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Biomedical subjects

R L Bowman

Publications and source records attributed to R L Bowman.

At least 19 recordsLinked to original sources
PubMed1992

Intra-blood-brain barrier synthesis of IgG: comparison of IgG synthesis formulas in a computer model and in 1,629 consecutive specimens.

We evaluated four formulas for estimating the intra-blood-brain barrier (IBBB) synthesis of IgG in a computer model of two types of BBB damage and in 1,629 consecutively received pairs of CSF and serum. These four formulas were the IgG synthesis rate (SR), IgG(loc) (ie, local), IgG index, and IgG extended index. Results from the 1,629 specimens and the computer model of type 2 BBB damage (partial or total loss of selective filtration) accurately predicted problems encountered with the IgG SR in clinical practice. In both the model and with the results from the 1,629 specimens, the combination of the IgG(loc) and IgG index formulas minimized the possibility of false-positive and false-negative results and yielded the most reliable results for IBBB synthesis of IgG in the presence or absence of increased permeability of the BBB. Additional studies with detailed clinical correlations will allow an accurate assessment of how effectively this combination of formulas can help to rule in or out the diagnosis of a particular disease or inflammatory condition of the CNS.

Albumins↗
PubMed1991

Multicentric papillary-cystic neoplasm of the pancreas.

Two distinct papillary-cystic neoplasms were found in the pancreas of a young black woman. She presented to the hospital in her first trimester of pregnancy with the chief complaint of sharp right upper quadrant abdominal pain that radiated to the right shoulder. This was associated with jaundice, vomiting, and pruritus. On examination, a large, nontender, midepigastric abdominal mass was palpated. Serum liver enzyme levels were moderately to markedly elevated. An abdominal computed tomographic scan revealed a 9-cm solid and cystic mass located within the head of the pancreas with associated marked bile duct dilatation. A total pancreatectomy was performed. Gross examination of the specimen revealed two separate well-circumscribed tumors of unequal size. The larger one was found within the head of the pancreas and contained multiple hemorrhagic, cystic cavities. The smaller one, located within the tail, consisted primarily of solid tissue. Microscopic examination of both lesions revealed papillary-cystic neoplasms. To our knowledge, this is the first report of two synchronous papillary-cystic tumors of the pancreas and the first reported demonstration of the potential of this tumor for multicentricity.

Adult↗
PubMed1979

Renal tubular transport of gentamicin in the rat.

The renal handling of gentamicin in the rat was examined by clearance, microinjection, and renal cortical-slice techniques. The steady-state renal clearance of 14C-gentamicin, when corrected for the 7.5% binding to plasma protein, was not significantly different from that of 3H-inulin. At the end of the renal clearance experiments, the cortical concentration of gentamicin was 93 +/- 7 microgram/g of tissue (N = 7), a concentration threefold greater than that of the medulla and 20-fold greater than that of serum. Absorption of 3H-gentamicin along the proximal convoluted tubule and loop of Henle was demonstrated by the tubular microinjection technique. No reabsorption of 3H-gentamicin was detected beyond the early distal convoluted tubule. The tubular absorption of 3H-gentamicin was load dependent. Fractional absorption of 3H-gentamicin averaged 30.1 +/- 2.7% when the dose of 3H-gentamicin injected into early proximal tubular convolutions averaged 132 +/- 17 pg. It was decreased to 13.6 +/- 2.6% when the microinjected dose of gentamicin was increased to 1996 +/- 388 pg. No evidence of transtubular absorption of 3H-gentamicin was detected during the microinjection experiments. Microperfusion of pertubular capillaries failed to demonstrate urinary precession of 3H-gentamicin over 14C-inulin, a finding which argues against a rapid transtubular secretory flux of gentamicin. Significant uptake of gentamicin was demonstrated by renal cortical slices incubated in medium containing 14C-gentamicin. The accumulation of 14C-gentamicin by renal cortical slices was not inhibited by probenecid or N1-methylnicotinamide but was inhibited by netilmicin and tobramycin. These data support the conclusion that the renal accumulation of gentamicin reflects transport of gentamicin across both the apical and basolateral membranes of proximal tubular epithelium.

Animals↗
PubMed1979

The microscopic characterization of multinucleated giant cells formed on polymeric surfaces perfused with blood.

Multinucleated, foreign body giant cells were formed by the fusion of blood monocytes on polymeric membranes perfused with blood during extended extracorporeal circulation. In the current study, heparinized blood, flowing in an arteriovenous shunt in a sheep, perfused polycarbonate, polypropylene and silicone rubber membranes of a recently developed bioartificial tissue culture system. The multinucleated giant cells were studied by light, scanning electron, and transmission electron microscopy, after membrane perfusion for periods of one to two weeks. The giant cells, which were the predominant cellular components of the blood-polymer interface layer, contained from a few to more that one hundred nuclei and varied in diameter up to 400 microns. The cellular interaction with the three membrane types was similar, although fewer mononuclear cells were observed adhering to the silicone rubber membrane. The presence or absence of micropores in the membranes had no effect on the formation of giant cells, nor did the presence of foreign tissue in culture behind the microporous membranes. High blood flow rates and chronic anticoagulation with heparin permitted observation of this foreign body reaction of blood independent of thrombosis.

