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Biomedical subjects

R A Cox

Publications and source records attributed to R A Cox.

At least 145 records · Page 8Linked to original sources
PubMed1981

Reconstruction of the smaller subparticle of rabbit ribosomes from core-particle and split-protein fractions.

The smaller subparticle of rabbit reticulocyte ribosomes was shown to yield core-particle and split-protein fractions on treatment with 2.5 M-NH4Cl/61 mM-MgCl2. The core-particle fraction was inactive in poly(U)-directed polyphenylalanine synthesis, but activity was restored after recombination with the split-protein fraction. Optimum ionic conditions for the reconstruction of active subparticles were found to be 0.75 M-NH4Cl/19 mM-MgCl2 at 0 degrees C. Improved extents of reconstruction were obtained when the core-particles were isolated by methods that avoided pelleting. Core-particles isolated from subparticles pretreated with either proteinases or ribonucleases had diminished capacity to become re-activated.

Animals↗
PubMed1981

The nucleotide sequence at the 3'-end of Neurospora crassa 25S-rRNA and the location of a 5.8S-rRNA binding site.

The sequence of 110 nucleotides adjacent to the 3'-end of Neurospora crassa 25S-rRNA has been derived by chemical sequencing methods. Sequences present between 40 and 85 nucleotides of the 3'-end were found to complement sequences at the 3'- and 5'-ends of 5.8S-rRNA. Interaction was shown to occur between 5.8S-rRNA and a specific 3'-terminal fragment of 85 nucleotides derived from 25S-rRNA. We have also demonstrated that the nucleotide sequence at the 3'-end of N. crassa 5.8S-rRNA (-UCAUUOH) is different from the published sequence (-UUUUOH) which was derived from rDNA.

Base Sequence↗
PubMed1981

Empyema of the gallbladder: a complication in the natural history of acute cholecystitis.

Empyema of the gallbladder was identified in 34 patients. Patients undergoing early operation without attempts at nonoperative treatment had less infectious morbidity and mortality. Delayed operative intervention, extrabiliary abscess, perforation of the gallbladder and common duct exploration are factors that contribute to increased risks in these patients.

Abscess↗
PubMed1981

Gangrene of the gallbladder: a complication of acute cholecystitis.

Eighteen cases of gangrenous cholecystitis were reviewed to better define causes of morbidity and mortality. All patients in the series presented with signs and symptoms of acute cholecystitis. Cholecystectomy was done as an emergency procedure in 12 patients, while in six patients cholecystectomy followed a failure of nonoperative therapy. Gangrenous cholecystitis in this series was commonly associated with empyema and perforation of the gallbladder. Three of six patients having cholecystectomy after failure of nonoperative treatment died, while only one of 12 patients with immediate cholecystectomy died. This series illustrates that gangrenous cholecystitis usually presents with a clinical picture identical to that of acute cholecystitis. Early operation in the natural history of acute cholecystitis should reduce the frequency as well as the morbidity and mortality of gangrenous cholecystitis.

Acute Disease↗
PubMed1981

Course of coccidioidomycosis in intratracheally infected guinea pigs.

Two hundred Hartley-inbred guinea pigs were infected intratracheally with 50 viable arthrospores of Coccidioides immitis. At weeks 1 through 10 postinfection, groups of 20 guinea pigs were assayed for skin test, macrophage migration inhibitory factor (MIF), and lymphocyte transformation (LT) responses to coccidioidin. Forty-eight hours after skin testing and just before MIF and LT assays, blood was obtained for complement-fixing (CF) antibody titers and the animals were autopsied to assess the extent of fungal dissemination. Immunological assays established that skin tests and MIF responses converted within 3 weeks of infection. LT responses were not demonstrable until week 5. Dissemination of C. immitis to the liver or spleen was an early event, with 21% of guinea pigs positive by week 2 and 70% positive by week 5. CF antibody titers were demonstrable at week 5, increased logarithmically through week 7, then increased at a slower rate thereafter. Concomitant with the decreased rate of antibody production, guinea pigs began to clear C. immitis from their extrapulmonary tissues. Skin test responses peaked at 6 weeks postinfection when CF antibody titers were less than or equal to 1:16 and then plateaued with increased CF titers. Although this overall immunological profile is consistent with the disease in humans, there was not a direct correlation between CF antibody titer and dissemination to the liver or spleen, nor was there an inverse correlation between CF antibody titers and skin test or MIF responses. Rather, CF antibody titers and cell-mediated immune responses were equally demonstrable in guinea pigs with disseminated or nondisseminated disease.

