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Biomedical subjects

R M Lewis

Publications and source records attributed to R M Lewis.

At least 145 records · Page 8Linked to original sources
PubMed1984

Spontaneous mesangiocapillary glomerulonephritis in Finn cross lambs from Alberta.

A spontaneous mesangiocapillary glomerulonephritis occurred in three, one to three month old Finnish Landrace cross lambs from a flock in northern Alberta. The ram was a purebred Finn sheep, and the ewes were Finn-Rambouillet and Finn-Suffolk-Rambouillet crosses. The lambs were found dead without previous clinical signs. Histologically there was marked thickening of glomerular capillary basement membranes, proliferation of mesangial cells, and peri-glomerular fibrosis. An interstitial infiltration of plasma cells and lymphocytes was present with occasional tubular degeneration and proteinaceous cast formation. Focal leukoencephalomalacia was present in one lamb. Electron microscopy demonstrated deposition of electron-dense deposits in a subendothelial location with occasional fusion of overlying foot processes in glomerular capillaries. Indirect immunofluorescence studies demonstrated positive staining material in glomerular capillary walls. These findings in Finnish Landrace cross lambs are characteristic of mesangiocapillary glomerulonephritis, a condition heretofore not reported in North America.

Animals↗
PubMed1984

Pitfalls in immunofluorescence testing in dermatology. III. Pemphigus-like antibodies in the horse and direct immunofluorescence testing in equine dermatophilosis.

Indirect immunofluorescence testing for pemphigus-like antibodies was performed on 79 horses: 28 horses with various nonpemphigus dermatologic diseases, 21 horses with various nondermatologic diseases, and 30 normal horses. Pemphigus-like antibodies were detected in 6 horses: 3 normal horses with titers of 1:40, 2 horses with dermatophilosis at titers of 1:10 and 1:80, and 1 horse with lymphosarcoma at a titer of 1:320. It was concluded that equine pemphigus-like antibodies are a potential source of misinterpretation and misdiagnosis in indirect immunofluorescence testing. Direct immunofluorescence testing for whole immunoglobulin, IgG, IgM, and IgA was performed on skin lesions from 2 horses with dermatophilosis. Diffuse intercellular deposition of whole immunoglobulin and IgG was found in both horses. It was concluded that equine dermatophilosis is a potential source of misinterpretation and misdiagnosis in direct immunofluorescence testing.

Actinomycetales Infections↗
PubMed1984

Hematologic and coagulation abnormalities in acute bovine sarcocystosis.

Calves inoculated with Sarcocystis cruzi sporocysts developed severe anemia 4 weeks later. The anemic crisis was paralleled by a hyperbilirubinemia, with up to 88% of the increased total bilirubin attributed to indirect reacting bilirubin. The anemia was characterized as normocytic and normochromic. In a few instances, according to Coombs's tests (antiglobulin test) and erythrocyte eluates from infected calves, immunoglobulin G was associated with the RBC membrane. In the histopathologic examinations of tissues from calves dying during the anemic crisis, there was deposition of iron in the splenic red pulp. The hematologic studies supported the claim that the anemia in acute bovine sarcocystosis is an extravascular hemolytic event, probably with an immunologic basis. In the coagulation studies, consumption coagulopathy consistent with disseminated intravascular coagulation was seen to occur during acute sarcocystosis. At 4 weeks after inoculations were done, there were prolongations of activated partial thromboplastin and 1-stage prothrombin times and decreased functional fibrinogen concentration, and thrombocytopenia, although increase of fibrinogen-fibrin degradation products were not demonstrable. These findings indicate that endothelial parasitism by schizonts of S cruzi may cause endothelial damage, resulting in coagulation abnormalities that include disseminated intravascular coagulation.

Acute Disease↗
PubMed1984

Renal ischemic injury in the dog: characterization and effect of various pharmacologic agents.

Renal ischemia has been implicated as a major factor in the pathogenesis of acute renal failure. Despite several differences between the intrarenal norepinephrine infusion and renal artery occlusion models, they have been assumed to be prototypic models of ischemic renal injury. In our previous studies, an intrarenal infusion of norepinephrine caused a marked reduction in inulin clearance 3 hours after infusion. This reduction could be significantly attenuated by the concurrent infusion of mannitol, furosemide, or bradykinin. The effects of these three protective agents were evaluated before and after variable durations of renal artery occlusion to establish the similarities between the models and the magnitude of versatility of these protective agents. In the renal artery occlusion model, capsular fascia was stripped to eliminate collateral flow and ensure maximal renal ischemia. Three hours after 120 minutes of renal artery occlusion (n = 7), inulin clearance returned to 5.7% +/- 2.2% (SEM) of the control values and was not statistically different from that observed in the norepinephrine model. Intrarenal infusion of mannitol, furosemide, or bradykinin prior to and during the occlusion period, however, had no protective effect. Shorter durations of renal artery occlusion were evaluated to ensure an equivalent or decreased severity of acute renal failure compared with the norepinephrine model. After 90 or 60 minutes of renal artery occlusion, the clearance of inulin returned to 10.9% +/- 3.3% (n = 8) and 31.1% +/- 8.2% (n = 4) of control values, respectively. An intrarenal infusion of mannitol, furosemide, or bradykinin still had no significant protective effect, despite the decreased insult in the 60-minute renal artery occlusion studies. In summary, these findings demonstrate fundamental differences between renal artery occlusion and the norepinephrine model of renal functional impairment, and they suggest that the insult associated with norepinephrine infusion may involve factors other than cessation of blood flow.

