STRUCTURAL FEATURES OF NUCLEAR GENES IN THE CENTRIC DIATOM THALASSIOSIRA WEISSFLOGII (BACILLARIOPHYCEAE)

Thalassiosira weissflogii (Grun.) Fryxell et Hasle is one of the more commonly studied centric diatoms, and yet molecular studies of this organism are still in their infancy. The ability to identify open reading frames and thus distinguish between introns and exons, coding and noncoding sequence is essential to move from nuclear DNA sequences to predicted amino acid sequences. To facilitate the identification of open reading frames in T. weissflogii , two newly identified nuclear genes encoding β-tubulin and t  -complex polypeptide (TCP)-γ, along with six previously published nuclear DNA sequences, were examined for general structural features. The coding region of the nuclear open reading frames had a G + C content of about 49% and could readily be distinguished from noncoding sequence due to a significant difference in G + C content. The introns were uniformly small, about 100 base pairs in size. Furthermore, the 5' and 3' splice sites of introns displayed the canonical GT/AG sequence, further facilitating recognition of noncoding regions. Six of the nuclear open reading frames displayed relatively little bias in the use of synonymous codons, as exemplified by the cDNAs encoding β-tubulin and TCP-γ. Two open reading frames displayed strong bias in the use of particular codons (although the codons used were different), as exemplified by the cDNA encoding fucoxanthin chlorophyll a/c binding protein. Knowledge of codon bias should facilitate, for example, design of degenerate PCR primers and potential heterologous reporter gene constructs.     

Flavonoids and eupahakonenin B from Stevia satureiaefolia

Extraction of Stevia satureiaefolia furnished the flavonoids cirsimaritin and eupatorin and the guaianolide eupahakonenin B.     

RELATIONSHIPS BETWEEN GROWTH RATE,CELL SIZE,AND INDUCTION OF SPERMATOGENESIS IN THE CENTRIC DIATOM THALASSIOSIRA WEISSFLOGII (BACILLARIOPHYTA)1

Patterns of changes in cell size, growth rate, and the inducibility of spermatogenesis were followed in eight sub‐clones of two isolates of the centric diatom Thalassiosira weissflogii (Grunow) Fryxell & Hasle grown at saturating light. One isolate originated from Long Island Sound, New York, USA and the other originated from Jakarta Harbor, Indonesia. As expected from previous studies, oscillations between intervals of cell size reduction and cell size enlargement were observed for each sub‐clone. For both isolates, sperm were easily detected, but cells resembling eggs and auxospores were rarely observed and fertilization was not confirmed, suggesting that the observed cell size increases may have resulted from a combination of asexual cell enlargement and rare auxosporulation. The two isolates differed in their minimum and maximum sizes, and the threshold size for the induction of sperm formation. However, the two sets of isolated sub‐clones displayed comparable relationships between growth rate, sperm inducibility, and cell size relative to the minimum, maximum, and threshold sizes. Growth rate increased as cell size decreased during vegetative divisions until the threshold for sperm inducibility was crossed. Below the size threshold for sperm inducibility, growth rate declined as cell size continued to decrease. Smaller cells were susceptible to failure of normal cytokinesis and valve deposition, resulting in the formation of abnormally long and often multinucleate cells. Culture conditions may select against restoration of cell size via auxosporulation due to the relationship between growth rate and cell size.     

Comparison of the Effects of Chlorpromazine,Dextroamphetamine and Methylphenidate on the Behaviour and Functioning of Hyperactive Children

Chlorpromazine, dextroamphetamine and methylphenidate were significantly superior to placebo in producing overall improvement in the behaviour of hyperactive children. Chlorpromazine was effective for the majority of the children, but reduced only hyperactivity, having no demonstrable effect on distractibility, aggressivity or excitability. Both stimulants produced more goal-oriented behaviour and reduced distractibility. Methylphenidate was the most effective of the drugs in prpducing exceptional improvement. All three active drugs had to be discontinued in a few of the children because of side effects. Not all hyperactive children were benefited by the drugs.No background variables (with the exception of mother-child relationship) were found in the present studies to predict favourable response to the drugs.Methylphenidate became our drug of choice for this group of hyperactive children.     

Ptelea trifoliata ssp. trifoliata (Rutaceae) in deciduous forest regions of Eastern North America

Relationships between floral elements of disjunct segments of the mixed mesophytic forest formation in eastern North America were investigated by comparison of populations ofPtelea trifoliata ssp.trijoliata in nine deciduous forest regions, using thin-layer chromatography as a supplement to morphological data. Details of leaf morphology and the presence of certain key spots in Chromatographic patterns visible under ultraviolet light were tabulated for comparison of populations. Similarities were noted between populations of the Appalachian highlands and the mountains of southern Mexico, and between the southeastern United States and the interior. Characteristics ofPtelea populations of glaciated regions indicated floral relationships with vegetation areas on both sides of the Mississippi Valley.     

New Species of Eimeria from Arizona Rodents

SUMMARY. In a survey of 52 rodents of 25 species from Grand Canyon National Park, Arizona and its vicinity, the following species of Eimeria are described: E. tamiasciuri n. sp. from the red or spruce squirrel, Tamiasciurus hudsonicus; E. lateralis n. sp. and Eimeria sp. from the mantled ground squirrel, Citellus lateralis; E. eutamiae n. sp. from the cliff chipmunk, Eutamias dorsalis; E. thomomysis n. sp. from the pocket gopher, Thomomys bottae; E. perognathi n. sp. from the rock pocket mouse, Perognathus intermedius; E. albigulae n. sp. from the white-throated woodrat, Neotoma albigula; E. operculata n. sp. from Stephens' woodrat, Neotoma stephensi; E. peromysci n. sp. and E. arizonensis n. sp. from the piñon mouse, Peromyscus truei; E. eremici n. sp. from the cactus mouse, Peromyscus eremicus ; and E. onychomysis n. sp. from the northern grasshopper mouse, Onychomys leucogaster.     

ACETYLCHOLINESTERASE IN FROG SYMPATHETIC AND DORSAL ROOT GANGLIA : A Study by Electron Microscope Cytochemistry and Microgasometric Analysis with the Magnetic Diver

The localization and chemical determination of acetylcholin esterase in the frog sympathetic and dorsal root ganglia were studied by a combination of the methods of electron microscopy, histochemistry, and microgasometric analysis with the magnetic diver. The Koelle-Friedenwald copper thiocholine histochemical method was modified by eliminating the sulfide conversion and by treatment of the tissue with potassium permanganate. In fixed tissue, enzymatic activity was demonstrated on the inner surface of the endoplasmic reticulum, nuclear envelope, subsurface cisternae, and agranular reticulum of the perikaryon and axon. In briefly fixed tissue, end product appeared also at the axon-sheath and the sheath-sheath interface. Activity at the synaptic junction was most readily obtained in unfixed tissue. Isolated neurons recovered from the diver following chemical analysis were studied with the electron microscope. Cells having a high enzyme activity showed a badly ruptured or absent neural plasmalemma and sheath. In this case the measured activity was apparently due to the enzyme present in the endoplasmic reticulum. Neurons having low activity exhibited an intact plasmalemma and sheath. This may reflect the effectiveness of the neural plasmalemma and sheath as a penetration barrier. The effects of fixation on enzyme activity are discussed. Electron microscopic examination of cells following microgasometric analysis is shown to be essential for the interpretation of the biochemical data.