bluuebunny/crossref_metadata_2025 huggingface dataset:
Dye coupling does not explain functional crosstalk within dorsal root ganglia
Authors: Zuriel Ella , Devor Marshall
Published: March 2003

Abstract  Most primary sensory neurons in rat dorsal root ganglia (DRGs) are depolarized during repetitive impulse activity in neighboring neurons that share the same ganglion. We wondered whether this functional crosstalk might be mediated by a network of cytoplasmic bridges (gap junctions) between neighboring neurons and their satellite glia. Neurobiotin was injected intracellularly in whole excised DRGs. Some of the animals were intact, and others underwent transection of the ipsilateral sciatic nerve 7 to 21 days prior to injection. A total of 44 directly injected neurons were recovered histologically. There was little or no evidence of dye spread to neighboring satellite cells or neurons that would have indicated the presence of cytoplasmic bridges, certainly not enough to account for the nearly universal functional coupling that occurs among these neurons. Functional crosstalk within DRGs must therefore employ a different mechanism.
Hereditary neuralgic amyotrophy (HNA) is genetically heterogeneous
Authors: Kuhlenbaumer G , Meuleman J , De Jonghe P , Falck B , Young P , Hunermund G , Van Broeckhoven C , Timmerman V , Stogbauer F
Published: March 2003

Hereditary Neuralgic Amyotrophy (HNA) is an autosomal dominantly inherited recurrent focal neuropathy affecting mainly the brachial plexus. Linkage to markers on chromosome 17q25 was found in 1996 and subsequent reports confirmed linkage of HNA to this locus. Recently a family with a chronic undulating rather than remitting‐relapsing clinical course of HNA was described by a Dutch group. This family did not have linkage to the 17q25 locus. Here we describe for the first time clinically and genetically two families with classic remitting‐relapsing HNA that are not linked to the previously described HNA locus on chromosome 17q25. These results demonstrate that clinically homogeneous classical HNA is genetically heterogeneous.
Limits of clinical tests to screen autonomic function in diabetes type 1
Authors: Ducher M , Bertram D , Sagnol I , Cerutti C , Thivolet C , Fauvel JP
Published: March 2003

OBJECTIVES: A precocious detection of cardiac autonomic dysfunction is of major clinical interest that could lead to a more intensive supervision of diabetic patients. However, classical clinical exploration of cardiac autonomic function is not easy to undertake in a reproducible way. Thus, respective interests of autonomic nervous parameters provided by both clinical tests and computerized analysis of resting blood pressure were checked in type 1 diabetic patients without orthostatic hypotension and microalbuminuria. MATERIAL AND METHODS: Thirteen diabetic subjects matched for age and gender to thirteen healthy subjects volunteered to participate to the study. From clinical tests (standing up, deep breathing, Valsalva maneuver, handgrip test), autonomic function was scored according to Ewing's methodology. Analysis of resting beat to beat blood pressure provided autonomic indices of the cardiac function (spectral analysis or Z analysis). RESULTS: 5 of the 13 diabetic patients exhibited a pathological score (more than one pathological response) suggesting the presence of cardiovascular autonomic dysfunction. The most discriminative test was the deep breathing test. However, spectral indices of BP recordings and baroreflex sensitivity (BRS) of these 5 subjects were similar to those of healthy subjects and of remaining diabetic subjects. CONCLUSION: Alteration in Ewing's score given by clinical tests may not reflect an alteration of cardiac autonomic function in asymptomatic type I diabetic patients, because spectral indices of sympathetic and parasympathetic (including BRS) function were within normal range. Our results strongly suggest to confront results provided by both methodologies before concluding to an autonomic cardiac impairment in asymptomatic diabetic patients.
Conditional Disruption Of Beta 1 Integrin In Schwann Cells Impedes Interactions With Axons
Authors: Feltri ML , Porta DG , Previtali SC , Nodari A , Migliavacca B , Cassetti A , Littlewood‐Evans A , Reichardt LF , Messing A , Quattrini A , Mueller U , Wrabetz L.
Published: March 2003

In dystrophic mice, a model of merosin‐deficient congenital muscular dystrophy, laminin‐2 mutations produce peripheral nerve dysmyelination and render Schwann cells unable to sort bundles of axons. The laminin receptor and the mechanism through which dysmyelination and impaired sorting occur are unknown. We describe mice in which Schwann cell‐specific disruption of beta1 integrin, a component of laminin receptors, causes a severe neuropathy with impaired radial sorting of axons. Beta1‐null Schwann cells populate nerves, proliferate, and survive normally, but do not extend or maintain normal processes around axons. Interestingly, some Schwann cells surpass this problem to form normal myelin, possibly due to the presence of other laminin receptors such as dystroglycan and α6β4 integrin. These data suggest that PI integrin links laminin in the basal lamina to the cytoskeleton in order for Schwann cells to ensheath axons, and alteration of this linkage contributes to the peripheral neuropathy of congenital muscular dystrophy.
Age‐Related Sympathetic Ganglionic Neuropathology: Human Pathology And Animal Models
Authors: Schmidt RE.
Published: March 2003

