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PubMed1984

Visible persistence as a function of spatial frequency, number of cycles and retinal area.

Using a variety of measures it has been shown that processing time increases with increasing spatial frequency. Long and Sakitt (1981) [Vision Res. 21, 1387-1393] investigated duration of visible persistence as a function of both spatial frequency and number of cycles present. They concluded that number of cycles and not spatial frequency is the crucial variable in determining duration of visible persistence. The present paper investigates this issue in three experiments. Experiments 1 and 2 determined duration of visible persistence with spatial frequencies of 2, 4, 8 and 10 c/deg while holding both number of cycles and grating area constant in a dark surround and in a light surround. Stimulus durations of 50 and 300 msec were used in Experiments 1 and 2 respectively. The results at each stimulus duration showed an increase in duration of visible persistence with increasing spatial frequency similar to that found in most previous reports. This increase was less with a 300 than with a 50 msec stimulus duration. Whether the gratings were presented in a light or a dark surround had no significant effect. Experiment 3 showed that at 2 c/deg duration of visible persistence increased with increasing size of the grating stimuli when all stimulus sizes fell within the area of spatial summation. This effect was greater in a dark than in light surround. It is concluded that visible persistence does increase with spatial frequency. Previous results inconsistent with this conclusion are explained in terms of spatial summation.

Afterimage↗
PubMed1985

Visual persistence from brief letters and pictures.

The visual persistence from briefly presented letters and pictures was assessed by the popular probe-matching procedure over a range of background and target luminance levels and for several color conditions. It was determined that the fading visible persistence measured in this way increased with increasing target luminance and with decreasing background luminance. For small foveal presentations, photopically-matched targets of differing wavelength produced equivalent persistences; but for larger, parafoveal presentations, scotopically-matched targets of differing wavelength produced equivalent persistences. This was true for both letter and picture targets. Results were discussed in terms of an early sensory locus to such persistence effects. The strong consistency of these findings to some previous work and the apparent inconsistency with other work were treated in terms of different kinds of visual persistence effects assessed by different experimental methods.

Afterimage↗
PubMed1993

On the confounding effects of phosphor persistence in oscilloscopic displays.

Phosphor persistence has been a source of confounding in studies of temporal integration in vision. We examined the confounding by assessing the effects of the persistence of two commonly-used phosphors (P15 and P31) on performance of a temporal-integration task. In one experiment we eliminated the visibility of phosphor persistence by closing two mechanical shutters upon display termination. In a second experiment we estimated the duration of phosphor persistence by displaying the image behind closed shutters which opened upon display termination. No detectable persistence was every produced by P15 phosphor. By contrast, P31 phosphor produced persistence that lasted several hundred milliseconds even when a veiling light was projected on the screen. We ascribe the earlier instances of confounding to inadequate interpretation of the technical data on phosphor decay.

Humans↗
PubMed1994

Effect of the ISI on the visible persistence of a stimulus in apparent motion.

The persistence of briefly flashed stimuli undergoing a horizontal apparent motion is assessed as a function of the temporal interval (inter-stimulus interval or ISI) between successive locations. The main result is that the duration of persistence is increased when the ISI is reduced (within the range 1-15 msec). An increase of persistence also occurs when the spatial separation (delta chi) between successive presentations of the moving stimulus becomes larger, a well established result which is replicated here. In both cases, the elevation of persistence suggests that inhibitory processes, which are assumed to underlie the persistence-suppression, have become less efficient. According to the data, it seems that the spatio-temporal parameters of motion, and not the speed as such, are responsible for the strength of inhibition. Namely, optimal inhibition, and thus suppression, would need a minimum amount of time to take place, and would improve with proximity (i.e. with smaller delta chi). Finally, a persistence-suppression decrease is observed when the angular size of the flashed stimuli is reduced (i.e. when higher spatial frequencies become more predominant). A model of transient-on-sustained inhibition accounts well for these results.

