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Biomedical subjects

M J Oliver

Publications and source records attributed to M J Oliver.

At least 19 recordsLinked to original sources
PubMed2005

Is the Rehydrin TrDr3 from Tortula ruralis associated with tolerance to cold, salinity, and reduced pH? Physiological evaluation of the TrDr3-orthologue, HdeD from Escherichia coli in response to abiotic stress.

We have employed EST analysis in the resurrection moss Tortula ruralis to discover genes that control vegetative desiccation tolerance and describe the characterization of the EST-derived cDNA TrDr3 ( Tortula ruralis desiccation-stress related). The deduced polypeptide TRDR3 has a predicted molecular mass of 25.5 kDa, predicted pI of 6.7, and six transmembrane helical domains. Preliminary expression analyses demonstrate that the TrDr3 transcript ratio increases in response to slow desiccation relative to the hydrated control in both total and polysomal mRNA (mRNP fraction), which classifies TrDr3 as a rehydrin. Bioinformatic searches of the electronic databases reveal that Tortula TRDR3 shares significant similarities to the hdeD gene product ( HNS- dependent expression) from Escherichia coli. The function of the HdeD protein in E. coli is unknown, but it is postulated to be involved in a mechanism of acid stress defence. To establish the role of E. coli HdeD in abiotic stress tolerance, we determined the log survival percentage from shaking cultures of wild-type bacteria and the isogenic hdeD deletion strain (Delta hdeD) in the presence of low temperature (28 degrees C), elevated NaCl (5 % (w/v)), or decreased pH (4.5), or all treatments simultaneously. The Delta hdeD deletion strain was less sensitive, as compared to wild-type E. coli, in response to decreased pH ( p > 0.009), and the combination of all three stresses ( p > 0.0001).

Acclimatization↗
PubMed2002

Randomized study of temporary hemodialysis catheters.

Temporary catheters are still essential for acute dialysis access but their performance has not been compared in randomized trials. We conducted a randomized trial of our standard catheter and a newly designed catheter. The primary outcome was maximized blood flow over the entire use of the catheter. Seventy-six patients provided maximum blood flows. The new catheter provided an average blood flow of 349 ml/min and the standard catheter provided flows of 320 ml/mm (p=0.09). Lumen reversal occurred in 56.8% of dialysis sessions with the standard catheter compared to 27.4% with the new catheter (p<0.001). Left-sided internal jugular catheters and catheters inserted in females provided 103 ml/min and 36 ml/min less blood flow, respectively, compared to right sided catheters and catheters placed in males. Approximately 20% of catheters were removed for poor blood flow. Left sided catheters and catheters in females were more likely to need removal for malfunction but catheter design did not influence removal rates.

Adolescent↗
PubMed2001

Tr288, a rehydrin with a dehydrin twist.

The rehydrin Tr288, originally isolated from a screen for differentially expressed transcripts during rehydration of desiccated moss (Tortula ruralis), was further characterized. Steady-state mRNA levels for Tr288 increase dramatically during slow drying even though protein synthesis is completely inhibited during this process. Tr288 transcripts do not accumulate during rapid drying of moss gametophytes. Conversely, during rehydration of rapidly dried tissue Tr288 transcript levels increase several-fold, while the relatively high amount of Tr288 mRNA sequestered in slowly dried material declines with time after the addition of water. Steady-state Tr288 mRNA also increases after treatment with salt (NaCl) and elevated temperature (37 degrees C). Genomic Southern analysis and isolation of a genomic clone suggest the presence of a single Tr288 gene containing two introns within the T. ruralis genome. The only sequence homology detected by a BLAST search of GenBank occurred at the 3' end of the Tr288 coding region and indicated a single copy of the K segment common to dehydrins. Computer translation of the Tr288 coding region revealed 15 copies of a protein segment (the GPN segment) that is predicted to form amphipathic alpha-helices.

Amino Acid Sequence↗
PubMed2001

Hemodialysis arteriovenous access: detection of stenosis and response to treatment by vascular access blood flow.

