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Biomedical subjects

R M Lee

Publications and source records attributed to R M Lee.

At least 109 records · Page 6Linked to original sources
PubMed1987

Serologic survey for evidence of exposure to vesicular stomatitis virus, pseudorabies virus, brucellosis and leptospirosis in collared peccaries from Arizona.

Two hundred eighteen usable serum samples were collected from hunter-killed collared peccaries (Tayassu tajacu) during March 1986, in three areas of Arizona. Evaluations for antibodies against vesicular stomatitis virus (VSV) New Jersey (NJ) type, VSV Indiana type, pseudorabies virus, brucellosis, and leptospirosis revealed positive test results in 8%, 0%, less than 1%, 0%, and 23% of the sera, respectively. Exposure of peccaries to VSV (NJ) was widespread, but variation in the prevalence of seropositive peccaries was not found between the three areas sampled. The exposure of peccaries to VSV (NJ) probably was related to the recent epizootics in livestock in the vicinity. Exposure to Leptospira interrogans serovars also was widespread, and geographic variation in the prevalence of peccaries with antibodies against L. interrogans was found.

Animals↗
PubMed1987

Preservation of in vivo morphology of blood vessels for morphometric studies.

Preservation of in vivo morphology of the blood vessels is important for morphometric studies. With each fixation method (e.g., immersion fixation, perfusion fixation), there are inherent pitfalls which can easily distort vessel wall morphology, thereby creating artifacts. Alteration of the vessel wall cell volume due to tissue preparation is another common source for errors. Selection of proper morphometric protocols for comparative studies is crucial. Lack of attention in these areas is a cause of confusion and contradiction in the literature. In this review, the merits of various commonly used methods for vessel wall preparation and measurements are discussed.

Blood Vessels↗
PubMed1987

Scanning electron microscopy of vascular smooth muscle cells from rat muscular arteries.

The use of scanning electron microscopy (SEM) for the examination of medial smooth muscle cells (SMC) is limited by the presence of connective tissue mass in the adventitia obscuring the detailed structure of the SMC. This study deals with the description of a method which selectively removes the connective tissue, allowing three dimensional observation of SMC using SEM. A number of methods were tried. One method involving post fixation with 2% OsO4 used in conjunction with HCl proved most successful in removing the extracellular matrix of large mesenteric arteries from spontaneously hypertensive rats (SHR) and age-matched Wistar-Kyoto normotensive rats (WKY). In both SHR and WKY, the spindle-shaped cells are circumferentially oriented, and ran parallel to one another and formed a continuous compact medial layer with a number of intercellular junctions being evident. Surface morphology of SMC changed between relaxed and contracted states. Relaxed SMC had a smooth regular surface with very fine longitudinal grooves or striations running parallel to the cell long axis. Contracted SMC possessed regular transverse folds on its surface giving a corrugated appearance. The nerve network possessed a fishnet appearance with many triangular bulges at nerve branch points. The internal elastic laminae showed longitudinal furrows and fenestrations, the number of which varied from vessel to vessel. In the superior mesenteric artery, the SMC were circular and helically arranged. Longitudinally and diagonally arranged SMC were evident at bifurcations. Mesenteric veins consisted of one layer of flattened circular SMC that ran parallel to one another and formed a compact and complete medial layer.

Animals↗
PubMed1986

Measurement of concentrations of the histamine H1 receptor antagonist temelastine in biological fluids.

A high-performance liquid chromatographic analysis of temelastine in biological fluids with UV detection at 229 nm is presented. The method involves ether extraction followed by re-extraction into phosphoric acid and chromatography on a reversed-phase column. The method has a lower limit of detection of 0.05 mg L-1 and is adequate for use in pharmacokinetic studies following oral administration.

Bile↗
PubMed1986

Recent advances in pharmaceutical chemistry--review II. Histamine H2-receptor antagonists.

