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J B Ross

Publications and source records attributed to J B Ross.

At least 19 recordsLinked to original sources
PubMed1992

Spectral enhancement of proteins: biological incorporation and fluorescence characterization of 5-hydroxytryptophan in bacteriophage lambda cI repressor.

We have used a tryptophan-requiring Escherichia coli auxotroph to replace the three tryptophan residues of lambda cI repressor with 5-hydroxy-L-tryptophan (5-OHTrp). By using a nonleaky promoter, we have achieved > 95% replacement of tryptophan in the repressor. We show that the absorbance and fluorescence properties of 5-OHTrp-lambda cI are clearly distinct from lambda cI repressor and that the fluorescence of 5-OHTrp-lambda cI repressor can be observed selectively in the presence of exogenous tryptophan. We also show that the 5-OHTrp-lambda cI repressor functional properties, as assessed by measurement of binding constants for self-association and for association to operator DNA, and structural properties, as assessed by fluorescence, are indistinguishable from the native repressor. Based on these results, we anticipate that the availability of spectrally enhanced proteins will significantly enhance the utility of both fluorescence and phosphorescence spectroscopies to study protein structure and function in complex interacting systems.

5-Hydroxytryptophan↗
PubMed1992

Tissue factor and its extracellular soluble domain: the relationship between intermolecular association with factor VIIa and enzymatic activity of the complex.

We find that the isolated, extracellular domain of tissue factor (TF1-218; sTF) exhibits only 4% of the activity of wild-type transmembrane TF (TF1-263) in an assay that measures the conversion of factor X to Xa by the TF:VIIa complex. Further, the activity of sTF is manifest only when vesicles consisting of phosphatidylserine and phosphatidylcholine (30/70 w/w) are present. To determine whether the decreased activity results from weakened affinity of sTF for VIIa, we studied their interaction using equilibrium ultracentrifugation, fluorescence anisotropy, and an activity titration. Ultracentrifugation of the sTF:VIIa complex established a stoichiometry of 1:1 and an upper limit of 1 nM for the equilibrium dissociation constant (Kd). This value is in agreement with titrations of dansyl-D-Phe-L-Phe-Arg chloromethyl ketone active site labeled VIIa (DF-VIIa) with sTF using dansyl fluorescence anisotropy as the observable. Pressure dissociation experiments were used to obtain quantitative values for the binding interaction. These experiments indicate that the Kd for the interaction of sTF with DF-VIIa is 0.59 nM (25 degrees C). This value may be compared to a Kd of 7.3 pM obtained by the same method for the interaction of DF-VIIa with TF1-263 reconstituted into phosphatidylcholine vesicles. The molar volume change of association was found to be 63 and 117 mL mol-1 for the interaction of DF-VIIa with sTF and TF1-263, respectively. These binding data show that the sTF:VIIa complex is quantitatively and qualitatively different from the complex formed by TF1-263 and VIIa.

Amino Acid Chloromethyl Ketones↗
PubMed1992

Correlation of tryptophan fluorescence intensity decay parameters with 1H NMR-determined rotamer conformations: [tryptophan2]oxytocin.

While the fluorescence decay kinetics of tyrosine model compounds [Laws, W. R., Ross, J. B. A., Wyssbrod, H. R., Beechem, J. M., Brand, L., & Sutherland, J. C. (1986) Biochemistry 25, 599-607] and the tyrosine residue in oxytocin [Ross, J. B. A., Laws, W. R., Buku, A., Sutherland, J. C., & Wyssbrod, H. R. (1986) Biochemistry 25, 607-612] can be explained in terms of heterogeneity derived from the three ground-state chi 1 rotamers, a similar correlation has yet to be directly observed for a tryptophan residue. In addition, the asymmetric indole ring might also lead to heterogeneity from chi 2 rotations. In this paper, the time-resolved and steady-state fluorescence properties of [tryptophan2]oxytocin at pH 3 are presented and compared with 1H NMR results. According to the unrestricted analyses of individual fluorescence decay curves taken as a function of emission wavelength and a global analysis of these decay curves for common emission wavelength-independent decay constants, only three exponential terms are required. In addition, the preexponential weighting factors (amplitudes) have the same relative relationship (weights) as the 1H NMR-determined chi 1 rotamer populations of the indole side chain. 15N was used in heteronuclear coupling experiments to confirm the rotamer assignments. Inclusion of a linked function restricting the decay amplitudes to the chi 1 rotamer populations in the individual decay curve analyses and in the global analysis confirms this correlation. According to qualitative nuclear Overhauser data, there are two chi 2 populations. Depending upon the degree of correlation between chi 2 and chi 1, there may be from three to six side-chain conformations for the tryptophan residue. The combined fluorescence and NMR results are consistent with a rotamer model in which either (i) the chi 2 rotations are fast compared to the fluorescence intensity decay of the tryptophan residue, (ii) environmental factors affecting fluorescence intensity decay properties are dominated by chi 1 interactions, or (iii) the chi 2 and chi 1 rotations are highly correlated.

