Polyamines and Anaerobic Elongation of Rice Coleoptile

The role of polyamines in the anaerobic elongation of rice (Oryzasativa L.) coleoptiles was studied. The reduced growth of ricecoleoptiles under anoxic conditions was accompanied by a massiveaccumulation of free putrescine. Putrescine was synthesizedfrom arginine in a reaction catalyzed by arginine decarboxylase(ADC). The anoxic titer of putrescine was closely correlatedwith elongation of coleoptiles. In experiments in which putrescineand inhibitors [-difluoromethylarginine (DFMA) and -difluoromethylornithine(DFMO)] of the synthesis of polyamines were exogenously supplied,we demonstrated an absolute requirement for putrescine, synthesizedby ADC, for anaerobic elongation of coleoptiles. The presenceof exogenous putrescine (alone or in combination with DFMA)increased the rate of anaerobic elongation of coleoptile by30–40%. (Received December 1, 1988; Accepted June 19, 1989)     

Accumulation and Interconversion of Amino Acids in Rice Roots under Anoxia

In excised rice roots, anaerobic degradation of proteins gaverise to an increase of free-amino acids. Anoxic accumulationof alanine, -aminobutyric acid and proline was the consequenceof the interconversion of glutamate, aspartate and amides. Theshift in the composition of the amino acid pool appears to becaused by changes in keto acid levels. The role of reactionsinvolved in amino acid interconversion and the physiologicalsignificance of these interconversions are considered and discussed. (Received November 25, 1988; Accepted June 9, 1988)     

Predation at a snail's pace: what's time to a gastropod?

Summary Predation by naticid gastropods shows evidence of adaptation to maximize the rate of energy intake. The predation rate of Polinices duplicatus feeding on artificially altered, thin-shelled Mercenaria mercenaria was faster than the predation rate on normal Mercenaria. The rate of energy intake was limited by handling time. The time saved by predation on thin-shelled prey was used to forage. Thus time was shown to be valuable to P. duplicatus, and cost-benefit functions using time and energy as currencies are appropriate for estimating dietary efficiency and predicting prey choice.Despite the clear superiority of thin-shelled prey, P. duplicatus did not learn to prefer this novel prey type, suggesting that predator choices are sterotyped, reflecting optima selected over evolutionary time.     

Reactions of the haloalcohols HO(CH2)nCl (n = 2, 3) with platinum(II) - alkynyl and -alkyne complexes. X-ray crystal structure of trans-[Pt(Me) {C(OCH2CH2Cl) (CH2Ph)} (PPh3)2] [BF4]

The chloro complexes trans-[Pt(Me)(Cl)(PPh₃)₂], after treatment with AgBF₄, react with 1-alkynes HC---C---R in the presence of NEt₃ to afford the corresponding acetylide derivatives trans-[Pt(Me) (C---C---R) (PPh₃)₂] (R = p-tolyl (1), Ph (2), C(CH₃)₃ (3)). These complexes, with the exception of the t-butylacetylide complex, react with the chloroalcohols HO(CH₂)_nCl (n = 2, 3) in the presence of 1 equiv. of HBF₄ to afford the alkyl(chloroalkoxy)carbene complexes trans-[Pt(Me) {C[O(CH₂)_nCl](CH₂R) } (PPh₃)₂][BF₄] (R = p-tolyl, N = 2 (4), N = 3 (5); R=Ph, N = 2 (6)). A similar reaction of the bis(acetylide) complex trans-[Pt(C---C---Ph)₂(PMe₂Ph)₂] with 2 equiv. HBF₄ and 3-chloro-1-propanol affords trans-[Pt(C---CPh) {C(OCH₂CH₂CH₂Cl)(CH₂Ph) } (PMe₂Ph)₂][BF₄] (7). T alkyl(chloroalkoxy)-carbene complex trans-[Pt(Me) {C(OCH₂CH₂Cl)(CH₂Ph) } (PPh₃)₂][BF₄] (8) is formed by reaction of trans-[Pt(Me)(Cl)(PPh₃)₂], after treatment with AgBF₄ in HOCH₂CH₂Cl, with phenylacetylene in the presence of 1 equiv. of n-BuLi. The reaction of the dimer [Pt(Cl)(μ-Cl)(PMe₂Ph)]₂ with p-tolylacetylene and 3-chloro-1-propanol yields cis-[PtCl₂{C(OCH₂CH₂CH₂Cl)(CH₂C₆H₄-p-Me}(PMe₂Ph)] (9). The X-ray molecular structure of (8) has been determined. It crystallizes in the orthorhombic system, space group Pna2₁, with a = 11.785(2), B = 29.418(4), C = 15.409(3) Å, V = 4889(1) ų and Z = 4. The carbene ligand is perpendicular to the Pt(II) coordination plane; the PtC(carbene) bond distance is 2.01(1) Å and the short C(carbene)-O bond distance of 1.30(1) Å suggests extensive electronic delocalization within the Pt---C(carbene)---O moietry.     

