Intrinsic OXPHOS limitations underlie cellular bioenergetics in leukemia

Currently there is great interest in targeting mitochondrial oxidative phosphorylation (OXPHOS) in cancer. However, notwithstanding the targeting of mutant dehydrogenases, nearly all hopeful 'mito-therapeutics' cannot discriminate cancerous from non-cancerous OXPHOS and thus suffer from a limited therapeutic index. Using acute myeloid leukemia (AML) as a model, herein, we leveraged an in-house diagnostic biochemical workflow to identify 'actionable' bioenergetic vulnerabilities intrinsic to cancerous mitochondria. Consistent with prior reports, AML growth and proliferation was associated with a hyper-metabolic phenotype which included increases in basal and maximal respiration. However, despite having nearly 2-fold more mitochondria per cell, clonally expanding hematopoietic stem cells, leukemic blasts, as well as chemoresistant AML were all consistently hallmarked by intrinsic OXPHOS limitations. Remarkably, by performing experiments across a physiological span of ATP free energy, we provide direct evidence that leukemic mitochondria are particularly poised to consume ATP. Relevant to AML biology, acute restoration of oxidative ATP synthesis proved highly cytotoxic to leukemic blasts, suggesting that active OXPHOS repression supports aggressive disease dissemination in AML. Together, these findings argue against ATP being the primary output of leukemic mitochondria and provide proof-of-principle that restoring, rather than disrupting, OXPHOS may represent an untapped therapeutic avenue for combatting hematological malignancy and chemoresistance.

Racial differences in the limb skeletal muscle transcriptional programs of patients with critical limb ischemia

Critical limb ischemia (CLI) is the most severe manifestation of peripheral artery disease (PAD) and is characterized by high rates of morbidity and mortality. As with most severe cardiovascular disease manifestations, Black individuals disproportionately present with CLI. Accordingly, there remains a clear need to better understand the reasons for this discrepancy and to facilitate personalized therapeutic options specific for this population. Gastrocnemius muscle was obtained from White and Black healthy adult volunteers and patients with CLI for whole transcriptome shotgun sequencing (WTSS) and enrichment analysis was performed to identify alterations in specific Reactome pathways. When compared to their race-matched healthy controls, both White and Black patients with CLI demonstrated similar reductions in nuclear and mitochondrial encoded genes and mitochondrial oxygen consumption across multiple substrates, indicating a common bioenergetic paradigm associated with amputation outcomes regardless of race. Direct comparisons between tissues of White and Black patients with CLI revealed hemostasis, extracellular matrix organization, platelet regulation, and vascular wall interactions to be uniquely altered in limb muscles of Black individuals. Among traditional vascular growth factor signaling targets, WTSS revealed only Tie1 to be significantly altered from White levels in Black limb muscle tissues. Quantitative reverse transcription polymerase chain reaction validation of select identified targets verified WTSS directional changes and supports reductions in MMP9 and increases in NUDT4P1 and GRIK2 as unique to limb muscles of Black patients with CLI. This represents a critical first step in better understanding the transcriptional program similarities and differences between Black and White patients in the setting of amputations related to CLI and provides a promising start for therapeutic development in this population.

Prescribed exercise to Reduce Recidivism After Weight Loss-Pilot (PREVAIL-P): Design, methods and rationale

Clinically significant weight loss is associated with health benefits for overweight and obese adults. Participation in adequate amounts of physical activity is critical for weight maintenance. However, the recommended amount of physical activity needed to promote weight maintenance is based primarily on retrospective studies that quantified physical activity levels through questionnaires which tend to overestimate physical activity levels. In addition, the present literature has provided little data on the impact of these physical activity levels on cardiovascular and diabetes risk factors, which may have equal or more clinical importance than weight changes. The Prescribed Exercise to Reduce Recidivism After Weight Loss-Pilot (PREVAIL-P) study will evaluate the effect of aerobic exercise training amount on weight maintenance following clinically significant weight loss in overweight and obese adults (BMI 25-40 kg/m2) age 30-65 years. Participants (N = 39) will complete a 10-week OPTIFAST® weight loss program with supervised aerobic exercise training. Individuals who achieve ≥7% weight loss from baseline will be subsequently randomized to levels of aerobic training consistent with physical activity recommendations (PA-REC) or weight maintenance recommendations (WM-REC) for 18 additional weeks. The primary outcome of the PREVAIL-P study will be change in weight from the completion of OPTIFAST® program to the end of the study. Notable secondary measures include changes in clinically relevant cardiometabolic risk factors between study groups (e.g. blood lipids concentrations, oral glucose tolerance, arterial stiffness). This pilot study will be used to estimate the effect sizes needed for a randomized controlled trial on this topic.

