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Biomedical subjects

R E Lewis

Publications and source records attributed to R E Lewis.

At least 127 records · Page 7Linked to original sources
PubMed1983

Angiotensin II and bradykinin: interactions between two centrally active peptides.

Two neuropeptides, bradykinin (BK) and angiotensin II (ANG II), produce an increase in blood pressure when injected into the brain ventricles. This study is an example of central peptide-peptide interaction and was carried out to determine if BK and ANG II share a common mechanism in the brain to control blood pressure and drinking in rats. Prior injection of saralasin [10 micrograms intraventricularly (ivt)] was found to enhance the pressor response to ivt BK (5 micrograms) by 44%. The same dose of saralasin attenuated the pressor response to ivt ANG II (200 ng) by 55%. 50 ng ANG II and 5 micrograms BK given together ivt did not significantly alter blood pressure or urine conductance compared to 50 ng ANG II alone. Drinking to ivt infusions of ANG II (14 ng/min) was significantly attenuated when combined with BK (0.7 micrograms or 2.8 micrograms/min). Pretreatment with 10 micrograms indomethacin ivt diminished the pressor response to 5 micrograms ivt BK. Prostaglandin E2 (1.4 micrograms/min), but not prostaglandin A2, inhibited drinking to 14 ng/min ivt infusions of ANG II. The results suggest that ANG II and BK share an interrelationship with respect to their central actions: ANG II inhibits the BK pressor response and BK acts to inhibit drinking induced by ANG II. Prostaglandins of the E series may mediate these central actions of bradykinins.

Angiotensin II↗
PubMed1981

Development and resolution of radiographic lesions in canine heartworm disease.

Thoracic radiography of 7 Beagles was performed before heartworm infection, during a 1-year heartworm infection, and for 1 year following appropriate treatment. Cardiac and vascular lesions on thoracic radiographs were compared with angiographic changes. Within 3 months of obstructed blood flow in the caudal lobar arteries, associated increased focal parenchymal densities were detected. These lesions were regarded as characteristic of heartworm disease. Although the most severe arteriographic changes were in the caudal lobar arteries, lobar arterial changes on a lateral view were best detected in the right cranial lobar artery. These arteries increased in size during infection and decreased in size after treatment. It was concluded that the dorsoventral view is best for evaluation of the caudal lobar arteries. The most marked parenchymal lesions were detected during the first 6 months following adulticide treatment. These lesions and the other radiographic alterations then decreased in severity. Persistence of the parenchymal lesions were related to persistence of heartworm infection.

Animals↗
PubMed1980

Halothane-induced suppression of cell-mediated immunity in normal and tumor-bearing C3Hf/He mice.

The present investigation was designed to demonstrate whether depression of cell-mediated immunity in tumor-bearing hosts is potentiated by halothane anesthesia. Both the in vivo and in vitro effects of halothane anesthesia on splenic lymphocytes from normal and tumor-bearing C3Hf/He mice were examined by lymphocyte transformation. The stimulation index (SI) of lymphocytes from normal C3Hf/He mice exposed to 1.5% halothane/98.5% oxygen anesthesia was significantly less than that of lymphocytes from normal C23Hf/He mice exposed to oxygen (SI of 25.3 and 33.6, respectively) (p < 0.001). Lymphocytes from tumor-bearing C3Hf/He mice demonstrated the greatest degree of immunosuppression by halothane when compared to those of normal (non-tumor-bearing) mice. That the tumor was the principal immunosuppressive factor was demonstraed by the SI of 34.6 for the non-tumor-bearing mouse lymphocytes and 4.1 for those of the mice with fibrosarcomas (p < 0.001). Lymphocytes from tumor-bearing hosts exposed to 1.5% halothane anesthesia demonstrated diminished lymphocyte transformation compared with those from control (tumor-bearing) mice exposed to oxygen (SI of 1.7 and 4.4, respectively) (p < 0.001). In both tumor-bearing and normal mice, there was a significant suppression of the cell-mediated immune response when the animals were exposed to halothane compared to exposure to oxygen. Results of this investigation demonstrate that halothane anesthesia potentiates the suppression of cell-mediated immunity observed in tumor-bearing hosts.

Animals↗
PubMed1980

Radiographic changes associated with developing dirofilariasis in experimentally infected dogs.

Experimental heartworm infection was established in ten dogs. Five had mild infections (8 to 21 worms) and five had severe infections (41 to 96 worms). After larval inoculation, dogs were radiographed each month for 1 year to evaluate cardiopulmonary changes occurring as the heartworm disease developed. Changes seen radiographically during the first year of heartworm infection were related to the magnitude of the worm burden. In mild infections, changes mainly involved the terminal portion of the right caudal lobar pulmonary artery and were minimal. In severe infections, changes mainly involved the entirety of the right caudal lobar pulmonary artery. In some dogs, an increase in size of the right cranial lobar pulmonary artery was seen. Gross changes in the size of the right ventricle and main pulmonary artery did not frequently occur during the first year.

Animals↗
PubMed1980

Canine excretory urogram: correlation with base-line measurements.

