bluuebunny/crossref_metadata_2025_split huggingface dataset:
l‐THREONINE DEAMINASE IN MARINE PLANKTONIC ALGAE. V. KINETIC EVALUATION OF FEEDBACK EFFECTS FROM STRUCTURAL ANALOGS OF l‐ISOLEUCINE ON THE DEAMINASE ACTIVITY OF SEVEN UNICELLULAR SPECIES AND ELUCIDATION OF THE ALLOSTERIC BASIS FOR ANOMALOUS FEEDBACK CONTROL SHOWN BY A DIATOM AND A CRYPTOMONAD1,2
Authors: Antia Naval J. , Kripps Robert S. , Desai Indrajit D. 
Published: August 2007

SUMMARYThe biosynthetic l‐threonine deaminase of 2 cyanophytes, 1 rhodophyte, 2 cryptomonads, and 1 chlorophyte showed sensitive and powerful feedback inhibition from l‐isoleucine, which effect was closely duplicated by its isosteric structural analog l‐O‐methylthreonine. The l‐isoleucine inhibition was maximal in the pH range 7.0–8.5 and was rapidly weakened with more alkaline pH. Glycine, l‐alanine, and d‐isoleucine had no effect, while l‐α‐amino‐n‐butyric acid, l‐norvaline, l‐leucine, and l‐valine caused insensitive partial inhibitions detectable only at high concentration (100‐fold greater than l‐isoleucine). Tests of these analogs at low concentration revealed the specific capacity of l‐valine to invoke sensitive stimulation of enzyme activity from all the algal strains, and this effect was markedly enhanced by decrease in substrate concentration. Valine also counteracted the inhibitory influence of isoleucine. It was concluded from the reaction kinetics observed with these effectors that the algal threonine deaminases conform to Monad's K system of allosteric enzymes. The activity from the cryptomonad Hemiselmis virescens was exceptional in showing 2 closely spaced pH optima, which were related to marked difference in effects from isoleucine and valine at these pH values. It was inferred from various pH‐related tests that this cryptomonad may contain 2 enzymes basically similar in biosynthetic function but differing only in pH optima and sensitivity to feedback regulation.The enzyme of the diatom Cyclotella nana was unique in showing insignificant feedback reaction from l‐isoleucine and its structural analogs, excepting l‐valine, which caused the strongest stimulation among the algae surveyed. It was concluded from the reaction kinetics that this deaminase is also of the biosynthetic type but that its feedback‐inhibition site is modified or unavailable, presumably from having this site already filled by endogenous isoleucine from the diatom.
THE ULTRASTRUCTURE OFSCENEDESMUS(CHLOROPHYCEAE). II. CELL DIVISION AND COLONY FORMATION1
Authors: Pickett‐Heaps Jeremy D. , Staehelin L. Andrew 
Published: August 2007

SUMMARYCell division in Scenedesmus is fairly typical of other chlorococcalean genera. The closed spindle has centrioles at polar fenestrae and apparently a series of nuclear divisions precedes cytokinesis. The phycoplast system of cytokinetic microtubules predicts the path of cleavage furrows whose mode of formation is obscure. Before and during cell division, the endoplasmic reticulum invariably accumulates granular material which later, during cytokinesis, appears to he secreted via the golgi bodies. Similar dense granular material then at accumulates outside the forming daughter cells but inside the parental wall, as the latter begins eroding away. By the end of colony formation, the cellulosic parental wall has disappeared, leaving its outer sheath and attached ornamentative features (spines, combs, reticulate or warty layer, etc.) intact as a “ghost.”The spines and combs of new colonies appear to condense out of the extracellular aggregate; their precise mode of formation is obscure. As they form, the daughter cells, having become rearranged within the parental wall, stick to one another apparently at specific sites on their outer surface. A trilaminar (sporopollenin‐containing) layer arises first in each cell at these adhesive sites and immediately afterwards, dense material aggregates between the adjacent layers to give rise to the coenobial adhesive. Plaques of the trilaminar layer later appear over the rest of the cell's surface; they grow and fuse so that eventually each cell is enclosed by one continuous Trilaminar Sheath (TLS). While the plaques are forming, another dense layer materializes around the whole coenobium. Depending on the species, this layer turns into either the warty layer, in which instance it is applied directly on to the surface of the TLS except near the coenobial adhesive, or else it becomes the reticulate layer, in which instance it remains entirely separate from the TLS, soon acquiring the complex system of propping spikelets which suspend it from the coenobial surface.When fully farmed, the daughter coenobium is tightly compressed within the parental TLS, with its spines folded lengthwise along the daughter cells. Release of the colony follows a quite explosive rupturing of the parental TLS, and immediately upon release, the daughter colony flattens out and erects its spines.
SEASONAL CHANGES IN THE PROXIMATE AND FATTY ACID COMPOSITION OF SOME NATURALLY GROWN FRESHWATER CHLOROPHYTES1
Authors: Moore J. W. 
Published: August 2007

