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Biomedical subjects

C Watson

Publications and source records attributed to C Watson.

At least 55 records · Page 3Linked to original sources
PubMed1999

Australia's contribution to global polio eradication initiatives.

OBJECTIVE: To provide evidence according to the requirements of the Global Commission for Certification of Poliomyelitis Eradication that poliomyelitis has been eliminated in Australia. METHODS: Documentation of the surveillance of poliomyelitis, the presence of a comprehensive national immunisation program, and a network of laboratories for viral diagnosis. Active surveillance of acute flaccid paralysis (AFP) cases was initiated in 1995 to prove that poliovirus does not cause such paralysis. Australia is also evaluating the surveillance of AFP through a retrospective hospital based study. RESULTS: The last case in Australia of polio due to wild poliovirus was seen in 1978 and the last case of vaccine-associated paralytic poliomyelitis detected by serology was in 1994. The latest immunisation coverage figures for OPV3 for children under one year of age is 85.6%. The Australian National Polio Reference Laboratory has tested 821 enteroviruses since 1994 and have not identified any wild poliovirus. The average rate of non-polio AFP based on 111 cases investigated for the period 1995-98 is 0.71 per 100,000 under the age of 15 years. Stool samples were collected from only 21% of cases. CONCLUSION: The process of certification of the eradication of poliomyelitis in Australia is almost complete. Although immunisation coverage is high, improvement in AFP surveillance and stool collection is vital for the certification process. The next challenge is the containment of polioviruses. IMPLICATIONS: Although Australia and other Western Pacific countries are likely to be certified as wild-polio free in 2000, a comprehensive immunisation program and surveillance must continue for three years after global certification (expected 2003-04).

Adolescent↗
PubMed1999

Brain activation during intermittent photic stimulation: a [15O]-water PET study on photosensitive epilepsy.

PURPOSE: Intermittent photic stimulation (IPS) is an activation procedure used during electroencephalogram (EEG) recording to elicit paroxysmal discharges in individuals with photosensitivity. Specific responses on EEG recording may be provoked by IPS at different frequencies of flickering in normal individuals and in patients with photosensitive epilepsy. METHODS: Changes in regional cerebral blood flow (rCBF) were studied during IPS in two groups of subjects by using [15O]-water positron emission tomography (PET): a control group consisting of eight healthy adults with photic driving response during IPS on EEG recording (mean age, 25 +/- 10.5 years) without history of neurologic or psychiatric abnormalities and a patient group consisting of four adults (mean age, 33 +/- 7.5 years) with history of photosensitive epilepsy. [15O]-water PET scanning with concomitant EEG monitoring was performed during baseline and IPS at 4-, 14-, and 30-Hz frequencies. RESULTS: The control group showed photic driving response at 14-Hz IPS frequency. The patient group showed photoparoxysmal response at 14 and 30 Hz, but not at 4 Hz. Changes in rCBF were determined by means of statistical parametric mapping. Increases in rCBF in occipital cortex (Brodmann's areas 17, 18, and 19) were observed in both groups. In addition, during photic driving responses, the control group showed rCBF increases in the insula and in the thalamus, on the right side. The patient group showed a significant rCBF increase in the hypothalamic region inferior to the left caudate nucleus during photoparoxysmal response. This activation was not found in the control group. Increased rCBF also was observed in the patient group in the head of the left caudate nucleus, in the left hippocampus, and in left insula during IPS without photoparoxysmal response. No activations in these regions were observed during photoparoxysmal response. CONCLUSIONS: These data may indicate involvement of the hypothalamus in photosensitive epilepsy and may suggest a modulatory function of the caudate nucleus, which might be associated with an inhibition of epileptic discharges during IPS in patients with photosensitive epilepsy.

Adult↗
PubMed1999

[11C]Flumazenil PET in patients with epilepsy with dual pathology.

