Mercuric chloride induced autoimmune disease in Brown-Norway rats: sequential search for anti-basement membrane antibodies and circulating immune complexes

Mercuric chloride induces in the Brown-Norway rat a biphasic autoimmune disease characterized initially by linear IgG deposits along the glomerular basement membrane followed later by granular IgG deposition. In the present study, anti-glomerular basement membrane antibodies and immune complex-like material were sequentially assessed in serial serum samples. Both were transiently found at the same period. Glomerular linear IgG deposits were present on day 11 but circulating anti-glomerular basement membrane antibodies were only found later on day 16. Circulating immune complexes were first detectable on day 8 before the earliest granular IgG deposits were first observed in the spleen vessels on day 16. The disappearance of circulating anti-glomerular basement membrane antibodies and of circulating immune complexes, although HgCl2 injections were pursued, is in agreement with the self-limited character of mercuric chloride induced autoimmune disease and suggests the induction of immunosuppressive mechanisms.     

Role of CD8+ T Cells in Mercury-Induced Autoimmunity or Immunosuppression in the Rat

In Brown-Norway (BN) rats mercuric chloride induces an autoimmune disease characterized by an increase in serum IgE concentration, and by the production of anti-glomerular basement membrane antibodies responsible for a glomerulonephritis with a heavy proteinuria. (i) This disease results from a B-cell polyclonal activation probably due to frequent anti-class II T cells. (ii) The self limitation observed in this model is associated with both a decrease in the frequency of anti-class II T cells and the emergence of CD8+ T cells able to suppress these autoreactive T cells. (iii) In Lewis (LEW) rats which do not develop autoimmunity, HgC12 provokes the appearance of non-antigen-specific CD8+ T cells responsible for a depression of T-cell functions. The aim of this work was to test the effect of treatment with an anti-CD8 monoclonal antibody (MoAb) in both BN and LEW rates, Anti-CD8 MoAb-treated rats were effectively depleted in CD8+ T cells. However, neither the induction nor regulation phases of mercury-induced autoimmunity were modified in BN rats. Mercury-induced immunosuppression in LEW rats was abrogated; however, depletion in CD8+ T cells did not allow the disease to occur in that strain. Finally, CD8 depletion induced in normal BN rats rats the appearance of rare anti-class II T cells showing that these cells are normally present in that strain but negatively controlled by suppressor T cells.     

14-Membered cyclic opioids related to dermorphin and their partially retro-inverso modified analogues II. Preferred conformations in solution as studied by 1H-NMR spectroscopy

The ¹H-NMR studies were extensively carried out to elucidate preferred conformations of a series of 14-membered cyclic dermorphin analogues containing two phenylalanines at both the third and fourth positions, e.g., Tyr-c[D-A₂bu-Phe-Phe-(l and d )-Leu], Tyr-c[d -A₂bu-Phe-gPhe-(S and R)-mLeu], and Tyr-c[d -Glu-Phe-gPhe-(L and D)-rLeu]. The temperature coefficients of the amide proton chemical shifts, vicinal ¹H-¹H coupling constants for the NH-CH groupings, and nuclear Overhauser effects provided information regarding the preferred conformations of the backbones. The conformational preferences and flexibility of the side chains were also estimated from the vicinal ¹H-¹H coupling constants around the C-Cβ and C-Cβ bonds in the articulated side chains. A comparison of the results obtained was made with the results previously obtained for the corresponding enkephalin analogues containing a glycine at the third position. It was found that the replacement of the glycine with the phenylalanine at the third position increases the conformational flexibility of the molecules with an l -, or S-, residue at the fifth position but reduces the flexibility of the molecules with d -, or R-, residue at the same position. The rotating frame nuclear Overhauser experiments gave direct evidence for compact conformations, with the Tyr side chain folding back over the 14-membered ring in Tyr-c[d -Glu-Phe-gPhe-rLeu], which displays relatively high selectivity for the δ-receptor over the μ-receptor. This observation is in agreement with our model proposed for the cyclic enkephalin analogues: folded forms with close aromatic ring placement are required for the activity at the δ-receptor.     

Improved Dual Chamber Pacing Mode in Paroxysmal Atrioventricular Conduction Disorders

GIRODO, S., ET AL.: Improved Dual Chamber Pacing Mode in Paroxysmal Atrioventricular Conduction Disorders. Dual chamber pacing may sometimes be directly indicated for carotid sinus hypersensitivity, vasovagal syndrome, and certain cases of sinoatrial block and intermittent atrioventricular (AV) block, although AV conduction is dominantly normal. At times of normal AV conduction, competition between ventricular pacing and spontaneous ventricular depolarization may occur, with its adverse hemodynamic effects on ventricular function and unnecessary drainage of pacemaker battery energy. A new mode of stimulation is described, called automatic DDD mode, which functions in 'pseudo-AAI' mode during normal AV conduction and reverts to classical DDD function during episodes of AV blocks. Furthermore, during pseudo-AAI function, the pacemaker measures certain physiological parameters that serve to automatically program certain parameters used in DDD mode. Preliminary clinical evaluation has shown that this new mode functions satisfactorily.     

