The binding and processing of monoclonal human IgG1 by cells of a human macrophage-like cell line (U937)

The goal of these experiments was to assess the relationship between the binding and processing of IgG by Fc-receptor-bearing cells. Cells of the U937 human macrophage-like cell line were incubated with 125I- labeled monomers, dimers, oligomers (composed of 2-4 IgG1 subunits), and HP (heavy polymers composed of 5 or more subunits per polymer) of monoclonal human IgG1 in vitro. Binding was assessed by spinning cells through a layer of phthalate oils. Internalization of IgG1 was assessed by quantitating residual binding to cells after surface-bound IgG was removed by a brief treatment with a solution containing 0.25 M acetic acid and 0.5 M sodium chloride. Catabolism was assessed by measuring the release of radioactive fragments of IgG1, which were not precipitated by 10% trichloroacetic acid. Unstimulated U937 bound about 10,000 molecules per cell of IgG1 monomer, with an equilibrium binding constant (Ka) of 5 X 10(8) M-1. After stimulation with a conditioned medium in vitro, binding per cell was increased 3-7--fold, and the Ka was decreased 2-4--fold. Both unstimulated and stimulated cells internalized and catabolized labeled IgG1 HP, but stimulated cells internalized and digested much more IgG1 HP per cell than unstimulated cells. Both monomers and dimers of IgG1 were internalized and degraded very slowly by stimulated cells, even though both preparations readily bound to cells. In contrast, oligomers and (to an even greater extent) IgG1 HP were internalized and degraded much more rapidly. Internalization of IgG1 HP was markedly inhibited by incubation at 4 degrees C, but not by incubation with a variety of metabolic inhibitors. Catabolism was inhibited by chloroquine and monensin (inhibitors of lysosomal acidification) and by cytochalasin (an inhibitor of microfilament polymerization). Binding to the surface of cells was not markedly inhibited by any agent tested. The capacity of cells to bind labeled IgG1 was markedly reduced by prior incubation in the presence of unlabeled IgG1. This reduction was in part due to the steric blockade of receptors caused by the avid, but reversible, binding of IgG1. In addition, IgG1 oligomers or HP (but not IgG1 monomers or dimers) also caused an irreversible reduction in the number of Fc receptors by a process analogous to receptor down-regulation, as observed in other receptor--ligand systems.     

Possibility of selection against mtDNA mutations in tumors

Several studies of tumors have revealed substantial numbers of clonally expanded somatic mutations in mitochondrial DNA (mtDNA), not observed in adjacent intact tissues. These findings were interpreted as indicating the involvement of mtDNA mutations in tumorigenesis. Such comparisons, however, ignore an important confounding factor: the monoclonal origin of tumors as opposed to the highly polyclonal nature of normal tissues. Analysis of recently published data on the incidence of somatic mutations in nontumor monoclonal cells suggests that, contrary to the prevailing view, the process of tumorigenesis may be accompanied by active selection against detrimental mtDNA mutations.     

Pregabalin for treatment of generalized anxiety disorder: a 4-week, multicenter, double-blind, placebo-controlled trial of pregabalin and alprazolam

BACKGROUND: Pregabalin inhibits release of excess excitatory neurotransmitters, presumably by binding to the alpha2-delta subunit protein of widely distributed voltage-dependent calcium channels in the brain and spinal cord. OBJECTIVE: To assess the anxiolytic efficacy of pregabalin in patients with generalized anxiety disorder. DESIGN: Double-blind, placebo-controlled, active-comparator trial. Patients were randomized to 4 weeks of treatment with pregabalin, 300 mg/d (n = 91), 450 mg/d (n = 90), or 600 mg/d (n = 89); alprazolam, 1.5 mg/d (n = 93); or placebo (n = 91). SETTING: Psychiatry research and clinic settings. PATIENTS: Outpatients meeting the DSM-IV criteria for generalized anxiety disorder, with a baseline Hamilton Anxiety Rating Scale (HAM-A) total score of 20 or greater. MAIN OUTCOME MEASURES: Change from baseline to end point in total HAM-A score in the pregabalin and alprazolam groups compared with the placebo group. The end point response criterion was 50% or greater reduction in the HAM-A total score. RESULTS: Pregabalin and alprazolam produced a significantly greater reduction in mean +/- SE HAM-A total score at last-observation-carried-forward end point compared with placebo (-8.4 +/- 0.8): pregabalin, 300 mg (-12.2 +/- 0.8, P<.001), 450 mg (-11.0 +/- 0.8, P = .02), and 600 mg (-11.8 +/- 0.8, P = .002), and alprazolam (-10.9 +/- 0.8, P = .02). By week 1 and at last-observation-carried-forward end point, the 3 pregabalin groups and the alprazolam group had significantly (P<.01) improved HAM-A psychic anxiety symptoms compared with the placebo group. Compared with the placebo group, HAM-A somatic anxiety symptoms were also significantly (P<.02) improved by the 300- and 600-mg pregabalin groups, but not by the 450-mg pregabalin (week 1, P = .06; week 4, P = .32) and the alprazolam groups (week 1, P = .21; week 4, P = .15). Of the 5 treatment groups, the 300-mg pregabalin group was the only medication group that differed statistically in global improvement at treatment end point not only from the placebo group but also from the alprazolam group. CONCLUSION: Pregabalin was significantly more efficacious than placebo for the treatment of psychic and somatic symptoms of generalized anxiety disorder and was well tolerated by most study patients.     

RENAL FUNCTION IN CHRONICALLY CATHETERIZED CONSCIOUS DIABETIC RATS USING CONSTANT AND SERVO-CONTROLLED INFUSION

1. Infusion experiments were performed on chronically catheterized conscious rats to assess kidney function before and after the induction of diabetes mellitus with streptozotocin. 2. Two infusion regimens were used, a conventional constant-infusion protocol and a novel computer-driven, servo-controlled fluid replacement technique. The latter enables body fluid status to be maintained throughout a study occasion by servo-controlled replacement of spontaneous urinary fluid losses. 3. The chronically catheterized conscious rat infused using a servo-controlled system appears to be the optimum model for a study of diabetic renal function. The conscious preparation circumvents problems associated with anaesthesia and acute surgery. The servo-controlled infusion protocol maintains the altered fluid status of the diabetic condition. Both hyperfiltration and polyuria, characteristics of human diabetes often absent in anaesthetized and/or constantly infused diabetic rats, were seen in all conscious servo-controlled diabetic animals. 4. The new regimen enables a more accurate assessment of renal function in experimental diabetes than with previous protocols. It should prove useful in future studies, particularly those assessing the role of anti-diabetic drugs on the kidney.     

Unexplained diarrhoea and failure to thrive in 2 siblings with unusual facies and abnormal scalp hair shafts: a new syndrome

A family is described in which 2 siblings born to healthy parents presented with abnormal facies, persistent diarrhoea, and early death. Exhaustive pathological and biochemical investigations failed to find a cause. The scalp hair of both babies had an abnormal amino-acid composition, and presented an appearance that was unique on scanning electron microscopical examination; this fact and the clinical picture probably represents a new syndrome.