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Biomedical subjects

S Nelson

Publications and source records attributed to S Nelson.

At least 235 records · Page 13Linked to original sources
PubMed1990

Kinetic and clinical studies of beta 2-microglobulin in continuous ambulatory peritoneal dialysis: influence of renal and enhanced peritoneal clearances using glucose polymer.

A risk of beta 2-microglobulin (beta 2-M)-associated amyloidosis in long-term CAPD patients has been recognised. We examined the kinetics of beta 2-M and potential clinical manifestations of amyloidosis in patients well-established on CAPD for 1-76 months (mean +/- SEM; 16.4 +/- 14 months). In 57 patients, serum beta 2-M concentration was elevated to 30 +/- 1.8 (mean +/- SEM, mg/l) and correlated positively with the duration on CAPD. In 18 patients studied with variable degrees of residual renal function, serum beta 2-M concentration increased with declining renal function; this was most marked when the creatinine clearance was less than 1 ml/min. Using an isosmolar solution (302 +/- 1.3 mOsm/kg) containing 5% glucose polymer (9.4 mmol/l; MW 16,800), the transperitoneal elimination of beta 2-M was significantly enhanced (1.6 times) compared to conventional 1.36% glucose solution, but without a detectable change in serum concentrations during a 6-h study. No significant difference was found between the estimated minimum volume of distribution of beta 2-M in CAPD and haemodialysis patients. Symptomatic amyloid-associated disease was absent in patients in this study, and may be attributed to the short duration of dialysis.

Adult↗
PubMed1990

Determinants of transdiaphragmatic pressure in dogs.

We measured the transdiaphragmatic pressure (Pdi) during bilateral phrenic nerve stimulation and evaluated the determinants of its change with lung volume, chest wall geometry, and respiratory system impedance in supine dogs. Four rows of radiopaque markers were sewn onto muscle bundles of the costal and crural diaphragm between their origin on the central tendon and their insertion on the rib cage and spine. The length of the diaphragm (L) was determined from the projection images of marker rows using biplane fluoroscopy. Measurements were made at lung volumes between total lung capacity and functional residual capacity before and after the infusion of Ringer lactate solution into the abdominal cavity. In contrast to relaxation, during tetanic stimulation the active lengths of the muscle bundles were similar at all volumes, but the diaphragm assumed different shapes. Although the small differences in active muscle length with volume and liquid loads are consistent with only small changes in muscle force output, Pdi varied by a factor of greater than or equal to 5. There was no single L/Pdi curve that fitted all data during 50-Hz stimulations. We conclude that under these experimental conditions Pdi is not a unique measure of the force produced by the diaphragm and that lung volume, chest wall geometry, and respiratory system impedance are important determinants of the mechanical efficiency of the diaphragm as a pressure generator.

Action Potentials↗
PubMed1990

Identification and characterization of an abundant phosphoprotein specific to the large luteal cell.

An abundant protein with a relative mol wt of 32K present specifically in the large cells of the pregnant rat corpus luteum has been identified. Separation of large and small luteal cells by elutriation, followed by protein analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), have revealed that the 32K protein was present as a major protein in the large luteal cells but was practically absent in the small cell population. This protein appears to be highly tissue and cell specific and resolves into three protein species by two-dimensional SDS-PAGE with the major protein having an isoelectric point (pI) greater than or equal to 8.5. It was not detected in preantral follicles or placentas of the same pregnant rats, or in any other tissue examined. After subcellular fractionation, the 32K protein(s) was found in the particulate fraction and was localized principally in the microsomal compartment. Autoradiographic analysis of 35S-amino acid-labeled tissue demonstrated that the 32K protein(s) is synthesized in the corpus luteum. When particulate fractions from small and large cells were incubated in the presence of [gamma-32P]ATP followed by SDS-PAGE, phosphorylation of the 32K protein was apparent. Phosphorylation of this protein was not enhanced by the addition of cofactors for cAMP, Ca2(+)-calmodulin- or Ca2(+)-phospholipid-dependent kinases. Experimental inhibition of steroidogenesis with amino-glutethimide caused a remarkable reduction in the luteal content of this 32K protein whereas estradiol and human CG treatment increased its content. In summary, we have discovered and partially characterized a unique 32K protein(s) which is expressed and phosphorylated only in large luteal cells of the corpus luteum. This protein(s), which is regulated by estradiol formed locally, may serve as a powerful marker for both the large luteal cell and estrogen action in the corpus luteum.

Animals↗
PubMed1990

Neuropathy in Navajo children: clinical and epidemiologic features.

