Association of Venezuelan equine encephalitis virus subtype IE with two equine epizootics in Mexico

Two outbreaks of encephalitis consistent with an etiology of Venezuelan equine encephalitis (VEE) virus occurred in equines on the Pacific coast of southern Mexico in 1993 (Chiapas State) and in 1996 (Oaxaca State). In Chiapas, there were 125 cases, of which 63 were fatal and in Oaxaca, there were 32 cases and 12 fatalities. Virus was isolated from two horses from each outbreak, including three brain isolates and one from blood. Virus isolates (93-42124, ISET-Chi93, Oax131, and Oax142) were shown by indirect immunofluorescence, hemagglutination inhibition, monoclonal antibody ELISA, and nucleotide sequencing to be VEE virus, subtype IE, a type previously thought to be equine-avirulent. Genetic characterization and phylogenetic analysis indicated that the outbreak viruses were identical or nearly identical to one another and that they were closely related to equine-avirulent IE strains from Guatemala and the Gulf coast of Mexico. In a plaque-reduction neutralization test, sera collected from healthy horses in Chiapas and Oaxaca reacted significantly better with isolate 93-42124 than with Guatemala IE isolate 68U201, suggesting that subtle genetic changes may have resulted in alteration of neutralization domains. It is not clear whether these differences may also influence equine virulence. However, renewed VEE virus subtype IE activity in Mexico, and its apparent conversion to equine virulence, underscores the need for increased surveillance, additional laboratory and epidemiologic studies in VEE-endemic regions, and possibly new vaccines.

[Survival of patients with myasthenia gravis after thymectomy. Analysis of 100 cases]

In order to evaluate the survival of patients with myasthenia gravis (MG) after thymectomy (T), 100 patients with MG in which T had been performed between 1967 and 1995 were studied. Patients were divided into different groups for their analysis: patients with thymoma (TI), 22 cases; and patients without thymoma (NTI), 78 cases. In addition those patients belonging to the latter group were further separated according to the date of their surgery into two other subgroups: patients operated before 1980 (A80), 43 cases; and after 1980 (D80), 35 cases; trying to evaluate the prognostic implications of the therapeutical advances achieved over the last 15 years. The population studied was composed mainly of women (78%) but with a slight predominance of men in TI. The mean age was 29.47 years (range 10-70) for the entire population, with a tendency toward older ages in TI (mean 46 years, range 23-70). The mean follow-up period was 4.3 years (range 0.08-23.2) without significant differences between TI and NTI. The results showed that the overall mortality rate was 16/100 (16%) [Fig. 1], with nine of those deaths corresponding to TI (9/22, 40.91%) and only the remaining seven to NTI (7/78, 8.97%). These differences in mortality rate between TI and NTI were statistically significant in all the specific times of follow-up analyzed up to 10 years after surgery (p < 0.05) [Fig. 2]. Notoriously, all deaths in NTI occurred in the A80 subgroup giving a p value < 0.001 when compared with D80 [Fig. 3]. In terms of morbidity, 55/100 (55%) reached complete clinical remission (CCR) defined by the complete absence of symptoms related to MG: 8/22 (36.36%) in TI and 47/78 (60.25%) in NTI [Fig. 4]. Most interestingly the differences were statistically significant (p < 0.01) when the rates of CCR in A80 and D80 were compared for all the times assessed [Fig. 5-6-7-8]. It can be concluded that the best results in survival in MG after T are obtained in patients without thymoma and also that the benefits of the rational use of modern therapeutic modalities, including surgery and immunosuppression with drugs, can offer those patients high possibilities of leading completely normal lives.

