Kinetics of Homologous Urea-soluble 131I-Fibrin and 125I-Fibrinogen in Rabbits

1975 ◽  
Author(s):  
G. Müller-Berghaus ◽  
I. Mahn ◽  
G. Kövecker
Keyword(s):  
Exponential Decay ◽  
Distribution Volume ◽  
Fibrinolytic System ◽  
Experimental Conditions ◽  
Soluble Fibrin ◽  
Kinetics Of ◽  
Deutsche Forschungsgemeinschaft

In order to study the in vivo behaviour of soluble fibrin, purified rabbit 13I-fibrinogen was clotted in the presence of EDTA (0.005 M) and aprotinin (100 units/ml), the generated clot dissolved in buffered urea (3.0 M, pH 7.4), and the formed ureasoluble 131I-fibrin injected into rabbits. The behaviour of homologous 125I-fibrinogen was simultaneously studied in the same animals. Results: The distribution volume of 131I-fibrin (44 ml/kg) as well as that of 125I-fibrinogen (45 ml/kf) was nearly identical indicating that the injected soluble fibrin was homogenously distributed in the circulation immediately after injection. The elimination of soluble fibrin from the circulating blood did not represent a monophasic exponential decay. 84% (range: 77–94%) of the injected soluble fibrin disappeared from the circulation during the first 24 hours after injection, whereas only 54% (range: 41–72%) of the injected fibrinogen disappeared during that interval. Under these experimental conditions, the T/2 of fibrinogen was 46 hours. The clearance of urea-soluble fibrin did not influence the kinetics of 13I-fibrinogen. The disappearance of soluble fibrin could not be influenced by treating the animals with aprotinin for fibrinolysis inhibition. The experiments demonstrate that soluble fibrin can be traced in the circulation and cleared from the blood by a mechanism independent of the fibrinolytic system.(Supported by the Deutsche Forschungsgemeinschaft, Bad Godesberg, Germany.)

Different mechanisms in the attachment of cells to native and denatured collagen

1979 ◽  
Vol 38 (1) ◽  
pp. 267-281
Author(s):  
S.L. Schor ◽  
J. Court
Keyword(s):  
Cell Attachment ◽  
Experimental Conditions ◽  
Cell Matrix ◽  
Matrix Interactions ◽  
Independent Mechanism ◽  
Cell Matrix Interactions ◽  
Serum Dependent ◽  
Kinetics Of ◽  
Dependent Mechanism

The attachment of cells to collagen has been reported previously to require the presence of serum and the particular serum protein involved in this process, variously known as CIG, CAP or fibronectin, has been isolated. This conclusion that cell attachment to collagen requires serum (or more precisely, fibronectin) is based on experiments measuring the kinetics of cell attachment to films of collagen. We have measured the kinetics of attachment of HeLa and attachment to films of collagen-containing substrata under a variety of experimental conditions and present evidence that the serum-dependent mechanism of cell attachment described by others is actually only the case for films of denatured collagen, while cell attachment to native collagen fibres occurs by a different, serum-independent, mechanism. The possible relevance of these findings to cell-matrix interactions in vivo is discussed.

Extracellular ATP regulates transcervical permeability by modulating two distinct paracellular pathways

1997 ◽  
Vol 272 (5) ◽  
pp. C1602-C1610 ◽  
Author(s):  
G. I. Gorodeski ◽  
J. Goldfarb
Keyword(s):  
Phase I ◽  
Phase Ii ◽  
Extracellular Atp ◽  
Acetoxymethyl Ester ◽  
Experimental Conditions ◽  
Mucus Production ◽  
Atp Regulation ◽  
Junctional Resistance ◽  
Kinetics Of

