scholarly journals Rhodopsin kinetics in the cat retina.

1981 ◽  
Vol 77 (3) ◽  
pp. 317-334 ◽  
Author(s):  
H Ripps ◽  
L Mehaffey ◽  
I M Siegel
Keyword(s):  
Time Course ◽  
Continuous Light ◽  
Regenerative Process ◽  
Full Time ◽  
Difference Spectra ◽  
Cat Retina ◽  
Simple Exponential Function ◽  
Fundus Reflectometry ◽  
The Difference ◽  
Kinetics Of

The bleaching and regeneration of rhodopsin in the living cat retina was studied by means of fundus reflectometry. Bleaching was effected by continuous light exposures of 1 min or 20 min, and the changes in retinal absorbance were measured at 29 wavelengths. For all of the conditions studied (fractional bleaches of from 65 to 100%), the regeneration of rhodopsin to its prebleach levels required greater than 60 min in darkness. After the 1-min exposures, the difference spectra recorded during the first 10 min of dark adaptation were dominated by photoproduct absorption, and rhodopsin regeneration kinetics were obscured by these intermediate processes. Extending the bleaching duration to 20 min gave the products of photolysis an opportunity to dissipate, and it was possible to follow the regenerative process over its full time-course. It was not possible, however, to fit these data with the simple exponential function predicted by first-order reaction kinetics. Other possible mechanisms were considered and are presented in the text. Nevertheless, the kinetics of regeneration compared favorably with the temporal changes in log sensitivity determined electrophysiologically by other investigators. Based on the bleaching curve for cat rhodopsin, the photosensitivity was determined and found to approximate closely the value obtained for human rhodopsin; i.e., the energy Ec required to bleach 1-e-1 of the available rhodopsin was 7.09 log scotopic troland-seconds (corrected for the optics of the cat eye), as compared with approximately 7.0 in man.

scholarly journals Delays in inactivation development and activation kinetics in myxicola giant axons.

1982 ◽  
Vol 80 (1) ◽  
pp. 83-102 ◽  
Author(s):  
L Goldman ◽  
J L Kenyon
Keyword(s):  
Time Constant ◽  
Time Course ◽  
Series Resistance ◽  
Activation Kinetics ◽  
Time To Peak ◽  
Exponential Decline ◽  
Na Inactivation ◽  
The Difference ◽  
True Property ◽  
Kinetics Of

Na inactivation was studied in Myxicola (two-pulse procedure, 6-ms gap between conditioning and test pulses). Inactivation developed with an initial delay (range 130-817 microseconds) followed by a simple exponential decline (time constant tau c). Delays (deviations from a simple exponential) are seen only for brief conditioning pulses were gNa is slightly activated. Hodgkin-Huxley kinetics with series resistance, Rs, predict deviations from a simple exponential only for conditioning pulses that substantially activate gNa. Reducing INa fivefold (Tris substitution) had no effect on either tau c or delay. Delay in not generated by Rs or by contamination from activation development. The slowest time constant in Na tails is approximately 1 ms (Goldman and Hahin, 1978) and the gap was 6 ms. Shortening the gap to 2 ms had no effect on either tau c or delay. Delay is a true property of the channel. Delay decreased with more positive conditioning potentials, and also decreased approximately proportionally with time to peak gNa during the conditioning pulse, as expected for sequentially coupled activation and inactivation. In a few cases the difference between Na current values for brief conditioning pulses and the tau c exponential could be measured. Difference values decayed exponentially with time constant tau m. The inactivation time course is described by a model that assumes a process with the kinetics of gNa activation as a precursor to inactivation.

scholarly journals Full Time Course Kinetics of the Streptokinase-Plasminogen Activation Pathway

2013 ◽  
Vol 288 (41) ◽  
pp. 29482-29493 ◽  
Author(s):  
Miranda Nolan ◽  
Samantha D. Bouldin ◽  
Paul E. Bock
Keyword(s):  
Time Course ◽  
Full Time ◽  
Plasminogen Activation ◽  
Activation Pathway ◽  
Kinetics Of

scholarly journals Kinetics of light-dependent Ca fluxes across the plasma membrane of rod outer segments. A dynamic model of the regulation of the cytoplasmic Ca concentration.

