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Biomedical subjects

D L Stevens

Publications and source records attributed to D L Stevens.

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

Lung clearance of neutron-activated Mount St. Helens volcanic ash in the rat.

To determine pulmonary deposition and clearance of inhaled volcanic ash, rats received a single 60-min, nose-only exposure to neutron-activated ash. Over a period of 128 days after exposure, the rats were sacrificed in groups of five animals. Lungs were analyzed for the radionuclide tracers 46Sc, 59Fe, and 60Co by gamma-ray spectrometry. The alveolar ash burdens, determined by the radionuclides 46Sc and 59Fe, are in good agreement for the majority of samples analyzed, indicating ash particulate levels in the lungs, rather than leached radionuclides. The ash deposition estimates based on 60Co were appreciably lower for the lungs, indicating that 60Co leached from the ash. Approximately 110 micrograms ash, or 6% of the inhaled ash, was initially retained in the deep lung. The biological half-time of the alveolar ash burden was 39 days. After 90 days, the mean lung burden had decreased to about 20% of its initial value; 128 days after exposure, about 10% remained.

Air Pollutants↗
PubMed1984

Use of trehalose-mannitol-phosphatase agar to differentiate Staphylococcus epidermidis and Staphylococcus saprophyticus from other coagulase-negative staphylococci.

Using a plate medium containing trehalose, mannitol, and phenolphthalein diphosphate (TMPA), we differentiated significant clinical isolates of Staphylococcus epidermidis by their lack of acid production in 18 h from other coagulase-negative staphylococci, with our results having a sensitivity (R. S. Galen and S. R. Gambino, Beyond Normality: The Predictive Value and Efficiency of Medical Diagnoses) of 100%, a specificity of 89.9%, and a positive predictive value of 94.8%. With a Taxo A bacitracin disk, which differentiates Staphylococcus species from Micrococcus species, no zone of inhibition was seen for 96% of all staphylococcal strains, with 5 of 26 strains of Staphylococcus saprophyticus exhibiting zone diameters up to 10 mm. By using resistance to a 5-microgram novobiocin disk, we differentiated S. saprophyticus, with our results having a sensitivity of 100%, a specificity of 97.1%, and a positive predictive value of 83.9% on TMPA. These two species represented 77.8% of coagulase-negative staphylococci isolated. Reference strains fo Staphylococcus and Micrococcus species were differentiated by TMPA. The cost of TMPA was compared with that of another method. TMPA was found to offer an inexpensive, sensitive method for rapidly differentiating coagulase-negative Staphylococcus isolates.

Agar↗
PubMed1984

Pseudallescheria boydii infections treated with ketoconazole. Clinical evaluations of seven patients and in vitro susceptibility results.

Seven patients infected with Pseudallescheria boydii were treated with oral ketoconazole, 200 to 600 mg/day for one to 13 months. Five patients had pulmonary infections; two had skeletal infections. Improvement of pretreatment abnormalities occurred in five patients, one of whom had concurrent arthrodesis of his infected knee. The other two patients were subsequently healed by surgical resection of their pulmonary lesions. Ketoconazole appeared less active than miconazole against 22 clinical isolates of P boydii when tested by two in vitro methods. We conclude that ketoconazole is effective treatment for some patients infected with P boydii, although this may not be predicted by current in vitro susceptibility tests. Further experience is needed to establish the optimal use of ketoconazole with respect to its dosage, duration of administration and concurrent surgical resection.

Aged↗
PubMed1981

Stimulation of human neutrophil chemiluminescence by soluble immune complexes and antibodies to neutrophils.

