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PubMed1993

Persistent sciatic artery: embryology, pathology, and treatment.

PURPOSE: The purpose of this article is to describe the embryologic development and anomalous persistence of the sciatic artery, pathologic changes that may occur in the persistent sciatic artery, and management of complications related to these pathologic changes. METHODS: Two patients with persistence of the sciatic artery treated in the authors' experience are reported. In addition, the computerized data base of the University of Mississippi Medical Center was searched for patients with other lower extremity arterial aneurysms, and their records were reviewed for possible aneurysm of a persistent sciatic artery. A review of the literature was undertaken to determine the embryologic development of the persistent sciatic artery, the pathologic changes that have been observed in the sciatic artery, clinical findings associated with these pathologic changes, and methods of treatment. RESULTS: Two patients with persistence of the sciatic artery were treated by the authors. No other cases were identified in 43 patients with 66 lower extremity aneurysms treated at our institution. The first patient presented with acute lower extremity ischemia caused by thrombosis of a sciatic artery aneurysm and was treated successfully with intraarterial thrombolytic therapy followed by interposition graft repair. In the second case an incidental unilateral persistent sciatic artery was identified in a patient with bilateral Buerger's disease presenting with digital gangrene of the contralateral extremity in whom below-knee amputation was eventually required. Bilateral tibial artery occlusion was observed on arteriography. Histologic examination of the amputated limb confirmed findings typical of Buerger's disease, and no microemboli were seen. DISCUSSION: The sciatic artery is a continuation of the internal iliac artery and is the primary blood supply to the lower limb bud during early fetal development. The sciatic artery normally involutes during fetal development, but remnants persist as the popliteal and peroneal arteries after the superficial femoral artery develops and establishes continuity with the popliteal artery. Persistence of the sciatic artery as the major blood supply to the lower extremity in adults is a rare vascular anomaly that may be of surgical significance. Failure to appreciate the persistent sciatic artery as the major inflow into the lower extremity may lead to inappropriate bypass of apparent occlusive disease of the superficial femoral artery. The persistent sciatic artery is also frequently aneurysmal, which may cause critical limb ischemia resulting from thrombosis or embolization of aneurysm thrombus. Options for vascular reconstruction include interposition graft replacement and standard femoropopliteal bypass grafting if the common femoral artery is sufficiently developed to provide adequate inflow. As with other peripheral arterial aneurysms resulting in thrombosis and extensive distal arterial embolization and thrombosis, intraarterial thrombolytic therapy may be useful in selected cases before definitive surgical revascularization.

Adult↗

PubMed1996

Morphologic changes and immunohistochemical detection of viral antigen in ovaries from cattle persistently infected with bovine viral diarrhea virus.

OBJECTIVE: To identify morphologic differences in ovaries from cows persistently infected with bovine viral diarrhea virus (BVDV) and determine ovarian cell types infected in these cows. DESIGN: A comparative study of ovaries in cattle persistently infected with BVDV and cattle not persistently infected with BVDV, using morphologic and immunohistochemical analysis. ANIMALS: 6 postpubertal cows persistently infected with BVDV and 6 postpubertal cows not persistently infected with BVDV. PROCEDURE: Ovaries were compared morphologically by counting the number of normal structures present on 3 histologic sections taken from each ovary. Immunohistochemistry was accomplished, using an indirect, monoclonal antibody-linked, avidin-biotin-peroxidase complex procedure. RESULTS: Significant (P < 0.01) decrease in the number of tertiary follicles, graafian follicles, atretic follicles, and corpus hemorrhagicum/luteum/albicans was observed in cows persistently infected with BVDV. No difference in numbers of primordial or secondary follicles was observed. Immunostaining of BVDV antigen in luteal cells and macrophage-like cells was evident in ovaries from cows persistently infected with BVDV. CONCLUSIONS: Cows persistently infected with BVDV appear to have significant morphologic changes in their ovaries that suggest reduction in normal ovarian activities. Furthermore, BVDV antigen can be identified in specific ovarian cell types in cattle persistently infected with BVDV. CLINICAL RELEVANCE: The changes observed may reduce reproductive performance in cows persistently infected with BVDV, and may be of importance when trying to salvage valuable genetic material from persistently infected cows through embryo transfer. It is yet to be determined whether similar findings are true in cows acutely infected with BVDV.

