Development of ELIP to Assess Physical Literacy for Emerging Adults: A Methodological and Epistemological Challenge

Purpose: Following increased interest in physical literacy (PL), development of appropriate tools for assessment has become an important next step for its operationalization. To forward the development of such tools, the objective of this study was to build the foundations of the Évaluation de la Littératie Physique (ELIP), designed to help reduce existing tensions in approaches to PL assessment that may be resulting in a low uptake into applied settings. Methods: We followed two steps: (1) the development of the first version of ELIP by deploying a Delphi method (n = 30); and (2) the modification of items through cognitive interviews with emerging adults (n = 32). Results: The expert consensus highlighted four dimensions of PL to be assessed-physical; affective; cognitive; and social-with new perspectives, including a preference for broad motor tests over fitness. Conclusion: Results offer new insights into the assessment of emerging adults' PL, but ELIP still requires further work concerning validity, reliability, and sensitivity.

Severe COVID-19 Is Characterized by an Impaired Type I Interferon Response and Elevated Levels of Arginase Producing Granulocytic Myeloid Derived Suppressor Cells

COVID-19 ranges from asymptomatic in 35% of cases to severe in 20% of patients. Differences in the type and degree of inflammation appear to determine the severity of the disease. Recent reports show an increase in circulating monocytic-myeloid-derived suppressor cells (M-MDSC) in severe COVID 19 that deplete arginine but are not associated with respiratory complications. Our data shows that differences in the type, function and transcriptome of granulocytic-MDSC (G-MDSC) may in part explain the severity COVID-19, in particular the association with pulmonary complications. Large infiltrates by Arginase 1+ G-MDSC (Arg+G-MDSC), expressing NOX-1 and NOX-2 (important for production of reactive oxygen species) were found in the lungs of patients who died from COVID-19 complications. Increased circulating Arg+G-MDSC depleted arginine, which impaired T cell receptor and endothelial cell function. Transcriptomic signatures of G-MDSC from patients with different stages of COVID-19, revealed that asymptomatic patients had increased expression of pathways and genes associated with type I interferon (IFN), while patients with severe COVID-19 had increased expression of genes associated with arginase production, and granulocyte degranulation and function. These results suggest that asymptomatic patients develop a protective type I IFN response, while patients with severe COVID-19 have an increased inflammatory response that depletes arginine, impairs T cell and endothelial cell function, and causes extensive pulmonary damage. Therefore, inhibition of arginase-1 and/or replenishment of arginine may be important in preventing/treating severe COVID-19.

Transcriptome and Functions of Granulocytic Myeloid-Derived Suppressor Cells Determine their Association with Disease Severity of COVID-19

COVID-19 ranges from asymptomatic in 35% of cases to severe in 20% of patients. Differences in the type and degree of inflammation appear to determine the severity of the disease. Recent reports show an increase in circulating monocytic-myeloid-derived suppressor cells (M-MDSC) in severe COVID 19, that deplete arginine but are not associated with respiratory complications. Our data shows that differences in the type, function and transcriptome of Granulocytic-MDSC (G-MDSC) may in part explain the severity COVID-19, in particular the association with pulmonary complications. Large infiltrates by Arginase 1 ⁺ G-MDSC (Arg ⁺ G-MDSC), expressing NOX-1 and NOX-2 (important for production of reactive oxygen species) were found in the lungs of patients who died from COVID-19 complications. Increased circulating Arg ⁺ G-MDSC depleted arginine, which impaired T cell receptor and endothelial cell function. Transcriptomic signatures of G-MDSC from patients with different stages of COVID-19, revealed that asymptomatic patients had increased expression of pathways and genes associated with type I interferon (IFN), while patients with severe COVID-19 had increased expression of genes associated with arginase production, and granulocyte degranulation and function. These results suggest that asymptomatic patients develop a protective type I IFN response, while patients with severe COVID-19 have an increased inflammatory response that depletes arginine, impairs T cell and endothelial cell function, and causes extensive pulmonary damage. Therefore, inhibition of arginase-1 and/or replenishment of arginine may be important in preventing/treating severe COVID-19.

Presence of antibody-dependent cellular cytotoxicity (ADCC) against SARS-CoV-2 in COVID-19 plasma

Background

Neutralizing-antibody (nAb) is the major focus of most ongoing COVID-19 vaccine trials. However, nAb response against SARS-CoV-2, when present, decays rapidly. Given the myriad roles of antibodies in immune responses, it is possible that antibodies could also mediate protection against SARS-CoV-2 via effector mechanisms such as antibody-dependent cellular cytotoxicity (ADCC), which we sought to explore here.

Methods

Plasma of 3 uninfected controls and 20 subjects exposed to, or recovering from, SARS-CoV-2 infection were collected from U.S. and sub-Saharan Africa. Immunofluorescence assay was used to detect the presence of SARS-CoV-2 specific IgG antibodies in the plasma samples. SARS-CoV-2 specific neutralizing capability of these plasmas was assessed with SARS-CoV-2 spike pseudotyped virus. ADCC activity was assessed with a calcein release assay.

Results

SARS-CoV-2 specific IgG antibodies were detected in all COVID-19 subjects studied. All but three COVID-19 subjects contained nAb at high potency (>80% neutralization). Plasma from 19/20 of COVID-19 subjects also demonstrated strong ADCC activity against SARS-CoV-2 spike glycoprotein, including two individuals without nAb against SARS-CoV-2.

Conclusion

Both neutralizing and non-neutralizing COVID-19 plasmas can mediate ADCC. Our findings argue that evaluation of potential vaccines against SARS-CoV-2 should include investigation of the magnitude and durability of ADCC, in addition to nAb.

