Effects of colchicine on cardiac cell function indicate possible role for membrane surface tubulin

The effects of the tubulin-binding drug colchicine on cultured neonate cardiac cell function were investigated. Application of low doses of colchicine (but not lumicolchicine) caused an early reversible increase in beating rate with a concomitant decrease in amplitude. Treatment of the cells with trypsin at a dose that removes surface tubulin but does not inhibit spontaneous beating, diminished the colchicine effect. Surface radio-iodination of the live cultures followed by two-dimensional gel electrophoresis and radioautography revealed that two spots were heavily labeled. These spots co-migrated with purified brain tubulin. Fibroblasts derived from the cardiac cultures did not label over the tubulin spots. Trypsin treatment removed the presumptive tubulin from the radioautographs but only removed the most basic portion of the alpha-tubulin spot from the stained gel. These results are consistent with a surface membrane role for an iso-form of tubulin in neonate cardiac cells.     

Photocontrol of Hypocotyl Elongation in Light-Grown Cucumis sativus L. : Responses to Phytochrome Photostationary State and Fluence Rate

The effects of the calculated photostationary state of phytochrome (_c) and the photon fluence rate on the elongation growth of the hypocotyl of light-grown seedlings of Cucumis sativus L. are examined. Two threshold responses to _c are found at values of 0.06 and 0.43. At _c = 0.06, there is no response at any fluence rate. In the _c range 0.1 to 0.43, elongation growth does not respond to changes in _c. Above the second threshold (_c = 0.43), there is a strong response to changes in _c. At all values of _c at and above 0.1, there is a response to fluence rate. A linear relationship can be demonstrated between a factor comprised of the logarithm of phytochrome cycling rate (a fluence-rate-dependent process) and _c, and the growth response.     

Ontogenetic and individual variation in size, shape and speed in the Australian agamid lizard Amphibolurus nuchalis

The present study investigates relationships among size, shape and speed in the Australian agamid lizard Amphibolurus nuchalis . Maximal running speed, body mass, snout-vent length, tail length, fore- and hind limb spans and thigh muscle mass were measured in 68 field-fresh individuals spanning the entire ontogenetic size range (1.3 48 g). Relative lengths of both foreand hind limbs decrease with increasing body mass (= negative allometry), whereas relative tail length and thigh muscle mass increase with body mass (= positive allometry). Repeatable and significant differences in maximal running speed exist among individuals. Maximal running speed scales as (body mass)^0.161, and 59% of the variation in maximal speed was related to body mass. Based on the results of the present and previous studies, data on scaling of body proportions alone appear inadequate to infer scaling relationships of functional characters such as top speed.
Surprisingly, individual variation in maximal speed is not related to individual variation in shape (relative limb, tail and body lengths). These components of overall shape are not independent; individuals tended to have either relatively long or relatively short limbs, tails and bodies for their body mass. Even the significant difference in multivariate shape between adult males and females has no measurable consequences for maximal speed. Speeds of field-fresh animals did not vary on a seasonal basis, and eight weeks of captivity had no effect on maximal running speeds. Gravid females and long-term (obese) captive lizards were both approximately 12% slower than field-fresh lizards.     

Catalytic properties of the resolved flavoprotein and cytochrome B components of the NADPH dependent O2−• generating oxidase from human neutrophils

The resolved flavoprotein and cytochrome b₅₅₉ components of the NADPH dependent $\text{O}{}_2{}^{\mathrm{?}}{}_{\mathrm{?}}$ generating oxidase from human neutrophils were the subject of further study. The resolved flavoprotein, depleted of cytochrome b₅₅₉, was reduced by NADPH under anaerobic conditions and reoxidized by oxygen. NADPH dependent $\text{O}{}_2{}^{\mathrm{?}}{}_{\mathrm{?}}$ generation by the resolved flavoprotein fraction was not detectable, however it was competent in the transfer of electrons from NADPH to artificial electron acceptors. The resolved cytochrome b₅₅₉, depleted of flavoprotein, demonstrated no measureable NADPH dependent $\text{O}{}_2{}^{\mathrm{?}}{}_{\mathrm{?}}$ generating activity and was not reduced by NADPH under anaerobic conditions. The dithionite reduced form of the resolved cytochrome b₅₅₉ was rapidly oxidized by oxygen, as was the cytochrome b₅₅₉ in the intact oxidase.     

