Effect of pulmonary emphysema on diaphragm capillary geometry

Poole, David C., and Odile Mathieu-Costello. Effect ofpulmonary emphysema on diaphragm capillary geometry.J. Appl. Physiol. 82(2): 599-606, 1997.In emphysema, the diaphragm shortens by losing sarcomeres. Wehypothesized that unless capillaries undergo a similar shortening,capillary geometry must be altered. Without quantifying this geometry,capillary length and surface area per fiber volume, which are criticalmeasurements of the structural potential for blood-tissue exchange,cannot be resolved. Five months after intratracheal elastase (E) orsaline (control; C) instillation, diaphragms from male Syrian goldenhamsters were glutaraldehyde perfusion fixed in situ at reference lungpositions (residual volume, functional residual capacity, total lungcapacity) to provide diaphragms fixed over a range of sarcomerelengths. Subsequently, diaphragms were processed for electronmicroscopy and analyzed morphometrically. Emphysema increased lungvolume changes from 20 to 25 cmH₂O airway pressure (i.e.,passive vital capacity) and excised lung volume (bothP < 0.001). In each region of thecostal diaphragm (i.e., ventral, medial, dorsal), sarcomere number wasreduced (all P < 0.05).Capillary-to-fiber ratio increased (C = 2.2 ± 0.1, E = 2.8 ± 0.1; P < 0.01) and fibershypertrophied (C = 815 ± 35, E = 987 ± 67 µm²;P < 0.05; both values at 2.5 µmsarcomere length). Capillary geometry was markedly altered by the lossof sarcomeres in series. Specifically, the additional capillary lengthderived from capillary tortuosity and branching was increased by 183%at 2.5 µm sarcomere length compared with C values (C, 359 ± 43;E, 1,020 ± 158 mm²,P < 0.01). This significantlyincreased total capillary length (C, 3,115 ± 173; E, 3,851 ± 219 mm² at 2.5 µm,P < 0.05) and surface area (C, 456 ± 13; E, 519 ± 24 cm¹,P < 0.05) per fiber volume. Thusemphysema substantially alters diaphragm capillary geometry andaugments the capillary length and surface area available forblood-tissue exchange.

     

P2 purinoceptors regulate calcium-activated chloride and fluid transport in 31EG4 mammary epithelia

It has been reported thatsecretory mammary epithelial cells (MEC) release ATP, UTP, and UDP uponmechanical stimulation. Here we examined the physiological changescaused by ATP/UTP in nontransformed, clonal mouse mammary epithelia(31EG4 cells). In control conditions, transepithelial potential (apicalside negative) and resistance were 4.4 ± 1.3 mV (mean ± SD, n = 12) and 517.7 ± 39.4  · cm², respectively. The apicalmembrane potential was 43.9 ± 1.7 mV, and the ratio of apicalto basolateral membrane resistance (R_A/R_B) was 3.5 ± 0.2. Addition of ATP or UTP to the apical or basolateral membranescaused large voltage and resistance changes with an EC₅₀ of~24 µM (apical) and ~30 µM (basal). Apical ATP/UTP (100 µM)depolarized apical membrane potential by 17.6 ± 0.8 mV (n = 7) and decreasedR_A/R_B by a factor of3. The addition of adenosine to either side (100 µM) hadno effect on any of these parameters. The ATP/UTP responses werepartially inhibited by DIDS and suramin and mediated by a transientincrease in free intracellular Ca²⁺ concentration (427 ± 206 nM; 15-25 µM ATP, apical; n = 6). This Ca²⁺ increase was blocked by cyclopiazonic acid, by BAPTA,or by xestospongin C. 31EG4 MEC monolayers also secreted or absorbedfluid in the resting state, and ATP or UTP increased fluid secretion by5.6 ± 3 µl · cm² · h¹(n = 10). Pharmacology experiments indicate that 31EG4epithelia contain P2Y₂ purinoceptors on the apical andbasolateral membranes, which upon activation stimulate apicalCa²⁺-dependent Cl channels and cause fluid secretion acrossthe monolayer. This suggests that extracellular nucleotides could playa fundamental role in mammary gland paracrine signaling and theregulation of milk composition in vivo.