The concept of histamine receptors is outlined and the rationale for the synthesis of H2-antagonists presented. Structure-activity relationships among these compounds are described and aspects of absorption, distribution and elimination discussed with particular reference to cimetidine and ranitidine. Oxmetidine, lupitidine and loxtidine are also considered. Methods for the analysis of these drugs in body fluids are presented followed by a discussion of their toxicology. Volunteer and patient studies are also surveyed.

Animals↗
PubMed1986

Dense-cored membrane structures in rat myometrial smooth muscle cells: increase in number during parturition.

Membrane-bound structures containing electron-dense material were found in the cytoplasm of the smooth muscle cells of rat myometrium. Most of these structures were observed as membrane-bound vesicles with a variable diameter in the range of 50-90 nm. Some of these were present underneath the cell membranes among the clusters of caveolae and some were found deep in the interior of the smooth muscle cell. The number of such structures progressively increased with gestation reaching the maximum during parturition and decreasing to a minimal level 2 days postpartum, suggesting that the occurrence of these structures is of physiological relevance in parturition. Ovariectomy of the pregnant rats had no influence upon the temporal distribution of these structures within the gestation period, indicating that hormones of ovarian origin are not responsible for the maintenance of these structures during their disappearance after parturition.

Animals↗
PubMed1986

Morphometric study of mesenteric arteries from genetically hypertensive Dahl strain rats.

Morphometric measurements on different arteries at the light-microscopic level and ultrastructural studies of the mesenteric arteries were carried out in salt-sensitive (DS) and salt-resistant (DR) Dahl rats given a high-salt (8%) or low-salt (0.4%) diet for 6-7 weeks. Hypertension was produced in DS rats given high-salt diet (DS-H), while only moderate hypertension was produced in DS rats given low-salt diet (DS-L). Blood pressure in DR rats given high salt (DR-H) and low salt (DR-L), however, was normal. Cross-sectional area of the media was increased significantly in the superior mesenteric artery (an elastic artery), large mesenteric arteries (muscular arteries) and small mesenteric arteries (small muscular arteries or arterioles) from DS-H rats. In all the vessel types, this increase was positively correlated with the increase in blood pressure. In the superior mesenteric artery, medial wall increase was probably due to an increase in intercellular space, and/or hypertrophy of the smooth muscle cells. Similarly, increase in the media of small mesenteric arteries was probably due to hypertrophy of the smooth muscle cells. In contrast, increase in the media of large mesenteric arteries was related to hyperplasia of the smooth muscle cells. Damage to endothelial cells was noted in the 3 vessel types from DS-H. Intimal lesions composed of myointimal cells were found in the superior mesenteric arteries of all the rat groups. Our results showed that the incidence of these lesion formations was higher in the following order: DS-H greater than DS-L greater than DR-H greater than DR-L, suggesting that the degree of hypertension (DS vs. DR rats) and the amount of salt in the diet (DR-H vs. DR-L) may be some of the factors contributing to the development of these lesions. We conclude that hyperreactivity of the arteries due to increase in medial smooth muscle mass (e.g. muscular arteries), and/or probably impaired relaxation capability of the arteries in the DS-H rats due to endothelial cell damage, may contribute to the elevation of BP in the Dahl model of genetic hypertension.

Animals↗
PubMed1985

Subcellular fractionation of pig coronary artery smooth muscle.