PFKFB3-mediated glycolysis rescues myopathic outcomes in the ischemic limb

Compromised muscle mitochondrial metabolism is a hallmark of peripheral arterial disease, especially in patients with the most severe clinical manifestation - critical limb ischemia (CLI). We asked whether inflexibility in metabolism is critical for the development of myopathy in ischemic limb muscles. Using Polg mtDNA mutator (D257A) mice, we reveal remarkable protection from hind limb ischemia (HLI) due to a unique and beneficial adaptive enhancement of glycolytic metabolism and elevated ischemic muscle PFKFB3. Similar to the relationship between mitochondria from CLI and claudicating patient muscles, BALB/c muscle mitochondria are uniquely dysfunctional after HLI onset as compared with the C57BL/6 (BL6) parental strain. AAV-mediated overexpression of PFKFB3 in BALB/c limb muscles improved muscle contractile function and limb blood flow following HLI. Enrichment analysis of RNA sequencing data on muscle from CLI patients revealed a unique deficit in the glucose metabolism Reactome. Muscles from these patients express lower PFKFB3 protein, and their muscle progenitor cells possess decreased glycolytic flux capacity in vitro. Here, we show supplementary glycolytic flux as sufficient to protect against ischemic myopathy in instances where reduced blood flow-related mitochondrial function is compromised preclinically. Additionally, our data reveal reduced glycolytic flux as a common characteristic of the failing CLI patient limb skeletal muscle.

Extensive skeletal muscle cell mitochondriopathy distinguishes critical limb ischemia patients from claudicants

The most severe manifestation of peripheral arterial disease (PAD) is critical limb ischemia (CLI). CLI patients suffer high rates of amputation and mortality; accordingly, there remains a clear need both to better understand CLI and to develop more effective treatments. Gastrocnemius muscle was obtained from 32 older (51-84 years) non-PAD controls, 27 claudicating PAD patients (ankle-brachial index [ABI] 0.65 ± 0.21 SD), and 19 CLI patients (ABI 0.35 ± 0.30 SD) for whole transcriptome sequencing and comprehensive mitochondrial phenotyping. Comparable permeabilized myofiber mitochondrial function was paralleled by both similar mitochondrial content and related mRNA expression profiles in non-PAD control and claudicating patient tissues. Tissues from CLI patients, despite being histologically intact and harboring equivalent mitochondrial content, presented a unique bioenergetic signature. This signature was defined by deficits in permeabilized myofiber mitochondrial function and a unique pattern of both nuclear and mitochondrial encoded gene suppression. Moreover, isolated muscle progenitor cells retained both mitochondrial functional deficits and gene suppression observed in the tissue. These findings indicate that muscle tissues from claudicating patients and non-PAD controls were similar in both their bioenergetics profile and mitochondrial phenotypes. In contrast, CLI patient limb skeletal muscles harbor a unique skeletal muscle mitochondriopathy that represents a potentially novel therapeutic site for intervention.

Fluid and Volume Monitoring

Background

Fluid resuscitation is not only used to prevent acute kidney injury (AKI) but fluid management is also a cornerstone of treatment for patients with established AKI and renal failure. Ultrafiltration removes volume initially from the intravascular compartment inducing a relative degree of hypovolemia. Normal reflex mechanisms attempt to sustain blood pressure constant despite marked changes in blood volume and cardiac output. Thus, compensated shock with a normal blood pressure is a major cause of AKI or exacerbations of AKI during ultrafiltration.

