Search PubMed⌕ Search

Biomedical subjects

J King

Publications and source records attributed to J King.

At least 271 records · Page 15Linked to original sources
PubMed1990

A comparative analysis of Ender's-rod and compression screw and side plate fixation of intertrochanteric fractures of the hip.

The purpose of this study is to compare the results of compression screw fixation and Ender's rods in the treatment of intertrochanteric fractures of the hip. A retrospective analysis of 77 cases of both unstable and stable cases of intertrochanteric fractures showed a higher incidence of complications in the Ender's group; these included backing out, distal femur fracture, need for a secondary procedure, external rotation deformity, and knee pain. Indications for the use of Ender's rods may be found among patients with burns, soft-tissue injuries of the proximal thigh, and patients refusing blood transfusions. Wiring of the distal ends of Ender's rods prevents backing out of the rods. Dacron tape has also been successfully used to prevent the distal ends of the rods from backing out in the last six of the 77 cases. The compression hip screw is a preferred treatment of choice in both stable and unstable intertrochanteric fractures.

Aged↗
PubMed1989

Prospective randomised controlled trial of methods of call and recall for cervical cytology screening.

OBJECTIVE: To discover whether systematic methods of call and recall are more effective than a non-systematic method and to see which of the two systematic methods was more effective. DESIGN: Prospective randomised controlled trial over a year. SETTING: One group general practice. PATIENTS: 416 Women over 35 eligible for a smear test who had never had a cervical smear test or in whom a smear test was overdue (previous test more than five years before). INTERVENTIONS: One group received written invitations to have a smear taken. The second group had their notes tagged so that the doctor would remind them (when they attended for another reason) to have a smear test. No special intervention was made in the third group. MAIN OUTCOME MEASURE: Performance of a cervical smear test during the year of the study. RESULTS: 32% (45/140) of the screened group, 27% (39/142) of the tagged group, and 15% (20/134) of the control group had a smear test during the year. The percentage of women having a smear test in the screened group was not significantly different from that in the tagged group, but the percentages in the two groups were significantly different from that in the control group. Whether a woman had had a previous smear test significantly affected the uptake of the invitation to have a smear test independently of the method of invitation. CONCLUSIONS: The systematic methods of call and recall were more effective than a non-systematic method. There was no significant difference between the two systematic methods (sending letters or tagging the notes) at one year.

Adult↗
PubMed1989

Reconstitution of the thermostable trimeric phage P22 tailspike protein from denatured chains in vitro.

Intermediates in the intracellular chain folding and association pathway of the P22 tailspike endorhamnosidase have been identified previously by physiological and genetic methods. Conditions have now been found for the in vitro refolding of this large (Mr = 215,000) oligomeric protein. Purified Salmonella phage P22 tailspikes, while very stable to urea in neutral solution, were dissociated by moderate concentrations of urea at acidic pH. The tailspike protein was denatured to unfolded polypeptide chains in 6 M urea, pH 3, as disclosed by analytical ultracentrifugation, fluorescence, and circular dichroism. Upon dilution into neutral buffer at 10 degrees C, the polypeptides fold spontaneously and associate to form trimeric tailspikes with high yield. Like native phage P22 tailspikes, the reconstitution product is resistant to denaturation by dodecyl sulfate in the cold and displays endorhamnosidase activity. Sedimentation coefficients, electrophoretic mobility, and fluorescence emission maxima of native and reconstituted tailspikes are identical within experimental error. By characterization of intermediates, localization of temperature-sensitive steps, and analysis of the effect of previously identified folding mutations, the reconstitution system described should allow comparison of in vivo and in vitro folding pathways of this large protein oligomer.

Electrophoresis, Polyacrylamide Gel↗
PubMed1989

Thermostability of temperature-sensitive folding mutants of the P22 tailspike protein.

