Amounts and distribution of intracellular magnesium and calcium in pancreatic beta-cells

beta-Cell-rich pancreatic islets were incubated for 60-120 min in the presence of 1 mM or 20 mM glucose and analysed with regard to their contents of magnesium and calcium and how these elements were distributed among subcellular fractions. The islets contained 42 mmol magnesium per kg protein with as much as 70 mmol per kg protein in the microsomal fraction. Both the total amount and intracellular distribution of magnesium remained unaffected after raising the glucose concentration of the incubation medium. The islet content of calcium was twice as high as that of magnesium, the mitochondria and secretory granules accounting for most of the calcium in the sedimentable fractions. In both organelles a substantial fraction of calcium was exchangeable as indicated from the incorporation of 45Ca during 90 min of incubation of the islets. When raising the glucose concentration to 20 mM the percentage exchange of calcium increased from 10 to 27 in the mitochondria and from 13 to 28 in the secretory granules. The glucose stimulation of 45Ca uptake was not associated with a statistically significant increase in the total amounts of calcium. However, in addition to stimulating calcium/calcium exchange, it cannot be excluded that glucose also induces a net accumulation of intracellular calcium in the beta-cells.     

Stimulation of murine B lymphocytes to IgG synthesis and secretion by the mitogens lipopolysaccharide and lipoprotein and its inhibition by anti-immunoglobulin antibodies.

The two mitogens, lipopolysaccharide (LPS) and lipoprotein (LP), both stimulate to an equal extent murine B lymphocytes to develop IgG-synthesizing and IgG-secreting cells. IgG synthesis and secretion was detected either by biosynthetic labeling of stimulated B cells, followed by immunoprecipitation and polyacrylamide gel electrophoresis of labeled Ig, or by the protein A plaque assay detecting all IgG-secreting cells with IgG-specific developing antisera. B cells from spleen, lymph node, thoracic duct and fetal liver of normal and T cell-deficient nu/nu mice are all stimulated by the two mitogens to develop IgG-secreting cells. Mitogen-induced IgG secretion, therefore, can occur independently of T cells and of external antigen. Anti-Ig antibodies inhibit the mitogen-induced development of Ig-secreting cells. Antibodies with specificities for μ chains when added before or soon after mitogenic stimulation of small, resting B cells, will inhibit these cells from developing into IgG-secreting cells. Later in culture, antibodies with specificities for γ chains also become inhibitory for the mitogen-induced development of IgG-secreting cells. These results indicate that the precursors of the IgG-secreting cells carry IgM in the outer surface membrane. They also suggest that during mitogen-stimulated growth of B cell clones, IgG becomes expressed in the surface membrane in a functional way which allows the inhibition of mitogen-induced IgG secretion by anti-γ antibodies.     

Leakage of macromolecules from guinea-pig tracheobronchial microcirculation. Effects of allergen, leukotrienes, tachykinins, and anti-asthma drugs

The tracheobronchial mucosa of anaesthetized guinea-pigs (normal or sensitized with ovalbumin to produce IgE and IgG antibodies) was superfused (0.02 ml min-1, 5 min) with saline, mediators, and (in sensitized animals) ovalbumin via a catheter atraumatically introduced orally. The intravascular blood pool and amount of macromolecules in excised trachea and adjoining main bronchi were quantified by measuring erythrocytes, that had been labelled in vivo with 99Tcm, and analysing for FITC-dextran, MW = 70,000, that had been given i.v. Extravasation of macromolecules was determined as the analysed total content minus the calculated intravascular content of FITC-dextran. Capsaicin 0.1 nmol extravasated 223 micrograms of FITC-dextran per g wet weight of airway tissue (P less than 0.001). Substance P 0.1 nmol, 41 micrograms g-1 (P greater than 0.05); substance P 0.3 nmol, 142 micrograms g-1 (P less than 0.001); eledoisine 0.1 nmol, 101 micrograms g-1 (P less than 0.01); ovalbumin 0.1 microgram, 179 micrograms g-1 (P less than 0.001); LTC4 0.2 pmol, 180 micrograms g-1 (P less than 0.001); LTD4 0.2 pmol 223 micrograms ml-1 (P less than 0.001). Bronchi and trachea were similarly affected by these agents. Prior superfusion (0.02 ml min-1, 30 min) with terbutaline 0.06 nmol, enprofylline 12 nmol, or lidocaine 6 nmol significantly reduced the effect of capsaicin. Enprofylline also reduced significantly the effect of LTC4. The degree of extravasation in this study was smaller than could be detected by changes in tissue wet to dry weight ratios. The present data support the view that tracheobronchial vascular permeability to macromolecules is subject to physiological and pharmacological control.     

