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Biomedical subjects

C H Lamar

Publications and source records attributed to C H Lamar.

30 records · Page 2Linked to original sources
PubMed1984

Abnormal response of tumor vasculature to vasoactive drugs.

The effects of the vasoconstrictor phenylephrine and the vasodilator hydralazine on blood flow to tumor were studied and compared to those on blood flow to normal tissues in vivo. Regional blood flow and cardiac output were measured with the use of radioactive microspheres in 150- to 250-g inbred Harlan F344 rats bearing subcutaneous nodules of two types of transplantable carcinoma ("hard" and "soft") with microscopically different vascular patterns. Three groups of rats were treated with hydralazine, saline, or phenylephrine, and regional blood flow was determined at the time of maximum blood pressure response. Results were correlated with quantitative morphometric analysis of arteriolar and capillary wall thickness in tumor and normal tissue. Phenylephrine decreased and hydralazine increased normal tissue perfusion as indicated by cardiac output. Tumor blood flow remained low and was not significantly influenced by drug treatment, except for the phenylephrine effect on hard tumors. Histologic study of tumor vessel walls revealed an absence of smooth muscle capable of responding to the vasoactive drugs by constriction or dilation. Evidently, by their selective action on normal vessels, vasoactive drugs can change the ratio of tumor:normal tissue perfusion. In particular, the increase of normal tissue: tumor blood flow by vasodilator drugs may enhance the selectivity of local heat therapy.

Animals↗
PubMed1984

Motility of the distal portion of the jejunum and pelvic flexure in ponies: effects of six drugs.

Bipolar stainless steel electrodes were surgically implanted in 4 ponies to record myoelectrical and mechanical activity of the distal portion of the jejunum and pelvic flexure. After determining normal activity, the effects of neostigmine, xylazine, flunixin meglumine, dipyrone, panthenol, and atropine sulfate were determined. Flunixin meglumine, dipyrone, and panthenol had no effect on the motility of the jejunum or pelvic flexure. Xylazine and atropine sulfate decreased motility of the distal portion of the jejunum and pelvic flexure, with atropine sulfate having a greater effect and lasting longer. Neostigmine stimulated propulsive motility in the pelvic flexure only.

Animals↗
PubMed1984

Impedance monitoring of equine intestinal motility.

Myoelectrical and myomechanical activities of the distal portion of the jejunum and pelvic flexure were studied in 7 ponies, using permanently implanted monopolar and bipolar stainless steel electrodes. Dental acrylic embedded recording electrodes were surgically sutured to the serosal surface of the distal portion of the jejunum and pelvic flexure. Myoelectrically, regular spike bursts and irregular spike bursts were observed in the jejunum. Short spike bursts and long spike bursts were recorded and associated with spike potentials, using impedance recording techniques. Electrical and mechanical data could be monitored simultaneously from the same recording electrode, using separate channels on a physiograph. This method proved effective to monitor periodically myomechanical activity at the same time that myoelectrical activity was being evaluated. The recording system required fewer recording devices to be attached to the intestinal tract, was an inexpensive method of obtaining myomechanical recordings, and did not alter markedly the myoelectrical activity when mechanical activity was being monitored.

Action Potentials↗
PubMed1980

Ultrastructure of timed isolates of in vitro canine articular chondrocytes.

Articular chondrocytes were enzymatically isolated from the distal end of the adult canine femur. The digestion procedure was conducted for 2- or 6-hour intervals, using 0.25% trypsin and 0.25% collagenase. Cells grown from the 2-hour digestion procedure were polygonal to stellate, had large vesicular nuclei with prominent nucleoli, and exhibited contact inhibition at confluency. Cells grown in cultures from the 6-hour digestion procedure were fusiform, had prominent nuclei with numerous nucleoli, and lacked contact inhibition. Cell cultures established, using cells from both procedures, were examined using the transmission electron microscope. Ultrastructurally, an extensive granular endoplasmic reticulum, prominent golgi complexes, and numerous autophagic vacuoles characterized the 2-hour cell population. The fine structures of the cells grown from the 6-hour process were characterized by numerous cytoplasmic microfilaments randomly dispersed and marginated beneath the plasmalemma of the cells. An extensive dilated rough-endoplasmic reticular system was present. The chondrocytes described in the present study provided morphologic evidence of a heterogeneous cell population in adult canine articular cartilage.