Animals↗
PubMed1981

Comparisons of mycelia- and spherule-derived antigens in cellular immune assays of Coccidioides immitis-infected guinea pigs.

The biological activities of four Coccidioides antigens were compared in skin test, macrophage migration inhibitory factor (MIF), and lymphocyte transformation (LT) assays fo 137 Coccidioides-infected and 20 noninfected guinea pigs. Antigens included: C-ASWS-M, the alkali-soluble, water-soluble cell wall extract from mycelia of C. immitis; C-ASWS-S, the alkali-soluble, water-soluble cell wall extract from spherules; CDN-TS, a toluene-induced lysate of C. immitis mycelia; and spherulin, an autolysate obtained from spherules. CDN-TS proved significantly more reactive (P less than 0.0001) in skin tests, eliciting a mean induration of 11.6 mm as compared with indurations of 6.6, 6.4, and 6.1 mm obtained with C-ASWS-S spherulin, and C-ASWS-M, respectively. CDN-TS, C-ASWS-S, and spherulin were equally reactive in MIF assays and elicited migration inhibitions of 31.8, 30.8, and 30.7%. C-ASWS-M was significantly less reactive (P less than 0.001), with a mean response of 23.5%. The highest level of activity in LT assays was obtained with C-ASWS-S with a mean response of 5,636 delta cpm as compared with responses of 3,624, 3,439, and 3,580 delta cpm with CDN-TS, spherulin, and C-ASWS-M, respectively (P less than 0.01). All antigens were effective in distinguishing responses of infected versus noninfected guinea pigs.

Animals↗
PubMed1981

Lymphocyte transformation assays as a diagnostic tool in tuberculosis in children.

Lymphocyte transformation (LT) assays were evaluated as a diagnostic aid in tuberculosis of children. Skin tests and LT assays were performed in 6 children with culture-proved tuberculosis (Group I), 32 children suspected of having tuberculosis (Group II), and 20 healthy children (Group III). Five of 6 children in Group I, 16 of 32 in Group II, and 8 of 20 in Group III had positive skin test reactions to PPD. The correlation between skin test reactivity and LT responses to PPD was highly significant (p less than 0.0001). Four (80%), 14 (88%), and 6 (75%) of the 29 subjects with positive skin test reactions in Groups I, II, and III showed a significant LT response to PPD. Only 2 (13%) of 16 tuberculosis suspects with negative skin test reactions in Group II exhibited an LT response to PPD. One (8%) of 12 healthy children with negative skin test reactions had a positive reaction in LT assays. All but 4 (7%) of 58 children in Groups I, II, and III were skin test reactive to PPD and/or 1 or more of 5 nonmycobacterial antigens. One (2% of 58) of these failed to exhibit an LT response to nonmycobacterial antigens. The strong correlation between LT responses and skin test reactivity to PPD and our finding that only 2 of 16 tuberculosis suspects had positive reactions in LT assays in the absence of PPD skin test reactivity argues against the likelihood that LT assays will prove useful in the diagnosis of this disease.

Antigens↗
PubMed1981

Serodiagnosis of tuberculosis by radioimmunoassay.