Animals↗

PubMed1997

Performance, survival, necropsy, and virological findings from calves persistently infected with the bovine viral diarrhea virus originating from a single Saskatchewan beef herd.

Fifty-one calves from 652 cows and heifers that calved on a Saskatchewan ranch in 1992 were identified as persistently infected with bovine viral diarrhea virus (BVDV), based on virological and necropsy findings. Herd records suggested a further 20 calves that died between birth and weaning were probably also persistently infected. Subsequent to weaning, all surviving persistently infected calves were transferred to one pen in a 10,000 head commercial feedlot, to mimic normal management practice in western Canadian beef herds. On average, when compared with healthy, BVDV-negative herdmates, persistently infected calves were "poor doers" and had poor survivability, with only 4 persistently infected calves surviving to 1 year of age. There was no difference (P > 0.05) in survival between male and female persistently infected calves. The clinical, pathological, and virological findings from these persistently infected calves varied over time. The majority of persistently infected calves had gross pathological lesions at necropsy, consistent with mucosal disease. However, approximately 25% of the persistently infected calves had gross pneumonic lesions at necropsy, with no or only mild lesions of mucosal disease. A wide variety of other lesions were also noted in persistently infected calves at necropsy. Therefore, the possibility that BVDV-induced lesions can be misdiagnosed is very real. The results of this study indicate that persistent infection with BVDV should always be considered in calves with chronic ill thrift, chronic enteritis, or respiratory disease.

Animals↗

PubMed1982

Use of the MMPI in predicting psychotherapeutic persistence in groups of male and female outpatients.

Attempted to predict therapeutic persistence, as measured by the total number of sessions attended, with the MMPI. High persisters were defined as patients who attended six or more sessions, while low persisters were patients who attended fewer than six sessions. Ss were 360 (180 high persisting, 180 low persisting) female outpatients and 204 (102 high persisting, 102 low persisting) male outpatients. All groups were divided into equal halves in order to allow for cross-validation of three separate discriminant functions: One for males, one for females, and one for the entire sample (male + female). Cross-validation revealed that only the discriminant function for males achieved a classification accuracy (60%) greater than chance expectations. A series of biserial correlations indicated that male persisters tended to be less defensive while experiencing greater distress and that female persisters tended to be more introverted and less impulsive relative to their respective low-persisting counterparts.

Ambulatory Care↗

PubMed2005

Differences in antihypertensive drug persistence associated with drug class and gender: a PHARMO study.

OBJECTIVE: The objective of the study is to investigate factors related to treatment persistence among users of antihypertensive (AHT) drugs in daily practice. METHODS: Data for this study were obtained from the PHARMO database including pharmacy records and hospitalizations in the Netherlands (n=950,000). Patients who newly received AHT therapy (n=17,113) between 1997 and 2001 were selected. Of these patients, random samples of 500 patients per drug class were drawn. One-year persistence was defined as (1) the percentage of patients using AHTs at least 270 days and receiving AHT in 3 months after the 1-year follow-up period, and (2) Catalan method (Kaplan-Meier curves). Gender specific persistence rates per drug class were adjusted for significant factors including age, use of antidiabetics and lipid lowering drugs, and prior cardiovascular hospitalizations (OR and 95%CI). RESULTS: Persistence was highest in users of angiotensin II receptor blockers (ARBs) (62.0%), progressively lower in users of angiotensin converting enzyme inhibitors (ACE-inhibitors, 59.7%), betablockers (35.0%), calcium channel blockers (34.7%), and diuretics (33.0%), resulting in the highest OR of 3.4 [95%CI: 2.6-4.5] for ARBs compared to diuretics. The persistence of AHT use in women was substantially lower (40.1% vs. 50.2%, OR 0.7 [95%CI: 0.6-0.8]) and differences between drug classes were larger than in men. CONCLUSIONS: These results demonstrate marked differences in persistence between AHT classes, with the highest persistence for ARBs and lowest for diuretics. Women were less persistent with their AHT compared to men. This low persistence leads to suboptimal treatment with a potential for substantial clinical consequences. Especially in women, more attention paid to AHT persistence patterns could improve their cardiovascular outcome.

