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Biomedical subjects

R Evans

Publications and source records attributed to R Evans.

At least 253 records · Page 14Linked to original sources
PubMed1992

Risk factors for increased airway responsiveness to methacholine challenge among laboratory animal workers.

As a first step in a prospective study of the incidence of asthma to laboratory animals, a group of 364 adults 18 to 48 yr of age who were beginning employment with laboratory animals were evaluated in terms of their past history, health status, allergy, and airway responsiveness to methacholine. At entry to the study, 269 had previous occupational contact with animals, 109 had chest symptoms in the previous year, 168 had a history of allergic symptoms to laboratory animals (any with asthmatic responses were systematically excluded), and 118 had positive immediate skin tests (29 had positive skin tests to laboratory animals). When defined as a PD20FEV1 of 80 breath units or less, 18.4% of these young adults had methacholine hyperresponsiveness (HRA). Significant risk factors for HRA were found to be younger age, female sex, lower educational level, a history of allergic symptoms to laboratory animals, and a history of chest symptoms. Positive skin tests to laboratory animals were present in 8% of workers; this was not a significant risk factor for HRA although positive skin tests to pollen and household allergens were. Previous work experience was a risk factor, especially among those with allergic symptoms, and a trend toward self-selection was suggested in that the rate of HRA was lowest in workers with more than 2 yr of experience or with two or more previous jobs with laboratory animals.

Adolescent↗
PubMed1992

Modifications of the guanidine hydrochloride procedure for the extraction of RNA: isolation from a variety of tissues and adherent/nonadherent cell types.

In a previous report dealing with the guanidine hydrochloride protocol for the extraction of RNA from mouse peritoneal macrophages, we identified a major source of RNA-degrading activity and showed that its removal early in the extraction procedure resulted in a more dependable method for the recovery of high-quality RNA. This report extends these findings and demonstrates the general applicability of the technique to a variety of fresh or frozen adherent cell types, cell suspensions and tissues, further highlighting stages at which degradation is most likely to occur and how to avoid a variety of pitfalls associated with the extraction procedure.

Animals↗
PubMed1992

Human cytochrome P450 metabolism of teniposide and etoposide.

Although teniposide (VM26) and etoposide (VP16) are eliminated mostly by nonrenal mechanisms, their cytochrome P450 metabolism in humans has not been reported. Our objective was to determine the affinity and capacity of P450 O-demethylation of VM26 and VP16 in a variety of human livers. Formation of catechols of VM26 and VP16 was detected in 24 and 26 of 26 liver microsomal preparations, respectively, with wide variability in maximum catechol formation rates from VM26 (41-fold) and VP16 (39-fold range), even among normal livers. Maximal activity measurements at 500 microM substrate were lower for VM26 catechol formation (mean = 1.5 nmol/mg/hr) than for VP16 catechol (mean = 3.2 nmol/mg/hr) in 26 livers (P less than .001). Maximal activities for VP16 and VM26 O-demethylation, and ethoxycoumarin O-deethylation were significantly higher in normal than in diseased livers. No differences were found in activities related to age, sex or race of the liver donor. In all five livers tested over a range of substrate concentrations, Km (19.7, 23.2, 43.5, 30.1 and 22.0 microM) and Vmax values (1.0, 1.2, 4.4, 8.2 and 4.0 nmol/mg/hr) for VM26 were lower compared to values for VP16 (Km = 60.2, 115.1, 87.3, 42.1 and 81.9 microM; Vmax = 1.4, 3.3, 10.3, 27.5 and 10.1 nmol/mg/hr). Despite higher VP16 catechol formation, VM26 underwent greater overall reduced nicotinamide adenine dinucleotide phosphate-dependent metabolism than VP16, consistent with greater nonrenal clearance of VM26 in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Results of the National Institute of Allergy and Infectious Diseases Collaborative Clinical Trial to test the predictive value of skin testing with major and minor penicillin derivatives in hospitalized adults.

