Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “persistence”

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 307 records · Page 17Linked to original sources
PubMed1991

Influence of larval and adult nutrition on biting persistence in Aedes aegypti (Diptera: Culicidae).

Biting persistence was measured for Aedes aegypti (L.) mosquitoes given different levels of larval and adult nutrition. Persistence was measured as the total number of times during a 60-min trial that a mosquito returned to land on a defensive host after being disturbed and dislocated from the host, and as the rate of decline of landings over the 60 min test (pattern of persistence). Large females were significantly more persistent than smaller females, regardless of whether the females were provided water or 5% sucrose for 3 d before the test. Access to sucrose for 3 or 7 d did not influence the total number of landings of large females. Large females starved for 7 d exhibited significantly reduced persistence compared with large females starved for only 3 d. Water-fed specimens displayed a more rapid decline in the pattern of persistence than sucrose-fed specimens. Field-collected females, intermediate in size between the large and small laboratory females, had dry weights indicating they were relatively starved. They had a total number of landings similar to the small laboratory females and a persistence pattern similar to sucrose-fed specimens. Size-related differences in persistence may be one factor causing differences in parity rates and vector potential observed between large and small females in Ae. aegypti field populations.

Aedes↗
PubMed2001

Risk factors for persistent chronic widespread pain: a community-based study.

BACKGROUND: Chronic widespread pain is the cardinal clinical feature of the fibromyalgia syndrome, which, in the majority of clinic patients, is persistent. By contrast, in community-derived patients, pain is persistent in only half of the affected individuals, particularly those with psychological distress. Whether such distress is a consequence of the pain or a manifestation of a wider process of somatization which is associated with the persistence of pain is unclear. OBJECTIVES: We tested in a large, prospective, population-based study the hypothesis that features of somatization predict the persistence of chronic widespread pain. METHODS: In all, 252 (13%) of 1953 adult subjects selected from a population register were classified as having chronic widespread pain based on a detailed questionnaire which included a pain drawing. The patients also completed a number of psychosocial instruments which measure features known to be associated with somatization. Two hundred and twenty-five (91%) of the patients were successfully followed up after 12 months and provided data on pain status using the same instruments. RESULTS: In all, 126 (56%) patients reported chronic widespread pain at follow-up, 74 (33%) reported other pain and 25 (11%) reported no pain. Persistent chronic widespread pain was strongly associated with baseline test scores for high psychological distress and fatigue. In addition, these subjects were more likely to display a pattern of illness behaviour characterized by frequent visits to medical practitioners for symptoms which disrupt daily activities. The prevalence of persistent pain increased with the number of risk factors the subjects were exposed to. CONCLUSIONS: Although almost half of the cases of chronic widespread pain resolved within 1 yr, this study has demonstrated for the first time that those subjects who display features of somatization are more likely to have widespread pain which persists. These findings have implications for the identification and treatment of persons with persistent chronic widespread pain.

Adolescent↗
PubMed2001

Oxidative stress is not enhanced in non-malnourished infants with persistent diarrhea.

Increased concentrations of reactive oxygen species (ROS) and depleted antioxidant defences have been implicated in a cycle of infection, malabsorption and malnutrition, leading to persistent diarrhea. In order to determine whether in non-malnourished children oxidative stress predisposes to the development of persistent diarrhea, infants with acute diarrhea (< 7 days) (n = 39) were compared to infants with persistent diarrhea (> 14 days) (n = 38). Lipid peroxidation was assessed by the TBARs assay and expressed as malondialdehyde equivalent content (nmol MDA/ml plasma), and levels of plasma antioxidants vitamin A and vitamin E were determined. In infants with acute and persistent diarrhea nutritional status, as assessed by weight/height and height-for-age, hemoglobin levels, serum albumin and immunoglobulin levels, did not differ between groups. Serum vitamin A and vitamin E levels did not differ in infants with acute or persistent diarrhea. TBARs, expressed as nmol MDA/ml plasma did not differ between infants with acute or persistent diarrhea and furthermore did not differ from levels in a healthy, similar age, control group. Non-malnourished infants with persistent diarrhea do not exhibit plasma antioxidant depletion or enhanced lipid peroxidation. In these infants, oxidative stress, as reflected in plasma, does not play a role in the pathogenesis of persistent diarrhea.

