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Biomedical subjects

C Davies

Publications and source records attributed to C Davies.

At least 109 records · Page 6Linked to original sources
PubMed1996

Helicase-contrahelicase interaction and the mechanism of termination of DNA replication.

Termination of DNA replication at a sequence-specific replication terminus is potentiated by the binding of the replication terminator protein (RTP) to the terminus sequence, causing polar arrest of the replicative helicase (contrahelicase activity). Two alternative models have been proposed to explain the mechanism of replication fork arrest. In the first model, the RTP-terminus DNA interaction simply imposes a polar barrier to helicase movement without involving any specific interaction between the helicase and the terminator proteins. The second model proposes that there is a specific interaction between the two proteins, and that the DNA-protein interaction both restricts the fork arrest to the replication terminus and determines the polarity of the process. The evidence presented in this paper strongly supports the second model.

Adenosine Triphosphatases↗
PubMed1996

Structural evidence for specific S8-RNA and S8-protein interactions within the 30S ribosomal subunit: ribosomal protein S8 from Bacillus stearothermophilus at 1.9 A resolution.

BACKGROUND: Prokaryotic ribosomal protein S8 is an important RNA-binding protein that occupies a central position within the small ribosomal subunit. It interacts extensively with 16S rRNA and is crucial for the correct folding of the central domain of the rRNA. S8 also controls the synthesis of several ribosomal proteins by binding to mRNA. It binds specifically to very similar sites in the two RNA molecules. RESULTS: S8 is divided into two tightly associated domains and contains three regions that are proposed to interact with other ribosomal components: two potential RNA-binding sites, and a hydrophobic patch that may interact with a complementary hydrophobic region of S5. The N-terminal domain fold is found in several proteins including two that bind double-stranded DNA. CONCLUSIONS: These multiple RNA-binding sites are consistent with the role of S8 in organizing the central domain and agree with the latest models of the 16S RNA which show that the S8 location coincides with a region of complicated nucleic-acid structure. The presence in a wide variety of proteins of a region homologous to the N-terminal domain supports the idea that ribosomal proteins must represent some of the earliest protein molecules.

Amino Acid Sequence↗
PubMed1996

Effect of the ATP level on the overall protein biosynthesis rate in a wheat germ cell-free system.

A sensitive assay which examines the effects of ATP level on the overall activity of a cell-free translation system in a protein synthesis is described. The translational activity of cell-free system was measured in terms of a rate of protein synthesis directed by the 'test' template. The test template encodes a photoluminescent protein, obelin accumulation was determined from the kinetic curves of obelin. The rate of obelin mRNA translation. Time-dependent nucleotide level measurements were conducted throughout the translation processes. It has been shown that the rate of translation decreases exponentially with the decrease of the ATP level. This fall in the overall translation rate is due in part to the mRNA becoming inactive in the translation process. This is not caused by degradation, this mRNA can be restored for translation in a fresh cell-free system by phenol treatment. The reported results provide evidence that the level of ATP unambiguously determines the translational activity of the system.

Adenosine Diphosphate↗
PubMed1996

Cell-to-cell movement of potato virus X is associated with a change in the size-exclusion limit of plasmodesmata in trichome cells of Nicotiana clevelandii.

To study the effect of cell-to-cell movement of potato virus X (PVX) on the size-exclusion limit of plasmodesmata we have microinjected virus particles and fluorescently labelled dextrans (F-dextrans) with average molecular mass of 4.4, 10, and 20 kDa into Nicotiana clevelandii trichome cells. A vector construct of PVX expressing GUS (PVX.GUS) moved from the injected cell and modified the plasmodesmata to allow passage of the 4.4- and 10-kDa F-dextrans but not the 20-kDa F-dextran. A mutant PVX with a deletion in the gene for the 25-kDa protein accumulated in inoculated protoplasts to the same level as the wild-type PVX. This mutant virus did not move from the injected cell and did not modify the plasmodesmata to allow passage of the 10-kDa F-dextran. However, the 4.4-kDa F-dextran moved from the cells infected with the mutant virus. These data therefore illustrate that movement of PVX is associated with modification of plasmodesmata. The full plasmodesmatal modification requires a functional 25-kDa protein but partial modification occurs when this protein is present in a mutant form.

Base Sequence↗
PubMed1996

The crystal structure of ribosomal protein L14 reveals an important organizational component of the translational apparatus.

