Odonates,gregarines and water mites: why are the same host species infected by both parasites?

1. Damselflies and dragonflies are widely parasitised insects and numerous studies have tried to understand this host–parasite relationship. However, most of these studies have concentrated on a single host species, neglecting the larger pattern within the Odonata order. 2. The aim of this paper was to examine different damselfly and dragonfly species for common endo‐ and ectoparasites and whether a general infection pattern can be found. Additionally, the goal was to investigate whether the phylogeny of the host species could explain these possible infection patterns. To this end, a dataset from the existing literature was compiled and the prevalence of endoparasitic gregarines and ectoparasitic water mites was analysed for 46 different odonate species. 3. Three distinct patterns were found: (i) most of the odonate host species had both gregarines and water mites, rather than only either one or neither; (ii) there appears to be a positive association between gregarine and water mite prevalences across host species; (iii) a weak phylogenetic signal was detected in gregarine prevalence and a strong one in water mite prevalence. 4. It is hypothesised that, due to the infection and transmission mechanisms by which water mites and gregarines infect different odonate host species, parasitism is aggregated to common, high‐density species. However, much research is needed in order to fully understand this relationship between odonates and their parasites, especially within the same host populations and host species assemblages.     

Mitochondrial and cytosolic hexokinase from rat brain: one and the same enzyme?

Rat brain mitochondrial hexokinase (ATP: D-hexose 6-phosphotransferase, EC 2.7.1.1) was solubilized by treatment of the mitochondria with glucose 6-phosphate and partly purified. The solubilized enzyme was compared with the cytosolic enzyme fraction. The solubilized and cytosolic enzymes were also compared with the enzyme bound to the mitochondrial membrane. The following observations were made. 1. There is no difference in electrophoretic mobility on cellulose-acetate between the cytosolic and the solubilized enzyme. Both fractions are hexokinase isoenzyme I. 2. There is no difference in kinetic parameters between the cytosolic or solubilized enzymes (P less than 0.001). For the cytosolic enzyme Km for glucose was 0.067 mM (S.E. = 0.024, n = 7); Km for MgATP2- was 0.42 mM (S.E. = 0.13, n = 7) and Ki,app for glucose 1,6-diphosphate was 0.084 mM (S.E. = 0.011, n = 5). For the solubilized enzyme Km for glucose was 0.071 mM (S.E. = 0.021, n = 6); Km for MgATP2- was 0.38 mM (S.E. = 0.11, n = 6) and Ki,app for glucose 1,6-diphosphate was 0.074 mM (S.E. = 0.010, n = 5). However when bound to the mitochondrial membrane, the enzyme has higher affinities for its substrates and a lower affinity for the inhibitor glucose 1,6-diphosphate. For the mitochondrial fraction Km for glucose was 0.045 mM (S.E. = 0.013, n = 7); Km for MgATP2- was 0.13 mM (S.E. = 0.02, n = 7) and Ki,app for glucose 1,6-diphosphate was 0.33 mM (S.E. = 0.03, n = 5). 3. The cytosolic and solubilized enzyme could be (re)-bound to depleted mitochondria to the same extent and with the same affinity. Limited proteolysis fully destroyed the enzyme's ability to bind to depleted mitochondria. 4. Our data support the hypothesis that soluble- and solubilizable enzyme from rat brain are one and the same enzyme, and that there is a simple equilibrium between the enzyme in these two pools.     

Do the constraints of human speciation cause expression of the same set of genes in brain, testis, and placenta?

Evolution appears to be especially rapid during speciation, and the genes involved in speciation should be evident in species such as humans that have recently speciated or are presently in the process of speciation. Haldane's rule is that when one sex is sterile or inviable in interspecific F(1) hybrids, it is usually the heterogametic sex. For mammals, this implicates genes on the X chromosome as those particularly responsible for speciation. A preponderance of sex- and reproduction-related genes on the X chromosome has been shown repeatedly, but also mental retardation genes are more frequent on the X chromosome. We argue that brain, testis, and placenta are those organs most responsible for human speciation. Furthermore, the high degree of complexity of the vertebrate genome demands coordinate evolution of new characters. This coordination is best attained when the same set of genes is redeployed for these new characters in the brain, testis, and placenta.     

Malaria,COVID-19 and angiotensin-converting enzyme 2: what does the available population data say?

