Utilization of low molecular weight organic compounds by the filterable fraction of a lotic microbiome

Abstract Filterable microorganisms participate in dissolved organic carbon (DOC) cycling in freshwater systems, however their exact functional role remains unknown. We determined taxonomic identity and community dynamics of prokaryotic microbiomes in the 0.22 µm-filtered fraction and unfiltered freshwater from the Conwy River (North Wales, UK) in microcosms and, using targeted metabolomics and 14C-labelling, examined their role in utilization of amino acids, organic acids, and sugars spiked at environmentally-relevant (nanomolar) concentrations. To identify changes in community structure, we used 16S rRNA amplicon and shotgun sequencing. Unlike the unfiltered water samples where the consumption of DOC was rapid, the filtered fraction showed a 3-days lag phase before the consumption started. Analysis of functional categories of clusters of orthologous groups of proteins (COGs) showed COGs associated with energy production increased in numbers in both fractions with substrate addition. The filtered fraction utilized low-molecular-weight (LMW) DOC at much slower rates than the whole community. Addition of nanomolar concentrations of LMW DOC did not measurably influence the composition of the microbial community nor the rate of consumption across all substrate types in either fraction. We conclude that due to their low activity, filterable microorganisms play a minor role in LMW DOC processing within short residence time of lotic freshwater systems.

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Drug-Protein Interaction: 8-Methoxy Psoralen as Photosensitizer of Enzymes and Amino Acids

Zeitschrift für Naturforschung C ◽

10.1515/znc-1979-5-612 ◽

1979 ◽

Vol 34 (5-6) ◽

pp. 392-396 ◽

Cited By ~ 14

Author(s):

F. M. Veronese ◽

O. Schiavon ◽

R. Bevilacqua ◽

G. Rodighiero

Keyword(s):

Amino Acids ◽

Molecular Weight ◽

Methylene Blue ◽

Mechanism Of Action ◽

Protein Interaction ◽

Rose Bengal ◽

Molecular Basis ◽

Minor Role ◽

Low Molecular Weight ◽

A Minor

Abstract For a better insight of the molecular basis of the photobiological effects of furocoumarins, the relevance of proteins oxydation by singlet oxygen produced by these substrates under irradiation with long u. v. light was studied.Complex oligomeric as well as simple monomeric purified enzymes with high or low molecular weight and different properties and simple amino acids were irradiated under oxygen in presence of 8-methoxy-psoralen. The effects on both proteins and amino acids were compared with those obtained under similar conditions with typical photosensitizers as methylene blue and Rose Bengal. The results indicated that the photooxydation of proteins, although possible, appears to play a minor role, if any, in the mechanism of action of furocoumarin.

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Mechanisms for altering phosphorus sorption characteristics induced by low-molecular-weight organic acids

Canadian Journal of Soil Science ◽

10.1139/cjss-2015-0068 ◽

2016 ◽

Vol 96 (3) ◽

pp. 289-298 ◽

Cited By ~ 10

Author(s):

Yongzhuang Wang ◽

Joann K. Whalen ◽

Xin Chen ◽

Yanhong Cao ◽

Bin Huang ◽

...

Keyword(s):

