The Effects of Pharmacological Agents on the Electrical Responses of Cells of Nitella flexilis

1971 ◽  
Vol 49 (9) ◽  
pp. 824-832 ◽  
Author(s):  
P. Belton ◽  
C. Van Netten
Keyword(s):  
Molecular Mechanism ◽  
Muscle Fibers ◽  
The Other ◽  
Procaine Hydrochloride ◽  
Animal Cells ◽  
Excitable Cells ◽  
Pharmacological Agents ◽  
Barium Ions ◽  
Two Agents ◽  
Nitella Flexilis

Procaine hydrochloride decreases potential and effective resistance of the membrane and does not produce prolonged spikes. Tetraethylammonium (TEA) and barium ions prolong the spikes of internodal cells of Nitella evidently by delaying K+ activation as is the case in many other excitable cells. The last two agents do not increase the amplitude of the spikes in contrast to their effect on some arthropod muscle fibers. The other effects of Ba2+ and TEA on the spikes of Nitella and animal cells are almost identical. We conclude that the same molecular mechanism is involved in K+ activation in animals and plants.

Electrophysiology of the Sodium-Potassium-ATPase in Cardiac Cells

2001 ◽  
Vol 81 (4) ◽  
pp. 1791-1826 ◽  
Author(s):  
Helfried Günther Glitsch
Keyword(s):  
Cell Membrane ◽  
Potential Gradient ◽  
Outward Current ◽  
Pump Current ◽  
Cardiac Cells ◽  
Animal Cells ◽  
Excitable Cells ◽  
Extracellular Medium ◽  
Enzymatic Isolation ◽  
Isolated Cardiac Cells

Like several other ion transporters, the Na+-K+ pump of animal cells is electrogenic. The pump generates the pump current I p. Under physiological conditions, I p is an outward current. It can be measured by electrophysiological methods. These methods permit the study of characteristics of the Na+-K+ pump in its physiological environment, i.e., in the cell membrane. The cell membrane, across which a potential gradient exists, separates the cytosol and extracellular medium, which have distinctly different ionic compositions. The introduction of the patch-clamp techniques and the enzymatic isolation of cells have facilitated the investigation of I p in single cardiac myocytes. This review summarizes and discusses the results obtained from I p measurements in isolated cardiac cells. These results offer new exciting insights into the voltage and ionic dependence of the Na+-K+ pump activity, its effect on membrane potential, and its modulation by hormones, transmitters, and drugs. They are fundamental for our current understanding of Na+-K+ pumping in electrically excitable cells.

Knowledge Attributions to Minimal Epistemic Agents

2020 ◽  
pp. 45-82
Author(s):  
Jody Azzouni
Keyword(s):  
The Other ◽  
Knowledge Attributions ◽  
Two Agents ◽  
Driverless Cars ◽  
Sensory Evidence ◽  
Usage Data

Widespread usage data for “know,” “learn,” “see,” “remember,” and other epistemic words are given. Such words are routinely and literally applied to animals ranging from sophisticated elephants and orcas to insects like ants and honeybees to nonconscious mechanisms like driverless cars, drones, and thermostats. Further, “S knows p” places no constraints on the agent S vis-à-vis the concepts exhibited in p: Rover need not have the concept of “cat” to know that a cat is trapped above him in a tree. How this data shows that a knowing agent need not know much, need not be self-conscious of what she knows, and need not be conscious or capable of metacognition is described. The modularity of agential knowledge is characterized: two agents may have the same sensory evidence for p, and yet one can know p while the other doesn’t because of other aspects of their methods for establishing p.

scholarly journals COLICINE K

1958 ◽  
Vol 108 (5) ◽  
pp. 731-752 ◽  
Author(s):  
Tsunehisa Amano ◽  
Walther F. Goebel ◽  
Elizabeth Miller Smidth
Keyword(s):  
Neutralizing Antibody ◽  
Protein Component ◽  
The Other ◽  
Serological Relationship ◽  
E Coli ◽  
O Antigen ◽  
Two Agents ◽  
Antigen Complex

By immunological means it has been shown that colicine K is associated with the O antigen of the colicinogenic bacillus E. coli K235 L+OC+. The colicine K-O antigen complex elicits the formation of at least two types of antibodies, one a precipitin, the other a colicine-neutralizing antibody. The first precipitates colicine K without neutralizing it, the second neutralizes the colicine without precipitating it. Unlike the purified colicine K complex, the colicine protein component of the O antigen is precipitable by the neutralizing antibody. There is no demonstrable serological relationship between colicine K and phage T6. These two agents must be considered to be separate and distinct entities.

