Biomedical subjects
J Shand
Publications and source records attributed to J Shand.
The relationship between the position of the retinal area centralis and feeding behaviour in juvenile black bream Acanthopagrus butcheri (Sparidae: Teleostei).
The topography of the neurons in the retinal ganglion cell layer of juvenile black bream Acanthopagrus butcheri changes during development. The region of high cell density the area centralis (AC), relocates from a temporal (central) to a dorsal (peripheral) position within the dorso-temporal retinal quadrant. To ascertain whether the differences in the position of the AC during development are related to feeding behaviour, we monitored fishes that were given a choice of food. A range of feeding behaviour patterns was recorded in individual fishes. The smallest fishes (8-15 mm standard length (SL)) took live food from the water column. Following weaning onto pellets, fishes exhibited a preference for taking food from either the substrate or the surface (but not both). When greater than 20 mm SL, a number of individuals then divided their time between surface and substrate feeding before all fishes became exclusive benthic feeders at a stage between 50 and 80 mm SL. Three individual fishes, for which behaviour patterns were categorized, were killed and the topography of the retinal ganglion cell layer analysed. A range of positions for the AC was found with the smallest fish (12 mm SL) possessing a region of high cell density in the temporal retina. In a larger fish (70 mm SL), feeding from both the substrate and the surface, the AC was found in an intermediate dorso-temporal position. The AC of a fish (51 mm SL) preferentially taking food from the substrate was located in a dorsal position.
Are dedicated bladder films necessary as part of intravenous urography for haematuria?
OBJECTIVE: To determine the use and assess the value of full-bladder films during intravenous urography (IVU) which, despite the widespread availability of flexible cystoscopy, remain part of IVU in many radiology departments. Materials and methods A telephone survey of all Scottish radiology departments where IVU is regularly used showed that half routinely included a full-bladder film in the series. The reports of all IVU over 2 years in the authors' department were analysed retrospectively. The index urogram of all patients with bladder tumours confirmed during this period was reviewed independently by three observers, and together with the initial radiological reports was correlated with the cystoscopic and histological findings. RESULTS: From 2625 patients, 139 (5.2%) IVU reports commented on the bladder; 1423 patients presented with no haematuria. None of the patients without haematuria, where a comment was made about the bladder, had pathological evidence of a tumour. Overall 121 of 464 (26%) new bladder tumours were diagnosed on IVU before cystoscopy. Multiple tumours were always undetected and large tumours were often overlooked. CONCLUSIONS: Despite its continuing popularity, IVU is a poor means of identifying bladder tumours and routine views of the full bladder should be abandoned.
Variability in the location of the retinal ganglion cell area centralis is correlated with ontogenetic changes in feeding behavior in the black bream, Acanthopagrus butcheri (Sparidae, teleostei).
The development of neural cell topography in the retinal ganglion cell layer was examined in a teleost, the black bream (Acanthopagrus butcheri). From Nissl-stained wholemounts, it was established that fish between 10 and 15 mm standard body length (SL) possess high cell densities throughout the dorso-temporal retinal quadrant, with peak cell densities located in temporal regions of the retina. However, in fish between 15 and 80 mm SL, a wide variation in the position of the peak cell density is revealed with the locations of the areae centrales (AC) ranging from exclusively temporal to periphero-dorsal retina. Fish larger than 80 mm SL always possess an AC located in the dorsal region of the dorso-temporal retinal quadrant. The topography of ganglion cells within the ganglion cell layer was determined by comparing the numbers of ganglion cells retrogradely-labeled from the optic nerve with the total population of Nissl-stained neurons (ganglion plus displaced amacrine cells) in a range of different-sized individuals. Ganglion cell topography was the same as that recorded for all Nissl-stained neurons. The feeding behavior of juveniles from metamorphosis to 80 mm SL was observed, where fish were given the choice of feeding on live food in mid-water (until 15 mm SL) or obtaining pellets from the surface or the bottom. A range of feeding patterns was recorded, with the smallest fish taking food from mid-water but individuals between 15 and 80 mm SL taking food either from the surface or the bottom or both. A correlation between the preferred mode of feeding and the position of the AC was found, such that those individuals feeding in mid-water or at the surface possess a temporal or intermediate (dorso- temporal) AC, whereas those predominantly feeding from the bottom possess a dorsal AC.