SUMMARYThe protein content of the filamentous Cladophora glomerata (L.) Kz., Ulothrix zonata (Web, & Mohr) Kz. and Spirogyra sp., collected from natural populations for 1 year, averaged 8.0–12.4% of the total dry weight; whereas, the corresponding levels of lipid, cellulose and ash were 11.9–16.1%, 10.0–17.8% and 14.6–24.0%, respectively. Mean values for carbohydrates, estimated by difference, ranged from 32.8 to 56.0%. The colonial Scenedesmus dimorphus (Turp.) Kz. and the unicellular Cosmarium laeve Rab., on the other hand, contained more protein, lipid and carbohydrate (estimated by difference) averaging 13–15.0%, 22.5–25.9% and 415–46.8%, respectively, and less cellulose (7.5–9.8%) and ash (8.2–9.8%). A consistent pattern of seasonal variation in the proximate composition was not normally evident for any species, reflecting the influence of several environmental parameters on the algae. Cladophora contained the greatest amount of phospholipid averaging; 10% by weight of total lipid with the smallest quantity (5%) in Scenedesmus. The predominant phospholipid fatty acid in all species was C18:1 followed by C18:2, C18:3 and C16:1 in Cladophora, Ulothrix and Spirogyra, and C16:1, C18:2 and C16:0 in Scenedesmus and Cosmarium. Oleic (C18:1) and hexadecanoic (C16:1) acids were predominant in the neutral lipids of all the algae, followed by C16:0, C18:2 and C18:3. The concentration of the different fatty acids of each Species varied considerably during the year with the proportion of C16:0 and C16:1, usually rising and that of C18:1 failing during the colder months.
COBALT EFFECTS ON CELL DIVISION AND CALCIUM UPTAKE IN THE COCCOLITHOPHORIDCRICOSPHAERA CARTERAE(HAPTOPHYCEAE)1
Authors: Blankenship Mayme Lee , Wilbur Karl M. 
Published: August 2007

SUMMARYCobalt was found to produce effects on cell division, cell protein, volume, calcium uptake, and ultrastructure of the calcifying algaCricosphaera carterae(Braarud & Fager.) Braarud. The rate of cell division increased slightly as the added Co concentration of the medium was increased from 0–10 μM. At higher added Co concentrations, the rate of division decreased approximately linearly with concentration until division was blocked almost completely at 100 μM Co. Inhibition of division was reversible after 2 days in Co. Protein content was elevated in Co‐treated nondividing cells but the rate of protein synthesis was markedly reduced. Cell volume also increased progressively with Co concentration, and after 72 h in 200 μM Co, the volume was 3.2 times that in culture medium (0.09 μM Co). Co had a dual effect on calcification as indicated by the uptake of45Ca. After 48 h treatment, Ca uptake had increased 53% in 100 μM and decreased 40% in 200 μM Co as compared with cells in 0.09 μM Co. Ultrastructurally, Co caused enlargement of the cell vacuole and the appearance of membrane‐bound vacuoles containing electron dense bodies.
HALOGENATION IN THE RHODOPHYTA1,2 A REVIEW
Authors: Fenical William 
Published: August 2007

SUMMARYThe halogens—chlorine, bromine and iodine—play an important, role in the biochemical processes of marine red algae. Recent studies show that various species from at least 5 orders of the Rhodophyta possess the unique ability to synthesize organic halogen‐containing compounds which are derived from seawater components. A variety of substances have been reported, with various structures from simple aliphatic halo‐ketones and brominated phenols to more sophisticated mono‐, sesqui‐ and diterpenes. While the biological functions of these compounds are not clearly understood, they appear to provide environmental advantage, probably involving predator avoidance responses and microflora antibiosis.
THE GENETIC BASIS OF MALE POTENCY IN VOLVOX CARTERI F. NAGARIENSIS (CHLOROPHYCEAE)1,2
Authors: Meredith Ruby F. , Starr Richard C. 
Published: August 2007

