Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Origin”

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 361 records · Page 20Linked to original sources
PubMed2005

[Hemosiderin-laden macrophages count in sputum in diagnosis of dyspnea of heart origin].

BACKGROUND AND OBJECTIVE: The respiratory or heart origin of dyspnea is not always easy to find out using the available diagnostic tools. Many patients present both heart and lung diseases that cause dyspnea. The role of hemosiderin-laden macrophages count (HC) in sputum in this context has not been well settled so far. The objective was to describe the prediction usefulness of HC in patients suffering from dyspnea of heart origin, and to find out if HC changed after administering treatment. PATIENTS AND METHOD: HC was analyzed in 61 patients whose main symptom was dyspnea in the emergency department, and it was evaluated by means of clinical history, clinical course and performance of lung function tests and echocardiography. RESULTS: 35 patients were classified as having dyspnea of heart origin, 17 as having dyspnea of lung origin and 9 had dyspnea of both origins. The HC was higher in patients with dyspnea of heart origin 37% (95% CI, 26-47) or cardiopulmonary origin 30% (95% CI, 8-52) than in patients with dyspnea of lung origin 15% (95% CI, 4-27), and it remained higher despite administering treatment. The sensitivity (52%), specificity (88%), positive predictive value (92%) and negative predictive value (58%) was established for a 30% HC cutoff. The prediction model of heart origin dyspnea presented an area under the ROC curve of 0.978 (95% CI, 0.95-1). CONCLUSIONS: HC reflects the severity of pulmonary venocapillar disturbance, identifies the majority of patients suffering from current or past heart failure or severe cardiac dysfunction, and is useful for the prediction of dyspnea of heart origin. HC utility should focus on selected patients.

Adult↗
PubMed2004

Variations in the tensor veli palatini muscle with special reference to its origin and insertion.

OBJECTIVE: Previous research on the tensor veli palatini muscle (TVP) has produced conflicting descriptions of its functions and topographical relationships with other orofacial structures. The goal of this study was to describe the morphology of the TVP in a systematic and comprehensive manner. METHODS: One hundred nineteen sides of 77 human heads from donated cadavers were partially dissected under a binocular microscope. Histological examination of the hard tissue-muscle interfaces was also undertaken. RESULTS: There were two adjacent origins of the TVP: the cranial base origin (CB origin) and the auditory tube cartilage origin (AT origin). The CB origin always lay anterior to the AT origin and there was no septum or loose tissue between the two muscular laminae leading from these origins. The muscle fibers converged on a central tendinous plate in the muscle belly, which gradually became a common tendon that rounded the pterygoid hamulus before inserting into the palatine aponeurosis. Notably, secondary insertions were found on the maxillary tuber (33.6%) and/or in the submucosal tissue near the palatoglossal arch (37.8%). Maxillary insertions were almost exclusively associated with an AT origin that was wide as or wider than the CB origin. Histological observations confirmed that the hamulus acted purely as a pulley and suggested that a connecting band to the tensor tympani had no or few functions of an intermediate tendon. CONCLUSIONS: The TVP appears to act as the dilator tubae and that this function can be maintained by preserving or reconstructing the maxillary insertion during push-back surgery, even if hamulotomy is necessary.

Adult↗
PubMed1979

dnaG (primase)-dependent origins of DNA replication. Nucleotide sequences of the negative strand initiation sites of bacteriophages St-1, phi K, and alpha 3.

