DUBOUX T, FERREIRA A, GASTALDO M
MIMD
DICTIONARY MACHINES - FROM THEORY TO PRACTICE
LECT NOTES COMPUT SC 634: 545-550 1992
Abstract:
We describe the implementation of a dictionary structure on a distributed
memory parallel computer. The dictionary is an important data structure used in
applications such as sorting and searching, symbol-table and index-table
implementations. Theoretical as well as practical aspects of the development of
the application are discussed. Our target machine was a Volvox IS860
with 8 nodes, each composed of one Transputer T800 from INMOS plus an Intel
i860. Extensive testing was carried out and the results reported. We also
address problems and solutions connected to the programming environment of such
a machine
BOWSER SS, ALEXANDER SP, STOCKTON WL, et al.
EXTRACELLULAR-MATRIX
AUGMENTS MECHANICAL-PROPERTIES OF PSEUDOPODIA IN THE CARNIVOROUS FORAMINIFERAN
ASTRAMMINA-RARA - ROLE IN PREY CAPTURE
J PROTOZOOL 39 (6): 724-732 NOV-DEC 1992
Abstract:
The seemingly delicate, strand-like pseudopodia of Astrammina rara, a
camivorous benthic foraminiferan, adhere to and withstand the rigorous
movements of meiofaunal prey. Previous electron microscopic studies identified
two novel structures that might account for the unusual tensile properties of
these pseudopodia: 1) an extensive, coiled microtubule cytoskeleton and 2) a
fibrous extracellular matrix vesting the pseudopodial surface. In the present
study, we found that pseudopodial networks microsurgically removed from A.
rara's cell body captured Artemia metanauplii as efficiently as intact
organisms, and therefore used them to test the role of microtubules and
extracellular matrix components in augmenting pseudopodial strength. Agents
that specifically disassemble microtubules (1 mM colchicine or 20 muM
nocodazole) or generally disrupt pseudopodial integrity (heat, 10 mM
formaldehyde, 1 mg/ml saponin) failed to inhibit prey capture. All of these
treatments left the extracellular matrix intact as revealed by
immunofluorescence and scanning electron microscopy. The elastic and tensile
properties of the extracellular matrix, isolated by solubilization of
pseudopodial cytoplasm using the nonionic detergent Triton X-100, were similar
to those of intact pseudopodial networks when assayed with calibrated
microneedles or a flexible rubber substrate. These observations indicate that
A. rara uses a fibrous extracellular matrix to augment cytoplasmic tensile
properties.
MISHRA SR, SHARMA S, YADAV RK
PHYTOPLANKTONIC
COMMUNITIES IN RELATION TO ENVIRONMENTAL-CONDITIONS OF LENTIC WATERS AT GWALIOR
(MP)
J ENVIRON BIOL 13 (4): 291-296 OCT 1992
Abstract:
A study was undertaken to determine the distribution of phytoplanktonic
communities in two lentic water bodies of variable nature in Gwalior city. The
study revealed that the water quality at Cotton mill waste water pond was
severely destructed. In this pond the abundance of Arthrospira platensis, Volvox
sp., Scenedesmus sp., Phacus sp., Euglena gracilis and E. acus was observed,
which depicts their possible sustainance power in stressed habitats.
FABRY S, NASS N, HUBER H, et al.
THE YPTV1
GENE ENCODES A SMALL G-PROTEIN IN THE GREEN-ALGA VOLVOX-CARTERI - GENE STRUCTURE AND PROPERTIES OF THE GENE-PRODUCT
GENE 118 (2): 153-162 SEP 10 1992
Abstract:
Small G-proteins encoded by ras-like genes are ubiquitous in eukaryotic cells.
These G-proteins are believed to play a role in central processes, such as
signal transduction, cell differentiation and membrane vesicle transport. By
screening genomic and cDNA libraries of the colonial alga, Volvox
carteri f. nagariensis, with ypt DNA probes from Zea mays, we have identified
the first member of a ypt gene family, yptV1, within a green alga. The 1538-bp
yptV1 gene of V. carteri consists of nine exons and eight introns and has three
potential polyadenylation sites 210, 420 and 500 bp downstream from the UGA
stop codon. The derived 203-amino-acid polypeptide, YptV1, exhibits 81%
similarity with Ypt1 from mouse, with the corresponding genes sharing four
identical intron positions. Recombinant YptV1 (reYptV1) produced in Escherichia
coli retains the ability to bind GTP after SDS-PAGE and immobilization on
nitrocellulose. Immunological studies using polyclonal antibodies against
reYptV1 indicate that the protein is present in the membrane fraction of a V.
carteri extract and is expressed throughout the whole life-cycle of the alga.
