Assessing the position of pacemaker leads via transthoracic echocardiography: a prospective study

Funding Acknowledgements

Type of funding sources: None.

BACKGROUND/ INTRODUCTION

Lead-induced tricuspid regurgitation (TR) in patients with cardiac implantable electronic devices (CIED) is associated with increased morbidity and mortality. Mechanisms proposed to explain CIED-induced TR can be classified as primary (implantation-related, lead-related) and secondary (pacing related). Primary CIED-induced TR results from the direct interaction of the lead with the tricuspid valve (TV). Determination of exact lead position via echocardiography is crucial however often difficult via standard views. Previous research has shown the value of an atypical subcostal 2D en-face view to describe the exact anatomy of the TV (Figure 1) (1-3).

PURPOSE

In this prospective observational investigation, we aimed to demonstrate the feasibility of the subcostal 2D en-face view of the TV to determine RV lead position at the level of TV passage and thereby to unmask potentially unfavorable lead-positions and interactions with the TV, which might otherwise remain unnoted.

METHODS

Consecutive patients who underwent implantation of CIED with at least one RV lead were prospectively included. Comprehensive transthoracic echocardiography (TTE) was performed before and after the procedure. An en-face view of the TV by an approximately 90° counter-clockwise rotation of the transducer from a standard subcostal 4-chamber view was attempted in all patients. Exact lead-position (e.g. postero-septal commissural, central, etc., see Figure 1) was described whenever possible.

RESULTS

A total of  35 patients were included in the final analysis, median age was 62 years, 27/35 (77%) were male.

Thirteen patients (37%) already had an RV lead prior to the recent procedure and therefore showed 2 or more leads passing the TV in post-procedural controls.

Implanted devices included cardiac contractility modulation (CCM) (7/35 patients, 20%), implantable cardioverter-defibrillator (ICD) (11/35 patients, 31%), cardiac resynchronization therapy (CRT) (7/35 patients 20%) and pacemaker (PM) (7/35 patients, 20%). Three patients (9%) received an additional RV lead due to RV lead dysfunction.

The exact position of the RV lead could be determined applying the en-face view in 27/35 patients (77%). In the majority of cases (20/35 patients, 57%), the RV lead passed through the tricuspid plane in a postero-septal commissural position. Central trajectory was observed in 5/35 patients (14%). Anteroseptal and anteroposterior passage were each found in one patient.

In the remaining 8/35 patients (23%), lead position could not be determined due to inferior image quality from the subcostal view.

CONCLUSIONS

RV lead position can be determined from a subcostal en-face view of the TV in a majority of patients after CIED implantation. Hereby, 2D-TTE can add significant value to the management, follow-up, and monitoring and should therefore be included in the standard TTE protocol of every patient with CIED. Abstract Figure 1

Transmembrane auxin carrier systems--dynamic regulators of polar auxin transport

Recent investigations of the biochemistry, physiology and molecular genetics of polar auxin transport have greatly advanced our understanding of the process and of the part it plays in the regulation of development and in the responses of cells, tissues and organs to internal and external stimuli. The molecular and physiological characterization of mutants which exhibit lesions in polar auxin transport has led to the isolation and sequencing of genes which encode putative components of auxin carrier systems, or proteins which directly or indirectly regulate these systems. This work has revealed that specific auxin uptake and efflux carriers are coded not by single genes, but by whole families of genes, the expression of which is tissue or stimulus specific. Furthermore, evidence is accumulating rapidly that at least the auxin efflux carrier is a multi-component system consisting of both catalytic and regulatory subunits, including a separate phytotropin-binding protein. Other genes have been tentatively identified which code proteins that regulate the expression of genes coding auxin carrier components, or which regulate the intracellular traffic or activity of auxin carriers. Investigations of the turn-over and Golgi-mediated trafficking of auxin carrier proteins have revealed that essential components of at least the efflux carrier have a very short half-life in the plasma membrane and are replaced without the need for concurrent protein synthesis, leading to speculation that they might cycle between internal stores and the plasma membrane. The way is now clear for the development of specific molecular probes with which to investigate the intracellular transport and targeting of auxin carrier proteins.

Risk factors for early filtration failure requiring suture release after primary glaucoma triple procedure with adjunctive mitomycin

PURPOSE

Postoperative release of scleral flap closure suture is useful in trabeculectomy combined with cataract surgery. We determined risk factors for early filtration failure requiring suture release during the first month after primary glaucoma triple procedure.

METHODS

The medical records of 71 consecutive patients with primary open-angle glaucoma who underwent a primary glaucoma triple procedure (primary trabeculectomy, phacoemulsification, and posterior chamber intraocular lens implantation) were reviewed. Suture release had been performed in 24 of the patients for early filtration failure with postoperative intraocular pressure greater than the target value during the first postoperative month. The long-term filtration failure was defined according to 2 criteria based on medical dependency and requirement of additional surgical procedure for intraocular pressure control. Cox proportional hazards multivariate analysis was performed to identify independent risk factors.

RESULTS

African American race (P = .02), more than 2 preoperative glaucoma drugs (P = .02), and intraocular pressure greater than 14 mm Hg during the first postoperative week (P = .006) were identified as significant independent risk factors requiring suture release for filtration failure during the first postoperative month. Their significance was further confirmed by Kaplan-Meier survival analysis with Mantel-Cox log-rank test (P = .03, P = .02, and P = .001, respectively).

