bluuebunny/crossref_metadata_2025 huggingface dataset:
SEASONAL VARIATIONS OF PHOTOSYNTHETIC PIGMENTS, TOTAL C, N, AND P CONTENT, AND PHOTOSYNTHESIS IN PHYLLARIOPSIS PURPURASCENS: (PHAEOPHYTA) FROM THE STRAIT OF GIBRALTAR
Authors: Flores‐Moya Antonio , Fernández José A. , Xavier Niell F.
Published: October 2004

Photosynthetic pigments, C, N, and P tissue composition, and photosynthetic rate were measured from April to October in the brown alga Phyllariopsis purpurascens (C. Agardh) Henry et South (Laminariales, Phaeophyta) growing at a 30‐m depth in the Strait of Gibraltar. Ir‐radiance reaching the population ranged from 13.5 to 27.5 mol.m‐2.mo‐1. The available light for this species, expressed as a percentage of the irradiance above the water, was 1.8%. Dissolved inorganic nitrogen forms, NO3‐and NH4+, were constant from April to October, whereas phosphate was depleted in August. Chlorophyll a decreased from 520.0 ± 165.0 to 199.6 ± 159.9 μg.g‐1 dry weight; in contrast, chlorophyll c and carotenoids did not change until September but increased threefold in October. C:N and N:P ratios changed in the same way and in the same range. They were constant until July but increased from 15–17 up to 42 (C:N) and from 14 to 40 (N:P) in October, suggesting a severe P limitation of growth of this species. The dark respiration rate and the light compensation point were constant from April to October (0.5 ± 0.1 μmol O2. m‐2.s‐1 and 6.5 ± 0.2 μmol.m‐2. s‐1, respectively), whereas the maximum rate of apparent photosynthesis, light onset saturation parameter, and half saturation constant for light were maximum in April to May (3.7 μmol O2. m‐2.s‐1and 40 and 41.5 μmol.m‐2. s‐1, respectively) and October (3.6 μmol O2. m‐2.s‐1 and 50 and 53.7 μmol.m‐2. s‐1, respectively). They were minimum in August (1.2 μmol O2.m‐2.s‐1 and 11.3 and 12 μmol.m‐2.s‐1, respectively). These minimum figures yielded a negative carbon budget in August and 0 in September, whereas it was positive the rest of the year. Photosynthetic efficiency, estimated by the ratio between maximum apparent photosynthesis and light half saturation constant, showed a strong agreement with productivity measured by means of an independent method. These results indicate that lamina expansion in this species is controlled by photosynthetic efficiency.
CYTOCHROME f LOSS IN ASTAXANTHIN‐ACCUMULATING RED CELLS OF HAEMATOCOCCUS PLUVIALIS (CHLOROPHYCEAE): COMPARISON OF PHOTOSYNTHETIC ACTIVITY, PHOTOSYNTHETIC ENZYMES, AND THYLAKOID MEMBRANE POLYPEPTIDES IN RED AND GREEN CELLS
Authors: Tan Shi , Cunningham Francis X. , Youmans Michelle , Grabowski Beatrice , Sun Zairen , Gantt Elisabeth
Published: October 2004

Photosynthetic activity, chloroplast enzymes, and poly‐peptides were compared in green and red (ketocarotenoid‐containing) cultures of the microalga Haematococcus pluvialis Flotow. Green cultures, grown at 80 μmol pho‐tons.m‐2. s‐1 in an acetate‐containing medium, had a mean generation time of 27 h. Ketocarotenoid accumulation was induced by transfer of green cultures to PO4‐deficient medium and exposure to 250 μmol photons.m‐2. s‐1. Under these conditions, there was no increase in cell number, and the cultures turned red. Relative amounts of enzymes and thylakoid polypeptides in red and green cells were ascertained by immunoprobing with standardization on a chlorophyll (Chl) basis. In red cultures, the level of cytochrome f was greatly decreased (< 1% of green cell level), which is expected to greatly impair the linear electron flow from photosystem (PS) II to PS I. Also, the levels of apoproteins in red cells, namely, of CPI, D2, CP47, LHC I, and ribulose‐1, 5‐bisphosphate carboxylase were reduced to 15, 18, 29, 48, and 80%, respectively, of those in green cells. Only adenosine triphosphate syn‐thase exhibited no significant change in the two types of cultures. The respiration rate of red cultures was much higher (100 μmoles O2. mg Chl‐1.h‐1) than that of green cells (16 μmoles O2. mg Chl‐1.h‐1). Conversely, net O2 evolution (at Pmax in green cultures was 80 μmoles O2. mg Chl‐1.h‐1 but was —40 μmoles O2. mg Chl‐1.h‐1 in red cultures. PS II activity was demonstrated in broken cells of both green and red cultures, showing activity of 40 and 15 μmoles DCPIP‐mg Chl‐1.h‐1 (with DPC as electron donor), respectively. In contrast, PS I activity measured by the Mehler reaction showed that red rather than green cells had a greater activity (64 vs. 46 μmoles O2. mg Chl‐1.h‐1, respectively). Thus, in spite of the decline of O2 evolution in red cells, the photosystems were still functional. We postulate that the decline of O2, evolution in red cells is largely attributable to an increase in the respiration rate and the impairment of linear electron flow from PS II to PS I and, to some extent, to a decrease in components of the photosystems.
MORPHOLOGICAL AND BIOCHEMICAL VARIABILITY OF THE TOXIC DINOFLAGELLATE PROROCENTRUM LIMA ISOLATED FROM THREE LOCATIONS AT HERON ISLAND, AUSTRALIA
Authors: Morton Steve L. , Tindall Donald R.
Published: October 2004

