Probing the role of Valine 185 of the D1 protein in the Photosystem II oxygen evolution

In Photosystem II (PSII), the Mn₄CaO₅-cluster of the active site advances through five sequential oxidation states (S₀ to S₄) before water is oxidized and O₂ is generated. The V185 of the D1 protein has been shown to be an important amino acid in PSII function (Dilbeck et al. Biochemistry 52 (2013) 6824–6833). Here, we have studied its role by making a V185T site-directed mutant in the thermophilic cyanobacterium Thermosynechococcus elongatus. The properties of the V185T-PSII have been compared to those of the WT*3-PSII by using EPR spectroscopy, polarography, thermoluminescence and time-resolved UV–visible absorption spectroscopy. It is shown that the V185 and the chloride binding site very likely interact via the H-bond network linking Tyr_Z and the halide. The V185 contributes to the stabilization of S₂ into the low spin (LS), S?=?1/2, configuration. Indeed, in the V185T mutant a high proportion of S₂ exhibits a high spin (HS), S?=?5/2, configuration. By using bromocresol purple as a dye, a proton release was detected in the S₁Tyr_Z?→?S₂^HSTyr_Z transition in the V185T mutant in contrast to the WT*3-PSII in which there is no proton release in this transition. Instead, in WT*3-PSII, a proton release kinetically much faster than the S₂^LSTyr_Z?→?S₃Tyr_Z transition was observed and we propose that it occurs in the S₂^LSTyr_Z?→?S₂^HSTyr_Z intermediate step before the S₂^HSTyr_Z?→?S₃Tyr_Z transition occurs. The dramatic slowdown of the S₃Tyr_Z?→?S₀Tyr_Z transition in the V185T mutant does not originate from a structural modification of the Mn₄CaO₅ cluster since the spin S?=?3?S₃ EPR signal is not modified in the mutant. More probably, it is indicative of the strong implication of V185 in the tuning of an efficient relaxation processes of the H-bond network and/or of the protein.     

A trans‐Atlantic examination of haddock Melanogrammus aeglefinus food habits

The food habits of Melanogrammus aeglefinus were explored and contrasted across multiple north‐eastern and north‐western Atlantic Ocean ecosystems, using databases that span multiple decades. The results show that among all ecosystems, echinoderms are a consistent part of M. aeglefinus diet, but patterns emerge regarding where and when M. aeglefinus primarily eat fishes v. echinoderms. Melanogrammus aeglefinus does not regularly exhibit the increase in piscivory with ontogeny that other gadoids often show, and in several ecosystems there is a lower occurrence of piscivory. There is an apparent inverse relationship between the consumption of fishes and echinoderms in M. aeglefinus over time, where certain years show high levels of one prey item and low levels of the other. This apparent binary choice can be viewed as part of a gradient of prey options, contingent upon a suite of factors external to M. aeglefinus dynamics. The energetic consequences of this prey choice are discussed, noting that in some instances it may not be a choice at all.     

The pecking order of skin Advanced Glycation Endproducts (AGEs) as long-term markers of glycemic damage and risk factors for micro- and subclinical macrovascular disease progression in Type 1 diabetes

To date more than 20 glycation products were identified, of which ~15 in the insoluble human skin collagen fraction. The goal of this review is to streamline 30 years of research and ask a set of important questions: in Type 1 diabetes which glycation products correlate best with 1) past mean glycemia 2) reversibility with improved glycemic control, 2) cross-sectional severity of retinopathy, nephropathy and neuropathy and 3) the future long-term risk of progression of micro- and subclinical macrovascular disease. The trio of glycemia related glycation markers furosine (FUR)/fructose-lysine (FL), glucosepane and methylglyoxal hydroimidazolone (MG-H1) emerges as extraordinarily strong predictors of existing and future microvascular disease progression risk despite adjustment for both past and prospective A1c levels. X² values are up to 25.1, p values generally less than 0.0001, and significance remains after adjustment for various factors such as A1c, former treatment group, log albumin excretion rate, abnormal autonomic nerve function and LDL levels at baseline. In contrast, subclinical cardiovascular progression is more weakly correlated with AGEs/glycemia with X² values?<?5.0 and p values generally <?0.05 after all adjustments. Except for future carotid intima-media thickness, which correlates with total AGE burden (MG-H1, pentosidine, fluorophore LW-1 and decreased collagen solubility), adjusted FUR and Collagen Fluorescence (CLF) are the strongest markers for future coronary artery calcium deposition, while cardiac hypertrophy is associated with LW-1 and CLF adjusted for A1c. We conclude that a robust clinical skin biopsy AGE risk panel for microvascular disease should include at least FUR/FL, glucosepane and MG-H1, while a macrovascular disease risk panel should include at least FL/FUR, MG-H1, LW-1 and CLF.     

