Life Cycle,Host Range,and Reproduction of Heterodera betulae

Heterodera betulae, a cyst-forming nematode, originally recovered from roots of river birch in Arkansas, appears to have a limited host range. Of 80 plant species in 20 families tested, only five species of Betula and Cleome spinosa supported reproduction. The minimum time for a complete life cycle was 52 days at 28 C. No reproduction occurred at 31 C or above, and development was very slow below 20 C. Successful population propagations from single larvae demonstrated that males were not necessary for reproduction.     

Heterodera betulae n. sp. (Heteroderidae), a Cyst-forming Nematode from River Birch

A new species of the genus Heterodera A. Schmidt, 1871 parasitic on river birch, Betula nigra L., is described and illustrated. Females and cysts are lemon-shaped to almost spherical with slight vulval protrusion. Female cuticles have a thick subcrystalline layer. The average cyst size is 763 by 616 [mu]. They are circumfenestrate with small anal opening and lack a yellow phase. The cyst wall pattern is typically network-like. All eggs are retained in the cyst, although a well-developed matrix is formed. The egg shell is without markings. The second-stage larvae average 462 [mu] in length and have 3 incisures in the lateral field. The tail terminal is shorter than the stylet. Males are rare. They have 4 incisures in the lateral field and bifid spicules. The relationship of H. betulae n. sp. to other Heterodera species is obscure.     

Effect of glycl-tRNA concentration on in vitro serine incorporation into the peptidoglycan of S. epidermidis

Seven species of seryl-tRNA have been isolated from $\text{S. epidermidis}$ strain Texas 26 by the use of Plaskon CTFE powder as the support for Adogen 464 in reversed-phase chromatography. All but one of these seven seryl-tRNA incorporated ¹⁴C-serine into $\text{in vitro}$ biosynthesized peptidoglycan. This suggested that at least one of the functional roles of six of the seven seryl-tRNA peaks isolated may be involved in $\text{in vivo}$ cell wall synthesis. It has also been shown that the ratio of glycine to serine in the pentapeptide bridge depended upon the concentration of glycyl-tRNA in the assay mixture. By increasing the concentration of glycyl-tRNA the amount of serine inserted into the bridge is increased. Thus the amount of serine incorporated into the pentapeptide bridge appears to be dependent upon the concentration of glycyl-tRNA.     

The self-association of the giant hemoglobin from the earthworm, Lumbricus terrestris

Background: The crystallographic structure of the gigantic hemoglobin (erythrocruorin) of the annelid worm, Lumbricus terrestris, provides a molar mass of 3.6 MDa for the hexagonal bilayer structure. Prior to this determination, some light-scattering and ultracentrifugal measurements indicated higher masses: 4.1–4.4 MDa. Values of 3.6 MDa were attributed to dissociation or subunit loss. However, early electron microscopy of the giant hemoglobin from a related annelid, Eumenia crassa by Öster Levin, showed that the hexagonal bilayer molecules were present mostly as oligomers; few were monomeric. Methods: Measurements by light-scattering of solutions of Lumbricus hemoglobin resolved by size-exclusion chromatography have been used to determine the weight-average molar mass of self-associating proteins. The X-ray structure has been re-examined. Results: Our measurements show that both 3.6 MDa monomers and self-association products are present as a mixture. Analysis of the X-ray structure indicates several different kinds of monomer–monomer interactions. Conclusions: We propose that the measured masses of Lumbricus hemoglobin as high as 4.4 MDa, result from oligomerization. These masses would result from the presence of an array of oligomers of various sizes together with monomers of 3.6 MDa. Furthermore, several different kinds of monomer–monomer interactions are clearly evident in the X-ray structure as well as in solution. General significance: The results demonstrate that self-association of monomers of the hemoglobin of Lumbricus terrestris explains the high molar masses of 4.1–4.4 MDa previously observed.     

Terminal transferase-dependent PCR: a versatile and sensitive method for in vivo footprinting and detection of DNA adducts.

We report here a new, sensitive and versatile genomic sequencing method, which can be used for in vivo footprinting and studies of DNA adducts. Starting with mammalian genomic DNA, single-stranded products are made by repeated primer extension; these products are subjected to homopolymeric ribonucleotide tailing at the 3' termini with terminal deoxynucleotidyl transferase and then ligated to a double-stranded linker having a complementary 3' overhang, and used for PCR. This terminal transferase-dependent PCR (TDPCR) method can generate band signals many-fold stronger than conventional ligation-mediated PCR (LMPCR). A UV photofootprint in the mouse Xist gene promoter can be easily detected using TDPCR. No special enzymes or chemical reagents are needed to convert DNA adducts into strand breaks. Any lesion that blocks primer extension should be detectable.     

Transport of amino acids into the oestrogen-primed uterus. Enhancement of the uptake by a preliminary incubation

1. Preincubation of the immature rat uterus under physiological conditions was found to increase its subsequent ability to transport alpha-aminoisobutyric acid, l-proline, l-alanine and 1-aminocyclopentanecarboxylic acid. Uptakes of l-valine, l-phenylalanine and l-leucine were not affected. With alpha-aminoisobutyric acid, a doubling of the uptake could be obtained after a 3-5h preincubation period. Uteri from oestradiol-primed rats gave increases similar to those found in tissues from untreated animals. In both cases the preincubation increased the V(max.) of alpha-aminoisobutyric acid uptake but did not affect the K(m). 2. The conditions during the preincubation period determined the increase in subsequent uptake of alpha-aminoisobutyric acid. No increase in uptake was found if the preincubation was carried out at 1 degrees C, in the presence of cyanide or dinitrophenol, under anaerobiosis or with a concentration of puromycin that depressed incorporation of l-leucine into protein by 95%. The puromycin was also shown to prevent the increase in V(max.) normally found after the preincubation period. In addition, no increase was found if Na(+) was omitted from the preincubation medium. Other inorganic ions had smaller effects. 3. The uptake of alpha-aminoisobutyric acid by uteri before and after a preincubation period showed the same general patterns of sensitivity to competitive inhibitors, K(+), pH, temperature and 2,4-dinitrophenol. 4. The results suggest that the preincubation leads to an increase in a protein component of the ;A system' for amino acid transport in the uterus, and that metabolic energy is required for the reactions involved.