bluuebunny/crossref_metadata_2025 huggingface dataset:
Correlates to Colonizations of New Patches by Translocated Populations of Bighorn Sheep
Authors: Singer Francis J. , Moses Michael E. , Bellew Susan , Sloan William
Published: March 2003

By 1950, bighorn sheep were extirpated from large areas of their range. Most extant populations of bighorn sheep (Ovis canadensis) in the Intermountain West consist of <100 individuals occurring in a fragmented distribution across the landscape. Dispersal and successful colonizations of unoccupied habitat patches has been rarely reported, and, in particular, translocated populations have been characterized by limited population growth and limited dispersal rates. Restoration of the species is greatly assisted by dispersal and successful colonization of new patches within a metapopulation structure versus the existing scenario of negligible dispersal and fragmented, small populations. We investigated the correlates for the rate of colonizations of 79 suitable, but unoccupied, patches by 31 translocated populations of bighorn sheep released into nearby patches of habitat. Population growth rates of bighorn sheep in the release patches were correlated to Ne of the founder group, and early contact with a second released population in a nearby release patch (logistic regression, p = 0.08). Largest population size of all extant released populations in 1994 was correlated to potential Ne of the founder group, the number of different source populations represented in the founder, and early contact with a second released population (p = 0.016). Dispersal rates were 100% higher in rams than ewes (p = 0.001). Successful colonizations of unoccupied patches (n = 24 of 79 were colonized) were associated with rapid growth rates in the released population, years since release, larger area of suitable habitat in the release patch, larger population sizes, and a seasonal migratory tendency in the released population (p = 0.05). Fewer water barriers, more open vegetation and more rugged, broken terrain in the intervening habitat were also associated with colonizations (p = <0.05). We concluded that high dispersal rates and rapid reoccupation of large areas could occur if bighorn sheep are placed in large patches of habitat with few barriers to movements to other patches and with no domestic sheep present. Many restorations in the past that did not meet these criteria may have contributed to an insular population structure of bighorn sheep with limited observations of dispersal.
Using Functional Trajectories to Track Constructed Salt Marsh Development in the Great Bay Estuary, Maine/New Hampshire, U.S.A.
Authors: Morgan Pamela A. , Short Frederick T.
Published: March 2003

A growing number of studies have assessed the functional equivalency of restored and natural salt marshes. Several of these have explored the use of functional trajectories to track the increase in restored marsh function over time; however, these studies have disagreed as to the usefulness of such models in long‐term predictions of restored marsh development. We compared indicators of four marsh functions (primary production, soil organic matter accumulation, sediment trapping, and maintenance of plant communities) in 6 restored and 11 reference (matched to restored marshes using principal components analysis) salt marshes in the Great Bay Estuary. The restored marshes were all constructed and planted on imported substrate and ranged in age from 1 to 14 years. We used marsh age in a space‐for‐time substitution to track constructed salt marsh development and explore the use of trajectories. A high degree of variability was observed among natural salt marsh sites, displaying the importance of carefully chosen reference sites. As expected, mean values for constructed site (n = 6) and reference site (n = 11) functions were significantly different. Using constructed marsh age as the independent variable and functional indicator values as dependent variables, nonlinear regression analyses produced several ecologically meaningful trajectories (r 2> 0.9), demonstrating that the use of different‐aged marshes can be a viable approach to developing functional trajectories. The trajectories illustrated that although indicators of some functions (primary production, sediment deposition, and plant species richness) may reach natural site values relatively quickly (<10 years), others (soil organic matter content) will take longer.
Restoration of Freshwater Intertidal Habitat Functions at Spencer Island, Everett, Washington
Authors: Tanner Curtis D. , Cordell Jeffery R. , Rubey Jane , Tear Lucinda M.
Published: March 2003

In November 1994 dikes were breached around Spencer Island, restoring tidal inundation and connections to the Snohomish River estuary, Washington. Approximately 23.7 ha (58.5 ac) of palustrine wetlands previously dominated by Phalaris arundinacea (reed canarygrass) now experience diurnal tides and are in the process of transition to a freshwater tidal system. It was expected that brackish water would accompany the return of tidal influence to the site, but post‐project monitoring has revealed little evidence of salinity. Pre‐ and post‐project monitoring of changes in habitat function included aerial photography, vegetation and fish sampling, and benthic prey studies. To date site changes include (1) die back of pre‐project vegetation, development of tidal mudflat, and emergent wetland habitats, with recruitment of vegetation typical of freshwater tidal wetlands; (2) presence of juvenile coho, chum, and chinook salmon that feed on invertebrate prey typical of the site; (3) presence of three distinct benthic invertebrate assemblages in the project area; and (4) some invasion by Lythrum salicaria (purple loosestrife). The unexpected freshwater conditions, the lack of published information about tidal oligohaline marshes in the Pacific Northwest, the use of the site by endangered salmonid species, and the invasion by an undesired plant species underscore the importance of long‐term monitoring at the site.
Pathogenesis Of Guillain‐Barre Syndrome
Authors: Hughes R.A.C. , Hadden R.D.M. , Gregson N.A. , Smith K.J.
Published: March 2003

