Continuous treatment with all-trans retinoic acid causes a progressive reduction in plasma drug concentrations: implications for relapse and retinoid "resistance" in patients with acute promyelocytic leukemia.

Although all-trans retinoic acid (RA) induces complete remission in a high proportion of patients with acute promyelocytic leukemia (APL), all groups have described clinical relapses despite continued RA treatment. This finding suggests that resistance to the cytodifferentiating effects of the retinoid had been acquired. To investigate potential mechanisms of clinical resistance to RA, we serially evaluated the clinical pharmacology of the drug in APL patients treated with this agent. Leukemic cells from patients relapsing from RA treatment were cultured in the presence of RA and examined for evidence of morphologic maturation. We also studied messenger RNA expression of the newly described gene product of the (15;17) translocation in APL, PML/RA receptor-alpha (PML/RAR-alpha). Serial pharmacokinetic studies showed that continuous daily RA treatment was associated with a marked decrease in plasma drug concentrations at the time of relapse compared with the initial day of therapy. Doubling the RA dose in six patients failed to reinduce response at the time of relapse and also failed to significantly augment plasma RA concentrations. However, leukemic cells obtained at the time of relapse from four patients retained in vitro sensitivity to the differentiating activity of RA (10(-6) mol/L). No change was observed in the pattern of PML/RAR-alpha expression assessed by Northern blot analysis at the time of relapse compared with pretreatment in two patients who were tested. These results indicate that clinical relapse and "resistance" to continuous treatment with all-trans RA in APL is associated with progressive reduction of plasma concentrations, potentially to levels below those that sustain differentiation of leukemic cells in vivo. Long-term success of this treatment will require the development of strategies that circumvent this pharmacologic phenomenon.     

Clinical pharmacology of oral all-trans retinoic acid in patients with acute promyelocytic leukemia.

All-trans retinoic acid (RA) induces leukemic cell differentiation and complete remission in a high proportion of patients with acute promyelocytic leukemia (APL). However, remissions induced by all-trans RA tend to be brief, and relapses are associated with resistance to further treatment in vivo, although the leukemic cells appear to retain sensitivity to the cytodifferentiating effects of all-trans RA in vitro. The clinical pharmacology of all-trans RA was examined in 13 patients with APL. The drug was administered at a constant dose of 45 mg/m2/day, given as a single dose on the first day of therapy and in two divided doses thereafter. Plasma and urinary concentrations of the parent drug and metabolites were quantitated by reverse-phase high-performance liquid chromatography and, where required, by a combination of normal-phase liquid chromatography/negative chemical ionization mass spectrometry. In patients with APL, basal levels of endogenous retinol and natural retinoids were within the normal range. Peak plasma levels of all-trans RA (347 +/- 266 ng/ml, mean +/- SD) were reached 1-2 h after drug ingestion and decayed in a monoexponential fashion with a half-life of 0.8 +/- 0.1 h. The only drug metabolite detected in plasma or urine was 4-oxo-all-trans RA (present in urine as the glucuronide conjugate). This metabolite accounted for less than 10% of the circulating drug in plasma, and its cumulative urinary excretion accounted for less than 1% of the administered dose. The drug was not found in cerebrospinal fluid. Continued oral administration of all-trans RA was associated with a significant decrease in both the plasma peak levels and the area under the concentration-time curve (P = 0.01 and 0.004, respectively) when measured after 2-6 weeks of treatment. We previously reported that a decrease in plasma area under the concentration-time curve was highly correlated with clinical relapse. Observations in a subset of patients in this study suggested that, in fact, the major decrease occurred early, within the first 7 days of treatment. These changes were associated with a 10-fold increase in urinary excretion of 4-oxo-all-trans RA glucuronide, suggesting that the accelerated clearance from plasma was associated with increased drug catabolism. The rapid disappearance may explain early relapse from remissions induced by all-trans RA; clinical "resistance" to all-trans RA may either wholly or in part result from an inability to sustain effective plasma concentrations of all-trans RA during continuous treatment.(ABSTRACT TRUNCATED AT 400 WORDS)     