Systematic studies of the autonomic nervous system of human subjects and development of well‐defined animal models have begun to substantially improve our understanding of the pathogenesis of autonomic dysfunction in aging and may eventually provide strategies for intervention. Neuropathological studies of the sympathetic ganglia of aged human subjects and rodent models have demonstrated that neuroaxonal dystrophy involving intraganglionic terminal axons and synapses is a robust, unequivocal and consistent neuropathological finding in the aged sympathetic nervous system of man and animals. Quantitative studies have demonstrated that markedly swollen argyrophilic dystrophic axon terminals develop in the prevertebral superior mesenteric (SMG) and coeliac, but to a much lesser degree in the superior cervical ganglia (SCG) as a function of age, sex (males more than females) and diabetes. Dystrophic axons were immunoreactive for neuropeptide Y, tyrosine hydroxylase, dopamine‐beta‐hydroxylase, trkA and p75(NTR), an immunophenotype consistent with their origin from postganglionic sympathetic neurons, and contained large numbers of highly phosphorylated neurofilaments or tubulovesicular elements. The sympathetic ganglia of aged rodents also showed the hallmark changes of neuroaxonal dystrophy as a function of age and location (many more in the SMG than in the SCG). Plasticity‐related synaptic remodeling could represent a highly vulnerable target of the aging process. The fidelity of animal models to the neuropathology of aged humans suggests that similar pathogenetic mechanisms may be involved in both and that therapeutic advances in animal studies may have human application.
Chronic Sensory Neuronopathy Associated With Human T‐Cell Lymphotropic Virus Type I Infection
Authors: Shimazaki R , Ueyama H , Mori T , Mori M , Fujimoto S , Kumamoto T , Tsuda T.
Published: March 2003

We described two patients with chronic sensory neuronopathy who had anti‐HTLV‐I antibody in serum and cerebrospinal fluid but no signs of myelopathy, A sural nerve specimen revealed severe degeneration of myelinated and unmyelinated axons. The second patient had subclinical Sjogren's syndrome suggestive of a possible link among human T‐cell lymphotropic virus type I (HTLV‐I), Sjogren's syndrome and sensory neuronopathy, respectively. The broad spectrum of neurologic disorders associated with HTLV‐T infection now would include chronic sensory neuronopathy.
A Novel Neutrotrophic Property Of Glucagon‐Like Peptide 1: A Promoter Of Nerve Growth Factor‐Mediated Differentiation In PC12 Cells
Authors: Perry T , Lahiri DK , Chen DM , Zhou J , Shaw KTY , Egan JM , Greig NH.
Published: March 2003

The insulinotropic hormone glucagon‐like peptide‐1 (7‐36)‐amide (GLP‐1) has potent effects on glucose‐dependent insulin secretion, insulin gene expression, and pancreatic islet cell formation and is presently in clinical trials as a therapy for type 2 diabetes mellitus. We report on the effects of GLP‐1 and two of its long‐acting analogs, exendin‐4 and exendin‐4 WOT, on neuronal proliferation and differentiation, and on the metabolism of two neuronal proteins in the rat pheochromocytoma (PC12) cell line, which has been shown to express the GLP‐1 receptor. We observed that GLP‐1 and exendin‐4 induced neurite outgrowth in a manner similar to nerve growth factor (NGF), which was reversed by coincubation with the selective GLP‐1 receptor antagonist exendin (9‐39). Furthermore, exendin‐4 could promote NGF‐initiated differentiation and may rescue degenerating cells after NGF‐mediated withdrawal. These effects were induced in the absence of cellular dysfunction and toxicity as quantitatively measured by 3‐(4,5‐cimethylthiazol‐2‐yl)‐2,5‐diphenyl tetrazolium bromide and lactate dehydrogenase assays, respectively. Our findings suggest that such peptides may be used in reversing or halting the neurodegenerative process observed in neurodegenerative diseases, such as the peripheral neuropathy associated with type 2 diabetes mellitus and Alzheimer's and Parkinson's diseases. Due to its novel twin action, GLP‐1 and exendin‐4 have therapeutic potential for the treatment of diabetic peripheral neuropathy and these central nervous system disorders.
Immunological Study Of Hereditary Motor And Sensory Neuropathy Type 1 A (HMSN1 A)
Authors: Gabriel CM , Gregson NA , Wood NW , Hughes RAC.
Published: March 2003

Objectives: Fifty three patients were studied to investigate whether autoimmune or inflammatory mechanisms could explain the phenotypic heterogeneity of patients with hereditary motor and sensory neuropathy type 1a (HMSN1a). Methods: Serum samples were examined for antibodies to peripheral nerve myelin protein 22 (PMP22), ganglioside GM1 and cauda equina homogenate, and interleukin‐6 (IL‐6) and soluble tumour necrosis factor receptor 1 (sTNF R1) concentrations. Serological results were compared with those from patients with other neuropathies (ONPs, n = 30) and with normal subjects (n = 51). Results: In the group as a whole, no relation emerged between clinical severity and any immune parameters. Immunohistochemical examination of four sural nerve biopsies did not show significant inflammatory infiltration. In a subset of 12 patients who experienced stepwise progression of disease, there was a trend towards a higher proportion having anti‐PMP22 antibodies (33% v 15% of those with gradual disease progression, 3% ONPs, and no normal controls) and complement fixing antibodies to human cauda equina (25% v 5% with gradual progression, 8.6% ONPs, 3.9% normal controls, p = 0.07). Conclusions: Patients with HMSN1a and a stepwise disease progression may have an inflammatory, autoimmune component superimposed on the genetic condition.
OXIDATIVE STRESS AND DIABETIC NEUROPATHY: PATHOPHYSIOLOGICAL MECHANISMS AND TREATMENT PERSPECTIVES
Authors: Van Dam PS
Published: March 2003