SUMMARYSexual males of Volvox carteri Stein f. nagariensis Iyengar secrete a hormone which induces sexual rather than asexual development in the next generation. Male recombinants from the original strains isolated from Japan showed an increase in potency of up to 100 times that of the original male clone, with later descendants showing potencies ranging from 100 times to 1/1000 the potency of this male. Potency is defined as the extent to which the hormone produced in 1 ml of medium by one parental spheroid containing 16 male spheroids can be diluted and retain its capacity to induce sexual differentiation. This is recorded as the percent of female response in the tube of limiting dilution, asexual females of the normal female strain being used as assay inoculum in a 1 in 10 dilution series of samples of male fluid containing the sexual hormone. Investigation of the genetic basis for potency in this species included selection of high and low potency male clones and crossing with sib females or backcrossing with original female. Results of the various crosses are interpreted as multigenic system not linked with sex, with more than one genotypic class per dilution level and with more than one genotypic class per apparent phenotypic class. Possible genic interactions are described in their relevance to the biosynthesis of a glycoprotein molecule, the sexual hormone having been characterized as a glycoprotein by Starr and Jaenicke (18).
THE ULTRASTRUCTURE AND CYTOCHEMISTRY OF RESTING CELL FORMATION INAMPHORA COFFAEFORMIS(BACILLARIOPHYCEAE)1
Authors: Anderson O. Roger 
Published: August 2007

SUMMARYThe ultrastructure of logarithmic‐growing cells and of resting cells in laboratory cultures ofAmphora coffaeformis(Ag.) Kütz. isolated from deep ocean water was examined using electron and light microscopy. The acid Phosphatase activity, chlorophyll a and lipid content were assessed at weekly intervals of resting cell formation during cold‐dark treatment, simulating deep ocean water. Approximately 4 wk are required to complete resting cell formation. During the first week, the cytoplasm undergoes extensive transformation and lysosomal activity is observed. Large vacules decrease in size and many small ones develop, the mitochondria become fewer and one or more massive mitochondria appear possibly by fusion of smaller ones; the cytoplasm becomes densely granular. During the second and third week, the cytoplasm continues to contract, lipid bodies begin to develop and the plastid becomes densely stained. At the fourth week, the mature resting cell is formed containing one or more massive mitochondria, a well‐formed plastid, and granular cytoplasm containing occasional lipid droplets. There is no change in frustule morphology and the cytoplasm does not produce a protective layer. The variation in chemical constituents correlates with microscopic structure of the cells. The fine structure of cells during growth resumption when exposed to light at 25 c is presented. Previous reports of viable, chlorophyll‐containing cells at great depths in the ocean may be explained by the results reported in this paper.
LONG‐TERM MAINTENANCE OF FERTILE ALGAL CLONES: EXPERIENCE WITHPANDORINA(CHLOROPHYCEAE)1,2
Authors: Coleman Annette W. 
Published: August 2007

SUMMARYThere is a need for simple, inexpensive methods to maintain algal clones of constant genotype over long periods of time.Pandorinazygospores survive many environmental rigors which destroy the vegetative cells. The zygospores are the preferable from for storage of the alga and remain viable for at least 15 yr. storage procedures and germination techniques are described for zygospores of 2 species. These are compared with reports in the literature concerning other algal genera. General procedures for storage and maintenance of both vegetative cells and spores are proposed.
CELL DIVISION IN THE FILAMENTOUS PLEURASTRUM AND ITS COMPARISON WITH THE UNICELLULARPLATYMONAS(CHLOROPHYCEAE)1
Authors: Molnar Kathy E. , Stewart Kenneth D. , Mattox Karl R. 
Published: August 2007

