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Biomedical subjects

W Martin

Publications and source records attributed to W Martin.

At least 127 records · Page 7Linked to original sources
PubMed1996

Respiratory dysfunction and white cell activation following cardiopulmonary bypass: comparison of membrane and bubble oxygenators.

OBJECTIVE: Cardiopulmonary bypass induces respiratory dysfunction postoperatively, with activation of both the complement system and white cells implicated. This study compared the effects of bubble and membrane oxygenators for cardiopulmonary bypass in terms of respiratory dysfunction and markers of white cell activation and endothelial damage. METHODS: Fifty patients undergoing cardiopulmonary bypass were randomly allocated either membrane or bubble oxygenation. Respiratory function was assessed serially by arterial oxygen tension and alveolar-arterial oxygen gradient. Complement activation was measured by serial sampling of serum C3a levels. White cell activation was assessed by serial measurement granulocyte elastase; other markers investigated were levels of thromboxane B2, von Willebrand factor and malondialdehyde. All sample measurements were made preoperatively, early and late during bypass, 4-6 h postoperatively and then on the 1st, 2nd and 6th postoperative day. All samples were corrected for haemodilution, and differences between groups tested non-parametrically. RESULTS: In both groups of patients there was a highly significant fall (P < 0.001) in arterial oxygen tension accompanied by a highly significant rise (P < 0.0001) in aleveolar-arterial oxygen gradient at 18 h compared to preoperative values persisting until 6 days postoperatively. Levels of C3a increased significantly in both groups at 10 min post bypass, increased further at 60 min peaking at 4-6 h post bypass. Granulocyte elastase serum levels increased significantly at 10 min postoperatively in both groups compared to control levels, remaining elevated till 48 h, but returning to control levels by 6 days. There was a small difference (P < 0.04) between the groups at 4-6 h only. Levels of von Willebrand factor increased significantly at 60 min post bypass in both groups, remaining elevated 6 days postoperatively. Levels of malondialdehyde increased at 10 min post bypass, remaining elevated until 6 days post bypass. Thromboxane levels showed no significant changes. For all markers measured, there were no significant differences between the groups other than those already indicated. CONCLUSIONS: This study demonstrated marked respiratory dysfunction, complement activation and white cell activation in patients undergoing cardiopulmonary bypass with either bubble or membrane oxygenators. There was marked variability in the response of individual patients with either oxygenation technique, but overall no significant differences between the groups.

Blood Gas Analysis↗
PubMed1996

Noncoding sequences from the slowly evolving chloroplast inverted repeat in addition to rbcL data do not support gnetalean affinities of angiosperms.

We developed PCR primers against highly conserved regions of the rRNA operon located within the inverted repeat of the chloroplast genome and used these to amplify the region spanning from the 3' terminus of the 23S rRNA gene to the 5' terminus of the 5S rRNA gene. The sequence of this roughly 500-bp region, which includes the 4.5S rRNA gene and two chloroplast intergenic transcribed spacer regions (cpITS2 and cpITS3), was determined from 20 angiosperms, 7 gymnosperms, and 16 ferns (21,700 bp). Sequences for the large subunit of ribulose bisphosphate carboxylase/oxygenase (rbcL) from the same or confamilial genera were analyzed in both separate and combined data sets. Due to the low substitution rate in the inverted repeat region, noncoding sequences in the cpITS region are not saturated with substitutions, in contrast to synonymous sites in rbcL, which are shown to evolve roughly six times faster than noncoding cpITS sequences. Several length polymorphisms with very clear phylogenetic distributions were detected in the data set. Results of phylogenetic analyses provide very strong bootstrap support for monophyly of both spermatophytes and angiosperms. No support for a sister group relationship between Gnetales and angiosperms in either cpITS or rbcL data was found. Rather, weak bootstrap support for monophyly of gymnosperms studied and for a basal position for the aquatic angiosperm Nymphaea among angiosperms studied was observed. Noncoding sequences from the inverted repeat region of chloroplast DNA appear suitable for study of land plant evolution.

