Accurate determination of mean cell volume by isotope dilution in erythrocyte populations with variable deformability.

Variations in erythrocyte deformability and morphology lead to artifacts in electronic determinations of mean cellular volume (MCV) by the aperture-impedance method. The micropipette-aspiration technique loses accuracy when applied to severely aberrant cells such as dense sickle cells. A new light-scattering technique requires that the cells be capable of undergoing isovolumetric sphering. In contrast, the isotope-dilution (ID) method measures absolute mean volume and is free of artifacts associated with abnormal deformability or morphology. It does not depend on any algorithms or correction factors and does not subject the cells to any stringent processing, not even centrifugation. The ID method can be used to determine the mean volume of red cells in hypo- or hypertonic media or in the presence of pharmacologic agents. It requires no more than a 1-ml aliquot of suspended cells at a hematocrit of at least 30%. The cells can be readily recovered, washed, and reused. Using EDTA labeled with 57Co as an extracellular space marker we have used ID to determine the MCV of fractionated normal human red blood cells (RBC), unfractionated RBC containing SS hemoglobin, and RBC from four other mammalian species. In the case of human RBC obtained from eight normal donors, we obtained mean MCV values (+/- SD) of 83.6 +/- 3.0, 87.5 +/- 3.9, and 76.5 +/- 5.3 fl for unfractionated and top and bottom 10% density fractions, respectively. The value 83.6 is significantly lower than the generally accepted range of 89-91 indicated by electronic analyzers calibrated against spun microhematocrits. The discrepancy of about 7% can account for the difference between mean cell hemoglobin concentration (MCHC) data determined by a calibrated Coulter Counter and corresponding data obtained with paired samples using a cyanmethemoglobin procedure specified in NCCLS Standard H15-A and corrected for trapped plasma.     

Genome-wide CRISPR Screens Reveal Host Factors Critical for SARS-CoV-2 Infection

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Identifying biochemical phenotypic differences between cryptic species

Molecular genetic methods can distinguish divergent evolutionary lineages in what previously appeared to be single species, but it is not always clear what functional differences exist between such cryptic species. We used a metabolomic approach to profile biochemical phenotype (metabotype) differences between two putative cryptic species of the earthworm Lumbricus rubellus. There were no straightforward metabolite biomarkers of lineage, i.e. no metabolites that were always at higher concentration in one lineage. Multivariate methods, however, identified a small number of metabolites that together helped distinguish the lineages, including uncommon metabolites such as Nε-trimethyllysine, which is not usually found at high concentrations. This approach could be useful for characterizing functional trait differences, especially as it is applicable to essentially any species group, irrespective of its genome sequencing status.     

Threonine synthetase from higher plants: Stimulation by S-adenosylmethionine and inhibition by cysteine

S-Adenosylmethionine greatly stimulates the formation of threonine from O-phosphohomoserine by an enzyme from sugar beet leaves. The stimulation due to S-adenosylmethionine is inhibited by cysteine. Cysteine and O-phosphohomoserine are incorporated into cystathionine by another enzyme. The results suggest that the conversion of O-phosphohomoserine to either threonine or cystathionine is regulated by the relative amounts of cysteine and S-adenosylmethionine present.     

Acidic fibroblast growth factor enhances peripheral nerve regeneration in vivo

When added to a collagen-filled nerve guide, purified acidic fibroblast growth factor (aFGF) increased the number of myelinated axons that regenerated across a 5-mm nerve gap distance. In addition, a greater number of primary sensory and motor neurons extended axons through the nerve guide in animals treated with aFGF. Thus the effect of aFGF on peripheral nerve regeneration is not simply an increase in axonal branching within the nerve guide tube. This is the first highly purified growth factor since nerve growth factor that has been shown to promote nerve regeneration in vivo. This experimental model provides a convenient and quantitative means to assess the effects of putative neuronotropic factors on peripheral nerve regeneration in vivo.     

Cyclic peptides revisited

A multistep computational scheme was used to deduce possible conformations for a cyclic antagonist analog of somatostatin that has been reported by Coy and coworkers. An algebraic algorithm was used to find dihedral angles that give cyclic structures, the energy was computed for these structures, the lower-energy structures were classified into conformational families, the energy was minimized for the lowest-energy member of each family, and finally, the structures from energy minimization were reclassified. Analysis revealed seven distinct conformational families that contain reverse turns. The families differ in the position of the turns in the primary sequence; frame-shifted turns are observed at each possible position.     

Constant light alters serum hormone levels related to thyroid function in male CD-1 mice

ABSTRACT

Disruptions to the circadian rhythm can lead to altered metabolism. Modification of thyroid function may be a reason why circadian misalignment may contribute to future metabolic disorders. We investigated whether circadian disruption through constant light (LL) can lead to variations in hormone levels associated with thyroid function. Mice were exposed to LL or a 12:12 Light:Dark (LD) cycle for 6 weeks; then glucose tolerance and thyroid hormone levels were measured at ZT 6 and ZT 18. There was day/night variation in glucose tolerance, but LL had no effect. LL reduced TSH, increased fT4, and abolished day/night variation in fT3 and leptin. These findings illustrate that LL alters thyroid-related hormones, providing evidence of a link between circadian disruption and thyroid function.