CONCLUSIONS

African American race, more than 2 preoperative medications, and intraocular pressure greater than 14 mm Hg in the first postoperative week are major independent risk factors for initial filtration failure requiring suture release during the first month after primary glaucoma triple procedure. Presence of the risk factors may warrant a more aggressive antiproliferative regimen and/or earlier suture release.

Foldable posterior chamber intraocular lens implantation in the absence of capsular and zonular support

PURPOSE

To implant foldable posterior chamber intraocular lenses in the absence of capsular and zonular support.

METHODS

Case reports. In two patients, two eyes with aphakia, lack of capsular or zonular support, and contact lens intolerance underwent the implantation of a silicone and an acrylic foldable posterior chamber intraocular lens, respectively.

RESULTS

In the two eyes, final visual acuity was 20/25 and 20/50, respectively. No intraoperative vitreal, retinal, or choroidal complications were noted. The postoperative recovery was rapid, and there was minimal induced astigmatism.

CONCLUSIONS

The implantation of foldable posterior chamber intraocular lenses in aphakic eyes without capsular and zonular support may result in fewer intraoperative complications. It also allows for faster postoperative recovery and less postoperative astigmatism.

Use of autologous Tenon's capsule and scleral patch grafts for repair of excessively draining fistulas with leaking filtering blebs

PURPOSE

To report the use of autologous Tenon's and partial-thickness scleral tissues for patch graft revisions of excessively draining fistulas associated with leaking filtering blebs.

METHODS

Appropriate sized pieces of autologous Tenon's tissue and partial-thickness scleral tissue were dissected near the surgical sites and used as patch grafts to effectively repair excessively draining fistulas with leaking filtering blebs.

RESULTS

Both Tenon's and partial-thickness scleral patch grafts were useful in adequately closing the excessively draining fistulas.

CONCLUSION

Autologous Tenon's and scleral tissue patch grafts appear to be safe and effective for the repair of excessively draining fistulas, and are useful when patch grafts are unexpectedly needed.

Postpartum blood pressure and insulin sensitivity in African-American women with recent preeclampsia

Pregnancy-induced hypertension and preeclampsia are relatively common in nulliparous, inner-city, African-American, pregnant women and contribute to considerable maternal, fetal, and neonatal morbidity and mortality in that population. Recently, insulin resistance has been related to the development of hypertension in young African-Americans and hyperinsulinemia and elevated insulin-to-glucose ratios, suggesting insulin resistance, have been demonstrated in women with preeclampsia. To investigate whether insulin resistance existed postpartum and, therefore, independently of the pregnant state, the hyperinsulinemic, euglycemic technique was used 3 to 6 months postpartum to assess insulin sensitivity in 10 young, black, primiparous, inner-city women with recent preeclampsia and seven age-, weight- and body-mass-index-matched black women with healthy pregnancies. The age, weight, body-mass index, waist-to-hip ratio, the duration since parturition, and fasting plasma glucose and insulin were similar in the preeclamptic and control groups. During the clamp procedure, the insulin levels and mean diastolic blood pressure and mean arterial pressure were also similar for both groups; however, the mean systolic blood pressure of the preeclamptic group (123 +/- 3 mm Hg) was higher than that of the control group (114 +/- 2 mm Hg) (P < .05). Insulin-stimulated glucose disposal was not different between the preeclamptic (5.6 +/- 0.3 mg/kg/min) and control groups (5.7 +/- 0.7 mg/kg/min). This suggests that the elevation in postpartum systolic blood pressure may reflect a persistent abnormality of blood pressure homeostasis which is not associated with insulin resistance.

Studies on the evolution of auxin carriers and phytotropin receptors: Transmembrane auxin transport in unicellular and multicellular Chlorophyta

The characteristics of transmembrane transport of (14)C-labelled indol-3yl-acetic acid ([1-(14)C]IAA) were compared in Chlorella vulgaris Beij., a simple unicellular green alga, and in Chara vulgaris L., a branched, multicellular green alga exhibiting axial polarity and a high degree of cell and organ specialization. In Chara thallus cells, three distinguishable trans-plasmamembrane fluxes contributed to the net uptake of [1-(14)C]-IAA from an external solution, viz.: a non-mediated, pH-sensitive influx of undissociated IAA (IAAH); a saturable influx of IAA; and a saturable efflux of IAA. Both saturable fluxes were competitively inhibited by unlabelled IAA. Association of [(3)H]IAA with microsomal preparations from Chara thallus tissue was competitively inhibited by unlabelled IAA. Results indicated that up-take carriers occurred in the membranes at a much higher density than efflux carriers. The efflux component of IAA net uptake by Chara was not affected by several phytotropins (N-1-naphthylphthalmic acid, NPA; 2-(1-pyrenoyl)benzoic acid; and 5-(2-carboxyphenyl)-3-phenylpyrazole), which are potent non-competitive inhibitors of specific auxin-efflux carriers in more advanced plant groups, and no evidence was found for a specific association of [(3)H]NPA with Chara microsomal preparations. It was concluded that Chara lacked phytotropin receptors. Net uptake of [1-(14)C]IAA also was unaffected by 2,3,5-triiodobenzoic acid except at concentrations (≥ 10(-1) mol · m(-3)) high enough to depress cytoplasmic pH (determined by uptake of 5,5-dimethyloxazolidine-2,4-dione). Chlorella cells accumulated [1-(14)C]IAA from an external solution by pH-sensitive diffusion of IAA across the plasma membrane and anion (IAA(-)) trapping, but no evidence was found in Chlorella for the occurrence of IAA carriers. These results indicate that carrier systems capable of mediating the transmembrane transport of auxins appeared at a very early stage in the evolution of green plants, possibly in association with the origin of a differentiated, multicellular plant body. Phytotropin receptors evolved independently of the carriers.