Maturation of mitogen-activated bone marrow-derived lymphocytes in the absence of proliferation

Mouse B lymphocytes respond by increased rates of DNA synthesis 14–24 hours after stimulation with the mitogen lipopolysaccharide. If, at this time, stimulated cells are treated for 12 hours with a “hot pulse” of thymidine, subsequent mitogen-induced maturation to high rate IgM-producing plaque-forming cells is abolished. Thus, B cells stimulated by mitogen to mature also incorporate thymidine into DNA and proliferate. DNA synthesis is inhibited to 99 % in 48-hour mitogen-stimulated B lymphocytes by 10^?2 M hydroxyurea or 10^?3 M cytosine arabinoside, while protein and IgM synthesis and secretion and the plaque-forming capacity of those cells are unaffected. When hydroxyurea is added to small, resting B cells at the time of initiation of mitogenic stimulation, these cells mature to 19 S IgM- secreting, plaque-forming cells in the absence of DNA synthesis and proliferation. Maturation in the absence of DNA synthesis is also manifested by an increase in ratios of rates of synthesis and secretion of IgM over those of all proteins in the cell and by the attachment of the “branch” sugars, galactoses and fucoses, to 19 S IgM secreted by the cells. This maturation of B cells in the absence of DNA synthesis occurs within 12 to 30 hours after stimulation and is mitogen dose dependent. The inhibition of B cells to synthesize DNA and to develop into clones of plaque-forming cells can be reversed by the removal of hydroxyurea for as long as 36 hours after mitogenic stimulation in the presence of the inhibitor. In the presence of hydroxyurea, B cells are stimulated to immature plasmablast-like cells containing surface-bound and little intracytoplasmic Ig within 16 to 24 hours of stimulation. Mature plasma cells containing no detectable surface-bound Ig, but abundant intracytoplasmic Ig are only developed in the uninhibited, but not in the hydroxyurea-inhibited mitogen-stimulated cells later in the response. Thus, two stages of B cell maturation and differentiation can be distinguished: the first stage of an immature plasmablast develops in the absence of DNA synthesis, while the later stage of the development of the mature plasma cell requires DNA synthesis.     

The kinectics of proliferation and maturation of mitogen-activated bone marrow-derived lymphocytes

The B cell mitogens lipopolysaccharide (LPS), purified protein derivative of tuberculin (PPD) and fetal calf serum (FCS) all stimulate spleen cells from nude mice to increased DNA-synthesis 14 to 16 h after the initiation of mitogenic stimulation. The three mitogens also induce the maturation of B cells to plaque-forming cells (PFC). All three mitogens stimulate largely identical B cell populations. The extent to which B cells are stimulated to DNA synthesis and to the development of PFC varies from mitogen to mitogen. PFC arise by clonal growth through proliferation and maturation. A “hot pulse” of radioactive thymidine given between 0 and 20 h of stimulation has no effect on the development of PFC during subsequent mitogenic stimulation. Pulses given between 24 and 36 h after stimulation abolish the development of over 90 % of the PFC. The minimum pulse time required for maximum inhibition of the development of PFC during that time is 6 h. Beyond 36 h of stimulation by either of the three mitogens, PFC emerge rapidly. Between 60 and 72 h less than 10 % of all PFC emerging at 72 h are abolished by a “hot pulse”. The kinetics of the clonal development of PFC after mitogenic stimulation are compared to that of antigenic stimulation. The comparison suggests that B cells stimulated by antigen in the in vivo primary immune response culture system go through a longer period of proliferation than when they are stimulated by mitogen before maturation to PFC.     

