Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “repeat interruptions”

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 73 records · Page 4Linked to original sources
PubMed1991

The coding of signals in the electric communication of the gymnotiform fish Eigenmannia: from electroreceptors to neurons in the torus semicircularis of the midbrain.

In the context of aggression and courtship, Eigenmannia repeatedly interrupts its electric organ discharges (EODs) These interruptions contain low-frequency components as well as high-frequency transients and, therefore, stimulate ampullary and tuberous electroreceptors, respectively. Information provided by these two classes of receptors is relayed along separate pathways, via the electrosensory lateral line lobe (ELL) of the hindbrain, to the dorsal torus semicircularis (TSd) of the midbrain. Some neurons of the torus receive inputs from both types of receptors and some respond predominantly to EOD interruptions while being rather insensitive to other forms of signal modulations. This high selectivity appears to result from convergence and gating of inputs from individually less selective neurons.

Aggression↗
PubMed1986

The slow phase of the staircase in guinea-pig papillary muscle, influence of agents acting on transmembrane sodium flux.

Guinea-pig papillary muscles contracting at frequencies of 0.25 to 1 Hz after rest periods long enough to be followed by a rested-state contraction showed a biphasic staircase phenomenon. An initial phase was completed within about 6 beats (fast phase of the staircase). Then a slow phase followed reaching a steady state after about 4 min only. The effect on this slow phase exerted by drugs known to influence transmembrane Na-flux was investigated. Dihydroouabain in concentrations (1.5-5 X 10(-5) mol/l), causing no increase in the rested-state contraction considerably augmented the slow phase of the staircase thereby prolonging the time from the onset to the steady state by severalfold. The fast phase, however, remained unchanged as far as the steepening slow phase did not influence it. The rest decline of force of contraction, measured by repeated interruption of stimulation, was considerably prolonged by dihydroouabain (to about sixfold the control value by 5 X 10(-5) mol/l). However, dihydroouabain did not influence the time course by which the force of contraction decreased after lowering the [Ca]0 from 3.2 to 0.8 mmol/l. Stimulation of the muscles in Ca-free medium produced a transient increase in force of contraction as visualized by test contractions after addition of Ca. This positive inotropic aftereffect which depended on the frequency of stimulation in the Ca free solution was augmented severalfold by 1.5 to 3 X 10(-5) mol/l dihydroouabain.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2007

The effects of spacer sequences on silencing efficiency of plant RNAi vectors.

RNA interference (RNAi) has been used to suppress gene expression in various eukaryotic organisms. In plants, RNAi can be induced by introduction of an RNAi vector that transcribes a self-complementary hairpin RNA. Most basic RNAi constructs have an inverted repeat interrupted with a spacer sequence. To test silencing capability of RNAi constructs, we developed an in vivo assay that is based on the RNAi-mediated changes of the alpha-linolenic acid content in hairy roots. A tobacco endoplasmic reticulum omega-3 fatty acid desaturase (NtFAD3) is the main enzyme for production of alpha-linolenic acid of root membrane lipids. Tobacco hairy roots transformed with the RNAi vectors against the NtFAD3 gene showed a decrease in alpha-linolenic acid content. The frequency of RNA silencing was more affected by spacer sequence than by spacer length, at least between 100 and 1800 bp. Since significant amounts of hairpin RNA against the NtFAD3 gene remained in the transgenic plants displaying a weak silencing phenotype, low degree of silencing was attributed to low efficiency of hairpin RNA processing mediated by Dicer-like proteins. Our results show the possibility of producing a broad range of the RNAi-induced silencing phenotypes by replacing the spacer sequence of RNAi construct.

DNA, Intergenic↗
PubMed1990

Repetitive DNA sequences linked to the sea urchin spec genes contain transcriptional enhancer-like elements.