Analysis of Variance↗
PubMed1991

Potential role of adherence traits of Escherichia coli in persistent diarrhea in an urban Brazilian slum.

We examined stools from 40 children with persistent diarrhea (duration, 14 days or more), from 50 children with acute diarrhea and from 38 control children to determine infectious etiologies for persistent diarrhea in Goncalves Dias, an urban favela (slum) in Fortaleza, Ceara, Brazil. Children with persistent diarrhea and children with acute diarrhea had similar rates of isolation of routine viral, bacterial and parasitic enteric pathogens. Routine pathogens were identified in at least 20% of cultures done more than 14 days into the diarrheal illness. We examined Escherichia coli isolated from these stools for adherence potential. Enteroaggregative E. coli were isolated significantly more often from children with persistent diarrhea than from control children or children with acute diarrhea (P less than 0.05). E. coli with hemagglutination patterns suggestive of adherence pili were also isolated more often from children with persistent diarrhea than from children with acute diarrhea (38% vs. 18%; P less than 0.05). Enterotoxigenic E. coli were isolated in combination with rotavirus more often from children with persistent diarrhea than from children with acute diarrhea. E. coli which were hydrophobic or exhibited hemagglutination were also seen more often in association with Giardia in children with persistent diarrhea. These findings suggest that the etiology of persistent diarrhea in children is complex and that the aggregative E. coli are associated with prolonged diarrheal illness. Although routine diarrheal pathogens may be present for more than 14 days, combinations of pathogens, including E. coli with adherence potential, may also contribute to prolonged diarrheal disease.

Animals↗
PubMed2003

Persistent bacteremia and outcome in late onset infection among infants in a neonatal intensive care unit.

BACKGROUND: Persistent bacteremia despite antibiotic therapy has been correlated with adverse outcomes, including focal suppurative complications and death. Coagulase-negative staphylococci (CONS) are the most common cause of nosocomial infection in infants requiring neonatal intensive care and might yield more substantial pathology if infection were persistent. METHODS: To compare the severity and features of persistent infection by CONS with those of other bacteria, we reviewed infants admitted to our neonatal intensive care unit from 1990 through 2001 who developed bacteremia at >5 days of age with recovery of the same bacterial species from blood for >24 h after initiation of antibiotic therapy to which the organism was susceptible. Cases were excluded if a focal complication was already present with the initial positive culture or if the medical record was unavailable. Outcomes of interest included focal suppurative complications, death attributable to infection and duration of hospitalization among survivors. RESULTS: We identified 62 infants with sustained infection, caused by CONS in 30 and by other organisms in 32 [10 Gram-negative, 22 Gram-positive (16 Staphylococcus aureus)]. Infants with persistent CONS had significantly lower birth weight and gestational age, but no difference was found for multiple other clinical and demographic risk factors. Indwelling vascular catheters were present at diagnosis in 85% of the infants (CONS 26 of 30, non-CONS 27 of 32). Responses of bacteremia to catheter removal vs. in situ treatment did not differ between the groups. No differences were observed for death from all causes (27 vs. 34%), death attributable to infection (6 vs. 12%) or duration of hospitalization among survivors [median (interquartile range): 102 (73 to 167) 107.5 (89 to 130) days]. Focal suppurative complications were significantly more frequent in infants persistently infected with non-CONS (28 vs. 3%; P = 0.01). Duration of persistence correlated with focal complication in non-CONS infants (r = 0.988; P < 0.001). CONCLUSIONS: Although persistent infection with CONS occurs in significantly smaller and less mature infants than with non-CONS, death is no more frequent and focal complications are significantly less frequent. Infants with persistent infection should undergo aggressive evaluation for focal complications, with the yield expected to be higher in those with non-CONS.

