Impact of reference gene selection for type 2 cannabinoid receptor gene expression studies in human spermatozoa

Quantitative real-time polymerase chain reaction (qRT-PCR) has been employed to study the gene expression profiles in human spermatozoa, but accurate analysis is dependent upon normalisation of data against an endogenous control. β-Actin (ACTB) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) are the most commonly used reference genes for normalisation of gene expression in human spermatozoa, but the expression of these genes in many tissues has considerable variation under different physiological, pathological and experimental conditions which limits their effectiveness in normalisation. The expression stability of a panel of 12 reference genes was studied in normal and pathological human spermatozoa using geNorm and NormFinder software. Although there were some discrepancies in the ranking of reference gene stability, each software program ranked B2 M, ACTB, CYC1 and 18S RNA within the top 5 and recommended the combined use of at least two reference genes. Normalisation of qRT-PCR data for the cannabinoid receptor type 2 in spermatozoa using the different housekeeping genes demonstrated how, without validation, conflicting results are obtained. We recommend that the arbitrary use of reference genes should be avoided and the validation of reference gene stability should be undertaken prior to every study. For normalisation of CB2 expression, we would recommend using the geometric mean of B2 M and ACTB.

Ground-state proton decay of 69Br and implications for the 68Se astrophysical rapid proton-capture process waiting point

We report on the first direct measurement of the proton separation energy for the proton-unbound nucleus (69)Br. Bypassing the (68)Se waiting point in the rp process is directly related to the 2p-capture rate through (69)Br, which depends exponentially on the proton separation energy. We find a proton separation energy for (69)Br of Sp((69)Br )= -785(-40)(+34) keV; this is less bound compared to previous predictions which have relied on uncertain theoretical calculations. The influence of the extracted proton separation energy on the rp process occurring in type I x-ray bursts is examined within the context of a one-zone burst model.

Factors influencing the success of conservative treatment of interstitial pregnancy

OBJECTIVE

To identify demographic, morphological and biochemical characteristics of interstitial pregnancies that are associated with a successful outcome of conservative treatment (expectant management or medical treatment with methotrexate).

METHODS

Over a period of 6 years all clinically stable women with a certain ultrasound diagnosis of interstitial ectopic pregnancy were managed either expectantly (no interventions) or medically (systemic or local methotrexate injection). The outcome of conservative treatment was compared to a number of diagnostic parameters, which were recorded at the initial visit. The treatment was classified as successful if serum human chorionic gonadotropin (hCG) level declined below 20 IU/L without the need for any additional interventions, such as the administration of methotrexate or surgery.

RESULTS

A total of 42 interstitial pregnancies were diagnosed during the study period. Out of 35 women included in the final analysis 7 (20%) were managed expectantly and 28 (80%) received either local (n = 23) or systemic methotrexate (n = 5). There were no significant differences in the success rates of expectant treatment and treatment with either systemic or local methotrexate. The initial median serum hCG was significantly lower in women with successful conservative management (3216 IU/L vs. 15 900 IU/L; P < 0.05) but there were no other significant differences between cases with successful and failed treatment.

CONCLUSION

The measurement of serum hCG at the initial visit may be used to predict the likelihood of successful conservative treatment of interstitial pregnancy.

Optical properties of multilayer metal-dielectric nanofilms with all-evanescent modes

We present a systematic study of mode characteristics of multilayer metal-dielectric (M-D) nanofilm structures. This structure can be described as a coupled-plasmon-resonantwaveguide (CPRW), a special case of coupled-resonator optical waveguide (CROW). Similar to a photonic crystal, the M-D is periodic, but there is a major difference in that the fields are evanescent everywhere in the M-D structure as in a nanoplasmonic structure. The transmission coefficient exhibits periodic oscillation with increasing number of periods. As a result of surface-plasmon-enhanced resonant tunneling, a 100% transmission occurs periodically at certain thicknesses of the M-D structure, depending on the wavelength, lattice constants, and excitation conditions. This structure indicates that a transparent material can be composed from non-transparent materials by alternatively stacking different materials of thin layers. The general properties of the CPRW and resonant tunneling phenomena are discussed.

Expectant management of miscarriage—prediction of outcome using ultrasound and novel biochemical markers

BACKGROUND

The aim of this study was to examine the value of various ultrasound and biochemical parameters for the prediction of successful expectant management of miscarriage.

