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At least 217 records · Page 12Linked to original sources
PubMed1990

[Long-loop muscle reflexes with a transcortical loop--mechanisms and practical applications].

The study of long latency muscle reflexes evoked by electrical stimulation of the digital nerves of the index finger and recorded from the first dorsal interosseous muscle with a mean latency of 50 ms provided some evidence on the potential existence of a transcortical loop. The method of long latency relexes can be used to advantage in electrophysiological diagnosis of disorders of the central nervous system, in stimulatory therapeutic rehabilitation and in motor reeducation. The study of supraspinal modulation of the H-reflex excitability curve by dermal and light stimuli inducing long loop reflexes yielded physiological characteristics of its course in healthy subjects and in patients with disorders of the central nervous system. The most striking abnormality of the curves was recorded in the different degree of their facilitation and in the absence of late inhibition in individual nosological units. The method served as the basis of the diagnostic test for the detection of cerebral dysfunction in arterial hypertension, focal cerebral lesions, and neurasthenias.

Adolescent↗
PubMed1989

Supercoiled loop organization of genomic DNA: a close relationship between loop domains, expression units, and replicon organization in rDNA from Xenopus laevis.

Analysis of the organization of a specific chromosomal gene, the gene for rRNA in Xenopus laevis, has evidenced a close relationship between loop organization, replication organization, and expression units. The nontranscribed spacer appears to be involved in all three levels of organization. Furthermore the replication origin region appears to be involved in nuclear matrix anchorage and is closely related to the 40 S transcription promoter. This organization suggests how expression domains may be regulated and how this functional organization may be transmitted to daughter cells after DNA replication, thus allowing selected expression patterns not to be lost during development.

Animals↗
PubMed2005

Comparison of autotriggered memory loop recorders versus standard loop recorders versus 24-hour Holter monitors for arrhythmia detection.

To determine the relative yields of Holter monitoring (HM), memory loop recording (MLR), and autotriggered MLR (AT-MLR), we retrospectively interrogated the very large database of Lifewatch (a Card Guard company and a commercial monitoring company) and compared the results obtained by each method. From among a total database of approximately 100,000 patients, records of 1,800 patients from 2003 were randomly selected and examined, 600 from each of the 3 different monitoring groups. Each session of MLR and AT-MLR was applied for 30 days. For each patient we determined the symptomatic and asymptomatic events that were documented, including those that met predefined immediate physician notification criteria and the time to first notification event. The groups were identical in age and symptoms that necessitated monitoring; fewer women had HM. Information on the type of underlying structural heart disease, if present, and medications taken, if any, was not available to us in this database. The AT-MLR approach provided a higher yield of diagnostic events (e.g., 37, 108, and 216 total patients who had events; 37, 212, and 524 total events; and 6.2%, 17%, and 36% with a diagnostic yield for HM, MLR, and AT-MLR, respectively) and an earlier diagnosis. AT-MLR was also the most effective technique for capturing asymptomatic significant events, such as atrial fibrillation (52 with AT-MLR vs 1 for standard MLR). AT-MLR detected more than half as many asymptomatic episodes of atrial fibrillation (n = 52) as the total number of symptomatic episodes detected by patient activated recording (n = 94), thus confirming the common presence of asymptomatic atrial fibrillation. AT-MLR provided electrocardiographic documentation of tachyarrhythmias (n = 392) more often than MLR (n = 47) or HM (n = 44) and bradyarrhythmias/pauses/atrioventricular block (n = 38) more often than MLR (n = 13) or HM (n = 18). Thus, MLR and AT-MLR provide a diagnosis more often than does HM, thus confirming the benefit of prolonged monitoring. Further, the higher yield of AT-MLR versus MLR demonstrates the significantly enhanced benefit of autotriggered programmable recording.

Adult↗
PubMed2001

The small extracellular loop of CD81 is necessary for optimal surface expression of the large loop, a putative HCV receptor.

