1,4-Thiomorpholine-3,5-dicarboxylic acid, a novel cyclic imino acid detected in bovine brain

Gas-liquid chromatography of enriched bovine brain extract revealed the occurrence of several sulfur-containing compounds. By co-chromatography with authentic product and by mass-spectrometric analysis, one of these compounds has been identified as 1,4-thiomorpholine-3,5-dicarboxylic acid (TMDA). The possible derivation of TMDA from lanthionine is discussed. This represents the second S-containing cyclic amino acid so far discovered in a mammalian brain whose physiological significance has not yet been explored.     

Similarity of the oxidation products of L-cystathionine by L-amino acid oxidase to those excreted by cystathioninuric patients

L-Cystathionine is oxidized by snake venom L-amino acid oxidase at a rate about half that with L-leucine at pH 8.5. The appearance of an absorbance at 296 nm and quantitation of the products of oxidation in the presence of catalase indicate formation in the solutions of a seven-membered ketimine ring produced by cyclization of the monoamino monoketo derivative of cystathionine. A limited double deamination has also been observed. In the absence of catalase, S-(carboxymethyl)homocysteine and S-(beta-carboxyethyl)cysteine have been identified together with ninhydrin-unreactive compounds yielding the above mentioned carboxy compounds upon hydrolysis with HCl. Authentic samples of the monoamino monoketo analogs of cystathionine have been prepared and compared with the enzymatic products. Cyclization of the synthetic products into the ketimine ring is pH-dependent as established by UV spectrum and other assays. Compounds derived from either the oxidation or the reduction of the ketimine have been prepared. It was found that many products of enzymatic and chemical changes of cystathionine and its ketimine described in the present paper are identical with those identified in the urine of cystathioninuric patients. This result indicates the occurrence in humans of secondary metabolic routes of cystathionine centered on the production of cystathionine ketimine, in equilibrium with the open form, which in cystathioninurics is revealed by the lack of cystathionase.     

Slow cortical potential biofeedback and the startle reflex

The negativity of slow cortical potentials (SCP) of the surface EEG is a measure of brain excitability, correlating with motor and cognitive preparation. Selfcontrol of SCP positivity has been shown to reduce seizure activity. Following SCP biofeedback from a central EEG electrode position, subjects gained bidirectional control over their SCP. The current study used a modified feedback methodology, and found a positive relationship between negativity and magnitude of EMG startle response (a measure of cortical and subcortical arousal, particularly aversive response disposition). Greater success in SCP differentiation was associated with self-report of less relaxation during negativity training.This research was supported by the Deutsche Forschungsgemeinschaft under grant No. SFB 307.     

Interaction between gamma-carboxyglutamic acid and glutamate dehydrogenase

The amino acid γ-carboxyglutamic acid, recently discovered in some vitamin K-dependent blood-clotting factors, shows interesting kinetic effects on glutamate dehydrogenase. It is not metabolized by the enzyme; it is a powerful competitive inhibitor (K_i = 3.8 × 10^?4 m) with respect to NAD⁺ and glutamate. On the other hand the reverse reaction is activated by γ-carboxyglutamate, both K_m and V being altered; this effect is additive with the well-known activating effect of ADP.     

Sulfur-containing cyclic ketimines and imino acids. A novel family of endogenous products in the search for a role.

Aminoethylcysteine, lanthionine, cystathionine and cystine are mono-deaminated either by L-amino-acid oxidase or by a transaminase exhibiting the properties described for glutamine transaminase. The deaminated products cyclize producing the respective ketimines. Authentic samples of each ketimine were prepared by reacting the appropriate aminothiol compound with bromopyruvate, except cystine ketimine which required the interaction of thiopyruvate with cystine sulfoxide. Reduction of the first three mentioned ketimines with NaBH4 yields the respective derivatives with the saturated rings of thiomorpholine and hexahydrothiazepine. The same reduction is carried out enzymically by a reductase extracted from mammalian tissues. Properties of the members of this family of compounds are described. Gas chromatography followed by mass spectrometry permits the identification of most of these products. HPLC is very useful for the determination of the ketimines by taking advantage of specific absorbance at 380 nm obtained by prior derivatization with phenylisothiocyanate. Adaptation of these and other analytical procedures to biological samples disclosed the presence of most of these compounds in bovine brain and in human urine. By using [35S]lanthionine ketimine as a representative member of the ketimine group, the specific, high-affinity, saturable and reversible binding to bovine brain membranes has been demonstrated. The binding is removed by aminoethylcysteine ketimine and by cystathionine ketimine indicating the occurrence in bovine brain of a common binding site for ketimines. The reduced ketimines are totally ineffective in competing with [35S]lanthionine ketimine. Alltogether these findings are highly indicative for the existence in mammals of a novel class of endogenous sulfur-containing cyclic products provided with a possible neurochemical function to be investigated further.     