Methods

We undertook a systematic review of the literature using MEDLINE, Google Scholar and PubMed searches. We determined a list of key questions and convened a 2-day consensus conference to develop summary statements via a series of alternating breakout and plenary sessions. In these sessions, we identified supporting evidence and generated clinical practice recommendations and/or directions for future research.

Results

We defined three aspects of fluid monitoring: i) normal and pathophysiological cardiovascular mechanisms; ii) measures of volume responsiveness and impending cardiovascular collapse during volume removal, and; iii) measured indices of each using non-invasive and minimally invasive continuous and intermittent monitoring techniques. The evidence documents that AKI can occur in the setting of normotensive hypovolemia and that under-resuscitation represents a major cause of both AKI and mortality ion critically ill patients. Traditional measures of intravascular volume and ventricular filling do not predict volume responsiveness whereas dynamic functional hemodynamic markers, such as pulse pressure or stroke volume variation during positive pressure breathing or mean flow changes with passive leg raising are highly predictive of volume responsiveness. Numerous commercially-available devices exist that can acquire these signals.

Conclusions

Prospective clinical trials using functional hemodynamic markers in the diagnosis and management of AKI and volume status during ultrafiltration need to be performed. More traditional measure of preload be abandoned as marked of volume responsiveness though still useful to assess overall volume status.

Effects of fish oils on ex vivo B-cell responses of obese subjects upon BCR/TLR stimulation: a pilot study

The long-chain n-3 polyunsaturated fatty acids (LC-PUFAs) eicosapentaenoic (EPA) and docosahexaenoic acid (DHA) in fish oil have immunomodulatory properties. B cells are a poorly studied target of EPA/DHA in humans. Therefore, in this pilot study, we tested how n-3 LC-PUFAs influence B-cell responses of obese humans. Obese men and women were assigned to consume four 1-g capsules per day of olive oil (OO, n=12), fish oil (FO, n=12) concentrate or high-DHA-FO concentrate (n=10) for 12 weeks in a parallel design. Relative to baseline, FO (n=9) lowered the percentage of circulating memory and plasma B cells, whereas the other supplements had no effect. There were no postintervention differences between the three supplements. Next, ex vivo B-cell cytokines were assayed after stimulation of Toll-like receptors (TLRs) and/or the B-cell receptor (BCR) to determine if the effects of n-3 LC-PUFAs were pathway-dependent. B-cell IL-10 and TNFα secretion was respectively increased with high DHA-FO (n=10), relative to baseline, with respective TLR9 and TLR9+BCR stimulation. OO (n=12) and FO (n=12) had no influence on B-cell cytokines compared to baseline, and there were no differences in postintervention cytokine levels between treatment groups. Finally, ex vivo antibody levels were assayed with FO (n=7) after TLR9+BCR stimulation. Compared to baseline, FO lowered IgM but not IgG levels accompanied by select modifications to the plasma lipidome. Altogether, the results suggest that n-3 LC-PUFAs could modulate B-cell activity in humans, which will require further testing in a larger cohort.

Assessment of in vivo skeletal muscle mitochondrial respiratory capacity in humans by near-infrared spectroscopy: a comparison with in situ measurements

The present study aimed to compare in vivo measurements of skeletal muscle mitochondrial respiratory capacity made using near-infrared spectroscopy (NIRS) with the current gold standard, namely in situ measurements of high-resolution respirometry performed in permeabilized muscle fibres prepared from muscle biopsies. Mitochondrial respiratory capacity was determined in 21 healthy adults in vivo using NIRS to measure the recovery kinetics of muscle oxygen consumption following a ∼15 s isometric contraction of the vastus lateralis muscle. Maximal ADP-stimulated (State 3) respiration was measured in permeabilized muscle fibres using high-resolution respirometry with sequential titrations of saturating concentrations of metabolic substrates. Overall, the in vivo and in situ measurements were strongly correlated (Pearson's r = 0.61-0.74, all P < 0.01). Bland-Altman plots also showed good agreement with no indication of bias. The results indicate that in vivo NIRS corresponds well with the current gold standard, in situ high-resolution respirometry, for assessing mitochondrial respiratory capacity.