Extracellular ATP stimulates a biphasic change in transepithelial electrical resistance (RTE) across cultures of human cervical epithelial cells: an acute decrease (phase I), followed by a delayed increase in resistance (phase II). The objective of this study was to determine the contributions of changes in the lateral intercellular space resistance (RLIS) and the tight junctional resistance (RTJ) to the changes in RTE. Phase I and phase II effects were uncoupled by treatment with 1,2-bis(2-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid (BAPTA)-acetoxymethyl ester, which blocks the ATP-induced increases in cytosolic Ca2+ and abolishes phase I. BAPTA-loaded cells differed from control cells in that 1) phase I began when ATP was added, in contrast to a delay of 1.5-3.5 min in phase II, 2) phase I decreases in RLIS followed a simple exponential pattern, in contrast to the complex kinetics of phase II, and 3) the magnitude of phase II varied between 20 and 100% for increases of RTJ in day 2-6 cultures; the phase I decrease of 50% in RLIS was unrelated to different experimental conditions. These results indicate that phase I and phase II are induced simultaneously and independently by ATP, and they contribute to the total changes in RTE. We conclude that ATP regulation of RLIS and RTJ may be important mechanisms of modulating cervical mucus production in vivo.

scholarly journals Kinetics of Enzymatic Mercury Methylation at Nanomolar Concentrations Catalyzed by HgcAB

2019 ◽  
Vol 85 (13) ◽  
Author(s):  
Swapneeta S. Date ◽  
Jerry M. Parks ◽  
Katherine W. Rush ◽  
Judy D. Wall ◽  
Stephen W. Ragsdale ◽  
...  
Keyword(s):  
Developmental Disorders ◽  
Anaerobic Bacteria ◽  
Significant Risk ◽  
Health Concern ◽  
Global Public Health ◽  
Microbial Conversion ◽  
Experimental Conditions ◽  
Cell Lysates ◽  
Kinetics Of

ABSTRACTMethylmercury (MeHg) is a potent bioaccumulative neurotoxin that is produced by certain anaerobic bacteria and archaea. Mercury (Hg) methylation has been linked to the gene pairhgcAB, which encodes a membrane-associated corrinoid protein and a ferredoxin. Although microbial Hg methylation has been characterizedin vivo, the cellular biochemistry and the specific roles of the gene products HgcA and HgcB in Hg methylation are not well understood. Here, we report the kinetics of Hg methylation in cell lysates ofDesulfovibrio desulfuricansND132 at nanomolar Hg concentrations. The enzymatic Hg methylation mediated by HgcAB is highly oxygen sensitive, irreversible, and follows Michaelis-Menten kinetics, with an apparentKmof 3.2 nM andVmaxof 19.7 fmol · min−1· mg−1total protein for the substrate Hg(II). Although the abundance of HgcAB in the cell lysates is extremely low, Hg(II) was quantitatively converted to MeHg at subnanomolar substrate concentrations. Interestingly, increasing thiol/Hg(II) ratios did not impact Hg methylation rates, which suggests that HgcAB-mediated Hg methylation effectively competes with cellular thiols for Hg(II), consistent with the low apparentKm. Supplementation of 5-methyltetrahydrofolate or pyruvate did not enhance MeHg production, while both ATP and a nonhydrolyzable ATP analog decreased Hg methylation rates in cell lysates under the experimental conditions. These studies provide insights into the biomolecular processes associated with Hg methylation in anaerobic bacteria.IMPORTANCEThe concentration of Hg in the biosphere has increased dramatically over the last century as a result of industrial activities. The microbial conversion of inorganic Hg to MeHg is a global public health concern due to bioaccumulation and biomagnification of MeHg in food webs. Exposure to neurotoxic MeHg through the consumption of fish represents a significant risk to human health and can result in neuropathies and developmental disorders. Anaerobic microbial communities in sediments and periphyton biofilms have been identified as sources of MeHg in aquatic systems, but the associated biomolecular mechanisms are not fully understood. In the present study, we investigate the biochemical mechanisms and kinetics of MeHg formation by HgcAB in sulfate-reducing bacteria. These findings advance our understanding of microbial MeHg production and may help inform strategies to limit the formation of MeHg in the environment.

scholarly journals Turnover Studies of Des-A Fibrin and Fibrinogen in Healthy Human Beings