Increased oxidative stress is a mechanism that probably plays a major role in the development of diabetic complications, including peripheral neuropathy. This review summarises recent data from in vitro and in vivo studies that have been performed both to understand this aspect of the pathophysiology of diabetic neuropathy and to develop therapeutic modalities for its prevention or treatment. Extensive animal studies have demonstrated that oxidative stress may be a final common pathway in the development of diabetic neuropathy, and that antioxidants can prevent or reverse hyperglycaemia‐induced nerve dysfunction. Most probably, the effects of antioxidants are mediated by correction of nutritive blood flow, although direct effects on endoneurial oxidative state are not excluded. In a limited number of clinical studies, antioxidant drugs including alpha‐lipoic acid and vitamin E were found to reduce neuropathic symptoms or to correct nerve conduction velocity. These data are promising, and additional larger studies with alpha‐lipoic acid are currently being performed.
DISEASE SEVERITY IN MULTIFOCAL MOTOR NEUROPATHY AND ITS ASSOCIATION WITH THE RESPONSE TO IMMUNOGLOBULIN TREATMENT
Authors: Van den Berg‐Vos RM , Franssen H , Visser J , De Visser M , De Haan RJ , Wokke JHJ , Van den Berg LH
Published: March 2003

Disease progression in multifocal motor neuropathy (MMN) was studied by comparing severity and duration of disease. We assessed disease severity by determining muscle weakness, disability, conduction block (CB), and distal and proximal compound muscle action potential (CMAP) amplitude in 38 patients with MMN in whom disease duration ranged from 6 months to 34 years. As indicator for an ongoing immune‐mediated process, the response to one course of IVIg treatment was measured in 34 patients and associated with disease severity. With increasing disease duration, weakness and disability became significantly more severe, and the distal and proximal CMAP‐amplitude decreased significantly. The number of CBs was significantly higher in patients with a disease duration longer than 10 years than in those affected less than 10 years. Thirty of the 34 patients responded to IVIg treatment. Non‐responsiveness to IVIg was not associated with any of the disease variables. Severe and widespread weakness was significantly associated with a response greater than or equal to 2 on the MRC‐sum‐score. Our results provide evidence for a slowly progressive disease course of MMN. The good response to IVIg treatment in patients with severe and prolonged disease indicates that progression may be the result of an ongoing immune‐mediated process. These findings imply that early treatment may prevent future progression of weakness and disability in patients with MMN.
PHOTORESPIRATION IN CONTINUOUS CULTURE OF DUNALIELLA TERTIOLECTA (CHLOROPHYTA): RELATIONSHIPS BETWEEN SERINE, GLYCINE, AND EXTRACELLULAR GLYCOLATE
Authors: Leboulanger Christophe , Martin‐Jézéquel Véronique , Descolas‐Gros Chantal , Sciandra Antoine , Jupin Henri J.
Published: March 2003

The concentrations of extracellular glycolate and intracellular free pools of serine and glycine were monitored in nitrogen‐limited continuous cultures of Dunaliella tertiolecta (Butcher) UTEX LB999, grown at two different irradiances on a light:dark cycle. Under steady‐state conditions, this microalga excreted into the medium a large amount of glycolate during the light phase, up to 100 nmol·(106 cells)−1 for a cell concentration of around 1.5 108 cells·L−1, but glycolate disappeared from the dissolved phase in the dark. Cells grown at 70 and those grown at 430 μmol photons·m−2·s−1 differed in maximal glycolate concentration, intracellular serine and glycine concentrations, and serine:glycine ratio. Reversal of these photon flux densities to which the cultures were exposed caused rapid modification of the extracellular glycolate and intracellular serine and glycine pools. These results suggest that photorespiratory metabolism in D. tertiolecta could be approximately quantified by measuring the changes in dissolved glycolate and intracellular serine and glycine concentrations, extending previous results from cultured phytoplankton and suggesting methods for field studies.
PHYLOGENETIC RELATIONSHIPS OF THE BROWN ALGAL ORDERS ECTOCARPALES, CHORDARIALES, DICTYOSIPHONALES, AND TILOPTERIDALES (PHAEOPHYCEAE) BASED ON RUBISCO LARGE SUBUNIT AND SPACER SEQUENCES
Authors: Siemer Berit L. , Stam Wytze T. , Olsen Jeanine L. , Pedersen Poul M.
Published: March 2003

Phylogenetic relationships among 23 species of morphologically simple brown algae belonging to the Ectocarpales sensu stricto, Chordariales, Dictyosiphonales, and Tilopteridales sensu stricto, Phaeophyceae (Fucophyceae), were analyzed using chloroplast‐encoded RUBISCO large subunit gene sequences (rbcL) and the associated RUBISCO spacer sequences. Comparison of the observed and expected sequence divergence at the three codon positions of rbcL showed that the level of mutational saturation within the brown algae is minor. Thus, rbcL is well suited for phylogenetic studies in this group. Unweighted parsimony analyses and a neighbor‐joining distance analysis were performed using unambiguously aligned rbcL sequences from the above four orders, one marine raphidophyte and two Tribophyceae (Xantophyceae). Polyphyly of Tilopteridales sensu lato (i.e. including Dictyosiphonales) is verified; we therefore recommend the use of Tilopteridales in the strict sense. The Ectocarpales, Chordariales, and Dictyosiphonales are paraphyletic with respect to each other, forming a highly interwoven clade. A separate parsimony analysis of the RUBISCO spacer as well as a combined rbcL and spacer analysis supported the close relationship among the latter three orders, adding to the evidence that they should be subsumed into the Ectocarpales sensu lato.
PLASTID FATTY ACID BIOSYNTHESIS IN THE DIATOMS NITZSCHIA ALBA AND NITZSCHIA LAEVIS
Authors: McGinnis K.M. , Sommerfeld M.R.
Published: March 2003