Adult↗

PubMed1989

An epidemiological follow-up survey of persistent pain sufferers in a group family practice and specialty pain clinic.

The course and prognosis of persistent pain are largely unknown. In addition, follow-up studies of chronic pain sufferers have come from specialized pain clinics and have ignored the question of how representative this special group is to the general population who suffer persistent pain. Because health care planners are assumed to require these data for projection of health care needs, it is important to determine the course of persistent pain in those persistent pain sufferers in the general population as well as those referred to a specialty clinic. An epidemiological study compared 2 groups of self-reported persistent pain sufferers from a Family Practice Clinic and a Specialty Pain Clinic over a 2 year period. All subjects reporting a persistent problem with pain at the time of the initial survey were contacted 2 years later to determine whether the initial differences between the 2 groups remained constant over time and whether there were any changes within each group over time. Despite the similarities between the study groups on multiple socioeconomic and demographic variables, the Specialty Pain Clinic group remained distinctly different from the Family Practice pain sufferers on many pain behavior and emotional variables. Thirteen percent of the persistent pain sufferers from the Pain Clinic group and 36% of the persistent pain sufferers from the Family Practice group no longer reported pain as a problem at follow-up. Of those pain sufferers from either group who continued to experience pain at 2 years follow-up, their pain became more intermittent, psychological distress factors improved, and the use of health services decreased. The implications are that persistent pain does not necessarily continue forever and that persistent pain sufferers in the general population have a better prognosis than those who are referred to a Specialty Pain Clinic. All follow-up studies need to be interpreted in light of these findings.

Chronic Disease↗

PubMed2000

Treatment of persistent corneal epithelial defect with extended wear of a fluid-ventilated gas-permeable scleral contact lens.

PURPOSE: To report treatment of persistent corneal epithelial defects unresponsive to other therapies by extended wear of a fluid-ventilated gas-permeable scleral contact lens. METHODS: In this retrospective study, 14 eyes of 13 consecutive patients referred for the treatment of persistent corneal epithelial defects that failed to heal with conventional therapies or developed epithelial defects after penetrating keratoplasty for persistent corneal epithelial defects were fitted with an extended-wear gas-permeable scleral lens. These included seven eyes of six patients with Stevens-Johnson syndrome and seven eyes of seven patients who did not have Stevens-Johnson syndrome. Twelve eyes had undergone recent penetrating keratoplasty. All 14 eyes were fitted with a gas-permeable scleral contact lens designed to avoid the intrusion of air bubbles under its optic. An antibiotic and corticosteroid were added to the lens fluid reservoir or instilled before each lens insertion in 12 of 14 eyes. The lenses were worn continuously except for brief periods of removal for purposes of cleaning, replacement of the lens fluid reservoir, and examination and photography of the cornea. RESULTS: Five of the seven persistent corneal epithelial defects associated with Stevens-Johnson syndrome healed. The persistent corneal epithelial defects of four of these eyes re-epithelialized within 7 days, and a fifth healed in 27 days of gas-permeable scleral lens extended wear. A sixth persistent corneal epithelial defect that failed to heal initially re-epithelialized after a subsequent penetrating keratoplasty and gas-permeable scleral lens extended wear. The seventh eye healed after 3 days of gas-permeable scleral lens extended wear, but the persistent corneal epithelial defect subsequently recurred. Three of seven non-Stevens-Johnson syndrome persistent corneal epithelial defects re-epithelialized within 36 hours, 6 days, and 36 days, respectively. Of the six (six of 14) persistent corneal epithelial defects that failed to heal with a gas-permeable scleral lens extended wear, one subsequently healed after multiple amniotic membrane grafts. Microbial keratitis occurred in four eyes (four of 14) and graft failure in one eye, all of which required repeat penetrating keratoplasty. CONCLUSION: Extended wear of an appropriately designed gas-permeable scleral contact lens was effective in promoting the healing of persistent corneal epithelial defects in some eyes that failed to heal after other therapeutic measures. Re-epithelialization appears to be aided by a combination of oxygenation, moisture, and protection of the fragile epithelium afforded by the scleral lens. However, microbial keratitis represents a significant risk.

