Enhanced unscheduled DNA synthesis in the cotyledons of Gossypium,barbadense L. by ethyl methanesulfonate (EMS)

When cotyledonary tissue of $\text{G.}\text{,}\text{barbadense}$ cotton are treated with the mutagen ethyl methanesulfonate and then germinated, an enhanced, unscheduled DNA synthesis response is observed, along with a concomitant increase in the thymidine triphosphate precursor pool size. The implications of these results are discussed in this paper.     

Chlamydia isopodii sp. n., an obligate intracellular parasite of Porcellio scaber

In an ultrastructural study of the hepatopancreas of Porcellio scaber, an obligate intracellular parasite, Chlamydia, was noted in the epithelial cells. Although the infection was found to extend the entire length of the hepatopancreas, it was most extensive in the glandular region. Indirect immunofluorescence testing revealed no cross-reactivity with either lymphogranuloma venereum or psittacosis antisera.     

On the non-existence of a tryptic peptide with biological activity derived from mouse nerve growth factor

Reverse-phase high-performance liquid chromatography was used to analyse the products of treatment of mouse nerve growth factor with cyanogen bromide followed by trypsin as described by Mercanti et al. All the biological activity was found to be due to incompletely cleaved starting material. Total digestion with trypsin led to complete loss of activity.     

Protein metabolism in the mouse during pregnancy and lactation.

Protein synthesis was measured in vivo in the whole body and in a number of individual tissues in mice at various stages of pregnancy and lactation. The absolute rate of protein synthesis in the whole body increased from 640 mg/day in virgin mice to 1590 mg/day by day 18 of pregnancy, and to 2100 mg/day by day 15 of lactation. Large proportions of these increments were contributed by the rapidly growing foetuses and placentae in the pregnant animals and by protein synthesis in the mammary glands during lactation. In addition, a substantial stimulation of growth and protein synthesis was also observed in the liver and the gastrointestinal tract. Gastrocnemius muscle showed no changes in protein metabolism, indicating that in the well-fed mouse this tissue is not required to play a role as a protein reserve during pregnancy and lactation.     

Properties of a small basic Peptide from pumpkin seeds

A small basic peptide with an unusual amino acid composition has been isolated from the seeds of pumpkin, Cucurbita maxima. Amino acid analysis and sequence data show the protein to be about 36 residues in length, with an approximate composition Lys₁, Arg₁₄, Asp₃, (Glu + Gln)₁₅, Gly₁, Pro₁, Trp₁. On the basis of composition, the molecular weight is approximately 5000 daltons and the nitrogen content by weight is 20.4%. Twelve amino acids are entirely lacking. The peptide is slightly toxic to mouse B-16 melanoma cells, but its in vivo function is unknown. It does not appear to be derived from cucurbitin, the pumpkin storage globulin; however, it could be a storage peptide involved in nitrogen mobilization during the early stages of germination.     

Host plant resistance for insect control in some important crop plants

Insect pests of cereal crop plants are among the most destructive and devastating factors limiting world food production. Insects often inflict losses of 15 to 50% of the yield of some crops in various parts of the world. Insects also provide infection courts for various pathogens that inflict even greater damage. The nature of these losses is especially tragic for poor farmers in the tropics since the insects consume dry matter already produced using limited resources. Reduction of these losses would enhance the world food supply available to man, even if actual production remains the same, by allotting to man and animals that proportion of production now consumed by insects. Control of insect‐inflicted damage on a world‐wide basis is a very difficult task. Chemical control is effective and readily available in some, but not all, countries. However, chemical control is often unavailable, ineffective, too expensive, and likely to create environmental and safety hazards that make it unsuitable for many parts of the world. Several excellent examples of biological control of insects also attest to the potential usefulness of this method of reducing insect‐inflicted losses, but this method also has been ineffective for certain major insect pests due to lack of effective identification, distribution, and maintenance of biological control agents. On the whole, host plant resistance (HPR) to insects has been the most successful and widely used method of control. HPR has been used successfully in a number of major crop species to help control damage inflicted by major insect pests. However, problems with identifying sources of resistance and transferring it to usable varieties have often been difficult to overcome. Also, once resistance is deployed, changes in insect populations which allow them to overcome the resistance sometimes eliminate the potential advantages of resistant varieties. However, methods to quantify host‐insect interactions have improved significantly over the past few years, and the prospects for developing and maintaining usable levels of resistance to several major insect pests of most major crops are good. Studies of the biochemical and biophysical mechanisms of insect resistance have added a new dimension to HPR work. Knowledge of specific factors that contribute to insect resistance can be extremely useful to plant breeders and entomologists. The ability to identify and select for one specific plant component or group of components can speed the development of resistant varieties. Studies of the effect of such resistance components on insect development and behavior can help determine the likelihood of insects being able to overcome the resistance factors. Studies of the effect of the resistance factors on host plant yield, performance, or quality may help plant breeders overcome the problems often associated with the development of high yielding and high quality resistant varieties. Identification of several different mechanisms of resistance could provide breeders the opportunity to adjust levels of several resistance components in order to arrive at a proper blend of resistance, quality, and yield. Furthermore, development of varieties with multiple mechanisms of resistance should slow the development of new biotypes of insects that could overcome the HPR since the insects would have to simultaneously or sequentially develop the ability to overcome several resistance factors. Therefore, knowledge of mechanisms of insect resistance could facilitate the development of more stable and long‐lasting types of resistance.