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Biomedical subjects

R L Campbell

Publications and source records attributed to R L Campbell.

At least 19 recordsLinked to original sources
PubMed1996

Interleukin-12 and B7.1 co-stimulation cooperate in the induction of effective antitumor immunity and therapy of established tumors.

Interleukin-12 (IL-12) promotes specific and long-lasting anti-tumor immunity mediated by T cells in a variety of murine tumor models. IL-12 also synergizes with B7.1 (CD80) co-stimulation to induce proliferation and cytokine production by both human and murine T cells in vitro. We evaluated the combined anti-tumor efficacy of IL-12 and B7.1 gene delivery in two apparently poorly immunogenic tumor models (TS/A and MCA207). In both of these models, expression of B7.1 and production of IL-12 in the inoculum led to improved anti-tumor immunity, with up to 80% long-term tumor-free animals (vs 0-20% of mice remaining tumor free when inoculated with either B7.1- or IL-12-transfected tumors alone). Tumor-free mice were capable of rejecting a subsequent rechallenge with the wild-type tumor in 66% of the cases. Cooperativity was dependent upon the level of IL-12 secreted by engineered cells. IL-12 delivery required B7 expression of therapeutic effects to be observed in these models. Vaccines provided at a site distal to a control, non-transfected tumor slowed (TS/A) or abrogated (MCA207) the progression of wild-type tumors. The synergistic anti-tumor effects associated with combined application of B7.1- and IL-12-transfected tumors were partially negated by systemic administration of the CD28-B7.1/B7.2 antagonist CTLA4-Ig or by inoculation with neutralizing antibodies directed against murine interferon-gamma or tumor necrosis factor-alpha, two cytokines elicited in response to IL-12 stimulation. These data support the potential clinical utility of combined gene therapy using IL-12- and B7.1-engineered autologous cells (tumor or fibroblasts) as a vaccine to elicit specific anti-tumor immunity.

Abatacept↗
PubMed1996

Studies on the three-dimensional structure of estrogenic 17 beta-hydroxysteroid dehydrogenase.

The structure-function relationship of the estrogenic 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD1), a pivotal enzyme in the synthesis of active sex hormones, has been studied via protein chemistry and crystallography. A highly active and homogeneous 17 beta-HSD1 was prepared with a rapid purification from human placenta. We then characterized the native and expressed enzyme, and concluded, for the first time, that 17 beta-HSD1 is formed by two identical subunits. The enzyme was also overproduced in insect cells with a baculovirus expression system. The highly active 17 beta-HSD1 preparation was successfully crystallized in the presence of NADP-, polyethylene glycol, beta-octylglucoside and glycerol, resulting in the first diffraction quality crystals of any steroid-converting enzyme from a human source. The three-dimensional structure of 17 beta-HSD1 was determined at 2.2 A resolution, showing that the overall structure of the enzyme is similar to the other enzymes in the short-chain dehydrogenase family, with a conserved Tyr-X-X-X-Lys sequence and a serine residue in the active site. It is distinguished from the other known structures reported for short-chain dehydrogenases by the insertion of two helix-turn-helix motifs that appear to govern membrane association and substrate specificity [corrected]. More recently, the complex of 17 beta-HSD1 with estradiol has been successfully crystallized and its structure determined. The latter demonstrates detailed information of the interactions between the substrate and residues Ser142, Tyr155, His221 and Glu282 of the enzyme. These interactions and the complementarity of the substrate with the hydrophobic binding pocket make critical contributions to the enzyme specificity. The above results provide a strong basis for the design of potent inhibitors of this pivotal steroid dehydrogenase.

Estradiol Dehydrogenases↗
PubMed1995

Abnormally high pKa of an active-site glutamic acid residue in Bacillus circulans xylanase. The role of electrostatic interactions.