Molecular Weight ◽

Organic Acids ◽

Low Molecular Weight ◽

Minor Effect ◽

Phosphorus Sorption ◽

Sorption Data ◽

P Fractionation ◽

Soil P ◽

P Sorption ◽

A Minor

Exudation of low-molecular-weight organic acids (LMWOAs) from plant roots enhances phosphorus (P) acquisition from soil, either by dissolving P fixed in secondary minerals or by reducing P sorption to organo-minerals. How LMWOAs may modify P sorption in soils with contrasting pH is not well understood, much less the mechanisms involved. The effects of three common LMWOAs (oxalic, citric, and malic acids) on P sorption in calcareous, neutral, and acidic soils were studied in batch experiments, followed by sequential P fractionation to elucidate the mechanisms whereby LMWOAs alter P sorption. The sorption data of the three soils fitted better to the Freundlich equation (r2 = 0.325–0.994, P < 0.05) than the Langmuir and linear equations. Oxalic, citric, and malic acids at 10 mmol kg−1 soil decreased the Freundlich P sorption parameters Kf and n, which represent P sorption capacity and energy, due to the fact that LMWOAs reduced P sorption in NaHCO3-Pi (soil soluble and exchangeable Pi, 23.8–30.9%) and NaOH-Pi (Fe-Pi and Al-Pi, 21.6–54.2%) fractions of the three soils. Comparing acidified P-LMWOAs solutions with the pH-adjusted P-LMWOAs solutions (pH = 7) had a minor effect on P sorption. Our results indicated that the reduction in soil P sorption was due to ligand exchange and chelation of LMWOAs with Fe and Al minerals, and the acid strength of LMWOAs had a minor effect on P sorption in calcareous, neutral, and acid soils.

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Feasibility of Using Recombinant Factor VIIa in Continuous Infusion

Thrombosis and Haemostasis ◽

10.1055/s-0038-1650292 ◽

1996 ◽

Vol 75 (03) ◽

pp. 432-436 ◽

Cited By ~ 90

Author(s):

S Schulman ◽

M Bech Jensen ◽

D Varon ◽

N Keller ◽

N Gitel ◽

...

Keyword(s):

Molecular Weight ◽

Continuous Infusion ◽

Low Molecular Weight Heparin ◽

Factor Viia ◽

Venous Access ◽

Factor Vii ◽

Low Molecular Weight ◽

Days Of Therapy ◽

Infusion Systems ◽

A Minor

SummaryRecombinant factor Vila (rFVIIa; NovoSeven®) is a recent addition to the hemostatic alternatives for the treatment of hemophiliacs with inhibitors. A drawback in the use of rFVIIa has been its half-life of only about 2 h, which necessitates very frequent and punctual injections. We evaluated the stability of reconstituted, but not further diluted, rFVIIa in 3 infusion systems (WalkMedTM 350 and CADD®-Plus minipumps and Meddex 2001 syringe pump). The factor VII (F VII) activity was maintained for at least 3 days at room temperature with only a minor and clinically insignificant increase in oxidized forms of rFVIIa and minimal leaching of the plastic softeners di-butylphthalate and di-octylphthalate after 24–48 h. Addition of heparin, 5–10 U/ml, to reconstituted rFVIIa caused a loss of about 50% of the activity within 4 h of storage in the infusion system, whereas low molecular weight heparin had no such effect. Repeated samples showed that the infusion systems maintained sterility. Reconstituted rFVIIa did not support bacterial growth when inoculated with Staphylococcus aureus or Escherichia coli to any greater extent than did reconstituted factor VIII, lidocaine in saline or heparin in saline. Two patients were treated with continuous infusion of rFVIIa on 4 occasions (total knee arthroplasty, wound revision, and twice straightening of a 90° contracture of the knee under general anaesthesia). A preoperative pharmacokinetic evaluation was performed, and the clearance was used to calculate the maintenance dose, aiming at a FVII level of 10 U/ml, which proved to be a hemostatic level. The first patient had no change in the clearance during the two treatment episodes. He suffered from repeated thrombophlebitis at the infusion site. The second patient had a progressive decrease of the clearance from 86.4 to 24.7 ml/h/kg. He received during the first treatment a parallel infusion with heparin (≈250 U/24 h) to the same venous access and did not develop thrombophlebitis during 3.5 days of therapy. For the second episode low molecular weight heparin was added directly to the infusion bag, and no adverse effects were observed. Continuous infusion with rFVIIa is thus feasible with the minipumps used by us, eliminates the need for 2 h injections and reduces the total dose of rFVIIa by 50–75%, depending on the behaviour of the clearance.