Seventeen clones of the toxic, epiphytic‐benthic dinoflagellate Prorocentrum lima (Ehrenberg) Dodge isolated from three separate sites on the reef flats of Heron Island, Australia, were acclimated under the same set of environmental conditions. Morphological features examined for each clone included cell surface configuration, size, and dry weight. Physiological and biochemical features determined for each clone included reproduction rates, pigments (chlorophyll a, chlorophyll c2, peridinin, and other xanthophylls), toxins (okadaic acid and methyl‐okadaic acid), and macromolecular compounds (total protein, lipid, and carbohydrate). Variation in morphological features and reproduction rates of clones within and between sites was minimal and not significant. Also, variation in biochemical features within an individual site was low, but pronounced differences existed among sites, the most notable of which was toxin content (okadaic acid and methyl‐okadaic acid). The greatest difference in biochemical features was between clones isolated from the southern site and clones isolated from the northern and southeastern sites. Results of a cluster analysis of clonal characters support the view that these two groups represent distinct genotypes. We suggest that these groups originated from separate seed sources and that the genetic integrity of each is maintained through asexual reproduction.
EFFECT OF DISSOLVED OXYGEN PARTIAL PRESSURE ON THE ACCUMULATION OF ASTAXANTHIN IN CHEMOSTAT CULTURES OF HAEMATOCOCCUS LACUSTRIS (CHLOROPHYTA)
Authors: Lee Yuan‐Kun , Ding Sun‐Yeun
Published: October 2004

The effect of dissolved oxygen partial pressure on the accumulation of astaxanthin in the green alga Haematococcus lacustris (Gir.) Rostaf (UTEX16) was studied in N‐limited continuous chemostat cultures. The steady‐state astaxanthin content measured against culture volume, cell number, and biomass dry weigh of Haematococcus cultures was proportional to the dissolved O2 partial pressure in the culture medium, over the range of 0–50% O2 The steady‐state biomass dry weight concentrations remained at between 0.52 and 0.57 g. L‐1 over the range of dissolved O2 partial pressure studied. Steady‐state cell densities at dissolved O2 partial pressures above the air saturation level (1.13–1.58 × 105 cells.mL‐1) were about half of that measured at lower dissolved O2 partial pressures (2.42–2.63 × 105 cells.mL‐1). Both biflagellated zoospores and nonmotile aplanospores were found at steady state. The fraction of nonmotile cells was higher at dissolved O2 partial pressures above the air saturation level (94.44–98.01%) than at dissolved O2 partial pressure below the air level (79.64–86.12 and 91.75%).
SUGAR‐CONTAINING COMPOUNDS ON THE CELL SURFACES OF MARINE DIATOMS MEASURED USING CONCANAVALIN A AND FLOW CYTOMETRY
Authors: Waite Anya M. , Olson Robert J. , Dam Hans G. , Passow Uta
Published: October 2004

Some diatom exudates may remain attached to the exterior cell surface, potentially altering cell stickiness and affecting important aspects of the diatom's ecology such as aggregation rates and grazing rates. We measured the accumulation of cell‐surface sugar‐containing compounds by labeling cultured marine diatoms with fluorescent‐tagged sugar‐binding lectins and measuring the fluorescence associated with each cell using flow cytometry. The binding of FITC‐labeled concanavalin A (FITC‐ConA), a lectin that binds to glucose and mannose residues, varied 5‐fold among different diatom species in exponential growth (on a per‐cell basis) and 2–3‐fold within a given species in different physiological states. Although transparent exopolymer particles followed a simple accumulation curve over time in batch culture, FITC‐ConA. cell‐1 did not follow the same pattern, suggesting that surface sugar accumulation is not driven simply by the accumulation of such particles in the medium. For Thalassiosira pseudonana (Hustedt) Hasle and Heimdal (3H clone), the amount of sugar‐containing compounds on the cell surface increased transiently as growth rate slowed in early stationary phase under both N and Si limitation. For Chaetoceros neogracile (Schuett) van Landingham, FITC‐ConA. cell‐1had a strong inverse relationship with growth rate across several Si‐limited batch culture experiments. Both results suggest some biological mediation of cell‐surface sugar‐containing compounds. Our study reveals the great potential for using lectin binding to investigate cell‐surface sugars on diatoms. Lectins allow us to investigate noninvasively the role of cell‐surface sugar‐containing compounds in modifying cell stickiness and aggregation, as well as the partitioning of exuded phytoplankton carbon. We suggest that cell‐surface sugar accumulation may be related to diatom stickiness, based on a correlation between our FITC‐ConA measurements and stickiness estimates in the literature on several of the species we studied.
REGULATION OF GROWTH PROCESSES DURING THE CELL CYCLE OF THE CHLOROCOCCAL ALGA SCENEDESMUS QUADRICAUDA UNDER A DNA REPLICATION BLOCK
Authors: Zachleder Vilém
Published: October 2004

