Isolation, characterization, and experimental infection of Streptococcus gallolyticus subspecies pasteurianus from commercial turkeys with acute septicemia: a pilot study.

Streptococcus gallolyticus (SG) is a Gram-positive cocci found as commensal gut flora in animals and humans. SG has emerged as a cause of disease in young poults between 1 and 3 wk of age. SG is associated with septicemia resulting in acute mortality with no premonitory signs in turkeys. Three SG isolates were obtained from clinical field cases of acute septicemia of commercial turkeys and used in three independent experiments. In Experiment 1, embryos were inoculated 25 d of embryogenesis with varying concentrations of SG1, SG2, or SG3. In Experiment 2, day of hatch, poults were inoculated with varying concentrations using different routes of administration of SG1, SG2, or SG3. In Experiment 3, day of hatch, poults were inoculated with only isolate SG1 using different paths. Poults were randomly selected for necropsy on d 8 and d 15 and sampled to collect spleen, heart, and liver for SG on d 21, the remaining poults were necropsied and cultured. Samples were plated on Columbia nalidixic acid and colistin agar (CNA) (40°C, 18-24 h). Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) confirmed suspect colonies. Data were analyzed using the chi-square test of independence, testing all possible combinations to determine significance (P < 0.05). Weight data were subjected to ANOVA using JMP with significance (P < 0.05). No differences were found in BW or BWG on d 0, 8, 15, or 22. Splenomegaly, focal heart necrosis, and pericarditis were observed in all groups in experiments 1 through 3. In Experiment 3, only airsacculitis was observed in a negative control in separate isolation (P > 0.05). On d 21 of Experiment 3, increased (P < 0.05) recovery of SG from spleens were observed in co-housed negative controls, as well as poults challenged by oral gavage (P > 0.05 for d 7 and d 14). These results confirm numerous previous studies indicating that SG subsp. pasteurianus is a primary infectious microorganism that causes septicemia in young poults.

The effect of proximity on open-loop accommodation responses measured with pinholes.

Open-loop accommodation levels were measured in 41 healthy, young subjects using a Shin-Nippon SRW-5000 autorefractor in the three viewing conditions: a small physical pinhole pupil (SP), an optically projected pinhole in Maxwellian view (MV) and in the dark (DF). The target viewed through the pinholes was a high-contrast letter presented at 0 D vergence in a +5 D Badal lens system. Overall, results showed that SP open-loop accommodation levels were significantly higher than MV and DF levels. Subjects could be divided into two distinct subgroups according to their response behaviour: responders to the proximal effect of the small physical pinhole (SP accommodation > MV accommodation) and non-responders to the proximal effect of the small physical pinhole (SP accommodation approximately MV accommodation). Correlation analysis demonstrated that open-loop accommodation for both pinhole conditions was correlated with DF for the responders, while for the non-responders SP and MV accommodation were correlated, but were not related to DF accommodation. This suggests that under open-loop conditions some individuals' accommodation levels are mainly affected by proximal and cognitive factors (responders) while others are guided primarily by the presence of the more distal target (non-responders). In conclusion, MV reduces the proximal effect of the physical pinhole and produces open-loop accommodation responses which are more consistent than SP and DF responses.

Accommodation dynamics as a function of age.

Experiments are described in which the dynamic accommodation response to a stimulus whose vergence was varying sinusoidally with time between 1.33 and 2.38 D was measured as a function of frequency for 19 subjects, with ages distributed between 18 and 49 years. Response to abrupt stimulus change between the same levels was also measured. The results showed that at any age, for the sinusoidal stimuli, gain fell with frequency and phase lag increased: at fixed frequency, gain fell with age and phase lag increased. Neither reaction nor response times for step stimuli changed with age. Analysis of the sinusoidal data suggests the possible existence of a cut-off frequency of about 2 Hz, which varies little with age and above which the system cannot respond. The phase data is compatible with the existence of a frequency-independent time delay, which increases with age from about 0.17 s at 20 years to 0.48 s at 40 years. The results are discussed in terms of current knowledge of the factors contributing to the development of presbyopia.

Translocation-specific conformation of adenylate cyclase toxin from Bordetella pertussis inhibits toxin-mediated hemolysis.