     

Interrelations between Phyllotaxis, Leaf Development and the Primary-secondary Vascular Transition in Populus deltoides

The procambial system of Populus deltoides Bartr. ex Marsh.plants progressed from phyllotaxy in the cotyledon stage throughthe phyllotactic orders 3/2;5/13. The nodal position at whicheach of these phyllotactic transitions occured was determinedby anatomical analyses; they were found to be remarkably consistentin a large population of young plants. The data were used todiagrammatically reconstruct the procambial system of a typical16 leaf plant. Because all plant parts grew continuously anduninterruptedly, it was not possible to verify the positionsof the phyllotactic transitions by morphological criteria. However,several measured parameters (the number and lengths of primordiawithin the terminal bud, the plastochron interval, and the numberof leaf traces with birefringent xylem elcments) attained constantvalues following establishment of the 5/13 phyllotaxy, suggestingthis to be the stable phyllotactic order for the species. Althoughbud size continued to increase in plants exhibiting 5/13 phyllotaxy,it could be accounted for by the increased number and size ofbasipetal subsidiary bundles in the procambial leaf traces.It was suggested that these phyllotactic transitions in theprocambial system are programmed in the plant to occur at ratherspecific stages of ontogeny. The process is mediated by theolder leaves and it is therefore modified by plant vigour. Locationof the primary-secondary vascular transition zone was also relatedto the order of phyllotaxy. It advanced acropetally in the stemin close association with leaf maturation, but this associationwas further influenced by plant vigour. Populus deltoides Bartr. ex Marsh., cottonwood, vascular anatomy, phyllotaxis, leaf growth, xylem     

MITOTIC ACTIVITY IN THE ROOT APICAL MERISTEM OF AZOLLA FILICULOIDES LAM., WITH SPECIAL REFERENCE TO THE APICAL CELL

The meristematic activity of the apical cell and its derivatives (merophytes) in the unbranched, determinate roots of Azolla filiculoides Lam. was investigated. The plane of division of the apical cell indicates that it is the initial of each merophyte. The division plane of each newly formed merophyte is strictly periclinal to the root surface and provides confirmation that the immediate derivatives of the apical cell cannot be the ultimate root initials. The frequency of cell division as determined by the mitotic index, and by the duration of the cell cycle as determined by the colchicine method, confirmed the meristematic activity of the apical cell. As roots increase in length, the duration of the cell cycle in the total meristem increases, with the apical cell possessing the longest cell cycle, whereas the immediate derivatives maintain approximately the same cycle duration as in shorter roots. In determinate Azolla roots, cell division appears to play a major role up to a certain root length, then increase in length is produced mainly by cell elongation.     

Innate immune response in CF airway epithelia: hyperinflammatory?

