scholarly journals THE EFFECT OF ENZYME INHIBITORS ON THE RESTING POTENTIAL AND ON THE ION DISTRIBUTION OF THE SARTORIUS MUSCLE OF THE FROG

1958 ◽  
Vol 41 (5) ◽  
pp. 879-900 ◽  
Author(s):  
William G. Van der Kloot
Keyword(s):  
Enzyme Inhibitors ◽  
External Medium ◽  
Resting Potential ◽  
Sartorius Muscle ◽  
Ion Distribution ◽  
Choline Acetylase ◽  
The Mean ◽  
High Concentrations ◽  
Sodium Extrusion

Isolated frog sartorii were exposed for 30 minutes to HETP—an irreversible anti-cholinesterase, and were then soaked in Ringer's at 15°C. for 16 hours. At the end of the period of soaking the mean resting potential of the muscle fibers was only 29 mv. The decrease in the resting potential of the HETP-treated muscles was accompanied by a loss of potassium and a gain in sodium by the muscles. The effect of anticholinesterases on sodium extrusion was studied by incubating the muscles in a Ringer's containing half of the normal amount of sodium. The muscles respond by extruding sodium against a concentration gradient into the external medium. Sodium extrusion was blocked by prior exposure of the muscle to HETP, and reversibly blocked by exposure to physostigmine. The inhibition of sodium extrusion by physostigmine was correlated with the inhibition of the intracellular cholinesterase. Sodium extrusion was also blocked by high concentrations of 2-methyl-1,4-napthaquinone 8-sulfonic acid and by α-ketoglutarate, which are known to inhibit choline acetylase in vitro. But sodium extrusion was not affected by a third inhibitor of choline acetylase, phenobarbital. Sodium extrusion was unaffected by KCN and partially blocked by IAA. The IAA block was eliminated by the addition of pyruvate. It is concluded that either glycolysis or oxidative metabolism can furnish the energy needed for sodium extrusion.

scholarly journals Identity and Proliferation of Small Lymphocyte Precursors in Cultures of Lymphocyte-rich Fractions of Guinea Pig Bone Marrow

Blood ◽  
1971 ◽  
Vol 37 (1) ◽  
pp. 73-86 ◽  
Author(s):  
Y. YOSHIDA ◽  
D. G. OSMOND
Keyword(s):  
Bone Marrow ◽  
Guinea Pig ◽  
Lymphoid Cells ◽  
Short Term ◽  
Small Lymphocyte ◽  
Undifferentiated Cells ◽  
The Mean ◽  
High Concentrations ◽  
Transitional Cells

Abstract Radioautography with 3H-thymidine was used to examine the proliferative activity of bone marrow lymphoid cells and to identify the precursor cells of small lymphocytes in short-term cultures of lymphocyte-rich marrow fractions. High concentrations of small lymphocytes (nuclear diameters less than 8.0 µ in smears) together with large lymphoid ("transitional") cells (nuclear diameters greater than 8.0 µ) were separated from suspensions of guinea pig bone marrow by centrifugation in linear sucrose-serum density gradients. When such lymphocyte-rich marrow fractions were cultured in vitro the labeling and mitotic indices following either continuous or terminal exposure to 3H-thymidine indicated that the large lymphoid cells were confined mainly to the pre-DNA-synthetic (G1) and early DNA-synthetic (S) phases at first, but proceeded subsequently through S phase and mitosis. From these data tentative values were derived for the in vitro duration of G1 (12 hours) and S (13.7 hours). Further cultures were followed radioautographically after a 1-hour pulse of 3H-thymidine at 6-7 hours of culture. The absolute numbers of labeled large lymphoid cells declined during the subsequent 21 hours but, simultaneously, labeled small lymphocytes appeared and increased progressively in absolute numbers to 44.4 ± 8.1 per cent of the initial numbers of labeled large lymphoid cells. The mean grain count of labeled small lymphocytes was half that of the initially labeled large lymphoid cells. Very few labeled undifferentiated cells other than large lymphoid cells were observed. The results demonstrate that lymphocyte-rich marrow fractions are capable of sustaining the production of small lymphocytes in short-term cultures and that the immediate precursors of marrow small lymphocytes are contained within a population of large lymphoid cells.

