A mechanism for multiphasic uptake of solutes in plants

A molecular mechanism is proposed for unitary multiphasic uptake in which the carrier has two binding sites for the substrate. The first site binds n-1 molecules of substrate, and then one additional substrate molecule can become bound at the second binding site. Only this last molecule is transported in the operation of the carrier molecule. In the free state, the carrier can be activated to successive states with increasing affinities for the substrate in the two binding sites. The mechanism is resolved for the steady state conditions, obtaining a simple uptake rate equation, which fits the experimental data. Methods for determining the parameters of the equation are presented. Evidence other than kinetics is discussed for the mechanism. The mechanism also provides a physiological interpretation for multiphasic uptake: the active transport mechanisms (energy-requiring mechanisms) are prevented from operating at high substrate concentrations, thus preventing a waste of energy by the cells.     

Expression of the Plastid ndhF Gene Product in Photosynthetic and Non-Photosynthetic Tissues of Developing Barley Seedlings

A fragment of the NDH-F subunit of the plastid NAD(P)H dehydrogenasecomplex (NAD(P)H-plastoquinone-oxidoreductase) from barley wasexpressed as a fusion protein in Escherichia coli and an antibodyto the fusion protein was prepared. Western blot analysis usingthe anti-NDH-F antibody showed specificity towards a plastidpolypeptide of approximately 70 kDa present in both photosyntheticand non-photosynthetic barley tissue. The polypeptide was foundin thylakoid membranes of green leaves whereas in etiolatedleaves it was shown to be associated with the membrane fractionof etioplasts. NDH-F levels were higher in roots and etiolatedtissue than in greening or young leaves. During leaf ontogeny,NDH-F levels decreased from young to mature tissue but increasedduring senescence. The accumulation of NDH-F in thylakoids ofyoung leaves was stimulated by photooxidative treatment. Theresults indicate a high degree of expression of plastid ndhgenes (which encode NAD(P)H dehydrogenase sub-units) in non-photosyntheticplastids and under conditions which impair the photosyntheticactivity of chloroplasts. In addition to its putative implicationin photosynthetic electron transport, a non-photosynthetic role,such as chloro-respiration, is proposed for the plastid NAD(P)Hdehydrogenase complex. (Received May 20, 1997; Accepted October 8, 1997)     

Inhaled porcine pancreatic elastase causes bronchoconstriction via a bradykinin-mediated mechanism.

Neutrophil elastase has been linked to inflammatory lung diseases such as chronic obstructive pulmonary disease, adult respiratory distress syndrome, emphysema, and cystic fibrosis. In guinea pigs, aerosol challenge with human neutrophil elastase causes bronchoconstriction, but the mechanism by which this occurs is not completely understood. Our laboratory previously showed that human neutrophil elastase releases tissue kallikrein (TK) from cultured tracheal gland cells. TK has been identified as the major kininogenase of the airway and cleaves both high- and low-molecular weight kininogen to yield lysyl-bradykinin. Because inhaled bradykinin causes bronchoconstriction and airway hyperresponsiveness in asthmatic patients and allergic sheep, we hypothesized that elastase-induced bronchoconstriction could be mediated by bradykinin. To test this hypothesis, we measured lung resistance (RL) in sheep before and after inhalation of porcine pancreatic elastase (PPE) alone and after pretreatment with a bradykinin B(2) antagonist (NPC-567), the specific human elastase inhibitor ICI 200,355, the histamine H(1)-antagonist diphenhydramine hydrochloride, the cysteinyl leukotriene 1 receptor antagonist montelukast, or the cyclooxygenase inhibitor indomethacin. Inhaled PPE (125-1,000 microg) caused a dose-dependent increase in RL. Aerosol challenge with a single 500 microg dose of PPE increased RL by 132 +/- 8% over baseline. This response was blocked by pretreatment with NPC-567 and ICI-200,355 (n = 6; P < 0.001), whereas treatment with diphenhydramine hydrochloride, montelukast, or indomethacin failed to block the PPE-induced bronchoconstriction. Consistent with pharmacological data, TK activity in bronchial lavage fluid increased 134 +/- 57% over baseline (n = 5; P < 0.02). We conclude that, in sheep, PPE-induced bronchoconstriction is in part mediated by the generation of bradykinin. Our findings suggest that elastase-kinin interactions may contribute to changes in bronchial tone during inflammatory diseases of the airways.     

