Evaluation of plasma retinol-binding protein as a surrogate measure for plasma retinol concentrations

Fasting growth hormone (GH) levels and GH responses to exercise were studied in normally menstruating women and in women taking oral contraceptives in order to find out whether the GH levels were related to the menstrual cycle or changed by oral contraceptives. The GH response to exercise was found to be higher when exercise was done in the midcycle period than when it was done at other points of time during the normal menstrual cycle. Fasting GH levels were unchanged throughout the menstrual cycle. Fasting GH levels and GH responses to exercise performed outside the midcycle period were identical in normally menstruating women and in women taking oral contraceptives. In conclusion, the GH response to exercise, but not fasting GH levels, were related to the menstrual cycle. The estrogen and progestin components of the contraceptives used in this study were balanced in such a way that the growth hormone levels and growth hormone responses to exercise were not changed by long-term therapy with these drugs.     

Mesenchymal progenitor cells derived from traumatized muscle enhance neurite growth

The success of peripheral nerve regeneration is governed by the rate and quality of axon bridging and myelination that occurs across the damaged region. Neurite growth and the migration of Schwann cells is regulated by neurotrophic factors produced as the nerve regenerates, and these processes can be enhanced by mesenchymal stem cells (MSCs), which also produce neurotrophic factors and other factors that improve functional tissue regeneration. Our laboratory has recently identified a population of mesenchymal progenitor cells (MPCs) that can be harvested from traumatized muscle tissue debrided and collected during orthopaedic reconstructive surgery. The objective of this study was to determine whether the traumatized muscle‐derived MPCs exhibit neurotrophic function equivalent to that of bone marrow‐derived MSCs. Similar gene‐ and protein‐level expression of specific neurotrophic factors was observed for both cell types, and we localized neurogenic intracellular cell markers (brain‐derived neurotrophic factor and nestin) to a subpopulation of both MPCs and MSCs. Furthermore, we demonstrated that the MPC‐secreted factors were sufficient to enhance in vitro axon growth and cell migration in a chick embryonic dorsal root ganglia (DRG) model. Finally, DRGs in co‐culture with the MPCs appeared to increase their neurotrophic function via soluble factor communication. Our findings suggest that the neurotrophic function of traumatized muscle‐derived MPCs is substantially equivalent to that of the well‐characterized population of bone marrow‐derived MPCs, and suggest that the MPCs may be further developed as a cellular therapy to promote peripheral nerve regeneration. Copyright © 2012 John Wiley & Sons, Ltd.     

Signal transduction by the platelet Fc receptor

We have evaluated the mechanism by which crosslinking human platelet Fc receptor (FcR) for IgG triggers platelet aggregation and the platelet release reaction. Platelet FcR was crosslinked by incubating purified human platelets with anti-FcRII monoclonal antibody and F(ab')2 anti- mouse Ig. The resultant [Ca2+]i increase, monitored by Fura-2 and measured in the absence of extracellular Ca2+, reached a peak of 750 +/- 50 nmol/L. The effects of cyclooxygenase inhibitors, aspirin and indomethacin, and a phospholipase A2 inhibitor, dibromoacetophenone, were examined. Regardless of the inhibitor, at least 25% of the [Ca2+]i increase remained. Thrombin (0.2 U/mL) stimulated an immediate [Ca2+]i increase that reached 1.95 +/- 0.8 mumol/L. The [Ca2+]i increase generated by thrombin was only slightly reduced by these inhibitors. Crosslinking the FcRII of platelets resulted in a fivefold increase in the production of [3H]inositol phosphates, (IP) which, in the absence of extracellular Ca2+ was insensitive to aspirin. The activation of a [Ca2+]i increase along with the measured increases in IP indicate that FcRII crosslinking leads to the activation of phospholipase C (PLC). In contrast to thrombin, platelet activation via FcRII depends to a large extent on arachidonic acid metabolites. However, neither cyclooxygenase nor phospholipase A2 inhibitors completely blocked FcRII-stimulated [Ca2+]i increase. These observations led us to propose that crosslinking of platelet FcRII initially activates PLC.     

Adhesion of normal and sickle erythrocytes to endothelial monolayer cultures.

Experiments were carried out to test the hypothesis that the differences between the surfaces of erythrocytes from normal and sickle cell patients are reflected in the degree of attachment to the capillary lining. An assay was used that measured the number of 51Cr-labeled erythrocytes (normal or sickle) attaching to a monolayer of endothelium cultured from calf aortas. Under these conditions, erythrocytes from sickle cell patients adhered better to the endothelium than did those from normal patients. The results suggested that the enhanced adhesion of the sickle cells to the endothelium may be partially responsible for the increased blockage of capillaries that produce the symptoms in sickle cell anemia.     