SUMMARYAt prophase inPleurastrum,extranuclear spindle microtubules develop from the region of centrioles, which lie lateral to the nucleus midway between the future sites of the metaphase spindle poles. The microtubules then move laterally to overarch the nucleus and finally become incorporated into the spindle. The centrioles do not migrate and therefore lie in the same plane as the chromosomes at metaphase. At telophase, 2, more different systems of microtubules develop from the vicinity of the centrioles—a phycoplast and extensive arrays of microtubules that ensheath the daughter nuclei. Cell division in the filamentousPleurastrumis compared to that in the green flagellate,Platymonas.The similarities between cell division in the 2 algae are interpreted as evidence: (i) that rhizoplasts (which inPlatymonasresemble myofibrils) are somehow homologous to microtubules; and, (ii) that cell division inPleurastrumdiffers from cell division in other examined filamentous chlorophycean genera because Pleurastrum has an independent evolutionary origin from a monad withPlatymonas‐like characteristics.
BLOOMS OF SURF‐ZONE DIATOMS ALONG THE COAST OF THE OLYMPIC PENINSULA, WASHINGTON. VI. DAILY PERIODICITY PHENOMENA ASSOCIATED WITH CHAETOCEROS ARMATUM IN ITS NATURAL HABITAT1,2
Authors: Lewin Joyce , Rao V. N. R. 
Published: August 2007

SUMMARYMicroscope observations of chains of Chaetoceros T. armatum T. West, collected, from its natural habitat, at Copalis Beach, Washington, have been made. A regular daily periodicity in the occurrence of cell division stages and length of the chains was found on each occasion (November, February, April, May, August). During the night, short chains of 3 cells predominated. In early morning hours, average chain lengths increased due to cell elongation, and nuclear and protoplast division occurred. This correlated with the time of day when cell masses of C. armatum first appeared at the surface of the water. In the late afternoon, the new silica valves of the daughter protoplasts were formed. Formation of special bristle‐bearing end valves effected the separation of long chains into shorter chains composed predominantly of 3 cells. (Cultured material was used to verify some of these stages.) This correlated with the time of day when cell masses disappeared from the water surface and dispersed.
PIGMENT AND CYTOLOGICAL EVIDENCE FOR RECLASSIFICATION OF NANNOCHLORIS OCULATA AND MONALIANTUS SALINA IN THE EUSTIGMATOPHYCEAE1
Authors: Antia N. J. , Bisalputra T. , Cheng J. Y. , Kalley J. P. 
Published: August 2007

SUMMARY Nannochloris oculata Droop and Monallantus salina Bourrelly produce similar chloroplast pigments and show alike ultrastructural features separating them from the Chlorophyceae and Xanthophyceae, respectively, and linking them to the Eustigmatophyceae. It is proposed that N. oculata should be removed from the chlorophyceaen genus Nannochloris and transferred to a new taxon of coccoid eustigmatophytes containing the closely related M. salina: nomenclatural revisions are required for both strains.
THE REQUIREMENT FOR SILICON IN SYNURA PETERSENII (CHRYSOPHYCEAE)1,2
Authors: Klaveness Dag , Guillard Robert R. L. 
Published: August 2007

SUMMARYA silicon requirement for growth is demonstrated for an alga other than a diatom. Concentrations of less than 1 μM silicate greatly decreased the growth rate of Synura petersenii Korshikov and caused morphological changes. Half of maximum growth rate (μmax= 1.12 divisions/day) appeared at a concentration of only 0.23 μM silicate. Germanium dioxide inhibited, growth considerably; the degree of inhibition varying from none to almost 100% depending upon both Si and Ge concentrations. The amount of silicon deposited in the external scales of S. petersenii is comparable per unit area to that of diatoms. S. petersenii is able to deplete the medium of silicate to very low levels. The feasibility of batch culture techniques for this kind of work is discussed briefly.
COMPARATIVE ULTRASTRUCTURE OF THE VALVES OF SOME CYCLOTELLA SPECIES (BACILLARIOPHYCEAE)1
Authors: Lowe Rex L. 
Published: August 2007

SUMMARY Cyclotella atomus Hust., C. meneghiniana Kütz., C. comta (Ehr.) Kütz., C. antiqua W. Sm., C. michiganiana Skv., C. ocellata Pant., C. glomerata Bachmann, C. pseudostelligera Hust., and C. stelligera (Cleve et Grun.) V. H., were selected for ultrastructure investigations on the basis of their ready availability. Specimens were examined employing both transmission and scanning electron microscopy. Strutted processes, labiate processes, spines and other special features were surveyed in all species. On the basis of these observations the species of Cyclotella observed seem to be in one of 3 morphological groups, the meneghiniana group, the comta group, and the stelligera group.
FLAGELLAR APPARATUS, EYESPOT AND BEHAVIOR OF MICROTHAMNION KUETZINGIANUM (CHLOROPHYCEAE) ZOOSPORES1,2,3
Authors: Watson Melvin William 
Published: August 2007