The 5' flanking DNA of three related Strongylocentrotus purpuratus genes, Spec1, Spec2a, and Spec2c, were analyzed with respect to structure and cis-regulatory activity. The structural features of DNA sequences upstream of the first intron were highly unusual and implicated certain regions as sites of coordinate control for gene expression. By aligning the genes with a common upstream 600-bp repetitive DNA sequence element, termed RSR, it was shown that a conserved DNA block of approximately 800 bp extended from the 3' end of the first exon to the 5' end of the RSR element. In Spec2a, the conserved sequence block was a continuous stretch of DNA, but in Spec1 and Spec2c, 2.5 to 3 kb of inserted DNA bounded by short direct repeats interrupted the conserved sequence block, thus changing the relative placement of the RSR element and other 5' flanking DNA. Deletion of XhoI fragments containing the 5' half but not the 3' half of the RSR element resulted in a significant decrease in chloroamphenicolacetyl transferase (CAT) activity when Spec-CAT reporter gene fusion plasmids were injected into Lytechinus pictus eggs. These results strongly suggested, but did not prove, that the sequences held in common among the XhoI fragments, that is, the 5' half of the RSR elements, were responsible for the decrease in CAT activity. The Spec2a gene was particularly sensitive to deletions of the XhoI fragment containing the 5' half of the RSR element. The deleted element had several enhancer-like properties when inserted back into various test plasmids: it could be positioned in locations different from the transcriptional start site; in some but not all cases, it could be made to work in the reverse orientation; and it could drive expression of the CAT gene using an SV40 promoter or cryptic promoter elements. These findings suggested that an enhancer-like element important for Spec gene expression was contained within a repetitive DNA sequence. Genomic DNA blots suggested that there are many more of these RSR elements than there are Spec genes.

Animals↗
PubMed1981

Differences in the pattern of milk intake between breast and bottle fed infants.

Two hundred and nine 6-day-old healthy term infants were test weighed either during bottle feeding (n= 77) or breast feeding (n=132). Cross-sectional data collection avoided repeated interruptions of individual feeds. Bottle fed infants (fed ad libitum) and breast fed infants consumed a similar feed volume (respectively, 67 +/- 2 ml versus 75 +/- 6ml, mean +/- S.E.M.) over a similar period of time (mean 25 min); yet the pattern of milk flow during feeding was significantly different in the two groups. In bottle fed infants, there was a linear pattern of milk intake over the first 10 min of feeding, by which time 81% of the feed has been consumed, contrasting with a biphasic intake pattern in breast fed infants in whom a total 84% of the feed was consumed either in the first 4 min or between 15 and 19 min after the start of the feed. It is speculated that these differences in the pattern of milk intake could influence the physiological responses to feeding and might account for differences between breast and bottle fed infants in gut hormonal responses to milk feeds.

Bottle Feeding↗
PubMed2006

Structural analysis of the plakin domain of bullous pemphigoid antigen1 (BPAG1) suggests that plakins are members of the spectrin superfamily.

Bullous pemphigoid antigen 1 (BPAG1) is a member of the plakin family of proteins. The plakins are multi-domain proteins that have been shown to interact with microtubules, actin filaments and intermediate filaments, as well as proteins found in cellular junctions. These interactions are mediated through different domains on the plakins. The interactions between plakins and components of specialized cell junctions such as desmosomes and hemidesmosomes are mediated through the so-called plakin domain, which is a common feature of the plakins. We report the crystal structure of a stable fragment from BPAG1, residues 226-448, defined by limited proteolysis of the whole plakin domain. The structure, determined by single-wavelength anomalous diffraction phasing from a selenomethionine-substituted crystal at 3.0 A resolution, reveals a tandem pair of triple helical bundles closely related to spectrin repeats. Based on this structure and analysis of sequence conservation, we propose that the architecture of plakin domains is defined by two pairs of spectrin repeats interrupted by a putative Src-Homology 3 (SH3) domain.

Amino Acid Sequence↗
PubMed2006

Co-induction of hepatic IGF-I and progranulin mRNA by growth hormone in tilapia, Oreochromis mossambiccus.