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Fate of [125I]insulin removed from the peritubular circulation of isolated perfused rat kidney

AJP Renal Physiology ◽

10.1152/ajprenal.1982.243.2.f126 ◽

1982 ◽

Vol 243 (2) ◽

pp. F126-F132 ◽

Cited By ~ 2

Author(s):

J. Petersen ◽

J. Kitaji ◽

W. C. Duckworth ◽

R. Rabkin

Keyword(s):

Molecular Weight ◽

Rat Kidney ◽

Low Molecular Weight ◽

Considerable Evidence ◽

Isolated Perfused Rat Kidney ◽

Mammalian Kidney ◽

Perfused Rat Kidney ◽

Specific Receptors ◽

A Minor ◽

Isolated Kidneys

Although there is considerable evidence that insulin is removed from the peritubular circulation of the mammalian kidney, it is unclear whether binding to insulin-specific receptors is involved in this process, whether after peritubular removal the hormone is degraded to small fragments with release into the circulation, or whether it merely undergoes a minor modification with loss of immunoreactivity. We examined the metabolism of [125I]insulin removed from the peritubular circulation of the nonfiltering isolated perfused rat kidney and compared it to that of [125I]insulin metabolized by filtering isolated kidneys and kidney homogenates. The results indicate that after peritubular removal, a small amount of insulin is degraded to form low-molecular-weight products similar to those seen with filtering kidneys and kidney homogenates. However, most of the insulin removed from the peritubular circulation is processed either to nonimmunoreactive products of molecular weight similar to that of insulin or, to a lesser extent, to products of larger molecular weight. Both these products are also formed by filtering kidneys. In the filtering kidney, the products having molecular weight similar to that of insulin probably originate from the peritubular process, because it is unlikely that material of this size could be derived from the filtration-absorption pathway. Of particular note was the finding that [125I]insulin trapped in the peritubular compartment of nonfiltering kidneys was displaced severalfold more effectively by unlabeled insulin than by several peptide hormones (P less than 0.01); the latter were no more effective than vehicle alone. The findings suggest the presence of peritubular insulin-specific receptors.

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Comparison of the Effects of Different Low Molecular Weight Heparins on the Hemostatic System Activation In Vivo in Man

Thrombosis and Haemostasis ◽

10.1055/s-0038-1657645 ◽

1997 ◽

Vol 78 (02) ◽

pp. 876-879 ◽

Cited By ~ 8

Author(s):

Michael Wolzt ◽

Michaela Eder ◽

Ansgar Weltermann ◽

Jesusa Entlicher ◽

Hans-Georg Eichler ◽

...

Keyword(s):

Molecular Weight ◽

Venous Blood ◽

Plasma Concentrations ◽

Low Molecular Weight ◽

Double Blind ◽

Shed Blood ◽

Hemostatic System ◽

Activated State ◽

A Minor

SummaryIn a double-blind, randomized, cross-over study the effects of single subcutaneous doses of 120 anti-Xa units/kg body wt. of three different low molecular weight heparin (LMWH) preparations were investigated in 15 healthy subjects by determination of thrombin-antithrombin El complex (TAT), prothrombin fragment 1.2 (fl.2), and β-thromboglobin (β-TG) in shed blood and in venous blood.Certoparin, dalteparin, and enoxaparin significantly inhibited coagulation activation marker formation in shed blood. The substantial inhibition of TAT and fl.2 formation was slightly more pronounced in response to certoparin. β-TG was decreased following certoparin and enoxaparin, but not following dalteparin. However, no difference between groups was detectable. A small but consistent decrease of fl.2 formation in venous blood was noted for all LMWHs and dalteparin and enoxaparin, but not certoparin, inhibited TAT formation. Only a minor impact of the three LMWH preparations was noted on β-TG plasma concentrations.Our data indicate that the studied LMWH preparations have a major impact on blood clotting in the activated state and inhibit in vivothe hemostatic system to a comparable extent.

