Reversible conversion of coenzyme F420 to the 8-OH-AMP and 8-OH-GMP esters,F390-A and F390-G,on oxygen exposure and reestablishment of anaerobiosis in Methanobacterium thermoautotrophicum

Intracellular levels of F₃₉₀ (AMP and GMP adducts of the 5-deazaflavin cofactor F₄₂₀) in Methanobacterium thermoautotrophicum were analysed after gasing fermenter cultures with several consecutive cycles of substrate gas and gas mixtures containing 5% oxygen. No F₃₉₀ was detected in growing cells, hydrogen starved cells and CO₂ starved cells prior to O₂ contamination. Also, no F₃₉₀ was found in hydrogen depleted cells after O₂ treatment. Exposure of exponentially growing cells and CO₂ starved cells to oxygen lead to the formation of F₃₉₀ species; the increase in the detected amount of F₃₉₀ was coupled to a decrease of the F₄₂₀ level. As soon as anaerobiosis was reestablished F₃₉₀ cofactors were degraded and growth proceeded. Independent of the physiological condition of Methanobacterium thermoautotrophicum methanopterin was formed upon O₂ exposure. After normal growth conditions were restored the level of detected methanopterin decreased again.     

Genetics of the quantitative Lp(a) lipoprotein trait

The Lp(a) lipoprotein is a complex particle composed of a low density lipoprotein (LDL)-like lipoprotein and the disulfide bonded Lp(a) glycoprotein. The complex represents a quantitative genetic trait. SDS gel electrophoresis under reducing conditions of sera followed by immunoblotting with affinity-purified polyclonal anti-Lp(a) demonstrated inter- and intra-individual size heterogeneity of the glycoprotein with apparent Mr in the range 400-700kDa. According to their relative mobilities compared to apo B-100 the Lp(a) patterns were categorized into phenotypes F, B, S1, S2, S3 und S4 and into the respective double-band phenotypes. This size heterogeneity seems to be controlled by multiple alleles designated LpF, LpB, LpS1, LpS2, LpS3, LpS4 and a null allele (LpO) at a single locus. Phenotype frequencies observed in 441 unrelated subjects were in good agreement with those expected from the genetic hypothesis. Comparison of Lp(a) lipoprotein concentrations in the different phenotypes revealed a highly significant association of phenotypes B, S1 and S2 with high, and phenotypes S3 und S4 with intermediate Lp(a) concentrations. A third mode is represented by the null phenotype were no Lp(a) band is detected upon immunoblotting and Lp(a) lipoprotein is low or absent. We conclude that the same gene locus is involved in determining Lp(a) glycoprotein phenotype and Lp(a) lipoprotein concentrations in plasma. This major gene seems to be the Lp(a) glycoprotein structural gene locus.     

Plasmids in toxic and nontoxic strains of the cyanobacteriumMicrocystis aeruginosa

The plasmid content and toxicity of nine different strains ofMicrocystis aeruginosa have been analyzed. The two toxic strains of the HUB Culture Collection were found to carry each two plasmids, pMA1 and pMA2, of 2.9 kb and 8.5 kb, respectively. In strains PCC 7813 and PCC 7820, also toxic, two different plasmids of 2.6 kb and 16 kb were detected. Hybridization experiments showed that there exists no sequence homology between the pMA plasmids and the plasmids found in the PCC strains; but the pMA plasmids hybridized to chromosomal DNA of the toxic strains PCC 7820, PCC 7813, HUB 063, and the nontoxic strain HUB 5-3. In nontoxic strains no or at most one plasmid of unstable occurrence could be detected. Only one of the toxic strains investigated, SAG 14.85 (NRC-1), contained no plasmid.     

Filtering of behaviourally relevant temporal parameters of a grasshopper's song by an auditory interneuron

Summary In females of the acridid grasshopperChorthippus biguttulus, thoracic auditory interneurons were investigated with respect to their selectivity for temporal parameters of the conspecific song. Special attention was given to the detection of small gaps in the syllables of the song, since behavioural experiments have shown that the presence or absence of gaps is critical for the female's Innate Releasing Mechanism (cf. Fig. 1).The spiking response of one ascending interneuron, the AN4, shows filtering properties which closely resemble the behavioural reactions (cf. Figs. 1, 3 and 5b). The difference in the AN4's reaction to stimuli with gaps and uninterrupted stimuli is maintained over the behaviourally relevant intensity range (Fig. 4). This reaction is reliable enough that the stimulus type could be inferred by higher centres even from single stimulus presentations. Hence, this neuron is likely to participate in the task of gap detection and probably is a part of the neuronal filter network which determines the characteristics of the Innate Releasing Mechanism of this species. However, this interneuron is not species-specific: A homologue exists in other acridids as well and, inLocusta migratoria, has similar response characteristics (Fig. 6). The inferences of this observation for the evolution of an Innate Releasing Mechanism are discussed.Abbreviations CNS central nervous system - PST-histogram post-stimulus-time-histogram - SPL sound pressure level - IRM Innate Releasing Mechanism     

Genetics of the quantitative Lp(a) lipoprotein trait

Summary Lp(a) glycoprotein exhibits an apparent size polymorphism that is associated with genetically controlled Lp(a) lipoprotein concentrations in plasma (Utermann et al. 1988). We have tested the hypothesis that this polymorphism is genetically controlled by studying 15 matings with a total of 44 offspring. This confirmed our conclusion that Lp(a) types are controlled by a series of codominant alleles Lp^F, Lp^B, Lp^S1, Lp^S2, Lp^S3 and Lp^S4 and by a null allele Lp^o. Together with the data from the accompanying paper this indicates that the structural gene for the Lp(a) protein is the major gene locus determining Lp(a) lipoprotein concentrations in plasma.     

Surface areas,lengths and volumes of Picea abies (L.) Karst. needles: determination,biological variability and effect of environmental factors

Summary A method for the rapid determination of the lengths and surface areas of very large samples of needles of Picea abies (L.) Karst. using a computer-aided image analysis system was developed. Two independent methods for measuring non-destructively the volumes of individual needles and of all needles attached to a twig were devised. The surface areas and lengths of about 38000 needles sampled from the three youngest needle age-classes (1986, 1985, 1984) of 48 trees approximately 130 years old at four sites in the Fichtelgebirge mountains (N. E. Bavaria, FRG) were measured. The frequency distributions of lengths and areas for each site and age-class are given. Variability of needle size was fairly large. Even though the sites differed in climate, soil, and air pollution levels no consistent effect of these factors on needle size could be detected. Needle lengths and surface areas did not correlate with either the total chlorophyll content of the needles or the degree of crown thinning. The needle surface area (in mm²) of fully developed P. abies needles can be estimated by the empirical equation surface area = 4.440 x needle length -24.8 (r = 0.937), and the needle volume (in mm³) by needle volume = 0.208 x projected needle area ^1.353 (r = 0.969).