Mycobacteria antigens derived from whole cells and cell walls of M. tuberculosis and M. bovis (BCG) and soluble purified protein derivative (PPD) prepared from M. tuberculosis were used in solid phase radioimmunoassays to measure the amount of reactive IgG antibody in serums from 54 patients with active (culture-positive) tuberculosis (Group I), 6 patients with inactive (culture-negative) tuberculosis (Group II), 15 healthy subjects who were skin test positive to PPD (Group III), and 30 healthy persons who were PPD skin test negative (Group IV). Patients with active tuberculosis had statistically larger (p less than 0.001) amounts of IgG antibody to M. tuberculosis whole cells, cell walls, and PPD and to BCG whole cells and cell walls when compared with the amount of antibody in serums from healthy subjects who were PPD skin test negative. However, no significant differences were detected in the mean antibody response or frequency of positive antibody responses between patients with active disease and those in clinical remission. Moreover, significant amounts of antibody were detected in 7 to 20% of healthy, tuberculin-reactive subjects. On the basis of these results, it is unlikely that antibody assays alone will prove useful in the diagnosis of this disease.

Adult↗
PubMed1980

Resistance of the peptidyltransferase centre of rabbit ribosomes to attack by nucleases and proteinases.

Larger ribosomal subparticles (L-subparticles) of rabbit ribosomes were treated with either ribonucleases (I or T1) or proteinases (trypsin or chymotrypsin), and their capacity to function in poly(U)-directed polyphenylalanine synthesis and in the puromycin reaction was investigated. The effects of pretreatment of L-subparticles on the reconstruction of active subparticles from core-particles derived by treatment with 2.75 M-NH4Cl/69 mM-MgCl2 and split-protein fractions were also examined. The protein moiety of proteinase-treated L-subparticles was analysed by one-dimensional sodium dodecyl sulphate/polyacrylamide- and two-dimensional polyacrylamide-gel electrophoresis. The introduction of 16--100 scissions in the RNA moiety had no effect on the activity of the L-subparticles in polyphenylalanine synthesis, and there was no effect on the stability of L-subparticles to high-salt shock treatment and a marginal effect on the reconstruction of L-subparticles from high-salt-shock core-particles and split-protein fractions. In contrast, L-subparticles treated with low amounts of trypsin (0.56 ng of trypsin/microgram of L-subparticle) were inactive in polyphenylalanine synthesis, and their capacity to function in partial-reconstruction experiments was diminished. Activity in the puromycin reaction was increased by 70% as a result of trypsin treatment (280 ng of trypsin/microgram of L-subparticle). At least two of the acidic proteins implicated in the translocation function were not affected by trypsin treatment. Trypsin-treated L-subparticles had lost their capacity to bind the smaller ribosomal subparticle (S-subparticle). The protein(s) needed for S-subparticle binding were shown to be present in high-salt-shock cores. At least six proteins associated with the core-particles were attack during trypsin treatment of L-subparticles. An examination of L-subparticles isolated from trypsin-treated polyribosomes showed that the amount of trypsin necessary to decrease the activity of the subparticle by 50% was about twice that needed in the treatment of L-subparticles alone. The largest protein of rabbit L-subparticles (approx. 51 000 daltons) was cleaved in a stepwise fashion by trypsin to fragments of approx. 40 000 daltons. This protein was also cleaved by chymotrypsin.

Acyltransferases↗
PubMed1980

N6-Trimethyl-lysine metabolism. 3-Hydroxy-N6-trimethyl-lysine and carnitine biosynthesis.

