Dynamics of the control of body pattern in the development of Xenopus laevis

Development ◽  
1985 ◽  
Vol 88 (1) ◽  
pp. 135-150
Author(s):  
Jonathan Cooke
Keyword(s):  
Pattern Formation ◽  
Onset Time ◽  
Early Failure ◽  
Larval Stages ◽  
Position Value ◽  
Brain Pattern ◽  
Xenopus Egg ◽  
The Brain ◽  
Experimental Group ◽  
Body Pattern

A series of Xenopus egg batches has been exposed to doses of u.v. (2537A) light on the vegetal hemisphere at precleavage stages, calculated to result in a range of minimal axial deficiency syndromes in the developing larvae. At the time of onset of gastrulation in synchronously fertilized but non-irradiated batch members, each experimental group was regularly scanned so that small subsamples of embryos could be set aside as showing particular, progressive degrees of delay in onset of the visible gastrulation movements. Such sampling was found to have preselected embryos showing generally progressive degrees of pattern impairment at larval stages, and this observation was extended by histological examination of the anterior axial anatomy. Such examination was also made of the least abnormal-looking members of a series of larvae resulting from excision of the presumptive head endo—mesoderm, traditionally called ‘the organizer’, from stage-10 gastrulae (Cooke, 1975). The results support the notion that production of the most anterior endo—mesodermal pattern parts (and of their inductive capacities in giving rise to the brain pattern) occurs only in material whose timing, in the onset of gastrulation activity, is close to the normal onset time after fertilization. Either an early failure of the egg to generate a location with the ‘position value’ corresponding with this extreme of the pattern, or the much later excision of the region from a physiologically normal gastrula, results in a system of pattern formation permanently truncated at its apical (head and dorsal) end. There is no evidence for any dynamic, in the system ascribing position value, that will cause regulative restoration of this cellular state (the most extreme ‘activation’ for development) in response to its absence after precleavage stages. An earlier statement (Cooke, 1975) that this could occur was based upon inadequate analysis of larvae with an often misleading external anatomy. The present results are discussed as supporting the overall view of the early Xenopus patterning system that has been developed in the previous two papers of the series.

scholarly journals The Effect of Hydroalcoholic Extract of Perovskia Abrotanoides on Neuronal Density of Rats under Chronic Immobility Stress

2020 ◽  
Author(s):  
Maryam Tehranipour ◽  
Rahele Pakjame ◽  
Saiede Zafar Balanezhad
Keyword(s):  
Antioxidant Properties ◽  
Negative Control ◽  
Male Rats ◽  
Hydroalcoholic Extract ◽  
Stress Group ◽  
Neuronal Density ◽  
Ca1 Region ◽  
The Mean ◽  
The Brain ◽  
Experimental Group

Introduction: The number of neurons in the hippocampus can have a direct effect on its function. The plant Brazembel from the mint family may have antioxidant properties. The aim of the present study was to investigate the effects of stress and Brazmble extract on neuronal density of CA1, CA2 in male rats. Methods: In this experimental study, Wistar rats were divided into 6 groups (n=5), including control, and negative control under stress, also experimental group,including stress and get Brazmbl doses of the extract mL 50, mL 75 and mL 100. Limiting stress for 21 days, the rats were exposed in 2 hours. Groups receiving the extract for 21 days, to get inside limiting extracts were gavaged. After removal of the brain by perfusion, the hippocampus was excised and stained, and the neuronal density was calculated by dissector and metasteriology. The results were analyzed by Minitab 16 software with t-test and ANOVA at a significant level (P <0.05). Results: Statistical analysis of the data showed that the mean neuronal density in the stress group compared to the control in CA1 and CA2 had a significant decrease (p <0.01). The mean neuronal density of CA1 region between the stress group (29 ± 3) and hydroalcoholic treatment at 50 mg / kg (25 ± 3) showed a significant increase. In addition, the mean neuronal density in the stress group with 75 mg / kg extract (27±3) and in the group treated with hydroalcoholic extract was 100 mg / kg (25 ± 3). Mean neuronal density of CA2 region between the stress (21 ± 3) and hydroalcoholic treatment at 50 mg / kg (28 ± 3) groups showed a significant increase (p <0.01). The mean neuronal density in the stress group with 75 mg / kg extract was 27 ± 3 and in the hydroalcoholic extract treatment group was 100 mg / kg (22 ± 3), which increased significantly compared to the stress group (p <0.01). Conclusion: The results of the current study show that the hydroalcoholic extract of plant Bromzebel probably increases the neuronal density of the brain hippocampus due to its polyphenolic substances such as flavonoids, which is due to its high antioxidant properties.