Ontogenetic changes in the retinal photoreceptor mosaic in a fish, the black bream, Acanthopagrus butcheri.
The morphological development of the photoreceptor mosaic was followed by light and electron microscopy in a specific region of dorsal retina of the black bream, Acanthopagrus butcheri (Sparidae, Teleostei), from hatching to eight weeks of age. The retina was differentiated when the larvae reached a total length of 3 mm (3-5 days posthatch). Single cones, arranged in tightly packed rows, were the only morphologically distinct type of photoreceptor present until the larvae were 6 mm (day 15) in standard length (SL). At this time, the rod nuclei had become differentiated and the ellipsoids of selected cones began to form subsurface cisternae along neighbouring cone membranes. In this way, double, triple, quadruple, and occasionally photoreceptor chains of up to 10 cones were formed. At 8 mm SL, there was little apparent order in the photoreceptor mosaic. However, concomitant with subsequent growth, quadruple and other multiple cone receptors disappeared, with the exception of the triple cones, which gradually reduced in both number and retinal coverage to be restricted to central retina by 15 mm SL (days 40-55). Following this stage, the arrangement of double and single cones peripheral to the region of triple cones in dorsal retina was transformed into the adult pattern of a regular mosaic of four double cones surrounding a single cone. These results demonstrate that an established photoreceptor mosaic of rows of single cones can be reorganised to form a regular square mosaic composed of single and double cones.
Optics of the developing fish eye: comparisons of Matthiessen's ratio and the focal length of the lens in the black bream Acanthopagrus butcheri (Sparidae, Teleostei).
Matthiessen's ratio (distance from centre of lens to retina:lens radius) was measured in developing black bream, Acanthopagrus butcheri (Sparidae, Teleostei). The value decreased over the first 10 days post-hatch from 3.6 to 2.3 along the nasal and from four to 2.6 along temporal axis. Coincidentally, there was a decrease in the focal ratio of the lens (focal length:lens radius). Morphologically, the accommodatory retractor lentis muscle appeared to become functional between 10-12 days post-hatch. The results suggest that a higher focal ratio compensates for the relatively high Matthiessen's ratio brought about by constraints of small eye size during early development. Combined with differences in axial length, this provides a means for larval fish to focus images from different distances prior to the ability to accommodate.
Retinal structure and visual acuity in a polyprotodont marsupial, the fat-tailed dunnart (Sminthopsis crassicaudata).
The visual system of the fat-tailed dunnart (Sminthopsis crassicaudata), a small polyprotodont marsupial, has been examined both anatomically and behaviourally. The ganglion cell layer was examined in cresyl-violet stained wholemounts and found to contain a mean of 81,400 ganglion cells (SD +/- 3,360); the identification of ganglion cells was supported by a correspondence to optic axon counts. Ganglion cells were distributed as a mid-temporally situated area centralis, embedded in a pronounced visual streak. Localised implants of horseradish peroxidase into retinal wholemounts revealed both A-type and B-type horizontal cells. Sections of the outer retina showed it to be rod-dominated, with a rod-to-cone ratio of 40:1 at the area centralis; cones were found to contain oil droplets but double cones were not a prominent feature. The retinal pigment epithelium consisted of squamous cells. Visual acuity, estimated from counts of peak ganglion cell density (8,300/mm2, SD +/- 1,180) and measurements of posterior nodal distance (2.9 mm), was found to be 2.30 cycles per degree. The value was close to that of 2.36 cycles per degree estimated by behavioural tests using a Mitchell jumping stand; values were similar at low, intermediate and high light levels. Our findings are discussed in relation to the lifestyle of the dunnart.