BACKGROUND: A history (or lack thereof) of penicillin allergy is known to be unreliable in predicting reactions on subsequent administration of the drug. This study tests the usefulness of four penicillin allergen skin tests in the prediction of IgE-mediated reactions subsequent to administration of penicillin. METHODS: Eight centers cooperated in the National Institute of Allergy and Infectious Diseases trial of the predictive value of skin testing with major and minor penicillin derivatives. Hospitalized adults were tested with a major determinant (octa-benzylpenicilloyl-ocytalysine) and a minor determinant mixture and its components (potassium benzylpenicillin, benzylpenicilloate, and benzylpenicilloyl-N-propylamine). Patients then received a therapeutic course of penicillin and were observed, for 48 hours, for adverse reactions compatible with an IgE-mediated immediate or accelerated allergy. RESULTS: Among 726 history-positive patients, 566 with negative skin tests received penicillin and only seven (1.2%) had possibly IgE-mediated reactions. Among 600 history-negative patients, 568 with negative skin tests received penicillin and none had a reaction. Only nine of the 167 positive skin test reactors received a penicillin agent and then usually by cautious incremental dosing. Two (22%) of these nine patients had reactions compatible with IgE-mediated immediate or accelerated penicillin allergy; both were positive to the two determinants. CONCLUSIONS: These data corroborate previous data about the negative predictive value of negative skin tests to these materials. The reaction rate in skin test-positive patients was significantly higher than in those with negative skin tests, demonstrating the positive predictive value of positive tests to both major and minor determinants. The number of patients positive only to the major determinant or only to the minor determinant mix was too small to draw conclusions about the positive predictive value of either reagent alone.

Adult↗
PubMed1991

Nonsurgical removal of a catheter embolus from the heart of a foal.

Nonsurgical, percutaneous, transvenous removal of a catheter fragment embolus was performed in a 14-day-old Thoroughbred foal. A basket retrieval catheter was introduced into the jugular vein and manipulated under fluoroscopic guidance to remove the fragment from the right side of the heart. Percutaneous retrieval should be considered as an alternative to thoracotomy for retrieval of intracardiac or intravascular foreign bodies.

Animals↗
PubMed1991

Differential in situ expansion and gene expression of CD4+ and CD8+ tumor-infiltrating lymphocytes following adoptive immunotherapy in a murine tumor model system.

In previous reports, we demonstrated that adoptively transferred T cells homed to the tumor site (among other sites) and that amplification of immune responses occurred in situ leading to the generation of cytotoxic CD8+ tumor-infiltrating lymphocytes (TIL) and macrophages. The present report extends these findings and shows that following adoptive immunotherapy (AIT) of mice bearing the immunogenic transplanted methylcholanthrene-induced rhabdomyosarcoma (MCA/76-9) there was a differential expansion of CD4+ and CD8+ TIL, the numbers peaking on days 6 and 8, respectively. At this time, CD8+ TIL accounted for the majority of Thy-1+ cells. Northern analyses of RNA extracted from positively selected (by panning) Thy-1+, CD8+ and CD4+ TIL isolated 8 days after AIT indicated the following: in five separate experiments, CD4+ cells expressed three- to sixfold more interleukin (IL)2 mRNA and six- to eightfold more IL6 mRNA than CD8+ cells, while CD8+ TIL expressed three- to sixfold more IL2 receptor (IL2R) mRNA and four- to sixfold more interferon-gamma mRNA than CD4+ cells. TIL cultured in 10% fetal bovine serum failed to release IL2 over a 24-h period, whereas both IL6 and interferon-gamma activities were demonstrable. The level of IL2R mRNA expression was reflected by a vigorous proliferative response of CD8+ TIL to exogenous recombinant IL2 and only a low response by CD4+ cells suggesting that most of the CD4+ TIL were in the resting stage. This was confirmed when it was shown that the incubation of panned CD4+ TIL with IL2 supplemented with irradiated spleen cells and "spent" 76-9 tumor culture supernatant (as a source of antigen) induced expansion of TIL resulting in a population consisting of greater than 90% CD4+ TIL. The overall data suggest that the relatively deactivated state of the CD4+ TIL at this particular time reflects the status of the rejection process in terms of the absence or low concentration of stimulating tumor-associated antigen.

