CONTRIBUTION OF POLLEN MORPHOLOGY TO SYSTEMATICS OF COLLOMIA (POLEMONIACEAE)

Pollen morphology of 14 species of Collomia (Polemoniaceae) was examined by light microscopy, and by both scanning and transmission electron microscopy. Four distinct pollen types were observed which are based principally upon 1) shape, number and distribution of apertures, and 2) surface sculpturing: Type 1—zonocolporate with striate ridges; Type 2—zonocolporate with striato-reticulate ridges; Type 3—pantoporate with radiate ridges; Type 4—pantoporate with irregularly reticulate ridges. Evaluation of pollen morphology reveals considerable discrepancy with respect to presently accepted sectional classification. Collomia grandiflora of sect. Collomia has a pollen type similar to that of members of sect. Collomiastrum and is now interpreted as representing an independent evolutionary line derived from the latter section. Collomia diversifolia of sect. Courtoisia has a pollen morphology similar to that of sect. Collomia. whereas C. heterophylla of the same section possesses pollen unique within the genus. This last pollen type shows close similarity to the pollen of members of Polemonium, Gilia, Leptodactylon, and Ipomopsis. Pollen of C. tinctoria and C. tracyi of sect. Collomia are anomalous within Polemoniaceae. No significant difference in exine stratification was discernible among the four pollen types.     

VEGETATIVE AND FLORAL RELATIONSHIPS AMONG WESTERN NORTH AMERICAN POPULATIONS OF COLLOMIA LINEARIS NUTTALL (POLEMONIACEAE)

Thirty-seven characters were measured on greenhouse grown progenies of twenty-three populations representing, for Collomia linearis, a broad geographical and ecological distribution in western North America. Twelve vegetative and seventeen floral characters showed significant among-population/within-population variance ratios (F-statistics). Overall, floral characters showed higher F-statistics than did vegetative characters. The F-statistics and character means were used to construct phenograms based on weighted similarity measures and single-linkage clustering. With the exception of a homogeneous cluster comprising northern Rocky Mountain OTUs, relationships based on floral characters were geographically random. No clearly defined morphological trends toward increased autogamy were observed in association with geographical or ecological distribution. Several clustering relationships, based on vegetative characters, were interpreted as representing geographically unrelated genotypes convergent with respect to ecotypic differentiation. The most distinctive clusters of OTUs in the vegetative phenogram were associated with subalpine and wet meadow sites, habitats considered as ecologically marginal for the species. Comparison of the two phenograms revealed considerable disparity between relationships based on floral characters and those based on vegetative characters. This disparity lends support to the hypothesis that floral and vegetative character combinations are subject to independent selective processes. The absence of polyploidy or mitotically detectable chromosomal rearrangements indicates that the observed variation among widely separated populations represents either divergence or convergence via genetic differentiation at the diploid level.     

Use of trypsin for rapid and efficient purification of murine sarcoma and leukemia virus

A method is described for purification of MSV-MuLV from culture supernatant of chronically infected 78A₁ rat embryo cell line. This method involves direct polyethylene glycol-NaCl precipitation of the low speed supernatant of culture fluid followed by digestion of the pellet with trypsin. This procedure efficiently disrupts large aggregates which normally entrap most of the virus. Highly purified virus can be obtained in very good yield by a combination of sedimentation velocity and isopycnic centrifugation : yields up to 100 A₂₈₀ units (17 mg of protein) of purified virus per liter of culture fluid can be observed. This procedure appears well suited for large scale isolation of virion associated enzymatic activities.     

Analysis of nucleolus organizer regions (NORs) in mitotic and polytene chromosomes ofPhaseolus coccineus by silver staining and Giemsa C-banding

Chromosomes with active nucleolus organizer regions (NORs) were visualized in root tip metaphases ofPhaseolus coccineus using the silver staining technique. A mean number of 5.5 Ag-NORs per cell was observed in 54 cells from eight plants. In the endopolyploid nuclei of the suspensor the silver technique did not demonstrate the reported specificity for nucleolus organizer activity, because there was usually pale staining of nucleoli and preferential staining of heterochromatic regions in the polytene chromosomes including pericentromeric material, telomeres and NORs. The mean number of NORs per nucleolus as detected by this method was 5.8 (28 nucleoli analysed). Using a modified preparation technique, giant chromosomes stained pale, but nucleoli of suspensor cells displayed darkly silver staining internal domains, each of which originating from a nucleolus organizer.—Giemsa C-banding of endopolyploid suspensor nuclei revealed C-positive nucleolus organizers with darkly staining intranucleolar fibrils. The latter were frequently involved in inter-NOR associations. In 34 nucleoli analysed, the mean number of Giemsa C-positive NORs per nucleolus was 6.0.Dedicated to Professor Dr.Lothar Geitler on the occasion of his 80th birthday.     

