Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Convergence”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 343 records · Page 19Linked to original sources
PubMed1999

Thermolysin and mitochondrial processing peptidase: how far structure-functional convergence goes.

The structure-functional convergence between two Zn-dependent proteases, namely thermolysin and mitochondrial processing peptidase (MPP), is described. These two families of nonhomologous enzymes show not only functional convergence of several active site residues as in chymotrypsin and subtilisin, but also structural convergence of overall molecular architectures including the beta-sheet arrangement and packing of the surrounding alpha-helices. The major functionally important structural elements are present in both enzymes with different topological connections and often in reverse main-chain orientation, but display similar packing. The structural comparison helps to rationalize sequence "inversion" of the HEXXH thermolysin consensus present as HXXEH in MPP. The described structural convergence may be due to a limited number of alternatives to build a Zn-protease that utilizes hydrogen bonding between a substrate main chain and the enzyme beta-sheet for substrate binding.

Amino Acid Sequence↗
PubMed2004

Convergent evolution of Darwin's finches caused by introgressive hybridization and selection.

Between 1973 and 2003 mean morphological features of the cactus finch, Geospiza scandens, and the medium ground finch, G. fortis, populations on the Galápagos island of Daphne Major were subject to fluctuating directional selection. An increase in bluntness or robustness in the beak of G. scandens after 1990 can only partly be explained by selection. We use 16 microsatellite loci to test predictions of the previously proposed hypothesis that introgressive hybridization contributed to the trend, resulting in genes flowing predominantly from G. fortis to G. scandens. To identify F1 hybrids and backcrosses we use pedigrees where known, supplemented by the results of assignment tests based on 14 autosomal loci when parents were not known. We analyze changes in morphology and allelic composition in the two populations over a period of 15-20 years. With samples that included F1 hybrids and backcrosses, the G. scandens population became more similar to the G. fortis population both genetically and morphologically. Gene flow between species was estimated to be three times greater from G. fortis to G. scandens than in the opposite direction, resulting in a 20% reduction in the genetic difference between the species. Nevertheless, removing identified F1 hybrids and backcrosses from the total sample and reanalyzing the traits did not eliminate the convergence. The two species also converged in beak shape by 22.2% and in body size by 45.5%. A combination of introgressive hybridization and selection jointly provide the best explanation of convergence in morphology and genetic constitution under the changed ecological conditions following a major El Niño event in 1983. The study illustrates how species without postmating barriers to gene exchange can alternate between convergence and divergence when environmental conditions oscillate.

Animals↗
PubMed1990

Are women drinking more like men? An empirical examination of the convergence hypothesis.

The convergence hypothesis predicts that women's drinking levels are increasing and are approaching those observed in men. To test this hypothesis, drinking practices of women and men were assessed at a large urban university at two points in time, 1977 (n = 1711) and 1985 (n = 1045). Although women's ethanol intake remained the same, significant changes in patterns of drinking were seen. The mean annual volume of beer consumed by females in 1985 showed a 33.9% increase over the mean annual volume in 1977. "Binge" drinking increased for both sexes from 1977 to 1985. A decrease in women's rate of abstention was also observed. Convergence with male drinking patterns was noted for several drinking parameters. This convergence was demonstrated by decreases in the ratios of men's drinking to women's drinking for these measures. Women consumed more wine per occasion than men in 1985. When corrections were made for differences in body fluid, the data suggested that convergence was not a trend, but had in fact occurred. The findings have serious implications, particularly in the light of recent findings that women are at greater health risk than men when they imbibe ethanol.

Adult↗
PubMed1990

Convergent and discriminant validity of FACES-III: family adaptability and cohesion.

Research on earlier versions of the Family Adaptability and Cohesion Evaluation Scales (FACES) has ostensibly shown that the scales lack discriminant and convergent validity (23). However, these studies have defined convergence as agreement between family members or as agreement between family members and family therapists. Such definitions confound real differences between respondents' perceptions of the family with the notion of convergent validity. In the current study, we take a different approach to construct validity. Multiple measures of family adaptability, cohesion, and talkativeness were administered to two family members (insiders) and two significant others (outsiders). The two insiders' responses were averaged together, as were the two outsiders' responses. Using confirmatory factor analysis, we demonstrated that family adaptability, cohesion, and talkativeness are distinct traits, and that the different sources of information about these traits, including FACES-III (24), have convergent validity.

