Anaesthesia in a patient with Noonan's syndrome and cardiomyopathy.

A 5-year-old girl with Noonan's syndrome and a hypertrophic cardiomyopathy presented for myelography and subsequently, laminectomy. The anaesthetic management of the patient is described and the potential problems of the facial, cardiovascular and skeletal abnormalities associated with the condition are discussed.

Ganglion cell size and distribution in the retina of the two-toed sloth (Choloepus didactylus L.).

The distribution of ganglion cell densities and sizes was studied in Nissl-stained flat-mount retinae of the two-toed sloth. The area centralis, a weak specialization with low ganglion cell density, is located in the temporal retina close to the center of the eye. The presence of a visual streak was noted. The distribution of different ganglion cell sizes was approximately equal throughout the retina. Although the retinal organization differs from that of the closely related three-toed sloth, the presumed function of retinal specializations in both species is to guide limb movements by permitting visualization of the branch along which the animal is climbing.

Ganglion cell size and distribution in the retina of the two-toed sloth (Choloepus didactylus L.)

The distribution of ganglion cell densities and sizes was studied in Nissl-stained flat-mount retinae fo the two-toed sloth. The area centrailis, a weak specializtion with low ganglion cell density, is located in the temporal retina close to the center of the eye. The presence of a visual treak was nsoted. The distribution of different ganglion cell sizes was approximately equal throughout the retina. Although the retinal organization differs from that of the closely related three-toed sloth, presumed function of retinl specializations in both species is to guide limb movements by permiting visualization of the branch along which the animal is climbing

Unusual distribution of ganglion cells in the retina of the three-toed sloth (Bradypus variegatus).

1. The distribution and size of retinal ganglion cells labelled with horseradish peroxidase (HRP) were studied in flat-mounted retinas of three-toed sloths. 2. Massive injections of HRP solution were made throughout the thalamus and midbrain in anesthetized sloths in order to retrogradely label the retinal ganglion cell population. Twenty to thirty h later the eyes were excised and the retinas flat-mounted and reacted with phenylenediamine-HCl and H2O2 to label ganglion cells, thus distinguishing them from other cells in the same retinal layer. 3. Ganglion cell density gradually increased from about 500 cells/mm2 at the far periphery to a peak of about 1,500 cells/mm2 in an area, termed the area centralis, deep in the inferior temporal retina. The presence of a vertical visual streak was also noted. 4. The area centralis contained a higher frequency of small ganglion cells than the peripheral retina where large cells predominated. 5. The unusual position of the area centralis and visual streak in the retina can be explained by the sloth's unique ability to rotate its head 180 degrees while climbing upside-down along horizontal branches so that the head is right-side-up. If it is assumed that the branch directly above the sloth's head needs to be visualized for accurate claw placement then the branch would be imaged on the inferior temporal retina in an area corresponding to the maximum density region.

Unusual distribution of ganglion cells in the retina of the three-toed sloth (Bradypus variegatus)

1. The distribution ans size of retinal ganglion cells labelled with horseradish preoxidase (HRP) were studied in flat-mounted retinas of three-toed sloths. 2. Massive injections of HRP solution were made throughout the thalamus and midbrain in anesthetized sloths in order to retrogradely label the retinal ganglion cell population. Twenty to thirty h later the eyes were and the retinas flat-mounted and reacted with phenylenediamine-HCL and H2O2 to label ganglion cells,thus distinguishing then from other cells int he same retinal layer. 3. Ganglion cell density graually increased from about 500 cell/mm2 at the far periphery to a peak of about 1,500 cells/mm2 in an area, termed the area centralis, deep in the inferior temporal retina. The presence of a vertical visual steak was also noted. 4. The area centralis contained a higher frequency of small ganglion cells than the peripheral retina where large cells preominated. 5. /the unusual postion of the area centralis and cisual streak in the retina can be explained by the slot's unique ability to rotate its head 180- while climbing upside-dow along horizontal branches so that the head is right-side-up. If it is assumed that the branch directly above the sloth's head needs to be visualized for accurate claw placement then the branch would be imaged on the inferior temporal retina in an area corresponding to the maximum density region

Some properties of extrastriate visual units in the cortex of the rabbit.

Receptive fields and trigger properties of 306 units in the visual cortex of the rabbit have been examined in detail. Reconstruction of the electrode tracks revealed that 276 of these recordings were made from cells located in the striate cortex, whilst the remaining 30 were found to lie in cortex lateral to the striate field. These latter units have been termed 'extrastriate'. Five penetrations involved both striate and extrastriate units enabling a direct comparison of their properties to be made. The most outstanding feature of the extrastriate units was their huge receptive field sizes (up to 80 degrees X 130 degrees) and high rates of spontaneous activity (usually between 10 and 20 imp./sec). None of these cells responded well to stationary stimuli and most preferred moving targets. Responses could be elicited regardless of the nature of stimulus-to-background contrast and were constant over a wide range of stimulus sizes. No cells were found which were orientation selective. Approximately half the extrastriate units were direction selective, the majority preferred anterior movement in the visual field. Movement in the counter-preferred direction generally resulted in suppression of the spontaneous discharge. In contrast to this the receptive fields of cells in the striate cortex were small, and were often sensitive to features such as stimulus size, orientation, and contrast, in addition to movement and direction of movement. The similarity between one class of extrastriate unit, and units recently observed in the pretectum of the rabbit is pointed out.

Rheotaxis and chemoreception in the freshwater snail biomphalaria glabrata (say): estimation of the molecular weights of active factors.

1. Dilute solutions of lettuce and wheatgerm extracts trigger positive rheotaxis in the freshwater snail, Biomphalaria glabrata. This response can be used as the basis of a sensitive bioassay for characterizing and identifying the chemicals to which the snail is attracted. 2. Using ultrafiltration techniques a range of different molecular weight fractions could be attenuated or removed from these extracts. By comparing the activity of these solutions with that of the original extract an estimate of the molecular weight of the attractant could be made. 3. In both cases the molecular weights of the attractants were estimated as being greater than 1000. Those in the lettuce were estimated at lying between 1000 and 10,000; whereas for wheatgerm the values were slightly higher and lay between 10,000 and 40,000. The ecological significance of these results is discussed.