Similar to other Ras-like proteins, YptV1 contains two conserved C-terminal
cysteine residues suggesting post-translational modification(s), such as
isoprenylation or palmitoylation, required for membrane anchoring. The
presumptive role of YptV1 in cytoplasmic vesicle transport is briefly
discussed.
VOYTAS DF, CUMMINGS MP, KONIECZNY A, et al.
COPIA-LIKE
RETROTRANSPOSONS ARE UBIQUITOUS AMONG PLANTS
P NATL ACAD SCI USA 89 (15): 7124-7128 AUG 1 1992
Abstract:
Transposable genetic elements are assumed to be a feature of all eukaryotic
genomes. Their identification, however, has largely been haphazard, limited
principally to organisms subjected to molecular or genetic scrutiny. We
assessed the phylogenetic distribution of copia-like retrotransposons, a class
of transposable element that proliferates by reverse transcription, using a
polymerase chain reaction assay designed to detect copia-like element reverse
transcriptase sequences. copia-like retrotransposons were identified in 64
plant species as well as the photosynthetic protist Volvox carteri. The
plant species included representatives from 9 of 10 plant divisions, including
bryophytes, lycopods, ferns, gymnosperms, and angiosperms. DNA sequence
analysis of 29 cloned PCR products and of a maize retrotransposon cDNA
confirmed the identity of these sequences as copia-like reverse transcriptase
sequences, thereby demonstrating that this class of retrotransposons is a
ubiquitous component of plant genomes.
DOMOZYCH DS, WELLS B, SHAW PJ
THE CELL-WALL
OF THE CHLAMYDOMONAD FLAGELLATE, GLOEOMONAS-KUPFFERI (VOLVOCALES, CHLOROPHYTA)
PROTOPLASMA 168 (3-4): 95-106 1992
Abstract:
The large unicellular flagellate, Gloeomonas kupfferi, has recently been used
as an important tool in chlamydomonad cell biology research, especially in
studies dealing with the structure and function of the endomembrane system.
However, little is known about the main secretory product, the cell wall. This
study presents structural, chemical and immunological information about this
wall. This 850-900 nm thick matrix is highly elaborate and consists of three
distinct layers: an inner stratum (325 nm thick) consisting of tightly
interwoven fibers, a medial crystalline layer consisting of 22-23 nm subunits
and an outer wall layer (500 nm thick) of outwardly-radiating fibrils. Rapid
freeze-deep etch analysis reveals that the 35-40 nm fibers of the outer layer
form a quasi-lattice of 160 nm subunits. The outer wall can be removed from
whole pellets using the chelator, CDTA. The medial wall complex can be
solubilized by perchlorate. SDS-gel electrophoresis reveals that the
perchlorate soluble-material consists of five high molecular weight
glycoproteins and five major low molecular weight glycoproteins. The
electrophoretic profile is roughly similar to that of Chlamydomonas
reinhardtii. Antibodies were successfully raised against the outer wall
component and were shown to label the outer wall layer.
BUCHHEIM MA, CHAPMAN RL
PHYLOGENY OF
CARTERIA (CHLOROPHYCEAE) INFERRED FROM MOLECULAR AND ORGANISMAL DATA
J PHYCOL 28 (3): 362-374 JUN 1992
Abstract:
Comparative ultrastructural data have shown that at least two distinct groups
exist within Carteria. Similarly, interpretations of variation in gross
morphological features have led to the discovery of morphologically distinct
groups within the genus. Partial sequences from the nuclear-encoded small- and
large-subunit ribosomal RNA molecules of selected Carteria taxa were studied as
a means of 1) testing hypotheses that distinct groups of species exist within
the genus and 2) assessing monophyly of the genus. Parsimony analysis of the sequence
data suggests that three Carteria species, C. lunzensis, C. crucifera, and C.
olivieri, form a monopkyletic group that is the basal sister group to all other
ingroup flagellate taxa (including species of Chlamydomonas, Haematococcus,
Stephanosphaera, Volvox, and Eudorina). Two other Carteria taxa, C.
radiosa and Carteria sp. (UTEX isolate LB 762), form a clade that is the sister
group to a clade that includes Haematococcus spp., Chlamydomonas spp., and
Stephanosphaera. Thus, the sequence data support the interpretations of
ultrastructural evidence that described two distinct Carteria lineages.