scholarly journals The Inhibitory Effect of Clindamycin onLactobacillus in vitro

2001 ◽  
Vol 9 (4) ◽  
pp. 239-244 ◽  
Author(s):  
Alla Aroutcheva ◽  
Jose A. Simoes ◽  
Susan Shott ◽  
Sebastian Faro
Keyword(s):  
Minimum Inhibitory Concentration ◽  
Inhibitory Concentration ◽  
Inhibitory Effect ◽  
Bacteriostatic Effect ◽  
The Mean ◽  
High Concentrations ◽  
Effect On Growth

Objective:To evaluate thein vitroeffect of varying concentrations of clindamycin onLactobacillusspp.Methods: Concentrations of clindamycin ranging from 1.95–20 000 mg/ml were studied for their effect on the growth of six strains ofLactobacillus.Results:Clindamycin concentrations between 1.95–31.25 mg/ml had no statistically significant effect on growth of lactobacilli (p> 0.05). Concentrations 125 and 250 mg/ml had a bacteriostatic effect. The mean minimum inhibitory concentration (MIC) for studiedLactobacillusstrains was determined as 1000 mg/ml.Conclusion:High concentrations of clindamycin achieved in the vagina by intravaginal application might be inhibitory forLactobacillus.

Control of ovarian follicular growth and maturation by the corpus luteum and the placenta during pregnancy in sheep

Reproduction ◽  
2000 ◽  
pp. 151-158 ◽  
Author(s):  
MA Driancourt ◽  
J Fevre ◽  
J Martal ◽  
KH Al-Gubory
Keyword(s):  
Caesarean Section ◽  
Corpus Luteum ◽  
Late Pregnancy ◽  
Aromatase Activity ◽  
Follicular Growth ◽  
Mating Experiment ◽  
The Mean ◽  
High Concentrations ◽  
Ovarian Follicular Growth

Ovarian follicular growth and maturation and its control throughout pregnancy have not been described fully in sheep. Experiment 1 characterized the size and maturation (steroid production in vitro and aromatase activity) of ovarian follicles obtained at days 20, 50, 80 and 110 of pregnancy compared with those obtained at day 12 of the oestrous cycle. There was no difference in the number of small follicles (< 3 mm in diameter) between cyclic and pregnant ewes, regardless of the stage of pregnancy. There was a marked reduction (P < 0.01) in the number of medium follicles (3-5 mm) starting at day 80 of pregnancy. Large follicles (> 5 mm) were not detected at day 110 of pregnancy. In vitro testosterone output by follicles was constant throughout pregnancy. Oestradiol output remained steady until day 80, but decreased markedly at day 110 of pregnancy. This decrease was associated with a reduction in aromatase activity in follicles obtained at this stage. Experiment 2 examined the effect of administration of high concentrations of progesterone between day 100 and day 120 after mating on resumption of follicular growth in ewes that underwent Caesarean section at day 99 of pregnancy. In ewes that underwent Caesarean section, progesterone supplementation was successful in mimicking the profile found in pregnant ewes, but did not prevent re-initiation of follicular growth, as demonstrated by the presence of large follicles (> 5 mm) at day 120 after mating. Experiment 3 examined the effects of PGF(2alpha)-induced regression of the corpus luteum of day 100 of pregnancy on resumption of follicular growth. High concentrations of PGF(2alpha) (0.28 mg kg(-1) body weight) administrated at day 100 of pregnancy were required to initiate regression of the corpus luteum. At day 120 after mating, the mean (+/- SEM) diameter of the largest follicle in PGF(2alpha)-treated ewes (3.40 +/- 0.47 mm) was significantly greater (P < 0.05) than that in control pregnant ewes (2.52 +/- 0.34 mm). Experiment 4 examined the effect of removal of the fetus and of the corpus luteum at day 100 of pregnancy on resumption of ovulation. Removal of the corpus luteum by PGF(2alpha) treatment at the time of removal of the fetus resulted in earlier occurrence of short luteal phases (27.8 versus 40.6 days, PGF(2alpha)-treated versus non-treated) but did not alter the timing of the first normal luteal phases (41 days). In conclusion, the results from these experiments indicate that placental compounds play a major role in inhibiting follicular growth and maturation during late pregnancy in sheep.

