Increased circulating interleukin-7 levels in HIV-1-infected women

Sex-based differences in CD4 T-cell (CD4) counts are well recognized, but the basis for these differences has not been identified. Conceivably, homeostatic factors may play a role in this process by regulating T-cell maintenance and repletion. Interleukin (IL)-7 is essential for normal T-cell production and homeostasis. We hypothesized that differences in IL-7 might contribute to sex-based differences in CD4 counts. Circulating IL-7 levels were analyzed in 299 HIV-1-infected women and men. Regression analysis estimated that IL-7 levels were 40% higher in women than in men (P = 0.0032) after controlling for CD4 count, age, and race. Given the important role of IL-7 in T-cell development and homeostasis, these findings suggest that higher IL-7 levels may contribute to higher CD4 counts in women.     

Cytoskeletal changes during neurogenesis in cultures of avian neural crest cells

Summary Neural crest cells are motile and mitotic, whereas their neuronal derivatives are terminally post-mitotic and consist of stationary cell body from which processes grow. The present study documents changes in the cytoskeleton that occur during neurogenesis in cultures of avian neural crest cells. The undifferentiated neural crest cells contain dense bundles of actin filaments throughout their cytoplasm, and a splayed array of microtubules attached to the centrosome. In newly differentiating neurons, the actin bundles are disrupted and most of the remaining actin filaments are reorganized into a cortical layer underlying the plasma membrane of the cell body and processes. Microtubules are more abundant in newly-differentiating neurons than in the undifferentiated cells, and individual microtubules can be seen dissociated from the centrosome. Neuron-specific -III tubulin appears in some crest cells prior to cessation of motility and cell division, and expression increases with total microtubule levels during neurogenesis. To investigate how these early cytoskeletal changes might contribute to alterations in morphology during neurogenesis, we have disrupted the cytoskeleton with pharmacologic agents. Microfilament disruption by cytochalasin immediately arrests the movement of neural crest cells and causes them to round-up, but does not significantly change the morphology of the immature neurons. Microtubule depolymerization by nocodazole slows the movement of undifferentiated cells and causes retraction of processes extended by the immature neurons. These results suggest that changes in the actin and microtubule arrays within neural crest cells govern distinct aspects of their morphogenesis into neurons.     

Brief report: child-rearing practices of caregivers with and without a child with juvenile rheumatoid arthritis: perspectives of caregivers and professionals

OBJECTIVE: To evaluate predictions from professionals in pediatric rheumatology regarding the child-rearing practices of caregivers of children with juvenile rheumatoid arthritis (JRA) and healthy classmates. METHODS: Sixteen professionals identified items from the Child-Rearing Practices Report (CRPR) that were expected to differentiate between caregivers of children with JRA (64 mothers, 45 fathers) and caregivers of healthy classmates (64 mothers, 40 fathers). Families were interviewed, and physician ratings of disease severity were obtained. RESULTS: Experts predicted difficulties in protectiveness, discipline, and worry. Ratings from parents of children with JRA showed modest agreement with the professionals, surprising similarity to controls, and a limited association with disease factors. CONCLUSIONS: Contrary to expert opinion, JRA has only a modest influence on some child-rearing practices. Educating health care providers may minimize misperceptions about caring for children with JRA, and screening parents of children with more severe disease may assist in allocating education and services for families.     

A trade-off in replication in mosquito versus mammalian systems conferred by a point mutation in the NS4B protein of dengue virus type 4

An acceptable live-attenuated dengue virus vaccine candidate should have low potential for transmission by mosquitoes. We have identified and characterized a mutation in dengue virus type 4 (DEN4) that decreases the ability of the virus to infect mosquitoes. A panel of 1248 mutagenized virus clones generated previously by chemical mutagenesis was screened for decreased replication in mosquito C6/36 cells but efficient replication in simian Vero cells. One virus met these criteria and contained a single coding mutation: a C-to-U mutation at nucleotide 7129 resulting in a Pro-to-Leu change in amino acid 101 of the nonstructural 4B gene (NS4B P101L). This mutation results in decreased replication in C6/36 cells relative to wild-type DEN4, decreased infectivity for mosquitoes, enhanced replication in Vero and human HuH-7 cells, and enhanced replication in SCID mice implanted with HuH-7 cells (SCID-HuH-7 mice). A recombinant DEN4 virus (rDEN4) bearing this mutation exhibited the same set of phenotypes. Addition of the NS4B P101L mutation to rDEN4 bearing a 30 nucleotide deletion (Delta30) decreased the ability of the double-mutant virus to infect mosquitoes but increased its ability to replicate in SCID-HuH-7 mice. Although the NS4B P101L mutation decreases infectivity of DEN4 for mosquitoes, its ability to enhance replication in SCID-HuH-7 mice suggests that it might not be advantageous to include this specific mutation in an rDEN4 vaccine. The opposing effects of the NS4B P101L mutation in mosquito and vertebrate systems suggest that the NS4B protein is involved in maintaining the balance between efficient replication in the mosquito vector and the human host.     

