Hypogammaglobulinemia in pediatric systemic lupus erythematosus.

OBJECTIVE: Systemic lupus erythematosus (SLE) is a systemic autoimmune disease typically associated with elevated serum immunoglobulin G (IgG). Hypogammaglobulinemia in SLE patients has been attributed to immunosuppressive treatment or a transient effect associated with nephrotic syndrome. We retrospectively reviewed pediatric SLE patients from a single institution to identify patients with hypogammaglobulinemia and risk factors for hypogammaglobulinemia. METHODS: A total of 116 pediatric SLE cases from 1997 to 2011 were reviewed and patients with hypogammaglobulinemia (IgG < 500 mg/dl) were identified. The two cohorts were evaluated for association with age, sex, presence of lupus nephritis at SLE diagnosis, disease activity at diagnosis, initial IgG level, and drug treatment. RESULTS: Eighty-six patients were included in our study, with a median age of 15 years and a median follow-up of 39.5 months. Seven percent (six of 86) of patients had hypogammaglobulinemia with a median onset of 27 months (0-72 months) after SLE diagnosis. Significant associations were noted for white race (p value 0.029), male sex (p value 0.009), and the presence of lupus nephritis at SLE diagnosis (p value 0.004). Use of immunosuppressive treatment did not show a statistical association with hypogammaglobulinemia, although two of the patients with hypogammaglobulinemia did receive rituximab. Most patients with hypogammaglobulinemia received intravenous immunoglobulin (IVIG) replacement therapy because of infections and/or concern for infection. CONCLUSION: Measurement of immunoglobulin levels during treatment in SLE could help identify patients with hypogammaglobulinemia who might require more aggressive follow-up to monitor for increased risk of infection and need for IVIG treatment. A prospective study is needed to validate associated risk factors identified in this study.

The use of electroconvulsive therapy in a patient with juvenile systemic lupus erythematosus and catatonia.

Catatonia is a rare manifestation in patients with systemic lupus erythematosus (SLE). As catatonia can be associated with both psychiatric and organic conditions, this could create a diagnostic dilemma once this occurs in SLE patients. The report describes a 15-year-old female with SLE who developed catatonia three days after the diagnosis of SLE was made. Her catatonia was refractory to the treatment with immunosuppressive therapy, which included pulse methylprednisolone, intravenous cyclophosphamide, rituximab, intravenous immunoglobulin (IVIG) and plasmapheresis. Given her persistent catatonia, electroconvulsive therapy (ECT) was initiated three months after the onset of her symptoms. After the third ECT treatment, her mental status dramatically improved and returned nearly to baseline while she was continued on the immunosuppression. This is the first report of a successful ECT therapy in catatonic lupus in children.

Increased mortality in adults with a history of juvenile rheumatoid arthritis: a population-based study.

OBJECTIVE: To assess mortality in a population-based cohort of adults with a history of juvenile rheumatoid arthritis (JRA). METHODS: The Rochester Epidemiology Project database was used to identify all cases of JRA diagnosed among Rochester, Minnesota residents under the age of 16 between January 1, 1960 and December 31, 1993. Fifty-seven patients in this cohort are now adults (ages 18-53 years, mean age 34.3 years), and this subgroup was contacted for a long-term followup study. The average length of followup from the time of diagnosis was 25.6 years. RESULTS: Four deaths occurred in this cohort of 57 adults with a history of JRA. All 4 deceased patients had other autoimmune illnesses and died of complications of these diseases. The observed frequency of 4 deaths was significantly greater (P < 0.0026 by one-sample log-rank test) than the 1 death that would be expected among Minnesota whites of similar age and sex, and corresponds to a mortality rate of 0.27 deaths per 100 years of patient followup compared with an expected mortality rate of 0.068 deaths per 100 years of followup in the general population. CONCLUSION: The results indicate a significant, unexpected increase in mortality in this population-based cohort of adults with a history of JRA in comparison with the rate in the general population. The deaths in this group were all associated with other autoimmune disorders, suggesting that special emphasis should be given to the diagnosis and treatment of other autoimmune diseases, including immunodeficiencies, in JRA patients. The frequency of deaths in this cohort suggests that JRA patients are at substantial risk for mortality, and highlights the need for longitudinal followup and care into adulthood.