The role of the plastid in fatty acid biosynthesis in the non‐photosynthetic diatom Nitzschia alba was studied and compared to that in the photosynthetic, closely related Nitzschia laevis. Transmission electron microscopy was used to analyze structural features of the plastid that may be relevant to biochemical function. Typical of a photosynthetic diatom, N. laevis had a chloroplast envelope composed of four membranes, and had abundant chloroplast ribosomes. The leucoplast of N. alba also had a multi‐membrane envelope, chloroplast ribosomes, and a genome that encodes plastid specific proteins. This suggested that the plastid of N. alba may still possess the biochemical functions of the chloroplast, aside from photosynthesis. To determine whether plastidial fatty acid biosynthesis occurred in N. alba, the response of the two diatoms to the compound thiolactomycin was compared. Thiolactomycin has been shown to effect keto‐acyl‐ACP‐synthases, and specifically inhibits the plastidial fatty acid biosynthetic pathway. While growth of N. alba was not impacted by thiolactomycin as in N. laevis, neutral lipid accumulation and fatty acid composition was impacted by thiolactomycin in both organisms. These findings suggest that the plastidial fatty acid biosynthetic pathway does exist in the leucoplast of N. alba, although it lacks photosynthetic capacity.
THE DISTRIBUTION AND ABUNDANCE OF DEEPWATER MACROALGAE IN CENTRAL CALIFORNIA
Authors: Spalding H. L.
Published: March 2003

Deepwater macroalgal assemblages (DWAAS) were sampled from 30m to their lower depth limits at 4 locations in central California using enriched air Nitrox and the ROV Ventana. The lowest observed depth limits were 78 m for nongeniculate (encrusting) coralline algae, 58 m for non‐calcified red algae (i.e. Maripelta rotata), 40 m for foliose brown algae (i.e. Desmarestia tabacoides), and 37 m for kelps (i.e. Pleurophycus gardneri). Green algae, such as Derbesia marina and an undescribed deep water species of Codium, were observed at 30m, while large patches of an unknown green or blue‐green algal film of coccoid cells were found from 45 to 48 m. DWAAS zonation was generally similar to that in southern California, with subtle differences in the zonation of foliose red algae and the occurrence of an unknown Chlorophyta or Cyanophyta from 45–49m. Twenty four species of algae (13 Rhodophyta, 11 Phaeophyta) were sampled during the percent cover analysis at 30 m. Nongeniculate corallines varied from 53% to 91% cover depending on location, while geniculate corallines (i.e. Bossiella schmittii) averaged ca. 25% cover. Pleurophycus gardneri, a stipitate kelp previously described as “rare” in central California, was the most abundant brown alga, averaging from 2.68 to 4.8 individuals m−2. Algal abundance (percent cover and density), zonation, and light levels at the lower algal depth limits were similar between sites and locations, suggesting that the environment of deep water algal populations in this region is less variable than that of the shallow water kelp forest communities above them.
BIOGEOGRAPHY AND ECOLOGY OF THE KELP/RED ALGAL SYMBIOSIS
Authors: Garbary D.J. , Kim K.Y.
Published: March 2003

A kelp/red algal symbiosis is described from nature based on extensive collections from the San Juan Islands, Washington. Kelp gametophytes were found as endophytes in the cell walls of seventeen species of red algae in three different kelp communities. Host red algae were mostly filamentous (e.g., Pleonosporium vancouverianum) or polysiphonous (e.g. Polysiphonia paniculata). The kelp gametophytes completed vegetative and reproductive development in the hosts with gametangia formed at the host surface and with sporophytes up to several mm in height being produced while still attached to the host. To date, none of the kelp gametophytes from nature have been identified to genus or species, although the gametophyte of Nereocystis luetkeana is a potential candidate for the symbiosis. Preliminary observations from Nova Scotia and the Isle of Man have not found the association in the Atlantic Ocean. Laboratory studies in Korea successfully reconstructed the symbiosis in the red alga Aglaothamnion oosumiense using zoospores of Undaria pinnatifida but not Laminaria religiosa. Here we outline the development of the symbiosis and discuss the potential adaptive significance of the kelp/red algal interaction.
CHANGES IN NITROGEN POOLS IN ULVA FENESTRATA (CHLOROPHYTA) AND GRACILARIA PACIFICA (RHODOPHYTA) UNDER NITRATE AND AMMONIUM ENRICHMENT
Authors: Naldi Mariachiara , Wheeler Patricia A.
Published: March 2003

The accumulation of nitrogen in different cellular pools by the macroalgae Ulva fenestrata (Postels and Ruprecht) (Chlorophyta) and Gracilaria pacifica (Abbott) (Rhodophyta) was studied in a laboratory experiment. After 8 or 9 days of nitrogen enrichment, nitrate, ammonium, free amino acid (FAA), protein, chlorophyll (chl), phycoerythrin (PE), and insoluble nitrogen pools were extracted and analyzed, and their relative contribution to total nitrogen (TN) was assessed. In U. fenestrata, the nitrate and ammonium enrichments resulted in a significant increase of TN from 2.41% dry weight (dw) to 4.19% and 4.71% dw, respectively. All the extracted N pools increased significantly. In G. pacifica, TN increased more under ammonium enrichment than under nitrate enrichment. In both macroalgae, proteins and FAA were the most important N storage pools. Protein‐N ranged from 700 to 2300 μmol N·g dw−1 (43%–66% of TN) and contributed the most to TN increase (41%–89%). The FAA pool was always larger in G. pacifica than in U. fenestrata. In both species, the FAA pool accounted for 4%–17% of TN (70–600 μmol N·g dw−1). In U. fenestrata, nitrate can represent a temporary storage pool: it accumulated up to 200 μmol N·g dw−1 (7% of TN) and contributed more than FAA to overall increase in cellular nitrogen. In contrast, G. pacifica had a small nitrate pool. The PE pool in G. pacifica increased with TN but was never more than 9% of total protein‐N or 6% of TN, and it was less important than FAA as a storage pool. All TN was recovered in the extracted and insoluble N pools at the end of the experiment in U. fenestrata. In G. pacifica, the extracted and insoluble N pools accounted on average for 83%–90% of TN.
REEXAMINATION OF PHYLOGENETIC RELATIONSHIPS WITHIN THE COLONIAL VOLVOCALES (CHLOROPHYTA): AN ANALYSIS OF atpB AND rbcL GENE SEQUENCES
Authors: Nozaki Hisayoshi , Ohta Niji , Takano Hiroyoshi , Watanabe Makoto M.
Published: March 2003