Objective measurement of the off-axis longitudinal chromatic aberration in the human eye

Longitudinal chromatic aberration (LCA) of the human eye has been studied repeatedly, but only at the fovea. Poor visual acuity prevents its subjective determination beyond a few degrees eccentricity. Consequently, we have used an objective approach, similar to that of Charman and Jennings [(1976). Vision Research 16, 999-1005], to measure ocular LCA across the visual field. To determine the validity of our double-pass approach, a direct comparison between objective and subjective results was established where possible, namely at the fovea and parafoveally (2.5 deg). In both cases we focused a monochromatic point source at four different wavelengths (458, 501.8, 543.5 and 632.8 nm). At the fovea, for a 3 mm pupil, we found a close match between subjective and objective results. However, as the subjective task became harder (off-axis or larger pupils), subjective results tended to yield slightly more myopic eyes than the results for objective refraction. In all cases, the offset was virtually independent of the wavelength used. Therefore, we have not found evidence of any biased estimates of the LCA, as determined objectively. Our foveal results show reasonable agreement with previous findings, except for slightly smaller amounts of LCA. Starting at the fovea, LCA tends to gradually increase with eccentricity, up to 40 deg, although such an increase is small, just approaching statistical significance. Computation of the LCA using a model eye predicts a slightly smaller increase with eccentricity.

Aberrations and relative efficiency of light pencils in the living human eye

We propose a new method for ray tracing in the living human eye. It consists of delivering a narrow light pencil from an unexpanded laser beam and recording the integrated energy and position of the aerial image formed by the outgoing beam (after reflection off the retina and passage through the fully open pupil of the eye and camera lens). The lateral displacement of the aerial image is proportional to the geometrical aberration (displacement) of the incoming ray at the retina. In addition, its integrated energy is proportional to retinal reflectance that is highly directional [related to the Stiles-Crawford (SC) effect and to the effective pupil transmittance]. This method permits us, by delivering rays through different equispaced positions at the pupil plane, to sample the complex pupil function: its magnitude is a measure of the effective pupil transmission and its phase is the wave aberration. Experimental results, aberrations, and reflectometric directionality for four subjects are consistent with previous findings.

Foveal cone spacing and cone photopigment density difference: objective measurements in the same subjects

Foveal cone spacing was measured in vivo using an objective technique: ocular speckle interferometry. Cone packing density was computed from cone spacing data. Foveal cone photopigment density difference was measured in the same subjects using retinal densitometry with a scanning laser ophthalmoscope. Both the cone packing density and cone photopigment density difference decreased sharply with increasing retinal eccentricity. From the comparison of both sets of measurements, the computed amounts of photopigment per cone increased slightly with increasing retinal eccentricity. Consistent with previous results, decreases in cone outer segment length are over-compensated by an increase in the outer segment area, at least in retinal eccentricities up to 1 deg.

Determination of the foveal cone spacing by ocular speckle interferometry: limiting factors and acuity predictions

We have developed a high-resolution imaging technique, based on speckle interferometry, for the objective determination of the cone spacing in the living human fovea. The spatial resolution attained with this technique is theoretically diffraction limited by the pupil size. However, the highest frequency that we measure varies greatly among subjects, especially for fully dilated pupils. We have conducted several experiments (determination of the cutoff frequency of ocular speckle interferometry, the double-pass modulation transfer function, and the Stiles-Crawford effect) that indicate that, as expected, the resolution is not limited by the incoherent modulation transfer function. We found, though, a high correlation between the cutoff frequency and the width of the eye's Stiles-Crawford function. This implies that the resolution depends on the structural properties of the cone mosaic itself. In addition, we have compared the Nyquist frequency of the cone mosaic, determined objectively by our technique, with the grating visual acuity measured in the same eyes at the same foveal eccentricities. For our subjects, visual resolution nearly matches the Nyquist frequency within the fovea, except at the foveal center, where the optical transfer function of the eye attenuates the contrast of frequencies close to the Nyquist limit to a value below threshold.

