Species differences in the kinetics of the renin-substrate reaction in plasma

Indirect micromethods were designed for the assay of human renin (lower limit 0.25 times 10-4 U and of antirenin to human renin (lower limit 3 times 10-4 U), with the rat used for the bioassay of the angiotensin produced by the action of renin on renin substrate. This made possible the assay of unusually small amounts (0.01 mu1) of serum for antirenin. The Michaelis-Menten concept of a dissociating complex can be applied to the antireninrenin reaction: the rate constants for the formation and for the breakdown of the complex were k1 equal to 1.65 (ml/U antirenin per min) and k3 equal to 1.97 times 10-3 (U inactivated renin/U antirenin per min), respectively; the apparent Michaelis constant was 12 times 10-4 (U renin/ml). A second method of analysis was also applied by assuming the formation of a rather tight complex, with antirenin functioning as an irreversible inactivator of renin. Both methods of analysis yielded practically the same rate constant (k1 equal to 1.65 and k1 equal to 1.71), but the treatment according to the Michaelis-Menten equation affords a slightly better fit of the experimental data (accuracy equal to plus or minus 15.5 percent) than the second method of calculation (accuracy equal to plus or minus 21.6 percent).

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Placental transport function

Reproduction Fertility and Development ◽

10.1071/rd9910345 ◽

1991 ◽

Vol 3 (4) ◽

pp. 345 ◽

Cited By ~ 25

Author(s):

H Schneider

Keyword(s):

Blood Flow ◽

Species Differences ◽

Transport Function ◽

Concentration Difference ◽

Flow Rates ◽

Placental Transport ◽

Carrier Mediated Transport ◽

Net Flux ◽

Kinetics Of ◽

Carrier Systems

Placental transport provides a means of supplying nutrients to and removing metabolites from the fetus. Transport is based on substrate exchange and net flux from mother to fetus or vice versa and can be a result of a concentration difference or of unidirectional carrier-mediated transport. Blood flow regulates delivery to and removal from the area of placental exchange, and rapidly crossing compounds are dependent on blood flow for their rate of passage. There are substantial species differences in terms of flow rates normalized for fetal weight and also in terms of vascular arrangement. The barrier can be overcome via paracellular water-filled channels or via a transcellular route. Hydrophilic molecules that are not actively transported diffuse through paracellular channels, and the placentae of rodents and primates are much more permeable than the placenta of the sheep. Many different substrates such as glucose, amino acids, electrolytes and vitamins are transported by carrier systems. Transport proteins are located in the microvillous and basal membranes of the trophoblast. Asymmetry in the kinetics of binding results in differences in influx and efflux at the interface with maternal and fetal blood, allowing directional net flux across the placenta. Immunoglobulins are believed to cross by receptor-mediated endocytosis.

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Some observations on the reactions of two annelid haemoglobins with oxygen and with carbon monoxide

Proceedings of the Royal Society of London Series B Biological Sciences ◽

10.1098/rspb.1955.0015 ◽

1955 ◽

Vol 143 (912) ◽

pp. 334-342 ◽

Cited By ~ 13

Keyword(s):

Carbon Monoxide ◽

Detailed Analysis ◽

Species Differences ◽

Intermediate Compound ◽

Recent Developments ◽

Kinetics Of

Recent developments in apparatus for the measurement of the rates of rapid reactions have made it possible to work with much smaller quantities of reactants than has previously been the case and have allowed the extension of work on the kinetics of mammalian haemoglobin to the haemoglobins of other species. In this paper the reactions of haemoglobin from the earthworm and lugworm with oxygen and carbon monoxide are described, and the results discussed in terms of the intermediate compound theory of Adair. The actual rates of reaction are of the same order as those for mammalian haemoglobin, but more detailed analysis shows appreciable species differences in the course of the reactions. These differences are probably attributable to variation in the arrangement of haem groups within the molecule.

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KINETICS OF THE REACTION OF RENIN WITH NINE SYNTHETIC PEPTIDE SUBSTRATES

Journal of Experimental Medicine ◽

10.1084/jem.128.1.13 ◽

1968 ◽

Vol 128 (1) ◽

pp. 13-34 ◽

Cited By ~ 115

Author(s):

Leonard T. Skeggs ◽

Kenneth E. Lentz ◽

Joseph R. Kahn ◽

Harry Hochstrasser

Keyword(s):