Adaptation, Psychological↗
PubMed1987

Heterotopic activation of A delta and C fibres triggers inhibition of trigeminal and spinal convergent neurones in the rat.

1. Extracellular recordings were made from fourteen non-noxious only and nineteen convergent neurones in trigeminal nucleus caudalis of halothane-anaesthetized rats. All the neurones studied were excited by the continuous micro-electrophoretic ejection of an excitatory amino acid, DL-homocysteic acid (DLH), with mean currents of 38.0 +/- 7.2 and 39.8 + 6.5 nA producing steady discharges of 35.0 +/- 3.3 and 31.8 +/- 1.3 spikes/s from the non-noxious only and convergent neurones respectively. 2. The repeated percutaneous application (100 trials; 0.66 Hz) of single square-wave stimuli (10 mA; 2 ms) to the tail always induced a biphasic depression of the activity of the convergent, but never of the non-noxious only, neurones. Both the early and late components of this inhibition occurred at shorter latencies when the base rather than the tip of the tail was stimulated. Differences in latencies from the two sites of stimulation (100 mm apart) were used to estimate the conduction velocities of the peripheral fibres which were triggering the inhibitions. 3. The cumulated results showed that, for the onset of the earlier component of the inhibition, the mean difference between the latencies from the two sites of stimulation was 13.6 +/- 1.9 ms, corresponding to a peripheral conduction velocity of 7.3 +/- 0.3 m/s, which is in the A delta-fibre range. For the onset of the late component of inhibition, the mean difference was 147.7 +/- 14.9 ms, corresponding to a peripheral conduction velocity of 0.68 +/- 0.07 m/s, which is in the C-fibre range. 4. When currents of different intensities were applied percutaneously to the two stimulation sites, the thresholds for obtaining the A delta component were in the range 0.25-0.5 mA whereas the C component appeared with currents 1-2 mA. A clear relationship between current intensity and magnitude of inhibition was observed in the 0.25-2 mA range for the A delta component and in the 1-5 mA range for the C component. 5. In an additional series of experiments recordings were made from eleven convergent neurones in the dorsal horn of the lumbar spinal cord. By using essentially the same experimental procedure the effects of repetitive application (100 trials, 0.66 Hz) of percutaneous electrical stimuli (1 or 10 mA, 2 ms) applied to the muzzle, were studied on the steady discharges (42.3 +/- 5.4 spikes/s) induced by DLH. The application of the 10 mA stimuli induced a biphasic depression of activity, whereas only an early component was observed following 1 mA stimuli.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1987

A convergent input from nasal receptors and the larynx to the rostral sensory trigeminal nuclei of the cat.

1. Extracellular recordings were made from ninety-one neurones in the vicinity of the rostral trigeminal nucleus in chloralose-anaesthetized cats. 2. Sixty-two neurones within this area were activated by electrical stimulation of the ipsilateral superior laryngeal nerve (s.l.n.). Only two of the twenty-one neurones tested had an additional input from the contralateral s.l.n. 3. Fifty of these sixty-two neurones were also activated synaptically by light mechanical stimulation of the ipsilateral nasal cavity and in the eight neurones tested electrical stimulation of the ipsilateral nostril evoked activity. All these neurones exhibited characteristics of postsynaptic responses to s.l.n. and nasal stimulation, showing a variable latency to onset to either stimulus, summation and facilitation of more than one stimulus. 4. None of those neurones receiving an s.l.n. input, or those with convergent inputs from the s.l.n. and nose, could be affected by mechanical stimulation of any part of the face. 5. The activity of a further twenty-nine neurones was also recorded within this same general region. Sixteen responded to movement of the whiskers, five to touching the skin of the lower jaw, two to touching the skin of the upper jaw, three to touch around the eyebrows and three to touching other parts of the face. None of these neurones were activated by s.l.n. stimulation. 6. The location of seventeen of these neurones showing a convergent s.l.n. and nasal input was determined histologically. They were closely grouped together in a region 3.5-4.5 mm rostral to obex in and around the main trigeminal sensory nucleus, dorsolateral to the retrofacial nucleus corresponding to the parvocellular division of the alaminar spinal trigeminal nucleus. 7. The lack of somatosensory input to those neurones receiving a convergent input from the nose and s.l.n. is discussed in relation to previous studies describing somatosensory-visceral convergence to neurones within trigeminal nuclei.

