Optic neuropathy in familial dysautonomia

Optic atrophy, which is indicative of a CNS disorder, is a rarely described manifestation of familial dysautonomia (Riley-Day syndrome). As these patients are now living longer, the prevalence of optic neuropathy also may be increasing. We present a man with familial dysautonomia and visual loss resulting from optic atrophy and visual field defect suggestive of chiasmal pathology.     

Clonidine blocks acquisition but not expression of conditioned opiate withdrawal in rats

Previous studies in rodents have reported that clonidine, an alpha 2-adrenergic receptor agonist, attenuated conditioned aversions to naloxone-precipitated opiate withdrawal when administered prior to each withdrawal conditioning episode. The current study was designed to determine whether clonidine could modify the expression of previously established conditioned place aversions and conditioned suppression of operant responding. Dose- and time-dependent effects of clonidine on activity and suppression of operant responding for food identified appropriate treatment parameters for subsequent studies in which rats rendered dependent on opiates through implantation of morphine pellets were tested for: (1) conditioned place aversion; and (2) conditioned suppression of operant responding for food (fixed ratio-15 schedule), in a paradigm wherein rats received four pairings of naloxone with a distinct tone and odor stimulus. Clonidine dose-dependently blocked the acquisition of both conditioned behaviors when administered prior to naloxone on each conditioning trial, but was ineffective in blocking the expression of these conditioned withdrawal signs when administered prior to the test session.     

The virus causing encephalomyelitis in sheep in Spain: a new member of the tick-borne encephalitis group

An analysis of endothelin in atherosclerotic plaques using immunohistochemical methods showed that endothelin not only existed in endothelial cells, large amounts were also found in the proliferating intimal vascular smooth muscle cells (VSMC). In the de-endothelized thoracic aorta of rats, significant amounts of endothelin could be produced by proliferating intimal VSMC. Radio-immunological studies demonstrated that the extent of VSMC proliferation was in direct ratio to endothelin content, which suggests that production of endothelin is related to proliferation of VSMC in atherosclerotic plaques.     

Heart rate during development in the turtle embryo: effect of temperature

Growth and development can occur over a wide range of physical conditions in reptiles. Cardiovascular function must be critical to this ability. However, information on cardiovascular function in developing reptiles is lacking. Previous work indicated that in reptiles the effects of temperature on growth and metabolism are largely restricted to early development. This study examined whether the previously observed effects of temperature and different perinatal patterns of metabolism observed in amniotic vertebrates are correlated with cardiovascular function. Embryonic and hatchling carcass mass, heart mass and heart rate (HR) were compared for snapping turtle eggs (Chelydra serpentina) incubated at 24 degrees and 29 degrees C. Incubation time was shorter at 29 degrees C (56.2 days) than at 24 degrees C (71.1 days). Carcass and heart growth showed a sigmoidal pattern at both temperatures. However, cardiac growth showed a relative decrease as incubation proceeded. Incubation temperature significantly affected the HR pattern during development. The HR of embryos incubated at 24 degrees C was constant for most of incubation (51.8 +/- 4.8 min-1). A small decrease was observed just prior to and a large decrease immediately following hatching (posthatch, 22.3 +/- 4.1 min-1). At 29 degrees C embryonic HR was greater than at 24 degrees C early in development (72.3 +/- 3 min-1). The HR steadily decreased to values equivalent to those at 24 degrees C. The HRs of 24 degrees C and 29 degrees C hatchlings were not different. Cardiac output (estimated as the product of heart mass and HR) increased rapidly during early development and then slowed dramatically at both temperatures. These data are consistent with the suggestion that temperature exerts its effects primarily early in development. Furthermore, the changes in cardiovascular function are correlated with metabolic changes in hatching vertebrates.     

Object shape dependent PSF model for SPECT imaging

An analytical expression for the point spread function (PSF) and the line spread function (LSF) of a parallel hole gamma camera is presented, for homogeneous media and for photons having mainly Compton interactions in the object. The PSF of scattered photons is described by convolving a zeroth-order modified Bessel function of the second kind with the unscattered PSF, which is approximated by a Gaussian. The complete PSF (scatter plus nonscatter) depends on the source distance ( z) and depth (d) of the source in the object. For convex-shaped emitting objects, the dependence of the PSF on the object contour can be incorporated by a simple correction. Thus, a complete mathematical model of the imaging of an activity distribution in a homogeneous medium is obtained. The model has been evaluated for ^99mTechnetium line sources by using a LEAP collimator at various energy windows (ΔE). It is shown that the model is valid to a high accuracy at ΔE=15%, for a large range of values of z and d