1987 ◽  
Vol 90 (3) ◽  
pp. 397-425 ◽  
Author(s):  
D L Miller ◽  
J I Korenbrot
Keyword(s):  
Plasma Membrane ◽  
Outer Segment ◽  
Time Course ◽  
Small Volume ◽  
Dynamic Balance ◽  
Light Sensitivity ◽  
Ca Ions ◽  
Concentration Changes ◽  
The Difference ◽  
Kinetics Of

We measured simultaneously in single toad rods the membrane photocurrent and the Ca concentration in a small volume surrounding the outer segment. Illumination causes a rise in the extracellular Ca concentration. Photocurrents and Ca concentration changes occur over the same range of light intensities. Analysis of the time course of the Ca concentration changes suggests that these concentration changes arise from the difference in the transport rates of light-activated Ca influx and efflux across the outer segment plasma membrane. The Ca influx occurs through the light-sensitive channels of the outer segment membrane and the efflux through Na/Ca exchangers. In 0.1 mM external Ca, approximately 1-2% of the dark current is carried by Ca ions. The Ca efflux in the dark is identical to the influx, approximately 2 X 10(6) ions/s. Upon illumination, the Ca influx decreases with a time course and light sensitivity identical to those of the photocurrent. The Ca efflux, on the other hand, has very different kinetics from those of the photocurrent. Upon illumination, the Ca efflux decreases with a time course and light sensitivity determined by the change in membrane voltage and in the free cytoplasmic Ca concentration near the plasma membrane. In response to bright stimuli, which saturate the photocurrent for prolonged periods of time, the Ca efflux decays with an exponential time course from its value in darkness. The average time constant of this decay is 2.5 s. From the kinetics of the light-activated Ca fluxes, it is possible to predict that illumination causes a decrease in the cytoplasmic Ca concentration. We present a model of the regulation of the cytoplasmic Ca concentration by the dynamic balance of the Ca influx and efflux from the rod outer segment. The model accounts for our experimental observations and allows us to predict the time course and extent of the light-dependent decrease in the free cytoplasmic concentration.

scholarly journals PO 8542 CLINICAL ILLNESS AND OUTCOMES IN NIGERIAN CHILDREN WITH PERSISTENT EARLY-APPEARING ANAEMIA FOLLOWING ARTEMISININ-BASED COMBINATION TREATMENTS OF UNCOMPLICATED PLASMODIUM FALCIPARUM MALARIA

2019 ◽  
Vol 4 (Suppl 3) ◽  
pp. A51.2-A51
Author(s):  
Kazeem Akano ◽  
Bayo Fatunmbi ◽  
Godwin Ntadom ◽  
Omobolaji T Alebiosu ◽  
Odafe Akpoborie ◽  
...  
Keyword(s):  
Time Course ◽  
Treatment Initiation ◽  
Plasmodium Falciparum Malaria ◽  
Compartment Model ◽  
Sub Saharan Africa ◽  
Combination Treatments ◽  
The Difference ◽  
Sub Saharan ◽  
Pre Treatment ◽  
Kinetics Of