Anesthesia, General↗
PubMed1993

Area postrema and aortic or vagal afferents converge to excite cells in nucleus tractus solitarius.

Area postrema neurons enhance baroreflex function, perhaps by augmenting baroreceptor afferent processing in the nucleus tractus solitarius (NTS). If so, NTS neurons should receive convergent excitatory inputs from area postrema neurons and baroreceptors. The aims of this study were to record extracellular activity of NTS neurons to determine whether 1) area postrema and aortic baroreceptor afferents converged in NTS, 2) area postrema and vagal afferents converged in NTS, and 3) the convergent inputs were facilitative. Studies were performed in pentobarbital sodium- or alpha-chloralose-anesthetized rabbits. Forty-six of 194 NTS neurons received inputs from the area postrema and aortic depressor nerve. Twelve of the 23 inputs showed facilitative summation; unit response rate evoked by paired inputs (79%) doubled the predicted (calculated) response rate for simple addition (37%). Fifty-eight of 114 NTS neurons received excitatory inputs from the area postrema and vagus. Eleven of the 13 inputs showed facilitative summation; unit response to paired inputs (87%) doubled the predicted response (44%). Area postrema neurons may augment the processing of aortic and vagal inputs by NTS neurons and, hence, enhance the reflex output of these afferent pathways.

Animals↗
PubMed2004

Excitatory convergence of periaqueductal gray and somatic afferents in the solitary tract nucleus: role for neurokinin 1 receptors.

Our previous studies (Boscan P, Kasparov S, and Paton JF. Eur J Neurosci 16: 907-920, 2002) showed that activation of somatic afferents attenuated the baroreceptor reflex via neurokinin type 1 (NK(1)) and GABA(A) receptors within the nucleus of the solitary tract (NTS). The periaqueductal gray matter (PAG) can also depress baroreceptor reflex function and project to the NTS. In the present study, we have tested the possibility that the dorsolateral (dl)-PAG projects to the NTS neurons that also respond to somatic afferent input. In an in situ, arterially perfused, unanesthetized decerebrate rat preparation, somatic afferents (brachial plexus), cervical spinal cord, and dl-PAG were stimulated electrically, whereas NTS neurons were recorded extracellularly. From 45 NTS neurons excited by either brachial plexus or dl-PAG stimulation, 41 received convergence excitatory inputs from both afferents. Onset latency and evoked peak discharge frequency from brachial plexus afferents were 39.4 +/- 4.7 ms and 10.7 +/- 1.1 Hz, whereas this was 43.9 +/- 6.4 ms and 7.9 +/- 1 Hz, respectively, following dl-PAG stimulation. As revealed by using a paired pulse stimulation protocol, monosynaptic connections were found in 9 of 36 neurons tested from both spinal cord and dl-PAG. We tested NK(1)-receptor sensitivity in 38 neurons that received convergent inputs from brachial plexus/PAG. Fifteen neurons were sensitive to selective antagonism of NK(1) receptors. CP-99994, the NK(1) antagonist, failed to alter ongoing firing activity but reduced the evoked peak discharge frequency following stimulation of both brachial plexus (from 12.3 +/- 1.8 to 7.2 +/- 1.3 Hz; P < 0.01) and PAG (from 7.8 +/- 1.5 to 4.5 +/- 1 Hz; P < 0.01). We conclude that 1) somatic brachial and PAG afferents can converge onto single NTS neurons; 2) this convergence occurs via either direct or indirect pathways; and 3) NK(1) receptors are activated by some of these inputs.

Afferent Pathways↗
PubMed2002

Vestibular convergence patterns in vestibular nuclei neurons of alert primates.