BACKGROUND: Detailed structural information on ribosomal proteins has increased our understanding of the structure, function and evolution of the ribosome. L14 is one of the most conserved ribosomal proteins and appears to have a central role in the ribonucleoprotein complex. Studies have indicated that L14 occupies a central location between the peptidyl transferase and GTPase regions of the large ribosomal subunit. RESULTS: The crystal structure of L14 from Bacillus stearothermophilus has been solved using a combination of isomorphous replacement and multiwavelength anomalous dispersion (MAD) methods. The structure comprises a five-stranded beta-barrel, a C-terminal loop region that contains two small alpha-helices, and a beta-ribbon that projects from the beta-barrel. An analysis of the structure and the conserved amino acids reveals three surface patches that probably mediate L14-RNA and L14-protein interactions within the ribosome. CONCLUSIONS: The accepted role of ribosomal proteins is to promote the folding and stabilization of ribosomal RNA. The L14 structure is consistent with this notion, and it suggests that the RNA binds in two sites. One RNA-binding site appears to recognize a distinct region of ribosomal RNA during particle assembly. The second site is smaller and may become occupied during the later compaction of the RNA. The surface hydrophobic patch is a likely site of protein-protein interaction, possibly with L19.

Amino Acid Sequence↗
PubMed1996

Expression of anthocyanin biosynthesis pathway genes in red and white grapes.

The expression of seven genes from the anthocyanin biosynthesis pathway was determined in different tissues of Shiraz grapevines. All of the tissues contained proanthocyanidins, but only the berry skin accumulated anthocyanins. In most tissues, all of the flavonoid genes except UDP glucose-flavonoid 3-o-glucosyl transferase (UFGT) were expressed, but UFGT expression was only detected in berry skin. Similar patterns of expression were observed in the skin of other red grapes. In white grapes, UFGT expression was not detected. White grape cultivars appear to lack anthocyanins because they lack UFGT, although they also had decreased expression of other flavonoid pathway genes.

Anthocyanins↗
PubMed1996

Sugar accumulation in grape berries. Cloning of two putative vacuolar invertase cDNAs and their expression in grapevine tissues.

During grape berry (Vitis vinifera L.) ripening, sucrose transported from the leaves is accumulated in the berry vacuoles as glucose and fructose. To study the involvement of invertase in grape berry ripening, we have cloned two cDNAs (GIN1 and GIN2) from berries. The cDNAs encode translation products that are 62% identical to each other and both appear to be vacuolar forms of invertase. Both genes are expressed in a variety of tissues, including berries, leaves, roots, seeds, and flowers, but the two genes have distinct patterns of expression. In grape berries, hexose accumulation began 8 weeks postflowering and continued until the fruit was ripe at 16 weeks. Invertase activity increased from flowering, was maximal 8 weeks postflowering, and remained constant on a per berry basis throughout ripening. Expression of GIN1 and GIN2 in berries, which was high early in berry development, declined greatly at the commencement of hexose accumulation. The results suggest that although vacuolar invertases are involved in hexose accumulation in grape berries, the expression of the genes and the synthesis of the enzymes precedes the onset of hexose accumulation by some weeks, so other mechanisms must be involved in regulating this process.

Amino Acid Sequence↗
PubMed1996

Factors influencing audit in general practice.

Since 1990, the changes introduced in UK general practice, such as fund holding and national incentives, have altered the process of care. Audit, defined as "the systematic critical analysis of the quality of medical care, including the procedures used for diagnosis and treatment, the use of resources, and the resulting outcome and quality of life for patients", is one method of monitoring change and raising standards. Presents a successful co-ordinated audit in Warwickshire, 1991-1993, involving 53 general practices. Highlights and influence of attitudes and communication within practices on the success of audit strategies. Associates aspects of practice culture, such as team working and decision-making processes with successful audit. Postulates six descriptive practice types, largely related to culture factors. Suggests that if cultural factors within practices are identified, external assistance with audit may be more focused and effective.

Attitude of Health Personnel↗
PubMed1996

Pleural effusion in cats: 82 cases (1987 to 1995).

Eighty-two cases of feline pleural effusion were identified and reviewed to assess the type of fluid, underlying disease process, predisposing conditions, historical and physical examination findings, laboratory and cytology data, response to treatment and outcome. Pertinent findings included a high occurrence of pleural effusion with mediastinal lymphoma (and other types of intrathoracic neoplasia), pyothorax, cardiomyopathy and feline infectious peritonitis virus infection. Sixteen cases, eight with chylous effusion, had no underlying disease identified. Cats with pyothorax and effusion secondary to trauma had the best prognosis for complete recovery. Otherwise, the outcome was variable and the prognosis was guarded to poor.