Shape of stars and optical quality of the human eye

Star images are entoptic phenomena that most people can perceive when looking at bright point sources in darkness. Diffraction and/or ocular aberrations seem to be a plausible cause for the star patterns, but to our knowledge no objective recordings of retinal optical images showing these characteristic patterns have been reported before. We have projected a small Gaussian spot of light onto the retina and registered the aerial image formed externally through a fully dilated pupil [one-and-a-half-pass method [J. Opt. Soc. Am. A 12, 2385 (1995)]]. We have verified that, for fully dilated pupils (> 9 mm), the blur caused by the finite size of the Gaussian spot is small. Consequently, these aerial images are a reasonably good approximation of the (inverted) optical point-spread function of the eye. These objectively recorded images displayed the distinctive radiating patterns of star images, which were compared with subjective patterns sketched out by the same observers. A strikingly close match was found between the objective and the subjective patterns of the same eyes. In addition, we computed the diffraction patterns produced by a simple schematic model of the suture lines of the anterior lens surface, also obtaining star-shaped images. These results support the commonly accepted hypothesis of a purely optical origin of subjective star images.

Third autologous stem cell transplants for late relapse of multiple myeloma

Double autologous bone marrow transplantation (ABMT) has been reported as an efficient form of consolidation for patients with multiple myeloma (MM). However, few data are available about feasibility and efficacy of a third ASCT in case of relapse. Here we report two patients with MM who received a third ASCT for late relapse (74 and 52 months) after a double ABMT. Both patients were male with IgG gamma MM (stage IIIA according to the Durie Salmon classification). The two patients were in PR > 50% after a first-line treatment. A double ABMT was performed after relapse and patients remained in PR > 50% after double intensification, lasting 71 and 49 months, respectively. The third ASCT was performed 7 and 10 months, after second relapse. One patient needed 15 months to reach 50 000 platelets, however he did not receive any transfusion after day 14. He was in PR > 50%. The other patient was in PR < 50%, 4 months after ABMT with a full hematological reconstitution. For patients with late relapse of MM after double ABMT, a third ABMT was a feasible treatment and patients seem to remain sensitive to high-dose therapy.

Coherent imaging of the cone mosaic in the living human eye

A new system for the recording of high-resolution images of the cone mosaic in the living room fovea has been developed. The experimental method is inspired by stellar speckle interferometry, used in astronomy to resolve binary stars. Series of short-exposure images of small areas of the fovea are registered under coherent illumination. These images show speckle patterns that have some correlation with the topography of the cone mosaic and retain high-resolution information. Such correlation is better revealed in the power spectrum (square modulus of the Fourier transform). The signal-to-noise ratio is increased, without loss of high frequencies, by averaging the power spectra of a number of such speckle patterns. The average power spectra show, in most of the cases, an elliptical ring (or hexagon), whose mean radius corresponds to the characteristic spatial frequency of the cone mosaic (or the inverse of the mean row-to-row cone spacing) at a given retinal location. Good results are obtained in the five normal observers tested, at various retinal eccentricities, up to 1 visual degree, including the center of the fovea for two eyes. We find a decrease in the spatial frequency of the mosaic with the eccentricity and an important intersubject variability, in agreement with anatomical studies.

Off-axis optical quality and retinal sampling in the human eye

Using the double pass procedure, Navarro et al. (1993; Journal of the Optical Society of America A, 10, 201-212) measured the monochromatic modulation transfer function (MTF) of the human eye as a function of retinal eccentricity. They chose conditions as similar as possible to those encountered in natural viewing. We report new measurements obtained with conditions chosen instead to optimize retinal image quality: we paralyzed accommodation, used a 3 mm pupil, and corrected defocus and oblique astigmatism at each retinal location. MTFs were estimated at the tangential focus, circle of least confusion, and sagittal focus produced by oblique astigmatism. Though optical blur is well-known to have little effect on peripheral visual acuity, it can nonetheless substantially reduce aliasing by receptoral and post-receptoral spatial sampling.

[Lawsuits against physicians in Chile]

Lawsuits against are becoming relevant in Chile. We analyzed 18 trials against physicians that occurred between 1977 and 1985 and that were ruled by Metropolitan Region courts. The causes of demands were death of patients in 8 trials and severe lesions in the rest. Twelve trials originated from surgical procedures (six from gynecological interventions), and nine came from private clinics. Nine trials lasted less than two years and three, more than 5 years. Sentence was pronounced by criminal courts in 12 cases and by appealing courts in six.