The Role of Serotonin (5-HT) in Behavioral Control: Findings from Animal Research and Clinical Implications

The neurotransmitters serotonin and dopamine both have a critical role in the underlying neurobiology of different behaviors. With focus on the interplay between dopamine and serotonin, it has been proposed that dopamine biases behavior towards habitual responding, and with serotonin offsetting this phenomenon and directing the balance toward more flexible, goal-directed responding. The present focus paper stands in close relationship to the publication by Worbe et al. (2015), which deals with the effects of acute tryptophan depletion, a neurodietary physiological method to decrease central nervous serotonin synthesis in humans for a short period of time, on the balance between hypothetical goal-directed and habitual systems. In that research, acute tryptophan depletion challenge administration and a following short-term reduction in central nervous serotonin synthesis were associated with a shift of behavioral performance towards habitual responding, providing further evidence that central nervous serotonin function modulates the balance between goal-directed and stimulus-response habitual systems of behavioral control. In the present focus paper, we discuss the findings by Worbe and colleagues in light of animal experiments as well as clinical implications and discuss potential future avenues for related research.     

Bioavailability of beryllium oxide particles: an in vitro study in the murine J774A.1 macrophage cell line model

Beryllium metal and its oxide and alloys are materials of industrial significance with recognized adverse effects on worker health. Currently, the degree of risk associated with exposure to these materials in the workplace is assessed through measurement of beryllium aerosol mass concentration. Compliance with the current mass-based occupational exposure limit has proven ineffective at eliminating the occurrence of chronic beryllium disease (CBD). The rationale for this research was to examine the mechanism of beryllium bioavailability, which may be pertinent to risk. The authors tested the hypothesis in vitro that dissolution of particles engulfed by macrophages is greater than dissolution in cellular medium alone. Physicochemical changes were evaluated in vitro for well-characterized high-purity beryllium oxide (BeO) particles in cell-free media alone and engulfed by and retained within murine J774A.1 monocyte-macrophage cells. The BeO particles were from a commercially available powder and consisted of diffuse clusters (aerodynamic diameter range 1.5 to 2.5 microm) of 200-nm diameter primary particles. Following incubation for 124 to 144 hours, particles were recovered and recharacterized. Recovered particles were similar in morphology, chemical composition, and size relative to the original material, confirming the relatively insoluble nature of the BeO particles. Measurable levels of dissolved beryllium, representing 0.3% to 4.8% of the estimated total beryllium mass added, were measured in the recovered intracellular fluid. Dissolved beryllium was not detected in the extracellular media. The BeO chemical dissolution rate constant in the J774A. 1 cells was 2.1 +/- 1.7 x 10(-8)g/(cm2 . day). In contrast, the BeO chemical dissolution rate constant in cell-free media was < 8.1 x 10(-9)g/(cm2 . day). In vivo, beryllium dissolved by macrophages may be released in the pulmonary alveolar environment, in the lymphatic system after transport of beryllium by macrophages, or in the alveolar interstitium after migration and dissolution of beryllium particles in tissue. These findings demonstrate a mechanism of bioavailability for beryllium, are consistent with previously observed results in canine alveolar macrophages, and provide insights into additional research needs to understand and prevent beryllium sensitization and CBD.     

Feline leukemia virus-induced erythroid aplasia: in vitro hemopoietic culture studies

Colony forming unit (CFU) assays were developed for feline granulocyte-macrophage (CFUGM), early erythroid (day 2 CFUE), and late erythroid (day 7 CFUE) colonies in methylcellulose medium. Feline CFUGM and both day 2 and day 7 CFUE were enhanced by feline macrophage conditioned medium and late CFUE often were intimately associated with macrophages. Kittens were inoculated with the Kawakami-Theilen (KT) strain of feline leukemia virus (FeLV) and sequential changes in marrow CFU determined. Erythroid aplasia, characterized by progressive non-regenerative anemia, lymphopenia, and a profound decrease in early and late CFUE but not CFUGM was induced by 3 to 5 weeks after FeLV-KT inoculation. The susceptibility of kittens to FeVL-induced erythroid aplasia was strongly age-related; neonatal kittens were most sensitive and substantial natural resistance developed by 4 weeks of age. The results demonstrate that FeLV-KT infection induced a rapid and selective suppression of erythroid progenitor cells and represents a suitable model of experimentally-induced acquired erythroid aplasia.