Recent neurophysiological and pathological studies have led to a reclassification of the diseases that underlie Guillain‐Barre syndrome (GBS) into acute inflammatory demyelinating polyradiculoneuropathy (AIDP), acute motor and sensory axonal neuropathy (AMSAN) and acute motor axonal neuropathy (AMAN). The Fisher syndrome of ophthalmoplegia, ataxia and areflexia is the most striking of several related conditions. Significant antecedent events include Campylobacter jejuni (4–66%), cytomegalovirus (5–15%), Epstein‐Barr virus (2–10%), and Mycoplasma pneumoniae (1–5%) infections. These infections are not uniquely associated with any clinical subtype but severe axonal degeneration is more common following C.jejuni and severe sensory impairment following cytomegalovirus. Strong evidence supports an important role for antibodies to gangliosides in pathogenesis. In particular antibodies to ganglioside GM1 are present in 14–50% of patients with GBS, and are more common in cases with severe axonal degeneration associated with any subtype. Antibodies to ganglioside GQ1b are very closely associated with Fisher syndrome, its formes frustes and related syndromes. Ganglioside‐like epitopes exist in the bacterial wall of C.jejuni. Infection by this and other organisms triggers an antibody response in patients with GBS but not in those with uncomplicated enteritis. The development of GBS is likely to be a consequence of special properties of the infecting organism, since some strains such as Penner O:19 and O:41 are particularly associated with GBS but not with enteritis. It is also likely to be a consequence of the immunogenetic background of the patient since few patients develop GBS after infection even with one of these strains. Attempts to match the subtypes of CBS to the fine specificity of anti‐ganglioside antibodies and to functional effects in experimental models continue but have not yet fully explained the pathogenesis. T cells are also involved in the pathogenesis of most or perhaps all forms of GBS. T cell responses to any of three myelin proteins, PZ, PO and PMP22, are sufficient to induce experimental autoimmune neuritis. Activated T cells are present in the circulation in the acute stage, up‐regulate matrix metalloproteinases, cross the blood‐nerve barrier and encounter their cognate antigens. Identification of the specificity of these T cell responses is still at a preliminary stage. The invasion of intact myelin sheaths by activated macrophages is difficult to explain according to a purely T cell mediated mechanism. The different patterns of GBS are probably due to the diverse interplay between antibodies and T cells of differing specificities.
Percutaneous Electrical Nerve Stimulation—A Novel Analgesic Therapy For Diabetic Neuropathic Pain
Authors: Hamza M.A. , Whit P.F. , Craig W.F. , Ghoname E.A. , Ahmed H.E. , Proctor T.J. , Noe C.E. , Vakharia A.S. , Gajraj N.
Published: March 2003

OBJECTIVE—To evaluate the use of percutaneous electrical nerve stimulation (PENS) in the management of patients with painful diabetic peripheral neuropathy. RESEARCH DESIGN AND METHODS—A total of 50 adult patients with type 2 diabetes and peripheral neuropathic pain openface> 6 months duration involving the lower extremities were randomly assigned to receive active PENS (needles with electrical stimulation at an alternating frequency of 15 and 30 nz) and sham (needles only) treatments for 3 weeks. Each series of treatments was administered for 30 min three times a week according to a standardized protocol. After a 1‐week washout period, all patients were subsequently switched to the other modality. A 10‐cm visual analog scale (VAS) was used to assess pain, physical activity and quality of sleep before each session. The changes in VAS scores and daily requirements for oral analgesic medication were determined during each 3‐week treatment period. Patients completed the MOS 36‐Item Short‐Form Health Survey (SF‐36), the Beck Depression Inventory (BDI), and the Profile of Mood States (POMS) before and after completion of each treatment modality. At the end of the crossover study, a patient preference questionnaire was used to compare the effectiveness of the two modalities. RESULTS—Compared with the pain VAS scores before active (6.2 +/− 1.0) and sham (6.4 +/− 0.9) treatments, pain scores after treatment were reduced to 2.5 +/− 0.8 and 6.3 +/− 1.1, respectively. With active PENS treatment, the VAS activity and sleep scores were significantly improved from 5.2 +/− 1.0 and 5.8 +/− 1.3 to 7.9 +/− 1.0 and 8.3 +/− 0.7, respectively. The VAS scores for pain, activity, and sleep were unchanged from baseline values after the sham treatments. Patient's daily oral nonopioid analgesic requirements de‐creased by 49 and 14% after active and sham PENS treatments, respectively. The post‐treatment physical and mental components of the SF‐36, the BDI, and the POMS all showed a significantly greater improvement with active versus sham treatments. Active PENS treatment improved the neuropathic pain symptoms in all patients. CONCLUSIONS—PENS is a useful nonpharmacological therapeutic modality for treating diabetic neuropathic pain. In addition to decreasing extremity pain, PENS therapy improved physical activity, sense of well‐being, and quality of sleep while reducing the need for oral nonopioid analgesic medication.
Sural Nerve Haemodynamics In Painful And Painless Neuropathy: Clues To The Cause Of Pain?
Authors: Eaton Sem , Ibrahim S , Harris Nd , Selmi F , Patel Ka , Tesfaye S , Ward Jd
Published: March 2003