Sensory signal convergence is a fundamental and important aspect of brain function. Such convergence may often involve complex multidimensional interactions as those proposed for the processing of otolith and semicircular canal (SCC) information for the detection of translational head movements and the effective discrimination from physically congruent gravity signals. In the present study, we have examined the responses of primate rostral vestibular nuclei (VN) neurons that do not exhibit any eye movement-related activity using 0.5-Hz translational and three-dimensional (3D) rotational motion. Three distinct neural populations were identified. Approximately one-fourth of the cells exclusively encoded rotational movements (canal-only neurons) and were unresponsive to translation. The canal-only central neurons encoded head rotation in SCC coordinates, exhibited little orthogonal canal convergence, and were characterized with significantly higher sensitivities to rotation as compared to primary SCC afferents. Another fourth of the neurons modulated their firing rates during translation (otolith-only cells). During rotations, these neurons only responded when the axis of rotation was earth-horizontal and the head was changing orientation relative to gravity. The remaining one-half of VN neurons were sensitive to both rotations and translations (otolith + canal neurons). Unlike primary otolith afferents, however, central neurons often exhibited significant spatiotemporal (noncosine) tuning properties and a wide variety of response dynamics to translation. To characterize the pattern of SCC inputs to otolith + canal neurons, their rotational maximum sensitivity vectors were computed using exclusively responses during earth-vertical axis rotations (EVA). Maximum sensitivity vectors were distributed throughout the 3D space, suggesting strong convergence from multiple SCCs. These neurons were also tested with earth-horizontal axis rotations (EHA), which would activate both vertical canals and otolith organs. However, the recorded responses could not be predicted from a linear combination of EVA rotational and translational responses. In contrast, one-third of the neurons responded similarly during EVA and EHA rotations, although a significant response modulation was present during translation. Thus this subpopulation of otolith + canal cells, which included neurons with either high- or low-pass dynamics to translation, appear to selectively ignore the component of otolith-selective activation that is due to changes in the orientation of the head relative to gravity. Thus contrary to primary otolith afferents and otolith-only central neurons that respond equivalently to tilts relative to gravity and translational movements, approximately one-third of the otolith + canal cells seem to encode a true estimate of the translational component of the imposed passive head and body movement.

Animals↗
PubMed1984

Convergence onto interneurons subserving primary afferent depolarization of group I afferents.

The aim of the study was to investigate whether common or independent neuronal pathways are used to evoke primary afferent depolarization (PAD) from selectively activated group Ia and Ib afferents of different muscles. To this end, the spatial facilitation of effects of various afferents, indicating convergence on the same interneurons, was used as a test. Its occurrence was assessed on dorsal root potentials (DRPs) evoked in unspecified fibers or using intra-axonal recording from identified group Ia muscle spindle afferents or group Ib tendon organ afferents. Spatial facilitation has been found in PAD pathways a) from various Ia-afferents, whether of flexors or extensors; b) from various Ib-afferents, whether of flexors or extensors; and c) from flexor Ib-afferents and flexor or extensor Ia-afferents. In contrast, no indications have been found for common pathways from extensor Ib- and any Ia-afferents under conditions that proved effective in other combinations. Latencies of those components of PAD that appeared as a result of the spatial facilitation ranged from 2 to more than 7 ms, indicating that the convergence occurred in the shortest (trisynaptic) as well as longer pathways. The same patterns of convergence have been found in PAD pathways to extensor and flexor Ia-afferents (in experiments with intraaxonal recording from these afferents). The possibility might thus be considered that some neuronal pathways are used to modulate transmission via Ia-afferents independently of their muscle origin. The same might hold true for extensor and flexor Ib-afferents. Generally, it is concluded that the minimal number of distinct neuronal populations subserving PAD of group I afferents may be two to six. Additionally, actions of cutaneous, joint, and interosseous afferents on DRPs from Ia-afferents were reexamined to further the comparison between neurons mediating PAD and those mediating postsynaptic excitation or inhibition of motoneurons. Only depression of Ia DRPs followed stimulation of these afferents at intensities of 1.5-2.0 times threshold and higher; lower threshold afferents were apparently ineffective. On the basis of lack of convergence of extensor Ib and Ia muscle afferents and of low-threshold cutaneous afferents, interneurons mediating PAD may thus be distinguished from the interneurons subserving Ib and Ia-like-Ib postsynaptic actions in motoneurons. The latter are coexcited by these three groups of afferents.