Afterimage↗
PubMed1989

Persistent albuminuria as an index of diabetic nephropathy in type 2 diabetic patients in Osaka, Japan-incidence, risk factors, prognosis and causes of death.

A group of 1196 type 2 (non-insulin-dependent) diabetic patients was followed for a mean of 10 years to determine the incidence of persistent albuminuria, its associated risk factors and prognosis, as well as causes of death in patients. None of the patients studied had albuminuria on entry. The mean annual incidence rate of persistent albuminuria per 1000 person-years in the patients was higher in males than in females (18.42 and 12.57, respectively). Development of persistent albuminuria was associated with age at entry, duration of known diabetes, systolic blood pressure, fasting glucose level, presence of diabetic retinopathy and type of treatment. Among 193 patients who developed persistent albuminuria during the observation period, 66 (34.2%) died before the end of the observation period, with a mean survival period (+/- SD) of 3.0 +/- 3.1 years after the onset of persistent albuminuria, indicating an extremely poor prognosis. Renal disease was the predominant cause of death in patients who developed persistent albuminuria, followed by heart disease and cerebrovascular disease.

Adult↗
PubMed1991

Disturbed secretion of atrial natriuretic peptide in patients with persistent atrial standstill: endocrinologic silence.

Persistent atrial standstill is a very rare pathophysiologic condition whose diagnosis is established when both electrical and mechanical silence of the atria are confirmed. To test the hypothesis that secretion of atrial natriuretic peptide is disturbed in patients with persistent atrial standstill, the response of atrial natriuretic peptide secretion and other neurohormonal factors during exercise was investigated in three patients with a rate-responsive ventricular demand (VVI) pacemaker implanted for confirmed persistent atrial standstill. The results were compared with those observed in eight normal subjects and patients with a rate-responsive VVI (Group A) or atrial demand (AAI) (Group B) pacemaker implanted for confirmed sick sinus syndrome. Patients in Group A displayed significant elevation of alpha-human atrial natriuretic peptide secretion both before and during exercise (122.5 +/- 14.8 and 207.5 +/- 8.3 pg/ml, respectively) compared with those in Group B (55 +/- 14.1 and 116.4 +/- 51.5 pg/ml, respectively) and the normal subjects (18.9 +/- 9.8 and 30.8 +/- 19.2 pg/ml, respectively). This indicated development of a nonphysiologic increase in atrial volume or pressure overload, or both, in rate-responsive VVI pacing because of lack of atrioventricular synchrony. However, patients with persistent atrial standstill had undetectable (less than 10 pg/ml) or almost undetectable secretion of atrial natriuretic peptide as well as lower levels of cyclic guanosine monophosphate in the circulation both before and during exercise. Changes in plasma catecholamines during exercise were similar in patients with persistent atrial standstill compared with the other groups. This study indicates that "endocrinologic silence" accompanies electrical and mechanical silence of the atria, which may constitute a third diagnostic clue to persistent atrial standstill.

Adult↗
PubMed1995

Chronic fatigue: risk factors for symptom persistence in a 2 1/2-year follow-up study.