The acute effects of light on murine sleep during the dark phase: importance of melanopsin for maintenance of light‐induced sleep

Light exerts a direct effect on sleep and wakefulness in nocturnal and diurnal animals, with a light pulse during the dark phase suppressing locomotor activity and promoting sleep in the former. In the present study, we investigated this direct effect of light on various sleep parameters by exposing mice to a broad range of illuminances (0.2–200 μW/cm²; equivalent to 1–1000 lux) for 1 h during the dark phase (zeitgeber time 13–14). Fitting the data with a three‐parameter log model indicated that ～0.1 μW/cm² can generate half the sleep response observed at 200 μW/cm². We observed decreases in total sleep time during the 1 h following the end of the light pulse. Light reduced the latency to sleep from ~30 min in darkness (baseline) to ~10 min at the highest intensity, although this effect was invariant across the light intensities used. We then assessed the role of melanopsin during the rapid transition from wakefulness to sleep at the onset of a light pulse and the maintenance of sleep with a 6‐h 20 μW/cm² light pulse. Even though the melanopsin knockout mice had robust induction of sleep (~35 min) during the first hour of the pulse, it was not maintained. Total sleep decreased by almost 65% by the third hour in comparison with the first hour of the pulse in mice lacking melanopsin, whereas only an 8% decrease was observed in wild‐type mice. Collectively, our findings highlight the selective effects of light on murine sleep, and suggest that melanopsin‐based photoreception is primarily involved in sustaining light‐induced sleep.     

Activation state and intracellular trafficking contribute to the repertoire of endogenous glycosphingolipids presented by CD1d

Myeloid antigen-presenting cells (APC) express CD1d molecules that present exogenous and endogenous lipid antigens that activate CD1d-restricted T cells, natural killer T (NKT) cells. NKT cell activation has been shown to mediate the potent downstream activation of other immune cells through cell–cell interactions and rapid, prolific cytokine production. Foreign antigens are not required for NKT cell activation. The endogenous lipids bound to CD1d are sufficient for activation of NKT cells in the setting of Toll-like receptor-induced cytokines. The most potent NKT cell antigens identified are glycosphingolipids (GSL). The GSL repertoire of endogenous ligands bound to CD1d molecules that are expressed in myeloid APC at steady state and in the setting of activation has not been delineated. This report identifies the range of GSL bound to soluble murine CD1d (mCD1d) molecules that sample the endoplasmic reticulum/secretory routes and cell surface-cleaved mCD1d that also samples the endocytic system. Specific GSL species are preferentially bound by mCD1d and do not solely reflect cellular GSL. GM1a and GD1a are prominent CD1d ligands for molecules following both the ER/secretory and lysosomal trafficking routes, whereas GM2 was eluted from soluble CD1d but not lysosomal trafficking CD1d. Further, after LPS activation, the quantities of soluble CD1d-bound GM3 and GM1a markedly increased. A unique α-galactose-terminating GSL was also found to be preferentially bound to mCD1d at steady state, and it increased with APC activation. Together, these studies identify the range of GSL presented by CD1d and how presentation varies based on CD1d intracellular trafficking and microbial activation.     

The role of computed tomography in the detection of bone metastases in breast cancer patients

Computed tomography (CT) of bone was carried out in 20 patients with breast cancer, all of whom had abnormal radionuclide uptake on skeletal scintigrams but normal conventional radiographs. Twenty-eight sites were examined and 13 showed metastases in 11 patients. Five of these patients had no evidence of extra-skeletal recurrent disease. Follow-up at eight of these sites showed healing, sclerosis or progression, all of which correlated well with clinical findings. CT showed benign causes of radionuclide accumulation in three patients (7 sites) but no abnormality in six patients (8 sites). None of these patients has subsequently developed bone metastases. CT is superior to conventional radiographs in the diagnosis of skeletal metastases and should be carried out when skeletal scintigraphy is positive and conventional examinations are normal.     

