Immunogenicity of synthetic peptides from circumsporozoite protein of Plasmodium falciparum

In a study of recombinant proteins that might be useful in developing a vaccine against malaria, synthetic peptides from the circumsporozoite (CS) protein of Plasmodium falciparum were found to be immunogenic for mice and rabbits. Antibody to peptides from the repeating region of the CS protein recognized native CS protein and blocked sporozoite invasion of human hepatoma cells in vitro. Antibodies to peptides from regions I and II had no biologic activity, although antibody to region I recognized processed CS protein by Western blot analysis. These data support the feasibility of developing a vaccine against the sporozoite stage of the malaria parasite by using synthetic peptides of the repeating region of the CS protein conjugated to a carrier protein.     

Evidence that the v-sis gene product transforms by interaction with the receptor for platelet-derived growth factor

A scheme for partial purification of biologically active v-sis-coded protein from cells transformed with simian sarcoma virus (SSV) has made possible a functional comparison of the transforming protein with platelet-derived growth factor (PDGF). The SSV-transforming gene product is capable of specifically binding PDGF receptors, stimulating tyrosine phosphorylation of PDGF receptors, and inducing DNA synthesis in quiescent fibroblasts. Each of these activities was specifically inhibited by antibodies to different regions of the v-sis gene product. Moreover, viral infection of a variety of cell types revealed a strict correlation between those cells possessing PDGF receptors and those susceptible to transformation by SSV. These findings provide evidence that SSV-transforming activity is mediated by the interaction of a virus-coded mitogen with PDGF receptors.     

Regional changes in calcium underlying contraction of single smooth muscle cells

The role of calcium in regulating the contractile state of smooth muscle has been investigated by measuring calcium and contraction in single smooth muscle cells with the calcium-sensitive dye fura-2 and the digital imaging microscope. The concentration of free calcium in the cytoplasm increased after stimulation of the cells by depolarization with high potassium or by application of carbachol. Changes in calcium always preceded contraction. The increase in calcium induced by these stimuli was limited to less than 1 microM. Calcium within the nucleus was also subject to a limitation of its rise during contraction. Intranuclear calcium rose from 200 nM at rest to no more than 300 nM while cytoplasmic calcium rose to over 700 nM. These apparent ceilings for both cytoplasmic and intranuclear calcium may result either from negative feedback of calcium on cytoplasmic and nuclear calcium channel gating mechanisms, respectively, or from the presence of calcium pumps that are strongly activated at the calcium ceilings.     

Estimating the mass of asteroid 253 mathilde from tracking data during the NEAR flyby

The terminal navigation of the Near Earth Asteroid Rendezvous (NEAR) spacecraft during its close flyby of asteroid 253 Mathilde involved coordinated efforts to determine the heliocentric orbits of the spacecraft and Mathilde and then to determine the relative trajectory of the spacecraft with respect to Mathilde. The gravitational perturbation of Mathilde on the passing spacecraft was apparent in the spacecraft tracking data. As a result of the accurate targeting achieved, these data could be used to determine Mathilde's mass as 1.033 (+/- 0.044) x 10(20) grams. Coupled with a volume estimate provided by the NEAR imaging team, this mass suggests a low bulk density for Mathilde of 1.3 grams per cubic centimeter.     

Site-Specific Weed Control in Maize,Sugar Beet,Winter Wheat,and Winter Barley

A four-year study of site-specific weed control is presented in this paper. Weed seedling distribution was sampled and mapped prior to and after post-emergence herbicide application in four fields planted with maize, sugar beets, winter wheat and winter barley, rotating on one site. Herbicides and other weed control strategies were applied site-specifically according to the spatial variation of weed populations. Different decision algorithms were used for chemical weed control methods in each crop. A weed treatment map was created to direct location and dosage of herbicide application. The sprayer was coupled with a differential Global Positioning System (DGPS). The solenoid valves of the sprayer were opened automatically when the tractor entered a weed patch characterized in the weed treatment map. For site specific herbicide application, a patch sprayer was developed that allowed variable rate application and the selective control of each section of the spray boom.     

THE ROLE OF GREEN SOILING IN THE ECONOMY OF THE DAIRY FARM

With modern machinery and modem techniques of grass production, mechanical-or zero-grazing offers a means of utilizing the crop to perfection. Whether this results in enhanced profits depends largely upon the farm and the specific circumstances. It may, it may not. What is evident is that the health of the cows is not affected by an unnatural manner of summer feeding; the sward, per se, may be improved by the regular and uniform defoliation; and under conditions of intensive production and the vital need to use profitably every blade of grass, as for instance on small, highly-rented farms, the practice of zero-grazing merits the most careful consideration. It cannot lightly be dismissed as merely a new fad.