The simplest known origins of DNA replication occur in the single-stranded bacteriophages. In one set of phages, negative strand synthesis is initiated by a single protein, the product of the Escherichia coli replication gene dnaG. Evidently, in these phages--G4, St-1, phi K, and alpha 3--the origin for negative strand synthesis consists of a nucleic acid element capable of direct recognition by the dnaG priming protein. We have located and sequenced the origins of negative strand synthesis in St-1, phi K, and alpha 3, and compared them with the origin sequence previously determined for G4. In each case, the point at which the negative strand is initiated can be identified at the nucleotide level. The data lead to the following conclusions: 1. In all four phages, the negative strand initiation site occurs within an intercistronic region of approximately 135 bases. While in G4, the origin lies between genes specifying the viral coat proteins F and G, the origin is shifted in St-1, phi K, and alpha 3 to a position between coat protein genes G and H. 2. Extensive nucleotide conservation exists at the negative strand origin, but does not extend into the adjacent coding regions. The conserved origin DNA occurs in two regions, 42 and 45 bases long, which are separated by 13 bases of divergent sequence. 3. Correlated with the two stretches of conserved nucleotide sequence are two regions of potential secondary structure. The start point of negative strand synthesis lies just prior to one of these hairpins. Similarities in both primary sequence and secondary structure can be found between the negative strand origins of G4, St-1, phi K, and alpha 3 and the general origin regions of bacteriophage lambda and of E. coli.

Base Sequence↗
PubMed2005

Ku80 binds to human replication origins prior to the assembly of the ORC complex.

The Ku heterodimer, an abundant nuclear protein, binds DNA replication origins in a sequence-specific manner and promotes initiation. In this study, using HCT116 Ku80+/- haplo-insufficient and Orc2(delta/-) hypomorphic cells, the order of binding of Ku and the human origin recognition complex (HsORC) was determined. The nuclear expression of Ku80 was found to be decreased by 60% in Ku80+/- cells, while its general association with chromatin was decreased by 33%. Coimmunoprecipitation studies indicated that the Ku heterodimer associates specifically with the human HsOrc-2, -3, -4, and -6 subunits. Chromatin immunoprecipitation (ChIP) experiments, using cells synchronized to late G1, showed that the association of Ku80 with the lamin B2, beta-globin, and c-myc origins in vivo was decreased by 1.5-, 2.3-, and 2.5-fold, respectively, in Ku80+/- cells. The association of HsOrc-3, -4, and -6 was consistently decreased in all three origins examined in Ku80+/- cells, while that of HsOrc-2 showed no significant variation, indicating that the HsOrc-3, -4, and -6 subunits bind to the origins after Ku80. In Orc2(delta/-) cells, the association of HsOrc-2 with the lamin B2, beta-globin, and c-myc origins was decreased by 2.8-, 4.9-, and 2.8-fold, respectively, relative to wild-type HCT116 cells. Furthermore, nascent strand abundance at these three origins was decreased by 4.5-, 2.3-, and 2.6-fold in Orc2(delta/-) relative to HCT116 cells, respectively. Interestingly, the association of Ku80 with these origins was not affected in this hypomorphic cell line, indicating that Ku and HsOrc-2 bind to origins independently of each other.

Antigens, Nuclear↗
PubMed2004

Prediction of Saccharomyces cerevisiae replication origins.

BACKGROUND: Autonomously replicating sequences (ARSs) function as replication origins in Saccharomyces cerevisiae. ARSs contain the 17 bp ARS consensus sequence (ACS), which binds the origin recognition complex. The yeast genome contains more than 10,000 ACS matches, but there are only a few hundred origins, and little flanking sequence similarity has been found. Thus, identification of origins by sequence alone has not been possible. RESULTS: We developed an algorithm, Oriscan, to predict yeast origins using similarity to 26 characterized origins. Oriscan used 268 bp of sequence, including the T-rich ACS and a 3' A-rich region. The predictions identified the exact location of the ACS. A total of 84 of the top 100 Oriscan predictions, and 56% of the top 350, matched known ARSs or replication protein binding sites. The true accuracy was even higher because we tested 25 discrepancies, and 15 were in fact ARSs. Thus, 94% of the top 100 predictions and an estimated 70% of the top 350 were correct. We compared the predictions to corresponding sequences in related Saccharomyces species and found that the ACSs of experimentally supported predictions show significant conservation. CONCLUSIONS: The high accuracy of the predictions indicates that we have defined near-sufficient conditions for ARS activity, the A-rich region is a recognizable feature of ARS elements with a probable role in replication initiation, and nucleotide sequence is a reliable predictor of yeast origins. Oriscan detected most origins in the genome, demonstrating previously unrecognized generality in yeast replication origins and significant discriminatory power in the algorithm.

