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R Viola

Publications and source records attributed to R Viola.

At least 19 recordsLinked to original sources
PubMed2001

The unique features of starch metabolism in red algae.

Red algae (Rhodophyceae) are photosynthetic eukaryotes that accumulate starch granules outside of their plastids. The starch granules from red algae (floridean starch) show structural similarities with higher plant starch granules but lack amylose. Recent studies have indicated that the extra-plastidic starch synthesis in red algae proceeds via a UDP glucose-selective alpha-glucan synthase, in analogy with the cytosolic pathway of glycogen synthesis in other eukaryotes. On the other hand, plastidic starch synthesis in green cells occurs selectively via ADP glucose in analogy with the pathway of glycogen synthesis in prokaryotes from which plastids have evolved. Given the emerging consensus of a monophyletic origin of plastids, it would appear that the capacity for starch synthesis selectively evolved from the alpha-glucan synthesizing machinery of the host ancestor and its endosymbiont in red algae and green algae, respectively. This implies the evolution of fundamentally different functional relationships between the different subcellular compartments with regard to photosynthetic carbon metabolism in these organisms. It is suggested that the biochemical and molecular elucidation of floridean starch synthesis may offer new insights into the metabolic strategies of photosynthetic eukaryotes.

Photosynthesis↗
PubMed2001

The use of micro-organisms for L-ascorbic acid production: current status and future perspectives.

L-Ascorbic acid (L-AA) has been industrially produced for around 60 years in a primarily chemical process utilising D-glucose (D-glc) as starting material. Current world production is estimated at approximately 80,000 tonnes per annum with a worldwide market in excess of U.S. $600 million. We present a brief overview of research geared to exploiting micro-organisms for the industrial production of vitamin C, with emphasis on recent approaches using genetically engineered bacterial strains. We also discuss the potential for direct production of L-AA exploiting novel biochemical pathways with particular reference to yeast fermentations. The potential advantages of these novel approaches over current chemical and biotechnological processes are outlined.

Ascorbic Acid↗
PubMed2001

Copy-DNA cloning and characterisation of a potato alpha-glucosidase: expression in Escherichia coli and effects of down-regulation in transgenic potato.

Polymerase chain reaction-based methodology was used to obtain a cDNA clone (MAL2) from potato (Solanum tuberosum L.) with the sequence characteristics of an alpha-glucosidase. Phylogenetic analysis of the deduced polypeptide encoded by this cDNA demonstrated that the most similar sequences were alpha-glucosidases and alpha-xylosidases of plant origin. The MAL2 cDNA was expressed in Escherichia coli and the recombinant MAL2 protein was affinity-purified. MAL2 catalysed the hydrolysis of a range of maltooligomers and p-nitrophenyl-alpha-D-glucopyranoside with a pH optimum of 5.5-5.7. The substrate with the lowest Km value was maltotetraose (3.7 mM). The MAL2 expression product did not catalyse the hydrolysis of xyloglucan oligosaccharides, p-nitrophenyl-alpha-D-xylopyranoside or gelatinised potato starch. MAL2 was down-regulated in transgenic potato plants using an antisense approach. In several independent transgenic antisense lines, MAL2 expression was severely down-regulated. Despite this, no decrease in total extractable alpha-glucosidase and alpha-xylosidase activity could be detected in tissues from the transgenic plants. In glasshouse trials, no visible phenotype, change in tuber yield or carbohydrate content was associated with MAL2 down-regulation. The implications of these results are discussed.

Cloning, Molecular↗
PubMed2001

Tuberization in potato involves a switch from apoplastic to symplastic phloem unloading.