The lack of functional cystic fibrosis (CF) transmembrane conductance regulator (CFTR) in the apical membranes of CF airway epithelial cells abolishes cAMP-stimulated anion transport, and bacteria, eventually including Pseudomonas aeruginosa, bind to and accumulate in the mucus. Flagellin released from P. aeruginosa triggers airway epithelial Toll-like receptor 5 and subsequent NF-B signaling and production and release of proinflammatory cytokines that recruit neutrophils to the infected region. This response has been termed hyperinflammatory because so many neutrophils accumulate; a response that damages CF lung tissue. We first review the contradictory data both for and against the idea that epithelial cells exhibit larger-than-normal proinflammatory signaling in CF compared with non-CF cells and then review proposals that might explain how reduced CFTR function could activate such proinflammatory signaling. It is concluded that apparent exaggerated innate immune response of CF airway epithelial cells may have resulted not from direct effects of CFTR on cellular signaling or inflammatory mediator production but from indirect effects resulting from the absence of CFTRs apical membrane channel function. Thus, loss of Cl^–, HCO₃^–, and glutathione secretion may lead to reduced volume and increased acidification and oxidation of the airway surface liquid. These changes concentrate proinflammatory mediators, reduce mucociliary clearance of bacteria and subsequently activate cellular signaling. Loss of apical CFTR will also hyperpolarize basolateral membrane potentials, potentially leading to increases in cytosolic [Ca²⁺], intracellular Ca²⁺, and NF-B signaling. This hyperinflammatory effect of CF on intracellular Ca²⁺ and NF-B signaling would be most prominently expressed during exposure to both P. aeruginosa and also endocrine, paracrine, or nervous agonists that activate Ca²⁺ signaling in the airway epithelia. Pseudomonas aeruginosa; Toll-like receptor; NF-B; oxidative stress; acidic airway surface liquid; calcium     

Xanthine derivatives without PDE effect stimulate voltage-activated chloride conductance of toad skin

The effect of xanthine derivativeson the voltage-activated Cl conductance(G_Cl) of amphibian skin was analyzed.3-Isobutyl-1-methylxanthine (IBMX) and the recently synthesizedxanthine derivatives 3,7-dimethyl-1-propyl xanthine (X-32) and3,7-dimethyl-1-isobutyl xanthine (X-33), which lack inhibitory effectson phosphodiesterases in CHO and Calu-3 cells, increasedvoltage-activated G_Cl without effect on baseline conductance at inactivating voltage. Half-maximal stimulation ofG_Cl occurred at 108 ± 9 µM for X-32 andX-33 after apical or basolateral application. The stimulation ofG_Cl, which occurs only in the presence ofCl in the mucosal solution, is caused by a shift of thevoltage sensitivity to lower clamp potentials and an increase of themaximally activated level. Furosemide reversed both the shift ofsensitivity and the increase in magnitude. These patterns arefundamentally different from those seen after application ofmembrane-permeant, nonmetabolized analogs of cAMP, and they indicatethat the xanthines stimulate G_Cl directly. Thisnotion is strengthened by the lack of influence on intracellular cAMPcontent, which is consistent with the observations in CHO and Calu-3cells. We propose that the xanthine derivatives increase the voltagesensitivity of a regulative component in the conductiveCl pathway across amphibian skin.

     

Pseudomonas aeruginosa inhibits endocytic recycling of CFTR in polarized human airway epithelial cells

The most common mutation in the CFTR gene in individuals with cystic fibrosis (CF), F508, leads to the absence of CFTR Cl^– channels in the apical plasma membrane, which in turn results in impairment of mucociliary clearance, the first line of defense against inhaled bacteria. Pseudomonas aeruginosa is particularly successful at colonizing and chronically infecting the lungs and is responsible for the majority of morbidity and mortality in patients with CF. Rescue of F508-CFTR by reduced temperature or chemical means reveals that the protein is at least partially functional as a Cl^– channel. Thus current research efforts have focused on identification of drugs that restore the presence of CFTR in the apical membrane to alleviate the symptoms of CF. Because little is known about the effects of P. aeruginosa on CFTR in the apical membrane, whether P. aeruginosa will affect the efficacy of new drugs designed to restore the plasma membrane expression of CFTR is unknown. Accordingly, the objective of the present study was to determine whether P. aeruginosa affects CFTR-mediated Cl^– secretion in polarized human airway epithelial cells. We report herein that a cell-free filtrate of P. aeruginosa reduced CFTR-mediated transepithelial Cl^– secretion by inhibiting the endocytic recycling of CFTR and thus the number of WT-CFTR and F508-CFTR Cl^– channels in the apical membrane in polarized human airway epithelial cells. These data suggest that chronic infection with P. aeruginosa may interfere with therapeutic strategies aimed at increasing the apical membrane expression of F508-CFTR. cystic fibrosis     

