Meiotic mutations in rye Secale cereale L

Spontaneous meiotic mutations of winter rye Secale cereale L. (2n = 14) were revealed in inbred F2 progenies, which were obtained by self-pollination of F1 hybrids resulting from crosses of individual plants of cultivar Vyatka or weedy rye with plants of self-fertile inbred lines. The mutations cause partial or complete sterility, and are maintained in heterozygote condition. Six types of mutations were distinguished as the result of cytological analysis of meiosis and genetic analysis. (1) Plants with nonallelic asynaptic mutations sy1 and sy9 lacked bivalents in 96.8 and 67.0% metaphase I cells, respectively, formed only axial elements but not the mature synaptonemal complex (SC), and had defects in telomere clustering in early prophase I. (2) Weak asynaptic mutant sy3 showed incomplete synapsis at the start of SC degradation at diplotene and lower chiasma number; yet only 2% meiocytes lacked bivalents in MI. (3) Mutations sy2, sy6, sy7, sy8, sy10, and sy19 caused nonhomologous synapsis; i.e., a varying number of univalents and occasional multivalents were observed in MI, which was preceded by switches of pairing partners and fold-back synapsis at mid-prophase I. (4) Mutation mei6 led to the formation of protrusions and minor branched structures of the SC lateral elements. (5) Allelic mutations mei8 and mei8-10 caused irregular chromatin condensation along the chromosome length in prophase I, which was accompanied by chromosome sticking and fragmentation in MI. (6) Allelic mutations mei5 and mei10 determined chromosome supercondensation, caused the disturbance of meiotic spindle assembly, arrested meiosis at various stages but did not affect formation of the pollen wall, thus arrested meiocytes got covered with the pollen wall. Analysis of double mutants revealed recessive epistatic interactions for some mutations; the epistatic group was sy9 > sy1 > sy3 > sy19. This reflects the sequence of meiotic events controlled by the corresponding genes. The expression of sy2 and sy19 proved to be modified by additional genes. Most meiotic mutations found in rye have analogs in other plants.     

An unusual presentation of a malignant jejunal tumor and a different management strategy

BACKGROUND: Malignant small bowel tumors are very rare and leiomyosarcoma accounts for less than 15% of the cases. Management of these tumors is challenging in view of nonspecific symptoms, unusual presentation and high incidence of metastasis. In this case report, an unusual presentation of jejunal sarcoma and management of liver metastasis with radiofrequency ablation (RFA) is discussed. CASE PRESENTATION: A 45-year-old male presented with anemia and features of small bowel obstruction. Operative findings revealed a mass lesion in jejunum with intussusception of proximal loop. Resection of bowel mass was performed. Histopathological findings were suggestive of leiomyosarcoma. After 3-years of follow-up, the patient developed recurrence in infracolic omentum and a liver metastasis. The omental mass was resected and liver lesion was managed with radiofrequency ablation. CONCLUSION: Jejunal leiomyosarcoma is a rare variety of malignant small bowel tumor and a clinical presentation with intussusception is unusual. We suggest that an aggressive management approach using a combination of surgery and a newer technique like RFA can be attempted in patients with limited metastatic spread to liver to prolong the long-term survival in a subset of patients.     

Distribution of mitochondrial NADH fluorescence lifetimes: steady-state kinetics of matrix NADH interactions

The lifetimes of fluorescent components of matrix NADH in isolated porcine heart mitochondria were investigated using time-resolved fluorescence spectroscopy. Three distinct lifetimes of fluorescence were resolved: 0.4 (63%), 1.8 (30%), and 5.7 (7%) ns (% total NADH). The 0.4 ns lifetime and the emission wavelength of the short component were consistent with free NADH. In addition to their longer lifetimes, the remaining pools also had a blue-shifted emission spectrum consistent with immobilized NADH. On the basis of emission frequency and lifetime data, the immobilized pools contributed >80% of NADH fluorescence. The steady-state kinetics of NADH entering the immobilized pools was measured in intact mitochondria and in isolated mitochondrial membranes. The apparent binding constants (K(D)s) for NADH in intact mitochondria, 2.8 mM (1.9 ns pool) and >3 mM (5.7 ns pool), were on the order of the estimated matrix [NADH] (approximately 3.5 mM). The affinities and fluorescence lifetimes resulted in an essentially linear relationship between matrix [NADH] and NADH fluorescence intensity. Mitochondrial membranes had shorter emission lifetimes in the immobilized poo1s [1 ns (34%) and 4.1 ns (8%)] with much higher apparent K(D)s of 100 microM and 20 microM, respectively. The source of the stronger NADH binding affinity in membranes is unknown but could be related to high order structure or other cofactors that are diluted out in the membrane preparation. In both preparations, the rate of NADH oxidation was proportional to the amount of NADH in the long lifetime pools, suggesting that a significant fraction of the bound NADH might be associated with oxidative phosphorylation, potentially in complex 1.     

Characterization of commercial laminin preparations from human placenta in comparison to recombinant laminins 2 (alpha2beta1gamma1), 8 (alpha4beta1gamma1), 10 (alpha5beta1gamma1).