Acute Kidney Injury↗
PubMed1984

A gamma camera for medical applications, using a multiwire proportional counter.

A multiwire proportional counter gamma camera, specifically designed for nuclear medicine applications, is portable and weighs less than 50 lb including shielding and collimator. The basic operating characteristics have been investigated with various radioactive sealed sources. The camera demonstrates a peak count rate of 850,000 cps, an intrinsic spatial resolution of 2.5 mm, and excellent image uniformity when used with x-ray sources in the range of 22-81 keV. Tests of the device with Ta-178--a very promising, short half-life (9.3 min), low-energy radionuclide--using 20 mCi injections provided images of quality comparable to those obtained from 15 mCi Tc-99m studies with conventional imaging devices. The camera used with Ta-178 offers particular promise in first-pass nuclear cardiology studies. Considerably improved study quality will likely result in this area because of the increased injectable dose levels offered by Ta-178 combined with the high-count rate capability and improved resolution.

Americium↗
PubMed1984

Characterization of spontaneous amyloidosis of Syrian hamsters using the potassium permanganate method.

Amyloid from 16 Syrian hamsters with spontaneous age-related systemic amyloidosis retained affinity for Congo red dye after treatment with potassium permanganate. Serum electrophoresis showed a slight rise in gamma globulins without a monoclonal spike. Bence-Jones proteins were not present in the urine. There was no histological evidence of plasmacytosis. Amyloidosis could not be associated with chronic inflammation. The lack of apparent etiology of this amyloid and its resistance to potassium permanganate treatment suggests that it is a primary non-AA amyloid. This finding varies with a report suggesting that the spontaneous amyloidosis of aged Syrian hamsters is associated with the AA fibril.

Amyloid↗
PubMed1983

Nucleoside-specific suppression in MRL/MP +/+ mice.

The induction of nucleoside-specific nonresponsiveness was further studied in the autoimmune strain MRL/MP +/+ (MRL/n). Experiments were undertaken to determine (i) whether nucleoside-conjugated spleen cells are able to induce specific nonresponsiveness to T-dependent nucleoside antigens in MRL/n mice, and (ii) whether periodic treatment with nucleoside-conjugated spleen cells would retard the development of spontaneous anti-DNA antibodies and associated indicators of autoimmunity. The results show that nonresponsiveness to nucleoside antigens is inducable in male, but not in female, MRL/n mice. Nonresponsiveness in male MRL/n was transferable and mediated by T cells. Treatment of male MRL/n mice with nucleoside-conjugated spleen cells (NSC) appeared to attenuate the progress of autoimmune symptoms in experimental animals. These results are discussed in the context of recent studies exploring the etiology of autoantibody production and the loss of self-tolerance in murine models of autoimmunity.

Animals↗
PubMed1983

Chronic epicardial His bundle recordings in awake nonsedated dogs: a new method.

Recording cardiac electrical potentials from the region of the bundle of His in the awake, nonsedated animal would allow a more physiologic evaluation of impulse transmission through the specialized atrioventricular conduction system than anesthetized preparations. We present a new technique to localize and record chronic His bundle potentials using standard electronic equipment which obviates the need for intravascular catheters or an atriotomy. Six mature and four immature mongrel dogs underwent a midline thoracotomy. The bundle of His electrogram was recorded from the right atrial epicardium alongside the noncoronary aortic cusp. A flexible tripolar electrode probe with 3 mm interelectrode distance attached to a standard electronic recorder was used to localize the area of greatest His bundle impulse. Silver solder electrodes were sutured to the designated area and the wires were externalized to the back. Electrophysiological measurements were made 1 to 20 weeks later to confirm the accuracy and stability of the His bundle electrogram. These recordings were comparable to the standard internal catheter measurements both before and during atrioventricular impulse interference caused by atrial pacing or pharmacologic intervention. Electrodes sutured to the designated area do not interfere with impulse conduction and allow stable His bundle recordings in all activity ranges in the chronic animal.