Adolescent↗

PubMed2002

Tumour necrosis factor-alpha, interleukin-1beta and interleukin-8 induce persistent mechanical nociceptor hypersensitivity.

It has been previously described that daily intraplantar (i.pl.) injections of prostaglandin E2 (PGE2) and dopamine in rats for 14 days cause the development of a persistent mechanical nociceptor hypersensitivity state lasting more than 30 days. Considering that during inflammation, the release of these hyperalgesic agents are mediated by cytokines, we investigated in the present study whether interleukin-1beta (IL-1beta), IL-8 and tumour necrosis factor-alpha (TNF-alpha) are able to induce persistent mechanical nociceptor hypersensitivity. Daily i.pl. administration of TNF-alpha, IL-1beta or IL-8 for 18 days led to persistent mechanical nociceptor hypersensitivity, which lasted at least 30 days after the cessation of treatment. The co-treatment of the animals with IL-1beta plus indomethacin, but not with atenolol, prevented the induction of persistent mechanical nociceptor hypersensitivity. The co-treatment of the animals with IL-8 plus atenolol, but not with indomethacin, prevented the induction of persistent mechanical nociceptor hypersensitivity. The daily co-treatment of TNF-alpha with either indomethacin or atenolol partially inhibited (+/-50%) the induction of persistent mechanical nociceptor hypersensitivity. However, the combined treatment with indomethacin plus atenolol abolished the induction of the persistent mechanical nociceptive hypersensitivity by TNF-alpha.A single injection of cytokines in the contralateral paws of the animals with persistent hypersensitivity caused only an acute nociceptive response. This observation, together with the demonstration of undetectable levels of immunoglobulins against TNF-alpha, IL-1beta or IL-8 in the sera of animals after the development of the persistent hypersensitivity induced by those cytokines, indicate that this event is not due to an ongoing immunological response against the cytokines. In conclusion, our results support the suggestion that IL-1beta- and IL-8-induced persistent mechanical nociceptor hypersensitivity results from the endogenous release of eicosanoids and sympathetic amines, respectively. However, TNF-alpha-induced mechanical nociceptor hypersensitivity results from the concomitant endogenous release of eicosanoids and sympathomimetic mediators.

Adrenergic beta-Antagonists↗

PubMed1998

An approach to understanding the mechanisms of poliovirus persistence in infected cells of neural or non-neural origin.

