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.

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.

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.

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.

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.

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.

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.

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.

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 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.

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.

A role for protein kinase CbetaI in the regulation of Ca2+ entry in Jurkat T cells

T cell activation leading to cytokine production and cellular proliferation involves a regulated increase and subsequent decrease in the intracellular concentration of Ca2+ ([Ca2+]i). While much is understood about agonist-induced increases in [Ca2+]i, less is known about down-regulation of this pathway. Understanding the mechanism of this down-regulation is critical to the prevention of cell death that can be the consequence of a sustained elevation in [Ca2+]i. Protein kinase C (PKC), activated by the diacylglycerol produced as a consequence of T cell receptor engagement, has long been presumed to be involved in this down-regulation, although the precise mechanism is not wholly clear. In this report we demonstrate that activation of PKC by phorbol esters slightly decreases the rate of Ca2+ efflux from the cytosol of Jurkat T cells following stimulation through the T cell receptor or stimulation in a receptor-independent manner by thapsigargin. On the other hand, phorbol ester treatment dramatically reduces the rate of Ca2+ influx following stimulation. Phorbol ester treatment is without an effect on Ca2+ influx in a different T cell line, HSB. Down-regulation of PKCbetaI expression by 18-h phorbol ester treatment is associated with a loss of the response to acute phorbol ester treatment in Jurkat cells, suggesting that PKCbetaI may be the isozyme responsible for the effects on Ca2+ influx. Electroporation of an anti-PKCbetaI antibody, but not antibodies against PKCalpha or PKCgamma, led to an increase in the rate of Ca2+ influx following stimulation. Taken together, these data suggest that PKCbetaI may be a component of the down-regulation of increases in [Ca2+]i associated with Jurkat T cell activation.

Screening for amblyopia: a comparison of paediatric letter tests

AIMS/BACKGROUND

The measurement of visual acuity is the most widely accepted indicator of amblyopia and is thought by some to be the only effective screening test. The aim of this study was to investigate the effectiveness of the traditional single optotype Sheridan-Gardiner test (SGT) in the measurement of visual acuity and the detection of amblyopia, compared with the log based linear format Glasgow acuity cards (GAC).

METHODS

In the present study visual acuity was measured monocularly in 702 primary 1 schoolchildren using both acuity tests.

RESULTS

A significant difference was found in the mean (SD) visual acuity measured with GAC (0.9 (0.08) modified logMAR) and SGT (1.13 (0.09) modified logMAR), df = 632, t = -59.08, p = 0.0001. The majority of children (89.3%) achieved visual acuities better than 6/6 in either eye when using the single optotype test. If the 95% confidence limits for a significant interocular difference in acuity are used as-criteria for the detection of unilateral amblyopia, GAC were found to be the most sensitive, correctly identifying 100%, while SGT identified 55% of the children with unilateral amblyopia.

CONCLUSION

The results of this study highlight several problems with both the test format and testing procedure in the present school screening system.

Clinical evaluation of infrared autorefractors for use in contact lens over refraction

We examined the ability of autorefractors to provide an accurate means of contact lens over-refraction measurement. Over-refraction measures, performed using six commercially available automated infrared autorefractors and retinoscopy, were compared with subjective refraction. A total of 40 contact lens wearers (20 soft lens wearers and 20 rigid gas permeable (RGP) lens wearers) participated in the study. All six autorefractors were able to provide over-refraction measures in all subjects. Data analysis revealed differences in autorefractor performance between the two types of contact lens wearer with greater accuracy and lower variability being found in the soft lens wearing subjects compared with the RGP group. The level of agreement between retinoscopy and subjective over-refraction results was lower in soft lens wear and higher in RGP wear than the levels found between the autorefractor and subjective over-refraction measures. We conclude that autorefractors provide a useful means of measuring contact lens over-refraction in soft lens wearers. Over-refraction results should be treated more cautiously in RGP wearers.