Bordetella pertussis adenylate cyclase (AC) toxin belongs to the RTX family of toxins but is the only member with a known catalytic domain. The principal pathophysiologic function of AC toxin appears to be rapid production of intracellular cyclic AMP (cAMP) by insertion of its catalytic domain into target cells (referred to as intoxication). Relative to other RTX toxins, AC toxin is weakly hemolytic via a process thought to involve oligomerization of toxin molecules. Monoclonal antibody (MAb) 3D1, which binds to an epitope (amino acids 373 to 399) at the distal end of the catalytic domain of AC toxin, does not affect the enzymatic activity of the toxin (conversion of ATP into cAMP in a cell-free system) but does prevent delivery of the catalytic domain to the cytosol of target erythrocytes. Under these conditions, however, the ability of AC toxin to cause hemolysis is increased three- to fourfold. To determine the mechanism by which the hemolytic potency of AC toxin is altered, we used a series of deletion mutants. A mutant toxin, DeltaAC, missing amino acids 1 to 373 of the catalytic domain, has hemolytic activity comparable to that of wild-type toxin. However, binding of MAb 3D1 to DeltaAC enhances its hemolytic activity three- to fourfold similar to the enhancement of hemolysis observed with 3D1 addition to wild-type toxin. Two additional mutants, DeltaN489 (missing amino acids 6 to 489) and DeltaN518 (missing amino acids 6 to 518), exhibit more rapid hemolysis with quicker onset than wild-type toxin does, while DeltaN549 (missing amino acids 6 to 549) has reduced hemolytic activity compared to wild-type AC toxin. These data suggest that prevention of delivery of the catalytic domain or deletion of the catalytic domain, along with additional amino acids distal to it, elicits a conformation of the toxin molecule that is more favorable for hemolysis.

The influence of tinted lenses upon ocular accommodation.

We determined the effect upon accommodative responses of tinted lenses prescribed for the relief of visual discomfort in a group of five long term lens wearers. Static and dynamic responses were measured under four viewing conditions (1) prescribed tinted lens (2) neutral density filter (3) tinted lens of complementary colour and (4) no absorptive lens. While similarity and normality of the mean stimulus-response functions between the four viewing conditions were evident, the low frequency component of the accommodation microfluctuations was significantly greater while viewing the target in the 'no lens' viewing condition. These increases in the low frequency components (LFC) of the accommodation may be a subtle indicator of visual stress in these patients. Colour specificity is not supported by this finding.

Accommodation microfluctuations and pupil size during sustained viewing of visual display terminals.

Accommodation microfluctuations comprise two dominant frequencies; a low frequency component (LFC < or = 0.6 Hz) and a high frequency component (1.0 Hz < HFC < 2.1 Hz). In the present experiment we examine accommodation microfluctuations and steady-state pupil responses during sustained viewing of visual display terminals (VDTs). Steady-state accommodation and pupil responses were measured continuously and simultaneously using a modified Canon Autoref R-1 infra-red objective optometer and an Hamamatsu C3160 Perceptscope Video Area Analyser. Measurements were obtained at three time intervals (0, 10 and 20 min) during a 20 min reading task presented on five different displays. With the displays placed at 50 cm, the task was to locate and identify typographical errors in one of five sets of standard text. Five young visually-normal emmetropic subjects with a mean age of 22.5 +/- 3.0 years participated in the study. Two-way ANOVA revealed no significant variation in the magnitude of the accommodation microfluctuations with either display or task duration, nor was there any significant interaction between these two factors. There was no significant variation in mean pupil diameter with either display or task duration. These measures may have the potential to provide objective information about visual display quality.

Improving the reliability of visual acuity measures in young children.