Temperature-sensitive folding mutations (tsf) of the thermostable P22 tailspike protein prevent the mutant polypeptide chain from reaching the native state at the higher end of the temperature range of bacterial growth (37-42 degrees C). At lower temperatures the mutant polypeptide chains fold and associate into native proteins. The melting temperatures of the purified native forms of seven different tsf mutant proteins have been determined by differential scanning calorimetry. Under conditions in which the wild type protein had a melting temperature of 88.4 degrees C, the melting temperatures of the mutant proteins were all above 82 degrees C, more than 40 degrees C higher than the temperature for expression of the folding defect. Because the folding defects were observed in vivo, the thermostability of the native protein was also examined with infected cells. Once matured at 28 degrees C, intracellular tsf mutant tailspikes remained native when the cells were transferred to 42 degrees C, a temperature that prevents newly synthesized tsf chains from folding correctly. These results confirm that the failure of tsf polypeptide chains to reach their native state is not due to a lowered stability of the native state. Such mutants differ from the class of ts mutations which render the native state thermolabile. The intracellular folding defects must reflect decreased stabilities of folding intermediates or alteration in the off-pathway steps leading to aggregation and inclusion body formation. These results indicate that the stability of a native protein within the cells is not sufficient to insure the successful folding of the newly synthesized chains into the native state.

Amino Acids↗
PubMed1989

Unstable mitochondrial DNA in natural-death nuclear mutants of Neurospora crassa.

The natural-death mutant of Neurospora crassa has an accelerated senescence phenotype caused by a recessive mutation, nd, in a nuclear gene that is located in linkage group I. An examination of mitochondrial functions, however, revealed that the mutant has phenotypic and molecular defects similar to those commonly associated with maternally transmitted fungal senescence syndromes, including (i) deficiencies in cytochromes aa3 and b; (ii) a deficit in small subunits of mitochondrial ribosomes, and hence defective mitochondrial protein synthesis; and (iii) accumulation of gross rearrangements, including large deletions, in the mitochondrial chromosome of vegetatively propagated cells. These traits indicate that the nd+ allele codes for a function that is essential for stable maintenance of the mitochondrial chromosome, possibly a protein involved in replication, repair, or recombination.

Cell Survival↗
PubMed1989

Vertebral bone density in Scheuermann disease.

The densities of the trabecular bone of two or three lumbar vertebral bodies in twenty adolescents, twelve to eighteen years old, who had Scheuermann disease were measured by quantitative computed tomography. These densities were then compared with those for the same vertebrae of twenty age, sex, and race-matched adolescents who were examined by computed tomography because of trauma. The same scanner and phantom were used in all examinations. Both the adolescents who had Scheuermann disease and the control patients were in good health before the quantitative computed-tomography examination and had not been taking any medications. The density of the trabecular bone density in the patients who had Scheuermann disease was not significantly different (p = 0.28) from that in the controls. There also were no significant differences between the patients and the controls with regard to height, weight, surface area, or body-mass index.

Adolescent↗
PubMed1988

Nature and distribution of sites of temperature-sensitive folding mutations in the gene for the P22 tailspike polypeptide chain.

Temperature-sensitive folding (tsf) mutations in gene 9 of bacteriophage P22 interfere with the folding and association of the tailspike polypeptide chain at restrictive temperature. We report here the location and amino acid substitutions for 24 independent tsf mutants. The distribution of these and previously identified mutations is distinctly non-random; all of the 32 unambiguous sites of tsf mutations are located in the central 350 residues of the 666 residue tailspike polypeptide chain. No ts mutation has been found among the N-terminal 140 amino acids, and none among the C-terminal 170 amino acids. Since the physiological defect in these mutants is the destabilization of an early intermediate in the folding pathway, the localization of the mutants suggests that the central region of the chain is critical for formation or stabilization of this early intermediate. The majority of amino acids that served as sites for the tsf mutations were hydrophilic residues. Sixty percent of the replacements of these residues represented charge changes. This probably reflects the selection for mutant sites at the mature protein surface where the substitutions can be best tolerated without interfering with function. None of the sites of tsf mutations were at aromatic residues, and only one proline site was found. Substitutions at these residues may cause lethal folding defects which are not recovered as tsf mutants. The local sequences at tsf sites resemble those reported for turns. Structural studies identify beta-sheet as the dominant secondary structure. These mutations may disrupt the formation of conformational features of beta-sheets which are repeated, such as turns, associations between pairs of strands, or sheet/sheet packing interactions. Such a model accounts for the occurrence of tsf mutations with similar defective phenotypes at multiple positions along the chain.