Reactive Oxygen Species Are Necessary for High Flow (Shear Stress)‐induced Diameter Enlargement of Rat Resistance Arteries

Objectives: Chronic increases in blood flow induce remodeling associated with increases in diameter and endothelium‐mediated dilation. Remodeling requires cell growth and migration, which may involve reactive oxygen species (ROS). Nevertheless, the role of ROS in flow‐mediated remodeling in resistance arteries is not known. Materials and Methods: Rat mesenteric resistance arteries (MRAs) were exposed to high flow (HF) by sequentially ligating second‐order MRAs in vivo. After three weeks, arteries were collected for structural, pharmacological, and biochemical analysis. Results: In HF arteries, luminal diameter (431±12 to 553±14 μm; n=10), endothelium (acetylcholine)‐mediated vasodilatation (61±6 to 77±6% relaxation) and NAD(P)H subunit (gp91phox and p67phox) expression levels, and ROS (dihydroethydine microphotography) and peroxynitrite (3‐nitro‐tyrosine) production were higher than in normal flow arteries. Acute ROS scavenging with tempol improved acetylcholine‐dependent relaxation (92±4% relaxation), confirming that ROS are produced in HF arteries. Chronic treatment with tempol prevented the increase in diameter, reduced ROS and peroxynitrite production, and improved endothelium‐mediated relaxation in HF arteries. Thus, ROS and NO were involved in HF‐induced diameter enlargement, possibly through the formation of peroxynitrite, while ROS reduced the increase in endothelium‐dependent relaxation. Conclusions: ROS production is necessary for flow‐mediated diameter enlargement of resistance arteries. However, ROS counteract, in part, the associated improvement in endothelium‐mediated relaxation.     

Intradermal immunization of rats with plasmid DNA encoding Schistosoma mansoni 28 kDa glutathione S-transferase

Direct administration of plasmid DNA encoding an antigen represents an attractive approach to vaccination against infectious diseases, particularly in developing countries where easy-to-handle and cost-effective vaccines are needed. We have investigated the potential of DNA immunization to induce a specific antibody response against Schistosoma mansoni , using plasmid-DNA encoding the protective antigen, S. mansoni 28 kDa glutathione S-transferase (Sm28GST). Since S. mansoni parasite penetrates into its host through the skin, this tissue was chosen for plasmid DNA delivery. Following plasmid DNA administration into the skin of rats, the parasite antigen was detected in skin cells by immunohistochemistry. Three administrations of 200 μg plasmid at 14 day intervals led to the induction of a long-lasting specific IgG antibody response in the sera of immunized rats, with a predominance of IgG2a and IgG2b subclasses. Sera of immunized animals were able to mediate antibody-dependent cellular cytotoxicity in vitro , leading to the specific killing of parasite larvae. A parasite challenge performed on plasmid DNA-immunized animals induced a strong and rapid boosting effect on the specific IgG antibody response. These results demonstrate the potential of genetic immunization via the skin with plasmid DNA encoding Sm28GST for inducing immune responses with protective patterns against an S. mansoni infection .     

Anti-Interleukin-2 Receptor Monoclonal Antibody Therapy Supports a Role for Thl-Like Cells in HgCl2-Induced Autoimmunity in Rats

Brown-Norway (BN) rats injected with HgCl₂ develop an autoimmune disease characterized by a T dependent polyclonal B-cell activation. Increase in major histocompatibility complex class II molecule expression on B cells concomitant with enhancement of serum IgE concentration supports the involvement of the T helper 2 (Th2)-like subset in the induction of the disease. The mercury disease is autoreguiated and does not develop in Lewis (LEW) rats. Considering the reciprocal regulation, well defined in mice, between the Th1 and Th2 subsets, we addressed the role of the Thl-like subset in this disease. Brown-Norway and LEW rats injected with HgCl₂ were treated wilh NDS61, a mouse anti-ral-IL-2R MoAb that blocks mainly Th1 cells. Data reported herein show that: (1) HgCl₂ treatment does not modify either the percentage of IL-2R⁺ cells or IL-2R expression in both BN and LEW rats; (2) treatment of BN rats with NDS61 MoAb does not modify the induction phase of the mercury disease but delays in parl the regulation phase; (3) such a treatment leads lo some immune abnormalities in LEW rals; (4) HgCl₂ markedly potentiates the anti-mouse Ig antibody response in BN rats which probably limits the effect of this treatment. This study supports a role for the Th1-like subset in HgCl₂-induced auloimmunity in the rat.     

Cross–reactive antigenic determinants present on different Plasmodium falciparum blood–stage antigens

A gene encoding a previously undescribed antigen of Plasmodium falciparum has been isolated from a genomic expression library by use of a pool of human immune sera. Northern blot analysis indicated that the gene is expressed at the late stages of the intra-erythrocytic cycle. This antigen, 332, contains a series of degenerated amino acid repeats. Human antibodies affinity-purified on the 332 recombinant antigen reacted with a family of parasite proteins that are products of different genes. We identified antigens 11.1 and Pf155-RESA as members of this family and confirmed, using a human monoclonal antibody, the presence of cross-reacting determinants. The sequences of these antigens also share some structural homologies. The significance of this family of blood-stage antigens is discussed.