Activation of the neutrophil surface membrane may occur with a variety of stimuli, leading to enhanced glucose oxidation via the hexose monophosphate shunt and production of toxic oxygen radicals such as superoxide anion. This metabolic stimulation may be accompanied by light emission or chemiluminescence. The objective of these studies was to determine the effects of soluble and insoluble immune complexes, IgG aggregates, and rabbit anti-neutrophil serum on neutrophil activation as measured by chemiluminescence. Also, the uptake of immune complexes by neutrophils was determined and was correlated with the solubility of the complexes and the levels of induced chemiluminescence. The results indicate that stimulation of neutrophil chemiluminescence and uptake of immune complexes by neutrophils were both closely correlated with the percent precipitation of the immune complexes. Insoluble immune complexes that were avidly ingested by neutrophils also stimulated maximum levels of chemiluminescence. Nevertheless, elevated levels of chemiluminescence were induced by soluble immune complexes that were poorly ingested by neutrophils. Similarly, soluble aggregated IgG induced elevated levels of neutrophil chemiluminescence in a dose-dependent manner. Aggregated IgG induced up to sixfold higher levels of neutrophil chemiluminescence than did equal amounts of monomeric IgG. Finally, rabbit anti-neutrophil serum also caused increased levels of neutrophil chemiluminescence. Since previous studies have shown that sera from some patients with rheumatoid arthritis and Felty's syndrome have increased amounts of neutrophil-binding IgG due to the presence of both immune complexes and neutrophil-reactive antibodies, the effect of these sera on neutrophil chemiluminescence was studied. Positive correlations were observed between the level of neutrophil chemiluminescence induced by the sera and the amount of serum IgG neutrophil-binding activity (r = 0.72, p less than 0.001) as well as the level of immune complexes determined by C1q binding (r = 0.76, p less than or equal to 0.001). Such neutrophil activation by immune complexes or antibodies may reflect production of toxic oxygen radicals and could subsequently affect neutrophil function.

Antibodies↗
PubMed1980

Halophilic Vibrio sepsis.

We have described a patient with fulminant sepsis and bullous skin lesions due to L + Vibrio. The histologic features of these lesions as well as the rapid onset of refractory shock and complete heart block at least suggest that potent bacterial toxins are involved in the pathogenesis of disease caused by this "unnamed lactose-positive marine Vibrio."

Aged↗
PubMed1980

False no-growth blood cultures in pneumococcal pneumonia.

The growth of Streptococcus pneumoniae in commercial media containing 14C-labeled substrates was studied experimentally; the results of blood cultures that were positive for S. pneumoniae over a 14-month period were analyzed to explain no-growth but radiometrically positive blood cultures from four patients with clinically diagnosed pneumococcal pneumonia. The growth of S. pneumonoiae in aerobic blood culture vials resulted in a chocolate color in the medium. S. pneumoniae grew rapidly in both aerobic and anaerobic media, but 14CO2 evolved from the metabolism of the labeled substrates was detected only in the aerobic culture vials. Radiometric detection lagged behind growth of the organisms and was accompanied by visual changes in the media. By 24 h, the viability of the culture was on the decline; radiometric readings remained positive even when the culture had died.

Aerobiosis↗
PubMed1980

Hyperbaric oxygen in the treatment of rhinocerebral mucormycosis.

Hyperbaric oxygen therapy was utilized in a case of fulminant mucormycosis of the maxilla, orbit and temporal bone. The patient had refused radical surgery and death seemed iminent in spite of aggressive medical management of diabetic ketoacidosis, amphotericin B and wide surgical drainage of the maxillary and ethmoid sinuses with orbital decompression. Hyperbaric oxygen was instituted on the following theoretical premises: 1. It would provide oxygenation of tissues distal to occluded arteries, thereby increasing local survival and decreasing acidosis, 2. resultant lessening of acidosis would slow or inhibit rapid growth of the organism, and 3. oxygen in sufficient concentration is fungicidal. The rapid progress of the mucormycosis was arrested. Cultures of tissue prior to hyperbaric oxygen treatment produced heavy growth of Rhizopus, and tissues cultured after therapy grew only bacterial contaminants. The patient survived for 3 mo. only to succumb to Pseudomonas meningitis secondary to necrotic bone and epidural abscess of the middle cranial fossa. Rhinocerebral mucormycosis is a fulminant and frequently fatal disease. No survivors were reported before extensive surgical debridement was utilized. Survival improved to 50% with the addition of amphotericin B. Early diagnosis and correction of underlying acidosis has further improved this to 85%. The response to hyperbaric oxygen in this case report possibly introduces a promising new adjunct to therapy of this serious disease.

