Energy transfer processes in Gloeobacter violaceus PCC 7421 that possesses phycobilisomes with a unique morphology

We examined energy transfer dynamics in phycobilisomes (PBSs) of cyanobacteria in relation to the morphology and pigment compositions of PBSs. We used Gloeobacter violaceus PCC 7421 and measured time-resolved fluorescence spectra in three types of samples, i.e., intact cells, PBSs, and rod assemblies separated from cores. Fremyella diplosiphon, a cyanobacterial species well known for its complementary chromatic adaptation, was used for comparison after growing under red or green light. Spectral data were analyzed by the fluorescence decay-associated spectra with components common in lifetimes with a time resolution of 3 ps/channel and a spectral resolution of 2 nm/channel. This ensured a higher resolution of the energy transfer kinetics than those obtained by global analysis with fewer sampling intervals. We resolved four spectral components in phycoerythrin (PE), three in phycocyanin (PC), two in allophycocyanin, and two in photosystem II. The bundle-like PBSs of G. violaceus showed multiple energy transfer pathways; fast ( approximately 10 ps) and slow ( approximately 100 ps and approximately 500 ps) pathways were found in rods consisting of PE and PC. Energy transfer time from PE to PC was two times slower in G. violaceus than in F. diplosiphon grown under green light.     

Effect of Growth pH on the Phospholipid Contents of the Membranes from Alkaliphilic Bacteria

An aerobic alkaliphile YN-2000 and a facultatively anaerobic alkaliphile BL77/1 are able to grow over the wide pH range of 7–10.5. Net surface charges on the membranes from YN-2000 and BL77/1 were negative above pH 4, and the amounts were significantly increased when the bacteria were cultured at pH 10 as compared with those cultured at pH 7.5. Phospholipid contents of the membranes from both bacteria grown at pH 10 were much higher than those from the bacteria grown at pH 7.5. Phospholipids of the membranes from YN-2000 and BL77/1 were composed mainly of cardiolipin (CL), phosphatidylethanolamine (PE), and phosphatidylglycerol (PG). It is suggested that the increases by growth at pH 10 of negative charges on the membranes from the bacteria result mainly from the increases of acidic phospholipids such as CL and PG. Increases of phospholipid contents and/or negative charges on the membranes seem to contribute to the adaptation of YN-2000 and BL77/1 to an alkaline environment. Received: 13 May 1999 / Accepted: 14 June 1999     

Genomic divergence and lack of introgressive hybridization between two 13‐year periodical cicadas support life cycle switching in the face of climate change

Life history evolution spurred by post‐Pleistocene climatic change is hypothesized to be responsible for the present diversity in periodical cicadas (Magicicada), but the mechanism of life cycle change has been controversial. To understand the divergence process of 13‐year and 17‐year cicada life cycles, we studied genetic relationships between two synchronously emerging, parapatric 13‐year periodical cicada species in the Decim group, Magicicada tredecim and M. neotredecim. The latter was hypothesized to be of hybrid origin or to have switched from a 17‐year cycle via developmental plasticity. Phylogenetic analysis using restriction‐site‐associated DNA sequences for all Decim species and broods revealed that the 13‐year M. tredecim lineage is genomically distinct from 17‐year Magicicada septendecim but that 13‐year M. neotredecim is not. We detected no significant introgression between M. tredecim and M. neotredecim/M. septendecim thus refuting the hypothesis that M. neotredecim are products of hybridization between M. tredecim and M. septendecim. Further, we found that introgressive hybridization is very rare or absent in the contact zone between the two 13‐year species evidenced by segregation patterns in single nucleotide polymorphisms, mitochondrial lineage identity and head width and abdominal sternite colour phenotypes. Our study demonstrates that the two 13‐year Decim species are of independent origin and nearly completely reproductively isolated. Combining our data with increasing observations of occasional life cycle change in part of a cohort (e.g. 4‐year acceleration of emergence in 17‐year species), we suggest a pivotal role for developmental plasticity in Magicicada life cycle evolution.     