Amino Acid Sequence↗
PubMed1992

A therapeutic trial of the use of penicillin V or erythromycin with or without rifampin in the treatment of psoriasis.

BACKGROUND: After the publication of an uncontrolled trial of nine patients with streptococcus-associated psoriasis who appeared to benefit from a course of oral penicillin or erythromycin with the addition of rifampin in the last 5 days, we wished to confirm or refute the validity of this observation. OBJECTIVE: Our purpose was to confirm the effectiveness of antibiotics in the treatment of streptococcus-associated psoriasis. METHODS: Twenty patients were placed randomly into two groups. One group was given penicillin or erythromycin for 14 days with a placebo added during the last 5 of the 14 days. The other group received the same medication with the addition of rifampin in the last 5 days. RESULTS: Although all the patients studied met the criteria of the reported preliminary study, we were unable to detect any evidence of improvement in their psoriasis. CONCLUSION: There was no apparent benefit for patients with streptococcus-associated psoriasis from a course of oral penicillin or erythromycin with the addition of rifampin in the last 5 days in a 14-day trial.

Adolescent↗
PubMed1992

Dissecting folliculitis of the scalp. A case report of combined treatment using tissue expansion, radical excision, and isotretinoin.

Dissecting folliculitis of the scalp can develop into an extensive, hypertrophic scarred lesion that is unresponsive to routine treatment. In these situations, radical excision of the affected area and concurrent perioperative treatment with isotretinoin (13-cis-retinoic acid) may be effective. The authors describe a case, illustrating the successful clinical application of this technique.

Adult↗
PubMed1991

Expression of biologically active human corticosteroid binding globulin by insect cells: acquisition of function requires glycosylation and transport.

Human corticosteroid binding globulin (hCBG) is a 50- to 55-kDa serum glycoprotein that binds cortisol and progesterone with high affinity. To map the steroid-binding domain and to investigate the folding pathways of hCBG, we have established an expression system based on infection of insect cells with a recombinant baculovirus encoding hCBG. Infected Spodoptera frugiperda (Sf9) cells secrete immunoreactive hCBG at high levels (16-24 pmol per 10(6) cells per 40 h), and the recombinant protein binds cortisol with an affinity and specificity equivalent to that of human serum-derived hCBG. Thus, this system has the potential to provide large amounts of wild-type and mutant hCBGs for physical-chemical analysis. Cotranslational asparagine-linked glycosylation is essential for acquisition of steroid-binding capability, as shown by the lack of cortisol-binding activity of unglycosylated hCBG secreted in the presence of tunicamycin. Golgi-associated oligosaccharide processing, however, is not required for activity, as demonstrated by the endoglycosidase H susceptibility of the fully active, secreted glycoprotein. Comparison of the steroid-binding properties of intracellular and secreted hCBG with that synthesized in vitro in the rabbit reticulocyte lysate system suggests that this protein undergoes a maturation process during transport through the secretory pathway. This system will be useful for identifying the molecular determinants of biological function in hCBG.

Animals↗
PubMed1991

Electronic thermography in the assessment of internal derangement of the temporomandibular joint. A pilot study.

Current diagnostic imaging methods to evaluate internal derangement of the temporomandibular joint (TMJ) include arthrotomography, arthroscopy, computed tomography, and magnetic resonance imaging. Most of these techniques either require ionizing radiation or are invasive, and all are expensive. Electronic thermography (ET) is an alternative diagnostic imaging modality that is inexpensive, nonionizing, and noninvasive. The purpose of this pilot study was to assess ET in the diagnosis of internal derangements of the TMJ. The study population consisted of 11 patients with internal derangement, and 12 normal patients. ET was conducted with an infrared thermographic unit, at 1.0 degrees and 0.5 degrees C sensitivity. Results from subjective blinded interpretations by two experts for the diagnosis of internal derangement of the TMJ were as follows: sensitivity, 86% (+/- 7.8%); specificity, 78% (+/- 7.1%). Results from objective measurements of thermal symmetry of the TMJ region were as follows: normal subjects, 89.3% (+/- 3.0%); internal derangement patients, 66.1% (+/- 16.2%); t21 = -4.89, p less than 0.01. In conclusion, ET appears to have some promise as a diagnostic aid in the evaluation of internal derangement of the TMJ. Additional, more extensive studies are needed before thermographic diagnosis of internal derangement is accepted clinically.

