Exploring size-action and number-action associations in infancy.

The mature morphology of most plants can usually be said to consist of three mutually exclusive organs: leaves, stems, and roots. The vast majority of mature morphologies may be easily grouped into one of these mutually exclusive categories. However, during very early stages of development and in many instances from inception, the division between organ categories becomes fuzzy due to the overlap in developmental processes that are shared between the aforementioned mutually exclusive categories. One such overlap has been described at the gene level where KNOXI homologues, transcription factors responsible for maintaining indeterminate cell fate, are expressed in the shoot apical meristem and during early stages of compound leaf development. This study characterizes the occurrence and spatial localization of mRNA of a KNOXI homologue, MaKN1, during the early stages of development in the simple leaves of Myriophyllum aquaticum, an aquatic angiosperm from the family Haloragaceae exhibiting pentamerous whorls of finely lobed leaves. A 300-bp KNOXI fragment was sequenced from M. aquaticum and used in an RNA localization study to determine the temporal and spatial expression of KNOXI during the early stages of leaf lobe development in M. aquaticum. The developmental sequence of leaves of M. aquaticum was also described using scanning electron microscopy. Lobe development of M. aquaticum occurs in two very distinct regions at the leaf base in an alternating fashion reminiscent of a distichous shoot system. It was discovered that MaKN1 expression is localized to both the shoot apical meristem and early stages of leaf primordia development (P1-P7). Initially, MaKN1 is expressed ubiquitously throughout primordia (P1-P3); however, as lobes develop, MaKN1 becomes localized to recently emerged lobe primordia, and disappears as lobes develop basipetally. The pattern of gene expression is indicative of shared developmental processes during early development between shoots, compound leaves, highly lobed simple leaves and unifoliate simple leaves which lack KNOXI expression. These findings are supportive of Arber's less rigid 'partial shoot' theory, which conceptualizes compound leaves as having shoot-like elements.

Neurons involved in grasp preparation with hand and mouth were previously recorded in the premotor cortex of monkey. The aim of the present kinematic study was to determine whether a unique planning underlies the act of grasping with hand and mouth in humans as well. In a set of four experiments, healthy subjects reached and grasped with the hand an object of different size while opening the mouth (experiments 1 and 3), or extending the other forearm (experiment 4), or the fingers of the other hand (experiment 5). In a subsequent set of three experiments, subjects grasped an object of different size with the mouth, while opening the fingers of the right hand (experiments 6-8). The initial kinematics of mouth and finger opening, but not of forearm extension, was affected by the size of the grasped object congruently with the size effect on initial grasp kinematics. This effect was due neither to visual presentation of the object, without the successive grasp motor act (experiment 2) nor to synchronism between finger and mouth opening (experiments 3, 7, and 8). In experiment 9 subjects grasped with the right hand an object of different size while pronouncing a syllable printed on the target. Mouth opening and sound production were affected by the grasped object size. The results of the present study are discussed according to the notion that in an action each motor act is prepared before the beginning of the motor sequence. Double grasp preparation can be used for successive motor acts on the same object as, for example, grasping food with the hand and ingesting it after bringing it to the mouth. We speculate that the circuits involved in double grasp preparation might have been the neural substrate where hand motor patterns used as primitive communication signs were transferred to mouth articulation system. This is in accordance with the hypothesis that Broca's area derives phylogenetically from the monkey premotor area where hand movements are controlled.

