Role of membrane-bound IgM in Trypanosoma cruzi evasion from immune clearance

We have recently described that Trypanosoma cruzi parasites of the reticulotropic Y strain increase their resistance to antibody-induced clearance during their interaction with the vertebrate host immune system. In the present study, we observed that trypomastigotes of the myotropic CL strain isolated from normal host also display an increased resistance to immune clearance when compared to parasites obtained from immunosuppressed donors. Through fluorescence-activated cell sorting analysis, we have observed that the high expression of membrane-bound IgM antibodies on Y and CL trypomastigotes correlates with their enhanced resistance to Ig-induced clearance. Trypomastigotes from normal mice were essentially refractory to the in vitro binding of immunoglobulins, showing that their membrane structures were completely covered by IgM antibodies. These findings suggest that this isotype does not efficiently mediate immune clearance. Moreover, membrane-bound IgM antibodies limited the amount of IgG attached to the parasite and, as a consequence, impaired efficient immune clearance. Through this mechanism, trypomastigotes of T. cruzi could increase their persistence in the bloodstream thus favoring parasite transmission to its hematophagous host vector in the early acute phase of the disease.

[The clinical characteristics of pulmonary tuberculosis in the elderly]

Pulmonary tuberculosis remains as a significant clinical problem in the elderly. To describe age-related differences in disease manifestations, a comparison was made taking in consideration predisposing factors, clinical features, radiographic findings and diagnostic approaches in cases of pulmonary tuberculosis between two groups: equal o higher of 60 years and lower of 60 years. Elderly patients had a higher number of antecedents of previous tuberculosis and underlying diseases than younger patients. At admission, symptoms like fever and hemoptysis were more frequent in the younger group. Radiographic findings revealed that upper lung infiltrates were still common in both groups, and that elderly patients presented less pleural effusions and cavitary lesions than younger patients. Since there were differences in the clinical presentations of pulmonary tuberculosis in the elderly group, a high index of suspicion for the disease should be maintained.

Pyrene-labeled DNA probes for homogeneous detection of complementary DNA sequences: poly(C) model system

DNA and RNA probes are important analytical reagents in molecular biology and in the detection of infectious and genetic diseases. However, the present polynucleotide probe technology is complex and labor-intensive. We have been investigating the possibility of using fluorescent-labeled DNA probes to develop assays which do not require the separation of free from hybridized probe (homogeneous assays). Such assays are possible if the fluorescence efficiency or fluorescence anisotropy of the fluorescent label changes upon hybridization of probe with target DNA. In this article we examine pyrene as a fluorescent label for DNA or RNA probes. Experiments were performed using a model system in which poly(C) and poly(I) are respectively the probe and target sequences. A small fraction of the nucleotide bases of poly(C) was randomly labeled with pyrene using the bisulfite-catalyzed diamine reaction. The results show that the uncorrected emission spectrum of pyrene-poly(C) decreases by a factor of 4 and shifts toward longer wavelengths upon hybridization with poly(I) at saturating concentrations. The average lifetime changes from 10.78 to 4 ns. These fluorescence changes occur in a wide range of chemical environments, including the high salt concentrations normally used to increase the velocity of the hybridization reaction in clinical assays. The pyrene label can thus be used to readily detect the amount of poly(I) in an unknown sample without having to separate free and bound labeled probe. To unravel the mechanism responsible for the observed changes in fluorescence intensity upon hybridization, we have performed polarized fluorescence intensity measurements and analyzed the results by approximate steady-state expressions that allow evaluation of the relative contributions of changes in lifetimes (fluorescence efficiency) and rotational motions to the changes in fluorescence intensity. The results indicate that the latter changes are due chiefly to changes in lifetime or fluorescence efficiency and that these changes seem to be due to the movement of the pyrene label to a more hydrophilic environment upon hybridization.

Experimental verification of analytic modeling of erbium-doped silica fiber amplifiers pumped at 1480 nm

Gain measurements are carried out for different lengths of three types of erbium-doped silica fiber with different pump powers at 1480 nm. From these measurements a relation is established for each type of fiber between gain and the attenuation factor of the pump power. This relation is in complete agreement with the one predicted by an analytic model based on overlapping factors, which makes it possible to obtain methods for the experimental characterization of doped fibers.