BACKGROUND: Hemodialysis access to the circulation is best provided by native and synthetic arteriovenous fistulae (AVF and AVG). Thromboses caused by venous outflow stenoses prevent the long-term use of AV access. This pilot study was performed to evaluate the ability of ultrasound dilution-derived access blood flows to detect AV access stenosis and to evaluate the response to treatment. METHODS: This pilot study was a single-center, prospective observational intervention trial. The monitoring technique used was ultrasound dilution access blood flow measurements performed monthly and after any intervention. Screening criteria for interventions were decrements in access flow of 20% when the flow value fell under 1000 mL/min or absolute flow of <600 mL/min. The primary intervention when flow criteria were met was biplanar venography of the access with percutaneous transluminal angioplasty (PTA) of detected stenoses. Stenoses unresponsive to PTA were sent for surgical revision. Access thrombosis was considered a study ending event. RESULTS: Baseline access flow at study entry for AVF was 919 and 1237 mL/min for AVG. Sequential measurement of AV access flow detected AV access stenosis. PTA and surgical revision significantly restored AV access flow back toward the baseline flow measurement. Failure to restore access flow by at least 20% following intervention occurred in 14% of AVF and 21% of AVG PTA attempts. Transluminal angioplasty, once successfully performed, was required at a mean of 5.8-month intervals in order to maintain AVG flow. In contrast, AVF flow was restored for a much longer period of time following angioplasty (11.4 month follow-up at the time of study end). Compared with historic controls, which used venous dialysis pressure as the primary monitoring technique, the overall (AVF-AVG) thrombosis rates improved from 25 to 16% per patient year, and AVF thrombosis rates improved from 16 to 7% per patient year. When flow was not successfully restored, thrombosis ensued. Eight of 10 thrombosis episodes were predicted based on inability to improve access flow either as a result of stenosis treatment failure or unsuccessful referral for treatment. CONCLUSION: Sequential measurement of AV access flow is an acceptable means of both monitoring for the development of access stenoses and assessing response to therapy. PTAs of AVF are more durable than PTAs of AV grafts.

Aged↗
PubMed2001

Comparison of transposed brachiobasilic fistulas to upper arm grafts and brachiocephalic fistulas.

BACKGROUND: Renewed interest in transposed brachiobasilic fistulas has occurred since the release of the National Kidney Foundation-Dialysis Outcomes Quality Initiative (NKF-DOQI) guidelines because it is an alternative method to achieve an upper arm fistula in patients who cannot achieve a functional brachiocephalic fistula. The objective of this study was to compare outcomes among transposed brachiobasilic fistulas, upper arm grafts, and brachiocephalic fistulas. METHODS: A cohort of patients with upper arm accesses was retrospectively identified. Access outcomes were determined from medical records and contact with physicians, dialysis providers, and patients. Primary outcome was thrombosis-free survival. Secondary outcomes were primary failure, time to use, risk of catheter-related bacteremia, need for intervention, incidence of access-related complications, cumulative, and functional patency. Group differences in age, sex, race, diabetes, peripheral vascular disease, and number of previous accesses were adjusted for in the analysis where appropriate. RESULTS: Transposed brachiobasilic fistulas, upper arm grafts, and brachiocephalic fistulas were compared in 59, 82, and 56 patients, respectively. Compared with transposed brachiobasilic fistulas, upper arm grafts were more likely to thrombose with an adjusted relative risk (RR) of 2.6 (95% CI, 1.3 to 5.3) excluding primary failures and 1.6 (95% CI, 1.0 to 2.7) when accounting for the lower risk of primary failure for grafts. Transposed brachiobasilic fistulas also required less intervention (0.7 vs. 2.4 per access-year, P < 0.01) and were less likely to become infected (0 vs. 13%, P < 0.05) than grafts. Mature brachiocephalic fistulas were less likely to fail (RR 0.3, 95% CI, 0.1 to 1.0) and showed a trend for less thrombosis (RR 0.3, 0.1 to 1.1) than mature brachiobasilic fistulas. There was no significant difference in cumulative patency (failure-free survival) among the three types of access if primary failure was included at the median follow-up of 594 days. Transposed brachiobasilic fistulas provided catheter-free access one month sooner than brachiocephalic fistulas and one month later than upper arm grafts. CONCLUSIONS: Transposed brachiobasilic fistulas provide cumulative patency equivalent to upper arm grafts and brachiocephalic fistulas. They are less likely to thrombose and become infected than upper arm grafts. Compared with brachiocephalic fistula, they are more likely to mature but are at increased risk of thrombosis after maturation. Transposed brachiobasilic fistulas should be considered before placing an upper arm graft for patients that cannot achieve a functional brachiocephalic fistula.