Base Sequence↗
PubMed1996

Exercise 201Tl/rest 99Tcm-tetrofosmin myocardial perfusion imaging: a convenient protocol for the assessment of coronary disease.

Standard exercise thallium-201 (201Tl)-redistribution protocols for the detection of coronary artery disease take about 4 h to complete. This is inconvenient for both patients and staff. The higher energy technetium-99m (99Tcm) emissions permit immediate imaging after 201Tl with minimal crosstalk. This study assessed exercise gated planar 201Tl scintigraphy (55 MBq) followed by rest gated planar 99Tcm-tetrofosmin scintigraphy (250 MBq) in 32 patients. The results showed a high sensitivity for the detection of coronary disease (100%) in this highly selective group of patients. In order to diagnose myocardial infarction accurately, it was necessary to view the gated 201Tl images and assess regional wall motion in a defect zone. This gave a specificity of 88% and a sensitivity of 71% for the prediction of myocardial infarction on the angiographic ventriculogram. Stress 201Tl/rest 99Tcm-tetrofosmin is a useful short protocol for patients unable to complete the full 4-h exercise 201Tl-redistribution study.

Adult↗
PubMed1996

Quantification of extracorporeal white cell and platelet deposition in cardiopulmonary bypass: comparison of membrane and bubble oxygenators.

Cardiopulmonary bypass is known to activate both white cells and platelets. The aim of this study was to investigate whether the use of bubble and membrane oxygenators results in different degrees of deposition in the filter and oxygenator of the bypass circuit. Dual-isotope imaging techniques were employed, with white cells labelled with 99Tcm and platelets with 111In, and with subsequent imaging of the filters and oxygenators on a gamma camera fitted with a medium-energy, parallel-hole collimator, relative to a known standard. The percentage white cell oxygenator deposition ranged from 0.011 to 4.91% in the bubble group (n = 20) and was not different from the membrane group (0.001 to 4.22%). Similarly, no difference in platelet deposition was found, with 0.605-45.17% deposited in the bubble oxygenators and 0.001-15.26% deposited in the membrane oxygenators. Filter deposition of both types of cell was substantially lower in both membrane and bubble groups with no difference between groups. The striking feature of the data is the non-normal distribution of the deposition in both types of oxygenator. This study demonstrated that both white cell and platelet deposition in the cardiopulmonary bypass circuit can be quantified using radiolabelled cells. No differences in oxygenator or filter deposition were found in patients randomly allocated to membrane or bubble oxygenation.

Blood Platelets↗
PubMed1996

Rest or redistribution thallium myocardial imaging for resting myocardial perfusion: a detailed comparison with regional wall motion.

Redistribution thallium-201 (201T1) imaging is the most common method of assessing resting myocardial perfusion. However, the equivalence of a redistribution image and a separate rest injection is unclear. Although the presence of a defect on rest imaging has normally been equated with the presence of a myocardial infarction, it has recently been shown that a significant proportion of fixed defects on exercise-redistribution 201T1 actually represent areas of viable myocardium. This study was a detailed comparison of rest and redistribution imaging in 30 patients undergoing routine exercise 201T1 scanning for the assessment of coronary artery disease. A small dose (15 MBq) of 201T1 was administered at rest following the imaging in three standard planar views. Similar stress images were acquired using a further 50-55 MBq of 201T1 administered at peak effort. Redistribution images were acquired 3-4 h later and equilibrium blood pool ventriculography performed using in vivo labelling with 600 MBq 99Tcm-pertechnetate. Of 150 abnormal segments on the exercise scans, 74 (49%) were identified as being reversible on the redistribution scans and 58 (39%) on the rest images. Only 39 (53%) of these reversible defects were identified on both the redistribution and rest scans. Only 41% of the fixed defects on the redistribution images (32% of fixed defects on the rest images) had abnormal wall motion. Therefore, rest and redistribution images are not equivalent. Both rest and redistribution images significantly overestimate myocardial infarction. This may have significant effects on patient selection for revascularization procedures and therefore all patients having perfusion scintigraphy should also have additional assessment of regional wall motion to allow accurate classification of the functional status of myocardial segments.

