Properties of chromatin subunits from developing trout testis.

When a sample of trout testis nuclei is digested with micrococcal nuclease, the DNA is cleaved almost entirely to discrete fragments approximately 200 base pairs long and multiples thereof. The same DNA fragments can be obtained when isolated chromatin, as opposed to intact nuclei, is nuclease digested. These DNA fragments can also be found in discrete chromatin "subunits" isolated from nuclease-digested nuclei. Sedimentation through sucrose gradients or velocity sedimentation in an analytical ultracentrifuge separates these chromatin subunits into 11 S (monomer), 16 S (dimer), and 22 S (trimer) etc. species. Subunits can also be fractionated on a Sepharose 2B column equilibrated and run in low salt. High salt (greater than 40 mM NaCl) or divalent cations (congruent to 5 mM) cause subunit precipitation. Chromatin subunits have a protein to DNA ratio of approximately 1.2 and contain all the histones, including the trout-specific histone T. There are, however, no detectable nonhistone chromosomal proteins. Mg-2+ precipitates of the 11 S chromatin monomers, when pelleted, are thin and clear, while oligomer Mg-2+ pellets are thick and white. This could reflect a more symmetrical or ordered packing of 11 S monomers, which are deficient in histone I. This histone may cross-link the larger oligomers, resulting in a disordered Mg-2+ complex. These results are consistent with the subunit model of chromatin structure, based on 200 base pair long regions of DNA associated with histones. These subunits would be separated by nuclease-sensitive DNA spacer regions and cross-linked by histone I.     

Formaldehyde mutagenesis in the nematode Caenorhabditis elegans

We have found that formaldehyde is capable of inducing mutations in the nematode Caenorhabditis elegans. 4 concentrations of formaldehyde were tested. At a concentration of 1%, formaldehyde is lethal to the nematode, and 0.01% formaldehyde did not induce any mutations in approx. 60 000 tested chromosomes. 2 concentrations of formaldehyde, 0.1% and 0.07%, were found to be mutagenic, inducing both point mutations and deficiencies in the unc-22 region of linkage group IV.4 of the point mutations have been demonstrated to be alleles of the unc-22 gene and have been mapped within the locus. 2 of the putative deficiencies have been confirmed. Each spans the unc-22 gene and at least 2 other genes in the region. A rough estimate of the forward mutation frequency using 0.1% formaldehyde in this region is 3 × 10⁻⁵, while for 0.07% the frequency is 2 × 10⁻⁴.     

Population structure and evolution of the Bacillus cereus group

Representative strains of the Bacillus cereus group of bacteria, including Bacillus anthracis (11 isolates), B. cereus (38 isolates), Bacillus mycoides (1 isolate), Bacillus thuringiensis (53 isolates from 17 serovars), and Bacillus weihenstephanensis (2 isolates) were assigned to 59 sequence types (STs) derived from the nucleotide sequences of seven alleles, glpF, gmk, ilvD, pta, pur, pycA, and tpi. Comparisons of the maximum likelihood (ML) tree of the concatenated sequences with individual gene trees showed more congruence than expected by chance, indicating a generally clonal structure to the population. The STs followed two major lines of descent. Clade 1 comprised B. anthracis strains, numerous B. cereus strains, and rare B. thuringiensis strains, while clade 2 included the majority of the B. thuringiensis strains together with some B. cereus strains. Other species were allocated to a third, heterogeneous clade. The ML trees and split decomposition analysis were used to assign STs to eight lineages within clades 1 and 2. These lineages were defined by bootstrap analysis and by a preponderance of fixed differences over shared polymorphisms among the STs. Lineages were named with reference to existing designations: Anthracis, Cereus I, Cereus II, Cereus III, Kurstaki, Sotto, Thuringiensis, and Tolworthi. Strains from some B. thuringiensis serovars were wholly or largely assigned to a single ST, for example, serovar aizawai isolates were assigned to ST-15, serovar kenyae isolates were assigned to ST-13, and serovar tolworthi isolates were assigned to ST-23, while other serovars, such as serovar canadensis, were genetically heterogeneous. We suggest a revision of the nomenclature in which the lineage and clone are recognized through name and ST designations in accordance with the clonal structure of the population.     

Age changes in the mitochondria and succinoxidase system of the Leydig cell

Summary The succinic dehydrogenase and cytochrome oxidase content of the Leydig cell were studied by histochemical means in the mouse during the first ten weeks of postnatal life; ultrastructural details of Leydig mitochondria were examined at the same time.Both enzymes appear at the end of the third week; mitochondria are present at all ages and do not change with advancing maturity. All three constituents increase with age, the increase is most marked during the 4th–6th weeks of life, and all increase at a compound rate of about 12% per day. The three components are closely related, though some succinic dehydrogenase may have an extra-mitochondrial locus; their increase is thought to be merely an expression of Leydig tissue growth and does not represent a true rise in cellular or mitochondrial enzyme concentrations. Acknowledgment. The author is grateful for the research facilities provided in the Anatomy Department of the University of Glasgow.     

Group A streptococcal phage T12 carries the structural gene for pyrogenic exotoxin type A

Summary In this paper we describe the meiotic pairing behavior of two free duplications in Caenorhabditis elegans. sDp1 is a duplication of approximately 30 map units of the right portion of linkage group I including unc-74 to unc-54. This duplication pairs, recombines, and apparently segregates from one of the normal homologues. A second duplication, sDp2, is a duplication of approximately 15 map units of the left portion of the linkage group. sDp2 was not observed to recombine with the normal homologue but did suppress exchange between the two normal homologues in a sDp2/ ++ / dpy-5 unc-35 heterozygote. Although a number of free duplications have been described previously in Caenorhabditis elegans, none of these have been shown to pair with normal homologues. The meiotic behavior of the duplications described in this paper can be understood assuming the existence in C. elegans chromosomes of pairing sites of the type described in D. melanogaster chromosomes (I. Sandler 1956; Hawley 1980).     