Repairing the degenerative mitral valve: ten- to fifteen-year follow-up

From January 1969 to December 1992, mitral valve reconstructive operations were performed on 155 patients with degenerative mitral valve disease. There were 102 male and 53 female patients, with a mean age of 60.5 +/- 9.2 years, a mean duration of symptoms of 3.8 +/- 2.7 years, and 34% were in atrial fibrillation. All patients were in New York Heart Association functional classes III and IV before operation. The degree of mitral regurgitation was severe in 94% and moderate in 6%, and 50.9% of patients had moderate to severe impairment of left ventricular function. Emergency operation was undertaken in 7.1% of cases; 19% of patients underwent additional procedures. All patients had posterior mitral leaflet pathology and 19 patients had anterior mitral leaflet pathology. Ring annuloplasty was used in only 3% of cases. The operative mortality rate was 3.9%, 9% of patients had morbid events, and 4.5% of patients had repair failure within 6 months. All patients have been followed up with serial echocardiography for a mean time of 5.2 +/- 0.3 years (range 0.5 to 24 years). Immediately after operation, 92.9% had no mitral regurgitation to mild mitral regurgitation. At last follow-up, 96.9% had no mitral regurgitation to mild mitral regurgitation by echocardiography and 98% of patients were in New York Heart Association functional classes I and II. The actuarial survival at 15 years was 46% +/- 11%, freedom from reoperation was 84.9% +/- 11%, freedom from infective endocarditis was 96.0% +/- 11%, freedom from thromboembolism was 90.4% +/- 11%, and freedom from all valve-related events was 36.7% +/- 11%. It is well documented that repair of degenerative mitral valves offers excellent short-term and medium long-term benefits. This series represents the longest follow-up reported outside Europe. Our results beyond 10 years support our conclusion that an annuloplasty ring is not an absolute prerequisite for achieving successful repair of proven durability in most patients with degenerative mitral valve disease.

Ig-isotype patterns of primary and secondary B cell responses to Plasmodium chabaudi chabaudi correlate with IFN-gamma and IL-4 cytokine production with CD45RB expression by CD4+ spleen cells

In this work, the authors analysed T and B lymphocyte subsets and cytokine production in the spleen of BALB/c mice during polyclonal lymphocyte activation (primary infection) and parasite-specific response to Plasmodium chabaudi chabaudi (secondary infection). The secondary response was evaluated in fully immunoprotected animals, 60 days after a chloroquine-cured infection. The authors observed that in polyclonal lymphocyte activation antibody-secreting cells of all isotypes increased, with predominance of IgG2a and IgG3 classes. At that time, IFN-gamma was largely produced, but IL-4/IL-5 were just slightly enhanced. In mice re-infected after 60 days, the Ig-isotype pattern was restricted to IgG1 and only IL-4/IL-5 were produced. In both responses, however, the levels of IL-2 were greatly reduced, while those of IL-10 were enhanced to similar levels. The different involvement of Th1 and Th2 cells in both responses was confirmed through analysis of CD45RB expression by CD4+ cells. The authors observed that CD45RBhigh cells were the major CD4+ subpopulation in primary infected mice, while CD45RBlow cells predominated in 60 days re-infected animals. Moreover, the great majority of activated (large) CD4+ cells in the primary infection belonged to the CD45RBhigh subset, while after reinfection most of the CD4+ large had a CD45RBlow phenotype.

Effect of pH on injection phlebitis

Formulation pH has been reported to be responsible for the incidence of phlebitis. In this study, the effect of pH on injection phlebitis is investigated. Buffers of varying pHs were examined for their ability to produce phlebitis in rabbits. Thermal measurements as well as visual evaluations were used for phlebitis quantitation. The results show that formulation pH between 3.0 and 11.0 does not contribute to the incidence of phlebitis when administered as an iv bolus injection.