Coronary Circulation↗
PubMed1996

Anthranilate synthase from Ruta graveolens. Duplicated AS alpha genes encode tryptophan-sensitive and tryptophan-insensitive isoenzymes specific to amino acid and alkaloid biosynthesis.

Anthranilate synthase (AS, EC 4.1.3.27) catalyzes the conversion of chorismate into anthranilate, the biosynthetic precursor of both tryptophan and numerous secondary metabolites, including inducible plant defense compounds. The higher plant Ruta graveolens produces tryptophan and elicitor-inducible, anthranilate-derived alkaloids by means of two differentially expressed nuclear genes for chloroplast-localized AS alpha subunits, AS alpha 1 and AS alpha 2. Mechanisms that partition chorismate between tryptophan and inducible alkaloids thus do not entail chloroplast/cytosol separation of AS isoenzymes and yet might involve differential feedback regulation of pathway-specific AS alpha subunits. The two AS alpha isoenzymes of R. graveolens were expressed as glutathione S-transferase fusion proteins in Escherichia coli deletion mutants defective in AS activity and were purified to homogeneity. Differential sensitivity of the transformed E. coli strains toward 5-methyltryptophan, a false-feedback inhibitor of AS, was demonstrated. Characterization of affinity-purified AS alpha isoenzymes revealed that the noninducible AS alpha 2 of R. graveolens is strongly feedback inhibited by 10 microns tryptophan. In contrast, the elicitor-inducible AS alpha 1 isoenzyme is only slightly affected even by tryptophan concentrations 10-fold higher than those observed in planta. These results are consistent with the hypothesis that chorismate flux into biosynthesis of tryptophan and defense-related alkaloid biosynthesis in R. graveolens is regulated at the site of AS alpha isoenzymes at both genetic and enzymatic levels.

Alkaloids↗
PubMed1996

Blockade of nitrergic transmission by hydroquinone, hydroxocobalamin and carboxy-PTIO in bovine retractor penis: role of superoxide anion.

1. The effects of inhibiting endogenous Cu/Zn superoxide dismutase (SOD) with diethyldithiocarbamate (DETCA) were examined on the ability of hydroquinone, hydroxocobalamin and carboxy-PTIO to block nitrergic relaxation in the bovine retractor penis (BRP) muscle. 2. Incubation of strips of BRP with DETCA (3 mM) for 2 h reduced SOD activity from 73.1 +/- 15.7 to 8.2 +/- 1.9 units mg-1 protein. 3. Hydroquinone (10 microM--1 mM) produced weak inhibition of nitrergic (4 Hz, 10 s) relaxation in control strips of BRP, but powerful inhibition in strips treated with DETCA (3 mM, 2 h). Exogenous SOD (250 units ml--1) produced a partial blockade of the ability of hydroquinone to inhibit nitrergic relaxation in DETCA-treated strips. 4. In an assay of SOD-inhibitable reduction of cytochrome C, hypoxanthine (0.1 mM)/xanthine oxidase (16 munits ml-1) and pyrogallol (10 microM), led to the rapid generation of superoxide anion. Hydroquinone (10 microM) also led to the generation of the free radical, although the rate of generation was slower. 5. Two NO-scavenging agents, hydroxocobalamin (0.1 microM--1 mM) and carboxy-PTIO (0.1-1 mM), produced concentration-dependent blockade of nitrergic relaxation of the BRP. The magnitude of the blockade induced by these agents was unaffected following treatment with DETCA or SOD. 6. The findings with hydroquinone support our previous proposal that endogenous Cu/Zn SOD plays a vital role in protecting nitrergic neurotransmission from inactivation by superoxide anion. Results with hydroxocobalamin and carboxy-PTIO are consistent with the known ability of these agents to scavenge NO. The nitrergic neurotransmitter in the BRP thus appears to have the properties of NO.

