Concentrations Of Certain Metabolites Research Articles

Single versus dual inoculation with indigenous Saccharomyces cerevisiae strains in winemaking.

Indigenous Saccharomyces cerevisiae strains and their combinations may be used to diversify wines and add complexity to sensory profiles. Here, two S. cerevisiae strains that represent regional genetic and phenotypic specificities for two major winegrowing areas of Greece were used in single- and mixed-culture fermentations. The kinetics and metabolic activities of the strains were analysed to evaluate the influence of each strain individually or in combination on wine quality. The two strains differentially affected the kinetics and the outcome of fermentation. They showed significant differences in the production of important metabolites that strongly affect the organoleptic profile of wines, such as volatile acidity, acetaldehyde, certain esters, and terpenes. Furthermore, the chemical and sensory profiles of wines produced by single cultures were different from those fermented by mixed culture inoculum. The concentration of certain metabolites was enhanced (e.g. isoamyl acetate, 1-heptanol), while others were suppressed (e.g. hexyl acetate, octyl acetate). Results highlight the potential worth of indigenous S. cerevisiae strains to differentiate local wines. The mixed culture S. cerevisiae inoculum was shown to generate novel wine characteristics, as compared to single cultures, thus offering alternatives to further diversify wines and increase their complexity.

Short-term exposure to antimony induces hepatotoxicity and metabolic remodeling in rats

Antimony (Sb) poses a significant threat to human health due to sharp increases in its exploitation and application globally, but few studies have explored the pathophysiological mechanisms of acute hepatotoxicity induced by Sb exposure. We established an in vivo model to comprehensively explore the endogenous mechanisms underlying liver injury induced by short-term Sb exposure. Adult female and male Sprague-Dawley rats were orally administrated various concentrations of potassium antimony tartrate for 28 days. After exposure, the serum Sb concentration, liver-to-body weight ratio, and serum glucose levels significantly increased in a dose-dependent manner. Body weight gain and serum concentrations of biomarkers of hepatic injury (e.g., total cholesterol, total protein, alkaline phosphatase, and the aspartate aminotransferase/alanine aminotransferase ratio) decreased with increasing Sb exposure. Through integrative non-targeted metabolome and lipidome analyses, alanine, aspartate, and glutamate metabolism; phosphatidylcholines; sphingomyelins; and phosphatidylinositols were the most significantly affected pathways in female and male rats exposed to Sb. Additionally, correlation analysis showed that the concentrations of certain metabolites and lipids (e.g., deoxycholic acid, N-methylproline, palmitoylcarnitine, glycerophospholipids, sphingomyelins, and glycerol) were significantly associated with hepatic injury biomarkers, indicating that metabolic remodeling may be involved in apical hepatotoxicity. Our study demonstrated that short-term exposure to Sb induces hepatotoxicity, possibly through a glycolipid metabolism disorder, providing an important reference for the health risks of Sb pollution.

Relationships between metabolic activity in the brain and circulating metabolites vary by sex

AbstractBackgroundGlucose hypometabolism in the brain measured by [F‐18] fluorodeoxyglucose (FDG) positron emission tomography has been observed in a number of neurological disorders. In both Down syndrome (DS) and non‐DS populations, it is associated with higher amyloid load and lower cognitive performance.MethodWe obtained plasma samples, FDG PET and [C‐11] Pittsburgh compound B (PiB) from a sample of 89 adults with DS (mean age [standard deviation] = 38.9[8.3] years). We measured levels of metabolites using targeted mass spectrometry. We calculated correlation constants between glucose uptake in discrete brain regions, global amyloid load, and plasma metabolite levels. We examined the effect of sex and age on these correlations.ResultWe found significant correlations between plasma metabolites, primarily lipids, and FDG PET signal in the brain with regional specificity. Additionally, metabolites which were positively associated with FDG PET signal in a specific brain region were negatively associated with amyloid load and vice versa. While FDG PET signal in each region were not significantly different between males and females, their correlation with metabolites did. When examining females only, we find primarily lipid correlates again. The lipid metabolites negatively associated with FDG PET signal were distinguished from those lipids positively correlated with FDG PET signal by lipid class and not fatty acid length. In males, a completely distinct set of associations between brain regions and metabolites were observed. The number of FDR significant correlations decrease dramatically, however the magnitudes of these correlation constants are higher than those observed in females and there is very little overlap between any of the brain regions correlated with each metabolite.ConclusionThe levels of brain amyloid and regional brain glucose metabolism in adults with DS are both reflected in the concentration of certain metabolites measured in blood plasma. Surprisingly, each brain region has its own orthogonal metabolic correlate. Moreover, these relationships are distinct in males and females. It will be important to explore the basis for these differences and determine if they are present in the general population. Future metabolic analysis of neurological diseases could also benefit from separate analysis in males and females so as not to obscure these differences.