Algorithms↗
PubMed1997

Differential DNA replication origin activities in human normal skin fibroblast and HeLa cell lines.

A modification of the extrusion method for the isolation of nascent DNA from mammalian cells and a PCR-based assay has been used in order to compare the in vivo activities of DNA replication origins in different cell lines. Conventional PCR was firstly applied to detect the chromosomal activities of several known (origins associated with c-myc, hsp70, beta-globin, immunoglobulin mu-chain enhancer) and putative DNA replication origins (autonomously replicating sequences obtained from enriched libraries of human origins of DNA replication from normal and transformed cells) in four human cell lines (HeLa, NSF, WI-38 and SK-MG-1). Then, in nascent DNA samples from normal skin fibroblast (NSF) and HeLa cells, abundance of DNA sequences in the regions of five of these origins was determined by competitive PCR. Our results suggest that autonomously replicating sequences NOA3, S14, S3 and F15 are associated with functional chromosomal origins of replication. Quantitative comparison of origin activities demonstrates that origins associated with c-myc and NOA3 are approximately twice as active in HeLa cells as in NSF cells. The described approach can facilitate the identification of origins which may be differentially active in normal cells and transformed cells or in different cell types.

Cell Line, Transformed↗
PubMed2004

DNA replication origins in the Schizosaccharomyces pombe genome.

Origins of DNA replication in Schizosaccharomyces pombe lack a specific consensus sequence analogous to the Saccharomyces cerevisiae autonomously replicating sequence (ARS) consensus, raising the question of how they are recognized by the replication machinery. Because all well characterized S. pombe origins are located in intergenic regions, we analyzed the sequence properties and biological activity of such regions. The AT content of intergenes is very high ( approximately 70%), and runs of A's or T's occur with a significantly greater frequency than expected. Additionally, the two DNA strands in intergenes display compositional asymmetry that strongly correlates with the direction of transcription of flanking genes. Importantly, the sequence properties of known S. pombe origins of DNA replication are similar to those of intergenes in general. In functional studies, we assayed the in vivo origin activity of 26 intergenes in a 68-kb region of S. pombe chromosome 2. We also assayed the origin activity of sets of randomly chosen intergenes with the same length or AT content. Our data demonstrate that at least half of intergenes have potential origin activity and that the relative ability of an intergene to function as an origin is governed primarily by AT content and length. We propose a stochastic model for initiation of DNA replication in the fission yeast. In this model, the number of AT tracts in a given sequence is the major determinant of its probability of binding SpORC and serving as a replication origin. A similar model may explain some features of origins of DNA replication in metazoans.

Base Composition↗
PubMed2001

Aphidicolin triggers a block to replication origin firing in Xenopus egg extracts.

DNA replication origins are located at random with respect to DNA sequence in Xenopus early embryos and on DNA replicated in Xenopus egg extracts. We have recently shown that origins fire throughout the S phase in Xenopus egg extracts. To study the temporal regulation of origin firing, we have analyzed origin activation in sperm nuclei treated with the DNA polymerase inhibitor aphidicolin. Sperm chromatin was incubated in Xenopus egg extracts in the presence of aphidicolin and transferred to a fresh extract, and digoxigenin-dUTP and biotin-dUTP were added at various times after aphidicolin release to selectively label early and late replicating DNA. Molecular combing analysis of single DNA fibers showed that only a fraction of potential origins were able to initiate in the presence of aphidicolin. After release from aphidicolin, the remaining origins fired asynchronously throughout the S phase. Therefore, initiation during the S phase depends on the normal progression of replication forks assembled at earlier activated origins. Caffeine, an inhibitor of the checkpoint kinases ATR and ATM, did not relieve the aphidicolin-induced block to origin firing. We conclude that a caffeine-insensitive intra-S phase checkpoint regulates origin activation when DNA synthesis is inhibited in Xenopus egg extracts.