PURPOSE: Coexistence of hippocampal sclerosis and a potentially epileptogenic cortical lesion is referred to as dual pathology and can be responsible for poor surgical outcome in patients with medically intractable partial epilepsy. [11C]Flumazenil (FMZ) positron emission tomography (PET) is a sensitive method for visualizing epileptogenic foci. In this study of 12 patients with dual pathology, we addressed the sensitivity of FMZ PET to detect hippocampal abnormalities and compared magnetic resonance imaging (MRI) with visual as well as quantitative FMZ PET findings. METHODS: All patients underwent volumetric MRI, prolonged video-EEG monitoring, and glucose metabolism PET before the FMZ PET. MRI-coregistered partial volume-corrected PET images were used to measure FMZ-binding asymmetries by using asymmetry indices (AIs) in the whole hippocampus and in three (anterior, middle, and posterior) hippocampal subregions. Cortical sites of decreased FMZ binding also were evaluated by using AIs for regions with MRI-verified cortical lesions as well as for non-lesional areas with visually detected asymmetry. RESULTS: Abnormally decreased FMZ binding could be detected by quantitative analysis in the atrophic hippocampus of all 12 patients, including three patients with discordant or inconclusive EEG findings. Decreased FMZ binding was restricted to only one subregion of the hippocampus in three patients. Areas of decreased cortical FMZ binding were obvious visually in all patients. Decreased FMZ binding was detected visually in nonlesional cortical areas in four patients. The AIs for these nonlesional regions with visual asymmetry were significantly lower than those for regions showing MRI lesions (paired t test, p = 0.0075). CONCLUSIONS: Visual as well as quantitative analyses of FMZ-binding asymmetry are sensitive methods to detect decreased benzodiazepine-receptor binding in the hippocampus and neocortex of patients with dual pathology. MRI-defined hippocampal atrophy is always associated with decreased FMZ binding, although the latter may be localized to only one sub-region within the hippocampus. FMZ PET abnormalities can occur in areas with normal appearance on MRI, but FMZ-binding asymmetry of these regions is lower when compared with that of lesional areas. FMZ PET can be especially helpful when MRI and EEG findings of patients with intractable epilepsy are discordant.

Adolescent↗
PubMed1999

Recombinant and tissue extract thromboplastins for determination of international normalised ratio in over-anticoagulated patients.

The international normalised ratio (INR)/international sensitivity index (ISI) system is established for calibration of thromboplastins for laboratory monitoring of oral anticoagulant therapy. The calibration procedure employs patients stabilised on oral anticoagulants, and is therefore validated for patients within the therapeutic range. For practical reasons, the system is used for patients at all levels of therapy, including over-anticoagulated patients with particularly low levels of factors II, VII and X. We studied patients within and above the therapeutic range, using a thromboplastin containing recombinant human tissue factor (Innovin) and two tissue extract thromboplastins. In samples with INRs from 2.0 to 4.0, there was good agreement between results obtained with the three systems (mean INRs within 4% of each other). In patients with INRs > 4.0, results with a human placental extract reagent (Thromborel S) were similar to those obtained with a rabbit brain thromboplastin (IL PT Fib Hs Plus); mean INRs were 6.30 and 6.32 respectively (not significant). Results with Innovin (mean INR: 7.67) were significantly (P < 0.001) greater (on average by 22%) than those obtained with the other two materials. The discrepancy between results with different reagents negatively correlated with factor VII levels. Thus, the lower the factor VII level, the greater was the discrepancy between INRs. Unexpectedly, there was a positive correlation between factor V level and the difference between INRs with different reagents. Thus, the higher the factor V level, the greater was the discrepancy between INRs. The effect of these differences at higher INRs on patient management is unknown, but the recently revised UK guidelines recommend that management of these patients should be influenced by clinical factors, reducing the relative importance of discrepancies between results obtained with different systems.

Anticoagulants↗
PubMed1999

Categorizing the response to Epoetin alfa therapy. Case study of the anemic patient.

Hyporesponse to Epoetin alfa therapy can be minimized by categorizing patients on the basis of trends in hemoglobin/hematocrit levels and initiating a continuous quality improvement effort that focuses on subnormal outcomes. An algorithm is provided that clinicians can use to proactively assess common causes that contribute to hyporesponse and limit the effect on patient outcomes.

Algorithms↗
PubMed1998

Objective method for localization of cortical asymmetries using positron emission tomography to aid surgical resection of epileptic foci.

