Understanding discrimination by the ribosome: stability testing and groove measurement of codon-anticodon pairs

The ribosome must discriminate between correct and incorrect tRNAs with sufficient speed and accuracy to sustain an adequate rate of cell growth. Here, we report the results of explicit solvent molecular dynamics simulations, which address the mechanism of discrimination by the ribosome. The universally conserved 16S rRNA base A1493 and the kink in mRNA between A and P sites amplify differences in stability between cognate and near-cognate codon-anticodon pairs. Destabilization by the mRNA kink also provides a geometric explanation for the higher error rates observed for mismatches in the first codon position relative to mismatches in the second codon position. For more stable near-cognates, the repositioning of the universally conserved bases A1492 and G530 results in increased solvent exposure and an uncompensated loss of hydrogen bonds, preventing correct codon-anticodon-ribosome interactions from forming.

Ovarian function in the Nile hippopotamus and the effects of Depo-Provera administration

The preliminary results of an investigation into the reproductive endocrinology of the hippopotamus (Hippopotamus amphibius) and the effects of the progestin Depo-Provera on ovarian function are presented. Faecal progestagen analysis indicated that hippos have an oestrous cycle of 29.2 +/- 0.9 days and faecal progestagen concentrations of 323.6 +/- 31.4 ng g(-1) during the luteal phase. Concentrations were higher (765.9 +/- 162.4 ng g(-1); P < 0.05) during pregnancy than during the luteal phase and remained high until parturition. A lactational anoestrus was usually, but not always, observed during nursing. The onset of puberty was observed in three animals and started at 2.5-3.5 years of age. After Depo-Provera treatment, increases in faecal progestagens indicative of ovulation were observed and were not significantly different from luteal concentrations observed before treatment (236.3 +/- 24.4 versus 340.1 +/- 47.9 ng g(-1), respectively); however, the duration of the luteal phase was shorter (P < 0.05) than before treatment (11.3 +/- 1.0 versus 18.9 +/- 1.0 days, respectively). Females returned to normal cyclicity at day 100.7 +/- 15.3 (range 70-116 days) after administration and one female conceived on day 100 after administration.

Impact of European Society of Cardiology/American College of Cardiology guidelines on diagnostic classification of patients with suspected acute coronary syndromes

BACKGROUND

Assessment of the relative diagnostic accuracy of investigation strategies for patients with suspected acute coronary syndromes (ACS).

METHODS

A prospective observational study followed two groups of patients over a 3-month period in a UK district general hospital. Group one: all admissions with suspected ACS (n = 576); group two: non-cardiac in-patients who were suspected of developing ACS (n = 87). Both were investigated by full clinical history, examination and serial electrocardiographs (ECGs). Conventional World Health Organization (WHO) criteria for myocardial damage were compared with diagnosis based on cardiac troponin T (cTnT). Clinical discharge diagnosis based on conventional WHO criteria was compared with the review diagnosis based on measurement of cTnT.

RESULTS

Diagnosis based on WHO criteria missed 58 patients (8.7%) admitted with suspected ACS who had high risk unstable angina. Thirty-three patients (5% of all admissions) who were diagnosed as non-Q wave acute myocardial infarction (AMI) were found to have normal troponin values and to have been incorrectly classified as AMI.

CONCLUSIONS

Diagnostic strategies based on WHO criteria are inaccurate. The measurement of cTnT in all patients with suspected ACS would have increased the number of those with a diagnosis of AMI by 58 (8.7%), while avoiding inaccurate diagnosis in 33 (5%), therefore producing an absolute increase of 25/663 (3.8%) but a relative increase of 58/138 (42%). In patients with a primary diagnosis of suspected ACS, the overall increase in patients with a diagnosis of AMI will be 55 (9.5%), a relative increase of 55/118 (46.6%) but an absolute increase of 36/576 (6.3%).

