Biomedical subjects

A Jordan

Publications and source records attributed to A Jordan.

At least 37 records · Page 2Linked to original sources

PubMed1999

[Tube feeding in malnutrition].

Malnutrition is known to be very common in geriatric patients. The incidence is ranging from 30 to 60% of all patients. Therefore, indication for nutritional support via nasogastric or percutaneous tubes is frequently given. Since percutaneous endoscopic gastrostomy (PEG) has several advantages over nasogastric tube feeding including reduced risk of tube displacement and blockage, and higher patient acceptance, it has become the method of choice in enteral tube feeding. Complication rates are low provided that guidelines for enteral tube feeding are considered. Early home enteral nutrition contributes to patients quality of life.

Aged↗

PubMed1999

Empowerment evaluation as a social work strategy.

This article explores the application of empowerment strategies to program evaluation within a community health setting and presents a case study to examine the policy, direct practice, and research issues associated with the plan to evaluate a community-based HIV-prevention program. Empowerment evaluation strategies were used to develop an innovative street outreach intervention that can be measured and evaluated, to transfer evaluation knowledge from the researcher-expert to the program stakeholders, and to help overcome evaluation implementation obstacles. The article addresses the benefits and risks inherent in an empowerment approach to the evaluative research process.

Community Health Services↗

PubMed1999

Visualization and registration of three-dimensional E-field distributions in annual-phased-array applicators.

A testing system is presented allowing registration, digitization, and evaluation of three-dimensional power distributions rendered by annular-phased-array applicators in homogeneous liquid media. The system is based on a lamp phantom originally developed to visualize power distributions. Now the brightness distribution is registered via a charge-coupled device camera and transferred to a PC-based evaluation system outside the shielding room. An appropriate mechanical coupling of camera and sensor matrix probing the phantom was built in order to keep optical image conditions constant under movement. For visualization and evaluation commercially customized software was employed. The evaluation of the system shows the linearity between sensor signal and power density magnitude to be sufficient for evaluation and graphical representation of three-dimensional data sets. In a first practical application the testing system was employed to evaluate dependencies of power distributions as a function of frequency and phase settings on temperatures and, subsequently, the relevance of those results for clinical hyperthermia in a SIGMA-60 applicator (BSD-2000 system). Now, the system is ready to evaluate more complex multiantenna array applicators like the SIGMA-Eye applicator. The measuring system is particularly suitable for a fast comparison of APA applicators applied for a homogeneous medium. Implications for heterogeneous structures (like in patients) are then possible via modeling calculations.

Calibration↗

PubMed1999

Ribonucleotide reduction in Pseudomonas species: simultaneous presence of active enzymes from different classes.

Three separate classes of ribonucleotide reductases exist in nature. They differ widely in protein structure. Class I enzymes are found in aerobic bacteria and eukaryotes; class II enzymes are found in aerobic and anaerobic bacteria; class III enzymes are found in strict and facultative anaerobic bacteria. Usually, but not always, one organism contains only one or two (in facultative anaerobes) classes. Surprisingly, the genomic sequence of Pseudomonas aeruginosa contains sequences for each of the three classes. Here, we show by DNA hybridization that other species of Pseudomonas also contain the genes for three classes. Extracts from P. aeruginosa and P. stutzeri grown aerobically or microaerobically contain active class I and II enzymes, whereas we could not demonstrate class III activity. Unexpectedly, class I activity increased greatly during microaerobic conditions. The enzymes were separated, and the large proteins of the class I enzymes were obtained in close to homogeneous form. The catalytic properties of all enzymes are similar to those of other bacterial reductases. However, the Pseudomonas class I reductases required the continuous presence of oxygen during catalysis, unlike the corresponding Escherichia coli enzyme but similar to the mouse enzyme. In similarity searches, the amino acid sequence of the class I enzyme of P. aeruginosa was more related to that of eukaryotes than to that of E. coli or other proteobacteria, with the large protein showing 42% identity to that of the mouse, suggesting the possibility of a horizontal transfer of the gene. The results raise many questions concerning the physiological function and evolution of the three classes in Pseudomonas species.

Aerobiosis↗

PubMed1999

Depression in Europe. Geographical distribution among older people.