The role of auxin efflux carriers in the reversible loss of polar auxin transport in the pea (Pisum sativum L.) stem

Correlatively inhibited pea shoots (Pisum sativum L.) did not transport apically applied (14)C-labelled indol-3yl-acetic acid ([(14)C]IAA), and polar IAA transport did not occur in internodal segments cut from these shoots. Polar transport in shoots and segments recovered within 24 h of removing the dominant shoot apex. Decapitation of growing shoots also resulted in the loss of polar transport in segments from internodes subtending the apex. This loss was prevented by apical applications of unlabelled IAA, or by low temperatures (approx. 2° C) after decapitation. Rates of net uptake of [(14)C]IAA by 2-mm segments cut from subordinate or decapitated shoots were the same as those in segments cut from dominant or growing shoots. In both cases net uptake was stimulated to the same extent by competing unlabelled IAA and by N-1-naphthylphthalamic acid. Uptake of the pH probe [(14)C]-5,5-dimethyloxazolidine-2,4-dione from unbuffered solutions was the same in segments from both types of shoot. Patterns of [(14)C]IAA metabolism in shoots in which polar transport had ceased were the same as those in shoots capable of polar transport. The reversible loss of polar IAA transport in these systems, therefore, was not the result of loss or inactivation of specific IAA efflux carriers, loss of ability of cells to maintain transmembrane pH gradients, or the result of a change in IAA metabolism. Furthermore, in tissues incapable of polar transport, no evidence was found for the occurrence of inhibitors of IAA uptake or efflux. Evidence is cited to support the possibility that the reversible loss of polar auxin transport is the result of a gradual randomization of effluxcarrier distribution in the plasma membrane following withdrawal of an apical auxin supply and that the recovery of polar transport involves reestablishment of effluxcarrier asymmetry under the influence of vectorial gradients in auxin concentration.

Applicability of the chemiosmotic polar diffusion theory to the transport of indol-3yl-acetic acid in the intact pea (Pisum sativum L.)

The transport of exogenous indol-3yl-acetic acid (IAA) from the apical tissues of intact, light-grown pea (Pisum sativum L. cv. Alderman) shoots exhibited properties identical to those associated with polar transport in isolated shoot segments. Transport in the stem of apically applied [1-(14)C]-or [5-(3)H]IAA occurred at velocities (approx. 8-15 mm·h(-1)) characteristic of polar transport. Following pulse-labelling, IAA drained from distal tissues after passage of a pulse and the rate characteristics of a pulse were not affected by chases of unlabelled IAA. However, transport of [1-(14)C]IAA was inhibited through a localised region of the stem pretreated with a high concentration of unlabelled IAA or with the synthetic auxins 1-napthaleneacetic acid and 2,4-dichlorophenoxyacetic acid, and label accumulated in more distal tissues. Transport of [1-(14)C]IAA was also completely prevented through regions of the intact stem treated with N-1-naphthylphthalamic acid (NPA) and 2,3,5-triiodobenzoic acid.Export of IAA from the apical bud into the stem increased with total concentration of IAA applied (labelled+unlabelled) but approached saturation at high concentrations (834 mmol·m(-3)). Transport velocity increased with concentration up to 83 mmol·m(-3) IAA but fell again with further increase in concentration.Stem segments (2 mm) cut from intact plants transporting apically applied [1-(14)C]IAA effluxed 93% of their initial radioactivity into buffer (pH 7.0) in 90 min. The half-time for efflux increased from 32.5 to 103.9 min when 3 mmol·m(-3) NPA was included in the efflux medium. Long (30 mm) stem sections cut from immediately below an apical bud 3.0 h after the apical application of [1-(14)C]IAA effluxed IAA when their basal ends, but not their apical ends, were immersed in buffer (pH 7.0). Addition of 3 mmol·m(-3) NPA to the external medium completely prevented this basal efflux.These results support the view that the slow long-distance transport of IAA from the intact shoot apex occurs by polar cell-to-cell transport and that it is mediated by the components of IAA transmembrane transport predicted by the chemiosmotic polar diffusion theory.