ENaC- and CFTR-dependent ion and fluid transport in mammary epithelia

Mammary epithelial 31EG4 cells (MEC) were grown as monolayers onfilters to analyze the apical membrane mechanisms that help mediate ionand fluid transport across the epithelium. RT-PCR showed the presenceof cystic fibrosis transmembrane conductance regulator (CFTR) andepithelial Na⁺ channel (ENaC) message, and immunomicroscopyshowed apical membrane staining for both proteins. CFTR was alsolocalized to the apical membrane of native human mammary ductepithelium. In control conditions, mean values of transepithelialpotential (apical-side negative) and resistance(R_T) are 5.9 mV and 829  · cm², respectively. The apical membranepotential (V_A) is 40.7 mV, and the mean ratioof apical to basolateral membrane resistance (R_A/R_B) is 2.8. Apicalamiloride hyperpolarized V_A by 19.7 mV andtripled R_A/R_B. AcAMP-elevating cocktail depolarized V_A by 17.6 mV, decreased R_A/R_B by60%, increased short-circuit current by 6 µA/cm²,decreased R_T by 155  · cm², and largely eliminated responses toamiloride. Whole cell patch-clamp measurements demonstratedamiloride-inhibited Na⁺ currents [linear current-voltage(I-V) relation] and forskolin-stimulated Clcurrents (linear I-V relation). A capacitance probe methodshowed that in the control state, MEC monolayers either absorbed orsecreted fluid (2-4µl · cm² · h¹). Fluidsecretion was stimulated either by activating CFTR (cAMP) or blockingENaC (amiloride). These data plus equivalent circuit analysis showedthat 1) fluid absorption across MEC is mediated byNa⁺ transport via apical membrane ENaC, and fluid secretionis mediated, in part, by Cl transport via apicalCFTR; 2) in both cases, appropriate counterions move throughtight junctions to maintain electroneutrality; and 3)interactions among CFTR, ENaC, and tight junctions allow MEC to eitherabsorb or secrete fluid and, in situ, may help control luminal[Na⁺] and [Cl].

     

Wheat Response to CO2 Enrichment: Growth and CO2 Exchanges at Two Plant Densities

Du Cloux, H. C, André, M., Daguenet, A. and Massinuno,J. 1987. Wheat response to CO₂ enrichment: Growth and CO₂ exchangesat two plant densities.—J. exp. Bot. 38: 1421–1431. The vegetative growth of wheat (Triticum aestivum L., var. Capitole)was followed for almost 40 d after germination in controlledconditions. Four different treatments were carried out by combiningtwo air concentrations of CO₂, either normal (330 mm³ dm ³)or doubled (660 mm³ dm ³) with two plant densities, either 200plants m ² or 40 plants m ². Throughout the experiment the CO₂gas exchanges of each canopy were measured 24 h d¹. These provideda continuous growth curve for each treatment, which were comparedwith dry weights. After a small stimulation at the start (first13 d), no further effect of CO₂ enrichment was observed on relativegrowth rate (RGR). However, RGR was stimulated throughout theexperiment when plotted as a function of biomass. The finalstimulation ol dry weight at 660 mm³ dm ³ CO₂ was a factor of1·45 at high density and 1·50 at low density,contrary to other studies, no diminution of this CO₂ effecton dry weight was observed over time. Nevertheless, at low density,a transient additional enhancement of biomass (up to 1·70)was obtained at a leaf area index (LAI) below 1. This effectwas attributed to a different build up of the gain of carbonin the case of an isolated plant or a closed canopy. In theformer, the stimulation of leaf area and the net assimilationrate are both involved; in the latter the enhancement becomesindependent of the effect on leaf area because the canopy photosynthesisper unit ground area as a function of LAI reaches a plateau. Key words: Triticum aestuum, L. var. Capitole, Vegetative growth, Canopy     