Bacteremia↗
PubMedDate not supplied

Survival, persistence, and progressive differentiation of adoptively transferred tumor-reactive T cells associated with tumor regression.

Objective clinical responses have been observed in approximately 50% of patients who received non-myeloablative chemotherapy prior to the adoptive transfer of autologous melanoma-reactive tumor-infiltrating lymphocytes (TILs). Recent studies carried out through the use of antibodies directed against T-cell-receptor beta chain variable region (TRBV) products, as well as by direct sequencing of the expressed TRBV gene products, indicated that clinical responses in this trial were associated with the level of persistence of adoptively transferred T cells. In an attempt to further characterize T cells that persist in vivo following adoptive transfer, five dominant T-cell clonotypes were identified in TIL 2035, an adoptively transferred TIL that was associated with the complete regression of multiple metastases. The most highly persistent clonotype, which expressed the BV1 TR gene product, recognized the MAGE-6 cancer/testis antigen in the context of HLA-A23. This clonotype was detected in peripheral blood for over 16 months following adoptive transfer, expressed relatively higher levels of the co-stimulatory markers CD28 and CD27, and possessed telomeres that were long relative to other clonotypes present in TIL 2035 that showed only short-term persistence. The long-term persistent BV1 clonotype appeared to differentiate more slowly toward an end-stage effector in vivo than short-term persistent clonotypes, as manifested by the downregulation of CD28, CD27, and CD45RO and upregulation of CD57 and CD45RA expression on these T cells. These results indicated that the differentiation stage and replicative history of individual TIL clonotypes might be associated with their ability to survive and to persist in vivo, and progressive differentiation of the persistent clonotypes occurred following adoptive transfer.

Adult↗
PubMed2003

Persistence in health expenditures in the short run: prevalence and consequences.

BACKGROUND: Knowing whether persons in the top percentiles of the health expenditure distribution exhibit persistently high expenditure is fundamental to developing health plan payment policies, containing costs, and understanding the consequences of costly illnesses. OBJECTIVES: To determine the extent of high expenditure persistence over a 2-year period. To identify the correlates and consequences of expenditure persistence. SUBJECTS: A national sample of the population from a longitudinal panel of the Medical Expenditure Panel Survey (MEPS). METHODS: Changes in a person's position in the expenditure distribution were examined. chi2 tests were used to identify differences in characteristics between high and low spenders. Logistic regression was used to predict the likelihood of expenditure persistence. Changes in income, employment, out-of-pocket expenditure burden, and health insurance were compared for high and low spenders. RESULTS: Of the top 5% of spenders in 1996, 30% retain this position in 1997 and 45% are in the top decile of 1997 spenders. High expenditures begin to regress to the mean over the study period. Cancer, mental disorders, diabetes, and infectious diseases and being in the top decile of 1996 spenders increase the probability of expenditure persistence (P < 0.05 for all). This probability also has a strong random component. An increased proportion of persons in the top expenditure decile for both years had out-of-pocket health spending greater than 20% of income in 1997 (P < 0.10). Persons with persistently high expenditures were less likely than low spenders to lose employment-based coverage (5.4% vs. 8.8%, P < 0.05) but no changes in income or employment status were detected. CONCLUSIONS: A sizable minority of persons exhibits persistently high expenditures, creating incentives for favorable risk selection. Few consequences of short-run expenditures persistence are observed.

Adult↗
PubMed1988

Oligo-2',5'-adenylate synthetase activity in K562 cell lines persistently infected with measles or mumps virus.