Age, Sex, Body Mass Index, Diet and Menopause Related Metabolites in a Large Homogeneous Alpine Cohort.

Metabolomics in human serum samples provide a snapshot of the current metabolic state of an individuum. Metabolite concentrations are influenced by both genetic and environmental factors. Concentrations of certain metabolites can further depend on age, sex, menopause, and diet of study participants. A better understanding of these relationships is pivotal for the planning of metabolomics studies involving human subjects and interpretation of their results. We generated one of the largest single-site targeted metabolomics data sets consisting of 175 quantified metabolites in 6872 study participants. We identified metabolites significantly associated with age, sex, body mass index, diet, and menopausal status. While most of our results agree with previous large-scale studies, we also found novel associations including serotonin as a sex and BMI-related metabolite and sarcosine and C2 carnitine showing significantly higher concentrations in post-menopausal women. Finally, we observed strong associations between higher consumption of food items and certain metabolites, mostly phosphatidylcholines and lysophosphatidylcholines. Most, and the strongest, relationships were found for habitual meat intake while no significant relationships were found for most fruits, vegetables, and grain products. Summarizing, our results reconfirm findings from previous population-based studies on an independent cohort. Together, these findings will ultimately enable the consolidation of sets of metabolites which are related to age, sex, BMI, and menopause as well as to participants’ diet.

Predictors of phthalate metabolites in urine and follicular fluid and correlations between urine and follicular fluid phthalate metabolite concentrations among women undergoing in vitro fertilization

BackgroundPhthalate metabolites in follicular fluid (FF) may negatively affect normal folliculogenesis; however, the predictors of phthalate metabolite concentrations in urine and FF and relationships between urine and FF phthalate metabolite concentrations among women undergoing in vitro fertilization (IVF) are poorly understood. ObjectiveTo investigate predictors of phthalate metabolites in urine and FF and correlations between urine and FF phthalate metabolite concentrations among women undergoing IVF. MethodWe recruited 305 women seeking infertility treatment at a reproductive center in Wuhan, China, from October to November 2016. Information regarding demographic characteristics, personal care product use and plastic material contact was obtained through direct interviews. Concentrations of 8 phthalate metabolites in urine and FF samples were measured using high-performance liquid chromatography and tandem mass spectrometry. Associations regarding metabolite concentrations in urine and FF samples were analysed by Spearman's correlation and linear regression. Generalized linear regression was used to examine potential predictors of phthalate metabolite concentrations in urine and FF. ResultsWeak to moderate associations between urine and FF samples were found for monoethyl phthalate (MEP) and mono(2-ethyl-5-oxohexyl) phthalate (MEOHP) (correlation coefficient: MEP, 0.350; MEOHP, 0.377); no associations were observed for other metabolites. The predictive powers of urinary metabolite concentrations in determining FF metabolite concentrations were uniformly low, with R2 ≤ 0.113. Body mass index (BMI) and educational level were inversely associated with the urinary concentrations of certain metabolites. Higher household income, intake of bottled drinks within 48 h, and use of shower gel and soap were frequently associated with higher urinary metabolite concentrations. BMI, higher household income and use of disposable plastic cups within 48 h were associated with higher metabolite concentrations in FF. ConclusionPhthalate metabolite concentrations in urine and FF vary according to sociodemographic characteristics and lifestyle factors. Phthalate metabolite concentrations in urine may not be appropriate for estimating ovary phthalate exposure.

