Development of rostrocaudal dendritic bundles in rat thoracic spinal cord: analysis of cholinergic sympathetic preganglionic neurons.

Using monoclonal antibodies to choline acetyltransferase (ChAT) and glial fibrillary acidic protein (GFAP), we have analyzed the development of the dendritic bundles formed by cholinergic sympathetic preganglionic neurons (SPNs) in relationship to changes in the organization of glial fibers. In adult rat thoracic spinal cord, SPNs in the intermediolateral (IML) and central autonomic (CA) regions extend dendrites in both the mediolateral and rostrocaudal directions, forming a ladder-like pattern in horizontal sections of thoracic spinal cord. We report that, while the mediolateral dendrites form prenatally, the rostrocaudal dendritic bundles are not detected until at least a week later, during early postnatal life. The rostrocaudal dendrites develop rapidly during the first postnatal week, and achieve an adult-like pattern by postnatal day 14. The observed ontogenetic arrangements of dendritic bundles were correlated with the developing organization of astroglial processes with which they are intimately associated. While the appearance of mediolateral dendrites is consistent with the radial organization of glial in the embryonic spinal cord, the developmental time course of the rostrocaudal dendritic bundles coincides with the transformation of glial cells from this predominantly radial or transverse orientation to the randomly-oriented, stellate pattern of mature astrocytes. This temporal association suggests that ontogenetic changes in the organization of glial cells may contribute to the differential development of mediolateral and rostrocaudal dendritic patterns in the spinal cord.     

Infectivity of African cassava mosaic virus clones to cassava by biolistic inoculation

Summary.  Clones of an African cassava mosaic virus isolate originating from Nigeria (ACMV-NOg) were shown to be infectious to cassava by biolistic inoculation. The production of pseudorecombinants between ACMV-NOg and clones of an ACMV isolate originating from Kenya (ACMV-K) indicated that the lack of infectivity of ACMV-K to cassava was due to defect(s) in the DNA B genomic component; this component encodes two proteins involved in cell-to-cell movement. This is the first demonstration of infectivity of a cloned geminivirus to cassava and conclusively proves that ACMV is the causative agent of cassava mosaic disease. The potential uses of infectious ACMV clones and the means by which to introduce them into cassava are discussed. Received January 18, 1998 Accepted May 27, 1998     

Improved power control during microwave heating in biological applications.

The heating performance of prototype variable power control units attached to two domestic microwave ovens, 500 W and 700 W, was investigated. The units employed the phase control method where rated voltage was obtained by switching AC supply at a particular angular position on the sinusoidal voltage. In order to create experimental conditions employed in a previous study, Sydney tap water (50 mL) was heated at a 10% power level in the 500 W oven. Water boiled at 10 min in both experiments. However, the precision and control of the heating was greatly improved with addition of the control unit. A disinfecting solution (50 mL) and a tissue fixative (10 mL) were included for experiments with the 700 W oven. A power level of only 1% was sufficient to maintain the temperature of the fixative at low temperatures (30-40 degrees C) where many biological reactions occur. The present results indicate that microwave heating power can be controlled by the variable power control method. This will make temperature control possible through the provision of an electronic feedback loop which links a thermocouple with the power control unit.     

Possible roles of vitamin E in immune response of calves.

The effect of vitamin E injections on immune responses of calves was investigated. Treatments were: 0, 900, 1800 and 2700 IU of D-alpha-tocopherol given by injection starting at birth and then a 3 wk interval until the age of 12 wk. Plasma vitamin E levels were significantly higher for supplemented calves than control calves at any of the sampling times. There were no significant differences in the concentrations of immunoglobulin IgG1, IgG2 and titre to Keyhole Limpet Haemocyanin among treatments. However, the general trend was to have higher concentrations of IgG1 and IgG2 with an increase in the levels of vitamin E. Immunoglobulin IgM was significantly higher for calves supplemented with 2700 IU of vitamin E than control calves.     

Expression of a single dopamine transporter cDNA can confer two cocaine binding sites.

Radiolabeled cocaine analogs can bind to low and high affinity sites on striatal dopamine transporters (DAT). Recently, a cDNA encoding a rat brain dopamine transporter pDAT1 has been cloned. COS cells transfected with the pDAT1 in a eukaryotic expression vector express both a high (KD = 3.4 nM) and low affinity (KD = 163.6 nM) cocaine binding sites, suggesting that both sites are provided by a single gene product.     

Further evidence to support disconjugate eye torsion as a predictor of space motion sickness.

Disconjugate eye torsion in hypo- and hypergravity of parabolic flight was examined in four former astronauts and four previously tested ex-astronauts to replicate an earlier study and to further test the asymmetry hypothesis of otolith function. Results in the new subjects supported the asymmetry hypothesis and confirmed previous findings that those with low scores of torsional disconjugacy on the KC-135 did not suffer space motion sickness in their prior Shuttle missions while those with high scores did. Tilting subjects with high disconjugacy scores slightly to one side and the other failed to find a position that decreased disconjugacy in hypergravity, leading to the conclusion that a simple planar asymmetry about the y-axis was probably not the cause of the observed torsional differences in the two eyes. Disconjugacy increased at 0 G with increasing parabolas, much more so in subjects who had suffered SMS. Because of this, 10 to 20 parabolas were deemed to be a more certain discriminator than a fewer number.     

Sexual and aggressive interactions in a visible burrow system with provisioned burrows

The visible burrow system (VBS) is a habitat providing burrows and an open area for mixed-set rat colonies. Provisioning of food and water in the burrows makes it unnecessary for potentially defensive animals to leave the burrows to eat/drink on the surface, and enables evaluation of new types of agonistic interactions that may emerge when this necessity is removed. In such colonies, subordinate males showed high magnitude tunnel guarding behavior, occupying a tunnel opening onto the surface and confronting the dominant. Dominants, in response, made lunges into the tunnels, but quickly retreated without gaining entry, apparently stopped by contact with the defender's vibrissae. Dominants also made and continued to make lateral attacks to the wall adjacent to the tunnels guarded by subordinates, although these were useless in terms of affording contact with the subordinate. Dominant-female agonistic interactions were more frequent than those of dominants and subordinates. These were largely initiated by the male, and involved female defensive behavior. Nonetheless, females, unlike subordinates, failed to show tunnel guarding and continued to utilize the surface freely. They also spent more time in the vicinity of the dominant over days of colony formation. This apparent paradox may reflect that females were seldom wounded, and that the initial site of male contact with females was the female's anogenital area, findings suggesting that interactions of males and females often reflect male sexual advances, countered by female defenses that effectively protect nonestrus females from mounting and copulation.