Effects of K+ on the twitch and tetanic contraction in the sartorius muscle of the frog, Rana pipiens. Implication for fatigue in vivo

1992 ◽  
Vol 70 (9) ◽  
pp. 1236-1246 ◽  
Author(s):  
Jean Marc Renaud ◽  
Peter Light
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Muscle Fibers ◽  
Resting Potential ◽  
Sartorius Muscle ◽  
Coupling Mechanism ◽  
Tetanic Force ◽  
Excitation Contraction Coupling ◽  
Contraction Coupling ◽  
The Mean

The effects of increasing the extracellular K+ concentration on the capacity to generate action potentials and to contract were tested on unfatigued muscle fibers isolated from frog sartorius muscle. The goal of this study was to investigate further the role of K+ in muscle fatigue by testing whether an increased extracellular K+ concentration in unfatigued muscle fibers causes a decrease in force similar to the decrease observed during fatigue. Resting and action potentials were measured with conventional microelectrodes. Twitch and tetanic force was elicited by field stimulation. At pHo (extracellular pH) 7.8 and 3 mmol K+∙L−1 (control), the mean resting potential was −86.6 ± 1.7 mV (mean ± SEM) and the mean overshoot of the action potential was 5.6 ± 2.5 mV. An increased K+ concentration from 3 to 8.0 mmol∙L−1 depolarized the sarcolemma to −72.2 ± 1.4 mV, abolished the overshoot as the peak potential during an action potential was −12.0 ± 3.9 mV, potentiated the twitch force by 48.0 ± 5.7%, but did not affect the tetanic force (maximum force) and the ability to maintain a constant force during the plateau phase of a tetanus. An increase to 10 mmol K+∙L−1 depolarized the sarcolemma to −70.1 ± 1.7 mV and caused large decreases in twitch (31.6 ± 26.1%) and tetanic (74.6 ± 12.1%) force. Between 3 and 9 mmol K+∙L−1, the effects of K+ at pHo 7.2 (a pHo mimicking the change in interstitial pH during fatigue) and 6.4 (a pHo known to inhibit force recovery following fatigue) on resting and action potentials as well as on the twitch and tetanic force were similar to those at pHo 7.8. Above 9 mmol K+∙L−1 significant differences were found in the effect of K+ between pHo 7.8 and 7.2 or 6.4. In general, the decrease in peak action potential and twitch and tetanic force occurred at higher K+ concentrations as the pHo was more acidic. The results obtained in this study do not support the hypothesis that an accumulation of K+ at the surface of the sarcolemma is sufficiently large to suppress force development during fatigue. The possibility that the K+ concentration in the T tubules reaches the critical K+ concentration necessary to cause a failure of the excitation–contraction coupling mechanism is discussed.Key words: excitation–contraction coupling, fatigue, potassium, tetanus, twitch.

scholarly journals Transmission-Blocking Activities of Quinine, Primaquine, and Artesunate

2006 ◽  
Vol 50 (6) ◽  
pp. 1927-1930 ◽  
Author(s):  
Kesinee Chotivanich ◽  
Jetsumon Sattabongkot ◽  
Rachanee Udomsangpetch ◽  
Sornchai Looareesuwan ◽  
Nicholas P. J. Day ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Standard Deviation ◽  
Anopheles Dirus ◽  
Transmission Blocking ◽  
Transmission Potential ◽  
Membrane Feeding ◽  
Blocking Activity ◽  
The Mean ◽  
High Concentrations