We designed a semiautomated method for the objective detection of abnormal regions of tracer accumulation in the brain. The purpose of the present study was to examine the diagnostic performance of this method by applying it to patients with clinically intractable epilepsy of unilateral origin; they underwent [F-18] deoxyglucose positron emission tomography (PET) prior to surgical resection of epileptic foci. A semiautomated method for assessment of asymmetries in the brain cortex was developed that compares activity concentrations in homotopic cortical areas. When these differences exceeded a predefined threshold, the areas with lower activity were marked and 3-dimensional surface rendered images were created to guide placement of intracranial electrodes (ECoG) followed by surgical resection. The normal amount of asymmetry between small (0.5-0.7 cm2) homotopic cortical regions was determined as 5.9 +/- 4.0% (mean +/- SD). The false-positive fraction was determined for cutoff thresholds of 1 SD (10%), 1.5 SD (12%), and 2 SD (15%) outside the mean and was found to be 89, 44, and 0%, respectively. The obtained sensitivity-specificity pairs for correct localization of epileptogenic lobes based on the ECoG results were best for the 15% threshold (80/94%, accuracy 0.90). This objective PET method allows the accurate determination of cortical asymmetries, and it proved to be highly efficient in guiding epilepsy surgery.

Adolescent↗
PubMed1998

Improved reproducibility of magnetic stimulation-evoked motor potentials in the human masseter by a new method for locating stimulation sites on the scalp.

In magnetic-stimulation studies where motor-evoked potentials (MEP) are measured on different occasions, accurate relocation of the stimulation site on the scalp is essential. Here a novel method of locating neural stimulation sites was tested and the reproducibility of MEPs in the human masseter assessed. The heads of the participants were immobilized in a plastic mask that incorporated a grid overlying the left cerebral hemisphere. A figure-of-eight coil was oriented with a micromanipulator. Electrodes were placed over the right masseter using a standardized method. Two discrete sites on the grid were stimulated alternately at threshold + 10% whilst participants clenched their teeth. Recordings were repeated after the mask and electrodes had been removed and replaced. Within individual participants, the latency and amplitude of the MEP were reproducible between trials and when the mask and electrodes were replaced. The new method appears to be accurate and practical when recording longitudinal MEP data in the masseter.

Adult↗
PubMed1998

Transcranial magnetic-stimulation mapping of the cortical topography of the human masseter muscle.

The cortical topography of several limb and trunk muscles has been disclosed using transcranial magnetic stimulation, but the corticomotor representation of the human jaw muscles has not yet been described. An experimental paradigm incorporating transcranial magnetic stimulation of verified sites on the scalp was used (a) to determine the cortical topography of the human masseter muscle and (b) to assess the reproducibility of the motor map, in seven healthy individuals. The results showed that the masseter was discretely represently on the motor and premotor cortex with interindividual variation in map area, volume and height (p < 0.05). Coefficients of variation and reliability were low (15-18%) and high (89-96%), respectively, for motor maps obtained at experimental sessions 2 weeks apart, indicating high reproducibility. The findings have clinical relevance in the management of patients with cerebral injury involving corticobulbar projections to the masseter.

Adult↗
PubMed1998

Measuring the impact of conjugate vaccines on invasive Haemophilus influenzae type b infection in Western Australia.

Haemophilus influenzae type b (Hib) causes serious infections in 26-59 per 100,000 non-Aboriginal Australian children under five years of age. Aboriginal children suffer much higher rates of infection (> or = 150 per 100,000), and at an earlier age, and have a greater risk of death and disability due to Hib infection. In 1992 and 1993, four conjugate Hib vaccines were introduced in Australia, and a nationally funded program of infant vaccination was begun in July 1993. This study aimed at evaluating the effectiveness of Hib vaccination in Aboriginal and non-Aboriginal children in Western Australia using a population-based active surveillance system for non-Aboriginal children and a case control study for Aboriginal children. The incidence of invasive Hib disease in non-Aboriginal children fell from 30.9 per 100,000 before vaccination was available to 6.3 per 100,000 in the second year after its introduction. The vaccine efficacy was estimated to be 80 per cent for Aboriginal children (odds ratio 0.20, 95 per cent CI 0.01-2.76) and, after adjustment for confounders, 75 per cent (odds ratio 0.25, CI 0.02-3.66). Based on the adjusted value (75 per cent), and using a Bayesian approach, we estimate that the posterior probability was 0.55 that the true vaccine efficacy is greater than 70 per cent, and 0.69 that the efficacy is greater than 50 per cent. We conclude that Hib vaccination is effective in preventing invasive Hib disease in Aboriginal and non-Aboriginal children in Australia.