Regulation of auxin transport in pea (Pisum sativum L.) by phenylacetic acid: inhibition of polar auxin transport in intact plants and stem segments

The transport of [(14)C]phenylacetic acid (PAA) in intact plants and stem segments of light-grown pea (Pisum sativum L. cv. Alderman) plants was investigated and compared with the transport of [(14)C]indiol-3yl-acetic acid (IAA). Although PAA was readily taken up by apical tissues, unlike IAA it did not undergo long-distance transport in the stem. The absence of PAA export from the apex was shown not to be the consequence of its failure to be taken up or of its metabolism. Only a weak diffusive movement of PAA was observed in isolated stem segments which readily transported IAA. When [1-(14)C]PAA was applied to a mature foliage leaf in light, only 5.4% of the (14)C recovered in ethanol extracts (89.6% of applied (14)C) had been exported from the leaf after 6.0 h. When applied to the corresponding leaf, [(14)C]sucrose was readily exported (46.4% of the total recovered ethanol-soluble (14)C after 6.0 h). [1-(14)C]phenylacetic acid applied to the root system was readily taken up but, after 5.0 h, 99.3% of the recovered (14)C was still in the root system.When applied to the stem of intact plants (either in lanolin at 10 mg·g(-1), or as a 10(-4) M solution), unlabelled PAA blocked the transport through the stem of [1-(14)C]IAA applied to the apical bud, and caused IAA to accumulate in the PAA-treated region of the stem. Applications of PAA to the stem also inhibited the basipetal polar transport of [1-(14)C]IAA in isolated stem segments. These results are consistent with recent observations (C.F. Johnson and D.A. Morris, 1987, Planta 172, 400-407) that no carriers for PAA occur in the plasma membrane of the light-grown pea stem, but that PAA can inhibit the carrier-mediated efflux of IAA from cells. The possible functions of endogenous PAA are discussed and its is suggested that an important role of the compound may be to modulate the polar transport and-or accumulation by cells of IAA.

Regulation of auxin transport in pea (Pisum sativum L.) by phenylacetic acid: effects on the components of transmembrane transport of indol-3yl-acetic acid

Phenylacetic acid (PAA), a naturally-occurring acidic plant growth substance, was readily taken up by pea (Pisum sativum L. cv. Alderman) stem segments from buffered external solutions by a pH-dependent, non-mediated diffusion. Net uptake from a 0.2 μM solution at pH 4.5 proceeded at a constant rate for at least 60 min and, up to approx. 100 μM, the rate of uptake was directly proportional to the external concentration of the compound. The net rate of uptake of PAA was not affected by the inclusion of indol-3yl-acetic acid (IAA) in the uptake medium (up to approx. 30 μM) and, unlike the net uptake of IAA, was not stimulated by N-1-naphthylphthalamic acid (NPA) or 2,3,5-triiodobenzoic acid. At an external concentration of 0.2 μM and pH 4.5, the net rate of uptake of PAA was about twice that of IAA. It was concluded that the uptake of PAA did not involve the participation of carriers and that PAA was not a transported substrate for the carriers involved in the uptake and polar transport of IAA. Nevertheless, the inclusion of 3-100 μM unlabelled PAA in the external medium greatly stimulated the uptake by pea stem segments of [1-(14)C]IAA (external concentration 0.2 μM). It was concluded that whilst PAA was not a transported substrate for the NPA-sensitive IAA efflux carrier, it interacted with this carrier to inhibit IAA efflux from cells. Over the concentration range 3-100 μM, PAA progressively reduced the stimulatory effect of NPA on IAA uptake, indicating that PAA also inhibited carrier-mediated uptake of IAA. The consequences of these observations for the regulation of polar auxin transport are discussed.

The pharmacokinetics of nedocromil sodium, a new drug for the treatment of reversible obstructive airways disease, in human volunteers and patients with reversible obstructive airways disease

1. The plasma concentrations and urinary excretion of nedocromil sodium have been determined following single dose administration in six healthy volunteers dosed orally (1 mg kg-1) and intravenously (0.2 microgram kg-1 for 30 min). Similar parameters were measured in six volunteers and twelve asthmatic patients dosed by inhalation (4 mg). Multiple dose kinetic measurements were also made. 2. The intravenous data demonstrated that nedocromil sodium is a high clearance drug (10.2 +/- 1.3 ml min-1 kg-1). The data were fitted by a two compartment model with very rapid elimination from the central compartment (k10 = 0.088 +/- 0.021 min-1; beta = 0.013 +/- 0.002 min-1). 81% of the dose was excreted in the urine. 3. Oral absorption was low (2-3% of the dose) and contributed negligibly to the plasma profile after inhalation. 4. After inhalation of single doses of 4 mg in volunteers and patients plasma concentration rose rapidly, plateaued and then fell monoexponentially with a half-life of approximately 2 h. The data fitted a 'flip-flop' model with two absorption components. The extent of absorption was up to 6% of the dose with less in patients. 5. After multiple dosing with 4 mg four times daily for 7 days in volunteers negligible accumulation was observed. The pattern was similar in patients treated with 4 mg four times daily after 1, 6 and 12 months.