Arm↗
PubMed2000

Risk of bacteremia from temporary hemodialysis catheters by site of insertion and duration of use: a prospective study.

BACKGROUND: Uncuffed, nontunneled hemodialysis catheters remain the preferred means to gain immediate access to the circulation for hemodialysis. Bacteremia is the primary complication that limits their use. The risk of bacteremia by site of insertion and duration of use has not been well studied. METHODS: Two hundred eighteen consecutive patients who required a temporary hemodialysis catheter were prospectively followed. RESULTS: Catheters were placed at 318 new insertion sites and remained in use for a total of 6235 days. The incidence of bacteremia was 5.4% after three weeks of placement in internal jugular vein and 10.7% after one week in femoral vein [relative risk for bacteremia 3.1 (95% CI, 1.8 to 5.2)]. The incidence of bacteremia was 1.9% one day after the onset of an exit site infection but increased to 13.4% by the second day if the catheter was not removed. Guidewire exchange for malfunction and patient factors did not significantly affect the risk of bacteremia. CONCLUSIONS: Internal jugular catheters may be left in place for up to three weeks without a high risk of bacteremia, but femoral catheters in bed-bound patients should be removed after one week. Catheter exchanges over a guidewire for catheter malfunction do not increase bacteremia rates. Temporary catheters should be removed immediately if an exit site infection occurs.

Acute Kidney Injury↗
PubMed2000

The translational apparatus of Tortula ruralis: polysomal retention of transcripts encoding the ribosomal proteins RPS14, RPS16 and RPL23 in desiccated and rehydrated gametophytes.

Tortula ruralis (Syntrichia ruralis) is an important model system for the study of plant vegetative desiccation tolerance. One of the most intriguing aspects of desiccation-tolerant plants is the maintenance of key cellular components in stable and viable forms in the desiccated state, particularly those related to the translational apparatus (i.e. ribosomes and ribosomal RNAs). This study investigated the third integral component of the translational apparatus, the ribosomal proteins. Three T. ruralis cDNAs encoding predicted polypeptides with significant similarity to ribosomal proteins were isolated from a cDNA expression library derived from the polysomal, messenger ribonucleoprotein particle (mRNP) fraction of desiccated gametophytes; Rps14 and Rps16 encode the small-subunit ribosomal proteins RPS14 and RPS16, respectively, and Rpl23 encodes the large-subunit ribosomal protein RPL23. RPS14, RPS16 and RPL23, the deduced polypeptides, have predicted molecular masses of 14.4 kDa, 16.2 kDa and 14.9 kDa and predicted pI's of 11.08, 10.34 and 10. 67, respectively. Phylogenetic analysis of the deduced amino acid sequences demonstrated that each of the T. ruralis proteins is most similar to ribosomal proteins from higher plants even though RPS14 and RPL23 show high divergence from their other plant counterparts. RNA blot hybridizations of RNAs present within the polysomal mRNP fraction (i.e. the 100 Kxg pellet) demonstrated that Rps14, Rps16 and Rpl23 are expressed in moss gametophytes during a desiccation-rehydration cycle and, according to the prior cDNA classification scheme in T. ruralis, are constitutive clones. These findings clearly demonstrated that Rps14, Rps16 and Rpl23 transcripts are retained within the polysomal fractions of desiccated gametophytes.