METHODS

This was a prospective observational study. Clinically stable women with an ultrasound diagnosis of miscarriage were offered expectant management. In all cases, gestational age, size of retained products of conception, serum HCG, progesterone, 17-hydroxyprogesterone, insulin growth factor-binding protein 1 (IGFBP-1), inhibin A and inhibin pro alpha-C RI levels were recorded. Follow-up continued until resolution of the pregnancy. Clinical data, ultrasound findings and biochemical markers were analysed using univariate analysis and decision tree analysis.

RESULTS

Fifty-four women underwent expectant management of miscarriage. Thirty-seven (69%) had successful expectant management and 17 (31%) required surgery. The size of retained products, serum HCG, progesterone, inhibin A and inhibin pro alpha-C RI were all significantly different in those pregnancies that resolved spontaneously (P<0.05). Serum inhibin A was the best predictor of a complete miscarriage.

CONCLUSION

This study shows that novel biochemical markers may be used to predict the likelihood of successful expectant management of miscarriage.

Local density of states analysis of surface wave modes on truncated photonic crystal surfaces with nonlinear material

The local density of states and response to an incident plane wave of a finite sized photonic crystal (PC) with nonlinear material (NLM) is analyzed. Of particular interest is the excitation of surface wave modes at the truncated surface of the PC, which is collocated with the NLM material. We compute the 2D Green function of the PC with linear material and then include the Kerr NLM in a self-consistent manner. The 2D PC consists of a square array of circular rods where one row of the rods is semi-circular in order to move the surface wave defect mode frequency into the band gap. Since the surface modes are resonant at the interface, the NLM should experience at least an order of magnitude increase in field intensity. This is a possible means of increasing the efficiency of the PC as a frequency conversion device.

Expectant management of tubal ectopic pregnancy: prediction of successful outcome using decision tree analysis

OBJECTIVE

To establish whether a decision tree based on a combination of clinical, morphological and biochemical parameters could be constructed to help in the selection of women with tubal ectopic pregnancies for expectant management.

METHODS

This was a prospective observational study in a tertiary referral early pregnancy unit in an inner city teaching hospital. The study group consisted of 179 women with ultrasound diagnosis of ectopic pregnancy. Demographic, clinical and ultrasound data were recorded in each case at the initial visit. In addition all women had a blood sample taken for the measurements of serum beta-human chorionic gonadotropin (beta-hCG) and progesterone. Clinically stable women with non-viable pregnancies and no signs of hematoperitoneum were managed expectantly on an outpatient basis until their serum beta-hCG declined to <20 IU/L. Women who developed pelvic pain during follow-up and those with non-declining serum beta-hCG were offered surgery.

RESULTS

A total of 107/179 (59.8%) tubal ectopics were considered suitable for expectant management. Ectopic pregnancy resolved spontaneously in 75/107 (70%) women, which was 41.9% of the total number of tubal ectopics. Maternal age, initial serum beta-hCG and progesterone were all significantly different in pregnancies that resolved spontaneously compared to those requiring surgery (P < 0.05). Initial serum beta-hCG level was the best predictor of the outcome of expectant management. These differences enabled a construction of a four-level decision tree to estimate the likelihood of successful expectant management.

CONCLUSIONS

There are significant differences in demographic, ultrasound and biochemical findings between spontaneously resolving ectopics and those requiring treatment. Decision tree analysis may be used as a guide to estimate the probability of successful expectant management in individual cases.

Characteristics of bound modes in coupled dielectric waveguides containing negative index media

We investigate the characteristics of guided wave modes in planar coupled waveguides. In particular, we calculate the dispersion relations for TM modes in which one or both of the guiding layers consists of negative index media (NIM)-where the permittivity and permeability are both negative. We fi nd that the Poynting vector within the NIM waveguide axis can change sign and magnitude, a feature that is re fl ected in the dispersion curves.

Prediction of early pregnancy viability in the absence of an ultrasonically detectable embryo

OBJECTIVE

To identify clinical, ultrasound and biochemical parameters that may allow prediction of pregnancy viability in women without a detectable embryo on ultrasound examination.

