EPR studies on the respiratory chain of wild-type Saccharomyces cerevisiae and mutants with a deficiency in succinate dehydrogenase

1. Three nuclear mutants of Saccharomyces cerevisiae deficient in succinate dehydrogenase have been isolated. Two of these mutants are allelic.

2. The amount of covalently bound flavin of submitochondrial particles of the two allelic mutants is about 14% and that of the third mutant about 50% of the amount in wild-type particles. The turnover number of succinate dehydrogenase of particles is decreased in all mutants. The turnover number of fumarate reductase is increased in the two allelic mutants, but decreased in the third mutant.

3. EPR spectra, measured at 82 °K, show that the amplitude of the g = 1.93 signal in particles of the two allelic mutants is less than 10% of that in wild-type particles. It is concluded that iron-sulphur centres other than those of succinate dehydrogenase make only a negligible contribution to the line at g = 1.93 in wild-type particles.

4. EPR measurements below 20 °K show that the amplitude of the signal at g = 2.01 detected in oxidized particles is decreased in particles of the two allelic mutants.

5. A signal with lines at g = 2.027 and g = 1.933 is detected at low temperatures in all particle preparations, even in those from a cytoplasmic petite mutant. It is suggested that this signal is derived from a contaminant and not from the inner membrane.     

Body fluid responses of heat-tolerant and intolerant men to work in a hot wet environment.

Acclimatization to heat before proceeding underground is a requirement for each South African mine laborer. Certain individuals among this large population cannot be acclimatized to heat (33.3 degrees C db, 31.7 degrees C wb) and are classified as heat intolerant. In this study certain body fluid responses to heat and work were compared between a group of 19 heat-tolerant (HT) and of 15 heat-intolerant (HI) subjects. To the factors known to affect heat tolerance such as age, weight, and oxygen consumption must now be added differences in body fluid responses. The HI group of subjects failed to hemodilute to the same degree as the HT group though working at the same relative work loads (30% and 50% VO2 max). As the 4-h work period (33.3 degrees C db, 31.7 degrees C wb) continued, the HI group did not maintain hemodilution in spite of the lower absolute work loads, sweat rates, and water deficits suffered by this group. From analysis of blood constituent changes it was suggested that the reason for the differences noted in body fluid dynamics concerned plasma protein equilibrium across capillary walls as well as the protein population of interstitial spaces.     

Morphometry, densitometry and pattern analysis of plastic-embedded histologic material from urothelial cell carcinoma of the bladder.

An image analysis method of grading histologic sections of bladder carcinoma was tested. The method was new in four respects. First, for fixation of the biopsies a coagulant fixative was used. Second, 2-microns plastic sections were used to ensure the reproducibility of nuclear imaging. Third, a new stereologic approach was used for calculation of the nuclear volume and DNA content. Fourth, for the classification rule the morphometric, densitometric and texture features were used in concert. The IBAS 2000 instrument was used for the measurements. Texture analysis of the chromatin patterns was performed using Markovian texture features. Using discriminant analysis, of 22 parameters, 2 morphometric, 2 densitometric and 3 texture features were selected for the classification rule. With them, 89% of the bladder carcinomas were correctly classified into the three grades. All grade III tumors were classified correctly. Among the features tested, the densitometry of the DNA had the highest F values. All of the grade III tumors and 45% of the grade II tumor group had DNA histograms indicating aneuploidy. This study showed that plastic-embedded material is well suited to morphometry and densitometry and can be used for quantitative grading of bladder carcinoma.     

Distribution of CT-rich tracts is conserved in vertebrate chromosomes

The distribution of d(CT)-rich pyrimidine tracts in the karyotypes of a variety of vertebrates was studied by in situ hybridization. The probe for these studies was a 56 bp homopyrimidine/homopurine sequence obtained from a mouse genomic library constructed with DNA prepared from a restriction enzyme digestion of metaphase chromosomes. Single-stranded DNA nuclease digestions and two-dimensional gel analysis of topoisomers of this sequence indicated that it is capable of adopting a triplex conformation in vitro. In situ hybridization with this probe to the karyotypes of ten different vertebrate species revealed a highly conserved chromosomal distribution of d(CT)-rich tracts. These tracts are found throughout the chromosomal arms and in some karyotypes they are clustered, producing a banding pattern. However, at the resolution of the light microscope these tracts appeared to be absent from the centromeric regions of all chromosomes examined except those of chicken. The non-random distribution of these tracts to the chromosomal arm regions implies an organizational or functional role for this repeat class. It is unlikely that the 56 bp sequence type contributed to the formation of the triplex DNA structure previously detected in centromeric domains of mouse.     