The chloroplast‐encoded atpB gene was sequenced from 33 strains representing 28 species of the colonial Volvocales (the Volvocaceae and its relatives) to reexamine phylogenetic relationships as previously deduced by morphological data and rbcL gene sequence data.1128 base pairs in the coding regions of the atpB gene were analyzed by MP, NJ, and ML analyses. Although supported with relatively low bootstrap values (75% and 65% in the NJ and ML analyses, respectively), three anisogamous/oogamous volvocacean genera—Eudorina, Pleodorina, and Volvox, excluding the section Volvox (=Euvolvox, illegitimate name), constituted a large monophyletic group (Eudorina group). Outside the Eudorina group, a robust lineage composed of three species of Volvox sect. Volvox was resolved as in the rbcL gene trees, rejecting the hypothesis of the previous cladistic analysis based on morphological data that the genus Volvox is monophyletic. In addition, the NJ and ML trees suggested that Eudorina is a nonmonophyletic genus as inferred from the morphological data and rbcL gene sequences. Although phylogenetic status of the genus Gonium is ambiguous in the rbcL gene trees and the paraphyly of this genus is resolved in the cladistic analysis based on morphological data, the atpB gene sequence data suggest monophyly of Gonium with relatively low bootstrap values (56–61%) in the NJ and ML trees. On the basis of the combined sequence data (2256 base pairs) from atpB and rbcL genes, Gonium was resolved as a robust monophyletic genus in the NJ and ML trees (with 68–86% bootstrap values), and Eudorina elegans Ehrenberg represented a paraphyletic species positioned most basally within the Eudorina group. However, phylogenetic status and relationships of the families of the colonial Volvocales were still almost ambiguous even in the combined analysis.
TRANSFER OF PROTEINS FROM THE CHLOROPLAST TO VACUOLES IN CHLAMYDOMONAS REINHARDTII (CHLOROPHYTA): A PATHWAY FOR DEGRADATION
Authors: Park Hyoungshin , Eggink Laura L. , Roberson Robert W. , Hoober J. Kenneth
Published: March 2003

Several chloroplast proteins were detected by immunoelectron microscopy within dense granules in cytoplasmic vacuoles in the alga Chlamydomonas reinhardtii Dangeard. Transfer from chloroplast to vacuoles of two major, pulse‐labeled polypeptides, the large subunit of rubisco and the α subunit of ATPase, which are synthesized on chloroplast ribosomes, was demonstrated by the recovery of these polypeptides in vacuolar granules over a several‐hour time period. The ultrastructure of cryofixed algal cells was examined to search for structures that would provide insight into the transfer of chloroplast proteins to vacuoles. Micrographs showed that the two membranes of the envelope were appressed, with no detectable intermembrane space, over most of the chloroplast surface. Protrusions of the outer membrane of the envelope were occasionally found that enclosed stroma, with particles similar in size to chloroplast ribosomes, but generally not thylakoid membranes. These observations suggest that chloroplast material, especially the stromal phase, was extruded from the chloroplast in membrane‐bound structures, which then interacted with Golgi‐derived vesicles for degradation of the contents by typical lysosomal activities. A protein normally targeted to vacuoles through the endomembrane system for incorporation into the cell wall was detected in Golgi structures and vacuolar granules but not the chloroplast.
THE FIBRILLAR POLYSACCHARIDES AND THEIR LINKAGE TO ALGAENAN IN THE TRILAMINAR LAYER OF THE CELL WALL OF COELASTRUM SPHAERICUM (CHLOROPHYCEAE)
Authors: Rodríguez María C. , Noseda Miguel D. , Cerezo Alberto S.
Published: March 2003

Methylation and spectroscopical analyses of DMSO‐LiCl‐solubilized fractions of the fibrillar cell wall of Coelastrum sphaericum Näg. established the presence of cellulose and β‐1,4‐linked mannan. A small proportion (2–7%) of (1→2) linkages in β‐mannan that introduced an interruption in the regular ribbon chain conformation was interpreted as a component that modulated the mechanical strength of the cell wall. The trilaminar layer fractions consisted mostly of algaenan and cellulose. Evidence for ether linkages between glucose C‐6 in the β‐1,4‐glucan and algaenan was obtained.
PHYTOPLANKTON DYNAMICS IN A STABLY STRATIFIED ANTARCTIC LAKE DURING WINTER DARKNESS
Authors: McKnight Diane M. , Howes B. L. , Taylor C. D. , Goehringer D. D.
Published: March 2003