Animals↗
PubMed1996

Somatostatin receptor imaging: predictive and prognostic considerations.

Compared with other imaging modalities and clinical investigation, the 111In-pentetreotide scan identified additional metastatic disease sites in 12 carcinoid patients and 2 occult primaries, and influenced the therapeutic outcome in 36 patients [29 carcinoids, 2 atypical carcinoids, 3 cancers of unknown primaries (CUPs) and 2 medullary thyroid carcinomas (MCTs)]. No adverse reactions were noted. Somatostatin receptors were detected in 59/60 carcinoid patients, 3/4 atypical carcinoid patients, 0/2 MCT patients, and 0/3 cases of CUP. Somatostatin receptor presence is underestimated in some patients using standard hormonal response criteria rather than scintigraphy. 18 patients with metastatic carcinoids who underwent 111In-pentetreotide scanning were all somatostatin receptor positive. Their mean (+/- SE) 5-hydroxyindoleacetic acid (5-HIAA) suppression with octreotide therapy was -53% (+/- 6%). 8 patients had < 50% and 10 had > 50% 5-HIAA suppression (ranges: -4 to -47% and -58 to -94%, respectively). To investigate the effect of somatostatin analogues on survival, 90 consecutive cases of carcinoid syndrome patients treated during the somatostatin analogue era were reviewed. Survival according to primary site was 12.01, 18.29 and 6.05 years (overall median 12.01 years) for patients with foregut, midgut and unknown primaries, respectively. The difference from historical controls is substantial (67 vs. 18% 5-year survival), although our series is neither prospective nor randomised. The heterogeneity in patient and tumour response to somatostatin analogue therapy is discussed.

Carcinoid Tumor↗
PubMed1995

A nuclear gene of eubacterial origin in Euglena gracilis reflects cryptic endosymbioses during protist evolution.

Genes for glycolytic and Calvin-cycle glyceraldehyde-3-phosphate dehydrogenase (GAPDH) of higher eukaryotes derive from ancient gene duplications which occurred in eubacterial genomes; both were transferred to the nucleus during the course of endosymbiosis. We have cloned cDNAs encoding chloroplast and cytosolic GAPDH from the early-branching photosynthetic protist Euglena gracilis and have determined the structure of its nuclear gene for cytosolic GAPDH. The gene contains four introns which possess unusual secondary structures, do not obey the GT-AG rule, and are flanked by 2- to 3-bp direct repeats. A gene phylogeny for these sequences in the context of eubacterial homologues indicates that euglenozoa, like higher eukaryotes, have obtained their GAPDH genes from eubacteria via endosymbiotic (organelle-to-nucleus) gene transfer. The data further suggest that the early-branching protists Giardia lamblia and Entamoeba histolytica--which lack mitochondria--and portions of the trypanosome lineage have acquired GAPDH genes from eubacterial donors which did not ultimately give rise to contemporary membrane-bound organelles. Evidence that "cryptic" (possibly ephemeral) endosymbioses during evolution may have entailed successful gene transfer is preserved in protist nuclear gene sequences.

Amino Acid Sequence↗
PubMed1995

Cloning of the amphibolic Calvin cycle/OPPP enzyme D-ribulose-5-phosphate 3-epimerase (EC 5.1.3.1) from spinach chloroplasts: functional and evolutionary aspects.