Derivation of a salinity target for the Lower Murray Darling Valley

The NSW Government commissioned catchment management boards (CMBs) to set the direction and process for catchment scale natural resource management. In the Lower Murray Darling, Rivers are highly regulated and water resources shared between three states. The Catchment Board only has jurisdiction over the northern bank of the Murray but salt and water enter the river from many locations upstream and along the area boundary. River salt and flow modelling has continually been improved to reflect and contribute to an increased understanding of salinity processes. The MDBC Salt Load study correlates 10 years of actual measured data with its modelled outputs, and estimates river salinities for 2020, 2050 and 2100. Routing models such as SALTFLO and MURKEY generate percentile salinity levels at different nodes in the River Murray downstream of the Lower Darling confluence. National, Murray-Darling Basin and NSW salinity management policy and legislative requirements were considered, MDBC model output was used to ensure the interim targets are achievable, auditable, and appropriate to the catchment. The method for an end-of-valley river based target for salinity is described. A target of less than 463 microS/cm for Lock 6, a point in the lower reaches of the Murray River is recommended for year 2010. Catchment management targets that express the main river salinity risk in five hydrologically distinct management zones are also recommended. Salinity management changes are needed in each zone to meet the end-of-valley target.

Epilepsia partialis continua--a clinical and electroencephalography study

Epilepsia partialis continua (EPC) is a rare type of localization-related motor epilepsy. Clinical spectrum, electroencephalography (EEG) characteristics and various prognostic factors in EPC were studied in 20 patients. Patients who fulfilled the criteria for EPC between the years 1985 and 1999 were included in this retrospective and prospective study. The mean age was 18 years (range 5 months-70 years). Eleven patients (55%) had Type 1 EPC and in the remaining nine (45%) patients there were features of Type 2 EPC. Among children Rasmussen's encephalitis and viral encephalitis were the commonest cause for EPC. Encephalitis and vascular aetiology were frequently observed in adults. Tuberculous meningitis and tuberculomas occurred evenly in both the groups. The cause was unknown in two cases. Focal EEG abnormalities commonly consisted of discrete spikes, sharp waves (or) slow wave activity and periodic lateralized epileptiform discharges. The mean duration of follow up was 9.6 months with a range between 1 month and 4 years. Cognitive decline, motor deficits and pharmacoresistance to drugs were significantly seen among children with Type 2 EPC. Patients with Type 1 EPC had mild impairment of functional status with good response to treatment. The long-term prognosis depends upon the underlying cause.

'Wine Glass' appearance: a unique MRI observation in a case of primary lateral sclerosis

Magnetic resonance images (MRI) in a patient with primary lateral sclerosis is described. T2WI, MRI of brain showed characteristic hyperintensities of the corticospinal tracts bilaterally, extending from the internal capsule to the brain stem - producing a 'wine glass' appearance on coronal sections, which has not been described so far to the best of our knowledge. Differential diagnosis of this interesting 'wine glass' appearance on MRI along with a review of the MR-signal abnormalities in motor neuron disease is discussed.

Prevalence of overweight in urban Indian adolescent school children

The prevalence of diabetes mellitus (DM) and cardiovascular disease (CVD) is increasing in urban India. Overweight in adolescence is a marker of overweight in adult age, and it shows an association with the above diseases. There have been meagre data from India on the prevalence of childhood obesity. The objective of the study was to quantify the prevalence of overweight and its risk factors in adolescent children in urban India. School students in the age group of 13-18 years (n = 4700, M:F 2382:2318) were studied. Body mass index (BMI) was measured. Data on physical activity, food habits, occupation of parents and their economic status, birth weight of the children and age at menarche in girls were obtained by questionnaire. Age-adjusted prevalence of overweight was 17.8% for boys and 15.8% for girls. It increased with age and was higher in lower tertiles of physical activity and in higher socio-economic group. Birth weight and current BMI were positively associated. The study highlighted the high prevalence of overweight in adolescent children in urban India. Life style factors influenced BMI in adolescent age.

An attenuated herpes vaccine may protect Gyr hybrids from fatal inclusion body hepatitis. A preliminary report

Four Gyr hybrids were used for this falcon herpes vaccine experiment. Three falcons were given 1 ml of an attenuated falcon herpesvirus vaccine (DuFaHe) subcutaneously twice within 14 days, whereas the fourth falcon was used as a control. Eighteen days after the booster vaccination, all four Gyr hybrids were intranasally and ocularly challenged with a virulent low-passage falcon herpesvirus. The control falcon died 9 days after challenge with typical lesions of herpesvirus inclusion body hepatitis. The three vaccinated falcons seroconverted and did not show any symptoms. Following the challenge their antibody titres to falcon herpesvirus increased. No herpesvirus was isolated from any of the cloacal swabs taken during this experiment, indicating that there was no danger for any other birds from DuFaHe. This experiment shows that falcons can be protected from herpesvirus infection by an attenuated herpesvirus vaccine. However, it should be stressed that only four falcons were used for this experiment.