Animals↗
PubMed2006

Perturbation of the activity of replication origin by meiosis-specific transcription.

We have determined the activity of all ARSs on the Saccharomyces cerevisiae chromosome VI as chromosomal replication origins in premeiotic S-phase by neutral/neutral two-dimensional gel electrophoresis. The comparison of origin activity of each origin in mitotic and premeiotic S-phase showed that one of the most efficient origins in mitotic S-phase, ARS605, was completely inhibited in premeiotic S-phase. ARS605 is located within the open reading frame of MSH4 gene that is transcribed specifically during an early stage of meiosis. Systematic analysis of relationships between MSH4 transcription and ARS605 origin activity revealed that transcription of MSH4 inhibited the ARS605 origin activity by removing origin recognition complex from ARS605. Deletion of UME6, a transcription factor responsible for repressing MSH4 during mitotic S-phase, resulted in inactivation of ARS605 in mitosis. Our finding is the first demonstration that the transcriptional regulation on the replication origin activity is related to changes in cell physiology. These results may provide insights into changes in replication origin activity in embryonic cell cycle during early developmental stages.

Cell Cycle Proteins↗
PubMed1997

Functional analysis of a replication origin from Saccharomyces cerevisiae: identification of a new replication enhancer.

Yeast replication origins have a modular arrangement of essential DNA sequences containing the ARS consensus sequence (ACS) flanked by auxiliary DNA elements which stimulate origin function. One of the auxiliary elements identified at several origins is a DNA replication enhancer that binds the Abf1p protein. We have isolated an ARS sequence from Saccharomyces cerevisiae based on its ability to bind Abf1p. Here we present a detailed molecular dissection of this ARS, designated ARS 1501, and we demonstrate that it functions as a genomic replication origin on chromosome XV . Mutagenesis of the Abf1p DNA-binding sites revealed that these sequences did not contribute significantly to ARS function. Instead, a new DNA element important for replication, designated REN1501, has been located 5' to the T-rich strand of the ACS. We show that REN1501 functions in either orientation and at variable distances from the ACS, defining this element as a DNA replication enhancer. Most significantly, point mutations within this element decreased the stability of plasmids bearing ARS 1501, suggesting that REN1501 binds a protein important for replication initiation. Only three elements found at origins are known to specifically bind proteins. These include the ARS essential sequences and the Abf1p and Rap1p DNA-binding sites. We show that the function of REN1501 at the origin cannot be replaced by a Rap1p DNA-binding site or a site that binds the transcriptional factor Gal4p and can only be partially substituted for by an Abf1p recognition sequence. This implies that the role of the REN1501 element at the ARS 1501 origin is specific, and suggest that the frequency of origin firing in eukaryotic cells may be regulated by origin-specific enhancers.

Base Sequence↗
PubMed2001

Coupling of asymmetric division to polar placement of replication origin regions in Bacillus subtilis.

Entry into sporulation in Bacillus subtilis is characterized by the formation of a polar septum, which asymmetrically divides the developing cell into forespore (the smaller cell) and mother cell compartments, and by migration of replication origin regions to extreme opposite poles of the cell. Here we show that polar septation is closely correlated with movement of replication origins to the extreme poles of the cell. Replication origin regions were visualized by the use of a cassette of tandem copies of lacO that had been inserted in the chromosome near the origin of replication and decorated with green fluorescent protein-LacI. The results showed that extreme polar placement of replication origin regions is not under sporulation control and occurred in stationary phase under conditions under which entry into sporulation was prevented. On the other hand, the formation of a polar septum, which is under sporulation control, was almost invariably associated with the presence of a replication origin region in the forespore. Moreover, cells in which the polar placement of origin regions was perturbed by deletion of the gene (smc) for the structural maintenance of chromosomes (SMC) protein were impaired in polar division. A small proportion ( approximately 1%) of the mutant cells were able to undergo asymmetric division, but the forespore compartment of these exceptional cells was generally observed to contain a replication origin region. Immunofluorescence microscopy experiments indicated that the block in polar division caused by the absence of SMC occurred at or prior to the step of bipolar Z-ring formation by the cell division protein FtsZ. A model is discussed in which polar division is under the dual control of sporulation and an event associated with the placement of a replication origin at the cell pole.