Amino Acids↗
PubMed1988

Scaffolding protein regulates the polymerization of P22 coat subunits into icosahedral shells in vitro.

Coat and scaffolding subunits derived from P22 procapsids have been purified in forms that co-assemble rapidly and efficiently into icosahedral shells in vitro under native conditions. The half-time for this reaction is approximately five minutes at 21 degrees C. The in vitro reaction exhibits the regulated features observed in vivo. Neither coat nor scaffolding subunits alone self-assemble into large structures. Upon mixing the subunits together they polymerize into procapsid-like shells with the in vivo coat and scaffolding protein composition. The subunits in the purified coat protein preparations are monomeric. The scaffolding subunits appear to be monomeric or dimeric. These results confirm that P22 procapsid formation does not proceed through the assembly of a core of scaffolding, which then organizes the coat, but requires copolymerization of coat and scaffolding. To explore the mechanisms of the control of polymerization, shell assembly was examined as a function of the input ratio of scaffolding to coat subunits. The results indicated that scaffolding protein was required for both initiation of shell assembly and continued polymerization. Though procapsids produced in vivo contain about 300 molecules of scaffolding, shells with fewer subunits could be assembled down to a lower limit of about 140 scaffolding subunits per shell. The overall results of these experiments indicate that coat and scaffolding subunits must interact in both the initiation and the growth phases of shell assembly. However, it remains unclear whether during growth the coat and scaffolding subunits form a mixed oligomer prior to adding to the shell or whether this occurs at the growing edge.

Capsid↗
PubMed1988

Sequence analysis and transcriptional regulation of the Escherichia coli grpE gene, encoding a heat shock protein.

We have sequenced the Escherichia coli grpE gene and shown that it encodes a 197-amino acid residue protein of 21,668-Mr. The predicted N-terminal amino acid sequence, as well as the overall amino acid composition agree well with that of the purified protein. From Northern analysis, we have shown that transcription of the grpE gene is under heat shock regulation, i.e., there is a rapid and transient increase in the rate of synthesis of grpE mRNA upon a shift-up in temperature. Forty-six bases upstream of the structural gene is a sequence closely related to the consensus heat shock promoter identified by Cowing et al. [Proc. Natl. Acad. Sci. U.S.A, 82, 2679-2683]. We have shown by S1 mapping and RNA sequencing that this is indeed the promoter for the grpE mRNA. It appears that all discernable transcription initiates only from this promoter, even under non-heat shock conditions.

Amino Acid Sequence↗
PubMed1988

Initiation of P22 procapsid assembly in vivo.

The procapsids of all double-stranded DNA phages have a unique portal vertex, which is the locus of DNA packaging and DNA injection. Procapsid assembly is also initiated at this vertex, which is defined by the presence of a cyclic dodecamer of the portal protein. Assembly of the procapsid shell of phage P22 requires the gene 5 coat protein and the gene 8 scaffolding protein. We report here that removal of gene product (gp) 1 portal protein of P22 by mutation does not slow the rate of polymerization of coat and scaffolding subunits into shells, indicating that the portal ring is dispensable for shell initiation. Mutant scaffolding subunits specified by tsU172 copolymerize with coat subunits into procapsids at restrictive temperature, and also correctly autoregulate their synthesis. However, the shell structures formed from the temperature-sensitive scaffolding subunits fail to incorporate the portal ring and the three minor DNA injection proteins. This mutation identifies a domain of the scaffolding protein specifically involved in organization of the portal vertex. The results suggest that it is a complex of the scaffolding protein that initiates procapsid assembly and organizes the portal ring.