Cell number in relation to primary pattern formation in the embryo of Xenopus laevis

Development ◽  
1979 ◽  
Vol 53 (1) ◽  
pp. 269-289
Author(s):  
Jonathan Cooke
Keyword(s):  
Cell Cycle ◽  
Pattern Formation ◽  
Cell Cycle Control ◽  
Cell Number ◽  
The Body ◽  
Morphological Evidence ◽  
Tail Bud ◽  
Cell Cycle Time ◽  
Mesodermal Cell ◽  
Body Pattern

Morphological evidence is presented that definitive mesoderm formation in Xenopus is best understood as extending to the end of the neurula phase of development. A process of recruitment of cells from the deep neurectoderm layers into mesodermal position and behaviour, strictly comparable with that already agreed to occur around the internal blastoporal ‘lip’ during gastrula stages, can be shown to continue at the posterior end of the presumptive body pattern up to stage 20 (earliest tail bud). Spatial patterns of incidence of mitosis are described for the fifteen hours of development between the late gastrula and stage 20–22. These are related to the onset of new cell behaviours and overt cyto-differentiations characterizing the dorsal axial pattern,which occur in cranio-caudal and then medio-lateral spatial sequence as development proceeds. A relatively abrupt cessation of mitosis, among hitherto asynchronously cycling cells,precedes the other changes at each level in the presumptive axial pattern. The widespread incidence of cells still in DNA synthesis, anterior to the last mitoses in the posterior-to-anteriordevelopmental sequence of axial tissue, strongly suggests that cells of notochord and somites in their prolonged, non-cycling phase are G2-arrested, and thus tetraploid. This is discussed in relation to what is known of cell-cycle control in other situations. Best estimates for cell-cycle time in the still-dividing, posterior mesoderm of the neurula lie between 10 and 15 h. The supposition of continuing recruitment from neurectoderm can resolve an apparent discrepancy whereby total mesodermal cell number nevertheless contrives to double over a period of approximately 12 h during neurulation when most of the cells are leaving the cycle. Because of pre-existing evidence that cells maintain their relative positions (despite distortion)during the movements that form the mesodermal mantle, the patterns presented in this paper can be understood in two ways: as a temporal sequence of developmental events undergone by individual, posteriorly recruited cells as they achieve their final positions in the body pattern, or alternatively as a succession of wavefronts with respect to changes of cellstate, passing obliquely across the presumptive body pattern in antero-posterior direction. These concepts are discussed briefly in relation to recent ideas about pattern formation in growing systems.

The impact of using divergent thinking strategies on reading comprehension

2021 ◽  
Vol 23 (10) ◽  
pp. 78-99
Author(s):  
A. Al Masri ◽  
T. Krishan ◽  
F. Al Talahin ◽  
S. Almassarweh
Keyword(s):  
Reading Comprehension ◽  
Divergent Thinking ◽  
Analysis Of Covariance ◽  
Motivation For Learning ◽  
Comprehension Skills ◽  
Thinking Strategies ◽  
The Impact ◽  
Reading Comprehension Skills ◽  
The Brain ◽  
Experimental Group

Introduction. Divergent thinking strategies are based on brain activity represented by a series of successive and branching questions related to a particular reading text. These strategies stimulate the minds of sixth graders to think of new stimuli such as finding a solution to a specific problem, or making a specific judgment, or predicting future events, which produces new and innovative solutions and achieves a deeper understanding of the target reading text.The present research aims to investigate the impact of divergent thinking strategies in developing reading comprehension skills among sixth-grade students in the English language.Methodology and research methods. The authors used the quasi-experimental approach. A pre-post design was used to identify the effect of employing divergent thinking strategies in developing reading comprehension skills. The study sample consisted of 136 students, who were selected purposefully and distributed into two groups: experimental and control groups. Students in experimental group were taught using divergent thinking strategies. Students in control group were taught in the usual way.Results and scientific novelty. The analysis of covariance (ANCOVA) found statistically significant differences between the two groups in favour of the experimental group in achievement. In addition, significant differences were found in the Motivation for Learning English between the two groups. It was found that divergent thinking strategies stimulate students’ thinking through various questions and allow them to look at their familiar knowledge with a new vision, to produce and generate new ideas with creative features.Practical significance. The current study is useful in determining the appropriate reading comprehension skills for students, and targeting them in developing these skills. This research also draws the attention of teachers to the importance of including strategies compatible with the brain, including divergent thinking strategies, when planning reading lessons. As for the educational supervisors, it puts in their hand’s strategies based on the theory of learning in the brain, including the divergent thinking strategies and how to employ them in reading lessons in order to develop reading comprehension. Moreover, these research materials can be employed by mentors in directing teachers to depart from the framework of traditional methods through the use of divergent thinking strategies in their classroom teaching practices.