Animals↗
PubMed1993

Validation of the proximal flow convergence method. Calculation of orifice area in patients with mitral stenosis.

BACKGROUND: It has been proposed recently that measuring the flow convergence region proximal to an orifice by Doppler flow mapping can provide a means of calculating regurgitant flow rate. Although verified in experimental models, this approach is difficult to validate clinically because there is no ideal gold standard for regurgitant flows in patients. However, this method also can be used to derive cardiac output or flow rate proximal to stenotic orifices and therefore to calculate their areas by the continuity equation (area = flow rate/velocity). Applying this method in mitral stenosis would provide a unique way of validating the underlying concept because the predicted areas could be compared with those measured directly by planimetry. METHODS AND RESULTS: We studied 40 patients with mitral stenosis using imaging and Doppler echocardiography. Doppler color flow recordings of mitral inflow were obtained from the apex, and the radius of the proximal flow convergence region was measured at its peak diastolic value from the orifice to the first color alias along the axis of flow. Flow rate was calculated assuming uniform radial flow convergence toward the orifice, modified by a factor that accounted for the inflow funnel angle formed by the mitral leaflets. Mitral valve area was then calculated as peak flow rate divided by peak velocity by continuous-wave Doppler. The calculated areas agreed well with those from three comparative techniques over a range of 0.5 to 2.2 cm2: 1) cross-sectional area by planimetry (y = 1.08x-0.13, r = .91, SEE = 0.21 cm2); 2) area derived from the Doppler pressure half-time (y = 1.02x-0.14, r = .89, SEE = 0.24 cm2); and 3) area calculated by the Gorlin equation in the 26 patients who underwent catheterization (y = 0.89x + 0.08, r = .86, SEE = 0.24 cm2). Agreement with planimetry was similar for 22 patients with mitral regurgitation and 18 without it (P > .6), as well as for 6 in atrial fibrillation (P > .2). CONCLUSIONS: These results validate the proximal flow convergence concept in the clinical setting and also demonstrate that it can be extended to orifice area calculation using the continuity equation.

Atrial Fibrillation↗
PubMed1994

Dynamics of mitral regurgitant flow and orifice area. Physiologic application of the proximal flow convergence method: clinical data and experimental testing.

