Cuticle sclerotization by the American cockroach: Differential incorporation of leucine and tyrosine during post-ecdysis

The incorporation of U-¹⁴C-leucine into the cuticle occurs within the first 2 hr after ecdysis whereas U-¹⁴C-tyrosine is incorporated at a steady rate for approximately 8 hr. These data suggest that most of the cuticle protein is synthesized and laid down within a short time after ecdysis. On the other hand, tyrosine and/or metabolites (such as N-acetyl-dopamine) are translocated into the cuticle for several hours. This indicates that the sclerotization process may take place over an extended period.     

A variable minisatellite sequence in the chloroplast genome of Sorbus L. (Rosaceae: Maloideae).

The chloroplast genome is now known to be more variable than was once thought. Reports of RFLP (restriction fragment length polymorphism) and sequence variation, as well as variation in chloroplast microsatellites, are common. Here, data are presented on the variability of a minisatellite sequence in the chloroplast genome of Sorbus species. RFLP analysis of a PCR product comprising the region between the trnM and rbcL genes of nine Sorbus species identified seven size variants. Sequencing revealed the observed size polymorphism to be due to differences in the number of copies of an imperfect 9-bp motif. A more intensive survey of the variability of the minisatellite was undertaken in populations of Sorbus aucuparia. The potential uses of such regions in chloroplast DNA are discussed and a possible mechanism for the evolution of the minisatellite is presented.     

Internalization and delivery to lysosomes of hydrazide horseradish peroxidase, a covalent membrane probe

Hydrazide horseradish peroxidase, (hydHRP), a hydrazide derivative of the common cytochemical tracer HRP, was covalently coupled to the surface of periodate-treated Chinese hamster ovary (CHO) cells and used to study the distribution and internalization of plasma membrane glycoconjugates. The Schiff-base coupling of hydHRP to the cell surface at 4 degrees C had little effect on cell viability. After coupling, cells were washed at 4 degrees C and the subcellular distribution of hydHRP was determined immediately or after incubation at 37 degrees C. Within 1 hr, hydHRP was observed to cap over pseudopodal-like extensions and then accumulate over a 2.5 h period in a punctate to perinuclear staining pattern over the cell body. By electron microscopy, the pseudopodal-like regions were found to be areas of extensive cell surface invaginations, rich in microfilaments. HydHRP internalized over a 2.5 to 18 hr period was observed in smooth vesicles resembling pinosomes/endosomes, multivesicular bodies (lysosomes), and small perinuclear vesicles. Little, if any, hydHRP activity was detected in association with elements of Golgi apparatus. By cell fractionation in 10% Percoll gradients, hydHRP was found to have accumulated in prelysosomal endocytic vesicles and lysosomes. For cells that were first surface labeled with 125I at 4 degrees C and then conjugated with hydHRP, little, if any, cotransport of the 125I label with hydHRP was observed. Over the entire capping and internalization period, most hydHRP activity remained membrane associated. Overall, these results indicate that the dominant intracellular transport route for a covalent membrane probe, hydHRP glycoconjugate, is similar if not identical to that previously reported for the solute probe native HRP (16) in CHO cells. HydHRP internalization provides further evidence for the independent sorting of proteins in endocytic transport.     

Influence of Meloidogyne hapla on Alfalfa Yield and Host Population Dynamics

Self-thinning in alfalfa, a dynamic process involving the progressive elimination of the weakest plants, was enhanced by Meloidogyne hapla. Alfalfa stand densities decreased exponentially with time and were reduced 62% (P = 0.05) in the presence of M. hapla. As stand densities decreased over time, mean plant weights increased at a rate 2.59 times faster in the absence of M. hapla. In a stepwise multiple regression analysis, 65% of the total variation in yield could be explained by changes in stand density and 85% by average weight of individual stems. Alfalfa yields were suppressed (P = 0.05) by M. hapla, with suppression generally increasing with time and as the nematode population density increased. Yield suppression was attributable primarily to the decline in plant numbers and to suppression in individual plant weights.     

Photochemical reactions in interstellar grains photolysis of co,NH3, and H2O

A simulation of the organic layer accreted onto interstellar dust particles was prepared by slow deposition of a CO:NH₃:H₂O gas mixture on an Al block at 10K, with concomitant irradiation with vacuum UV. The residues were analyzed by GC-MS, HPLC, and near IR; a reaction pathway leading from NH₃ to complex alcohol, fatty acid, and amide products in 27 stages is postulated. The astronomical relevance and significance of the observations are discussed.     

Chromatographic behavior of cyclic AMP dependent protein kinase and its subunits from Dictyostelium discoideum

An adenosine cyclic 3',5'-monophosphate (cAMP) dependent protein kinase has recently been shown to exist in Dictyostelium discoideum and to be developmentally regulated. In this report we have followed the chromatographic behavior of both the holoenzyme and its subunits. A cAMP-dependent holoenzyme could be obtained from the 100000 g soluble fraction after passage through DE-52 cellulose (pH 7.5) and Sephacryl S300. Under conditions of low pH the holoenzyme could be further purified by flat-bed electrofocusing (pI = 6.8). Application of the holoenzyme to electrofocusing at high pH resulted in dissociation of the holoenzyme into a cAMP binding component (pI = 6.1) and a cAMP-independent catalytic activity (pI = 7.4). Dissociation of the holoenzyme into subunits also occurred during histone affinity chromatography and gel filtration chromatography (S300) in the presence of a dissociating buffer. Although the subunit structure was clearly evident during chromatography, the holoenzyme could not be dissociated by simple addition of cAMP to the extract. The catalytic subunit could be purified further by CM-Sephadex, DE-52 cellulose (pH 8.5), histone affinity, and hydrophobic chromatography. The regulatory subunit was further purified by DE-52 cellulose (pH 8.5) and cAMP affinity chromatography. Proof that the cAMP binding activity and the cAMP-independent catalytic activity were in fact the regulatory and catalytic subunits was shown by reconstitution of the cAMP-dependent holoenzyme from the purified subunits. By using these separation procedures, one can obtain from extracts of Dictyostelium the subunits that are free of each other as well as free of any endogenous protein substrates.     

Dispersion and Distribution of Pratylenchus scribneri and Hoplolaimus galeatus in Soybean Fields

Examination of dispersional characteristics of Pratylenchus scribneri and Hoplolaimus galeatus indicated that there were patches within soybean fields in which both survival and reproduction wexe enhanced in spite of apparent homogeneity of soil type and topography. Treatment with carbofuran reduced the patchiness (or increased the dispersion) for H. galeatus while it had the opposite effect for P. scribneri. P. scribneri was less highly dispersed in conventional tillage plots than in the zero tillage plots. Populations from quadrats contained entirely within the patches could be described by the normal distribution (in the case of P. scribneri) or by the Poisson distribution (in the case of H. galeatus), while populations from quadrats contained entirely outside the patches could be described by the Poisson distribution for both nematodes. None of the distributions tested (Poisson, normal, negative binomial, Neyman''s) gave an adequate fit when populations from both inside and outside the patches were considered together. In all instances, log₁₀ and ln transformations reduced the goodness of fit of the data to all of the distributions tested. Even with logarithmic transformations, parametric statistics were not appropriate for analysis of data in most instances.