Rats injected with N6-[Me-3H]trimethyl-lysine excrete in the urine five radioactively labelled metabolites. Two of these identified metabolites are carnitine and 4-trimethylammoniobutyrate. A third metabolite, identified as 5-trimethylammoniopentanoate, is not an intermediate in the biosynthesis of carnitine; the fourth and major metabolite, N2-acetyl-N6-trimethyl-lysine, is not a precursor of carnitine. The remaining metabolite (3-hydroxy-N6-trimethyl-lysine) is converted into trimethylammoniobutyrate and carnitine by rat liver slices and into trimethylammoniobutyrate by rat kidney slices. In rat liver and kidney-slice experiments, radioactivity from DL-N6-trimethyl-[1-14C]lysine and DL-N6-trimethyl-[2-14C]lysine was incorporated into N2-acetyl-N6-trimethyl-lysine and 3-hydroxy-N6-trimethyl-lysine, but not into trimethylammoniobutyrate or carnitine. A procedure was devised to purify milligram quantities of 3-hydroxy-N6-trimethyl-lysine from the urine of rats injected chronically with N6-trimethyl-lysine (100 mg/kg body wt. per day). The structure of 3-hydroxy-N6-trimethyl-lysine was confirmed chemically and by nuclear-magnetic-resonance spectrometry [Novak, Swift & Hoppel (1980) Biochem. J. 188, 521--527]. The sequence for carnitine biosynthesis in liver is: N6-trimethyl-lysine leads to 3-hydryxy-N6-trimethyl-lysine leads to leads to 4-trimethylammoniobutyrate leads to carnitine.

Animals↗
PubMed1980

Distribution of sequences common to the 25--28S-ribonucleic acid genes of Xenopus laevis and Neurospora crassa.

The extent of homology between the nucleotide sequence of L-rRNA (the major RNA component of the larger ribosomal subparticle) of a lower eukaryote (Neurospora crassa) and an amphibian (Xenopus laevis) was investigated by utilizing rDNA (DNA coding for rRNA) of X. laevis cloned in plasmids pMB9 and pML2, and rDNA of N. crassa cloned in bacteriophage lambda. Hybridization studies revealed that sequences common to both N. crassa and X. laevis L-rRNA comprise a total of approx. 1050 /+- 200 nucleotides. The thermal stability of the X. laevis rDNA.N. crassa L-rRNA hybrid was 5 degrees C lower than that of the X. laevis rDNA.X. laevis L-rRNA duplex, indicating the presence of fewer than 10% mismatches in homologous sequences. X. laevis rDNA was analysed by means of restriction endonucleases and hybridization with 125I-labelled N. crassa L-rRNA. Most (at least 95%) of the conserved sequences were present in a 3000-base-pair fragment produced by restriction with endonucleases HindIII and BamHI. This fragment, which includes the 3'-OH terminus of the L-rRNA-coding region, was used as an adaptor in the construction of a bacteriophage-lambda recombinant. One section of the recombinant phage terminating in a HindIII-specific site was obtained from bacteriophage lambda plac5 (after restriction with endonuclease HindIII). A second section terminating in a BamHi-specific site was obtained from bacteriophage lambda 540 (after restriction with endonuclease BamHI). These two parts were joined by means of the X. laevis rDNA fragment. Further analysis of cloned rDNA by means of restriction endonucleases confirmed that conserved sequences were widely distributed throughout the 3000-base-pair fragment produced by HindIII and BamHi endonucleases. A 3400-base-pair fragment of N. crassa rDNA cloned in a bacteriophage lambda [Cox & Peden (1979) Mol. Gen. Genet. 174, 17--24] was restricted with endonucleases. The products were hybridized with 125I-labelled X. laevis L-rRNA. Conserved sequences were shown to be distributed over a range of approx. 1600--2700 base-pairs. Hence, in neither X. laevis nor N. crassa L-rRNA can be conserved sequences from a single block; instead regions of high and low (or no) homology must be intermingled. Both N. crassa rDNA and X. laevis rDNA were found to hybridize with Drosophila melanogaster L-rDNA sequences. Those rDNA fragments with sequences common to X. laevis and N. crassa L-rRNA also hybridized with D. melanogaster L-rRNA probe. Thus the same set of conserved sequences may be present in all three species.

Animals↗
PubMed1980

Protein synthesis by hybrid ribosomes reconstructed from rabbit reticulocyte ribosomal core-particles and amphibian or fungal split-proteins.