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Characterization of a platelet membrane protein of low molecular weight associated with platelet activation following binding by monoclonal antibody AG-1

Blood ◽

10.1182/blood.v68.3.743.bloodjournal683743 ◽

1986 ◽

Vol 68 (3) ◽

pp. 743-751

Author(s):

JL Miller ◽

JM Kupinski ◽

KO Hustad

Keyword(s):

Molecular Weight ◽

Monoclonal Antibody ◽

Platelet Aggregation ◽

Human Platelet ◽

Platelet Membrane ◽

Antibody Concentration ◽

Lag Phase ◽

Low Molecular Weight ◽

Glycoprotein Ib ◽

Platelet Surface

With the exception of the major platelet glycoproteins IIb/IIIa and Ib, which function as receptors for fibrinogen and von Willebrand factor, little is presently known regarding the possible role of other platelet surface proteins in mediating platelet aggregation. We report the production of a murine monoclonal antibody (AG-1) recognizing human platelet membrane surface protein of relatively low molecular weight (mol wt) that may be involved in this process. AG-1 added to human platelet-rich plasma induces dense granule secretion and aggregation, with lag phase and maximal extent of aggregation dependent on antibody concentration. Aggregation induced by AG-1 is inhibited by AG-1 Fab fragments, indicating that the response is not Fc receptor-mediated. Although AG-1 continues to produce platelet shape change in the presence of EDTA, aggregation is fully inhibited and appears to be mediated by fibrinogen binding to glycoproteins IIb/IIIa. AG-1 is a potent stimulus of thromboxane formation, but full inhibition of thromboxane production by 30 mumol/L indomethacin does not significantly inhibit platelet aggregation induced by 25 micrograms/mL AG-1, indicating that aggregation induced by AG-1 may proceed by way of an endoperoxide-independent pathway. Quantitation of AG-1 Fab binding to platelets reveals approximately 65,000 binding sites per platelet. When intact platelets are radioiodinated, immunoprecipitation of NP-40 lysates by AG-1 reveals an intensely labeled protein with an apparent mol wt of approximately 21,000 daltons, and several additional bands in the mol wt range of 22,000 to 28,000 daltons, all sharing the AG-1 epitope. These bands appear to be distinct from glycoprotein IX or from the beta-chains of glycoprotein Ib or IIb. Finally, studies with platelets labeled by the periodate-[3H]borohydride procedure suggest the possibility of complex formation between subpopulations of glycoprotein Ib and the low-mol-wt glycoproteins recognized by AG-1.

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Distribution of the head-activating substance in hydra and its localization in membranous particles in nerve cells

Development ◽

10.1242/dev.29.1.39 ◽

1973 ◽

Vol 29 (1) ◽

pp. 39-52

Author(s):

H. Schaller ◽

A. Gierer

Keyword(s):

Molecular Weight ◽

Specific Activity ◽

Nerve Cells ◽

Low Molecular Weight ◽

Basal Region ◽

Bud Formation ◽

Minor Portion ◽

A Minor ◽

Bud Initiation ◽

Head Regeneration

The low-molecular-weight substance activating head and bud formation in hydra is shown to occur in the animal as a gradient decreasing from the hypostomal to the basal region. The concentration of head-activating substance increases during head regeneration and during bud initiation. Most of the low-molecular-weight head-activating substance is present in the animal in a structure-bound form. More than 90% was sedimentable; 70% was recovered in a highly purified fraction consisting of membranous particles of ∼ 1200 Å diameter. This implies that in the animal only a minor portion of the total activating activity is freely diffusible, i.e. present in the low-molecular-weight form. The head-activating substance is mainly produced by and/or stored in nerve cells or a subgroup of the nerve cells. Nerve cells were enriched tenfold in a fraction containing most of the head-activating substance in a more than 10 times higher specific activity than in the animal. In addition, it is shown that only the nerve cells are positively correlated with the distribution of head-activating activity both with regard to localization within the animal as to time sequence of appearance during head regeneration and bud formation.