METHODS

This was a prospective observational study of pregnant women with an ultrasound finding of a gestational sac measuring < 20 mm mean diameter without a visible embryo. Women's age, menstrual dates, clinical symptoms (pain and bleeding), mean gestational sac diameter and measurements of serum beta-human chorionic gonadotropin and progesterone were recorded in all cases. All women were managed expectantly until the pregnancy viability was established conclusively based on clinical and ultrasound findings. All parameters were tested by univariate analysis and then analyzed in a stepwise procedure to form a logistic regression model for predicting pregnancy viability.

RESULTS

One hundred and eighteen (59%) women had a normal intrauterine pregnancy and 82 (41%) had a miscarriage. Stepwise analysis showed that three diagnostic parameters (maternal age, gestational sac diameter and serum progesterone) contributed significantly to the predictive power of the logistic model. With this model, at a cut-off value of 10% probability, the diagnosis of viable pregnancy was made with a sensitivity of 99.2% (95% CI, 95.8-99.97) and specificity of 70.7% (95% CI, 61.3-78.9).

CONCLUSION

The use of a logistic regression model allows prediction of pregnancy viability when an embryo cannot be visualized on ultrasound scan.

Reproductive outcomes in women with congenital uterine anomalies detected by three-dimensional ultrasound screening

OBJECTIVE

To determine reproductive outcomes in women with congenital uterine anomalies detected incidentally by three-dimensional ultrasound.

METHODS

We studied 1089 women with no history of infertility or recurrent miscarriage who were seen for a transvaginal ultrasound scan. They were screened for uterine abnormalities using three-dimensional ultrasound. We determined prevalence of miscarriage and preterm labor in women with normal and abnormal uterine morphology.

RESULTS

We found that 983 women had a normally shaped uterine cavity, 72 an arcuate, 29 a subseptate, and five a bicornuate uterus. Women with a subseptate uterus had a significantly higher proportion of first-trimester loss (Zeta = 4.68, P <.01) compared with women with a normal uterus. Women with an arcuate uterus had a significantly greater proportion of second-trimester loss (Zeta = 5.76, P <.01) and preterm labor (Zeta = 4.1, P <.01). There were no other significant differences in pregnancy outcomes between women with normal and abnormal uterine morphology.

CONCLUSION

This study shows the potential value of three-dimensional ultrasound and confirmed that women with congenital uterine anomalies were more likely to have adverse pregnancy outcomes than women with a normal uterus.

Expectant management of early pregnancies of unknown location: a prospective evaluation of methods to predict spontaneous resolution of pregnancy

OBJECTIVE

To assess prospectively the ability of two multiparameter diagnostic models and their individual components to predict the outcome of early pregnancies which could not be identified on transvaginal ultrasound scan.

DESIGN

Prospective observational study.

SETTING

Dedicated early pregnancy unit in an inner city teaching hospital.

POPULATION

Women with a positive urine pregnancy test and clinical suspicion of early pregnancy complications.

METHODS

A full medical history, clinical examination and transvaginal ultrasound scan were carried out at the initial visit. When the location of the pregnancy could not be ascertained by ultrasound, serum beta-human chorionic gonadotrophin (beta-hCG) and progesterone levels were measured. All women were managed expectantly until either a normal pregnancy was visualised on scan; the pregnancy resolved spontaneously or intervention was required due to a worsening of clinical symptoms or non-declining beta-hCG levels.

MAIN OUTCOME MEASURES

Spontaneous resolution of pregnancy (i.e. cessation of symptoms and decline in serum beta-hCG level to < 20 iu/L) without need for any active intervention.

RESULTS

Of the 104 women recruited, 72 (69%) pregnancies resolved spontaneously. Both multiparameter diagnostic models identified resolving pregnancies with positive predictive values > or = 95%. Their performances were not significantly better compared with individual progesterone levels which achieved a positive predictive value of 97% using a cutoff level of 20 nmol/L.

CONCLUSION

Serum progesterone measurement alone is as accurate as more complex diagnostic models for the prediction of successful expectant management in pregnancies of unknown location.

Electrocardiographic changes in central nervous system disease

This article gives a basic description of neurophysiologic control of cardiac function. Specific electrocardiographic abnormalities related to various central nervous system insults are discussed also.

