An Analysis of Seed Development in Pisum sativum: VI. ABSCISIC ACID ACCUMULATION

The abscisic acid (ABA) content of wrinkled (rr) pea seed tissueshas been quantified during development using multiple-ion-monitoringcombined gas chromatography-mass spectrometry and a deuteratedinternal standard. The level of ABA in the embryo generallyincreased with increasing cotyledon fresh weight while thatin the testa showed a distinct maximum at the time of maximumendosperm volume and the slowing in the growth of the testa.Pods contained relatively little ABA on a fresh weight basis.The total seed ABA content showed a biphasic distribution, thefirst maximum following the maximum growth rate of the testaand the second that of the embryo. The biphasic distributionof ABA in the pea seed was confirmed using a second pea genotype,near-isogenic to the first except for the r locus, and by theanalysis of individual seeds using a radioimmunoassay for ABA.The first maximum was composed mainly of a testa component andthe second mainly of an embryo component. When plants were grownin different environments, wrinkled seeds were found to containslightly more ABA than round (RR) but this was only significantlate in development. Immature seeds were capable of metabolizing17'-deoxy ABA to ABA, as determined by incorporation of either³H or ²H, and the metabolite was present mainly in the testa.The production of ABA in pea seeds is discussed in relationto the development of the different seed tissues. Key words: Abscisic acid, peas, seed development     

Bryozoan frontal shields: the type species of Desmacystis, Rhamphostomella, Rhamphosmittina, Rhamphostomellina, and new genus Arctonula

Frontal shields have been examined in the type species of several genera of ascophorine cheilostomates. Desmacystis (Desmacystidae) is not an'anascan'as previously thought, but has a cryptocystal shield which is here interpreted to be derived from an umbonuloid shield by foreshortening, possibly from a rhamphostomellan ancestor. Rhamphostomella (type species Rscabra ) and Rhamphosmittina (type species R. bassleero ) (both in the family Porellidae Vigneaux, here raised from subfamily rank) also have umbonuloid shields. Arctomula , new genus, is established for Lepralia arctica M. Sars and transferred from the Umbonulidae to the Exochellidac. Rhamphostomellina (type species R. posidoniue ) has a lepralioid shield. It is here included in the family Celleporidae.     

Class Seticoronaria and Phylogeny of the Phylum Priapulida

The Recent class Seticoronaria (Priapulida) as represented by the genus Maccabeus is compared with the newly described Priapulida from the Middle Cambrian Burgess Shale. It is concluded that the Seticoronaria retained such plesiomorphic characters of the Cambrian Priapulida as sedentary life and food trapping tentacles, whereas the other Recent class, the Priapulomorpha, is the derived, apomorphic branch of this small phylum. The bearing of this hypothesis on an eventual phylogenetic sequence of the Metazoa is discussed.     

Tumour Induction by Cell-free Extracts derived from Mice with Graft versus Host Disease

A SUBSTANTIAL proportion of inbred mice, in which a protracted form of the graft versus host reaction (GVHR) is induced, eventually develop lymphoreticular tumours¹. This experimental mouse model can be used to study the role of immune reactions in cancer induction. One possibility is that the immune disturbance activates a latent oncogenic virus. That such activation can occur has been demonstrated in C57BL mice². In this strain, with its low spontaneous leukaemic incidence, thymic lymphomas are induced by an irradiation-activated leukaemogenic virus. In man, there is suggestive evidence that Burkitt's lymphoma may be caused by a combination of virus infection and immunological stimulation³.     

Analysis of the Antigenic Relationships Among Trichomonas,Histomonas, Dientamoeba,and Entamoeba. I. Quantitative Fluorescent Antibody Methods*

SYNOPSIS. Antigens were prepared from axenic Entamoeba histolytica, Entamoeba invadens, and Trichomonas gallinae; dixenic Dientamoeba fragilis; and agnotobiotic Histomonas meleagridis cultures. Antisera were developed in rabbits against each of these species by subcutaneous inoculations of homogenized organisms with complete Freund's adjuvant. The globulin fraction of each serum was conjugated with fluorescein isothiocyanate (FITC) and then processed on Sephadex G-25 and DEAE-cellulose columns. Fluorescein/protein ratios were determined for the several DEAE fractions obtained from each of the 5 conjugated globulins, and those with ratios of approximately 3.0 were selected for use in all experiments. Conjugated anti-Dientamoeba and anti-Histomonas fractions were absorbed with the bacterial flora present in the respective cultures before being used for staining. Intact, formalin-fixed organisms of each of the species were subjected to direct staining, inhibition staining, and staining with cross-absorbed conjugated fractions. The emitted fluorescence was measured in an ultramicrofluorimeter. Cross reactions among the 5 antigens and 5 conjugated antisera suggested that very few, if any, common antigens were shared by Trichomonas and Entamoeba. They indicated also a close antigenic relationship between Trichomonas and Histomonas on the one hand and between Histomonas and Dientamoeba on the other. Trichomonas and Dientamoeba appeared to be less closely related, and still less relationship was noted between Dientamoeba and Entamoeba. Only very weak reactions were recorded between Histomonas and Entamoeba. Entamoeba invadens emitted much fluorescence after being stained with anti-Entamoeba histolytica conjugate and similar results were obtained by reciprocal staining. The phylogenetic implications of the immunologic findings are discussed.