A detailed procedure for subcellular fractionation of the smooth muscle from pig coronary arteries based on dissection of the proper tissue, homogenization, differential centrifugation and sucrose density gradient centrifugation is described. A number of marker enzymes and Ca2+ uptake in presence or absence of oxalate, ruthenium red and azide were studied. The ATP-dependent oxalate-independent azide- or ruthenium red-insensitive Ca2+ uptake, and the plasma membrane markers K+-activated ouabain-sensitive p-nitrophenylphosphatase, 5'-nucleotidase and Mg2+-ATPase showed maximum enrichment in the F2 fraction (15-28% sucrose) which was also contaminated with the endoplasmic reticulum marker NADPH: cytochrome c reductase, and to a small extent with the inner mitochondrial marker cytochrome c reductase, and also showed a small degree of oxalate stimulation of the Ca2+ uptake. F3 fraction (28-40% sucrose) was maximally enriched in the ATP- and oxalate-dependent azide-insensitive Ca2+ uptake and the endoplasmic reticulum marker NADPH: cytochrome c reductase but was heavily contaminated with the plasma membrane and the inner mitochondrial markers. The mitochondrial fraction was enriched in cytochrome c oxidase and azide- or ruthenium red-sensitive ATP-dependent Ca2+ uptake but was heavily contaminated with other membranes. Electron microscopy showed that F2 contained predominantly smooth surface vesicles and F3 contained smooth surface vesicles, rough endoplasmic reticulum and mitochondria. The ATP-dependent azide-insensitive oxalate-independent and oxalate-stimulated Ca2+ uptake comigrated with the plasma membrane and the endoplasmic reticulum markers, respectively, and were preferentially inhibited by digitonin and phosphatidylserine, respectively. This study establishes a basis for studies on receptor distribution and further Ca2+ uptake studies to understand the physiology of coronary artery vasodilation.

4-Nitrophenylphosphatase↗
PubMed1985

Primary versus secondary structural changes of the blood vessels in hypertension.

Various researchers have hypothesized that the thickening of the vascular wall plays an important role in the maintenance of hypertension. Such an alteration can increase the vascular resistance by exerting two effects. A thickened vascular wall could occlude the lumen of the blood vessel and (or) cause the artery to hyperreact to contractile stimuli. Until recently, it has been a general conclusion that such alterations were a secondary adaptation produced by the elevation of blood pressure. Consistent with this view, certain classes of larger arteries do exhibit a thickened vascular wall late during hypertension development and such changes can be prevented from occurring by antihypertensive treatment. However, recent studies involving the mesenteric and renal arteries of Wistar-Kyoto spontaneously hypertensive rats have shown that wall thickening of the vasculature occurs prior to hypertension development and is present even under conditions where the blood pressure has been normalized throughout the animal's life. These latter observations suggest that some structural alterations in the blood vessels observed in hypertension are pressure independent and could be of etiological importance in the initiation of hypertension.

Animals↗
PubMed1985

Vascular changes at the prehypertensive phase in the mesenteric arteries from spontaneously hypertensive rats.

Morphometric measurements of three categories of mesenteric vessels (representing elastic, muscular and arteriolar vessels) from prehypertensive spontaneously hypertensive rats (SHR) and age-matched Wistar-Kyoto rats (WKY) were carried out at the light and electron microscope levels. Structural alterations of the blood vessels were already present in the SHR, even though the blood pressure was not yet elevated as compared with age-matched WKY. No change was found in the elastic vessels (superior mesenteric artery). Among the muscular arteries (i.e. large mesenteric arteries), the increase in vessel wall cross-sectional area was due to the increase in the intima, media and adventitia. Increase in media was due to hyperplasia of the smooth muscle cells. The smooth muscle cells were not hypertrophied. Nerve density was also higher in the large mesenteric arteries of SHR. In the arteriolar vessels (i.e. small mesenteric arteries), wall to lumen ratio, as well as media to lumen ratio, were increased in the SHR. The number of smooth muscle cell layers was also increased. In all these vessel types, the cross-sectional area of the lumen under maximal relaxation was similar between SHR and WKY, except in small mesenteric arteries where the lumen was smaller in the SHR. Our results suggest that structural alteration of the blood vessels at the prehypertensive phase may be one of the contributing factors leading to the development of hypertension in the SHR.

Age Factors↗
PubMed1984

Dense-cored membranous structures in smooth muscle cells of the vas deferens of the rat.