ABSTRACT The infectivity of Plasmodium falciparum gametocytes after exposure in vitro to quinine, artesunate, and primaquine was assessed in Anopheles dirus, a major vector of malaria in Southeast Asia. Mature gametocytes (stage 5) of a Thai isolate of P. falciparum were exposed to the drugs for 24 h in vitro before membrane feeding to A. dirus. After 10 days, the mosquito midguts were dissected and the oocysts were counted. In this system, artesunate showed the most potent transmission-blocking activity; the mean (standard deviation [SD]) 50% and 90% effective concentrations (EC50, and EC90, respectively, in nanograms per milliliter) were 0.1 (0.02) and 0.4 (0.15), respectively. Transmission-blocking activity of quinine and primaquine was observed at relatively high concentrations (SDs): EC50 of quinine, 642 (111) ng/ml; EC50 of primaquine, 181 (23) ng/ml; EC90 of quinine, 816 (96) ng/ml; EC90 of primaquine, 543 (43) ng/ml. Artesunate both prevents the maturation of immature P. falciparum gametocytes and reduces the transmission potential of mature gametocytes. Both of these effects may contribute to reducing malaria transmission.

scholarly journals Antifungal Effects of Paraquat and Glyphosate on Rhizoctonia solani (Kühn) in Potato in vitro Condition

2021 ◽  
Vol 10 (1) ◽  
pp. 16
Author(s):  
José L. Arispe Vázquez ◽  
Abiel Sánchez Arizpe ◽  
Ma E. Galindo Cepeda ◽  
Cristina Trejo Ramos
Keyword(s):  
Rhizoctonia Solani ◽  
Petri Dish ◽  
Factor B ◽  
Morphological Criteria ◽  
Statistical Program ◽  
The Mean ◽  
High Concentrations ◽  
Open Markets ◽  
Higher Doses

Potato is one of the main crops worldwide. It this research, antifungal activity in vitro of paraquat and glyphosate were evaluated for Rhizoctonia solani control. R. solani was identified from potato tubers collected out from at open markets in Saltillo, Coahuila, Mexico. Two types of herbicides were applied: paraquat and glyphosate, at four different dosage treatments of: 10, 100, 1 000 and 10 000 &mu;L. One 5 mm diameter PDA disc with R. solani mycelium was placed at the center of the Petri dish, with a radial registry fungal every 24 h for 192 h. Pathogen was identified by morphological criteria and the data was evaluated randomly with a factorial arrangement, on which, herbicides represented factor A and dosage treatments were represented by factor B. Thus experimental design had two levels for factor A and five levels for factor B with six replications. The results were analyzed by the SAS version 9.1 statistical program, the mean separation with the Tukey test (p=0.05). Glyphosate achieved inhibition of R. solani by 35.5882% and paraquat up to 80.0399%. Results reveal the importance of the need for more studies of these herbicides as fungicides. High concentrations of paraquat (10 000 &mu;L) inhibits R. solani, and glyphosate does not affect R. solani mycelium development at low dosages (10 and 100 &mu;L) and inhibits it at higher doses (10 000 &mu;L).

Chloride self-exchange in toad skeletal muscle in vivo and in vitro

1982 ◽  
Vol 242 (3) ◽  
pp. C207-C217 ◽  
Author(s):  
D. D. Macchia
Keyword(s):  
Muscle Cells ◽  
Ringer Solution ◽  
Resting Potential ◽  
Electrochemical Gradient ◽  
Hindlimb Muscles ◽  
A Value ◽  
Hindlimb Muscle ◽  
The Mean

