Plasma concentrations of temazepam,a 3-hydroxy benzodiazepine,determined by electron-capture gas—liquid chromatography

A simple and sensitive high-performance liquid chromatographic assay of methotrexate (MTX) and its two active metabolites, 7-hydroxymethotrexate (7-OH-MTX) and 2,4-di-amino-N¹⁰-methylpteroic acid (APA) in plasma, saliva and urine was developed. The method involved deproteinization with acetonitrile followed by addition of isoamyl alcohol and ethyl acetate. After extraction the sample was chromatographed on a cation-exchange column and monitored at 313 nm. The retention times were 5, 7 and 9 min and detection limits 20, 10 and 5 ng/ml for 7-OH-MTX, MTX and APA, respectively. For concentrations greater than 100 ng/ml one-step deproteinization of 0.1 ml sample with 0.25 ml acetonitrile was satisfactory for sample preparation. The method has been evaluated in samples from patients and rabbits receiving MTX.     

Auxin Asymmetry during Gravitropism by Tomato Hypocotyls

Gravitropic asymmetry of auxin was observed in hypocotyls of tomato (Lycopersicon esculentum Mill.) soon after horizontal placement: the ratio of apically supplied [³H]IAA collected from the lower sides to that from the upper sides was about 1.4 between 5 and 10 minutes. This was adequately early to account for the beginning of curvature. The auxin asymmetry ratio rose to about 2.5 between 20 and 25 minutes, and to 3.5 during the main phase of curvature. This compares reasonably well with the roughly 3.9 ratio for elongation on the lower side to elongation on the upper side that is the basis for the curvature. These data extend evidence that the Went-Cholodny theory for the mediation of tropisms is valid for dicot stems. Also consistent with the theory, an auxin asymmetry ratio of 2.5 was observed when wrong-way gravitropic curvature developed following application of a high level of auxin. In addition to reversing the asymmetry of elongation, the large supplement of auxin resulted in lower net elongation. Previous data established that ethylene is not involved in this decrease of growth as a function of increasing level of auxin.     

Nanoplanktonic coccolithophorids (Prymnesiophyceae, Haptophyceae) from the Weddell Sea, Antarctica

The examination of whole mounts prepared for transmission electron microscopy has resulted in the finding of thirteen taxa of nanoplanktonic coccolithophorids from the Weddell Sea, Antarctica. The material was collected as part of the AMERIEZ programme, March 1986. Cold-water adapted nanoplanktonic coccolithophorids have previously been shown to constitute a recurrent plankton element at subarctic and arctic localities. Three of the Weddell Sea species, Wigwamma annulifera, W. arctica , and Papposphaera sagittifera , are conspecific with northern hemisphere material, while two species, Calciarcus alaskensis and Turrisphaera arctica , are possibly identical with previously described arctidsubarctic material. Six taxa new to science have been described from the Weddell Sea, Wigwamma antarctica, W. triradiata, Trigonaspis melvillea, Pappomonas weddellensis, Papposphaera obpyramidalis , and P. simplicissima . The cooccurrence of identical forms at the two poles, and the fact that the species described are allocated to "arctic" genera, indicate a geologically relatively recent exchange of biological material between the poles.     

Uses of 3D planning in addition to creating a good treatment: Ongoing studies at MGH/HCL

Summary Ongoing studies and 3D treatment planning and its clinical impact will be described.Invited paper given on the fourth workshop on Heavy Charged Particles in Biology and Medicine GSI, Darmstadt, FRG, September 23–25, 1991     

ATP-dependent Ca2+ transport and Ca2+-ATPase activities in an enriched plasma membrane fraction from gypsy moth larval midgut tissue

A subcellular fraction enriched in plasma membranes was obtained from gypsy moth (Lymantria dispar) larval midgut tissue. Using [⁴⁵Ca]²⁺ as a tracer, Ca²⁺ transport activity by membrane vesicles in the enriched fraction was measured and shown to be ATP-dependent, with a very high affinity for Ca²⁺ (apparent K_m for [Ca²⁺ _free]

1 Abbreviations used: [Ca²⁺free] = concentration of free (unbound) calcium ion;CaM = calmodulin; F = fraction; IOV = inside-out membrane vesicles; W-5 = N-(6-aminohexyl)-1-naphthalenesulfonamide; W-7 = N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide.