A dialogue concerning the philosophy of health care.
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A structured approach to the interpretation and reporting of ventilation/perfusion scans.
The aim of this study was to develop a structured approach to the reporting and in particular the clinical interpretation of ventilation/perfusion (V/Q) scan results. An initial audit indicated that there were significant variations in the clinical management of patients particularly after a non-diagnostic V/Q scan report. There were also differences in the approaches used to interpret the scan itself. In an attempt to improve this, a set of interpretation guidelines was produced based on the revised PIOPED data. To combat the problems with clinical interpretation, a standard method for assessing the pre-test clinical probability of pulmonary embolism was established. This clinical risk was then combined with the V/Q scan result to give an overall probability for the presence of pulmonary embolism. The more precise risk stratification which resulted allowed explicit clinical advice on patient management to be incorporated into the final report. A second audit was performed with the revised methodology in place. The level of inter-observer variability for scan reporting decreased from 30% to 12%. The prior assessment of clinical risk and the standardized method of combining this with the scan result led to an improvement in patient management. This was particularly true for the non-diagnostic group, in whom additional investigations were more appropriately used. A structured approach which allows the pre-test probability of pulmonary embolism to be combined in an explicit fashion with the V/Q scan result can provide a more precise risk stratification allowing appropriate recommendations to be made. Such an approach can result in improved patient management.
Car driving for the severely physically disabled: the American experience.
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Changes in retinal structure during development and settlement of the goatfish Upeneus tragula.
The retinal structure of the goatfish Upeneus tragula was examined at various stages of the fish's development from pre-settlement pelagic larvae to benthic juveniles. Histological investigation revealed a double layer of cone inner segments in the dorsal retina and high cone and bipolar cell densities in both dorsal and ventral retina prior to settlement. During settlement reorganisation of the dorsal retina was found to occur, with the two cone layers slotting together to form a single layer. In both the dorsal and ventral retina cone and bipolar cell densities were rapidly reduced. Visual acuity, as calculated from histological data on cone density and lens diameter, was found to increase rapidly prior to settlement to an asymptote of approximately 27 minutes of arc, which corresponded to settlement. The changes in the visual system are thought to be associated with changes in both habitat and feeding behaviour at settlement when the fish leave the surface waters and begin a benthic mode of life using sensory barbels to search for sediment dwelling prey.
A comparison of 10 MHz ultrasound and 201-thallium/99m-technetium subtraction scanning in primary hyperparathyroidism.
Both high resolution (10 MHz) ultrasound and 201-thallium/99m-technetium subtraction scanning (Tl/Tc) were carried out preoperatively in 25 patients with primary hyperparathyroidism. Operative findings were the standard against which these two imaging methodologies were compared. Tl/Tc scanning showed a sensitivity of 42% and a specificity of 97%. By comparison, sensitivity of ultrasound was 38% and specificity 89%. Both techniques were positive together in nine instances and correctly localized the parathyroid adenoma in eight of these. In 44% of cases, however, both methods together failed to localize any abnormal parathyroid tissue. The ability of these modalities to localize abnormal parathyroid tissue correctly tended to vary with gland size. Where both ultrasound and Tl/Tc scans were negative, median gland size was smaller at 170 mg (range 50-2,500 mg), compared with where Tl/Tc scanning was correct (750 mg, 150-6,820 mg; P < 0.03), ultrasound was correct (960 mg, 100-6,820 mg; P < 0.03) and both techniques together were correct (980 mg, 600-6,820 mg; P = 0.002). These results suggest that neither Tl/Tc scanning or ultrasound has sufficient sensitivity or specificity to be used routinely in the preoperative evaluation of patients with primary hyperparathyroidism.
Microspectrophotometric determinations of rod visual pigments in some adult and larval Australian amphibians.