Smooth muscle cells from rat vas deferens were studied by electron microscopy. Vesicular and tubular membranous structures containing an electron-opaque material were found in the smooth muscle cells. Similar structures were also found in a subfraction (F3) of microsomes of vas deferens smooth muscle which was shown to be rich in both plasma membrane and putative endoplasmic reticulum markers. Treatment of the tissues with calcium-free Krebs solution containing EGTA prior to fixation eliminated almost completely the presence of these dense-cored membranous structures (DMS), whereas incubation of the subcellular membrane fraction with EGTA solution had no effect on the appearance of the DMS. Plasma membrane infoldings were found in the smooth muscle cells extending well into their interior. Horseradish peroxidase penetrates vesicles in a location similar to that of DMS in smooth muscle cells, suggesting that some of the DMS may be connected to the extracellular space. We conclude that the dense-core material within the DMS is calcium dependent. We also suggest that some of the DMS represent infoldings of the plasma membrane extending into the cell's interior.

Animals↗
PubMed1984

Membrane fractionation of canine aortic smooth muscle: subcellular distribution of calcium transport activity.

Various subcellular membrane fractions were isolated from dog aortic smooth muscle by conventional differential centrifugation followed by isopycnic centrifugation on a sucrose density gradient. These subcellular fractions were characterized by membrane marker enzyme activities, morphological features and the electrophoretic patterns on a sodium dodecyl sulfate polyacrylamide gel. Our results showed that the microsomal membrane fraction isolated by differential centrifugation was very heterogeneous and contained substantial amount of plasma membranes which could be further enriched as a light density fraction on the sucrose density gradient. The subcellular distribution of Ca2+ binding in the absence of ATP and Ca2+ transport in the presence of ATP closely paralleled the distribution of plasma membrane markers. The ATP-supported Ca2+ transport was inhibited by several Ca2+ ionophores, enhanced by inorganic phosphate and oxalate ions and cosedimented toward higher density in a continuous source density gradient with plasma membrane marker enzyme activity in the presence of digitonin. Our present work strongly suggests that plasma membrane is the predominant component of microsomal fraction and responsible for most, if not all, of the azide-insensitive ATP-supported Ca2+ accumulation.

Adenosine Triphosphate↗
PubMed1984

Early structural changes in precapillary vessels in hypertension and their relationship to functional changes.

This presentation has reviewed evidence from our laboratory that both structural and functional changes participate in the initiation and maintenance of hypertension in spontaneously hypertensive rats (SHR). Structural changes are present in the muscular arteries of the mesenteric and renal vasculature at 3- to 5-week-old SHR as compared with WKY. The major structural change in SHR arteries was increased cross-section area with increased thickness of the media owing to hyperplasia of smooth muscle; lumen sizes were interchanged. Later, at 10-12, 21, and 28 weeks of age, there was further increase in medial thickness owing to hyperplasia, and some hypertrophy and changes in elastic arteries also became evident. Increases in medial thickness of elastic arteries included hypertrophy as well as hyperplasia. Changes in lumen diameter were never observed in arteries fixed in a relaxed state at physiological flow rates. In addition, a deficit in Ca handling (decreased ATP-dependent Ca2+ accumulation) was observed in plasma-membrane vesicles from mesenteric arteries of SHR prior to and after the development of hypertension. It persisted when hypertension was reversed by hydralazine in SHR. It was present in various forms of experimental hypertension. It was present whenever hypertension was present and disappeared with normalization of blood pressure by withdrawal of the stimulus. The Ca-handling deficit was found in several nonarterial tissues and may be a generalized genetic defect in SHR. It was always accompanied by increased alkaline phosphatase activity of plasma membranes, and this was suggested to reflect the smooth-muscle hyperplasia occurring simultaneously. A model of the initiation and maintenance of hypertension based on medial thickening and deficient Ca handling as primary, interacting causes of genetic hypertension is proposed.

Animals↗
PubMed1984

Smooth muscle cell herniation in the contracted arterial wall of spontaneously hypertensive and normotensive rats.