The active site of Bacillus circulans xylanase (1,4-beta-D-xylanohydrolase, EC 3.2.1.8) contains two glutamic acid residues, Glu78 and Glu172, which are crucial for the catalytic activity of the enzyme. Fourier-transform infrared spectroscopy was used to determine the ionization state of these residues as a function of pH. For the wild-type enzyme, titration of one of the carboxylate groups occurs at pH 6.8. This titration is absent in the Glu78-->Gln and Glu172-->Gln variants of the enzyme. This, together with crystallographic data, indicates that Glu172 has an abnormally high pKa of 6.8, caused largely by electrostatic interactions of this residue with the proximal Glu78. Differential scanning calorimetry experiments with the wild-type xylanase and a number of its mutants have shown that the presence of two nearby carboxyl groups results in a pH-dependent destabilization of the protein structure.

Anions↗
PubMed1995

An unusual case of sympathetically maintained facial pain complicated by telangiectasia.

A 32-year-old woman with a history of maxillary sinusitis, multiple surgical interventions in the maxillary sinus, and a hyperalgesic, erythematous skin lesion in her left infraorbital area, had severe burning pain in the left face. The dermal lesion was diagnosed as atypical telangiectasia and the sinus pathoses determined to be unrelated to her symptoms. Two diagnostic stellate ganglion blocks were performed with concurrent bilateral monitoring of blood flow in the infraorbital skin. Blood flow was significantly increased in the painful erythematous patch although no significant change in flow occurred in the unaffected contralateral skin. The changes correlated to patient's relief from pain. The patient's symptoms were subsequently controlled with an oral sympatholytic agent. This article demonstrates the usefulness of laser doppler flowmetry to establish the diagnosis of sympathetically maintained facial pain despite several confounding conditions and supports the theory that sympathetically maintained pain involves altered function of alpha-1 adrenoreceptors.

Adult↗
PubMed1995

A comparison of cardiac rate-pressure product and pressure-rate quotient in healthy and medically compromised patients.

Healthy and medically compromised patients were studied to compare blood pressure and heart rate changes in response to stress of routine dental extractions performed while they were under local anesthesia. Thirty-nine patients divided into American Society of Anesthesiologists (ASA) I and II groups were noninvasively monitored every 5 minutes. Systolic, diastolic, and mean arterial pressures and heart rate were recorded. Rate pressure products (RPP) and pressure rate (PRQ) quotients were calculated and compared in each group. Significant results were measures of RPP greater than 12,000 and PRQ less than one. Of the 24 patients in the ASA I category, 50% demonstrated elevated RPP values, but only two of 24 had coincidental PRQ abnormalities. Of the 15 patients in the ASA II category, 80% demonstrated elevated RPP values, but two of 15 had coincidental PRQ abnormalities. Patients in the ASA II category had a higher incidence of RPP and PRQ abnormalities, as was expected. However, it is not known which of these two measures is a more sensitive indicator of increased risk associated with stimulation of the sympathetic-adrenergic axis during oral surgery performed with patients under local anesthesia. Correlation studies with continuous Holter monitoring for ST-T wave changes on electrocardiography are forthcoming.

Adult↗
PubMed1995

A survey of drinking behaviors of Canadian correctional officers.

77 correctional officers from two Canadian medium security penitentiaries were surveyed concerning their use of alcohol. 94% reported drinking at least once during the preceding year. 45 men consumed alcohol more frequently than the 29 women, more often felt obligated to drink at social gatherings, and were more likely to believe that drinkers do not suffer health problems related to their drinking. Although other studies have indicated correctional officers have special problems with drinking, more similarities with the general population than differences were found in the present drinking patterns.

Adult↗
PubMed1995

Past and current drug use among Canadian correctional officers.

Current and past drug use was assessed in a sample of 77 Canadian correctional officers working in two medium-security penitentiaries. 58% of correctional officers indicated past illicit drug use. This compares with 20% of Canadians who indicate illicit drug use. Correctional officers were more likely than the general population to have used marijuana and cocaine.

Adolescent↗
PubMed1994

Mutational and crystallographic analyses of the active site residues of the Bacillus circulans xylanase.