Maps of optical action potentials and NADH fluorescence in intact working hearts

Voltage-sensitive dyes were used to stain intact perfused hearts and to simultaneously measure optical action potentials (APs) from 124 sites on the epicardium. Patterns of electrical depolarization (activation) and repolarization (recovery) along the surface of the heart were determined from the upstrokes and repolarization phases of optical APs. Standard surface extracellular techniques can detect electrical activation but not the recovery or the duration of APs. The optical recordings were previously shown to be equivalent to intracellular electrode measurements (Salama and Morad, Science Wash. DC 191: 485-487, 1976) and now reveal that AP durations are heterogeneous throughout the epicardium, with durations increasing from the base to the apex of the ventricles. In hearts beating under normal sinus rhythm, the direction and conduction velocity of the activation waves could be altered by electrical stimulation. The normal heterogeneities in AP durations became more pronounced in the presence of the Ca2+-entry blocker, verapamil. The local metabolic state of the tissue was also monitored optically through its intrinsic NADH fluorescence measured from 124 separate regions on the heart. The time course and extent of metabolic injury caused by general anoxia or by a local ischemia induced by a coronary ligation was monitored through maps of NADH fluorescence. The present technique makes it possible to correlate changes in the metabolic state of the muscle with detailed changes in patterns of electrical activity and thus provides a powerful new tool to study fundamental aspects of normal and abnormal cardiac rhythm.

General concepts and mechanisms of ventricular tachycardia

The predominant mechanism of ventricular tachycardia is thought to be reentry, although this has been proved to exist in definitely a minority of patients studied owing to technical limitations. Other mechanisms, such as spontaneous triggered automaticity, undoubtedly also cause clinical ventricular tachycardia. During electrophysiologic testing, sustained unimorphic ventricular tachycardia can be induced in the majority of patients who have this arrhythmia clinically. It is extremely rare to induce this rhythm in a patient who has not had ventricular tachyarrhythmias. Nonsustained ventricular tachycardia, repetitive ventricular responses, and pleomorphic ventricular tachycardia and ventricular fibrillation are all nonspecific responses to electrical stimulation and thus are not suitable end points for either the baseline study or serial drug testing. Although an optimal pacing protocol for all subjects does not exist, an adequate test should include pacing with multiple drive rates, at least two (and in some cases, three) extrastimuli, and more than one pacing site in the right ventricle. Isoproterenol infusion and left ventricular pacing may also be necessary in selected patients. During serial drug testing, a drug should not be considered effective if more than 15 repetitive beats are induced unless an extremely aggressive pacing protocol is used. Patients treated with drugs predicted to be effective at electrophysiologic study have a better prognosis than those treated with drugs predicted to be ineffective or those treated with drugs selected empirically.

Percutaneous transluminal angioplasty: the treatment of choice for renovascular hypertension due to fibromuscular dysplasia

Twenty-three renal artery stenoses in 21 hypertensive patients, caused by fibromuscular dysplasia, were treated with percutaneous transluminal angioplasty (PTA). Follow-up over a period of 1 to 30 months, including angiography, renal vein renin assay, and radionuclide flow studies, was performed in 8 patients, each with one stenosis. Dilatation was initially successful in all cases and was successfully repeated in 1 case. The mean systolic pressure decreased by 61.81 mm Hg and the mean diastolic pressure by 36.28 mm Hg in response to treatment. Thirteen patients were cured, 8 were felt to have better control of blood pressure on medication, and there was no failures. This study demonstrates that PTA is a clinically effective method of treating renovascular hypertension due to fibromuscular dysplasia.

Cellular electrophysiological marker of irreversible ischemic myocardial injury

Glass microelectrode studies on posterior papillary muscle (PPM) slice preparations from 20 pentobarbital-anesthetized dogs (15 subjected to prior circumflex coronary artery ligation, 5 to sham ligation) have resulted in the definition of an electrophysiological marker of irreversible ischemic injury, namely, findings of areas composed of cells unable to generate a significant resting potential (less than -25) mV), designated "electrically inactive areas." Electrically inactive areas were essentially confined to PPM from dogs with circumflex coronary ligation; the incidence and distribution of the areas was related to duration of ischemia. Correlative phase- and light-microscopic studies demonstrated close correspondence between such areas and morphological evidence of irreversible ischemic injury. Analysis of frequency and distribution of electrically inactive areas permits quantitative assessment of the extent and spatial distribution of irreversible injury. This method has been used to quantitate injury in PPM from dogs that had been subjected to ligation for varying time periods. The potential utility of this method for evaluation of interventions designed to protect against ischemic injury and to assess electrical properties of surviving cells is considered.