The exchange of cellular Cl with 36Cl has been measured in saline-perfused hindlimb muscles of the pithed toad and compared with cellular Cl exchange in isolated muscles incubated in the vitro either in toad Ringer solution or in toad plasma. In the perfused hindlimb, the rate of 36Cl efflux from muscle cells [17.0 +/- 0.9 pmol Cl.(cm2 plasma membrane.s)-1] was only 40% as fast as that of the 36Cl influx. The discrepancy between Cl influx and efflux was accompanied by a cellular accumulation of Cl against the electrochemical gradient for this anion. Concurrently, the cells took up Na in amounts at least equal to the accumulated Cl. During this accumulation of Na and Cl, the mean resting potential remained constant at a value of -89.2 +/- 1.9 (SE) mV. Na and Cl were taken up by the muscle cells of the perfused hindlimb without a concomitant decrease in cellular K content; i.e., without evidence of inhibition of the Na-K pump. The rate constant for cellular 36Cl efflux from isolated toad muscles preincubated for 3 h in vitro in toad Ringer solution was about five times faster than that of muscles in the perfused hindlimb and similar in magnitude to published values for Cl fluxes in frog muscle. Cellular Cl efflux from muscles briefly preincubated in vitro for 15 min instead of 3 h was significantly slower than after prolonged preincubation. In vitro incubation of isolated toad muscles in toad plasma slowed the cellular 36Cl efflux to values approaching those measured in the perfused hindlimb, without comparably depressing the 36Cl influx. It is suggested that the uptake of NaCl by the cells of perfused hindlimb muscle may proceed by an electroneutral inward cotransport of Na and Cl on the same carrier.

Multiple potassium conductances and their functions in neurons from cat sensorimotor cortex in vitro

1988 ◽  
Vol 59 (2) ◽  
pp. 424-449 ◽  
Author(s):  
P. C. Schwindt ◽  
W. J. Spain ◽  
R. C. Foehring ◽  
C. E. Stafstrom ◽  
M. C. Chubb ◽  
...  
Keyword(s):  
Voltage Clamp ◽  
Sensorimotor Cortex ◽  
Divalent Cations ◽  
Resting Potential ◽  
Equilibrium Potential ◽  
Delayed Rectifier ◽  
Outward Currents ◽  
Potassium Conductances ◽  
The Mean

1. Potassium conductances were studied in large layer V neurons using an in vitro slice preparation of cat sensorimotor cortex. The kinetics and pharmacological sensitivity of K+ currents were studied directly using single microelectrode voltage clamp and indirectly by evoking single or multiple spikes and recording the spike repolarization and subsequent afterhyperpolarizations (AHPs). 2. A fast-decaying afterhyperpolarization (fAHP) and a subsequent medium-duration afterhyperpolarization (mAHP) followed a single spike. The amplitude and duration of the mAHP increased when multiple spikes were evoked at a fast rate (e.g., 100 Hz), and a slower afterhyperpolarization (sAHP) appeared only after sustained repetitive firing. 3. All AHPs were reduced by membrane potential hyperpolarization and raised extracellular K+ concentration, suggesting they were caused by an increased K+ conductance. Only the mAHP and sAHP reversed at the estimated value of potassium equilibrium potential (-100 mV), whereas the mean reversal potential of the fAHP was nearly identical to the mean value of resting potential (-71 mV). 4. Mechanisms underlying spike repolarization, the fAHP, and the mAHP were investigated. Two rapidly activating outward currents, a fast-inactivating current and a slowly inactivating delayed rectifier, were detected by voltage clamp. Both currents were reduced rapidly by tetraethylammonium (TEA). The fast transient current was reduced slowly after divalent cations were substituted for Ca2+ (through a mechanism unrelated to blockade of Ca2+ channels), whereas the delayed rectifier was unaffected. 5. Spike duration was increased and the fAHP was abolished only by blocking agents that reduced the fast outward currents. Effects of extracellular and intracellular TEA were similar. Effects of TEA and Ca2+-free perfusate were additive and resembled the effects of intracellular Cs+. The addition of apamin, d-tubocurare, or Cd2+ was ineffective. We conclude that the two fast outward currents reflect pharmacologically and kinetically separate K+ conductances that are primarily responsible for spike repolarization and the fAHP. 6. Voltage-clamp studies revealed two additional outward currents, which were persistent and Ca2+-mediated. Each current activated and deactivated slowly, but the kinetics of one component were approximately 10 times slower than the other. The decay of these currents gave rise to AHPs resembling the mAHP and the early sAHP. 7. Neither the mAHP nor the sAHP was reduced by TEA. The mAHP was reduced when divalent cations were substituted for Ca2+ or when Cd2+, apamin, or d-tubocurare were added.(ABSTRACT TRUNCATED AT 400 WORDS)