BACKGROUND: The prolonged disability of patients suffering from chronic fatigue may be due to sustaining factors that are independent of the cause and subject to intervention. This study reexamined a cohort of patients with chronic fatigue to define medical and psychiatric predictors of persistent symptoms. METHODS: Seventy-eight patients with chronic fatigue present for 6 months or more (not required to meet the Centers for Disease Control case definition for chronic fatigue syndrome [CFS]) completed a self-report, follow-up questionnaire to measure the overall improvement or worsening of their condition at a mean of 2.5 years after their initial examination. At the time of initial evaluation, patients underwent a structured psychiatric examination, physical examination, laboratory studies, and self-report measures of psychological distress and functional disability. The psychiatric examination queried the patient about 28 somatic symptoms that are separate from those associated with CFS. Discriminant analysis was used to determine which variables present at the initial examination were significant predictors of persistent symptoms and disability at 2.5 years. RESULTS: The factors most important at the time of initial presentation in predicting persistent illness were: (1) more than eight medically unexplained physical symptoms separate from those associated with CFS case definition; (2) lifetime history of dysthymia; (3) duration of chronic fatigue symptoms greater than 1.5 years; (4) less than 16 years of formal education; and (5) age older than 38 years. None of the results of the initial physical examination, or immunologic, general laboratory, or viral antibody measurements were significant in predicting persistence of symptoms. Recovery rates for those who met the criteria for CFS by either of two case definitions were lower than the rate of noncases, but the differences were not statistically significant. The five aforementioned variables formed a significant discriminative function, correctly classifying 78% of those who recovered and 74% of those with persistent symptoms. CONCLUSIONS: At initial examination, patients with chronic fatigue, more than eight medically unexplained physical symptoms (excluding symptoms in the case criteria for CFS), a lifetime history of dysthymic disorder, longer than 1.5 years of chronic fatigue, less than 16 years of formal education, and who were older than 38 years were the most likely to have persistence of symptoms of chronic fatigue at the 2.5-year follow-up.

Adult↗
PubMed1984

Visible persistence as a function of viewing condition and eye-handedness relationship.

Duration of visible persistence was investigated as a function of spatial frequency, orientation and viewing condition (binocular, dominant eye and non-dominant eye). Persistence increased with increasing spatial frequency and was longer for oblique than vertical gratings. Viewing condition also influenced visible persistence such that binocular persistence was significantly shorter than for either monocular condition. A post-hoc analysis indicated that this was only true with subjects who were right-handed and right-eyed. Subjects mixed on this relationship showed no differences in persistence across viewing conditions. A second experiment which selected subjects on the basis of this relationship confirmed the results of Experiment 1. The results for the right-right group broaden the generality of the rule showing an inverse relationship between response strength and persistence duration. The results for the Mixed group indicate a lack of binocular summation.

Dominance, Cerebral↗
PubMed1988

Persistent ovarian cysts following administration of human menopausal and chorionic gonadotropins: an attenuated form of ovarian hyperstimulation syndrome.

Ovarian cysts persisting after the onset of menses were demonstrated by ultrasound (US) in 40 of 71 (56%) nonconception cycles following ovulation induction with human menopausal gonadotropins (hMG) and human chorionic gonadotropin (hCG). Persistent cysts were self-limited and all resolved spontaneously within two cycles. They developed more frequently during stimulation cycles with (1) higher mean pre-hCG serum estradiol (E2), (2) a greater number of medium and large follicles at peak pre-hCG E2, and (3) a larger leading follicle diameter at peak pre-hCG E2. Persistent ovarian cysts frequently occurred despite a peak pre-hCG E2 lower than 1000 pg/ml. Although ovarian enlargement in the presence of cysts exceeded 5 X 5 cm in 25% of cases, no patient developed clinical symptoms of ovarian hyperstimulation syndrome (OHSS). Repeated induction of ovulation with hMG/hCG in the presence of nonfunctional, persistent cysts resulted in pregnancies in 6 of 15 cases (40%). Asymptomatic persistent ovarian cysts frequently follow an hMG/hCG regimen and, when nonfunctional, are not a contraindication to repeated ovarian stimulation. Persistent ovarian cysts appear to be an attenuated form of OHSS.

Adult↗
PubMed1985

Multiple-dose vials: persistence of bacterial contaminants and infection control implications.