Split phosphorus fertiliser applications as a strategy to reduce incidental phosphorus losses in surface runoff

Organic soils have low sorption capacities for phosphorus (P), and may pose a risk of P loss to water if P applications to these soils coincide with runoff events. Little is known about the magnitude of exports of P in overland flow following application of P fertiliser onto these soils, or on the influence of the frequency on P losses and persistence. The number of P fertiliser applications was surveyed across 39 commercial farms to assess current practice and inform the design of a rainfall runoff experiment to evaluate the effect of frequency of P applications on losses and persistence across time. Superphosphate (16% P) was applied in single (equivalent to 30 and 55 kg P ha^-1 applied at day 0) and split (equivalent to 15 and 27.5 kg P ha^-1 applied in two doses at days 0 and 55) applications to an organic soil inclined at a slope of 6% in a rainfall simulator experiment. The surface runoff of dissolved reactive phosphorus (DRP) was measured in controlled 30-min rainfall simulations conducted intermittently over an 85-day period. The DRP losses in surface runoff after the first rainfall event were 44.6 and 97.8 mg L^-1 for single applications of 30 and 55 kg ha^-1, respectively, and 13.3 and 21.8 mg L^-1 for the same rates split in two doses, indicating that single P applications had disproportionately bigger impacts on losses than split applications. This supports the idea that frequent, but smaller, P applications can minimise the impact of fertilisation on waters. Dissolved reactive P concentrations remained significantly higher than those from the control samples until the end the experiment for almost all the P treatments, highlighting the long-lasting effects of added P and the elevated risk of P losses on organic soils. For climates with frequent rainfall events, which are likely to coincide with fertiliser applications, smaller but more frequent P applications can reduce the risk of P transfer as opposed to one single application.

The problem of temporal scale in optimization: three contrasting views of hummingbird visits to flowers

We modeled hummingbird visits to flowers on three temporal scales: tongue loading, the licking cycle, and entire visits to flowers. The nectar concentration that maximizes energy intake rate increases with the temporal scale of integration; therefore, optimal nectar concentration for nectar volumes that require many licks is higher than predicted by models that assume single licks. Since birds must position, insert, and withdraw their bills in addition to licking nectar, the optimum at the scale of flower visits is even higher. This "overhead time cost" of handling flower morphology, for most nontraplining hummingbirds under most natural conditions, is as great as or greater than the cost of handling nectar. For these birds, the potential variation in the fine-scale factors that determine nectar intake rate during licking has little effect on flower-handling time and therefore is unlikely to determine optimal nectar concentration or the profitability of visiting flowers. The conclusion that energy intake rate and optimal nectar concentration are sensitive to temporal scale of integration applies at all scales in hummingbird foraging systems, and we suggest that it also generalizes across systems.

Risk classification at the time of diagnosis differentially affects the level of residual disease in children with B-precursor acute lymphoblastic leukemia after completion of therapy

We have previously reported that children with B-precursor acute lymphoblastic leukemia (ALL) who remained in remission after successfully completing therapy had leukemia cells detectable by polymerase chain reaction (PCR) (N Engl J Med 1997;336(5):317-23). These patients were treated by an institutional protocol (P89-04) that lacked the post-remission intensification features of the contemporary Berlin-Frankfurt-Münster (BFM) based ALL protocols. In this report, we compared residual leukemia levels for patients on the P89-04 (n=15) and BFM-based Children's Cancer Group (CCG) studies (n=23) and for patients stratified according to risk group. Our goal was to establish which risk factors correlated with level of residual disease. Patients enrolled on the CCG protocols had lower levels of residual disease after completion of therapy than the P89-04 patients (P<0.019). Patients with high-risk disease also had lower levels of residual disease than patients with low risk disease (P<0.0001). Three-way analysis including time off treatment, risk group determined by features at presentation, and treatment protocol showed that risk group was the only significant independent variable (P<0.001).

Molecular monitoring of cerebrospinal fluid can predict clinical relapse in acute lymphoblastic leukemia with eosinophilia

In a patient with precursor B-cell acute lymphoblastic leukemia (ALL) associated with eosinophilia that completely responded to induction chemotherapy, we assayed serial remission cerebrospinal fluid and bone marrow specimens for minimal residual disease using a quantitative polymerase chain reaction assay to assess for clone-specific immunoglobulin heavy-chain gene cluster (IGH) gene rearrangement. Cerebrospinal fluid eosinophilia and minimal residual disease were detected on day 406, preceding the morphologic diagnosis of central nervous system relapse on day 578. By day 841, the bone marrow had 35% blasts. Despite aggressive therapy, including unrelated umbilical cord blood transplantation, the patient developed testicular and bone marrow relapses and died of disease. We conclude that increasing levels of minimal residual disease in cerebrospinal fluid can predict recurrence of ALL prior to clinical and morphologic relapse. Furthermore, we demonstrate a novel translocation in this tumor, the t(5;9)(q31;p24), that possibly led to fusion of the interleukin-3 (IL3) (5q31) and JAK2 (9p24) genes and may explain the concomitant appearance of eosinophilia and ALL.

Residual leukaemia after bone marrow transplant in children with acute lymphoblastic leukaemia after first haematological relapse or with poor initial presenting features

Relapse is the major obstacle to cure for children with acute lymphoblastic leukaemia (ALL) after allogeneic bone marrow transplant (BMT). Development of salvage therapy for post-transplant relapse could be expedited by understanding the post-transplant behaviour of microscopically undetectable leukaemia and the ability to predict impending relapse. We have used a quantitative polymerase chain reaction method (sensitivity of 5.0 x 10-6) to measure residual leukaemia before the conditioning regimen, and at five time-points after transplantation. In total, 18 patients with ALL transplanted in first or second remission were studied for 1 year: For the first year post BMT, 12 remained in remission, four had haematological relapses, one had a cutaneous relapse, and one died of severe graft-versus-host disease. The post-engraftment levels of the leukaemia-specific immunoglobulin heavy (IgH) chain gene rearrangement for patients with haematological relapses were significantly different from those who remained in remission. The levels for the patients who remained in remission decreased with time, although there were occasional increases consistent with the known standard deviation of the measurement assay. In contrast, all clinical relapses were preceded by a rapid increase in levels. Both the rate of this increase and its timing were variable. These results suggest that residual leukaemia measurements can be used to direct post-transplant interventions and measure their effects.

Minocycline-ethylenediaminetetraacetate lock solution for the prevention of implantable port infections in children with cancer

In this prospective cohort study, minocycline-ethylenediaminetetraacetate (M-EDTA) was used as a lock solution in indwelling ports inserted in 14 children with cancer. No port infections, thrombotic events, or other adverse events were observed, compared with 10 port infections that occurred in 48 control patients whose ports were flushed with heparin. M-EDTA is a promising lock solution in long-term catheters.