Like IGF-I, progranulin (pgrn) is a growth factor involved in tumorigenesis and wound healing. We report here the identification and characterization of pgrn cDNA in tilapia and the regulation of its expression by growth hormone (GH). The tilapia pgrn cDNA was cloned by RT-PCR amplification, using gene specific oligonucleotides as amplification primers. The cDNA contains an open reading frame encoding a peptide of 206 amino acid residues (aa) that contains a presumptive signal peptide (23 aa) and two repeat units of granulin (grn, 51 and 52 aa, respectively) franked by a GAP of 49 aa and the carboxyl terminus with 31 aa. The two predicted grn peptides are arranged in tandem repeats interrupted by a GAP peptide. RT-PCR analysis revealed that high levels of prgn mRNA were present in several tissues such as spleen, gastric cecum, intestine, fat tissue, gill, kidney, eye and pancreas, and lower levels in liver, muscle, heart, brain, skin and stomach. Administration of a single dose (500 ng/g body weight) of recombinant seabream growth hormone (rbGH) by intraperitoneal (ip) injection into one-month-old tilapia resulted in an obvious increase of IGF-I and pgrn mRNA (2.7-fold and 2.5-fold, respectively) in the liver at three hours post-GH treatment. The peptide levels of pgrn in the liver of GH-treated fish also were substantially induced over controls at 12h post-GH treatment as detected by western immuno-blot analysis. The co-induction of IGF-I and pgrn following GH treatment may suggest the involvement of pgrn in GH regulated growth in tilapia.

Amino Acid Sequence↗
PubMed2002

Is the nonREM-REM sleep cycle reset by forced awakenings from REM sleep?

In selective REM sleep deprivation (SRSD), the occurrence of stage REM is repeatedly interrupted by short awakenings. Typically, the interventions aggregate in clusters resembling the REM episodes in undisturbed sleep. This salient phenomenon can easily be explained if the nonREM-REM sleep process is continued during the periods of forced wakefulness. However, earlier studies have alternatively suggested that awakenings from sleep might rather discontinue and reset the ultradian process. Theoretically, the two explanations predict a different distribution of REM episode duration. We evaluated 117 SRSD treatment nights recorded from 14 depressive inpatients receiving low dosages of Trimipramine. The alarms were triggered by an automatic mechanism for the detection of REM sleep and had to be canceled by the subjects themselves. The REM episodes were determined as in undisturbed sleep-they had to include the remaining REM activity and were separated by 30 min without REM epochs. The frequency histogram of REM episodes declined exponentially with episode duration for each of the first four sleep cycles. The duration of nonREM intervals revealed bimodal distributions. These results were found consistent with the model assuming a reset of the ultradian cycle upon awakening. Whether REM or nonREM activity is resumed on return to sleep can be modeled by a random decision whereby the probability for REM sleep might depend on the momentary REM pressure.

Activity Cycles↗
PubMed1979

Pattern of milk flow in breast-fed infants.

122 six-day-old infants were test-weighed during breast feeding. Cross-sectional data collection avoided repeated interruptions of individual feeds. Milk flow conformed to a definite pattern: a mean of 50% of the feed from each breast was taken in the first two minutes of sucking and a mean of 80-90% was taken by four minutes. The second half of a ten-minute feed from either breast was almost non-nutritive. Preliminary studies suggest that the pattern is the same after one month of lactation.

Breast Feeding↗
PubMedDate not supplied

Epileptogenesis and neuropathology after different types of status epilepticus induced by prolonged electrical stimulation of the basolateral amygdala in rats.