A voltage-operable current is involved in Ca2+ entry in human lymphocytes whereas ICRAC has no apparent role

Presently, it is thought that a non-voltage-gated current is responsible for activation-induced Ca2+ entry in nonelectrically excitable cells such as lymphocytes. However, it has also been proposed that the pathway instead involves a second messenger-regulated Ca2+ channel that is voltage operable, where "voltage operable" is defined as an intrinsic property of the channel protein(s) rather than a requirement of normal gating. To evaluate the contribution of these currents to activation-induced Ca2+ influx, each was examined with respect to its ability to account for Ca2+ influx as reported by Ca(2+)-sensitive dyes. We identified a set of reagents, nordihydroguaiaretic acid and various calmodulin inhibitors, that inhibits Ca2+ entry and blocks the voltage-operable current but leaves the non-voltage-gated current unaltered. Further-more, nordihydroguaiaretic acid inhibited Ca(2+)-dependent proliferation of mitogen-activated human peripheral blood mononuclear cells or Jurkat T cells and specifically blocked Ca(2+)-dependent interleukin 2 production by Jurkat T cells to a degree similar to the immunosuppressant drug cyclosporin A. We also identified compounds, amiloride and Mn2+, that block the non-voltage-gated current but have no effect on either the voltage-operable current or Ca2+ entry. Correspondingly, amiloride had no effect on Ca(2+)-dependent proliferation of Jurkat cells. These observations imply that blockade of the non-voltage-gated current does not block either Ca2+ entry or Ca(2+)-dependent lymphocyte proliferation, whereas blockade of the voltage-operable current does. The data suggest that the voltage-operable current may be a mediator of activation-induced Ca2+ entry in lymphocytes.

Comparison of age-related changes in short-wavelength-sensitive cone thresholds between normals and patients with primary open-angle glaucoma

PURPOSE

To establish the effect of aging upon short-wavelength-sensitive cone (S-cone) sensitivity for both normals and patients with primary open-angle glaucoma (POAG).

METHODS

S-cone thresholds were established for the detection of blue test spots on a bright yellow adapting background. Detection thresholds for combined medium- and long-wavelength-sensitive cones (M/L-cones) were also established for a yellow test spot upon a yellow background. A group of 177 normal subjects (age range 20 to 80 years) and 46 glaucoma subjects were examined.

RESULTS

The rate of decline of S-cone sensitivity with increasing age was found to be similar in patients with POAG and age-matched normals (approximately 0.2 log units/decade), although S-cone sensitivity in the POAG population was significantly lower (p < 0.05) than that in age-matched normals by approximately 0.3 log units.

CONCLUSIONS

The results of the present investigation show an age-related decline in S-cone sensitivity for both normals and patients with POAG. The decline in S-cone sensitivity within the POAG population is similar to that occurring in normal subjects when the two populations are matched for age.

Lack of evidence for human T cell lymphotrophic virus type I or II infection in patients with systemic lupus erythematosus or rheumatoid arthritis

OBJECTIVE

Human retroviruses including human immunodeficiency virus (HIV) and human T cell lymphotrophic virus Types I and II (HTLV-I/II) have been associated with forms of connective tissue autoimmune diseases including systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). We looked for evidence of HTLV-I/II infection in a large population of SLE, RA, and control patients.

METHODS

One hundred fifteen patients with connective tissue autoimmune disease and other rheumatological disorders were screened for antibodies to HTLV-I/II by Western immunoblots (WIB). Due to the transforming characteristic of these retroviruses, the patients' peripheral blood mononuclear cells (PBMNC) were cultured in attempts to establish continuous cell lines. Furthermore, PBMNC culture supernatants were analyzed for reverse transcriptase activity and/or HTLV-I/II gag antigen production. The presence of HTLV-I/II proviral sequences in short term culture and fresh PBMNC was determined by Southern blot analysis and polymerase chain reaction (PCR), respectively. respectively.

RESULTS

All 115 patients were HTLV-I/II and HIV seronegative. Seventy-four attempts to establish PBMNC cell lines from 65 patients were unsuccessful with a mean culture survival time of 3.6 (+/- 1.4) months. Reverse transcriptase activity and HTLV-I/II gag antigen production were not detected in 51 and 16 culture supernatants tested, respectively. Cells from 11 patients tested by Southern blot analysis and from 57 patients tested by PCR were negative for HTLV-I/II related sequences.

CONCLUSION

Our results failed to establish an association between human retroviruses (HTLV-I/II and HIV) and SLE, RA, or other rheumatological disorders. However, these results do not rule out other exogenous or endogenous retroviruses that may play a role in the initiation and/or promotion of these diseases.