Development of Vacuolar Volume in the Root Tips of Pea

Cell and vacuole areas were measured by light microscopy inlongitudinal and transverse sections cut at 0.4-mm intervalsalong the apical 7.2 mm of the primary root of pea. The vacuolararea (or volume) fraction — that is, vacuole area (orvolume) divided by cell area (or volume) — increased fromabout 15 % in cells 0.4 mm from the distal boundary of the apicalmeristem (the cap /root junction), to about 85% in cells situated6.8–7.2 mm from that boundary. At each distance, vacuoledevelopment tended to be greater in the cortex than in the stele.Vacuoles occupied about 22% of the tissue volume in the first1 mm length of root (measured from the cap/root junction), about31 % of the tissue volume in the first 2 mm, and about 45% whensummed over the apical 5-mm length of root. Phosphorus supplyor deprivation produced only minor and non-significant changesin vacuole development. The results have implications affectingprevious estimates of cytoplasmic and vacuolar phosphate concentrationsin pea root tips. Pisum sativum L., pea, root, vacuole, volume     

Luminal L-alanine stimulates exocytosis at the K+-conductive apical membrane of Aplysia enterocytes

In Aplysia intestine,stimulation of Na⁺ absorption withluminal alanine increases apical membraneK⁺ conductance(G_K,a), whichpresumably regulates enterocyte volume during stimulatedNa⁺ absorption. However, themechanism responsible for the sustained increase in plasma membraneK⁺ conductance is not known forany nutrient-absorbing epithelium. In the present study, we have begunto test the hypothesis that the alanine-induced increase inG_K,a inAplysia enterocytes results fromexocytic insertion of K⁺ channelsinto the apical membrane. We used the fluid-phase marker horseradishperoxidase to assess the effect of alanine on apical membraneexocytosis and conventional microelectrode techniques to assess theeffect of alanine on fractional capacitance of the apical membrane(fC_a). Luminalalanine significantly increased apical membrane exocytosis from 1.04 ± 0.30 to 1.39 ± 0.38 ng · min¹ · cm².To measure fC_a,we modeled the Aplysia enterocyte as adouble resistance-capacitance (RC) electric circuit arranged in series. Several criteria were tested to confirm application of the model to theenterocytes, and all satisfied the model. When added to the luminalsurface, alanine significantly increasedfC_a from 0.27 ± 0.02 to 0.33 ± 0.04 (n = 10)after 4 min. There are two possible explanations for our findings:1) the increase in exocytosis, whichadds membrane to the apical plasma membrane, prevents plasma membranefracture, and 2) the increase inexocytosis delivers K⁺ channels tothe apical membrane by exocytic insertion. After the alanine-induceddepolarization of apical membrane potential (V_a), there isa strong correlation (r = 0.96)between repolarization ofV_a, whichreflects the increase inG_K,a, andincrease in fC_a. This correlation supports the exocytic insertion hypothesis for activation ofG_K,a.

     

Buckminsterfullerene (C-60 Carbon Allotrope) Inhibits Ethylene Evolution from 1-Aminocyclopropane-1-carboxylic acid (ACC)-treated Shoots of Pea (Pisum sativum), Broadbean (Vicia faba) and Flowers of Carnation (Dianthus caryophyllus)

When applied either in the form of a colloidal solution or inliposomes, buckyballs (C-60—buckminsterfullerene) markedlyreduced ethylene evolution from cut carnation (Dianthus caryophyllus)flowers, as well as pea (Pisum sativum) and broadbean (Viciafaba) foliage treated with ethylene precursor l-aminocyclopropane-l-carboxylicacid (ACC). The liposome preparation was approximately twiceas effective as colloidal solutions. Moreover, upon being incubatedin a closed atmosphere with ethylene, buckyballs induced a significantdepletion of ambient ethylene which was temperature and C-60—concentrationdependent. This mode of C-60 action is attributed to ethyleneadsorption stemming from the vast C-60 surface area, calculatedto be 1317 m² g_-1, and the affinity of its carbon atoms forthe component in the ethylene double bond.Copyright 1993, 1999Academic Press Dainthus caryophyllus, Pisum sativum, Vicia faba, adsorption, ethylene, fullerene     

