Coralloid root regeneration on Macrozamia megagametophites

Abstract

Megagametophytes of Macrozamia communis were incubated in White's Basal Medium and in White's Basal Medium modified with 2,4-D and kinetin. On the medium enriched with growth substances, regeneration of coralloid roots was induced. These are morphologically identical to sporophytic coralloid roots, without any endosymbiont and displaying negative geotropism. These results confirm the fact that coralloid roots represent an inherent feature of the root system of the Cycadales rather than being the result of induction by microbial factors. Therefore it is possible to suggest that coralloid roots represent vestigial pneumatophores.     

Mono-, bi-, or tridentate ligands? The labeling of peptides with 99mTc-carbonyls

The labeling of targeting peptides with (99m)Tc is a useful concept for the diagnosis of various diseases such as cancer. Although in research for at least one decade, only a very few radiopharmaceuticals based on peptides are in clinical use. The difficulty of labeling, and the resulting authenticity of the new vector, is largely responsible for this observation. In this overview, we present an alternate strategy based on the organometallic fac-[(99m)Tc(CO)(3)](+) core for introducing (99m)Tc in biomolecules in general and in peptides in particular. The three coordination sites available in [(99m)Tc(OH(2))(3)(CO)(3)](+) can be occupied with many different ligand types, pendant to a biomolecule and serving as the anchor group for labeling. This makes the appropriate choice difficult. We intend to present some useful concepts for the practice. Monodentate chelators are robust but bear the risk of multiple binding of biomolecules. Coordinating a bidentate ligand of choice prior to labeling bypasses this problem and enables a systematic drug discovery by variation of the bidentate ligand. Bidentate ligands attached to the biomolecule are stronger but occasionally require protection of the remaining site by a monodentate ligand. Both approaches refer to a mixed-ligand [2+1] approach. Tridentate chelators are the most efficient but need some protecting group chemistry in order to achieve selectivity for the coupling process. Examples with cysteine and histidine are presented. This article aims to provide versatile and reproducible approaches for the labeling of biomolecules while not focusing on particular systems. It should be left to the readers to derive a strategy for their own peptide.     

Enhanced dopaminergic differentiation of human neural stem cells by synergistic effect of Bcl-xL and reduced oxygen tension

Neural stem cells constitute a promising source of cells for transplantation in Parkinson's disease, but a protocol for controlled dopaminergic differentiation is not yet available. Here we investigated the effect of the anti-apoptotic protein Bcl-x_L and oxygen tension on dopaminergic differentiation and survival of a human ventral mesencephalic stem cell line (hVM1). hVM1 cells and a Bcl-x_L over-expressing subline (hVMbcl-x_L) were differentiated by sequential treatment with fibroblast growth factor-8, forskolin, sonic hedgehog, and glial cell line-derived neurotrophic factor. After 10 days at 20% oxygen, hVMbcl-x_L cultures contained proportionally more tyrosine hydroxylase(TH)-positive cells than hVM1 control cultures. This difference was significantly potentiated from 11 ± 0.8% to 17.2 ± 0.2% of total cells when the oxygen tension was lowered to 3%. Immunocytochemistry and Q-PCR-analysis revealed expression of several dopaminergic markers besides of TH just as dopamine was detected in the culture medium by HPLC analysis. Although Bcl-x_L-over-expression reduced cell death in the cultures, it did not alter the relative content of GABAergic, neurons, while the content of astroglial cells was reduced in hVMbcl-x_L cell cultures compared with control. We conclude that Bcl-x_L and lowered oxygen tension act in concert to enhance dopaminergic differentiation and survival of human neural stem cells.     

The thyroid hormone receptor β induces DNA damage and premature senescence

There is increasing evidence that the thyroid hormone (TH) receptors (THRs) can play a role in aging, cancer and degenerative diseases. In this paper, we demonstrate that binding of TH T3 (triiodothyronine) to THRB induces senescence and deoxyribonucleic acid (DNA) damage in cultured cells and in tissues of young hyperthyroid mice. T3 induces a rapid activation of ATM (ataxia telangiectasia mutated)/PRKAA (adenosine monophosphate–activated protein kinase) signal transduction and recruitment of the NRF1 (nuclear respiratory factor 1) and THRB to the promoters of genes with a key role on mitochondrial respiration. Increased respiration leads to production of mitochondrial reactive oxygen species, which in turn causes oxidative stress and DNA double-strand breaks and triggers a DNA damage response that ultimately leads to premature senescence of susceptible cells. Our findings provide a mechanism for integrating metabolic effects of THs with the tumor suppressor activity of THRB, the effect of thyroidal status on longevity, and the occurrence of tissue damage in hyperthyroidism.     