Fluctuation of oligo-2',5'-adenylate synthetase (2-5AS) activity was examined in K562 cells infected with vaccine strains of measles virus (strains AIK-C and CAM-70) and mumps virus (strains Torii and Miyahara). Persistent infection was easily established in the mumps virus-infected cells without significant cytolysis or cell killing. In contrast, most of the cells infected with measles virus were killed by extensive cytolysis within 3 to 4 days. The small number of cells that did survive became persistently infected. That these persistently infected cells carried a virus antigen was confirmed by fluorescein isothiocyanate-labelled anti-measles virus rabbit antiserum and anti-mumps virus rabbit antiserum. The cells produced infectious progeny virus as well as interferon (IFN). Little induction of 2-5AS activity by IFN was demonstrated during the early stages of infection by these viruses. Similar results were observed in some of the persistently infected cells but not, however, K-CMP cells (K562 cells persistently infected with CAM-70) or K-MMP cells (K562 cells persistently infected with Miyahara). Failure to induce 2-5AS activity was unchanged in cells cultured for more than 6 months. The decrease of 2-5AS activity observed in K-MTP cells (K562 cells persistently infected with Torii) was the result of suppression of transcription of 2-5AS mRNA. On the other hand, a normal level of mRNA was found in K-AKP cells (K562 cells persistently infected with AIK-C). Therefore, it is suggested that the decrease of 2-5AS activity in K-AKP cells may be due to a failure to translate 2-5AS mRNA.

2',5'-Oligoadenylate Synthetase↗
PubMed1994

Persistent infection of MT-4 cells by human immunodeficiency virus type 1 becomes increasingly likely with in vitro serial passage of wild-type but not nef mutant virus.

Our previous studies have shown that human immunodeficiency virus type 1 (HIV-1), with mutations in accessory genes such as vif, vpr or vpu, can generate persistent infection of MT-4 cells, whereas infection by wild-type or nef mutant HIV-1 causes extensive cell death. The possibility of generating a naturally attenuated form of HIV-1 with reduced cytopathogenicity in MT-4 cells was examined by in vitro serial passage of the wild-type and a nef mutant form of HIV-1, each derived from the infectious molecular clone pNL432. The ability to cause persistent infection was observed after four passages of wild-type HIV-1 with the frequency of persistence becoming progressively higher with serial passage. In contrast, persistent infection was not observed even after 50 passages of the nef mutant virus. Sequence analysis of the accessory gene loci in genomes recovered from the persistent infections caused by passaged virus revealed mutations in vif and vpr, but not in vpu. The processing of the Env precursor to mature forms was not modified in any of the passages of either wild-type or nef mutant HIV-1. However, when compared with acute infections caused by similarly passaged virus of both wild-type and nef mutant HIV-1, persistent infections by passaged wild-type HIV-1 showed a significant decrease in the cell surface expression and function of Env. Cell surface CD4 was only partially down-regulated on cells acutely infected with the passaged viruses, whereas on cells persistently infected with passaged wild-type HIV-1 it was completely down-regulated. These results suggest that, during serial passage of HIV-1, mutations accumulate at least in the accessory genes vif and vpr in parallel with a lesser interaction between cell surface Env and CD4 molecules, and lead to the generation of less cytopathogenic viruses capable of persistent infection. Our results also suggest an important role for the nef gene product in the generation of HIV-1 strains that are less cytopathogenic.

Amino Acid Sequence↗
PubMed1996

Influenza C virus RNA is uniquely stabilized in a steady state during primary and secondary persistent infections.

The ability to establish persistent infections in vitro and in vivo has been illustrated for different human RNA viruses. However, little insight has been gained regarding the intracellular state of viral RNA species and the regulatory processes governing their long-term continuance. In this report, primary persistence of a variant of influenza C/Ann Arbor/1/50 virus in infected MDCK cells and secondary infections in human cell lines were investigated. Different PCR and staining techniques were applied for the description of low viral loads. The RNA pattern in primary persistence indicates that viral RNA synthesis is quantitatively linked to productive and non-productive phases, with negative-strand RNA being present continuously. In single cells cultures, derived from the primary line, all clones tested were positive by nested PCR and Southern blot screening. This suggests that a true steady-state persistence of influenza C virus is established in each individual cell of the infected population. Secondary infection experiments, in terms of transfer of the persistent virus variant to different cell types, showed that a re-establishment of persistence can be accomplished in vitro. The stable persistent status remained reserved for distinct host cell lines. Hereby, vRNA is stably maintained in cell-type specific manner, whereas gene expression (e.g. HEF glycoprotein production) occurs in a variable fashion. These data point out novel characteristics in the understanding of influenza virus persistence.