Rapidly inactivating and non-inactivating calcium-activated potassium currents in frog saccular hair cells

1. Using a semi-intact epithelial preparation we examined the Ca(2+)-activated K(+) (K(Ca)) currents of frog (Rana pipiens) saccular hair cells. After blocking voltage-dependent K(+) (K(V)) currents with 4-aminopyridine (4-AP) an outward current containing inactivating (I(transient)) and non-inactivating (I(steady)) components remained. 2. The contribution of each varied greatly from cell to cell, with I(transient) contributing from 14 to 90 % of the total outward current. Inactivation of I(transient) was rapid (tau approximately 2-3 ms) and occurred within the physiological range of membrane potentials (V(1/2) = -63 mV). Recovery from inactivation was also rapid (tau approximately 10 ms). 3. Suppression of both I(transient) and I(steady) by depolarizations that approached the Ca(2+) equilibrium potential and by treatments that blocked Ca(2+) influx (application Ca(2+)-free saline or Cd(2+)), suggest both are Ca(2+) dependent. Both were blocked by iberiotoxin, a specific blocker of large-conductance K(Ca) channels (BK), but not by apamin, a specific blocker of small-conductance K(Ca) channels. 4. Ensemble-variance analysis showed that I(transient) and I(steady) flow through two distinct populations of channels, both of which have a large single-channel conductance (~100 pS in non-symmetrical conditions). Together, these data indicate that both I(transient) and I(steady) are carried through BK channels, one of which undergoes rapid inactivation while the other does not. 5. Inactivation of I(transient) could be removed by extracellular papain and could later be restored by intracellular application of the 'ball' domain of the auxiliary subunit (beta2) thought to mediate BK channel inactivation in rat chromaffin cells. We hypothesize that I(transient) results from the association of a similar beta subunit with some of the BK channels and that papain removes inactivation by cleaving extracellular sites required for this association.

Sodium channel distribution on uninnervated and innervated embryonic skeletal myotubes

Acetylcholine receptor (AChR) and sodium (Na(+)) channel distributions within the membrane of mature vertebrate skeletal muscle fibers maximize the probability of successful neuromuscular transmission and subsequent action potential propagation. AChRs have been studied intensively as a model for understanding the development and regulation of ion channel distribution within the postsynaptic membrane. Na(+) channel distributions have received less attention, although there is evidence that the temporal accumulation of Na(+) channels at developing neuromuscular junctions (NMJs) may differ between species. Even less is known about the development of extrajunctional Na(+) channel distributions. To further our understanding of Na(+) channel distributions within junctional and extrajunctional membranes, we used a novel voltage-clamp method and fluorescent probes to map Na(+) channels on embryonic chick muscle fibers as they developed in vitro and in vivo. Na(+) current densities on uninnervated myotubes were approximately one-tenth the density found within extrajunctional regions of mature fibers, and showed several-fold variations that could not be explained by a random scattering of single channels. Regions of high current density were not correlated with cellular landmarks such as AChR clusters or myonuclei. Under coculture conditions, AChRs rapidly concentrated at developing synapses, while Na(+) channels did not show a significant increase over the 7 day coculture period. In vivo investigations supported a significant temporal separation between Na(+) channel and AChR aggregation at the developing NMJ. These data suggest that extrajunctional Na(+) channels cluster together in a neuronally independent manner and concentrate at the developing avian NMJ much later than AChRs.

Experience with 2-chlorodeoxyadenosine in previously untreated children with newly diagnosed acute myeloid leukemia and myelodysplastic diseases

PURPOSE

To develop more effective chemotherapy regimens for childhood acute myelogenous leukemia (AML).

PATIENTS AND METHODS

Between June 1991 and December 1996, we administered the nucleoside analog 2-chlorodeoxyadenosine (2-CDA) to 73 children with primary AML and 20 children with secondary AML or myelodysplastic syndrome (MDS). Patients received one or two 5-day courses of 2-CDA (8.9 mg/m(2)/d) given by continuous infusion. All patients then received one to three courses of daunomycin, cytarabine, and etoposide (DAV) remission induction therapy.

RESULTS

Seventy-two patients with primary AML were assessable for response. Their rate of complete remission (CR) was 24% after one course of 2-CDA, 40% after two courses of 2-CDA, and 78% after DAV therapy. Of the 57 patients who entered CR, 11 subsequently underwent allogeneic bone marrow transplantation (BMT), and 40 underwent autologous BMT. Twenty-nine patients remain in continuous CR after BMT. Two patients remain in CR after chemotherapy only. The 5-year event-free survival (EFS) estimate was 40% (SE = 0.080%). Patients with French-American-British (FAB) M5 AML had a higher rate of CR after treatment with 2-CDA (45% after one course and 70.6% after two courses) than did others (P =.002). In contrast, no patient with FAB M7 AML (n = 10) entered CR after treatment with 2-CDA. Similarly, no patient with primary MDS (n = 6) responded to 2-CDA. Seven patients with secondary AML or MDS (n = 14) had a partial response to one course of 2-CDA.

CONCLUSION

This agent was well tolerated, and its toxicity was acceptable. Future trials should examine the effectiveness of 2-CDA given in combination with other agents effective against AML.

Calretinin modifies presynaptic calcium signaling in frog saccular hair cells

To determine whether the concentrations of calcium-binding proteins present in some neurons and sensory cells are sufficient to influence presynaptic calcium signaling, we studied the predominant calcium-binding protein in a class of sensory hair cells in the frog ear. Based on antibody affinity and molecular weight, we identified this protein as calretinin. We measured its cytoplasmic concentration to be approximately 1.2 mM, sufficient to bind approximately 6 mM Ca2+. Calcium signaling was altered when the diffusible cytoplasmic components were replaced by an intracellular solution lacking any fast calcium buffer, and was restored by the addition of 1.2 mM exogenous calretinin to the intracellular solution. We conclude that calretinin, when present at millimolar concentration, can serve as a diffusionally mobile calcium buffer/transporter capable of regulating calcium signaling over nanometer distances at presynaptic sites.

Outpatient treatment of fever and neutropenia for low risk pediatric cancer patients

BACKGROUND

Fever and neutropenia (F&N) is a common complication of cancer chemotherapy. It is conveniently managed by hospitalization and empiric administration of parenteral antibiotics. This study attempted to determine whether pediatric cancer patients with F&N identified as low risk for morbidity and mortality by clinical criteria at the time of presentation could be treated safely as outpatients.