BackgroundEarly-appearing anaemia (EAA) is not uncommon in malarious children following artemisinin-based combination treatments (ACTs) of uncomplicated infections and it may become persistent (PEAA). There is little evaluation of the factors contributing to and the kinetics of the resolution of haemoglobin deficit characteristic of ACT-related PEAA.MethodsPEAA was defined as haemoglobin concen„tration <10 g/dL for at least 1 week after treatment initiation with artemether-lumefantrine (AL), artesunate-amodiaquine (ASAQ) or dihydroartemisinin-piperaquine (DP) in malarious children with haemoglobin ≥10 g/dL pre-treatment. Drug-attributable fall in haemoglobin (DAFHb) was defined as the difference between pre-treatment and the lowest recorded haemoglobin value in the first week after treatment initiation. Stepwise multiple logistic regression model was used to evaluate independent predictors of PEAA. Time course of deficits in haemoglobin from baseline was used to estimate the disposition kinetics of haemoglobin deficits using a one compartment model.ResultsAsymptomatic PEAA occurred in 46 of 540 children. A duration of illness ≤3 days before presentation, haemoglobin <11.7 g/dL pre-treatment and 8.3 g/dL 1 day after treatment initiation. DAFHb ≥2 g/dL and treatment with DP independently predicted PEAA. Time to 90% reduction in haemoglobin deficit was significantly longer in AL-treated children compared with other treatments. Declines in haemoglobin deficits were monoexponential with the following overall estimated parameters: Cmax 2.6 g/dL (95% CI 2.3–2.9), Tmax 3.2 days (95% CI 2.2–4.1), AUC 31.9 g.dL-1.day (95% CI 25–38.8), Kel0.3 day-1 (95% CI 0.3–0,4), t1/23.9 days (95% CI 2.6–5.1), CLp 0.6L.day-1 (95% CI 0.5–0.7), and Vd 2.4L (95% CI 1.7–3). Overall, mean anaemia recovery time of 17.9 days (95% CI 15.5–20.2, n=39) was equivalent to 5 multiples of half-time of haemoglobin deficit on Bland-Altman analysis. Eight children, after recovery from PEAA progressed to asymptomatic late-appearing anaemia (LAA).ConclusionAsymptomatic PEAA, which may progress to LAA, is not uncommon in young children following ACTs. Its occurrence, and progression to LAA, may have implications for case management and control efforts for ACT-related anaemia in sub-Saharan Africa.

A comparison of spontaneous EPSCs in layer II and layer IV-V neurons of the rat entorhinal cortex in vitro

1996 ◽  
Vol 76 (2) ◽  
pp. 1089-1100 ◽  
Author(s):  
N. Berretta ◽  
R. S. Jones
Keyword(s):  
Entorhinal Cortex ◽  
Time Course ◽  
Cell Voltage ◽  
Amplitude Distribution ◽  
Mean Amplitude ◽  
Decay Phase ◽  
Similar Extent ◽  
The Difference ◽  
Kinetics Of

1. We have compared the characteristics of spontaneous excitatory postsynaptic currents (sEPSCs) in neurons of layer IV-V and layer II of the rat entorhinal cortex (EC) using whole cell voltage-clamp recordings in a slice preparation. 2. The frequency of sEPSCs was similar in the two layers, but the events in layer IV-V had a larger mean amplitude, faster rise time, and were faster to decay. The difference in amplitude could be attributed to the presence of a population of larger events in the layer IV-V neurons that were not present in layer II. 3. Electrotonic length was greater in layer II neurons, suggesting that the difference in kinetics of the sEPSCs may be explained partly by electrotonic attenuation. 4. The frequency of sEPSCs in both layers was reduced by tetrodotoxin (TTX) to a similar extent (15-20%). However, the amplitude distribution was unchanged in layer II, whereas in layer IV-V TTX abolished most of the larger amplitude sEPSCs. 5. 6-cyano-7-nitroquinoxaline-2,3-dione or 6-nitro-7-sulphamoylbenzo (f)-quinoxaline-2,3-dione, abolished most of the sEPSCs in neurons of both layers. However, even at negative holding potentials, a population of slower time-course sEPSCs remained in the presence of these antagonists. 6. The slow sEPSCs were more frequent in layer IV-V but had similar characteristics in both layers, being increased in amplitude at more positive holding potentials or in Mg2+-free medium, and blocked by 2-amino-5-phosphonovalerate (AP5). 7. AP5 alone (i.e., without addition of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid antagonists) reduced the peak amplitude and decay phase of sEPSCs in layer IV-V neurons but appeared to have little effect on amplitude and only a weak effect on decay phase in layer II. 8. Thus both layer IV-V and layer II neurons of the EC suffer continuous spontaneous excitation. However, layer IV-V neurons exhibit larger amplitude sEPSCs, probably mediated by release of multiple quanta of neurotransmitter. In addition, although both types of neurons display spontaneous excitation mediated by N-methyl-D-aspartate receptors, this component appears more pronounced in the deeper layers.