Using site-directed mutagenesis we have investigated the catalytic residues in a xylanase from Bacillus circulans. Analysis of the mutants E78D and E172D indicated that mutations in these conserved residues do not grossly alter the structure of the enzyme and that these residues participate in the catalytic mechanism. We have now determined the crystal structure of an enzyme-substrate complex to 108 A resolution using a catalytically incompetent mutant (E172C). In addition to the catalytic residues, Glu 78 and Glu 172, we have identified 2 tyrosine residues, Tyr 69 and Tyr 80, which likely function in substrate binding, and an arginine residue, Arg 112, which plays an important role in the active site of this enzyme. On the basis of our work we would propose that Glu 78 is the nucleophile and that Glu 172 is the acid-base catalyst in the reaction.

Amino Acid Sequence↗
PubMed1994

Thermostabilization of the Bacillus circulans xylanase by the introduction of disulfide bonds.

The thermostability of the 20 396 Da Bacillus circulans xylanase was increased by the introduction of both intra- and intermolecular disulfide bridges by site-directed mutagenesis. Based on the 3-D structure of the enzyme, sites were chosen where favourable geometry for a bridge existed; in one case, to obtain favourable geometry additional mutations around the cysteine sites were designed by computer modelling. The disulfide bonds introduced into the xylanase were mostly buried and, in the absence of protein denaturants, relatively insensitive to reduction by dithiothreitol. The mutant proteins were examined for residual enzymatic activity after various thermal treatments, and were assayed for enzymatic activity at elevated temperatures to assess their productivity. We have examined one of these mutants by X-ray crystallography. All of the disulfide bond designs tested increased the thermostability of the B. circulans xylanase, but not all enhanced the activity of the enzyme at elevated temperatures.

Bacillus↗
PubMed1994

Gender and age differences in the drinking behaviors of university students.

A sample of 457 university students were queried concerning their use of alcohol. The majority (90%) of students reported drinking at least once over the past year, with men drinking more often. Age differences were noted, with older students (Mdn = 32.0 yr. vs 19.0 yr.) more likely to report drinking 4 to 6 times per week. Women generally had healthier attitudes concerning alcohol consumption, e.g., more likely to try to prevent a friend from driving after drinking, pay for use of a taxi, or have a designated driver. Men were more likely to indicate that it is socially acceptable to be intoxicated occasionally and also that most drinkers do not suffer health problems as a result of their drinking. The present study indicates a need to educate university students about the effects of alcohol with a particular emphasis needed for male students.

Adolescent↗
PubMed1994

Hemorrhagic dilation of the fourth ventricle: an ominous predictor.

Very little is known about the effect of computerized tomography (CT)-documented fourth intraventricular hemorrhage (IVH). An analysis of 50 patients with CT-documented fourth IVH treated between 1987 and 1992 is presented. The various etiologies included intraparenchymal hemorrhage with secondary fourth IVH (19 cases), spontaneous subarachnoid hemorrhage (18 cases), spontaneous IVH (seven cases), and trauma (six cases). Overall, 28 patients (56%) had hemorrhagic dilation of the fourth ventricle and all 28 suffered brain death, despite aggressive therapy in 79% of cases. Twenty-two patients (44%) had fourth IVH without dilation; of these, nine (41%) died and 13 (59%) experienced functional survival, despite aggressive care in 90% of cases. The survival rate was significantly worse for patients with dilation of the fourth ventricle (p < 0.01, chi-squared test). Of the 28 patients with fourth IVH associated with dilation, 25 (89%) had diffuse clot, involving the lateral and third ventricles as well, and three (11%) had isolated fourth IVH. Of the 22 patients with fourth IVH and no dilation, 13 (59%) had diffuse IVH (eight of these died and five had functional recovery) and nine (41%) had isolated fourth IVH (one died and eight had functional recovery). Diffuse ventricular clot was associated with an increased mortality rate for patients with fourth IVH and no dilation (p < 0.05). Of the 28 patients with fourth IVH associated with dilation, 24 (86%) presented with a Glasgow Coma Scale (GCS) score of 3 or 4, one with a GCS score of 6, and three with a GCS score of 13 to 15; all 28 died. For the 22 patients with fourth IVH and no dilation, nine presented with a GCS score of 3 to 5 (eight died and one had functional recovery), three had a GCS score of 6 to 8 (all three had functional survival), two had a GCS score of 9 to 12 (both had functional survival), and eight had a GCS score of 13 to 15 (one died and seven had functional survival). There was a greater chance of higher GCS scores in patients with fourth IVH and no hemorrhagic dilation (p < 0.01). Logistic regression multivariate analysis showed hemorrhagic fourth ventricular dilation to be the most significant outcome predictor (p = 0.0001), followed by GCS score (p = 0.007) and the presence of diffuse IVH (p = 0.0279).