Amino Acid Sequence↗
PubMed2000

Isolation of Arabidopsis mutants lacking components of acquired thermotolerance.

Acquired thermotolerance is a complex physiological phenomenon that enables plants to survive normally lethal temperatures. This study characterizes the temperature sensitivity of Arabidopsis using a chlorophyll accumulation bioassay, describes a procedure for selection of acquired thermotolerance mutants, and provides the physiological characterization of one mutant (AtTS02) isolated by this procedure. Exposure of etiolated Arabidopsis seedlings to 48 degrees C or 50 degrees C for 30 min blocks subsequent chlorophyll accumulation and is eventually lethal. Arabidopsis seedlings can be protected against the effects of a 50 degrees C, 30-min challenge by a 4-h pre-incubation at 38 degrees C. By the use of the milder challenge, 44 degrees C for 30 min, and protective pretreatment, mutants lacking components of the acquired thermotolerance system were isolated. Putative mutants isolated by this procedure exhibited chlorophyll accumulation levels (our measure of acquired thermotolerance) ranging from 10% to 98% of control seedling levels following pre-incubation at 38 degrees C and challenge at 50 degrees C. The induction temperatures for maximum acquired thermotolerance prior to a high temperature challenge were the same in AtTS02 and RLD seedlings, although the absolute level of chlorophyll accumulation was reduced in the mutant. Genetic analysis showed that the loss of acquired thermotolerance in AtTS02 was a recessive trait. The pattern of proteins synthesized at 25 degrees C and 38 degrees C in the RLD and AtTS02 revealed the reduction in the level of a 27-kD heat shock protein in AtTS02. Genetic analysis showed that the reduction of this protein level was correlated with the acquired thermotolerance phenotype.

Arabidopsis↗
PubMed1999

Protein conformational stability in the hydrofluoroalkane propellants tetrafluoroethane and heptafluoropropane analysed by Fourier transform Raman spectroscopy.

Due to the inherent structural instability of proteins, development of chlorofluorocarbon (CFC) free metered dose inhalers (MDIs) containing these biomolecules is beset with numerous challenges. In assessing the conformation of proteins in any medium, both secondary and tertiary structures need to be elucidated. This study uses Fourier transform (FT-) Raman spectroscopy to probe protein conformational stability in hydrofluoroalkane (HFA) propellants. Assignments of molecular modes for lysozyme as a solid and in aqueous solution, and for the first time, HFAs tetrafluoroethane (HFA 134a) and heptafluoropropane (HFA 227) are given. The Raman spectra provided molecular structural information on the peptide backbone, disulfide bonds and C-C stretching vibrations of hen egg lysozyme, enabling the secondary conformation of protein in HFA propellants to be determined; structural integrity of this robust model protein was maintained in both propellants. These results demonstrate that FT-Raman may be a useful tool for the optimisation of protein MDI formulations.

Drug Stability↗
PubMed1999

Characterization of a desiccation-responsive small GTP-binding protein (Rab2) from the desiccation-tolerant grass Sporobolus stapfianus.

We have used differential display to detect altering mRNA levels in response to desiccation and rehydration in leaves of the desiccation tolerant grass Sporobolus stapfianus. One of the RT-PCR products identified was used to isolate a cDNA of 999 bp which encodes a protein of 210 amino acids (predicted size 23 kDa). This protein displays considerable sequence similarity to mammalian and plant Rab2, a small GTP-binding protein, possessing several conserved motifs common to these regulatory proteins. Sporobolus Rab2 was expressed in Escherichia coli yielding a protein with an apparent molecular mass of ca. 30 kDa which was shown to have the ability to bind GTP. Rab2 transcript accumulated early in response to a decrease in relative water content (RWC) and remained high even in dried leaves. Rehydration of desiccated leaves resulted in a decrease in levels within 3 h of rewetting, with a brief increase at ca. 12 h. Accumulation of Rab2 transcript was also evident during drying and rehydration of the roots of S. stapfianus, as well as in leaves of the desiccation-sensitive grass Sporobolus pyramidalis. Earlier work on S. stapfianus concluded that the plant hormone ABA has little effect on inducing desiccation tolerance, however Rab2 transcript does exhibit a small increase in accumulation in response to exogenous ABA. A possible role for Rab2 with respect to desiccation tolerance and damage repair is discussed.