Detection of receptors for immunoglobulin on human placenta by EA rosette formation

Direct evidence for the existence of Fc receptors on the surface of first trimester and term human placental cells has been obtained by the use of an antibody-coated red cell (EA) rosette assay. The modification of a Ficoll density gradient separation procedure for placental cell population in conjunction with dye uptake experiments, cytocentrifuge preparations and cytological analysis has enabled an identification of the rosette-forming cells in the mature placenta as predominantly, if not entirely, syncytiotrophoblastic. The significance of these findings, together with those demonstrating the presence of cell-surface Fc receptors on the chorionic membrane, are considered in relation to the transmission of immunoglobulin from mother to foetus and to the protection of the foetus as an intra-uterine allograft.

Detection of alloantigens during preimplantation development and early trophoblast differentiation in the mouse by immunoperoxidase labeling

An immunoperoxidase-labeling technique allowing visualization of antibody binding to the cell surface at the electron microscopical level has been employed an an analysis of H-2 and non-H-2 alloantigen expression on the early mouse embryo. The presence of non-H-2 antigenic determinants has been confirmed on eight-cell, morula, and blastocyst stages of development. Contrary to previous reports, however, low levels of H-2 antigen have also been detected on the blastocyst. This is the earliest stage at which H-2 has been shown to be expressed on the fertilized mouse egg and may reflect the greater resolution of the immunoperoxidase technique. Using two different models to study the critical peri-implantation stages, those of experimentally induced blastocyst activation and blastocyst outgrowth in vitro, it has been demonstrated that antigen loss occurs on the trophectoderm at the time of implantation, and that this is not necessarily dependent upon maternal influence. It is suggested that the loss may be an important factor in the prevention of maternal immune rejection during the establishment of the fetal allograft. The two major components of the early postimplantation conceptus display a striking differential in antigenic status. The embryonic sac shows a high degree of peroxidase labeling, while the ectoplacental cone trophoblast is unlabeled. These findings add support to the concept of antigenic neutrality of the early trophoblast and its role in the maintenance of a normal fetomaternal immunological equilibrium.

Antiarrhythmic potency of N-acetylprocainamide

Compared to procainamide in an animal arrhythmic model, the antiarrhythmic potency of the N-acetylated metabolite of procainamide (NAPA) was 92% with respect to dose and 70% with respect to plasma level. The antiarrhythmic effects of combinations of the drugs were additive. Measurements of procainamide and NAPA plasma levels needed to suppress ventricular extrasystoles suggested that both compounds are nearly equipotent in patients as well. The average plasma level required for arrhythmia control in these patients was equivalent to 5.1 mcg/ml procainamide. Since patients on long-term procainamide therapy have plasma concentrations of NAPA that are usually comparable to, and occasionally greater than, their procainamide levels, dose regiments based on procainamide levels alone need revision to include consideration of the levels of this metabolite.

The relationship between the morphology of rosette-forming cells and their mode of rosette formation

Rats were injected in the footpad with sheep erythrocytes. The proportion of each morphological type of rosette-forming cell in the popliteal lymph node was measured, in vitro, performing the immunocyto-adherence technique at 4° and 37°. Among the different morphological types of rosette-forming cell, which appear after immunization, few plasmacytes form rosettes at 4°.

The number of rosettes formed at 37° was increased by the addition of anti-rat immunoglobulin (Ig) to aliquots of lymph node preparations from rats 7 days after immunization. This increase was accounted for by an increase in the number of rosette-forming plasmacytes and rosette-forming cells intermediate between small blasts and plasmacytes, and was thought to be due to the detection of cells secreting non-haemagglutinating antibody. The enhancing effect of anti-rat Ig at 37° contrasted with its inhibitory effect at 4°. The presence of 10^-3 M puromycin only slightly reduced the number of rosettes as compared with untreated control aliquots, but it prevented or reduced the enhancing effect of anti-rat Ig. The addition of anti-rat Ig to aliquots of lymph node preparations from rats 4 days after immunization reduced the number of rosettes formed as compared with control aliquots. It is considered that plasmacytes lack a surface associated antigen-binding receptor and depend for their rosette-forming ability on the secretion of antibody.