Animals↗
PubMed2001

A bovine macrophage cell line supports bovine herpesvirus-4 persistent infection.

Although bovine herpesvirus-4 (BHV-4), a gammaherpesvirus lacking a clear disease association, has been demonstrated in many tissues during persistent BHV-4 infection, a likely site of virus persistence is in cells of the monocyte/macrophage lineage. To establish an in vitro model of persistent infection potentially useful for examining the molecular mechanisms of BHV-4 persistence/latency, we infected the bovine macrophage cell line BOMAC. Following extensive cell death, surviving cells were found to be persistently infected, maintaining the viral genome over many passages and producing low levels of infectious virus. Although selection was unnecessary for the maintenance of the viral genome, cells persistently infected with recombinant BHV-4 containing a neomycin-resistance gene could be selected with geneticin, thus confirming that persistent BHV-4 infection was compatible with cell survival and replication. Furthermore, persistent BHV-4 infection caused no decrease in the growth rate of BOMAC cells. Sodium butyrate, which reactivates latent gammaherpesviruses in vitro, or dexamethasone, which reactivates latent BHV-4 in vivo, increased viral DNA by 10- to 15-fold in persistently infected BOMAC cells. This suggests that reactivation of latent BHV-4 by dexamethasone in vivo might involve direct action of dexamethasone on latently infected cells.

Animals↗
PubMed2002

Persistence in cluster-cluster aggregation.

Persistence is considered in one-dimensional diffusion-limited cluster-cluster aggregation when the diffusion coefficient of a cluster depends on its size s as D(s) approximately s(gamma). The probabilities that a site has been either empty or covered by a cluster all the time define the empty and filled site persistences. The cluster persistence gives the probability of a cluster remaining intact. The empty site and cluster persistences are universal whereas the filled site depends on the initial concentration. For gamma>0 the universal persistences decay algebraically with the exponent 2/(2-gamma). For the empty site case the exponent remains the same for gamma<0 but the cluster persistence shows a stretched exponential behavior as it is related to the small s behavior of the cluster size distribution. The scaling of the intervals between persistent regions demonstrates the presence of two length scales: the one related to the distances between clusters and that between the persistent regions.

Journal Article↗
PubMed2005

Costs associated with persistent allergic rhinitis are reduced by levocetirizine.

BACKGROUND: Allergic rhinitis was recently classified by the ARIA guidelines as persistent or intermittent. Levocetirizine was shown to improve symptoms and health-related quality of life of patients with persistent allergic rhinitis in the XPERT study, a 6-month randomized double blind placebo-controlled trial. OBJECTIVE: To assess the total costs of persistent allergic rhinitis, and the effect of long-term treatment with levocetirizine on these costs from several perspectives (societal, social security system, and employers). METHODS: Direct medical cost parameters (medications, physician visits and hospitalizations) and time lost parameters (workdays and Usual Daily Activities (UDA) lost) related to persistent allergic rhinitis and its comorbidities (asthma, sinusitis, otitis and upper respiratory infection) were measured. A cost analysis was performed using 2002 French costing data. RESULTS: From a societal perspective, the total cost of persistent allergic rhinitis without long-term treatment was estimated at 355.06/patient/month. From a social security perspective, levocetirizine treatment yielded an additional cost of 2.78/patient/month, compared to no-treatment. However, levocetirizine reduced the total cost of persistent allergic rhinitis and its comorbidities by 152.93/patient/month from a societal perspective and by 64.70/patient/month from an employer perspective. Most gains resulted from a decrease in the lost workdays and UDA in the levocetirizine group. CONCLUSION: The cost of persistent allergic rhinitis is substantial. Treatment with levocetirizine reduces the cost of persistent allergic rhinitis and its comorbidities to the society by 152.93/patient/month while improving symptoms and health-related quality of life.

