GROWTH STIMULATION OF ALEXANDRIUM TAMARENSE (DINOPHYCEAE) BY HUMIC SUBSTANCES FROM THE MANICOUAGAN RIVER (EASTERN CANADA)1

In the St. Lawrence Estuary, annual recurrent blooms of the toxic dinoflagellate Alexandrium tamarense L. Balech are associated with brackish waters. Riverine inputs are suspected to favor bloom development by increasing water column stability and/or by providing growth stimulants such as humic substances (HS). A 17‐day culture experiment was conducted to evaluate the importance of HS as growth factors for A. tamarense. Nonaxenic cultures were exposed to four HS extracts from three different sources: humic and fulvic acids isolated from the Manicouagan River, Quebec, Canada; humic acids from the Suwannee River, Georgia, United States; and a desalted alkaline soil extract. For each extract, four concentrations were tested as supplements to the artificial Keller medium, a nitrate‐rich algal culture medium. Additions of HS from all sources significantly enhanced the overall growth rates relative to the controls. Concentrations of HS, estimated by UV spectrophotometry, remained constant throughout the exponential growth phase, suggesting that the HS were acting mainly as growth promoters during our experiment. Dose–response curves indicated that HS could increase the growth rate of A. tamarense even at low concentrations, such as those encountered in the St. Lawrence Estuary. Our results support the hypothesis that HS from the Manicouagan River plume can stimulate the development of toxic dinoflagellate blooms.     

Salt-induced changes in protein composition in light-grown callus of Mesembryanthemum crystallinum

The halophyte Mesembryanthemum crystallinum (ice plant) has been suggested as a model for salt-tolerance in higher plants. To investigate salt-induced changes in polypeptide patterns at the cellular level, a light-grown callus of M. crystallinum with substantial chlorophyll content, was established and the effect of NaCl on the composition of phenol-extracted protein was examined by SDS- and 2D-polyacrylamide gel electrophoresis (PAGE). SDS-PAGE showed the accumulation of five polypeptides with estimated molecular masses of 40, 34, 32, 29 and 14 kDa was enhanced by the addition of 200 m M NaCl to the culture media. The addition of ABA (10 μ M ) or mannitol (400 m M ) did not elicit the same degree of accumulation of these salt-specific proteins. These polypeptides were classified into two groups according to their course of induction: early responsive (40, 34, 29 kDa) and late-responsive (32, 14 kDa) proteins. In addition, two polypeptides (20, 18 kDa) were transiently accumulated during salt treatment. Further separation of soluble proteins by 2-D gel electrophoresis, either isoelectric focusing (IEF) or non-equilibrium pH-gradient electrophoresis (NEPHGE) followed by SDS-PAGE, showed more alterations in accumulation of polypeptides by NaCl than 1-D gel electrophoresis. Overall, levels of more than 30% of basic polypeptides, detected by NEPHGE/SDS-PAGE, were altered by 200 m M NaCl treatment, while only 10% of neutral and acidic polypeptides, detected by IEF/SDS-PAGE, were changed. The enhanced expression of these proteins by salt in cultured cells is most likely related to the cellular responses to salinity, and not to the mechanism of CAM induction in this facultative halophyte.     

ERK is involved in the reorganization of somatosensory cortical maps in adult rats submitted to hindlimb unloading

Sensorimotor restriction by a 14-day period of hindlimb unloading (HU) in the adult rat induces a reorganization of topographic maps and receptive fields. However, the underlying mechanisms are still unclear. Interest was turned towards a possible implication of intracellular MAPK signaling pathway since Extracellular-signal-Regulated Kinase 1/2 (ERK1/2) is known to play a significant role in the control of synaptic plasticity. In order to better understand the mechanisms underlying cortical plasticity in adult rats submitted to a sensorimotor restriction, we analyzed the time-course of ERK1/2 activation by immunoblot and of cortical reorganization by electrophysiological recordings, on rats submitted to hindlimb unloading over four weeks. Immunohistochemistry analysis provided evidence that ERK1/2 phosphorylation was increased in layer III neurons of the somatosensory cortex. This increase was transient, and parallel to the changes in hindpaw cortical map area (layer IV). By contrast, receptive fields were progressively enlarged from 7 to 28 days of hindlimb unloading. To determine whether ERK1/2 was involved in cortical remapping, we administered a specific ERK1/2 inhibitor (PD-98059) through osmotic mini-pump in rats hindlimb unloaded for 14 days. Results demonstrate that focal inhibition of ERK1/2 pathway prevents cortical reorganization, but had no effect on receptive fields. These results suggest that ERK1/2 plays a role in the induction of cortical plasticity during hindlimb unloading.     