The heart functions like a pump derived by electrical impulses known as action potentials. A remarkable feature of cardiac action potentials is that they initiate autonomously by specialized cells in the right atrium located in the sinoatrial (SA) node. The action potentials generated by the SA node are then conveyed to atrial myocytes and subsequently to the atrio-ventricular node where the electrical activity is delayed, allowing the atrium to pump the blood into the ventricles. Thereafter, the electrical excitation of ventricles ensues through fibres known as bundle branches. During embryonic development and organogenesis of heart, intrinsic pacemaker activity is one of the many requirements for generation of autonomous electrical impulse and cardiac function. An equally critical aspect of cardiac development is the generation of non-pacing contracting myocytes such as the atrail and ventricular myogenic lineage. Propagation of action potentials in heart, and hence the ability to pump blood into circulation, relies on flow of ions in and out of cardiac myocytes. This intricate balance of ionic flow is generated by proteinaceous gates referred to as ion channels. The so called pacemaker channels, also known as funny channels, If or Ih, control the autonomous electrical activity of the heart as well as the pacemaker activity in certain regions of the brain. Electrophysiological studies have identified distinct functional hallmarks of If channels which make them good candidate for pacemaker activity (reviewed in Accili et al. 2002). Unlike most voltage-gated channels, If is activated upon membrane hyperpolarization. This property allows inward flow of sodium ions during the repolarization phase of the action potential which then depolarizes the membrane potential back towards a threshold for generation of the next action potential. In addition, If current is directly modulated by cyclic nucleotides, independent of kinases, thus allowing quick changes in the duration of action potential and the rapid control of heart beat by the autonomic nervous system. The molecular identity of If channels remained largely unknown until three independent groups simultaneously cloned its gene approximately 20 years after it was first discovered by electrophysiological measurements (Accili et al. 2002 and therein). When expressed in heterologous systems, isolated cDNA clones produce currents that are activated by voltage and modulated by cyclic nucleotides. With regard to this dual mode of activation, these channels are now referred to as hyperpolarization-activated cyclic nucleotide-modulated (HCN). In vertebrates, four such genes (HCN1–4) have been identified. Autonomous pacemaker activity of the heart starts remarkably early during embryogenesis and it is considered one of the first signs of a healthy human embryo. In order to investigate the molecular bases of early cardiac activity, Qu et al. (2008) have examined the contribution of the pacemaker channels to spontaneous beating of cells derived from mouse embryonic stem cells (mESCs) during development in culture, chosen arbitrarily after plating differentiated cells for 2–4 days (early), 5–8 days (intermediate) or 9–15 days (late). Briefly, their study examines the current density of If, its correlation to rhythmicity and HCN isoform expression as well as its modulation by automonic stimulation in early, intermediate and late developmental stages. The authors have drawn several important conclusions which significantly advance our understanding of the mechanisms involved in early rhythmic activity of cardiac stem cells and which suggest that stem cells can be utilized as a faithful model recapitulating the features of heart development. Qu et al. (2008) start by demonstrating a developmental increase in the proportion of cell expressing If and the density of If per individual cell concomitant with an increase in action potential frequency and beating rate. The authors then examine the effect of a specific If blocker (ZD7288) on rhythmicity of single cells and report that micromolar concentrations of ZD7288 reduce beating frequency and inhibit If current in mESCs. These experimental observations make a solid case for the involvement of the pacemaker current in the maintenance of fast and regular beating rate of mESCs. In their study, Qu et al. (2008) also correlate functional expression of the native pacemaker current to expression of specific HCN isoforms. Of the four isoforms tested, HCN2 and HCN3 are the only two that were detectable by Western blots which were performed using vigilantly selected antibodies. Whereas the expression levels of HCN2 remain constant throughout the development, the expression of HCN3 is dramatically decreased in late developmental stages. Qu et al. (2008) then go on to investigate the role of autonomic regulation in mESCs and they test whether modulation of If current contributes to regulation of rhythmicity. They find that treatment of cells with the β-adrenergic agonist isoproterenol (isoprenaline) significantly increased beating rate in early and late developmental stages. Accompanying the increase in beating rate is a positive shift in activation range of If current by isoproterenol. On the other hand, micromolar concentrations of the muscarinic agonist acetylcholine shifted the voltage dependence of If to more negative voltages and decreased the beating rate of differentiated stem cells. Therefore, the authors conclude that the cellular machinery required for autonomic regulation is present and functional at early developmental stages in mESCs. In addition, they propose that modulation of If is a central component of autonomic regulation in mESCs. It is noteworthy to point out that HCN isoform expression and spontaneous beating rate accompanying maturation reported by Qu et al. (2008) are in contrast to previous studies. These variations have been extensively referenced and discussed by Qu et al. (2008) as being either species specific or due to cell line differences obtained from the same species. Qu et al. (2008) demonstrate a steady expression of HCN2 and a decreased expression of HCN3 during development of cells in culture and they argue that the dynamic change in expression level of HCN3 is consistent with the change in activation rate of If during development in culture. However, at face value, the decrease in expression of HCN3 is inconsistent with the increase in If current density during development. Several possibilities can explain this seemingly counterintuitive observation. Firstly, it is possible that high levels of HCN3 in early developmental stages inhibit the functional expression of pacemaker channels. This possibility can easily be addressed experimentally in heterologous systems expressing HCN2 and variable amounts of HCN3. Assuming that HCN3 exerts inhibitory effects, increasing amounts of HCN3 expression is expected to suppress generation of functional channels. Interestingly, one group has reported that HCN3 does not form functional homomers when expressed in heterologous systems (Chen et al. 2001). Secondly, it is possible that robust functional If current is present in early developmental stages but masked by a current flowing in the opposite direction. Although this explanation is formally possible, the authors have carefully chosen an external solution to suppress potassium and calcium channels during the measurements of If. Lastly, it is possible that pacemaker current in early developmental stages is activated at extreme hyperpolarization test pulses outside the range of those used by Qu et al. (2008). Indeed, one proposed mechanism of differentiation of a non-pacing region of the heart is a shift in activation range of If to potentials that are outside the physiological range (Yu et al. 1993). Another intriguing observation by Qu et al. (2008) is the heterogeneity of cells with respect to If and beating rhythmicity in early developmental stages. This heterogeneity can be explained by the presence of a mixture of pacing and quiescent cells, reminiscent of nodal and contracting myocytes in cardiac tissue. This assumption implies that the cells in later stages of development in tissue culture are less differentiated than those in earlier stages. Consistent with this assumption, several studies (extensively referenced in Maltsev et al. 1993) have reported changes in differentiation stage of cells in culture and reversion of differentiated ventricular cells back to embryonic stages. In summary, analogous to all well-conducted scientific inquiries, the studies of Qu et al. (2008) have raised several important questions which will certainly lead to other exciting studies in the future. I am grateful to the Heart and Stroke Foundation of Canada for their continuous support throughout my postdoctoral fellowship.