Capsid↗
PubMed1988

Formation of aggregates from a thermolabile in vivo folding intermediate in P22 tailspike maturation. A model for inclusion body formation.

The in vivo accumulation of polypeptide chains in the form of aggregated non-native states is a problem in many applications of biotechnology. In the maturation pathway of the thermostable P22 tailspike endorhamnosidase, the folding and chain association intermediates can be distinguished from the native tailspikes in crude extracts of phage-infected Salmonella cells. Temperature-sensitive folding mutations, at many sites in the chain, destabilize these conformational intermediates preventing the formation of native tailspikes at restrictive temperatures (Goldenberg, D. P., Smith, D. H., and King, J. (1983) Proc. Natl. Acad. Sci. U. S. A. 80, 7060-7064). We report here that both wild type and mutant tailspike polypeptide chains which fail to reach the native state accumulate in an aggregated state. These off-pathway aggregates form from a thermolabile intermediate in the productive folding pathway. These aggregation reactions are suppressed by lowering the temperature of maturation. Similar off-pathway steps from folding intermediates may account for the non-native aggregates often found in the expression of cloned genes in heterologous hosts.

Kinetics↗
PubMed1988

Purification and organization of the gene 1 portal protein required for phage P22 DNA packaging.

The gene 1 protein of Salmonella bacteriophage P22 is located at the DNA packaging vertex of the mature particle. The protein is incorporated into the procapsid shell during shell assembly and is required for DNA packaging. The unassembled precursor form of the gene 1 protein has been purified from cells infected with mutants blocked in procapsid assembly. The purified 90,000-dalton protein was dimeric or monomeric; upon storage in the cold it formed 20S cyclic dodecamers. Computer filtering of negatively stained electron micrographs revealed 12 arms and knobs projecting from a central ring, with a 30-A channel at the center. Similar dodecameric rings were released from disrupted procapsid shells. These results indicate that the gene 1 protein is organized as a cyclic dodecamer within the procapsid shell and serves as the portal through which P22 DNA is threaded during DNA packaging. The presence of a 12-fold ring located at a 5-fold portal vertex appears to be a conserved structural theme of the DNA packaging apparatus of double-stranded DNA phages.

Capsid↗
PubMed1988

Secondary structure and thermostability of the phage P22 tailspike. XX. Analysis by Raman spectroscopy of the wild-type protein and a temperature-sensitive folding mutant.

The thermostable tailspike endorhamnosidase of bacteriophage P22 has been investigated by laser Raman spectroscopy to determine the protein's secondary structure and the basis of its thermostability. The conformation of the native tailspike, determined by Raman amide I and amide III band analyses, is 52 to 61% beta-sheet, 24 to 27% alpha-helix, 15 to 21% beta-turn and 0 to 10% other structure types. The secondary structure of the wild-type tailspike, as monitored by the conformation-sensitive Raman amide bands, was stable to 80 degrees C, denatured reversibly between 80 and 90 degrees C, and irreversibly above 90 degrees C. The purified native form of a temperature-sensitive folding mutant (tsU38) contains secondary structures virtually identical to those in the wild-type in aqueous solution at physiological conditions (0.05 M-Na+ (pH 7.5], at both permissive (20 degrees C) and restrictive (40 degrees C) temperatures. This supports previous results showing that the mutational defect at 40 degrees C affects intermediates in the folding pathway rather than the native structure. At temperatures above 60 degrees C the wild-type and mutant forms were distinguishable: the reversible and irreversible denaturation thresholds were approximately 15 to 20 degrees C lower in the mutant than in the wild-type protein. The irreversible denaturation of the mutant tailspikes led to different aggregation/polymerization products from the wild-type, indicating that the mutation altered the unfolding pathway. In both cases only a small percentage of the native secondary structure was altered by irreversible thermal denaturation, indicating that the aggregated states retain considerable native structure.