scholarly journals "Rapid regeneration" in the cat retina: a case for spreading depression.

1981 ◽  
Vol 77 (3) ◽  
pp. 335-346 ◽  
Author(s):  
H Ripps ◽  
L Mehaffey ◽  
I M Siegel
Keyword(s):  
Spreading Depression ◽  
Physiological Condition ◽  
Spectral Characteristics ◽  
Spectral Change ◽  
Difference Spectra ◽  
The Poor ◽  
Cat Retina ◽  
Fundus Reflectometry ◽  
Tissue Alterations ◽  
Experimental Runs

Fundus reflectometry of the cat retina showed that under certain circumstances a rapid increase in density may follow intense bleaching exposures. The spectral characteristics of the density changes indicated that neither rhodopsin nor its bleach products could be responsible for this effect. The poor condition of the animals in which the phenomenon was observed and its conspicuous absence in the majority of the experimental runs suggested that the effect was associated with a process other than the resynthesis of rhodopsin. It was shown that an extrareceptoral event, spreading depression (SD) of the retina, is the most likely source of the rapid spectral change. The well-known tissue alterations associated with SD were induced in the retina independently of pigment density change. The resultant difference spectra resembled those produced when the rapid density increase occurred spontaneously. It seems likely that the abnormal physiological condition of those cats in which the phenomenon is more frequently observed primes the retina for the light-induced generation of spreading depression.

Destruction of Actin Filaments by Osmium Tetroxide

1977 ◽  
Vol 35 ◽  
pp. 466-467
Author(s):  
P. Maupin-Szamier ◽  
T. D. Pollard
Keyword(s):  
Actin Filaments ◽  
Time Course ◽  
Osmium Tetroxide ◽  
Rabbit Muscle ◽  
Muscle Actin ◽  
Sodium Phosphate Buffer ◽  
Transmission Electron ◽  
The Difference ◽  
Rates Of Decay ◽  
Short Time

We have studied the destruction of rabbit muscle actin filaments by osmium tetroxide (OSO4) to develop methods which will preserve the structure of actin filaments during preparation for transmission electron microscopy.Negatively stained F-actin, which appears as smooth, gently curved filaments in control samples (Fig. 1a), acquire an angular, distorted profile and break into progressively shorter pieces after exposure to OSO4 (Fig. 1b,c). We followed the time course of the reaction with viscometry since it is a simple, quantitative method to assess filament integrity. The difference in rates of decay in viscosity of polymerized actin solutions after the addition of four concentrations of OSO4 is illustrated in Fig. 2. Viscometry indicated that the rate of actin filament destruction is also dependent upon temperature, buffer type, buffer concentration, and pH, and requires the continued presence of OSO4. The conditions most favorable to filament preservation are fixation in a low concentration of OSO4 for a short time at 0°C in 100mM sodium phosphate buffer, pH 6.0.