Bacillus subtilis↗
PubMed1996

[Fever of unknown origin in patients infected with the human immunodeficiency virus].

BACKGROUND: To describe the clinical features and the final diagnosis of patients infected with human immunodeficiency virus who presented fever of unknown origin. METHODS: Retrospective study, from November 1989 to January 1994, of all patients infected with HIV who had fever of unknown origin and who were admitted to a community hospital in a Mediterranean area in Alicante (Spain). Fever of unknown origin was defined as fever exceeding 38.3 degrees C lasting for at least three weeks with no diagnosis in the first three days of hospitalization after fulfilling clinical exam, three blood cultures, acid-fast bacilli stain in sputum and chest-X-ray. RESULTS: Of a cohort of 231 patients, 27 (12%) were evaluated because of fever of unknown origin during their follow-up. Patients' mean age was 31 years (interval, 22-75) and intravenous drug use (81%) was the most common risk factor for HIV infection. A total of 31 episodes of fever of unknown origin were reviewed. Twenty-three (74%) episodes occurred in patients with less than 200 CD4 lymphocytes/mm3. A final diagnosis of fever of unknown origin was achieved in 24 (77%) episodes: visceral leishmaniasis (n = 11), tuberculosis (n = 9), non-Hodgkin's lymphoma (n = 1), CNS toxoplasmosis (n = 1), cryptococcal meningitis (n = 1) and drug adverse reaction (n = 1). CONCLUSIONS: HIV-infected patients with fever of unknown origin very often show severe immunodeficiency. Cryptococcal antigen testing should be carried out in the initial evaluation of fever of unknown origin in HIV-infected patients. In our area, 64% of episodes of fever of unknown origin were caused by visceral leishmaniasis or tuberculosis.

Adult↗
PubMed1996

Sites of origin and patterns of migration of vasotocin/mesotocin neurons in developing brain of the chick.

Vasotocin/mesotocin (VT/MT) producing neurons are known to migrate extensively during development of the hypothalamus. Birthdating studies as well as immunohistochemical studies suggested the possibility that VT/MT producing neurons originate from specific sites of the neural tube. Furthermore, a relationship between the site of origin and the eventual fate of VT/MT cells has been suggested. This study proposes to identify the sites of origin of VT/MT cells and to establish whether magnocellular and parvocellular VT/MT, and neuromodulatory and neurosecretory VT/MT arise from common or different areas of the developing neural tube. To do so, the embryological distribution of VT/MT producing neurons of the chick was studied with immunohistochemistry. Analysis of the youngest brains in which VT/MT cells could be detected (embryonic day 7.25, E7.25) suggested the presence of two separate sites of origin. The first site was located in the hypothalamic anlage, next to the third ventricle, and the second in the mesencephalon, next to the fourth ventricle. Three-dimensional reconstructions of the location of VT/MT cells throughout development substantiated the hypothesis that diencephalic VT/MT cells originate from the first site while mesencephalic ones originate from the second site. Mesencephalic VT/MT producing cells were confined to the nucleus of Edinger-Westphal and were only detectable during a brief period in development (E7.25-E10). Diencephalic VT/MT producing neurons were noted to form two main paths from their sites of origin to the rostral diencephalon. Quantitative analysis confirmed this caudal to rostral displacement. Magnocellular and parvocellular VT/MT+ cells were intermingled at the diencephalic site of origin as well as in the migratory paths. Neuromodulatory and neurosecretory VT/MT cells of the diencephalon appeared to be derived from a common diencephalic site of origin. These studies support the hypothesis that while specific groups of progenitors may be important in allowing their offspring to produce VT/MT, they do not appear to influence the morphological attributes (magnocellular vs. parvocellular), nuclear locations, or functional characteristics of these cells.

