Preparation of isolated cells by alkaline dissociation of formalin fixed tissue]

A procedure is described for preparation of isolated cells by treating formaldehyde fixed tissues with a 50%-solution of KOH. This results in complete yield of cells from a variety of organs (liver, kidney, heart, spleen, etc.). The alkali-treated cells entirely retain their morphological and tinctorial peculiarities. It was shown that preparations derived from alkali-treated tissues were useful for a series of quantitative cytological and cytochemical techniques: cytofluorometric estimation of nuclear DNA; interferometric determination of dry cell mass; autoradiographic studies of nuclear DNA synthesis; cell number counts; evaluation of cell distribution according to the number of their nuclei; estimation of the mitotic index.     

Steric analysis of glycerophospholipids by circular dichroism. Stereospecifity of phospholipase D catalyzed transesterification.

The circular dichroism spectra of natural glycerophospholipids and synthetic 1-$\text{sn}$-phosphatidic acid were recorded. 3-$\text{sn}$-phosphatidic acid derivatives were found to show a positive Cotton effect, while 1-$\text{sn}$-phosphatidic acid revealed a negative Cotton effect. The results are interpreted in terms of the carboxyl sector rule. By this method phospholipase D was shown to produce stereospecifically 3-$\text{sn}$-phosphatidyl-1-$\text{sn}$-glycerol when incubated with egg yolk lecithin and exess of glycerol.     

Comparative analysis of methods for measurements of food intake and utilization using the soybean looper, Pseudoplusia includens and artificial media

An analysis of intake and utilization of an artificial medium by larvae of the soybean looper, Pseudoplusia includens Walker, Lepidoptera: Noctuidae, was performed using 4 methods: standard gravimetric, chromic oxide, Calco Oil Red, and ¹⁴C-glucose. Each method was used in conjunction with standard gravimetry. The relative merits of the indirect methods were analyzed in terms of precision and accuracy for ECI and ECD estimation, cost, and overall versatility. Only the gravimetric method combined ca. 80% precision in ECI and ECD estimation with low cost and maximum versatility. Calco Oil Red at 0.1% w/v was detrimental to the larvae. Cr₂O₃ caused reduced intake but conversion was increased resulting in normal development and growth of larvae. The radioisotopic method had the advantage of providing a direct means of measuring expired CO₂. The need to operate under a totally enclosed system, however, poses some serious difficulties in the use of radioisotopes. There seems to be little advantage in any of the proposed indirect methods, except if there are unusual difficulties in separating the excreta from the medium.Supported in part by the Brazilian Programa de Ensino Agricola Superior (PEAS/Michigan State University Contract); by NSF and EPA through grant (NSF GB-37418) to the University of California; and USDA-SEA grant 616-15-68. The findings and opinions expressed herein are those of the authors and not necessarily those of the sponsoring agencies or institutions.     

Cloning of segments of the Drosophila melanogaster genome using artificial chromosomes of the yeast Saccharomyces cerevisiae]

A partial genomic library from the Batumi L stock of Drosophila melanogaster was constructed using yeast artificial chromosomes as vectors. The DNA was restricted by Not1 and large fragments were inserted into the YAC5 vector. The size of cloned DNA varied from 90 to 500 kb. 48 random clones were characterized by in situ hybridization to the Batumi L polytene salivary gland chromosome. Single euchromatic sites of hybridization were detected for 27 clones; 11 clones revealed the main euchromatic hybridization site and several additional sites scattered along the chromosomes; 8 clones carried repeats which hybridized to chromocenter and other chromosomal sites; clones with 500 and 90 kb inserts originated from the Y chromosomes and nucleolus, respectively. The library is enriched by the repeated sequences related to the b-heterochromatin.     

Effect of water stress on abundance of twospotted spider mite on soybeans under greenhouse conditions

A rope wick technique was used to establish different levels of water stress in potted, greenhouse-grown soybean, Glycine max (L.) Merrill, plants. Water stress reduced, within a single generation, the overall abundance (number of mites/cm² leaf) of the twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae) and particularly influenced female mites and eggs. Mites were most numerous in the upper strata of soybean plants on youger and possibly more nutritious leaves.

---

Influence de l'arrosage sur l'abondance de Tetranychus urticae sur soja, Glycine max en serre

Résumé Un arrosage par capillarité contrôlé a été utilisé pour maintenir différentes teneurs en eau dans des pieds empotés de G. max. Le stress hydrique a réduit, en une génération, la densité de T. urticae (nombre d'acariens/cm² de feuille), et particulièrement celle des femelles et des oeufs. Les acariens étaient plus nombreux sur les feuilles les plus jeunes et peut-être les plus nutritives des strates supérieures des pieds de soja.

     

Electronic effects in the acylation of alpha-chymotrypsin by substituted N-benzoylimidazoles

Rate constants for the acylation of alpha-chymotrypsin by a series of acyl-substituted N-benzoylimidazoles have been determined by proflavin displacement from the active site. The second-order acylation rate constants k2/Km are large [e.g., that for N-(m-nitrobenzoyl)imidazole is 1.7 X 10(4) M-1 s-1 at pH 7.5], even though Km must be quite large (plots of k vs. k/[S]0 have infinite slopes). The values of k2/Km are nearly independent of pH in the range 5.0-9.0 when the substituent group is electron donating. Electron-withdrawing substituents produce an increase in k2/Km with increasing pH until a maximum is reached near pH 7. This is also the case in acylation by the N-[p-(dimethylamino)benzoyl]-N'-methylimidazolium ion (pKapp = 6.5). While the reaction of the N'-methylated derivative is via a positively charged species at all pH values, the unmethylated compounds react through both the neutral species and the conjugate acids, with the observed pH dependence depending on the relative values of the rate constants. The limiting value of k2/Km for the N-[p-(dimethylamino)benzoyl]-N'-methylimidazolium ion is 2.1 times less in D2O than in H2O. Thus, His-57 must be participating in the acylation reaction as a general base. The limiting values of k2/Km for the corresponding N'-methylated and unmethylated derivatives differ by a factor of only 150, which is similar to the difference in the second-order rate constants for nonenzymatic OH- -catalyzed hydrolysis.(ABSTRACT TRUNCATED AT 250 WORDS)     

A Belonostomus tenuirostris (Actinopterygii: Aspidorhynchidae) from the Late Jurassic of Kelheim (southern Germany) preserved with its last meal

A Belonostomus tenuirostris (Agassiz, 1833) from Late Kimmeridgian (Late Jurassic) of Kelheim (Solnhofen area; Bavaria, southern Germany) that was preserved with three prey fishes in its digestive tract is described. Two of the prey fishes can be assigned to cf. Leptolepides (Orthogonikleithridae), whereas the third possibly represents a juvenile Caturus sp. (Caturidae). This is the first record of a Belonostomus with several prey animals, and the first evidence of a caturid predated by an aspidorhynchid.