Some Umbelliferae of the Andean paramos of South America

Two Colombian species described earlier by the authors underPrionosciadium, and a hitherto unnamed collection from the same country are systematically compared with North AmericanPrionosciadium and the monotypic generaCotopaxia (Ecuador) andPerissocoeleum (Colombia). Habit, foliage, inflorescence, fruit, and distribution all suggest that the páramo species exhibit considerable unity ifCotopaxia is excluded. It is indicated also that the genusPrionosciadium has been attributed to South America incorrectly. Despite the somewhat discordant evidence obtained from pollen morphology, it is concluded that the most feasible disposition of the four Colombian plants is to unite them underPerissocoeleum.     

The neurosecretory system of the adult Calliphora erythrocephala

Summary Neurosecretory cells in the brain and suboesophageal ganglion of the adult female Calliphora erythrocephala have been studied in the light microscope. The paraldehydefuchsin stain (PAF) gave by far the clearest pictures.The medial neurosecretory cells of the protocerebrum (m.n.c.) show definite cyclic changes as to the size of the nuclei and the content of secretory material. The cytological changes depend on the age of the fly and the diet given and are correlated with ovarian development.The nuclear size is held to express the metabolic activity of the cells. Cells with large nuclei, as found in young sugar-flies (S1D) and meat-fed flies with developing ovaries (S4D/M2D), contain less secretory material which is released through the axons, while the m.n.c. of old sugar-flies (S6D) have small nuclei and are stuffed with secretory material which is stored in the perikarya.These results confirm those obtained by darkfield microscopy of living m.n.c. by Lea and E.Thomsen (1962 and unpublished).No really convincing evidence for the existence of more than one type of m.n.c. was found.Two small groups of lateral cells were observed. Possibly neurosecretory are further: 1-(2) cells at the base of each optic lobe, two groups of 2–3 cells on the caudal side of the brain, and 2 cells ventrally in the suboesophageal ganglion.Giant neurons of unknown function are situated very near the m.n.c. Their axons join those from the m.n.c., but end in the suboesophageal ganglion.The same region comprises a number of peculiar cells, each containing a large, fluid-filled vacuole (the vacuolated cells). Similar cells are associated with the possibly neurosecretory cells on the caudal side of the brain.My sincere thanks are due to my wife Dr. Ellen Thomsen, who made all the excisions of the brains and the measurements of the nuclei, to T.C.Normann for valuable assistance with the photographic work, and to Mrs. K. Bahnert for technical help with the gallocyanin method. The Carlsberg Foundation has supported the work with grants.     

Magic,myth and medicine

Carrots, celery, caraway and cumin and their relatives in the Apiaceae (Umbelliferae) have a long history of human use dating from our earliest written records. A large body of folklore has accumulated on their magical and mythical curative properties. Many of the early uses have persisted as part of 20th century folklore, sometimes supplementary to modern medicine. Studies largely during the last half of this century have provided the chemical bases for some of the ancient cures.     

Multiple adenovirus serotypes use alpha v integrins for infection.

The nucleotide sequence encoding the penton base integrin-binding domains of several human adenoviruses was obtained by homology PCR. Each of the penton base proteins contains a conserved Arg-Gly-Asp (RGD) sequence that is predicted to lie at the apex of two extended alpha helices. The penton base RGD domain promotes efficient infection of host cells by multiple adenovirus serotypes via interaction with alpha v integrins, thus indicating that alpha v integrins play a central role in the entry of adenoviruses into host cells.     

PET1402, a nuclear gene required for proteolytic processing of cytochrome oxidase subunit 2 in yeast

The nuclear mutation pet ts1402 prevents proteolytic processing of the precursor of cytochrome oxidase subunit 2 (cox2) in Saccharomyces cerevisiae. The structural gene PET1402 was isolated by genetic complementation of the temperature-sensitive mutation. DNA sequence analysis identified a 1206-bp open reading frame, which is located 215 by upstream of the PET122 gene. The DNA sequence of PET1402 predicts a hydrophobic, integral membrane protein with four transmembrane segments and a typical mitochondrial targeting sequence. Weak sequence similarity was found to two bacterial proteins of unknown function. Haploid cells containing a null allelle of PET1402 are respiratory deficient.     