Serum Metabolites as Diagnostic Biomarkers for Cholangiocarcinoma, Hepatocellular Carcinoma, and Primary Sclerosing Cholangitis.

Early and differential diagnosis of intrahepatic cholangiocarcinoma (iCCA) and hepatocellular carcinoma (HCC) by noninvasive methods represents a current clinical challenge. The analysis of low‐molecular‐weight metabolites by new high‐throughput techniques is a strategy for identifying biomarkers. Here, we have investigated whether serum metabolome can provide useful biomarkers in the diagnosis of iCCA and HCC and could discriminate iCCA from HCC. Because primary sclerosing cholangitis (PSC) is a risk factor for CCA, serum metabolic profiles of PSC and CCA have also been compared. The analysis of the levels of lipids and amino acids in the serum of patients with iCCA, HCC, and PSC and healthy individuals (n = 20/group) showed differential profiles. Several metabolites presented high diagnostic value for iCCA versus control, HCC versus control, and PSC versus control, with areas under the receiver operating characteristic curve (AUC) greater than those found in serum for the nonspecific tumor markers carbohydrate antigen 19‐9 (CA 19‐9) and alpha‐fetoprotein (AFP), commonly used to help in the diagnosis of iCCA and HCC, respectively. The development of an algorithm combining glycine, aspartic acid, SM(42:3), and SM(43:2) permitted to accurately differentiate in the diagnosis of both types of tumors (biopsy‐proven). The proposed model yielded 0.890 AUC, 75% sensitivity, and 90% specificity. Another algorithm by combination of PC(34:3) and histidine accurately permitted to differentiate PSC from iCCA, with an AUC of 0.990, 100% sensitivity, and 70% specificity. These results were validated in independent cohorts of 14‐15 patients per group and compared with profiles found in patients with nonalcoholic fatty liver disease/nonalcoholic steatohepatitis. Conclusion: Specific changes in serum concentrations of certain metabolites are useful to differentiate iCCA from HCC or PSC, and could help in the early diagnosis of these diseases.

Serum metabolomic profiling predicts synovial gene expression in rheumatoid arthritis

BackgroundMetabolomics is an emerging field of biomedical research that may offer a better understanding of the mechanisms of underlying conditions including inflammatory arthritis. Perturbations caused by inflamed synovial tissue can lead to correlated changes in concentrations of certain metabolites in the synovium and thereby function as potential biomarkers in blood. Here, we explore the hypothesis of whether characterization of patients’ metabolomic profiles in blood, utilizing 1H-nuclear magnetic resonance (NMR), predicts synovial marker profiling in rheumatoid arthritis (RA).MethodsNineteen active, seropositive patients with RA, on concomitant methotrexate, were studied. One of the involved joints was a knee or a wrist appropriate for arthroscopy. A Bruker Avance 700 MHz spectrometer was used to acquire NMR spectra of serum samples. Gene expression in synovial tissue obtained by arthroscopy was analyzed by real-time PCR. Data processing and statistical analysis were performed in Python and SPSS.ResultsAnalysis of the relationships between each synovial marker-metabolite pair using linear regression and controlling for age and gender revealed significant clustering within the data. We observed an association of serine/glycine/phenylalanine metabolism and aminoacyl-tRNA biosynthesis with lymphoid cell gene signature. Alanine/aspartate/glutamate metabolism and choline-derived metabolites correlated with TNF-α synovial expression. Circulating ketone bodies were associated with gene expression of synovial metalloproteinases. Discriminant analysis identified serum metabolites that classified patients according to their synovial marker levels.ConclusionThe relationship between serum metabolite profiles and synovial biomarker profiling suggests that NMR may be a promising tool for predicting specific pathogenic pathways in the inflamed synovium of patients with RA.

Relationships between tyrosine, phenylalanine, chlorogenic acid, and ascorbic acid concentrations and blackspot biochemical potential and blackspot susceptibility in stored russet potatoes.