BACKGROUND: Poliovirus (PV) is the etiologic agent of paralytic poliomyelitis, which is sometimes followed, after decades of clinical stability, by new symptoms, including progressive muscular atrophy, collectively known as the post-polio syndrome. This raises the question of possible PV persistence in post polio patients. OBJECTIVE: To test the capacity of PV to establish persistent infections in human cells, three models were developed. STUDY DESIGN: This review focuses on the viral and cellular parameters involved in persistent PV infection. RESULTS: Many PV strains, which are generally lytic in primate cell lines, are able to establish persistent infections in human neuroblastoma cells. During persistent infection, PV mutants (PVpi) are consistently selected, and several of their capsid substitutions occur at positions known to be involved in PV-PV receptor interactions. PVpi have a particular property: they can establish persistent infections in non-neural HEp-2 cells. PV can also persistently infect primary cultures of human fetal brain cells and the majority of cells which survive infection belong to the neuronal lineage. CONCLUSIONS: The results obtained with the three models of persistent PV infection in human cells suggest that several mechanisms are used by PV to establish and maintain persistent infections in neural and non-neural cells. The interactions of the virus with its receptor seem to be a key-step in all cases. In the future, the elucidation of the etiology of the post-polio syndrome will require the characterization of PV sequences having persisted for decades in post-polio patients.

Animals↗

PubMed1999

Persistent corneal oedema following ICCE. Influence of IOL type.

PURPOSE: To examine the frequency of persistent corneal oedema following intracapsular cataract extraction (ICCE). To examine whether the type of intraocular lens has any influence on persistent corneal oedema following ICCE. METHODS: A retrospective study of 1041 consecutive ICCE operations followed for at least eight years. The cumulative incidence of persistent corneal oedema was calculated for the whole group and compared to the incidence in subgroups defined by type of intraocular lens. RESULTS: The cumulative incidence of persistent corneal oedema following ICCE was 2.3% for the whole group. The highest incidence (10.3%) was found in the group of patients, who received a 3-M style 77 anterior chamber lens while the lowest incidence (1.0%) were found among patients receiving a Choyce anterior chamber lens. Compared to this, the patients who received no intraocular lens showed a frequency of persistent corneal oedema of 1.4%. Among the patients who developed persistent corneal oedema the number of re-operations was higher (27.3%) compared to the patients who did not develop persistent corneal oedema (4.4%). The frequency of preoperative dystrophy was the same whether or not the patients developed persistent corneal oedema. There were no difference in gender, age or other pre-operative data between the two groups. CONCLUSION: After ICCE 2.3% developed persistent corneal oedema. There was a significant difference between the frequencies of persistent corneal oedema depending on the type of intraocular lens from 1.0% in eyes receiving a Choyce anterior chamber lens to 10.3% in eyes receiving a semi-flexible 3-M style 77 anterior chamber lens.

Aged↗

PubMed1997

The genetic basis of persistence and recovery in stuttering.

Although past research has provided evidence of a genetic component to the transmission of susceptibility to stuttering, the relationship between the genetic component to stuttering and persistence and recovery in the disorder has remained unclear. In an attempt to characterize this relationship, the immediate and extended families of 66 stuttering children were investigated to determine frequencies of cases of persistent and recovered stuttering. Pedigree analysis and segregation analysis were used to examine patterns of transmission. The following questions were investigated: 1. Is there a sex effect in recovery from stuttering? Here, we sought to test the hypothesis that females are more likely to recover than males, leading to the change in sex ratio from approximately 2:1 males to females close to onset of the disorder, to 4 or 5:1 in adulthood. 2. Is persistence/recovery in stuttering transmitted in families? If recovery/ persistence appears to be transmitted, (a) are recovered and persistent stuttering independent disorders?; (b) is recovery a genetically milder form of persistent stuttering?; or (c) is persistence/recovery transmitted independent of the primary susceptibility to stuttering? Results indicated sharply different sex ratios of persistent versus recovered stutterers in that recovery among females is more frequent than among males. It was found that recovery or persistence is indeed transmitted, and further, that recovery does not appear to be a genetically milder form of stuttering, nor do the two types of stuttering appear to be genetically independent disorders. Data are most consistent with the hypothesis that persistent and recovered stuttering possess a common genetic etiology, and that persistence is, in part, due to additional genetic factors. Segregation analyses supported these conclusions and provided statistical evidence for both a single major locus and polygenic component for persistent and recovered stuttering.