Exploiting the differential expression of genes for Calvin cycle enzymes in bundle-sheath and mesophyll cells of the C4 plant Sorghum bicolor L., we isolated via subtractive hybridization a molecular probe for the Calvin cycle enzyme D-ribulose-5-phosphate 3-epimerase (R5P3E)(EC 5.1.3.1), with the help of which several full-size cDNAs were isolated from spinach. Functional identity of the encoded mature subunit was shown by R5P3E activity found in affinity-purified glutatione S-transferase fusions expressed in Escherichia coli and by three-fold increase of R5P3E activity upon induction of E. coli overexpressing the spinach subunit under the control of the bacteriophage T7 promoter, demonstrating that we have cloned the first functional ribulose-5-phosphate 3-epimerase from any eukaryotic source. The chloroplast enzyme from spinach shares about 50% amino acid identity with its homologues from the Calvin cycle operons of the autotrophic purple bacteria Alcaligenes eutrophus and Rhodospirillum rubrum. A R5P3E-related eubacterial gene family was identified which arose through ancient duplications in prokaryotic chromosomes, three R5P3E-related genes of yet unknown function have persisted to the present within the E. coli genome. A gene phylogeny reveals that spinach R5P3E is more similar to eubacterial homologues than to the yeast sequence, suggesting a eubacterial origin for this plant nuclear gene.

Amino Acid Sequence↗
PubMed1995

Intron-dependent transient expression of the maize GapA1 gene.

Transient expression experiments show that the maize GapA1 promoter exhibits a requirement for sequences contained within intron 1 and surrounding exon border regions for expression in maize Black Mexican Sweet cells. Maize GapA1-promoter constructs lacking intron 1 are inactive. Intron 1 and its exon border sequences, when reintroduced into constructs lacking introns, restore gene activity whereas intron 2 and its exon borders to not. The minimal promoter so defined encompasses roughly 250 bp upstream of the in vivo transcription start and appears also to include intron 1. An octameric sequence was identified in intron 1 of maize GapA1 which is similar to sequence motifs found in other maize introns known to increase transient expression. Partial restoration of gene expression in GapA1 constructs lacking intron 1 was achieved through insertion of the identified octameric sequence.

Base Sequence↗
PubMed1995

Intraoperative stimulation of pedicle screws: a new method for verification of screw placement.

Pedicular fixation of the lumbosacral spine has become a popular procedure for improving fusion rates. Even in experienced hands, it can be associated with a significant rate of screw malpositioning and potential nerve root injury. In this report, we describe a technique for improving screw localization utilizing evoked electromyography responses from direct stimulation of pedicle instrumentation.

Adult↗
PubMed1995

Transurethral ultrasound-guided laser-induced prostatectomy: clinical outcome and data analysis.

OBJECTIVES: To analyze efficacy and side effects of the transurethral ultrasound-guided laser-induced prostatectomy (TULIP) procedure for the treatment of bladder outlet obstruction due to benign prostatic hyperplasia (BPH). Based on the results obtained so far, the influence of preoperative and intraoperative parameters on clinical outcome is analyzed. METHODS: Between May 1991 and March 1994, 89 men with symptomatic and obstructive BPH underwent a TULIP procedure and were followed after 3 and 6 weeks, and 3, 6, and 12 months postoperatively. RESULTS: On average, mean urinary peak flow increased from 7 to 15 mL/s, postvoidal residual urine decreased from 215 to 40 mL and symptoms (assessed by modified Boyarsky score) decreased from 17 to 5 at 12 months after TULIP: In about half of the patients peak flow increased to more than 20 mL/s on average, and approximately 85% of all men reported that their symptoms improved on average 80% during this time. Because of insufficient micturition, 7 patients subsequently underwent conventional transurethral resection of the prostate (TURP) and 1 had an open prostatectomy. Either partial or complete retrograde ejaculation was reported by 13 of 58 sexually active men. No blood transfusion was required and no post-transurethral resection syndrome occurred in any case. Analyses of preoperative and intraoperative parameters and clinical outcome with respect to prostate volume, urinary retention, type of BPH enlargement, sleeve size, and good and poor responders did not reveal any significant influence of any factor. There is, however, a trend toward a lower laser energy delivered in patients who failed or may be considered to be poor responders. CONCLUSIONS: In this unselected group of patients with BPH, who otherwise would have been TURP candidates, the TULIP procedure demonstrated the efficacy of this technique to relieve bladder outlet obstruction. Compared with TURP, the TULIP procedure proved to be advantageous in regard to less blood loss and rate of retrograde ejaculation. In addition, TULIP can be performed under analgesic sedation, which is especially advantageous in high-risk patients. Disadvantages, however, are that it takes a considerably longer time to obtain substantial improvements in subjective and objective symptoms and there are more irritative symptoms in the early postoperative phase.

