A human antibody binds to alpha-galactose receptors and mimics the effects of Clostridium difficile toxin A in rat colon

BACKGROUND & AIMS: Nearly all human sera contain an immunoglobulin G antibody (antigalactose) that binds the trisaccharide Gal alpha 1-3Gal beta 1-4GlcNAc expressed on cells from most mammals but not humans. Because the Clostridium difficile toxin A receptor in rodents contains this trisaccharide, the aim of this study was to examine whether antigalactose could mimic the enterotoxic effects of toxin A and bind to receptors containing this trisaccharide. METHODS: Fluid secretion, [3H]-mannitol permeability, and release of rat mast cell protease II and prostaglandin E2 were measured after luminal exposure of rat colon to either purified human anti-galactose, control immunoglobulin G, toxin A, or buffer. RESULTS: Toxin A (5 micrograms) and antigalactose (250 micrograms) but not control immunoglobulin (250 micrograms) stimulated colonic fluid secretion and caused increased mannitol permeability and rat mast cell protease II release. Antigalactose and toxin A and, to a lesser degree, control immunoglobulin G also stimulated release of prostaglandin E2, but only toxin A produced acute inflammation of rat colonic mucosa. Antigalactose and toxin A bound specifically to a single class of colonic brush border receptors with dissociation constants of 10(-6) mol/L and 5.4 x 10(-8) mol/L, respectively. CONCLUSIONS: Fluid secretion, increased permeability, and mast cell activation occur in rat colon when toxin A or human antigalactose immunoglobulin G bind to receptors bearing the trisaccharide Gal alpha 1-3Gal beta 1-4GlcNAc. (Gastroenterology 1996 Jun;110(6):1704-12)     

Fibrinogen biosynthesis in isolated guinea pig megakaryocytes

Fibrinogen synthesis was investigated in guinea pig megakaryocytes. Purified megakaryocytes were incubated with 35S-methionine in methionine-free incubation medium for 18 hours. Newly synthesized fibrinogen in megakaryocyte lysates enriched with purified carrier guinea pig fibrinogen was immunoprecipitated with a specific anti- guinea pig fibrinogen antiserum produced in rabbits. Proteins in the immunoprecipitates were analyzed with a 3.5% to 10.0% gradient polyacrylamide slab gel electrophoresis and auto-radiography. Radioactivity was detected in a protein band of 340,000 daltons. In order to verify fibrinogen synthesis, immunoprecipitate was analyzed by two-dimensional slab gel electrophoresis: (1) the first dimension separated unreduced fibrinogen using a 3.5% to 10.0% gradient gel; (2) following reduction by 2-beta-mercaptoethanol, fibrinogen chains were separated in the second dimension using a 10% gel. Alpha, beta, and gamma fibrinogen chains, which represented carrier guinea pig plasma fibrinogen, were visualized by Coomassie brilliant blue. Autoradiography identified the incorporation of radioactivity into the three fibrinogen chains. In control experiments, immunoprecipitates, produced by exposing megakaryocyte lysates to preimmune rabbit serum and goat anti-rabbit IgG, were also analyzed by the two-dimensional gel system. Radioactivity was not detected in sites corresponding to the migration of fibrinogen subunits. The study demonstrates that isolated guinea pig megakaryocytes can synthesize fibrinogen. The electrophoretic mobility of newly synthesized fibrinogen and subunits is similar to that of guinea pig plasma fibrinogen.     

Correlation of drug sensitivity in vitro with clinical responses in childhood acute myeloid leukemia

Clonogenic cells from 41 children with newly diagnosed acute myeloid leukemia (AML) were tested in vitro for their sensitivity to cytarabine (Ara-C) and daunorubicin (DNR). The findings were then compared with the patients' responses to induction chemotherapy that uniformly included Ara-C and DNR. Light-density marrow cells were incubated with either or both drugs for one hour and cultured over leukocyte feeder layers; clusters and colonies were scored on days 7, 10, and 14. Only the percentage of cell kill in the presence of 1.8 mumol/L DNR was significantly associated with responses to induction therapy: median of 45% (range, 0% to 98%) for patients achieving complete remission v 16% (range, 4% to 23%) for nonresponders (P = .007). The relationship between clonogenic cell kill less than or equal to 23% and clinical responses was striking. Of the 11 evaluable patients with in vitro findings in this category, ten either failed induction therapy or relapsed within 1 year after attaining remission. Kaplan-Meier analysis of relapse-free survival times indicated longer durations of remission for patients whose blast cells showed increased sensitivity in vitro to Ara-C alone, DNR alone, or a combination of the two agents. Seven of 11 patients with cell kills of greater than or equal to 49% in the presence of 1.25 mumol/L Ara-C remain free of leukemia, compared with only one of 12 whose cells were less sensitive to the drug (P = .006). We conclude that the in vitro sensitivity of clonogenic leukemic progenitors to DNR and Ara-C correlates with treatment outcome in children with newly diagnosed AML.     

