Treatment of murine lupus with F(ab')2 fragments of monoclonal antibody to L3T4. Suppression of autoimmunity does not depend on T helper cell depletion

Treatment with mAb to the L3T4 Ag on Th cells can inhibit autoimmunity in mice. However, the mechanism by which anti-L3T4 inhibits autoimmunity is not known. In these studies, lupus-prone NZB/NZW F1 (B/W) mice were treated with F(ab')2 fragments of mAb to L3T4 to determine whether Th cell depletion is required for the beneficial effects of anti-L3T4. We first showed that treatment of female B/W mice with F(ab')2 anti-L3T4 from age 5 to 9 mo significantly reduced autoantibody production without depleting L3T4+ cells. However, treatment was complicated by the development of a host immune response to the rat mAb fragments. To circumvent this problem, female B/W mice were treated with a single high-dose of intact rat mAb to L3T4 (GK1.5) at age two mo. to induce immune tolerance to the mAb. Then, after recovery of L3T4+ cells, the mice were treated from age four to 14 mo with either F(ab')2 anti-L3T4 (0.5 mg 3 times per wk), intact anti-L3T4, or saline. In mice tolerized by this regimen, neither the F(ab')2 rat mAb nor the intact rat mAb elicited a host response. The mAb fragments bound target Ag but did not deplete the Th cells, whereas intact mAb to L3T4 profoundly depleted the L3T4+ cells. Despite this difference, both therapies had the same substantial beneficial effects on autoimmunity. They significantly decreased anti-DNA Ab production, improved renal function and prolonged survival. The initial tolerizing dose, by itself, did not inhibit autoimmunity. These findings show that anti-L3T4 suppresses autoimmunity by directly altering Th cell function through the L3T4 Ag, and not solely by depleting Th cells. They also document the detrimental effects of the host immune response to therapy with anti-L3T4 mAb, and they demonstrate a new strategy by which this response may be prevented.     

Characterization of β-amylase and its deficiency in various rice cultivars

 β-Amylase deficiency in various cultivars of rice was examined at the molecular level. Using an antibody against β-amylase purified from germinating seeds of rice, we were able to demonstrate the expression and organization of the β-amylase gene in normal and deficient cultivars. Although β-amylase is a starch-hydrolyzing enzyme, as is α-amylase, the β-amylase protein/gene is expressed differently from the α-amylase protein/gene; i.e. (1) β-amylase is synthesized only in aleurone cells, (2) the enzyme production in the embryo-less half-seeds is not under hormonal control. We identified some cultivars of rice that are deficient for β-amylase activity. We present new evidence that synthesis is blocked at the level of mRNA synthesis in the deficient cultivars. The usefulness of β-amylase as a crop trait is also discussed. Received: 8 May 1998 / Accepted: 5 June 1998     

Loss of nitrous oxide reductase in Pseudomonas aeruginosa cultured under N2O as determined by rocket immunoelectrophoresis

The mass ratio of nitrous oxide reductase to total protein in the soluble protein fraction of Pseudomonas aeruginosa P2 was highest in cells grown on nitrate, decreased in cells grown on N(2)O following the exhaustion of the initial charge of nitrate, and was nearly zero in cells exposed solely to N(2)O.     

Apple Proliferation Epidemics Detected in Scab-Resistant Apple Trees

In the Friuli-Venezia Giulia, a region of Italy, where serious epidemics of apple proliferation (AP) are known to occur, varieties resistant to scab (Venturia inaequalis (Cke.) Wint.) are increasingly being used in new orchards. The most important cvs are Florina. Prima and Priscilla. These varieties were cultivated according to organic farming regimes with no insecticides used. The results obtained in two orchards during a 7-year period of investigation indicated that the three varieties resistant to scab are highly susceptible to AP. Florina was most susceptible (high infection rate) to AP while Priscilla was most sensitive (severely affected). The identification of the disease was based on symptom expression, DAPI (4–6-diamidino-2-phenylindole) fluorescence technique, electron microscopy observations and by polymerase chain reaction (PCR). Neither complete spontaneous recovery nor death of AP-infected plants was noticed. The pattern of natural diffusion of AP does not seem to be uniform, the affected trees may be in line or grouped in certain spots of the orchards. This may indicate the activity of a not very mobile vector. It can be concluded that planting of Florina, Prima and Priscilla should be discouraged in areas where AP is a problem, particularly when organic farming regimes are being applied.     

Female sex steroid induced epithelial changes in the gallbladder of the ovariectomized Syrian hamster.

Ovariectomized Syrian hamsters treated by female sex steroids during a 1-month period show gallbladder surface epithelial changes in the fundic area consistent with apical bulging and decapitations of the epithelial cells. These events were detected in the infundibulum and the fundic or body regions of estrogen- and estrogen+progesterone-treated hamsters. In control hamsters, these events were restricted to the region in the vicinity of the bile duct. Following steroid treatment, intraluminal deposits detected resembled Ca-bilirubinate deposits described in previous studies while decapitations are similar to endometrial epithelium changes associated with hormonal physiological changes or treatments. Moreover some small electron-dense deposits are comparable to those found in human cholesterol gallstones. This report indicates that, besides an alteration in bile composition, cell fragments originating from the surface epithelium of the bile duct and/or of the gallbladder mucosal epithelium could participate in gallstone nucleation.     

Effects of cortisol on calcium contents of lymphocytes in patients with bronchial asthma]

A fluorescent probe was used to study hydrocortisone (10 microM) action on mitogen-stimulated free cytoplasmic calcium level in lymphocytes of patients with bronchial asthma. The patients were divided into two groups according to their sensitivity to glucocorticoid therapy. Hydrocortisone-specific calcium-blocking effect was absent in hormone-resistant patients. Lymphocytes of hormone-sensitive patients responded to hydrocortisone administration by a decline of mitogen-induced calcium level.     

Dynamic Light Regulation of Photosynthesis (A Review)

Regulatory reactions providing the photosynthetic apparatus with the ability to respond to variations of irradiance by changes in activities of the light and the dark stages of photosynthesis within a time range of seconds and minutes are considered in the review. At the light stage, such reactions are related to the changes in both distribution of light energy between two photosystems and probability of nonphotochemical dissipation of absorbed quanta in PSI and PSII. These regulatory reactions operate in a negative feedback mode, thus avoiding overreduction of electron transport chain and minimizing the probability of generation of reactive oxygen species. The crucial role in preventing the generation of reactive oxygen species belongs to dynamic regulation of electron transport activity despite the presence of complex system of their detoxification in chloroplasts. In dark reactions of Calvin cycle, the regulatory responses involve a positive feedback principle being related to redox regulation of activities of several enzymes, which is sensitive to the reduction status of PSI acceptor side. The complex of regulatory reactions based on negative and positive feedback principles provides prolonged functioning of a chloroplast and high stability of photosynthetic activity under various light conditions.     

Effect of ionizing radiation on the functional state of the vascular-thrombocytic component of the hemostasis system

The influence of ionizing radiation (gamma-rays 60Co) on aggregation activity of the vascular wall and functional (aggregation) platelet activity was studied in the course of the development of acute radiation sickness. The decrease in the aggregation properties of the vascular wall and high functional activity of platelets were inversely proportional, correlating with the periods of acute radiation sickness development and depending on the radiation dose. It is suggested that the changes detected may play a role in the pathogenesis of the development of the postirradiation thrombohemorrhagic syndrome.