METHODS

Seventy-three episodes of F&N in 41 patients were studied prospectively over 2 years. Eligibility criteria included age > or =2 years, reliable caretakers, and residence within 1 hour of the hospital. Exclusion criteria included hemodynamic instability, dehydration, severe mucositis, pneumonia, leukemia/lymphoma induction therapy, bone marrow transplantation, or other serious comorbidity. Patients were evaluated, received a single dose of intravenous ceftazidime, and were observed for 3-16 hours. They were randomized to receive either oral ciprofloxacin or intravenous ceftazidime as outpatients. Patients were seen daily until they had been afebrile for at least 48 hours and had a rising absolute phagocyte count of >500 cells/microL.

RESULTS

Sixty-three of 73 episodes (86%) were successfully managed on an outpatient basis. For 31 of 33 episodes in the ceftazidime arm, the patients remained outpatients, compared with 32 of 40 in the ciprofloxacin arm; this difference was not statistically significant. On average, patients remained febrile for 2.7 days and were treated for 4.7 days. Seventy-seven percent of episodes required no modification of initial antibiotic therapy. Of the 10 patients who were hospitalized, 4 had prolonged fever and 3 had emesis. Protracted neutropenia was associated with the need for hospitalization. There were no deaths, intensive care unit transfers, or serious complications.

CONCLUSIONS

Carefully selected low risk children with fever and neutropenia can be treated safely as outpatients. Close daily medical scrutiny is required.

Economic and resource utilization analysis of outpatient management of fever and neutropenia in low-risk pediatric patients with cancer

PURPOSE

To measure resource allocation in outpatient management of fever and neutropenia in low-risk pediatric patients with cancer and its impact on their families.

PATIENTS AND METHODS

A prospective clinical trial was conducted. Eligible patients received a single dose of intravenous (IV) antibiotics and were observed for several hours in clinic. Patients were randomly assigned to continue either IV or oral antibiotics and were seen daily as outpatients. Charges were calculated based on the number of resources used and Medicare/Medicaid reimbursement schedules. A questionnaire was used to measure the impact of outpatient treatment on the family.

RESULTS

Seventy-three episodes of fever and neutropenia were studied. The median duration of treatment was 4 days. Eighty-six percent of the episodes were managed without hospitalization. The median calculated charge was $1840. The median calculated charge for patients receiving oral antibiotics was $1544 and was significantly less than the $2039 median charge for outpatients treated with IV antibiotics. The estimated charge for comparable inpatient treatment was $4503. Nearly all families preferred outpatient care, and few reported a loss of work hours or increased child care expenses.

CONCLUSIONS

Outpatient treatment of low-risk episodes of fever and neutropenia is substantially less costly than inpatient care and is preferred by most families.

Synaptic vesicle populations in saccular hair cells reconstructed by electron tomography

We used electron tomography to map the three-dimensional architecture of the ribbon-class afferent synapses in frog saccular hair cells. The synaptic body (SB) at each synapse was nearly spherical (468 +/- 65 nm diameter; mean +/- SD) and was covered by a monolayer of synaptic vesicles (34.3 nm diameter; 8.8% coefficient of variation), many of them tethered to it by approximately 20-nm-long filaments, at an average density of 55% of close-packed (376 +/- 133 vesicles per SB). These vesicles could support approximately 900 msec of exocytosis at the reported maximal rate, which the cells can sustain for at least 2 sec, suggesting that replenishment of vesicles on the SB is not rate limiting. Consistent with this interpretation, prolonged K+ depolarization did not deplete vesicles on the SB. The monolayer of SB-associated vesicles remained after cell lysis in the presence of 4 mM Ca2+, indicating that the association is tight and Ca2+-resistant. The space between the SB and the plasma membrane contained numerous vesicles, many of which ( approximately 32 per synapse) were in contact with the plasma membrane. This number of docked vesicles could support maximal exocytosis for at most approximately 70 msec. Additional docked vesicles were seen within a few hundred nanometers of the synapse and occasionally at greater distances. The presence of omega profiles on the plasma membrane around active zones, in the same locations as coated pits and coated vesicles labeled with an extracellular marker, suggests that local membrane recycling may contribute to the three- to 14-fold greater abundance of vesicles in the cytoplasm (not associated with the SB) near synapses than in nonsynaptic regions.

A novel voltage clamp technique for mapping ionic currents from cultured skeletal myotubes

The biophysical properties and cellular distribution of ion channels largely determine the input/output relationships of electrically excitable cells. A variety of patch pipette voltage clamp techniques are available to characterize ionic currents. However, when used by themselves, such techniques are not well suited to the task of mapping low-density channel distributions. We describe here a new voltage clamp method (the whole cell loose patch (WCLP) method) that combines whole-cell recording through a tight-seal pipette with focal extracellular stimulation through a loose-seal pipette. By moving the stimulation pipette across the cell surface and using a stationary whole-cell pipette to record the evoked patch currents, this method should be suitable for mapping channel distributions, even on large cells possessing low channel densities. When we applied this method to the study of currents in cultured chick myotubes, we found that the cell cable properties and the series resistance of the recording pipette caused significant filtering of the membrane currents, and that the filter characteristics depended in part upon the distance between the stimulating and recording pipettes. We describe here how we determined the filter impulse response for each loose-seal pipette placement and subsequently recovered accurate estimates of patch membrane current through deconvolution.

Electrical properties of frog saccular hair cells: distortion by enzymatic dissociation

Although it is widely accepted that the electrical resonance seen in many types of auditory and vestibular hair cells contributes to frequency selectivity in these sensory systems, unexplained discrepancies in the frequency (f) and sharpness (Q) of tuning have raised serious questions. For example, enzymatically dissociated hair cells from bullfrog (Rana catesbeiana) sacculus resonate at frequencies well above the range of auditory and seismic stimuli to which the sacculus is most responsive. Such disparities, in addition to others, have led to the proposal that electrical resonance alone cannot account for frequency tuning. Using grassfrog (Rana pipiens) saccular hair cells, we show that the reported discrepancies in f and Q in this organ can be explained by the deleterious effects of enzyme (papain) exposure during cell dissociation. In patch-clamp studies of hair cells in a semi-intact epithelial preparation, we observed a variety of voltage behaviors with frequencies of 35-75 Hz. This range is well below the range of resonant frequencies observed in enzymatically dissociated hair cells and more in tune with the frequency range of natural stimuli to which the sacculus is maximally responsive. The sharpness of tuning also agreed with previous studies using natural stimuli. In contrast to results from enzymatically dissociated hair cells, both a calcium-activated K+ (KCa) current and a voltage-dependent K+ (KV) current contributed to the oscillatory responses of hair cells in the semi-intact preparation. The properties of the KCa and the Ca2+ current were altered by enzymatic dissociation. KV and a small-conductance calcium-activated K+ current were apparently eliminated.

