pattern of distribution of blood vessels in the placenta and the microvasculature were examined primarily by scanning electron microscopy using single and double latex (Cementex) injections of the placentae. The results of these latex injections of the baboon placenta demonstrate that (1) all the fetal arterial vessels of the baboon placenta at about three-quarters of the gestation period have a characteristic tortuosity while the venous vessels have a straight appearance, with no distinct coiling, (2) the arterial vessels exhibit a rough surface contour, (3) on the venous side the wide-calibre vessels are fairly straight and exhibit a smooth luminal surface contour, and (4) the capillary network on the arterial side is dense and highly convoluted, while on the venous side the capillary network is less tortuous. Moreover, no arterial-venous anastomosis was observed by scanning electron microscopy (SEM). The main findings based on observations of the SEM appearance of the human placental casts at three-quarter gestation and at term include the following: (1) the arterial vessels do not exhibit a marked tortuosity but do retain a rough surface contour, (2) stem vessels appear to branch at a horizontal plane before dividing into numerous smaller branches, (3) the venous side has straight, wide-calibre vessels with smooth surface contour, and (4) the capillary bed is densely tortuous on the arterial side and less tortuous on the venous side.

Animals↗
PubMed1981

Large scale isolation of human erythrocyte membranes by high volume molecular filtration.

A molecular filtration procedure for preparing large quantities of human erythrocyte ghost membranes is presented. Hemolysate ghost membranes are rapidly cycled in the retentate channel of the filtration apparatus, while hemoglobin is removed as it passes through Pellicon filters into the filtrate channel. Several-liter quantities of washed packed erythrocytes can be processed in a few hours with this system, and the filtration procedure does not appear to alter intact erythrocyte or ghost membranes. Intact erythrocytes in isotonic solution can be circulated through the retentate channel for 16 h with only 3% hemolysis and with preservation of their original morphology in scanning electron microscopy. Ghost membranes isolated by the procedure are virtually identical in morphology, polypeptide composition and acetylcholinesterase content to membranes isolated by conventional centrifugation techniques.

Cell Fractionation↗
PubMed1981

A comparison of attitudes and final grades among freshman dental students.

A study was conducted to determine if a change in dental students' attitudes toward three preselected concepts would occur as a result of a traditionally difficult gross anatomy course. In addition, an attempt was made to determine the predictive value of a student's attitudes in determining his or her final grade. The study employed Campbell and Stanley's one group pretest-posttest design. The results indicated that students' attitudes toward a difficult course and themselves did not change significantly, but that a significant negative change did occur in their attitude toward the entire dental educational experience. The results also indicated that students' attitudes toward specific concepts can be successfully employed to predict a portion of their final grade.

Anatomy↗
PubMed1981

Development and testing of self-instruction programs in nutrition for dental students.

A study was undertaken to test the hypothesis that self-instructional programs in nutrition and dentistry are as effective a teaching method as traditional lectures. Five programmed self-instructional manuals accompanied by 191 slides were developed and evaluated for effectiveness, as compared to six lectures containing the same information. The study population of 83 freshmen dental students was randomly assigned to a control (lecture) group and an experimental (self-instruction) group. Cognitive tests, performance criteria for diet counseling, and an attitudinal questionnaire were used to compare the two groups. The results of the analysis demonstrated that there was no significant difference in the test scores in the lecture and self-instruction groups.

Attitude↗
PubMed1979

Morphologic effects of pressure changes on canine carotid artery endothelium as observed by scanning electron microscopy.

By using scanning electron microscopy (SEM) we were able to follow the sequence of ultrastructural alterations of the luminal surface which occurred when specimens of canine carotid artery were subjected to controlled transmural pressures. Specimens of carotid artery were removed from dogs following fixation at experimental pressures ranging from 0 mm Hg to 100 mm Hg. The endothelium of specimens fixed at 0 mm Hg has parallel longitudinal ridges formed by the contraction of the underlying internal elastic lamina. With increasing transmural pressure, the luminal surface undergoes a gradual flattening of the endothelial ridges so that at 100 mm Hg, these ridges have completely disappeared. The observed morphologic changes of the arterial endothelium indicate that SEM can provide good ultrastructural information on blood vessels subjected to controlled transmural pressure and that the pressure-dependent alterations must be considered in studies on vascular structure and function.

Animals↗
PubMed1976

Microcirculation of the rat placenta. Scanning and transmission electron microscopic observations on fetal blood vessels.

The fetal circulation of normal rat placenta was studied by parallel examination with the scanning electron microscope (SEM) and the transmission electron microscope (TEM). By examining casts of vessels injected with latex and prepared by corrosion in hypochlorite solutions, the fetal arteries, veins, and capillaries of the placenta could be traced in the scanning electron microscope and, in addition, the ultrastructural details of microcirculation and luminal surfaces could be studied. Cast specimens showed fetal arteries entering the center of the placenta and branching into long, thin vessels which traversed almost the entire thickness of the placenta before dividing into a markedly tortuous capillary network. The smooth-surfaced capillary vessels located at the arteriolar end flowed into a much less tortuous prevenous capillary network which conducted the blood into collecting venules and veins. Placental blood vessels examined by the TEM provided evidence that details observed by the SEM were accurate for the ultrastructural appearance of fetal arteries, capillaries, and veins.

Animals↗
PubMed1976

Vibrio cholerae infection and immunity in mice.

Lyophilized cultures of V. cholerae 569B slowly lose their virulence for neonatal and adult mice during long term storage. Following a single passage in orally infected 6-day old mice, a highly virulent strain (designated 569B/MP) was isolated. This organism causes rapidly fatal intestinal infections in 6-day old mice; large numbers can be isolated in pure culture from the intestinal fluid. Freezing and storage at -60 degrees of dead animal provides a simple means of maintaining the high virulence of the culture over a period of at least 9 months. This strain produces choleracic symptoms and death in approx. 50% of adult mice following oral infection. Large numbers of viable organisms may also be isolated from the small intestine over a period of at least 40 h. These criteria have been used as a basis for assessing protection against cholera infection induced by immunization with living or heat-killed V. cholerae given orally or intraperitoneally.

Animals↗