Hunger and Food Insecurity in Nairobi’s Slums: An Assessment Using IRT Models

Although linked to poverty as conditions reflecting inadequate access to resources to obtain food, issues such as hunger and food insecurity have seldom been recognized as important in urban settings. Overall, little is known about the prevalence and magnitude of hunger and food insecurity in most cities. Yet, in sub-Saharan Africa where the majority of urban dwellers live on less than one dollar a day, it is obvious that a large proportion of the urban population must be satisfied with just one meal a day. This paper suggests using the one- and two-parameter item response theory models to infer a reliable and valid measure of hunger and food insecurity relevant to low-income urban settings, drawing evidence from the Nairobi Urban Health and Demographic Surveillance System. The reliability and accuracy of the items are tested using both the Mokken scale analysis and the Cronbach test. The validity of the inferred household food insecurity measure is assessed by examining how it is associated with households’ economic status. Results show that food insecurity is pervasive amongst slum dwellers in Nairobi. Only one household in five is food-secure, and nearly half of all households are categorized as “food-insecure with both adult and child hunger.” Moreover, in line with what is known about household allocation of resources, evidence indicates that parents often forego food in order to prioritize their children.     

Failure of lower motor neuron radial outgrowth precedes retrograde degeneration in a feline model of spinal muscular atrophy

Feline spinal muscular atrophy (SMA) is a fully penetrant, autosomal recessive lower motor neuron disease in domestic cats that clinically resembles human SMA Type III. A whole genome linkage scan identified a ～140-kb deletion that abrogates expression of LIX1, a novel SMA candidate gene of unknown function. To characterize the progression of feline SMA, we assessed pathological changes in muscle and spinal cord from 3 days of age to beyond onset of clinical signs. Electromyographic (EMG) analysis indicating denervation occurred between 10 and 12 weeks, with the first neurological signs occurring at the same time. Compound motor action potential (CMAP) amplitudes were significantly reduced in the soleus and extensor carpi radialis muscles at 8-11 weeks. Quadriceps femoris muscle fibers from affected cats appeared smaller at 10 weeks; by 12 weeks atrophic fibers were more prevalent than in age-matched controls. In affected cats, significant loss of L5 ventral root axons was observed at 12 weeks. By 21 weeks of age, affected cats had 40% fewer L5 motor axons than normal. There was no significant difference in total L5 soma number, even at 21 weeks; thus degeneration begins distal to the cell body and proceeds retrogradely. Morphometric analysis of L5 ventral roots and horns revealed that 4 weeks prior to axon loss, motor axons in affected cats failed to undergo radial enlargement, suggesting a role for the putative disease gene LIX1 in radial growth of axons.     

Incidence and impact of hyperviscosity on sperm parameters of Malawian men seeking assisted reproduction

BackgroundSeminal hyperviscosity has been shown to be associated with male infertility. The aim of this study was to assess the prevalence of hyperviscosity in semen of Malawian males seeking infertility treatment.MethodsA total of 120 men visiting our laboratory for fertility assessment donated semen samples. The semen samples were assessed for hyperviscosity, volume, concentration, total motility, progressive motility, viability, and morphology.ResultsOut of the 120 samples analyzed, 34 samples were hyperviscous representing 28.3%. No significant statistical difference in semen volume between samples with normal viscosity compared to those with hyperviscosity (p>0.05). Sperm concentration, progressive motility, total motility, viability, and normal morphology were significantly higher in the normal viscosity group when compared to the abnormal viscocity group (p<0.05).ConclusionHyperviscosity affects a significant number of men in Malawi and may be the cause of decreased fertility as it was associated with poor sperm concentration, total motility, progressive motility, viability, and morphology.