Pertussis toxin activates platelets through an interaction with platelet glycoprotein Ib

Platelets present a unique model to study the B-oligomer effects of pertussis toxin because they become activated in response to the B oligomer but are not susceptible to ADP-ribosylation by the holotoxin. In these studies, the B oligomer of pertussis toxin caused concentration-dependent platelet activation, as determined by increases in intracellular calcium concentration, dense granule secretion, and platelet aggregation. Stirring was required for pertussis toxin to increase intracellular calcium. A monoclonal antibody against platelet glycoprotein Ib abolished increases in intracellular calcium concentration and increased the latency and reduced the slope of the aggregation response elicited by the B oligomer. Pertussis toxin also evoked [14C]serotonin release from platelets, and this effect was inhibited, though not eliminated, by an antibody against platelet glycoprotein Ib. Binding of pertussis toxin to glycoprotein Ib was observed after nonreducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These data suggest that the B oligomer of pertussis toxin induces platelet activation mediated, at least in part, by an interaction with platelet glycoprotein Ib.

Accommodative microfluctuations and pupil diameter

The nominally steady-state accommodation response exhibits temporal variations which can be characterized by two dominant regions of activity; a low frequency component (LFC < 0.6 Hz) and a high frequency component (1.0 < or = HFC < or = 2.1 Hz). There is no consensus as to the relative contribution made by each of the frequency components of the microfluctuations to the control of steady-state accommodation. We investigate the effect of variations in artificial pupil diameter (0.5, 1, 2, 3, 4 and 5 mm pupils) on the microfluctuations of accommodation, while three young emmetropic subjects view, monocularly, a photopic high contrast Maltese cross target placed at a dioptric distance equal to their open-loop accommodation level. Average power spectra were calculated for five accommodation signals, each of 10 sec duration, collected for each viewing condition at a sampling rate of 102.4 Hz using a continuously recording infrared objective optometer. For artificial pupil diameters < or = 2 mm the power of the LFC was found to increase as a function of reducing pupil diameter, while for artificial pupil diameters > 2 mm the LFC was found to be relatively constant. No systematic change in the HFC with varying artificial pupil diameter was observed. Changes in the root-mean-square (r.m.s.) value of the fluctuations with varying pupil diameter were significant (one-way ANOVA, F = 8.507, P = 0.0001, d.f. = 89) and showed a similar form to the changes in the LFC.(ABSTRACT TRUNCATED AT 250 WORDS)

Objective concurrent measures of open-loop accommodation and vergence under photopic conditions

PURPOSE

To investigate the relationship between photopic open-loop accommodation and vergence and the effect of mental effort on these positions.

METHODS

Twenty subjects (11 men and 9 women) viewed monocularly a photopic (25 cdm-2), high-contrast (90%) Maltese cross-target for 3 minutes, through a 0.5-mm pinhole drilled into an infrared filter. Accommodation was measured objectively at 1-second intervals using a Canon Autoref R-1 infrared optometer, and vergence was recorded continuously and objectively using a differential infrared eye tracking system.

RESULTS

Under passive viewing conditions there was a significant correlation between photopic open-loop accommodation and vergence (R = 0.671, P = 0.0012); for the majority of subjects the imposition of mental effort shifted the passive levels of both open-loop accommodation and vergence, but these shifts were unsystematic and uncorrelated (R = 0.259, P = 0.270). The active open-loop positions of accommodation and vergence were also found to be correlated (R = 0.692, P = 0.0007).

CONCLUSIONS

The influence of proximal stimuli can explain the correlations identified between photopic open-loop positions of accommodation and vergence. The uncorrelated responses of the accommodation and vergence systems to mental effort are likely to reflect interactions between various spatiotopic stimuli including mental effort and perceived proximity.

Effect of target luminance on microfluctuations of accommodation

It is feasible that small temporal variations in steady-state accommodation may provide feedback to the accommodation control system through changes in retinal image contrast and that this feedback may be used to maintain an optimal accommodation response. The complex waveform of microfluctuations is dominated by two distinct regions of activity; a low frequency component (LFC < 0.6 Hz) and a high frequency component (1.0 < or = HFC < or = 2.3 Hz). Whereas the HFCs appear to be correlated with some intraocular manifestation of arterial pulse the contribution of the LFCs to the control of steady-state accommodation is unclear. The present study investigates the effect of target luminance on the waveform of accommodative microfluctuations. Three young emmetropic observers viewed monocularly a high contrast (90%) Maltese cross target placed at a vergence equal to their dark-focus level of accommodation in a Badal stimulus system. The luminance of the target was varied from 0.002 to 11.63 cd m-2 in nine equal logarithmic steps. Five continuous accommodation signals were collected for each viewing condition at a sampling rate of 102.4 Hz, and average power spectra subsequently calculated with a frequency resolution of 0.1 Hz. One-way ANOVA revealed a significant variation in the root-mean-square (r.m.s.) value of the microfluctuations (F = 19.795, d.f. 124, P = 0.0001) which could be attributed mainly to increases in the r.m.s. value for the two lowest luminances (0.002 and 0.004 cd m-2). Power spectrum analysis revealed that these changes in the microfluctuations could be attributed to increases of power in the LFC.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical and blood bank factors in the management of platelet refractoriness and alloimmunization