Phloem unloading was studied in potato plants in real time during the early stages of tuberization using carboxyfluorescein (CF) as a phloem-mobile tracer, and the unloading pattern was compared with autoradiography of tubers that had transported (14)C assimilates. In stolons undergoing extension growth, apoplastic phloem unloading predominated. However, during the first visible signs of tuberization, a transition occurred from apoplastic to symplastic transport, and both CF and (14)C assimilates subsequently followed identical patterns of phloem unloading. It is suggested that the switch to symplastic sucrose unloading may be responsible for the upregulation of several genes involved in sucrose metabolism. A detailed analysis of sugar levels and (14)C sugar partitioning in tuberizing stolons revealed a distinct difference between the apical region of the tuber and the subapical region. Analysis of invertase activity in nontuberizing and tuberizing stolons revealed a marked decline in soluble invertase in the subapical region of swelling stolons, consistent with the switch from apoplastic to symplastic unloading. However, cell wall-bound invertase activity remained high in the apical 1 to 2 mm of tuberizing stolons. Histochemical analysis of potato lines transformed with the promoter of an apoplastic invertase gene (invGE) linked to a reporter gene also revealed discrete gene expression in the apical bud region. Evidence is presented that the apical and lateral tuber buds function as isolated domains with respect to sucrose unloading and metabolism.

Carbohydrate Metabolism↗
PubMed2001

Postoperative infections following total knee replacement: an epidemiological study.

From January 1991 to June 1997 217 patients undergoing monolateral or bilateral total knee replacement (TKR) were consecutively enrolled in a prospective study on the incidence of postoperative infections and related risk factors. Regional antimicrobial prophylaxis (teicoplanin 400 mg) was used in 263 (95%) prostheses implanted; in the remaining 14 implants (5%) perioperative antibiotic prophylaxis (teicoplanin 800 mg) was administered as usual by systemic route. None of the patients experienced local or systemic adverse effects. Over the 2-year follow-up period, 8 (2.9%) primary site infectious complications were recorded, i.e. 4 superficial infections, which were cured without involvement of the prostheses, and 4 deep infections, which required prosthesis removal. Six infections occurred in patients who had undergone previous surgery of the same knee joint, and 2 in patients undergoing primary TKR (p= 0.0005); diabetic patients had infections (13%) more frequently than non-diabetic patients (1.9%, p=0.01). Staphylococci were the leading organisms isolated from infections; however 3 strains of Escherichia coli were isolated from patients who had undergone a previous prosthesis implantation at the same knee joint. Regional administration of teicoplanin appears to be a safe and valuable prophylactic technique; however, in patients at risk of infection a prophylactic regimen which is also active against gram-negative bacteria should probably be considered.

Adult↗
PubMed2000

Biosynthesis of L-ascorbic acid (vitamin C) by Saccharomyces cerevisiae.

Saccharomyces cerevisiae cells incubated with D-glucose (D-Glc), D-galactose or D-mannose (D-Man) synthesised D-erythroascorbic acid (D-EAA) but not L-ascorbic acid (L-AA). Accumulation of D-EAA was observed in cells incubated with D-arabinose (D-Ara) whilst accumulation of L-AA occurred in cells incubated with L-galactose (L-Gal), L-galactono-1,4-lactone and L-gulono-1,4-lactone. When S. cerevisiae cells were incubated with D-[U-(14)C]Glc, D-[U-(14)C]Man or L-[1-(14)C]Gal, incorporation of radioactivity into L-AA was observed only with L-[1-(14)C]Gal. Pre-incubation of yeast cells with D-Ara substantially reduced the incorporation of L-[1-(14)C]Gal into L-AA. Our results indicate that, under appropriate conditions, yeast cells can synthesise L-AA via the pathway naturally used for D-EAA biosynthesis.

Ascorbic Acid↗
PubMed2000

An unusual epidemic of Staphylococcus-negative infections involving anterior cruciate ligament reconstruction with salvage of the graft and function.

