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Chicken erythrocyte membranes: comparison of nuclear and plasma membranes from adults and embryos

These experiments were designed to determine whether the migration of RNA molecules from an implanted nucleus to the host cytoplasm and from there into the host cell nucleus against a concentration gradient might reflect an artefact induced by the process of nuclear transplantation. That is, are RNA molecules, as previously shown for certain nuclear proteins, caused to artefactually leave a manipulated nucleus and then move into the host cell nucleus (as well as return to the grafted nucleus) during the recovery period?A variety of experiments involving different kinds of manipulative sequences and different numbers of nuclear transplantations suggest—but do not prove—that no artefact is involved in the migration of RNA from one nucleus to another but two experiments strongly support the view that the shuttling activity is a normal physiological process. One of the latter involved a determination of the rate of egress of ³H-RNA from an implanted nucleus and reveals that that rate, in contrast with the equivalent rate of egress for labeled proteins which is clearly abnormal after micromanipulation, is totally consonant with the rate of movement of RNA from nucleus to cytoplasm established from experiments that do not involve micromanipulation. The other experiment involves comparison of (1) the amount of radioactivity acquired by an unlabeled nucleus present in the cell at the time a labeled nucleus is implanted with (2) the amount of radioactivity acquired by an unlabeled nucleus implanted after a labeled nucleus had been implanted and had time to recover from any possible operation-induced trauma. With ³H-protein nuclei the host nuclei of (1) acquired much more label than the host nuclei of (2) because in (1) the host nuclei were able to acquire much of the artefactually-released ³H-protein. For the ³H-RNA experiments, however, little difference was found between (1) and (2) in the amount of label acquired by the host cell nuclei. It can be concluded that little, if any, of the non-random shuttling activity of RNA molecules can be a reflection of an artefact.     

GABA receptors in Deiters nucleus modulate posturokinetic responses to cortical stimulation in the cat.

The early component of the postural responses which accompany the limb flexion during unilateral stimulation of the motor cortex in the cat is not of reflex origin, but results from a central command. These postural adjustments are characterized by a decreased force under the limb diagonally opposite to the moving one and an increased force under the other two. Since the lateral vestibular nucleus (LVN) exerts an excitatory influence on ipsilateral limb extensor motoneurons, experiments were performed in cats to establish whether the cortical-induced postural changes were mediated through the LVN. This structure is tonically inhibited by GABAergic synapses originating from Purkinje cells of the cerebellar vermis, so that local microinjection into the LVN of GABA agonists or antagonists should either decrease or increase the spontaneous discharge of their neurons. Unilateral microinjection of 0.25 microliters of the GABA-A agonist muscimol or the GABA-B agonist baclofen (at 2-4 micrograms/microliters saline) into the LVN produced a short-lasting episode of ipsilateral postural hypotonia and contralateral hypertonia, during which the cats were unable to stand on the measurement platform. When, shortly after, some recovery of the postural activity appeared, no changes in threshold, latency or amplitude of the cortical-induced flexion movement were observed; however, the early component of the postural responses decreased in the other three limbs. Moreover, the slope of the response curve of the moving limb remained unmodified, while that of the early component of the postural responses, which involved the remaining limbs, decreased following stimulation of the motor cortex at different stimulus intensities. These effects started a few min after the injection and lasted for about 2-3 h. The effects described above were dose-dependent. Moreover, histological controls indicated that the structure responsible for these postural changes corresponded to the middle part of the LVN. The specificity of the results was shown by the fact that unilateral microinjection of 0.25 microliters of the GABA-A antagonist bicuculline or the GABA-B antagonist phaclofen (at 5-8 micrograms/microliter saline) into the LVN produced a postural asymmetry opposite in sign to that elicited in the same experiments by the corresponding agonists. These injections did not modify the amplitude of the cortical-induced limb flexion, but rather enhanced the amplitude of the early component of the postural responses in the other three limbs.(ABSTRACT TRUNCATED AT 400 WORDS)     

The microbiological fate of polycyclic aromatic hydrocarbons: carbon and oxygen balances for bacterial degradation of model compounds

A series of pure bacterial strains belonging mainly to theRhodococcus andPseudomonas genera were grown on one of the following polycyclic aromatic hydrocarbons (PAH) supplied as sole carbon and energy source: naphthalene, fluorene, phenanthrene, anthracene, fluoranthene and pyrene. In each case, a quantitative evaluation of the carbon repartition of the PAH degraded into CO₂, biomass and water-soluble metabolites was carried out. In addition, the kinetics of oxygen consumption and of water-soluble metabolite accumulation during PAH biodegradation was followed with respirometric equipment. Satisfactory carbon balances were obtained and the data correlated well with oxygen consumption values. The results show that growth on PAH presents high mineralization yields (from 56% to 77% of carbon) and sizeable production of biomass (from 16% to 35% of carbon) and limited but significant accumulation of metabolites (from 5% to 23% of carbon). The mineralization yields were higher and biomass yields lower in the case of higher PAH. Some differences between strains were also observed.     