Adult↗
PubMed1991

A 12-month treatment of severe psoriasis with acitretin: results of a Canadian open multicenter study.

Both etretinate and its principal metabolite, acitretin, are efficacious in the treatment of psoriasis. Because patients with severe psoriasis often require chronic therapy, this study was undertaken to determine the efficacy, tolerability, and safety of acitretin in patients on continuous treatment for 12 months. The initial daily dose of 50 mg was taken for 4 weeks. Thereafter the dose was increased or decreased by 10 mg at monthly intervals (10 to 70 mg) to produce the optimal response with minimal toxicity. Seventy percent of the patients who completed 12 months of treatment showed marked improvement. All patients experienced adverse reactions; dry lips, hair loss, skin peeling, pruritus, and nail disorders were the most frequent. Fourteen patients were withdrawn from the study because of one or more intolerable adverse reactions.

Acitretin↗
PubMed1990

Fluorescence investigation of the sex steroid binding protein of rabbit serum: steroid binding and subunit dissociation.

The relationship between steroid binding and protein subunit interactions of rabbit sex steroid binding protein (rSBP) has been studied by steady-state and time-resolved fluorescence spectroscopy. The high-affinity (Ka approximately 10(8) M-1 at 4 degrees C), fluorescent estrogen d-1,3,5(10),6,8-estrapentaene-3,17 beta-diol [dihydroequilenin (DHE)] was used as a fluorescent probe of the steroid-binding site. Perturbation of the binding site with guanidinium chloride (Gdm.Cl) was monitored by changes in the steady-state fluorescence anisotropy of DHE as well as by changes in fluorescence quenching of DHE with acrylamide. The results of acrylamide quenching at 11 degrees C show that, while between 0 and 1 M Gdm.Cl the steroid-binding site is completely shielded from bulk solvent, there is decreased DHE binding. To study the subunit-subunit interactions, rSBP was covalently labeled with dansyl chloride in the presence of saturating 5 alpha-dihydrotestosterone (DHT), which yielded a dansyl-conjugated protein that retained full steroid-binding activity. The protein subunit perturbation was monitored by changes in the steady-state fluorescence anisotropy of the dansyl group. At 11 degrees C, the dansyl anisotropy perturbation, reflecting changes in global and segmental motions of the dimer protein, occurs at concentrations of Gdm.Cl above 1 M. The Gdm.Cl titration in the presence of steroids with equilibrium association constants less than 10(8) M-1 shows a plateau near 3 M Gdm.Cl at 11 degrees C; at this Gdm.Cl concentration, no DHE is bound. No plateau is observed at 21 degrees C. At higher Gdm.Cl concentrations, the dansyl fluorescence anisotropy decreases further and shows no steroid dependence. Recovery of steroid-binding activity (assayed by saturation binding with [3H]DHT), under renaturation conditions, is dependent on both steroid concentration and affinity. Both unlabeled and dansyl-labeled protein recovery the same amount of activity, and according to fluorescence anisotropy, dansyl-labeled rSBP re-forms a dimer upon dilution below 1 M or removal of Gdm.Cl. From the steroid requirement for recovery of steroid-binding activity, it appears that a conformational template is required for the dimeric protein to re-form a steroid-binding site with native-like properties.

Animals↗
PubMed1990

Relief of the photosensitivity of erythropoietic protoporphyria by pyridoxine.

Twenty-five years ago the use of pyridoxine was described for the treatment of photosensitivity eruptions. We report two cases of erythropoietic protoporphyria, which were only moderately responsive to beta-carotene and sunscreens, whereas the use of pyridoxine has been associated with a marked reduction in photosensitivity without evidence of adverse effects. Regarding the mechanism of action, we can only speculate that pyridoxine could be mediated by increased endogenous nicotinamide production. We believe that our results warrant therapeutic trial of oral pyridoxine in patients with unrelieved photosensitivity as a result of erythropoietic protoporphyria.