SUMMARYThe flagellar apparatus of Microthamnion kuet‐zingianum Naegeli differs from, that of Chlamydomonas reinhardtii Dangeard in that the zoospores can autonomously orient their basal bodies for different types of swimming behavior, including forward, and backward progression with, stationary intervals. Reorientation of the basal regions of the flagella and of the basal bodies were documented by cinefilms and by stroboscopic and electron micrographs. Even when the flagella. were sheared off, the remaining stubs (containing the basal bodies) were capable of being reoriented, by the organism. Thus the mechanism of basal body reorientation cannot reside in the 9 + 2 flagellar shaft. Rather, the reorienting process involves a shortening or lengthening of the distal fiber and of the plasma membrane region overlying an anterior papilla. In their helical and spiral motions, the zoospores trace complicated, but surprisingly regular curves. Such motion might result from the inherent 3‐dimensional structure and beat of the flagella.The eyespot has an invariable, highly asymmetric location within the cell in direct proximity with a specific microtubular band (MTE), but nevertheless may occur in either the anterior or posterior region of the chloroplast. Further, multiple eyespots may occur along the same side of MTE. This observation is consistent with the discovery (in Fucus sperm) that microtubules serve to align individual eyespot granules in eyespot‐ontogeny. By this means the position of the eyespot within a cell could well be determined.
STEROLS OF PORPHYRIDIUM(RHODOPHYTA)1,2
Authors: Cargile Nancy L. , Edwards Henry N. , McChesney James D. 
Published: August 2007

SUMMARYSpecies of the unicellular Porphyridium have been examined for their sterol content. Clones of 4 species maintained in axenic, chemically‐defined culture were analyzed—these included P. sordidum Geitler, P. purpureum (Bory) Ross, P. aerugineum Geitler and P. violaceum Kormnann(P. griseum Geitler was not available to use for examination). The major sterol was 22‐dehydrocholesterol in all except P. aerugineum in which there was a mixture of this sterol, cholesterol and higher sterols. Traces of C28 and C29 sterols were detected in most instances as well.
ELECTRON MICROSCOPE OBSERVATIONS OF TELOPHASE II IN THE FLORIDEOPHYCEAE1
Authors: Scott J. L. , Thomas J. P. 
Published: August 2007

SUMMARYTetrahedral tetrasporangia of several florideophycean red, algae were examined with the electron microscope for details of meiosis. Only telophase II nuclei are described since earlier stages were not, observed. Both divisions of meiosis are presumed to occur within the confines of the original tetrasporangial mother cell nuclear envelope. Four nuclei are then formed simultaneously. These observations essentially support Yamanouchi's description of telophase II inPolysiphonia flexicaulis(Harvey) Collins (asP. violacea)and suggest that meiosis in these algae could be basically similar to “uninuclear meiosis” in the fungiSaprolegniaandSaccharomyces.
Parametric and Optimal Design in Electronic Packaging Using DSC:
Computational, Geometrical, and Material Aspects
Authors: Whitenack Russell , Desai Chandra , Rassaian Mostafa 
Published: August 2007

Abstract
The disturbed state concept (DSC) with the hierarchical single surface (HISS) plasticity model have been proposed and validated previously for a wide range of problems in electronic packaging. In this paper, detailed analyses are performed with the DSC∕HISS model to study the effect of various factors, such as computational and geometrical aspects and material parameters, on the failure life of chip substrate systems. The results and the methodology can be used for parametric analyses and optimal design of problems in electronic packaging.
The Development of a Practical Evaluation Tool for Urban Sustainability
Authors: Jones P. , Patterson J. 
Published: August 2007

Sustainability is deeply rooted in the built environment and is inherently holistic reaching across environmental, social and economic issues at local and global scales. There is therefore a need for cross disciplinary working to ensure a sustainable approach. Although industry and government recognise the need to develop a more sustainable approach the built environment, it is slow to be achieved in practice. This paper describes the development and operation of a computer based interactive guidance system that assists with the incorporation of sustainability in built environment policies, plans, programmes and projects allowing all stakeholders to be involved. PETUS was informed by the needs of practice and designed and developed to provide a mechanism for cross disciplinary working for sustainability.