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Biomedical subjects

G R Parr

Publications and source records attributed to G R Parr.

At least 73 records · Page 4Linked to original sources
PubMed1985

Disease activity indexes in rheumatoid arthritis; a prospective, comparative study with thermography.

There are many difficulties associated with the assessment of disease activity in rheumatoid arthritis. Infrared thermography has been used to quantify joint inflammation. The heat distribution index (HDI) is reproducible, sensitive, quantifiable, and not subject to circadian variation or interobserver error. In this study the HDIs for both elbows, wrists, knees, and ankles were summated and compared with other parameters of disease activity. There were 167 sets of observations in 20 patients with classical, seropositive, rheumatoid arthritis followed up over 12 months. There was a significant correlation (p less than 0.001) for thermography with the Ritchie articular index, Mallya score, grip strength, morning stiffness, erythrocyte sedimentation rate, and pain score. Significant correlations (p less than 0.05) for thermography with these parameters were found in individual patients. The summated HDI is a suitable, objective method for the assessment of response to therapy in patients with rheumatoid arthritis.

Adult↗
PubMed1984

The diagnosis of stress fractures in athletes.

Eighteen patients with shin pain that was clinically considered to be caused by a stress fracture of the tibia or fibula underwent radiological, thermographic, and scintigraphic studies and a test of ultrasound-induced pain. When initially seen, 15 had stress fractures confirmed by scintigraphy. Of these, 12 had abnormal thermograms, eight had positive test results for ultrasound-induced pain, and seven had abnormal radiographs. Thermography used alone seemed to be a safe, rapid means of diagnosis for stress fractures in the tibia or fibula and was not found to be related to symptom duration. In the radiologically normal group of stress fractures, four (50%) had positive test results for ultrasound stress tests and normal thermograms. The combination of these two tests should provide an early method of detecting stress fractures in the tibia and fibula, thereby avoiding scintiscans in some athletes.

Adolescent↗
PubMed1984

Preparation and properties of nickel hemoglobin.

Hemoglobin A reconstituted with nickel protoporphyrin IX (NiHbA) has been prepared and characterized. Kinetics of its reaction with p-mercuribenzoate and with haptoglobin, absorption and circular dichroism spectra, and x-ray crystallographic properties have been investigated as probes of its structural conformation. The results suggest that NiHbA exists in a structure that is similar to the deoxy, or T-state of HbA. It is proposed that NiHbA and its derivatives may serve as a useful model for future studies of hemoglobin allosteric changes.

Crystallization↗
PubMed1983

Evidence of a compact structure for kinetic intermediates in the folding of a fragment complex of tuna cytochrome c.

A noncovalently bound, ordered complex consisting of fragments (1-25)H and (14-103) derived from tuna cytochrome c has been prepared and characterized. The equilibrium properties of this complex are indistinguishable from those of the corresponding complex, (1-25)H X (23-104), of horse cytochrome c. The tuna species possesses a second tryptophan residue (at position 33 of the amino acid sequence and replacing the histidine residue of the horse protein) whose fluorescence is also essentially fully quenched in the native form and in the complex. It is found that for the tuna complex, the fluorescence of both tryptophans is fully quenched during the second order phase of the reaction mechanism. This provides evidence for the compact nature of the intermediate complexes formed at this stage of the complementation process (Parr, G. R., and Taniuchi, H. (1982) J. Biol. Chem. 257, 10103-10111). The observed second order rate constant for the tuna fragments is reduced by a factor of two from that for the horse fragments. During the first order kinetic phase corresponding to the transition from the intermediate complexes to the native complex, qualitative as well as quantitative differences are also observed between the tuna and the horse species. The kinetics of complementation of the "hybrid" complexes is also reported. This exchangeability of both the heme fragment and the apofragment of the complex between these two species indicates close similarity of the folding mechanism. Nonetheless, the results also serve to highlight the subtle effects exerted on the folding process by a relatively small number of changes (17%) in the amino acid sequence.

Amino Acid Sequence↗
PubMed1981

Ordered complexes of cytochrome c fragments. Kinetics of formation of the reduced (ferrous) forms.