Synthetic Peptide ◽

Complete Loss ◽

Moderate Increase ◽

Substrate Molecule ◽

Renin Substrate ◽

Peptide Substrates ◽

Chemical Assay ◽

Michaelis Constants ◽

Kinetics Of

A number of peptides have been synthesized which represent portions of the tetradecapeptide renin substrate molecule, and which contain the hydrolyzable leu-leu bond. An automatic chemical method for determination of the velocity of the reaction of renin with these compounds was developed. Application of the method at several levels of substrate concentration permitted construction of Lineweaver-Burk plots, and calculation of Michaelis constants (Km) and maximal velocities (Vmax). The results show that the maximum affinity of the enzyme (lowest Km) for substrate is achieved only with the full tetradecapeptide molecule (asp1-arg2-val3-tyr4-ileu5-his6-pro7-phe8-his9-leu10-leu11-val12-tyr13-ser14). Removal of asp1 and arg2 from the N-terminal increases the Km eight-fold. Further, moderate increase in Km occurs when the next amino acids, val3, tyr4 and ileu5, are removed. The further removal of his6 results in a marked reduction in the Vmax. Removal of ser14 from the C-terminal of the nonapeptide his6-pro7-phe8-his9-leu10-leu11-val12-tyr13-ser14 does not greatly affect the Km nor the Vmax. Further removal of tyr13 from this compound results in complete loss of substrate activity. It is suggested that the compounds his6-pro7-phe8-his9-leu10-leu11-val12-tyr13-ser14 or his6-pro7-phe8-his9-leu10-leu11-val12-tyr13 might be used as substrates for the chemical assay and standardization of renin.

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Factors affecting species differences in the kinetics of metabolites of trichloroethylene

Journal of Toxicology and Environmental Health ◽

10.1080/15287399509531972 ◽

1995 ◽

Vol 44 (4) ◽

pp. 435-447 ◽

Cited By ~ 31

Author(s):

M. V. Templin ◽

D. K. Stevens ◽

R. D. Stenner ◽

P. L. Bonate ◽

D. Turnan ◽

...

Keyword(s):

Species Differences ◽

Factors Affecting ◽

Kinetics Of

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Kinetics of the renin-substrate reaction employing a synthetic substrate

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1966.210.3.595 ◽

1966 ◽

Vol 210 (3) ◽

pp. 595-598 ◽

Cited By ~ 10

Author(s):

D Montague ◽

B Riniker ◽

F Gross

Keyword(s):

Renin Substrate ◽

Synthetic Substrate ◽

Kinetics Of

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Single-cell RNA sequencing of human, macaque, and mouse testes uncovers conserved and divergent features of mammalian spermatogenesis

10.1101/2020.03.17.994509 ◽

2020 ◽

Cited By ~ 2

Author(s):

Adrienne Niederriter Shami ◽

Xianing Zheng ◽

Sarah K. Munyoki ◽

Qianyi Ma ◽

Gabriel L. Manske ◽

...

Keyword(s):

Germ Cell ◽

Single Cell ◽

Rna Sequencing ◽

Species Differences ◽

Cell Types ◽

Rna Turnover ◽

Differentiation Potential ◽

Single Cell Rna Sequencing ◽

Kinetics Of

SummarySpermatogenesis is a highly regulated process that produces sperm to transmit genetic information to the next generation. Although extensively studied in mice, our current understanding of primate spermatogenesis is limited to populations defined by state-specific markers defined from rodent data. As between-species differences have been reported in the process duration and cellular differentiation hierarchy, it remains unclear how molecular markers and cell states are conserved or have diverged from mice to man. To address this challenge, we employ single-cell RNA-sequencing to identify transcriptional signatures of major germ and somatic cell-types of the testes in human, macaque and mice. This approach reveals differences in expression throughout spermatogenesis, including the stem/progenitor pool of spermatogonia, classical markers of differentiation, potential regulators of meiosis, the kinetics of RNA turnover during spermatid differentiation, and germ cell-soma communication. These datasets provide a rich foundation for future targeted mechanistic studies of primate germ cell development and in vitro gametogenesis.

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Soot-Ozone Reaction Kinetics: Spectroscopic and Gravimetric Studies

Applied Spectroscopy ◽

10.1366/0003702884429779 ◽

1988 ◽

Vol 42 (8) ◽

pp. 1473-1482 ◽

Cited By ~ 34

Author(s):

D. M. Smith ◽

W. F. Welch ◽

J. A. Jassim ◽

A. R. Chughtai ◽

D. H. Stedman

Keyword(s):

Species Differences ◽

Initial Rate ◽

Flow Conditions ◽

Concentration Data ◽

First Order ◽

Second Stage ◽

Elovich Equation ◽

Static Conditions ◽

Kinetics Of ◽

Equivalent Conditions

Studies on the kinetics of soot-O3 reactions, at various soot and ozone concentrations, have been conducted under flow conditions with ozone ranging from 50 to 15,000 ppm and soot from 2 to 350 mg. At lower concentrations, the initial rates of CO2 and CO formation are found to be half order with respect to soot and first order with respect to ozone. At higher concentrations, CO2 formation exhibits a more complex pattern. The initial rate for the formation of CO2 for a first stage is half order with respect to soot and 1.5 order with respect to O3, while the second stage is zero order in both species. Differences between data at higher and lower concentrations are discussed, and mechanisms for the formation of CO2 CO, and carboxylics during ozonation are suggested. Mass balance calculations on low concentration data reveal that only a small portion of the ozone is used to produce CO2, CO, H2O, and carboxylic species, most of it being decomposed catalytically over soot. At higher concentrations of O3 the rate of formation of carboxylic functionalities during the hexane soot-ozone reaction under static conditions has been examined. The initial rate, as determined by the Elovich equation, suggests that the soot-ozone reaction is nearly 6 times faster under equivalent conditions than the sool-NO2/N2O4 reaction reported earlier from this laboratory.

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