Reduced glutathione, dithiothreitol and cytochrome P-450 inhibitors do not influence hypoxic chemosensory responses in the rat carotid body

Glomus cells and carotid sinus afferents are anatomically connected, and the chemical events in the glomus cells are expected to be conveyed reflexly as afferent signals. Accordingly, K(+) channel inhibition of the glomus cell membrane is expected to be followed by excitation of the afferents. In order to test the redox inhibition of K(+) channels of glomus cells by reduced glutathione (GSH), dithiothreitol (DTT) and by cytochrome P-450 inhibitors (clotrimazole and miconazole), we measured the carotid sinus nerve (CSN) discharge using an in vitro perfused adult rat carotid body (CB) in the presence and absence of these chemicals which are expected to excite the afferents. Our findings were that these agents did not stimulate the CSN activities during normoxia and kept the hypoxic responses intact. These results led us to conclude that the redox modulation of glomus cells was not conveyed to the afferents, and this functional disconnection did not support the redox hypothesis of O(2) chemoreception in the whole carotid body.

Effects of 2,4-dinitrophenol (DNP) on the relationship between the chemosensory activities of the rat carotid body and the intracellular calcium of glomus cells

To test the hypothesis that the uncoupler 2,4-dinitrophenol (DNP) increases [Ca2+]i equally well, independent of pHi, we studied the effects of 250 microM DNP on [Ca2+]i and carotid sinus nerve (CSN) activity of rat carotid body (CB). CSN activity was measured in CB perfused and superfused with hypocapnic (pHo 7.80) and normocapnic (pHo 7.42) Tyrode solutions. [Ca2+]i of glomus (type I cells) was assessed by superfusion techniques under identical conditions as for CSN recording experiments. The results indicate that 250 microM DNP increased [Ca2+]i of type I cells as well as CSN activity at both pHos, although alkalosis diminished these responses. Given that pHi will change with pHo, DNP did not make any additional pHi change, although [Ca2+]i changed. We conclude that DNP effects were due to [Ca2+]i change alone, and the relationship between [Ca2+]i and CSN activity are internally consistent.

Effects of low-copper diets on human immune response

We examined the effects of low-copper diets on indexes of immune response of 11 healthy men (aged 21-32 y) during a 90-d metabolic suite study. Daily copper intake for the first 24 d, next 42 d, and the last 24 d of the study was 0.66, 0.38, and 2.49 mg, respectively. Feeding the diet with 0.38 mg Cu/d was associated with a significant (P < or = 0.05) decrease in the proliferation of peripheral blood mononuclear cells cultured with phytohemagglutinin, Concanavalin A, or pokeweed, and an increase in the percentage of circulating B cells (CD 19+), but had no effect on the concentration of serum interleukin 2 receptor, the percentage of peripheral monocytes, neutrophils, CD3+, CD4+, or CD8+ T cells; or on the neutrophil phagocytic activity. Feeding 2.49 mg Cu/d for 24 d prevented further decreases in the indexes affected by the low-copper diet but did not restore them to the prestudy concentrations, even though plasma copper and ceruloplasmin concentrations were restored to normal.

Effect of a low beta-carotene diet on the immune functions of adult women

We examined the effect of beta-carotene depletion and repletion on the immune status of nine healthy women who lived in the metabolic suite for 100 d. For the first 4 d all women were fed a basal diet supplemented with 1.5 mg beta-carotene/d (baseline). During the next 68 d, the basal diet without beta-carotene supplementation was fed to all subjects (depletion), and during the last 28 d the diet of each women was supplemented with 15.0 mg beta-carotene/d (repletion). Neither beta-carotene depletion nor repletion significantly (P < or = 0.05) altered proliferation of peripheral blood mononuclear cells cultured with phytohemagglutinin or concanavalin A, in vitro production of soluble interleukin 2 receptor, or the concentration of circulating lymphocytes and their subsets. Thus, in healthy adults consuming adequate vitamin A, beta-carotene depletion had no adverse effect on the indexes tested, nor was there any beneficial effect of modest beta-carotene supplementation.