Effects of ear canal occlusion and masking on the perception of voice

This study examined the effect of ear canal occlusion and masking noise on four parameters of voice: (1) average fundamental frequency, (2) intensity in decibel (dB), (3) maximum fundamental frequency observed in a given sample (max), and (4) minimum fundamental frequency observed in a given sample (min). 12 normal hearing undergraduates produced the vowel /i/ ten times under conditions of unoccluded ear canal, ear canal occluded with a sound attenuating earplug, or masking noise. Other than a small (.73 dB) decrease in intensity, analysis showed no significant changes under the occluded condition; however, the masking condition showed statistically significant increases in the fundamental frequency, the intensity, and the maximum and minimum frequency as well as an increased range of frequencies.

Phase transfer and point-spread function of the human eye determined by a new asymmetric double-pass method

A recent study has shown that the double-pass method provides a good estimate of the ocular modulation transfer function (MTF) but that it does not yield the phase transfer function (PTF) [J. Opt. Soc. Am. A 12, 195 (1995)]. Therefore, one cannot recover the true retinal point-spread function (PSF). We present a modification of the double-pass method to overcome this problem. The key is to break the symmetry between the two passes. By using an unexpanded Gaussian input beam, we produce a diffraction-limited PSF for the first passes. Then, by using a large exit pupil, we get an aberrated PSF for the second pass. The double-pass aerial image is the cross correlation of both PSF's, so that the Fourier transform of such an aerial image directly provides the true retinal PTF, up to the cutoff frequency of the effective (small), diffraction-limited entrance pupil. The resulting double-pass aerial image is a blurred version of the true retinal PSF. Thus it shows the effect not only of even symmetric aberrations but also of odd and irregular aberrations such as coma. We have explored two different ways to retrieve the true retinal PSF: (a) deblurring of the aerial image and (b) PSF reconstruction combining PTF data with conventional double-pass MTF. We present promising initial results with both artificial and real eyes.

Antidepressant utilization in managed care: an evaluation of SSRI use in two HMO settings

Antidepressant costs and utilization are growing rapidly as newer selective serotonin reuptake inhibitors (SSRIs) comprise an ever-increasing share of the market. A number of factors and related costs must be considered when evaluating antidepressant products. An antidepressant drug utilization review study performed in two different HMO models revealed important variations among available SSRI therapies in terms of dosage escalation and discontinuation, as well as concomitant medication costs associated with treating side effects. New antidepressants may alleviate some of these problems.

alpha-Interferon therapy for congenital dyserythropoiesis type I

We report the case of a 28-year-old female followed for congenital dyserythropoiesis type I which required repeated transfusions. Alpha-2a interferon treatment was started because of post-transfusion chronic viral hepatitis type C. Following this treatment, haemoglobin level increased and reached normal value during the 24 weeks of interferon treatment. When interferon therapy was stopped, haemoglobin level returned to previous values, requiring more transfusions. Resumption of interferon therapy resulted again in a complete normalization of haemoglobin level. Erythrokinetic studies demonstrated a striking reduction of the ineffective erythropoiesis, and electron microscopy study a reduction in nuclear structure abnormalities. To our knowledge, this is the first report of the efficacy of interferon in congenital dyserythropoiesis.

Odd aberrations and double-pass measurements of retinal image quality

We investigated the formation of the aerial image in the double-pass method to measure the optical quality of the human eye. We show theoretically and empirically that the double pass through the eye's optics forces the light distribution in the aerial image to be an even-symmetric function even if the single-pass point-spread function is asymmetric as a result of odd aberrations in the eye. The reason for this is that the double-pass imaging process is described by the autocorrelation rather than the autoconvolution of the single-pass point-spread functions, as has been previously assumed. This implies that although the modulation transfer function can be computed from the double-pass aerial image, the phase transfer function cannot. We also show that the lateral chromatic aberration of the eye cannot be measured with the double-pass procedure because it is canceled by the second pass through the eye's optics.