The unexpected long period of elevated CH4 emissions from an inundated fen meadow ended only with the occurrence of cattail (Typha latifolia)

Drainage and agricultural use transform natural peatlands from a net carbon (C) sink to a net C source. Rewetting of peatlands, despite of high methane (CH₄) emissions, holds the potential to mitigate climate change by greatly reducing CO₂ emissions. However, the time span for this transition is unknown because most studies are limited to a few years. Especially, nonpermanent open water areas often created after rewetting, are highly productive. Here, we present 14 consecutive years of CH₄ flux measurements following rewetting of a formerly long-term drained peatland in the Peene valley. Measurements were made at two rewetted sites (non-inundated vs. inundated) using manual chambers. During the study period, significant differences in measured CH₄ emissions occurred. In general, these differences overlapped with stages of ecosystem transition from a cultivated grassland to a polytrophic lake dominated by emergent helophytes, but could also be additionally explained by other variables. This transition started with a rapid vegetation shift from dying cultivated grasses to open water floating and submerged hydrophytes and significantly increased CH₄ emissions. Since 2008, helophytes have gradually spread from the shoreline into the open water area, especially in drier years. This process was periodically delayed by exceptional inundation and eventually resulted in the inundated site being covered by emergent helophytes. While the period between 2009 and 2015 showed exceptionally high CH₄ emissions, these decreased significantly after cattail and other emergent helophytes became dominant at the inundated site. Therefore, CH₄ emissions declined only after 10 years of transition following rewetting, potentially reaching a new steady state. Overall, this study highlights the importance of an integrative approach to understand the shallow lakes CH₄ biogeochemistry, encompassing the entire area with its mosaic of different vegetation forms. This should be ideally done through a study design including proper measurement site allocation as well as long-term measurements.     

Physiological effects of translation initiation factor IF3 and ribosomal protein L20 limitation inEscherichia coli

To investigate the physiological roles of translation initiation factor IF3 and ribosomal protein L20 inEscherichia coli, theinfC, rpmI andrpIT genes encoding IF3, L35 and L20, respectively, were placed under the control oflac promoter/operator sequences. Thus, their expression is dependent upon the amount of inducer isopropyl thiogalactoside (IPTG) in the medium. Lysogenic strains were constructed with recombinant lambda phages that express eitherrpmI andrplT orinfC andrpmI in trans, thereby allowing depletion of only IF3 or L20 at low IPTG concentrations. At low IPTG concentrations in the IF3-limited strain, the cellular concentration of IF3, but not L20, decreases and the growth rate slows. Furthermore, ribosomes run off polysomes, indicating that IF3 functions during the initiation phase of protein synthesis in vivo. During slow growth, the ratio of RNA to protein increases rather than decreases as occurs with control strains, indicating that IF3 limitation disrupts feedback inhibition of rRNA synthesis. As IF3 levels drop, expression from an AUU-infC-lacZ fusion increases, whereas expression decreases from an AUG-infC-lacZ fusion, thereby confirming the model of autogenous regulation ofinfC. The effects of L20 limitation are similar; cells grown in low concentrations of IPTG exhibited a decrease in the rate of growth, a decrease in cellular L20 concentration, no change in IF3 concentration, and a small increase in the ratio of RNA to protein. In addition, a decrease in 50S subunits and the appearance of an aberrant ribosome peak at approximately 41–43S is seen. Previous studies have shown that the L20 protein negatively controls its own gene expression. Reduction of the cellular concentration of L20 derepresses the expression of anrplT-lacZ gene fusion, thus confirming autogenous regulation by L20.     

Cell-free reconstitution of Fas-, UV radiation- and ceramide-induced apoptosis.

Cell-free systems are valuable tools for the dissection of complex cellular processes. Here we show that cytoplasmic extracts from cells exposed to anti-Fas antibody or UV radiation contain an activity capable of reproducing morphological changes typical of apoptosis in nuclei added to these extracts, as well as internucleosomal cleavage of DNA and proteolysis of a protein known to be cleaved during the apoptosis of intact cells. Extracts from control cell populations were inactive in this respect. These effects were partly blocked by the addition of purified Bcl-2 protein or a competitive inhibitor peptide of interleukin-1 beta-converting enzyme to the extracts. Furthermore, apoptotic activity was induced in cytoplasmic extracts from untreated cells by the addition of ceramide, a lipid second messenger implicated recently in apoptosis signaling. These extracts should prove highly useful in the dissection of molecular events that occur during apoptosis.