Using automated overwinter sampling devices, we collected preserved phytoplankton samples from multiple depths in Lake Fryxell, a permanently ice‐covered lake in southern Victoria Land, Antarctica. Photosynthetic algae were maintained in a stable water column throughout winter darkness. The algal taxa overwintered in different ways in a species‐specific manner. Typical vegetative cells were the most abundant form for all species found in the water column. Populations of one chlorophyte, Stichococcus sp., were observed in winter, but the species was absent in both summers. Two cryptophyte species were more abundant in winter than in summer. We interpret the increase in algal population size as evidence of heterotrophic growth in winter and of mixotrophic behavior throughout the year. For two chlorophyte species, some portion of the population had a distinctive morphology, for example, many Chlamydomonas subcaudata Wille. formed akinetes, whereas many Chlorella sp. contained a large amount of starch or other storage material. During winter, vegetative cells of the most abundant cyanobacterial species, Phormidium angustissimum West et West, occurred at the depth of the summer maximum and at depths below the oxycline. The presence of P. angustissimum below the oxycline may have resulted from the accumulation of settling cells at a depth with a greater density. In contrast to the settling of P. angustissimum, the general absence of the other algal species below the oxycline in winter indicated that these species were not influenced by overwinter settling.
Mixotrophy in gyrodinium galatheanum (DINOPHYCEAE): grazing responses to light intensity and inorganic nutrients*
Authors: Li Aishao , Stoecker Diane K. , Coats D. Wayne
Published: March 2003

This paper presents results of field and laboratory studies on mixotrophy in the estuarine dinoflagellate Gyrodinium galatheanum (Braarud) Taylor. We tested the hypotheses that this primarily photosynthetic organism becomes phagotrophic when faced with suboptimal light and/or nutrient environments. In Chesapeake Bay, incidence of feeding of this species on cryptophytes is positively correlated with prey density and concentrations of nitrate and nitrite, but negatively correlated with depth, salinity, and phosphate concentration. Feeding in natural assemblages and cultures increased hyperbolically with light intensity. The stoichiometric proportions of dissolved inorganic P and N (DIP:DIN) at the stations where G. galatheanum was present were far below the optimal growth P:N (1:10). Incidence of feeding was negatively related to the ratio of DIP to DIN, suggesting that P limitation may have induced feeding. Addition of nitrate, or addition of both nitrate and phosphate, inhibited feeding in a natural population, indicating that N limitation may also induce feeding. Ingestion of the cryptophyte, Storeatula major, by cultured G. galatheanum was higher in media low in nitrate or phosphate or both, but moderate rates of feeding occurred in nutrient‐replete cultures. When cells were grown in media with varying concentrations of nitrate and phosphate, N deficiency resulted in greater cellular N and Chl a losses than did P deficiency, but P deficiency stimulated feeding more than N deficiency. Both N and P deficiency, or P:N ratios that deviated greatly from 1:10, result in an increase of cellular carbon content and an increase in propensity to feed. Our results suggest that feeding in G. galatheanum is partly a strategy for supplementing major nutrients (N and P) that are needed for photosynthetic carbon assimilation. Feeding in G. galatheanum may also be a strategy for supplementing C metabolism or acquiring trace organic growth factors, since feeding occurs, although at a reduced rate, in nutrient‐replete cultures.
The reversible effect of flow on the morphology of ceratocorys horrida (PERIDINIALES, DINOPHYTA)*
Authors: Zirbel Marnie J. , Veron Fabrice , Latz Michael I.
Published: March 2003

Most cells experience an active and variable fluid environment, in which hydrodynamic forces can affect aspects of cell physiology including gene regulation, growth, nutrient uptake, and viability. The present study describes a rapid yet reversible change in cell morphology of the marine dinoflagellate Ceratocorys horrida Stein, due to fluid motion. Cells cultured under still conditions possess six large spines, each almost one cell diameter in length. When gently agitated on an orbital shaker under conditions simulating fluid motion at the sea surface due to light wind or surface chop, as determined from digital particle imaging velocimetry, population growth was inhibited and a short‐spined cell type appeared that possessed a 49% mean decrease in spine length and a 53% mean decrease in cell volume. The reduction in cell size appeared to result primarily from a 39% mean decrease in vacuole size. Short‐spined cells were first observed after 1 h of agitation at 20°C; after 8 to 12 d of continuous agitation, long‐spined cells were no longer present. The morphological change was completely reversible; in previously agitated populations devoid of long‐spined cells, cells began to revert to the long‐spined morphology within 1 d after return to still conditions. During morphological reversal, spines on isolated cells grew up to 10 μm·d−1. In 30 d the population morphology had returned to original proportions, even though the overall population growth was zero during this time. The reversal did not occur as a result of cell division, because single‐cell studies confirmed that the change occurred in the absence of cell division and much faster than the 16‐d doubling time. The threshold level of agitation causing morphology change in C. horrida was too low to inhibit population growth in the shear‐sensitive dinoflagellate Lingulodinium polyedrum. At the highest level of agitation tested, there was negative population growth in C. horrida cultures, indicating that fluid motion caused cell mortality. Small, spineless cells constituted a small percentage of the population under all conditions. Although their abundance did not change, single‐cell studies and morphological characteristics suggest that the spineless cells can rapidly transform to and from other cell types. The sinking rate of individual long‐spined cells in still conditions was significantly less than that of short‐spined cells, even though the former are larger and have a higher cell density. These measurements demonstrate that the long spines of C. horrida reduce cell sinking. Shorter spines and reduced swimming would allow cells to sink away from turbulent surface conditions more rapidly. The ecological importance of the morphological change may be to avoid conditions that inhibit population growth and potentially cause cell damage.
COMBINED EFFECTS OF TEMPERATURE AND IRON ON THE GROWTH AND PHYSIOLOGY OF THE MARINE DIATOM PHAEODACTYLUM TRICORNUTUM (BACILLARIOPHYCEAE)
Authors: Kudo Isao , Miyamoto Makiko , Noiri Yoshifumi , Maita Yoshiaki
Published: March 2003