Double-pass and interferometric measures of the optical quality of the eye

We compare two methods for measuring the modulation transfer function (MTF) of the human eye: an interferometric method similar to that of Campbell and Green [J. Physiol. (London) 181, 576 (1965)] and a double-pass procedure similar to that of Santamaria et al. [J. Opt. Soc. Am. A 4, 1109 (1987)]. We implemented various improvements in both techniques to reduce error in the estimates of the MTF. We used the same observers, refractive state, pupil size (3 mm), and wavelength (632.8 nm) for both methods. In the double-pass method we found close agreement between the plane of subjective best focus for the observer and the plane of objective best focus, suggesting that much of the reflected light is confined within individual cones throughout its double pass through the receptor layer. The double-pass method produced MTF's that were similar to but slightly lower than those of the interferometric method. This additional loss in modulation transfer is probably attributable to light reflected from the choroid, because green light, which reduces the contribution of the choroid to the fundus reflection, produces somewhat higher MTF's that are consistent with the interferometric results. When either method is used, the MTF's lie well below those obtained with the aberroscope method [Vision Res. 28, 659 (1988)]. On the basis of the interferometric method, we propose a new estimate of the monochromatic MTF of the eye.

Justifying the cost of pharmacy's clinical services

Internally, when pharmacy managers have attempted to argue for the positive contribution of pharmacy on hospital and physician costs, they were generally unable to definitively prove the linkage between drug use and outcome. They were, however, able to demonstrate an ability to reduce the overall pharmacy program costs by applying a full array of cost-containment strategies to their internal executives as well as plan sponsor's benefit managers and consultants.

Humans anesthetized with sevoflurane or isoflurane have similar arrhythmic response to epinephrine

BACKGROUND

Anesthetics can alter the dose of exogenously administered epinephrine that causes cardiac arrhythmias. The purpose of this study was to test the hypothesis that in humans anesthetized with sevoflurane, the arrhythmic response to epinephrine is not different from the response in humans anesthetized with isoflurane.

METHODS

We determined the arrhythmogenicity of submucosally administered epinephrine in 40 ASA physical status 1 or 2 patients who were to undergo transsphenoidal surgery. Patients were assigned randomly to be given 1.0-1.3 minimum alveolar concentration sevoflurane or isoflurane. A surgeon, blinded to the anesthetic and the concentration of epinephrine, injected into the nasal submucosa epinephrine 10, 13.3, or 20 micrograms/ml in saline of volume sufficient for surgical need. We defined a "positive" response as three or more premature ventricular contractions within 5 min after initiation of injection. Responses between anesthetic groups within each dose range of epinephrine were compared by chi-squared analysis.

RESULTS

No patient given either anesthetic developed premature ventricular contractions with doses of epinephrine less than 5 micrograms/kg. At larger doses of epinephrine (5-9.9 and 10-14.9 micrograms/kg), the frequency of arrhythmias did not differ between patients given sevoflurane and patients given isoflurane. Patients anesthetized with 1.2 minimum alveolar concentration sevoflurane had blood pressure similar to and heart rate less than those of patients anesthetized with similar concentrations of isoflurane. Blood pressure and heart rate were increased similarly in both groups after laryngoscopy and tracheal intubation and after epinephrine injection.

CONCLUSIONS

Sevoflurane and isoflurane do not differ in their sensitization of the human myocardium to the arrhythmogenic effect of exogenously administered epinephrine.

Monochromatic modulation transfer function of the human eye for different pupil diameters: an analytical expression

The modulation transfer function (MTF) of human eyes for different pupil sizes was measured in a group of normal young subjects by use of a double-pass method. Measurements were carried out in the fovea, with monochromatic red light, paralyzed accommodation, artificial pupils, and optimum spherical refraction in each subject. For each pupil size both the averaged MTF and the intersubject variability were calculated. MTF's were approximated by the sum of two exponential functions. This three-parameter function provides a better approximation to our ocular MTF's than do most of the previous parametric models (usually one exponential), especially at intermediate and high spatial frequencies. Further curve fitting of the parameters allowed us to obtain a general expression for the mean MTF as a function of both pupil diameter and normalized spatial frequency. This equation summarizes our estimates of the average monochromatic retinal image quality of the human eye for any pupil diameter with good accuracy and in a compact way, which allows one to incorporate the eye's image quality easily in any particular study.

