Some effects of humidity on the light reaction of photosynthesis in the lichens Cladonia impexa and Collema flaccidium

Luminescence and fluorescence were measured at different relative humidities in the lichen Cladonia impexa Harm. Both parameters showed a constant value at relative humidities lower than 80%: thereafter they increased. Low relative humidity was found to decrease energy transfer from chlorophyll b to chlorophyll a. inhibit electron transport, lower electron holding capacity on the reduced side of photosystem two and impair far-red-induced afterglow, reflecting photophosphorylation. In Collema flaccidium Ach. Ach. energy transfer from the accessory pigments phycocyanin and phycoerythrin to chlorophyll a was only possible at high relative humidity. The results are interpreted as due to conformational changes caused by changed water content in the lichen.     

Decarboxylation and Transport of Auxin in Segments of Sunflower and Cabbage Roots. II. A Chromatographic Study Using IAA-1-14C and IAA-5-3H

The polar movement of IAA has been examined in 5-mm root segments of Brassica oleracea and Helianthus annum. The movement was studied partly with IAA-1-¹⁴C and partly with IAA-5-³H. In both plants a slight acropetal flux of ¹⁴C and IAA-³H was found through the segments. The recovered radioactivity in the agar receiver blocks and in the receiver end of the segments increased as a function of time. A large portion of the applied IAA was converted on the cut surfaces and in the tissues of the segments. Chromatographic analysis indicated different destruction products when estimated by scintillation counting and by spraying with in-dole reagent (DMCA). Chromatograms run in isopropanol: ammonia: water, 8:1:1, yielded three different substances, one spot near the starting line and one near the front, neither of which has been identified. Finally there was a spot with R_f 0.4–0.6, probably representing IAA.     

1:1 Distribution between Induced Mutants and Phenocopies

BY ultraviolet irradiation of germiings of the multicellular alga Ulva mutabilis Føyn, it is possible to obtain chimaeric plants which consist of two morphologically different parts of different genetic constitution, one part wild type and the other mutant^{1, 2}. Other plants found have been identical in appearance to the chimaeras, though the morphologically different parts were both genetically wild type. They should be considered phenocopies of the genetic chimaeras. Surprisingly, the genetical chimaeras and their phenocopies were found in equal numbers. This observation and the previous one that only complete mutations are found after ultraviolet irradiation of Ulva cells¹, can be explained if only one of the two strands in the DNA molecule is genetically conserved.     

The State of Protochlorophyll and Chlorophyll in Corn Roots

The protochlorophyll(ide) present in primary roots of dark-grown corn (Zea mays) seedlings has an in vivo absorption maximum at 634 nm. Red light converts the pigment to chlorophyll(ide) a with an absorption maximum at 675 nm.     

Action Spectra for in vivo and in vitro Conversions of Phycochrome b, a Reversibly Photochromic Pigment in a Blue-Green Alga, and Its Separation from Other Pigments

Phycochrome b, one of the reversibly photochromic pigments found in Tolypothrix distorta seems to exist in only two forms: P^b₅₀₀ and P^b₅₇₀. The pigment has been spectroscopically demonstrated in vivo. It has also been separated from other pigments. Two different methods for separation have been used: isoelectric focusing and gel filtration. Preparations of purified phycobilisomes contain phycochrome b. The in vivo and in vitro absorption difference spectra were determined as well as action spectra for the conversions in vitro and in vivo of P^b₅₀₀ to P^b₅₇₀ and vice versa. Transformation kinetics of phycochrome b show that the conversions in both directions are initially first-order reactions.     

Comparison of Established Cell Lines at Different Passages by Karyotype and Comparative Genomic Hybridization

Two established cancer cell lines, MCF-7 and Ishikawa, were both obtained directly from a cell repository and through another laboratory. The karyotypes from the two MCF-7 cell lines had up to 83 chromosomes and similarities for chromosomal gain and structural abnormalities. The two Ishikawa cell lines had up to 60 chromosomes with only a missing X as the common chromosome abnormality. CGH studies were performed by co-hybridizing the two Ishikawa or MCF-7 cell lines to normal metaphases. The differences seen between the two MCF-7 cell cultures reflect changes due to passage number and culture conditions. For Ishikawa, DNA polymorphic data and mutation studies suggest that the two cell lines are not derived from the same established tumor cell line. Our study shows the utilization of CGH in comparing cell lines originating from the same specimen. Our study also demonstrates the necessity for periodically evaluating cell lines to confirm their origin.     

Human pyruvate kinase M2: A multifunctional protein

Glycolysis, a central metabolic pathway, harbors evolutionary conserved enzymes that modulate and potentially shift the cellular metabolism on requirement. Pyruvate kinase, which catalyzes the last but rate‐limiting step of glycolysis, is expressed in four isozymic forms, depending on the tissue requirement. M2 isoform (PKM2) is exclusively expressed in embryonic and adult dividing/tumor cells. This tetrameric allosterically regulated isoform is intrinsically designed to downregulate its activity by subunit dissociation (into dimer), which results in partial inhibition of glycolysis at the last step. This accumulates all upstream glycolytic intermediates as an anabolic feed for synthesis of lipids and nucleic acids, whereas reassociation of PKM2 into active tetramer replenishes the normal catabolism as a feedback after cell division. In addition, involvement of this enzyme in a variety of pathways, protein–protein interactions, and nuclear transport suggests its potential to perform multiple nonglycolytic functions with diverse implications, although multidimensional role of this protein is as yet not fully explored. This review aims to provide an overview of the involvement of PKM2 in various physiological pathways with possible functional implications.