Due to sporadic infections attributed to contaminated multiple-dose medication vials (MDV), some authorities have suggested discarding all MDV within 24 hours. We inoculated 11 commonly used medications with suspensions of 10 bacterial species previously associated with contaminated parenteral solutions and determined microbial persistence at both room and refrigerator temperature. At 22 degrees C, atropine, curare, folic acid, NPH insulin and triamcinolone did not allow microbial persistence beyond 4 hours. Lidocaine and heparin were sterile by 24 hours. Regular insulin, immune serum globulin, and myochrysine allowed persistence for up to 7 days. At 4 degrees C, bacterial persistence was significantly prolonged for all medications including those MDV requiring refrigeration. No organisms proliferated; however, F. meningosepticum and P. maltophilia were particularly persistent at both temperatures. The risk of persistent MDV contamination appears to be dependent upon specific pharmaceutical, microbe and storage temperature interactions. Recommendations for the refrigeration of MDV medications may require reevaluation on a product-by-product basis.

Bacteria↗
PubMed1991

Effects of display luminance, stimulus meaningfulness, and probe duration on visible and schematic persistence.

Partial report performance is conceived of as consisting of two independent sources of information: visible persistence and schematic persistence. Following the work of Di Lollo and Dixon (1988), these two sources of information were separated experimentally by varying interstimulus interval and stimulus onset asynchrony independently. In the present experiment we asked whether visible persistence and schematic persistence would be affected by display luminance, stimulus meaningfulness, or probe duration. The results were fit accurately by an extension of the Di Lollo and Dixon independent-decay model in which display luminance affected visible persistence but stimulus meaningfulness and probe duration affected neither form of persistence directly.

Adult↗
PubMed2026

Microbiome features associated with persistent intestinal carriages of Escherichia coli ST131 in a Southeast Asian cohort study.

Escherichia coli sequence-type 131 (ST131) is the dominant global extraintestinal pathogen capable of asymptomatic intestinal carriage and sustained household transmission, challenging infection control. Despite its clinical significance, the ecological determinants of gut persistence remain poorly understood. We performed shotgun metagenomics on fecal samples to investigate gut microbiome features associated with ST131-positive samples, distinct host carrier statuses (persistent, intermittent and non-carriers) and household risks in a study of a Southeast Asian cohort. Here, we show that ST131 carriage was associated with compositional shifts without reducing species alpha-diversity. Regression analyses identified depletion of commensal taxa and the 1,5-anhydrofructose degradation pathway in ST131-positive samples. Persistent carriers exhibited highly perturbed microbiome enriched with pathobionts, aerobactin- and lipopolysaccharide (LPS)-biosynthesis pathways. Comparing household risk groups to control, revealed that biotin biosynthesis and 1,5-anhydrofructose degradation may influence ST131 co-colonization through both direct and indirect mechanisms. Machine learning analyses identified metabolic pathways as stronger discriminators of persistent carriage than taxonomic features. Genomic-resolved analysis of clinical ST131 isolates revealed conserved genes for iron-acquisition, LPS and antibiotic resistance determinants. Overall, while commensals and metabolism may influence initial ST131 colonization, persistent carriage is associated with specific microbial and metabolic adaptations, providing potential targets to limit intestinal ST131 persistence.

Humans↗
PubMed1983

Recovery and persistence of stuttering among relatives of stutterers.

Recovery and persistence of stuttering were examined in the first-degree relatives of a large group of adult persistent stutters. The percentage of recovered individuals reported in these families supports the hypothesis that recovered and persistent stuttering are not independent disorders. Sex and type of relative were significant variables in the distributions of recovery and persistence of stuttering. Handedness in male subjects and birth order did not distinguish between recovered and persistent stutterers. Female recovered stutterers had significantly earlier ages of stuttering onset than the other groups (male recovered stutterers and male and female persistent stutterers). Female recovered stutterers also tended to recover earlier than male recovered stutterers, and the durations of stuttering symptoms were similar in both sexes.

Adolescent↗
PubMed1996

In vitro and in vivo persistence of reticulocytes from donor red cells.