We describe a rare and apparently unique neuropathic syndrome among Navajo children living on the Navajo Reservation. Clinical features include sensorimotor neuropathy, corneal ulcerations, acral mutilation, poor weight gain, short stature, sexual infantilism, serious systemic infections, and liver derangement including Reye's syndrome-like episodes. Progressive CNS white matter lesions were diagnosed through magnetic resonance imaging. We identified 20 definite and 4 probable cases occurring between 1959 and 1986. Mean age at the time of 1st recognized symptom was 13 months (range, 1 month to 4 years 6 months). Ten individuals have died; 6 of the deaths occurred before 5 years of age. The incidence of this syndrome on the western Navajo reservation is 5 times higher than that on the eastern reservation (38 compared with 7 cases per 100,000 births). Although the etiology is unknown, this syndrome is consistent with an inborn error of metabolism, inherited in an autosomal recessive manner.

Adolescent↗
PubMed1990

Endotoxin-induced suppression of lung host defenses.

Respiratory tract infections are major causes of excessive morbidity and mortality in hospitalized patients. Persons with systemic sepsis have an especially high risk of acquiring these infections, which indicates that their lung antibacterial defenses are compromised. To evaluate the effects of sepsis on pulmonary antibacterial defenses, we injected either saline or 5 mg/kg of Escherichia coli lipopolysaccharide intravenously into Sprague-Dawley rats. Two hours later, the animals were challenged by aerosol inhalation with either Staphylococcus aureus or Pseudomonas aeruginosa. It is known that phagocytic defenses against aerosolized S. aureus challenges are provided solely by the alveolar macrophage; in normal animals challenged with P. aeruginosa, however, an intrapulmonary inflammatory response is elicited. Animals pretreated with endotoxin showed a significant decrease in pulmonary bactericidal activity against S. aureus with 31 +/- 3% bacteria remaining viable at 4 hr compared with 20 +/- 2% in the controls, which indicates a defect in alveolar macrophage antimicrobial activity. After P. aeruginosa challenge, saline-injected control animals developed a marked intrapulmonary inflammatory response and killed greater than 85% of their initial inoculum by 4 hr. By contrast, endotoxin-treated animals failed to recruit neutrophils into the alveoli in response to P. aeruginosa, resulting in a proliferation of this pathogen within the lung (212 +/- 6% bacteria remaining viable at 4 hr). Endotoxin is known to be a potent stimulus for the production of tumor necrosis factor (TNF) by the host. TNF is a potent inflammatory mediator and promotes neutrophil adhesion to the vascular endothelium. In these experiments, serum TNF peaked at 28,390 +/- 7,766 Units/ml. 90 min after intravenous endotoxin. Histopathology of the lungs in these animals showed considerable sequestration of the neutrophils within the pulmonary vasculature. These data show that systemic endotoxin significantly impairs lung host defenses against intrapulmonary bacterial challenges and suggest that TNF-mediated events may play a central role.

Animals↗
PubMed1990

Allied health education in Oklahoma.

This article is the first of several dealing with medical education and recruitment in Oklahoma and generated at the request of the OSMA-OUHSC Liaison Committee. The articles were sought out and submitted with the assistance of Edward N. Brandt, Jr., MD, PhD, executive dean at the University of Oklahoma College of Medicine.

Allied Health Occupations↗
PubMed1989

Aerosol bronchodilator delivery methods. Relative impact on pulmonary function and cost of respiratory care.

Thirty-six acutely III, hospitalized patients with acute exacerbations of obstructive airway disease and a greater than 10% increase in forced expiratory volume in 1 s after administration of aerosolized bronchodilator were randomized to receive either metaproterenol sulfate delivered by updraft-compressor nebulization (UDN) or terbutaline sulfate delivered by metered-dose inhaler (MDI) with a spacer. Serial analyses of pulmonary function measurements were performed with the use of 95% confidence intervals for the percentage response ratios of MDI to UDN. The response to MDI was at least equivalent to that of UDN, and MDI use was associated with no prolongation of hospital stay. Equivalent bronchodilation was achieved with MDI therapy with a lower daily charge for therapy for each patient and less respiratory therapist time. In hospitalized bronchodilator-responsive patients with acute exacerbations of obstructive airway disease, the MDI/spacer combination is the preferred approach when the status of the patient allows its use.

Aerosols↗
PubMed1989

Alcohol suppresses lipopolysaccharide-induced tumor necrosis factor activity in serum and lung.

Ethanol intoxication has been shown to suppress selected functions of the immune system thereby compromising host defense against bacterial infections. Tumor necrosis factor, a secretory protein produced by the macrophage in response to lipopolysaccharide, mediates the inflammatory cascade and stimulates phagocyte functions. Acute ethanol intoxication markedly suppressed both serum and lung tumor necrosis factor elicited in response to lipopolysaccharide. Furthermore, ethanol inhibited intratracheal lipopolysaccharide-induced neutrophil recruitment into the alveoli and prevented the fall in circulating neutrophils in response to intravenous lipopolysaccharide. Thus, the anti-inflammatory effects of ethanol may be secondary to suppression of macrophage-derived tumor necrosis factor.

