STRUCTURE OF THE ANISOGAMETES OF THE GREEN SIPHON PSEUDOBRYOPSIS SP. (CHLOROPHYTA)1

The fine structure of the male and female gametes of Pseudobryopsis, particularly that of the flagellar apparatus, is compared with that of swarmers of other green algae. There is general similarity, with differences in detail, to the Ulvales and other green siphons that have been studied. The similarities include overlapping basal bodies, the capping plate type of connective between basal bodies, terminal caps, and system II fibrous roots (rhizoplasts). The capping plate of the female gamete differs from that in other green siphons and the Ulvales in form and in the presence of a faint striation. A diagram illustrating the actual arrangement of the components of the flagellar apparatus is given, along with a discussion of the fact that the mirror image of the true arrangement has been given in some reports on ulvaphycean algae.     

The taxonomic and ecological status of the environmentally restricted spongillid species of North America. I. Spongilla sponginosa Penney 1957

The taxonomic validity, present distribution, and specific threats to the existence of the freshwater sponge,Spongilla sponginosa Penney were investigated. This species, reported only from the type locality, Week's Pond, Sumter County, South Carolina, has apparently been extirpated due to highly acidic pH levels in the pond water. Examination of holotype materials indicate some question of the validity of S. sponginosa as a distinct species.     

Induction of dopaminergic mesolimbic receptor supersensitivity by haloperidol

Prior exposure to neuroleptics augments the severity of apomorphine-induced stereotypy. This is regarded as a manifestation of increased sensitivity of striatal dopaminergic receptors and has been offered as a model of tardive dyskinesia. The purpose of this study was to determine if neuroleptics modify the sensitivity of mesolimbic dopaminergic receptors. Haloperidol or saline was administered to rats for four weeks. There followed a one week withdrawal period in which cannulae were placed bilaterally in the nucleus accumbens. Histological examination confirmed cannulae placement. Animals received 0, 1.0, 2.5, 5.0 or 10 μg of dopamine through both cannulae beginning eight days after the discontinuation of haloperidol or saline. Locomotor activity was measured in photocell-equipped cages. Animals with a prior exposure to haloperidol had significantly more locomotor activity than control animals. These results indicate that, in the rat, haloperidol can produce a supersensitive dopaminergic mesolimbic receptor.     

The XbaI-BlnI-CeuI genomic cleavage map of Salmonella enteritidis shows an inversion relative to Salmonella typhimurium LT2

We have established the genomic cleavage map of Salmonella enteritidis strain SSU7998 using pulsed-field gel electrophoresis. The chromosome of 4600kb was analysed by XbaI (16 fragments), I-CeuI (7 fragments) and BlnI (12 fragments); the genome also contains a plasmid of 60 kb. Cleavage sites of I-CeuI, in the large subunit ribosomal RNA gene, are conserved from Salmonella typhimurium and Escherichia coli K-12, and the XbaI and BinI sites in glt-tRNA are also conserved, but other sites are less conserved. Transposon Tn10, located at 60 different positions in the chromosome of S. typhimurium, was transduced by bacteriophage P22 into S. enteritidis and the insertion mapped using the XbaI and BlnI sites on Tn10. Gene order in S. enteritidis is identical to S. typhimurium LT2 and similar to E. coli K-12 except for an inversion of 815 kb, which covers the terminus region including T1 and T2. Endpoints are in the NDZs, or non-divisible zones, in which inversion endpoints were not detected in experiments in E. coli K-12 and S. typhimurium LT2. This inversion resembles the inversion between S. typhimurium and E. coli, but is longer at both ends.     

THE ROLE OF CYTOKININS IN THE “FASCIATION” DISEASE CAUSED BY CORYNEBACTERIUM FASCIANS

The disease caused by Corynebacterium fascians can be imitated by treatment with kinetin. Cultures of the bacteria were grown on a purine-free medium of known composition. They require thiamine. Two assays for cytokinin were developed; one depends on the release of lateral pea buds from apical dominance and is highly specific but of only moderate sensitivity. The other depends on the retention of chlorophyll in senescing oat leaves and is very sensitive (detecting 2 × 10^–4 μg of kinetin equivalents), though it is somewhat less specific and, therefore, requires care in usage. Both give results in 3–4 days and are thus far more rapid than tissue culture methods. With these assays C. fascians has been shown to produce a chloroform-soluble cytokinin active in both tests. The substance is stable to heat in acid or basic media, is soluble in non-polar solvents, and behaves as a base. It is precipitated from water solution by Ag ions and may, therefore, be a purine derivative. Pea tissue infected with C. fascians, but not uninfected tissue, yields a compound of similar solubilities and biological activity. Reasons are given for believing that the synthesis of cytokinins may be important, not only for C. fascians, but also for many other plant parasites.     

Sex and hormonal modification of 6-keto-PGF1α release by rat aorta

The stable breakdown product of prostacyclin, 6-keto-PGF_1α, was estimated in plasma samples after incubation with rat aortic rings. The 6-keto-PGF_1α concentration obtained with the male aortae was two-fold higher than that of the female. Ovariectomy markedly increased 6-keto-PGF_1α six-fold, but castration had no effect. Estradiol and progesterone treatment of the ovariectomized female suppressed (by 50%) and enhanced (two-fold) 6-keto-PGF_1α. Testosterone was without effect in gonadectomized males and females. Castrate males did not respond to gonadal steroid treatment.     

Simple inheritance,complex regulation: Supergene‐mediated fire ant queen polymorphism

The fire ant Solenopsis invicta exists in two alternate social forms: monogyne nests contain a single reproductive queen and polygyne nests contain multiple reproductive queens. This colony‐level social polymorphism corresponds with individual differences in queen physiology, queen dispersal patterns and worker discrimination behaviours, all evidently regulated by an inversion‐based supergene that spans more than 13 Mb of a “social chromosome,” contains over 400 protein‐coding genes and rarely undergoes recombination. The specific mechanisms by which this supergene influences expression of the many distinctive features that characterize the alternate forms remain almost wholly unknown. To advance our understanding of these mechanisms, we explore the effects of social chromosome genotype and natal colony social form on gene expression in queens sampled as they embarked on nuptial flights, using RNA‐sequencing of brains and ovaries. We observe a large effect of natal social form, that is, of the social/developmental environment, on gene expression profiles, with similarly substantial effects of genotype, including: (a) supergene‐associated gene upregulation, (b) allele‐specific expression and (c) pronounced extra‐supergene trans‐regulatory effects. These findings, along with observed spatial variation in differential and allele‐specific expression within the supergene region, highlight the complex gene regulatory landscape that emerged following divergence of the inversion‐mediated Sb haplotype from its homologue, which presumably largely retained the ancestral gene order. The distinctive supergene‐associated gene expression trajectories we document at the onset of a queen’s reproductive life expand the known record of relevant molecular correlates of a complex social polymorphism and point to putative genetic factors underpinning the alternate social syndromes.