Child↗

PubMed2003

Characterization of the hipA7 allele of Escherichia coli and evidence that high persistence is governed by (p)ppGpp synthesis.

The ability of a high frequency (10(-2)) of Escherichia coli to survive prolonged exposure to penicillin antibiotics, called high persistence, is associated with mutations in the hipA gene. The hip operon is located in the chromosomal terminus near dif and consists of two genes, hipA and hipB. The wild-type hipA gene encodes a toxin, whereas hipB encodes a DNA-binding protein that autoregulates expression of the hip operon and binds to HipA to nullify its toxic effects. We have characterized the hipA7 allele, which confers high persistence, and established that HipA7 is non-toxic, contains two mutations (G22S and D291A) and that both mutations are required for the full range of phenotypes associated with hip mutants. Furthermore, expression of hipA7 in the absence of hipB is sufficient to establish the high persistent phenotype, indicating that hipB is not required. There is a strong correlation between the frequency of persister cells generated by hipA7 strains and cell density, with hipA7 strains generating a 20-fold higher frequency of persisters as cultures approach stationary phase. It is also demonstrated that relA knock-outs diminish the high persistent phenotype in hipA7 mutants and that relA spoT knock-outs eliminate high persistence altogether, suggesting that hipA7 facilitates the establishment of the persister state by inducing (p)ppGpp synthesis. Consistent with this proposal, ectopic expression of relA' from a plasmid was shown to increase the number of persistent cells produced by hipA7 relA double mutants by 100-fold or more. A model is presented that postulates that hipA7 increases the basal level of (p)ppGpp synthesis, allowing a significantly greater percentage of cells in a population to assume a persistent, antibiotic-insensitive state by potentiating a rapid transition to a dormant state upon application of stress.

Alleles↗

PubMed2003

Subscapular skinfold thickness distinguishes between transient and persistent impaired glucose tolerance: Study on Lifestyle-Intervention and Impaired Glucose Tolerance Maastricht (SLIM).

AIMS: To assess whether adding anthropometric measurements to an oral glucose tolerance test (OGTT) can help to distinguish between transient and persistent impaired glucose tolerance (IGT). METHODS: From the SLIM project (Study on Lifestyle-Intervention and IGT Maastricht), a study designed to evaluate whether diet and physical activity intervention can improve glucose tolerance in subjects at risk for diabetes, 108 subjects with IGT underwent a repeated OGTT 2-4 months after the initial OGTT. Following the second test, subjects were classified as transient IGT, or persistent IGT. Anthropometric measurements, including body mass index, waist and hip circumference, sagittal and transverse abdominal diameters and skinfold thickness measurements, were done during the second OGTT. RESULTS: Persistent IGT was diagnosed in 47 subjects (44%), transient IGT in 40 (37%), impaired fasting glucose in eight subjects (7%), and diabetes in 13 cases (12%). Two-hour blood glucose levels at the initial OGTT and subscapular skinfold thickness were significantly higher in subjects with persistent IGT (2-h blood glucose 9.8+/-0.1 mmol/l vs. 10.2+/-0.1 mmol/l for transient IGT and persistent IGT, respectively; subscapular skinfold thickness 25.4+/-1.4 mm vs. 29.8+/-1.2 mm for transient IGT and persistent IGT, respectively). After adjustment for age, sex and family history of diabetes mellitus, logistic regression indicated that 2-h blood glucose level during the initial OGTT represented the strongest predictor of persistent IGT (P<0.02), followed by subscapular skinfold thickness (P<0.05). After adjustment for 2-h blood glucose levels during the first OGTT, subscapular skinfold thickness remained significantly associated with persistent IGT (odds ratio 1.84; P<0.05). CONCLUSIONS: In addition to the 2-h blood glucose level, subscapular skinfold thickness was the best predictor of persistent IGT, suggesting that adding simple anthropometric measures to oral glucose tolerance testing may improve the distinction between persistent and transient glucose intolerance.