It has previously been shown that prolonged (60-min) low-intensity electrical stimulation of a kindled focus in the basolateral nucleus of the amygdala (BLA) of Wistar rats resulted in the development of self-sustained status epilepticus (SSSE) with predominantly partial seizures and subsequent brain damage in the ipsilateral hemisphere. In the present study, using high-intensity (700 microA) pulsed-train electrical stimulation of the BLA for 25 min, SSSE was induced in both kindled and non-kindled Wistar rats, demonstrating that under these experimental conditions prior kindling is not necessary to induce SSSE. Thus, all subsequent experiments were done in non-kindled rats of different strains (Wistar, Sprague-Dawley) and genders. Three distinct behavioral types of SSSE were observed: (1) continuous partial seizures; (2) continuous partial seizures, repeatedly interrupted by generalized convulsive seizures; and (3) continuous generalized convulsive seizures. These three forms of SSSE were seen in both strains and genders, although the percentage of rats in each strain and gender developing a specific type of SSSE differed. Rats spontaneously recovered from SSSE after between 3 and 8h on average, the SSSE duration depending on SSSE type, rat strain and gender. Following SSSE, rats were monitored with a video- and EEG-recording system for occurrence of spontaneous recurrent seizures (SRS). Overall, about 80% of the rats developed epilepsy with SRS after SSSE, but the proportion of rats developing SRS depended on the type of SSSE. Only 33% of the rats developed SRS after a partial SSSE, compared to >90% in case of either type 2 or type 3 SSSE with generalized convulsive seizures. Interruption of different forms of SSSE with diazepam after 90 min prevented development of epilepsy, while a generalized SSSE duration of 4h consistently produced epilepsy in >90% of rats. Histologic analysis of rat brains after the different SSSE types indicated that neuronal loss after partial SSSE was much more regionally restricted and less severe compared to neuronal damage after SSSE with generalized convulsive seizures, which was similar to the brain damage seen in the kainate and pilocarpine models of temporal lobe epilepsy. These experiments establish that prolonged electrical stimulation of the BLA induces different forms of SSSE that resemble nonconvulsive and convulsive types of SE in humans. These different forms of SSSE induce epilepsy with SRS and brain pathology reminiscent of temporal lobe epilepsy with hippocampal sclerosis. The rat model provides a new tool to mimic different types of SE and investigate the pathogenesis underlying their long-term complications.

Amygdala↗
PubMed2006

Apoptosis in the hair follicle.

Apoptosis plays an important role in many physiological processes, ranging from morphogenetic events to adult tissue homeostasis, and defects in its regulation contribute to many disorders. Here we review molecular mechanisms of apoptosis in the hair follicle (HF), whose cyclical growth pattern is repeatedly interrupted by apoptosis-driven involution (catagen). We review the common mechanisms underlying apoptosis in the HF during catagen, as well as differences in the regulation of apoptosis between distinct HF cell populations. An overview is provided on the expression and function of molecules involved in the control of various phases of the apoptotic process during catagen.

Animals↗
PubMed1996

Transcriptional control of the agr-dependent virulence gene regulator, RNAIII, in Staphylococcus aureus.

Many of the genes coding for extracellular toxins, enzymes and cell-surface proteins in Staphylococcus aureus are regulated by a 510 nt RNA molecule, RNAIII. Expression of the RNAIII gene is positively controlled by the closely linked agr operon, which encodes a multicomponent signal-transduction system, and by an unlinked operon called sar. We have analysed the 120 bp region that separates the RNAIII promoter, P3, from the divergent agr promoter, P2. By transcription analysis, it was shown that P3 can function in trans of the agr operon. A stretch of 53 bp upstream of P3, containing an interrupted repeat of 7 bp, was found to be required for the agr-dependent expression of RNAIII. A single cytoplasmic protein was shown to bind to at least two sites within this regulatory region. The protein, which was absent in extracts from a sarA mutant, was identified as the sarA product by N-terminal amino acid sequencing. A DNA fragment from the P2 region, encompassing an almost identical repeated DNA motif, competed for the same protein. No interaction between the regulatory DNA sequence and any agr-dependent products could be demonstrated. The results of this study suggest that P3 and P2 are controlled by a mechanism involving the binding of the SarA protein to multiple sites within the regulatory regions immediately upstream of each promoter, and the as yet unknown activity of AgrA.

Base Sequence↗
PubMed1998

Optimizing transurethral microwave thermotherapy: a model for studying power, blood flow, temperature variations and tissue destruction.