The kinetics of formation of noncovalently bound ferrous complexes derived from fragments of horse heart cytochrome c have been investigated. When the reactions are initiated by combining ferrous heme fragments with an appropriate apofragment, in the presence of 50 mM imidazole, second order rate processes are observed with rate constants essentially the same as those reported with ferric heme fragments (Parr, G. R., and Taniuchi, H. (1979) J. Biol. Chem. 254, 4836-4842). An additional, probably consecutive, kinetic process is also demonstrated. If imidazole is not present in the reaction buffer, the kinetic profiles are dramatically altered. While this is partially due to aggregation (dimerization) of the ferrous heme fragments, it can nevertheless be demonstrated that the complementation reactions with apofragments are much faster than those observed with the corresponding ferric heme fragments (in the absence of imidazole). These results reflect the effect of the oxidation state of the heme iron on the folding mechanism and, thus, the manifold nature of protein folding pathways. The rate of reduction of productive ferric complexes by sodium ascorbate was investigated and biphasic reactions were found in all cases. The data indicate an equilibrium between two forms of the ferric complexes. The results of an experiment in which the complementation of ferric (1-25)H and (23-104) was carried out in the presence of sodium ascorbate indicate that the intermediate complex (Parr, G. R., and Taniuchi, H. (1980) J. Biol. Chem. 255, 8914-8918) is not reducible by ascorbate. Thus, the increase in oxidation-reduction potential occurring on formation of the productive complex from the unbound heme fragment occurs at a late stage of the overall reaction, possibly coinciding with ligation of methionine 80 to the heme iron.

Animals↗
PubMed1981

Maxillofacial prosthetic principles in the surgical planning for facial defects.

In many localities, particularly in larger medical centers, presurgical communication and planning is increasing because the prosthodontist is becoming a more active member of the oncology, trauma, and cleft palate teams. Individuals involved both directly or indirectly in maxillofacial prosthetic therapy should be cognizant of the situations and solutions discussed in this article. In this way the prosthodontist and surgeon will be able to provide a better consultancy and rehabilitation service for their patients.

Ear, External↗
PubMed1980

Kinetic intermediates in the formation of ordered complexes from cytochrome c fragments. Evidence that methionine ligation is a late event in the folding process.

The reactions of ferric heme-containing fragments with apofragments to form ordered complexes resembling native horse heart cytochrome c have been studied under conditions which resolve the overall process into consecutive second order and first order kinetic steps. In the initial, second order step the two fragments combine to form an intermediate complex which exhibits tryptophan 59 fluorescence quenching similar to native cytochrome c, but which has not yet achieved the native ligation state of the heme iron. The existence of first order processes following the second order step is demonstrated by absorbance changes in the Soret region. the entire absorbance change at 695 nm, relating to ligation of the sulfur atom of methionine 80 to the heme iron, is also associated with these first order processes. Thus, ligation of methionine is a late event in this self ordering of the polypeptide chains. Since the conformational energy is assumed to distinctly decrease in this late process of folding (Parr, G.R., and Taniuchi, H. (1980) J. Biol. Chem. 255, 2616-2623), it would follow that small spatial rearrangements of the polypeptide chains in the late stage of folding (as manifested by the ligation of methionine) are associated with a specific decrease in energy.

Animals↗
PubMed1979

A kinetic study of the folding of nuclease B, a possible precursor of staphylococcal nuclease A.

Nuclease B, which contains an additional flexible amino acid sequence of 19 amino acid residues bound to the NH2-terminus of nuclease A, an extracellular nuclease of Staphylococcus aureus, has been investigated in order to determine the influence of the extra residues on the refolding of the nuclease A portion from the acid denaturated state by monitoring the change in tryptophan fluorescence using a stopped-flow technique. It was found that the kinetic parameters of this refolding is similar within experimental error for nuclease A and nuclease B for the entire course (up to 40 s) studied. Therefore, the extra residues do not appear to have any detectable effect on the dynamic events involved in the refolding process. Thus, the folding of the nuclease A portion of nuclease B appears to be thermodynamically and kinetically independent of the 19 residues at the amino-terminus.

Amino Acid Sequence↗
PubMed1979

A combination obturator.

A combination of flexible and rigid extensions can be used on a prosthesis to provide stability, retention, decreased weight, and obturation of residual palatal defects. The combination extensions present a design of a maxillofacial prosthesis which takes maximum advantage of the patient's remaining anatomy.

Acrylic Resins↗