Blackspot in potato is an internal tissue discoloration that occurs during handling and transport of potato tubers. Blackspot is cosmetically undesirable and represents a huge economic cost for the potato industry. The aim of this study was to test whether concentrations of certain metabolites in the potato tuber cortex could predict blackspot susceptibility. Seven russet potato varieties were stored for eight months at 8.8 °C. Stored tubers were subjected to mechanical impact and evaluated for blackspot susceptibility. A blackspot susceptibility index was calculated for each variety by determining an index for the percentage of the tuber cortex area that was covered with blackspot, and an index for the intensity of blackspot discoloration. Concentrations of tyrosine, chlorogenic acid, phenylalanine, and ascorbic acid, and blackspot biochemical potential of tubers to synthesize pigments were measured in the tuber cortex. Blackspot indices, metabolites concentrations and blackspot biochemical potential varied significantly between varieties. Tyrosine concentrations strongly, significantly, and positively correlated with blackspot biochemical potential. Phenylalanine concentrations showed good, significant, and positive correlation with blackspot biochemical potential and discoloration index. None of the analyzed metabolites correlated with blackspot susceptibility. Concentrations of tyrosine and phenylalanine explained up to ∼80% of the variation in blackspot biochemical potential between varieties but did not correlate with blackspot susceptibility. © 2018 Society of Chemical Industry.

16-Channel Surface Coil for 13C-Hyperpolarized Spectroscopic Imaging of Cardiac Metabolism in Pig Heart

Magnetic resonance spectroscopy (MRS) of hyperpolarized 13C pyruvate and its metabolites in large animal models is a powerful tool for assessing cardiac metabolism in patho-physiological conditions. In 13C studies, a high signal-to-noise ratio (SNR) is crucial to overcome the intrinsic data quality limitation due to the low molar concentration of certain metabolites as well as the low flux of conversion. Since 13C-MRS is essentially a semi-quantitative technique, the SNR of the spectra acquired in different myocardial segments should be homogeneous. MRS coil design plays an important role in achieving both targets. In this study, a 16-channel receive surface coil was designed for 13C hyperpolarized studies of the pig heart with a clinical 3-T scanner. The coil performance was characterized by phantom experiments and compared with that of a birdcage coil used in transmit/receive mode. Segmental signal distribution in the left ventricle (LV) was assessed by experiments on six healthy mini pigs. The proposed coil showed a significant increase in SNR for the LV wall close to the coil surface with respect to that for the birdcage but also significant segmental inhomogeneity. Hence, the use of the 16-channel coil is recommended for studies of septal and anterior LV walls.

Biochemical and molecular characteristics of patients with organic acidaemias and urea cycle disorders identified through newborn screening

BackgroundIn recent years it has become clear that newborn screening (NBS) programmes using tandem mass spectrometry identify “patients” with “classical” inborn errors of metabolism who are asymptomatic. This observation raises issues regarding medicalization of “non-diseases,” potentially unnecessary treatment and unnecessary anxiety to parents. AimsThis study aims to identify possible markers that may assist in predicting the need for treatment of infants with “classical” organic acidaemias (OA) and urea cycle disorders (UCD) diagnosed through NBS. MethodsMedical records of all patients with classical OA and UCD detected through the Victorian NBS programme from February 2002 to January 2014, or diagnosed clinically between 1990 and January 2002 were retrospectively reviewed. ResultsNeonatal presentation did not always predict the need for on-going strict treatment. Blood concentrations of amino acids and acyl-carnitines and the changes thereof in follow-up samples correlated with severity in citrullinaemia-I, possibly isovaleric acidaemia but not in argininosuccinic aciduria or propionic acidaemia. Some specific mutations correlate with “attenuated” citrullinaemia-I. Gender may affect clinical outcome in propionic acidaemia. ConclusionsChanges in blood concentration of certain metabolites (amino acids, acyl-carnitines) in the first weeks of life may be predictive of the need for treatment in some disorders but not in others. Mutation analysis may be predictive in some disorders but whether or not this should be considered as second-tier testing in NBS should be discussed separately.