Animals↗
PubMed1989

Compartmentalization of intraalveolar and systemic lipopolysaccharide-induced tumor necrosis factor and the pulmonary inflammatory response.

Tumor necrosis factor-alpha (TNF), a monokine produced by lipopolysaccharide (LPS)-stimulated macrophages, is an activator of phagocytic functions and may modulate host responses during infection. To determine the effects of LPS on TNF activity and the pulmonary inflammatory response in vivo, we challenged rats systemically or intratracheally with LPS. Intravenous LPS significantly increased serum TNF content from nondetectable levels in control specimens to peak levels at 90 min, which declined to baseline by 3 h. In response to intratracheal LPS, levels of TNF both in bronchoalveolar lavage fluid and associated with alveolar macrophages increased significantly from near nondetectable levels in control animals. Increases in TNF levels were confined to the LPS-challenged compartment. Intravenous LPS resulted in a decrease in the number of peripheral blood neutrophils and in sequestration of these cells within the pulmonary vasculature. In contrast, intratracheal LPS elicited a marked intraalveolar inflammatory response.

Animals↗
PubMed1989

The effects of acute and chronic alcoholism on tumor necrosis factor and the inflammatory response.

Ethanol intoxication has been shown to suppress selected functions of the immune system, thereby compromising host defenses against bacterial infections. Because the macrophage secretory protein, tumor necrosis factor (TNF), plays a central role in the inflammatory cascade, the effect of acute and chronic alcoholism on lipopolysaccharide (LPS)-induced TNF activity was studied. Saline or ethanol was given intraperitoneally to normal or chronic alcoholic rats followed 30 min later by either intravenous or intratracheal LPS. Intravenous LPS caused a substantial increase in serum TNF at 90 min in both normal and chronic alcoholic rats. In marked contrast, peak serum TNF levels were significantly suppressed in normal and chronic alcoholic rats given an acute injection of ethanol. When LPS was instilled intratracheally into normal rats, high levels of TNF appeared in the bronchoalveolar lavage fluid. Similar levels of TNF were found in chronic alcoholic rats after intratracheal LPS. However, acute ethanol intoxication significantly inhibited LPS-induced TNF in bronchoalveolar lavage fluid. In a similar manner, acute ethanol intoxication, but not chronic alcohol consumption, markedly inhibited both systemic and intrapulmonary polymorphonuclear leukocyte aggregation in response to either intravenous or intratracheal LPS. Alcohol-induced inhibition of TNF is a potential mechanism of the antiinflammatory effects of ethanol.

Alcoholic Intoxication↗
PubMed1989

Acute alcohol infusion suppresses endotoxin-induced serum tumor necrosis factor.

Tumor necrosis factor (TNF) is suggested to play an important role in host defense as well as in eliciting some of the metabolic alterations in endotoxemia. Bacteria and their products are involved in triggering the production and release of TNF. Alcohol consumption is known to suppress the immune system and increase susceptibility to infections. The present study was undertaken to investigate the effect of acute ethanol administration on the ability of endotoxin to increase circulating TNF levels and to determine the relationship between blood ethanol levels and endotoxin-induced serum TNF. A 50% decrease in serum TNF levels was seen 1-1.5 h after endotoxin challenge in conscious rats with blood alcohol levels between 75-175 mg/dl. A dose-related depression of serum TNF was observed with increasing blood alcohol levels. This was accompanied by a markedly diminished hyperlactacidemia seen following endotoxin administration. These data suggest that impaired TNF release may have a role in the altered immune response of alcoholics to infection.

Animals↗
PubMed1989

[Contribution of experimental models to the treatment of respiratory tract infections].

The need for more effective and potentially less toxic antimicrobial agents than aminoglycosides for treatment of gram negative bacilli pneumonia specially Pseudomonas aeruginosa, explains the interest for experimental models of pneumonia. These models allow to study the efficacy and safety of antibiotics alone or in combination. Aminoglycosides and new quinolones are more effective than beta-lactams for life threatening infection with high inoculum, the only exception to this finding has been for N-formimidoyl thienamycin, whereas for less severe infections aminoglycosides and beta-lactams are equivalent in efficacy. In contrast to high inocula pneumonia, combining beta-lactams with aminoglycosides give additive of synergic benefits for treating low inocula. Experimental models allow to compare continuous versus intermittent administration of antibiotics, different regimens of the same antibiotics (single daily dose of aminoglycosides versus conventional administration) and new antiinfectious agents as anti-pseudomonas hyperimmune globulins.

4-Quinolones↗