Animals↗
PubMed1978

A rapidly polymerizing polyurethane for transcatheter embolization.

A polyurethane prepolymer was evaluated as a transcatheter embolizing agent. Low viscosity permits injection through small catheters. Polymerization is initated on contact with blood and completed within 10 seconds. Downstream propagation is better then that of cyanoacrylate and comparable to that of silicone rubber. No systemic toxicity was observed in acute animal experiments. However, dissolution of arterial walls and extravasation out of the vascular bed of chronically embolized organs suggest significant local tissue toxicity and make further evaluation necessary before clinical testing.

Abscess↗
PubMed1978

Evidence that the brain participates in the humoral natriuretic mechanism of blood volume expansion in the dog.

We examined the role of the central nervous system in the activation of the humoral natriuretic mechanism elicited by blood volume expansion. Studies were performed in anesthetized dogs pretreated with deoxycorticosterone acetate (15 mg/day) and sodium chloride for 12 days. An isolated dog kidney perfused with blood from the femoral artery of the volume expanded dog served as the bioassay system for the humoral natriuretic factor. In group I volume expansion of intact dogs (n = 14) with equilibrated blood promoted an increase in fractional sodium excretion (FE(Na)) from a control level of 2.6+/-0.5 to 13.6+/-1.6%, P <0.001. In the isolated kidney FE(Na) increased from 3.6+/-0.8 to 6.8+/-1.1%, P <0.01. The natriuresis from the isolated kidney occurred in the absence of significant changes in renal arterial pressure, glomerular filtration rate, plasma protein concentration, or packed cell volume, whereas renal blood flow decreased slightly. In group II (n = 20) the dogs were decapitated by means of a specially designed neck vise. In 10 dogs blood pressure was supported by a constant infusion of dopamine (3.8+/-0.7 mug/min per kg body weight). Despite the fact that in response to the same volume stimulus, decapitated dogs manifested an increase in blood volume and cardiac output similar in magnitude to that of intact dogs whereas the rise in mean arterial pressure of decapitated dogs exceeded that of intact dogs, the natriuretic response of decapitated dogs was significantly less than that of intact dogs. FE(Na) in decapitated dogs increased 4.7+/-1.1 compared to 11.1+/-1.4% in intact dogs (p <0.01). Furthermore, volume expansion of decapitated dogs failed to elicit a natriuretic response from the isolated kidney. FE(Na) in the isolated kidney measured 2.6+/-0.4 before and 2.6+/-0.4% after blood volume expansion. These data indicate that decapitation inhibits activation of the humoral natriuretic mechanism elicited by blood volume expansion and are consistent with the interpretation that the brain is the source of the natriuretic factor or that the brain participates in the activation of the humoral natriuretic mechanism at some other site in the body.

Animals↗
PubMed1978

High density tissue culture on microporous membranes perfused by blood: report of a new bioartificial system.

A new tissue culture system has been developed to support high density cell growth using the sheep as the host. Cellular nutrition is provided by plasma solutes as they diffuse from arterial blood across microporous polycarbonate membranes into a device attached to an arteriovenous shunt. Culture chambers are constructed with transparent polycarbonate to allow photomicroscopy of the tissue in situ. System performance is demonstrated by the high density growth of fetal sheep thymus allografts and rat soft tissue sarcoma xenografts.

Animals↗
PubMed1977

Preparative countercurrent chromatography with a slowly rotating helical tube.

The capability of a simple countercurrent chromatographic scheme for obtaining high-resolution preparative-scale separations was demonstrated with the separations of a series of dinitrophenyl (DNP) amino acids and peptides. Basic studies on stationary phase retention and partition efficiency with a low-viscosity chloroform-acetic acid-0.1 N hydrochloric acid (2:2:1) phase system together with the results previously obtained with a vascous n-butanol system suggest a general applicability of low-interfacial tension phase systems by the present method.

Amino Acids↗
PubMed1977

Comparison of the nephrotoxicity of netilmicin and gentamicin in rats.

The nephrotoxicity of netilmicin relative to that of gentamicin was examined in Sprague-Dawley rats. Balance studies were performed on rats injected with netilmicin or gentamicin (50 mg/kg per day for 14 days, 100 mg/kg per day for 8 days, and 150 mg/kg per day for 8 days). Control rats were injected with saline. Both drugs caused a dose-related decrease in urine osmolality and increases in urine volume, water intake, and serum creatinine; however, the magnitude of these changes was significantly less in netilmicin- than in gentamicin-injected rats. Light microscopy of renal tissue revealed less proximal tubular cell necrosis in netilmicin- than in gentamicin-injected rats. There was no significant difference between the renal cortical concentrations of the two drugs. Both drugs stimulated uptake of p-aminohippurate in rat renal cortical slices to the same degree. The data indicate that netilmicin is less nephrotoxic than gentamicin in rats, that the difference in nephrotoxicity cannot be explained by a difference in drug concentration in the renal cortex, and that the ability of aminoglycosides to stimulate the organic acid transport system of proximal tubular cells does not correlate with their nephrotoxic potential.

Animals↗