Bacteremia↗
PubMed1998

Recombinant human CXC-chemokine receptor-4 in melanophores are linked to Gi protein: seven transmembrane coreceptors for human immunodeficiency virus entry into cells.

This article describes the transient expression of the CXC chemokine receptor-4 in Xenopus laevis melanophores and the resulting functional assay for the endogenous ligand for this receptor stromal cell-derived factor (SDF)-1alpha. Specifically, it will be shown that SDF-1alpha produces increased light transmittance in transfected cells that is consistent with the activation of Gi protein. This stimulus pathway is further implicated by the abolition of this response after pretreatment of the cells with pertussis toxin, a known method for the inactivation of Gi protein. The fact that SDF-1alpha does not produce responses in nontransfected cells and that treatment of the cells with 12G5, an antibody specific for the CXC chemokine receptor-4, eliminates this response indicates that this ligand produces responses by activation of this receptor in these cells. The possible relevance to human immunodeficiency virus (HIV) entry into cells was explored by observing the effects of SDF-1alpha on HIV-mediated cell fusion. It was found that SDF-1alpha blocked cell-to-cell fusion (as has been previously reported) at concentrations 1200-fold greater than those required to produce Gi protein mediated responses. The implications of the functional assay to screening for new drugs to block HIV-mediated fusion is discussed.

Amino Acid Sequence↗
PubMed1998

Intraperitoneal rhabdomyosarcoma in children: incidence and imaging characteristics on CT.

OBJECTIVE: The purpose of this study was to determine the incidence and CT imaging features of intraperitoneal rhabdomyosarcoma in children. CONCLUSION: Approximately 10% of children with rhabdomyosarcoma may have intraperitoneal neoplastic involvement either at the time of diagnosis or subsequently. On CT, intraperitoneal rhabdomyosarcomas are associated with ascites, enhancing nodules, masses, a pseudomyxoma peritonei-like appearance, and omental caking.

Adolescent↗
PubMed1998

Glove usage and reporting of needlestick injuries by junior hospital medical staff.

The use of gloves when conducting invasive procedures and the reporting of needlestick injuries have been strongly encouraged. Despite this, neither practice appears to be universal. In order to determine the rates of glove usage and needlestick injury reporting, we conducted a survey of junior doctors in three hospitals in the UK. Of the 190 respondents, the majority rarely wore gloves for venesection, insertion of intravenous cannulas or arterial blood gas sampling. For more major procedures (insertion of central venous lines, insertion of thoracostomy tubes, suturing) gloves were invariably worn. Only 17.5% of needlestick injuries were reported. The rates of glove usage and needlestick injury reporting were lower than previous studies have demonstrated in North America. Surgeons suffered the most needlestick injuries and were the least likely to report them. The low reporting rate may have serious implications, particularly in view of the new Government guidelines on needlestick injuries which involve HIV-infected blood. By failing to use gloves and report needlestick injuries, junior doctors, in particular surgeons, are placing themselves and patients at increased risk of blood-borne transmissible diseases.

Gloves, Surgical↗
PubMed1997

Specificity of volumetric magnetic resonance imaging in detecting hippocampal sclerosis.

BACKGROUND: Magnetic resonance imaging (MRI)-based volumetric measurements of the hippocampal formation are useful in detecting unilateral hippocampal sclerosis (HS) in patients with temporal lobe epilepsy. In this pathologic entity, volumetric MRI analysis shows the epileptogenic structure to be atrophic when compared with the normal, nonepileptogenic side. Some authors have suggested that the radiological features of atrophy of medial temporal lobe structures are common in patients with complex partial seizures, but also are seen frequently in other seizure types and can occur even in patients without epilepsy. OBJECTIVE: To determine if seizures originating in extrahippocampal sites cause gliosis, cell loss, and atrophy of medial temporal lobe structures (i.e., HS). METHODS: We studied 110 patients with chronic epilepsy using volumetric MRI measurements of the hippocampal formation. Seventeen patients had pathologically proven HS, 27 patients had seizures due to extratemporal structural lesions, 15 patients had seizures caused by extrahippocampal temporal lobe lesions, 29 patients had primary generalized epilepsy, and 22 patients had secondary generalized epilepsy. RESULTS: All 17 patients with HS showed significantly reduced absolute hippocampal formation volumes of greater than 2 SDs below the mean of the control groups. The preoperative hippocampal formation volume measurements correlated well with the severity of HS on pathological examination. Hippocampal volumes were within the normal range in all patients with primary generalized epilepsy, secondary generalized epilepsy, extratemporal structural lesions, and extrahippocampal temporal lobe lesions. CONCLUSIONS: Seizures originating at extrahippocampal sites do not cause gliosis, cell loss, or atrophy of medial temporal structures. Significant reduction in hippocampal volumes is a specific marker for HS.