The use of ultra-low-dose aprotinin to reduce blood loss in cardiac surgery

One hundred patients due to undergo primary cardiac surgery were prospectively randomized to receive aprotinin or placebo. In the aprotinin group, 250,000 kallikrein inhibitory units (KIU) of aprotinin were added to the cardiopulmonary bypass prime solution. A further 250,000 KIU of aprotinin were infused intravenously over 30 minutes immediately before the start of cardiopulmonary bypass. The control group received 0.9% saline in equal volumes at identical times. The study was designed to have a 90% chance of demonstrating a 30% reduction in blood loss. No significant differences were found between the two groups. The median blood loss in the aprotinin group was 750 mL (interquartile range 556 to 1025 mL, 95% confidence interval 600 to 800 mL). In the control group, the median blood loss was also 750 mL (interquartile range 500 to 988 mL, 95% confidence interval 625 to 925 mL). In the aprotinin group, 12 patients received postoperative autotransfusion of shed mediastinal blood of median volume of 665 mL (interquartile range 500 to 925 mL, 95% confidence interval 450 to 1000 mL). In the control group, 14 patients received postoperative autotransfusion of mediastinal blood of median volume of 663 mL (interquartile range 600 to 800 mL, 95% confidence interval 600 to 700 mL). Five patients in the aprotinin group and seven patients in the control group required postoperative homologous blood transfusion. Reassessment of inclusion criteria showed a 19% reduction in blood loss in patients undergoing only aortocoronary bypass receiving aprotinin compared with controls.(ABSTRACT TRUNCATED AT 250 WORDS)

A new mutant hairless mouse with lymph node hyperplasia and late onset of autoimmune pathology

Adult BALB/c male mice were injected with a single dose of ethyl nitroso urea (ENU; 250 mg/kg, i.p.) and mated to C57BL/6, DBA/2 and A/J adult females 13 weeks later. F1 males were mated with BALB/c females and F2 females were than backcrossed to the F1 parents. One BALB/c male mouse thus treated gave origin to a mutant presenting hair and skin alterations similar to those of natural hairless mutants. The new mutation is located on chromosome 14 near the Es10 locus, and probably at the same locus for the hairless mutation. Similar to the hairless mouse, this new mutant has a normal phenotype at birth and after three weeks starts to loose hair which is never replaced. Additionally, the skin becomes thickened and wrinkled. One feature that distinguishes this mutant from other hairless mice is the peculiar enlargement of its axillary and cervical lymph nodes. The new mutant develops membranoproliferative glomerulonephritis similar to the rhino mouse, one of the hairless allele mutants already described in the literature, but with a much later onset.

[The female sex and mortality after acute myocardial infarct]

INTRODUCTION

To study the possible influence of gender on in-hospital mortality in patients suffering acute myocardial infarction.

PATIENTS AND METHODS

We analyzed 1,951 consecutive patients admitted to our Coronary Unit between January 1986 and December 1991 with this diagnosis and with a delay of no more than 24 hours prior to admission.

RESULTS

In-hospital mortality was 12.8% in the 1,603 males and 25.6% in the 348 females (p < 0.001). Age, previous history of: not smoking, diabetes, heart failure, stable angina, myocardial infarction, stroke, right branch block, atrial fibrillation, and treatment with digoxin were variables significantly associated with greater mortality (p < 0.05) as well as the localization of the infarction, the Forrester grade and/or presence of atrioventricular block on admission and not treatment with intravenous fibrinolytics and beta-blockers. Multivariate analysis of variables associated with mortality (selection criterion for variable entry p < 0.20) shows that age, gender, previous angina, situation and extension of the infarction determined by ECG and Forrester on admission are independent predictors of in-hospital mortality.

CONCLUSIONS

Gender is an independent predictor of in-hospital mortality in acute myocardial infarction (female/male odds ratio = 1.63).

Repair of the anterior mitral leaflet

BACKGROUND

Repair rather than replacement of the diseased mitral valve has been the goal of the cardiac surgeon. Although well accepted for posterior leaflet pathology, a diseased anterior leaflet was believed by some to be irreparable.

AIMS

To assess the result of reconstructive mitral valve surgery involving the anterior mitral leaflet in a selected group of patients.

METHODS

Twenty consecutive patients with degenerative (19), ischaemic (one) and congenital/calcific mitral regurgitation were evaluated. There were five females and 15 males with a mean age of 62 +/- 12 years (41-75 years). The technique used to repair these valves included chordal transposition, leaflet plication commissuroplasty and a new technique we call leaflet repositioning.

RESULT

There were no deaths, follow-up is complete with mean follow-up of 31 +/- five months (two-102) months. All patients have had 2DE and 13 TOE as well. There have been no reoperations due to failure of the repair, 95% of patients are in NYHA Class I-II post operative, while 15% have significant residual regurgitation.

Stress modulation and wavelength tuning of an erbium-doped optical fiber laser

The stress on either the erbium-doped or the normal optical fiber inside a cavity can cause output modulation, wavelength tuning in the gain band, and selection of the transition at 1.53 or 1.56 microm in an erbium-doped optical fiber laser. These phenomena are explained with the birefringence of the optical fiber under stress, the polarization properties of the directional coupler loop, and the condition of the laser oscillation. These phenomena may have some practical use in output power control, wavelength tuning, and sensors.