Controlling receptor/ligand trafficking: effects of cellular and molecular properties on endosomal sorting.

Receptor-mediated endocytosis is the process by which cells internalize ligands that have specifically interacted with cell surface receptors. Within intracellular endosomal compartments, receptor/ligand complexes can be targeted to lysosomes for degradation, recycled back to the plasma membrane, or sorted separately to these destinations. We have developed a mechanistic mathematical model that can account for the spectrum of experimentally observed endosomal sorting outcomes. The central hypothesis of this model is that receptors may be selectively retained by putative endosomal retention components and that this process may be modulated by receptor occupancy. This hypothesis is supported by the recent discovery of an endosomal retention component involved in targeting epidermal growth factor receptors to lysosomes. In this paper, we use the model to predict how changes in key cellular and molecular parameters alter sorting outcomes. This analysis provides guidance for rationally modulating the sorting process in a variety of biomedical applications, either by the manipulation of cellular parameters or the design of ligand properties.

Intracellular receptor/ligand sorting based on endosomal retention components.

Endocytosed molecules are sorted in endosomes to different cellular destinations (e.g., to lysosomes or to the plasma membrane). Diverse endosomal sorting results have been reported for different ligands and receptors in a variety of cell types, but the general principles governing these sorting outcomes are not well understood. For example, we observed a wide range of sorting outcomes with the epidermal growth factor (EGF)/receptor system in fibroblasts using several members of the EGF family and site-directed ligand and receptor mutants. In this article we describe a mechanistic mathematical model of endosomal sorting based on the hypothesis that receptors may be selectively retained by the endosomal sorting apparatus and that this process may be modulated by receptor occupancy. Our results show that this single mechanism can account for the wide variety of observed sorting outcomes. By providing a conceptual framework for understanding endosomal sorting, this model not only helps interpret our experimental results for the EGF/receptor system, but also provides some insight into the principles governing sorting. For example, the model predicts that the influence of selective endosomal retention of receptor/ligand complexes is seen in deviations of ligand sorting outcomes from pure fluid phase sorting behavior. Furthermore, the model suggests that selective endosomal retention of complexes within endosomes gives rise to three sorting regimes characterized by distinguishable qualitative trends in the dependence of ligand sorting fractions on intracellular ligand concentrations.

Intracellular trafficking of epidermal growth factor family ligands is directly influenced by the pH sensitivity of the receptor/ligand interaction.

Using members of the epidermal growth factor (EGF) family as well as site-directed recombinant human EGF mutants, we investigated how ligand binding properties influence endosomal sorting. Mouse EGF (mEGF), human EGF (hEGF), and transforming growth factor alpha (TGF alpha) bind to the human EGF receptor (EGFR) with similar affinities at pH 7.4. However, the binding properties of these ligands have substantially different pH sensitivities resulting in varying degrees of dissociation from the receptors at lower pH levels characteristic of endosomes. We employed a steady-state sorting assay to determine the fraction of ligand sorted to recycling versus degradation as a function of the number of intracellular ligand molecules in mouse B82 fibroblasts. mEGF, hEGF, and TGF alpha display significantly different steady-state endosomal sorting patterns which correspond to the extent of their dissociation at endosomal pH. Moreover, several recombinant hEGF mutants with differing affinities exhibit altered endosomal sorting compared to hEGF, demonstrating a similar direct relationship between ligand binding properties and endosomal sorting outcomes. Intracellular trafficking of the EGF ligands was also monitored by measuring the observed degradation rate constants. These likewise show marked differences that correlate with the differing pH sensitivities of the ligands' binding properties.

Postendocytic trafficking of epidermal growth factor-receptor complexes is mediated through saturable and specific endosomal interactions.