Anthropometry↗

PubMed2002

Effect of electrical and structural remodeling on spatiotemporal organization in acute and persistent atrial fibrillation.

INTRODUCTION: Atrial fibrillation (AF) may originate from discrete sites of periodic activity. We studied the effect of structural and electrical remodeling on spatiotemporal organization in acute and persistent AF. METHODS AND RESULTS: Atrial effective refractory periods (AERPs) were recorded from five different sites at baseline and after pacing in acute AF (n = 8 dogs) and persistent AF (n = 8). Four persistent AF dogs subsequently were cardioverted to sinus rhythm to allow AERP recovery. Periodicity was quantified by calculating power spectra on left atrial electrograms obtained from a 64-electrode basket catheter. Left atrial size was measured by intracardiac echocardiography and structural changes were assessed by electron microscopy. Mean AERPs decreased after pacing in acute (128 +/- 16 msec to 108 +/- 29 msec, P < 0.001) and persistent AF (135 +/- 16 msec to 104 +/- 24 msec, P < 0.0001). AERP recovery was established after 7 days of sinus rhythm. Structural changes were mild in acute AF, severe in persistent AF, and remained severe after AERP recovery. A single dominant frequency was identified in 94% of acute AF bipoles, 57% in persistent AF, and 76% after AERP recovery. Average correlation coefficient was 0.82 among acute AF bipoles, 0.63 in persistent AF, and 0.73 after AERP recovery. CONCLUSION: Transition from acute to persistent AF is associated with loss of spatiotemporal organization. A single dominant frequency recruits the majority of the left atrium in acute AF. Persistent AF, however, is associated with structural remodeling and dominant frequency dispersion. Recovery of refractoriness only partially restores spatiotemporal organization, indicating a major role for structural remodeling in the maintenance of persistent AF.

Acute Disease↗

PubMed1980

The persistences of vision.

Human observers continue to experience a visual stimulus for some time after the offset that stimulus. The neural activity evoked by a visual stimulus continues for some time after its offset. The information extracted from a visual stimulus continues to be registered in a visual form of memory ('iconic memory') for some time after its offset. We may thus distinguish three distinct senses in which a visual stimulus may be said to persist after its physical offset: there is phenomenological persistence, neural persistence and informational persistence. Various assumptions have been made about the relation between these forms of visual persistence. The most frequent assumption is that they correspond simply to three different methods for studying a single entity. Detailed consideration of what is known about the properties of these three forms of persistence suggests, however, that this assumption is not correct. It can reasonably be proposed that visible persistence is the phenomenological correlate of neural persistence occurring at various stages of the visual system: photoreceptors, ganglion cells and the stereopsis system. Iconic memory on the other hand, does not correspond to visible persistence, nor to neural persistence in any stage of the visual system. Recent work, in fact, suggests that iconic memory is a property of some relatively late stage in the visual information-processing system, rather than being a peripheral sensory buffer store. This suggestion raises some fundamental theoretical issues concerning the psychology of visual perception, issues with which cognitive psychology has yet to come to grips.

Afterimage↗

PubMed1984

Establishment and maintenance of persistent infection by the Phlebovirus Toscana in Vero cells.

Persistent infections were established by serial undiluted passages of the Toscana virus of the genus Phlebovirus in Vero cells. Persistence was maintained through more than 70 passages over a period of 2 years. The persistently infected cells were morphologically similar to the parental Vero cells and released variable amounts of infectious virus. A small percentage of the persistently infected cells produced infectious virus while a larger percentage was shown to possess viral antigens by fluorescent antibody staining. Temperature sensitivity and host cell interferon production were not involved in establishment or maintenance of persistence. The persistently infected cultures were resistant to superinfection with homologous Toscana virus, but they were susceptible to superinfection with heterologous viruses of different genera or families. Toscana virus persistently infected cells showed a selective graded resistance to the replication of other Phleboviruses. Additionally, the virus from persistently infected cells interfered with the replication of standard Toscana virus when they co-infected normal cells. The characteristics of the persistently infected cultures are compatible with some of the characteristics described for the persistence mediated by defective-interfering particles of other viruses.