1977 ◽  
Author(s):  
G. Müller-Berghaus ◽  
I. Mahn
Keyword(s):  
Exponential Decay ◽  
Elimination Rate ◽  
Distribution Volume ◽  
Human Beings ◽  
Healthy Human ◽  
Homogenous Distribution ◽  
The Mean ◽  
Deutsche Forschungsgemeinschaft ◽  
Urea Method ◽  
Elimination Curve

Soluble fibrin was injected into man. Two methods were used to prepare soluble des-A fibrin. Purified human 1-125-fibrinogen was transformed into soluble des-A fibrin (des-A FM):(1) by thrombin in the presence of 2.0 M urea (method according to Hogg and Blombäck, 1975), (2) by ancrod. Eight male volunteers were injected either with thrombin-induced soluble I-125-fibrin (FM-T) or ancrod-induced soluble I-125-fibrin (FM-A). The control consisted of I-131-fibrinogen injected simultaneously with soluble I-125-fibrin.The mean distribution volume of des-A FM-T was 48.9 ml/kg and that of des-A FM-A 50.3 ml/kg which is similar to that of the injected fibrinogen (43.0 ml/kg) indicating a homogenous distribution of the injected FM in the circulating blood. The injected des-A FM disappeared faster from the circulating blood than des-AB fibrin monomer. Six hours after injection 99.5% of the injected FM-A and 95% of the injected FM-T were removed from the circulating blood. The FM were cata-bolized since free I-125 were quantitatively recovered from the urine. The elimination curve of des-A FM-A as well as des-A FM-T does not represent a mono-phasic exponential decay.The experiments demonstrate that des-A fibrin can be traced in man and is cleared from the circulating blood at a high elimination rate.(Supported by the Deutsche Forschungsgemeinschaft, Bonn-Bad Godesberg)

scholarly journals Behaviour of Soluble DES-AB Fibrin and Fibrinogen in Man

1977 ◽  
Author(s):  
I. Mahn ◽  
G. Müller-Berghaus
Keyword(s):  
Healthy Volunteers ◽  
Exponential Decay ◽  
Distribution Volume ◽  
Homogeneous Distribution ◽  
Initial Value ◽  
Soluble Fibrin ◽  
Exponential Curve ◽  
Long Period ◽  
The Mean ◽  
Elimination Curve

Human des-AB fibrin was generated from I-131-fibrinogen by clotting with thrombin in the presence of EDTA and aprotinin, and solubilized in buffered urea. About 1 to 2 mg of fibrin was injected simultaneously with I-125-fibrinogen dissolved in buffered urea into 14 male healthy volunteers.The mean distribution volume of the soluble fibrin was 48.5 ml/kg in comparison to 46.1 ml/kg of the injected fibrinogen demonstrating a homogeneous distribution of both the labelled proteins in the circulating blood. The elimination characteristics of the soluble fibrin did not represent a monophasic exponential decay. 24 hours after injection a mean of 24.3 % of the initial value of the fibrin was traced in the blood in comparison to a mean of 53.3 % of the fibrinogen at that time. The terminal slope of the fibrin elimination curve between 2 and 8 days after injection was a monophasic exponential curve with a mean T 1/2 of 2.3 days. The fibrinogen elimination curve showed a T 1/2 of 4.2 days during that period of time.These experiments indicate that solubilized fibrin injected into man can be traced in the circulating blood for a long period of time. The catabolic behaviour of fibrin differs significantly from that of fibrinogen.

scholarly journals Contraction kinetics of intact and skinned frog muscle fibers and degree of activation. Effects of intracellular Ca2+ on unloaded shortening.