The basement membrane, which separates the inner enamel epithelium from the dental papilla in the early stages of tooth development, is known to play a significant role in odontogenesis. In this review article, this basement membrane was described in detail based on our recent findings with the use of high-resolution electron microscopy. Tooth germs of a monkey (Macaca fuscata) and a shark (Cephaloscyllium umbratile) were processed for thin-section observations. During the early stage of development, the basement membrane of the inner enamel (dental) epithelium was composed of a lamina lucida, lamina densa, and much wider lamina fibroreticularis. At higher magnification, the lamina densa in both species was made up of a fine network of cords, which are generally the main constituents of the basement membranes. In the monkey tooth, the lamina fibroreticularis was rich in fibrils, which were now characterized as basotubules, 10-nm-wide microfibril-like structures. The space between the basotubules was filled with a cord network that extended from the lamina densa. Dental papilla cell processes were inserted into the lamina fibroreticularis, and their surface was closely associated with numerous parallel basotubules via 1.5- to 3-nm-wide filaments. In the shark tooth during its early stage of development, the basotubules were absent in the lamina fibroreticularis and only narrow extensions, 60-90 nm wide and 1-2 microm long, of the cord network of the lamina densa were present. The dental papilla cells were immobilized by means of the binding of their processes to the extensions. These results indicate that basement membranes in both monkey and shark teeth at early stage of development are specialized for functions as anchoring and firm binding, which are essential for the successful differentiation of the odontoblasts.

Egg presence and developmental stage influence spawning-site choice by female garibaldi