L-DOPA and the Brain Pattern of Dopamine Extracellular Levels

2014 ◽  
pp. 251
Author(s):  
Philippe De Deurwaerdère ◽  
Sylvia Navailles ◽  
Léa Milan
Keyword(s):  
Brain Pattern ◽  
The Brain

scholarly journals Re-membering the body: applications of computational neuroscience to the top-down control of regeneration of limbs and other complex organs

2015 ◽  
Vol 7 (12) ◽  
pp. 1487-1517 ◽  
Author(s):  
G. Pezzulo ◽  
M. Levin
Keyword(s):  
Information Processing ◽  
Pattern Formation ◽  
Computational Neuroscience ◽  
Memory System ◽  
The Body ◽  
Signaling Networks ◽  
Control Mechanisms ◽  
Top Down ◽  
The Brain

How do regenerating bodies know when to stop remodeling? Bioelectric signaling networks guide pattern formation and may implement a somatic memory system. Deep parallels may exist between information processing in the brain and morphogenetic control mechanisms.

Greater Movement-Related Cortical Potential During Human Eccentric Versus Concentric Muscle Contractions

2001 ◽  
Vol 86 (4) ◽  
pp. 1764-1772 ◽  
Author(s):  
Yin Fang ◽  
Vlodek Siemionow ◽  
Vinod Sahgal ◽  
Fuqin Xiong ◽  
Guang H. Yue
Keyword(s):  
Muscle Activation ◽  
Onset Time ◽  
Muscle Contractions ◽  
Elbow Flexor ◽  
Movement Planning ◽  
Cortical Activation ◽  
Cortical Potential ◽  
Eeg Signals ◽  
Muscle Actions ◽  
The Brain

Despite abundant evidence that different nervous system control strategies may exist for human concentric and eccentric muscle contractions, no data are available to indicate that the brain signal differs for eccentric versus concentric muscle actions. The purpose of this study was to evaluate electroencephalography (EEG)-derived movement-related cortical potential (MRCP) and to determine whether the level of MRCP-measured cortical activation differs between the two types of muscle activities. Eight healthy subjects performed 50 voluntary eccentric and 50 voluntary concentric elbow flexor contractions against a load equal to 10% body weight. Surface EEG signals from four scalp locations overlying sensorimotor-related cortical areas in the frontal and parietal lobes were measured along with kinetic and kinematic information from the muscle and joint. MRCP was derived from the EEG signals of the eccentric and concentric muscle contractions. Although the elbow flexor muscle activation (EMG) was lower during eccentric than concentric actions, the amplitude of two major MRCP components—one related to movement planning and execution and the other associated with feedback signals from the peripheral systems—was significantly greater for eccentric than for concentric actions. The MRCP onset time for the eccentric task occurred earlier than that for the concentric task. The greater cortical signal for eccentric muscle actions suggests that the brain probably plans and programs eccentric movements differently from concentric muscle tasks.

Parallel changes of blood flow and heterogeneity of capillary plasma perfusion in rat brains during hypocapnia

1996 ◽  
Vol 270 (4) ◽  
pp. H1441-H1445
Author(s):  
J. Vogel ◽  
R. Abounader ◽  
H. Schrock ◽  
K. Zeller ◽  
R. Duelli ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Coefficient Of Variation ◽  
Blue Dye ◽  
Capillary Perfusion ◽  
Brain Capillary ◽  
Arterial Pco2 ◽  
Transit Times ◽  
The Brain ◽  
Experimental Group