Influence of Radioiodine Therapy on Urinary Iodine Excretion

1998 ◽  
Vol 37 (03) ◽  
pp. 107-112 ◽  
Author(s):  
I. Lauer ◽  
M. Bähre ◽  
E. Richter ◽  
B. Melier
Keyword(s):  
Time Course ◽  
Radioiodine Therapy ◽  
Urinary Iodine ◽  
Target Volume ◽  
Urinary Iodine Excretion ◽  
Urinary Creatinine ◽  
Iodine Excretion ◽  
Kinetics Of ◽  
Persistent Elevation ◽  
Benign Thyroid

Summary Aim: In 214 patients with benign thyroid diseases the time-course of urinary iodine excretion (UIE) was investigated in order to identify changes after radioiodine therapy (RITh). Method: UIE was measured photometrically (cerium-arsenite method) and related to urinary creatinine on the first and last day of the radioiodine test and then three days, seven days, four weeks, and six months after 1311 administration. Results: As compared with the level found immediately before radioiodine therapy, median UIE had almost doubled four weeks after therapy and was still significantly elevated six months after therapy. This increase correlated significantly with the target volume as measured by scintigraphy and sonography. Conclusions: The persistent elevation of UIE for months after RITh is a measure of treatment-induced damage to thyrocytes. Therefore, in view of the unfavourable kinetics of iodine that follow it, RITh should if possible be given via a single-dose regime.

Women and Entrepreneurship – Albanian Case

2016 ◽  
Vol 1 (1) ◽  
pp. 249
Author(s):  
Anna Xheka
Keyword(s):  
Gender Equality ◽  
Gender Gap ◽  
Secondary Data ◽  
Special Focus ◽  
Full Time ◽  
Men And Women ◽  
Women’S Entrepreneurship ◽  
Part Time ◽  
Women's Entrepreneurship ◽  
The Difference

Women’s entrepreneurship is a powerful source, regarding to the women’s economic independence and empowerment, as well as regarding employment generation, economic growth and innovation, development and the reduction of poverty as well as one of the terms of gender equality. This poster presents the situation of women's entrepreneurship in Europe in comparative terms, with special focus in Albania. The paper has a descriptive nature. Describes three different plans in comparative terms; the representation of men and women in entrepreneurship, the representation of women in entrepreneurship in different countries of Europe and of Europe as a whole, as well as compare to gender quota. Through the processing of secondary data from various reports and studies, this poster concludes that although that the gender equality goal is the equal participation of men and women in all sectors, including the entrepreneurship, in this sector, gender gap it is still deep. Another significant comparative aspect, it is the difference between full and part –time women entrepreneurship. While in full time entrepreneurship in a convince way, men are those that dominate, in part time entrepreneurship clearly it’s evident the opposite trend, women's representation is much higher. It’s very interesting the fact, that the women’s entrepreneurship in Albania, presented in a significant optimistic situation, ranking in the second place, after Greece in the European level

Contemporary Trends in PSW Teaching: Challenges and Opportunity to Expand

2018 ◽  
Vol 9 (2) ◽  
pp. 60
Author(s):  
Kamlesh Kumar Sahu
Keyword(s):  
Mental Health ◽  
Social Work ◽  
Time Course ◽  
Full Time ◽  
Private Institutions ◽  
Centre Of Excellence ◽  
Part Time ◽  
The Government ◽  
National Mental Health ◽  
Psychiatric Social Work

Psychiatric Social Work teaching has completed seven decades in India which was started with master course in medical and psychiatric social work at Tata Institute of Social Sciences, Mumbai in 1948 followed by various schools of social work across the country but unfortunately even after two year full time or part time course they are not counted as a mental health professional; still they need two more years of specialized training in mental health as Master of Philosophy in Psychiatric Social Work (M.Phil. PSW) which was offered in just a few institutions. Recently the Government of India formulated manpower development schemes under the national mental health programme to address the shortage of men power in mental health. Under this scheme, 25 centre of excellence in mental health are already stabilised and various post graduate departments were upgraded and M.Phil. PSW course is started or will be started. This figure is in raise in Government intuitions and few private institutions also. The prominence of social work in mental health is expected to enhance by this effort as highly trained social workers will be available to practice in the mental health field but there are some challenges to overcome to get the maximum outcome from this opportunity to expand.    Keywords:Psychiatric social work, mental health, men power development, India  Â

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