Despite extensive research the cause of painful diabetic neuropathy remains elusive. Vascular factors and nerve hypoxia are known to be important in the pathogenesis of diabetic neuropathy although their contribution to painful neuropathy has not been fully determined. Using a combination of microlightguide spectrophotometry and fluorescein angiography we have recently confirmed that sural nerve intracapillary oxygen saturation and blood flow are reduced in diabetic neuropathy. We have applied these techniques to examine differences between painful and painless diabetic neuropathy by comparing 11 patients with pain to 8 patients without. There were no significant differences in neurophysiological parameters in each group. Intracapillary oxygen saturation (%HbO2) was significantly higher in those subjects with painful symptoms compared to those without (median values 73.8% vs 67.7%, p < 0.05). Fluorescein rise time (FRT) was also significantly faster in those with painful neuropathy (18.3 vs 53.6 seconds, p < 0.05). These results indicate that there are distinct differences in sural nerve haemodynamics between painful and painless neuropathy. The higher %HbO2 and faster FRT suggest the nerve is not hypoxic in painful neuropathy. These results would suggest that haemodynamic factors might have an important role in the pathogenesis of neuropathic pain.
HIV neuropathy: Insights in the pathology of HIV peripheral nerve disease
Authors: Pardo Carlos A. , McArthur Justin C. , Griffin John W.
Published: March 2003

Abstract  HIV‐associated neuropathies (HIV‐N) have become the most frequent neurological disorder associated with HIV infection. The most common forms of HIV‐N are the distal sensory polyneuropathy (DSP) and antiretroviral toxic neuropathies (ATN), disorders characterized mostly by sensory symptoms that include spontaneous or evoked pain that follow a subacute or chronic course. The main pathological features that characterize DSP and ATN include “dying back” axonal degeneration of long axons in distal regions, loss of unmyelinated fibers, and variable degree of macrophage infiltration in peripheral nerves and dorsal root ganglia. Marked activation of macrophages as well as the effect of proinflammatory cytokines appear to be the main immunopathogenic factors in DSP. Interference with DNA synthesis and mitochondrial abnormalities produced by nucleoside antiretrovirals have been hypothesized as pathogenic factors involved in ATN. The use of skin biopsy has become a useful tool in the evaluation of HIV‐N. Reduction in fiber density, increased frequency of fiber varicosities and fiber fragmentation are prominent features of skin biopsies from patients with HIV‐N. Other forms of HIV‐N include acute or chronic inflammatory polyneuropathies, uncommon disorders that may ocur during seroconversion or early stages of HIV infection. Opportunisitic infections, mostly associated with cytomegalovirus or herpes zoster virus infection occur in late stages of AIDS and produce characteristic clinical features such as mononeuritis multiple or radiculopathies.
Gender And Peripheral Neuropathy In Chronic Alcoholism: A Clinical‐Electroneurographic Study
Authors: Ammendola A , Gemini D , Iannaccone S , Argenzio F , Ciccone G , Ammendola E , Serio L , Ugolini G , Bravaccio F.
Published: March 2003

In some alcohol‐related pathologies of chronic alcoholism women are more vulnerable than men. A consecutive sample of 62 chronic alcoholics was studied, 18 females and 44 males, aged between 28 and 69 years to assess the incidence and distribution of peripheral neuropathy with regard to gender. All patients underwent clinical and neurological observations, laboratory tests, and electroneurography. Total lifetime dose of ethanol (TLDE) and other risk factors for neuropathy (disease duration, age, nutritional status) were calculated and correlated to sural nerve sensory‐evoked potential (SEP) amplitude. In 42 patients (67.7%), we observed the presence of clinical and/or infraclinical neuropathy, mostly axonal, in 29 males (65.9%) and 13 females (72.2%). In women, compared to men, TLDE and disease duration were significantly inversely correlated to sural nerve SEP amplitude, i.e in women, SEP amplitude is significantly reduced in relation to TLDE and disease duration increase. These data indicate a higher sensitivity of females towards the toxic effects of ethanol, other than malnutrition, on peripheral nerve fibres.
Diagnostic yield by testing small fiber function in patients examined for polyneuropathy
Authors: Sindrup Søren H. , Gaist David , Johannsen Lis , Havsager Anne‐Mette , Homburg Annemette , Kjeldsen Marianne Juel , Madsen Claus , Dalsgaard Niels J. , Ellemann Karsten , Smith Torben
Published: March 2003

Abstract  We assessed the diagnostic yield of adding quantitative sensory testing to the standard work‐up for polyneuropathy in unselected patients. All patients aged 18 to 70 years referred to our department for electrodiagnosis with a tentative diagnosis of polyneuropathy and symptoms complying with predefined criteria were included in the study. We performed near nerve conduction studies in 4 nerves and determined heat and cold detection thresholds on hand and foot with a Thermotest (Somedic AB, Sweden). In order to uncover CNS diseases, somatosensory‐evoked potentials were recorded in patients with abnormal quantitative sensory testing and normal nerve conduction studies. A total of 198 patients completed the study and 149 were considered to have polyneuropathy. Twenty‐five patients remained undiagnosed and in 24 patients, other diseases were responsible for the symptoms. Of the patients with either polyneuropathy or no other diagnosis, 76% (n = 174) had abnormal nerve conduction. Abnormal cold sensation, heat sensation or abnormality in at least 1 of these and normal nerve conduction were found in 14, 12 and 17 patients. Of the 174 patients, 86% (95% CI 80–90%) had an abnormality in at least 1 of the tests (i.e. abnormal nerve conduction and/or abnormal quantitative testing of temperature sensation). In conclusion, quantitative testing of temperature sensation improves the diagnostic yield in patients examined for chronic polyneuropathy.
PROGRESS IN CLINICAL NEUROSCIENCES: CHARCOT‐MARIE‐TOOTH DISEASE AND RELATED INHERITED PERIPHERAL NEUROPATHIES
Authors: Benstead TJ , Grant IA.
Published: March 2003