We performed a retrospective study of 13 patients who had postoperative clinical and laboratory signs of infection after autogenous bone-patellar tendon-bone (BPTB) anterior cruciate ligament (ACL) reconstructions. From January 1991 to November 1996 we experienced only 2 infected knees in 1,300 reconstructions, but between December 1996 and February 1997 10 patients in 70 ACL reconstructions developed a postoperative suspected infection. We found the origin of contamination (coagulase-negative Staphylococcus) in the supposedly sterile inflow cannula. When we changed this device, we had only 1 infection in the next 400 reconstructions. The diagnosis in these cases was derived from clinical signs and laboratory results, but only 2 of 11 samples of aspirated synovial fluid tested positive for Staphylococcus. The mean interval between the surgery and the onset of signs of infection and the start of antibiotic therapy was 7.7 days. All the patients had antibiotic association at the highest level. Six knees underwent arthroscopic debridement when the clinical signs indicated resistence to antibiotics. The normal postoperative rehabilitation program was modified but was not discontinued. Although recovery time was longer, overall results were similar to uncomplicated reconstructions. On the basis of our experience, we believe that when there is a notable increase in infection rates, a thorough search for contamination is indicated. Our source of infection was material that was thought to be sterile. Ultimately, early diagnosis and treatment is of critical importance to obtain good results. Even suspicion of infective postoperative complication should be sufficient cause to search for responsible microorganisms and begin antibiotic therapy. Arthroscopic debridement should be proposed to patients with resistence to antibiotics.

Adult↗
PubMed2000

How useful is docusate in patients at risk for constipation? A systematic review of the evidence in the chronically ill.

The effectiveness of docusate for constipation has not been studied in the terminally ill. Controversy also exists concerning its effectiveness in the chronically ill. Because chronically ill patients and terminally ill patients have several risk factors for constipation in common, we undertook a systematic review of prospective controlled trials of oral docusate in the chronically ill to clarify the utility of this drug in populations with advanced disease. The data sources were Medline 1966-April 1997, CINAHL 1982-April 1997, Current Contents August 1996-April 1997, Cochrane Library, a hand search of Index Medicus 1940-1966, three palliative care journals, references in relevant articles and texts, and direct contact with experts. Prospective controlled trials evaluating oral docusate in humans with chronic illness and identifiable risk factors for, or preexisting, constipation were selected. Only materials abstracted in English or French were considered. Information was collected by two independent reviewers and included patient demographic data, study design, dose of docusate, outcomes of stool consistency, stool frequency, need for other laxatives, and assessment of methodologic and reporting quality. Of nine identified studies, four were eligible. These incorporated three different designs and sample sizes that ranged from 15 to 74. Quality assessment scores were low (range 0.46-0.52 with a perfect score being 1.0). Three studies were flawed in blinding of treatment allocation and the use of co-interventions. All studies showed a small trend toward increased stool frequency on docusate. Because of significant clinical heterogeneity in the identified studies, pooled data analysis was not feasible. At present, the use of docusate for constipation in palliative care is based on inadequate experimental evidence. Randomized controlled trials with chronically ill patients and patients with advanced disease are needed to determine its role in prevention and treatment of constipation.

Adolescent↗
PubMed2000

Regional prophylaxis with teicoplanin in monolateral or bilateral total knee replacement: an open study.

From January 1991 to June 1997, patients undergoing primary elective monolateral or bilateral total knee replacement (TKR) were consecutively enrolled in a prospective, open clinical study on the efficacy and safety of regional prophylaxis with teicoplanin (TEC). Those scheduled for monolateral TKR (115 patients) received 400 mg of TEC in 100 ml of saline as a 5-min infusion into a foot vein of the leg to be operated on immediately after the tourniquet was inflated to 400 mm Hg (ca. 50 kPa). For patients undergoing bilateral surgery (45 patients), regional administration of TEC was also repeated for the second knee operation. Follow-up ranged from a minimum of 2 years to 8 years. None of the patients experienced local or systemic adverse effects following regional administration of TEC. In the immediate postoperative and 2-year follow-up periods, only one superficial infection of the primary site attributable to intraoperative contamination (prophylaxis failure) out of the 205 prostheses implanted was observed. Deep infections involving the prosthesis did not occur. Infectious complications at distant sites were observed in nine cases (urinary tract infection due to Escherichia coli in eight cases, and Salmonella enteritidis gastroenteritis in one case) in the immediate postoperative period; they all were rapidly cured after antibiotic treatment. A delayed prosthetic infection, related to hematogenous spread of the etiological agent and therefore not considered a prophylactic failure, was observed in a patient who had undergone TKR 5 years before. Regional administration of TEC in monolateral and bilateral TKR appears to be a safe and valuable prophylactic technique.