Manganese status,gut endogenous losses of manganese,and antioxidant enzyme activity in rats fed varying levels of manganese and fat

We hypothesized that manganese deficient animals fed high vs moderate levels of polyunsaturated fat would either manifest evidence of increased oxidative stress or would experience compensatory changes in antioxidant enzymes and/or shifts in manganese utilization that result in decreased endogenous gut manganese losses. Rats (females in Study 1, males in Study 2,n = 8/treatment) were fed diets that contained 5 or 20% corn oil by weight and either 0.01 or 1.5 μmol manganese/g diet. In study 2,⁵⁴Mn complexed to albumin was injected into the portal vein to assess gut endogenous losses of manganese. The manganese deficient rats:

Particle size influences decay rates of environmental DNA in aquatic systems

Environmental DNA (eDNA) analysis is a powerful tool for remote detection of target organisms. However, obtaining quantitative and longitudinal information from eDNA data is challenging, requiring a deep understanding of eDNA ecology. Notably, if the various size components of eDNA decay at different rates, and we can separate them within a sample, their changing proportions could be used to obtain longitudinal dynamics information on targets. To test this possibility, we conducted an aquatic mesocosm experiment in which we separated fish-derived eDNA components using sequential filtration to evaluate the decay rate and changing proportion of various eDNA particle sizes over time. We then fit four alternative mathematical decay models to the data, building towards a predictive framework to interpret eDNA data from various particle sizes. We found that medium-sized particles (1–10 μm) decayed more slowly than other size classes (i.e., <1 and > 10 μm), and thus made up an increasing proportion of eDNA particles over time. We also observed distinct eDNA particle size distribution (PSD) between our Common carp and Rainbow trout samples, suggesting that target-specific assays are required to determine starting eDNA PSDs. Additionally, we found evidence that different sizes of eDNA particles do not decay independently, with particle size conversion replenishing smaller particles over time. Nonetheless, a parsimonious mathematical model where particle sizes decay independently best explained the data. Given these results, we suggest a framework to discern target distance and abundance with eDNA data by applying sequential filtration, which theoretically has both metabarcoding and single-target applications.     

Expression of wild-type GBSS transgenes in the off-spring of partially and fully complementedamylose-free transformants of potato

Theamylose-free (amf) potato mutant can easily be complemented through introduction of the wild-type gene coding for granule-bound starch synthase (GBSS). After iodine staining the starch of theamf mutant is red whereas that of the wild type and the complementedamf mutant is blue. The level of complementation of selected transformants and their sexual off-spring after backcrossing withamf was investigated using sporophytic tuber cells and gametophytic microspore cells. Two diploid and two tetraploid transformants with full complementation demonstrated the expected segregation patterns of 1:1 (one active insert) or 3:1 (two independently segregating active inserts) in the microspores and in the F1 offspring based on staining of tubers. All expected genotypes in the F1 generation were found, based on microspore segregation patterns of the individual F1 plants. Two transformants with partial complementation (mixed phenotypes) were investigated. One of them, B1, was tetraploid and duplex for the GBSS insert, which had originated through mitotic doubling of the transformed diploid cells. In the F1 generation three phenotypic classes were found:amf, fully complemented and partially complemented. The latter two classes exist independently of a simplex or duplex gene status. The second transformant with partial complementation, B10, appeared to have a complex molecular composition. One cluster of five transgenes caused the partial complementation. Fully and partially complemented phenotypic classes were found after crossing B10 with theamf mutant. Indications were found that the ploidy level of the tissue in which the genes were introduced and expressed played an important role. Firstly, partial complementation was found after transformation of the diploid and not of the tetraploidamf genotypes. Secondly, the level of complementation was higher in tissue with lower ploidy levels, as illustrated by the colour of the starch inin vitro tubers (2x–4x cells) versus field-grown tubers (16x–64x).