Iodine-131--metaiodobenzylguanidine double infusion with autologous stem-cell rescue for neuroblastoma: a new approaches to neuroblastoma therapy phase I study

PURPOSE

Iodine-131-metaiodobenzylguanidine ((131)I-MIBG) provides targeted radiotherapy with more than 30% response rate in refractory neuroblastoma, but activity infused is limited by radiation safety and hematologic toxicity. The goal was to determine the maximum-tolerated dose of (131)I-MIBG in two consecutive infusions at a 2-week interval, supported by autologous stem-cell rescue (ASCR) 2 weeks after the second dose.

PATIENTS AND METHODS

The (131)I-MIBG dose was escalated using a 3 + 3 phase I trial design, with levels calculated by cumulative red marrow radiation index (RMI) from both infusions. Using dosimetry, the second infusion was adjusted to achieve the target RMI, except at level 4, where the second infusion was capped at 21 mCi/kg.

RESULTS

Twenty-one patients were enrolled onto the study at levels 1 to 4, with 18 patients assessable for toxicity and 20 patients assessable for response. Cumulative (131)I-MIBG given to achieve the target RMI ranged from 22 to 50 mCi/kg, with cumulative RMI of 3.2 to 8.92 Gy. No patient had a dose-limiting toxicity. Reversible grade 3 nonhematologic toxicity occurred in six patients at level 4, establishing the recommended cumulative dose as 36 mCi/kg. The median time to absolute neutrophil count more than 500/microL after ASCR was 13 days (4 to 27 days) and to platelet independence was 17 days (6 to 47 days). Responses included two partial responses, eight mixed responses, three stable disease, and seven progressive disease. Responses by semiquantitative MIBG score occurred in eight patients, soft tissue responses occurred in five of 11 patients, but bone marrow responses occurred in only two of 13 patients.

CONCLUSION

The lack of toxicity with this approach allowed dramatic dose intensification of (131)I-MIBG, with minimal toxicity and promising activity.

Adrenocortical tumor with left renal vein, vena cava and intrahepatic venous extension

A 41 year old white female presented with upper respiratory distress and shortness of breath appeared on initial computed tomography (CT) scan to have a large left retroperitoneal mass with left renal vein extension including a mass up to the level of the atrium. This presentation suggested hypernephroma. She proved, however, to have an adrenal cortical carcinoma which displaced the kidney, exhibiting vascular invasion within the gland and non-adherent extension into the vena cava, atrium, common hepatic vein and left renal vein, where some adherence was present. This unusual tumor required extensive surgery for removal, including use of cardiopulmonary bypass, with good results.

Phase II study on the effect of disease sites, age, and prior therapy on response to iodine-131-metaiodobenzylguanidine therapy in refractory neuroblastoma

PURPOSE

To evaluate the effect of disease sites and prior therapy on response and toxicity after iodine-131-metaiodobenzylguanidine (131I-MIBG) treatment of patients with resistant neuroblastoma.

PATIENTS AND METHODS

One hundred sixty-four patients with progressive, refractory or relapsed high-risk neuroblastoma, age 2 to 30 years, were treated in a limited institution phase II study. Patients with cryopreserved hematopoietic stem cells (n = 148) were treated with 18 mCi/kg of 131I-MIBG. Those without hematopoietic stem cells (n = 16) received 12 mCi/kg. Patients were stratified according to prior myeloablative therapy and whether they had measurable soft tissue involvement or only bone and/or bone marrow disease.

RESULTS

Hematologic toxicity was common, with 33% of patients receiving autologous hematopoietic stem cell support. Nonhematologic grade 3 or 4 toxicity was rare, with 5% of patients experiencing hepatic, 3.6% pulmonary, 10.9% infectious toxicity, and 9.7% with febrile neutropenia. The overall complete plus partial response rate was 36%. The response rate was significantly higher for patients with disease limited either to bone and bone marrow, or to soft tissue (compared with patients with both) for patients with fewer than three prior treatment regimens and for patients older than 12 years. The event-free survival (EFS) and overall survival (OS) times were significantly longer for patients achieving response, for those older than 12 years and with fewer than three prior treatment regimens. The OS was 49% at 1 year and 29% at 2 years; EFS was 18% at 1 year.