Structure determination of five sulfated oligosaccharides derived from tracheobronchial mucus glycoproteins

The structure of five sulfated oligosaccharide units of highly anionic tracheobronchial mucous glycoproteins, isolated from a cystic fibrosis patient's sputum, were established. Reduced oligosaccharides (84%) were released under alkaline borohydride conditions, and the acidic oligosaccharides (63%) were isolated by Dowex 1-X2 chromatography. Following the removal of acidic oligosaccharides possessing N-acetylneuraminic acid and L-fucose by lectin affinity chromatography a heterogeneous mixture of sulfated oligosaccharides was obtained. From this fraction, five short chain monosulfated oligosaccharides (S-I to S-V) were purified by sequential separation by SynChroprep AX300 anion exchange high pressure liquid chromatography, gel filtration on Bio-Gel P-2, and high voltage paper electrophoresis. Based on the results of carbohydrate composition, sequential exoglycosidase degradation, permethylation analysis, lectin affinity chromatography, and periodate oxidation, the following structures (where GalNAcol is N-acetylgalactosaminitol) were proposed for these oligosaccharides. (formula; see text)

Recurrent conjunctival melanoma with neuroidal spindle cell features

A 66-year-old white woman had had a 20-year history of flat primary acquired melanosis involving the left inferior forniceal and palpebral conjunctiva. Over the ensuring 12 years, the patient experienced multiple recurrences of invasive malignant melanoma that emerged from the progressive primary acquired melanosis. Two of these recurrences were composed of nonpigmented spindle cells, and in the most florid invasive malignant melanoma that developed, the spindle cells formed a nodule 7.5 mm thick. The spindle cells were organized into fascicles and small bundles, the latter separated by a loose stroma that was devoid of mucopolysaccharides. The fascicular and neuroidal features in this case were sufficiently well developed to suggest the incorrect diagnosis of a neural tumor or a neurofibroma. However, the presence of intraepithelial atypical melanocytes at the edge of the spindle cell lesion, the absence of mucopolysaccharides in the stroma, the mitotic activity, and the absence of intercellular reticulin fibers favored the diagnosis of a spindle cell invasive malignant melanoma. This morphologic variant of conjunctival melanoma is compared with related cutaneous lesions of melanoma featuring a spindle cell population.

Normal values for forced oscillatory respiratory resistance in children

Forced oscillatory respiratory resistance was measured in 138 healthy children aged 2- to 16-years-old using a commercial unit. Regression analysis was performed using the resistance measurements obtained at frequencies of 6 Hz and 26 Hz and averages of measurements obtained at frequencies of from 6-26 Hz, 6-10 Hz, and 22-26 Hz. The analysis suggested that regression curves and 95% confidence intervals obtained using a quadratic model with height as the independent variable provided the best prediction of normal values and their ranges. Three independent sets of resistance measurements, which were obtained for all 138 subjects, were used to calculate the average individual coefficients of variation (CV) for the five resistance parameters noted above; these ranged from 9 to 13%. This analysis suggested that the expected CV of repeated measurements would be about 10%. Finally, values from 13 children who had asthma with mild bronchial obstruction (FEV1 less than 80% of predicted) were compared with the normal values derived from the regression curves. Values from all but two of the children fell within the reference intervals, suggesting that FEV1 may be a more sensitive measure of obstruction than forced oscillatory resistance. The main applications of this new approach may be in the evaluation of young children, in following individual patients, and in bronchodilation and bronchial challenge tests.

Conjunctival synthetic fiber granuloma. A lesion that resembles conjunctivitis nodosa

Histopathologic examination of forniceal conjunctival lesions excised from five young patients revealed granulomatous inflammation surrounding filamentous foreign material. Polarization microscopy, special histochemical stains, scanning electron microscopy and energy dispersive x-ray elemental analysis identified the inciting material as predominantly synthetic fabric fiber. Three of these cases initially were diagnosed as conjunctivitis nodosa, an inflammatory reaction to caterpillar setae. Many synthetic fibers contained numerous granules of titanium, barium, or zinc delustering agent, which served to differentiate them from natural fibers or caterpillar hairs. Synthetic fabric fiber is a previously unrecognized cause of conjunctival inflammatory mass lesions.

The influence of small direct electric currents on the transport of auxin in intact plants

When a d.c. potential of 9.0 V was applied to the stem of intact pea seedlings (Pisum sativum L. cv. Meteor and cv. Alderman) via 10 mM KCl-soaked filter paper electrodes placed ca. 50 mm apart the stem passed a steady current of 15-20 μA (resistance ca. 100 kΩ cm(-1)). The basipetal transport of [1-(14)C]IAA applied to the apical bud was completely inhibited over the portion of the stem through which current flowed and (14)C-labelled compounds accumulated in the vicinity of the upper electrode. The inhibition of transport was independent of the polarity of the applied potential. The basipetal transport of IAA in the stem above the electrode was not affected.Labelled auxin accumulated at the upper electrode both as unchanged IAA and as a compound tentatively identified as indol-3yl-acetyl aspartic acid (IAAsp). These compounds were only slowly remobilised when the current was interrupted. However, the ability of the transport system to move freshly-applied IAA was rapidly and fully restored when the potential was removed. No injury to the plant was detected after maintaining a current flow for up to 72 h. No leakage of (14)C-labelled compounds into the KCl solution bathing the electrodes was detected.