Dimerization and other changes of aminoethylcysteine ketimine.

High performance liquid chromatography and gas liquid chromatography have been used for the study of the stability of aminoethylcysteine-ketimine (AECK) in different experimental conditions. Concentration and acidic pH lead to the formation of the dimer of AECK which is very sensitive to temperature and is slowly converted to the corresponding decarboxylated dimer even at room temperature. In the presence of air at neutral and alkaline pH AECK is converted to an unknown compound having spectral characteristics similar to AECK and to other compounds not detectable by HPLC. Under nitrogen at neutral pH AECK is more stable and only undergoes the dimerization reaction to some extent.     

NLRP3 inflammasome suppression improves longevity and prevents cardiac aging in male mice

While NLRP3‐inflammasome has been implicated in cardiovascular diseases, its role in physiological cardiac aging is largely unknown. During aging, many alterations occur in the organism, which are associated with progressive impairment of metabolic pathways related to insulin resistance, autophagy dysfunction, and inflammation. Here, we investigated the molecular mechanisms through which NLRP3 inhibition may attenuate cardiac aging. Ablation of NLRP3‐inflammasome protected mice from age‐related increased insulin sensitivity, reduced IGF‐1 and leptin/adiponectin ratio levels, and reduced cardiac damage with protection of the prolongation of the age‐dependent PR interval, which is associated with atrial fibrillation by cardiovascular aging and reduced telomere shortening. Furthermore, old NLRP3 KO mice showed an inhibition of the PI3K/AKT/mTOR pathway and autophagy improvement, compared with old wild mice and preserved Nampt‐mediated NAD⁺ levels with increased SIRT1 protein expression. These findings suggest that suppression of NLRP3 prevented many age‐associated changes in the heart, preserved cardiac function of aged mice and increased lifespan.     

Program and Abstracts of the 16th Transgenic Technology Meeting (TT2020)

The world stands at a new threshold today. As a planet, we face various challenges, and the key one is how to continue to produce enough food, feed, fiber, and fuel to support the burgeoning population. In the past, plant breeding and the ability to genetically engineer crops contributed to increasing food production. However, both approaches rely on random mixing or integration of genes, and the process can be unpredictable and time-consuming. Given the challenge of limited availability of natural resources and changing environmental conditions, the need to rapidly and precisely improve crops has become urgent. The discovery of CRISPR-associated endonucleases offers a precise yet versatile platform for rapid crop improvement. This review summarizes a brief history of the discovery of CRISPR-associated nucleases and their application in genome editing of various plant species. Also provided is an overview of several new endonucleases reported recently, which can be utilized for editing of specific genes in plants through various forms of DNA sequence alteration. Genome editing, with its ever-expanding toolset, increased efficiency, and its potential integration with the emerging synthetic biology approaches hold promise for efficient crop improvement to meet the challenge of supporting the needs of future generations.

     

Serum Iron Levels and the Risk of Parkinson Disease: A Mendelian Randomization Study

Background

Although levels of iron are known to be increased in the brains of patients with Parkinson disease (PD), epidemiological evidence on a possible effect of iron blood levels on PD risk is inconclusive, with effects reported in opposite directions. Epidemiological studies suffer from problems of confounding and reverse causation, and mendelian randomization (MR) represents an alternative approach to provide unconfounded estimates of the effects of biomarkers on disease. We performed a MR study where genes known to modify iron levels were used as instruments to estimate the effect of iron on PD risk, based on estimates of the genetic effects on both iron and PD obtained from the largest sample meta-analyzed to date.

Methods and Findings

We used as instrumental variables three genetic variants influencing iron levels, HFE rs1800562, HFE rs1799945, and TMPRSS6 rs855791. Estimates of their effect on serum iron were based on a recent genome-wide meta-analysis of 21,567 individuals, while estimates of their effect on PD risk were obtained through meta-analysis of genome-wide and candidate gene studies with 20,809 PD cases and 88,892 controls. Separate MR estimates of the effect of iron on PD were obtained for each variant and pooled by meta-analysis. We investigated heterogeneity across the three estimates as an indication of possible pleiotropy and found no evidence of it. The combined MR estimate showed a statistically significant protective effect of iron, with a relative risk reduction for PD of 3% (95% CI 1%–6%; p = 0.001) per 10 µg/dl increase in serum iron.

Conclusions

Our study suggests that increased iron levels are causally associated with a decreased risk of developing PD. Further studies are needed to understand the pathophysiological mechanism of action of serum iron on PD risk before recommendations can be made. Please see later in the article for the Editors'' Summary