BACKGROUND: The proximal flow convergence method, a quantitative color Doppler flow technique, has been validated recently for calculating regurgitant flow and orifice area. We investigated the potential of the method as a tool to study different pathophysiological mechanisms of mitral valve incompetence by assessing the time course of regurgitant flow and orifice area and analyzed the implications for quantification of mitral regurgitation. METHODS AND RESULTS: Fifty-six consecutive patients with mitral regurgitation of different etiologies were studied. The instantaneous regurgitant flow rate Q(t) was computed from color M-mode recordings of the proximal flow convergence region and divided by the corresponding orifice velocity V(t) to obtain the instantaneous orifice area A(t). Regurgitant stroke volume (RSV) was obtained by integrating Q(t). Mean regurgitant flow rate Qm was calculated by RSV divided by regurgitation time. Peak-to-mean regurgitant flow rates Qp/Qm and orifice areas Ap/Am were calculated to assess the phasic character of Q(t) and A(t). In the first 24 patients (group 1), computation of Qm and RSV from the color Doppler recordings was compared with the conventional pulsed Doppler method (r = .94, SEE = 29.4 mL/s and r = .95, SEE = 9.7 mL) as well as with angiography (rs = .93 and rs = .94, P < .001). The temporal variation of Q(t) and A(t) was studied in the next 32 patients (group 2): In functional regurgitation in dilated cardiomyopathy (n = 12), there was a constant decrease in A(t) throughout systole with an increase during left ventricular relaxation; Ap/Am was 5.49 +/- 3.17. In mitral valve prolapse (n = 6), A(t) was small in early systole, increasing substantially in midsystole, and decreasing mildly during left ventricular relaxation; Ap/Am was 2.48 +/- 0.26. In rheumatic mitral regurgitation (n = 14), a roughly constant regurgitant orifice area during most of systole was found in 4 patients. In the other patients there was significant variation of A (t) and the time of its maximum; Ap/Am was 1.81 +/- 0.56. ANOVA demonstrated that the differences in Ap/Am were related to the etiology of mitral regurgitation (P < .0001). To verify that the calculated variation in regurgitant orifice area during the cardiac cycle reflects an actual variation, the ability of the method to predict a constant orifice area throughout systole was tested experimentally in a canine model of mitral regurgitation. Five flow stages were produced by implanting fixed grommet orifices of different sizes into the anterior mitral leaflet. A constant regurgitant orifice area was correctly predicted throughout systole with a mean percent error of -1.8 +/- 4% (from -6.9% to +5.8%); the standard deviation of the individual curves calculated at 10% intervals during systole averaged 13.3% (from 3.6% to 19.6%). In addition, functional mitral regurgitation caused by ventricular dysfunction was produced pharmacologically in five dogs, and the color M-mode recordings of the proximal flow convergence region were obtained with the transducer placed directly on the heart instead of the chest, thus ruling out a significant effect of translational motion on the observed flow pattern. The pattern of regurgitant flow variation was identical to that observed in patients. CONCLUSIONS: The proximal flow convergence method demonstrates that regurgitant flow and orifice area vary throughout systole in distinct patterns characteristic of the underlying mechanism of mitral incompetence. Therefore, in addition to the potential of the method as a tool to quantify mitral regurgitation, it allows analysis of the pathophysiology of regurgitation in the individual patient, which may be helpful in clinical decision making. Calculating mitral regurgitant flow rate and volume from the time-varying proximal flow field (ie, without assuming a constant orifice area that would produce overestimation in individual patients) provides excellent agreement with independent te

Adult↗
PubMed2005

On convergence conditions of an extended projection neural network.

The output trajectory convergence of an extended projection neural network was developed under the positive definiteness condition of the Jacobian matrix of nonlinear mapping. This note offers several new convergence results. The state trajectory convergence and the output trajectory convergence of the extended projection neural network are obtained under the positive semidefiniteness condition of the Jacobian matrix. Comparison and illustrative examples demonstrate applied significance of these new results.

Algorithms↗
PubMed2003

Analysis of convergence of an evolutionary algorithm with self-adaptation using a stochastic Lyapunov function.

This paper analyses the convergence of evolutionary algorithms using a technique which is based on a stochastic Lyapunov function and developed within the martingale theory. This technique is used to investigate the convergence of a simple evolutionary algorithm with self-adaptation, which contains two types of parameters: fitness parameters, belonging to the domain of the objective function; and control parameters, responsible for the variation of fitness parameters. Although both parameters mutate randomly and independently, they converge to the "optimum" due to the direct (for fitness parameters) and indirect (for control parameters) selection. We show that the convergence velocity of the evolutionary algorithm with self-adaptation is asymptotically exponential, similar to the velocity of the optimal deterministic algorithm on the class of unimodal functions. Although some martingale inequalities have not be proved analytically, they have been numerically validated with 0.999 confidence using Monte-Carlo simulations.

Adaptation, Biological↗
PubMed2003

Expressing functional siRNAs in mammalian cells using convergent transcription.