Interaction of lysophosphatidylcholine with phosphatidylcholine bilayers. A photo-physical and NMR study

Several photo-physical methods together with 31P-NMR have been used to investigate the effect of lysophosphatidylcholine on phosphatidylcholine bilayers. 31P-NMR shows that the permeability of the vesicle to Eu3+ increases sharply above approx. 40% lysophosphatidylcholine: fluorescence-quenching studies also show this type of behavior. Similar sharp changes in vesicle properties are observed via the photo-physical technique at this lysophosphatidylcholine/phosphatidylcholine composition. Fluorescence spectra of pyrene and pyrene carboxaldehyde show that increasing lysophosphatidylcholine composition increases the polarity of the environments of these probes up to 40% lysocompound. Above this composition the photo-physical properties of the probes slowly revert to those characteristic of the micellar lyso-compound. The pyrene fluorescence lifetime, the fine structure of the fluorescence, and the case of formation of pyrene excimer in these bilayer mixtures suggest that pyrene complexes weakly with the charged nitrogen of the choline group of the phosphatidylcholine and that the physical state of the system has a striking effect on this complexation process. Similar experiments with simple quaternary compounds lend strong support to this suggestion. The studies monitor in several ways the effect of bilayer composition on movement of molecules in these systems. The degree or site of solubilization of carcinogens is also uniquely affected by composition.

Cell length, light and(14)C-labelled indol-3yl-acetic acid transport inPisum satisum L. andPhaseolus vulgaris L

The putative auxin-transporting cells of the intact herbaceous dicotyledon are the young, differentiating vascular elements. The length of these cells was found to be considerably greater in dwarf (Meteor) than in tall (Alderman) varieties ofPisum sativum L., and to be greater in etiolated than in light-grown plants ofP. sativum cv Meteor andPhaseolus vulgaris L. cv Mexican Black. Under given light conditions during transport these large differences in cell length did not influence the shapes of the transport profiles or the velocity of transport of(14)C-labelled indol-3yl-acetic acid (IAA) applied to the apical bud. However, in both etiolated and light-grown bean and dwarf pea plants the velocity of transport in darkness was ca. 25% lower than that in light. Under the same conditions of transport velocities in bean were about twice those observed in the dwarf pea. Exposure to light during transport increased the rate of export of(14)C from the labelled shoot apex in green dwarf pea plants but not in etiolated plants. The light conditions to which the plants were exposed during growth and transport had little effect on the rates of uptake of IAA from the applied solutions. The results indicate that the velocity of auxin transport is independent of the frequency of cell-to-cell interfaces along the transport pathway and it is suggested that in intact plants auxin transport is entirely symplastic.

Effects of temperature and sink activity on the transport of (14)C-labelled indol-3yl-acetic acid in the intact pea plant (Pisum sativum L.)

The velocity and intensity of basipetal transport of (14)C-labelled indol-3yl-acetic acid (IAA) applied to the apical bud of the intact pea plant were influenced by the temperature to which the stem was exposed and were not influenced by changes in the temperature of the root system when this was controlled independently between 5°C and 35°C. The velocity of transport increased steadily with temperature to a maximum in excess of 35°C and then fell sharply with further increase in temperature. The Q10 for velocity, determined from Arrhenius plots, was low (ca. 1.3). Transport intensity increased to a maximum at about 25°C (Q10=2.2) and then declined gradually with further increase in temperature. It is suggested that transport velocity and transport intensity are controlled independently.The characteristics of auxin transport through the stem were not affected by removal of the root system, or by the withdrawl of root aeration. Labelled IAA did not pass a region of the stem cooled to about 1.0°C, or through a narrow zone of stem tissue killed by heat treatment. In the latter case the heat treatment was shown not to interfere with the upward transport of water in the xylem. Labelled IAA continued to move into, and to accumulate in, the tissues immediately above a cooled or heat-killed region of the stem. It was concluded that the long-distance basipetal transport of auxin through the stem of the intact plant is driven by the transporting cells themselves and is independent of the activity of sinks for the transported auxin.The fronts of the observed tracer profiles in the stem were closely fitted by error function diffusion analogue curves. However, diffusion of IAA alone could not account for the observed characteristics of the transport and it is suggested that the curvilinear fronts of the profiles resulted from a diffusive mixing of exogenous IAA (or IAA-carrier complexes) with endogenous IAA already in the transport pathway.

The effect of temperature on the velocity of exogenous auxin transport in intact chilling-sensitive and chilling-resistant plants

The velocity of exogenous indol-3yl-acetic acid ([1-(14)C]IAA) transport from the apical buds of intact pea, sunflower and cotton plants was determined from 0.5° C to 47° C. The minimum temperature at which transport occurred varied from 2° C (pea and sunflower) to 7° C (cotton). Above these temperatures the velocity of transport increased steadily to maxima near 44° C in all three species. Further increase in temperature resulted in a complete cessation of transport, suggesting a sudden high-temperature breakdown of the auxin transport system. Temperature coefficients (Q10) for transport velocity calculated from Arrhenius plots were low (1.36 to 1.41 between 15° C and 30° C).Arrhenius plots for the chilling-sensitive cotton and sunflower plants exhibited abrupt discontinuities at 14.6° C and 8.7° C respectively. An Arrhenius plot for the chilling-resistant pea exhibited no such discontinuity over the whole temperature range at which transport occurred.

Accumulation of (14)C from exogenous labelled auxin in lateral root primordia of intact pea seedlings (Pisum sativum L.)