Adult↗
PubMed1999

Structure of aspartate-beta-semialdehyde dehydrogenase from Escherichia coli, a key enzyme in the aspartate family of amino acid biosynthesis.

Aspartate beta-semialdehyde dehydrogenase (ASADH) lies at the first branch point in an essential aspartic biosynthetic pathway found in bacteria, fungi and the higher plants. Mutations in the asd gene encoding for ASADH that produce an inactive enzyme are lethal, which suggests that ASADH may be an effective target for antibacterial, herbicidal and fungicidal agents. We have solved the crystal structure of the Escherichia coli enzyme to 2.5 A resolution using single isomorphous replacement and 3-fold non-crystallographic symmetry. Each monomer has an N-terminal nucleotide-binding domain and a dimerisation domain. The presence of an essential cysteine locates the active site in a cleft between the two domains. The functional dimer has the appearance of a butterfly, with the NADP-binding domains forming the wings and the dimerisation domain forming the body.A histidine residue is identified as a likely acid/base catalyst in the enzymic reaction. Other amino acids implicated in the enzymic activity by mutagenesis are found in the active site region and define the substrate binding pocket.

Amino Acid Sequence↗
PubMed1999

Intra-articular ACL reconstruction in the over-40-year-old patient.

We compared two groups of patients who had undergone anterior cruciate ligament (ACL) reconstruction. The groups were similar in regard to sex distribution, index injury, absence of meniscal or chondral lesions, surgical technique, and postoperative rehabilitation programs, but different in age. In the study group the mean age was 42.6 years, while in the control group the mean age was 20 years. The clinical results were assessed at a mean of 29 months after surgery using the Lysholm score, International Knee Documentation Committee form, Tegner activity level, and the KT-1000 arthrometer test. No significant differences were reported. Standard X-ray studies showed no variation between the two groups in the postoperative period. Intra-articular ACL reconstruction using a bone-patellar tendon-bone graft can be recommended in selected patients over 40 years of age as an alternative to conservative treatment.

Adult↗
PubMed1999

Purification and characterisation of a novel starch synthase selective for uridine 5'-diphosphate glucose from the red alga Gracilaria tenuistipitata.

Red algae (Rhodophyceae) are photosynthetic eukaryotes that accumulate starch granules in the cytosol. Starch synthase activity in crude extracts of Gracilaria tenuistipitata Chang et Xia was almost 9-fold higher with UDP[U-14C]glucose than with ADP[U-14C]glucose. The activity with UDP[U-14C]glucose was sensitive to proteolytic and oxidative inhibition during extraction whilst the activity with ADP[U-14C]glucose appeared unaffected. This indicates the presence of separate starch synthases with different substrate specificities in G. tenuistipitata. The UDPglucose: starch synthase was purified and characterised. The enzyme appears to be a homotetramer with a native M(r) of 580 kDa and displays kinetic properties similar to other alpha-glucan synthases such as stimulation by citrate, product (UDP) inhibition and broad primer specificity. We propose that this enzyme is involved in cytosolic starch synthesis in red algae and thus is the first starch synthase described that utilises UDPglucose in vivo. The biochemical implications of the different compartmentalisation of starch synthesis in red algae and green algae/plants are also discussed.

Kinetics↗
PubMed1999

Role of MR imaging in the management of "skier's thumb" injuries.

"Skier's thumb" is an acute rupture of the ulnar collateral ligament (UCL) of the metacarpophalangeal (MCP) joint of the thumb. As the method of choice in evaluating soft tissue injuries, MR imaging is useful in evaluating UCL injuries. This article reviews current concepts regarding the rupture of the UCL, including a study of 34 UCL injuries in which MR imaging was used as the main diagnostic tool. When correlated with surgical findings, MR imaging resulted in identifying UCL tears with 96% sensitivity and 95% specificity.