Whilst the methodology of adult letter acuity measurement has been substantially refined over the last two decades, relatively little development has occurred in methods for quantifying letter acuity in young children. This study compares a recently developed visual acuity test (Glasgow Acuity Cards), which incorporates several key design features used in adult test charts to improve the sensitivity and reliability of visual acuity measurements. The equivalence of acuity measurements made with Glasgow Acuity Cards were compared with the Bailey-Lovie logMAR chart and Snellen chart in adults, and with traditional Single Letter Acuity and a modified Single Letter Acuity test in children. The test-retest reliability of acuity measurements made with Glasgow Acuity Cards and the Single Letter Acuity tests were also assessed in a large group of visually normal children. In addition, the ability of the pre-school letter acuity tests to detect differences in acuity between the two eyes, and to detect amblyopia were examined. Ninety-five percent of vision measurements made with the Bailey-Lovie chart and Glasgow Acuity Cards differ by less than 0.07 log unit. Furthermore, the sensitivity of Glasgow Acuity Cards to detecting changes in acuity longitudinally and inter-ocular differences in acuity is considerably greater as compared with traditional Single Letter Acuity tests. Improvements in paediatric acuity chart design are important for the effective detection and management of children with amblyopia.

Modelling adaptation effects in vergence and accommodation after exposure to a simulated virtual reality stimulus.

Natural viewing conditions place equal demands on the vergence and accommodation systems. The two responses are co-ordinated via the interactive components which couple the two systems: accommodative vergence and vergence accommodation. The crosslink components are usually quantified by the AC/A and CA/C ratios. Whether these ratios are stable entities, genetically determined, or modifiable by experience has been the subject of some debate. A 'Virtual Reality' stimulus was used to place unequal demands on the vergence and accommodation systems. Pre-task and post-task measures of AC/A and CA/C were objectively determined. The changes in the post-task measures are discussed with reference to a dual interactive model of vergence and accommodation. Model simulations suggest that adaptation of the vergence and accommodative controllers (tonic adaptation) may also play a part by altering the open loop bias. The results therefore support the idea that vergence accommodation and accommodative vergence are capable of adaptation.

Open-loop accommodation in emmetropia and myopia.

PURPOSE: To investigate the influence of method of measurement and refractive error on the open-loop accommodation response. METHODS: Open-loop accommodation was measured in darkness (dark accommodation, DA) and using a pinhole pupil (pinhole accommodation, PA) in emmetropic subjects (EMMs, n = 63), subjects with late-onset myopia (LOMs, n = 50) and subjects with early onset myopia (EOMs, n = 51). Further a control experiment examined the differences between DA and bright-field accommodation (BA) conditions in a subset of subjects. All measurements of open-loop accommodation were carried out monocularly using a Canon R1 infra-red optometer in static recording mode. All myopic subjects were fully corrected using soft contact lenses. RESULTS: A significant variation (p < 0.001) in open-loop accommodation was found between DA and PA, but no variation in open-loop level was observed between the three refractive groups. There was no interaction between these two factors. No significant difference was found between the BA level and DA level in any of the refractive groups. CONCLUSIONS: Open-loop accommodation response positions vary according to the experimental conditions employed during measurement. No refractive group differences in the open-loop response were apparent.

Inhibition of human prostate cancer proliferation in vitro and in a mouse model by a compound synthesized to block Ca2+ entry.

Accelerated Ca2+ entry may be one component of the pathway regulating the proliferative phenotype of some types of cancer. Thus, a pharmacological agent with the ability to retard Ca2+ influx in susceptible cancers might inhibit proliferation of them by a cytostatic mechanism rather than by inducing cytotoxicity. We have developed a chemical synthetic scheme that has produced a small library of novel compounds that block Ca2+ entry induced by occupancy of the P2 receptor in two prostate cancer cell lines and inhibit proliferation of these cells in vitro. One of the agents, named TH-1177, was used to treat severe combined immunodeficient mice inoculated with the human prostate cancer line PC-3. Although the doses used and treatment schedule were chosen arbitrarily, treatment extended the mean life span of mice bearing tumors by up to 38%. Treatment of mice without cancer at doses 18 times that used in mice with tumors was not associated with any obvious toxicity, either grossly or on histological examination. These results suggest that novel cytostatic agents with efficacy against human prostate cancer cells can be developed by chemical synthesis of agents directed at the Ca2+ entry pathway.

Visual function thresholds in children.