REPRODUCTIVE CYCLE AND FECUNDITY OF THE DATE MUSSEL LITHOPHAGA LITHOPHAGA (BIVALVIA: MYTILIDAE)

The reproductive cycle and fecundity of the date mussel Lithophagalithophaga, L. a well-known, ediblespecies has been examined.Sexes are separate and the mean number of eggs per each gonadis 1.894 x 10⁶ ± 1.044 x 10⁶ S.D. Reproduction firstoccurs at an age of 2⁺years and at a shell length greater than0.9 cm. Gonad activity is annual and is observed at all ages.The sex ratio for individuals up to 7 cm is 3:1 in favour ofthe males, whereas it becomes 1:1 for individuals greater than7 cm. The release of gametes by males and females occurs almostsimultaneously and begins immediately after a decline in thehighest water temperature ( 27°C), an increase in salinity(>31) and a decrease in the dissolved oxygen (6.5 ppm). Smallpercentages of mature individuals appear during the first wintermonths thus lengthening the reproductive period. This phenomenonis attributed to the temperature difference in deeper waters,the delay in gamete release by young individuals, tide, waveaction and changes in salinity. The fecundity of Lithophagalithophaga is high because its life-cycle is adversely affectedby environmental factors such as waves and tides. Fecundityincreases with shell length, more so with total wet weight andmainly with the age of the animals. Summer seems to be the suitableseason to exploit the date mussel of shell lengths > 5 cm. (Received 6 September 1993; accepted 10 March 1994)     

Ovine male genital duct epithelial cells differentiate in vitro and express functional CFTR and ENaC

To investigate the biology of the malegenital duct epithelium, we have established cell cultures from theovine vas deferens and epididymis epithelium. These cells develop tightjunctions, high transepithelial electrical resistance, and alumen-negative transepithelial potential difference as a sign of activetransepithelial ion transport. In epididymis cultures the equivalentshort-circuit current (I_sc) averaged 20.8 ± 0.7 µA/cm² (n = 150) and was partially inhibited byapical application of amiloride with an inhibitor concentration of 0.64 µM. In vas deferens cultures, I_sc averaged 14.4 ± 1.1 µA/cm² (n = 18) and was also inhibited byapical application of amiloride with a half-maximal inhibitorconcentration (K_i) of 0.68 µM. The remainingamiloride-insensitive I_sc component in epididymisand vas deferens cells was partially inhibited by apical application ofthe Cl channel blocker diphenylamine-2-carboxylicacid (1 mM). It was largely dependent on extracellularCl and, to a lesser extent, on extracellularHCO₃. It was further stimulated bybasolateral application of forskolin (10⁵ M), which increasedI_sc by 3.1 ± 0.3 µA/cm² (n=65) in epididymis and 0.9 ± 0.1 µA/cm² (n =11) in vas deferens. These findings suggest that cultured ovine vasdeferens and epididymis cells absorb Na⁺ viaamiloride-sensitive epithelial Na⁺ channels (ENaC) andsecrete Cl and HCO₃via apical cystic fibrosis transmembrane conductance regulator (CFTR)Cl channels. This interpretation is supported byRT-PCR data showing that vas deferens and epididymis cells express CFTRand ENaC mRNA.