Action Potentials↗
PubMed1983

The effect of ingestion of meat on hepatic extraction of insulin and glucagon and hepatic glucose output in conscious dogs.

The effect of ingestion of protein on hepatic extraction of insulin and glucagon and hepatic glucose output were investigated in conscious dogs. The ingestion of meat stimulated both insulin and glucagon secretion but the glucagon response was much more rapid and greater than that of insulin. Secretion of glucagon demonstrated a biphasic pattern while insulin release was monophasic. The fractional hepatic extraction of glucagon increased gradually from the basal value of 15 +/- 3% to a peak of 36 +/- 5% at 90 min, and that of insulin increased from the basal level of 41 +/- 2% to 54 +/- 4% at 45 and 60 min. The increased hepatic extraction of glucagon and insulin after meat ingestion may be explained by neural or hormonal signals from the gut. The blood glucose and hepatic glucose output did not increase significantly despite the significant decrease of the portal vein insulin to glucagon molar ratio as well as the significant decrease of the molar ratio of the hepatic uptake of these hormones. The absence of greater hepatic glucose production despite the augmented glucagon secretion and decreased portal vein insulin to glucagon molar ratio could reflect down regulation by glucagon.

Animals↗
PubMed1983

Chlordiazepoxide increases the force of two topographically distinct operant responses in rats.

By using operant conditioning techniques one group of 8 rats was trained to reach through a hole in the wall of an operant chamber, and to exert downward responses on a force-sensing circular disk. Eight other rats learned to reach through the hole and grasp and pull toward them a wire bail attached to a force transducer. Both behaviors were maintained on a fixed ratio 20 schedule of water reinforcement. The effects of chlordiazepoxide (CDP, 2.5, 5.0, 10.0 mg/kg) on response force and rate were assessed for both groups. CDP significantly increased response force in a dose-related manner in both groups; regardless of topography, response rate was little affected by the 2.5- and 5.0 mg/kg doses but was decreased by the highest dose. Results were discussed in terms of CDP's antipunishment and neuromuscular effects.

Animals↗
PubMed1983

Absence of hepatic extraction of pancreatic polypeptide in conscious dogs.

In 15 conscious dogs basal portal vein pancreatic polypeptide (PP) (306 +/- 8 pg/ml) exceeded both hepatic vein PP (255 +/- 8 pg/ml) and arterial PP (244 +/- 9 pg/ml) and increased rapidly 10 min after oral glucose administration. In contrast to oral glucose, intraportal glucose infusion decreased PP levels from 45 min until the end of the infusion. Meat ingestion rapidly and promptly increased PP. During the basal state, hepatic extraction of total immunoreactive PP was 10 +/- 4%, not significantly different from zero, of the 150 +/- 14 ng/min presented to the liver. Fractional hepatic extraction of PP did not change after oral glucose, meat ingestion, or intraportal glucose infusion. Chromatographic analysis showed at least four different components of immunoreactive PP. The first peak eluted with the void volume, the second peak between the void volume and authentic PP, and the third peak coincided with authentic PP. When present, the fourth peak eluted after authentic PP. More than half of the immunoreactive PP in the basal state eluted with authentic PP, whereas about one-third was found in the second peak. The marked alterations in PP after meat, oral glucose, or intraportal glucose and atropine reflected primarily changes in the third peak. The fractional hepatic extraction of all the components was very similar.

Animals↗
PubMed1983

Sodium-calcium exchange in dog heart mitochondria: effects of ischemia and verapamil.

Na+ - Ca2+ exchange was studied in two preparations of dog heart mitochondria isolated from normal and ischemic muscle following occlusion of the circumflex (CFX) coronary artery with or without prior verapamil infusion. Na+ - Ca2+ exchange in mitochondria isolated using polytron homogenization showed sigmoidal kinetics with phosphate, whereas mitochondria isolated using gentle nagarse treatment showed hyperbolic kinetics and a Vmax 60% greater than the polytron preparation. Nagarse did not alter the sigmoidal kinetics or exchange velocities of the polytron mitochondria observed with phosphate. With acetate, both preparations exhibited hyperbolic kinetics, and the sodium required for half-maximum activity was increased. Verapamil inhibited Na+ - Ca2+ exchange in both preparations with phosphate, but not with acetate. Thirty or sixty minutes of acute ischemia following CFX occlusion produced significant epicardial surface S-T elevation in the ischemic area and a decrease in myocardial segment shortening. Na+ - Ca2+ exchange of both ischemic preparations was depressed, and the kinetics of the polytron preparation changed to hyperbolic. Pretreatment of the experimental animals with verapamil (0.3 mg/kg) before 60 min of ischemia protected the exchange rates in both preparations, and the sigmoidicity of the polytron mitochondria was retained.

Animals↗