Bone marrow transplantation in Shwachman-Diamond syndrome: report of two cases and review of the literature

Patients with Shwachman-Diamond syndrome (SDS) have an increased frequency of myelodysplasia and leukemic transformation. We described two patients who received allogeneic stem cell transplantation and developed multiple complications, including seizure, hyperglycemia and renal tubular acidosis. A review of the literature showed that patients with SDS appeared to have an increased incidence of various transplant-associated problems. These patients frequently have underlying organ dysfunction and should be managed with extreme caution when treated with allogeneic stem cell transplantation.

Systemic hemophagocytosis masking the diagnosis of large cell non-Hodgkin lymphoma

An 11-year-old female presented with clinical features suggestive of malignant histiocytosis: fever, weight loss, subcutaneous nodules, pulmonary infiltrates, adenopathy, and hepato-splenomegaly. On biopsy, lymph node and bone marrow demonstrated necrosis and extensive hemophagocytosis with no definitive evidence of malignancy: the subcutaneous nodules, however, demonstrated large-cell non-Hodgkin lymphoma. This clinicopathologic picture has been reported in adults, but not in children. Although serum G-CSF, M-CSF, and TNF levels were not elevated in this child, it is possible that other cytokines induced either directly or indirectly by the subcutaneous lymphoma resulted in hemophagocytosis.

Measurement of residual leukemia during remission in childhood acute lymphoblastic leukemia

BACKGROUND

Complete remission of B-precursor acute lymphoblastic leukemia (ALL) has traditionally been defined as the near absence of lymphoblasts in a light-microscopical examination of stained bone marrow smears, but a patient in remission may still harbor up to 10(10) leukemia cells. We investigated whether there is a relation between the outcome of treatment and submicroscopic evidence of residual disease.

METHODS

We conducted a prospective study of patients during a first clinical remission using a quantitative polymerase-chain-reaction (PCR) assay capable of detecting 1 viable leukemia cell among 200,000 normal marrow mononuclear cells and a clonogenic blast-colony assay. Bone marrow specimens from 24 children were sequentially evaluated during a five-year period, and the results were compared with the clinical outcome.

RESULTS

Seven patients relapsed and 17 remained in remission 2 to 35 months after the completion of treatment. The levels of residual leukemia-cell DNA in the two groups were significantly different (P<0.001; 95 percent confidence interval for the difference in the mean log-transformed ratio of leukemia-cell DNA to normal bone marrow-cell DNA, 0.38 to 1.28). Autoregression analyses identified trends for individual patients that were associated with relapse. Despite continued remission in 17 patients, evidence of residual leukemia was detected by PCR in 15 and by both PCR and blast-colony assays in 7.

CONCLUSIONS

Molecular signs of residual leukemia can persist up to 35 months after the cessation of chemotherapy in children with ALL in remission. This suggests that eradication of all leukemia cells may not be a prerequisite for cure.

Geographic Distribution of Endangered Species in the United States

Geographic distribution data for endangered species in the United States were used to locate "hot spots" of threatened biodiversity. The hot spots for different species groups rarely overlap, except where anthropogenic activities reduce natural habitat in centers of endemism. Conserving endangered plant species maximizes the incidental protection of all other species groups. The presence of endangered birds and herptiles, however, provides a more sensitive indication of overall endangered biodiversity within any region. The amount of land that needs to be managed to protect currently endangered and threatened species in the United States is a relatively small proportion of the land mass.

The clinical significance of residual disease in childhood acute lymphoblastic leukemia as detected by polymerase chain reaction amplification by antigen-receptor gene sequences

The polymerase chain reaction (PCR) has been applied to detect occult leukemia cells in children with acute lymphoblastic leukemia who are otherwise considered in complete remission by traditional morphological examination of bone marrow specimens. To determine whether PCR provides unique prognostic information of use for the clinical investigator, we reviewed the 20 clinical studies published to date. From this review, it is evident that discrepancies exist for the detection of residual disease for patients who remain in complete remission and for those who relapse. However, because of the fundamentally different approaches used to apply the PCR method to each of these studies, an entirely different interpretation can be reached when critical technical factors are considered. The combined data from the various studies suggest that a consistent pattern for residual disease disappearance over many months exists for patients who remain in extended complete remission and a pattern of residual disease persistence and reappearance preceding clinical findings exists for the majority of those who ultimately relapse in the bone marrow.

Detection of minimal residual disease in all: biology, methods, and applications

The PCR technique appears to be the most sensitive method for detecting residual disease in ALL and can be applied to a high percentage of cases by amplifying sequences of the antigen-receptor genes. The PCR studies to date suggest that this sensitive technique can detect residual disease in virtually all patients during the first year of treatment. The residual disease becomes undetectable in the majority of patients by the end of treatment; however, a subset of patients remain PCR positive at a time when therapy is electively discontinued. The development of a highly accurate quantitative PCR technique may allow the possibility of distinguishing the patterns of residual disease for patients who will be cured by treatment from those who relapse. If such a pattern can be discerned, then an immediate benefit for PCR monitoring will be that clinicians will have the opportunity to test whether treating patients at the time of 'molecular relapse' will help to improve the cure rate for this disease. The PCR studies of remission marrows at the end of treatment raise a number of questions about the biology of disease persistence in patients who remain in extended 'remission.' A commitment to obtaining and analyzing bone marrow specimens in patients who have completed therapy is necessary to discern whether novel strategies, such as immunomodulatory manipulations, are needed to control or eradicated residual disease in patients who have completed planned chemotherapy. Thus, the long-term benefit of residual disease monitoring by PCR may be a better understanding of the biology and definition of 'cure' in ALL.

Monitoring residual disease in acute lymphoblastic leukemia: therapeutic implications

The polymerase chain reaction (PCR) has been applied to detect occult leukemia (ALL) cells in patients with acute lymphoblastic leukemia who are otherwise considered in complete remission by traditional morphological examination of bone marrow specimens. The combined data from the clinical studies published to date suggest that a consistent pattern for residual disease disappearance over many months exists for patients who remain in complete remission for an extended period of time. Conversely, a pattern of residual disease persistence and reappearance preceding clinical findings exists for the majority of patients who ultimately relapse. The ability to detect residual ALL disease near the end of chemotherapy or after the completion of treatment in some patients who otherwise are deemed likely to be cured of their malignancy raises the possibility that mechanisms other than leukemia cell cytotoxicity are influencing the outcome for this disease.

