Nodularin uptake by seafood during a cyanobacterial bloom.

The problem of blue-green algal toxin contamination of recreational waters and drinking water catchments is well described, as is the potential contamination of associated seafood. Algal contamination of Victorian waterways is now a widespread annual occurrence and, in some regions, the intersection of blooms and commercial fishing threatens the food safety of large numbers of people. Toxin levels which produce no observed adverse effect in animal studies were used to derive safe tolerable daily intake levels. These 'acceptable levels' were then modified to protect against potential acute health risks associated with short-term exposures. National food surveys were used to derive likely seafood intakes and thus, in combination with 'safe toxin levels', health alert levels for seafood were formulated. During the summer of 2001 a bloom of Nodularia spumigena occurred in the Gippsland Lakes area of Southern Victoria. During the bloom, seafood samples were collected and nodularin concentrations were estimated. Nodularin concentrations reached levels of concern in mussels and in prawn viscera at cell counts as low as 30,000 cells/ml. Nodularin concentrations in the flesh of finfish remained low. Boiling the seafood redistributed toxin between viscera and flesh. The results were used to restrict some seafood harvesting.

A comparison of rCBF patterns during letter and semantic fluency.

To evaluate the functional neuroanatomies underlying letter and category fluency, 18 normal controls were studied with oxygen-15 water regional cerebral blood flow positron emission tomography. Three counterbalanced conditions each consisted of 6 trials (45 s each): letter fluency (generating words when cued with a particular letter), semantic fluency (generating words when cued with a particular category), and a control condition (generating days of the week and months of the year). Relative to the control, participants activated similar brain regions during both fluency tasks, including the anterior cingulate, left prefrontal regions, thalamus, and cerebellum; reductions were found in parietal and temporal regions. In a direct comparison of the 2 fluency tasks, inferior frontal cortex and temporoparietal cortex (hypothesized to participate in a phonologic loop for accessing word pronunciation) were activated more during letter than semantic fluency, whereas left temporal cortex (associated with access to semantic storage) was activated more during semantic than letter fluency. This study identifies subtle differences in the neural networks underlying letter and semantic fluency that may underlie the dissociation of these abilities in patients.

Context-dependent, neural system-specific neurophysiological concomitants of ageing: mapping PET correlates during cognitive activation.

We used PET to explore the neurophysiological changes that accompany cognitive disability in ageing, with a focus on the frontal lobe. Absolute regional cerebral blood flow (rCBF) was measured in 41 healthy volunteers, evenly distributed across an age range of 18-80 years, during two task paradigms: (i) the Wisconsin Card Sorting Test (WCST), which depends heavily on working memory and is particularly sensitive to dysfunction of the dorsolateral prefrontal cortex (DLPFC); and (ii) Raven's Progressive Matrices (RPM), which may also have a working memory component, but depends more on visuo-spatial processing and is most sensitive to dysfunction of postrolandic regions. We used voxel-wise correlational mapping to determine age-related changes in WCST and RPM activation and developed a method to quantitate and localize statistical differences between the correlation maps for the two task paradigms. Because both WCST and RPM performance declined with age, as expected, correlational analyses were performed with and without partialling out the effect of task performance. Task-specific reductions of rCBF activation with age were found in the DLPFC during the WCST and in portions of the inferolateral temporal cortex involved in visuo-spatial processing during the RPM. We also found reduced ability to suppress rCBF in the right hippocampal region during the WCST and in mesial and polar portions of the prefrontal cortex during both task conditions. Task-dependent alterations with age in the relationship between the DLPFC and the hippocampus were also documented; because the collective pattern of changes in the hippocampal-DLPFC relationship with ageing was opposite to that seen in a previous study using dextroamphetamine, we postulated a dopaminergic mechanism. These results indicate that, despite some cognitive overlap between the two tasks and the age-related cognitive decline in both, many of the changes in rCBF activation with age were task-specific, reflecting functional alteration of the different neural circuits normally engaged by young subjects during the WCST and RPM. Reduced activation of areas critical for task performance (i.e. the DLPFC during the WCST and posterior visual association areas of the inferolateral temporal cortex during the RPM), in conjunction with the inability to suppress areas normally not involved in task performance (i.e. the left hippocampal region during the WCST and mesial polar prefrontal cortex during both the WCST and RPM), suggest that, overall, reduced ability to focus neural activity may be impaired in older subjects. The context dependency of the age-related changes is most consistent with systems failure and disordered connectivity.

Functional mapping of human sensorimotor cortex with 3D BOLD fMRI correlates highly with H2(15)O PET rCBF.