Genetic interaction between the nip1 mutation and genes affecting integration and excision in phage P2

Summary The excision of prophage P2 is controlled by two genes, int and cox. (The cox gene discussed in this report is defined by the cox class II mutants, defined by Six and Lindqvist, 1978). The combined activity of these two genes is rather inefficient, however, since only about 1% of the lysogens carrying an int ⁺ cox ⁺ prophage actually produce phage when derepressed. The efficiency of phage production (and presumably excision) can be increased 100-fold by an additional mutation called nip1 (Calendar et al., 1972), which is dominant and is located in or near the int gene.The nip1 mutation was mapped between c5, a mutation in the C gene, and an amber int mutation, int150. Phages carrying nip1 and either int150 or a cox mutation, cox3, were prepared by recombination. The nip1 mutation was found to increase excision only when it was located on the same chromosome as an active int ⁺ gene and only if cox ⁺ gene product was also available. The cox gene, known to be located between genes B and C (Lindahl and Sunshine, 1972), was further localized to a region between 77.2 to 78.1% from the conventional left end of the P2 chromosome by comparing the ability of phages with overlapping deletions to promote excision of the prophage in a P2 nip1 c5 cox3 lysogen.Other features of the integration-excision system in P2 are discussed.     

Further physical characterization of deletion and substitution mutants affecting the control of lysogeny in bacteriophage P2

Summary A deletion of phage P2, del6 (L.E. Bertani, 1980), thought to remove the structural gene int, and a deletion/substitution, vir94, thought to remove genes int, C and cox, were mapped by electron microscopy, using the heteroduplex technique.Four independent deletion/substitution mutations, all affecting the regulatory region of P2, were compared in all possible combinations with the same technique: two showed sequence homology in their substitution DNA. The results confirm the model proposed for the origin of these mutants, analogous to that for the origin of transducing variants in phage , but suggest in first approximation that the exchange between the P2 DNA and the chromosome of the host bacterium may occur at several different bacterial sites.A map of the regulatory region of P2, based on all data available from the study of deletions and insertions, is presented.     

Tandem pentuplication of a DNA segment in a derivative of bacteriophage P2: its use in the study of the mechanism of DNA annealing.

From a tandem duplication mutant of phage P2, triplication, quadruplication and pentuplication forms were derived. They were recognized by decreased virion heat stability resulting from the increase in DNA content, and were confirmed by electron microscope heteroduplex mapping. These forms of partially repeated DNA are quite stable in P2 because of the low level of recombination typical of this phage. Under conditions normally employed for full DNA renaturation, these high order repeat chromosomes gave often incomplete renaturation over the repeated segments. Based on current models for DNA renaturation, several predictions were made and tested. The results, although not quantitatively exhaustive, indicated that base pairing proceeding from a nucleation site was sufficiently slow to allow a second nucleation to occur with a fair probability over a length of a few thousand base pairs.     

Genome-Wide and Locus Specific Alterations in CDC73/HRPT2-Mutated Parathyroid Tumors

Mutations in the hyperparathyroidism type 2 (HRPT2/CDC73) gene and alterations in the parafibromin protein have been established in the majority of parathyroid carcinomas and in subsets of parathyroid adenomas. While it is known that CDC73-mutated parathyroid tumors display specific gene expression changes compared to CDC73 wild-type cases, the molecular cytogenetic profile in CDC73-mutated cases compared to unselected adenomas (with an expected very low frequency of CDC73 mutations) remains unknown. For this purpose, nine parathyroid tumors with established CDC73 gene inactivating mutations (three carcinomas, one atypical adenoma and five adenomas) were analyzed for copy number alterations and loss of heterozygosity using array-comparative genomic hybridization (a-CGH) and single nucleotide polymorphism (SNP) microarrays, respectively. Furthermore, CDC73 gene promoter methylation levels were assessed using bisulfite Pyrosequencing. The panel included seven tumors with single mutation and three with double mutations of the CDC73 gene. The carcinomas displayed copy number alterations in agreement with previous studies, whereas the CDC73-mutated adenomas did not display the same pattern of alterations at loci frequently deleted in unselected parathyroid tumors. Furthermore, gross losses of chromosomal material at 1p and 13 were significantly (p = 0.012) associated with parathyroid carcinomas as opposed to adenomas. Quantitative PCR-based copy number loss regarding CDC73 was observed in three adenomas, while all the carcinomas were diploid or showed copy number gain for CDC73 gene. Hypermethylation of the CDC73 gene promoter was not observed. Our data could suggest that CDC73-mutated parathyroid adenomas exhibit a partly unique cytogenetic profile in addition to that of carcinomas and unselected adenomas. Furthermore, CDC73-mutated carcinomas displayed losses at 1p and 13 which are not seen in CDC73-mutated adenomas, making these regions of interest for further studies regarding malignant properties in tumors from CDC73-mutated cases. However, due to the small sample size, validation of the results in a larger cohort is warranted.