Habitat and host associations of the fish‐burrowing parasite Artystone minima (Cymothoidae: Isopoda) in eastern Amazonia

Cymothoid fish parasites settle on hosts in ways that may impact fish health and energetics. High abundances of Artystone minima observed in Nannostomus beckfordi from the Jeju River in eastern Amazonia were investigated to answer the following questions: (a) What factors are associated with the high prevalence at this locality?; (b) Is high abundance associated with co‐infestation of alternative hosts?; and (c) Is parasite presence associated with host species growth and/or reproduction? Fish assemblages were sampled quarterly (August 2017–May 2018) from five habitats along with environmental data. Parasitic indices were calculated, and parasite presence used to evaluate differences in growth of hosts using analysis of covariance considering host sex and sampling season (wet vs. dry). Parasites were only abundant in one of the habitats, a large, shallow backwater bay with macrophytes. Abiotic environmental factors (flow and depth) likely impact parasite transmission and are, therefore, particularly important in producing these local patterns. Two secondary hosts, Hyphessobrycon cf. rosaceus and Moenkhausia collettii, were found in the wet season. Based on host biology compared to other fish in the habitat, parasite infestation is inferred to be depth associated and long‐term infestation is apparently limited in alternative hosts. Parasite presence was significantly associated with reduced weight (standardized for length) of female Nannostomus beckfordi in the wet season. Furthermore, ovaries of non‐parasitized females from the wet season presented a range of maturation stages, while parasitized females were all immature, indicating a significant association of parasites with host reproductive capacity. Abstract in Portuguese is available with online material     

The ortholog of the human proto‐oncogene ROS1 is required for epithelial development in C. elegans

The orphan receptor ROS1 is a human proto‐oncogene, mutations of which are found in an increasing number of cancers. Little is known about the role of ROS1, however in vertebrates it has been implicated in promoting differentiation programs in specialized epithelial tissues. In this study we show that the C. elegans ortholog of ROS1, the receptor tyrosine kinase ROL‐3, has an essential role in orchestrating the morphogenesis and development of specialized epidermal tissues, highlighting a potentially conserved function in coordinating crosstalk between developing epithelial cells. We also provide evidence of a direct relationship between ROL‐3, the mucin SRAP‐1, and BCC‐1, the homolog of mRNA regulating protein Bicaudal‐C. This study answers a longstanding question as to the developmental function of ROL‐3, identifies three new genes that are expressed and function in the developing epithelium of C. elegans, and introduces the nematode as a potentially powerful model system for investigating the increasingly important, yet poorly understood, human oncogene ROS1. genesis 51:545–561. © 2013 Wiley Periodicals, Inc.     

Lipidomics Reveals Early Metabolic Changes in Subjects with Schizophrenia: Effects of Atypical Antipsychotics

There is a critical need for mapping early metabolic changes in schizophrenia to capture failures in regulation of biochemical pathways and networks. This information could provide valuable insights about disease mechanisms, trajectory of disease progression, and diagnostic biomarkers. We used a lipidomics platform to measure individual lipid species in 20 drug-naïve patients with a first episode of schizophrenia (FE group), 20 patients with chronic schizophrenia that had not adhered to prescribed medications (RE group), and 29 race-matched control subjects without schizophrenia. Lipid metabolic profiles were evaluated and compared between study groups and within groups before and after treatment with atypical antipsychotics, risperidone and aripiprazole. Finally, we mapped lipid profiles to n3 and n6 fatty acid synthesis pathways to elucidate which enzymes might be affected by disease and treatment. Compared to controls, the FE group showed significant down-regulation of several n3 polyunsaturated fatty acids (PUFAs), including 20:5n3, 22:5n3, and 22:6n3 within the phosphatidylcholine and phosphatidylethanolamine lipid classes. Differences between FE and controls were only observed in the n3 class PUFAs; no differences where noted in n6 class PUFAs. The RE group was not significantly different from controls, although some compositional differences within PUFAs were noted. Drug treatment was able to correct the aberrant PUFA levels noted in FE patients, but changes in re patients were not corrective. Treatment caused increases in both n3 and n6 class lipids. These results supported the hypothesis that phospholipid n3 fatty acid deficits are present early in the course of schizophrenia and tend not to persist throughout its course. These changes in lipid metabolism could indicate a metabolic vulnerability in patients with schizophrenia that occurs early in development of the disease.     

Species traits explain variation in detectability of UK birds

Capsule Heterogeneous detectability amongst species may impact multi-species bird surveys and if not accounted for, may bias community level conclusions. Estimates of detectability were produced for 195 UK bird species, and detectability was significantly affected by bird size, diet and habitat specialization.

Aims To estimate detectability and understand which species traits may impact detectability.

Methods We estimated the detectability of 195 species of birds in the UK using distance sampling methods and examined the average detectability of genetically related groups. We tested the significance of species traits in describing variation in detectability, whilst controlling for phylogenetic relationships.

Results Passeriformes had the lowest median detectability of 0.37 and Charadriiformes the highest median detectability of 0.65, of the seven largest orders considered. Species most associated with closed habitats such as woodland and urban areas had the lowest detectability. Smaller species had lower detectability than larger species.

Conclusion Heterogeneity in species detectability could lead to biased conclusions, particularly when calculating multi-species indices such as species richness or diversity. Accounting for detectability will be most important in studies that cover a wide range of habitat types or a diverse spread of taxa.