The Molecular Mechanism of Photoinhibition — Facts and Fiction

1988 ◽  
Vol 15 (2) ◽  
pp. 27 ◽  
Author(s):  
C Critchley
Keyword(s):  
Photosystem Ii ◽  
Molecular Mechanism ◽  
Functional Group ◽  
Structure And Function ◽  
The Other ◽  
Proteolytic Degradation ◽  
Reaction Centre ◽  
Herbicide Binding ◽  
Recent Developments ◽  
And Function

In this paper, the evidence supporting two different models for the molecular mechanism of photoinhibition is discussed. One hypothesis centres around the suggestion that photoinhibition is due to the loss of the herbicide-binding Dl polypeptide of photosystem II. The other model suggests that damage to a functional group in the reaction centre is the primary cause of photoinhibition. In order to put the apparent controversy into context, recent developments in our understanding of the structure and function of the photosystem II reaction centre are described. Interpretation and judgement of all available evidence suggest primary photoinhibitory damage to be incurred by the reaction-centre chlorophyll P680 destabilising the apoprotein(s) and eventually resulting in their proteolytic degradation and removal from the photosystem II complex and the thylakoid membrane.

scholarly journals Betting, Selection, and Luck: A Long-Run Analysis of Repeated Betting Markets

Entropy ◽  
2019 ◽  
Vol 21 (6) ◽  
pp. 585 ◽  
Author(s):  
Giulio Bottazzi ◽  
Daniele Giachini
Keyword(s):  
Relative Risk ◽  
The Other ◽  
Risk Averse ◽  
Quantal Response ◽  
Two Agents ◽  
Long Run ◽  
Binary Event ◽  
Betting Market ◽  
Betting Markets ◽  
The Difference

We consider a repeated betting market populated by two agents who wage on a binary event according to generic betting strategies. We derive new simple criteria, based on the difference of relative entropies, to establish the relative wealth of the two agents in the long-run. Little information about agents’ behavior is needed to apply the criteria: it is sufficient to know the odds traders believe fair and how much they would bet when the odds are equal to the ones the other agent believes fair. Using our criteria, we show that for a large class of betting strategies, it is generically possible that the ultimate winner is only decided by luck. As an example, we apply our conditions to the case of Constant Relative Risk Averse (CRRA) and quantal response betting.

A Novel Heterozygous Point Mutation Causing Coagulation Factor XII Deficiency as the Molecular Mechanism of Fatal Thrombosis Event in a Chinese Pedigree.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 4080-4080
Author(s):  
Ying Feng ◽  
Ye Xu ◽  
Ying Pang ◽  
Jing Dai ◽  
Wei Xie ◽  
...  
Keyword(s):  
Molecular Mechanism ◽  
Coagulation Factor ◽  
Laboratory Diagnosis ◽  
Factor Ix ◽  
The Other ◽  
Heterozygous Mutation ◽  
Factor Xii ◽  
Phenotypic Analysis ◽  
Factor Xii Deficiency ◽  
Pcr Products

Abstract Objective: To study on the laboratory diagnosis and molecular mechanism of a pedigree with fatal cerebral thrombosis event caused by hereditary coagulation factor XII deficiency. Methods: Activated partial thromboplastin time (APTT), prothrombin time (PT), coagulation factor VIII activity (FVIII:C), factor IX activity (FIX:C), factor XI and factor XII activity (FXI:C and FXII:C) were determined in the propositus and the other kindred member for phenotypic analysis. All the 14 exons and their flank sequences of factor XII gene form the propositus were amplified by PCR. The purified PCR products were sequenced directly. After mutation was found, the corresponding gene fragments covering the mutated point from the other member of the kindred were amplified and sequenced. Results: The APTT of the propositus was significantly elongated (>120 seconds), while her PT was normal. Her FVIII:C,FIX:C and FXI:C were all normal. But her FXII:C was only 1 %, lower than normal. A heterozygous G3774C missense mutation in exon 4 was identified, which has led to the substitution of serine (TCT) 73 for cysteine (TGT). The sequencing results from the pedigree suggested that the other asymptomatic member of the kindred also had the same heterozygous mutation. Conclusion: The Propositus was diagnosed with inherited coagulation factor XII deficiency. The novel gene mutation found in this pedigree is the molecular mechanism leading to the fatal thrombosis events in the propositus.

scholarly journals Molecular Mechanisms of Macrolide Resistance in Clinical Isolates of Mycoplasma pneumoniae from China

2009 ◽  
Vol 53 (5) ◽  
pp. 2158-2159 ◽  
Author(s):  
Deli Xin ◽  
Zuhuang Mi ◽  
Xu Han ◽  
Ling Qin ◽  
Jing Li ◽  
...  
Keyword(s):  
Respiratory Tract ◽  
Molecular Mechanism ◽  
Mycoplasma Pneumoniae ◽  
Respiratory Tract Infections ◽  
Molecular Mechanisms ◽  
Point Mutations ◽  
Macrolide Resistance ◽  
The Other ◽  
23S Rrna ◽  
Tract Infections

ABSTRACT Fifty clinical Mycoplasma pneumoniae strains were isolated from 370 children with respiratory tract infections. Four strains were susceptible to macrolides, while the other 46 (92%) were macrolide resistant. The molecular mechanism of resistance was shown to be associated with point mutations in 23S rRNA at positions 2063 and 2064.