Numerous independent and interdependent factors are involved in the posttransfusion platelet response. Factors such as ABO match and platelet age are related to circumstances potentially under the control of the blood bank physician and therefore may permit circumvention by an active transfusion service. On the other hand, factors such as fever or sepsis may be unavoidable, being related more to the individual patient or clinical condition. To evaluate which factors could be circumvented, we prospectively followed the 1-hour corrected count increments (CCIs) for 962 single-donor apheresis platelet transfusions to 71 refractory hematologic oncology inpatients, with concomitant recording of implicated factors. Stepwise regression analysis allowed for determination of which concurrent and confounding clinical-, patient-, and blood bank-related factors significantly affected the CCIs. Although many implicated factors proved to be independently associated with an increased or decreased CCI, we found that no single variable consistently explained the CCI variation across the patient population. Each patient appeared sensitive to one or a few particular factors, but because of marked intraindividual variation, it was not possible to identify a priori which factors were important for a given patient. The single exception was a solid-phase red blood cell adherence assay used to cross-match platelets, but only for alloimmunized patients. We also evaluated the utility of requesting HLA-matched platelets from the local suppliers and maintained a clear distinction between platelets simply ordered as HLA matched and actually HLA-identical platelets. Accounting for the confounding clinical-, patient-, and blood bank-related factors, the cross-match assay was a better predictor of an adequate CCI than ordering platelets as HLA matched.

Increased intracellular Ca2+ induces Ca2+ influx in human T lymphocytes

One current hypothesis for the initiation of Ca2+ entry into nonelectrically excitable cells proposes that Ca2+ entry is linked to the state of filling of intracellular Ca2+ stores. In the human T lymphocyte cell line Jurkat, stimulation of the antigen receptor leads to release of Ca2+ from internal stores and influx of extracellular Ca2+. Similarly, treatment of Jurkat cells with the tumor promoter thapsigargin induced release of Ca2+ from internal stores and also resulted in influx of extracellular Ca2+. Initiation of Ca2+ entry by thapsigargin was blocked by chelation of Ca2+ released from the internal storage pool. The Ca2+ entry pathway also could be initiated by an increase in the intracellular concentration of Ca2+ after photolysis of the Ca(2+)-cage, nitr-5. Thus, three separate treatments that caused an increase in the intracellular concentration of Ca2+ initiated Ca2+ influx in Jurkat cells. In all cases, Ca(2+)-initiated Ca2+ influx was blocked by treatment with any of three phenothiazines or W-7, suggesting that it is mediated by calmodulin. These data suggest that release of Ca2+ from internal stores is not linked capacitatively to Ca2+ entry but that initiation is linked instead by Ca2+ itself, perhaps via calmodulin.

A voltage-gated calcium channel is linked to the antigen receptor in Jurkat T lymphocytes

Activation of T lymphocytes results in an increase in intracellular Ca2+ due in large part to influx of extracellular Ca2+. Using the patch clamp technique, an inward current in Jurkat T lymphocytes was observed upon depolarization from a holding potential of -90 mV but not from -60 mV. This whole-cell current was insensitive to tetrodotoxin, carried by Ba2+, and blocked by Ni2+. Occupancy of the T lymphocyte antigen receptor increased the current's magnitude. These data suggest that antigen receptor-induced Ca2+ entry in T lymphocytes may be mediated by a voltage-regulated Ca channel.