Moreover, the sequence data suggest that these two Carteria groups do not form
a monophyletic assemblage. Parsimony analysis of a suite of organismal (morphological,
ultrastructural, life history, and biochemical) character data also suggest two
distinct lineages among the five Carteria taxa; however, the organismal data
are ambiguous regarding monophyly of these Carteria taxa. When the two
independent data sets are pooled, monophyly of Carteria is not supported;
therefore, the weight of available evidence, both molecular and organismal,
fails to support the concept of Carteria as a natural genus.
BLAKEFIELD MK, CALKINS J
INHIBITION OF
PHOTOTAXIS IN VOLVOX-AUREUS BY
NATURAL AND SIMULATED SOLAR ULTRAVIOLET-LIGHT
PHOTOCHEM PHOTOBIOL 55 (6): 867-872 JUN 1992
Abstract:
Exposure to artificial UV wavelengths and the UV component of sunlight delays
positive phototaxis in the green alga Volvox aureus. Broad band
wavelength filters were used to modify the Output from UV-B sources (280-320
nm) and natural sunlight. The delay in phototaxis by artificial UV is increased
with exposure to shorter UV-B wavelengths. Natural sunlight experiments were
performed with exposure to full sunlight and to its UV component only. The UV
component present in summer sunlight Produced long periods of inhibition in
phototaxis and even lethality, while exposure to the total spectrum of sunlight
had no significant effects on movement or survival. The data indicate that
although this species of alga is well equipped to deal with present levels of
UV exposure, increases in the short UV-B wavelengths in sunlight may force an
alteration in patterns of photomovement.
ERTL H, HALLMANN A, WENZL S, et al.
A NOVEL
EXTENSIN THAT MAY ORGANIZE EXTRACELLULAR-MATRIX BIOGENESIS IN VOLVOX-CARTERI
EMBO J 11 (6): 2055-2062 JUN 1992
Abstract:
ISG is a sulphated, extracellular glycoprotein synthesized for only a few
minutes in inverting Volvox embryos and inverting sperm cell packets.
This control operates at the level of transcription. ISG has been characterized
by studies of protein chemistry and electron microscopy. The primary structure
of ISG has been derived from genomic DNA and cDNA. ISG is composed of a
globular and a rod-shaped domain. The rod-shaped domain represents a member of
the extensin family with numerous repeats of Ser-(Hyp)4-6 motifs. A synthetic
decapeptide matching the C-terminal sequence is able to disaggregate the
organism into individual cells. Immunofluorescence microscopy localizes ISG
within the boundary zone of the ECM.
DESNITSKI AG
CELLULAR MECHANISMS OF THE
EVOLUTION OF ONTOGENY IN VOLVOX
ARCH PROTISTENKD 141 (3): 171-178 APR 1992
Abstract:
The green flagellates of the genus Volvox can be conditionally
subdivided into two groups according to the size of gonidia (asexual
reproductive cells) at the onset of cleavage. In Volvox carteri and
several other species the gonidium undergoes an extended period of
hypertrophied growth, after which a series of rapid fissions occurs. Embryonic
cells do not grow during the intervals between consecutive divisions. In
representatives of the second group (e.g., V. aureus) the period of gonidial
enlargement is comparatively nondurable; thus the cleavage begins when the
gonidium is relatively small, and each division is followed by a period of
cellular growth.
In this paper the evolutionary relationships between two types of asexual life cycle in Volvox are analysed on the basis of literary and our own data. It is supposed that the V. aureus type of development with slow divisions of small gonidia is more advanced in the evolutionary respect than the V. carteri type of development with rapid divisions of large gonidia.
Experimental analysis of the role of light and dark for embryonic cleavage progression in V. aureus, V. carteri f. nagariensis and V. tertius as well as the experiments with several metabolic inhibitors (aminopterin, actinomycin D, cycloheximide and streptomycin) have enabled us to elucidate cellular mechanisms of the evolution of ontogenesis in Volvox.