Multiple pathways governing Cdx1 expression during murine development

Cdx1 encodes a mammalian homeobox gene involved in vertebral patterning. Retinoic acid (RA) is likewise implicated in vertebral patterning. We have previously shown that Cdx1 is a direct retinoid target gene, suggesting that Cdx1 may convey some of the effects of retinoid signaling. However, RA appears to be essential for only early stages of Cdx1 expression, and therefore other factors must be involved in maintaining later stages of expression. Based on function and pattern of expression, Wnt family members, in particular Wnt3a, are candidates for regulation of expression of Cdx1. Consistent with this, we confirm prior results which demonstrated that Cdx1 can be directly regulated by Wnt signaling, and identify functional LEF/TCF response motifs essential for this response. We also find that Cdx1 expression is markedly attenuated in a stage- and tissue-specific fashion in the Wnt3a hypomorph vestigial tail, and present data demonstrating that Wnt3a and RA synergize strongly to activate Cdx1. Finally, we show that Cdx1 positively regulates its own expression. These data prompt a model whereby retinoid and Wnt signaling function directly and synergistically to initiate Cdx1 expression in the caudal embryo. Expression is then maintained, at least in part, by an autoregulatory mechanism at later stages.

Identification of molecular interactions between P-site tRNA and the ribosome essential for translocation

Translocation of the tRNA-mRNA complex is a fundamental step in the elongation cycle of protein synthesis. Our studies show that the ribosome can translocate a P-site-bound tRNA(Met) with a break in the phosphodiester backbone between positions 56 and 57 in the TPsiC-loop. We have used this fragmented P-site-bound tRNA(Met) to identify two 2'-hydroxyl groups at positions 71 and 76 in the 3'-acceptor arm that are essential for translocation. Crystallographic data show that the 2'-hydroxyl group at positions 71 and 76 contacts the backbone of 23S rRNA residues 1892 and 2433-2434, respectively, in the ribosomal E site. These results establish a set of functional interactions between P-site tRNA and 23S rRNA that are essential for translocation.

Electrostatics of nanosystems: application to microtubules and the ribosome

Evaluation of the electrostatic properties of biomolecules has become a standard practice in molecular biophysics. Foremost among the models used to elucidate the electrostatic potential is the Poisson-Boltzmann equation; however, existing methods for solving this equation have limited the scope of accurate electrostatic calculations to relatively small biomolecular systems. Here we present the application of numerical methods to enable the trivially parallel solution of the Poisson-Boltzmann equation for supramolecular structures that are orders of magnitude larger in size. As a demonstration of this methodology, electrostatic potentials have been calculated for large microtubule and ribosome structures. The results point to the likely role of electrostatics in a variety of activities of these structures.

Electrostatics of nanosystems: application to microtubules and the ribosome

Evaluation of the electrostatic properties of biomolecules has become a standard practice in molecular biophysics. Foremost among the models used to elucidate the electrostatic potential is the Poisson-Boltzmann equation; however, existing methods for solving this equation have limited the scope of accurate electrostatic calculations to relatively small biomolecular systems. Here we present the application of numerical methods to enable the trivially parallel solution of the Poisson-Boltzmann equation for supramolecular structures that are orders of magnitude larger in size. As a demonstration of this methodology, electrostatic potentials have been calculated for large microtubule and ribosome structures. The results point to the likely role of electrostatics in a variety of activities of these structures.

Vascular access problems in dialysis patients: pathogenesis and strategies for management

Repetitive hemodialysis was made possible through the development of a chronic means of accessing the circulation. This was accomplished through the use of arteriovenous fistulae or grafts, using autologous veins or synthetic materials. Although the arteriovenous fistula remains the access of choice, synthetic arteriovenous grafts are used in most patients because of problems with late referral to a nephrologist and poor vasculature. This article describes the means of accessing the circulation for hemodialysis, the pathogenesis of access failure through progressive stenosis followed by thrombosis, methods of detecting access dysfunction before thrombosis, and therapeutic options. Although angiographic or surgical intervention remain the mainstays of management, medical treatments to decrease stenosis and delay thrombosis are currently under investigation.

