Atriopeptins and nitroprusside provoke opposite changes in cGMP and cAMP levels in human macrophages.

Atrial natriuretic factor (ANF, 10(-7) M) and, even more potently, sodium nitroprusside (SNP, 10(-5)-10(-3) M) stimulated cGMP formation in human peritoneal macrophages. This suggests that the two forms of guanylate cyclase, the particulate form stimulated by ANF and the soluble form activated by SNP, coexist in this cell type. A fall in cAMP levels in parallel with the rise of cGMP levels provoked by ANF and SNP was noticed that was amplified by an increase in the concentration of the phosphodiesterase inhibitor, IBMX. Our finding that ANF, contrary to its action in other tissues, was unable to exert direct inhibitory effects on the adenylate cyclase activity in isolated macrophage membranes, together with the observation that SNP was able to mimic the effect of ANF on cAMP levels indicates that the cAMP-lowering effect of ANF is most likely mediated through the cGMP signal.     

GTP-related difference in cyclic AMP production between resident and inflammatory human peritoneal macrophages.

In macrophages cyclic AMP (c-AMP) plays an important role in regulating many activities such as phagocytosis, migration and tumoricidal activity. High intracellular levels of c-AMP are negatively correlated with these activities. In earlier studies we have shown that c-AMP levels in inflammatory human peritoneal macrophages (IM) were markedly lower when compared to levels in resident macrophages (RM). This is in line with the fact that c-AMP down-regulates macrophage activity. To our knowledge no data are available on the mechanism underlying the difference in c-AMP production between RM and IM. In this study the difference in c-AMP production between RM and IM has been investigated on the level of receptor and G-protein-related mechanisms. Macrophage membranes were incubated with different agents i.e. prostaglandin E2 (PGE2), prostacyclin I2 (PGI2), isoprenalin (ISO) and sodium fluoride (SF). Additionally, the capacity of IM and RM to hydrolyse quanosine triphosphate (GTP) was measured. Only in the presence of GTP (10(-4) M) could the c-AMP difference be detected (RM = 51 +/- 4.4 pmol/mg protein/min +/- S.E., n = 22, IM = 32.8 +/- 5.2 pmol/mg protein/min +/- S.E., n = 10, p less than 0.01). After receptor stimulation with PGE2, PGI2 and ISO, c-AMP levels increased to the same extent in both IM and RM with no effect on the GTP-related difference. After SF stimulation, c-AMP levels in RM and IM increased to the same level (RM = 63 +/- 8 pmol/mg protein/min, n = 14, IM = 58 +/- 11 pmol/mg protein/min, n = 13).(ABSTRACT TRUNCATED AT 250 WORDS)     

How physical therapists instruct patients with stroke: an observational study on attentional focus during gait rehabilitation after stroke

Purpose: People without neurological impairments show superior motor learning when they focus on movement effects (external focus) rather than on movement execution itself (internal focus). Despite its potential for neurorehabilitation, it remains unclear to what extent external focus strategies are currently incorporated in rehabilitation post-stroke. Therefore, we observed how physical therapists use attentional focus when treating gait of rehabilitating patients with stroke.

Methods: Twenty physical therapist-patient couples from six rehabilitation centers participated. Per couple, one regular gait-training session was video-recorded. Therapists’ statements were classified using a standardized scoring method to determine the relative proportion of internally and externally focused instructions/feedback. Also, we explored associations between therapists’ use of external/internal focus strategies and patients’ focus preference, length of stay, mobility, and cognition.

Results: Therapists’ instructions were generally more external while feedback was more internal. Therapists used relatively more externally focused statements for patients with a longer length of stay (B?=??0.239, p?=?0.013) and for patients who had a stronger internal focus preference (B?=??0.930, p?=?0.035).

Conclusions: Physical therapists used more external focus instructions, but more internally focused feedback. Also, they seem to adapt their attentional focus use to patients’ focus preference and rehabilitation phase. Future research may determine how these factors influence the effectiveness of different attentional foci for motor learning post-stroke.

• IMPLICATIONS FOR REHABILITATION

• Physical therapists use a balanced mix of internal focus and external focus instructions and feedback when treating gait of stroke patients.

• Therapists predominantly used an external focus for patients in later rehabilitation phases, and for patients with stronger internal focus preferences, possibly in an attempt to stimulate more automatic control of movement in these patients.

• Future research should further explore how a patients’ focus preference and rehabilitation phase influence the effectiveness of different focus strategies.

• Awaiting further research, we recommend that therapists use both attentional focus strategies, and explore per patient which focus works best on a trial-and-error basis.