BACKGROUND: Reticulocytes are important in the phenotyping of transfused patients. Reticulocytes can persist in blood units for the shelf life of the unit. STUDY DESIGN AND METHODS: Temperature dependence of reticulocyte persistence was examined in vitro at 4, 24, and 37 degrees C by using thiazole orange staining and flow cytometric analysis. Two-color flow cytometric analysis was used to evaluate the persistence of donor reticulocytes in transfused patients. RESULTS: Flow cytometric analysis using thiazole orange demonstrated that persistence of reticulocytes in units of stored CPDA-1 blood was temperature-dependent. Reticulocytes disappeared over 13 and 6 days at 24 degrees C and 37 degrees C, respectively, but at 4 degrees C the reticulocyte count changed little over 35 days. Two-color flow cytometric analysis of reticulocyte antigens was used to follow donor reticulocytes in 14 transfusion events in nine different patients. Donor reticulocytes persisted through 24 hours in 75 percent of the patients and were detectable at 48 hours in three patients. CONCLUSION: This study demonstrates that reticulocytes persist during refrigerated storage; they are detectable in the circulation of most recipients for the first 24 hours after transfusion and in the circulation of a few recipients after 48 hours. These findings may have relevance for separation techniques based on reticulocyte density in samples drawn shortly after transfusion and for evaluation of reticulocyte counts in patients with hematologic abnormalities.

Blood Donors↗
PubMed1994

Relationships between broodiness expression laying persistency and concentrations of hormones during the first productive period in turkey hens (Meleagris gallopavo).

The changes in egg production, in broodiness index and in plasma concentrations of LH, prolactin, oestradiol and progesterone were monitored throughout the first period of laying in turkey hens. The hens were subsequently classified according to their ability to express broodiness (33%) and their laying persistency; 25% were out-of-lay by the end of the experiment. A high percentage (67%) of the hens that went out-of-lay had previously been identified as broody. Altogether, a significant (p < 0.05) physiological stage effect was found when comparing prolactin, oestradiol and progesterone data obtained from short and long laying persistency hens and this stage effect was also significant for oestradiol and progesterone data obtained from broody and non-broody hens. Otherwise, plasma LH concentrations decreased slightly but significantly throughout the laying year in all hens but no significant differences between physiological states were observed, although the decrease was more pronounced in the hens that went out-of-lay. Plasma progesterone concentrations remained stable throughout in laying hens but decreased significantly in broody and/or out-of-lay hens. Plasma prolactin concentrations were maximal between the 5th and 12th week of egg production and the levels observed in laying hens that did not become broody or had a long laying persistency were twice those measured in broody and/or out-of-lay hens. In the meantime, plasma oestradiol concentrations were lower and stable in laying hens, whereas they were higher during the first half of the productive period in broody and short laying persistency hens. These results suggest that, under our experimental conditions, the hormonal profiles of prolactin and oestradiol for a given hen during the first 10 weeks of the laying cycle may provide predictive information for future changes in its physiological status. The inverse relationship that was observed here between high early plasma concentrations of oestradiol and laying persistency is original. In addition, the relationship between the ability to express broodiness and high and low early plasma concentrations of oestradiol and prolactin, respectively, in hens submitted to preventive broody treatment has not been reported previously. Furthermore, it seems clear that high initial concentrations in prolactin, far from exerting any deleterious effects on egg production are closely associated with a longer persistency of egg laying.

Animals↗
PubMed1994

Medical aspects of the persistent vegetative state (1).

