Buoyancy regulation in light-limited continuous cultures of Microcystis aeruginosa

Microcystis aeruginosa was grown in light-limited continuouscultures at different growth rates on light-dark cycles at variousphotopenods. Due to the strength of the gas vesicles the organismwas not able to collapse its gas vesicles by turgor pressure.Below the maximal growth rate, the organism was buoyant dueto its high gas vesicle content. The results suggested thatthe rate of gas vesicle synthesis was not regulated. Upon atransition to high irradiance it took several hours before thecells lost their buoyancy due to polyglucan accumulation. Theresults are interpreted in an ecological context and it is suggestedthat Microcystis is an epilimnetic species due to its buoyancyregulation.     

Malaria sporozoites leave behind trails of circumsporozoite protein during gliding motility

As Plasmodium sporozoites undergo gliding motility in vitro, they leave behind trails of circumsporozoite (CS) protein that correspond to their patterns of movement. This light microscopic observation was made using Plasmodium berghei sporozoites, a monoclonal antibody (MAb H4) directed against the immunodominant repetitive epitope of the CS protein of P. berghei, and an immunogold-silver staining (IGSS) technique. Sporozoites pretreated with agents that inhibit sporozoite motility and invasiveness did not produce trails. Sporozoites that glided on microscope slides coated with MAb H4 left behind considerably longer CS protein trails than those on uncoated slides, and the staining of these trails was more intense. The fact that the CS protein is an exoantigen continuously released as trails by motile sporozoites, together with our previous finding that anti-CS protein antibodies inhibit sporozoite motility, strongly suggests that the CS protein plays a role in gliding motility. The sensitive IGSS technique used in this study may be a useful tool in the study of the translocation of surface proteins during gliding of other apicomplexans, other protists, and bacteria.     

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.     

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.     

Ultra sensitive detection of Listeria monocytogenes in milk by the polymerase chain reaction (PCR)

The polymerase chain reaction (PCR) has been used to detect Listeria monocytogenes in whole milk at a level of 0.1 cfu per 30 ml. This high degree of sensitivity has been achieved following enzymatic digestion, polysulphonone membrane filtration and amplification of a nucleotide sequence within the promoter region of hlyA. Key elements of the procedure are the absence of enrichment culture and a complete solubilization of the membrane filter, ensuring total nucleic acid recovery. The simplicity of the protocol coupled with high sample volumes and exquisite sensitivity extends the relevance of PCR within food and environmental microbiology.