OBJECTIVE: To examine the role of microwave power and blood flow on temperature variations and tissue destruction in the prostate, using a theoretical model of transurethral microwave thermotherapy (TUMT), and thus compare fixed-energy TUMT with no intraprostatic temperature monitoring (constant microwave power applied over a fixed period) with 'feedback' TUMT in which the microwave power is adjusted according to the monitored intraprostatic temperature. MATERIALS AND METHODS: The temperature distribution in the prostate was modelled for a typical TUMT catheter at various blood flow rates. The volume of tissue destroyed was simultaneously calculated from cell survival data after thermal exposure. The calculated quantity of tissue destroyed at the different microwave power levels and blood flow rates was used to describe qualitatively the simulated treatments. RESULTS: Treatment monitoring and consistency were better during feedback TUMT than fixed-energy TUMT, in that the former compensated for variations in blood flow rate. The modelled values agreed with observations during real TUMT. CONCLUSIONS: Blood flow rate is a key factor in the outcome of TUMT. Only by measuring intraprostatic temperature is it possible to compensate for the large variations in prostatic blood flow and obtain consistent treatment results. Repeated interruptions prompted by high rectal temperatures should be minimized and preferably avoided, as the quantity of tissue destroyed is then greatly reduced, and in extreme cases the treatment is totally ineffective.

Blood Flow Velocity↗
PubMed2003

The beta fibrinogen gene G-455-A polymorphism is a risk factor for Legg-Perthes disease.

Legg-Perthes disease is a pediatric hip disorder characterized by avascular necrosis of the femoral head. The etiology of Legg-Perthes disease may involve repeated interruptions of the blood supply to the proximal femur. Thus, the role of thrombosis in Legg-Perthes disease is of interest. The focus of this analysis is an evaluation of the relationship between Legg-Perthes disease and the beta fibrinogen gene G-455-A polymorphism in 55 cases of Legg-Perthes disease and 56 age, race, and gender-matched healthy controls. Parents of subjects completed a questionnaire about their child's lifestyle and medical history. Blood was obtained for plasma and DNA analysis. Study subjects were predominantly white (93%), male (77%) and under age 16 (70%). Cases were more likely to be exposed to passive smoke than were controls (odds ratio 5.6, 95% confidence interval 2.0-12.0). Assuming a dominant genetic model, individuals who possessed either the G/A or A/A genotype were over three times more likely to have Legg-Perthes disease compared to those without the polymorphism (odds ratio 3.4, 95% confidence interval 1.5-7.8). Separate analyzes by smoke exposure revealed that the excess risk of the G-455-A polymorphism occurred in those exposed (odds ratio 7.0) as opposed to those unexposed to passive smoke (odds ratio 1.9). Although this difference in the odds ratios is not statistically significant (P=0.2), it suggests a possible interactive effect of cigarette smoke and the b fibrinogen gene G-455-A polymorphism in the risk of developing Legg-Perthes disease.

Adolescent↗
PubMed2004

Pneumonia in children in the developing world: new challenges, new solutions.

Pneumonia has been a leading cause of death in both developed and developing countries as long as health indicators have been available. Yet the issues of concern for this syndrome are far from static. Improvements in access to health services have lowered infant mortality rates, benefiting children around the world and lowering the fraction of child deaths caused by pneumonia. However, progress has been interrupted repeatedly by the emergence of new pathogens. Landmark randomized controlled trials have now demonstrated the effectiveness of Haemophilus influenzae type b (Hib) and multivalent pneumococcal conjugate vaccines against childhood pneumonia, as well as meningitis and bacteremic disease. Momentum has gathered to tackle long-standing economic obstacles to expand access to new vaccines and programs for the poorest countries of the world. A pressing challenge for the control of pneumonia in developing countries is to identify better metrics for pneumonia. Surveillance tools are needed that will bridge studies of interventions, establish preventable disease burden, and serve as indicators for monitoring new programs.

Child, Preschool↗
PubMed2002

A comparison of MCNP4C electron transport with ITS 3.0 and experiment at incident energies between 100 keV and 20 MeV: influence of voxel size, substeps and energy indexing algorithm.