Neurocysticercosis: a clinical and radiological appraisal from Kerala State, South India

OBJECTIVES

Little has been published on Neurocysticercosis (NCC) in the State of Kerala, South India. This study was conducted to describe the clinical and radiological features of NCC in Kerala and also to study the frequency of NCC as seen in a tertiary referral setting.

MATERIALS AND METHODS

We evaluated retrospectively 11 patients who were admitted with a diagnosis of NCC from 1986 to 1998. A pre-abstracted proforma containing detailed demographic data, dietary habits, clinical features and history of travel outside Kerala and neuroimaging findings were obtained from patient records and the data was tabulated and analysed. Follow up assessment was made three months after treatment.

RESULTS

There were a total of 11 patients, including nine males and two females in the age range of 24 to 62 years and a mean age of 35.2 years. All were nonvegans, only 36% were pork eaters while 18% claimed consumption of salads and uncooked vegetables. 55% of patients were migrants. Migrants were defined as those who lived outside the state of Kerala for more than six months. Seizure was the most common presenting complaint and occurred in all patients (100%). Multiple ring enhancing lesions were seen on computerised tomography (CT) and magnetic resonance imaging (MRI) scans in 60%. Calcified lesions were noted in two patients. An isolated instance of miliary or disseminated cysticercosis with subcutaneous nodules and multiple brain lesions in MRI scan was observed. All patients received anticysticercal therapy besides anticonvulsants.

CONCLUSIONS

It appears that NCC is rather uncommon in Kerala. Better socioeconomic status, high literacy rate, improved sanitation and health care in the state of Kerala could be reasons for this observation. A prospective case-control study of NCC in Kerala is needed to study these factors.

Selective intra arterial thrombolysis in acute carotid territory stroke

The safety and efficacy of selective intraarterial administration of urokinase in five male patients, (age range 30 to 65 years, mean 41.2 years), with occlusive stroke involving the carotid territory and a normal cranial computed tomography scan was evaluated. The time elapsed before treatment ranged from one to 10 hours. Digital subtraction angiography disclosed distal internal carotid artery occlusion in one patient and occlusion of the middle cerebral artery or its branches in the others. The urokinase dose ranged from 120,000 to 500,000 units. In two patients who received thrombolytic treatment within three hours of the onset of symptoms, there was a 100% recanalisation associated with excellent neurological recovery. In the remaining three patients, recanalisation rate varied from 0 to 50% with partial recovery in two and no recovery in one patient. None had a haemorrhagic transformation of the infarct. Although no firm conclusions can be drawn because of the small number of patients studied, selective intraarterial urokinase therapy appears to be safe and useful in patients with carotid territory stroke if undertaken early. Only through a multicenter, randomized, controlled trial, enough number of patients can be recruited to verify these observations.

Conformational changes in the ribosome induced by translational miscoding agents

Ribosomes are dynamic complexes responsible for translating the genetic information encoded in mRNAs to proteins. The accuracy of this process is vital to the survival of an organism, and is often compromised by translational miscoding agents. Aminoglycosides are a group of miscoding agents that bind to the ribosome and reduce the fidelity of translation. Previous studies have shown that aminoglycosides alter the higher order structure of the ribosome. Here, we used a toeprinting assay to how that streptomycin, neomycin, kanamycin, gentamycin, and hygromycin B trigger conformational changes within Escherichia coli ribosome. Miscoding agents viomycin and 30% ethanol also cause similar structural changes within the ribosome. In contrast, antibiotics that do not cause miscoding, such as tetracycline, chloramphenicol, erythromycin, fusidic acid and spectinomycin, do not induce the conformational changes triggered by miscoding agents. Furthermore, ribosomes isolated from strains that are either streptomycin resistant or dependent for growth do not show these conformational changes in the presence of streptomycin. These results correlate structural changes in the ribosome induced by miscoding agents in vitro with their in vivo phenotype.