The classification of Charcot‐Marie‐Tooth disease and related hereditary motor and sensory neuropathies has evolved to incorporate clinical, electrophysiological and burgeoning molecular genetic information that characterize the many disorders. For several inherited neuropathies, the gene product abnormality is known and for others, candidate genes have been identified. Genetic testing can pinpoint a specific inherited neuropathy for many patients. However, clinical and electrophysiological assessments continue to be essential tools for diagnosis and management of this disease group. This article reviews clinical, electrophysiological, pathological and molecular aspects of hereditary motor and sensory neuropathies.
AN EXPERIMENTAL EVALUATION OF DENSITY AND PLANT SIZE IN TWO LARGE BROWN SEAWEEDS
Authors: Creed Joel C. , Kain (Jones) Joanna M. , Norton Trevor A.
Published: March 2003

The effects of density on the growth rate and survival of individual plants as well as changes in population structure (hierarchy) and biomass accumulation (self‐thinning) were experimentally evaluated in two brown macroalgae. Laminaria digitata (Hudson) Lamouroux and Fucus serratus Linnaeus populations were constructed at five (650–5156 plants·m−2) and four densities (650–2668 plants·m−2), respectively, and were cultivated in tanks. The relative growth rates and survivorship of individuals and the populations’ biomass and density (estimated dry mass) were periodically measured. To investigate how plant population size hierarchies influence conspecifics, single density populations of L. digitata were constructed of up to three sizes of plants in equal proportions, and these parts of the populations were compared through time with plants of the three sizes grown singly. At higher density, L. digitata plants grew more slowly, while F. serratus populations showed a similar trend that was never statistically significant. Survival of plants of both species was lower at high densities, and mortality selectively removed smaller plants. Plants of both species exhibited zero growth rates before death, when parts of the fronds were lost, but meristems (apical in F. serratus, at the base of the frond in L. digitata) were preserved until the death of the plant. All singly grown L. digitata plants survived, but survivorship was low in the fractions of small plants in mixed‐size populations compared with that of the largest size plant fractions. Small L. digitata plants grew relatively faster than did large ones singly, but in mixed‐size populations, small plants grew relatively slowly. Plant sizes became progressively more unequal (Gini and skewness coefficients) until self‐thinning started reducing the size variability. The seaweeds followed self‐thinning (density‐biomass) trajectories predicted by the self‐thinning “rule”, and self‐thinning appeared to be seasonal‐ rather than species‐dependent, as it occurred at a time of year when ambient light levels start to fall in the Isle of Man. Culture studies of this kind, despite their considerable potential, are a tool as yet underexploited by marine ecologists as a means of assessing intraspecific competitive interaction among seaweeds.
V‐ AND P‐TYPE Ca2+‐STIMULATED ATPases IN A CALCIFYING STRAIN OF PLEUROCHRYSIS SP. (HAPTOPHYCEAE)
Authors: Araki Yoko , González Elma L.
Published: March 2003

Coccolithophorids are marine unicellular algae characterized by their ability to carry out controlled, subcellular calcification. The biochemical and kinetic features of membrane‐bound Ca2+‐stimulated ATPases have been examined. Membranes and organelles from axenic cultures of Pleurochrysis sp. (CCMP299) were isolated by means of sucrose density centrifugation. High levels of Ca2+‐stimulated ATPase were detected in chloroplasts, Golgi apparatus, plasma membrane, and coccolith vesicles. The sensitivity of the enzyme activity in the organelles and membranes was assessed with pharmacologic agents that are known to be specific for the several isoforms of Ca2+‐stimulated ATPase. The Ca2+‐stimulated ATPase activity in the Golgi and coccolith vesicle preparations was sensitive to nitrate, thiocyanate, and sodium azide and insensitive to vanadate, cyclopiazonic acid, and thapsigargin. ATP‐dependent H+ movement, but not 45Ca2+ transport, across the coccolith vesicle was demonstrated. The Ca2+‐stimulated ATPase in the plasma membrane preparation was sensitive to vanadate. ATP‐dependent, vanadate‐sensitive efflux of 45Ca2+ was demonstrated for microsomal material derived from gradient‐isolated plasma membrane. Polypeptides from isolated Golgi and coccolith vesicle preparations cross‐reacted to an antibody raised against a subunit of the oat root proton pump, whereas polypeptides from the chloroplast preparations did not cross‐react. These findings show that a V‐type Ca2+‐stimulated ATPase is located on the coccolith vesicle membrane and a P‐type Ca2+‐stimulated ATPase is located on the plasma membrane.
PHOTOSYSTEM II QUANTUM YIELDS AND XANTHOPHYLL‐CYCLE PIGMENTS OF THE MACROALGA SARGASSUM NATANS (PHAEOPHYCEAE): RESPONSES UNDER NATURAL SUNLIGHT
Authors: Schofield Oscar , Evens Terence J. , Millie David F.
Published: March 2003