BACKGROUND: This is the first report of results from the EURODEP Programme. AIMS: To assess the prevalence of depression judged suitable for intervention in randomised samples of those aged > or = 65 in nine European centres. METHOD: The GMS-AGECAT package. RESULTS: Differences in prevalence are apparent, 8.8% (Iceland) to 236% (Munich). When sub-cases and cases are added together, five high- and four low-scoring centres emerge. Women predominated over men. Proportions of sub-cases to cases revealed striking differences but did not explain prevalence. There was no constant association between prevalence and age. A meta-analysis (n = 13,808) gave an overall prevalence of 12.3%, 14.1% for women and 8.6% for men. CONCLUSIONS: Considerable variation occurs in the levels of depression across Europe, the cause for which is not immediately obvious. Case and sub-case levels taken together show greater variability, suggesting that it is not a matter of case/sub-case selection criteria, which were standardised by computer. Substantial levels of depression are shown but 62-82% of persons had no depressive level. Opportunities for treatment exist.

Age Distribution↗

PubMed1999

Cross-cultural comparison of depressive symptoms in Europe does not support stereotypes of ageing.

BACKGROUND: Stereotypes of older people suggest that they are depressed. AIMS: To examine depression symptoms among people aged > or = 65 in the general population and to ask the following questions. Are there high proportions of depressive symptoms among otherwise well people? Do these levels reflect the prevalence of depression? Do key symptoms vary with age and do they confirm stereotypes? METHOD: Nine centres contributed data from community-based random samples, using standardised methods (GMS-AGECAT package). RESULTS: Proportions of depressive symptoms varied between centres. Some often associated with ageing were rare. Many were more common in women. Low-prevalence centres tended to have fewer symptoms among 'well' people, but there were inconsistencies. Low levels of symptoms among the well population of a centre did not necessarily predict lower levels in the depressed. CONCLUSIONS: Variations in the prevalence of depressive symptoms occurred between centres, not always related to levels of illness. There was no consistent relationship between proportions of symptoms in well persons and cases for all centres. Few symptoms were present in > 60% of the older population--stereotypes of old age were not upheld.

Age Factors↗

PubMed1998

Structure of Salmonella typhimurium nrdF ribonucleotide reductase in its oxidized and reduced forms.

The first class Ib ribonucleotide reductase R2 structure, from Salmonella typhimurium, has been determined at 2.0 A resolution. The overall structure is similar to the Escherichia coli class Ia enzyme despite only 23% sequence identity. The most spectacular difference is the absence of the pleated sheet and adjacent parts present in the E. coli R2 structure; the heart-shaped structure loses its tip. From sequence comparisons, it appears that this feature is shared with all other class Ib enzymes and, in this respect, is more like the mammalian class Ia enzymes. Both the oxidized and reduced iron forms have been investigated. In the ferric iron center, both iron ions are octahedrally coordinated and bridged by one carboxylate and one oxide ion. The ferrous form has lost the bridging oxide ion but is bridged by two carboxylates. Accompanying the change in redox state, helix E changes its conformation from one covering the metal center in the oxidized form to a more open reduced form. A narrow channel is opened which may permit easier access of oxygen to the ferrous iron site and to efficiently generate the tyrosyl radical.

Amino Acid Sequence↗

PubMed1998

The manganese-containing ribonucleotide reductase of Corynebacterium ammoniagenes is a class Ib enzyme.

Ribonucleotide reductases (RNRs) are key enzymes in living cells that provide the precursors of DNA synthesis. The three characterized classes of RNRs differ by their metal cofactor and their stable organic radical. We have purified to near homogeneity the enzymatically active Mn-containing RNR of Corynebacterium ammoniagenes, previously claimed to represent a fourth RNR class. N-terminal and internal peptide sequence analyses clearly indicate that the C. ammoniagenes RNR is a class Ib enzyme. In parallel, we have cloned a 10-kilobase pair fragment from C. ammoniagenes genomic DNA, using primers specific for the known class Ib RNR. The cloned class Ib locus contains the nrdHIEF genes typical for class Ib RNR operon. The deduced amino acid sequences of the nrdE and nrdF genes matched the peptides from the active enzyme, demonstrating that C. ammoniagenes RNR is composed of R1E and R2F components typical of class Ib. We also show that the Mn-containing RNR has a specificity for the NrdH-redoxin and a response to allosteric effectors that are typical of class Ib RNRs. Electron paramagnetic resonance and atomic absorption analyses confirm the presence of Mn as a cofactor and show, for the first time, insignificant amounts of iron and cobalt found in the other classes of RNR. Our discovery that C. ammoniagenes RNR is a class Ib enzyme and possesses all the highly conserved amino acid side chains that are known to ligate two ferric ions in other class I RNRs evokes new, challenging questions about the control of the metal site specificity in RNR. The cloning of the entire NrdHIEF locus of C. ammoniagenes will facilitate further studies along these lines.