Animals↗
PubMed1996

Psychological evaluation and support during EXEMSI. Experimental Campaign for the European Manned Space Infrastructure.

The aim of this study was to investigate changes in the psychological state of the crew members and the needs for psychological support during prolonged isolation. For the purpose methods employed that have been widely used in psychological evaluation during Soviet spaceflights. Communication between Commander and Crew Interface Coordinator (CIC) was analyzed. Crew disposition was observed and analyzed for information about the process of group formation and the role of each crew member in this process. Operation of the CIC's was investigated for evidence of a psychological support function. During isolation certain adaptive changes in communication took place: (1) use of unplanned contacts and intensive contacts with a preferred ground crew member, (2) resistance to penetration in the life of the crew (increase of aggressive statements and self-justifications, reduction of report length and claims), and (3) closing communication to "outsiders" by using a special code and decreasing discussion of problems. A process of group formation was noted in the course of isolation, but the final structure of the group was not stable. The relations of subjects B, D and G were crucial in the creation of an effective crew. The woman in the crew was never involved in conflicts and acted as a peacemaker. The crew regarded the communication channel between Commander and CIC as belonging to the entire crew for expressing feelings about crew relations, administration and services, and the CIC can provide needed psychological support, confirming earlier experience from Soviet simulated and actual spaceflights.

Astronauts↗
PubMed1995

An STS content map of human chromosome 11: localization of 910 YAC clones and 109 islands.

Physical mapping of human chromosomes at a resolution of 100 kb to 1 Mb will provide important reagents for gene identification and framework templates for ultimately determining the complete DNA sequence. Sequence-tagged site (STS) content mapping, coupled with large fragment cloning in yeast artificial chromosomes, provides an efficient mechanism for producing first-generation, low-resolution maps of human chromosomes. Previously, we produced a set of standardized STSs for human chromosome 11 regionally localized by fluorescence in situ hybridization or somatic cell hybrid analysis. In this paper, we used these as well as other STS content, and identify 109 islands spanning an estimated 218 Mb on the 126-Mb chromosome. Since about 62% of the islands contain markers ordered on chromosome 11 by genetic or radiation hybrid analysis, this data set represents a first-order approximation of a physical map of human chromosome 11. This set of clones, contigs, and associated STSs will provide the material for the production of a continuous overlapping set of YACs as well for high-resolution physical mapping based upon sampled and complete DNA sequencing.

Base Sequence↗
PubMed1995

Indefinite allograft survival induced by the combination of multiple donor-specific transfusions, cyclosporine, and an anti-T cell monoclonal antibody in a protocol relevant to cadaveric organ transplantation. The importance of prolonged posttransplant cyclosporine coverage.

A single donor specific transfusion (DST) 24 hr pretransplant and Cyclosporine (CsA) are synergistic in inducing prolongation of allograft survival. This synergy was further potentiated by giving 3 additional DSTs at weekly intervals posttransplant, or by the additional administration of a small dose of the anti-T cell monoclonal antibody OX-52 24 hr pretransplant to the above protocol. This study determined whether indefinite survival can be achieved in the ACI-to-Lewis heart allograft model by combining an anti-T cell monoclonal antibody, 4 DSTs given once 24 hr pretransplant and weekly 3 times posttransplant, and CsA. CsA was given daily for 28 days or 60 days posttransplant. The dose consisted of CsA 5 mg/kg/day starting 24 hr pretransplant and continuing until day 7 posttransplant and followed by 2.5 mg/kg/day for either 21 more days (total CsA days = 28 days) or 53 days (total CsA days = 60 days). The anti-T cell monoclonal antibody OX52 (200 micrograms i.v.) was given once 24 hr pretransplant. DST (1 ml) was given 24 hr pretransplant and on days 7, 14, and 21 posttransplant. Low-dose CsA for 28 days never induced indefinite allograft survival. CsA for 60 days, however, resulted in the occasional indefinite allograft survival (> 1 year) even in this difficult model. The addition of DST 24 hr pre- and posttransplant on days 7, 14, and 21 to both 28 days and 60 days of CsA further prolonged allograft survival. The best survival was seen in the group given DST 24 hr pre- and on days 7, 14, and 21 posttransplant and 60 days of CsA, with all the allografts surviving beyond 100 days of CsA, with all the allografts surviving beyond 100 days and more than 50% surviving indefinitely (> 1 year). The addition of a single dose of OX52 24 hr pretransplant to the multiple DSTs and 28 days of CsA protocol significantly improved indefinite allograft survival but its influence was less dramatic when given to the multiple DSTs and 60 days of CsA protocol. This beneficial interaction between CsA, DST, and an anti-T cell MoAb offers a clinically applicable protocol for both living donor and cadaveric organ transplantation in inducing donor-specific hyporesponsiveness, and further investigations are warranted.