The etiopathogenesis of COVID-19 and its differential geographic spread suggest some populations are apparently ‘less affected’ through many host-related factors that involve angiotensin-converting enzyme 2 (ACE2) protein, which is also the entry receptor for SARS-CoV-2. The role of ACE2 has been well studied in COVID-19 but not in the context of malaria and COVID-19. We have previously suggested how malaria might intersect with COVID-19 through ACE2 mutation and here we evaluate the currently available data that could provide a link between the two diseases. Based on the existing global and Indian data on malaria, COVID-19 and the suggested ACE2 mutation, the association could not be examined robustly, neither accepting nor refuting the suggested hypothesis. We strongly recommend targeted evaluation of this hypothesis through carefully designed robust molecular epidemiological studies.     

Body temperature and sleep: Are they controlled by the same mechanism?

Simultaneous changes in sleep and body temperature, produced either by lesion or by stimulation of the medial preoptic area (mPOA), have given reasons to suggest that thermoregulation and sleep regulation are controlled by the same set of neurons. The reasons for simultaneous changes in these parameters are discussed in the present paper with a view to explaining the relationship between thermoregulation and sleep regulation. Changes in body temperature and sleep on destruction of the preoptic area (POA) neurons and the sequence of these changes, suggest a separate control mechanism in the mPOA for regulation of sleep and body temperature. Evidence is put forward in the present paper to show that the mPOA is not involved in the downregulation or upregulation of changes in body temperature with alteration in the vigilance state. On the other hand, circadian modulation of body temperature is possibly involved in altering sleep propensity. A clear indication regarding separate control of sleep and body temperature came from the studies in which noradrenergic agents were applied into the mPOA of animals with and without lesion of the noradrenergic fibers projecting to the mPOA. Experiments in which sleep was analyzed after experimental manipulations of ambient temperature and body temperature, including peripheral, core and brain temperature, are presented here to show a close relationship between thermoregulation and sleep regulation. Various theories regarding the regulation of body temperature during slow wave sleep and rapid eye movement sleep are also discussed. The functional integrity of the mPOA may be essential not only for the regulation of body temperature and sleep-wakefulness but even for the homeostatic regulation of energy balance of the body in response to alterations in environmental temperature and sleep-wakefulness.

     

Maturation characteristics of Rubus pennsylvanicus fruit: are black and red the same?

Summary Fruit of the blackberry, Rubus pennsylvanicus Poir. (Rosaceae), were examined to determine variation in maturation characteristics. Maturation timing and rate varied greatly among individual fruits, resulting in a bi-colored fruiting display comprised largely of two maturation stages, pre-ripe (salmon and scarlet) and ripe (dark brown and black). While ripe fruit were generally larger and heavier than pre-ripe fruit, exhibiting greater fresh and dry fruit weight, diameter, water content, and total seed weight, no significant differences were found in energy content, i.e. numbers of calories per gram pulp, or in pulp:seed ratio. The differences between ripe and pre-ripe fruit appear to be due largely to an increase in water content and seed weight with maturity. The fact that little energetic benefit accrues to the preferential selection of ripe fruit suggests that bi-colored Rubus displays may be considered to be unicolored.     

Are fear memories made and maintained by the same NMDA receptor-dependent mechanisms?

A recent finding indicates that inducible knockout of the NR1 NMDA receptor subunit promotes the loss of fear memories formed months earlier. One view is that posttraining NMDA receptor activation protects modified synapses from "synaptic drift." An alternative view is that NMDA receptors help maintain appropriate connectivity in memory-encoding networks.     

Are NADP-dependent isocitrate dehydrogenases and ferredoxin-dependent glutamate synthase co-regulated by the same photoreceptors?