The kinetics of two growth parameters (total RNA and total protein accumulation) was followed in synchronized cultures of the chlorococcal alga Scenedesmus quadricauda (Turp.) Bréb. under conditions of inhibited DNA replication in the presence of 5‐fluorodeoxyuridine (25 mg.L‐1). In the control culture, growth processes occurred in several steps with a decreasing rate of accumulation of RNA and protein amount approximately at each doubled value of the preceding step. Oscillations in the rate of growth processes in the control culture were temporally related to the initiation of individual reproductive steps. At each doubling, the cell became committed to triggering a sequence of reproductive processes, starting with DNA replication and ending with protoplast fission. Three commitment points were attained in the control culture and, consequently, three replication rounds of DNA followed by three nuclear divisions and three protoplast fissions occurred during one cell cycle. If 5‐fluorodeoxyuridine (FdUrd) was added at the beginning of the cell cycle, no reproductive processes occurred, and the cells remained uninuclear with one genome and did not divide. RNA accumulation did not seem to be affected by the presence of FdUrd for at least one cell cycle, and three or four doublings in the amount of RNA occurred during this period. Protein accumulation was even more independent of reproductive processes in the cell and continued for a period of about two or three cell cycles, attaining six doublings at the end of this period. Therefore, oscillations in the rate of protein or RNA accumulation remained even if reproductive processes were inhibited.
GENERAL ULTRASTRUCTURE AND FLAGELLAR APPARATUS ARCHITECTURE OF WOLOSZYNSKIA LIMNETICA (DINOPHYCEAE)
Authors: Roberts Keith R. , Hansen Gert , Taylor F. J. R.
Published: October 2004

The ultrastructure of Woloszynskia limnetica Bursa was examined using serial thin section electron microscopy. Sections of W. limnetica reveal numerous chloroplast profiles without any obvious pyrenoids. The extensive pusular complex consists of a “smooth” part and a part lined with electron‐dense particles. The nucleus is located in the episome. A stigma (=eyespot) consisting of numerous electron‐dense globules is situated beneath the amphiesmal vesicles of the sulcal groove. The longitudinal microtu‐bular root extends between the stigma and the amphiesma vesicles. Subthecal fibers occur in conjunction with the microtubules and the stigma. Both flagellar exit apertures are encircled by a broad striated collar, each giving rise to a fiber that extends along the pusular canal opening. The striated collars are interconnected by the ventral ridge fiber. The basal part of the transverse flagellum has, in addition to the normal paraxonemal rod (=striated strand or fiber), a semicircular structure consisting of fibrils. The flagellar apparatus is complex but possesses components typically found in the Dinophyceae. The longitudinal mi‐crotubular root is broad and is connected to both striated collars. The transverse basal body gives rise to the transverse microtubular root, which in turn is associated with microtubules that extend to the interior of the cell and with the transverse striated root. The transitional region of both basal bodies possesses a distinctive fibrous ring attached to each microtubular triplet by short fibers that collectively appear as spokes of a wheel. Not unexpectedly, the flagellar apparatus of Woloszynskia limnetica is much like that of the related Woloszynskia sp.; however, some dif ferences were discovered. A phylogenetic relationship between Woloszynskia limnetica, W. coronata (Wolosz.) Thompson, and W. sp. is indicated based on similarities in pusule and stigma structure.
SYNCHRONIZATION OF CHLOROPLAST DIVISION IN THE ULTRAMICROALGA CYANIDIOSCHYZON MEROLAE (RHODOPHYTA) BY TREATMENT WITH LIGHT AND APHIDICOLIN
Authors: Terui Sachiko , Suzuki Kuninori , Takahashi Hidenori , Itoh Ryuuichi , Kuroiwa Tsuneyoshi
Published: October 2004

A system of highly synchronized chloroplast divisions was developed in the unicellular red alga Cyanidioschyzon merolae De Luca, Taddei, & Varano. Chloroplast divisions were examined by epifluorescence microscopy following treatments with light and inhibitors. When the cells during stationary phase were transferred into a new medium under a 12:12 h LD cycle, chloroplasts, mitochondria, and cell nuclei divided synchronously in that order soon after the initiation of dark periods. More than 40% of the cells contained dividing chloroplasts. To obtain a system of highly synchronized cell division and chloroplast division, the cells synchronized by a 12:12 h LD cycle were treated with various inhibitors. Nocodazole and propyzamide did not affect cell and organelle divisions, whereas aphidicolin markedly inhibited cell‐nuclear divisions and cytokinesis and induced a delay in chloroplast division. More than 80% of the cells contained dividing chloroplasts when cells synchronized by light were treated with aphidicolin for 12 h. This synchronized system will be useful for studies of the molecular and cellular mechanisms of organelle divisions.
PHYLOGENETIC RELATIONSHIPS WITHIN THE COLONIAL VOLVOCALES (CHLOROPHYTA) INFERRED FROM rbcL GENE SEQUENCE DATA
Authors: Nozaki Hisayoshi , Itoh Motomi , Sano Ryosuke , Uchida Hidenobu , Watanabe Makoto M. , Kuroiwa Tsuneyoshi
Published: October 2004

The chloroplast‐encoded large subunit of the ribulose‐1, 5‐bisphosphate carboxylase / oxygenase (rbcL) gene was sequenced from 20 species of the colonial Volvocales (the Volvacaceae, Goniaceae, and Tetrabaenaceae) in order to elucidate phylogenetic relationships within the colonial Volvocales. Eleven hundred twenty‐eight base pairs in the coding regions of the (rbcL) gene were analyzed by the neighbor‐joining (NJ) method using three kinds of distance estimations, as well as by the maximum parsimony (MP) method. A large group comprising all the anisogamous and oogamous volvocacean species was resolved in the MP tree as well as in the NJ trees based on overall and synonymous substitutions. In all the trees constructed, Basichlamys and Tetrabaena (Tetrabaenaceae) constituted a very robust phylogenetic group. Although not supported by high bootstrap values, the MP tree and the NJ tree based on nonsynonymous substitutions indicated that the Tetrabaenaceae is the sister group to the large group comprising the Volvocaceae and the Goniaceae. In addition, the present analysis strongly suggested that Pandorina and Astrephomene are monophyletic genera whereas Eudorina is nonmonophyletic. These results are essentially consistent with the results of the recent cladistic analyses of morphological data. However, the monophyly of the Volvocaceae previously supported by four morphological synapomorphies is found only in the NJ tree based on nonsynonymous substitutions (with very low bootstrap values). The genus Volvox was clearly resolved as a polyphyletic group with V. rousseletii Pocock separated from other species of Volvox in the rbcL gene comparisons, although this genus represents a monophyletic group in the previous morphological analyses. Furthermore, none of the rbcL gene trees supported the monophyly of the Goniaceae; Astrephomene was placed in various phylogenetic positions.
OBSERVATION OF SAND‐DWELLING TOXIC DINOFLAGELLATES (DINOPHYCEAE) FROM WIDELY DIFFERING SITES, INCLUDING TWO NEW SPECIES
Authors: Faust Maria A.
Published: October 2004