Amino Acid Sequence↗

PubMed1998

Intensive training, physiotherapy, or manipulation for patients with chronic neck pain. A prospective, single-blinded, randomized clinical trial.

STUDY DESIGN: A randomized, prospective clinical study was conducted that included 119 patients with chronic neck pain of greater than 3 months' duration. OBJECTIVES: To compare the relative effectiveness of intensive training of the cervical musculature, a physiotherapy treatment regimen, and chiropractic treatment on this patient group. SUMMARY OF BACKGROUND DATA: There are only a few studies involving chronic neck pain patients representative of those seeking care in primary health care centers. Mobilization techniques and intensive training have been shown to be useful, but cervical manipulation has not been assessed. Clinical results involving these commonly used therapies have not been compared. METHODS: A total of 167 consecutive patients were screened. One hundred nineteen patients were admitted to the study and were randomized according to Taves' minimization principles. Primary outcome measures included self-reported pain, disability, medication use, patients' perceived effect, and physician's global assessment. Patients were assessed at enrollment and at completion of the study. Postal questionnaires were used to carry out 4- and 12-month follow-up assessments. Secondary outcome measures included active range of motion of the cervical spine as well as strength and endurance measurements of the cervical musculature. These measurements were carried out at enrollment and completion of the study. RESULTS: A total of 88% of the patients completed the study. Of these, 97% completed the 4-month questionnaire and 93% the 12-month questionnaire. Patients from all three groups demonstrated significant improvements regarding self-reported pain and disability on completion of the study. Improvements were maintained throughout the follow-up period. Medication use was also significantly reduced in all groups. There was, however, no significant difference between groups at any assessment period. Physician's and patients' assessments were also positive, and again group scores were essentially equal. Patients who underwent intensive training demonstrated significantly greater endurance levels at the completion of treatment. CONCLUSIONS: There was no clinical difference between the three treatments. All three treatment interventions demonstrated meaningful improvement in all primary effect parameters. Improvements were maintained at 4- and 12-month follow-up. However, whether this was a result of the treatments or simply a result of time is unknown. Future studies will be necessary to delineate ideal treatment strategies.

Adult↗

PubMed1998

Tubulin as a target for anticancer drugs: agents which interact with the mitotic spindle.

Tubulin is the biochemical target for several clinically used anticancer drugs, including paclitaxel and the vinca alkaloids vincristine and vinblastine. This review describes both the natural and synthetic agents which are known to interact with tubulin. Syntheses of the more complex agents are referenced and the potential clinical use of the compounds is discussed. This review describes the biochemistry of tubulin, microtubules, and the mitotic spindle. The agents are discussed in relation to the type of binding site on the protein with which they interact. These are the colchicine, vinca alkaloid, rhizoxin/maytansine, and tubulin sulfhydryl binding sites. Also included are the agents which either bind at other sites or unknown sites on tubulin. The literature is reviewed up to October 1997.

Antibiotics, Antineoplastic↗

PubMed1998

Ribonucleotide reductases.

Ribonucleotide reductases provide the building blocks for DNA replication in all living cells. Three different classes of enzymes use protein free radicals to activate the substrate. Aerobic class I enzymes generate a tyrosyl radical with an iron-oxygen center and dioxygen, class II enzymes employ adenosylcobalamin, and the anaerobic class III enzymes generate a glycyl radical from S-adenosylmethionine and an iron-sulfur cluster. The X-ray structure of the class I Escherichia coli enzyme, including forms that bind substrate and allosteric effectors, confirms previous models of catalytic and allosteric mechanisms. This structure suggests considerable mobility of the protein during catalysis and, together with experiments involving site-directed mutants, suggests a mechanism for radical transfer from one subunit to the other. Despite large differences between the classes, common catalytic and allosteric mechanisms, as well as retention of critical residues in the protein sequence, suggest a similar tertiary structure and a common origin during evolution. One puzzling aspect is that some organisms contain the genes for several different reductases.

Allosteric Regulation↗

PubMed1998

Intensive dynamic training for females with chronic neck/shoulder pain. A randomized controlled trial.