Visual pigments from the red rods of adults of eight species of Australian anuran amphibians, from a variety of habitats, were analyzed by microspectrophotometry. The lambda max in all cases fell between 502 nm and 506 nm, and the absorption spectra were well fitted by an A1-based visual pigment template curve. Red rod pigments were also analyzed for a number of tadpoles. In some cases the data were best fitted with an A1-based visual pigment template, in other cases with an A2-based template, and finally some tadpoles appeared to have mixtures of the two pigments.
Mid-life crises in career people.
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The value of immediate ultrasound in acute abdominal conditions: a critical appraisal.
A randomized prospective controlled trial was carried out comparing the value of immediate ultrasound examination with conventional management (selective ultrasound examination) in patients with acute abdominal symptoms. Immediate ultrasound led to earlier establishment of a final diagnosis but did not shorten the duration of in-patient care. Selective ultrasound improved diagnostic yield compared to immediate ultrasound and is believed to be the better option. It implies that a prompt but selective ultrasound service should be available for in-patients in the acute specialties.
Hyperostosis frontalis interna, acromegaly and hyperprolactinaemia.
The association between hyperostosis frontalis interna (HFI), acromegaly and hyperprolactinaemia was investigated. Thirty six acromegalic patients, of whom 19 had hyperprolactinaemia, were compared with 36 randomly-selected, age-sex matched controls. There was a higher prevalence of HFI in the skull X-rays of the acromegalic cohort (P = 0.0002) when compared to the control group. This difference was apparent in both men (P = 0.01) and women (P = 0.01). Acromegalic patients with hyperprolactinaemia also expressed HFI in a higher proportion of individuals than the control group (P = 0.0001). Intra- and interobserver variability was assessed and concordance with 100% and 97% in the moderate and severe HFI sub-groups. The following sub-group analysis was undertaken: acromegalics and those acromegalics with hyperprolactinaemia were compared with the controls and a highly significant distinction was confirmed (P = 0.0007 and P = 0.00001 respectively). A relationship between HFI severity and the patient's age was noted in both male and female acromegalics. Also, the severity of HFI appeared related to disease duration in female acromegalics. The cause of HFI remains unknown but appears to be strongly associated with acromegaly, particularly in the presence of co-existent hyperprolactinaemia. The association may have symptomatic significance and the presence of HFI should be confirmed or refuted in all patients with acromegaly.
The isolated iridescent cornea of the sand goby is photoresponsive.
After a 2 h period of dark adaptation the iridescent cornea of the sand goby, Pomatoschistus minutus, responds to illumination by increasing the amplitude of iridescent reflexions and shifting the wavelength of maximum reflexion towards longer wavelengths. This characteristic response is found to occur in both the intact eye and in the isolated cornea, indicating that the light-induced colour changes are mediated by extra-retinal photoreceptors.
Interspecific variation in the visual pigments of deep-sea fishes.
Visual pigments in the rods of 38 species of deep-sea fish were examined by microspectrophotometry. 33 species were found to have a single rhodopsin with a wavelength of maximum absorbance (lambda max) in the range 470-495 nm. Such visual pigments have absorbance maxima close to the wavelengths of maximum spectral transmission of oceanic water. 5 species, however, did not conform to this pattern and visual pigments were found with lambda max values ranging from 451 nm to 539 nm. In 4 of these species two visual pigments were found located in two types of rod. Some 2-pigment species which have unusual red sensitivity, also have red-emitting photophores. These species have both rhodopsin and porphyropsin pigments in their retinae, which was confirmed by HPLC, and the two pigments are apparently located in separate rods in the same retinal area. In deep-sea fishes the occurrence of 'unusual' visual pigments seems to be correlated with aspects of the species' depth ranges. In addition to ecological influences we present evidence, in the form of lambda max spectral clustering, that indicates the degree of molecular constraint imposed on the evolution of visual pigments in the deep-sea.