Degradation of Microcystin-RR by Sphingomonas sp. CBA4 isolated from San Roque reservoir (Córdoba – Argentina)

We report the aerobic biodegradation of Microcystin-RR (MC-RR) by a bacterial strain isolated from San Roque reservoir (Córdoba – Argentina). This bacterium was identified as Sphingomonas sp. (CBA4) on the basis of 16S rDNA sequencing. The isolated strain was capable of degrading completely MC-RR (200 μg l⁻¹) within 36 h. We have found evidence that MC-RR biodegradation pathway by this Sphingomonas sp. strain would start by demethylating MC-RR, affording an intermediate product, which is finally biodegraded by this strain within 72 h. Our results confirm that certain environmental bacteria, living in the same habitat as toxic cyanobacteria, have the capability to perform complete biodegradation of MC, leading to natural bioremediation of waterbodies. The bacterium reported here presents genetic homologies with other strains that degrade MC-LR. However, initial demethylation of MC-RR has been not described previously, raising questions on the probable presence of different biodegradation pathways for different MC variants.     

Development of a new class of potential antiatherosclerosis agents: NO-donor antioxidants

A new class of NO-donor phenol derivatives is described. The products were obtained by joining appropriate phenols with either nitrooxy or 3-phenylsulfonylfuroxan-4-yloxy moieties. All the compounds proved to inhibit the ferrous salt/ascorbate induced lipidic peroxidation of membrane lipids of rat hepatocytes. They were also capable of dilating rat aorta strips precontracted with phenylephrine.     

Right‐handed fossil humans

Fossil hominids often processed material held between their upper and lower teeth. Pulling with one hand and cutting with the other, they occasionally left impact cut marks on the lip (labial) surface of their incisors and canines. From these actions, it possible to determine the dominant hand used. The frequency of these oblique striations in an array of fossil hominins documents the typically modern pattern of 9 right‐ to 1 left‐hander. This ratio among living Homo sapiens differs from that among chimpanzees and bonobos and more distant primate relatives. Together, all studies of living people affirm that dominant right‐handedness is a uniquely modern human trait. The same pattern extends deep into our past. Thus far, the majority of inferred right‐handed fossils come from Europe, but a single maxilla from a Homo habilis, OH‐65, shows a predominance of right oblique scratches, thus extending right‐handedness into the early Pleistocene of Africa. Other studies show right‐handedness in more recent African, Chinese, and Levantine fossils, but the sample compiled for non‐European fossil specimens remains small. Fossil specimens from Sima del los Huesos and a variety of European Neandertal sites are predominately right‐handed. We argue the 9:1 handedness ratio in Neandertals and the earlier inhabitants of Europe constitutes evidence for a modern pattern of handedness well before the appearance of modern Homo sapiens.     

Influence of aging on murine neutrophil and macrophage function against Candida albicans

Previous work by our group showed that aged C57BL/6 mice develop an altered innate and adaptive immune response to Candida albicans and are more susceptible to systemic primary candidiasis. In this work, we used young (2-3 months old) and aged (18-20 months old) C57BL/6 mice to study in vitro the influence of aging on (1) the fungicidal activity of neutrophils and macrophages, (2) the production of cytokines by resident peritoneal macrophages in response to C. albicans, and (3) cell surface Toll-like receptor (TLR) 2 expression on resident peritoneal macrophages. Our results indicate that murine phagocytes have a fungicidal activity well preserved with aging. In vitro production of proinflammatory cytokines (IL-6, IL-1beta, and tumor necrosis factor-alpha and chemokines (MIP-2) by purified (CD11b(+)) peritoneal macrophages in response to yeasts and hyphae of C. albicans was significantly lower in aged mice as compared with young mice. However, the production of IL-10 by macrophages, in response to C. albicans, was similar in both young and aged animals. Moreover, baseline TLR2 surface expression level was lower on aged macrophages than on control macrophages. Taken together, these data indicate that the increased susceptibility to C. albicans disseminated infections in aged mice is correlated with defects in TLR2 expression and in cytokine production, but not with an impaired fungicidal activity.