Phaeodactylum tricornutum Bohlin (Bacillariophyceae) was maintained in exponential growth under Fe‐replete and stressed conditions over a range of temperatures from 5 to 30° C. The maximum growth rate (GR) was observed at 20° C (optimal temperature) for Fe‐replete and ‐stressed cells. There was a gradual decrease in the GR decreasing temperatures below the optimum temperature; however, the growth rate dropped sharply as temperature increased above the optimum temperature. Fe‐stressed cells grew at half the growth rate of Fe‐replete cells at 20° C, whereas this difference became larger at lower temperatures. The change in metabolic activities showed a similar pattern to the change in growth rate temperature aside from their optimum temperature. Nitrate reductase activity (NRA) and respiratory electron transport system activity (ETS) per cell were maximal between 15 and 20° C, whereas cell‐specific photosynthetic rate (Pcell) was maximal at 20° C for Fe‐replete cells. These metabolic activities were influenced by Fe deficiency, which is consistent with the theoretical prediction that these activities should have an Fe dependency. The degree of influence of Fe deficiency, however, was different for the four metabolic activities studied: NRA > Pcell > ETS = GR. NRA in Fe‐stressed cells was only 10% of that in Fe‐replete cells at the same temperature. These results suggest that cells would have different Fe requirements for each metabolic pathway or that the priority of Fe supply to each metabolic reaction is related to Fe nutrition. In contrast, the order of influence of decreasing the temperature from the optimum temperature was ETS > Pcell > NRA > GR. For NRA, the observed temperature dependency could not be accounted for by the temperature dependency of the enzyme reaction rate itself that was almost constant with temperature, suggesting that production of the enzyme would be temperature dependent. For ETS, both the enzyme reactivity and the amount of enzyme accounted for the dependency. This is the first report to demonstrate the combined effects of Fe and temperature on three important metabolic activities (NRA, Pcell, and ETS) and to determine which activity is affected the most by a shortage of Fe. Cellular composition was also influenced by Fe deficiency, showing lower chl a content in the Fe‐stressed cells. Chl a per cell volume decreased by 30% as temperature decreased from 20 to 10° C under Fe‐replete conditions, but chl a decreased by 50% from Fe‐replete to Fe‐stressed conditions.
INSIGHTS INTO THE PHYLOGENY OF THE BATRACHOSPERMALES (RHODOPHYTA) FROM rbcL SEQUENCE DATA OF AUSTRALIAN TAXA
Authors: Vis Morgan L. , Entwisle Timothy J.
Published: March 2003

Thirteen representatives of the freshwater red algal order Batrachospermales from Australia were analyzed with previously published sequences in a phylogenetic analysis of RUBISCO large subunit (rbcL) gene sequence data. The newly sequenced taxa represented putative endemics to the Australia–New Zealand region (Batrachospermum antipodites, B. deminutum, B. discors, B. kraftsii, B. theaquum, B. wattsii, and Nothocladus lindaueri) and more cosmopolitan species (B. ambiguum, B. atrum, B. cayennense, B. gelatinosum[two samples], and Sirodotia suecica). From parsimony, distance, and maximum likelihood analyses, three clades of batrachospermalean taxa were suggested: a “mixed” clade composed of taxa sampled from Australia and North America, a clade of primarily Australian collections, and a clade of predominantly North American samples. The latter two clades appeared to be more closely related to each other than to the mixed clade. It is hypothesized that the Australian clade may be of Gondwanic origin, but more sampling of other continents is needed to confirm this statement. The collections of B. gelatinosum from Australia did not form a monophyletic clade with B. gelatinosum from North America, and a new species, B. pseudogelatinosum, is proposed for the Australian collections. Unlike the B. gelatinosum results, B. atrum and S. suecica samples from Australia were very closely related to collections of the same species from other continents. With the addition of B. deminutum and B. ambiguum to the analysis, Batrachospermum section Contorta is shown to be monophyletic if section Hybrida is included. The expansion of the description for section Contorta is proposed to accommodate species from section Hybrida. The validity of Batrachospermum section Aristata is questioned based on the distant relationship of B. macrosporum and B. cayennense.
IDENTIFICATION AND DNA SEQUENCE OF A NEW H+‐ATPase IN THE UNICELLULAR GREEN ALGA CHLAMYDOMONAS REINHARDTII (CHLOROPHYCEAE)
Authors: Campbell A. Malcolm , Coble Alison J. , Cohen Lindsay D. , Ch'Ng Toh Hean , Russo Kristin M. , Long Elizabeth M. , Armbrust E. Virginia
Published: March 2003

Insertional mutagenesis was used to identify genes involved in mating and/or zygote formation in the unicellular green alga Chlamydomonas reinhardtii Dangeard. Approximately 800 insertionally mutagenized transformants were examined, and a single nonagglutinating mutant was identified. Plasmid rescue was used to clone a genomic fragment containing transforming DNA. This fragment was then used to identify the wild‐type copy of the gene disrupted during mutagenesis. The wild‐type gene is transcribed during all stages of the life cycle and, based on sequence similarity, encodes a P2‐type proton transporting ATPase. The gene is referred to as Pmh1 for plasma membrane H+‐ATPase. PMH1 displays the greatest sequence similarity to ATPases from two parasitic flagellates and a raphidophytic alga but not to the ATPase from a closely related green alga. We propose that PMH1 represents a distinct H+‐ATPase isoform expressed in flagellates.
EVOLUTIONARY RELATIONSHIPS OF CULTIVATED ANTARCTIC OSCILLATORIANS (CYANOBACTERIA)
Authors: Nadeau Tracie‐Lynn , Milbrandt Eric C. , Castenholz Richard W.
Published: March 2003

