Lysine biosynthesis inMethanobacterium thermoautotrophicum is by the diaminopimelic acid pathway

Methanobacterium thermoautotrophicum, an archaebacterium, possesses the first and last enzymes of the diaminopimelic acid pathway for lysine biosynthesis, dihydrodipicolinate synthase, and diaminopimelate decarboxylase. It does not have saccharopine dehydrogenase, the last enzyme of the aminoadipate pathway for lysine biosynthesis. The dihydrodipicolinate synthase is inhibited but not repressed by lysine. We conclude that this microbe uses the diaminopimelate pathway for synthesis of lysine.Deceased.     

Rat striatal dopamine and tetrahydrobiopterin content following an intrastriatal injection of manganese chloride

Injection of manganese into the rat corpus striatum causes a rapid fall in the biopterin and dopamine (DA) content ipsilateral to the lesion. Two weeks after the lesion both biopterin and DA are partially recovered. Controls, injected with saline or magnesium, do not show alterations in their DA or cofactor levels. It is proposed that the fall in DA levels results from a rapid displacement of the amine from its storage sites by manganese followed by a decrease in the rate of DA synthesis causes by the drop in cofactor levels.     

Delimitation of morphologically similar sponge crab species of the genus Pseudodromia (Crustacea, Decapoda, Dromiidae) from South Africa

Stewart, B. A., Gouws, G., Daniels, S. R. & Matthee, C. A. (2004). Delimitation of morphologically similar sponge crab species of the genus Pseudodromia (Crustacea, Decapoda, Dromiidae) from South Africa. — Zoologica Scripta , 33 , 45–55.
Presently, three Pseudodromia sponge crab species are recognized, all of which are endemic to the continental shelf off the coast of South Africa. Two of these differ only in the morphology of their rostral teeth, making them difficult to distinguish, and can thus be considered as cryptic species. In addition they have very similar distribution ranges, thus raising doubts as to their specific status. Discriminant function analysis of morphometric data, differentiation at 10 allozyme loci, and sequence data derived from the 12S rRNA mitochondrial gene were used to test whether specimens identified as P. latens and P. rotunda are morphological forms of a single, widespread species, or represent two, distinct, reproductively isolated species, and to establish whether these two taxa are sister species, and thus form a monophyletic entity. The presence of fixed allele differences at three, and strong genetic heterogeneity at five other allozyme loci, indicating no gene flow occurring between sympatric populations, as well as the relatively high degree of 12S rRNA and allozyme genetic differentiation observed, supported the recognition of P. latens and P. rotunda as separate species. The 12S rRNA topology suggested that the genus Pseudodromia , as presently constituted, is paraphyletic, thus inferring that the morphological characters used to define this taxon might not be useful for phylogenetic inferences. It was concluded that in view of the uncertainties raised regarding the designation and composition of certain genera within the family Dromiidae, further rigorous analyses of morphological and genetic data are needed to further our understanding of the taxonomy of the sponge crabs.     

Localization of the alpha 1 and alpha 2 subunits of the dihydropyridine receptor and ankyrin in skeletal muscle triads

We have studied the subcellular distribution of the alpha 1 and alpha 2 subunits of the dihydropyridine (DHP) receptor and ankyrin in rat skeletal muscle with immunofluorescence and immunogold labeling techniques. All three proteins were concentrated in the triad junction formed between the T-tubules and sarcoplasmic reticulum. The alpha 1 and alpha 2 subunits of the DHP receptor were colocalized in the junctional T-tubule membrane, supporting their proposed association in a functional complex and the possible participation of the alpha 2 subunit in excitation-contraction coupling. Ankyrin label in the triad showed a distribution different from that of the DHP receptor subunits. In addition, ankyrin was found in longitudinally oriented structures outside the triad. Thus, ankyrin might be involved in organizing the triad and in immobilizing integral membrane proteins in T-tubules and the sarcoplasmic reticulum.     