When [(14)C]indol-3yl-acetic acid was applied to the apical bud of 5-day old dwarf pea seedlings which possessed unbranched primary roots, a small amount of (14)C was transported into the root system at a velocity of 11-14 mm h(-1). Most of the (14)C which entered the primary root accumulated in the young lateral root primordia, including the smallest detectable (20-30 mm from the primary root tip). In older (8-d old) seedlings in which the primary root bore well-developed lateral roots, (14)C also accumulated in the tertiary root primordia. In contrast, little (14)C was detected in the apical region of the primary root or, in older plants, in the apices of the lateral roots.

Transport of exogenous auxin in two-branched dwarf pea seedlings (Pisum sativum L.) : Some implications for polarity and apical dominance

Dwarf pea plants bearing two cotyledonary shoots were obtained by removing the epicotyl shortly after germination, and the patterns of distribution of (14)C in these plants was investigated following the application of [(14)C]IAA to the apex of one shoot. Basipetal transport to the root system occurred, but in none of the experiments was (14)C ever detected in the unlabelled shoot even after transport periods of up to 48 h. This was true both of plants with two equal growing shoots and of plants in which one shoot had become correlatively inhibited by the other, and in the latter case applied whether the dominant or subordinate shoot was labelled. In contrast, when [(14)C]IAA was applied to a mature foliage leaf of one shoot transfer of (14)C to the other shoot took place, although the amount transported was always low. Transport of (14)C from the apex of a subordinate shoot on plants bearing one growing and one inhibited shoot was severely restricted compared with the transport from the dominant shoot apex, and in some individual plants no transport at all was detected. Removal of the dominant shoot apex rapidly restored the capacity of the subordinate shoot to transport apically-applied [(14)C]IAA, and at the same time led to rapid cambial development and secondary vascular differentiation in the previously inhibited shoot. Applications of 1% unlabelled IAA in lanolin to the decapitated dominant shoot maintained the inhibition of cambial development in the subordinate shoot and its reduced capacity for auxin transport. These results are discussed in relation to the polarity of auxin transport in intact plants and the mechanism of correlative inhibition.

Surface immune precipitation: a new method for rapid quantitative antigen analysis

A new method for quantitative antigen analysis is described which precludes necessity for long incubation periods. The new technique, Surface Immune Precipitation (SIP), entails the application of an antigen sample droplet directly onto the surface of a gel containing antibody, the gel being supported by a reflecting substrate. Within a few minutes, a visible uniform opaque precipitate area appears at the location of the antigen droplet when antigen-specific antibody is present in the gel. The reflecting substrate enhances the contrast between the precipitate area and the surrounding gel. The scattering intensity of the precipitate, which may be measured with simple photodetection apparatus, is related to the antigen concentration in the droplet. Good correlation is demonstrated between the Surface Immune Precipitation method and radial immunodiffusion for the analysis of serum IgG.

The specificity of auxin transport in intact pea seedlings (Pisum sativum L.)

When eight (14)C-labelled auxin and non-auxin compounds were applied to the apical buds of intact dwarf pea seedlings (Pisum sativum L.), only [1-(14)C]indoleacetic acid ([(14)C]IAA) and α-[1-(14)C] naphthaleneacetic acid ([(14)C]NAA) underwent appreciable basipetal transport during the first 24 h; over a longer period (72 h) considerable basipetal transport of the auxin [1-(14)C]2,4-dichlorophenoxyacetic acid ([(14)C]2,4-D) also occurred, but at a very much lower velocity (ca. 1.4-2.2 mm·h(-1)). The movement of 2,4-D possessed many of the characteristics of a typical auxin transport. During uptake and transport IAA and NAA were extensively metabolised to the corresponding aspartates, and to ethanol-insoluble/NaOH-soluble compounds; little metabolism of 2,4-D was observed. None of the non-auxin compounds applied (sorbose, sucrose, leucine, adenine and kinetin) underwent appreciable basipetal transport from the apical bud. All but sorbose were extensively metabolised by the apical tissues. Little metabolism of sorbose itself was detected.The results suggest that the long-distance basipetal auxin transport system from the apical bud of intact plants is specific for auxins; the specificity may result from the affinity of auxins for specific transport sites.

Auxin transport in intact pea seedlings (Pisum sativum L.): The inhibition of transport by 2,3,5-triiodobenzoic acid

The application of 2,3,5-triiodobenzoic acid (TIBA, 10 mg·g(-1) in lanolin) to the stem of intact pea seedlings (Pisum sativum L.) inhibited the basipetal transport of (14)C from indoleacetic acid-1-(14)C (IAA-1-(14)C) applied to the apical bud, but not the transport of (14)C in the phloem following the application of IAA-1-(14)C or sucrose-(14)C to mature foliage leaves. It was concluded that fundamentally different mechanisms of auxin transport operate in these two pathways.When TIBA was applied at the same time as, or 3.0 h after, the application of IAA-1-(14)C to the apical bud, (14)C accumulated in the TIBA-treated and higher internodes; when TIBA was applied 24.0 h before the IAA-1-(14)C, transport in the stem above the TIBA-treated internode was considerably reduced. TIBA treatments did not consistently influence the total recovery of (14)C, or the conversion of free IAA to indoleaspartic acid (IAAsp). These results are discussed in relation to the possible mechanism by which TIBA inhibits auxin transport,.Attention is drawn to the need for more detailed studies of the role of the phloem in the transport of endogenous auxin in the intact plant.