Animals↗
PubMed1980

The fine structure of lipofuscin in the mouse hippocampus.

Lipofuscin was ultrastructurally evaluated in the hippocampus of C57B1/6 male mice at 8, 14, 20 and 24 months of age. The mice were anesthetized, perfused intracardially with 3% glutaraldhyde, and routinely processed for transmission electron microscopic evaluation. Lipofuscin was found in the hippocampus of mice of all age groups. Granules were small and randomly dispersed in the younger animals with clustered complexes being present in the older ones. Lipofuscin was present in neurons, neuroglia, and endothelial cells. Pigment granules in the older mice were observed adjacent to capillaries, were found in vacuolating cytoplasmic structures of pericytes but were not associated with microtubules. This morphological evidence supports the normal removal of lipofuscin from the central nervous system by phagocytosis and enzymatic digestion.

Age Factors↗
PubMed1978

Cadmium induced endothelial cell alterations in the fetal brain from prenatal exposure.

Pregnant rats received a single administration of 0.5, 1.0, or 2.0 mg/kg of cadmium on day 18 or 20 or gestation. Maternal animals were killed on day 21 and samples of the caudate nucleus from fetal brains were examined using the transmission electron microscope. A 2.0 mg/kg dose of cadmium administered to maternal rats on day 20 of gestation caused the formation of vacuoles in the endothelial cells of capillaries in the fetal brain. Significant endothelial cell vacuolization was not observed in the brain of fetuses from other treatment groups. The vacuoles occurred singly, were spherical in shape, were located adjacent to the intercellular junctions and caused focal distortion of the endothelial cell. Vacuoles were the only ultrastructural alteration observed in the caudate nucleus of fetal brains.

Animals↗
PubMed1976

Alterations in the hippocampus of aged mice.

The hippocampus of C57B1/6 mice was examined histologically and electron microscopically. Male and female mice at 3 and 8 months of age and female mice at 16 months of age were studied. PAS positive foci, containing particles 1-2 mu in diameter, were observed in the hippocampal region of 8 and 16 month old mice. These particles were diastase sensitive. Electron microscopically, in similar mice, a vacuolating change was observed in the cytoplasm of perithelial cells (pericytes) in the same area.

Aging↗
PubMed1975

Evaluation of chromatin clumping and myelination of the spinal cord of pigs with congential tremor.

Clumps of chromatin in the spinal cord of 2- to 10-day-old pigs with congenital tremor were of no diagnostic value since they were present also in unaffected pigs of the same age. No difference in shape, size, number, location, and staining characteristics of the clumps were found. The clumps were thought to be evidence of cellular necrobiosis. The cords of pigs with tremor had distinctly less myelin than those of normal pigs.

Animals↗
PubMedDate not supplied

Effect of betamethasone and exercise on equine carpal joints with osteochondral fragments.

Osteochondral fragments were created arthroscopically on the distal aspect of both radial carpal bones in 12 horses. On day 14 after surgery, one middle carpal joint of each horse was injected with 2.5 mL Betavet Soluspan (3.9 mg betamethasone sodium phosphate and 12 mg betamethasone acetate per milliliter) and the contralateral joint was injected with 2.5 mL saline as a control. Intra-articular treatments were repeated on day 35. On day 17, six horses began exercising 5 days per week on a high-speed treadmill. The other six horses were kept in box stalls throughout the study as nonexercised controls. On day 56, all horses were examined clinically and radiographically and then were euthanatized. Samples were obtained for histological, histochemical, and biochemical evaluation. Mild lameness was observed in five of the six exercised horses at day 56; four horses were lame in the control limb and one horse was lame in the treated limb. Of the five nonexercised horses evaluated for lameness, two were lame in the control limb, two were lame in the treated limb, and one was lame in both the control and the treated limb. No differences were noted on radiographs or palpation of steroid treated limbs versus control limbs. Firm reattachment of the osteochondral fragment to the radial carpal bone occurred in all but three joints. Gross cartilage damage was not different between steroid-treated joints and joints injected with saline. Histologically, there were no significant detrimental effects of beta-methasone with or without exercise, but there was a tendency for more pathological change in treated joints. No significant difference in the water content or uronic acid concentration was detected between treated and control joints. Intra-articular betamethasone administration in this carpal chip model was not associated with any significant detrimental effects in either rested or exercised horses.

Animals↗