Steady-state response of quadriplegic subjects to inspiratory resistive load

Normal subjects preserve tidal volume (VT) in the face of added inspiratory resistance by increasing maximal amplitude and duration of the rising phase of respiratory driving pressure (DP) and by changing the shape of this phase to one that is more concave to the time axis. To explore the possible role of chest wall afferents in mediating these responses, we determined averaged DP in eight quadriplegic subjects during steady-state unloaded breathing and while breathing through an inspiratory resistance (8.5 cmH2O X 1(-1) X s). As with normal subjects, quadriplegics preserved VT (loaded VT = 106% control) by utilizing all three mechanisms. However, prolongation of the inspiratory duration derived from the DP waveform (+22% vs. +42%) and shape response were significantly less in the quadriplegic subjects. Shape response was completely absent in subjects with C4 lesions. The results provide strong evidence that respiratory muscle spindles are responsible for shape response and that changes in afferent feedback from the chest wall play an important role in mediating inspiratory prolongation.     

Effect of temperature on the spectral properties of coenzyme F420 and related compounds.

The uv-visible spectra of 7,8-didemethyl-8-hydroxy-5-deazaflavin-5'-phosphoryllactyl glutamate (coenzyme F420), a naturally occurring 5-deazaflavin derivative, in three different buffers changed with a rise in temperature; the effect on the extinction coefficient at 420 nm (epsilon 420) was as follows: In phosphate-buffered solutions at pH less than 7.5, the epsilon 420 increased (at pH 5.0 for a temperature shift from 15 to 60 degrees C, delta epsilon 420 was +87%), but between pH 7.5 and 8, epsilon 420 changed very little. At pH greater than 8.0 in phosphate- or borate-buffered solutions, epsilon 420 decreased slightly. In morpholineethanesulfonic acid (Mes)-buffered F420 solutions at pH 5 and 5.5, epsilon 420 changed very little, whereas at pH 6-8, the epsilon 420 decreased. Absorbance of F420 at 401 nm in phosphate buffer at pH 5 to 9 was not significantly affected by temperature. Changes in epsilon 420 due to temperature change corresponded to changes in the pKa of 8-OH of the deazaflavin molecule; studies with adenylated F420 showed that the 8-OH of F420 was responsible for these changes.(ABSTRACT TRUNCATED AT 250 WORDS)     

P Element Transposition in Drosophila Melanogaster: An Analysis of Sister-Chromatid Pairs and the Formation of Intragenic Secondary Insertions during Meiosis

The gap-repair model proposes that P elements move via a conservative, ``cut-and-paste' mechanism followed by double-strand gap repair, using either the sister chromatid or homolog as the repair template. We have tested this model by examining meiotic purturbations of an X-linked ry(+) transposon during the meiotic cycle of males, employing the mei-S332 mutation, which induces high frequency equational nondisjunction. This system permits the capture of both sister-X chromatids in a single patroclinous daughter. In the presence of P-transposase, transpositions within the immediate proximity of the original site are quite frequent. These are readily detectible among the patroclinous daughters, thereby allowing the combined analysis of the transposed element, the donor site and the putative sister-strand template. Molecular analysis of 22 meiotic transposition events provide results that support the gap-repair model of P element transposition. Prior to this investigation, it was not known whether transposition events were exclusively or predominantly premeiotic. The results of our genetic analysis revealed that P elements mobilize at relatively high frequencies during meiosis. We estimated that approximately 4% of the dysgenic male gametes have transposon perturbations of meiotic origin; the proportion of gametes containing lesions of premeiotic origin was estimated at 32%.     

Studies on the mechanism of suppression of delayed hypersensitivity by the antischistosomal compund niridazole.

Niridazole given in a single oral dose of 100 mg/kg to guinea pigs sensitized to ortho-chlorobenzoyl chloride-bovine gamma-globulin (OCB-BGG) regularly abolished delayed cutaneous reactivity. Little effect was observed, however, when cells from these animals were tested in vitro with either direct or indirect assays for migration inhibitory factor (MIF). On the other hand, sera taken from nonsensitized guinea pigs after they had received 100 mg/kg of niridazole markedly diminished antigen-induced inhibition of migration of sensitized peritoneal exudate cells in vitro. The immunosuppressive effects of such sera could not be produced by niridazole itself, thereby suggesting an effect of niridazole metabolites. This suppressive activity was readily removed from the serum by dialysis. The active serum blocked the production of MIF by sensitized lymph node cells but did not affect the action of preformed MIF on macrophages. The effect of this serum was reversible; lymph node cells incubated for 24 hr with active serum, then washed and reincubated with antigen in normal serum, produced normal amounts of MIF. These studies suggest that metabolites of niridazole, but not the parent compound itslef, suppress delayed hypersensitivity in guinea pigs and prevent MIF production by lymphocytes without affecting the macrophage response to MIF.