Intra-aortic balloon rupture causing femoral entrapment

Rupture of an intra-aortic balloon counterpulsator (IABCP) demands immediate removal. We report a case of thrombus formation within a Datascope IABCP secondary to IABCP rupture, necessitating surgical exploration for removal. There is a disturbing pattern of balloon ruptures with this type of IABCP.

Repairing the degenerative anterior mitral leaflet

This is a consecutive, nonselected series of 18 patients with degenerative mitral regurgitation requiring a reparative operation on the anterior mitral leaflet. A new technique of double-breasting the two leaflets when flail septal segments are encountered is introduced.

Resistance of Trypanosoma cruzi to blood clearance induced by acute-phase immune mouse serum

To investigate functional changes in Trypanosoma cruzi parasites induced during their interaction with the vertebrate host, we compared the blood clearance profiles of blood forms isolated from infected normal mice (Reg-Tc) or from infected mice immunodepressed after treatment with cyclophosphamide (Cy-Tc). Parasite blood numbers were measured at various time intervals in animals injected intravenously (i.v.) with 1-2 x 10(6) T. cruzi of either isolate. In the absence of added immune sera (spontaneous clearance), Reg-Tc and Cy-Tc were cleared from blood at similar rates. However, when acute immune mouse serum (Ac-IMS) was injected i.v. 2 min after inoculation of parasites, a significant proportion of Cy-Tc only was cleared from the blood an hour later, whereas Reg-Tc were not, their clearance profile being identical to that observed in mice injected with normal mouse serum. Cy-Tc susceptibility to Ac-IMS was not the result of a toxic effect of cyclophosphamide over T. cruzi as parasites recovered from animals immunodepressed by irradiation before infection were cleared similarly by acute serum. Contrary to Ac-IMS, chronic immune mouse serum induced similar rates of disappearance of Reg-Tc and Cy-Tc from blood. Our results suggest the occurrence of T. cruzi selection or modification during the acute phase, which leads to an increased parasite resistance to the clearance properties of acute-phase antibodies.

Technical improvements in the repair of acute postinfarction ventricular septal rupture

Postinfarction ventricular septal rupture (VSR) is a high-risk complication following myocardial infarction (MI). Surgical treatment has evolved to improve an otherwise poor prognosis. Certain subsets of patients remain a formidable challenge. The presence of cardiogenic shock has consistently been found to have the highest risk. Over a 10-year period, our technique of repair has evolved from established procedures to one we believe confers superior results. Endocardial patching to viable myocardium reinforced with an epicardial patch not only corrects the shunt but maintains ventricular geometry and avoids tension on friable muscle. We report on a series of nine consecutive patients in cardiogenic shock. The operative mortality was 22%, none due to low cardiac output syndrome, shunt recurrence, or bleeding. All patients have been followed with transesophageal echocardiography at a mean period of 14 months (range 3-31 months). One patient is in New York Heart Association (NYHA) Class I, four are in NYHA Class II, and two in NYHA Class III.

Complications from intra-aortic balloon counterpulsation: a review of 303 cardiac surgical patients

From January 1980 to January 1990 all patients undergoing cardiac surgery at the Royal North Shore Hospital, Sydney, and requiring intra-aortic balloon counterpulsation (IABCP) were retrospectively reviewed. A total of 99 patients (32.6%) developed complications. Vascular/haemorrhagic complications occurred in 46 patients (15.2%); 79 patients (26%) required platelet transfusions. We have found that only a history of hypertension was predictive of an increased incidence of developing vascular complications. Surgical intervention was required in 17 patients (5.6%), or 47% of the patients who developed a vascular complication. The mortality among patients requiring IABCP was 36.6%. Intra-aortic balloon pump-related deaths occurred in 6 patients (2%). Use of the intra-aortic balloon pump can be a life-saving procedure, but it carries a significant morbidity and mortality rate. This makes it imperative to temper our indications to those patients who demonstrate a need for it.