This consensus statement of the Multi-Society Task Force summarizes current knowledge of the medical aspects of the persistent vegetative state in adults and children. The vegetative state is a clinical condition of complete unawareness of the self and the environment, accompanied by sleep-wake cycles, with either complete or partial preservation of hypothalamic and brain-stem autonomic functions. In addition, patients in a vegetative state show no evidence of sustained, reproducible, purposeful, or voluntary behavioral responses to visual, auditory, tactile, or noxious stimuli; show no evidence of language comprehension or expression; have bowel and bladder incontinence; and have variably preserved cranial-nerve and spinal reflexes. We define persistent vegetative state as a vegetative state present one month after acute traumatic or nontraumatic brain injury or lasting for at least one month in patients with degenerative or metabolic disorders or developmental malformations. The clinical course and outcome of a persistent vegetative state depend on its cause. Three categories of disorder can cause such a state: acute traumatic and non-traumatic brain injuries; degenerative and metabolic brain disorders, and severe congenital malformations of the nervous system. Recovery of consciousness from a posttraumatic persistent vegetative state is unlikely after 12 months in adults and children. Recovery from a nontraumatic persistent vegetative state after three months is exceedingly rare in both adults and children. Patients with degenerative or metabolic disorders or congenital malformations who remain in a persistent vegetative state for several months are unlikely to recover consciousness. The life span of adults and children in such a state is substantially reduced. For most such patients, life expectancy ranges from 2 to 5 years; survival beyond 10 years is unusual.

Coma↗
PubMed1992

Visible persistence is reduced by fixed-trajectory motion but not by random motion.

Despite the sluggish temporal response of the human visual system, moving objects appear clear and without blur, which suggests that visible persistence is reduced when objects move. It has been argued that spatiotemporal proximity alone can account for this modulation of visible persistence and that activation of a motion mechanism per se is not necessary. Experiments are reported which demonstrate that there is a motion-specific influence on visible persistence. Specifically, points moving in constant directions, or fixed trajectories, show less persistence than points moving with the same spatial and temporal displacements but taking random walks, randomly changing direction each frame. Subjects estimated the number of points present in the display for these two types of motion conditions. Under conditions chosen to produce 'good' apparent motion, ie small temporal and spatial increments, the apparent number of points for the fixed-trajectory condition was significantly lower than the apparent number in the random-walk condition. The traditional explanation of the suppression of persistence based on the spatiotemporal proximity of objects cannot account for these results. The enhanced suppression of persistence observed for a target moving in a consistent direction depends upon the activation of a directionally tuned motion mechanism extended over space and time.

Female↗
PubMed1982

Molecular comparison of delta beta-thalassemia and hereditary persistence of fetal hemoglobin DNAs: evidence of a regulatory area?

The hematological phenotypes of several Mediterranean patients with delta beta-thalassemia and hereditary persistence of fetal hemoglobin have been characterized. Although clinical and hematological characteristics are essentially superimposable in all heterozygous delta beta-thalassemics, these patients show typical G gamma/A gamma ratios in their Hb F, ranging from approximately 0.07 in Sardinian to approximately 0.15 in Sicilian and approximately 0.35 in Spanish patients. A gamma Sardinian-(isoleucine-75 leads to threonine) is found in Spanish patients and accounts for all of the A gamma production in heterozygotes, indicating that persistent production of gamma chains occurs cis to the delta beta-thalassemia gene. The molecular heterogeneity of these conditions is demonstrated by restriction enzyme mapping of DNA; Sicilian and Calabrian patients show a deletion starting from the delta-globin intron and extending several kilobases 3' to the beta-globin gene; in Spanish patients the deletion starts approximately 2-3 kilobases 5' to the delta-globin gene and extends well beyond the beta-globin gene. Comparison of these deletions with previously described ones in Negro and in a new Southern Italian case of hereditary persistence of fetal hemoglobin suggests that the deletion of a region centered at a cluster of repetitive sequences approximately 3.5 kilobases 5' to the delta-globin gene may be critical for the persistent expression of high levels of gamma-globin in hereditary persistence of fetal hemoglobin compared to delta beta-thalassemia. The concept that the deletion or mutation of specific areas (rather than nonspecific changes brought about by large deletions in the globin cluster) is important in determining the persistent expression of gamma-globin genes is supported by the finding of a nondeletion type of delta beta-thalassemia in Sardinians.

Chromosome Deletion↗