Animals↗

PubMed2006

Use of IgG avidity ELISA to differentiate acute from persistent infection with Salmonella Dublin in cattle.

AIMS: To investigate whether an immunoglobulin (Ig)G avidity ELISA can be used to differentiate between acute and persistent infection with Salmonella (S.) Dublin in cattle. To determine whether the IgG isotype, IgG(1) and IgG(2) responses in acute and persistent infections differ. METHODS AND RESULTS: Animals were selected from two herds with long-term infection (years) and two herds recently infected (<3 months). Forty-seven animals were categorized into groups based on the persistence of their antibody level in milk. Based on titre from two serial dilutions the avidity index (AI) was calculated for IgG (IgG-AI), IgG(1) (IgG(1)-AI) and IgG(2) (IgG(2)-AI). The mean IgG-AI for suspected carrier animals with either persistently high (group 1) or persistently high to medium high (group 2) antibody levels was significantly (P = 0.003) higher (32.1% and 38.4%) than for acutely infected animals (21.7% and 22.3%). The probability of being a suspect carrier was associated with IgG-AI, antibody level in the sample and age. However, the effect of age could be the result of a biased sample selection. Specificities and sensitivities were calculated at a range of cut-off values for IgG-AI and IgG(1)-AI. Overall, IgG(2)-AI was high compared with IgG(1)-AI, and there was no difference in IgG(2)-AI between infection groups. There was no difference in the ratio IgG(2):IgG(1) for acute and persistent infection groups. CONCLUSIONS: Assuming that a persistently high antibody response is indicative of persistent infection with S. Dublin in cattle, it can be concluded that the IgG-AI can aid in differentiating between acute and long-term infection on herd level. However, for the test to be useful as an alternative tool to repeated sampling over time for detection of persistently infected carriers during control strategies in cattle herds, the test needs to be optimized and studied further in a larger sample of well-characterized infections in cattle. The affinity of IgG(2) is higher than IgG(1) early in the S. Dublin infection. There appears to be no difference in the IgG(2)-AI between the acute and chronic infection stages. SIGNIFICANCE AND IMPACT OF THE STUDY: For decades the strategies for detection of persistently infected cattle in S. Dublin infected herds have involved repeated bacteriological culture of faecal samples or repeated antibody measurements over several months. Both methods are time consuming and costly, leaving a new method for detection of carrier animals based on a single sampling highly desirable. This study illustrates a tool, IgG-AI, which may prove useful, although more validation of the method is required before it is used in practice.

Acute Disease↗

PubMed2006

Duration and outcome of persistent candidaemia in newborn infants.

The aims of the study were to define the duration of candidaemia in newborn infants and to determine the incidence of persistent hospital-acquired candidaemia and its associated morbidity and mortality compared with non-persistent candidaemia. This retrospective study, included 56 neonates admitted to the neonatal intensive care unit from 1996 to 2000 who had one or more positive blood cultures for Candida spp. The most prevalent pathogen was Candida albicans (64.3%). Mean disease duration was 6.9 +/- 5.5 days (median 6 days). Twenty-nine patients (52%) had a positive blood culture for >5 days (persistent candidaemia). There were no statistically significant differences between the infants with persistent and non-persistent candidaemia in background or predisposing clinical factors. Fungal endocarditis was present in four patients (13.7%) with persistent disease and one patient (3.7%) with non-persistent disease (odds ratio 4.19), and uveitis developed in one patient. Ten patients (17.8%) died--five with persistent and five with non-persistent disease (P = 1.0). These findings indicate that persistent neonatal candidaemia may be associated with an increased risk of Candida endocarditis, but not with other complications or increased mortality.

Candida↗