CONCLUSION

The high response rate and low nonhematologic toxicity with 131I-MIBG suggest incorporation of this agent into initial multimodal therapy of neuroblastoma.

131I-Metaiodobenzylguanidine (131I-MIBG) double infusion with autologous stem cell transplant for neuroblastoma: A New Approaches to Neuroblastoma Therapy (NANT) study

9011

Background: 131I-MIBG provides targeted radiotherapy with >30% response in refractory neuroblastoma, but the activity infused is limited by radiation safety and hematologic toxicity. The goal was to determine the maximum tolerated dose of 131I-MIBG in two consecutive infusions at a 2-week interval, supported by autologous stem cell transplant (ASCT) 2 weeks after the second dose. Methods: The 131I-MIBG was escalated in a 3+3 Phase I trial design, with levels calculated by total red marrow radiation index (RMI) from the double infusion. The first infusion of 131I-MIBG was 12, 15, 18 and 21 mCi/kg for levels 1, 2, 3 and 4 respectively. Using detailed dosimetry, the second infusion was adjusted to achieve the target RMI, except at Level 4, where the second infusion was capped at 21 mCi/kg. Results: Twenty-one patients were enrolled at Level 1–4, with 18 evaluable for toxicity. Median age at enrollment was 7 years, all were heavily pretreated, including 12 with prior high dose therapy and ASCT, and 12 patients had bone marrow tumor. Cumulative 131I-MIBG given to achieve the target RMI ranged from 18 mci/kg to 49 mCi/kg. RMI delivered per mCi of MIBG decreased in 15/19 patients by mean of 0.21 cGy/mCi with the second infusion. Hematologic toxicity was acceptable, with median time to ANC>500 after ASCT of 13 (4–27) days. Platelet transfusion was required in 15/18 patients, with median time to platelet independence of 18 (6–47) days after ASCT. There were no non-hematologic toxicities above grade 2 attributed to therapy, though 9 patients had grade 1–2 elevations of transaminase, and 1 had grade 2 hypothyroidism. Responses in 17 evaluable patients included 1 PR, 4 MR, 6 SD, and 6 PD. Eleven patients are alive at median of 361 days (46–483); 5 died of PD and 1 of unrelated toxicity. Conclusion: The lack of toxicity with this approach allowed dramatic dose intensification of 131I-MIBG, with minimal toxicity and the possibility of improved response.

[Table: see text]

No significant financial relationships to disclose.

Biodistribution of post-therapeutic versus diagnostic (131)I-MIBG scans in children with neuroblastoma

BACKGROUND

To evaluate the biodistribution of therapeutic (131)I-metaiodobenzylguanidine (MIBG) and assess the sensitivity of diagnostic versus therapeutic (131)I-MIBG scans to detect metastatic disease.

PROCEDURE

This retrospective study included 44 diagnostic and post-therapy scans (PTS) in 18 children with neuroblastoma treated with (131)I-MIBG (2.0-33.1 GBq). The findings of diagnostic scans (DS) (2.6-44.4 MBq) were compared to those of corresponding PTS.

RESULTS

In terms of biodistribution, the PTS identified (131)I-MIBG activity in one or more patients in the following regions not detected on the DS: nasal mucosa, cerebellum, central brain, adrenals, spleen, kidneys, thyroid, salivary glands, lower halves of the lungs, bladder, bowel, and an incisional scar. Conversely, the DS identified activity in the thorax, heart, kidneys, and bladder each in one patient without being visualized on the PTS. In terms of sensitivity to detect metastatic disease, 210 lesions were seen on the PTS compared to 151 on the DS. The PTS demonstrated sites of disease not evident in the DS in 16 cases.

CONCLUSIONS

The biodistribution of (131)I-MIBG is different using therapeutic doses as compared to pre-therapy doses. (131)I-MIBG imaging following high therapeutic doses often reveals sites of occult metastatic disease that may be clinically relevant.