Our understanding of the physiological mechanisms that allow marine photoautotrophs to thrive in a high light environment is limited. The pelagic phaeophyte, Sargassum natans (L.) Gaillon, exists at the air–sea interface and often is exposed to high irradiances. During a cruise in the Gulf of Mexico, aggregates of S. natans were collected and maintained in a shipboard incubator under natural sunlight. In vivo fluorescence and pigmentation dynamics were assessed over two daily cycles to characterize the photophysiological responses of this taxon to varying irradiance (i.e. overcast and sunny conditions). The relative proportion of the photosynthetic carotenoid, violaxanthin, to the photoprotective carotenoid, zeaxanthin, decreased during daylight hours. This mirrored the dynamics in the maximum quantum yield for stable charge separation at photosystem II (FV/FM[variable fluorescence/maximum fluorescence]), which decreased (relative to predawn levels) by 50%–60% during periods of sustained bright light and recovered to predawn values 3 h after sunset. The ratio of de‐epoxidized to epoxidized components of the xanthophyll‐cycle pigment pool (violaxanthin, zeaxanthin) was associated with energy dissipation activity within the pigment bed. The operational quantum yield for photosystem II activity (φIIe) was substantially lower than FV/FM due to both a decreased probability that absorbed photons reached open reaction centers and to the induction of nonphotochemical fluorescence quenching (which was rapidly reversible). Bright light also affected the rate of electron flow from the reaction center chlorophyll through to the secondary electron acceptor, quinone B (QB); specifically, single turnover decay curves indicated that the proportion of QB bound to the D1–D2 complex in photosystem II decreased during the protracted periods of bright light. Kautsky curves suggested that the relative proportion of inactive light‐harvesting complexes also increased during periods of bright light. Taken together, these findings suggest that S. natans can tolerate high irradiances by down‐regulating its quantum yield during the day, decreasing its functional absorption coefficient through the uncoupling of light‐harvesting complexes, and decreasing the efficiency with which absorbed light is utilized. These cellular responses appear to be driven by the absolute flux of light and not by an endogenous rhythm, which is phased to a particular time of day.
TEMPERATURE DEPENDENCE OF UV RADIATION EFFECTS ON ANTARCTIC CYANOBACTERIA
Authors: Roos Jan C. , Vincent Warwick F.
Published: March 2003

The mat‐forming cyanobacterium Phormidium murrayi West and West isolated from a meltwater pond on the McMurdo Ice Shelf was grown in unialgal batch cultures to evaluate the temperature dependence of ultraviolet radiation (UVR) effects on pigment composition, growth rate, and photosynthetic characteristics. Chlorophyll a concentrations per unit biomass were generally reduced in cells grown under UVR (low UV‐A plus UV‐B). In vivo absorbance spectra showed that the carotenoid/chlorophyll a ratio increased as a function of photosynthetically available radiation (PAR) and UVR exposure and varied inversely with temperature. Ultraviolet inhibition of growth (percentage reduction of μmax at each temperature) increased linearly with decreasing temperature, consistent with the hypothesis that net inhibition represents the balance between temperature‐independent photochemical damage and temperature‐dependent biosynthetic repair. There was no significant effect of UVR on photosynthesis over the first hour of exposure, but significant UV inhibition was observed after 5 days. Unlike growth, however, there was no apparent effect of temperature on the magnitude of UV inhibition of photosynthesis. These results imply that assays of UVR effects on photosynthesis are not an accurate guide to growth responses and that low ambient temperatures can have a major influence on the UV sensitivity of polar organisms. In a set of assays at 20° C (preacclimation under 300 μmol photons·m−2·s−1 and 20° C), growth was strongly depressed by UVR over the first day of exposure but then gradually increased over the subsequent 4 days, approaching the growth rates in the minus UVR control. This evidence of acquired tolerance indicates that the damaging effects of UVR will be most severe in environments where there is a mismatch between the timescale of change in exposure and the timescale of UV acclimation.
DIATOM PALEOLIMNOLOGY OF TWO FLUVIAL LAKES IN THE ST. LAWRENCE RIVER: A RECONSTRUCTION OF ENVIRONMENTAL CHANGES DURING THE LAST CENTURY
Authors: Reavie Euan D. , Smol John P. , Carignan Richard , Lorrain Stéphane
Published: March 2003

Water quality degradation is a serious concern for the St. Lawrence River. While some environmental data are available for the St. Lawrence ecosystem, long‐term monitoring data are generally lacking. To infer past environmental changes, we undertook a paleolimnological assessment of diatom assemblages preserved in four 210Pb‐ and 137Cs‐dated sediment cores from two fluvial lakes in the river, and used diatom transfer functions to infer past shoreline habitat characteristics. At sites in Lake Saint‐François, a fluvial lake downstream from Cornwall, water quality decreased this century in response to human impacts (e.g. macrophyte density and nutrient levels increased). These trends were apparent from an increase in epiphytic diatom taxa, followed by an increase in eutrophic planktonic taxa. Water quality, however, appears to have improved somewhat in response to rehabilitation measures during the last two decades. From a sediment core near Montréal (Lake Saint‐Louis), we also noted a large proportion of eutrophic and epiphytic taxa, but less evidence was recorded of a recent improvement in water quality. The diatom‐based inference model for habitat characteristics appeared to reconstruct environmental conditions in the St. Lawrence River during the last century. The most notable shift has been an increase in diatom taxa commonly associated with macrophyte substrates. Trends in some of the planktonic diatoms were similar to those recorded in paleolimnological investigations from Lake Ontario, but cores from the river also may be reflecting local environments. This study shows that diatom‐based paleolimnological studies are possible in large river systems, if coring sites (e.g. fluvial lakes) are carefully selected.
LOCAL EXTIRPATION OF STEPHANODISCUS NIAGARAE (BACILLARIOPHYCEAE) IN THE RECENT LIMNOLOGICAL RECORD OF LAKE ONTARIO
Authors: Julius Matthew L. , Stoermer Eugene F. , Taylor Christine M. , Schelske Claire L.
Published: March 2003