Structural changes of blood vessels from hypertensive animals during contraction were studied using light and transmission microscopy. In the arteries, maximally contracted with norepinephrine, vacuoles were found in the media of three categories of mesenteric arteries from two age groups (10-12, 28-30 weeks) of spontaneously hypertensive (SHR) and age-matched normotensive Wistar-Kyoto (WKY) rats. These vacuoles were related to contraction of the smooth muscle cells involving shape change, as they were absent in relaxed vessel walls, and also in muscles that underwent isometric contraction. In the SHR, the number of vacuoles/1,000 microns 2 of media was positively correlated with the degree of contraction of the vessels. Electron microscopic examination of these vacuoles showed that they were the result of herniation (or evagination) of smooth muscle cells into the intercellular space as well as into the neighbouring cells. When the number of herniae per unit cross-sectional area of the contracted media was used as the basis for comparison between SHR and WKY, we found no difference between the two strains of rats at 10-12 weeks of age. At 28-30 weeks, however, the number of herniae was significantly lower in the SHR as compared with age-matched WKY and younger SHR, suggesting that functional changes, that functional changes, probably related to the physical property of the plasma membrane in the smooth muscle cells, have taken place in older SHR.

Animals↗
PubMed1984

Nasal ciliary ultrastructure and function in patients with primary ciliary dyskinesia compared with that in normal subjects and in subjects with various respiratory diseases.

In an attempt to establish the relevance of ciliary ultrastructure to the pathophysiologic aspects of respiratory tract disease, we compared quantitatively the ultrastructure and function of cilia from healthy subjects (atopic and nonatopic nonsmokers, asymptomatic smokers) and patients with a variety of respiratory diseases (cystic fibrosis, chronic rhinitis, bronchiectasis associated with hypogammaglobulinemia, chronic bronchitis) with cilia from patients with primary ciliary dyskinesia (PCD). In healthy subjects and patients with non-PCD respiratory disease, approximately 5% of the cilia evaluated had ultrastructural abnormalities. Ciliary beat frequency was significantly higher in the chronic rhinitis group (15.3 +/- 1.2 Hz) than in the other non-PCD groups, which were within the normal range (12.5 +/- 1.7 Hz), and in all non-PCD cases ciliary wave form was normal. In each of these groups, normal mucociliary transport had been previously demonstrated. By contrast, in patients with PCD, the proportion of cilia with ultrastructural abnormalities was significantly greater than in the normal subjects and those with non-PCD respiratory disease (p less than 0.0001). In addition, beat frequency was significantly reduced, ciliary wave form was grossly abnormal, and pulmonary and nasal mucociliary transport were virtually absent. These findings demonstrate the relevance of ciliary ultrastructural abnormalities to altered ciliary function and lend support to the primary role of the demonstrated abnormalities in the respiratory tract disease of PCD.

Adolescent↗
PubMed1984

Ciliary defects associated with the development of bronchopulmonary dysplasia. Ciliary motility and ultrastructure.

We have on several occasions studied the nasal respiratory epithelium of an infant with hyaline membrane disease that evolved into bronchopulmonary dysplasia and observed an association between the clinical status and naso-ciliary motion and ultrastructure. At 4 months of age, when the patient had significant respiratory disease, few cilia were present and they beat with a slow dyskinetic motion. The specimens contained primarily necrotic and squamous epithelial membranes; the occasional cilia present had swollen or ruptured membranes. Partial recovery of the epithelium was noted at 4.5 months, with 45% of the cilia having normal ultrastructure. The beat frequency was 15.2 +/- 1.5 Hz (mean +/- SD), and although some degree of dyskinesia was evident, primarily normal ciliary motion was observed. By 10 months of age, significant clinical improvement had occurred and the nasal epithelium had regenerated; 96% of the cilia had normal ultrastructure, and the ciliary beat frequency (12.4 +/- 1.2 Hz) and motion were normal.

Bronchopulmonary Dysplasia↗