Targeted radiotherapy with submyeloablative doses of 131I-MIBG is effective for disease palliation in highly refractory neuroblastoma

PURPOSE

Treatment of refractory neuroblastoma remains a significant clinical problem. Targeted radiotherapy with 131I-MIBG has demonstrated antitumor activity in heavily pretreated neuroblastoma patients with recurrent disease. Response rates may be correlated with total radionuclide dose per kilogram body weight delivered, but higher dose levels are associated with protracted grade 4 hematologic toxicity. The optimal method for using single-agent 131I-MIBG for patients with relapsed high-risk neuroblastoma has not been defined. This study was designed to retrospectively determine the clinical response to 131I-MIBG therapy at submyeloablative doses in patients with refractory neuroblastoma and to describe the toxicities.

PATIENTS AND METHODS

A retrospective chart review of 20 patients with neuroblastoma treated with 131I-MIBG at the Children's Hospital of Philadelphia from 1988 to 2000 was performed. Demographic data, 131I-MIBG dose delivered, toxicities, and clinical responses were reviewed.

RESULTS

A median dose of 9.5 mCi/kg of 131I-MIBG was delivered in 32 courses to 20 patients. Three patients were treated in first complete response, and the remaining 17 patients for residual and/or progressive disease. The objective response rate to the first therapy was 31%, and the remaining patients achieved disease stabilization. In addition, 9 of 11 patients with pain at study entry had significant improvement. Disease response was not correlated with 131I-MIBG dose delivered. No unanticipated toxicities were observed.

CONCLUSIONS

Submyeloablative-dose 131I-MIBG is an effective and relatively nontoxic method for neuroblastoma disease palliation. Most patients show subjective improvement in pain and/or performance status. Increased availability and experience with 131I-MIBG therapy would benefit a large number of children with end-stage neuroblastoma and no realistic hope for cure.

Pharmacologic and psychologic interventions for procedural pain

OBJECTIVE

This study evaluated a combined pharmacologic and psychologic intervention (combined intervention, CI) relative to a pharmacologic-only (PO) intervention in reducing child distress during invasive procedures in childhood leukemia. Predictors of child distress included age, group (CI, PO), and procedural variables (medications and doses, technical difficulty, number of needles required).

METHODOLOGY

This was a randomized, controlled prospective study that compared the PO (n = 45) and CI arms (n = 47), at 1, 6, and >12 months after diagnosis. A cross-sectional control group consisted of parents of 70 patients in first remission before the prospective study. Parent questionnaires, staff and parent ratings, and data on medications administered, technical difficulty of the procedure, and needle insertions were obtained for each procedure. This article reports on the final data point for the project (>12 months).

RESULTS

Mothers and nurses reported lower levels of child distress in the CI than the PO group. The CI and PO groups showed lower levels of child and parent distress than the cross-sectional control group. Distress decreased throughout the time, and child age was inversely related to distress (younger children had more distress) regardless of group. Child distress was associated with staff perceptions of the technical difficulty of the procedure and with child age, but not with medications administered.

CONCLUSIONS

The data showed that pharmacologic and psychologic interventions for procedural distress were effective in reducing child and parent distress and support integration of the two approaches. Younger children experienced more distress and warranted additional consideration. Staff perceptions of the technical difficulty of procedures were complex and potentially helpful in designing intervention protocols.

A randomized controlled prospective outcome study of a psychological and pharmacological intervention protocol for procedural distress in pediatric leukemia

Evaluated distress during invasive procedures in childhood leukemia. Child and parent distress, assessed by questionnaires and ratings, were compared in two arms of a randomized, controlled prospective study, one a pharmacologic only (PO) (n = 45) and the other a combined pharmacologic and psychological intervention (Cl) (n = 47), at 1, 2, and 6 months after diagnosis. The cross-sectional control group (CC) consisted of parents of 70 patients in first remission prior to the prospective study. Mothers' and nurses' ratings of child distress indicated less child distress in the Cl group than the PO. When contrasted with the CC group, the Cl group showed lower levels of child distress. Data showed decreases over time in distress and concurrent improvements in quality of life and parenting stress and supported an inverse association between distress and child age.