The role of protein kinase C in the increased generation in isolated rat hepatocytes of the hydroxyl radical by puromycin aminonucleoside

Puromycin aminonucleoside (PAN) has been known to induce proteinuria. The increased generation of reactive oxygen species (ROS) has been implicated in this toxicity of PAN. We have reported that PAN increases the synthesis of methylguanidine (MG) and creatol which are the products of the reaction of creatinine and the hydroxyl radical in isolated rat hepatocytes. However, the mechanism for the increased ROS induced by PAN is still unclear. In this paper, we investigate the role of protein kinase C (PKC) on the PAN induced reactive oxygen generation in isolated rat hepatocytes. Isolated hepatocytes were incubated in Krebs-Henseleit bicarbonate buffer containing 3% BSA, 16.6 mM creatinine and tested reagents. MG and creatol were determined by high-performance liquid chromatography using 9,10-phenanthrenequinone for the post-labeling. PAN increased MG and creatol synthesis in isolated rat hepatocytes by 60%. 1-(5-Isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H-7), a PKC inhibitor, at 10 and 100 μM significantly inhibited MG and creatol synthesis with or without PAN. The inhibition rate is dose dependent from 10 to 100 μM. H1004, a reagent used as control for H-7, did not affect (at 10 μM) or increased little (at 100 μM) the synthesis of MG and creatol. Ro31-8425, a potent PKC inhibitor, significantly inhibited (at 10 μM) MG synthesis in the presence of PAN. PKC in the membrane fraction, a marker of PKC activation, increased over the initial concentration by a factor of 1.65-fold at 60 min incubation and 2.16-fold at 120 min with PAN, while it changed little without PAN. These results indicate that PAN activates PKC resulting in increased hydroxyl radical generation in isolated rat hepatocytes.     

The covalent modification of spectrin in red cell membranes by the lipid peroxidation product 4-hydroxy-2-nonenal

Spectrin strengthens the red cell membrane through its direct association with membrane lipids and through protein-protein interactions. Spectrin loss reduces the membrane stability and results in various types of hereditary spherocytosis. However, less is known about acquired spectrin damage. Here, we showed that α- and β-spectrin in human red cells are the primary targets of the lipid peroxidation product 4-hydroxy-2-nonenal (HNE) by immunoblotting and mass spectrometry analyses. The level of HNE adducts in spectrin (particularly α-spectrin) and several other membrane proteins was increased following the HNE treatment of red cell membrane ghosts prepared in the absence of MgATP. In contrast, ghost preparation in the presence of MgATP reduced HNE adduct formation, with preferential β-spectrin modification and increased cross-linking of the HNE-modified spectrins. Exposure of intact red cells to HNE resulted in selective HNE-spectrin adduct formation with a similar preponderance of HNE-β-spectrin modifications. These findings indicate that HNE adduction occurs preferentially in spectrin at the interface between the skeletal proteins and lipid bilayer in red cells and suggest that HNE-spectrin adduct aggregation results in the extrusion of damaged spectrin and membrane lipids under physiological and disease conditions.     

Maternal responses to dead and dying infants in wild troops of ring-tailed lemurs at the Berenty Reserve,Madagascar

We describe responses of seven mothers and other troop members to dead and dying infants in several troops of ring-tailed lemurs(Lemur catta) at the Berenty Reserve, Madagascar. In contrast to mothers in simian species, ring-tailed lemur mothers rarely carried their dying, immobile or dead infants. However, they sniffed, licked, and touched them even after they had died. While the dying infants were still peeping, their mothers remained near them, and 15 to 76 min after the infants ceased to peep, they were left by their mothers. Six of the seven mothers returned to their dead infants several times within the first few hours after they had left them. All seven mothers gave repeated calls, such as “mew” and “pyaa,” when they were separated from either their dead infants or other troop members or both. Thus, each mother exhibited some form of maternal behavior toward her dead infant for hours after its death. These results indicate that there may not be a great gap in terms of maternal affection between simian and prosimian mothers. We also discuss visuospatial memory ability in ring-tailed lemurs and the causes of the infants’ deaths.     