Sound localization in anurans. I. Evidence of binaural interaction in dorsal medullary nucleus of bullfrogs (Rana catesbeiana)

1976 ◽  
Vol 39 (4) ◽  
pp. 871-881 ◽  
Author(s):  
A. S. Feng ◽  
R. R. Capranica
Keyword(s):  
Rana Catesbeiana ◽  
Single Cells ◽  
Tone Burst ◽  
Excitatory Input ◽  
The Other ◽  
Excitable Cells ◽  
Tuning Curves ◽  
Contralateral Ear ◽  
Dorsal Medullary Nucleus ◽  
Stimulation Of

1. The response patterns of single cells to monaural and binaural acoustic stimuli were studied in the dorsal medullary nucleus of the bullfrog (Rana catesbeiana). This nucleus represents the first ascending center in the anuran's central auditory nervous system. 2. Of the 142 cells isolated, 75 units responded only to monaural stimulation. Approximately 80% of these monaural cells could be excited by the ipsilateral ear, while the remaining 20% received their excitatory input from the contralateral ear. The other 67 units responded to binaural stimuli. Of these binaural cells, 14 could be excited by either contralateral or ipsilateral stimuli, and the threshold and best excitatory frequency were similar for each ear (EE). The other 53 binaural cells (EI) could be excited by stimulation of one ear and inhibited by stimulation of the other ear; for almost all of these cells the contralateral ear was excitatory and the ipsilateral ear was inhibitory. The best inhibitory frequency for one ear was approximately the same as the best excitatory frequency for the other ear, and the threshold for inhibition was near the threshold for excitation. 3. The tuning curves for all of the cells in the dorsal medullary nucleus were unimodal with "Q" values ranging from 0.4 to 4. The excitatory thresholds were widely scattered between 22 and 115 dB SPL. 4. The distribution of best excitatory frequencies for the monaural cells comprised three groups: 200-300, 500-800, and 900-1,600 Hz. The best excitatory frequencies of the binaural cells were scattered over this entire range, with a broad peak around 200-800 Hz. 5. Approximately 80% of the cells in the dorsal nucleus responded tonically throughout the duration of an excitatory tone burst. The remaining 20% of the cells responded phasically during the transient stages of a tone burst over a wide intensity range. 6. Response latencies were compared for the two types of monaural cells to tones at their best exciatatory frequencies at 10 dB above threshold. The latencies for the contralaterally excitable cells were just a few milliseconds longer than the latencies for the ipsilaterally excitable cells. For binaural cells the latency for contralateral stimulation was only 1-2 ms longer than for ipsilateral stimulation. It was concluded that the contralateral input to the dorsal medullary nucleus is not of efferent descending origin from higher auditory centers. 7. All of the binaural EI cells were sensitive to small interaural intensity differences and many were also sensitive to minute interaural time differences.These cells likely play a role in localization of sounds of significance to anurans.

scholarly journals Aging histological changes in the cartilages of the cricoarytenoid joint

2004 ◽  
Vol 19 (2) ◽  
pp. 136-140 ◽  
Author(s):  
Rogério Aparecido Dedivitis ◽  
Márcio Abrahão ◽  
Manoel de Jesus Simões ◽  
Osvaldo Alves Mora ◽  
Onivaldo Cervantes
Keyword(s):  
Hyaline Cartilage ◽  
Muscle Fibers ◽  
Collagen Fibers ◽  
The Other ◽  
Elastic Fibers ◽  
Lamellar Bone ◽  
Fat Tissue ◽  
Hematopoietic Tissue ◽  
Group Iii ◽  
Group I

PURPOSE: Analysis of ossification, bone marrow formation, perichondrium thickness, muscle fibers, collagen fibers and elastic fibers quantities of cricoid and arytenoid cartilages. Design: Correlation morphologic study. METHODS: Twenty-four cricoarytenoid joints were obtained from Caucasian male fresh cadavers divided into three groups with eight specimens in each: group I - adolescents, from 15 to 20; group II - adults, from 25 to 35; and group III - elderly, from 60 to 75. The specimens were stained with H-E; trichrome; Picrosirius; and elastic stain. Histometry was performed for quantitative analysis. Bonferroni Test, Fisher Test and the Variance Analysis were used. RESULTS: At the microscopic analysis, the group I specimens presented typical hyaline cartilage, thin perichondrium, bulky muscle fibers and were surrounded by collagen fibers. In group II, there were ossification in small well defined central areas of four specimens, with lamellar bone tissue. In two of these cases there were central bone cavity full of fat tissue. The other parameters were similar to group I. In group III, most part of hyaline cartilage was replaced by typical lamellar bone tissue with poorly outlined haversian systems. Hematopoietic tissue was noted in six cases and fat tissue in the other two. Perichondrium was thicker. Small muscle fibers were smaller and surrounded by collagen in great quantity. Elastic fibers were present in small quantity in the outer portion of perichondrium in all the groups. CONCLUSIONS: In spite of its lack in adolescence, ossification occurs in cricoid and arytenoid cartilages during adulthood and intensifies with age; bone marrow is formed in ossification tissue with hematopoietic tissue in group III; perichondrium becomes thicker in group III; muscle tissue atrophies in group III and is replaced by collagen fibers; these fibers thicken with age; and elastic fibers is always present in the perichondrium in low quantity.

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