Adult↗
PubMed1998

Sedation for intractable distress in the dying--a survey of experts.

Terminal sedation is a phrase that has appeared in the palliative care literature in the last few years. There has not been a clear definition proposed for this term, nor has there been any agreement on the frequency with which the technique is used. A postal survey of 61 selected palliative care experts (59 physicians, two nurses) was carried out to examine their response to a proposed definition for 'terminal sedation', to estimate the frequency of this practice and the reasons for its use, to identify the drugs and dosages used, to determine the outcome, and to explore the decision-making process. Opinions on physician-assisted suicide and voluntary euthanasia were also sought. Eighty-seven per cent of the experts responded from eight countries, although predominantly from Canada and the United Kingdom. Forty per cent agreed unequivocally with the proposed definition, while 4% disagreed completely. Eighty-nine per cent agreed that 'terminal sedation' is sometimes necessary and 77% reported using it in the last 12 months--over half of these for up to four patients. Reasons for using this method included various physical and psychological symptoms. The most common drugs used were midazolam and methotrimeprazine. Decision making usually involved the patient or family, and varied with respect to the ease with which the decision was made. The use of sedation was perceived to be successful in 90 out of 100 patients recalled. Ninety per cent of respondents did not support legalization of euthanasia. In conclusion, sedating agents are used by palliative care experts as tools for the management of symptoms. The term 'terminal sedation' should be abandoned and replaced with the phrase 'sedation for intractable distress in the dying'. Further research into the management of intractable symptoms and suffering is warranted.

Adult↗
PubMed1997

Prospects for advancing the understanding of complex biochemical systems.

The application of mathematical theories to understanding the behaviour of complex biochemical systems is reviewed. Key aspects of behaviour are identified as the flux through particular pathways in a steady state, the nature and stability of dynamical states, and the thermodynamic properties of systems. The first of these is dealt primarily in theories of metabolic control, and metabolic control analysis (MCA) is an important example. The valid application of this theory is limited to steady-state systems, and the cases where the essential features of control can be derived from calibration experiments which perturb the state of the system by a sufficiently small amount from its operating point. In practice, time-dependent systems exist, it is not always possible to know a priori whether applied perturbations are sufficiently small, and important features of control may lie farther from the operating point than the application of the theory permits. The nature and stability of dynamical and thermodynamical states is beyond the scope of MCA. To understand the significance of these limitations fully, and to address the dynamical and thermodynamical properties, more complete theories are required. Non-linear systems theory offers the possibility of studying important questions regarding control of steady and dynamical states. It can also link to thermodynamic properties of the system including the energetic efficiency of particular pathways. However, its application requires a more detailed characterisation of the system under study. This extra detail may be an essential feature of the study of non-equilibrium states in general, and non-ideal pathways in particular. Progress requires considerably more widespread integration of theoretical and experimental approaches than currently exists.

Biochemistry↗
PubMed1994

IFN gamma and TNF alpha cause an increased release of C3 by murine macrophages.

Macrophages from mice bearing Lewis lung carcinoma release higher amounts of C3 molecules than macrophages from healthy mice. The C3 pro-releasing activity operating in vivo was suspected to be due to an immunological network. Indeed, the supernatants of splenocytes from tumor bearing mice, but not from normal mice, induced in vitro an increased release of C3 molecules by macrophages. Recombinant IFN gamma and TNF alpha were strong inducers of C3 release, while IL-2 acted poorly. The C3 pro-releasing activity of splenocyte supernatants was largely prevented by their pretreatment with specific mAb anti IFN gamma or anti TNF alpha, but not completely prevented by the simultaneous neutralization of the two cytokines. Taken together, these results show that murine macrophages increase the release of C3 molecules upon treatment with IFN gamma or TNF alpha and that these cytokines released in vivo by splenocytes from tumor bearing mice may account, together with a yet unknown factor, for a humoral network causing the increased release of C3 by peritoneal macrophages.

Animals↗