MENGELE R, SUMPER M
GULOSE AS A
CONSTITUENT OF A GLYCOPROTEIN
FEBS LETT 298 (1): 14-16 FEB 17 1992
Abstract:
The aldohexose gulose was identified as a constituent of a hydroxyproline-rich
glycopeptide derived from the glycoprotein SSG 185. This glycoprotein is part
of the extracellular matrix of the green alga Volvox carteri. The gulose
residue occupies a terminal position in the corresponding saccharide.
ALHASANI H, JAENICKE L
CHARACTERIZATION
OF THE SEX-INDUCER GLYCOPROTEIN OF VOLVOX-CARTERI
F WEISMANNIA
SEX PLANT REPROD 5 (1): 8-12 JAN 1992
Abstract:
Sexual inducer pheromones from Volvox carteri f. weismannia, strains
65-30(12) and 1B were purified and characterized as glycoproteins with apparent
molecular weights of 27 kDa and 28.5 kDa, respectively. This subspecies yielded
20-40 times more pheromone based on weight per spheroid than Volvox
carteri f. nagariensis, but its specific activity (threshold dilution) is four
to five orders of magnitude less (10(-12) to 10(-13) M). Gas-chromatographic
sugar analysis revealed quantitative differences in the composition of the O-
and N-glucans compared with the V. carteri f. nagariensis inducer. The V.
carteri f. weismannia pheromones showed antigenic cross-reaction with an
antiserum directed against chemically deglycosylated inducer from V. carteri f.
nagariensis. However, there is only unilateral biological cross-induction. The
V. carteri f. nagariensis inducer is strictly competent for its own gonidia
only; the inducers from V. carteri f. weismannia also cross-induce V. carteri
f. nagariensis. This pattern of cross-induction suggests the existence of
related pheromone receptors but with different ligand specificities.
LARSON A, KIRK MM, KIRK DL
MOLECULAR
PHYLOGENY OF THE VOLVOCINE FLAGELLATES
MOL BIOL EVOL 9 (1): 85-105 JAN 1992
Abstract:
Phylogenetic studies of approximately 2,000 bases of sequence from the large
and small nuclear-encoded ribosomal RNAs are used to investigate the origins of
the genus Volvox. The colonial and multicellular genera currently placed
in the family Volvocaceae form a monophyletic group that is significantly
closer phylogenetically to Chlamydomonas reinhardtii than it is to the other
unicellular green flagellates that were tested, including Chlamydomonas
eugametos, Chlorella pyrenoidosa, and Haematococcus lacustris. Statistical
analysis of 251 phylogenetically informative nucleotide positions rejects the "volvocine
lineage" hypothesis, which postulates a monophyletic evolutionary
progression from unicellular organisms (such as Chlamydomonas), through
colonial organisms (e.g., Gonium, Pandorina, Eudorina, and Pleodorina)
demonstrating increasing size, cell number, and tendency toward cellular
differentiation, to multicellular organisms having fully differentiated somatic
and reproductive cells (in the genus Volvox). The genus Volvox
appears not to be monophyletic. Volvox capensis falls outside a lineage
containing other representatives of Volvox(V. aureus, V. carteri, and V.
obversus), and both of these Volvox lineages are more closely related to
certain colonial genera than they are to each other. This implies either a
diphyletic origin of Volvox from different colonial volvocacean
ancestors, a phylogenetic derivation of some of the colonial genera from a
multicellular (i.e., Volvox) ancestor, or both. Considered together with
previously published observations, these results suggest that the different
levels of organizational and developmental complexity found in the Volvocaceae
represent alternative stable states, among which evolutionary transitions have
occurred several times during the phylogenetic history of this group.
SCHMITT R, FABRY S, KIRK DL
IN SEARCH OF
MOLECULAR-ORIGINS OF CELLULAR-DIFFERENTIATION IN VOLVOX AND ITS RELATIVES
INT REV CYTOL 139: 189-265 1992
MENGELE R, SUMPER M
GULOSE AS A
CONSTITUENT OF A GLYCOPROTEIN
FEBS LETT 298 (1): 14-16 FEB 17 1992