Structural and membrane modifying properties of suzukacillin,a peptide antibiotic related to alamethicin: Part B. Pore formation in black lipid films

Suzukacillin, a polypeptide consisting of presumably 23 amino acids and 1 phenylalaninol, is produced by a Trichoderma viride strain No. 1037 and it can be isolated from the culture medium. It shows membrane-modifying properties similar to those of alamethicin. Discrete conductance fluctuations indicate the formation of oligomer pores of varying diameter. On the basis of voltage jump relaxation experiments evidence is given that the dimer is the nucleation state from which pore formation tion starts and the oligomer disappears. According to the voltage-current characteristics, voltage-dependent and voltage-independent conductances are observed. A slow process is involved, which can be interpreted as a change in the equilibrium distribution between different conformations of the suzukacillin monomer at the membrane interphase. This change results from its interaction with the lipid matrix. Differences in experimental observations between suzukacillin and alamethicin are attributed to the relatively larger α-helix and higher number of aliphatic side chains of the suzukacillin monomer and to a more intense interaction with the lipid membrane. This leads to a higher probability of forming dimers from monomers and to the occurrence of “inactivation”.     

Antigen-binding cells in central and peripheral lymphoid tissues of the rabbit

The rosette assay was used to study antigen-binding activity by cells in lymphoid tissues of rabbits immunized with sheep red blood cells and in unimmunized controls. Percentages of rosette-forming cells (RFC) observed were compared with those of cells which secreted antibody (plaque-forming cells, PFC) and cells which both bound antigen and secreted antibody. Rosette-forming cells and PFC were shown to be two distinct reactive cell populations. Thus, in the spleen less than 1% of RFC also formed plaques. Immediately following antigen stimulation, the number of RFC in the bone marrow decreased to below detectable limits. After an initial rise, the number of RFC in the appendix declined similarly. In contrast, RFC levels in the spleen rose steadily from the time of immunization. These patterns suggest that bone marrow and appendix may function as a reservoir of antigen-binding cells which are released to other sites following antigenic stimulation. Rosette-forming cells were rarely observed in the thymus. Rosette-inhibition studies using antisera specific for bone marrow-derived cells (anti-B) and thymus-derived cells (anti-T) revealed a markedly greater proportion of T-RFC in the appendix than in the spleen.     

Expression of the argA Gene Carried by a Defective Lambda Bacteriophage of Escherichia coli

Evidence is presented that the increase in specific activity of N-acetylglutamate synthase observed upon heat induction of Escherichia coli (lambdadargA) is primarily due to a gene dosage effect.     

Der Zug des Sperbers(Accipiter nisus) auf Helgoland

Zusammenfassung Der Sperber ist auf Helgoland nur Durchzügler. Im langjährigen Mittel werden pro Jahr im Winter 0,4, auf dem Heimzug 2,1 und im Herbst 23,0 Fänglinge festgestellt. Der Zugablauf läßt eine Trennung der Zugzeiten der Alt- und Jungvögel einerseits sowie der und andererseits erkennen. Altvögel stellen 14,1%, 40,1% der Fänglinge. Anhand der Flügelmaße und Gewichte läßt sich mit fortschreitender Zugzeit keine klinale Variation nachweisen. Ältere Literaturangaben, Helgoland betreffend, werden teils korrigiert, teils präzisiert. Der geringe Anteil der Altvögel bzw. wird auf deren geringer ausgeprägten Zugtrieb zurückgeführt.

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The migration of the sparrow-hawk on Heligoland

Summary On Heligoland the Sparrow-Hawk occurs as a passage visitor only. Mean numbers (17 years) of birds trapped are 0.4 in winter, 2.1 during spring and 23.0 in autumn. Adults and juveniles as males and females as well show different periods of migration. Among birds trapped there are 14.1% adults and 40.1% females. No clinal variation of wing length and weight according to time of passage could be found. Former literature concerning Heligoland is partly corrected, partly rendered more precise. The low proportions of adults and females respectively are caused by weaker migratory urge.

     

Diosgenin saponins from Dioscorea floribunda

Five spirostanol glycosides and two furostanol glycosides were isolated from Dioscorea floribunda. In addition to the IR spectra of the free glycosides and the MS of the peracetates and permethyl ethers, the most effective method for structural determination proved to be the NMR spectra of the free saponins in pyridine-d₅.