Interaction of myasthenic immunoglobulins and cholinergic agonists on acetylcholine receptors of rat myotubes

Acetylcholine receptor (AChR) antibodies from patients with myasthenia gravis (MG) impair neuromuscular transmission by altering the number of AChRs at the skeletal muscle motor endplate. Cholinergic agonists similarly impair transmission by altering the number and affinity of AChRs. The frequent clinical resistance ot anticholinesterase medication in patients with MG has raised the question of possible synergistic effects of these agents on regulation of AChRs and neuromuscular transmission. To investigate this question, rat myotube cultures were incubated with MG globulin and carbamylcholine (CMC) for 20 hours. The number of AChRs was assayed by 125I-alpha-bungarotoxin binding. Incubation of cultures with both MG globulins and CMC consistently produced greater reductions of AChRs than incubation with either substance alone. Cholinergic antagonists blocked the CMC effect but not the MG globulin effect. A muscarinic antagonist had no effect. The effects of short-term incubation with these substances on the affinity of AChR were assessed by the rate of 125I-alpha-bungarotoxin-AChR complex formation. CMC desensitized AChRs, but MG globulins did not alter the affinity of AChRs. Results with this in vitro model suggest that chronic anticholinesterase therapy in the presence of MG AChR antibodies may aggravate failure of neuromuscular transmission in MG.

Disruption of the purine nucleotide cycle. A potential explanation for muscle dysfunction in myoadenylate deaminase deficiency

A patient with symptoms of easy fatigability, postexercise myalgias, and delayed recovery of muscle strength after activity is described. Skeletal muscle from this patient had <1.0% normal myoadenylate deaminase activity and NH(3) was not released from muscle after ischemic exercise. In association with this enzyme deficiency, exercise led to a >90% reduction in muscle content of adenine nucleotides. No inosine monophosphate accumulated after exercise and total purine content of the muscle fell to 21% of control. Repletion of the adenine nucleotide pool in this patient was delayed compared to controls, and ATP content had only returned to 68% of control at 165 min after exercise. These studies demonstrate that disruption of the purine nucleotide cycle as a consequence of myoadenylate deaminase deficiency results in marked alterations in ATP content of muscle, and potentially, these changes in ATP content could account for muscle dysfunction in this patient.

Antitumor activity of 7-N-phenyl derivatives of mitomycin C in the leukemia P388 system

The antitumor activity of 7-N-phenyl derivatives of mitomycin C was tested in an ip-ip system of mouse leukemia P388 by single administration. The compounds tested were 7-N-phenyl-, 7-N-(p-aminophenyl)-, 7-N-(p-hydroxyphenyl)- and 7-N-(p-chlorophenyl)-mitomycin C. The maximum increases in life span (ILSmax) obtained were 124, 169, > 386 and 112%, respectively, that with mitomycin C being 104%. 7-N-(p-Hydroxyphenyl)-mitomycin C showed a higher ILS% than its ortho and meta isomers. Thus, 7-N-(p-hydroxyphenyl)-mitomycin C was the most effective of these compounds.

Meige's syndrome

We present two women with Meige's syndrome, a condition in which the clinical presentation differs from tardive dyskinesia by the lack of exposure to neuroleptic drgus, greater severity of blepharospasms, and more prolonged dystonic contractions of oromandibular muscles. In this condition we used triaxial accelerometry to detect dystonia, which may also appear in limb and respiratory muscles. Although psychologic factors may affect the symptoms, the basic pathogenesis of this syndrome does not seem to be psychogenic. We think that biochemical abnormalities in the basal ganglia are responsible for the dyskinesias and submit data suggesting a reduction of dopamine turnover in the central nervous system of one patient. Both patients have evidence of autoimmune diseases, and one patient's dystonic movements responded to immunosuppressive therapy, suggesting that autoimmune processes contribute to the pathogenic mechanism of Meige's syndrome in some instances.

Antigenic determinants of hen egg-white lysozyme in delayed hypersensitivity. II. Antigenicity and immunogenicity of the N- and C-terminal peptide

Various small fragments of (see article) which is one of the immunodominant groups of hen egg-white lysozyme (HL), were tested for macrophage migration inhibition (MMI) of peritoneal exudate cells (PEC) from guinea pigs immunized with HL. P17 was split in the middle with cyanogen bromide. The terminal portion of (see article) showed positive MMI, whereas the non-terminal half of P17, P17i (sequence 13-27) only showed very weak MMI activity. A fragment derived from the middle portion of P17, P17m (sequence 11-22), was inactive. When P17 were reduced and alkylated, one of the resultant peptides, P17N (sequence 1-[CM-Cys-6]-27) still has MMI activity with PEC taken from guinea pigs immunized with HL, although no antibody reacting with it was detected, but P17C (sequence 123-[CM-Cys-127]-129) was inactive. The peptides P17 and P17N were both immunogenic in guinea pigs in respect to the delayed hypersensitivity response. Again P17t and P17N were immunodominant groups, but the reactivity of P17i in MMI assay of this group of animals was greater than that in guinea pigs immunized with HL. The reactivities of HL with PEC taken from guinea pigs immunized with P17 or P17N were generally weaker than those of the antigens used for immunization.

Antigenic determinants of hen egg-white lysozyme in delayed hypersensitivity. I. Macrophage migration inhibition activities of lysozyme fragments

Five kinds of fragments of hen egg-white lysozyme (HL) were tested by macrophage migration inhibition (MMI) assay using peritoneal exudate cells (PEC) of guinea pigs immunized with HL in complete Freund's adjuvant. (See article). These four kinds of HL fragments were also shown to be composed of the immunodominant groups of the HL molecule for circulating antibody against HL in guinea pigs. The relationships between the antigenic sites related to circulating antibody and the cellular recognition sites are discussed.

An experimental postoperative metastasis system using Yoshida sarcoma inoculated subcutaneously into footpad

When Yoshida sarcoma cells were inoculated subcutaneously into the left footpad of Donryu rats, the weight of the left lumbar lymph nodes increased proportionally to the number of the inoculated cells. Resection of primary implants the day after the inoculation of 5 x 10(6) cells failed to rescue the host rats and they died of metastases within 12 days. There was no significant difference in mean survival days between the rats (8.9 days) whose primary implants were resected on the 5th day after inoculation and the control rats (8.6 days) bearing the primary implants. Mitomycin-C, a highly effective drug against Yoshida sarcoma cells, produced many long survivors (over 30 days) in the treated rats whose primary implants were resected the day after inoculation, but failed to do so when resected 5 days after inoculation. All of them died of metastases within 20 days. Based on these results, this present system is discussed for its usefulness as a screening and evaluation model for antitumor agents.