Animals↗
PubMed1991

Tumor-derived products induce Il-1 a, Il-1 b, Tnf a, and Il-6 gene expression in murine macrophages: distinctions between tumor- and bacterial endotoxin-induced gene expression.

The ability of progressing tumors to regulate host physiology is an important consideration in our understanding of tumor-host relationships. Previous data indicated that several lines of murine sarcoma cells produced one or more activities that were able to regulate both Il-1 a and Il-1 b gene transcription in macrophages (MO). We now describe an indepth analysis using Northern analysis and bioassays and show that two of these tumors produce one or more activities that when incubated with peritoneal MO result in the transcription of the Il-1a, Il-1 b, Tnf a, and Il-6 genes. Concordant with the Northern analyses was the finding that interleukin-1 (IL-1) and tumor necrosis factor (TNF) biological activities were detected in lysates of induced MO, fixed MO, and supernates of MO cultures. Induction of gene expression was shown to be distinct from that induced by bacterial endotoxin or lipopolysaccharide by a number of criteria. The data suggest that tumor cell products may play an important role in regulating several host physiological processes, particularly those involving Il-1a, Il-1 b, Tnf a, and Il-6 gene expression.

Animals↗
PubMed1991

Orthodontic bonding using glass ionomer cement: an in vitro study.

The aim of this study was to investigate the in vitro 24-hour tensile/peel bond strength of glass ionomer cement (GIC) together with the amount of cement left attached to the enamel surface after bond failure. The effect of contamination with moisture during setting/hardening and changing the powder/liquid mixing ratio of the GIC was also studied. Five GIC's (Intact, Fuji II, Orthocem B, ChemFil II, and Ketac Fil[capsulated]) and one composite resin (Concise) were tested by bonding GAC eyelets, with a curved photo-etched base, to the buccal surface of human premolars. Bond strength testing was performed on an Instron 1185 testing machine and the amount of cement left attached to the enamel surface quantified using the ARI index. The tensile/peel bond strengths achieved with all the GIC's were significantly lower than the composite resin (P less than 0.0002). Increasing the powder/liquid ratio resulted, in general, in higher bond strengths, the increase being significant for Intact and Orthocem B (P less than 0.05). Protection from moisture did not significantly affect the bond strength with the exception of Fuji II, for which, there was a significant decrease when the material was mixed at the recommended powder/liquid ratio.

Acrylic Resins↗
PubMed1991

Tibial torsion measured by ultrasound in children with talipes equinovarus.

Previous clinical studies have studied tibiofibular torsion by measuring the angular difference between a proximal (often bicondylar) plane and a distal bimalleolar plane. We measured the angular difference between the proximal and distal posterior tibial planes as defined by ultrasound scans. We found no significant torsional difference between the right and left tibiae of 87 normal children, nor between their different age groups. The mean external torsion of 58 legs with congenital talipes equinovarus was 18 degrees; significantly less than the mean 40 degrees in the normal children and 27 degrees in the clinically normal legs of the 22 patients with unilateral congenital talipes equinovarus. We did not confirm the previously reported increase in external torsion with increasing age. The relative internal tibial torsion we have demonstrated in patients with congenital talipes equinovarus must be differentiated from the posterior displacement of the distal fibula observed by others and which may result from manipulative treatment. The relative internal tibial torsion we found in the clinically normal legs of children with congenital talipes equinovarus is further evidence that in this condition the pathology is not confined to the clinically affected foot.

Adolescent↗