Ten healthy, adult mongrel dogs were each given various dose levels of sodium iothalamate IV, and postinjection radiographs were made. Base-line plasma and urine osmolality, glomerular filtration rate, packed cell volume, plasma protein concentration, serum urea nitrogen concentration, serum creatinine concentration, and urine specific gravity were measured. The base-line values and the dose of contrast medium were compared statistically with linear and density measurements made from the post-injection radiographs. Base-line plasma osmolality was directly related to the pyelographic and nephrographic density. The dose of contrast medium directly influenced the kidney length, the kidney, pelvic, diverticular, and ureteral widths, and the renal and diverticular densities despite variations in base-line values within accepted limits.

Animals↗
PubMed1980

Intimal lesions of the pulmonary artery in dogs with experimental dirofilariasis.

Microscopic examination, particularly by scanning electron microscopy, of the tunica intima of the pulmonary arteries of dogs experimentally infected with a known number of larvae of Dirofilaria immitis revealed various numbers and shapes of intimal thickenings. The number and morphology of these thickenings were related to the degree of infection. At 11 months after infection, dogs having adult worm populations of 8 to 21 worms had scattered discrete intimal lesions, whereas in dogs with 41 to 68 adult worms, the intima was diffusely affected. Discrete lesions took the form of rugous or verrucous protrusions, and in severely affected animals, the intima was extensively covered with anatomosing ridges. Light microscopy and transmission electron microscopy confirmed earlier reports that the thickenings were mainly confined to the tunica intima, that the surface was covered by endothelium, and that many of the cells in the intimal swellings were derived from smooth muscle.

Animals↗
PubMed1979

Effects of thyroid deficiency and sympathectomy on cardiac enzymes.

The effects of thyroid deficiency (Td) and of chemical sympathectomy (Sx) were studied on marker enzymes of energy metabolism in cardiac muscle of neonatal and of adult rats. Td prevented the normal development of neonatal body weight, relative heart mass, and cardiac levels of cytochrome c (-22%), citrate synthase (-27%), phosphofructokinase (-20%) and Mg2+- and Ca2+-ATPase activity of purified myofibrils (-33%, -44%). Exogenous thyroxin replacement restored those parameters studied to normal with the exception that it persistently elevated citrate synthase activity significantly above normal control levels. Responses similar to those of Td neonates occurred when adult rats were similarly treated. Sx produced no consistent effects on respiratory and glycogenolytic marker enzymes, but caused a 20% reduction in Ca2+-ATPase activity of both neonatal and adult cardiac myofibrils. These findings suggest that cardiac muscle cells require thyroxin for normal growth and enzyme development. Also, Sx may impair cardiac functional capacity by altering Ca2+ activity of actomyosin ATPase.

Animals↗
PubMed1979

Scintigraphic evaluation of pulmonary perfusion in dogs experimentally infected with Dirofilaria immitis.

Pulmonary arterial perfusion was evaluated by perfusion lung scans in ten dogs experimentally infected with heartworm. After larval inoculation, scans were done once a month for 11 months. In 8 of 10 dogs, pulmonary arterial perfusion deficits were detected. The perfusion deficits involved the left cranial, right cranial, and right caudal lung lobes. Generally, there was a poor correlation between vascular abnormalities detected on the survey thoracic radiographs and the perfusion deficits detected by lung scanning. The perfusion deficits did not produce clinical signs or pulmonary infarction.

Animals↗
PubMed1979

Normal canine excretory urogram: effects of dose, time, and individual dog variation.

Ten healthy, young, adult mongrel dogs were given sodium iothalamate at dose levels of 200, 400, and 800 mg of iodine/0.45 kg of body weight on separate occasions by rapid IV injection; urinary bladders of the dogs were empty before injections were begun. Seven of the ten dogs were given an additional dose of sodium iothalamate (400 mg of iodine/0.45 kg) with the bladder partially distended with sterilized saline solution. Ventrodorsal abdominal radiographs were obtained immediately and at 5, 10, 20, 40, 60, and 120 minutes after injection of contrast medium. The kidneys, renal pelves, pelvic diverticula, and ureters were evaluated for radiographic density (radiopacity). The lengths and widths of the kidneys, pelves, and diverticula and the width of the ureters were determined, and those measurements were standardized by dividing the values by the corresponding length of the second lumbar vertebral body. From these evaluations, it was determined that postinjection radiographs should be obtained immediately and at 5, 20, and 40 minutes. The optimal dose of contrast medium was 400 mg of iodine/0.45 kg of body weight. It was also determined that the dose of contrast medium, as well as the time of postinjection radiography, significantly influenced many of the measurements (both linear and density) in the excretory urogram of normal dogs. Values for the measurements of the urinary structures based on the results of the present study are also presented.

Animals↗
PubMed1978

The topography of the exoskeleton of Cediopsylla simplex (Baker 1895) (Siphonaptera: Pulicidae). I. The head and its appendages.

A topography of the exoskeleton of the head of Cediopsylla simplex (Baker 1895) is presented, based on an examination with the scanning electron microscope. Major sensory regions were observed on the fronto-occipital region, on the antennae, and on the maxillary palps. Sensilla basiconica were observed in all 3 regions, chemosensory hairs are absent, and unique pit sensilla were observed in the clubs of the antennae. The mouthparts are described and illustrated in detail. Other cuticular structures are illustrated, such as hairs, bristles, combs, cuticular teeth, and microtrichia. Sexual dimorphism is evident in the distribution of sensilla basiconica in the fronto-occipital regional and the clubs of the antennae. The validity of the generic name Cediopsylla Jordan 1925 is questioned.

Animals↗