     

Histology of the Morphogenic Response in Thin Cell Layer Explants from Vegetative Tobacco Plants

The morphogenic response of thin cell layers (TCLs) from vegetativetobacco (Nicotiana tabacum L.) plants can be directed very preciselyby varying the concentrations of benzyladenine (BA) and -naphthaleneacetic acid (NAA) in the culture medium. Medium containing 1·6µM BA and 0·5 µM NAA was optimal for shootformation, concentrations of 0·5 µM BA and 1·6µM NAA were optimal for the induction of shoots and rootson the same explant, whereas concentrations of NAA higher than16 µM resulted in callus proliferation only. Polarityin the distribution of the shoot buds was observed, i.e. a switchfrom basal to apical shoot formation occurred with increasingNAA concentrations, suggesting basipetal transport of NAA. Histologicalexamination of TCLs on shoot induction medium revealed thatfirst cell divisions occurred within 2 d in cortical cells whichwere directly in contact with the medium along the longitudinalcut surface, and after 2 d in subepidermal cells along the lateraledges of the explants. Individual lateral buds originated fromone subepidermal and one or more epidermal cells, while apicalbuds originated from single subepidermal or cortical cells locateddirectly at the apical end of the explant. After culture ofTCLs for 2-3 d on root/shoot induction medium cells in the regeneration-competentsubepidermis elongated, while on callus induction medium subepidermalcells elongated and dedifferentiated. The regeneration systemas described in this study will be used to identify cells competentfor regeneration as well as for transformation.Copyright 1994,1999 Academic Press Nicotiana tabacum L., tobacco, thin cell layer explants, cell competence, shoot development, polarity     

Spatial heterogeneity and genetic variation in the copepod Neocalanus cristatus along two transects in the North Pacific sampled by the Continuous Plankton Recorder

We present a macrogeographic study of spatial heterogeneityin an important subarctic Pacific copepod and describe the firstgenetic analysis of population structure using Continuous PlanktonRecorder (CPR) samples. Samples of Neocalanus cristatus werecollected at a constant depth of 7 m from two CPR tow-routes,(i) an east–west 6500-km transect from Vancouver Island,Canada to Hokkaido Island, Japan, and (ii) a north–southtransect of 2250 km from Anchorage, Alaska to Tacoma, Washington.Analysis of these samples revealed three features of the biologyof N. cristatus. First, N. cristatus undergoes small-scale dielvertical migration that is larger among stages CV–adult(3–6 times more abundant at 7 m at night), than stagesCI–CIV (only 2–4 times higher at night). Secondly,while there were no regions where N. cristatus did not appear,each transect sampled a few large-scale macrogeographic patches.Thirdly, an analysis of molecular variation, using a partialsequence of the N. cristatus cytochrome oxidase I gene, revealedthat 7.3% (P < 0.0001) of the total genetic variation amongN. cristatus sampled from macrogeographic patches by the CPRcould be explained by spatial heterogeneity. We suggest thatspatial heterogeneity at macrogeographic scales may be importantin plankton evolution.     

Response of Gonyaulax tamarensis to the presence of a pycnocline in an artificial water column

In nature, large concentrations of the toxic bloom-forming dinoflagellate,Gonyaulax tamarensis, are frequently observed in the vicinityof the pycnocline. In the absence of a pycnocline the organismis usually recorded near the surface, where light levels aremore advantageous for photosynthesis. In this paper we examinethe swimming behaviour of G.tamarensis when exposed to varyingdegrees of stratification and investigate whether the maintenanceof a subsurface (pycnocline) population is the result of retentionof the algae by a physical barrier or active accumulation ofthe organisms at a density interface. The study indicates thatG.tamarensis cells presented with a halocline of S<{smalltilde}6–7 (occurring over a few centimeters) cross thissalinity barrier and accumulate at the highest available photonflux density ({small tilde}100 µmol m^–2 s^–1).Cells exposed to a gradient of S>{small tilde}7remain atthe halocline (pfd={small tilde}40 µmol m^–2 s^–1).However, when light above the pycnocline is attenuated by theaddition of food colour to the medium, the cells cross a haloclineof S=10 and accumulate at the highest available photon fluxdensity. In the absence of added nutrients (inorganic N andP) the organism fails to exhibit a phototactic response. Thus,the presence of a strong halocline does not represent an inpenetrablephysical barrier for G.tamarensis and the development of pycnoclinepopulations of this organism is a function of density, lightand nutrient climate.     