The evolutionary relationships of cultivated psychrophilic and psychrotolerant polar oscillatorians were examined, based on small subunit rDNA sequences. Psychrophilic oscillatorians from the Antarctic were affiliated in one well‐supported clade, which also includes two Arctic strains. Two of the Antarctic psychrophiles contain an 11‐nucleotide insertion that is identical to, and previously only described in, an Arctic oscillatorian. The psychrotolerant phenotype, conversely, has arisen multiple times in the cyanobacterial lineage, and psychrotolerant strains are sometimes most closely related to organisms of temperate latitudes. These findings support the hypothesis that oscillatorians in both polar regions originated from more temperate species. Furthermore, morphological designations of these filamentous cyanobacteria often do not have phylogenetic significance.
NITROGEN LIMITATION IN DUNALIELLA TERTIOLECTA (CHLOROPHYCEAE) LEADS TO INCREASED SUSCEPTIBILITY TO DAMAGE BY ULTRAVIOLET‐B RADIATION BUT ALSO INCREASED REPAIR CAPACITY1
Authors: Shelly Kirsten , Heraud Philip , Beardall John
Published: March 2003

Chl fluorescence was used to measure the photosynthetic capacity of the green alga Dunaliella tertiolecta in order to investigate interactions between susceptibility to acute UV‐B radiation (UVBR, 280–320 nm) exposure and decreased nitrogen availability. Under UVBR exposure the decline in the fluorescence parameters Fv/Fm (the maximum effective quantum yield ΦPSIIe‐max) and Fv′/Fm′ (the operational quantum yield of PSII, ΦPSIIe) were enhanced with higher UVBR fluxes, with the data well described by the Kok model, inferring that a dynamic balance existed between damage and repair with the repair proportional to the pool size of inactivated targets. When UVBR exposure was coupled with nitrogen limitation, the inhibition of photosynthesis was intensified. Under the more severely N‐limited conditions, the damage rate increased. Unexpectedly, repair rates were also stimulated under N‐limited conditions, although this was insufficient to counteract the increase in damage, so the overall effect of N limitation was an enhancement of UVBR‐induced inhibition of photosynthesis.
SINGAPORE ISOLATES OF THE DINOFLAGELLATE GYMNODINIUM CATENATUM (DINOPHYCEAE) PRODUCE A UNIQUE PROFILE OF PARALYTIC SHELLFISH POISONING TOXINS1
Authors: Holmes Michael James , Bolch Christopher J. S. , Green David H. , Cembella Allan D. , Teo Serena Lay Ming
Published: March 2003

We investigated the cell morphology, toxicity and toxin composition, and rDNA sequences of clonal cultures of the chain‐forming dinoflagellate Gymnodinium catenatum H.W.Graham isolated from the port of Singapore. The cell morphology was consistent with most descriptions of this species except for sparsely distributed putative trichocyst pores visible on some cells under SEM. Nucleotide sequences (697 base pair) of the D1–D2 conserved regions and intervening variable domain of the large subunit rDNA were identical among isolates from Singapore and those of all other global populations examined so far (from Australia, China, Japan, Korea, New Zealand, Spain, and Uruguay), and this is consistent with the morphological conservatism of the species. Among isolates of G. catenatum that produce toxins associated with paralytic shellfish poisoning, the cellular toxicity of Singapore clones, as determined by intraperitoneal mouse bioassay (30–50 pg saxitoxin equivalents·cell−1) and immunoassay (24 ± 8 saxitoxin equivalents·cell−1) was relatively high. The mouse bioassay toxicity was comparable with that of Spanish and Philippine isolates that have undergone acid hydrolysis. However, analysis of toxin composition of Singapore clones by HPLC with fluorescence detection or HPLC‐mass spectrometry/mass spectrometry revealed a unique toxin profile that was dominated by the highly potent carbamate toxins, primarily gonyautoxin (GTX) 1 and 4 with lesser amounts of GTX2, GTX3, neosaxitoxin, and saxitoxin. No N  ‐  sulfocarbamoyl, decarbamoyl, or deoxy‐decarbamoyl toxins were detected. In contrast, less potent N  ‐  sulfocarbamoyl toxins dominate the toxin profiles of all other global populations examined to date (from Australia, China, Japan, New Zealand, the Philippines, Portugal, Spain, and Uruguay). The lack of genetic diversity found among broadly distributed populations of G. catenatum is consistent with the hypothesis of a relatively recent global spread of this species. Yet the unique toxin profile of Singapore strains indicates that it is unlikely that this strain has been recently translocated from any of the populations with characterized toxin profiles. In any case, the unique carbamate‐dominated toxin profile may be a useful signature to identify the potential spread of this strain from the port of Singapore, one of the world's busiest.
MORPHOLOGY AND SYSTEMATICS OFSCIUROTHAMNION STEGENGAEGEN. ET SP. NOV. (CERAMIACEAE, RHODOPHYTA) FROM THE INDO‐PACIFIC1
Authors: De Clerck Olivier , Kraft Gerald T. , Coppejans Eric
Published: March 2003

A new ceramiaceous alga,Sciurothamnion stegengaeDe Clerck et Kraft, gen. et sp. nov., is described from the western Indian Ocean and the Philippines.Sciurothamnionappears related to the tribe Callithamnieae on the basis of the position and composition of its procarps and by the majority of post‐fertilization events. It differs, however, from all current members of the tribe by the presence of two periaxial cells bearing determinate laterals per axial cell. Additionally, unlike any present representative of the subfamily Callithamnioideae, no intercalary foot cell is formed after diploidization of the paired auxiliary cells. The genus is characterized by a terminal foot cell (“disposal cell”), which segregates the haploid nuclei of the diploidized auxiliary cell from the diploid zygote nucleus. The nature of three types of foot cells reported in the Ceramiaceae (intercalary foot cells containing only haploid nuclei, intercalary foot cells containing haploid nuclei and a diploid nucleus, and terminal foot cells containing only haploid nuclei) is discussed.