Dinoflagellate associations, including toxic and potentially toxic benthic species, were examined in sand from South Water Cay and Carrie Bow Cay, Belize. The inshore sand habitat in localized areas of warm shallow lagoonal waters supported blooms of toxic assemblages of dinoflagellates. In the sand, the dominant microalgae were dinoflagellates; cyanobacteria were a minor component and diatoms were absent. Ciliates and nematodes were present. Assemblages of microorganisms in colored sand were examined for 4 consecutive days after which a storm washed away the patch. The sand‐dwelling dinoflagellate assemblage included 16 species where densities ranged from as low as 1.3% to 15% of total cell densities. The dominant species was Scrippsiella subsalsa, having 1.8 × 105 to 2.6 × 105 cells g‐1 sand. Toxic dinoflagellates identified in the sand were Gambierdiscus toxicus, Ostreopsis lenticularis, Prorocentrum lima, Prorocentrum mexicanum, and Amphidinium carteri. The potentially toxic Ostreopsis labens, Gambierdiscus belizeanussp. nov., and Coolia tropicalis sp. nov. were also identified. Toxic and potentially toxic species represented 36% to 60% of total microalgal cell assemblage.

The morphology of a new sand‐dwelling species, Gambierdiscus belizeanus sp. nov., was examined with the scanning electron microscope. The plate formula was Po, 3′, 7″, 6c, s?, 5‴, 1p, and 2″″.Dimensions of G. belizeanus cells were 53–67 pm long, 54–63 μm wide, and 92–98 μm in dorsoventral depth. Cells were deeply areolated, ellipsoid in apical view, and compressed anteroposteriorly. The cells of G. belizeanus were identified by the cell's long, narrow, pentagonal, posterior intercalary plate (1p) wedged between the wide postcingular plates 2″’and 4″; 1p occupied 20% of the width of the hypotheca.

The plate formula for Coolia tropicalis sp. nov. was Po, 3′, 7″, 7c, 8s?, 5″″, and 2″″, Cell size ranges were 23–40 μm long, 25–39 μm wide, and 35–65 μm in dorsoventral diameter. Cells were spherical, smooth, and covered with scattered round pores. The epitheca was smaller than the hypotheca. Precingular plates 1″ and 7″ were small and narrow, and the first apical plate 1″ and precingular plate 6″ were the largest plates on the epitheca. The apical pore was straight and 7 μm long, and was situated in the apical plate complex. Cells of C. tropicalis were distinguished from C. monotis by the wedge‐shaped plate 1′, a four‐sided 3’plate, and a short apical pore.
GENETIC TRANSFORMATION OF THE DIATOMS CYCLOTELLA CRYPTICA AND NAVICULA SAPROPHILA
Authors: Dunahay Terri G. , Jarvis Eric E. , Roessler Paul G.
Published: October 2004

Two species of diatoms were genetically transformed by introducing plasmid vectors containing the Escherichia coli neomycin phosphotransferase II (nptII)gene. Expression of the bacterial nptII gene in the diatoms was achieved using the putative promoter and terminator sequences from the acetyl‐CoA carboxylase gene from the centric diatom Cyclotella cryptica T13L Reimann, Lewin, and Guillard. The vectors were introduced into C. cryptica and the pennate diatom Navicula saprophila NAVIC1 Lange‐Bertalot and Bonik by microprojectile bombardment. Putative transformants were selected based on their ability to grow in the presence of the antibiotic G418, and production of the neomycin phosphotransferase protein by the transformed cells was confirmed by western blotting. The foreign DNA integrated into one or more random sites within the genome of the transformed algal cells, often in the form of tandem repeats. This is the first report of reproducible, stable genetic transformation of a chlorophyll c‐containing alga.
A NEW, NONRADIOACTIVE WHOLE‐MOUNT IN SITU HYBRIDIZATION PROTOCOL FOR FUCUS (PHAEOPHYTA) EMBRYOS
Authors: Bouget François‐Yves , Gerttula Suzanne , Kloareg Bernard , Quatrano Ralph S.
Published: October 2004