A comparison of the contractile activity of PGD2 and PGF2 alpha on human isolated bronchus

Prostaglandins may be implicated in the bronchoconstriction which occurs in asthma. Prostaglandins F2 alpha (PGF2 alpha) and D2 (PGD2) have been reported to produce bronchoconstriction in asthmatic subjects in vivo and PGF2 alpha contracts human isolated airway smooth muscle. We examined the relative efficacy and potency of PGF2 alpha and PGD2 on human bronchial spiral strips taken from 6 patients at thoracotomy. PGF2 alpha had greater efficacy than PGD2. The mean % Tmax (percentage of maximal contractile response) +/- s.e. mean were 84 +/- 7 and 54 +/- 7 respectively (P less than 0.05). PGF2 alpha (mean pD2 +/- s.e. mean = 6.39 +/- 0.6) tended to be more potent than PGD2 (5.68 +/- 0.2). Since, in vivo, PGD2 has greater efficacy and potency than PGF2 alpha, our results suggest that the in vivo effect of these prostaglandins does not result solely from an action on airway muscle.     

Arginine vasopressin causes morphological changes suggestive of fluid transport in rat choroid plexus epithelium

Summary The experiments described herein use an in vitro preparation of choroid plexus to demonstrate that it is a vasopressin-responsive organ by morphologic criteria. Choroid plexus from rats was incubated for one hour in graded concentrations of arginine vasopressin (AVP). Within physiologic range of molar concentration, incubation in vasopressin induced a decrease in basal and lateral spaces in choroid plexus epithelial cells as well as an increase in number of dark cells. The number of cells with basal spaces decreased significantly from 82.7±9.2 in control tissue to 19±18 in tissue incubated in 10^-12 M AVP; similarly, the number with lateral cellular spaces decreased from 20±8.8 to 7.6±2.2 cells in 10^-10 M AVP. Dark cells increased in number from 3.8±2.6 in control conditions to 49±4 with 10^-9 M vasopressin. These data suggest important effects of arginine vasopressin in cerebrospinal fluid (CSF) on choroid plexus, compatible with enhanced fluid transport across choroid epithelial cells.     

A novel chlorophyll a/b binding (Cab) protein gene from petunia which encodes the lower molecular weight Cab precursor protein.

The 16 petunia Cab genes which have been characterized are all closely related at the nucleotide sequence level and they encode Cab precursor polypeptides which are similar in sequence and length. Here we describe a novel petunia Cab gene which encodes a unique Cab precursor protein. This protein is a member of the smallest class of Cab precursor proteins for which no gene has previously been assigned in petunia or any other species. The features of this Cab precursor protein are that it is shorter by 2-3 amino acids than the formerly characterized Cab precursors, its transit peptide sequence is unrelated, and the mature polypeptide is significantly diverged at the functionally important N terminus from other petunia Cab proteins. Gene structure also discriminates this gene which is the only intron containing Cab gene in petunia genomic DNA.     

A test of the hypothesis of pheromone attraction in salmonid migration

Synopsis We tested the hypothesis that anadromous salmonids are guided on their homeward migration by population-specific pheromones. Our findings do not support the hypothesis. Wild migrant Arctic charr,Salvelinus alpinus, from Ikarut River, Labrador were transferred and held in a tributary previously uninhabited by anadromous fish. None of the charr migrating up Ikarut River entered the tributary after fish were transferred. Similarly, migrant charr, which were caught in Ikarut River and released in the tributary below the captive fish, did not remain in the tributary. We re-evaluated the data which have been used to uphold the concept of pheromone attraction in salmonid migration and concluded that support for the hypothesis is unsubstantiated.