1985 ◽  
Vol 86 (4) ◽  
pp. 479-500 ◽  
Author(s):  
J Gulati ◽  
A Babu
Keyword(s):  
Experimental Conditions ◽  
Bathing Medium ◽  
Internal Load ◽  
Skinned Fiber ◽  
Fiber Properties ◽  
Partial Activation ◽  
A Minor ◽  
Kinetics Of ◽  
Speed Of Shortening

This study addresses a long-standing controversy on the effects of the degree of activation on cross-bridge kinetics in vivo, by utilizing isolated intact and skinned fiber preparations. Steady force levels ranging from 0.1 to 0.76 P0 were achieved at 0 degrees C with temperature-step stimulation of intact fibers by varying the amount of caffeine in the bathing medium. The speed of unloaded shortening (by slack test) was found to be practically constant, which suggests that intracellular Ca2+ in the intact preparation has relatively little effect on isotonic shortening. Along with the results on tetanically stimulated fibers (force, P0), we observed a minor but significant trend for the speed to decline with lowered force levels. This trend is explained by the presence of a constant internal load equaling approximately 1% P0. The effect of Ca2+ on the shortening behavior of skinned fibers was examined at 0 and 10 degrees C. At 0 degrees C, there was practically no effect of Ca2+ on the shortening response in slack tests. At 10 degrees C, there was also no Ca2+ effect during the first activation cycle, but in subsequent cycles the speed of shortening was reduced during partial activation, which indicates that there were permanent changes in the fiber properties under these experimental conditions. The latter result could be explained if the internal load had increased to approximately 5% P0 in the modified skinned fiber (compared with 1% P0 in intact fiber). These findings show that isotonic contraction of frog fibers is intrinsically unaffected by the variations in intracellular Ca2+ that modulated the force over a nearly complete range. The results provide support for the idea that Ca2+ influences the force development in vivo by on-off switching mechanisms.

The Structure of Soluble Fibrin Complexes and Fdp After Defibrination by Echis Carinatus Bite

1979 ◽  
Author(s):  
W. Edgar ◽  
M.J. Warrell ◽  
P.A. Warrell ◽  
C.R.M. Prentice
Keyword(s):  
Factor Xiii ◽  
Degradation Products ◽  
Fibrinolytic System ◽  
Fibrinopeptide A ◽  
Soluble Fibrin ◽  
Echis Carinatus ◽  
Secondary Activation ◽  
D Dimer ◽  
Soluble Complexes

Studies on fibrinogen, fibrinogen-fibrin soluble complexes and FDP were made on eleven patients in Nigeria who had defibrination following Echis carinatus bite. On admission, before treatment with antivenom, all patients had non-clotting blood, reduced or zero fibrinogen levels, low factor Xtll levels and increased concentrations of soluble complexes and FDP, The fibrin component of the soluble complexes, separated by fibrinogen-sepharose chromatography, consisted of both intact fibrin and fibrin degraded at the ∞ chain. After isolation by Biogel chromatography the soluble complexes were also found to contain γ dimer chains. The FDP consisted of several X species, Y, D and D-dimer, and fragment E. The major fragment in all patients was D, but a few samples contained significant quantities of D-dimer, indicating in vivo activation of factor XIII. Fibrinopeptide A studies showed degraded fibrinogen, as well as fibrin, in the soluble complexes and degradation products, suggesting that fibrinogenolysis, in addition to fibrinolysis, had occurred, probably as a result of secondary activation of the fibrinolytic system in response to defibrination.

Absorption of Galactose by the Rat Small Intestine in Vivo: Proximal—Distal Kinetic Gradients and a New Method to Express Absorption Per Enterocyte

1976 ◽  
Vol 50 (6) ◽  
pp. 499-509 ◽  
Author(s):  
R. M. Batt ◽  
T. J. Peters
Keyword(s):  
Small Intestine ◽  
Absorptive Capacity ◽  
Proximal Jejunum ◽  
Rat Small Intestine ◽  
Experimental Conditions ◽  
Carrier Mediated Transport ◽  
Saturation Kinetics ◽  
Kinetics Of ◽  
Diffusive Component