Amino Acid Sequence↗
PubMed1999

The involvement of ubiquitin in vegetative desiccation tolerance.

We have isolated a polyubiquitin cDNA from the modified desiccation-tolerant grass Sporobolus stapfianus. This cDNA, along with a commercially available polyclonal ubiquitin antibody, was used to characterize desiccation/rehydrated-associated changes in ubiquitin-mediated protein degradation in S. stapfianus and the fully desiccation-tolerant moss Tortula ruralis. Northern analysis demonstrated that in S. stapfianus leaves two ubiquitin transcripts, of ca. 1.4 and 1.2 kb, accumulated above control levels during drying and rehydration but were barely detectable in desiccated tissue. The peak in rehydration-associated transcript accumulation coincided with a depletion in ubiquitin monomer levels indicating an increase in protein degradation. Analysis of T. ruralis revealed three ubiquitin transcripts of ca. 1.9, 1.3 and 0.65 kb, with only the 1.3 kb transcript level varying in response to drying and rehydration and all transcripts being stable in dried tissue. Western analysis revealed that conjugated ubiquitin, indicative of proteins targeted for removal, was evident in all samples of Sporobolus but detectable only in slow-drying Tortula which also displayed reduced levels of ubiquitin monomer. These results demonstrate that desiccated T. ruralis gametophyte possesses stable ubiquitin transcripts which can be translated upon rehydration enabling rapid initiation of cellular repair through degradation of certain proteins. This is in contrast to S. stapfianus which requires several hours to replenish depleted ubiquitin transcripts. The ubiquitin response to drying and rehydration in evolutionarily diverse systems is characterized, and the role of repair mechanisms such as ubiquitin-mediated protein degradation in desiccation tolerance is assessed.

Abscisic Acid↗
PubMed1999

Expressed sequence tags (ESTs) from desiccated Tortula ruralis identify a large number of novel plant genes.

The desiccation-tolerant moss Tortula ruralis [Hedw.] Gaerten., Meyer & Scherb. has both a constitutive protection system and an active rehydration induced recovery mechanism apparently unique to bryophytes. Immediately following rehydration, desiccated T.ruralis gametophytes produce a set of polypeptides whose synthesis is unique to the rehydrated state. We report the construction of a cDNA expression library from the polysomal mRNA of desiccated gametophytes and the single-pass sequencing of randomly selected clones. 152 expressed sequence tags (ESTs) were generated representing more than 60,000 bp of non-redundant DNA sequence. 44 ESTs (29%) demonstrated significant homology to previously identified nucleotide and/or polypeptide sequences, such as ribosomal proteins, desiccation-related peptides, early light-inducible proteins and a V-type ATPase. Analysis of a subset of these homologous ESTs reveals that codon preference in T.ruralis is similar to that of vascular plants, particularly the Magnoliopsida. 108 ESTs (71%) demonstrated no significant homology to deposited sequences and represent a large number of novel plant genes. Analysis of these ESTs will define the range of genes involved in cellular repair and recovery and may provide greater insight to the complex phenotype of vegetative desiccation-tolerance.

Bryopsida↗
PubMed1995

Extension creep in the lumbar spine.