Lymphocyte adhesion mediated by lymphocyte function-associated antigen-1. I. Long term augmentation by transient increases in intracellular cAMP

Lymphocyte adhesion to target cells is mediated, in part, by the interaction of lymphocyte function-associated Ag-1 (LFA-1) with intercellular adhesion molecule-1 (ICAM-1). Cells of the B cell line, JY, express both coreceptors and have been used as a model for intercellular adhesion mediated by these molecules. Elevation of the intracellular cAMP concentration ([cAMP]i), by any of several reagents, for periods as brief as 30 min, led to enhanced intercellular adhesion in a concentration dependent manner 5 to 8 h later. Two protein kinase A inhibitors, KT5720 and H-89, but not the protein kinase C inhibitor calphostin C, blocked the effects of elevated [cAMP]i. These data suggest a role for protein kinase A in this response. The adhesion augmented by increased [cAMP]i was due to LFA-1/ICAM-1 interactions between cells because it was blocked by either anti-LFA-1 or anti-ICAM-1 mAb. Elevated [cAMP]i induced cell surface patching of LFA-1, but not ICAM-1, and this redistribution preceded intercellular adhesion. Finally, redistribution of LFA-1 was not mediated by the cytoskeleton. These results suggest a model in which transient activation of protein kinase A results in increased local concentration of LFA-1 at the cell surface and in augmented long term adhesion mediated by this integrin.

Lymphocyte adhesion mediated by lymphocyte function-associated antigen-1. I. Long term augmentation by transient increases in intracellular cAMP

Lymphocyte adhesion to target cells is mediated, in part, by the interaction of lymphocyte function-associated Ag-1 (LFA-1) with intercellular adhesion molecule-1 (ICAM-1). Cells of the B cell line, JY, express both coreceptors and have been used as a model for intercellular adhesion mediated by these molecules. Elevation of the intracellular cAMP concentration ([cAMP]i), by any of several reagents, for periods as brief as 30 min, led to enhanced intercellular adhesion in a concentration dependent manner 5 to 8 h later. Two protein kinase A inhibitors, KT5720 and H-89, but not the protein kinase C inhibitor calphostin C, blocked the effects of elevated [cAMP]i. These data suggest a role for protein kinase A in this response. The adhesion augmented by increased [cAMP]i was due to LFA-1/ICAM-1 interactions between cells because it was blocked by either anti-LFA-1 or anti-ICAM-1 mAb. Elevated [cAMP]i induced cell surface patching of LFA-1, but not ICAM-1, and this redistribution preceded intercellular adhesion. Finally, redistribution of LFA-1 was not mediated by the cytoskeleton. These results suggest a model in which transient activation of protein kinase A results in increased local concentration of LFA-1 at the cell surface and in augmented long term adhesion mediated by this integrin.

Lymphocyte adhesion mediated by lymphocyte function-associated antigen-1. II. Interaction between phorbol ester- and cAMP-sensitive pathways

Ag independent adhesion between lymphocytes and target cells is mediated in part by the interaction between lymphocyte function associated Ag-1 (LFA-1) and its coreceptor intercellular adhesion molecule-1 (ICAM-1). Within minutes, PMA treatment of JY cells, which express both LFA-1 and ICAM-1, induced capping of LFA-1 and augmentation of intercellular adhesion lasting for several hours. However, over the course of 15 to 30 min, both of these events were blocked by elevation of intracellular cAMP concentration ([cAMP]i) presumably via activation of protein kinase A. This short term inhibition of protein kinase C-induced adhesion was in contrast to the long term augmentation of adhesion caused by increased [cAMP]i as demonstrated in the companion article. Intercellular adhesion, due to LFA-1/ICAM-1 interactions, could also be induced by LPS treatment of JY cells. At submaximal concentrations, the extent of aggregation induced by LPS had two maxima, one at 30 to 60 min and the other with a plateau at 5 to 8 h. LPS is known to activate protein kinase C and we show that LPS treatment induced increased [cAMP]i. Using inhibitors of protein kinases C and A, possible mediators of the two components of adhesion induced by LPS could be identified. The early component was abrogated by inhibition of protein kinase C although the later component was unaffected. In contrast, an inhibitor of protein kinase A had no affect on the early component and attenuated, but did not entirely eliminate, the late component. These results suggest a model of sequential induction, inhibition, and reinduction of LFA-1/ICAM-1-mediated lymphocyte adhesion that is regulated by temporally ordered actions and interactions of protein kinases C and A.