Antioxidant Responses and Renal Crystal Formation in Rainbow Trout Treated with Melamine Administered Individually or in Combination with Cyanuric Acid

In 2007 and 2008, renal stone formation and kidney damage in human infants were linked to consumption of melamine (MEL)-contaminated infant formula, as well as renal failure and death in pets due to pet food containing both MEL and cyanuric acid (CYA). The aim of this study was to examine the effects of MEL and CYA administered individually or in combination on concentrations of certain metabolites and enzyme activities that serve as markers for oxidative stress in kidney and liver of rainbow trout. In addition, the levels of muscle MEL and renal crystal formation were determined. Trout were fed MEL and/or CYA for 8 wk at 250, 500, or 1000 mg of each compound/kg in feed. Fish muscle residues of MEL exhibited a dose-response relationship. Coexposure of trout to MEL and CYA at the highest dose led to lower MEL residue concentrations in muscle compared to exposure to MEL alone. Renal MEL–CYA complexes were found in kidneys of fish treated with combined MEL and CYA. A dose response was evident with respect to both (1) number of trout displaying renal crystals and (2) number of crystals per fish. Changes in concentration of antioxidant parameters, such as glutathione, superoxide dismutase, catalase, glutathione peroxidase, and glutathione S-transferase, were recorded in both tissues of MEL- and CYA-dosed trout. Lipid peroxidation was more pronounced in kidney than liver. Therefore, feed contaminated with both MEL and CYA could be problematic for fish, as MEL administered to trout, individually or in combination with CYA, may facilitate the onset of oxidative damage in trout.

The Structural and Functional Diversity of Metabolite-Binding Riboswitches

The cellular concentrations of certain metabolites are assiduously monitored to achieve appropriate levels of gene expression. Although proteins have long been known to act as sensors in this capacity, metabolite-binding RNAs, or riboswitches, also play an important role. More than 20 distinct classes of riboswitches have been identified to date, and insights to the molecular recognition strategies of a significant subset of these have been provided by detailed structural studies. This diverse set of metabolite-sensing RNAs is found to exploit a variety of distinct mechanisms to regulate genes that are fundamental to metabolism.

Metabolite pattern of Cysticercus cellulosae metacestode from different predilection sites of swine using proton magnetic resonance spectroscopy.

Cysticercosis due to Taenia solium is one of the most common public health problems in various regions of the world. We have performed prolon magnetic resonance spectroscopy (1H MRS) experiments of the fluid aspirated from cysticerci excised from skeletal muscle (n = 16) and brain (n = 9) of infected swine to compare the metabolite pattern of cysticerci in different predilection sites. Perchloric acid extract of cysticercus cysts excised from skeletal muscles (n = 16) was also prepared to ascertain water-soluble, low molecular weight metabolites using 1H MRS. Absolute quantification and statistical analysis of different metabolites was done to look for any significant differences in different locations of cysts. The metabolite pattern of cysticerci was found to be similar in the various predilection sites. Metabolites observed were leucine, valine, alanine, lysine, glycine, lipid contents, lactate, glutamate, acetate, succinate, creatine, choline, and glucose. Concentration of creatine in cysticercus fluid of cysts removed from the muscle was found to be significantly higher (p = 0.001) than the cysts located in the brain. We conclude that the metabolite pattern in the cysticerci is not influenced by the surrounding tissue location; however concentration of certain metabolites may depend upon the tissue location.

Assessment of mammary gland metabolism in the sow: I. Development of methods for the measurement of cellular metabolites in milk and colostrum

We have modified deproteinization methods and a number of spectrophotometric and bioluminescent methods in order to measure the concentrations of cellular metabolites in small volumes (< 0.3 ml) of sows' colostrum and milk. For the majority of the assays, recoveries ranged from 92 to 105%. The binding of ATP and UTP to a calcium phosphate-citrate-caseinate complex in milk, and the decrease in ATP (92%/h) and UTP (18.1%/h) concentrations during in vitro incubation of the whey fraction suggested that it was unlikely ATP and UTP (both < 1 microM) could exist free in sows' milk. The mean concentrations (range) of cellular metabolites in milk (6-11 d post partum) were: glucose, 669 microM (220-1367); glucose 6-phosphate, 63.0 microM (27.6-101.4); glucose 1-phosphate, 18.3 microM (13.1-24.8); UDPglucose, 296 microM (170-494); UDPgalactose, 635 microM (230-945); lactose, 162 mM (124-187); UDP, 105 microM (85-130); UMP, 1760 microM (1326-2587); inorganic phosphate, 13.5 mM (1.4-29.3); ATP, < 0.5 microM; ADP, 53.6 microM (10.5-171.25); AMP, 215 microM (61.6-491.6); cAMP, 22.3 microM (3.5-61.6); galactose, 198 microM (118-474) and fructose, 226 microM (172-283). Differences in the concentrations of glucose, glucose 6-phosphate, glucose 1-phosphate, UDPgalactose and cAMP between fore and hind milk samples indicated postsecretory changes in the concentrations of certain metabolites. Changes in the concentrations of metabolites during in vitro incubation of milk and of colostrum suggested that these postsecretory changes were probably due to the actions of enzymes present in mammary secretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolic Appraisal of the Effects of Dietary Modification on Hypersensitive Bladder Symptoms