Adult↗
PubMed1979

Infectious mononucleosis with severe neutropenia and opsonic antineutrophil activity.

Severe granulocytopenia is an uncommon complication of infectious mononucleosis, only 18 cases having been reported previously. Our review and experience with this case would indicate that (1) severe granulocytopenia is usually diagnosed at about the third or fourth week of illness, (2) bone marrow examination most commonly reveals lack of mature neutrophil precursors in the myelocytic series, (3) the duration of usually short, lasting about a week, and (4) most patients recover without treatment. The laboratory findings in our case suggests that the neutropenia may be antibody mediated.

Adolescent↗
PubMed1979

Antibiotic susceptibilities of human isolates of Pasteurella multocida.

Seventeen human strains of Pasteurella multocida, biochemically similar to, if not identical with, isolates of animal origins, were tested for susceptibility to 16 antimicrobial agents utilizing a microtiter broth dilution technique. Ten of these isolates were also tested against 11 antibiotics by disk diffusion. The most active drugs with respect to the median minimal inhibitory concentration (micrograms per milliliter) were tetracycline (0.09), penicillin G (0.78), ampicillin (0.78), carbenicillin (1.56), cephalothin (1.56), and chloramphenicol (1.56). With the exception of tetracycline, the median minimal inhibitory concentration and minimal bactericidal concentration values were equal or differed by no more than a factor of two. The semisynthetic penicillins clindamycin, erythromycin, and aminoglycosides had relatively low activities, suggesting that these agents would be poor choices for the treatment of P. multocida infections.

Anti-Bacterial Agents↗
PubMed1979

Amebic liver abscess. Report of a case presenting with nonreactive serologic tests for Entamoeba histolytica.

We present a patient with an acute amebic liver abscess with nonreactive serologic tests. Motile hematophagous trophozoites of Entamoeba histolytica were seen microscopically in scrapings from the wall of the abscess. Postoperative serologies revealed rapidly rising then falling titers by SAFA and IHA antibody assays. Serologic tests for amebiasis may be reative in greater than 95% of patients with invasive amebiasis. Nevertheless, a reactive serologic test should not be relied upon exclusively to establish the diagnosis. Sequential serologic testing and surgical intervention to obtain material for microscopic examination, gram stain and bacteriologic culture are warranted in patients with hepatic abscess and nonreactive serologic tests for antibodies to E. histolytica.

Adult↗
PubMed1978

Standardization of a rapid microbiologic assay for aminoglycosides using Enterobacter cloacae.

The standardization of a rapid serum aminoglycoside assay using Enterobacter cloacae is described. This includes the sensitivity testing of the organism and its performance on various media, with Mueller-Hinton agar being the medium of choice. The precision and reproducibility of the assay, as measured by the within-run and between-run coefficients of variation, were 5.0 and 5.9, respectively. A significant positive correlation was obtained between the microbiologic assay for gentamicin and a 125I-labeled gentamicin radioimmunoassay with the use of both normal and uremic sera. When known amounts of gentamicin, tobramycin, and amikacin were added to antibiotic-free sera from normal persons, recovery rates of 80.0% to 97.9% were found. In the case of gentamicin, recovery rates of 85.0% to 97.9% were found with the use of sera from patients undergoing either hemodialysis or peritoneal dialysis. There were no effects on the recovery rates of the aminoglycosides from normal serum if high concentrations of clindamycin, methicillin, ampicillin, penicillin G, cephalothin, cefamandole or cefoxitin were also present in the sera. The newer cephalosporins, cefamandole and cefoxitin, had no in-vitro effect on the Kirby-Bauer sensitivity patterns of gentamicin, tobramycin, or amikacin, when tested against the assay organism.

Agar↗
PubMed1978

Group B streptococcal osteomyelitis in adults.

Osteomyelitis due to group B Streptococcus occurred in two adult male patients. Both patients responded to parenteral penicillin G. A review of the literature verifies that group B Streptococcus has been an exceedingly rare cause of osteomyelitis in adults.

Humans↗