Cetirizine↗
PubMed2006

Persistent urinary incontinence and delivery mode history: a six-year longitudinal study.

OBJECTIVE: To investigate the prevalence of persistent and long term postpartum urinary incontinence and associations with mode of first and subsequent delivery. DESIGN: Longitudinal study. SETTING: Maternity units in Aberdeen (Scotland), Birmingham (England) and Dunedin (New Zealand). POPULATION: Women (4214) who returned postal questionnaires three months and six years after the index birth. METHODS: Symptom data were obtained from both questionnaires and obstetric data from case-notes for the index birth and the second questionnaire for subsequent births. Logistic regression investigated the independent effects of mode of first delivery and delivery mode history. MAIN OUTCOME MEASURES: Urinary incontinence-persistent (at three months and six years after index birth) and long term (at six years after index birth). RESULTS: The prevalence of persistent urinary incontinence was 24%. Delivering exclusively by caesarean section was associated with both less persistent (OR=0.46, 95% CI 0.32-0.68) and long term urinary incontinence (OR=0.50, 95% CI 0.40-0.63). Caesarean section birth in addition to vaginal delivery, however, was not associated with significantly less persistent incontinence (OR 0.93, 95% CI 0.67-1.29). There were no significant associations between persistent or long term urinary incontinence and forceps or vacuum extraction delivery. Other significantly associated factors were increasing number of births and older maternal age. CONCLUSIONS: The risk of persistent and long term urinary incontinence is significantly lower following caesarean section deliveries but not if there is another vaginal birth. Even when delivering exclusively by caesarean section, the prevalence of persistent symptoms (14%) is still high.

Chronic Disease↗
PubMed1992

Association of indicators of hygiene behavior with persistent diarrhea of young children.

We examined the association between water and hygiene-related behaviors and persistent diarrhea (duration > or = 14 days) among children under age three years in an indigenous rural Guatemalan community. Behavior indicators were specific aspects of the appearance of the mother, study child, other children and household that could be observed using a spot observation technique. Thirty-four percent of children had one or more episodes of persistent diarrhea during the year of study. Bivariate analyses found that a higher proportion of observations in which the anti-hygienic condition was observed was significantly associated with persistent diarrhea for 11 of 26 behavior indicators; these 11 indicators were also strongly correlated with each other. In individual logistic regression models, which included overall rate of diarrhea and other child characteristics associated with persistent diarrhea, six behavior indicators maintained significant association with persistent diarrhea: presence of toy on the ground, presence of baby bottle on the ground, the hands of the mother being dirty, presence of a fecally soiled diaper on the ground in the household compound, presence of feces in the yard, and the study child wearing a fecally soiled diaper. Three additional indicators closely approached significant association with persistent diarrhea. Excluding the three soiled diaper indicators, which might be the result rather than the cause of diarrhea, we found the six other behavior indicators to demonstrate a significant dose-response effect in increasing risk of persistent diarrhea. These findings suggest that behaviors which promote increased exposure of young children to enteric pathogens increase risk of persistent diarrhea.

Behavior↗
PubMed1997

Detection of calves persistently infected with bovine pestivirus in a sample of dairy calves in south-eastern Queensland.