Accurate quantitation of residual B-precursor acute lymphoblastic leukemia by limiting dilution and a PCR-based detection system: a description of the method and the principles involved

The detection of residual leukemia cells in the bone marrow of patients during morphologic remission has been greatly facilitated by use of the polymerase chain reaction (PCR) to amplify leukemia-specific sequences. While the current PCR strategies for estimating the amount of residual leukemia claim a detection sensitivity of one leukemia cell amongst 10(5) or 10(6) normal cells, a rigorous assessment of the relative error associated with these techniques has not been presented. We have developed a method of estimating the amount of residual leukemia in remission marrows that is analogous to the limiting dilution assays used to determine the frequency of immunocompetent cells in a responder cell population. Using this method we measured the fraction of all-or-none (i.e. positive or negative) reactions of the PCR amplification of the leukemia-specific IgH gene rearrangement in replicate samples of serial dilutions of DNA obtained from diagnostic bone marrow specimens from 15 children with B-precursor acute lymphoblastic leukemia (ALL). A sigmoid curve representing the fraction of positive PCR reactions at a given dilution of leukemia DNA was found to be the best fit to the data. The narrowness of the log-linear region of this curve prevents the direct application of the analysis methodology that has previously been described for limiting dilution assays. However, the residual leukemia burden during morphological remission in these 15 patients and in two additional patients who experienced relapse could be estimated by the described dilution analysis method using the best-fit equation. Furthermore, the data generated for diagnostic, remission and relapse marrow samples exhibited a small interspecimen variation. The results suggest that this method can reliably estimate residual leukemia over a range of five orders of magnitude. Although the PCR reaction appears to be one of the most sensitive methods for detecting residual leukemia, all techniques based on this procedure, including our own, must exhibit limitations inherent to the amplification process. Our estimates or relative error suggest that a realistic limit for the PCR estimation of residual leukemia lies in the range of one leukemia cell per 10(5) normal cells. The suggested method is rapid, technically simple and relatively inexpensive. Furthermore, the principles that it is based upon can be applied to any PCR-based strategy.

Clinicopathologic features and treatment outcome of children with large-cell lymphoma and the t(2;5)(p23;q35)

The t(2;5)(p23;q35) was detected in 9 of the 18 cases of large-cell lymphoma with an abnormal karyotype among 115 children with large-cell lymphoma treated at St Jude Children's Research Hospital from 1975 to 1993. When the cases containing the t(2;5) were classified according to the National Cancer Institute Working Formulation, 7 were large-cell, immunoblastic and 2 were diffuse large cell; according to the Kiel classification system, 6 were anaplastic large cell, 2 immunoblastic, and 1 centroblastic. CD30 expression was documented in 6 of 8 cases tested. All patients had nodal disease and 6 had extranodal involvement (bone in 4 cases and skin in 3). Eight of nine had advanced disease at diagnosis (stage Ill in 7 and stage IV in 1). Complete remission (CR) was attained in all patients and 6 remain in first CR for 19+ to 97+ months. Three relapsed, but successfully obtained second remissions; 2 are 58+ and 80+ months after retrieval therapy for local recurrences, and 1 patient died of recurrent disease. The t(2;5)(p23;q35) is associated with, but not limited to, anaplastic histology, a CD30+ T-cell phenotype, advanced stage disease with nodal (+/- extranodal) involvement, and chemosensitivity at diagnosis and relapse.

Calcium-triggered exocytosis and endocytosis in an isolated presynaptic cell: capacitance measurements in saccular hair cells

Depolarization of isolated frog saccular hair cells caused Ca(2+)-dependent increases in membrane capacitance that we interpret as the fusion of synaptic vesicles with the plasma membrane. During a maintained depolarization to -10 mV, the capacitance increased at a rate corresponding to the fusion of approximately 500 vesicles per second at each active zone. Release continued at this high rate for up to 2 s, long enough to exhaust > 5 times the number of vesicles initially in close apposition to the plasma membrane at active zones. We therefore propose that hair cells are specialized for rapid replenishment of vesicles at release sites. Upon repolarization to -70 mV, the capacitance returned exponentially (time constant, approximately 14 s) to near the prestimulus level in perforated-patch recordings, but not in whole-cell recordings, suggesting that a mobile intracellular factor is required for membrane retrieval.

Complete hematologic remissions induced by 2-chlorodeoxyadenosine in children with newly diagnosed acute myeloid leukemia

The majority of children with acute myeloid leukemia (AML) who are treated exclusively with chemotherapy die of progressive disease. Improvement in outcome will likely require new active drugs capable of eradicating resistant blast cells early in the clinical course. We therefore assessed the cytoreductive potential of 2-chlorodeoxyadenosine (2-CdA), a halogenated purine analogue, in 22 consecutive children with newly diagnosed AML. The drug was administered as a single 120-hour continuous infusion (8.9 mg/m2 of body surface area per day) before the introduction of standard remission induction therapy. Six patients (27%) had complete hematologic remissions by a median of 21 days after treatment with the nucleoside (range, 14 to 33 days). Seven others had partial responses, yielding a total response rate of 59%. The drug also eliminated leukemic cells from cerebrospinal fluid in 4 of the 6 patients tested. Concentrations of 2-CdA in cerebrospinal fluid on day 5 after the initiation of treatment ranged from 12.4% to 38.0% (mean, 22.7%) of the steady-state plasma concentrations. Severe but reversible myelosuppression and thrombocytopenia developed in all patients. Analysis of factors that may have influenced the complete remission rate suggested a better outcome in patients with myeloblastic leukemia (M0-M2 subtypes in the revised French-American-British classification system). These results demonstrate clinically significant activity by 2-CdA against previously untreated AML in children, including leukemic blast cells in the central nervous system. Its use in combination chemotherapy may improve the outlook for patients with this often fatal hematologic cancer.