OBJECTIVES: To compare the clinical effectiveness of an intensive three-month training programme with a less intensive programme on females suffering from chronic neck/shoulder pain. STUDY DESIGN: A prospective observer-blinded clinical trial including 12-month pretreatment follow-up. SETTING: Patients were referred to the Departments of Rheumatology and Physical Medicine at Hvidovre Hospital by their general practitioners. Training was undertaken at a satellite clinic for physiotherapy of Hvidovre Hospital. SUBJECTS: Female patients aged 18-65 years suffering from chronic neck/shoulder pain for a minimum of six months. INTERVENTION: Patients were examined by a physician in order to exclude serious diseases. They were then randomized to either an intensive neck/shoulder training programme or a programme of lesser intensity but of similar duration. MAIN OUTCOME MEASURES: Scales measuring pain and activities of daily living (ADL) were used, and strength and endurance measurements of the cervical and shoulder muscles were carried out at baseline and completion of the study. Follow-up measurements were carried out by postal questionnaire at 6 and 12 months after inclusion, and included pain, ADL and treatment satisfaction measurements. RESULTS: Seventy-seven patients were included in the trial, of whom 27 (69%) completed the intensive programme and 25 (61%) the lighter programme. Forty-one (>80%) completed the follow-up questionnaires. The patients in the two groups did not differ with regard to age, pain, ADL scores and physical measurements prior to training. Patients in both groups that completed the trial demonstrated statistically significant improvements in nearly all of the outcome measurements at completion. ADL scores maintained statistical significance at 12 months in both groups, but pain scores were only significantly improved in the intensive group at 12 months follow-up. There was no statistically significant difference between groups regarding pain or ADL, but overall 50% of all patients showed improvement. CONCLUSIONS: The type of low-tech dynamic training used in either of our two programmes resulted in both subjective and objective improvements in patients suffering from chronic neck/shoulder pain, but there were no statistically significant differences in outcome between the two approaches. The subjective improvements were maintained throughout the follow-up period.

Activities of Daily Living↗

PubMed1998

The Copenhagen Neck Functional Disability Scale: a study of reliability and validity.

OBJECTIVE: To determine whether a newly developed disability scale for patients with neck pain demonstrated acceptable reliability and validity. METHODS: Testing was conducted using three different samples of patients with neck pain (n = 162). Test-retest reliability of the scale was carried out on the same day with one sample (n = 39), and between-day reliability was carried out with another (n = 21). Differential item functioning with regard to the influence of gender and age was carried out with these two patient groups, as was construct validity. Responsiveness was measured using patients participating in a clinical trial involving patients with chronic neck pain (n = 102). Additionally, scale scores were compared with a wide range of physical measurements using the patients in the clinical trial. RESULTS: Short-term, between-day and postal questionnaire reliability coefficients were all extremely high. The Cronbach's alpha coefficient for internal consistency was 0.9 for the entire scale, and the coefficients for individual items were all greater than 0.88. Disability scale scores correlated strongly to pain scores as well as to doctor and patient global assessments, indicating good construct validity. Relative changes in disability scores demonstrated a moderately strong correlation to changes in pain scores after treatment. Scale scores correlated weakly to all physical measurements. CONCLUSIONS: The disability scale demonstrated excellent practicality and reliability. The scale accurately reflects patient perceptions regarding functional status and pain as well as doctor's global assessment and is responsive to change over long periods of time. We feel that this scale can be a valuable tool for the assessment of patients in future clinical trials and quality of care studies.

Adult↗

PubMed1997

B12-dependent ribonucleotide reductases from deeply rooted eubacteria are structurally related to the aerobic enzyme from Escherichia coli.

The ribonucleotide reductases from three ancient eubacteria, the hyperthermophilic Thermotoga maritima (TM), the radioresistant Deinococcus radiodurans (DR), and the thermophilic photosynthetic Chloroflexus aurantiacus, were found to be coenzyme-B12 (class II) enzymes, similar to the earlier described reductases from the archaebacteria Thermoplasma acidophila and Pyrococcus furiosus. Reduction of CDP by the purified TM and DR enzymes requires adenosylcobalamin and DTT. dATP is a positive allosteric effector, but stimulation of the TM enzyme only occurs close to the temperature optimum of 80-90 degrees C. The TM and DR genes were cloned by PCR from peptide sequence information. The TM gene was sequenced completely and expressed in Escherichia coli. The deduced amino acid sequences of the two eubacterial enzymes are homologous to those of the archaebacteria. They can also be aligned to the sequence of the large protein of the aerobic E. coli ribonucleotide reductase that belongs to a different class (class I), which is not dependent on B12. Structure determinations of the E. coli reductase complexed with substrate and allosteric effectors earlier demonstrated a 10-stranded beta/alpha-barrel in the active site. From the conservation of substrate- and effector-binding residues we propose that the B12-dependent class II enzymes contain a similar barrel.