Right-Left Symmetry in Phyllotaxy and Imbrication of Flowers of Hibiscus furcartus L.

The phyllotaxy in Hibiscus furcartus is spiral. It is foundthat there is a general tendency for lateral branches to acquirethe same sense (right-handed or left-handed) of phyllotaxy asthe parent branch. H. furcartus has two kinds of flowers, right-handedflowers with clockwise imbricated petals and left-handed flowerswith anticlockwise imbricated petals. It is found that brancheswith right-handed phyllotaxy yield only left-handed flowersand those with left-handed phyllotaxy yield only right-handedflowers. Hibiscus furcartus L., phyllotaxy, imbrication of flowers     

Cryptdin-3 induces novel apical conductance(s) in Cl- secretory, including cystic fibrosis, epithelia

Opening ofanion-conductive pathways in apical membranes of secretory cells liningmucosal surfaces is a critical step in salt and water secretion and,thus, hydration of sites including airway and intestine. In intestine,Paneth cells are positioned at the base of the secretory gland (crypt)and release defensin peptide, in mice termed cryptdins, into the cryptlumen. Because at least some defensins have been shown to formanion-conductive channels in phospholipid bilayers, we tested whetherthese endogenous antimicrobial peptides could act as soluble inducersof channel-like activity when applied to apical membranes. To directlyevaluate the possibility of cryptdin-3-mediated apical anionconductance (G_ap), we have utilized amphotericinB to selectively permeabilize basolateral membranes of electricallytight monolayers of polarized human intestinal secretory epithelia (T84cells), thus isolating the apical membrane for study. Cryptdin-3induces G_ap that is voltage independent(G_ap = 1.90 ± 0.60 mS/cm²) and exhibits ion selectivity contrasting to thatelicited by forskolin or thapsigargin (for cryptdin-3,Cl = gluconate; for forskolin and thapsigargin,Cl gluconate). We cannot exclude the possibility thatthe macroscopic current induced by cryptdin could be the sum of cationand Cl currents. Cryptdin-3 induces a current inbasolaterally permeabilized epithelial monolayers derived from airwaycells harboring the F508 mutation of cystic fibrosis (CF;G_ap = 0.80 ± 0.06 mS/cm²), demonstrating that cryptdin-3 restores anionsecretion in CF cells; this occurs independently of the CFtransmembrane conductance regulator channel. These results support theidea that cryptdin-3 may associate with apical membranes ofCl-secreting epithelia and self-assemble into conductingchannels capable of mediating a physiological response.

     

The Effects of Salinity upon Galactosyl-Glycerol Content and Concentration of the Marine Red Alga Porphyra purpurea (Roth) C.Ag.

Changes in the major alcohol-soluble, low molecular weight carbohydratesof P. purpurea, O--D-galactopyranosyl-(1-2)-glycerol (‘floridoside’)and O--D-galactopyranosyl-(1-1)-glycerol (‘isofloridoside’),have been examined in response to salinity variation. ‘Floridoside’is shown to vary in absolute amount, increasing in hypersalineand decreasing in hyposaline media. ‘Isofloridoside’content per cell does not change in a similar manner. Responsesare almost identical under light or dark conditions, ‘floridoside’changes being complete within 24 h. Decreasing the externalwater potential using ionic and non-ionic solutes has the sameeffect upon galactosyl-glycerol content. The amount of ‘floridoside’synthesized, and degraded under hypersaline and hyposaline conditionsrespectively is shown to be insufficient to restore cell volumeto its original value. It is therefore suggested that the primaryfunction of ‘floridoside’ increases in concentratedsea-waters is that of a compatible solute, serving to protectthe cell during periods when the external salt content is increaseddramatically.