It was shown that high-salt (2.75 M-NH4Cl/69mM-MgCl2) shock treatment at 0 degrees C of the larger subparticles (L-subparticles) of rabbit, Xenopus laevis and Neurospora crassa cytoplasmic ribosomes yielded split-protein fractions that were not only functionally equivalent but also interchangeable. Thus, although the remaining core-particles were inactive in both the puromycin reaction and in poly(U)-directed polyphenylalanine synthesis, activity was restored when they were combined with either homologous or heterologous split-protein fractions. This technique was used to prepare active hybrid L-subparticles, e.g. rabbit cores/N. crassa split-proteins, and also active hybrid ribosomes, e.g. rabbit smaller subparticle/X. laevis core-particle/rabbit split-proteins. Rabbit and X. laevis split-protein fractions labelled with 14C by reductive methylation with [14C]formaldehyde and sodium cyanoborohydride were both shown to bind to rabbit core-particles in approximate correlation with the degree of re-activation. The split-protein fractions of rabbit and X. laevis L-subparticles were analysed by two-dimensional and sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. The molecular weights (measured in sodium dodecyl sulphate gels) of the split-proteins of rabbit and X. laevis L-subparticles were found to be similar. These results demonstrate that the peptidyltransferase active centre of cytoplasmic ribosomes of eukaryotes has components that are interchangeable over a wide evolutionary range. Evidently the essential molecular architecture of the active centre is highly conserved.

Animals↗
PubMed1980

Massive pulmonary embolism associated with a right ventricular myxoma.

A 12 year old boy had a massive pulmonary embolism associated with a right ventricular myxoma. This caused complete occlusion of the main trunk of the left pulmonary artery and of a branch of the right pulmonary artery supplying the basal area of the lower lobe of the right lung. The patient died despite two surgical attempts to remove the tumor clots. To our knowledge this constitutes the first report of a massive pulmonary artery embolism associated with a right ventricular myxoma.

Child↗
PubMed1980

Immunoglobulin E in histoplasmosis.

Immunoglobulin M, G, A, and E serum levels were quantitated in 20 patients with active histoplasmosis (group I), 24 healthy subjects who were skin test positive to histoplasmin (group II), and 47 healthy persons who were skin test negative to histoplasmin (group III). The results established that patients with this disease have increased immunoglobulin G (P less than 0.05), immunoglobulin A (P less than 0.001), and immunoglobulin E (P less than 0.01) serum levels when compared with the 71 healthy subjects in groups II and III.

Acute Disease↗
PubMed1980

Circulating immune complexes in coccidioidomycosis. Detection and characterization.

Sera of 22 patients with active and 13 with inactive coccidioidomycosis, as well as 15 healthy subjects who were skin-test positive to coccidioidin and 39 healthy subjects who were coccidioidin skin-test negative, were assayed for immune complexes. Circulating immune complexes were measured by the Clq-binding assay, the Clq-solid phase assay, the monoclonal rheumatoid factor inhibition assay, and the monoclonal rheumatoid factor solid phase assay. An increased concentration of circulating immune complexes was detected in 73% of those with active disease by at least one assay compared with 13% of the healthy controls. Significantly increased levels of immune complexes were detected in sera of patients with active coccidioidomycosis by the Clq-binding assay (P < 0.001), the Clq-solid phase assay (P < 0.001), the monoclonal rheumatoid factor inhibition assay (P < 0.005), and the monoclonal rheumatoid solid phase assay (P < 0.05) compared with the results obtained in the 54 healthy subjects. In contrast, those with inactive disease did not show significantly increased concentrations of circulating immune complexes. Sucrose density gradient ultracentrifugation of patients' sera established that the immune complexes were of intermediate size, sedimenting between the 6.6S and 19S markers. Immune complexes were shown to contain both coccidioidin antigen and anticoccidioidin antibody. In addition, a radioimmunoassay was developed to quantitate coccidioidin antigen-containing immune complexes. The latter assay proved highly sensitive in detecting immune complexes in patients with active coccidioidomycosis.

Antibodies, Fungal↗