Modulation transfer functions of eyes implanted with intraocular lenses

An experimental study of the retinal image quality in aged subjects after their eyes have been implanted with intraocular lenses (IOL's) has been performed. The method is based on recording in vivo the aerial image of a point test, after a double pass through the ocular media, and subsequent computation of the eye's modulation transfer function. The optical performance of three different types of bifocal IOL is compared with that of conventional monofocal IOL's. The results show that eyes implanted with bifocals exhibit a mean reduction in the modulation transfer function (contrast in the retinal image) of a factor of 2, while keeping a resolution similar to that of monofocal IOL's (which explains why visual acuities are also similar in these two cases). The mean retinal image modulation in eyes implanted with monofocal IOL's is ∼2.5 times lower than that obtained with young emmetropic subjects, but it seems to be similar to that corresponding to # of persons of the same age (∼60 years) normal eyes.

Relative contributions of optical and neural limitations to human contrast sensitivity at different luminance levels

The relative contributions of optical and neural constraints on human contrast sensitivity as a function of spatial frequency were assessed for a range of luminances. First, the overall two-dimensional contrast sensitivity function (CSF) was obtained for three eyes at three luminances (0.05, 0.5 and 20 cd/m2) using a standard two-alternative forced-choice procedure. Second, the two-dimensional modulation transfer function (MTF) of the optics was measured for the same eyes and pupil sizes using a hybrid optical-digital method. The two-dimensional neural transfer function (NTF) was obtained as the ratio between the CSF and the MTF. Minor factors, such as the effect of cone aperture, were also considered in the computations. Our results show that at all luminances, the fall off in contrast sensitivity at high spatial frequencies is mainly due to optical factors. The losses in contrast sensitivity with decreasing luminance are, however, primarily due to noise limitations.

Effects of aging in retinal image quality

The retinal image quality characterized by the modulation-transfer function of the eye was measured for two groups of subjects aged in the late twenties and mid sixties, respectively. In both groups, we obtained modulation transfer functions by using a double-pass method under the same experimental conditions: 4-mm artificial pupil, paralyzed accommodation, and objective control of the refractive state and centering. Results showed lower values of modulation in the retinal image for older subjects compared with the younger subjects. The modulation transfer function ratio is similar to that previously found for contrast-sensitivity measurements with subjects in the same age groups. These results suggest that a significant fraction of the loss in spatial vision with age has an optical origin. Apart from the well-known increase in intraocular scattering, there also appears to be an increment in ocular aberration that causes an additional reduction in the contrast of retinal images.

Modulation transfer of the human eye as a function of retinal eccentricity

We measured the monochromatic image quality of the eye across a wide visual field (120 degrees), with natural pupil (4 mm) and accommodation (3 diopters). The method is based on the acquisition and the posterior processing of double-pass aerial images of a point source imaged on the retina, which was kept at a fixed distance from the eye at all retinal eccentricities. The two-dimensional modulation transfer functions (MTF's) computed from the aerial images show that astigmatism is the dominant monochromatic aberration in both the fovea and the periphery and is also the major cause of variability among individuals. We found a slower decline in optical quality with eccentricity than had been found by previous measurements. Our foveal results are in close agreement with those of Campbell and Gubisch [J. Physiol. (London) 186, 558-578 (1966)], but off-axis optical quality is much better than found previously by Jennings and Charman [Am. J. Optom. Physiol. Opt. 55, 582-590 (1978); Vision Res. 21, 445-454 (1981)]. The optical system of the eye seems to follow a wide-angle lens design: the optical quality in the center (fovea) is not particularly good (it is far from the diffraction limit at this pupil size), but the modulation transfer function remains roughly constant for a wide visual field.

