Phytochrome-mediated phototropism in maize seedling shoots

Unilateral irradiation with red light (R) or blue light (BL) elicits positive curvature of the mesocotyl of maize (Zea mays L.) seedlings raised under R for 2 d from sowing and kept in the dark for 1 d prior to curvature induction. The fluenceresponse curve for R-induced mesocotyl curvature, obtained by measuring curvature 100 min after phototropic induction, shows peaks in two fluence ranges, designated first positive range (from the threshold to the trough), and second positive range (above the trough). The fluence-response curve for BL is similar to that for R but shifted two orders of magnitude to higher fluences. Blue light elicits the classical first positive curvature of the coleoptile, whereas this response is not found with R. Positive mesocotyl curvature induced by either R or BL is eliminated by R given from above just before the unilateral irradiation, whereas BL-induced coleoptile curvature is not eliminated. The above results collectively offer evidence that phototropic curvature of the mesocotyl is induced by R-sensitive photosystem(s). Mesocotyl curvature in the second positive range is reduced by vertical far-red light (FR) applied after phototropic induction with R, but is not affected by FR applied before R. Unilateral irradiation with FR following vertical irradiation with a high R fluence leads to negative curvature of the mesocotyl. It is concluded that mesocotyl curvature in the second positive range results from a gradient in the amount of the FR-absorbing form of phytochrome (Pfr) established across the plant axis. Mesocotyl curvature in the first positive range is inhibited by vertical FR given either before or after phototropic induction with R. Since the FR used here is likely to produce more Pfr than the very low fluences of R eliciting the mesocotyl curvature in the first positive range, it is assumed that FR reduces the response in this case by adding Pfr at both sides of the plant axis. By rotating seedlings on a clinostat with its axis horizontal, the kinetics of mesocotyl curvature can be studied in the absence of a counteracting gravitropic response. On the clinostat, the R-induced mesocotyl curvature develops after a lag, through two successive phases having different curvature rates, the late phase is slower than the early phase. Negative curvature of the coleoptile can be induced by either R or BL; the BL-induced negative curvature is found at fluences higher than those giving positive curvature. The clinostat experiments show that the negative coleoptile curvature induced by either R or BL is a gravitropic compensation for positive mesocotyl curvature.Abbreviations BL blue light - FR far-red light - Pfr phytochrome in the far-red-absorbing form - Pr phytochrome in the red-absorbing form - R red light C.I.W.-D.P.B. Publication No. 824     

Thermodynamical model for insertion and aggregate binding of caffeine to the homopolymer poly(riboadenylate) and model choice by data analysis

This paper describes the model used to estimate the parameters of caffeine-poly(riboadenylate) (poly(A)) interactions from corresponding 1H-NMR measurements. The model of insertion and aggregate binding describes the non-cooperative insertion of a molecule C into an interspace between two monomers of a homopolymer in competition with aggregate binding. It contains two binding constants, K1 for insertion and K2 for the interaction of monomeric A units of the polymer with C molecules in bound aggregates, and two cooperativity parameters, Kcc for stacking of C molecules within aggregates and tau which is thought to be due to conformational adaptation of the polymer to those bound aggregates which cover more than one A unit. In contrast to other models, the size of a binding site (within the aggregates) is less than one monomeric unit, with n denoting the maximum number of C molecules per A unit in bound aggregates. The model is developed for general n by means of the method of sequence-generating functions. For n = 2 and n = 3, the correctness of the model treatment was checked by the matrix method. The model is applicable to the binding of aggregates to homopolymers, which are flexible enough to fit their structure to the aggregates.     

The fluidity of plasma membranes from ethanol-treated rat liver

Summary Male Wistar rats were maintained for 35–40 days on a liquid diet containing 36% of calories as ethanol. Ethanol was replaced by carbohydrates in the isocaloric diet fed to control animals. The effect of ethanol consumption has been studied on the fluorescence polarization of rat liver plasma membranes and artificial lipid vesicles and on the lipid composition of the membranes. Fluorescence polarization in both membranes and vesicles was determined using DPH and TMA-DPH as fluorescence markers; from these data, the polarization term (r_o/r–1)^–1 and flow activation energy (E) were calculated. The ethanol consumption induces a more fluid environment within the membrane core of liver plasma membranes; the ethanol-fed rat membranes are more resistant to the in vitro effect of ethanol disordering the membrane structure. Vesicles obtained with lipids from either control membranes or ethanol-fed rat membranes were treated with ethanol and the changes in polarization paralleled to those exhibited by the membranes. The absence of phase transitions and of E changes was also shown in temperature-dependence studies. The lower cholesterol content found in ethanol-fed rat plasma membranes might be responsible for observed variations in the microviscosity.Abbreviation OG octyl -D-glucopyranoside     

Phytochrome Control of Its Own Synthesis in Pisum sativum

An analysis of phytochrome synthesis in Pisum seedlings by measuringthe activity of polysomal polyadenylated RNA (poly-A⁺-RNA) codingfor phytochrome apoprotein showed phytochrome control of itsown synthesis; brief red-light irradiation of pea seedlingsinhibited the activity of the RNA, and the red-light effectwas red/far-red reversible. ⁴ Permanent address: Biology Department, Faculty of Science,University of Tokyo, Hongo, Tokyo 113, Japan. (Received August 13, 1984; Accepted September 17, 1984)     

Substrate slope and orientation in a land hermit crab,Coenobita clypeatus (Decapoda,Coenobitidae)

Summary Coenobita clypeatus were tested on an underwater inclined plane in order to determine their behavioral threshold for perceiving slope, and to investigate the relative importance of input from the statocyst organ and from the weight of the body and gastropod shell on upward orienting ability. The shell's weight was compensated for by a neutral float and increased by weights. The crabs perceive an inclination of less than 5°, and do so with increasing certainty as the slope increases. Perception of the slope seems to be both by statocyst and proprioceptive input, but the latter is not essential for upward orientation.     