Geographical distribution of schistosomiasis and soil-transmitted helminths among school children in informal settlements in Kisumu City, Western Kenya

This cross-sectional study determined the prevalence and distribution of schistosome and soil-transmitted helminth (STH) infections among 1,308 children aged 10-18 years in 34 primary schools in 8 informal urban settlements in Kisumu City, western Kenya. Stool samples were collected and examined for eggs of Schistosoma mansoni and STH (Hookworms, Ascaris lumbricoides and Trichuris trichiura) using the Kato-Katz technique. Haematuria was used as a proxy indicator of urinary schistosomiasis. Schools and water bodies were mapped using a geographical information system. Overall, 34% of children were infected with one or more helminth species whereas 16·2% of children were infected with one or more STH species. Schools in closest proximity to Lake Victoria and River Nyamasaria had the highest S. mansoni prevalence while schools with STH were more homogenously distributed. Mean school prevalence of S. mansoni infection was 21% (range=0-69·7%), S. haematobium 3·6% (range=0-12%), hookworms 6·1% (range=0-20%), A. lumbricoides 4·9% (range=0-18·4%), and T. trichiura 7·7% (range=0-18·6%). Helminth-related morbidities were not associated with infection. Our study demonstrates that schistosomiasis and STH are important health priorities among schools in informal settlements of Kisumu City, and highlights the need for routine deworming in similar settings.     

Isoenzymes of hypoxanthine-guanine-phosphoribosyl transferase in a family with partial deficiency of the enzyme

The isoenzymes of hypoxanthine-guanine-phosphoribosyl transferase (HGPRT; E. C. 2.4.2.8) were studied by polyacrylamide gel disc electrophoresis in the erythrocytes of a family in which there was a partial deficiency of this X-linked enzyme. Hyperuricemic males, in whom HGPRT activity was 4% of normal, were found to have a variant enzyme which had altered kinetic and electrophoretic properties. In acrylamide gel, this variant migrated about 15% faster than the normal enzyme, and its K _m for hypoxanthine was twice that of the normal. The sister of two patients had 34% of normal activity in her erythrocytes and was thought to be a heterozygote. Electrophoresis of her hemolysate yielded profiles in which there were two zones of HGPRT activity. The more slowly migrating isoenzyme behaved electrophoretically like the normal isoenzyme. The faster-migrating isoenzyme had a mobility identical to that of the variant enzyme found in hemolysates from her hyperuricemic siblings. However, in her profile the activity of the variant enzyme was three times greater than that of the HGPRT found in the boys. This increased activity appears to be due to an interaction of the variant enzyme with the normal enzyme. Electrophoresis of a mixture of normal enzyme and the variant from a hyperuricemic male yielded a profile similar to that observed in this girl and a dramatic increase in the amount of activity in the variant zone.Aided by U.S. Public Health Service Grants No. HD04608 and GM 17702 from the National Institute of Child Health and Human Development and from the National Institute of General Medical Sciences, respectively, National Institutes of Health. Presented in part at the 1971 Annual Meeting of the Western Society for Pediatric Research, Carmel, California.     

ULTRASTRUCTURAL STUDIES OF VASOPRESSIN EFFECT ON ISOLATED PERFUSED RENAL COLLECTING TUBULES OF THE RABBIT

Isolated cortical collecting tubules from rabbit kidney were studied during perfusion with solutions made either isotonic or hypotonic to the external bathing medium. Examination of living tubules revealed a reversible increase in thickness of the cellular layer, prominence of lateral cell membranes, and formation of intracellular vacuoles during periods of vasopressin-induced osmotic water transport. Examination in the electron microscope revealed that vasopressin induced no changes in cell structure in collecting tubules in the absence of an osmotic difference and significant bulk water flow across the tubule wall. In contrast, tubules fixed during vasopressin-induced periods of high osmotic water transport showed prominent dilatation of lateral intercellular spaces, bulging of apical cell membranes into the tubular lumen, and formation of intracellular vacuoles. It is concluded that the ultrastructural changes are secondary to transepithelial bulk water flow and not to a direct effect of vasopressin on the cells, and that vasopressin induces osmotic flow by increasing water permeability of the luminal cell membrane. The lateral intercellular spaces may be part of the pathway for osmotically induced transepithelial bulk water flow.     