We investigated microfossil assemblages in recent sediments from nine stations across Lake Ontario. Stephanodiscus niagarae was not present in any of these sediment samples, marking the taxon’s extirpation from its type locality. This observation documents the end of a general reduction in size and alteration in valve morphology associated with habitat disturbance. Stephanodiscus niagarae may have been directly eliminated from the lake, or sexual reproduction may have been delayed beyond the species’ ability to sustain numbers through asexual reproduction.
BIOCHEMICAL COMPOSITION AND FATTY ACID CONTENT OF FILAMENTOUS NITROGEN‐FIXING CYANOBACTERIA
Authors: Vargas M. A. , Rodríguez H. , Moreno J. , Olivares H. , Campo J. A. Del , Rivas J. , Guerrero M. G.
Published: March 2003

The biochemical composition and fatty acid content of twelve strains of filamentous, heterocystous, nitrogen‐fixing cyanobacteria have been determined. When grown under diazotrophic conditions, protein, carbohydrate, lipid, and nucleic acids comprised 37–52%, 16–38%, 8–13%, and 8–11% of the dry weight, respectively. The presence of a combined nitrogen source resulted in an increase in the protein content of the cells and a decrease in the levels of lipids and carbohydrates, although biomass productivity was not affected significantly. Biochemical composition also changed during culture growth, with the highest levels of proteins and lipids occurring as the culture entered stationary phase, whereas the highest levels of carbohydrate and nucleic acids were found during the exponential phase. Total fatty acid levels in the strains assayed ranged between 3 and 5.7% of the dry weight. With regard to fatty acid composition, all strains showed high levels of polyunsaturated fatty acids (PUFAs) and saturated fatty acids (SAFAs), with values of 24–45% and 31–52% of total fatty acids, respectively, whereas the levels of monounsaturated fatty acids (MUFAs) were in general lower (11– 32%). Palmitic acid (16:0) was the most prevalent SAFA, whereas palmitoleic (16:1n‐ 7) and oleic acid (18:1n‐9) were the most abundant MUFAs in all the strains. Among PUFAs, γ‐linolenic acid (GLA, 18:3n‐6) was present at high levels (18% of total fatty acids) in Nostoc sp. (Chile) and at lower levels (3.6% of total fatty acids) in Anabaenopsis sp. The presence of GLA has not been previously reported in these genera of cyanobacteria. The rest of the strains exhibited high levels (12–35% of total fatty acids) of α‐linolenic acid (ALA, 18:3n‐3). Linoleic acid (18:2n‐6) was also present at a substantial level in most of the strains. Eicosapentaenoic acid (EPA, 20:5n‐3) was also detected in Nostoc sp. (Albufera). Some filamentous nitrogen‐fixing cyanobacteria therefore represent potential sources of commercially interesting fatty acids.
THE PHYCOBILIN SIGNATURES OF CHLOROPLASTS FROM THREE DINOFLAGELLATE SPECIES: A MICROANALYTICAL STUDY OF DINOPHYSIS CAUDATA, D. FORTII, AND D. ACUMINATA (DINOPHYSIALES, DINOPHYCEAE)
Authors: Hewes Christopher D. , Mitchell B. Greg , Moisan Tiffany A. , Vernet Maria , Reid Freda M. H.
Published: March 2003

The absorbance and fluorescence emission spectra for three species of Dinophysis, D. caudata Saville‐Kent, D. fortii Pavillard, and D. acuminata Claparède et Lachmann, were obtained through an in vivo microanalytical technique using a new type of transparent filter. The pigment signatures of these Dinophysis species were compared to those of Synechococcus Nägeli, a cryptophyte, and two wild rhodophytes, as well as those of another dinoflagellate, a diatom, and a chlorophyte. Phycobilins are not considered a native protein group for dinoflagellates, yet the absorption and fluorescence properties of the three Dinophysis species were demonstrated to closely resemble phycobilins and chlorophylls of Rhodomonas Karsten (Cryptophyceae). Analyses of Dinophysis species using epifluorescence microscopy found no additional nucleus or nuclear remnant as would be contributed by an endosymbiont.
QUANTITATIVE PCR DATA FALSIFY THE CHROMOSOMAL ENDOREDUPLICATION HYPOTHESIS FOR VOLVOX CARTERI (VOLVOCALES, CHLOROPHYTA)
Authors: Kobl Iris , Kirk David L. , Schmitt Rüdiger
Published: March 2003

Two conflicting hypotheses for chromosome replication in the Volvocaceae, one postulating multiple rounds of replication prior to cell division (endoreduplication) and the other claiming a canonical sequence of one round of nuclear DNA replication preceding each cell division, have been tested experimentally. Competitive PCR of the single‐copy actin gene (target) of Volvox carteri f. nagariensis Iyengar and a shortened gene version (competitor) containing the same primer binding sites were used to assess the genome equivalents present in a given number of cells. Determining the molar ratio of the PCR products generated from target DNA (extracted from a known number of cells) and defined numbers of competitor molecules revealed that Volvox embryos between the one‐ and 16‐cell stages possess an average of between one and two—but never more than two—copies of the actin gene. This led us to conclude that the number of genome equivalents per nucleus in dividing Volvox embryos varies only between one and two and that, unlike the case predicted by endoreduplication, the nuclear genome undergoes only one round of replication prior to each cell division.
EVIDENCE FOR A LACK OF PHOTOSYSTEM SEGREGATION IN CHLAMYDOMONAS REINHARDTII (CHLOROPHYCEAE)
Authors: Bertos Nicholas R. , Gibbs Sarah P.
Published: March 2003