Activities of NADP-dependent isocitrate dehydrogenases (cytosolic and plastidic isoforms, ICDH1 and ICDH2; EC 1.1.1.42) and ferredoxin-dependent glutamate synthase (Fd-GOGAT; EC 1.4.7.1) in turions of Spirodela polyrhiza were all stimulated by light. Single or repeated red light (R) pulses induced the activity of the enzymes and this effect was reverted by subsequent far-red light (FR) pulses. The enzymes are, therefore, co-regulated by the low-fluence response of phytochrome. For ICDH, this is reported here for the first time. Neither an effect of the very low-fluence response nor of the FR-mediated high-irradiance response was detectable. Irradiance with continuous R resulted in enhanced enzyme activities and protein levels (Western analysis using polyclonal antibodies against ICDH1 and Fd-GOGAT). These additional effects of continuous R (called a non-induction effect) could be inhibited for ICDH1 and ICDH2 by the inhibitor of photosynthetic electron transport, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, and are therefore related to the effect of photosynthesis. In contrast, the non-induction effect of Fd-GOGAT was resistant against this inhibitor. Moreover, hourly R pulses did not replace the effect of continuous R. The non-induction effect of light on the activity and protein level of Fd-GOGAT was therefore tentatively classified as an R-mediated high-irradiance response. The activity of Fd-GOGAT but not that of ICDHs was additionally regulated by a specific blue-light receptor. It can be concluded that the levels of ICDHs and Fd-GOGAT were coordinated by light but were not co-regulated by the same photoreceptors. Nitrate is necessary for the light regulation of both enzymes, contributing to the coordinated expression of the relevant genes.Abbreviations DCMU 3-(3,4-Dichlorophenyl)-1,1-dimethylurea - Fd-GOGAT Ferredoxin-dependent glutamate synthase - FR Far-red light - HIR High-irradiance response - ICDH NADP-dependent isocitrate dehydrogenase - ICDH1 Cytosolic ICDH - ICDH2 Chloroplastic ICDH - LFR Low-fluence response - R Red light - SDS–PAGE Denaturing polyacrylamide gel electrophoresis - VLFR Very low-fluence response     

Are egg yolk lipoproteins metabolized by the chick embryo in the same manner as plasma lipoproteins are in the adult?

• 1.1. Egg yolk very low density lipoproteins were found to contain proteins with cofactor activity for lipoprotein lipase.
• 2.2. Lipoprotein lipase activity in adipose tissue of chick embryos increased several-fold on days 16 and 17, coinciding with the time when utilization of yolk lipoproteins by the embryo becomes rapid.
• 3.3. Embryonic blood plasma was found to contain cholesterol esterifying activity.

     

Transmission stages of Plasmodium: does the parasite use the one same signal, provided both by the host and the vector, for gametocytogenesis and sporozoite maturation?

Among the microorganisms that strictly depend upon other organisms (hosts or vectors) for achieving their life cycle, protozoan and metazoan parasites have been often primarily distinguished through the major pathogenic processes they could induce. A variety of different mechanisms linked to parasitism can indeed systemically (e.g. Plasmodium falciparum) or locally (e.g. Toxoplasma gondii) induce important alterations of tissue homeostasis. But more than obvious pathogenicity, it is the capacity to be transmitted that is essential for parasite survival and there is increasing evidence that certain parasites can achieve their life cycle to the point of transmission in the absence of clinically detectable processes. For this, constitutive microenvironments of the host or vector can be exploited. Moreover, parasites are sometimes able to highjack effectors of the host's immune response towards conditioning the microenvironments which are permissive to differentiation of transmissible developmental stages. Based on a few examples taken from studies on the transmission stages of Leishmania, Toxoplasma and Plasmodium, we have here attempted to formulate a few hypothesis on the biology of the transmission stages of P. falciparum, i.e. on gametocytogenesis and sporozoite maturation. As discussants, we may have been somewhat dwarfed by issues evoked by the organizers of this meeting in the title of the session, i.e. 'Vector-parasite-man interactions'!... In reaction, we may have taken refuge in somewhat over-selective comments, biased by the objects of our personal research....     

Synthesis,and In Vitro and In Silico α-Glucosidase Inhibitory Studies of 5-Chloro-2-Aryl Benzo[d]thiazoles

Twenty-five derivatives of 5-chloro-2-aryl benzo[d]thiazole (1–25) were synthesized and evaluated for their α-glucosidase (S. cerevisiae EC 3.2.1.20) inhibitory activity in vitro. Among them eight compounds showed potent activity with IC₅₀ values between 22.1 ± 0.9 and 136.2 ± 5.7 μM, when compared with standard acarbose (IC₅₀ = 840 ± 1.73 μM). The most potent compounds 4, 9, and 10 showed IC₅₀ values in the range of 22.1 ± 0.9 to 25.6 ± 1.5 μM. Compounds 2, 5, 11, and 19 showed IC₅₀ values within the range of 40.2 ± 0.5 to 60.9 ± 2.0 μM. Compounds 1 and 3 were also found to be good inhibitors with IC₅₀ values 136.2 ± 5.7 and 104.8 ± 9.9 μM, respectively. Their activities were compared with α-glucosidase inhibitor drug acarbose (standard) (IC₅₀ = 840 ± 1.73 μM). The remaining compounds were inactive. Structure-activity relationships (SAR) have also been established. Kinetics studies indicated compounds 2, 3, 10, 19, and 25 to be non-competitive, while 1, 5, 9, and 11 as competitive inhibitors of α-glucosidase enzyme. All the active compounds (1–5, 9–11, and 19) were also found to be non-cytotoxic, in comparison to the standard drug i.e., doxorubicin (IC₅₀ = 0.80 ± 0.12 μM) in MTT assay. Furthermore, molecular interactions of active compounds with the enzyme binding sites were predicted through molecular modeling studies.     