Plasma perfusion patterns were investigated in brain capillaries during decreased cerebral blood flow induced by hyperventilation. Anesthetized rats were decapitated 3-4 s after being given an intravenous bolus injection of Evans blue dye. the measured steep increase of the arterial dye concentration at this moment ensures that different capillary plasma transit times are reflected in different intracapillary dye concentrations. The observed heterogeneity of capillary plasma transit time was expressed as the coefficient of variation (means +/- SD) of the intracapillary dye concentrations. For comparison, cerebral blood flow was determined at comparable PCO2 values in a second experimental group. At arterial PCO2 values between 40 and 25 mmHg, the cerebral blood flow and the coefficient of variation of the intracapillary dye concentration decreased with decreasing PCO2, whereas at PCO2 values <25 mmHg cerebral blood flow and coefficient of variation did not correlate with the arterial PCO2. However, it cannot be excluded that the coefficient of variation of the intracapillary dye concentration increases between 25 and 14 mmHg and decreases between 14 and 10 mmHg. It is concluded that the reduction of cerebral blood flow measured during moderate hypocapnia is paralleled by a decreased heterogeneity of the brain capillary perfusion. During severe hypocapnia this relationship is lost, indicating a potential disturbance of the cerebral microcirculation.

scholarly journals Cerebral and gonadal aromatase expressions are differently affected during sex differentiation of Pleurodeles waltl

2004 ◽  
Vol 33 (3) ◽  
pp. 717-727 ◽  
Author(s):  
Sandra Kuntz ◽  
Amand Chesnel ◽  
Stéphane Flament ◽  
Dominique Chardard
Keyword(s):  
Sex Differentiation ◽  
Temperature Sensitive ◽  
Aromatase Activity ◽  
Gonadal Differentiation ◽  
Aromatase Expression ◽  
Larval Stages ◽  
Exon 1 ◽  
The Individual ◽  
Pleurodeles Waltl ◽  
The Brain

In vertebrates, sex is determined essentially by two means, genetic factors located on sex chromosomes and epigenetic factors such as temperature experienced by the individual during development. Steroids, especially estrogens, are clearly involved in gonadal differentiation in non-mammalian vertebrates. In this regard, the expression of the estrogen-producing enzyme, aromatase, has been shown to be temperature-sensitive in species where temperature can reverse sex differentiation, especially in our model, the amphibian Pleurodeles waltl. We investigated here the regulation of aromatase expression in the brain during sex differentiation in Pleurodeles. We first isolated a brain isoform of aromatase mRNA which differs in its 5′ untranslated region from the isoform previously isolated from adult gonads. In adult Pleurodeles, the brain isoform is mainly expressed in brain tissue while the other isoform is gonad specific. Thus, regulation of aromatase expression in P. waltl could occur by alternative splicing of non-coding exon 1 as previously described in mammals. We then investigated aromatase expression in the brain of male and female larvae and found no differences with regard to sex. Measures of aromatase activity in the brain also showed no differences between sexes at larval stages whereas activity markedly increases in the ovary concomitant with the start of gonadal differentiation. These results support the hypothesis that aromatase could be a target of a temperature-sensitive sex-reversing effect in the gonads but not in the brain.

scholarly journals Decreased Heterogeneity of Capillary Plasma Flow in the Rat Whisker-Barrel Cortex during Functional Hyperemia

1996 ◽  
Vol 16 (6) ◽  
pp. 1300-1306 ◽  
Author(s):  
Johannes Vogel ◽  
Wolfgang Kuschinsky
Keyword(s):  
Evans Blue ◽  
Barrel Cortex ◽  
Stimulation Frequency ◽  
Blue Dye ◽  
Functional Hyperemia ◽  
Transit Times ◽  
Mystacial Vibrissae ◽  
The Right ◽  
The Brain ◽  
Experimental Group

The pattern of capillary plasma perfusion was investigated in the rat brain during functional activation. Functional hyperemia was induced in the left whisker-barrel cortex by deflection of the right mystacial vibrissae for 2 min at frequencies of 1–7 Hz. Rats were decapitated under anesthesia 3 s after i.v. bolus injection of Evans blue dye. The steep increase of the arterial dye concentration ensures that divergent capillary plasma transit times result in unequal intracapillary dye concentrations. Plasma perfusion heterogeneity was determined from the coefficient of variation (CV) of Evans blue concentrations measured in numerous single capillaries of the whisker-barrel cortex. Functional hyperemia was quantified from measurements of CBF using the [14C]-iodoantipyrine technique in a second experimental group. CBF in the left whisker-barrel cortex increased with the stimulation frequency and was maximal at 5 Hz compared to the right side. Conversely, plasma perfusion heterogeneity decreased with stimulation frequency in a reciprocal way, being minimal at 5 Hz. Results indicate a decrease in the microcirculatory flow heterogeneity during functional hyperemia in the brain.

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