Interactions among coexisting larval Odonata: an in situ experiment using small enclosures

Field experiments using small replicated enclosures focused on interactions between larval populations of Epitheca cynosura and Ladona deplanata (Odonata: Anisoptera) — two species that emerge in early spring. The presence of Epitheca reduced the total biomass of Ladona, but Ladona had no significant effect on Epitheca. These early-emerging species reduced the biomass of small instars of late-emerging Anisoptera which colonized enclosures during the experiments; and the late-emerging Anisoptera seem to have inhibited colonization by Zygoptera larvae. Results are consistent with the importance of predatory (cannibalism or mutual predation) interactions in this community.     

Extraction and immunochemical assays of a tubulin-like factor in cotton seedlings

Antibodies to tubulin were prepared in rabbits by immunization with reduced-carboxymethylated calf-brain tubulin. In immunodiffusion tests the antibodies showed full cross reactivity with the immunogen as well as with native calf-brain tubulin. The same antibodies showed cross reactivity with a factor in extract of cotton (Gossypium hirsutum L.) cotyledons but there was no full immunological identity between calf-brain tubulin and this factor. A solid-phase radioimmunoassay for quantitative estimation of this plant tubulin-like factor was developed. It measured the binding of antibodies to immobilized calf-native tubulin. Competition between the unknown soluble tubulin-like factor, and immobilized tubulin was assayed at serum dilution of 1:50. Extraction conditions which preserved the antigenic properties of the tubulin-like factor from cotton cotyledons were defined. The radioimmunoassay measured quantities of the tubulin-like factor in the range of 0.1–10 g-equivalents of calf-brain tubulin. Immediately after homogenization of the tissue only 25% of the total amount of tubulin-like activity was present in soluble form, while most of it remained in the insoluble fraction. Apparent maximal solubilization was achieved spontaneously 10 h after homogenization or by treatment with guanidine hydrochloride. These results indicate that in this material, tubulin is not released immediately by homogenization but remains assembled in microtubules and-or in a bound or sequestered form.Abbreviations NRS normal rabbit serum - RCM reduced-carboxymethylated     

Crystallization,crystal structure analysis and molecular model of the third domain of Japanese quail ovomucoid,a Kazal type inhibitor

The third domain of Japanese quail ovomucoid, a Kazal type inhibitor, has been crystallized and its crystal structure determined at 2.5 Å resolution using multiple isomorphous replacement techniques. The asymmetric unit contains four molecules. In the crystal the molecules are arranged in two slightly different octamers with approximate D4 symmetry. The molecules are held together mainly by interactions of the N-terminal residues, which form a novel secondary structural element, a β-channel.The molecule is globular with approximate dimensions 35 Å × 27 Å × 19 Å. The secondary structural elements are a double-stranded anti-parallel β-sheet of residues Pro22 to Gly32 and an α-helix from Asn33 to Ser44. The reactive site Lys18-Asp19 is located in an exposed loop. It is close to Asn33 at the N terminus of the helical segment. The polypeptide chain folding of ovomucoid bears some resemblance to other inhibitors in the existence of an anti-parallel double strand following the reactive site loop.     

Chilling Injury in Cotton {Gossypium hirsutum L.): Light Requirement for the Reduction of Injury and for the Protective Effect of Abscisic Acid

Pretreatment by darkness increased chilling (4°C) injuryin whole cotton (Gossypium hirsutum L.) seedlings and isolatedcotyledonary tissue. Addition of sucrose in the dark periodprevented the effect of darkness. Application of the photosyntheticinhibitor DCMU in light simulated the effect of darkness. ABA(10^–5 M) decreased chilling injury when applied in lightas a pretreatment before the onset of chilling. The same pretreatmentin darkness was almost ineffective, unless sucrose was added.ABA applied in light together with DCMU was ineffective in decreasingchilling injury. Lower light intensity resulted in increasedchilling injury and a decreased effect of ABA in the preventionof chilling injury. The antimicrotubular drug colchicine increased the chillinginjury. Pretreatment with ABA in light decreased the chillingand colchicine injury while the same pretreatment in darknesswas ineffective. These results suggest that a deficiency of a photosyntheticproduct increases the chilling sensitivity of the tissue. ABAapparently increases chilling resistance through a metabolicprocess which depends on photosynthetic activity. ³ Incumbent of the Seagram Chair in Plant Sciences (Received November 20, 1980; Accepted January 31, 1981)     

Site-specific integration of an F'' lac pro factor in the region of the replication origin (oriC) of E. coli

Summary An episome, F 128, which carries approximately 8x10⁴ base pairs of chromosomal DNA homologous to the lac pro region of the E. coli chromosome, has been found to integrate into the oriC region of the chromosome in a site specific reaction. While the event appears to be recA-dependent, no homology between the episome and this region of the chromosome was detected. The Hfr strains formed result from the integration of intact F 128 molecules. The structure of the Hfr strains generated has been determined and their transfer properties analyzed.     