= 22 nM). Ca²⁺ transport was abolished upon addition of the calcium ionophore, A23187. Ca²⁺-stimulated, Mg²⁺-dependent ATPase activity peaked between 100 and 200 nM Ca²⁺_free. Ca²⁺-Mg²⁺-ATPase activity was inhibited by vanadate, 2 phenothiazine drugs (trifluoperazine and chlorpromazine), and the naphthalene sulfonamide, W-7; the related compound, W-5, and ouabain had a negligible effect. These results suggest the presence of a high affinity plasma membrane Ca²⁺ pump in gypsy moth larval midgut cells and are discussed in light of earlier work involving calcium transport in isolated midguts of larval Hyalophora cecropia. Ionic and other conditions that characterize the midgut physiology of larval Lepidoptera (e.g., luminal pH; electrochemical gradient for Ca²⁺; effect of certain ions and inhibitors on Ca²⁺ transport) contrast significantly with those found in adult Diptera. The implications that these differences may have for calcium regulation are discussed. © 1992 Wiley-Liss, Inc.     

Osteogenesis imperfecta due to recurrent point mutations at CpG dinucleotides in the COL1A1 gene of type I collagen

Summary Most individuals with osteogenesis imperfecta (OI) are heterozygous for dominant mutations in one of the genes that encode the chains of type I collagen. Each of the more than 30 mutations characterized to date has been unique to the affected member (s) of the family. We have determined that two individuals with a progressive deforming variety of OI, OI type III, have the same new dominant mutation [1(I)gly154 to arg] and that two unrelated infants with perinatal lethal OI, OI type II, share a second new dominant muation [1(I)gly1003 to ser]. These mutations occurred at CpG dinucleotides, in a manner consistent with deamination of a methylated cytosine residue, and raise the possibility that CpG dinucleotides are common sites of recurrent mutations in collagen genes. Further, these findings confirm that the OI type-III phenotype, previously thought to be inherited in an autosomal recessive manner, can result from new dominant mutations in the COL1A1 gene of type-I collagen.     

Channel formation in phospholipid bilayer membranes by the toxin ofHeminthosporium maydis,race T

Summary Southern Corn Leaf Blight is caused by a toxin produced by a virulent form ofHelminthosporium maydis (Race T). The toxin has been shown to uncouple oxidative phosphorylation and dissipate Ca²⁺ gradients in mitochondria isolated from susceptible, but not resistant, corn. The possibility that the toxin acted by increasing the permeability of membranes to ions was tested using a planar bilayer membrane system. Addition of the toxin to the bilayer system, under voltage-clamp conditions, resulted in stepwise increases in current across the phospholipid bilayer, a response characteristic for channel formers. Single-channel conductance in 1m KCl is 27 pS which corresponds to 1.7×10⁷ ions sec^–1 channel^–1 at 100 mV applied potential. The toxin channels are: (i) fairly uniform in conductance, (ii) ideally selective for K⁺ over Cl^–, and (iii) most conductive to H⁺. The channel showed the following selectivity for alkali metal cations: Rb⁺>K⁺>Cs⁺>Na⁺>Li⁺ (169731) based on the most frequently observed conductance in 1m chloride salts. The toxin showed no voltage dependence over the range of –100 to +100 mV. Channel formation was also a property of a synthetic analog (Cmpd IV) of the toxin. The ability of the native toxin to form channels may be a mode of toxin action on mitochondrial membranes from susceptible corn.     

Immunofluorescent and calcofluor white staining of developing tracheary elements inZinnia elegans L. Suspension cultures

Summary Xylogenesis has been studied in primary suspension cultures ofZinnia elegans L.: The wall patterns produced in culture closely resemble those described for intact tissues (annular, spiral, reticulate, scalariform, pitted). Using fluorescence microscopy and immuno-cytochemical techniques we have followed both the changes in wall deposition and microtubule organization during xylogenesis. Calcofluor white has been used to detect secondary wall deposition before it can be observed using either phase contrast or polarization optics. The development of tracheary elements can be divided into three stages: 1. microtubules grouped into bands without secondary wall deposition evident; 2. groups of microtubules subtending wall material only visible using Calcofluor white; 3. a complex microtubule pattern reflected by well developed wall thickenings detected using Calcofluor, phase contrast and polarization optics.     

Kinetics of Micronucleus Expression In Synchronized Irradiated Chinese Hamster Ovary Cells

The kinetics of expression of radiation-induced micronuclei (MN) in synchronized Chinese hamster cells (CHO) was examined. the purpose of the study was to determine if the cell cycle distribution of a population significantly influences the levels of radiation induced MN, thereby obscuring the exact quantification of the radiation effect. Cells were synchronized by centrifugal elutriation, irradiated, and then different phases of the cell cycle were examined for: cell cycle progression, division probability, and temporal expression of MN. the results demonstrate that the time interval for maximal MN expression is long enough that the position of cells in the cell cycle and radiation induced division delays do not prevent the majority of cells from completing their first post-irradiation mitosis, therefore, expressing MN. By following the progression of synchronized cell populations by flow cytometry and also examining the time of division of individual cells for 24 hr after irradiation, we observed that the maximum number of cells from all phases of the cell cycle are in their first post-irradiation interphase at that time, thus explaining the MN results.