Lymphocyte adhesion mediated by lymphocyte function-associated antigen-1. II. Interaction between phorbol ester- and cAMP-sensitive pathways

Ag independent adhesion between lymphocytes and target cells is mediated in part by the interaction between lymphocyte function associated Ag-1 (LFA-1) and its coreceptor intercellular adhesion molecule-1 (ICAM-1). Within minutes, PMA treatment of JY cells, which express both LFA-1 and ICAM-1, induced capping of LFA-1 and augmentation of intercellular adhesion lasting for several hours. However, over the course of 15 to 30 min, both of these events were blocked by elevation of intracellular cAMP concentration ([cAMP]i) presumably via activation of protein kinase A. This short term inhibition of protein kinase C-induced adhesion was in contrast to the long term augmentation of adhesion caused by increased [cAMP]i as demonstrated in the companion article. Intercellular adhesion, due to LFA-1/ICAM-1 interactions, could also be induced by LPS treatment of JY cells. At submaximal concentrations, the extent of aggregation induced by LPS had two maxima, one at 30 to 60 min and the other with a plateau at 5 to 8 h. LPS is known to activate protein kinase C and we show that LPS treatment induced increased [cAMP]i. Using inhibitors of protein kinases C and A, possible mediators of the two components of adhesion induced by LPS could be identified. The early component was abrogated by inhibition of protein kinase C although the later component was unaffected. In contrast, an inhibitor of protein kinase A had no affect on the early component and attenuated, but did not entirely eliminate, the late component. These results suggest a model of sequential induction, inhibition, and reinduction of LFA-1/ICAM-1-mediated lymphocyte adhesion that is regulated by temporally ordered actions and interactions of protein kinases C and A.

Lymphocyte adhesion can be regulated by cytoskeleton-associated, PMA-induced capping of surface receptors

Intercellular adhesion in lymphocytes is mediated in part by the interaction of the integrin lymphocyte function-associated antigen-1 (LFA-1) with intercellular adhesion molecule-1 (ICAM-1). The B lymphoblastoid line JY expresses both LFA-1 and ICAM-1, and intercellular adhesion is enhanced by treatment with the phorbol ester phorbol 12-myristate 13-acetate (PMA), which also induced capping of LFA-1, ICAM-1, and human leukocyte antigen. Capping of LFA-1 is likely to result from protein kinase C (PKC) activation because receptor-mediated stimulation of PKC also led to capping. Additionally, adhesion mediated by PMA or lipopolysaccharide was blocked by either of two PKC inhibitors, calphostin C and staurosporine. PMA induced the apparent condensation of cytoskeletal elements that colocalized with the membrane protein cap. Cytoskeletal condensation and capping occurred in the absence of intercellular adhesion. Alteration in the distribution of cytoskeletal components and membrane redistribution of LFA-1 were inhibited by cytochalasin D, which also abolished intercellular adhesion. Taken together, these data suggest that intercellular adhesion is the result of PKC-mediated membrane redistribution of LFA-1 and ICAM-1, which is in turn associated with modification of the actin-based cytoskeleton.

The amelioration of myopia using biofeedback of accommodation: a review

The purpose of this review is to give an account of the issues raised by reports that myopia can be treated by operant conditioning or biological feedback. Devices are available that provide auditory feedback of accommodative state such that variation in tone frequency provides a means by which the patient can monitor his or her ability to induce changes in accommodation response, the task thus being to change the pitch of the tone in a direction corresponding to a more distant far point. The aim of a training programme is to reinforce and establish control over the accommodative response by a process akin to operant conditioning and subsequently to transfer the skill to normal visual environments such that a manifest reduction in myopia becomes apparent. Although there are reports that the technique can induce a reduction in myopia by up to 3 D the findings are of limited value owing to the lack of objective data, for example pre- and post-training cycloplegic refraction. The pre- and post-training measures of subjective letter acuity used by many studies are, with repeated trials, particularly vulnerable to individual differences in the ability to learn how to discriminate and interpret blurred images. The review concludes that more comprehensive clinical trials are needed before accommodation biofeedback can qualify as an established method of clinical treatment of myopia. The trials should be designed to encompass the following issues: the characteristics of a feasible physiological model linking accommodation and myopia development; the rationale with regard to patient selection; the technical performance of the optometer employed; the characteristics of the control group used; the criteria for assessment of myopic change; the transfer of training to performance in normal visual environments; the economic viability of the programme of training and equipment; and the skill, training and knowledge of the clinician implementing the training programme.