The condensed-history electron transport algorithms in the Monte Carlo code MCNP4C are derived from ITS 3.0, which is a well-validated code for coupled electron-photon simulations. This, combined with its user-friendliness and versatility, makes MCNP4C a promising code for medical physics applications. Such applications, however, require a high degree of accuracy. In this work, MCNP4C electron depth-dose distributions in water are compared with published ITS 3.0 results. The influences of voxel size, substeps and choice of electron energy indexing algorithm are investigated at incident energies between 100 keV and 20 MeV. Furthermore, previously published dose measurements for seven beta emitters are simulated. Since MCNP4C does not allow tally segmentation with the *F8 energy deposition tally, even a homogeneous phantom must be subdivided in cells to calculate the distribution of dose. The repeated interruption of the electron tracks at the cell boundaries significantly affects the electron transport. An electron track length estimator of absorbed dose is described which allows tally segmentation. In combination with the ITS electron energy indexing algorithm, this estimator appears to reproduce ITS 3.0 and experimental results well. If, however, cell boundaries are used instead of segments, or if the MCNP indexing algorithm is applied, the agreement is considerably worse.

Algorithms↗
PubMed1985

Identification of pacemaker dependent patients by serial decremental rate inhibition.

In a study of the concept of pacemaker dependence, 86 patients who had permanent ventricular demand (VVI) pacemakers implanted for more than six months and were in predominantly paced rhythm underwent repeated interruption of pacing both abruptly and after gradual reduction of paced rate. Non-invasive pace slowing was accomplished by timed inhibiting pulses applied to the chest wall. The results identified a small group (A) of patients, 8% of those tested, who consistently failed to develop an adequate escape rhythm and may thus be considered highly pacing dependent. A second group B, 26%, developed an adequate intrinsic rhythm with serial decremental rate inhibition (SDRI) but suffered symptoms with abrupt complete inhibition (ACI). The remaining 66%, group C, developed no symptoms in any test. Analysis of clinical pre-test data showed that syncope, atrioventricular block and a low rate prior to implant, and a long duration of pacing were associated with a higher degree of pacing dependence, but were not reliably predictive. The clinical significance and value of the results are discussed. We conclude that SDRI is a reliable test for the high degree of pacemaker dependence and can be helpful especially in planning a procedure which may involve interruption of pacing.

Adult↗
PubMed2004

The bcr1 DNA repeat element is specific to the Bacillus cereus group and exhibits mobile element characteristics.

Bacillus cereus strains ATCC 10987 and ATCC 14579 harbor an approximately 155-bp repeated element, bcr1, which is conserved in B. cereus, B. anthracis, B. thuringiensis, and B. mycoides but not in B. subtilis and B. licheniformis. In this study, we show by Southern blot hybridizations that bcr1 is present in all 54 B. cereus group strains tested but absent in 11 Bacillus strains outside the group, suggesting that bcr1 may be specific and ubiquitous to the B. cereus group. By comparative analysis of the complete genome sequences of B. cereus ATCC 10987, B. cereus ATCC 14579, and B. anthracis Ames, we show that bcr1 is exclusively present in the chromosome but absent from large plasmids carried by these strains and that the numbers of full-length bcr1 repeats for these strains are 79, 54, and 12, respectively. Numerous copies of partial bcr1 elements are also present in the three genomes (91, 128, and 53, respectively). Furthermore, the genomic localization of bcr1 is not conserved between strains with respect to chromosomal position or organization of gene neighbors, as only six full-length bcr1 loci are common to at least two of the three strains. However, the intergenic sequence surrounding a specific bcr1 repeat in one of the three strains is generally strongly conserved in the other two, even in loci where bcr1 is found exclusively in one strain. This finding indicates that bcr1 either has evolved by differential deletion from a very high number of repeats in a common ancestor to the B. cereus group or is moving around the chromosome. The identification of bcr1 repeats interrupting genes in B. cereus ATCC 10987 and ATCC 14579 and the presence of a flanking TTTAT motif in each end show that bcr1 exhibits features characteristic of a mobile element.

Bacillus anthracis↗