Disposition of a novel recombinant antithrombotic agent, RG 12986, in cynomolgus monkeys

RG 12986, a novel antagonist of platelet aggregation, is a recombinant peptide based on the sequence in von Willebrand factor, which contains the GP1b binding site. Disposition of the peptide in cynomolgus monkeys was determined using nonlabeled and 35S-labeled product. After iv administration, the peptide underwent a triphasic decay in the plasma. The first phase of elimination, after distribution, had a t1/2 (approximately 20 min) similar to that observed for inhibition of platelet aggregation (approximately 25 min). The correlation between the logarithm of the plasma peptide concentration and activity was r = 0.9989. The effective duration of pharmacological activity was approximately 2 hr. After this period, a slower terminal phase of plasma elimination was observed (t1/2 approximately 2 hr). Plasma clearance (7-15 ml/min/kg) and volume of distribution at steady-state (0.4-0.9 L/kg) estimates appeared to have a slight dose dependency, but the scope of the investigation did not allow this to be verified. There was a linear correlation between dose and AUC (r2 = 0.9998), but for each 4-fold increase in dose there was a greater than 4-fold increase in AUC. Immediately after iv administration, significant fragmentation of the peptide was observed with polyacrylamide gel electrophoresis analysis of the plasma. This initial rate of metabolism was subsequently slowed to t1/2 estimates of 2 hr, followed by a very long terminal half-life of plasma radioactivity of 12 days. It is likely that this terminal half-life represents metabolic recycling of 35S. Elimination of the label was primarily via the kidneys.

Prenatal diagnosis and carrier screening for fragile X by PCR

During the past three years, we have conducted fragile X DNA studies for carrier screening and prenatal diagnosis using a previously described PCR protocol that accurately resolves normal FMR1 alleles and premutations and detects most full mutations [Brown et al., JAMA 270:1569-1575, 1996]. A total of 344 pregnant women with a family history of mental retardation of unknown cause were screened and 6 fragile X carriers were identified: two had full mutations, and four had premutations. The mentally retarded relatives of two other women were found to be fragile X positive although the women themselves were not carriers. In all, 6 carriers and 8 fragile X families were identified by this screening. We have also screened 40 pregnant women who were members of previously identified fragile X families, but whose carrier status was unknown. Ten were found to be carriers and were offered prenatal diagnosis. Prospective prenatal testing of 84 carrier women correctly detected 31 fetal samples (19 females, 12 males) with full mutations and 6 with premutations (2 females, 4 males). No false positives but one false negative occurred early on due to undetected maternal cell contamination. In addition, screening of 806 males with developmental delays of unknown cause gave positive results in 33 (4.1%). Potential problems and pitfalls of direct DNA testing are discussed. Because of the proven success of fragile X screening with direct molecular analysis, screening of all undiagnosed individuals with mental retardation and at risk pregnant women should now be considered. The identification of fragile X carriers and prenatal diagnosis of their pregnancies should significantly reduce the prevalence of this syndrome.

Parental Perceptions of Procedure-Related Distress and Family Adaptation in Childhood Leukemia

Child and parental distress related to lumbar punctures and bone marrow aspirates and general family adaptation are evaluated in a cross-sectional study of children currently in treatment with leukemia in first remission (N = 70). A parental self-report measure developed for this study--the Perception of Procedures Questionnaire (PPQ)--yielded three factors: (a) parental satisfaction, (b) parental distress or involvement, and (c) child distress. Data from the PPQ showed high levels of both satisfaction and distress in the context of invasive procedures. Data from standardized measures of family adaptation demonstrated a range of functioning. Analyses by length of time since diagnosis indicated that parental distress remains stable over the course of treatment. The data are discussed with respect to the newly developed measure of parental procedures (the PPQ) and the need for research in this field that provides an integration of procedural distress with parent and family perceptions and adjustment.