Simultaneous measurement of two-point-spread functions at different locations across the human fovea

An experimental system for measuring simultaneously the retinal images of two-point tests has been developed. In particular we present one experiment in which one of the points is located at the center of the fovea and the other one is at 1 deg of eccentricity. At these two foveal locations the optical image quality is expected to be approximately the same, while the structure of the retina is known to be quite different. Our results of aerial images show small but systematic differences between the two-pointspread functions that are measured at 0 and 1 deg of eccentricity. The image quality is always slightly better in the center of the fovea with the differences more marked in the nasal and inferior orientations. That could be explained by a small but noticeable contribution of the retinal thickness to the optical aberrations of the eye. The possible increment of scattering caused by the increase in retinal thickness at 1 deg was barely measurable in our experiment. An indirect consequence is that retinal reflection has little practical influence on our particular double-pass measurements of the eye's image quality.

Development of a program of behavior modification directed to the rehabilitation of drug-dependent patients: treatment and follow-up of 223 cases

The study reports treatment and follow-up of compulsive drug-consuming patients (mainly of coca paste). The program used was based on a behavioral cognitive and instructional model. The traditional functional analysis was modified to include the therapeutical work in seven behavioral areas: (1) drug use; (2) behavior during free time; (3) behavior at work; (4) social behavior; (5) self- and environmental management behaviors; (6) problem solving and decision-making behaviors; (7) recognition, evaluation, and modification of irrational beliefs. For each area objectives, therapeutical procedures, control and evaluation methods, and termination criteria were determined. Patients engaged in a multiple activity program and received individual and group therapy. Out of 223 male patients, 130 were discharged (that is, they fulfilled all the conditions stated by the program) and 93 patients abandoned treatment. For evaluation purposes a test was used to determine the accomplishment of the behavioral objectives. Follow-up interviews after 6 to 72 months showed that although 24 patients relapsed to drug use, 106 (81.48%) of the patients who had finished the program restrained from using drugs and obtained high scores in all seven behavioral areas.

Rat thymic cultures: morphological and phenotypical characterization

Rat thymic cultures have been established in order to analyse the morpho-functional characteristics of thymic epithelial and non-epithelial cells in vitro. Stromal cultures, originating from implanted thymic fragments, consist of fibroblasts occupying most of the culture surface, epithelial cells forming discrete colonies, thymocytes and bone marrow-derived cells. Epithelial cells show a low class II MHC antigen expression, which is highly increased in semi-adherent cells, and do not interact with thymocytes. Thymocytes proliferate extensively at the beginning of the culture, but almost disappear at the end of the first week; however, restarting of thymocyte proliferation occurs during the second week of culture. Bone marrow-derived cells include ED- Ia+ CR3- IL-2R- dendritic cells (DC), ED+ Ia+ CR3+ IL-2R+ non-adherent thymic phagocytic cells (PTR) and ED+ Ia- CR3- IL-2R- adherent type 1 and 2 macrophages, derived from PTR. Both PTR and DC establish lympho-stromatic complexes with thymocytes present in the cultures. These results suggest that PTR and DC present in rat thymic cultures belong to different cell lineages, and that they are, respectively, the in vitro equivalents of intrathymic macrophages and interdigitating cells.

In vitro characterization of rat thymic macrophages

Thymic macrophages have been isolated from Wistar rats and maintained in long-term culture. Day 1-isolated thymic macrophages expressed MHC class I and II antigens, Thy-1, CR3, CD4, ED1, ED2, as well as acid phosphatase and non-specific esterase activities. Whereas cultured macrophages were positive for the activation antigen recognized by the mAb OX48, which was not expressed after isolation, MHC class II and Thy-1 expression were down-regulated during the culture, but could be induced with human rIL-2 or with Con A-SCM, which are also inducers of IL-2R, a cell-surface marker not expressed on Day 1 or on cultured macrophages.