Responsiveness of genetically epilepsy-prone rats to intracerebroventricular morphine-induced convulsions

The sensitivity to intracerebroventricular morphine-induced convulsions was determined in members of the severe seizure (GEPR-9) and moderate seizure (GEPR-3) colonies of genetically epilepsy-prone rats as well as in non-epileptic control rats. GEPR-9s were more sensitive to morphine-induced wet-dog shakes, rearing with bilateral forelimb clonus and generalized clonus than controls of GEPR-3s. GEPR-3s were less sensitive to morphine-induced wet-dog shakes and rearing with bilateral forelimb clonus than controls. Both high and extremely low doses of morphine in GEPR-9s elicited tonic extensor convulsions resembling the characteristic sound-induced convulsion of GEPR-9s. The results suggest that opiotergic systems may contribute to the pathophysiology of the seizure-prone condition in GEPR-9s. Further, differences in responsiveness of opiotergic systems in GEPR-3s and GEPR-9s may partially account for differences in seizure severity in the characteristic sound-induced seizures of these two types of GEPRs.     

Computer-designed prostheses for orbitocranial reconstruction

Three-dimensional imaging is an adjunct to preoperative evaluation and surgical management in some patients with complex anatomic defects of various etiologies. Deformities defined by conventional computerized tomography can be viewed as accurate three-dimensional images calculated from the original scan. The images are viewed on a high-resolution video monitor and can be photographed for a permanent record. A computer-controlled milling device can use these data to fabricate prostheses. The prostheses aid reconstructive surgery through use as an alloplastic implant, as a template to fashion autogenous bone grafts, or as a model for tissue removal. We have utilized three-dimensional imaging in combination with computer-assisted prosthesis manufacture in six patients with complex orbitocranial deformities. Four patients have undergone reconstructive surgery with satisfactory results and no complications thus far. The use of computer-designed prostheses adds a new aspect to orbitocranial reconstructive surgery that facilitates increased accuracy in the correction of anatomic defects.     

The plasma membrane and generative cell organization in pollen of the mimosoid legume,Acacia retinodes

Summary Cytological changes associated with the final maturation, and dehiscence of the 16-grain compound pollen (polyads) have been followed in anthers at female and male phase of flowering. InAcacia retinodes, the transition from female to male phase takes approximately 24 h. The spherical generative cell at female phase is connected with the vegetative cell plasma membrane by a junction zone. This is sited adjacent to a germinal aperture, comprising wall ingrowths and membrane labyrinths. By male phase, the generative cell has elongated into a spindle-shape, and its surface is characteristically scalloped. The membrane labyrinths, especially those at the apertures, now contain masses of coated vesicles, implicated in the transport and secretion of proteins. Two-dimensional projections indicate that the generative cell and vegetative nucleus are closely associated forming a male germ unit.     

Transverse alternating field electrophoresis (TAFE)

The rapid development of electrophoretic technology during the past five years has given us a stream of improvements in the area of pulsed-field separation techniques. This progression has culminated in the conception of TAFE, a simple, high resolution technique providing straight lane geometry and separation of fragments up to 9 million base pairs in length. Pulsed-field techniques will unquestionably play a major role in the forthcoming analysis of the human genome by facilitating restriction mapping and cloning of large fragments. We have no doubt that TAFE will allow scientists to do this type of genetic analysis, faster and better than ever before.     

TRACE METALS AND METHYL MERCURY: ASSOCIATIONS AND TRANSFER IN HARP SEAL (PHOCA GROENLANDICA) MOTHERS AND THEIR PUPS

Milk samples from the stomachs of harp seal pups were analysed for Cu, Zn, Se, Cd and Hg, as were liver, kidney, and muscle from mother-pup pairs. Tissues were also analysed for MeHg. Milk contained, in addition to essential trace metals, Cd and Hg (57 ng/g and 6.5 ng/g respectively).
Pups had mercury in all three tissues. The percent methyl mercury in liver of pups was higher than in liver of mothers. Mercury in muscle was mostly methyl mercury in both mothers and pups. Total mercury in liver of mothers but not pups was correlated positively with selenium. Estimates of ingested mercury by pups indicated they had acquired most of their mercury during gestation.
Although mothers had cadmium in liver and kidney, it was not detected in tissues of pups. Cadmium did not transfer across the placenta, while mercury did. Tissue concentrations of Cu and Zn were higher in pups than mothers. The presence of metallothionein in pup tissues was postulated.
A strong positive correlation of copper and selenium between mothers and pups indicated transfer of these elements from mother to pup in direct proportion to their concentrations in maternal liver and kidney.     