The distribution of photosystems I and II (PSI and PSII) in cells of Chlamydomonas reinhardtii Dangeard was studied by immunogold electron microscopy using cultures grown autotrophically at moderate irradiance and harvested in the middle of the light period. Sections of Lowicryl‐embedded cells were labeled with monospecific heterologous antisera raised against the reaction center proteins of PSI (CP1‐e) or the core antenna proteins of PSII (CP40 and CP47). All three antisera labeled both the appressed and the nonappressed thylakoid membranes at essentially similar densities. Labeling with both PSI and PSII antisera was slightly more concentrated over the outer nonappressed membranes of the thylakoid bands (1.7‐ to 2.4‐fold with anti‐CP1‐ e and 1.5‐ to 1.8‐fold with anti‐CP47 and anti‐CP40). However, since appressed membranes comprised 73% of the total thylakoid membranes, 50%–62% of the PSI and 58%–65% of the PSII labeling were localized on appressed membranes. We conclude that photosystem distribution in C. reinhardtii is similar to that reported for other algae and different from the lateral heterogeneity observed in higher plants.
A RAPID, HIGHLY EFFICIENT METHOD FOR COLLECTING, FIXING, AND EMBEDDING PLANKTONIC AND OTHER SMALL CELLS FOR ELECTRON MICROSCOPY
Authors: Pickett‐Heaps Jeremy D.
Published: March 2003

A rapid, highly efficient method is described for fixation, dehydration, and embedding of small (e.g. planktonic) cells dispersed in large volumes of culture medium. The entire protocol, based on continuous filtration, can be completed within about an hour, and the yield of cells is very high. Fixation quality has been excellent with several different types of samples.
INTERACTION OF CHLOROPLAST AND VACUOLES IN CHLAMYDOMONAS
Authors: Park H. , Roberson R.W. , Eggink L. L. , Hoober J.K.
Published: March 2003

Proteins synthesized within the chloroplast of Chlamydomonas reinhardtii were recovered in granules within vacuoles (Park et al., J. Phycol. 35,528‐538, 1999). Apoproteins of light‐harvesting complexes, synthesized in the cytosol in excess of the capacity of the chloroplast to synthesize chlorophyll, also were recovered in vacuolar granules. The ultrastructure of conventionally‐ and cryo‐fixed cells revealed protuberances of the chloroplast envelope outer membrane that contained stroma‐like material and also connections between the outer membrane and vacuolar membrane. Transfer of proteins via these structures to vacuoles appeared to be a pathway for degradation of chloroplast material. Purified granules contained polyphosphate as the major component, which seemed to protect proteins in the vacuole from breakdown. A predominant 70 kDa protein in purified granules accumulated in the cell wall of wild‐type cells and in granules of wall‐deficient cells, as revealed by immunolocalization. This protein entered vacuoles via small vesicles from Golgi, which probably also introduced degradative enzymes into this compartment. Vacuoles thus apparently serve as lysosome‐like structures as well as secretory vesicles. The membranes of the chloroplast envelope in cryo‐fixed green cells were tightly appressed except where the inner membrane invaginated or the outer membrane protruded into the cytosol. Whereas conventional fixation showed lack of appression of thylakoid membranes in a chlorophyll b‐less mutant, these membranes appeared as large grana in images of cryofixed cells. The enhanced images obtained with cryofixation allowed substantial refinement of our knowledge of the ultrastructure of these algal cells.
REACTIVE OXYGEN METABOLISM IN INTERTIDAL FUCUS SPP. (PHAEOPHYCEAE)
Authors: Collén Jonas , Davison Ian R.
Published: March 2003

Our previous research suggests that interspecific variation in stress tolerance in intertidal Fucus spp. (Phaeophyceae) is partially mediated by differences in the production of, or ability to detoxify, reactive oxygen. Here we report on the content of antioxidants (ascorbate, glutathione, carotenoids, and tocopherols) and protective enzymes (catalase, superoxide dismutase, ascorbate peroxidase, and glutathione reductase) involved in reactive oxygen metabolism in three species of intertidal brown algae—Fucus spiralis L., F. evanescens C. Ag., and F. distichus L.—that differ in stress tolerance and position in the intertidal zone. Contents of the major antioxidants were similar in the three species and were not correlated with stress tolerance. The least stress tolerant species, F. distichus, had the lowest activity of reactive‐oxygen‐scavenging enzymes, although F. spiralis, the species with the highest stress tolerance, and F. evanescens contained similar activities of antioxidant enzymes on a fresh‐weight basis. However, the activities of superoxide dismutase and ascorbate peroxidase in F. evanescens are lower than those of F. spiralis when expressed on the basis of chlorophyll. These data show that the ratio between reactive oxygen protection and production might be more important than the absolute content of antioxidants and protective enzymes. It also shows the importance of localization of detoxifying mechanisms and avoidance of oxidative stress.
THE LIFE HISTORY OF ALEXANDRIUM TAYLORI (DINOPHYCEAE)
Authors: Giacobbe Maria Grazia , Yang Xuemei
Published: March 2003