This in vitro study was designed to examine extension creep of the lumbar spine under conditions of sustained loading. By means of a weight and pulley circuit, loads simulating lumbar extension and flexion were applied to 25 male lumbar spines removed at postmortem. Sagittal ranges of movement and the amount of creep occurring in a 20-min period at the limit of extension were recorded. The data were classified into three age group categories representing young adults, the middle-aged and the elderly. The results indicated that extension creep behaviour was similar to that of flexion creep previously reported. The elderly lumbar spines appeared to have a greater range of extension creep than those of the young and middle-aged groups, but analysis of variance showed that the difference in creep between age groups was not significant. The viscoelastic behaviour of the spinal ligaments, zygapophyseal joint capsules and intervertebral discs during extension are sufficient to produce a characteristic creep-recovery curve, but perhaps the important role that the zygapophyseal joints play in limiting extension is sufficient to prevent significant change in creep behaviour with increasing age. RELEVANCE:--This study provides information on the biomechanical responses of the lumbar spine to sustained end range extension loading. Results suggest that in the living, even brief periods of sustained extension loading may cause significant extension creep.

Journal Article↗
PubMed1995

Injury in laparoscopic surgery.

A prospective study was made to evaluate injury caused by laparoscopic surgery, in terms of physiological response. Two groups of patients were established: Group 1 (laparoscopic surgery, n = 26) and Group 2 (open surgery, n = 18). The groups were homogeneous in terms of age, sex, body mass index (BMI), duration of surgery, and anesthetic technique. Both groups exhibited significant postoperative increases in plasma adrenocorticotropic hormone (ACTH), growth hormone (GH), insulin, and cortisol (p < 0.05), with a significant decrease in follicle-stimulating hormone (FSH) and T3 (p < 0.05). Significant increases were noted in 24-h urine cortisol and catecholamine levels in Group 2 (p < 0.05). No correlation was noted between the duration of surgery and the intensity of neuroendocrine response. Acute-phase postoperative metabolic response was greater in Group 2 and was correlated to the duration of surgery. No postoperative hydrosaline or acid-base alterations were recorded in either group. Injury was graded in terms of neuroendocrine and metabolic response and proved highest in Group 2. Complex laparoscopic surgery (e.g., sigmoid colon and esophageal hiatus) exhibited the least neuroendocrine response, whereas laparoscopic inguinal hernioplasty involved the least metabolic response. To conclude, laparoscopic surgery globally involves less neuroendocrine and metabolic response than does open surgery.

Acute-Phase Reaction↗
PubMed1993

Inhibition of tobacco NADH-hydroxypyruvate reductase by expression of a heterologous antisense RNA derived from a cucumber cDNA: implications for the mechanism of action of antisense RNAs.

Tobacco plants were genetically transformed to generate antisense RNA from a gene construct comprised of a full-length cucumber NADH-dependent hydroxypyruvate reductase (HPR) cDNA placed in reverse orientation between the cauliflower mosaic virus 35S promoter and a nopaline synthase termination/polyadenylation signal sequence. In vivo accumulation of antisense HPR RNA within eight independent transgenic tobacco plants resulted in reductions of up to 50% in both native HPR activity and protein accumulation relative to untransformed tobacco plants (mean transgenote HPR activity = 67% wild type, mean transgenote HPR protein = 63% wild type). However, in contrast to previous reports describing antisense RNA effects in plants, production of the heterologous HPR antisense RNA did not systematically reduce levels of native tobacco HPR mRNA (mean transgenote HPR mRNA level = 135% wild type). Simple regression comparison of the steady-state levels of tobacco HPR mRNA to those of HPR antisense RNA showed a weak positive correlation (r value of 0.548, n = 9; n is wild type control plus eight independent transformants; significant at 85% confidence level), supporting the conclusion that native mRNA levels were not reduced within antisense plants. Although all transgenic antisense plants examined displayed an apparent reduction in both tobacco HPR protein and enzyme activity, there is no clear correlation between HPR activity and the amount of either sense (r = 0.267, n = 9) or antisense RNA (r = 0.175, n = 9). This compares to a weak positive correlation between HPR mRNA levels and the amount of HPR activity observed in wild-type SR1 tobacco plants (r = 0.603, n = 5).(ABSTRACT TRUNCATED AT 250 WORDS)

Carbohydrate Dehydrogenases↗