Exudative macular degeneration and intravitreal triamcinolone: 18 month follow up

Purpose: To evaluate the safety and efficacy of intravitreal triamcinolone after 18 months of follow up in patients with age-related macular degeneration and subfoveal or juxtafoveal choroidal neovascularization considered unsuitable for laser photocoagulation. Methods: Thirty eyes of 28 patients, referred from general eye clinics as well as the private clinic of one of the authors to a hospital-based retinal out-patient clinic, were treated with an intravitreal injection of triamcinolone (4mg). The primary outcome measure was the proportion of eyes with loss of six or more lines on a Bailey-Lovie Chart. The incidence of adverse events associated with treatment was also observed. Results: Of the 20 eyes with initial visual acuity (VA) of 6/60 or better, the vision was maintained (± 1 Bailey-Lovie lines) in 11 eyes (55%), while six eyes (30%) suffered severe visual loss (six or more lines). The VA improved by five to six lines in three of 10 eyes with initial vision of 3/60 or worse. Three of four eyes receiving a second injection suffered either progressive cataract or elevated intra-ocular pressure (IOP) requiring cataract surgery and/or filtering surgery. One of 26 eyes (3%) receiving a single injection showed progression of cataract and elevation of IOP within 6 weeks of treatment and required anti-glaucoma medication for 6 weeks. Progression of nuclear sclerosis 8–12 months after treatment was observed in six of 26 eyes (23%) receiving a single injection. Conclusions: The results of the present study suggest that a single intravitreal injection of 4 mg triamcinolone is reasonably well tolerated by the human eye. The rate of development of severe visual loss was less than reported for historical controls. Because the results are preliminary and uncontrolled, the treatment should not be used routinely until its benefit to patients is established by a prospective, randomized controlled study.     

Primary idiopathic hypomagnesemia in two female siblings

Two female siblings with primary idiopathic hypomagnesemia, born to consanguineous parents, are described. Both presented at 6 weeks of age, with convulsions and persistent hypocalcemia (calcium 1.5 and 1.6 mmol/1; normal range (NR) 2.2-2.6 mmol/1), which could not be controlled with anticonvulsants and/or calcium gluconate. On further investigation they were also found to have hypomagnesemia (magnesium 0.17 mmol/1 and 0.22 mmol/l; NR 0.65-1.05 mmol/l). Convulsions and the low serum calcium and magnesium levels were first managed by im and then by oral administration of magnesium supplements. A burst in circulating parathyroid hormone levels to well above the physiological range was observed at the start of therapy. Serum magnesium values of the mother and father were just below the normal range, with normal serum calcium. This type of infantile primary hypomagnesemia appears to be a hereditary disease with autosomal recessive characteristics, although a partially penetrant X-linked or autosomal dominant trait cannot be excluded.
Convulsions,primary hypomagnesemia     

Magnetic resonance imaging of the craniovertebral junction in rheumatoid arthritis

Conventional radiography and magnetic resonance imaging (MRI) of the craniovertebral junction were evaluated in 12 patients with longstanding rheumatoid arthritis (RA) and neck pain with or without other neurologic signs or symptoms of cervical myelopathy. MRI demonstrated abnormal soft tissue masses thought to represent pannus in 9 patients. Three patients showed cord or brainstem compression due to pannus or atlantoaxial subluxation. The 3 patients with MRI evidence of cord or brainstem compression had neurologic signs or symptoms of cervical myelopathy, and appropriate therapy was instituted based on these findings. This study indicates that MRI is able to detect abnormal soft tissue masses which probably represent pannus and their relationship to the spinal cord or brainstem, and confirms the utility of the procedure in the management of craniovertebral involvement in RA.     

Chronic relapsing polyneuropathy associated with immunoblastic lymphadenopathy

Two episodes of severe, relapsing sensorimotor polyneuropathy closely paralleled the course of systemic illness in a patient with immunoblastic lymphadenopathy. A review of the literature shows three other cases, although none with documented pathologic changes in muscles and nerves. Based on the pathologic findings in this patient, the peripheral neuropathy associated with immunoblastic lymphadenopathy can be classified under the group of relapsing inflammatory polyneuropathies associated with systemic disorders. Whether prednisone therapy helped this condition is uncertain.