Animals↗
PubMed1995

Characterization of a cDNA encoding the protein moiety of a putative arabinogalactan protein from Lycopersicon esculentum.

The nucleotide sequence of a cDNA prepared from poly(A)+ RNA from Lycopersicon esculentum fruit codes for a protein, M(r) 20,812, with features representative of the protein core of arabinogalactan proteins. The deduced amino acid sequence resembles that of peptides of arabinogalactan proteins isolated from carrot and rose and is most similar to the sequence of tryptic peptides from Lolium multiflorum (Gleeson et al., Biochem J 264 (1989) 857-862). The similar sequences include a number of Ala-Pro repeats, a feature considered distinctive of arabinogalactan proteins. The amino acid composition is similar to that of the peptide core of the Lolium multiflorum arabinogalactan protein; alanine, serine and proline account for 57% of the polypeptide. The mRNA corresponding to the cDNA sequence was detected in roots, leaves and fruit. The levels of mRNA are reduced in older leaves, in fruit that have commenced ripening and in leaves and fruit that have been wounded.

Amino Acid Sequence↗
PubMed1995

The use of air or CO2 as insufflation agents for double contrast barium enema (DCBE): is there a qualitative difference?

One hundred consecutive out-patients referred for double contrast barium enema (DCBE) were randomized in a double-blind prospective study to receive either air or CO2 as an insufflation agent. Each examination was performed by the same radiologist and radiographer. The two groups were equally matched for age and sex. Each completed examination was independently assessed by three radiologists for a variety of parameters. The results show that the patients receiving air as an insufflation agent had better overall colonic distension than the group receiving CO2 and that this was statistically significant (P = 0.0004). There was no significant difference in the mean time taken to perform the examination in the two groups nor was there any significant difference in mucosal coating or preparation. In conclusion, our results suggest that poor colonic distension is a potential problem when CO2 is used for DCBE and that this cannot be solely attributed to the time taken to perform the examination. Poor distension could lead to diagnostic errors and this may outweigh the advantages in patient acceptability when using CO2 as an insufflation agent.

Adult↗
PubMed1995

Development and implementation of an innovative intern training programme.

The quality of medical education during internship is a cause for concern. This paper describes a structured educational programme for interns that was based around learning modules, clinical attachments and bedside teaching. The programme was incorporated into the term rotation of interns within an Area Health Service, and evaluated. Learning modules were timetabled by a Programme Coordinator and interns were reminded to attend. Clinical attachments were organized by the interns from a list of willing supervisors. Attendance at timetabled learning modules averaged 67%, which was greater than the 27% attendance at clinical attachments. Both sessions received high ratings for quality and clinical relevance. This structured education programme was based upon adult learning methods and was both feasible and well received by interns. Intern training programmes need to be programmed into the working week to ensure attendance, and modified following evaluation by interns. Such programmes should be considered by all hospitals to which interns are allocated.

Australia↗
PubMed1995

Suspected ciprofloxacin-induced hepatotoxicity.

OBJECTIVE: To report a case of probable ciprofloxacin-induced hepatotoxicity. CASE SUMMARY: A 44-year-old woman developed severe hepatitis 3 weeks after initiation of a 7-day course of oral ciprofloxacin therapy. Liver biopsy showed severe hepatic necrosis, and other causes of liver injury were excluded. Liver function test results returned to normal 4 months after the appearance of jaundice. DISCUSSION: The time course of events suggested that ciprofloxacin was the cause of severe hepatitis in this patient, and other causes of hepatitis were ruled out. Hepatotoxicity has been reported with other fluoroquinolone antibiotics, and there have been previous unpublished reports to the manufacturer of possible hepatotoxicity caused by ciprofloxacin. CONCLUSIONS: It is suggested that ciprofloxacin can cause severe hepatic injury and that healthcare providers should be aware of this possible adverse drug reaction.

Administration, Oral↗