Accessing the Two‐Electron Charge Storage Capacity of MnO2 in Mild Aqueous Electrolytes

Rechargeable batteries based on MnO₂ cathodes, able to operate in mild aqueous electrolytes, have attracted attention due to their appealing features for the design of low‐cost stationary energy storage devices. However, the charge/discharge mechanism of MnO₂ in such media is still a matter of debate. Here, an in‐depth quantitative spectroelectrochemical analysis of MnO₂ thin‐films provides a set of unrivaled mechanistic insights. A major finding is that charge storage occurs through the reversible two‐electron faradaic conversion of MnO₂ into Mn²⁺ in the presence of a wide range of weak Brønsted acids, including the [Zn(H₂O)₆]²⁺ or [Mn(H₂O)₆]²⁺ complexes present in aqueous Zn/MnO₂ batteries. Furthermore, it is shown that buffered electrolytes loaded with Mn²⁺ are ideal to achieve highly reversible conversion of MnO₂ with both high gravimetric capacity and remarkably stable charging/discharging potentials. In the most favorable case, a record gravimetric capacity of 450 mA·h·g^?1 is obtained at a high rate of 1.6 A·g^?1, with a Coulombic efficiency close to 100% and a MnO₂ utilization of 84%. Overall, the present results challenge the common view on MnO₂ the charge storage mechanism in mild aqueous electrolytes and underline the benefit of buffered electrolytes for high‐performance rechargeable aqueous batteries.     

Applying Pharmacogenomics to Antifungal Selection and Dosing: Are We There Yet?

This review summarizes recent literature for applying pharmacogenomics to antifungal selection and dosing, providing an approach to implementing antifungal pharmacogenomics in clinical practice. The Clinical Pharmacogenetics Implementation Consortium published guidelines on CYP2C19 and voriconazole, with recommendations to use alternative antifungals or adjust voriconazole dose with close therapeutic drug monitoring (TDM). Recent studies demonstrate an association between CYP2C19 phenotype and voriconazole levels, clinical outcomes, and adverse events. Additionally, CYP2C19-guided preemptive dose adjustment demonstrated benefit in two prospective studies for prophylaxis. Pharmacokinetic–pharmacodynamic modeling studies have generated proposed voriconazole treatment doses based on CYP2C19 phenotypes, with further validation studies needed. Sufficient evidence is available for implementing CYP2C19-guided voriconazole selection and dosing among select patients at risk for invasive fungal infections. The institution needs appropriate infrastructure for pharmacogenomic testing, integration of results in the clinical decision process, with TDM confirmation of goal trough achievement, to integrate antifungal pharmacogenomics into routine clinical care.     

GeSUT4 mediates sucrose import at the symbiotic interface for carbon allocation of heterotrophic Gastrodia elata (Orchidaceae)

Gastrodia elata, a fully mycoheterotrophic orchid without photosynthetic ability, only grows symbiotically with the fungus Armillaria. The mechanism of carbon distribution in this mycoheterotrophy is unknown. We detected high sucrose concentrations in all stages of Gastrodia tubers, suggesting sucrose may be the major sugar transported between fungus and orchid. Thick symplasm‐isolated wall interfaces in colonized and adjacent large cells implied involvement of sucrose importers. Two sucrose transporter (SUT)‐like genes, GeSUT4 and GeSUT3, were identified that were highly expressed in young Armillaria‐colonized tubers. Yeast complementation and isotope tracer experiments confirmed that GeSUT4 functioned as a high‐affinity sucrose‐specific proton‐dependent importer. Plasma‐membrane/tonoplast localization of GeSUT4‐GFP fusions and high RNA expression of GeSUT4 in symbiotic and large cells indicated that GeSUT4 likely functions in active sucrose transport for intercellular allocation and intracellular homeostasis. Transgenic Arabidopsis overexpressing GeSUT4 had larger leaves but were sensitive to excess sucrose and roots were colonized with fewer mutualistic Bacillus, supporting the role of GeSUT4 in regulating sugar allocation. This is not only the first documented carbon import system in a mycoheterotrophic interaction but also highlights the evolutionary importance of sucrose transporters for regulation of carbon flow in all types of plant‐microbe interactions.     

The community structure of bird assemblages on urban strangler figs

Figs have been regarded as keystone plant resources that support diverse tropical vertebrate frugivore communities. Planting or conserving large fig trees, such as stranglers, have therefore been proposed for enhancing urban biodiversity. We compared the diversity and community structure of bird assemblages on strangler figs with non‐fig urban trees as well as between the fruiting and non‐fruiting fig trees in an urban setting in Singapore. The total bird abundance across all the fig trees when in fruit was 4.5‐fold higher than on non‐fig trees and 3.5‐fold higher than when the same fig trees were not fruiting, but only attracted two more species. On individual trees, after accounting for the presence of mistletoes, tree height, the area covered by buildings, road lane density, and the distance to natural vegetation, mean diversity was not different between non‐fig trees and fig trees when they were not in fruit. On the other hand, when fruiting, each fig tree on average had 1.4 more species, 3 more counts of non‐native birds, and 1.6 more counts of insectivorous birds than when not fruiting. There was significant compositional turnover between non‐fig trees and non‐fruiting fig trees, while community dispersion was significantly lower among fig trees in fruit. Our results demonstrate that fig trees provide fruit and non‐fruit resources for birds in an urban landscape but do not necessarily support more diverse total bird assemblages than non‐fig trees. Instead, bird communities on fruiting urban figs would be highly homogeneous and dominated by a few species. Abstract in Malay is available with online material.