OBJECTIVE: To determine the proportion and incidence of calves persistently infected with bovine pestivirus in calves (n = 1521) supplied to the Tick Fever Research Centre and to assess the test regime to detect calves persistently infected with bovine pestivirus. DESIGN: Calves, 1 to 6 weeks old, selected for use in the production of the tick fever vaccine were collected from 21 properties in 56 separate groups between October 1990 and December 1996. Each group was examined for the presence of calves persistently infected with bovine pestivirus. PROCEDURE: All calves were routinely tested for antibody to bovine pestivirus and bovine pestivirus antigen using a serum neutralisation test and an antigen-capture ELISA, respectively. Pooled lymphocyte samples from calves were also monitored for bovine pestivirus by inoculation of sheep. Whole herd testing was carried out in eight herds, using a serum neutralisation test as a screen test followed by an antigen-capture ELISA of cattle with a serum neutralisation test titre of less than 32. RESULTS: Fourteen of the 1521 calves tested (0.9%), were detected as persistently infected and the incidence ranged from 0.0 to 3.0% per year over 6 years. Persistently infected calves were found in 13 of the 59 groups and originated from 7 of the 21 herds used. In whole herd testing on the properties of origin, cattle persistently infected with bovine pestivirus were detected in four of the eight herds tested. CONCLUSIONS: The proportion of calves persistently infected with bovine pestivirus is similar to that in other countries and indicates that bovine pestivirus could be a significant cause of economic loss in Australian cattle herds. In detecting calves persistently infected with bovine pestivirus, the combination of sheep inoculation, paired antigen-capture ELISA and serum neutralisation tests appeared to be highly sensitive and specific.

Animals↗
PubMed1996

Hypoxia increases persistent sodium current in rat ventricular myocytes.

1. A persistent inward current activated by depolarization was recorded using the whole-cell, tight seal technique in rat isolated cardiac myocytes. The amplitude of the inward current increased when cells were exposed to a solution with low oxygen tension. 2. The persistent inward current had the characteristics of the persistent Na+ current described previously in rat ventricular myocytes: it was activated at negative potentials (-70 mV), reversed close to the equilibrium potential for Na+ (ENa), was blocked by TTX and was resistant to inactivation. 3. Persistent single Na+ channel currents activated by long (200-400 ms) depolarizations were recorded in cell-attached patches on isolated ventricular myocytes. Hypoxia increased the frequency of opening of the persistent Na+ channels. 4. Persistent Na+ channels recorded during hypoxia had characteristics similar to those of persistent Na+ channels recorded at normal oxygen tensions. They had a null potential at ENa, their amplitude varied with [Na+], they were resistant to inactivation and their mean open time increased with increasing depolarization. 5. The persistent Na+ channels in cell-attached patches were blocked by TTX (50 microM) in the patch pipette and by lidocaine (100 microM). 6. It was concluded that hypoxia increases the open probability of TTX-sensitive, inactivation-resistant Na+ channels. The voltage dependence of these channels, and their greatly increased activity during hypoxia, suggest that they may play an important role in the generation of arrhythmias during hypoxia.

Animals↗
PubMed2006

Protein expression profiles of Chlamydia pneumoniae in models of persistence versus those of heat shock stress response.

Chlamydia pneumoniae is an obligate intracellular pathogen that causes both acute and chronic human disease. Several in vitro models of chlamydial persistence have been established to mimic chlamydial persistence in vivo. We determined the expression patterns of 52 C. pneumoniae proteins, representing nine functional subgroups, from the gamma interferon (IFN-gamma) treatment (primarily tryptophan limitation) and iron limitation (IL) models of persistence compared to those following heat shock (HS) at 42 degrees C. Protein expression patterns of C. pneumoniae persistence indicates a strong stress component, as evidenced by the upregulation of proteins involved in protein folding, assembly, and modification. However, it is clearly more than just a stress response. In IFN persistence, but not IL or HS, amino acid and/or nucleotide biosynthesis proteins were found to be significantly upregulated. In contrast, proteins involved in the biosynthesis of cofactors, cellular processes, energy metabolism, transcription, and translation showed an increased in expression in only the IL model of persistence. These data represent the most extensive protein expression study of C. pneumoniae comparing the chlamydial heat shock stress response to two models of persistence and identifying the common and unique protein level responses during persistence.

Cell Line, Tumor↗