Coronary capillary network remodeling and hypofibrinolysis in aged obese diabetic rats: Implications for increased myocardial vulnerability to ischemia

Despite the known abnormalities of cardiac function in patients with overt non-insulin dependent diabetes mellitus (NIDDM) the temporal changes of coronary capillary network remodeling leading to potential microcirculatory dysfunction have not been elucidated. To this end, left ventricular subendocardial capillary network of Otsuka Long-Evans Tokushima Fatty (OLETF) rats, characterized by hypertension, obesity, hyperglycemia, hyperinsulinemia and mild NIDDM, and control Long-Evans Tokushima (LETO) rats were investigated. Total capillary density in OLETF was significantly higher than that in LETO at 20 weeks, suggesting compensatory improvement of O₂ transport at early stages of NIDDM. The increase in capillary density in OLETF was lost at 40 and 60 weeks due to the decreases of intermediate capillary portions and venular capillary portions. Although capillary domain area (area innervated by single capillary) in OLETF was lower than that in LETO at 20 weeks, the values were similar between OLETF and LETO at 40 and 60 weeks, suggesting that adaptive improvement in the capacity for O₂ transport with a high perfusion was lost in late stages of NIDDM. Activity of plasma plasminogen activator inhibitor-1 (PAI-1), the major physiologic inhibitor of proteo(fibrino)lysis, in OLETF was higher than that in LETO at 40 and 60 weeks, suggesting that increase of PAI-1 may downregulate compensatory adaptive capillary network remodeling by inhibiting proteolysis and angiogenesis in the cardiac interstitium. Loss of adaptive myocardial microcirculation may therefore contribute to increased vulnerability in ischemic injury and to cardiac dysfunction in NIDDM.     

Cloning and sequence analysis of tryptophan synthetase genes of an extreme thermophile, Thermus thermophilus HB27: plasmid transfer from replica-plated Escherichia coli recombinant colonies to competent T. thermophilus cells.

Tryptophan synthetase genes (trpBA) of the extreme thermophile Thermus thermophilus HB27 were cloned by a novel method of direct plasmid transfer from replica-plated Escherichia coli recombinant colonies to competent T. thermophilus HB27 trpB cells. The nucleotide sequences of the trpBA genes were determined. The amino acid sequences deduced from the nucleotide sequences of Thermus trpB and trpA were found to have identities of 54.8 and 28.7%, respectively, with those of E. coli trpB and trpA genes. Low cysteine content (one in trpB; zero in trpA) is a striking feature of these proteins, which may contribute to their thermostability.     

Plasmid mutations affecting self-maintenance and host growth in Escherichia coli.

As reported in the accompanying paper, a number of mutants of the ColVBtrp plasmid that can not be maintained stably in the host cell of Escherichia coli have been isolated. Each of the mutated plasmids has been transferred to an isogenic Col minus strain, and the resulting Col+ strains were studied to examine the effects of plasmid mutations on some properties of the host bacteria. Many of the strains harboring a mutated plasmid were thus found to be temperature sensitive; they failed to grow and divide normally at high temperatures. Some of them formed "filaments" under these conditions. These abnormal growth characteristics were accompanied by an increased susceptibility to sodium deoxycholate and methylene blue, suggesting that the cytoplasmic membrane has been altered. Moreover, studies of temperature-independent revertants obtained from two of these temperature-sensitive Col+ strains suggested that a single mutation on the plasmid is responsible for the pleiotropic effects exerted on the host cell. The bearing of these findings on the mode of replication and segregated of stringent-type plasmids such as ColVBtrp in the host bacteria is discussed.     

Isolation and Structure of γ-l-Glutamyl-l-β-Phenyl-β-Alanine,a New γ-Glutamyl Peptide from Phaseolus angularis W F. Wight (Azuki bean)

From the nonprotein acidic amino acid fraction of Phaseolus angularis W. F. Wight, Azuki bean of commerce in Japan, a new γ-glutamyl peptide has been isolated by ion exchange techniques. This compound has been shown to be γ-l-glutamyl-l-β-phenyl-β-alanine. The characterization is based on elementary analysis, hydrolysis with hydrochloric acid or Amber lite CG-120 resin in H⁺ form, ultraviolet and infrared spectra, and the reaction of fluorodinitrobenzene with the peptide. The glutamic acid separated from the hydroiysates was decarboxylated to γ-aminobutyric acid with l-glutamic acid decarboxylase prepared from squash. β-Phenyl-β-alanine component in the peptide had the same infrared spectrum, elementary analysis, melting point, optical rotation and behavior in paper chromatography as authentic l-β-phenyl-β-alanine.