Three intracellular signals for cytotoxic T lymphocyte-mediated killing. Independent roles for protein kinase C, Ca2+ influx, and Ca2+ release from internal stores

Ligation of the TCR after interaction of a CTL with a relevant target cell results in a change in CTL shape with reorientation and secretion of cytoplasmic granules. Secretion can be induced by treating CTL with the combination of a phorbol ester to activate protein kinase C and ionomycin to increase the intracellular Ca2+ concentration by ion-selective permeabilization of both the plasma membrane and internal Ca2+ storage depots. Treatment of cloned murine CTL with PMA induced a change in cell shape without movement of cytoplasmic granules, whereas increased intracellular [Ca2+] after treatment with ionomycin resulted in granule movement without shape change. Granule movement induced by ionomycin did not lead to secretion in the absence of PMA. Direct activation of the TCR resulted in increased intracellular Ca2+ predominately from influx of extracellular Ca2+ with a substantially smaller contribution from release of Ca2+ from internal stores. By independently inhibiting either component of the TCR-initiated increase in intracellular Ca2+, it was determined that both sources of Ca2+ were required for granule movement and secretion. Thus, increases in intracellular Ca2+ concentration mediated by these two sources appear not to be functionally equivalent. Taken together, these results indicate that the CTL functional response that normally occurs after interaction with an antigenically relevant target cell is regulated by three independent signals.

Three intracellular signals for cytotoxic T lymphocyte-mediated killing. Independent roles for protein kinase C, Ca2+ influx, and Ca2+ release from internal stores

Ligation of the TCR after interaction of a CTL with a relevant target cell results in a change in CTL shape with reorientation and secretion of cytoplasmic granules. Secretion can be induced by treating CTL with the combination of a phorbol ester to activate protein kinase C and ionomycin to increase the intracellular Ca2+ concentration by ion-selective permeabilization of both the plasma membrane and internal Ca2+ storage depots. Treatment of cloned murine CTL with PMA induced a change in cell shape without movement of cytoplasmic granules, whereas increased intracellular [Ca2+] after treatment with ionomycin resulted in granule movement without shape change. Granule movement induced by ionomycin did not lead to secretion in the absence of PMA. Direct activation of the TCR resulted in increased intracellular Ca2+ predominately from influx of extracellular Ca2+ with a substantially smaller contribution from release of Ca2+ from internal stores. By independently inhibiting either component of the TCR-initiated increase in intracellular Ca2+, it was determined that both sources of Ca2+ were required for granule movement and secretion. Thus, increases in intracellular Ca2+ concentration mediated by these two sources appear not to be functionally equivalent. Taken together, these results indicate that the CTL functional response that normally occurs after interaction with an antigenically relevant target cell is regulated by three independent signals.

Red cell survival studies in a patient with anti-Tca

A radiolabeled, allogenic red cell survival study was performed on a patient who lacked the Cromer-related antigen Tca and who had developed the corresponding antibody. Red cell survival was 92% at 1 hour and 88% at 24 hours. Monocyte monolayer assays (MMA) and IgG subclass determinations were performed on samples from: (1) 1965, the period of initial antibody formation; (2) approximately two years before the red cell survival study; and (3) four months after the study. All samples reacted w+ to 1+ by the antiglobulin test. The earliest sample contained IgG1, IgG2, and IgG4 anti-Tca. Because there were 20.5% reactive monocytes in the MMA (normal range 0-3%), this antibody may have produced extravascular red cell destruction. In contrast to the initial example, the samples before and after the red cell survival study both contained IgG2 and IgG4 subclasses with 1.3% and 2.2% MMA reactivity, respectively. The current pattern of antibody subclass, the lack of reactivity in the MMA, and a red cell survival of 88% at 24 hours indicate that short-term transfusion support would have been well tolerated. This contrasts to the in vitro results obtained with the earliest sample, which suggest a clinically significant antibody. This appears to be the first report of a red cell alloantibody that remained serologically reactive but underwent a loss of its IgG1 fraction, which appeared capable of red cell destruction based on the MMA results.

Multicompartment analysis of the effects of plasmapheresis. Application to lipid kinetics in humans

The quantitative effect of plasmapheresis on concentrations of intravascular solutes is described by a minimal two-compartment model, which allows exit to and entry from a nonplasma body pool of the solute. This novel method is simple and capable of determining endogenous metabolic turnover of physiologically important plasma constituents in both therapeutic and experimental settings. The model was suggested by the therapeutic use of plasmapheresis in hyperlipidemia, and the turnover rates of triglyceride and cholesterol were calculated for one patient treated with chronic plasmapheresis. It is concluded that at least a two-compartment model is necessary to quantitatively describe the effect of plasmapheresis on any substance that undergoes appreciable endogenous turnover (metabolic clearance rate greater than 1.1 times plasmapheresis rate when both rates are in units of volume per time). Calculation of endogenous turnover rate with the use of measurements of the concentration of a solute in plasma before and after plasmapheresis and in the total plasmapheresate and measurement of the volume of plasma removed, volume of plasma substitute infused, and total plasmapheresis time is detailed. This method avoids the use of isotopic labeling experiments. In turn, the endogenous turnover rate may predict the efficacy of therapeutic plasmapheresis.