Calcium signalling in hair cells: multiple roles in a compact cell

Ca2+ is critical for mechanosensory adaptation, frequency tuning, afferent synaptic transmission, and efferent modulation in hair cells. These four processes involve cytoplasmic Ca2+ in three independent signalling pathways. Recent work suggests that Ca2+ regulates a myosin adaptation motor, and that a mobile Ca2+ buffer is highly concentrated in hair cells. Focal Ca2+ entry and the cytoplasmic Ca2+ buffer help to separate these pathways by limiting the spread of Ca2+ signals.

Direct demonstration that autologous bone marrow transplantation for solid tumors can return a multiplicity of tumorigenic cells

Patients with solid tumors are increasingly being treated by autologous bone marrow transplantation (BMT). Although response rates appear to be increased, disease recurrence is the commonest cause of treatment failure. Whether relapse is entirely due to residual disease in the patient or arises also from infiltrating malignant cells contained in the autologous marrow transplant has not been resolved. If the latter explanation is correct, then purging would be required as part of the transplantation procedure. We used retrovirally mediated transfer of the neomycin-resistance gene to mark BM harvested from eight patients with neuroblastoma in clinical remission. The marked marrow cells were subsequently reinfused as part of an autologous BMT. At relapse, we sought the marker gene in malignant cell populations. Three patients have relapsed, and in each the marker gene was detected by phenotypic and genetic analyses of resurgent malignant cells at medullary and extramedullary sites. Analysis of neuroblast DNA for discrete marker gene integration sites suggested that at least 200 malignant cells, each capable of tumor formation, were introduced with the autologous marrow transplant and contributed to relapse. Thus, autologous BMTs administered to patients with this solid tumor may contain a multiplicity of malignant cells that subsequently contribute to relapse. The marker-gene technique we describe should permit evaluation of the mechanisms of relapse and the efficacy of purging in patients receiving autologous marrow transplantation for other solid tumors that infiltrate the marrow.

Localization of calcium signals by a mobile calcium buffer in frog saccular hair cells

A recent study (Roberts, 1993) of saccular hair cells from grass frogs (Rana pipiens) has suggested a mechanism by which the unusually high concentrations of calcium-binding proteins found in certain sensory receptors and neurons, particularly in the auditory system, can influence short-range intracellular calcium signaling. In frog saccular hair cells, the mechanism operates within arrays of calcium channels and calcium-activated potassium channels that are involved in the cells' electrical resonance and synaptic transmission. The present study tests the hypothesis that calbindin-D28k, one of the most abundant proteins in these cells, can serve as a mobile calcium buffer that reduces and localizes changes in the intracellular free-calcium concentration ([Ca2+]i) by shuttling calcium away from the channel arrays. Based upon theoretical analysis and computer modeling, it is shown that [Ca2+]i near one or more open channels quickly reaches a steady-state level determined primarily by two properties of the buffer, the mean time (tau c) before it captures a free-calcium ion and a replenishment factor (R), which are related to the buffer's diffusional mobility (DBu), association rate constant (kon), and concentration (Bo) by tau c = (konB0)-1 and R = B0DBu. Simulation of calcium entry through a channel array showed that approximately 1.5 mM of a molecule with the diffusional and binding properties expected for calbindin-D28k (Bo approximately 8 mM calcium-binding sites) is needed to reproduce the previous experimental results. A lower concentration (B0 = 2 mM) was almost completely depleted within the channel array by a modest calcium current (8 pA = 12% of calcium channels open), but still had two important effects: it caused [Ca2+]i to fall steeply with distance outside the array (space constant < 50 nm), and returned [Ca2+]i quickly to the resting level after the channels closed. A high concentration of calbindin-D28k can thus influence the cell's electrical resonance and synaptic transmission. Its most important functions may be to localize regions of high [Ca2+]i and speed the return of [Ca2+]i toward the resting level.

Clinical features and treatment outcome for children with CD30+ large-cell non-Hodgkin's lymphoma

PURPOSE

To determine the frequency of CD30 expression and its relationship to clinical features, immunophenotype, histotype, and outcome in childhood large-cell non-Hodgkin's lymphoma (NHL).

PATIENTS AND METHODS

We reviewed 45 cases of large-cell NHL in children treated at St Jude Children's Research Hospital from 1975 to 1990 for whom there was sufficient tissue to perform immunophenotypic studies. All 45 were screened with a panel of antibodies to detect the presence of CD30 and T-cell and B-cell antigens. Cases were classified according to the National Cancer Institute (NCI) Working Formulation and the Kiel classification system. Clinical features, immunophenotype, pathologic classification, and treatment outcome were compared for CD30+ and CD30- cases.

RESULTS

CD30 expression was documented in 18 cases (40%). These 13 boys and five girls had a median age of 13 years at diagnosis. Most (n = 14) had advanced-stage (III and IV) disease. Nodal disease was equally common in CD30+ and CD30- cases, whereas skin involvement was significantly more frequent in CD30+ cases (P = .007). There was no significant association of CD30 expression with histologic subtype according to the NCI Working Formulation, but CD30+ cases were more likely to be anaplastic by the Kiel classification (P < .001). All CD30+ cases had either T-cell or null-cell phenotype, while the majority of CD30- cases were B-cell phenotype (P < .001). Among patients with limited-stage disease, the mean +/- SE estimated 5-year event-free survival (EFS) was 75% +/- 22% for CD30+ cases and 92% +/- 9% for CD30- cases (P = .10); estimates for advanced-stage disease were 57% +/- 17% and 29% +/- 17%, respectively (P = .096). For patients with advanced-stage disease, CD30 expression was associated with a significantly better overall 5-year survival probability (84% +/- 12% v 27% +/- 16%, P = .0016).

CONCLUSION

CD30 is frequently expressed in pediatric large-cell NHL and is significantly associated with T-cell or null-cell phenotype, anaplastic morphology, skin involvement, and better overall survival among advanced-stage patients.

Intensive chemotherapy for Philadelphia-chromosome-positive acute lymphoblastic leukaemia

Childhood acute lymphoblastic leukaemia with the classic Philadelphia chromosome translocation is fatal in patients treated with chemotherapy alone. We report probable cures in three adolescents and one child who received extensively reinforced, early chemotherapy followed by rotational treatment with pairs of non-cross-resistant drugs. The median duration of leukaemia-free survival in this subgroup is 6.5 years (range 6-8 years). The two patients with long-term bone marrow surveillance for residual disease showed no evidence of the Philadelphia chromosome at 31 and 53 months post-remission. Such intensive chemotherapy is a reasonable option for patients who are not able to undergo bone marrow transplantation.