Human tetraspanin CD81 is a putative receptor for hepatitis C virus (HCV), because it has been shown to bind 'bona fide' HCV particles. CD81, as all tetraspanins, spans the membrane four times forming two extracellular loops: a small (SEL) and a large one (LEL). We have shown previously that a recombinant form of LEL is sufficient for binding HCV through the major envelope glycoprotein E2. The role of SEL in the CD81-HCV interaction was questioned. We found that transfectants expressing LEL alone bind the recombinant HCV-E2 protein at much lower levels than cells expressing the wild type CD81. And therefore whether SEL contributes to the CD81-HCV interaction or whether it influences the expression of LEL was examined. We have found that in the absence of SEL, LEL is expressed at significantly reduced levels on the cell surface because it is retained intracellularly, while HCV-E2 still binds LEL. Our data suggest that SEL of CD81 does not mediate interaction with HCV, but contributes to optimal cell surface expression of LEL by mediating translocation of the whole CD81 molecule to the cell surface.

3T3 Cells↗
PubMed1986

The DNA loop model for ara repression: AraC protein occupies the proposed loop sites in vivo and repression-negative mutations lie in these same sites.

Two sets of experiments have been performed to test the DNA loop model of repression of the araBAD operon of Escherichia coli. First, dimethyl sulfate methylation protection measurements on normally growing cells show that the AraC regulatory protein occupies the araI site in the presence and absence of the inducer arabinose. Similarly, the araO2 site is shown to be occupied by AraC protein in the presence and absence of arabinose; however, its occupancy by AraC is greatly reduced when araI and adjacent sequences are deleted. Thus, AraC protein binds to araO2 cooperatively with some other component of the ara system located at least 60 base pairs away. Second, the mutational analysis presented here shows that the DNA components required for repression of araBAD are araI, araO2, and perhaps the araBAD operon RNA polymerase binding site.

AraC Transcription Factor↗
PubMed1994

Enhanced activation of human T cell clones specific for virus-like particles expressing the HIV V3 loop in the presence of HIV V3 loop-specific polyclonal antibodies.

Recombinant virus-like particles (VLP), formed by the yeast Ty p1 protein, carrying the HIV gp120 V3 loop on their surface (V3-VLP) have been tested in vitro for immunogenicity and antigenicity by using VLP p1-specific human CD4+ T cell lines and clones. VLP-specific human T cell lines and clones were generated from normal individuals, indicating that VLP-specific precursor cells present in the peripheral lymphocyte pool can be induced to expand clonally upon antigen challenge in vitro, in the absence of previous immunization. It was also shown that V3-specific polyclonal antibodies enhance V3-VLP-induced activation of VLP-specific T cell clones. Antibody-dependent potentiation has been shown previously in other antigen systems, and it depends on enhanced uptake of complexed antigen by Fc receptor-positive antigen-presenting cells. Since in this case antigen is internalized by presenting cells as a complex, it can be inferred that a similar event of antibody-mediated antigen uptake can take place with V3-specific B cells, resulting in presentation by the B cells of T helper epitopes derived from processing of the VLP p1 moiety. This suggests that T helper cells specific for the carrier VLP p1 protein can be activated to provide help to V3-specific B cells in the presence of the appropriate antigen construct.

Amino Acid Sequence↗
PubMed1979

Closed-loop system in evaluation of insulin infusion rates for an open-loop system.

The daily insulin requirements as calculated with a closed-loop system (Biostator), were used for insulin infusion with a portable, miniaturized pump in 6 juvenile-onset, insulin-requiring diabetics. Three diabetics were given insulin in a manner like that of the Biostator, e.g., maximal insulin infusion about 1 hour after start of meals. The MBG was 8.7 +/- 3.9 (SD) mmol/l. Three other diabetics had insulin in a fixed profile with peaks beginning simultaneously with meals. MBG of these patients was 4.4 +/- 1.9 mmol/l. Knowing the daily insulin dosage as calculated from the Biostator, normal blood glucose levels can be achieved with a fixed profile of insulin given by a portable pump.

Adult↗
PubMed2002

Distinct patterns of downstream target activation are specified by the helix-loop-helix domain of proneural basic helix-loop-helix transcription factors.