Uncoupling of hypomyelination and glial cell death by a mutation in the proteolipid protein gene

Proteolipid protein (PLP; M(r) 30,000) is a highly conserved major polytopic membrane protein in myelin but its cellular function remains obscure. Neurological mutant mice can often provide model systems for human genetic disorders. Mutations of the X-chromosome-linked PLP gene are lethal, identified first in the jimpy mouse and subsequently in patients with Pelizaeus-Merzbacher disease. The unexplained phenotype of these mutations includes degeneration and premature cell death of oligodendrocytes with associated hypomyelination. Here we show that a new mouse mutant rumpshaker is defined by the amino-acid substitution Ile-to-Thr at residue 186 in a membrane-embedded domain of PLP. Surprisingly, rumpshaker mice, although myelin-deficient, have normal longevity and a full complement of morphologically normal oligodendrocytes. Hypomyelination can thus be genetically separated from the PLP-dependent oligodendrocyte degeneration. We suggest that PLP has a vital function in glial cell development, distinct from its later role in myelin assembly, and that this dichotomy of action may explain the clinical spectrum of Pelizaeus-Merzbacher disease.

Establishment and characterization of ferret cells in culture

Cells derived from the brain of a 6 wk-old ferret have been subcultured over 100 times and have undergone over 400 population doublings in vitro. These cells, referred to as Mpf cells, have an absolute efficiency of colony formation in excess of 45%, exhibit a mean population doubling time of 12.5 h, possess ferret-specific antigens, and have isozymes with electrophoretic properties that are the same as those of isozymes found in ferret liver. The cells exhibit a cytopathic effect and support the synthesis of progeny virus when they are infected with the viruses of lymphocytic choriomeningitis, Newcastle disease, pseudorabies, Sindbis, vaccinia, and vesicular stomatitis. The passage level of the Mpf cells, their elapsed number of population doublings, their possession of ferret-specific antigens, and the comigration of four isozymes obtained from these cells and ferret liver define the cells as an established line of ferret cells.

Carcinoma of the lung in nonsmoking Chinese women

The records of 452 lung cancer patients seen in San Francisco between 1972 and 1979 were retrospectively analyzed according to race, sex, findings at histology and smoking history. Of 31 Chinese women with adenocarcinoma or large cell undifferentiated carcinoma, 20 (64.5 percent) had never smoked, which is in sharp contrast to all other subsets. At least 12 of the women were of Cantonese origin. These data support the findings of previous studies carried out in Cantonese women residing in Hong Kong, Singapore and Hawaii. As the incidence of adenocarcinoma in nonsmokers is appreciably higher than that noted in Canton, the possibility must be considered that the cause may be the result of an interaction between some traditional and nontraditional exposures.

Wild-type temperature-sensitive and -resistant visna viruses: isolation and biological comparison

The plaques formed by wild-type (WT) populations of strain K485 visna (V-K485) virus, strain K796 visna (V-K796) virus, and of progressive pneumonia virus in sheep choroid plexus (SCP) cell cultures are heterogeneous in size. Plaque purification procedures showed that this heterogeneity was due to the presence of two biologically different viruses, large plaque-forming (Lpf) virus and small plaque-forming (Spf) virus. The V-K796 Lpf virus, the V-K796 Spf virus, and the V-K796 WT virus are antigenically similar to each other. Although the V-K796 Spf virus is less cytopathic than the V-K796 Lpf virus, both viruses have a 14- to 16-hour latent period in SCP cells and have similar rates of synthesis for the initial 24 to 30 hours after infection. The V-K796 Spf virus is considered a temperature-sensitive visna virus since, unlike the V-K796 Lpf virus, it does not produce plaques at 41 degrees C and it is more thermosensitive than the V-K796 Lpf variant. Population analyses of two strains of wild-type visna virus and one strain of progressive pneumonia virus demonstrated that these populations contain variants with the phenotypes of V-K796 Spf virus and V-K796 Lpf virus, that the Spf virus was not selected against in sheep, and that cultivation of the wild type visna viruses at 37 degrees C selected against the temperature-sensitive variants. The existence of the temperature-sensitive Spf viruses in these wild-type virus populations suggests that the Spf variants maintain the persistent visna virus infection in sheep and delay the development of the host's cell-mediated immune response to the viral proteins.