Tolerance of the nitrogen-fixing system ofAzotobacter vinelandii for four commonly used pesticides

The effects of two insecticides, DDT and lindane, and two herbicides, Dalapon-Na and 2, 4, 5-T, upon the growth and nitrogen-fixing capacity ofAzotobacter vinelandii in pure culture were investigated using concentrations of the pesticides equivalent to the usual field application rates, and fifty times these levels. The acetylene reduction technique was used to assay nitrogen fixation. No significant effects of the pesticides at either concentration were detected upon growth or acetylene reduction. This study was supported by a grant from the Rural Credits Development Fund of the Reserve Bank of Australia.     

The Ulcerating Tuberculous Hilar Gland

In primary infection tuberculosis, the infected hilar gland(s) may cause involvement of peripheral lung tissue not only by pressure but also by rupture and discharge of caseous material into a bronchus. Atelectasis or lung infection or both may result and bronchiectasis may ensue.Early bronchoscopy is required when this form of tuberculosis fails to subside promptly under treatment.Bronchography is indicated to detect residual bronchiectasis which should be removed surgically.Three of six proved cases of Group A tuberculous tracheobronchitis caused by an ulcerating hilar gland required pulmonary resection for removal of residual bronchiectasis; two of these were complicated by atelectasis. All six patients are alive and well.     

ArHsp40, a type 1 J-domain protein<Emphasis Type="Italic">,</Emphasis> is developmentally regulated and stress inducible in post-diapause <Emphasis Type="Italic">Artemia franciscana</Emphasis>

Upon diapause termination and exposure to favorable environmental conditions, cysts of the crustacean Artemia franciscana reinitiate development, a process dependent on the resumption of metabolic activity and the maintenance of protein homeostasis. The objective of the work described herein was to characterize molecular chaperones during post-diapause growth of A. franciscana. An Hsp40 complementary DNA (cDNA) termed ArHsp40 was cloned and shown to encode a protein with an amino-terminal J-domain containing a conserved histidine, proline, and aspartic acid (HPD) motif. Following the J-domain was a Gly/Phe (G/F) rich domain, a zinc-binding domain which contained a modified CXXCXGXG motif, and the carboxyl-terminal substrate binding region, all characteristics of type I Hsp40. Multiple alignment and protein modeling showed that ArHsp40 is comparable to Hsp40s from other eukaryotes and likely to be functionally similar. qRT-PCR revealed that during post-diapause development, ArHsp40 messenger RNA (mRNA) varied slightly until the E2/E3 stage and decreased significantly upon hatching. The immunoprobing of Western blots demonstrated that ArHsp40 was also relatively constant until E2/E3 and then declined dramatically. The drop in ArHsp40 when metabolism and protein synthesis were increasing was unexpected and demonstrated developmental regulation. The reduction in ArHsp40 at such an active life history stage indicates, as one possibility, that A. franciscana possesses additional Hsp40s, one or more of which replaces ArHsp40 as development progresses. Increased synthesis upon heat shock established that in addition to being developmentally regulated, ArHsp40 is stress inducible and, because it is found in mature cysts, ArHsp40 has the potential to contribute to stress tolerance during diapause.     

Stress tolerance during diapause and quiescence of the brine shrimp,Artemia

Oviparously developing embryos of the brine shrimp, Artemia, arrest at gastrulation and are released from females as cysts before entering diapause, a state of dormancy and stress tolerance. Diapause is terminated by an external signal, and growth resumes if conditions are permissible. However, if circumstances are unfavorable, cysts enter quiescence, a dormant stage that continues as long as adverse conditions persist. Artemia embryos in diapause and quiescence are remarkably resistant to environmental and physiological stressors, withstanding desiccation, cold, heat, oxidation, ultraviolet radiation, and years of anoxia at ambient temperature when fully hydrated. Cysts have adapted to stress in several ways; they are surrounded by a rigid cell wall impermeable to most chemical compounds and which functions as a shield against ultraviolet radiation. Artemia cysts contain large amounts of trehalose, a non-reducing sugar thought to preserve membranes and proteins during desiccation by replacing water molecules and/or contributing to vitrification. Late embryogenesis abundant proteins similar to those in seeds and other anhydrobiotic organisms are found in cysts, and they safeguard cell organelles and proteins during desiccation. Artemia cysts contain abundant amounts of p26, a small heat shock protein, and artemin, a ferritin homologue, both ATP-independent molecular chaperones important in stress tolerance. The evidence provided in this review supports the conclusion that it is the interplay of these protective elements that make Artemia one of the most stress tolerant of all metazoan organisms.     

Tyrosinated, but not detyrosinated, α-tubulin is present in root tip cells

Summary The distribution of tyrosinated and detyrosinated tubulin in microtubule arrays of pine and onion cells was investigated by immunofluorescence techniques. Staining of isolated cells and methacrylate sections ofPinus radiata andAllium cepa root tips indicated that all microtubule structures contained tyrosinated tubulin but not the posttranslationally modified detyrosinated tubulin. The detyrosinated tubulin epitope was, however, created in vitro by treating both sections and fixed whole cells with carboxypeptidase A.     

An isotope dilution model for partitioning leucine uptake by the liver of the lactating dairy cow.

An isotope dilution model for partitioning leucine uptake by the liver of the lactating dairy cow is constructed and solved in the steady state. If assumptions ae made, model solution permits calculation of the rate of leucine uptake from portal and hepatic arterial blood supply, leucine export into the hepatic vein, leucine oxidation and transamination, and synthesis and degradation of hepatic constitutive and export proteins. The model requires the measurement of plasma flow rate through the liver in combination with leucine concentrations and plateau isotopic enrichments in arterial, portal and hepatic plasma during a constant infusion of [1-13C]leucine tracer. The model can be applied to other amino acids with similar metabolic fates and will provide a means for assessing the impact of hepatic metabolism on amino acid availability to peripheral tissues. This is of particular importance when considering the dairy cow and the requirements of the mammary gland for milk protein synthesis.     

The binding of haem and zinc in the 1.9 Å X-ray structure of Escherichia coli bacterioferritin

The crystal structure of Escherichia coli bacterioferritin has been solved to 1.9 Å, and shows the symmetrical binding of a haem molecule on the local twofold axis between subunits and a pair of metal atoms bound to each subunit at the ferroxidase centre. These metals have been identified as zinc by the analysis of the structure and X-ray data and confirmed by microfocused proton-induced X-ray emission experiments. For the first time the haem has been shown to be linked to both the internal and the external environments via a cluster of waters positioned above the haem molecule.