Identification of the protein encoded by rodC, a cell division gene from Bacillus subtilis

The rodC1 mutation of Bacillus subtilis is a temperature-sensitive marker which affects the orientation of the plane of cell division. We have cloned the rodC gene and have localized the site of the rodC1 lesion. To identify the rodC gene product, we have subjected several plasmid clones containing B. subtilis chromosomal DNA from the rodC region to maxicell analysis in Escherichia coli. A 68 kiloDalton protein has been identified as the rodC gene product. This is the initial cloning of a cell division gene and the identification of its product from B. subtilis. The rodC gene has also been implicated as being directly associated with the synthesis of glycerol teichoic acid.     

Development and characterization of continuous avian cell lines depleted of mitochondrial DNA

Summary Populations of quail and chicken cells were treated with ethidium bromide, an inhibitor of mitochondrial DNA replication. After long-term exposure to the drug, the cell populations were transferred to ethidium bromide (EtdBr)-free medium, and cloned. Clones HCF7 (quail) and DUS-3 (chicken) were propagated for more than a year, and then characterized. Analysis of total cellular DNA extracted from these cells revealed no characteristic mitochondrial DNA molecule by Southern blot hybridization of HindIII- or AvaI-digested total cellular DNA probed with cloned mitochondrial DNA fragments. Reconstruction experiments, where a small number of parental cells was mixed with HCF7 cells and DUS-3 cells before extraction of total cellular DNA, further strengthen the notion that the drug-treated cells are devoid of mitochondrial DNA molecules. The cell populations were found to proliferate at a moderately reduced growth rate as compared to their respective parents, to be auxotrophic for uridine, and to be stably resistant to the growth inhibitory effect of EtdBr and chloramphenicol. At the ultrastructural level, mitochondria were considerably enlarged and there was a severe reduction in the number of cristae within the organelles and loss of cristae orientation. Morphometric analysis revealed a fourfold increase of the mitochondrial profile area along with a twofold decrease of the numerical mitochondrial profiles. Analysis of biochemical parameters indicated that the cells grew with mitochondria devoid of a functional respiratory chain. The activity of the mitochondrial enzyme dihydroorotate dehydrogenase was decreased by 95% and presumably accounted for uridine auxotrophy. This work was supported by a grant from the Medical Research Council of Canada.     

Species specificity of iron delivery in hybridomas

Summary Studies with Human x Human (HxH), Human x Mouse (HxM), and Mouse x Mouse (MxM) hybridomas have enabled us to define specific factors that affect hybridoma growth in a species-specific manner. Three transferrins and three lipophilic iron chelates have been tested for their ability to support hybridoma proliferation and antibody production. The results of these studies demonstrate that HxH hybridomas do not respond to bovine transferrin a⁺ concentrations up to 100 μg/ml and are approximately 100-fold less responsive to mouse transferrin than to human transferrin. HxM and MxM hybridomas respond equally to human or mouse transferrin but are 100-fold less sensitive to bovine transferrin. An antibody to the human transferrin receptor inhibited the growth-promoting activity of human or mouse transferrin on HxH hybridomas but was ineffective on HxM hybridomas. This semonstrated the functionality of the human transferrin receptor in HxH hybridomas and that human, mouse, and bovine transferrin were interacting through the mouse transferrin receptor in HxM hybridomas. HxH and HxM hybridomas respond similarly to three different iron chelates exhibiting 80 to 110% of the growth response to human transferrin. MxM hybridomas fail to respond to the iron chelates at similar concentrations, suggesting that the human genome present in the other hybridoma species confers a unique ability for utilizing iron when delivered in this form.