The gonyaulacoid dinoflagellate Alexandrium taylori Balech is reported for the first time from Italian waters. In July 1997, nonmotile stages of this species, both temporary and sexual resting cysts, were found in surface Ionian coastal waters (Mediterranean Sea) producing localized brownish‐yellow patches. Clonal cultures were established, and the life history of A. taylori was studied in the laboratory. Asexual reproduction took place during a motile phase and produced two daughter cells remaining temporarily attached in pairs. This species exhibited isogamy. Small gametes were produced from vegetative cells through the release of a division cyst and multiple fission of the protoplast. Isogametes from the same clonal strain fused and underwent sexual reproduction, forming planozygotes that subsequently developed storage bodies and dark pigmentation. The maturation of the planozygote into hypnozygote also involved an increase in size and final shedding of flagella and theca. Hypnozygotes germinated within 15 days of their formation, and a naked planomeiocyte emerged from the archeopyle to undergo successive divisions and reestablish a haploid motile population.
THE SITES OF CELLULOSE SYNTHESIS IN ALGAE: DIVERSITY AND EVOLUTION OF CELLULOSE‐SYNTHESIZING ENZYME COMPLEXES
Authors: Tsekos Ioannes
Published: March 2003

Information on the sites of cellulose synthesis and the diversity and evolution of cellulose‐synthesizing enzyme complexes (terminal complexes) in algae is reviewed. There is now ample evidence that cellulose synthesis occurs at the plasma membrane‐bound cellulose synthase, with the exception of some algae that produce cellulosic scales in the Golgi apparatus. Freeze‐fracture studies of the supramolecular organization of the plasma membrane support the view that the rosettes (a six‐subunit complex) in higher plants and both the rosettes and the linear terminal complexes (TCs) in algae are the structures that synthesize cellulose and secrete cellulose microfibrils. In the Zygnemataceae, each single rosette forms a 5‐nm or 3‐nm single “elementary” microfibril (primary wall), whereas rosettes arranged in rows of hexagonal arrays synthesize criss‐crossed bands of parallel cellulose microfibrils (secondary wall). In Spirogyra, it is proposed that each of the six subunits of a rosette might synthesize six β‐1,4‐glucan chains that cocrystallize into a 36‐glucan chain “elementary” microfibril, as is the case in higher plants. One typical feature of the linear terminal complexes in red algae is the periodic arrangement of the particle rows transverse to the longitudinal axis of the TCs. In bangiophyte red algae and in Vaucheria hamata, cellulose microfibrils are thin, ribbon‐shaped structures, 1–1.5 nm thick and 5–70 nm wide; details of their synthesis are reviewed. Terminal complexes appear to be made in the endoplasmic reticulum and are transferred to Golgi cisternae, where the cellulose synthases are activated and may be transported to the plasma membrane. In algae with linear TCs, deposition follows a precise pattern directed by the movement and the orientation of the TCs (membrane flow). A principal underlying theme is that the architecture of cellulose microfibrils (size, shape, crystallinity, and intramicrofibrillar associations) is directly related to the geometry of TCs. The effects of inhibitors on the structure of cellulose‐synthetizing complexes and the relationship between the deposition of the cellulose microfibrils with cortical microtubules and with the membrane‐embedded TCs is reviewed In Porphyra yezoensis, the frequency and distribution of TCs reflect polar tip growth in the apical shoot cell.The evolution of TCs in algae is reviewed. The evidence gathered to date illustrates the utility of terminal complex organization in addressing plant phylogenetic relationships.
THE EFFECT OF GROWTH IRRADIANCE ON THE COUPLING OF CARBON AND NITROGEN METABOLISM IN CHAETOMORPHA LINUM (CHLOROPHYTA)
Authors: McGlathery Karen J. , Pedersen Morten Foldager
Published: March 2003

The influence of growth irradiance on the non‐steady‐state relationship between photosynthesis and tissue carbon (C) and nitrogen (N) pools in Chaetomorpha linum (Muller) Kutzing in response to abrupt changes in external nitrogen (N) availability was determined in laboratory experiments. For a given thallus N content, algae acclimated to low irradiance consistently had a higher rate of light‐saturated photosynthesis (Pmax normalized to dry weight) than algae acclimated to saturating irradiance; for both treatments, Pmax was correlated to thallus N. Both Pmax and the photosynthetic efficiency (αdw) were correlated in C. linum grown at either saturating or limiting irradiance over the range of experimental conditions, indicating that variations in electron transport were coupled to variations in C‐fixation capacity despite the large range of tissue N content from 1.1% to 4.8%. Optimizing both α and Pmax and thereby acclimating to an intermediate light level may be a general characteristic of thin‐structured opportunistic algae that confers a competitive advantage in estuarine environments in which both light and nutrient conditions are highly variable. Nitrogen‐saturated algae had the same photosynthesis–irradiance relationship regardless of light level. When deprived of an external N supply, photosynthetic rates did not change in C. linum acclimated to low irradiance despite a two‐fold decrease in tissue N content, suggesting that the active pools of chlorophyll and Rubisco remained constant. Both α and Pmax decreased immediately and continuously in algae acclimated to high irradiance on removal of the N supply even though tissue N content was relatively high during most of the N‐starvation period, indicating a diversion of energy and reductant away from C fixation to support high growth rates. Carbon and nitrogen assimilation were equally balanced in algae in both light treatments throughout the N‐saturation and ‐depletion phases, except when protein synthesis was limited by the depletion of internal N reserves in severely N‐starved high‐light algae and excess C accumulated as starch stores. This suggests that the ability for short‐term adjustment of internal allocation to acquire N andC in almost constant proportions may be especially beneficial to macroalgae living in environments characterized by high variability in light levels and nutrient supply.