Sequence-dependent molecular conformation of polynucleotides: right and left-handed helices

Based upon a stereochemical guideline, two topologically distinct types of helicalduplexes have been deduced for a polynucleotide duplex with alternating purine pyrimidine sequence (PAPP): (a) right-handed uniform (RU) helix and (b) left-handed zig-zag (LZ) helix. Both structures have trinucleoside diphosphate as the basic unit wherein the purine pyrimidine fragment has a different conformation from the pyrimidine-purine fragment. Thus, RU and LZ helices represent two different classes of sequence-dependent molecular conformations for PAPP. The conformationalf eatures of an RU helix of PAPP in B-form and three LZ-helices for B-, D- and Z-forms are discussed.     

Down and Turner syndromes in a female infant with 47,X,del(X)(p11),+21

Summary This report describes a female infant with a 47,X,del(X)(p11),+21 karyotype who has clinical features of both Down and Turner syndromes. The majority of her clinical features are suggestive of Down syndrome.     

The effect of adenylate cyclase inhibitor (ACI) on guanylate cyclase, phosphodiesterase and other enzymes in heart.

The effect of an inhibitor of adenylate cyclase (ACI) was measured on some enzymes associated with cyclic nucleotide-regulated metabolism. Soluble guanylate cyclase was inhibited; both soluble and particulate cyclic GMP-phosphodiesterases were stimulated. Cyclic AMP phosphodiesterases were unaffected. In contrast, the activities of Na, K-ATPase, protein kinase, phosphorylase kinase, glycogen synthetase and a number of glycosidases were not altered by equipotent amounts of the inhibitor. It is concluded that this substance acts as a modulator of both cyclic AMP and cyclic GMP metabolism in heart and other tissues.     

Auxin-binding Sites of Maize Coleoptiles Are Localized on Membranes of the Endoplasmic Reticulum

Sites in maize (Zea mays L.) coleoptile homogenates that reversibly bind naphthalene-1-acetic acid with high affinity and may represent receptor sites for auxins are located primarily on cellular membranes that show the enzymic and buoyant density characteristics of membranes of the rough endoplasmic reticulum. The sites remain attached to the endoplasmic reticulum (ER) membranes after the ribosomes have been stripped off them. Binding sites for naphthylphthalamic acid, an inhibitor of auxin transport, are located on membranes different from those that carry the naphthalene-1-acetic-acid (NAA)-binding sites, and which are probably plasma membrane. The two kinds of binding sites can be largely separated by appropriate density gradient centrifugation. The results raise the possibility that primary auxin action occurs at ER membranes and could represent facilitation of the transfer of hydrogen ions and nascent secretory protein into the ER lumen followed by secretory transport of these products to the cell exterior via the Golgi system.     

Thermocouple psychrometer for in situ leaf water potential determinations

Summary An in situ thermocouple psychrometer was tested to determine its capability for tracking the changing leaf water potentials of aspen (Populus tremuloides Michx.) under controlled conditions and in the field. The results agreed with theoretical expectations — a sharp decline in leaf water potential during the photoperiods and recovery during the dark periods, each to progressively lower levels during a soil drying cycle. In the field, a mid-day pause in the declining leaf water potentials was noted and attributed to transient stomatal closure. Details of the construction and use of the assembly are given.The authors are plant physiologists, USDA Forest Service, Intermountain Forest and Range Experiment Station, Ogden, Utah 84401, stationed in Logan, Utah, at the Forestry Sciences Laboratory.     

Effect of sodium selenite and methyl methanesulfonate or N-hydroxy-2-acetylaminofluorene co-exposure on sister-chromatid exchange production in human whole blood cultures.

Sodium selenite (Na2SeO3) was tested for its sister-chromatid exchange (SCE)-inducing ability in human whole blood cultures and for the effect of its co-exposure with methyl methanesulfonate (MMS) or N-hydroxy-2-acetylaminofluorene (N-OH-AAF) on SCE frequency. Long exposure times (77 h and 96 h) to 3.95 X 10(-6) M Na2SeO3 resulted in cell death as measured by mitotic indices, but mitotic figures were present after exposure to higher concentrations for a shorter time (19 h). High Na2SeO3 concentrations (7.90 X 10(-6) and 1.19 X 10(-5) M) resulted in a three-fold increase in the SCE frequency above background level (6--7 SCEs/cell). Exposure of lymphocytes to 1 X 10(-4) M MMS for the last 19 h of culture yielded an average SCE frequency of 30.17 +/- 0.75 while a similar exposure to 2.7 X 10(-5) M N-OH-AAF resulted in 13.61 +/- 0.43 SCEs/cell. Simultaneous addition of the high Na2SeO3 concentrations and MMS or N-OH-AAF to the cultures resulted in SCE frequencies that were 25--30% and 11--17%, respectively, below the sum of the SCE frequencies produced by the individual compounds.     

Labeling of the Plasma Membrane of Pea Cells by a Surface-localized Glucan Synthetase

When radioactive UDP-glucose is supplied to 1-millimeter-thick slices of pea (Pisum sativum) stem tissue, radioactive glucose becomes incorporated into membrane-bound polysaccharides. Evidence is given that this incorporation does not result from breakdown of UDP-glucose and utilization of the resultant free glucose, and that the incorporation most likely takes place at the cell surface, leading to a specific labeling of the plasma membrane. The properties of the plasma membrane that are indicated by this method of recognition, including the association of K⁺-stimulated ATPase activity with the plasma membrane, resemble properties inferred using other approaches. The membrane-associated polysaccharide product formed from UDP-glucose is largely 1,3-linked glucan, presumably callose, and does not behave as a precursor of cell wall polymers. No substantial amount of cellulose is formed from UDP-glucose in this procedure, even though these cells incorporate free glucose rapidly into cellulose. This synthetase system that uses external UDP-glucose may serve for formation of wound callose.     

Plating procedure for the enumeration of coliforms from dairy products.

A "repair-detection" procedure consisting of pour plating of food samples with Trypticase soy agar, followed by 1-h repair incubation at room temperature and subsequent overlay with violet red bile agar, was found to be an effective method for the detection of injuried and uninjuried coliforms from dairy products. This method was relatively less effective for the detection of coliforms in many semipreserved foods as compared with dairy products, but more effective than the most-probable-number method.     

Method for the detection of injured Vibrio parahaemolyticus in seafoods.

The sensitivity of Vibrio parahaemolyticus cells to refrigeration and frozen storage and the development of a method for detecting injured and uninjured V. parahaemolyticus cells were studied. Cell suspensions in different kinds of seafood homogenates were either regrigerated (4 degrees C) or frozen (-20 degrees C), stored, and examined for cell survival during storage. V. parahaemolyticus cells were sensitive to both storage temperatures. Many cells died, and many survivors were sublethally injured. In general, refrigeration storage appeared to be more injurious than frozen storage. The initial recovery of the sublethally injured cells was highest in a nutritionally rich, nonselective liquid medium such as Trypticase soy broth, whereas maximum cell multiplication was observed in Trypticase soy broth containing 3% NaCl. The sublethally injured V. parahaemolyticus cells demonstrated sensitivity to the selective enrichment medium, glucose salt teepol broth. From these findings, a new method (designated as the "repair-detection" method) was developed for the isolation and enumeration of V. parahaemolyticus. Comparative studies between the recommended and the repair-detection methods showed that injured V. parahaemolyticus cells were present in commercial seafoods and that the repair-detection method was definitely more effective for the detection of total numbers of V. parahaemolyticus cells.