Amino Acid Sequence↗

PubMed1997

Characterization of Escherichia coli NrdH. A glutaredoxin-like protein with a thioredoxin-like activity profile.

Ribonucleotides are converted to deoxyribonucleotides by ribonucleotide reductases. Either thioredoxin or glutaredoxin is a required electron donor for class I and II enzymes. Glutaredoxins are reduced by glutathione, thioredoxins by thioredoxin reductase. Recently, a glutaredoxin-like protein, NrdH, was isolated as the functional electron donor for a NrdEF ribonucleotide reductase, a class Ib enzyme, from Lactococcus lactis. The absence of glutathione in this bacterium raised the question of the identity of the intracellular reductant for NrdH. Homologues of NrdH are present in the genomes of Escherichia coli and Salmonella typhimurium, upstream of the genes for the poorly transcribed nrdEF, separated from it by an open reading frame (nrdI) coding for a protein of unknown function. Overexpression of E. coli NrdH protein shows that it is a functional hydrogen donor with higher specificity for the class Ib (NrdEF) than for the class Ia (NrdAB) ribonucleotide reductase. Furthermore, this glutaredoxin-like enzyme is reduced by thioredoxin reductase and not by glutathione. We suggest that several uncharacterized glutaredoxin-like proteins present in the genomes of organisms lacking GSH, including archae, will also react with thioredoxin reductase and be related to the ancestors from which the GSH-dependent glutaredoxins have evolved by the acquisition of a GSH-binding site. We also show that NrdI, encoded by all nrdEF operons, has a stimulatory effect on ribonucleotide reduction.

Amino Acid Sequence↗

PubMed1997

Detection of isoprene in expired air from human subjects using proton-transfer-reaction mass spectrometry.

A new analytical method using proton-transfer-reaction mass spectrometry (PTRMS) is described for the determination of trace constituents in human breath. PTRMS is sufficiently sensitive and specific that it does not require preconcentration or separation. At its present stage of development it is capable of detecting trace constituents present in air at the part-per-billion level. These capabilities are illustrated for isoprene, one of the most abundant endogenous hydrocarbons. Our results confirm recent observations of a diurnal level variation associated with sleep or wakefulness; a new finding is that young children have much lower levels of isoprene in breath than adults. To address the metabolic origin of human isoprene, we used PTRMS to analyze expired air for allylic C5 alcohols that have been proposed to be non-enzymatic precursors of isoprene. The lack of correlation between peak breath isoprene and these alcohols suggests that the hydrocarbon is formed by some other mechanism.

Adult↗

PubMed1997

Analysis of the effect of prior therapy on progenitor cell yield: use of a chemotherapy scoring system.

A quantitative analysis of peripheral blood stem cell (PBSC) yield, measuring absolute numbers of CD34+ cells x 10(6)/kg and CFU-C x 10(4)/kg was performed in 74 consecutive patients. The interval or 'gap' from the end of previous chemotherapy to the date of priming was recorded in weeks. Geometric mean CD34 and CFU-C values were significantly higher in patients with a score of < or = 60 compared to those with score > 60 (P = 0.003 and 0.02, respectively) and a significant difference in CD34 values was also found when scores of < or = 38 were compared with scores > 38 (P = 0.003), with the difference in CFU-C values approaching significance (P = 0.08). Patients exposed to toxicity factor 4 drugs had significant lowering of both CD34 and CFU-C values (P < 0.001 and P = 0.038) and this emerged as the only independent factor when analysed using linear regression. No significant difference in the geometric mean CD34 or CFU-C values of patients was found in any of the gap categories analysed. Prior exposure to toxicity factor 4 drugs had a significant adverse effect on stem cell yield and should be avoided or minimized prior to stem cell harvesting.

Adolescent↗

PubMed1997

Endogenous production of methanol after the consumption of fruit.

After the consumption of fruit, the concentration of methanol in the human body increases by as much as an order of magnitude. This is due to the degradation of natural pectin (which is esterified with methyl alcohol) in the human colon. In vivo tests performed by means of proton-transfer-reaction mass spectrometry show that consumed pectin in either a pure form (10 to 15 g) or a natural form (in 1 kg of apples) induces a significant increase of methanol in the breath (and by inference in the blood) of humans. The amount generated from pectin (0.4 to 1.4 g) is approximately equivalent to the total daily endogenous production (measured to be 0.3 to 0.6 g/day) or that obtained from 0.3 liters of 80-proof brandy (calculated to be 0.5 g). This dietary pectin may contribute to the development of nonalcoholic cirrhosis of the liver.

Acetone↗