Intracellular trafficking of the epidermal growth factor receptor (EGF-R) is regulated by receptor occupancy. To investigate this, we developed an assay to study endosomal sorting under steady-state conditions. Using a cell line transfected with EGF-R variants, we found that the fraction of internalized EGF.EGF-R complexes sorted to lysosomes was a function of the number of intracellular complexes and required sequences in the cytoplasmic domain of the receptor. As the number of intracellular occupied wild-type receptors increased from 3 x 10(2) to 2 x 10(5)/cell, the fraction of internalized EGF that was degraded dropped from 70 to 20%. Transforming growth factor-alpha, which dissociates from the EGF-R at endosomal pH, was degraded to a uniform extent of approximately 50% at all intracellular ligand concentrations. EGF internalized by receptors lacking a cytoplasmic domain (c'647) was degraded to an extent of only 5-10% independent of the number of intracellular complexes. Mutant receptors truncated either at residues 1022 or 973 displayed sorting patterns intermediate between wild-type and c'647 receptors. Despite large differences in their internalization rates, the fractional sorting patterns of c'1022 and c'973 receptors were indistinguishable. Receptor tyrosine kinase activity appeared to have a small effect on sorting pattern, but only in the context of full-length receptors. Our results indicate that the default pathway of internalized receptors is rapidly recycling and that lysosomal targeting of occupied EGF-R is due to endosomal retention that is both specific and saturable. In addition, internalization and endosomal retention of EGF-R appear to be mediated by distinct structural elements.

Age-class differences in the pattern of hibernation in yellow-bellied marmots, Marmota flaviventris.

Age-related differences in the patterns of body temperature regulation during hibernation were found in yellow-bellied marmots. The timing of all entrances into and arousals from torpor was determined from continuous records of thermocouples mounted in each animal's nest box. Older marmots spent more time at high body temperatures following periodic arousals from torpor than did juveniles undergoing their first season of hibernation. In addition, older marmots spontaneously terminated their hibernation seasons in the spring, whereas most juveniles continued to hibernate until either they were emaciated from starvation or they were fed. These two patterns of hibernation reflect age- and size-related differences in the degree to which the animals are constrained energetically and the probability that they can successfully reproduce in spring. The patterns also are consistent with age-related differences in the timing of dormancy in nature.

Reconstruction of the probe angular distribution from a series of electron spin resonance spectra of tilted oriented samples.

Model-independent methods for the reconstruction of the nitroxide spin probe angular distribution of labeled oriented biological assemblies from electron spin resonance (ESR) spectra were investigated. We found that accurate probe angular distribution information could be obtained from the simultaneous consideration of a series of ESR spectra originating from a sample at differing tilt angles relative to the Zeeman magnetic field. Using simulated tilt series data sets, we developed a consistent criteria for judging the reliability of the simulated fit to the data as a function of the free spectral parameters and thereby have increased the significance of the model-independent reconstruction of the probe angular distribution derived from the fit. We have also enhanced the angular resolution measurable with the model-independent methodology by increasing the rank of the order parameters that we can reliably deduce from a spectrum. This enhancement allows us to accurately deduce higher resolution features of the spin probe distribution. Finally we investigated the usefulness of fitting the tilt series data in multiple data sets such that tilt series data from many identical sample preparations are fitted simultaneously. This method proved to be useful in rapidly reducing a large amount of data by eliminating any redundant computations in the application of the enhanced model-independent analysis to identical sets of tilt series data. We applied the methodology developed here to ESR spectra from probe labeled muscle fibers to study the orientation of myosin cross-bridges in fibers. This application is described in the accompanying paper.

Myosin cross-bridge orientation in rigor and in the presence of nucleotide studied by electron spin resonance.

The tilt series electron spin resonance (ESR) spectrum from muscle fibers decorated with spin labeled myosin subfragment 1 (S1) was measured from fibers in rigor and in the presence of MgADP. ESR spectra were measured at low amplitude modulation of the static magnetic field to insure that a minimum of spectral lineshape distortion occurs. Ten tilt series ESR data sets were fitted simultaneously by the model-independent methodology described in the accompanying paper (Burghardt, T. P., and A. R. French, 1989. Biophys. J. 56:525-534). By this method the average and standard error in the mean of order parameters for the probe angular distribution were calculated for the two states of the fiber investigated. The average order parameters were used to reconstruct the probe angular distribution in two dimensions, one angular dimension corresponding to a polar angle measured relative to the fiber axis, and the other a torsional angular degree of freedom of the probe. We find that the probe angular distributions for the rigor and MgADP states of the fiber differ such that the rigor distribution is broader and shifted relative to the distribution in the presence of MgADP. The shape of the rigor distribution suggests the presence of two probe orientations, one similar to that in the presence of MgADP, and another at a different orientation. The shape of the distribution in the presence of MgADP suggests that the binding of the nucleotide to the rigor cross-bridge shifts the spin population into a more homogeneous one by causing a cross-bridge rotation.