Inhibition of yeast Δ-pyrroline-5-carboxylate dehydrogenase by common amino acids and the regulation of proline catabolism

A yeast glutamate auxotroph (glt_{1 − 1}), blocked in the tricarboxylic acid cycle at aconitase, is shown to possess catabolic pathways to glutamate from proline, arginine and glutamine, and grows on any of these amino acids in a minimal medium. This mutant does not, however, grow on these amino acids in a medium containing the full complement of common amino acids minus glutamate. The mechanism of this growth failure involves partial inhibition of the catabolic routes to glutamate by more than half the common amino acids. In the case of proline catabolism, this inhibition is localized principally at the enzyme Δ¹-pyrroline-5-carboxylate: NAD(P)⁺ oxidoreductase by in vitro studies. Similar results with this enzyme prepared both from yeast and from beef kidney mitochondria suggest that the inhibition observed may be the basis of a regulatory mechanism of general significance.     

Specific Labeling of Stem Cell Activity in Human Colorectal Organoids Using an ASCL2-Responsive Minigene

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Characterization of bacterial composition and diversity in a long-term petroleum contaminated soil and isolation of high-efficiency alkane-degrading strains using an improved medium

Bacterial community and diversity in a long-term petroleum-contaminated soil of an oilfield were characterized using 16S rRNA gene-based Illumina MiSeq high-throughput sequencing. Results indicated that Proteobacteria (49.11%) and Actinobacteria (24.24%) were the most dominant phyla, and the most abundant genera were Pseudoxanthomonas (8.47%), Luteimonas (3.64%), Alkanindiges (9.76%), Acinetobacter (5.26%) and Agromyces (8.56%) in the soil. Meanwhile a series of cultivations were carried out for isolation of alkane degraders from petroleum-contaminated soil with gellan gum and agar as gelling agents. And the isolates were classified by their 16S rRNA genes. Nine of the isolates including Enterobacter, Pseudomonas,Acinetobacter, Rhizobium, Bacillus, Sphingomonas, Paenibacillus, Variovorax and Rhodococcus showed strong biodegradability of alkane mixture (C9–C30) in a wide range of chain-length, which could be potentially applied in enhancement of bioremediation.     

Calcium-Independent Release of Acetylcholine from Electric Organ Synaptosomes and Its Changes by Depolarization and Cholinergic Drugs

Chemiluminescent detection was applied to measure the continuous spontaneous Ca2+-independent liberation of acetylcholine (ACh) from Torpedo electric organ synaptosomes. Differentiation between the release of ACh and choline was achieved by inhibiting cholinesterases with phospholine, and a way to quantify the continuous release was devised. The method permitted measurements during short time intervals from minute amounts of tissue and without an accumulation of ACh in the medium. Synaptosomes continuously liberated small amounts of ACh during incubations in the presence of 3 mM K+ and in the absence of Ca2+. The spontaneous liberation of ACh was similar both quantitatively and qualitatively at pH values of 8.6 and 7.8. It was unaltered by MgCl2 (10.4 mM), 2-(4-phenylpiperidino)cyclohexanol (10 microM), ouabain (104 microM), atropine (10 microM), and valinomycin (102 nM). Carbamoylcholine brought about a decrease, which could be partially reversed by atropine. The Ca2+-independent output of ACh was increased considerably when the concentration of K+ ions was raised (eightfold at 103 and 35-fold at 203 mM K+). Carbamoylcholine (104 microM) blocked the increase in ACh release produced by high K+; this effect of carbamoylcholine was not reversed by atropine (10 microM). When Ca2+ was added to synaptosomes depolarized by a high concentration of K+, the amount of ACh released during the first 1-3 min after the addition of Ca2+ was at least 20 times higher than in the absence of Ca2+, but the release returned rapidly to predepolarization values. Similarly high values of ACh release could be achieved by adding Ca2+ plus the ionophore A23187 and even higher values by adding Ca2+ plus gramicidin.(ABSTRACT TRUNCATED AT 250 WORDS)