Animals↗
PubMed2003

Unusual extended fibular origin of the human soleus muscle: possible morpho-physiologic significance based on comparative anatomy.

A bilateral anomalous extended origin of the soleus muscle was observed in a 73-year-old female cadaver. It arose from the head, neck, and proximal two-thirds of the medial crest of the fibula and ran through the posterior intermuscular septum of the leg, from the lateral border of the fibula. The soleus muscle formed the vault of a muscular tunnel, overcoming the deep flexor muscles of the leg that was about 15 cm in length and directed inferiorly and laterally. The extended fibular origin delimited a blind recess lateral to the muscular tunnel and parallel to the posterior surface of the fibula. This recess measured 6.5 cm in length and extended 3.5 cm above the inferior opening of the muscular tunnel; the superior portion of the flexor hallucis longus was housed within it between the portions of the extended origin from the medial crest of the fibula and posterior intermuscular septum. The neurovascular bundle of the posterior leg coursed in the muscular tunnel. The tibial origin and calcaneal insertion of the soleus muscle were normal. Phylogenetic studies of the muscles of the lower limbs in mammals indicate that the fibular origin of soleus is more constant than the tibial origin and, in primates, the fibular origin is the only one observed in most monkeys. The case reported might be considered a conspicuous enlargement of the fibular origin observed in primates. This large fibular origin of the soleus muscle may prove to be a difficulty during surgery when accessing the proximal two-thirds of the fibula for ligation of the peroneal artery.

Aged↗
PubMed1981

Efferent systems of the rabbit visual cortex: laminar distribution of the cells of origin, axonal conduction velocities, and identification of axonal branches.

Several efferent systems of visual area I in Dutch rabbits were studied with anatomical (horseradish peroxidase) and physiological (antidromic) methods. Anatomical studies provided information regarding the laminar origin of the projections to the contralateral hemisphere, visual area II, the dorsal lateral geniculate nucleus, and the superior colliculus. Physiological studies provided information regarding conduction velocities and multiple destinations of efferent axons. Both the callosal projection and the projection to V-II were shown to originate primarily in layer II-III. However, approximately 10-20% of the callosal projection and 20-40% of the projection to V-II originated in layers IV and V. In contrast, the projection to the dorsal lateral geniculate nucleus originated nearly exclusively in layer VI, while corticotectal neurons occurred primarily in layer V. A significant number of corticotectal neurons were, however, found in layer IV. Thus, the above efferent systems were found to differ in their principal laminar origin and in the diffuseness of that origin. The origins of corticocortical projections were considerably more diffuse than those of corticofugal projections. In addition to differences in laminar origin, efferent systems also differed significantly in the conduction velocities of their axons. The projection to visual area II and to the lateral geniculate nucleus consisted primarily of very slowly conducting axons, while the projection to the superior colliculus was fast conduction. The callosal projection consisted of both slow and fact conduction axons. Finally, the question of branching of V-I efferent axons was addressed. Although the laminar origin of the projections to the contralateral hemisphere and to visual area II overlapped considerably, none of these corticocortical axons could be shown to project to both locations or to a subcortical destination. In contrast, approximately one-third of corticotectal axons were shown to project a collateral into the thalamus. Although the destination of this collateral is unclear, it is medial to the lateral geniculate nucleus and may be the pulvinar.

Animals↗
PubMed1997

Reconstitution of a functional bovine papillomavirus type 1 origin of replication reveals a modular tripartite replicon with an essential AT-rich element.