Ontogenetic sequence comparison of extant and fossil tadpole shrimps: no support for the “living fossil” concept

The tadpole shrimp Triops cancriformis (Branchiopoda, Eucrustacea) is often referred to as a “living fossil.” This term implies that the morphology of a species has barely changed for hundreds of millions of years; in the case of T. cancriformis, for about 200 million years. In 1938, Trusheim documented fossil notostracans from the Upper Triassic of southern Germany (237–200 million years) and named them T. cancriformis minor due to their small size compared to modern forms of T. cancriformis. We compared the ontogenetic sequence of the fossil forms to that of modern forms. Fossil material came from the Museum Terra Triassic in Euerdorf and originated from the same geological formation (the Hassberge Formation) as the Trusheim material, which is considered to be nearly entirely lost. The specimens were documented using cross-polarized light and processed into high-resolution images. Fluorescence microscopy was used to document exuviae and carcasses of extant representatives of T. cancriformis. Both forms showed an elongation and similar trends in the length/width ratio of the shield during ontogeny. However, differences were found in the starting point of the developmental processes. Fossil forms start out with a more roundly shaped shield, which becomes more elliptical, while extant forms already start with a more elliptical shield shape. Further differences between extant and fossil forms were found upon comparing shield to trunk ratios. All differences are highly significant statistically. These differences in ontogeny cast severe doubt on the interpretation that T. cancriformis has been static for 237 million years. While the term “living fossil” is misleading and its use should be discouraged in general, it seems to be especially inappropriate to apply it to T. cancriformis.     

Low genetic diversity in Polish populations of sibling ant species: <Emphasis Type="Italic">Lasius niger</Emphasis> (L.) and <Emphasis Type="Italic">Lasius platythorax</Emphasis> Seifert (Hymenoptera,Formicidae)

We present preliminary data on mitochondrial DNA diversity within and among populations of the ants Lasius niger and Lasius platythorax in Poland. Phylogenetic analysis based on the mitochondrial DNA markers: cytochrome c oxidase subunit I (cox1) and 16S ribosomal RNA (16S rRNA) confirms the species status of L. niger and L. platythorax. Intraspecific variability is low in both species, which might be a result of severe bottlenecks and rapid postglacial expansion into Central Europe.     

Nitric oxide is a central component in neuropeptide regulation of appetite

In recent years, there have been a large number of neuropeptides discovered that regulate food intake. Many of these peptides regulate food intake by increasing or decreasing nitric oxide (NO). In the current study, we compared the effect of the food modulators ghrelin, NPY and CCK in NOS KO mice. Satiated homozygous and heterozygous NOS KO mice and their wild type controls were administered ghrelin ICV. Food intake was measured for 2 h post injection. Ghrelin did not increase food intake in the homozygous NOS KO mice compared to vehicle treated NOS KO mice, whereas food intake was increased in the wild type controls compared to vehicle treated wild type controls. NPY was administered ICV and food intake measured for 2 h. Homozygous NOS KO mice showed no increase in food intake after NPY administration, whereas the wild type controls did. In our final study, we administered CCK intraperitoneally to homozygous and heterozygous NOS KO mice and their wild type controls after overnight food deprivation. Food intake was measured for 1 h after injection. CCK inhibited food intake in wild type mice after overnight food deprivation, however, CCK failed to inhibit food intake in the NOS KO mice. The heterozygous mice showed partial food inhibition after the CCK. The current results add further support to the theory that NO is a central mediator in food intake.     

A re-evaluation of aff. Megaloolithidae eggshell fragments from the uppermost Cretaceous of the Pyrenees and implications for crocodylomorph eggshell structure

The Upper Cretaceous outcrops of the Pyrenees yield one of the most extensive and continuous records of paleoological remains anywhere in the world. Most of eggs and eggshells have been referred to the oofamily Megaloolithidae. In this study, we present a revision of eggshell fragments from the Blasi 2 locality, lattermost Maastrichtian in age, previously assigned to aff. Megaloolithidae. The presence of a blocky extinction pattern and basal knobs supports a crocodilian affinity of these materials. We classify them as Krokolithidae indet. Three structural layers can be recognised in the Blasi 2 eggshells, a feature that is shared with other recent eggshells (e.g. Crocodylus porosus and Crocodylus niloticus) and fossil crocodylomorph eggshells (Krokolitheswilsoni), which were previously described as single layered. The new proposed affinity of the Blasi 2 eggshells reduces the Megaloolithidae oodiversity of the last few million years of the Cretaceous in the Pyrenees to only two valid ootaxa, Megaloolithusmamillare and Megaloolithusbaghensis. The lack of more complete material precludes the erection of new ootaxa based on the Blasi 2 material.     

Molecular analysis confirms that Botryodontia millavensis and Oxyporus philadelphi are conspecific

The aim of the present study is to elucidate if Oxyporus philadelphi (Parmasto) Ryvarden and Botryodontia millavensis (Bourdot & Galzin) Duhem & H. Michel are conspecific, as suggested by their similar morphology. The analysis of ribosomal DNA ITS sequences indicate that the specimens of O. philadelphi and B. millavensis belong to a single species. The species is closely related to the type species (B. cirrata) of the genus Botryodontia, and therefore the name B. millavensis should currently be used for this taxon. Botryodontia millavensis grows on a wide selection of host species—Juniperus communis, Philadelphus coronarius, Picea abies, Fraxinus excelsior, Lonicera sp., J. turcomanica—and is distributed widely in temperate Eurasia.     

Callus induction, somatic embryogenesis and organogenesis in Narcissus confusus: correlation between the state of differentiation and the content of galanthamine and related alkaloids

In vitro cultures from two strains of Narcissus confusus (Amaryllidaceae) initiated from mature seeds were screened for their ability to produce alkaloids. Protocols for callus induction, somatic embryogenesis and organogenesis were established. The alkaloid contents were determined by HPLC. Undifferentiated calli produced small amounts of galanthamine, which increased with the degree of tissue differentiation. Scanning electron micrographs of the cultures at different stages of development were made. Embryogenic friable calli were maintained in culture for more than 2 years, retaining a high regeneration capability. All regenerated plants showed normal morphological characteristics. Received: 20 August 1997 / Revision received: 20 December 1997 / Accepted: 1 February 1998