We present a nonradioactive protocol to localize mRNA in Fucus distichus ssp. edentatus (de la Pyl.) Powell (Phaeophyta) embryos using whole‐mount in situ hybridization. Hybridization of a digoxygenin (DIG)‐labeled oligo‐dT probe to poly A+ RNA, and DIG‐labeled riboprobes to specific mRNAs, was detected with an antibody to DIG (anti‐DIG) that was coupled to alkaline phosphatase. Our protocol, a modification of one developed for higher plants, includes a treatment of fixed embryos with specific cell‐wall‐degrading enzymes to permeabilize the cells to anti‐DIG, progressive osmotic changes to prevent plasmolysis, and a RNase A treatment to reduce nonspecific background. Using this protocol, we show the intracellular distribution of poly A+ RNA and mRNAs for actin and the fucoxanthin chlorophyll protein A (Fcp A). This method to detect mRNA localization is rapid because it does not require embedding, sectioning, or the use of radioactivity. With the availability of a variety of enzymes to degrade plant cell walls, this protocol should be applicable to many algal cells.
Comparison of regional vasomotor responses to acetazolamide and CO2 in rabbit cerebrum and cerebellum, measured by a hydrogen clearance method
Authors: Csete K. , Vezekényi Z. , Dóczi T. , Papp J. Gy. , Bodosi M. , Barzó P.
Published: October 2004

Aim:  Many investigators have proved the usefulness of acetazolamide provocation and the carbon dioxide test for assessment of the local cerebrovascular reactivity by measurement of the regional cerebral blood flow in patients with occlusive cerebrovascular disease. Data originating from a comparison of these two different vasomotor stimuli as concerns the differences in sensitivity to them in various parts of the central nervous system are scarce. Our aim was to compare the cerebral blood flow responses to hypercapnic and acetazolamide stimuli in different brain regions.

Methods:  The cerebral blood flow was measured in the cerebrum (cortex and caudate nucleus) and cerebellum (cortex), as measured by a hydrogen clearance method in anaesthetized, artificially ventilated rabbits.

Results:  In normocapnia, the cerebral blood flow values in the cerebrum and the cerebellum differed significantly. The cerebral blood flow responses to both vasodilatory stimuli were to be significantly higher in the cerebrum than in the cerebellum, but the relative increases, i.e. the mean relative reactivities, were similar in the different regions measured.

Conclusion:  The regional dissimilarity might explain to some extent the different sensitivities of the various brain areas to sudden blood pressure changes (infarction or haemorrhage). The results further suggest that heterogeneity in cerebrovascular reactivity should be considered in the assessment of vasoreactivity in patients with occlusive cerebrovascular disease. Since the comparison of the carbon dioxide and acetazolamide – induced cerebrovascular reactivities revealed a strong linear relationship, it was concluded that acetazolamide provocation is equivalent to the carbon dioxide test in the evaluation of cerebrovascular reactivity.
Partial reversal of conduction slowing during repetitive stimulation of single sympathetic efferents in human skin
Authors: Campero M. , Serra J. , Bostock H. , Ochoa J. L.
Published: October 2004

Aims:  To describe and identify the function of a class of human C fibre with an unusual response to repetitive electrical stimulation. Other C fibres slow progressively at 2 Hz (type 1), reach a latency plateau (type 2) or hardly slow at all (type 3).

Methods:  C fibres innervating hairy skin were recorded by microneurography in the superficial peroneal nerves of 19 healthy volunteers. Baseline electrical stimulation of the skin was at 0.25 Hz, and activity‐dependent slowing recorded during stimulation at 2 Hz for 3 min and after a 3‐min pause in stimulation.

Results:  In 41 units, there was a partial recovery of latency during repetitive stimulation. These were classified as ‘type‐4’ units, and identified as sympathetic efferents, since they exhibited spontaneously activity, which was enhanced by manoeuvres that increase sympathetic outflow (15 of 16 cases) and/or suppressed by a proximal anaesthetic block (eight of eight cases). The peak slowing during 2 Hz trains averaged 6.47 ± 2.06% (mean ± SD, n = 41), but after 3 min the slowing had reduced to 4.90 ± 2.20%, which was less than in all type 1 (nociceptor) fibres but similar to that in type 2 (cold) fibres. Compared with cold fibres, type‐4 sympathetic fibres slowed more after the first 10 impulses at 2 Hz (2.57 ± 0.45%) and also after a pause in stimulation (1.66 ± 0.51%).

Conclusions:  The distinctive activity‐dependent slowing profiles of these type‐4 sympathetic C units may help identification in vitro, and suggest that hyperpolarization‐activated channels have a particularly prominent role in the axonal membrane.
Human motor compensations for thixotropy‐dependent changes in muscular resting tension after moderate joint movements
Authors: Axelson H. W.
Published: October 2004

Aim: This study on healthy subjects explores history‐dependent changes in the resting tension of relaxed wrist muscles after moderate joint excursions and the motor control consequences of these changes during voluntary wrist joint position maintenance.

Methods: Integrated surface electromyogram (IEMG) was recorded from wrist extensor/flexor muscles. Angular position and torque were recorded from the wrist joint. Changes in wrist flexor muscle resting tension were sensed by a force transducer pressed against the tendons.

Results: Consecutive stepwise changes (7.5°) in wrist joint position (within the dorsiflexed range) were either imposed on relaxed subjects or actively performed while the subjects under visual guidance tried to mimic the passive movements. In relaxed subjects, passive joint torque resistance at a given steady dorsiflexed position either gradually declined or rose depending on the direction of the previous transition movements. In corresponding voluntary contraction experiments, the IEMG amplitude from position holding wrist extensors was found to vary in a similar way as the passive torque resistance. Further, there was a strong correlation between history‐dependent changes in extensor IEMG amplitude and stress alterations exhibited by the relaxed antagonist flexors. The above described, slowly subsiding post‐movement mechanical and motor adaptations were accelerated by brief forceful cocontractions of the forearm muscles.