Adult↗
PubMed1994

Respiratory effects of a balanced anesthetic technique--revisited fifteen years later.

Five hundred and fifty patients underwent general anesthesia with fentanyl, diazepam, and methohexital. Forty-seven (8.5%) developed signs of hypoventilation or airway obstruction. Arterial blood gas analysis revealed mild hypoxemia in three of the 47 cases and mild hypercarbia in six. Airway obstruction was more predictive of abnormal blood gas values than was hypoventilation.

Airway Obstruction↗
PubMed1993

26-10 Fab-digoxin complex: affinity and specificity due to surface complementarity.

We have determined the three-dimensional structures of the antigen-binding fragment of the anti-digoxin monoclonal antibody 26-10 in the uncomplexed state at 2.7 A resolution and as a complex with digoxin at 2.5 A resolution. Neither the antibody nor digoxin undergoes any significant conformational changes upon forming the complex. Digoxin interacts primarily with the antibody heavy chain and is oriented such that the carbohydrate groups are exposed to solvent and the lactone ring is buried in a deep pocket at the bottom of the combining site. Despite extensive interactions between antibody and antigen, no hydrogen bonds or salt links are formed between 26-10 and digoxin. Thus the 26-10-digoxin complex is unique among the known three-dimensional structures of antibody-antigen complexes in that specificity and high affinity arise primarily from shape complementarity.

Amino Acid Sequence↗
PubMed1993

Site specificity of glycation of horse liver alcohol dehydrogenase in vitro.

The site specificity of in vitro glycation of horse liver alcohol dehydrogenase (ADH) was examined and the results interpreted in terms of structural features of the enzyme molecule. In a phosphate buffer solution, glycation occurred at Lys231 (the main site of glycation in vivo), at Lys228 (which is not glycated in vivo), and at several unidentified positions. Buffer anions or NAD+ did not affect glycation of Lys231; this supported our hypothesis that the base catalyst which removes a proton from carbon 2 of a Lys231-attached aldimine is part of the ADH molecule [Shilton, B.H. & Walton, D.J. (1991) J. Biol. Chem. 266, 5587-5592]. Use of a molecular modelling programme indicated that this catalyst was likely to be the imidazole group of His348, exerting its effect through the hydroxyl of Thr347. Glycation of Lys228 occurred only in the presence of phosphate; in this case molecular modelling showed that the base catalyst could be a phosphate ion, bound to ADH at a positive region of the coenzyme binding site. NAD+ inhibited glycation of Lys228 by binding to the enzyme and restricting access to glucose.

Alcohol Dehydrogenase↗
PubMed1993

Age, gender, and location as factors in permission to smoke among university students.

A sample of 457 (177 men, 280 women) university undergraduates were surveyed on their use of tobacco and locations where smokers have been told not to smoke. 21% of the students (20% of men, 22% of women) surveyed indicated that they smoked. Age differences were noted, with the older men and women more likely to use tobacco than their younger peers. In general, men were more likely than women to be asked not to smoke. The large number of smokers who have been asked not to smoke may indicate an increase in social pressure to reduce the use of tobacco in public.

Adult↗