1. The absorption in vivo of d-galactose by the rat small intestine has been examined in proximal jejunum and distal ileum by use of a recirculation—perfusion technique. 2. Multiple sequential perfusions over 4 h produced no subsequent functional or morphological damage in the perfused segments. 3. Absorption of galactose from 8 and 64 mmol/l solutions was found to be independent of flow rate over the range 1·0–6·5 ml/min. 4. Galactose absorption in both the jejunum and the ileum exhibited saturation kinetics of the Michaelis—Menten type, and phlorrhizin sensitivity. Sorbose was only absorbed minimally. These observations demonstrate that galactose is absorbed by carrier-mediated transport and that there is no significant passive diffusive component in vivo. 5. Under the stated experimental conditions, the maximum absorptive capacity was 4·5 times greater in the jejunum than in the ileum. The Michaelis constant for galactose was higher in the jejunum than in the ileum. 6. Enterocytes were isolated from perfused segments and quantified by DNA assay with a correction for yield. In this manner, the absorptive capacity per enterocyte was calculated. 7. The maximum absorptive capacity per enterocyte was 3·5 times greater in the jejunum than in the ileum.

scholarly journals Kinetics of enzymatic mercury methylation at nanomolar concentrations catalyzed by HgcAB

2019 ◽  
Author(s):  
Swapneeta S. Date ◽  
Jerry M. Parks ◽  
Katherine W. Rush ◽  
Judy D. Wall ◽  
Stephen W. Ragsdale ◽  
...  
Keyword(s):  
Anaerobic Bacteria ◽  
Desulfovibrio Desulfuricans ◽  
Experimental Conditions ◽  
Cell Lysates ◽  
Oxygen Sensitive ◽  
Kinetics Of ◽  
Substrate Concentrations ◽  
Insight Into

ABSTRACTMethylmercury (MeHg) is a potent neurotoxin that bioaccumulates in fish. MeHg is generated by anaerobic bacteria and archaea possessing the gene pair hgcAB. Although bacterial mercury (Hg) methylation has been characterized in vivo, the specific role of HgcAB in catalyzing Hg methylation is not well understood. Here we report the kinetics of HgcAB-mediated Hg methylation in cell lysates of Desulfovibrio desulfuricans ND132 at nanomolar Hg concentrations. The enzymatic Hg methylation mediated by HgcAB is highly oxygen-sensitive, irreversible, and follows Michaelis-Menten kinetics with an apparent KM of 3.2 nM and Vmax of 19.7 fmol·min-1·mg-1 total protein for the substrate Hg(II). Although the abundance of HgcAB in the cell lysates is extremely low, Hg(II) was quantitatively converted to MeHg at subnanomolar substrate concentrations. Supplementation with ATP, methyltetrahydrofolate, or pyruvate did not enhance MeHg production under the experimental conditions. Insight into the kinetics of Hg methylation catalyzed by HgcAB advances our understanding of the complex global Hg cycle.

scholarly journals Kinetic Studies of Soluble Fibrin Complexes in Vivo

1977 ◽  
Author(s):  
F. Schönbach ◽  
I. Mahn ◽  
G. Müller-Berghaus
Keyword(s):  
Kinetic Studies ◽  
Distribution Volume ◽  
Control Group ◽  
Coagulation Disorders ◽  
Soluble Fibrin ◽  
Group A ◽  
The Mean ◽  
Group B

Soluble fibrin complexes may occur in vivo in a variety of coagulation disorders. The aim of this investigation was to elucidate the in vivo behaviour of fibrin-fibrinogen complexes prepared in vitro in a ratio of 1 part fibrin to 20 parts fibrinogen. 12 rabbits (group A) were injected with soluble fibrin complexes containing homologeous I-131-fibrin and I-125-fibrinogen. Another group of 12 rabbits served as control (group B) and received I-131-fibrin solubilized in urea and I-125-fibrinogen separately from each other. Studies were performed over a period of 6 days.The mean distribution volume of fibrin as well as of fibrinogen did not significantly differ between both groups. The elimination characteristics of I-131-fibrin of the soluble fibrin complexes (group A) as well as of the solubilized fibrin (group B) were similiar. The fibrinogen elimination did not differ significantly between the groups: a mean T 1/2 of 47.8 h in group A and a T 1/2 of 46.7 h in group B was calculated.The experiments demonstrate that non-crosslinked soluble fibrin complexes distribute homogeneously in the circulation and dissociate into its subunits. Fibrin is eliminated from the circulating blood without influencing the normal catabolism of fibrinogen.

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