Both gain- and loss-of-function analyses indicate that proneural basic/helix-loop-helix (bHLH) proteins direct not only general aspects of neuronal differentiation but also specific aspects of neuronal identity within neural progenitors. In order to better understand the function of this family of transcription factors, we have used hormone-inducible fusion constructs to assay temporal patterns of downstream target regulation in response to proneural bHLH overexpression. In these studies, we have compared two distantly related Xenopus proneural bHLH genes, Xash1 and XNgnr1. Our findings indicate that both Xash1 and XNgnr1 induce expression of the general neuronal differentiation marker, N-tubulin, with a similar time course in animal cap progenitor populations. In contrast, these genes each induce distinct patterns of early downstream target expression. Both genes induce expression of the HLH-containing gene, Xcoe2, at early time points, but only XNgnr1 induces early expression of the bHLH genes, Xath3 and XNeuroD. Structure:function analyses indicate that the distinct pattern of XNgnr1-induced downstream target activation is linked to the XNgnr1 HLH domain, demonstrating a novel role for this domain in mediating the differential function of individual members of the proneural bHLH gene family.

Amino Acid Sequence↗
PubMed2005

c-Myc creates an activation loop by transcriptionally repressing its own functional inhibitor, hMad4, in young fibroblasts, a loop lost in replicatively senescent fibroblasts.

c-Myc transcriptional activity in cells is dampened by the Mad family of transcriptional repressors. The expression of one member, hMad4, is increased in growth-arrested states such as quiescence or replicative senescence; hMad4 mRNA levels in replicatively senescent fibroblasts are about twice those seen in their young contact-inhibited quiescent counterparts. Moreover, the repression of hMad4 transcription following serum stimulation observed in quiescent young fibroblasts is lost in senescent cells. This loss results in persistent expression of hMad4, which leads to an inability to switch from an hMad4/Max complex to a c-Myc/Max complex on selected c-Myc target genes following serum stimulation. We have located an initiator element (Inr), a candidate for Miz-1 binding, in the hMad4 promoter. In reporter assays, Miz-1 enhances reporter GFP expression; this enhancement is inhibited by co-expressing c-Myc. Thus hMad4, as does its murine counterpart, contains the Inr element through which Miz-1 activates its expression; but this action is inhibited in the presence of c-Myc. This inhibition may explain the down-regulation of hMad4, corresponding to the up-regulation of c-Myc, in young serum-starved quiescent fibroblasts upon serum stimulation. However, this reciprocal change does not occur in replicatively senescent fibroblasts upon serum stimulation; instead, hMad4 persists in the presence of high levels of c-Myc activation. Our results suggest that: (1) replicative senescence-specific factors may block c-Myc inhibition of Miz-1 activation of hMad4 expression; and (2) the continual presence of hMad4 protein may transcriptionally repress selected c-Myc target genes, whose functions are key to the signaling pathways leading to apoptosis inhibition and permanent exit of cell cycle traverse in normal human fibroblasts.

Base Sequence↗
PubMed1986

Permselectivity for cations over anions in the upper portion of descending limbs of Henle's loop of long-loop nephron isolated from hamsters.

The permselectivity of the upper portion of long descending limb of Henle (LDLu) was investigated with electrophysiological methods in the isolated perfused tubule preparation of hamster kidney. The diffusion potential (Vt) was determined in three different protocols. In protocol 1, the tubules were initially perfused with modified Krebs Ringer's solution on both sides of the epithelium. Then the bath solution was exchanged consecutively with another solution in which 50 mmol/l NaCl replaced by 50 mmol/l KCl, RbCl, NH4Cl, CsCl, LiCl, NaBr, NaNO3, NaI, Na acetate or 75 mmol/l NaCl replaced by mannitol. The permeabilities for these ions relative to chloride were calculated by Goldman's constant field equation. The segment was found to be cation selective, with all cations being 5-9 times more permeable than all anions. The sequence of permeability was K+ greater than Rb+ greater than Li+ greater than NH+4 = Cs+ greater than or equal to Na+ much greater than Cl- greater than or equal to Br- greater than or equal to NO3- greater than or equal to I- greater than Acetate-. In protocol 2, pure 150 mM NaCl was used for the basal solution to avoid interference by other ions. The bathing solution was exchanged by other solutions which contained 150 mmol/l KCl, NH4Cl, CsCl, RbCl, LiCl, NaI, NaBr, NaNO3, Na acetate or 75 mmol/l NaCl with mannitol. Thus simple biionic substitution was performed. Again, the segment was found to be cation selective, with all cations being 4-10 times more permeable than all anions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