Evolution of subpatent parasitaemia in Trypanosoma cruzi chronically infected mice with the help of a cyclophosphamide amplification transfer assay

We have evaluated the sensitivity of the classical blood subinoculation method, modified through cyclophosphamide treatment of transferred mice, for the detection of occult parasitaemias in Trypanosoma cruzi chronically infected mice. Besides its simplicity, the method was shown to be highly sensitive for both the "chronic" phase parasites (99% of chronic cases were shown to harbour occult parasitaemias) and for the acute phase parasites (T. cruzi could be detected in 53.8% of animals transferred with one Y strain parasite and in 20% of animals transferred with one CL strain parasite). Using acute phase bloodforms, the assay proved to be more sensitive than conventional subinoculation when dealing with the CL, but not the Y strain of the parasite. With the help of this parasite detection tool, we have studied during a one year period, the evolution of subpatent parasitaemias in a group of mice which survived through chemotherapy from lethal acute phase of T. cruzi infection. Cyclophosphamide transfer assay revealed occult parasitaemias in 100% of the chronic animals, nevertheless, continuous and discontinuous patterns of positivity were observed.

High performance liquid chromatographic separation of cisplatin and its hydrolysis products on alumina and application to studies of their interaction with cysteine

An alumina stationary phase has been assessed in the study of the retention behaviour of the anticancer drug cisplatin and its major hydrolysis products. Parameters such as buffer concentration in the mobile phase, pH, organic modifier and competing ion have been investigated in order to optimize chromatographic separation with ultraviolet detection. The separation scheme developed has been used to monitor the hydrolysis of cisplatin in aqueous and saline media, and to monitor the interaction of hydrolysed solutions of cisplatin with the amino acid cysteine. A new peak was observed in the chromatograms of such mixtures when they had been allowed to stand for periods of greater than 16 h and, from analysis of the data obtained, it was concluded that this new peak was due to a complex formed between the mono-aquo hydrolysis product of cisplatin and the amino acid.

Comparison between intensity correlation and Fourier transform of the time interval probability techniques applied to laser Doppler velocimetry

In this paper we study the improvement in a laser Doppler velocimetry experiment when the Fourier transform of the time interval probability is measured instead of the intensity correlation function. The errors involved in determination of the velocity are found to be greatly improved for low scattered intensities.

Determination of microscopic dissociation constants of 3-hydroxy-alpha-(methylamino)methyl-benzenemethanol by a spectral deconvolution method

Microscopic dissociation constants of 3-hydroxy-alpha-(methylamino)methyl-benzenemethanol have been calculated from the titration spectrophotomeric data (c = 3.8 x 10(-4) M. Ionic strength = 0.16; buffer system: H3BO3/KOH) by application of a spectral deconvolution method. The results found (pKa = 9.48; pKb = 9.71; pKc = 10.12 and pKd = 9.88) are in good concordance with those obtained from the conventional regression linear method (pKa = 9.45; pKb = 9.77; pKc = 10.14 and pKd = 9.81).

Determination of a Fabry-Perot multipass interferometer instrumental function

Theoretical determination of the instrumental function of a Fabry-Perot multipass interferometer as a function of the single pass instrumental function is studied. The polynomial dependences between the respective parameters characterizing the instrumental functions are given. An experimental check of the theoretical predictions is also presented.

Specific binding of 3H-estradiol to rat prostate nuclear matrix

Specific estradiol binding activities can be demonstrated in nuclear matrix preparations obtained from intact rat prostate nuclei. Some of the characteristics of these in vitro binding activities to intranuclear components are presented and compared to those exhibited by purified nuclear fractions. Examination of the effects of exposure to castration and testosterone on the number of nuclear matrix binding sites revealed that the quantity and quality (Type) of receptors was modified. Furthermore, these changes are prevented when protein synthesis was inhibited.

Insulin regulation of insulin-like growth factor action in rat hepatoma cells

We have reported previously that insulin causes a complete but reversible desensitization to insulin action in rat hepatoma HTC cells in tissue culture, and that this insulin resistance is mediated by postbinding mechanisms rather than receptor down-regulation (Heaton, J. H., and Gelehrter, T. D. (1981) J. Biol. Chem. 256, 12257-12262). We report here that insulin causes a similar desensitization to the induction of tyrosine aminotransferase by the insulin-like growth factors IGF-I and IGF-II isolated from human plasma, and by multiplication-stimulating activity, the rat homologue of IGF-II. The results of both competition-binding studies and affinity cross-linking experiments indicate that insulin-like growth factors (IGFs) bind primarily to IGF receptors rather than to insulin receptors. The low concentrations at which these factors induce transaminase is consistent with their acting primarily via IGF receptors. This is confirmed by experiments utilizing anti-insulin receptor antibody which both inhibits 125I-insulin binding and shifts the concentration dependence of insulin induction of tyrosine aminotransferase to the right. This same immunoglobulin does not inhibit 125I-multiplication-stimulating activity binding and only minimally inhibits 125I-IGF-I binding. Anti-insulin receptor antibody also does not significantly shift the concentration dependence for the IGFs, suggesting that IGFs induce transaminase by acting via IGF receptors. Although insulin down regulates insulin receptors, it does not decrease IGF-I or IGF-II binding. We conclude that insulin causes desensitization of HTC cells to IGFs by affecting a postbinding step in IGF action, which may be common to the actions of both insulin and insulin-like growth factors.