Pertussis toxin effects on T lymphocytes are mediated through CD3 and not by pertussis toxin catalyzed modification of a G protein

Pertussis toxin (PT) has been shown to have a variety of effects on T lymphocyte function, and its activity has been used to suggest the involvement of a G protein in the early events of T lymphocyte activation. In this report, the effects of PT on T lymphocytes have been investigated in detail. PT at a concentration of 10 micrograms/ml rapidly stimulated early events that are normally induced by occupancy of the TCR complex in Jurkat cells and cloned, murine CTL including increased intracellular Ca2+ concentration, serine esterase release, and induction of Ag non-specific target cell lysis. However, 1-h treatment with this concentration of PT induced a state that was refractory to further receptor stimulation in Jurkat cells but not cloned CTL although substrate membrane proteins were modified to a similar extent in both cell lines. The functional effects of PT were mimicked by the B oligomer of PT which did not, however, catalyze ADP-ribosylation of membrane proteins. In addition, overnight exposure of Jurkat cells to a lower concentration of PT also modified substrate membrane proteins but did not inhibit receptor stimulation. These findings indicate that PT catalyzed ADP-ribosylation of a G protein does not account for the actions of the toxin on T lymphocytes. Finally, direct stimulation of increased intracellular Ca2+ concentration by PT and the B oligomer only occurred in T lymphocytes expressing CD3. This suggests that the mitogenic effect of PT holotoxin is mediated by the interaction of the B oligomer with CD3 and that this may account for many of the effects of PT holotoxin both in vivo and in vitro.

Pertussis toxin effects on T lymphocytes are mediated through CD3 and not by pertussis toxin catalyzed modification of a G protein

Pertussis toxin (PT) has been shown to have a variety of effects on T lymphocyte function, and its activity has been used to suggest the involvement of a G protein in the early events of T lymphocyte activation. In this report, the effects of PT on T lymphocytes have been investigated in detail. PT at a concentration of 10 micrograms/ml rapidly stimulated early events that are normally induced by occupancy of the TCR complex in Jurkat cells and cloned, murine CTL including increased intracellular Ca2+ concentration, serine esterase release, and induction of Ag non-specific target cell lysis. However, 1-h treatment with this concentration of PT induced a state that was refractory to further receptor stimulation in Jurkat cells but not cloned CTL although substrate membrane proteins were modified to a similar extent in both cell lines. The functional effects of PT were mimicked by the B oligomer of PT which did not, however, catalyze ADP-ribosylation of membrane proteins. In addition, overnight exposure of Jurkat cells to a lower concentration of PT also modified substrate membrane proteins but did not inhibit receptor stimulation. These findings indicate that PT catalyzed ADP-ribosylation of a G protein does not account for the actions of the toxin on T lymphocytes. Finally, direct stimulation of increased intracellular Ca2+ concentration by PT and the B oligomer only occurred in T lymphocytes expressing CD3. This suggests that the mitogenic effect of PT holotoxin is mediated by the interaction of the B oligomer with CD3 and that this may account for many of the effects of PT holotoxin both in vivo and in vitro.

Spatial and temporal characteristics of the increase in intracellular Ca2+ induced in cytotoxic T lymphocytes by cellular antigen

The increase in intracellular Ca2+ concentration [( Ca2+]i) in cytolytic T lymphocytes in response to target cell binding was investigated by ratio image fluorescence microscopy. Ca2+ mobilization from intracellular stores occurred at a site distal to target cell contact and was transient. Extracellular Ca2+ influx resulted in an increase in [Ca2+]i that was prolonged and distributed more proximal to the target cell. Oscillations in [Ca2+]i were observed after target cell contact, although the periodicity was dependent on the presence of extracellular Ca2+. The Ag-specific reorientation of cytoplasmic granules occurred well after [Ca2+]i had begun to decline to a resting level, but was dependent on extracellular Ca2+. These studies indicate that the Ag-stimulated increase in [Ca2+]i exhibits considerable spatial and temporal variation, and that these characteristics are altered by the availability of extracellular Ca2+. The results also suggest that these changes in [Ca2+]i may play a role in the cytoplasmic events that accompany T cell-mediated cytolysis.