A functional replication origin was reconstituted using oligonucleotide cassettes corresponding to three sequence subelements within the Bovine Papillomavirus Type 1 (BPV-1) replication origin: the 23-bp AT-rich region (ATR), the 18-bp binding site for the viral replication initiator protein E1 (E1BS), and a binding site for the viral transcriptional transactivator and replication enhancer protein E2 (E2BS). Replication of the reconstituted origin depended on heterologous expression of both the E1 and E2 proteins and on the presence of both the E1BS and E2BS, indicating that it is functionally analogous to the authentic BPV-1 origin. In addition, pairwise testing of subelement combinations revealed that the ATR was also essential and that a functional origin required at least one copy of all three subelements. While the E1BS and E2BS are sequence-specific elements, the function of the BPV-1 ATR could be at least partially substituted with heterologous AT-rich sequences, suggesting that the role of this element is primarily AT content-dependent rather than sequence-dependent. A stringent requirement for the ATR was also observed in the context of an authentic minimal origin sequence confirming that it is an intrinsic property of the BPV-1 origin and not simply an artifact of the reconstitution system. This study indicates that the minimal functional BPV-1 origin shares the tripartite modular organization characteristic of other simple eukaryotic replication origins. The reconstitution system described now provides a convenient approach to define the physical and functional interrelationships between the three subelements in a systematic fashion.

Adenovirus E2 Proteins↗
PubMed2005

Prediction of the origin of intracanalicular neoplasms with high-resolution MR imaging.

Correct diagnosis of intracanalicular neoplasms is important to avoid unnecessary operations or an unsuitable surgical approach. We investigated the capability of high-resolution three-dimensional MR imaging in predicting the origin of intracanalicular neoplasms. Twenty cases underwent three-dimensional Fourier-transformation (3DFT) constructive interference in steady state and contrast-enhanced 3DFT-fast low angled shot MR imaging and surgery. Seventeen cases underwent caloric test. MR diagnosis on the origin of intracanalicular neoplasms was compared with surgical results. For MR diagnosis, the origin of intracanalicular neoplasms was predicted according to the location of the tumor in the internal auditory canal (IAC) in two ways, i.e., determining (1) a single specific nerve of origin and (2) whether the tumor originated from the superior or inferior aspect of the IAC. Surgery could determine the nerve of origin in 16 cases (14 inferior and 2 superior vestibular schwannomas), but it was indeterminate in 4. Comparison between MR prediction and surgical results on a single nerve origin revealed exact agreement in five, but inconsistent in three. Regarding whether the tumor was derived from superior or inferior aspect of the IAC, agreement was found in 10 of the 16 cases (62.5%). Caloric test was abnormal in all patients examined but one with superior vestibular schwannoma. 3DFT-MR imaging was not particularly useful in predicting a precise nerve of origin of intracanalicular neoplasms. The prediction on whether the tumor originated in the superior or inferior aspect of the IAC was superior to caloric test, which might have clinical significance in treatment planning especially for hearing preservation surgery.

Adult↗
PubMed1990

Replication enhancer-independent mutation increases the co-operativity with which an initiator protein binds its origin.

The plus-strand replication origin of bacteriophage fl has a bipartite structure consisting of a required core origin region and an adjacent A + T-rich enhancer sequence that potentiates replication approximately 100-fold. The core origin binds the initiator protein (gpII) and the enhancer binds the Escherichia coli integration host factor (IHF). gpII binds the core origin in two steps, forming a binding intermediate (complex I) and a functional complex for nicking (complex II). We have used a double-label gel binding assay to determine the stoichiometry of the gpII-origin interaction. The results indicate that complex I contains two gpII molecules per origin, and complex II contains four gpII molecules per origin. Enhancer-independent mutations in gpII allow wild-type levels of replication in the absence of either the enhancer or IHF. We have examined the binding of an enhancer-independent gpII mutant (mp1) protein to the replication origin. The mp1 mutation in gpII (Met40----Ile) increases the co-operativity with which the protein binds to form complex II. In addition, the mutant gpII forms both complexes with a DNA fragment containing only two (beta-gamma) of the three repeats from the core origin sequence, while the wild-type protein forms only complex I with this fragment. We discuss how a mutation that increases the co-operativity of binding of an initiator protein might stimulate DNA replication.

Base Sequence↗