Conclusion: Moderate stepwise changes in joint position are sufficient to induce history‐dependent after‐effects in passive muscular resting tension, after‐effects which during voluntary position holding are effectively compensated for by the motor control system.
Control of oxygen transport in the microcrustacean Daphnia: regulation of haemoglobin expression as central mechanism of adaptation to different oxygen and temperature conditions
Authors: Paul R. J. , Zeis B. , Lamkemeyer T. , Seidl M. , Pirow R.
Published: October 2004

The pathway for oxygen, the control of oxygen transport and the role of haemoglobin expression for the physiological adaptation to different oxygen and temperature conditions were studied in the ecological model organism Daphnia magna. Ventilation of the inner walls of the carapace as the main gas exchange area as well as of the embryos in the brood pouch are controlled, oxygen‐dependent processes. The PO2‐dependent increase of heart rate as well as perfusion rate during short‐term, progressive hypoxia improves the circulatory oxygen transport within the body. The regulation of haemoglobin (Hb) expression is the central mechanism for a medium‐term adaptation to hypoxia. Genetic control elements and oxygen conditions near the two Hb synthesis sites (fat cells, epipodite epithelial cells) determine, which types of Hb subunits and, accordingly, hetero‐multimeric Hb macromolecules are produced. One synthesis site may respond mainly to internal, the other one to external oxygen conditions. Depending on environmental condition, either higher quantities of macromolecules of unchanged functionality (P50) or increasing amounts of macromolecules with higher oxygen affinity are synthesized. The Hb subunit DmHbA is probably of considerable importance for this functional change. The physiological benefits of haemoglobin in Daphnia are discussed. Physiological adaptation of Daphnia to different temperatures is also related to the control of oxygen transport processes with the regulation of haemoglobin expression again as a central mechanism.
Review article: relationship between the metabolism and efficacy of proton pump inhibitors – focus on rabeprazole
Authors: Horn J.
Published: October 2004

Proton pump inhibitors are now considered the mainstay of treatment for acid‐related disease. Although all proton pump inhibitors are highly effective, the antisecretory effects of different drugs in this class are not completely consistent across patients. One reason for this is the acid‐suppressing effect of Helicobacter pylori infection, which may augment the actions of proton pump inhibitors. A second important reason for interpatient variability of the effects of proton pump inhibitors on acid secretion involves genetically determined differences in the metabolism of these drugs. This article focuses on the impact of genetic polymorphism of cytochrome P450 (CYP)2C19 on the pharmacokinetics and pharmacodynamics of proton pump inhibitors, particularly rabeprazole. Results reviewed indicate that the metabolism and pharmacokinetics of rabeprazole differ significantly from those of other proton pump inhibitors. Most importantly, the clearance of rabeprazole is largely nonenzymatic and less dependent on CYP2C19 than other drugs in its class. This results in greater consistency of pharmacokinetics for rabeprazole across a wide range of patients with acid‐related disease, particularly those with different CYP2C19 genotypes. The pharmacodynamic profile for rabeprazole is also characterized by more rapid suppression of gastric acid secretion than with other proton pump inhibitors, which is also independent of CYP2C19 genotype. The favourable pharmacokinetic/pharmacodynamic profile for rabeprazole has been shown to result in high eradication rates for H. pylori in both normal and poor metabolizers. Pharmacodynamic results have also suggested that rabeprazole may be better suited than omeprazole as on‐demand therapy for symptomatic gastro‐oesophageal reflux disease. Finally, the use of rabeprazole is not complicated by clinically significant drug–drug interactions of the type that have been reported for omeprazole.
Review article: pH, healing and symptom relief with rabeprazole treatment in acid‐related disorders
Authors: Robinson M.
Published: October 2004

Control of gastric acid secretion by antisecretory agents has been the cornerstone of therapy in the successful management of all acid‐related disorders, including gastro‐oesophageal reflux disease (GERD), and duodenal and gastric ulcer. Treatment efficacy has been strongly correlated with degree and duration of acid suppression within the 24‐h period and with total duration of therapy. All proton pump inhibitors are highly effective for the healing of ulcers and erosive oesophagitis. All have closely similar mechanisms of action, yet important pharmacological differences exist, which can significantly impact certain aspects of their clinical efficacy. Rabeprazole's rapid activation over a wide pH range may be the explanation for its early onset of effective acid inhibition compared with other proton pump inhibitors such as omeprazole, lansoprazole and pantoprazole. Like rabeprazole, esomeprazole is also a potent inhibitor of gastric acid at steady state, although it is thought that rabeprazole may provide enhanced first‐day acid suppression compared with esomeprazole. First‐day antisecretory efficacy should produce faster symptom relief, a hypothesis supported by clinical data. Moreover, drugs with pharmacological profiles that include both rapid onset and potent antisecretory effects should help control healthcare costs by reducing the need for otherwise commonly used twice‐daily proton pump inhibitor administration.
Obstacles in large‐scale epidemiological assessment of sensory impairments in a Dutch population with intellectual disabilities
Authors: Evenhuis H. , Van Splunder J. , Vink M. , Weerdenburg C. , Van Zanten B. , Stilma J.
Published: October 2004

Background  A population‐based epidemiological study on visual and hearing impairment was planned in a random sample of 2100 clients, drawn from a base population of 9012 users of Dutch residential and day‐care intellectual disability (ID) services with the whole range of IDs. Stratification was applied for age 50 years and over and Down syndrome. Visual and hearing functions were assessed according to a standardized protocol, in cooperation with regular ophthalmologists and regional audiological centres. Anticipated obstacles in sample collection, random inclusion, informed consent, expertise of investigators, time and costs were eliminated by a careful preparation. However, inclusion and participation were incomplete.

Method  In a descriptive retrospective design, we collected data from our study files on inclusion and participation as well as reasons for non‐participation, to identify unanticipated obstacles for this kind of research.