PURPOSE: The aim of the present study was to establish a range of values for individual visual function measurements in Primary 1 schoolchildren. METHODS: 93 visually normal children with a mean age of 5.4 +/- 0.3 years were recruited with parental consent. Measures of visual acuity obtained included 1) High Contrast (CAT) 2) Low Contrast (LC) 3) Single Letter (SLA) and 4) Repeat Letter Acuity (RRL). These measurements were randomised and obtained during the same visit. Hyperacuity thresholds were obtained at a separate visit, using both Vernier and oscillatory motion displacement stimuli (OMDT). Re-test data for all tests was collected from a random sample of 30 children after a period of at least two weeks. RESULTS: For all measures the distribution of scores was found to be normal. All visual acuity scores are in log units. Mean ( +/- SD) values for each test were as follows; CAT = 0.11 +/- 0.07; LC = 0.38 +/- 0.08; RRL = 0.04 +/- 0.07; SLA = -0.02 +/- 0.09; Vernier threshold = 69 +/- 21 arcsec; OMDT = 60 +/- 9 arc sec. The confidence limits of the test-retest discrepancies were as follows; CAT = +/- 0.05; LC = +/- 0.07; RRL = +/- 0.04; SLA = +/- 0.04; Vernier = +/- 17 arcsec; OMDT = +/- 6 arcsec. The confidence limits of the interocular discrepancies were as follows; CAT = +/- 0.08; LC = +/- 0.08; RRL = +/- 0.08; SLA = +/- 0.11; Vernier = +/- 14 arcsec; OMDT = +/- 11 arcsec. CONCLUSIONS: To fully describe an individual's visual capacity it is important that new tests of visual function are developed based on emerging knowledge of visual physiology. In this study confidence limits can be constructed for each visual function measure, test-retest and interocular discrepancies using the normal distributions found above. This will provide the clinician with further age-matched values and contribute to our understanding of functional visual development.

Functional visual loss in amblyopia and the effect of occlusion therapy.

PURPOSE: The aim of this study was to define the nature of functional visual loss in amblyopia and to identify those subjects whose amblyopia is chiefly due to one or more of the following deficits: abnormal contour interaction, abnormal eye movements, abnormal contrast perception, or positional uncertainty. METHODS: Fifty amblyopic children with a mean age of 5.6+/-1.3 years were referred from diverse sources. In addition to routine orthoptic and optometric evaluation the principal visual deficits in the amblyopic eye of each subject were identified using the following measures of visual acuity: high contrast linear, single optotype, repeat letter and low contrast linear, plus Vernier and displacement thresholds. These measures were repeated as the children underwent a prescribed occlusion therapy regime, after parental consent. RESULTS: All amblyopic subjects demonstrated a functional loss in each of the tests used, and occlusion therapy appeared to improve all aspects of the amblyopia. High contrast visual acuity was not always the primary deficit in visual function, and when amblyopic subjects were divided according to their primary visual loss, this visual function was found to show the greatest improvement with treatment. CONCLUSIONS: These results suggest that to successfully identify the primary visual deficit and monitor the success of occlusion therapy it is necessary to assess other aspects of visual function in amblyopia.

Accommodation responses and ageing.

PURPOSE: To study the impact of age on accommodation dynamics. METHODS: Monocular accommodation responses were measured continuously using a modified Canon Auto Ref R1 infrared optometer. The stimulus was a single letter oscillating sinusoidally between 2.38 and 1.33 D providing a stimulus amplitude of 0.52 D, about a mean level of 1.86 D. Response characteristics were used to quantify gain and phase. Step responses were also recorded between these stimulus vergence levels for calibration purposes and to measure reaction and response times. Nineteen visually normal subjects 18 to 49 years of age participated, and 11 frequencies were used in the range 0.05 to 1.0 Hz. A key feature of the experimental design was to use a stimulus vergence range that lay within the amplitude of accommodation of all the observers. RESULTS: Accommodation gain reduced and phase lag increased with age, particularly at the higher frequencies used. No strongly significant change with age was found for reaction and response times or accommodation velocity, and results were similar for both far-to-near and near-to-far responses. Response amplitude for the step change in target vergence declined with age, and substantial differences were found between the measured and predicted (from reaction time) phase lags at 1.0 Hz as a function of age. Young observers showed a phase lag that was shorter than predicted, whereas older observers' measured phase lags were considerably larger than predicted. CONCLUSIONS: Results show that for a target oscillating sinusoidally in a predictable manner at a modest amplitude, the main ageing effects occur in phase lag, which is appreciably longer than predicted from reaction times in the older observers. The effects of ageing on gain were not as marked. Although responses to small step changes do reduce with age, there is no evidence of increased response times with ageing. In general, accommodation function in the middle-aged eye is quite robust despite a dwindling amplitude of accommodation. These results provide evidence of accommodative vigor in youth and a slowing of accommodation with ageing.

