B‐cell capacity for differentiation changes with age

BackgroundAge‐related immune deficiencies are thought to be responsible for increased susceptibility to infection in older adults, with alterations in lymphocyte populations becoming more prevalent over time. The loss of humoral immunity in ageing was attributed to the diminished numbers of B cells and the reduced ability to generate immunoglobulin.AimsTo compare the intrinsic B‐cell capacity for differentiation into mature plasma cells (PCs), between young and old donors, using in vitro assays, providing either effective T‐cell help or activation via TLR engagement.MethodsB cells were isolated from healthy individuals, in younger (30–38 years) and older (60–64 years) donors. An in vitro model system of B‐cell differentiation was used, analysing 5 differentiation markers by flow cytometry, under T‐dependent (TD: CD40/BCR stimulation) or T‐independent (TI: TLR7/BCR activation) conditions. Antibody secretion was measured by ELISA and gene expression using qPCR.ResultsTI and TD differentiation resulted in effective proliferation of B cells followed by their differentiation into PC. B‐cell‐executed TI differentiation was faster, all differentiation marker and genes being expressed earlier than under TD differentiation (day 6), although generating less viable cells and lower antibody levels (day 13). Age‐related differences in B‐cell capacity for differentiation were minimal in TD differentiation. In contrast, in TI differentiation age significantly affected proliferation, viability, differentiation, antibody secretion and gene expression, older donors being more efficient.ConclusionAltogether, B‐cell differentiation into PC appeared similar between age groups when provided with T‐cell help, in contrast to TI differentiation, where multiple age‐related changes suggest better capacities in older donors. These new findings may help explain the emergence of autoantibodies in ageing.     

The presence or absence of light during flotation restricted environmental stimulation: Effects on plasma cortisol,blood pressure,and mood

This study examined the effect of light on relaxation associated with flotation restricted environmental stimulation therapy (REST), as measured by plasma cortisol, mean arterial pressure, and psychometric parameters. Twenty-one subjects were paired by baseline cortisol levels into two groups: one experiencing flotation REST in the presence of light (REST-L) and one experiencing flotation REST in the absence of light (REST-D). Subjects were 15 male and 6 female students aged 22–28 in normal health who had not experienced REST. Repeated flotation REST (8 sessions) either with light or without light was associated with a decrease in plasma cortisol and a decrease in mean arterial pressure, with no differences in effectiveness between groups. The psychometric assessment of mood, using the POMS scale, before and after sessions 1 and 8 revealed mood state improvement in both REST-L and REST-D groups. These data suggest that the presence of light did not compromise the flotation REST experience, as evidenced by the lack of difference between REST-L and REST-D groups.     

Plasmalemma Redox Chain and H Extrusion: II. Respiratory and Metabolic Changes Associated with Fusicoccin-Induced and with Ferricyanide-Induced H Extrusion

Ferricyanide reduction by Elodea densa leaves is associated with a release of protons in the cytoplasm, a fraction of the increase in protons being then extruded by the ATP-driven proton pump (20). The data presented here show that ferricyanide induces a marked increase in O₂ uptake, additive to that induced by fusicoccin plus K⁺, and here interpreted as depending on the utilization of ATP by the H⁺ pump. Glucose 6-phosphate and malate levels are markedly increased by fusicoccin plus K⁺. The simultaneous presence of ferricyanide reduces by about 50% the increase of malate, while it completely suppresses that of glucose 6-phosphate. The ferricyanide-induced decrease of malate is interpreted as due to the acidification of the cytosol associated with ferricyanide reduction, while the more marked decrease of glucose 6-phosphate might depend in part on the pH change and in part on a faster oxidation of this substrate. In fact, ferricyanide reduction is accompanied by a marked decrease of the incorporation into RNA ribose of C-1 as compared with C-2 of [¹⁴C]glucose. This suggests a stimulation of the release of C-1 as CO₂ at the level of the glucose 6-phosphate oxidation pathway, as expected if NADPH was the electron donor for ferricyanide reduction. These results are interpreted as confirming that the H⁺ efflux associated with ferricyanide reduction depends on the activation of the ATP-driven plasmalemma H⁺ pump. They also suggest that NADPH is used as an electron donor to some initial component of the plasmalemma redox system.     

Developmental toxicity evaluation of Bendectin in CD rats

Bendectin, composed of doxylamine succinate and pyridoxine HCl (1:1), is an antinauseant previously prescribed for nausea and vomiting during pregnancy. The present study examined the maternal and developmental effects of Bendectin (0, 200, 500, or 800 mg/kg/day, po) administered to timed-pregnant CD rats (36-41/group) during organogenesis (gestational days [gd] 6-15). At death (gd 20), all live fetuses were examined for external, visceral, and skeletal abnormalities. At 500 and 800 mg/kg/day, maternal toxicity included reduced food consumption during treatment and for the gestation period, increased water consumption in the posttreatment period, reduced weight gain during treatment, and sedation; water consumption was reduced during treatment and for the gestation period, and maternal mortality (17.1%) was observed only at the high dose. Developmental toxicity included reduced prenatal viability (800 mg/kg/day) and reduced fetal body weight/litter (500 and 800 mg/kg/day). In addition, reduced ossification of metacarpals (800 mg/kg/day), phalanges of the forelimbs (500 and 800 mg/kg/day), and of caudal vertebral centra (all doses) was observed. No increase in percent malformed live fetuses/litter was observed. The proportion of litters with one or more malformed fetuses was higher than vehicle controls only at 800 mg/kg/day, with short 13th rib (to which the test species is predisposed) as the predominant observation. By contrast, a positive control agent (nitrofen, 50 mg/kg/day, po, 14 dams) produced 85% malformed fetuses/litter with the predominant malformation being diaphragmatic hernia. In conclusion, the incidence of litters with one or more malformed fetuses was increased only at a dose of Bendectin which produced maternal mortality (17.1%) and other indices of maternal and developmental toxicity (see Discussion).     

Occurrence of Prorocentrum lima,a DSP toxin-producing species from the Atlantic coast of Canada

A species of Prorocentrum (Dinophyta, Prorocentrales), isolated from a phytoplankton net sample from the Atlantic coast of Nova Scotia, has been brought into unialgal culture. The sample was collected at an aquaculture site immediately following an incident of diarrhetic shellfish poisoning (DSP) due to the consumption of contaminated mussels. This clonal isolate has been identified as P. lima, based on its morphological characteristics. Analysis of the culture extract, using high performance liquid chromatography (HPLC) with fluorescence detection, indicated the presence of the DSP toxins, okadaic acid (OA) and dinophysistoxin-1 (DTX-1).     

Isolation and partial characterization of a protein kinase NII from wheat germ chromatin

A protein kinase, type NII, has been purified from wheat germ chromatin. The enzyme, which uses both ATP and GTP as phosphoryl donors, catalyzes the phosphorylation of casein, phosvitin and E. coli RNA polymerase, but not of histone proteins. Polypeptide bands at 46 kDa, 37 kDa and 25 kDa were estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Autophosphorylation of the 25 kDa subunit was observed following incubation of the purified kinase with (-³²P)ATP and (-³²P)GTP.