Energy restriction decreases number of circulating natural killer cells and serum levels of immunoglobulins in overweight women

We examined the effects of energy restriction on immune response and also compared the effects of low fat (LF, 18.6 E%) and high fat (HF, 40.7 E%) diets during energy restriction on immunological parameters. Ten overweight women were fed the HF diet for 42 days (P1) to maintain their body weights. For the next 84 days (P2), the energy intake was reduced to 50% of the intake during P1 for all the women, five of them were fed the HF diet and the other five the LF diet. For the last 35 days of the study (P3), subjects remained on their respective diets, but the energy intake was increased to maintain BW to the level reached at the end of energy restriction. Serum concentrations of IgG, IgA, IgM, C3 and C4, numbers of lymphocytes and their subsets, blastogenesis of peripheral blood mononuclear cells cultured with phytohemagglutinin, concanavalin A and protein A were determined several times during the study. Delayed hypersensitivity skin (DHS) response to seven recall antigens was determined towards the end of each study period. None of the parameters studied were different between the HF and LF dietary groups. During energy restriction the subjects lost an average of 7 kg in the LF group and 9 kg in the HF group. Energy restriction caused a significant (P < 0.005) decrease in the serum concentration of IgG, IgA, C3, and the number of circulating natural killer (NK) cells. An increase in energy intake during P3 reversed some of the decreases caused by energy restriction, but the levels did not return to pre-restriction levels during these 35 days of refeeding adequate dietary energy. The numbers of circulating lymphocytes and their subsets with the exception of NK cells, serum levels of IgM and C4, and the DHS response monitored 48 h after the application of antigens were not affected by energy restriction. Health status of the women in our study did not seem to be compromised; however, it could be compromised under more drastic restrictions or with moderate restrictions in high risk subjects.

Fat intake and immune response

Changing the concentration or the type of fat intake impacts several aspects of the immune response involving lymphocytes, monocytes, and neutrophils. An increase in the intake of fat inhibited immune response in humans and in several animal models. Polyunsaturated fatty acids (PUFA) of N-6 type lowered immune response in several animal models, but a moderate increase in the consumption of N-6 PUFA by humans did not have any detectable adverse effect on the immune response. In humans, several indices of immune response were inhibited by the N-3 PUFA, but in animals both inhibition and stimulation were found, depending upon the species, the fatty acids used and the index being examined. Whether the absolute amounts or the ratios between individual fatty acids or fatty acid classes are critical in determining their effects on immune response need to be investigated. Manipulation of fat intake has already found limited success in managing some of the disorders of the immune system and further use of this treatment is anticipated.

Benzene-induced inhibition of erythroid colony formation in vitro

The erythroid colony forming unit assay technique was used to study the inhibitory effect of benzene on mouse bone marrow cell culture in vitro. The ability of vitamin B6 to prevent benzene-induced inhibition of erythroid colony formation was also tested. At concentrations equal to or higher than the lowest inhibitory concentration of benzene, pyridoxine HCl significantly prevented benzene-induced inhibition of erythroid colony formation in vitro. However, when benzene concentration was higher, the added pyridoxine HCl was ineffective in preventing benzene-induced inhibition of erythroid colony formation in vitro, even when it was preincubated with the bone marrow cells for 30 minutes prior to adding benzene. On the basis of this finding, it is proposed that benzene-induced inhibition of erythroid colony formation may involve two different mechanisms, one of which involves interaction with vitamin B6 added as pyridoxine HCl.

Numbers of T-cell rosettes in the peripheral blood of patients receiving maintenance hemodialysis

We evaluated 21 maintenance hemodialysis (MHD) patients and 23 healthy control subjects quantitatively for levels of peripheral blood T-cells. Mononuclear cells isolated from peripheral blood by the Ficoll-Hypaque gradient technic were used to determine the percentage of T-cells that formed E-rosettes (%RFC) in each group. Total blood lymphocytes were also determined for each group and the results were compared. The absolute number of lymphocytes/cu mm for 21 MHD patients averaged 1,737 +/- 112 SE and the mean %RFC was 70.0 +/- 1.15 SE; comparable values for 23 normal controls were 2,081 +/- 83 and 60.2 +/- 1.01, respectively. Although MHD patients had significantly lower average values for number of lymphocytes/cu mm (t = 2.490, P less than .02), the mean value of %RFC for MHD patients was significantly higher than that of normal controls (t = 6.118, P less than .001). The data indicate that MHD patients are lymphopenic but have a significantly higher %RFC (T-cells) than do normal subjects. Based on this finding, we hypothesize that there is selective depletion of a specific subpopulation of lymphocytes in MHD patients.