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Characterization of a platelet membrane protein of low molecular weight associated with platelet activation following binding by monoclonal antibody AG-1

Blood ◽

10.1182/blood.v68.3.743.743 ◽

1986 ◽

Vol 68 (3) ◽

pp. 743-751 ◽

Cited By ~ 36

Author(s):

JL Miller ◽

JM Kupinski ◽

KO Hustad

Keyword(s):

Molecular Weight ◽

Monoclonal Antibody ◽

Platelet Aggregation ◽

Human Platelet ◽

Platelet Membrane ◽

Antibody Concentration ◽

Lag Phase ◽

Low Molecular Weight ◽

Glycoprotein Ib ◽

Platelet Surface

Abstract With the exception of the major platelet glycoproteins IIb/IIIa and Ib, which function as receptors for fibrinogen and von Willebrand factor, little is presently known regarding the possible role of other platelet surface proteins in mediating platelet aggregation. We report the production of a murine monoclonal antibody (AG-1) recognizing human platelet membrane surface protein of relatively low molecular weight (mol wt) that may be involved in this process. AG-1 added to human platelet-rich plasma induces dense granule secretion and aggregation, with lag phase and maximal extent of aggregation dependent on antibody concentration. Aggregation induced by AG-1 is inhibited by AG-1 Fab fragments, indicating that the response is not Fc receptor-mediated. Although AG-1 continues to produce platelet shape change in the presence of EDTA, aggregation is fully inhibited and appears to be mediated by fibrinogen binding to glycoproteins IIb/IIIa. AG-1 is a potent stimulus of thromboxane formation, but full inhibition of thromboxane production by 30 mumol/L indomethacin does not significantly inhibit platelet aggregation induced by 25 micrograms/mL AG-1, indicating that aggregation induced by AG-1 may proceed by way of an endoperoxide-independent pathway. Quantitation of AG-1 Fab binding to platelets reveals approximately 65,000 binding sites per platelet. When intact platelets are radioiodinated, immunoprecipitation of NP-40 lysates by AG-1 reveals an intensely labeled protein with an apparent mol wt of approximately 21,000 daltons, and several additional bands in the mol wt range of 22,000 to 28,000 daltons, all sharing the AG-1 epitope. These bands appear to be distinct from glycoprotein IX or from the beta-chains of glycoprotein Ib or IIb. Finally, studies with platelets labeled by the periodate-[3H]borohydride procedure suggest the possibility of complex formation between subpopulations of glycoprotein Ib and the low-mol-wt glycoproteins recognized by AG-1.

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A high-performance oil-free backing pump for electron microscopes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100107691 ◽

1978 ◽

Vol 36 (1) ◽

pp. 110-111

Author(s):

G.K.W. Balkau ◽

E. Bez ◽

J.L. Farrant

Keyword(s):

Molecular Weight ◽

Electron Microscope ◽

Hot Spots ◽

High Performance ◽

Carbonaceous Material ◽

Contamination Rate ◽

Low Molecular Weight ◽

Principal Source ◽

Rotary Pumps ◽

Electron Microscopes

The earliest account of the contamination of electron microscope specimens by the deposition of carbonaceous material during electron irradiation was published in 1947 by Watson who was then working in Canada. It was soon established that this carbonaceous material is formed from organic vapours, and it is now recognized that the principal source is the oil-sealed rotary pumps which provide the backing vacuum. It has been shown that the organic vapours consist of low molecular weight fragments of oil molecules which have been degraded at hot spots produced by friction between the vanes and the surfaces on which they slide. As satisfactory oil-free pumps are unavailable, it is standard electron microscope practice to reduce the partial pressure of organic vapours in the microscope in the vicinity of the specimen by using liquid-nitrogen cooled anti-contamination devices. Traps of this type are sufficient to reduce the contamination rate to about 0.1 Å per min, which is tolerable for many investigations.

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