EFFECT OF COPPER ON ALGAL COMMUNITIES FROM OLIGOTROPHIC CALCAREOUS STREAMS1

Two sets of experiments were done to quantify the effects of chronic copper exposure on natural peri‐ phyton in a nonpolluted calcareous river. The results of short‐term (up to 6 h exposure) experiments corroborated the significance of pH on copper toxicity. Copper toxicity increased when pH was reduced from 8.6 to 7.7, and this was related to the effect of pH on copper speciation (free copper concentration increased from 0.2% to 2.3% of total copper). Longer term experiments demonstrated that periphyton communities exposed to copper under pH variation (8.2–8.6) were already affected at 10 μg·L ^{? 1} (20–80 ng·L ^{? 1} Cu^{2 +} ) after 12 days of exposure. Copper exposure caused stronger effects on structural (algal biomass and community structure) than on functional (photosynthetic efficiency) parameters of peri‐ phyton. Changes in community composition included the enhancement of some taxa (Gomphonema gracile), the inhibition of others (Fragilaria capucina and Phormidium sp.), and the appearance of filament malformations (Mougeotia sp.). The results of our study demonstrated that several weeks of exposure to copper (10–20 μg·L ^{? 1}) were sufficient to cause chronic changes in the periphyton of oligotrophic calcareous rivers. This degree of copper pollution can be commonly found in the Mediterranean region as a result of agricultural practices and farming activities.     

Neoadjuvant Sequential Docetaxel Followed by High‐Dose Epirubicin in Combination With Cyclophosphamide Administered Concurrently With Trastuzumab. The DECT Trial

To report the results of the DECT trial, a phase II study of locally advanced or operable HER2‐positive breast cancer (BC) treated with taxanes and concurrent anthracyclines and trastuzumab. Eligible patients (stage IIA‐IIIB HER2‐positive BC, 18–75 years, normal organ functions, ECOG ≤1, and left ventricular ejection fraction (LVEF) ≥55%) received four cycles of neoadjuvant docetaxel, 100 mg/m² intravenously, plus trastuzumab 6 mg/kg (loading dose 8 mg/kg) every 3 weeks, followed by four 3‐weekly cycles of epirubicin 120 mg/m² and cyclophosphamide, 600 mg/m², plus trastuzumab. Primary objective was pathologic complete response (pCR) rate, defined as ypT0/is ypN0 at definitive surgery. We enrolled 45 consecutive patients. All but six patients (13.3%) completed chemotherapy and all underwent surgery. pCR was observed in 28 patients (62.2%) overall and in 6 (66.7%) from the inflammatory subgroup. The classification and regression tree analysis showed a 100% pCR rate in patients with BMI ≥25 and with hormone negative disease. The median follow up was 46 months (8–78). Four‐year recurrence‐free survival was 74.7% (95%CI, 58.2–91.2). Seven patients (15.6%) recurred and one died. Treatment was well tolerated, with limiting toxicity being neutropenia. No clinical cardiotoxicity was observed. Six patients (13.4%) showed a transient LVEF decrease (<10%). In one patient we observed a ≥10% asymptomatic LVEF decrease persisting after surgery. Notwithstanding their limited applicability due to the current guidelines, our findings support the efficacy of the regimen of interest in the neoadjuvant setting along with a fairly acceptable toxicity profile, including cardiotoxicity. Results on BMI may invite further assessment in future studies. J. Cell. Physiol. 231: 2541–2547, 2016. © 2016 The Authors. Journal of Cellular Physiology Published by Wiley Periodicals, Inc.     

Higher plants possess two different types of ATX1-like copper chaperones

Copper (Cu) chaperones constitute a family of small Cu+-binding proteins required for Cu homeostasis in eukaryotes. The ATX1 family of Cu chaperones specifically delivers Cu to heavy metal P-type ATPases. The plant Arabidopsis thaliana expresses the ATX1-like Cu chaperone CCH, which exhibits a plant-specific carboxy-terminal domain (CTD) with unique structural properties. We show that CCH homologues from other higher plants contain CTDs with structural properties similar to Arabidopsis CCH. Furthermore, we identify a new ATX1-like Cu chaperone in Arabidopsis, AtATX1, which functionally complements yeast atx1Delta and sod1Delta associated phenotypes, and localizes to the cytosol of Arabidopsis cells. Interestingly, AtATX1, but not full-length CCH, interacts in vivo with the Arabidopsis RAN1 Cu-transporting P-type ATPase by yeast two-hybrid. We propose that higher plants express two types of ATX1-like Cu chaperones: the ATX1-type with a predominant function in Cu delivery to P-type ATPases, and the CCH-type with additional CTD-mediated plant-specific functions.