Environmental variability and population dynamics: do European and North American ducks play by the same rules?

Density dependence, population regulation, and variability in population size are fundamental population processes, the manifestation and interrelationships of which are affected by environmental variability. However, there are surprisingly few empirical studies that distinguish the effect of environmental variability from the effects of population processes. We took advantage of a unique system, in which populations of the same duck species or close ecological counterparts live in highly variable (north American prairies) and in stable (north European lakes) environments, to distinguish the relative contributions of environmental variability (measured as between‐year fluctuations in wetland numbers) and intraspecific interactions (density dependence) in driving population dynamics. We tested whether populations living in stable environments (in northern Europe) were more strongly governed by density dependence than populations living in variable environments (in North America). We also addressed whether relative population dynamical responses to environmental variability versus density corresponded to differences in life history strategies between dabbling (relatively “fast species” and governed by environmental variability) and diving (relatively “slow species” and governed by density) ducks. As expected, the variance component of population fluctuations caused by changes in breeding environments was greater in North America than in Europe. Contrary to expectations, however, populations in more stable environments were not less variable nor clearly more strongly density dependent than populations in highly variable environments. Also, contrary to expectations, populations of diving ducks were neither more stable nor stronger density dependent than populations of dabbling ducks, and the effect of environmental variability on population dynamics was greater in diving than in dabbling ducks. In general, irrespective of continent and species life history, environmental variability contributed more to variation in species abundances than did density. Our findings underscore the need for more studies on populations of the same species in different environments to verify the generality of current explanations about population dynamics and its association with species life history.     

Are contents of Rubisco, soluble protein and nitrogen in flag leaves of rice controlled by the same genetics?

Genetic relations among the contents of Rubisco, soluble protein and total leaf nitrogen (N) in leaves of rice (Oryza sativa L.) were studied by quantitative trait loci (QTL) analysis with a population of backcross inbred lines (BILs) of japonica Nipponbarexindica Kasalath. The ratio of Rubisco to total leaf N in leaves is the main target in improving photosynthetic N-use efficiency in plants. QTLs controlling Rubisco content were not detected near QTLs for total leaf N content. These results indicate that contents of Rubisco and total leaf N are controlled by different genetics. QTLs that controlled the ratio of Rubisco to total leaf N (CORNs) were detected. These results suggest that some mechanism(s) may be involved in determining this ratio, while the contents of Rubisco and total leaf N are controlled in other ways. In elite BILs, the ratios of Rubisco to total leaf N were higher than those of both parents. These results suggest a good possibility of improving N-use efficiency by CORNs in cultivated rice. A QTL controlling Rubisco content was mapped near a QTL for soluble protein content on chromosome 8 at 5 d after heading and on chromosome 9 at 25 d. In each chromosome region, the peaks of both QTLs overlapped accurately, giving a high possibility of pleiotropic effects by the same genes. Different QTLs controlling soluble protein or Rubisco were detected from those detected at 5 d or 25 d after heading. This suggests that these traits are genetically controlled depending on the growth stages of leaves.     

How are the phenologies of ripening and seed release affected by species' ecology and evolution?

