Regulation of homocysteine metabolizing enzymes in Aspergillus nidulans

Summary Mutants of Aspergillus nidulans blocked in the main pathway of cysteine synthesis show an elevated level of the enzymes involved in the synthesis of cysteine from homocysteine i.e. cystathionine -synthase and -cystathionase and a depressed level of homocysteine methyltransferase. This results in a considerable change in the sulfur amino acids pool as compared to the wild type. Upon addition of cysteine to the growth medium the first two enzymes are repressed while the level of the third one increases. These data indicate that the two diverging pathways of homocysteine metabolism are anti-coordinately regulated.     

Computer Modeling of the Solution Conformation of Cyclic Enkephalins

The probable conformations of two cyclic enkephalin analogs, DNS-cyclo[D-Dab-Gly-Trp-Leu] (I) and DNS-cyclo[D-Dab-Gly-Trp-D-Leu] (II) (DNS = dansyl), were determined by combining the results of NOE, vicinal coupling constant and fluorescence energy transfer measurements with theoretical calculations. The common feature of the conformations for both peptides is the presence of a -turn at residues 2 and 3.     

Specific distribution pattern of nerve fibers containing catecholamine-synthesizing enzymes, neuropeptide Y (NPY) and C-terminal flanking peptide of NPY (CPON) in the pineal gland of the chinchilla (Chinchilla laniger)--an immunohistochemical study

The sympathetic nerve fibers originating from the superior cervical ganglia and supplying the pineal gland play the most important role in the control of the pineal activity in mammals. NPY and CPON are also present in the majority of the pinealopetal sympathetic neurons. In this study, immunohistochemical techniques were used to demonstrate the existence and coexistence of tyrosine hydroxylase (TH), dopamine beta-hydroxylase (DbetaH) as well as NPY and CPON in the nerve fibers supplying the chinchilla pineal gland. Ten two-year-old female chinchillas housed in natural light conditions were used in the study. The pineals were fixed by perfusion. ABC immunohistochemical technique and immunofluorescence labelling method were employed. TH-immunoreactive (TH-IR) varicose nerve fibers were observed in the pineal gland as well as in the posterior commissural area. Within the chinchilla pineal gland, TH-IR nerve fibers were located in the capsule and connective tissue septa. Numerous varicose TH-IR branches penetrated into the parenchyma and formed a network showing the highest density in the proximal region of the gland. In the central and distal parts of the pineal parenchyma, a subtle network, composed of thin varicose nerve branches, was observed. Double immunostaining revealed that the majority of TH-IR nerve fibers was positive for DbetaH or NPY. TH- and DbetaH-positive neuron-like cells were observed in the proximal region of the gland. The pattern of pineal innervation immunoreactive to CPON was similar to the innervation containing NPY, TH and DbetaH. The chinchilla intrapineal innervation containing TH, DbetaH, NPY and CPON is characterized by the higher density in the proximal part of the gland than in the middle and distal ones. The specific feature of the chinchilla pineal is also the presence of single TH/DbetaH-immunoreactive neuron-like cells in the proximal part of the gland.     

Susceptibility of previously damaged strawberry plants to mite attack

Using radioactive labelling techniques on two cultivars of strawberry (Fragaria grandiflora Duch.) and on the two-spotted spider mite (Tetranychus urticae Koch) which fed on them, differential feeding was monitored. Leaves of the susceptible cultivar Georg Soltwedel previously damaged by mites were more attractive for spider mites than leaves of undamaged plants. The opposite was observed when the resistant cultivar Macherauch's Frühernte was investigated. The results are discussed according to the induced resistance hypothesis.     

Circular Dichroism Studies of the Interaction of Tat Analogues Substituted in the Arg52 Position with TAR RNA HIV-1

The Tat wild-type fragment of sequence Arg⁴⁹-Lys-Lys-Arg⁵²-Arg-Gln-Arg-Arg-Arg⁵⁷-NH₂ (labelled as Tat1) and three analogues of this fragment with the substitution Arg⁵² D-Arg⁵² (labelled as Tat2) or L-citrulline (Cit) (labelled as Tat3) or L-ornithine (Orn) (labelled as Tat4) were synthesized to study Tat-TAR RNA HIV-1 (27-nucleotide fragment of sequence 5-AGAUCUGAGCCUGGAGCUCUCU-3) interactions by circular dichroism. -helical structure was the most readily adopted by the Tat3 analogue with Arg⁵² Cit substitution. All the peptides investigated caused conformational changes in the TAR structure. The most dramatic changes were observed for the Tat2-TAR complex.     

Aggressiveness in Two Male Morphs of the Bulb Mite Rhizoglyphus robini

We studied differences in aggressiveness between two male morphs of the bulb mite Rhizoglyphus robini (Acari: Acaridae). Heteromorphic males have a thickened and sharply terminating third pair of legs, whereas homeomorphic males have unmodified legs. In another genus ( Caloglyphus ) of the family Acaridae, modified legs are used during fights to stab (often mortally) other males, but fights have not so far been observed in the genus Rhizoglyphus .
In this study we showed that in Rhizoglyphus robini males fight in a way similar to that previously described for the genus Caloglyphus. The presence of females increased the duration of aggressive interactions and caused earlier initiation, but fights were also observed in the absence of females. Pairs of heteromorphic males spent more time on aggressive interactions than did mixed pairs of heteromorphs and homeomorphs or pairs of homeomorphic males. Although the proportion of pairs involved in aggressive interactions did not differ between these three morph combinations, clasping of the opponent with legs, which is a typical behaviour of killer Caloglyphus males that precedes stabbing, occurred more often between pairs of heteromorphs than between mixed pairs and pairs of homeomorphs. This is consistent with our other finding that mortality attributable to male aggression was only recorded in pairs of males containing at least one heteromorphic male. We conclude that the modified legs of heteromorphic R. robini males function as a weapon in aggressive interactions between males and that, as previously described for the genus Caloglyphus , male morphs differ in aggressiveness.