Child↗
PubMed1989

Temporomandibular joint comparative imaging: diagnostic efficacy of arthroscopy compared to tomography and arthrography.

This comparative imaging study of the TMJ was conducted to examine the diagnostic data obtained from arthroscopy as compared to data from tomography and arthrography. Six joints from cadaver material were imaged by each technique and subsequently dissected. Each technique had value, but none was comprehensive. Tomography was the technique of choice for imaging osseous changes. Double joint space arthrotomography was useful for examining articular disk position and morphology. Diagnostic arthroscopy, through direct visualization of surface morphology, showed localized surface pathosis, such as synovitis; provided data on the location and size of disk perforations; and contributed reliably to a diagnosis of disk displacement on the basis of associated pathosis such as stretching of the posterior attachment.

Arthrography↗
PubMed1989

Phosphorescence maxima and triplet state lifetimes of NAD+ and epsilon-NAD+ in ternary complexes with horse liver alcohol dehydrogenase.

This paper describes the phosphorescence emission and decay times of NAD+ and its fluorescent etheno derivative, epsilon-NAD+, in the pyrazole ternary complex with horse liver alcohol dehydrogenase (ADH). We show that the epsilon-NAD+ triplet state, as well as the tryptophan triplet state, can be utilized to monitor the coenzyme-enzyme interaction. The decays of NAD+ and AMP are single exponential, and the lifetimes are the same within experimental error. The phosphorescence lifetimes, evaluated as single exponentials, are slightly shorter in epsilon-NAD+ than they are in epsilon-AMP. Whereas the decay of epsilon-AMP was adequately fit by a single exponential with a time constant of very close to 0.5 s, it was necessary to fit the decay of epsilon-NAD+ to a double exponential. Ternary complexes with NAD+ excited at 297 nm exhibit decay kinetics nearly identical to those of ADH by itself. On the other hand, when excitation of the epsilon-NAD+ ternary complex is provided at 313 nm, where there is very little absorption by either tryptophan residue, the decay law of the ternary complex is similar to that of epsilon-NAD+ in solution. Our results demonstrate that NAD+ and epsilon-NAD+ quench tryptophan phosphorescence in ADH. Normalizing the phosphorescence intensity to the 0-0 vibronic band assigned to Trp-15 (blue-edge), we calculate a 21% decrease in the phosphorescence associated with Trp-314 at stoichiometric saturation of the coenzyme binding sites with NAD+ in the ternary complex. When the active sites are saturated with epsilon-NAD+, the relative phosphorescence due to Trp-314 decreases by 63%.(ABSTRACT TRUNCATED AT 250 WORDS)

Alcohol Dehydrogenase↗
PubMed1989

The teaching of dermatology to Canadian undergraduates in the mid-1980s.

The Canadian Association of Professors of Dermatology (CAPD) has approved new goals, objectives, and a core curriculum for Canadian undergraduate dermatology teaching. This followed a survey by mailed questionnaire of the 16 Canadian medical schools. The previous core curriculum approved by the Canadian Dermatological Association (CDA) was modified and received additions. This paper draws attention to the prevalence of dermatology problems in clinical practice, shows the reported state of dermatology teaching in 16 Canadian schools in the mid-1980s, and tabulates goals, objectives, and a core curriculum.

Canada↗
PubMed1989

The intracapsular therapeutic modalities in conjunction with arthrography: case reports.

Manipulation and lavage of the temporomandibular joint has been shown to add an important therapeutic dimension to arthrography. These therapeutic modalities were prescribed by the primary treating practitioner in conjunction with diagnostic arthrography in a group of patients. The therapeutic modalities consisted of joint mobilization (Farrar manipulation or distraction) augmented by (1) increased hydraulic pressure in the superior compartment, or (2) with small amounts of contrast in both compartments, and/or (3) with lavage of the superior joint compartment. The therapeutic modalities were prescribed in association with the arthrography as a logical extension of the arthrographic technique. The result of the mobilization and lavage was an increase in the mandibular range of motion (ROM) and a decrease in pain in cases with adhesions as well as those with anteriorly displaced disks without reduction. Patients with anteriorly displaced disks with reduction, redundant tissue in the fossa, osteochondritis, and adhesive capsulitis also showed benefit, although patient populations treated with these conditions were small. There were no adverse sequelae. Manipulation and lavage should now be viewed as one more tool in the treatment of intracapsular pathology.

Adolescent↗