The relative contributions of C3 photosynthesis and crassulacean acid metabolism (CAM) during the earliest stages of development were investigated to assess how much each might contribute to cactus pear (Opuntia ficus-indica) productivity. The developmental progression of C3 photosynthesis and CAM was assessed in seedlings and daughter cladodes of mature plants by titratable acidity, δ13C isotopic values and diel gas exchange measurements. Nocturnal acidification was observed in seedling cladodes and cotyledons at the earliest stages of development and became highly significant by 75 days of development. Seedling cotyledons showed mean δ13C values of -21.4 and -17.1 ‰ at 30 and 100 days of age, respectively. Seedling cladodes showed mean δ13C values of -19.4 and -14.5 ‰ at 30 and 100 days of age, respectively. These values are typical of CAM plants. Net CO2 assimilation was negative, then occurred in both the day and the night, with nighttime fixation becoming predominant once the primary cladode reached 5 cm in size. Emergent daughter cladodes growing on mature plants showed nocturnal titratable acidity at the earliest stages of development, which became significant when daughter cladodes were >2.5-5 cm in height. Emergent daughter cladodes showed mean δ13C values of -14.5 to -15.6 ‰, typical of CAM plants. CO2 assimilation studies revealed that net CO2 uptake was negative in daughter cladodes <12 cm in length, but then exhibited net positive CO2 assimilation in both the day and the night, with net nocturnal CO2 assimilation predominating once the daughter cladode grew larger. Developing O. ficus-indica primary and daughter cladodes begin as respiring sink tissues that transition directly to performing CAM once net positive CO2 fixation is observed. Overall, these results demonstrate that CAM is the primary form of photosynthetic carbon assimilation for O. ficus-indica even at the earliest stages of seedling or daughter cladode development.

The organogenesis of floral development in the dioecious clonal tree species Rhus hirta (Anacardiaceae) offers an excellent model system to study gender expression in dioecious plants. Pistillate and staminate flowers from developing inflorescences were collected from Grover Island, located off the northern shore of Prince Edward Island, Canada. The developmental morphology of both floral types was studied using scanning electron microscopy. The early stages of floral development of R. hirta are essentially the same in the two sexes. Both the stamen and carpel primordia are initiated in male and female flowers. Furthermore, the primordial sex organs on both flower types show striking similarities in size and symmetry as well as sequence of initiation in the early stages of development. During the later stages of development, the stamens in the female flowers and the gynoecium in the male flowers abort, resulting in very different morphologies at maturity. Statistical analyses revealed that the height of the mature gynoecium and stamens as well as the length of the petals differed significantly between sexes. This species may be reflecting its relationship to hermaphroditic ancestors during the early stages of development.

The nucellus, which is the maternal tissue of the wheat grain, degenerates during the early stages of development. We have investigated whether or not this degenerative process may be considered as programmed cell death (PCD). The analysis of DNA of tissues dissected from developing wheat (Triticum aestivum L. cv Chinese Spring) grains at 5-20 days post anthesis (dpa) showed the presence of DNA laddering, which is indicative of internucleosomal fragmentation of nuclear DNA, in maternal tissues but not in the endosperm. The TUNEL assay showed in-situ internucleosomal fragmentation of DNA in nuclei of parenchymal and epidermal cells of the nucellus, as well as in the pericarp, during the early stages of grain development (5 dpa). Furthermore, internucleosomal fragmentation of nuclear DNA was observed in nucellar projection cells in the middle stages of grain development (13-18 dpa), thus showing a process of PCD in these maternal tissues. Electron-transmission microscopy analysis allowed the morphology of PCD to be characterized in this plant tissue. Initially, fragmentation of the cytoplasm was observed, the nuclear envelope appeared dilated and to be forming vacuoles, and the content of heterochromatin increased. A progressive degradation of the cytosolic contents and organelles was observed, and the plasma membrane was disrupted. However, the Golgi apparatus remained intact and apparently functional even in the final stages of cell death.

The main purpose of this study was to explore the early stages of L2 inner speech development. A secondary aim was to test the effectiveness of the diary and stimulated recall techniques in the elucidation of L2 inner speech phenomena. Over a period of four months, 16 beginning ESL college students kept diaries on the inner speech they had experienced in their L2 during class and outside the classroom. The stimulated recall technique was used to encourage clarification and expansion of diary entries. Four main types of reported L2 inner speech were found. From the most frequent to the least frequent, these categories were (1) concurrent processing of language being heard or read, (2) recall of language heard, read, or used previously, (3) preparation before writing or speaking, and (4) silent verbalization of thoughts for private purposes. Results suggest that, at the early stages of development, inner speech in the L2 is characterized by deliberate and spontaneous attempts to internalize external social L2 speech. It is hypothesized that such inner speech activity is necessary for the eventual development of the L2 as a tool for thought. Notwithstanding the elusive and covert nature of inner speech, the diary – complemented by the stimulated recall technique – proved to be a rich source of insights into the nature of inner speech activity in the L2.