The loss of the immunosuppressive properties of anti-lymphocytic globulin following absorption with immunizing antigen (sheep erythrocytes)

The treatment of Carworth Wistar rats with normal equine IgG or ALG preabsorbed with sheep erythrocytes sensitized the rats to sheep erythrocytes and prevented ALG from suppressing the primary immune response to this antigen.

Studies on immunological paralysis. 3. Recirculation and antibody-neutralizing activity of 14C-labelled type 3 pneumococcal polysaccharide in paralysed mice

Clearance of a paralysing dose of ¹⁴C-labelled type III pneumococcal polysaccharide from the circulation in CBA mice was found to be exponential for about 6 days, but slowed thereafter. A persisting `tail' of free immunogenic ¹⁴C-SIII remained at levels between 0·1–1%, even after 100 days. This was not prevented by active or passive immunization, although the latter promoted early clearance. The mechanism responsible for this heterogeneity of elimination was investigated. Normal clearance of colloidal carbon and a second dose of ¹⁴C-SIII excluded reticuloendothelial blockade. The application of parabiosis followed by separation excluded the presence of a phagocytosis-resistant fraction of ¹⁴C-SIII. Continual leakage of phagocytosed ¹⁴C-SIII into the circulation was implicated by its gradual reappearance after total elimination by anti-SIII, a procedure which could be repeated.

The ability of recirculating ¹⁴C-SIII to continuously neutralize antibody synthesis on a `treadmill' basis was investigated by parabiosis of paralysed to optimally-immunized mice. Serum antibody was eliminated throughout 6 weeks of union. The data implied that serum ¹⁴C-SIII levels rather than tissue depots largely determined antibody neutralization. The contribution of this mechanism to polysaccharide paralysis is discussed.

Extra-hepatic derivation of Kupffer cells during oestrogenic stimulation of parabiosed mice

(CBA × CBA-T6T6)F₁ mice were given 850 r whole body irradiation and “repopulated” with CBA-T6T6 bone marrow and CBA lymph node cells. Macrophages were isolated from the liver 2 weeks later, following stimulation with 5 daily injections of diethylstilboestrol and analysed karyotypically. The majority of dividing cells were donor-derived, and predominantly of bone marrow ancestry. The phagocytic identity of these proliferating cells was established by the association of ingested Thorotrast with metaphases and with cells labelled by ³H-thymidine incorporation.

Similar evidence for extra-hepatic derivation of a substantial number of dividing liver macrophages without prior irradiation was obtained when diethylstilboestrol was administered to CBA and CBA-T6T6 mice separated after 1 week to 5 months of parabiosis. Partner-derived mitoses were found in all animals studied, varying between 4 and 29 per cent. Reciprocal colonisation in the liver was greater when oestrogenic stimulation was applied during parabiosis and near-equilibrium was found after 6 months union. The association of phagocytosed particles with ³H-thymidine labelling or mitoses confirmed the functional identity of these cells.

It is proposed that normal Kupffer cells are not a separate self-replicating population of phagocytes, but rather can be replaced and augmented by haematogenous recruitment of the same precursor in bone marrow as are “free” macrophages.

Studies on immunological paralysis. II. The detection and significance of antibod-forming cells in the spleen during immunological paralysis with type 3 pneumococcal polysaccharide

The immunocytoadherence (rosette) technique has been adapted to study the immune response to varying doses of type III pneumococcal polysaccharide (SIII). Syngeneic erythrocytes coated with SIII were incubated with washed spleen cell suspensions isolated 0·5–39 days after i.v. injection into CBA strain mice of immunogenic (0·5 or 5·0 μg) or paralysing (500 μg) doses of SIII; the immunizing or paralysing effect of these doses of SIII was confirmed by a passive haemagglutination technique. The number of rosette-forming cells per spleen was significantly increased above the background range in twenty-seven out of forty-two, twenty-four out of thirty-seven and forty-one out of forty-six animals injected with 0·5, 5·0 and 500 μg SIII, respectively. Not only was there a greater incidence of `positive' values in the paralysed group, but the response was better maintained than in the immunized groups.

In view of the apparent lack of central inhibition in these experiments, paralysis with SIII was considered to be attributable to the antibody-neutralizing effect of persisting undegraded antigen. It is suggested that the phenomenon of polysaccharide paralysis may be the expression of more than one mechanism.