Tretinoin toxicity in children with acute promyelocytic leukaemia

Tretinoin is effective in acute promyelocytic leukaemia in adults. Data about its efficacy and safety in children are limited. We have treated 9 children with tretinoin at 45 mg/m2 per day. Pseudotumour cerebri or hyperleucocytosis occurred in 5 patients. Retinoic acid syndrome was seen in 3 cases. 1 of 2 children who developed hyperleucocytosis, pseudotumour cerebri, and retinoic acid syndrome died despite steroids and mechanical ventilation. Complete remissions with tretinoin alone were achieved in 15 patients. All 8 surviving children received consolidation chemotherapy. Our experience with tretinoin therapy suggests that toxicity is frequent in children.

Spatial calcium buffering in saccular hair cells

The potential importance of intracellular calcium-binding proteins in rapid and highly localized Ca2+ signalling is poorly understood. During fast synaptic transmission, which occurs at specialized active zones where Ca2+ diffuses only a few tens of nanometers from channels to neurotransmitter release sites, a cytoplasmic Ca2+ buffer would have to be extremely fast or present in millimolar concentrations to intercept a significant fraction of the calcium ions en route to their targets. Therefore, Ca2+ buffers have been presumed to be unimportant in fast exocytosis and another fast calcium-mediated process, electrical resonance in hair cells. Here I present evidence to the contrary by showing that hair cells in the frog sacculus contain millimolar concentrations of a mobile cytoplasmic calcium buffer that captures Ca2+ within a few microseconds after it enters through presynaptic Ca2+ channels and carries it away from the point of entry. This spatial buffering reduces the presynaptic free Ca2+ by up to 60 per cent and probably restricts the region in which the internal calcium ion concentration exceeds 1 microM to within < 250 nm of each synaptic site. The buffer can thus influence both electrical resonance and synaptic transmission. Calbindin-D28K or a related protein may serve as the mobile calcium buffer, an action similar to its function in transporting Ca2+ across intestinal epithelial cells.

Detection of N-myc gene amplification by fluorescence in situ hybridization. Diagnostic utility for neuroblastoma

We assessed fluorescence in situ hybridization (FISH) as an alternative to Southern blot analysis for determination of N-myc gene amplification in neuroblastoma. In the 44 pediatric solid tumor cell lines examined (20 neuroblastomas), the mean number of N-myc copies determined by FISH correlated closely with Southern blot results. There was wide intercellular variability in gene copy number in tumors that had evidence of amplification; however, tumors judged to be non-amplified completely lacked any cells with high N-myc copy number. FISH provided reliable estimates of N-myc amplification in 12 clinical samples even when the percentage of tumor was low. The other advantages of FISH over Southern blot analysis were speed and technical simplicity, ability to discern heterogeneous gene amplification among tumor cells in the same specimen, and capacity to determine the source of the amplified N-myc signal, whether extrachromosomal double-minute chromosomes, expanded intrachromosomal regions, or chromosome 2 aneuploidy. We conclude that FISH would refine the analysis of N-myc amplification in neuroblastoma and thus improve the assignment of patients to prognostic groups based on this unfavorable risk factor.

Effect of sexual dimorphism in bill length on foraging behavior: an experimental analysis of hummingbirds

We examined whether sexual differences in trophic morphology are associated with sexual differences in foraging behavior through two laboratory experiments on rufous hummingbirds (Selasphorus rufus) designed to compare probing abilities (maximum extraction depths) and handling times of sexes at flowers. Bills of female S. rufus are about 10.5% longer than bills of males, and this difference was associated with sexual differences in foraging abilities. Maximum extraction depths of female S. rufus were significantly greater than those of males, and no overlap between the sexes was observed. Moreover, handling times of females were shorter than handling times of males at flowers having longer corollas (≥15 mm). Thus, because of their longer bills, female S. rufus have the potential to feed from longer flowers than males, and can do so more quickly. We suggest that no single mechanism is responsible for the evolution of sexual dimorphism in bill lengths of hummingbirds, but rather that the dimorphism probably reflects the combined effects of reproductive role division and intersexual food competition, and possibly, sexual selection.

Sublocalization of the chromosome 5 breakpoint of the 3;5 translocation in myelodysplastic syndromes and acute myeloid leukemia

A t(3;5)(q25.1;q34) reciprocal translocation identifies a subset of cases of myelodysplastic syndrome or acute myeloid leukemia (AML) that are characterized by increased numbers of megakaryocytes and severe trilineage dysplasia. As a first step in characterizing the t(3;5) breakpoints, we asked whether the translocation involves the CSFIR/PDGFRB locus at 5q33-q35. Pulsed-field gel electrophoretic analysis of a region extending 580 kb 5' to the PDGFRB gene and 120 kb 3' to the CSFIR gene did not reveal aberrant restriction fragments in leukemic cell DNA, confirming that the breakpoint does not occur in the vicinity of these genes. To sublocalize the breakpoint, we performed Southern blot hybridizations using DNA from human x hamster somatic cell hybrids containing the normal 3, the normal 5, the derivative 3, or the derivative 5 human chromosome. Using a series of polymorphic DNA probes from the long arm of chromosome 5, which have been linked by genetic recombination, we bracketed the breakpoint to within a region that spans approximately 13 centimorgans (sex average) and is flanked by the q34-qter markers cKK5.19 and L1200 (D5S62). This analysis places the chromosome 5 breakpoint of the t(3;5) considerably telomeric to the CSFIR/PDGFRB locus, confirming our studies with pulsed-field electrophoresis. Future efforts to identify the genes affected by the t(3;5) should focus on the 5q segment described in this study.

Fusion of the leucine zipper gene HLF to the E2A gene in human acute B-lineage leukemia

A t(17;19) chromosomal translocation in early B-lineage acute leukemia was shown to result in chimeric transcripts that contain sequences from the E2A basic helix-loop-helix transcription factor gene on chromosome 19, fused to sequences from a previously unidentified gene (HLF) on chromosome 17 that encodes a hepatic leukemia factor. The chimeric protein consisted of the amino-terminal transactivation domain of E2A linked to the carboxyl-terminal basic region-leucine zipper domain of HLF. HLF was normally expressed in liver and kidney, but not in lymphoid cells, and was found to be closely related to the leucine zipper-containing transcription factors DBP (albumin D-box binding protein) and TEF (thyrotroph embryonic factor), which regulate developmental stage-specific gene expression.