Using a flow sheet to improve performance in treatment of elderly patients with type 2 diabetes.

BACKGROUND AND OBJECTIVES: Numerous studies have shown that physicians do not provide all the preventive and therapeutic care recommended for patients with diabetes. This study determined if use of a medical record flow sheet could increase compliance with seven quality-of-care indicators developed by the American Diabetes Association. METHODS: Subjects included Medicare enrollees with type 2 diabetes. Following an analysis of baseline data, physicians in the practice used a flow sheet that contained recommended guidelines for diabetes care. Staff inserted the flow sheet into the records of patients included in the baseline sample. Physicians and staff also received education about use of the flow sheet. The post-intervention sample consisted of the same subjects, if they had been seen by the practice during a 3-month period. RESULTS: The records of 114 subjects were reviewed at baseline. Of these subjects, 109 received care during the study period. Improvement was shown in six of the seven quality indicators and was also observed in the performance of post-intervention rates for patients whose flow sheet was used, compared with those for whom it was not used. CONCLUSIONS: The results indicate that education and performance in diabetes care can improve with the use of a flow sheet.

The effect of abnormal fixational eye movements upon visual acuity in congenital nystagmus.

PURPOSE: The purpose of this study was to investigate the role that abnormal eye movements play in the degradation of visual acuity. METHODS: Visual acuity was measured monocularly in 10 normal subjects (26.7+/-4.3 years) and 5 subjects with congenital nystagmus (34.9+/-8.8 years), using Regan Repeat Letter charts (RRL) and a logMAR based test (LogMAR Crowded Acuity Test (CAT)) while eye movements were continuously recorded using a commercially available infrared limbal eye tracker (Type 54, Optoelectronic Developments, UK). The eye tracker was controlled via a virtual oscilloscope (Viewdac, Keighly Instruments, UK) on an IBM PC clone (Opus Technology 486). RESULTS: The mean visual acuity obtained with RRL was significantly higher than that obtained by CAT in the subjects with congenital nystagmus. A significant correlation was found between the root mean square value of the nystagmus waveform and the angular extent of CAT. Linear regression analysis revealed a correlation between the duration of the foveation periods and the linear acuity of the subjects with congential nystagmus. The nystagmus waveforms also demonstrated increased amounts of high frequency components (HFC: >3.0 Hz) when compared to the normal eyes. CONCLUSIONS: The results of this study reveal 1) RRL charts provide a measure of a subjects resolution limit which is less dependent on eye movements; 2) the duration of foveation periods has a significant effect on visual acuity measurements obtained using a linear test chart format; 3) the predominance of high frequency components in the congenital nystagmus waveforms lead to short foveation periods adding to the degree of fixation instability.

Improvement of visual function in an adult amblyope.

PURPOSE: In this case report, the efficacy of occlusion therapy was investigated in a strabismic amblyope above the currently accepted age for treatment. Success was assessed not simply by a change in visual acuity, but by examining a number of parameters which relate to both sensory and motor aspects of visual function. METHODS: As well as routine orthoptic and optometric evaluation, additional tests were administered as follows: high and low contrast LogMAR Crowded Acuity, repeat letter acuity, and hyperacuity measurements. RESULTS: A functional loss in each of the tests used was demonstrated, and occlusion therapy appeared to improve all aspects of the amblyopia, with a significant difference in pre- and post-therapy results. CONCLUSIONS: The results of this study suggest that: (1) occlusion therapy can produce substantial improvements in visual function in adult amblyopia; (2) many aspects of visual function can improve beyond the traditional critical periods for development in amblyopia; and (3) with good patient compliance and cooperation, age should not be the critical factor in the initiation of treatment for amblyopia.

Contour interaction for high and low contrast optotypes in normal and amblyopic observers.