     

Systemic hematologic effects of PEG-rHuMGDF-induced megakaryocyte hyperplasia in mice

PEG-rHuMGDF injected daily in normal mice causes a rapid dose-dependent increase in megakaryocytes and platelets. At the same time that platelet numbers are increased, the mean platelet volume (MPV) and platelet distribution width (PDW) can be either decreased, normal, or increased depending on the dose and time after administration. Thus, PEG-rHuMGDF at a low dose causes decreases in MPV and PDW, MGDF at an intermediate dose causes an initial increase followed by a decrease in MPV and PDW, and PEG-rHuMGDF at higher doses causes an increase in MPV and PDW followed by a gradual normalization of these platelet indices. In addition to the expected thrombocytosis after 7 to 10 days of daily injection of high doses of PEG-rHuMGDF, a transient decrease in peripheral red blood cell numbers and hemoglobin is noted accompanied in the bone marrow by megakaryocytic hyperplasia, myeloid hyperplasia, erythroid and lymphoid hypoplasia, and deposition of a fine network of reticulin fibers. Splenomegaly, an increase in splenic megakaryocytes, and extramedullary hematopoiesis accompany the hematologic changes in the peripheral blood and marrow to complete a spectrum of pathologic features similar to those reported in patients with myelofibrosis and megakaryocyte hyperplasia. However, all the PEG-rHuMGDF-initiated hematopathology including the increase in marrow reticulin is completely and rapidly reversible upon the cessation of administration of PEG-rHuMGDF. Thus, transient hyperplastic proliferation of megakaryocytes does not cause irreversible tissue injury. Furthermore, PEG-rHuMGDF completely ameliorates carboplatin-induced thrombocytopenia at a low-dose that does not cause the hematopathology associated with myelofibrosis.     

Human taurine metabolism: fluxes and fractional extraction rates of the gut, liver, and kidneys

Taurine is involved in numerous biological processes. However, taurine plasma level decreases in response to pathological conditions, suggesting an increased need. Knowledge on human taurine metabolism is scarce and only described by arterial-venous differences across a single organ. Here we present taurine organ fluxes using arterial-venous concentration differences combined with blood flow measurements across the 3 major organ systems involved in human taurine metabolism in patients undergoing hepatic surgery. In these patients, we collected blood from an arterial line, portal vein, hepatic vein, and renal vein, and determined blood flow of the hepatic artery, portal vein, and renal vein using Doppler ultrasound. Plasma taurine was determined by high-performance liquid chromatography, and net organ fluxes and fractional extraction rates were calculated. Seventeen patients were studied. No differences were found between taurine concentrations in arterial, portal venous, hepatic venous, and renal venous plasma. The only significant finding was a release of taurine by the portally drained viscera (P = .04). Our data show a net release of taurine by the gut. This probably is explained by the enterohepatic cycle of taurine. Future studies on human taurine metabolism are required to determine whether taurine is an essential aminosulfonic acid during pathological conditions and whether it should therefore be supplemented.     

Biphasic transmittance waveform in the APTT coagulation assay is due to the formation of a Ca(++)-dependent complex of C-reactive protein with very-low-density lipoprotein and is a novel marker of impending disseminated intravascular coagulation

A decrease in light transmittance before clot formation, manifesting as a biphasic waveform (BPW) pattern in coagulation assays, was previously correlated with the onset of disseminated intravascular coagulation (DIC). In this study of 1187 consecutive admissions to the intensive care unit, the degree of this change on admission predicts DIC better than D-dimer measurements. Additionally, the BPW preceded the time of DIC diagnosis by 18 hours, on average, in 56% (203 of 362) of DIC patients. The BPW is due to the rapid formation of a precipitate and coincident turbidity change on recalcification of plasma. The isolated precipitate contains very-low-density lipoprotein (VLDL) and C-reactive protein (CRP). The addition of CRP and Ca(++) to normal plasma also causes the precipitation of VLDL and IDL, but not LDL or HDL. The K(d) of the CRP/VLDL interaction is 340 nM, and the IC(50) for Ca(++) is 5.0 mM. In 15 plasmas with the BPW, CRP was highly elevated (77-398 microg/mL), and the concentration of isolated VLDL ranged from 0.082 to 1.32 mM (cholesterol). The turbidity change on recalcification correlates well with the calculated level of the CRP-VLDL complex. Clinically, the BPW better predicts for DIC than either CRP or triglyceride alone. The complex may have pathophysiological implications because CRP can be detected in the VLDL fraction from sera of patients with the BPW, and the VLDL fraction has enhanced prothrombinase surface activity. The complex has been designated lipoprotein complexed C-reactive protein.     

Colorectal cancer extracellular acidosis decreases immune cell killing and is partially ameliorated by pH-modulating agents that modify tumor cell cytokine profiles

Tumor cells upregulate myriad proteins that are important for pH regulation, resulting in the acidification of the extracellular tumor microenvironment (TME). Abnormal pH is known to dampen immune function, resulting in a worsened anti-tumor immune response. Understanding how extrinsic alterations in pH modulate the interactions between immune cells and tumors cells will help elucidate opportunities for new therapeutic approaches. We observed that pH impacts the function of immune cells, both natural killer (NK) and T cells, which is relevant in the context of a highly acidic TME. Decreased NK and T cell activity was correlated with decreasing pH in a co-culture immune cell-mediated tumor cell-killing assay. The addition of pH-modulating drugs cariporide, lansoprazole, and acetazolamide to the co-culture assay was able to partially mitigate this dampened immune cell function. Treatment of colorectal cancer (CRC) cells with NHE1 inhibitor cariporide increased CRC cell-secreted cytokines involved in immune cell recruitment and activation and decreased cytokines involved in epithelial-mesenchymal transition (EMT). Cariporide treatment also decreased CRC cell shed TRAIL-R2, TRAIL-R3, and PD-L1 which is relevant in the context of immunotherapy. These experiments can help inform future investigations into how the pH of the tumor microenvironment may be extrinsically modulated to improve anti-tumor immune response in solid tumors such as colorectal cancer.