The phenology of seed ripening and release are important for dispersal, reproductive success and survival of plants. Most phenological studies, however, consider early phenological phases. Here, we examined the ecological and evolutionary basis of ripening and seed release phenology. We monitored single flower phenology for 104 plant species from 30 families and three life forms from central Europe. Further, we undertook an associate monitoring study along an elevational gradient over two years. We calculated temperature demands (as growing degree days) for ripening and seed release and examined them with respect to the species’ seed mass, life form, dispersal mode and phylogeny. We found a strong correlation between species’ seed mass and temperature demands for ripening. For both variables seed mass and temperature demands for seed ripening, we found a strong effect of the species phylogeny. These phylogenetic signals indicate that the evolutionary history of the species’ lineage affects its seed mass and the temperature demands for seed ripening. Among the studied life forms, shrub species showed the most efficient ripening process. Anemochorous species showed lower relative humidity during seed release than epizoochorous species. For anemochorous species, the synchronisation of release timing with periods that show favourable environmental conditions for wind dispersal could be interpreted as a phenological adaptation to increase dispersal distances. According to the monitoring along the elevational gradient, individuals from higher altitudes showed lower temperature demands for ripening than individuals from lower altitudes. This might tentatively indicate physiological adaptations to lower temperature demands for locations with a shorter growing season. Our study provides basic insights into the ecological, environmental and evolutionary constraints that shape the ripening and seed release phenology of plants. We introduce data that can be used to advance existing models of ripening phenology, seed release and plant spread.     

Analysis of [2H7]methionine, [2H4]methionine,methionine, [2H4]homocysteine and homocysteine in plasma by gas chromatography–mass spectrometry to follow the fate of administered [2H7]methionine

Homocysteine plays a key role in several pathophysiological conditions. To assess the methionine–homocysteine kinetics by stable isotope methodology, we developed a simultaneous quantification method of [²H₇]methionine, [²H₄]methionine, methionine, [²H₄]homocysteine and homocysteine in rat plasma by gas chromatography–mass spectrometry (GC–MS). [¹³C]Methionine and [¹³C]homocysteine were used as analytical internal standards to account for losses associated with the extraction, derivatization and chromatography. For labeled and non-labeled homocysteine measurements, disulfide bonds between homocysteine and other thiols or proteins were reduced by dithiothreitol. The reduced homocysteine and methionine species were purified by cation-exchange chromatography and derivatized with isobutyl chlorocarbonate in water–ethanol–pyridine. Quantification was carried out by selected ion monitoring of the molecular-related ions of N(O,S)-isobutyloxycarbonyl ethyl ester derivatives on the chemical ionization mode. The intra- and inter-day precision of the assay was less than 6% for all labeled and non-labeled methionine and homocysteine species. The method is sensitive enough to determine pharmacokinetics of labeled methionine and homocysteine.     

What are the roles of substrate-assisted catalysis and proximity effects in peptide bond formation by the ribosome?

The action of the peptidyl transferase center of the large ribosomal unit presents a fundamental step in the evolution from the RNA world to the protein world. Thus, it is important to understand the origin of the catalytic power of this ancient enzyme. Earlier studies suggested that the ribosome catalyzes peptide bond formation by using one of its groups as a general base, while more recent works have proposed that the catalysis is due to proximity effects or to substrate-assisted catalysis. However, the actual nature of the catalytic mechanism remains controversial. This work addresses the origin of the catalytic power of the ribosome by using computer simulation approaches and comparing the energetics of the peptide bond formation in the ribosome and in water. It is found that a significant part of the observed activation entropy of the reference solution reaction is due to solvation entropy, and that the proximity effect is smaller than previously thought. It is also found that the 2'-OH of the A76 ribose, which is associated with a large rate acceleration in the ribosome reaction, does not catalyze peptide bond formation in water. Thus, the catalytic effect cannot be attributed to substrate-assisted catalysis but rather to the effect of the ribosome on the reacting system. Overall, our calculations indicate that the reduction of the activation free energy is mainly due to electrostatic effects. The nature of these effects and their relationship to catalytic factors in modern enzymes is analyzed and discussed.     

In vitro metabolism of testosterone to 17ß-hydroxy-5α-androstane-3-one and 5α-androstane-3α, 17ß-diol by the rat intestine

The metabolism of testosterone to 17ß-hydroxy-5α-androstane-3-one and 5α-androstane-3α, 17ß-diol by the 800 g supernatant fraction by different parts of the gastrointestinal tract from male rats was investigated. This metabolism tended to be higher in immature than in mature animals. Administration of dexamethasone or long-acting ACTH to immature and mature rats increased testosterone metabolism to 17ß-hydroxy-5α-androstane-3-one and 5α-androstane-3α, 17ß-diol by ileum tissue. No such effect could be observed following administration of progesterone, estradiol, prolactin, LH or FSH in mature animals. Development of the gastrointestinal tract from the immature to themmature stage was associated with augmented metabolism of testosterone to 17ß-hydroxy-5α-androstane-3-one and 5α-androstane-3α,17ß-diol in the ileum.