Laminins, a family of large heterotrimeric (alphabetagamma) proteins, are major components of basement membranes implicated in a variety of cellular functions. Different commercial laminin preparations isolated from human placenta have been widely used in functional studies but their molecular properties are poorly known. In the present study, we characterized several of these preparations by ELISA, silver staining and Western blotting, in comparison to mouse laminin 1 (alpha1beta1gamma1), and recombinant human laminins 2 (alpha2beta1gamma1), 8 (alpha4beta1gamma1) and 10 (alpha5beta1gamma1). The cell migration-promoting activity of different batches was also tested. The placenta laminin preparations differed from one another and consisted of highly fragmented proteins, a mixture of laminin isoforms, and/or contaminating fibronectin. Major functional differences between batches were also observed, reflecting molecular heterogeneity. Previous data obtained in functional studies using these preparations need to be interpreted with caution and may require revision, and future functional studies demand prior molecular characterization of the laminins, particularly their alpha-chain.     

A generalization of the van-der-Pol oscillator underlies active signal amplification in Drosophila hearing

The antennal hearing organs of the fruit fly Drosophila melanogaster boost their sensitivity by an active mechanical process that, analogous to the cochlear amplifier of vertebrates, resides in the motility of mechanosensory cells. This process nonlinearly improves the sensitivity of hearing and occasionally gives rise to self-sustained oscillations in the absence of sound. Time series analysis of self-sustained oscillations now unveils that the underlying dynamical system is well described by a generalization of the van-der-Pol oscillator. From the dynamic equations, the underlying amplification dynamics can explicitly be derived. According to the model, oscillations emerge from a combination of negative damping, which reflects active amplification, and a nonlinear restoring force that dictates the amplitude of the oscillations. Hence, active amplification in fly hearing seems to rely on the negative damping mechanism initially proposed for the cochlear amplifier of vertebrates.     

Chaperones that cure yeast artificial [PSI+] and their prion-specific effects

The [PSI(+)] nonsense-suppressor determinant of Saccharomyces cerevisiae results from the ability of Sup35 (eRF3) translation termination factor to undergo prion-like aggregation [1]. Although this process is autocatalytic, in vivo it depends on the chaperone Hsp104, whose lack or overexpression can cure [PSI(+)] [2]. Overproduction of the chaperone protein Ssb1 increased the [PSI(+)] curing by excess Hsp104, although it had no effect on its own, and excess chaperone protein Ssa1 protected [PSI(+)] against Hsp104 [3,4]. We used an artificial [PSI(+)(PS)] based on the Sup35 prion-forming domain from yeast Pichia methanolica [5] to find other prion-curing factors. Both [PSI(+)(PS)] and [PSI(+)] have prion 'strains', differing in their suppressor efficiency and mitotic stability. We show that [PSI(+)(PS)] and a 'weak' strain of [PSI(+)] can be cured by overexpression of chaperones Ssa1, Ssb1 and Ydj1. The ability of different chaperones to cure [PSI(+)(PS)] showed significant prion strain specificity, which could be related to variation in Sup35 prion structure. Our results imply that homologs of these chaperones may be active against mammalian prion and amyloid diseases.     

Plant genera and species new to China recently found in northwest Xinjiang

Two genera new to China, Fibigia and Pachyneurum and 10 species found in China for the first time, Puccinellia kalininae, Stellaria pulvinata, Nanophyton mongolicum, Capsella orienalis, Pachyneurum grandiflorum, Fibigia spathulata, Craniospermum tuvinicum, Euphrasia schischkinii, E. syreitschikovii, Veronica schmakovii along with 3 species previously unknown in Xinjiang, Rorippa indica, Acalypha australis, and Phalaris canariensis, found in northwest Xinjiang are reported. In addition, the distribution of two species in China is corrected: Lepidium densiflorum is firstly reported for Nei Mongol while the occurrence of Draba sibirica in Gansu is not confirmed. Results of floristic studies by the Chinese–Russian Altai expedition during 2004–2007 are also summarized including 34 species and 1 subspecies revealed as new for China; 7 species confirmed to occur in China; one genus and 5 species not confirmed for China, as well as a number of new records for various provinces, mostly Xinjiang.     

Species loss of stoneflies (Plecoptera) in the Czech Republic during the 20th century

1. Rapid expansion and intensification of anthropogenic activities in the 20th century has caused profound changes in freshwater assemblages. Unfortunately, knowledge of the extent and causes of species loss (SL) is limited due to the lack of reliable historical data. An unusual data set allows us to compare changes in the most sensitive of aquatic insect orders, the Plecoptera, at some 170 locations in the Czech Republic between two time periods, 1955–1960 and 2006–2010. Historical data (1890–1911) on assemblages of six lowland rivers allow us to infer even earlier changes. 2. Regional stonefly diversity decreased in the first half of the 20th century. Streams at lower altitudes lost a substantial number of species, which were never recovered. In the second half of the century, large‐scale anthropogenic pressure caused SL in all habitats, leading to a dissimilarity of contemporary and previous assemblages. The greatest changes were found at sites affected by organic pollution and a mixture of organic pollution and channelisation or impoundment. Colonisation of new habitats was observed in only three of the 80 species evaluated. 3. Species of moderate habitat specialisation and tolerance to organic pollution were most likely to be lost. Those with narrow specialisations in protected habitats were present in both historical and contemporary collections. 4. Contemporary assemblages are the consequence of more than a 100 years of anthropogenic impacts. In particular, streams at lower altitude and draining intensively exploited landscapes host a mere fragment of the original species complement. Most stonefly species are less frequently present than before, although their assemblages remain almost intact in near‐natural mountain streams. Our analyses demonstrate dramatic restriction of species ranges and, in some cases, apparent changes in altitudinal preference throughout the area.