In Vitro Effects of Ethanol on Rabbit Platelet Aggregation, Secretion of Granule Contents, and Cyclic AMP Levels in the Presence of Prostacyclin

1989 ◽  
Vol 61 (02) ◽  
pp. 254-258 ◽  
Author(s):  
Margaret L Rand ◽  
Peter L Gross ◽  
Donna M Jakowec ◽  
Marian A Packham ◽  
J Fraser Mustard
Keyword(s):  
Cyclic Amp ◽  
Inhibitory Effect ◽  
Rabbit Platelet ◽  
Inhibitory Effects ◽  
Low Concentrations ◽  
Rabbit Platelets ◽  
High Concentrations ◽  
In Vitro Effects ◽  
Aggregation Of Platelets

SummaryEthanol, at physiologically tolerable concentrations, inhibits platelet responses to low concentrations of collagen or thrombin, but does not inhibit responses of washed rabbit platelets stimulated with high concentrations of ADP, collagen, or thrombin. However, when platelet responses to high concentrations of collagen or thrombin had been partially inhibited by prostacyclin (PGI2), ethanol had additional inhibitory effects on aggregation and secretion. These effects were also observed with aspirin- treated platelets stimulated with thrombin. Ethanol had no further inhibitory effect on aggregation of platelets stimulated with ADP, or the combination of ADP and epinephrine. Thus, the inhibitory effects of ethanol on platelet responses in the presence of PGI2 were very similar to its inhibitory effects in the absence of PGI2, when platelets were stimulated with lower concentrations of collagen or thrombin. Ethanol did not appear to exert its inhibitory effects by increasing cyclic AMP above basal levels and the additional inhibitory effects of ethanol in the presence of PGI2 did not appear to be brought about by further increases in platelet cyclic AMP levels.

Influence of Platelet Membrane Sialic Acid and Platelet-Associated IgG on Ageing and Sequestration of Blood Platelets in Baboons

1993 ◽  
Vol 70 (04) ◽  
pp. 676-680 ◽  
Author(s):  
H F Kotzé ◽  
V van Wyk ◽  
P N Badenhorst ◽  
A du P Heyns ◽  
J P Roodt ◽  
...  
Keyword(s):  
Sialic Acid ◽  
Life Span ◽  
Blood Platelets ◽  
Senescent Cell ◽  
Platelet Membrane ◽  
Antigen Complex ◽  
The Mean ◽  
Aggregation Of Platelets

SummaryPlatelets were isolated from blood of baboons and treated with neuraminidase to remove platelet membrane sialic acid, a process which artificially ages the platelets. The platelets were then labelled with 111In and their mean life span, in vivo distribution and sites of Sequestration were measured. The effect of removal of sialic acid on the attachment of immunoglobulin to platelets were investigated and related to the Sequestration of the platelets by the spleen, liver, and bone marrow. Removal of sialic acid by neuraminidase did not affect the aggregation of platelets by agonists in vitro, nor their sites of Sequestration. The removal of 0.51 (median, range 0.01 to 2.10) nmol sialic acid/108 platelets shortened their life span by 75 h (median, range 0 to 132) h (n = 19, p <0.001), and there was an exponential correlation between the shortening of the mean platelet life span and the amount of sialic acid removed. The increase in platelet-associated IgG was 0.112 (median, range 0.007 to 0.309) fg/platelet (n = 25, p <0.001) after 0.79 (median, range 0.00 to 6.70) nmol sialic acid/108 platelets was removed (p <0.001). There was an exponential correlation between the shortening of mean platelet life span after the removal of sialic acid and the increase in platelet-associated IgG. The results suggest that platelet membrane sialic acid influences ageing of circulating platelets, and that the loss of sialic acid may have exposed a senescent cell antigen that binds IgG on the platelet membrane. The antibody-antigen complex may then provide a signal to the macrophages that the platelet is old, and can be phagocytosed and destroyed.

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