Distinct expression and localization of serine protease HtrA1 in human endometrium and first-trimester placenta.

Mammalian embryos cannot survive without the placenta. Development of the human placenta requires trophoblast proliferation, differentiation, and invasion as well as highly coordinated modulation of the maternal uterus. HtrA1 is a member of the recently identified mammalian HtrA (high temperature requirement factor A) serine protease family with a high level of expression in the placenta. In this study, we examined whether HtrA1 expression (mRNA and protein) is associated with placental development in the human. HtrA1 is up-regulated in both endometrial glands and decidual cells during endometrial preparation for embryo implantation and during first-trimester pregnancy at placentation. HtrA1 expression was also detected in certain trophoblast subtypes during early pregnancy. The villous syncytiotrophoblast and cytotrophoblast showed the strongest expression while the interstitial extravillous trophoblast showed the lowest or no expression of HtrA1. The distinct distribution of HtrA1 at the maternal-trophoblast interface suggests that HtrA1 may play a role in placental development.     

Mitochondrial Ca(2+) buffering regulates synaptic transmission between retinal amacrine cells

The diverse functions of retinal amacrine cells are reliant on the physiological properties of their synapses. Here we examine the role of mitochondria as Ca(2+) buffering organelles in synaptic transmission between GABAergic amacrine cells. We used the protonophore p-trifluoromethoxy-phenylhydrazone (FCCP) to dissipate the membrane potential across the inner mitochondrial membrane that normally sustains the activity of the mitochondrial Ca(2+) uniporter. Measurements of cytosolic Ca(2+) levels reveal that prolonged depolarization-induced Ca(2+) elevations measured at the cell body are altered by inhibition of mitochondrial Ca(2+) uptake. Furthermore, an analysis of the ratio of Ca(2+) efflux on the plasma membrane Na-Ca exchanger to influx through Ca(2+) channels during voltage steps indicates that mitochondria can also buffer Ca(2+) loads induced by relatively brief stimuli. Importantly, we also demonstrate that mitochondrial Ca(2+) uptake operates at rest to help maintain low cytosolic Ca(2+) levels. This aspect of mitochondrial Ca(2+) buffering suggests that in amacrine cells, the normal function of Ca(2+)-dependent mechanisms would be contingent upon ongoing mitochondrial Ca(2+) uptake. To test the role of mitochondrial Ca(2+) buffering at amacrine cell synapses, we record from amacrine cells receiving GABAergic synaptic input. The Ca(2+) elevations produced by inhibition of mitochondrial Ca(2+) uptake are localized and sufficient in magnitude to stimulate exocytosis, indicating that mitochondria help to maintain low levels of exocytosis at rest. However, we found that inhibition of mitochondrial Ca(2+) uptake during evoked synaptic transmission results in a reduction in the charge transferred at the synapse. Recordings from isolated amacrine cells reveal that this is most likely due to the increase in the inactivation of presynaptic Ca(2+) channels observed in the absence of mitochondrial Ca(2+) buffering. These results demonstrate that mitochondrial Ca(2+) buffering plays a critical role in the function of amacrine cell synapses.     

Bone growth in zebrafish fins occurs via multiple pulses of cell proliferation.

Fin length in the zebrafish is achieved by the distal addition of bony segments of the correct length. Genetic and molecular data provided evidence that segment growth uses a single pulse of growth, followed by a period of stasis. Examination of cell proliferation during segment growth was predicted to expose a graphical model consistent with a single burst of cell division (e.g., constant, parabolic, or exponential decay) during the lengthening of the distal-most segment. Cell proliferation was detected either by labeling animals with bromodeoxyuridine (during S-phase) or monitoring histone3-phosphate (mitosis). Results from both methods revealed that the number of proliferating cells fluctuates in apparent pulses as a segment grows (i.e., during the growth phase). Thus, rather than segment size being the result of a single burst of proliferation, it appears that segment growth is the result of several pulses of cell division that occur approximately every 60 microns (average segment length approximately 250 microns). These results indicate that segment lengthening requires multiple pulses of cell proliferation.