Positron emission tomography (PET) functional imaging is based on changes in regional cerebral blood flow (rCBF). Functional magnetic resonance imaging (fMRI) is based on a variety of physiological parameters as well as rCBF. This study is aimed at the cross validation of three-dimensional (3D) fMRI, which is sensitive to changes in blood oxygenation, with oxygen-15-labeled water (H2(15)O) PET. Nine normal subjects repeatedly performed a simple finger opposition task during fMRI scans and during PET scans. Within-subject statistical analysis revealed significant ("activated") signal changes (p < 0.05, Bonferroni corrected for number of voxels) in contralateral primary sensorimotor cortex (PSM) in all subjects with fMRI and with PET. With both methods, 78% of all activated voxels were located in the PSM. Overlap of activated regions occurred in all subjects (mean 43%, SD 26%). The size of the activated regions in PSM with both methods was highly correlated (rho = 0.87, p < 0.01). The mean distance between centers of mass of the activated regions in the PSM for fMRI versus PET was 6.7 mm (SD 3.0 mm). Average magnitude of signal change in activated voxels in this region, expressed as z-values adapted to timeseries, zt, was similar (fMRI 5.5, PET 5.3). Results indicate that positive blood oxygen level-dependent (BOLD) signal changes obtained with 3D principles of echo shifting with a train of observations (PRESTO) fMRI are correlated with rCBF, and that sensitivity of fMRI can equal that of H2(15)O PET.

Cognitive activation during PET: a case study of monozygotic twins discordant for closed head injury.

Using positron emission tomography (PET), we studied physiological changes in a patient with frontal lobe damage resulting from closed head injury by assessing his regional cerebral blood flow (rCBF) pattern relative to that of his uninjured monozygotic (MZ) cotwin and against normal variability between cotwins in 10 comparably-aged, uninjured MZ twin pairs. rCBF was measured during the Wisconsin Card Sorting Test (WCST) and a sensorimotor control task. Differences between the index twins in rCBF activation (WCST-control) in regions determined on coplanar MRIs were compared to within-pair differences in the control group using the Z-statistic. Activation differences between the index twins extending beyond normal variability were found in two regions-relative to his uninjured cotwin, the injured twin showed less activation in the inferior portion of the left inferior frontal gyrus while showing greater activation in the left hippocampus (P < 0.04). This pattern contrasts with that of normal subjects during WCST performance of augmented rCBF in the prefrontal cortex and not in the hippocampus. These rCBF differences appear to reflect the utilization of different neural systems when performing a frontal-lobe task. The use of the hippocampus by the injured twin might reflect an attempt to compensate for compromised frontal lobe functioning.

Modified midfacial degloving. A practical approach to extensive bilateral benign tumours of the nasal cavity and paranasal sinuses.

Midfacial degloving is a well-known technique for entering the nasal and paranasal cavities, the rhinopharynx and the base of the skull. We report our experience with a modification of midfacial degloving, applied to two patients with extensive bilateral benign tumours in the nasal cavities and the paranasal sinuses. No rhinoplastic procedure is necessary in this modification, and the access to the upper part of the nasal cavity is improved.

A new tracheostomy tube. III. Bronchofiberoptic examination of the trachea after prolonged intubation with the NL tracheostomy tube.

Recent publications show that severe damage to the trachea is still a problem with high-volume, low-pressure cuffs. The NL tracheostomy tube was used in 86 patients for 3 days to 2 months (mean 16 days). This tube has a high-volume, low-pressure cuff with automatic regulation of the cuff pressure at 3 kPa. The tube has a flexible tip. Fiberoptic examination at extubation showed minimal damage to the tracheal mucosa: 33 patients had normal mucosa and the rest had hyperaemia and/or fibrin formation. Four patients had ulcerations from suction catheters and four patients had small, superficial ulcerations produced by the tip of the tube. Of these last four patients, three had skin flaps that exerted pressure on the tube. Severe tracheal damage was prevented due to the combination of automatic regulation of cuff pressure and a flexible tip of the tube.

Experience with the deltopectoral flap.

One hundred and three non-delayed deltopectoral flaps were used for head and neck reconstruction in 86 patients. A retrospective analysis to detect factors with negative influence on the reconstruction resulted in two significant risk factors (p less than 0.05): irradiated recipient site and internal location of recipient site. The flap failure rate was not significantly affected by variations in flap length, age, sex or concomitant diseases. The mean stay in hospital was 10 weeks and was significantly prolonged for patients having had radiotherapy, internal reconstructions or flap failure (p less than 0.05).

The deltopectoral flap: a historical review with comments on its role in neurovascular reconstruction.

The history of the clinical, anatomical and haemodynamic aspects of the deltopectoral flap is reviewed, with some comments on its use as a neurovascular flap.

Immediate reconstruction of a resected segment of the lower jaw, using a compound flap of clavicle and sternomastoid muscle.

A brief account is given of the experimental data and the laboratory findings relative to the use of compound bone flaps of clavicle on a pedicle of sternomastoid muscle for restoration of mandibular defects. The clinical data on this method in 18 consecutive patients are presented and discussed.

A new tongue flap for closure of a pharyngo-cutaneous fistula. Case report.

An apparently original version of the several available tongue flaps is presented for the reconstruction of a lateral pharyngo-cutaneous fistula in a patient where several reconstructive attempts after excision for a malignant tumour had failed.