Immunogenicity of outer membrane derivatives ofHaemophilus influenzae type b

We prepared outer membrane derivatives ofHaemophilus influenzae type b to determine whether the residual capsular and noncapsular surface components are immunogenic and protective. These fragments consist primarily of six major proteins and lipopolysaccharide. By transmission electron microscopy, they appeared as small, membrane-like fragments or larger, cellshaped double-track ghosts. Rabbits immunized with ghosts responded with increases in serum anticapsular antibody and bactericidal activity. Antisera absorbed with capsular antigen to remove anticapsular antibody remained bactericidal and passively protected infant rats. These data suggest that antibodies to noncapsular surface antigens are protective, and that outer membrane derivatives retain some of the constituents responsible for stimulating immunity.     

Control mechanisms regulating gene expression during normal differentiation of myeloid leukemic cells: Differentiation defective mutants blocked in mRNA production and mRNA translation

Regulation of gene expression during myeloid cell differentiation has been analyzed using clones of myeloid leukemic cells that differ in their competence to be induced to differentiate by the normal macrophage- and granulocyte-inducing protein MGI. Changes in the relative rate of synthesis for specific proteins were compared to changes in the relative amounts of corresponding translatable poly(A)⁺ mRNAs, assayed in the reticulocyte cell-free translation system, using two-dimensional gel electrophoresis. Of the 217 proteins which changed during MGI-induced differentiation of normally differentiating MGI⁺D⁺ leukemic cells, 136 could be identified as products of cell-free translation. Eighty-four percent of the 70 decreases in synthesis, most of which occurred early during differentiation, were not accompanied by a parallel decrease in the amount of translatable mRNA, but were accompanied by a parallel shift of the corresponding mRNAs from the polysomal to the monosomal and free mRNA fractions. These results indicate that most of the early decreases in the synthesis of proteins were translationally regulated. In contrast, 81% of the proteins which increased in synthesis and 71% of the proteins that were induced de novo were regulated at the level of mRNA production. Experiments with differentiation defective mutants have shown that they were blocked both at the level of mRNA production and mRNA translation. The data with these mutants have suggested that there were different subsets of translationally regulated proteins which were separately regulated. The translational blocks for several proteins in these mutant clones have also made it possible to identify additional translational sites of regulation for protein changes that were controlled at the level of mRNA production during normal differentiation. The results indicate that translational regulation may predominantly have a different function in cell differentiation than regulation by mRNA production, and that differentiation-defective mutants can be blocked at either level.     

Trois nouvelles especes du genre mixtacandona (ostracoda,cyprididae, candoninae)

The authors describe Mixtacandona elegans n. sp.,M. pietrosanii n. sp., M. tabacarui n. sp. and present new data on the systematics and biogeography of the following Mixtacandona groups: ljovuschkini,hvarensis and riongessa. Mixtacandona elegans n. sp. belongs to the group ljovuschkini. The carapace is very elongated and has markedly assymetrical valves. The species has been found in a porous aquifer in southeastern Bulgaria. M. pietrosanii n. sp. belongs to the group hvarensis. The 3rd antennular segment and the 2nd endopodial segment of the cleaning leg have each two setae. The species lives in porous aquifers in the Danube plain in Roumania. M. tabacarui n. sp. (gr. riongessa) has a triangular left valve with a pointed dorsal protuberance. The species has been found in wells fed by karstic water in southern dobrodgea (Roumania), on the Black Sea coast.     

Neuromuscular dysfunction induced by acetylcholinesterase inhibition.

The organophosphate cholinesterase inhibitor paraoxon produces a dose-dependent necrosis in rat skeletal muscle fibers after a single administration. The pathology, which is initiated at the motor end-plate region, is evident as early as 30 minutes after paraoxon administration and is characterized by dilated mitochondria, expanded sarcoplasmic reticulum, fused and widened subsynaptic folds, and coated cleft vesicles. By 24 hours, a generalized breakdown of muscle fiber architecture is evident with an accompanying infiltration of phagocytes. Electrophysiological studies have shown that paraoxon increases neurotransmitter release and causes spontaneous and impulse-related antidromic nerve activity, both of which can be reduced significantly by reactivation of inhibited acetylcholinesterase (AChE) with pyridine-2-aldoxime methiodide. The severity of the myopathy has been found to be positively correlated to the degree and duration of AChE inhibition. It appears that 2 hours of inhibition, with a critical loss in activity, viz., 85%, is necessary to initiate severe muscle fiber necrosis. Prior nerve transection prevents myopathic development and current data support the hypothesis that the induction of skeletal muscle fiber necrosis is triggered by inhibition of a neurally regulated fraction of AChE.