Allometries of the durations of torpid and euthermic intervals during mammalian hibernation: a test of the theory of metabolic control of the timing of changes in body temperature.

The durations of the intervals of torpor and euthermia during mammalian hibernation were found to be dependent on body mass. These relationships support the concept that the timing of body temperature changes is controlled by some metabolic process. Data were obtained from species spanning nearly three orders of magnitude in size, that were able to hibernate for over six months without food at 5 degrees C. The timing of body temperature changes was determined from the records of copper-constantan thermocouples placed directly underneath each animal. Because all species underwent seasonal changes in their patterns of hibernation, animals were compared in mid-winter when the duration of euthermic intervals was short and relatively constant and when the duration of torpid intervals was at its longest. Large hibernators remained euthermic longer than small hibernators (Fig. 2). This was true among and within species. The duration of euthermic intervals increased with mass at the same rate (mass 0.38) that mass-specific rates of euthermic metabolism decrease, suggesting that hibernators remain at high body temperatures until a fixed amount of metabolism has been completed. These data are consistent with the theory that each interval of euthermia is necessary to restore some metabolic imbalance that developed during the previous bout of torpor. In addition, small species remained torpid for longer intervals than large species (Fig. 3). The absolute differences between different-sized species were large, but, on a proportional basis, they were comparatively slight.(ABSTRACT TRUNCATED AT 250 WORDS)

[Open comparative study between the combination clyndamicin/gentamycin and penicillin/gentamycin in septic abortion]. / Estudio abierto comparativo entre la asociacion clindamicina/gentamicina contra penicilina/gentamicina en aborto septico.

PIP: Septic abortion is not uncommon in countries where abortion is illegal, and antibiotics are second only to uterine evacuation in the treatment of such cases. Although the combination of penicillin and gentamycin has given excellent results, the high incidence of Bacteroides fragilis and other anerobics in septic abortion prompted a comparison of penicillin and gentamycin with clindamycin and gentamycin at the Hospital Santo Tomas in Panama City, Panama, beginning in May 1984. Among 30 febrile patients with diagnoses of septic abortion, 14 were treated with penicillin/gentamycin and 16 with clindamycin/gentamycin. The penicillin group ranged in age from 17-29 with an average age of 21.9, while the clindamycin group ranged from 18-32 years with an average of 24.3. The average gestational ages were 10.2 weeks for the penicillin group and 10.7 for the clindamycin group. The average body temperature of both groups was 38.9 degrees Celsius. 1 patient had a blood pressure of 80/60 without clinical evidence of shock. The average duration of fever was 43 hours in the penicillin group and 40.6 hours in the clindamycin group. The hospital stay ranged from 3-7 days with an average of 5.4 in the penicillin group and from 3-6 days with an average of 4.2 in the clindamycin group. Patients recovered rapidly after uterine curettage and initiation of antibiotic therapy. Bacteremia was not detected in any patient. Tolerance to the drugs was similar in both groups.^ieng

Effects of temperature on the duration of arousal episodes during hibernation.

The length of time that the ground squirrels Spermophilus beldingi and S. lateralis remained at high body temperatures following periodic arousals from hibernation increased as environmental temperature increased over the range of 5-20 degree C. This trend was evident in comparisons among different animals that hibernated at different temperatures and in individuals that hibernated at different temperatures in successive years. At any one temperature, the duration of these euthermic intervals in S. beldingi was correlated with body size. Large adult males remained at high body temperatures longer than adult females, which in turn remained euthermic longer than small juveniles. In addition, these squirrels spent less time at high body temperatures following bouts of torpor that were interrupted prematurely by environmental disturbances. These results are consistent with an amplify the theory that arousals are initiated by, and necessary for the elimination of, some chemical imbalance, which develops while hibernators metabolize at low body temperatures.