Inhibitory effects of clonidine on the allergen-induced wheal-and-flare reactions in patients with extrinsic asthma

We investigated the possibility that clonidine, an alpha 2-adrenoceptor agonist, can reduce the wheal-and-flare reactions induced by intradermal injections of allergen in patients with extrinsic asthma. Ten adult subjects with asthma with positive skin tests to one or several pollens were selected. They received, in random order and double-blind manner, clonidine (two doses, each 75 micrograms) or placebo for 3 days, and then, after a 1-week washout period, they crossed over to the other treatment for 3 days. Treatment with clonidine reduced the area of wheal-and-flare reaction induced by allergen without significantly changing the blood pressure or the plasma cortisol level. There was a drop in the histamine content of leukocytes and in the number of eosinophils in peripheral blood after allergen challenge during the placebo treatment, whereas clonidine prevented these changes. The results suggest that treatment with clonidine can reduce the inflammatory reactions induced by allergens in subjects with extrinsic asthma.     

Somatotopic organization along the central sulcus, for pain localization in humans, as revealed by positron emission tomography

Regional cerebral blood flow was measured with positron emission tomography (PET) in six healthy volunteers at rest and during experimentally induced, sustained cutaneous pain on the dorsum of the right hand or on the dorsum of the right foot. Pain was inflicted by intracutaneous injection of capsaicin, providing a mainly C-fibre nociceptive stimulus. Statistical analysis showed significant activations along the central sulcus (SI) area when comparing pain in the hand to pain in the foot. Separate comparison of both pain states to a baseline revealed different locations along the central sulcus for hand pain and foot pain. The encountered differences are consistent with what is previously known about the somatotopics of non-painful stimuli. When comparing painful stimuli to baseline, the contralateral anterior cingulate gyrus, the ipsilateral anterior insular cortex and the ipsilateral prefrontal cortex were implicated. The results are consistent with an involvement of SI in the spatial discrimination of acute cutaneous pain. Received: 17 October 1996 / Accepted: 12 May 1997     

The seroepidemiology of human T-lymphotropic viruses: types I and II in Europe: a prospective study of pregnant women

BACKGROUND: Up to 20 million persons are infected with the human retroviruses human T-lymphotropic virus (HTLV)-I and HTLV-II globally. Most data on the seroprevalence of HTLV-I and HTLV-II in Europe are from studies of low-risk blood donors or high-risk injection drug users (IDUs). Little is known about the general population. METHODS: A prospective anonymous study of HTLV-I and HTLV-II seroprevalence among 234,078 pregnant women in Belgium, France, Germany, Italy, Portugal, Spain, and the United Kingdom was conducted. Maternal antibody status was determined by standard methods using sera obtained for routine antenatal infection screens or eluted from infant heel prick dried blood spots obtained for routine neonatal metabolic screens. RESULTS: Anti-HTLV-I/II antibodies were detected and confirmed in 96 pregnant women (4.4 per 10,000, 95% confidence interval [CI]: 3.5-5.2). Of these, 73 were anti-HTLV-I, 17 were anti-HTLV-II, and 6 were specifically anti-HTLV but untyped. The seroprevalence ranged from 0.7 per 10,000 in Germany to 11.5 per 10,000 in France. CONCLUSIONS: Pregnant women better reflect the general population than blood donors or IDUs. The seroprevalence of HTLV-I and HTLV-II in Western Europe is 6-fold higher among pregnant women (4.4 per 10,000) than among blood donors (0.07 per 10,000). These data provide a robust baseline against which changes in HTLV-I and HTLV-II seroprevalence in Europe can be measured.