Aged↗
PubMed1995

Psychosis in Parkinson's disease: diagnosis and treatment.

1. This article reviews the prevalence, diagnosis, pathophysiology and management of psychosis in Parkinson's disease. 2. Psychosis in Parkinson's disease has been associated with all antiparkinsonian medications. The most common symptoms are vivid disturbing dreams, visual hallucinations and paranoid delusions. 3. The emergence of psychosis reduces the patient's functional capacity and increases caregiver burden. It also poses a therapeutic dilemma because effective treatment of psychotic symptoms may result in worsening of motor symptoms and vice versa. 4. Increased physician awareness is essential for proper diagnosis and management. Withdrawal of anticholinergic medications and amantadine followed by levodopa dose adjustment is effective in many patients. 5. Atypical neuroleptics, in low doses, may be successful when other measures have failed. However, these agents are not approved for treating Parkinsonian psychosis and must be considered as investigational therapies.

Clozapine↗
PubMed1995

Purification and cDNA cloning of anthranilate synthase from Ruta graveolens: modes of expression and properties of native and recombinant enzymes.

Ruta graveolens utilizes anthranilate synthase (AS) for the synthesis both of tryptophan in primary metabolism and acridone alkaloids in secondary metabolism. AS has been purified from plants and cell cultures of R. graveolens 670- and 1700-fold, respectively. Glutamine- and ammonia-dependent AS activities were strictly co-purified in all steps. Through cDNA cloning and complementation of Escherichia coli deletion mutants defective for AS, it is shown that young Ruta plants express two genes for functional AS alpha subunits, AS alpha 1 and AS alpha 2. The data indicate that AS alpha from Ruta requires an AS beta subunit with a native molecular weight of 60-65 kDa for the glutamine-dependent reaction. Protein synthesized in vitro from cloned cDNA is processed upon import into isolated chloroplasts, indicating that mature AS alpha subunits are active in plastids in vivo. AS alpha 1 and AS alpha 2 are constitutively expressed in Ruta cell cultures, but AS alpha 1 steady-state mRNA levels are increased 100-fold 6 h subsequent to elicitation whereas AS alpha 2 expression remains constitutive. Increased AS alpha 1 transcription corresponds to elicitor-induced alkaloid accumulation. The data indicate that Ruta regulates anthranilate flux into primary and secondary metabolism through differential regulation of AS genes specific to these pathways.

Amino Acid Sequence↗
PubMed1995

Laser profiling: a technique for the study of prosthetic heart valve leaflet motion.

A detailed understanding of the stresses and strains developed in functioning flexible-leaflet valves is necessary if a durable, non-thrombogenic heart valve replacement is to be realized. A new experimental tool, laser profiling, is presented for the study of flexible-leaflet heart valve dynamics. Profiles of moving leaflet surfaces are obtained by projecting parallel sheets of laser light onto valve leaflets as the valves open and close in a mock circulatory loop. Two versions of laser profiling have been developed. In two-dimensional mode multiple profiles are generated on a fixed plane in space but at discrete intervals in time, whereas in three-dimensional mode multiple profiles are generated across the leaflet surface at (effectively) a single instant in time. Highlighted leaflet profiles are captured by camera and transferred to an image processing system for analysis. A simple algorithm permits digitized profiles to be reconstructed within a computer-aided design software package, providing detailed visualization and quantification of valve motion. Extensive validation studies have been performed using the Medtronic-Hall mechanical prosthetic heart valve. Laser profiling enables computer reconstruction of the rigid occluder to an accuracy of +/- 200 microns from a 0.7 ms exposure taken during the period at which the occluder moves with greatest velocity. The technique has been applied to investigate the leaflet dynamics of a bovine pericardial heart valve prosthesis.

Acoustic Stimulation↗