Adolescent↗
PubMed1997

Volumetric magnetic resonance imaging. Clinical applications and contributions to the understanding of temporal lobe epilepsy.

In recent years, magnetic resonance imaging-based volumetric measurements of the amygdala and hippocampus have proved useful in the diagnosis and treatment of patients with temporal lobe epilepsy. This imaging modality allows amygdaloid and hippocampal volumes to be correlated with neurophysiological, neuropathological, and neuropsychological findings, surgical outcome, and clinical findings. We evaluated the technical and anatomical aspects underlying the successful use of the modality that were reported in previous studies. We also evaluated issues such as the sensitivity and specificity of volumetric magnetic resonance imaging, its use in bilateral temporal lobe epilepsy, and the debate concerning the sensitivity of qualitative visual analysis vs quantitative volumetric analysis of magnetic resonance images. Volumetric magnetic resonance imaging, when used in conjunction with video electroencephalographic monitoring, neuropsychological studies, and other neuroimaging studies, will enable patients with temporal lobe epilepsy to be treated in an appropriate, efficient, and cost-effective manner.

Amygdala↗
PubMed1997

Periventricular nodular heterotopia and intractable temporal lobe epilepsy: poor outcome after temporal lobe resection.

We describe 5 women and 5 men with periventricular nodular heterotopia and electroclinical features suggestive of temporal lobe epilepsy, who were surgically treated for control of medically refractory seizures. Magnetic resonance imaging revealed bilateral periventricular nodular heterotopia in 7 of the 10 patients. Because of the lack of clear localization, 6 patients were studied with intracranial depth electrode recordings. Seizures were of hippocampal onset (3 patients), regional temporal lobe onset (2 patients), or occipital-temporal onset (1 patient). Anterior temporal lobectomy was performed in 6 patients; selective amygdalohippocampectomy, in 1; and anterior temporal lobectomy plus resection of the heterotopic tissue, in 3. None of the 9 patients followed for more than 12 months postoperatively were seizure free. Two patients were initially seizure free for approximately 18 months, but then seizures recurred. One patient had a major reduction in seizure frequency at a 39-month follow-up after most of the unilateral heterotopic tissue was included in the temporal resection. Temporal resection did not lead to a long-term favorable outcome in this group of patients with periventricular nodular heterotopia and epileptogenic discharges involving the temporal lobe. This suggests a more widespread disorder with epileptogenic activity possibly originating in or near the heterotopic tissue. The clinical and electrographic features of periventricular nodular heterotopia pointing to temporal lobe origin are misleading and temporal resection does not result in long-term cessation of seizures.

Adult↗
PubMed1997

Isolation and characterization of phenoloxidase from egg masses of the gastropod mollusc, Biomphalaria glabrata.

Previous studies have shown that phenoloxidase activity is present in the albumen gland and egg masses of Biomphalaria glabrata, and its potential role in egg formation in this snail has been proposed. In the present study, a phenoloxidase enzyme has been isolated from the supernatant of egg mass homogenates using a combination of hydrophobic interaction chromatography and gel filtration high-performance liquid chromatography (GF-HPLC). The isolated phenoloxidase eluted as a single peak of activity upon GF-HPLC (representing a 132-fold purification) and subsequently was detected as a single band with an estimated molecular mass of 35 kDa by SDS-PAGE analysis. Phenylthiourea-inhibitable mono- and diphenoloxidase activities were demonstrated for the isolated enzyme suggesting that both enzyme activities are associated with a single, tyrosinase-type molecule.

Ammonium Sulfate↗