Electron microscopic demonstration of calcitonin in human medullary carcinoma of thyroid by the immuno gold staining method

In a human medullary carcinoma of thyroid gland containing calcitonin in light microscopic demonstration by the avidin biotin complex (ABC) method characteristic secretory granules were found electron microscopically in the cytoplasm of the tumour cells. They consisted in so-called type I granules (270 +/- 25 nm) and type II granules (135 +/- 17 nm). By the immuno gold staining (IGS) method the content of many secretory granules measuring 85-270 nm (152 +/- 18 nm) in diameter could be identified as calcitonin. These granules seemed to be predominantly of type II because of their nearly corresponding size and feature. The type I granules were less frequent in number and they showed no or little immunoreactivity. The results indicate that the IGS-method is practicable to demonstrate the ultrastructural localization of calcitonin and to identify clearly the nature of intracytoplasmic granules in electron microscopy.     

Potassium accumulation in growing Methanobacterium thermoautotrophicum and its relation to the electrochemical proton gradient

Cultures of Methanobacterium thermoautotrophicum (Marburg) growing on media low in potassium accumulated the cation up to a maximal concentration gradient ([K⁺]_{intracellular}/[K⁺]_{extracellular}) of approximately 50,000-fold. Under these conditions, the membrane potential was determined by measuring the equilibrium distribution of the lipophilic cation (¹⁴C) tetraphenylphosphonium (TPP⁺). This cation was accumulated by the cells 350-to 1,000-fold corresponding to a membrane potential (inside negative) of 170–200 mV. The pH gradient, as measured by equilibrium distribution of the weak acid, benzoic acid, was found to be lower than 0.1 pH units (extracellular pH=6.8). The addition of valinomycin (0.5–1 nmol/mg cells) to the culture reduced the maximal concentration gradient of potassium from 50,000-to approximately 500-fold, without changing the membrane potential. After dissipation of the membrane potential by the addition of ¹²C-TTP⁺ (2 mol/mg cells) or tetrachlorosalicylanilide (3 nmol/mg cells), a rapid and complete efflux of potassium was observed.These data indicate that potassium accumulation in the absence of valinomycin is not in equilibrium with the membrane potential. It is concluded that at low extracellular K⁺ concentrations potassium is not accumulated by M. thermoautotrophicum via an electrogenic uniport mechanism.Non-common abbreviations TPP⁺ Tetra phenylphosphonium bromide - DTE Dithioerythritol - TCS 3,5,3,4-Tetrachlorosalycylanilide     

Studies on the (pro) insulin biosynthesis of islets of Langerhans of sand rats (Psammomys obesus).

By feeding a regular laboratory chow, sand rats (Psammomys obesus) from our breeding colony gained different body weights, though they received approximately the same quantity of calories. Sand rats, reaching a body weight above 160 g (group B) showed significantly increased blood glucose values in contrast to the animals with a body weight under 160 g (group A). Isolated pancreatic islets of these two groups of sand rats were incubated with [3H]-leucine to study the incorporation of this amino acid into proinsulin and insulin. The incorporation into proteins of pancreatic islets of sand rats of group B was stimulated by 0.45 mg and 3.0 mg/ml glucose. In group A there was no further stimulation from 0.45 mg to 3.0 mg/ml glucose. Insulin secretion could be stimulated by glucose in both groups, but the stimulation was stronger in group B than in group A.     

In vitro synthesis and stability of RNA in isolated nuclei from bovine lymphocytes

Nuclei from Concanavalin A-stimulated lymphocytes (30 hr after Con A addition) incorporate up to 5 times more (3-H)UTP into RNA than nuclei from resting lymphocytes. The incorporation kinetics is linear for almost 60 min. 14–20% of the $\text{in vitro}$ labeled RNA is polyadenylated. Poly(A) (?)RNA from both types of nuclei sediments from 4–5S up to more than 30S on sucrose gradients. Nuclei from stimulated cells synthesize about double the amount of RNA larger than 18S than nuclei from resting cells. The same holds for poly(A) (+)RNA. Poly(A) (?) RNA labeled during 10 min in both types of nuclei is stable during a 30 min chase. Under the same conditions poly(A) (+)RNA in nuclei from resting cells is degraded to about 50% during the chase whereas it is stable in nuclei from stimulated cells.     

Role of carbohydrate in biological functions of Friend murine leukemia virus gp71.

Purified gp71 of Friend murine leukemia virus (FLV) can interfere with virus infection, absorb neutralizing antibody, and in the presence of group-specific anti-gp71 antibody, hemagglutinate sheep erythrocytes. Interference by FLV gp71 with several murine leukemia viruses (MuLV) was tested in the XC and S + L- assay systems. Treatment of gp71 with trypsin or Pronase eliminated its interfering capacity. However, treatment with neuraminidase or a mixture of glycosidase enzymes, which left the major serological properties of gp71 intact, did not reduce the interference potential of gp71 for FLV or AKR MuLV. The capacity of gp71 to absorb type- or group-specific virus-neutralizing antibodies was similarly affected by the various enzyme treatments. In contrast, indirect hemagglutination by gp71 was abolished not only by proteases but also by treatment with glycosidase enzymes, although neuraminidase had no effect. Preliminary data indicate that infectivity of FLV or xenotropic MuLV was not affected by short treatment with glycosidase enzymes.