The concentration of certain metabolites and amino acids appears to be changed in patients with the painful bladder syndrome interstitial cystitis. A study of the metabolism of the arylalkylamines (tryptophan, tyrosine, tyramine, phenylalanine) was carried out in 250 patients (237 females, 13 males), revealing an inability to synthesise normal amounts of serotonin and MHPG, a noradrenaline metabolite. Furthermore, the absence of ammonia and tryptophan in urine confirmed the presence of a membrane leak. Dietary restriction lessened the symptoms but did not alter specific abnormalities in dopamine metabolism. Dietary management offers a cost-effective therapeutic approach.

Feeding frequency for lactating cows: diurnal patterns of hormones and metabolites in peripheral blood in relation to milk-fat concentration.

1. The present paper reports the effects of dietary modifications on the diurnal pattern of concentrations of certain metabolites and hormones in the peripheral blood of lactating dairy cows. The cows were given fixed rations of hay and high-cereal concentrates in the proportions of 30:70 or 10:90 (w/w). The concentrates were given in either two or six equal meals daily; the hay was given twice daily. 2. Previous reports of the same experiment had shown that milk-fat yield and concentration were reduced by increasing the proportion of concentrates in the diet and increased by more frequent feeding of the concentrates. These changes could be explained in part by changes in rumen volatile fatty acid (VFA) proportions and mean daily concentrations of VFA, particularly propionic acid, and insulin in the peripheral blood, but these factors failed to explain all the increase in milk-fat concentration caused by more frequent feeding. 3. Analysis of blood samples taken at hourly intervals for 24 h at two stages of lactation showed that, in the cows fed six times daily, the concentrations of metabolites and hormones remained relatively constant over the day. In the cows fed twice daily, the concentrations of VFA, 3-hydroxybutyric acid and insulin all increased after both meals whereas the concentrations of glucose and growth hormone tended to fall. The concentration of non-esterified fatty acids tended to increase overnight and fall rapidly after the morning feed. The concentrations of glucagon, thyroxine and prolactin showed no clear pattern in relation to meals. The postprandial responses of propionate, insulin and growth hormone were greater with the higher concentrate diet. 4. The maximum concentration and the diurnal range of concentrations were reduced by more frequent feeding of both diets in the case of propionic acid and of the higher concentrate diet in the case of insulin, but the effects on insulin concentrations of more frequent feeding of the lower concentrate diet were smaller and not significant. The maximum concentration and the diurnal range of concentrations of growth hormone were unaffected by meal frequency. 5. It is concluded that the severity of milk-fat depression in cows fed twice daily is increased by the rapid rise in propionic acid concentration in the peripheral blood after a meal, which in turn increases insulin secretion and may be accompanied by a suppression of growth hormone release. This causes lipogenesis to be diverted towards adipose tissue at the expense of the mammary gland.(ABSTRACT TRUNCATED AT 400 WORDS)

Formaldehyde-treated proteins for dairy cows--effects on blood hormone concentrations.