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;This study aims to build a conceptual simulation used at the early stage of PHEV development. This simulation enables to design vehicle concept and fundamental architecture with regard to fuel economy, vehicle acceleration and electric range. The model based on forward-looking method comprises of plant-model and controller-model which are made by one-dimensional simulation tool “GT-SUITE” and Matlab/SIMULINK respectively. In order to automatically couple between them and to implement iterative calculations of SOC (State-of-Charge) convergence, optimization and automation tool “modeFRONTIER” was used. As a case study of this simulation, we adopted series-parallel type plug-in hybrid electric vehicle (PHEV) and demonstrated the results on fuel economy of a legislative driving cycle and 0-60mph vehicle acceleration. Moreover, procedures to identify component specifications meeting vehicle targets and requirements at the early stage of vehicle development were concretely described. In conclusion, through a case study of specific PHEV, it was demonstrated that this methodology contributes to design vehicle concept and to define system and component specifications.&lt;/div&gt;&lt;/div&gt;

Differential expression and localization of brain-type and mitochondrial creatine kinase isoenzymes during development of the chicken retina: Mi-CK as a marker for differentiation of photoreceptor cells

Changes in nucleolar size and nucleolar vacuolation at early stages of fiber development and final fiber dimensions were determined for cotton of different species: Gossypium hirsutum L. cv. B49, Gossypium barbadense L. cv. Menoufi and Gossypium arboreum L. cv. Virnar. Size of the nucleolus in combination with its vacuolation at an early stage of development was found to be clearly associated with the final result of fiber development.

Analytical hierarchy processes (AHP) for the selection of solvents in early stages of pharmaceutical process development

A number of Cucurbita pepo genotypes showing instable monoecy or partial andromonoecy, i.e. an incomplete conversion of female into bisexual flowers, have been detected. Given that in melon and cucumber andromonoecy is the result of reduction of ethylene production in female floral buds, caused by mutations in the ethylene biosynthesis genes CmACS7 and CsACS2; we have cloned and characterized two related C. pepo genes, CpACS27A and CpACS27B. The molecular structure of CpACS27A and its specific expression in the carpels of female flowers during earlier stages of flower development suggests that this gene is the Cucurbita ortholog of CmACS7 and CsACS2. CpACS27B is likely to be a paralogous pseudogene since it has not been found to be expressed in any of the analyzed tissues. CpACS27A was sequenced in Bolognese (Bog) and Vegetable Spaghetti (Veg), two monoecious inbred lines whose F2 was segregating for partial andromonoecy. The Bog allele of CpACS27A carried a missense mutation that resulted in a substitution of the conserved serine residue in position 176 by an alanine. Segregation analysis indicated that this mutant variant is necessary but not sufficient to confer the andromonoecious phenotype in squash. In concordance with its involvement in stamen arrest, a reduction in CpACS27A expression has been found in bisexual flower buds at earlier stages of development. This reduction in CpACS27A expression was concomitant with a downregulation of other ethylene biosynthesis and signaling genes during earlier and later stages of ovary development. The role of CpACS27A is discussed regarding the regulation of ethylene biosynthesis and signaling genes in the control of andromonoecy-associated traits, such as the delayed maturation of corolla and stigma as well as the parthenocarpic development of the fruit.

Lipids, proteins and starch are the main storage products in oat seeds. As a first step in elucidating the regulatory mechanisms behind the deposition of these compounds, two different oat varieties, 'Freja' and 'Matilda', were analysed during kernel development. In both cultivars, the majority of the lipids accumulated at very early stage of development but Matilda accumulated about twice the amount of lipids compared to Freja. Accumulation of proteins and starch started also in the early stage of kernel development but, in contrast to lipids, continued over a considerably longer period. The high-oil variety Matilda also accumulated higher amounts of proteins than Freja. The starch content in Freja kernels was higher than in Matilda kernels and the difference was most pronounced during the early stage of development when oil synthesis was most active. Oleosin accumulation continued during the whole period of kernel development.