We investigate the influence of stimulus contrast upon contour interaction in normal and amblyopic subjects. Using a computer generated acuity task, flanked and unflanked acuities were measured psychometrically at both high contrast (80%) and low contrast (6%), in a group of 19 normal and 11 amblyopic subjects. The crowding ratio for high contrast letters was found to be significantly higher than that for low contrast letters. The extent of the crowding zone was measured at high and low contrast by varying the separation of the optotype and flanking bars. The crowding zone measurement was repeated for the high contrast optotypes using dioptric blur. The position of the flanking contours was found to have a significant effect on letter resolution at high contrast but no significant effect was demonstrable at low contrast. With the addition of dioptric blur the effect of contour interaction became negligible at high contrast. These findings support the hypothesis that the crowding effect is: (1) similar in normal and amblyopic eyes when tested at threshold; (2) is contrast dependent appearing only for high contrast optotypes.

The magnitude and distribution of open-loop accommodation using three different methods of opening the loop.

PURPOSE: The present study examines the magnitude, distribution, and relationship of open-loop accommodation obtained using the three most common methods of opening the accommodation loop. METHODS: Open-loop accommodation was measured in 93 young, emmetropic subjects using a Canon R1 objective infrared optometer, and the accommodation loop was opened using the following methods: (1) dark empty field (DA), (2) bright empty field (BA), and (3) viewing a target through a small artificial pupil (PA). RESULTS: PA was found to elicit significantly (p = 0.0001) higher values of open-loop accommodation than either DA or BA and demonstrated a much wider distribution of values than DA or BA. A further experiment demonstrated that the higher PA was attributable to the proximal effect of placing a small artificial pupil close to the eye. CONCLUSIONS: Our results suggest that using a small artificial pupil to open the accommodation loop may not produce a veridical measure of open-loop accommodation.

Calmodulin regulation of Ca2+ entry in Jurkat T cells.

We have previously proposed a role for calmodulin (CaM) in the regulation of initiation of Ca2+ entry in Jurkat T cells, as well as in the regulation of the current that mediates Ca2+ entry, IT. In this report, we provide evidence for the mechanism of CaM action. We have previously shown that activation-induced Ca2+ entry into Jurkat T cells is mediated by a current we have called IT. In the whole cell variation, but not the perforated patch variation, of the patch clamp technique, this current is short-lived (under 6 min) suggesting that the current is under the control of a diffusible component of the cytosol. Addition of CaM to the whole cell recording pipette solution maintained IT for up to 20 min, suggesting that CaM may be this diffusible component. Pharmacological inhibitors of CaM blocked the augmentation of IT normally induced by an activating stimulus. Cells electroporated in the presence of anti-CaM antibodies had reduced influx of extracellular Ca2+, with no change in release of Ca2+ from the internal stores. These observations suggest that T cell receptor engagement initiates Ca2+ influx by a pathway that likely includes CaM, which may in turn regulate IT. Influx of extracellular Ca2+ is required for cellular proliferation, and inhibition of CaM by pharmacological inhibitors reduced cellular proliferation. This same inhibition of proliferation was seen in cells electroporated with anti-CaM antibodies. This suggests that inhibition of CaM and/or IT may be a target for therapeutic inhibition of inappropriate T cell proliferation.

Grating detection and orientation discrimination in amblyopia.

PURPOSE: We examined whether the misperceptions associated with amblyopic visual perception can be revealed under natural viewing conditions by comparing the ability to detect the presence of a grating with the ability to identify the grating orientation. METHODS: Grating detection and orientation discrimination performance (horizontal versus vertical) were determined, using stimuli that consisted of sinusoidal gratings of fixed contrast (75%) but with variable spatial frequency. A total of four amblyopic subjects (two strabismic and two non-strabismic) and four age-matched normals participated in the experiment. RESULTS: Psychometric functions for grating detection and orientation identification were found to be closely matched in the normal subjects and in all four amblyopic subjects, indicating that orientation could be correctly identified at detection threshold. CONCLUSIONS: The absence of orientation uncertainty in the psychophysical data for the amblyopic observers is not consistent with the several previous reports of spatial aliasing in the central field of amblyopes. Our results suggest that non veridical visual perception in central amblyopic vision can not be revealed under natural viewing conditions by comparing the ability to detect the presence of a grating with the ability to identify its orientation. Possible reasons for the failure of this technique to reveal spatial aliasing in amblyopes are discussed.