Inversion technique for IR heterodyne sounding of stratospheric constituents from space platforms

The techniques which have been employed for inversion of IR heterodyne measurements for remote sounding of stratospheric trace constituents usually rely on either geometric effects based on limb-scan observations (i.e., onion peel techniques) or spectral effects by using weighting functions corresponding to different frequencies of an IR spectral line. An experimental approach and inversion technique are discussed which optimize the retrieval of concentration profiles by combining the geometric and the spectral effects in an IR heterodyne receiver. The results of inversions of some synthetic ClO spectral lines corresponding to solar occultation limb scans of the stratosphere are presented, indicating considerable improvement in the accuracy of the retrieved profiles. The effects of noise on the accuracy of retrievals are discussed for realistic situations.

Human interleukin 2: production by both TG cells and other T cells

We have investigated the production of interleukin 2 (IL-2) by human T cells after their stimulation by phytohaemagglutinin (PHA). T cells isolated by rosetting with sheep erythrocytes produced high levels of IL-2. Further separation of rosette-forming cells, according to the expression of Fc receptors for IgG, showed that TG and non-TG cells are equally able to produce IL-2. The release of IL-2 by TG cells did not require DNA synthesis or functional Rc gamma receptors, since positively selected TH cells produced IL-2, even though they lacked lymphoproliferative responses to PHA and antibody-dependent cell-mediated cytotoxicity.

Intensity transmitted by a Fabry-Perot etalon with another internal Fabry-Perot interferometer

The intensity transmitted by a device made up of a F.P. etalon that contains another internal tunable F.P. has been studied. The theoretical predictions about the wavelengths of the intensity transmission maxima of the device are derived as functions of the optical path length of the internal F.P. An experimental check of the theoretical predictions is also presented.

Impact of Saturn Ring Particles on Pioneer 11

The particle flux measured by the meteoroid detectors on Pioneer 11 increased greatly while the spacecraft was near the rings of Saturn. The data suggest that the particles were associated with the rings and were not interplanetary meteoroids concentrated near the planet by gravitational focusing. The data also suggest that the E ring may be 1800 kilometers thick with an optical thickness greater than 10(-8).

Cytotoxic activities of normal cultured human T cells

Normal human T cells grown in continued cultures in medium containing conditioned medium (CM) from PHA-stimulated lymphocytes were studied for their ability to manifest three known forms of cell-mediated cytotoxicity: lectin-induced cellular cytotoxicity (LICC), natural killer cell (NK) activity, and antibody-dependent cellular cytotoxicity (ADCC). The cultured T cells (CTC) were very effective mediators of LICC, being cytotoxic even at very low attacker-target cell ratios in the presence of different lectins, and against different types of targets. When tested without the addition of lectin, the CTC demonstrated a low degree of spontaneous cytotoxicity. This spontaneous cytotoxicity might not be due to conventional NK cells however, since the CTC failed to show significant numbers of cells with Fc receptors (FcR) for IgG, and had no detectable ADCC activity. CTC could represent a population enriched in polyclonal activated T cells with low spontaneous cytotoxicity against a variety of allogeneic target cells, which is greatly enhanced by the addition of lectins dur ing the 51Cr release assay.

Pioneer 11 Meteoroid Detection Experiment: Preliminary Results

The concentration of meteoroids of mass ~ 10(-8) gram in interplanetary space, in the asteroid belt, and near Jupiter has been measured. The data confirm the Pioneer 10 observation that the asteroid belt is not highly populated with small meteoroids, suggest that the high concentration of small particles around Jupiter is the result of gravitational focusing, and provide an indication of the mass distribution of meteoroids in interplanetary space.