Pathways of auxin transport in the intact pea seedling (Pisum sativum L.)

When small colonies of the pea aphid [Acyrthosiphon pisum (Harris)] were established on the stem of Meteor Dwarf Pea seedlings (Pisum sativum L.), (14)C was found in the honeydew 4.5 h after applying IAA-1-(14)C to a fully-expanded foliage leaf. In contrast, no activity was found in the honeydew or aphids 4.5 h after the application of IAA-1-(14)C to the intact apical bud even though the internode upon which the aphids were feeding contained high levels of (14)C. The lack of radio-activity in aphids feeding on stems to which IAA-1-(14)C was applied via the apical bud was found not to be influenced by the internode position or by the transport interval allowed (up to 24 h).Radioactivity derived from either foliar or apical applications of IAA-1-(14)C was not transported through stem tissues killed by heat treatment. Xylem function was shown not to be impared by the heat treatment employed.It was concluded that the long-distance transport of IAA from the apical bud of intact pea seedlings does not take place in the phloem sieve tubes involved in the transport of metabolites from foliage leaves, or in the non-living tissues of the xylem.

Light and the transport and metabolism of indoleacetic acid in normal and albino dwarf pea seedlings

The patterns of transport and metabolism of IAA-2-(14)C applied to the apices of intact normal and albino dwarf pea seedlings were essentially similar under given light conditions. Light greatly reduced the decarboxylation of the applied IAA and stimulated the synthesis of indoleaspartic acid (IAAsp) in both normal and albino plants.In light considerably more (14)C was exported from the apices of normal than albino plants; this result was attributed to the reduced capacity of the transport system in the latter.The specific activity of (14)C in the stem decreased logarithmically with increasing distance from the treated apex. Light increased the steepness of the logarithmic profile. These results are discussed in relation to the rate of immobilization of IAA along the transport pathway by conversion to IAAsp.No evidence was found to support a previous suggestion (Pilet and Phipps, 1968) that IAA-oxidase activity and chlorophyll levels were causally linked.

Study of the retinal circulation. I. Effect of light

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The transport and metabolism of (14)C-labelled indoleacetic acid in intact pea seedlings

Part of the IAA-I- or IAA-2-(14)C applied at low concentrations to the apices of intact, light-grown dwarf pea seedling was transported unchanged to the root system The calculated velocity of transport in the stem was 11 mm per hour. In the root the label accumulated in the developing lateral root primordia.A large proportion of the applied IAA was converted by tissues of the apical bud, stem and root to indole-3-acetyl-aspartic acid (IAAsp). This compound was not transported. In addition evidence was obtained for the formation of IAA-protein complexes in the apex and roots, but not in the fully-expanded internodes.Large quantities of a decarboxylation product of IAA, tentatively indentified as indole-3-aldehyde (IAld), and several minor metabolites of IAA, were detected in extracts of the roots and first internodes, but not in the above-ground organs exposed to light. These compounds were readily transported through stem and root tissues. Together, the decarboxylation of IAA and the formation of IAAsp operated to maintain a relatively constant level of free IAA-(14)C in the root system.

Distribution of (14)C-labelled sucrose in seedlings of Pisum sativum L. Treated with indoleacetic acid and kinetin

The influence of decapitation and treatment with IAA and/or kinetin on the pattern of distribution of (14)C-labelled sucrose applied to the third leaf of 14-day old dwarf pea seedlings was investigated. Decapitation resulted in a diversion of the labelled metabolites to the lateral buds, and greatly increased the radioactivity present in the root system indicating that in these seedlings the roots and apex actively competed for translocates from the third leaf. Application of IAA to the decapitated internode prevented the growth of the lateral buds for the duration of the experiment and restored the pattern of distribution of labelled metabolites found in the intact plant. Application of kinetin alone resulted in a marked accumulation of labelled materials in the lateral buds, but when kinetin was applied with IAA metabolites were once again diverted from the lateral buds to the treated internode. Neither of these treatments had any influence on the proportion of the translocated materials which accumulated in the root system when compared with intact plants. The results are discussed in relation to current concepts of 'hormone-directed transport' of nutrients in plants.

The influence of light, gibberellic acid and CCC on sprout growth and mobilization of tuber reserves in the potato (Solanum tuberosum L.)

'Warm white' fluorescent light inhibited the elongation of potato sprouts and reduced the rate at which reserve materials in the mother tuber were mobilized. The evidence indicated that the influence of light on mobilization was independent of light effects on the magnitude of the 'sink' for translocates in the sprout. However, dark-grown sprouts exerted a greater directive influence than illuminated sprouts on the translocation of the mobilized materials.The rate of elongation and increase in dry weight of sprouts was promoted by exogenous GA independently of the effects of light on these processes, and the absence of any effects of CCC on sprout length and dry weight in these experiments was interpreted to indicate that light did not influence these parameters by controlling the level of endogenous gibberellins. Neither GA nor CCC modified the effects of light on the dry matter content of the sprouts, suggesting that growth in darkness and growth induced by GA were qualitatively different. The results are compared with the effects of light and GA on growth and stem elongation in other species.