Results  Consent was obtained for 1660 clients, and 1598 clients participated in the data collection (76% of intended sample of 2100). Inclusion and participation rates were especially lower in community‐based care organizations, resulting in unintentional skewing of the sample towards more severe levels of ID. Complete and reliable data to diagnose visual impairment were obtained for 1358/1598 (85%) and to diagnose hearing impairment for 1237/1598 participants (77%). Unanticipated obstacles had to do with the quality of coordination within care organizations, with characteristics of screening methods, and with collaboration with the regular health care system. Assessments of visual function were more easy to organize than were those of hearing. Based on our current experience, practical recommendations are given for future multicentre research, especially in community‐based settings.
Improving functional skills and physical fitness in children with Rett syndrome
Authors: Lotan M. , Isakov E. , Merrick J.
Published: October 2004

Background  To investigate the feasibility of a physical exercise programme with treadmill for persons with Rett syndrome (RS) in order to promote fitness and health.

Methods  A daily training programme on a treadmill was designed for four females with RS over a period of 2 months with tests performed in three intervals, at time 1, 2 and 3, 2 months apart with intervention taking place between tests 2 and 3. Participants were four girls with RS aged 8.5–11 years (mean: 10 years) attending the educational facility Beit Issie Shapiro, Raanana, Israel, all with independent mobility and with typical characteristics of RS stage III. The training took place at the educational facility, on a 1400 model treadmill (Trimline, capable of very low speeds < 0.5 k/h), with very long side rails. Special low side rails were adapted to the treadmill in order to fit the height of the children and velcro straps were added to assist in safely placing the hands. Pulse was monitored constantly during exercise by an A3 polar pulse belt. Pulse measurements at rest during training were considered as evaluators of aerobic physical condition. Functional measurement was based on a scale specially established for the present study. The scale was a 31‐item motor‐functioning tool that measures the ability of participants to knee walk and knee stand, to get up to a standing position, duration of walking different paths, and to go up and down stairs and slopes.

Results  The study showed that physical fitness of the children at the end of the training programme had improved considerably (P < 0.05). Tests showed that general functional abilities had improved considerably (P < 0.0001). Although all items of the functional ability measure showed impressive positive change, some of the 31 items on it showed statistically significant improvement (knee walking, going up and down stairs and speed of walking for 25 m. Pearson correlation showed high linkage (r = −0.76) between functional improvement and change in physical fitness.

Conclusions  Physical fitness programme executed on a daily basis is capable of improving functional ability of children with RS. Nonprofessional personnel can execute such a programme under supervision of a qualified physical therapist.
Attitude to medication of parents/primary carers of people with intellectual disability
Authors: Rasaratnam R. , Crouch K. , Regan A.
Published: October 2004

Objective  To investigate the influence of attitudes of carers of people with intellectual disability (ID) towards giving medication.

Method  Ninety‐three carers of service users who are currently attending outpatients clinic (Harrow Learning Disability service) were interviewed, using the RAMS (Rating of Attitude to Medication Scale) interview schedule.

Results  A significant association was found between relationship of the carer to the service user and overall positive or negative attitude towards medication, with a disproportionate number of parents expressing a negative attitude in comparison with professional carers (46% vs. 11%).

Conclusion  This study suggests more work needs to be done with family carers than with professional carers to improve compliance with medication. Stigma is still associated with ID and psychiatric disorders. The family carers responses may be projecting their feelings related to the impact of having a child not only with ID, but also with additional psychiatric problems. The implication of the study for psychiatrists is the identification of a number of areas that could be usefully explored before writing a prescription.
Morphology and sexual dimorphism of the New Caledonian Crow Corvus moneduloides, with notes on its behaviour and ecology
Authors: Kenward Benjamin , Rutz Christian , Weir Alex A. S. , Chappell Jackie , Kacelnik Alex
Published: October 2004

New Caledonian Crows Corvus moneduloides are known to be extraordinary tool makers and users, but little is known of other aspects of their biology. Here, we report recent field observations of their behaviour and ecology, along with measurements of 19 morphological traits and two flight performance parameters taken from 22 captured Crows. These measurements showed that the Crows were sexually dimorphic in size (the males were larger) but not in shape. We also found that the crows lived in mixed‐sex groups, and we observed juvenile‐type begging behaviour and feeding by regurgitation, which supports the hypothesis that these may be family groups.
Matrix‐based calculation scheme for toric intraocular lenses*
Authors: Langenbucher Achim , Reese Sven , Sauer Tomas , Seitz Berthold
Published: October 2004

Background and purpose:  While a number of intraocular lens power prediction formulas are well established for determination of spherical lenses, no common strategy is published for the computation of toric intraocular lenses. The purpose of this study is to describe a paraxial computing scheme using 4 × 4 system matrices to describe the ‘optical system eye’ containing astigmatic refractive surfaces with their axes at random.

Methods:  Based on the definition of a centred optical system in the paraxial Gaussian space containing astigmatic surfaces using 4 × 4 refraction and translation matrices, we derived a methodology for calculating the refractive power of thin and thick toric intraocular lenses by solving a linear equation system. In a second step, we derived a methodology for prediction of the residual spectacle refraction after implantation of any toric lens implant with any orientation.

Results:  The capabilities of this computing scheme are demonstrated with three examples. In example 1 we calculate a ‘thin toric lens’ for compensation of a corneal astigmatism to achieve a spherical target refraction. In example 2 we compute a ‘thick toric lens’, which has to compensate for an oblique corneal astigmatism and rotate the spectacle cylinder to the ‘against the rule’ position to enhance near vision. In example 3 we predict the residual refraction at the corneal plane after implantation of a thick toric lens, when the cylinder of the lens implant is compensating the corneal cylinder in part and the axis of implantation is not fully aligned with the axis of the corneal astigmatism.