BACKGROUND: The use of small interfering RNAs (siRNAs) as genetic inhibitors of gene expression has been shown to be an effective way of studying gene function in mammalian cells. Recently, different DNA vectors for expression of small hairpin RNAs (shRNAs) or co-expression of sense and antisense RNAs have been developed that direct siRNA-mediated gene silencing. One expression cassette design that has been used to express long sense and antisense RNAs in non-mammalian cell types is symmetric transcription using convergent promoters. However, convergent transcription as a way to generate functional siRNAs in mammalian cells has not been reported. This vector design permits the generation of expression constructs containing no repeat sequences, but capable of inducing RNA interference (RNAi)-mediated gene silencing. RESULTS: With the aim of simplifying the construction of RNAi expression vectors, we report on the production and application of a novel convergent promoter cassette capable of expressing sense and antisense RNAs, that form double-stranded RNA, and mediate gene silencing in mammalian cells. We use this cassette to inhibit the expression of both the EGFP transgene and the endogenous TP53 gene. The gene silencing effect is Dicer-dependent and the level of gene inactivation achieved is comparable to that produced with synthetic siRNA. Furthermore, this expression system can be used for both short and long-term control of specific gene expression in mammalian cells. CONCLUSION: The experiments performed in this study demonstrate that convergent transcription can be used in mammalian cells to invoke gene-specific silencing via RNAi. This method provides an alternative to expression of shRNAs and co-expression of sense and antisense RNAs from independent cassettes or a divergent promoter. The main advantage of the present vector design is the potential to produce a functional siRNA expression cassette with no repeat sequences. Furthermore, the cassette design reported is ideal for both routine use in controlling specific gene expression and construction of randomised RNAi expression libraries for use in unbiased forward genetic selections.

Cell Line↗
PubMed2004

Converging technologies for enhancing human performance: science and business perspectives.

Our goal is to provide a rough sketch of some of the possible implications of converging technologies for enhancing human performance ((Roco and Bainbridge, 2002)) from both a science and a business perspective. Converging technologies refers to a type of coevolutionary progress that is characterized by rapid advances across multiple areas of technology (nano-bio-info-cogno or NBIC), accelerated by interdisciplinary cross-fertilization as the advances in one area spill over and speed progress in other areas. The rapid, multi-front progress characteristic of converging technologies results in better technological capabilities which are faster and cheaper, and can be broadly applied for many different purposes. In this paper, we specifically explore applications of converging technologies for enhancing human performance, that is, enhancing our human ability to achieve goals both individually and collectively. These applications hold the promise to make people healthier, wealthier, and wiser as well as to make businesses more responsive, resilient, and adaptive.

Biological Evolution↗
PubMed2003

Xbra functions as a switch between cell migration and convergent extension in the Xenopus gastrula.

During Xenopus gastrulation, the dorsal mesoderm exhibits two different cell behaviors in two different regions: active cell migration of prechordal mesoderm and convergent extension of chordamesoderm. Although many genes involved in specification and differentiation of the dorsal mesoderm have been studied, the role of these genes in controlling cell behaviors is poorly understood. To understand better the link between the development and cell behaviors of the dorsal mesoderm, we have examined these behaviors in dissociated cells and explants, where activin protein can induce both active cell migration and convergent extension. We find that Xbra, a transcription factor necessary for convergent extension, actively inhibits cell migration, both in animal cap explant assays and in the endogenous dorsal mesoderm. In addition, Xbra appears to inhibit cell migration by inhibiting adhesion to fibronectin. We propose that Xbra functions as a switch to keep cell migration and convergent extension as mutually exclusive behaviors during gastrulation.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Grating theory: new equations in Fourier space leading to fast converging results for TM polarization.

Using theorems of Fourier factorization, a recent paper [J. Opt. Soc. Am. A 13, 1870 (1996)] has shown that the truncated Fourier series of products of discontinuous functions that were used in the differential theory of gratings during the past 30 years are not converging everywhere in TM polarization. They turn out to be converging everywhere only at the limit of infinitely low modulated gratings. We derive new truncated equations and implement them numerically. The computed efficiencies turn out to converge about as fast as in the TE-polarization case with respect to the number of Fourier harmonics used to represent the field. The fast convergence is observed on both metallic and dielectric gratings with sinusoidal, triangular, and lamellar profiles as well as with cylindrical and rectangular rods, and examples are shown on gratings with 100% modulation. The new formulation opens a new wide range of applications of the method, concerning not only gratings used in TM polarization but also conical diffraction, crossed gratings, three-dimensional problems, nonperiodic objects, rough surfaces, photonic band gaps, nonlinear optics, etc. The formulation also concerns the TE polarization case for a grating ruled on a magnetic material as well as gratings ruled on anisotropic materials. The method developed is applicable to any theory that requires the Fourier analysis of continuous products of discontinuous periodic functions; we propose to call it the fast Fourier factorization method.

Journal Article↗