Evidence of functional somatotopy in GPi from results of pallidotomy

The objective of this study was to explore the functional anatomy of the globus pallidus internus (GPi) by studying the effects of unilateral pallidotomy on parkinsonian 'off' signs and levodopa-induced dyskinesias (LID). We found significant positive correlations between the preoperative levodopa responsiveness of motor signs and the levodopa responsiveness of scores in timed tests (Core Assessment Program for Intracerebral Transplantations) in the contralateral limbs and the improvement in these scores after surgery, whereas there was no correlation with the improvement in LID. We also found a highly significant correlation (P: < 0.0001, r = 0.8) between the volume of the ventral lesion in the GPi and the improvement in LID in the contralateral limbs, whereas there was no correlation between the ventral volume and the improvement in parkinsonian 'off' signs. The volumes of the total lesion cylinder and the dorsal lesion did not correlate with the outcome of either dyskinesias or parkinsonian 'off' signs. The differential predictive value of levodopa responsiveness for the outcome of parkinsonian 'off' signs and LID and the different correlations of ventral lesion volume with dyskinesias and parkinsonian 'off' signs indicate that different anatomical or pathophysiological substrates may be responsible for the generation of parkinsonian 'off' signs and dyskinesias. Whereas cells in a wider area of the GPi may be implicated in parkinsonism, the ventral GPi seems to be crucial for the manifestation of LID. We suggest that our observations are additional proof of the functional somatotopy of the systems within the GPi that mediate parkinsonism and dyskinesias, especially along the dorsoventral trajectory used in pallidotomy. The outcome of pallidotomy in which the lesion involves the ventral and dorsal GPi could be the net effect of alteration in the activity of pathways which mediate different symptoms, and hence could be variable.

'Face of the giant panda' sign in Wilson's disease: revisited

We report a patient, with Wilson's disease, who showed the characteristic radiological sign known as 'Face of the giant panda sign' on magnetic resonance imaging (MRI) of the brain.

Increased marine production of N2O due to intensifying anoxia on the Indian continental shelf

Eutrophication of surface waters and hypoxia in bottom waters has been increasing in many coastal areas, leading to very large depletions of marine life in the affected regions. These areas of high surface productivity and low bottom-water oxygen concentration are caused by increasing runoff of nutrients from land. Although the local ecological and socio-economic effects have received much attention, the potential contribution of increasing hypoxia to global-change phenomena is unknown. Here we report the intensification of one of the largest low-oxygen zones in the ocean, which develops naturally over the western Indian continental shelf during late summer and autumn. We also report the highest accumulations yet observed of hydrogen sulphide (H2S) and nitrous oxide (N2O) in open coastal waters. Increased N2O production is probably caused by the addition of anthropogenic nitrate and its subsequent denitrification, which is favoured by hypoxic conditions. We suggest that a global expansion of hypoxic zones may lead to an increase in marine production and emission of N2O, which, as a potent greenhouse gas, could contribute significantly to the accumulation of radiatively active trace gases in the atmosphere.

The Herald of Free Enterprise disaster. Lessons from the first 6 years

A substantial body of data has been collected on survivors of the Herald of Free Enterprise disaster over the first 6 years. These data show the psychological effects to be considerable, and although they appear to decrease over time, 6 years later there remains a substantial minority that remains highly distressed. Our research has also pointed to those factors that appear to be important in determining the severity and chronicity of symptoms. Levels of crisis support early on seem to be protective. Not everyone has access to supportive others, and these people would seem to be at increased risk of disturbance. But even if crisis support is potentially available from family and friends, not everyone is in a position to draw on these resources. Those individuals who possess negative attitudes toward emotional expression might be less likely to seek out support. Evidence would suggest that modifying such attitudes might be an important component of intervention. A further target for intervention would seem to be the causal attributions made by survivors. It was found that those who perceived the causes of events during the disaster as internal and controllable were at greatest risk of psychological disturbance. The data gathered in the wake of this disaster suggest that intervening early with respect to these three components (crisis support, attitude to emotional expression, and attributional style) is highly likely to mitigate against long-term distress.

Attitudes towards emotional expression: factor structure, convergent validity and associations with personality

The aim of the present study was to investigate the structure of the Attitudes towards Emotional Expression scale (AEE), its convergent validity with the Ambivalence over Emotional Expressiveness Questionnaire (AEQ), and its association with the Big 5 personality dimensions. The AEE was found to consist of four clearly identifiable factors, which loaded together on a higher order single factor. Higher scores on the AEE were associated with higher scores on the AEQ. Regression of scores on the AEE onto the Big 5 personality dimensions showed that scores on the AEE were associated with agreeableness, extraversion, and openness to experience.