Conclusion:  We present an en bloc matrix‐based strategy for the calculation of thick or thin toric intraocular lenses, with the flexibility of crossing an unlimited number of cylinders with restrictions to paraxial optics. The resulting system matrix S is written as a product of 4 × 4 refraction and translation matrices. Residual refraction at the corneal (contact lens) or spectacle plane can be derived by inverting the order of matrices for calculation of the system matrix.
Measurement of refractive error and accommodation with the photorefractor PowerRef II
Authors: Jainta Stephanie , Jaschinski Wolfgang , Hoormann Jörg
Published: October 2004

The infrared photorefractor PowerRef II (PR II; PlusoptiX AG, Nürnberg, Germany) uses the principle of eccentric photorefraction. In eight subjects the mean non‐cycloplegic refraction measured with the ‘Full Scan’ mode of the PR II at a far viewing distance (0.2 D) was significantly more hypermetropic by 0.6 D compared with subjective refraction. The mean accommodation differed by about this same amount between the PR II and the Canon R1 at three different viewing distances (3, 2 and 1 D). The PR II refraction at the 1 m reference distance was 0.25 D more hypermetropic compared with the subjective refraction at far (5 m); these measures were moderately correlated (r = 0.7). To determine temporal changes, the ‘Dynamic Scan’ mode was used over a 2‐min period: the mean intraindividual standard deviation was 0.32 mm for pupil diameter and 0.29 D for accommodation, while the absolute measurement error of the ‘Dynamic Scan’ was found to be <0.12 D for the accommodation data. Interindividual reliabilities were satisfactory. However, the PR II did not provide a continuous stream of data and the specified sampling frequency of 25 Hz was rarely realized.
Microfluctuations of wavefront aberrations of the eye
Authors: Zhu Mingxia , Collins Michael J. , Robert Iskander D.
Published: October 2004

To investigate fluctuations in the wavefront aberrations of the eye and their relation to pulse and respiration frequencies we used a wavefront sensor to measure the dynamics of the Zernike aberrations up to the polynomial fourth radial order. Simultaneously, the subject's pulse rate was measured, from which the instantaneous heart rate was derived. We used an auto‐regressive process to derive the power spectra of the Zernike aberration signals, as well as pulse and instantaneous heart rate signals. Linear regression analysis was performed between the frequency components of Zernike aberrations and the pulse and instantaneous heart rate frequencies. Cross‐spectrum density and coherence analyses were also applied to investigate the relation between fluctuations of wavefront aberrations, and pulse and instantaneous heart rate. The correlations between fluctuations of individual Zernike aberrations were also determined. A frequency component of all Zernike aberrations up to the fourth radial order was found to be significantly correlated with the pulse frequency (all R2 ≥ 0.51, p < 0.02), and a frequency component of nine out of 12 Zernike aberrations was also significantly correlated with instantaneous heart rate frequency (all R2 ≥ 0.46, p < 0.05). The major correlations among Zernike aberrations occurred between second‐order and fourth‐order aberrations with the same angular frequencies. Higher order aberrations appear to be related to the cardiopulmonary system in a similar way to that reported for the accommodation signal and pupil fluctuations.
Macular pigment optical density in young Chinese adults
Authors: Tang Churk‐Yan , Yip Hoi‐shan , Poon Ming‐yeung , Yau Wai‐lam , Yap Maurice K. H.
Published: October 2004

Purpose:  The purpose of this study was to determine the macular pigment optical density (MPOD) in a group of Chinese subjects using a simple customized light emitting diode‐based device.

Methods:  Heterochromatic flicker photometry was used in this study. With a 1° diameter circular test stimulus, MPOD was estimated by comparing the relative sensitivities to a blue light, against a green reference, between foveal and parafoveal 4° temporal locations. Fixed alternating frequencies were used. Repeatability was determined on a small group of subjects. A further group of 67 young healthy subjects provided data for MPOD norms.

Results:  All results were corrected to the common MPOD reference wavelength of 460 nm. The group‐averaged MPOD was 0.48 (S.D. 0.23). We found no gender difference in MPOD. The coefficient of variability was 7.2–8.0% and the coefficient of repeatability was 0.12.

Conclusions:  The MPOD of Chinese subjects did not differ greatly from the reported MPOD in white subjects.
Reliability, normative data, and the effect of age‐related macular disease on the Eger Macular Stressometer photostress recovery time
Authors: Bartlett Hannah , Davies Leon N. , Eperjesi Frank
Published: October 2004

Purpose:  To assess repeatability and reproducibility, to determine normative data, and to investigate the effect of age‐related macular disease, compared with normals, on photostress recovery time measured using the Eger Macular Stressometer (EMS).

Method:  The study population comprised 49 healthy eyes of 49 participants. Four EMS measurements were taken in two sessions separated by 1 h by two practitioners, with reversal of order in the second session. EMS readings were also taken from 17 age‐related maculopathy (ARM), and 12 age‐related macular degeneration (AMD), affected eyes.

Results:  EMS readings are repeatable to within ±7 s. There is a statistically significant difference between controls and ARM affected eyes (t = 2.169, p = 0.045), and AMD affected eyes (t = 2.817, p = 0.016). The EMS is highly specific, and demonstrates sensitivity of 29% for ARM, and 50% for AMD.

Conclusions:  The EMS may be a useful screening test for ARM, however, direct illumination of the macula of greater intensity and longer duration may yield less variable results.