Seven Friesian heifers in mid-lactation were used in an experiment to measure the effects of including casein, formaldehyde-treated casein or formaldehyde-treated soya-bean meal in the diet on performance and on the concentrations of certain metabolites and hormones in the blood. 2. Milk yield and the concentration of fat, protein and lactose in milk were not affected by the treatments. 3. The concentration of growth hormone (GH) in jugular venous blood was higher with both formaldehyde-treated proteins than it was with untreated casein (P less than 0.05). Diet had no effect on insulin, prolactin or thyroxine concentrations in blood. 4. Urea concentration tended to be higher and non-esterified fatty acids lower in blood from heifers offered the diet containing untreated casein, but these differences were not statistically significant. Blood glucose concentration was not affected by dietary treatment. 5. It was concluded that blood GH concentration can be increased by offering protein supplements which will increase total amino acid supply to the intestines in lactating cattle. This appears to be a direct effect on GH status independent of effects on milk yield.

Large Amounts of Ribosomal RNA in Colchicine-induced Tetraploids of Solanum tuberosum L.

CHANGES of ploidy cause various phenotypic effects, and alterations in metabolism have also been noted1–5. These alterations are reflected in differences in concentration of certain metabolites in the various ploid levels. The variation in amount of a given metabolite depends on genotype and species involved4,5. A consistent relationship has, however, been established between the amount of DNA and ploid level regardless of genotype6,7. This communication presents a relationship between ploid level, DNA content, and RNA fractions in 2n and 4n potato analogues.

Societies and Academies

LONDON. Royal Society, Nov. 5.—Sir F. Gowland Hopkins and K. A. C. Elliott: The relation of glutathione to cell respiration with special reference to hepatic tissue. The relative capacity of various mammalian tissues to reduce the disulphide form of glutathione under anaerobic conditions has been determined. The course of the oxidation of the thiol group during the survival respiration of the hepatic tissue of various animals has been followed. That the concentration of certain metabolites in the liver is wholly, or in part, responsible for the maintenance and amount of reduction is shown by the effects of administering or withholding food. In general the initial marked delay in the disappearance of the – SH group during aeration is observed only in the liver of well-fed animals; after relatively brief periods of fasting it is much lessened and may not be observed. If extra glutathione in the disulphide form be added to the freshly excised tissue before aeration, the existence of residual active hydrogen is revealed. In spite of vigorous aeration the concentration of – SH then rises during the earlier periods of survival, though ultimately the whole is oxidised. The amount of this extra pressure-head of hydrogen consistently differs in the livers of different species. The origin of the active hydrogen which reduces the disulphide grouping is at present unknown. The transport of hydrogen to molecular oxygen by the path in question, though representing but a small part of the total respiration, may, therefore, prove to represent a specialised and significant aspect of tissue oxidations.—Lord Rutherford and C. D. Ellis: The origin of γ-rays. Calculations are made of the probability of escape of the α-particles from radium C and of the average tune of transition of the γ-particle for different energies of the γ-ray. The strongest γ-ray group, which corresponds to the emission of a β- or γ-ray of energy l.426 × 106 volts, represents an abnormal mode of transition compared with other groups. The time of transition is very long, and it may be, as suggested by R. H. Fowler, that the transition is radiationless, the surplus energy being directly transferred to one or more of the outer electrons of the atom. Many of the lines in the β-ray spectrum may be a result of similar radiationless transitions. In explanation of the complicated γ-ray spectrum of radium C it is suggested that more than one α-particle in the nucleus may occupy the same energy level.—A. V. Hill: Myothermic experiments on the frog's gastrocnemius. An arrangement is described by which the ‘initial’ heat set free in the contraction of a frog's gastrocnemius can be measured in absolute units. A single fine thermocouple of constantan-iron is employed, the ‘hot’ junction lying inside the muscle. It may be applied to single twitches, to groups of twitches, or to tetani up to 25 seconds in duration. The mean value of Tl/H, the isometric heat coefficient in a twitch, is 13.4. This is twice the mean value found in sartorii. The difference is due to the fact that in gastrocnemii the fibres, or parallel fibre bundles, run, on the average, only half the length of the muscle. A modification is described of the method recently suggested by Bozler of “calibrating” by condenser discharges. This is far simpler and more accurate than the old method employing an alternating current. The specific heats of muscle and blood have been determined. For a given water content they are the same. The density of a tissue depends upon the amount of solid it contains. This provides a simple and accurate method of measuring, without the labour of drying and weighing, the percentage of solid in a muscle.