Glycoside Hydrolases↗
PubMed1988

Surface amino acids as sites of temperature-sensitive folding mutations in the P22 tailspike protein.

Temperature-sensitive folding (tsf) mutations in the gene for the thermostable P22 tailspike interfere with the polypeptide chain folding and association pathway at restrictive temperature without altering the thermostability of the protein once correctly folded and assembled at permissive temperature. Though the native proteins matured at permissive temperature are biologically active, many of them display alterations in electrophoretic mobility. The native forms of 15 of these tsf mutant proteins have been purified and characterized. The purified proteins differed in electrophoretic mobility and isoelectric point from wild type but did not show evidence of major conformational alterations. The results suggest that the electrophoretic variations conferred by the 15 tsf amino acid substitutions are due to changes in the net charge at solvent-accessible sites in the native form of the mutant protein. During the maturation of the chains at restrictive temperature, these sites influence the conformation of intermediates in chain folding and association. The amino acid sequences at these sites resemble those found at turns in polypeptide chains. The isolation of tsf mutations requires that the mature structure of the tailspike accommodates the mutant amino acid substitution without loss of function. The solvent-accessible sites are probably at the surface of this structural protein. This would explain how bulky mutant substitutions, such as arginines for glycines, are accommodated in the native tailspike structure. Such sites, stabilizing intermediates in the folding pathway and located on the surface of the mature protein, probably represent a general class of conformational substrates for tsf mutations.

Amino Acids↗
PubMed1988

Serum lipid response to a fat-modified, oatmeal-enhanced diet.

The purpose of this study was to confirm and extend previous findings that serum cholesterol response to a fat-modified diet is enhanced by oat fiber. Participants (n = 236) were recruited from the Continental Illinois National Bank in Chicago. Data including weight, serum lipid level, lipoproteins, and 3-day food records were collected at baseline and every 4 weeks for 12 weeks. All participants were instructed to follow the fat-modified (Phase II) diet recommended by the American Heart Association (AHA). After 4 weeks, participants were randomly assigned to one of two groups. While both groups continued to follow the AHA diet, Group 1 was instructed to include 2 oz (56 g, dry wt) of oatmeal, isocalorically substituted for other carbohydrate foods. Group 2 served as the control and consumed no oat products throughout the study. Serum cholesterol values at baseline and after 4 weeks of the AHA diet were similar for both groups (203.9 and 193.0 mg/dl for Group 1 and 205.3 and 194.5 mg/dl for Group 2). After 4 weeks of oatmeal intervention, mean group differences were -6.8 and -2.1 mg/dl (P = 0.008 one-tailed t test) for Groups 1 and 2, respectively. Following an additional 4 weeks of oatmeal intervention, the Group 1 mean cholesterol increased slightly (0.9 mg/dl), while the Group 2 level decreased slightly (-0.7 mg/dl). Overall serum cholesterol responses for the two groups from Visit 2 to Visit 4 were -6.0 and -2.8 mg/dl for Groups 1 and 2, respectively (P = 0.074, one tail). Changes in weight were small and nonsignificant. Subgroup analyses revealed greater reductions in serum cholesterol among participants with the highest baseline serum cholesterol (-8.0 mg/dl vs -1.7 mg/dl for Subgroups 1 and 2, respectively). These data support previous findings that inclusion of oatmeal in a fat-modified diet is helpful in lowering serum cholesterol, particularly for individuals with elevated serum cholesterol levels.

Adult↗
PubMed1988

Computed tomography and ultrasound imaging of jumper's knee-patellar tendinitis.

We present nine cases of this relatively unreported condition affecting the patellar ligament in athletes. A comparison between ultrasound and computed tomography of this lesion, shows that whilst neither modality gives false positives, ultrasound is capable of greater distinction between the histological abnormalities confirmed at surgery.

Adolescent↗