Absence of an association between mannose-binding lectin polymorphism and rheumatoid arthritis

It has been proposed that mannose-binding lectin (MBL) interactions with agalactosyl forms of IgG immunoglobulins found in rheumatoid synovial fluid might lead to enhanced complement activation, an important mediator of the joint damage in rheumatoid arthritis (RA). In order to investigate this possible link between increased MBL-mediated activation of complement and perpetuation of rheumatoid synovitis, we have compared the frequency of an allelic form of MBL, known to be incapable of activating complement, in a group of hospital patients with severe RA and control subjects. No evidence was found to support an association between the presence of this MBL allele and protection from rheumatoid disease; genotype frequencies were similar in both groups. This suggests that complement activation via MBL-agalactosyl IgG complexes is unlikely to play a major role in the pathophysiology of RA.      

Loss of bone mineral density in Chinese pre-menopausal women with systemic lupus erythematosus treated with corticosteroids

The adverse effect of disease and chronic corticosteroid therapy on bone mineral density (BMD) in patients with systemic lupus erythematosus (SLE) has been reported in several studies of Caucasian populations. As the factors controlling bone homeostasis may be different in Asian populations, we measured BMD in 52 pre-menopausal Chinese women (mean age 34.1 +/- 8.0 yr) with SLE (mean disease duration 6.4 +/- 4.5 yr) treated with prednisone (mean daily dose 11.4 +/- 10.8 mg/day). Lumbar spine, hip (total and subregions) and total body BMDs were measured in the SLE patients using dual-energy X-ray absorptiometry (DEXA), and compared with those from healthy controls matched for age, sex and body mass index. Compared to controls, SLE patients were found to have lower BMD (g/cm2) at several sites: the lumbar spine (0.98 vs 0.90, P = 0.001), Ward's triangle (0.72 vs 0.67, P = 0.03), total body (1.04 vs 1.01, P = 0.04) and total hip (0.87 vs 0.82, P = 0.05). There was no correlation between BMD at any region and duration of disease, activity of disease or prednisone therapy (mean daily dose, cumulative dose or treatment duration). When BMDs were compared between controls and SLE patients, subgrouped according to those not on calcium and those arbitrarily receiving calcium supplements (1 g/day), significantly lower BMDs were found in those not on calcium compared to both controls and SLE patients on calcium. BMDs in SLE patients on calcium were not different from those in controls. The low prevalence of osteoporosis in our SLE patients (4-6%) suggests significant loss of BMD in Chinese SLE patients on corticosteroid therapy is less than that reported in Caucasians (12-18%).      

Catalysis of soluble hemoglobin oxidation by free iron on sickle red cell membranes

Abnormal deposition of hemichrome on the inner aspect of the sickle red cell membrane promotes premature cell demise. The steps proximate to hemichrome formation in these cells are poorly understood. To test the hypothesis that the pathologic deposits of free ferric iron located on the inner aspect of sickle cell membranes would be redox active and promote oxidation of soluble oxyhemoglobin, we incubated native versus iron-stripped sickle or normal ghost membranes with oxyhemoglobin S. We found that sickle membranes exerted an exaggerated effect on methemoglobin formation in solution, an effect completely accounted for by their abnormal content of free iron. This ability of sickle membranes to promote hemoglobin oxidation was not diminished by catalase or by presence of a high-affinity, iron-inactivating chelator that is unable to remove membrane iron. Examination of those membranes likewise revealed that their free iron content promoted deposition of additional heme-protein. These results establish that the potential redox couple formed by membrane-associated ferric iron and cytoplasmic oxyhemoglobin is promotive of hemoglobin oxidation and deposition of hemichrome on the membrane. This predicts that removal of pathologic membrane iron might help prevent the detrimental formation of methemoglobin and hemichrome in vivo, insofar as this is accelerated by transition metal.     

Human mast cells synthesize new granules during recovery from degranulation. In vitro studies with mast cells purified from human lungs

Secretory cells undergoing release and recovery events related to constitutive and/or stimulus-initiated secretion might be expected to undergo distinctive changes in morphology as well. We studied the release and recovery events of human mast cell secretion stimulated by antibody to immunoglobulin E. We used enzymatically digested mast cells from human lung specimens further purified by countercurrent centrifugation elutriation. Release kinetics were like those reported for isolated human lung mast cells. In two complete kinetic experiments we restudied these early release patterns (0 to 30 minutes). Mast cells, either stimulated or controls, were then cultured and sampled for electronmicroscopic studies at periodic intervals (3 to 48 hours). We describe events of the late recovery period here, although some overlap with processes seen in early recovery samples occurred. Mast cells that released nearly all their cytoplasmic granules and exteriorized the containers, eg, granule-channel membranes, underwent progressive enlargement of Golgi structures and development of numerous small cytoplasmic vesicles and small, membrane-bound granules filled with particulate and dense content. Ultimately, new mature cytoplasmic granules of all substructural patterns occurred. Nuclear blast changes and expansion of cytoplasmic mass accompanied this period of new granule synthesis. Mixed recovery patterns were present in individual cells. These represented the morphological expression of a variety of recovery events. Thus, some cells showed a combination of channel recovery and remodeling to form new granule containers within which condensation of content produced crystalline patterns, as well as synthesis of new granules, as described here. This morphological versatility resulted in multiple mast cell morphological phenotypes during these release and recovery processes.     

Therapeutic and neurotoxic effects of 2-chlorodeoxyadenosine in adults with acute myeloid leukemia

Despite expectations that 2-chlorodeoxyadenosine (2-CdA) would prove active primarily in lymphoproliferative diseases, early reports suggested unexpected high activity of this drug in heavily pretreated children with acute myeloblastic leukemia (AML) at a maximally tolerated dose of 8.9 mg/m2/day for 5 days. In view of these findings, we conducted an escalating dose trial of 2-CdA in adult patients with relapsed or resistant AML. Thirty-six patients who had received extensive prior therapy were treated at 9 dose levels of 2-CdA at daily doses ranging from 5 to 21 mg/m2 for 5 days. 2-CdA eliminated leukemic blasts from the peripheral blood in 32 of 36 cases; however, bone marrow hypoplasia was seen only at daily dose levels > or = 15 mg/m2. We observed a total of 3 complete remissions: 1 at the 15 mg/m2/d dose level and 2 at the 21 mg/m2/d dose level; these responses persisted for 3, 2, and 3 months, respectively. Although prolonged myelosuppression would have been dose-limiting at 21 mg/m2/d for 5 days, the most important adverse effect was the development of a sensorimotor peripheral neuropathy. This reaction, whose onset was substantially delayed after completion of drug treatment, was observed in 2 of 5 patients at the 19 mg/m2/d level and in 4 of 4 evaluable patients at the 21 mg/m2/d level. Pathologically, this process was characterized by axonal degeneration and secondary demyelination. Other side effects included reactivation of a posttransplant Epstein-Barr virus-related lymphoma in 1 patient and tumor lysis syndrome. We conclude that the maximally tolerable dose of 2-CdA in adult patients (17 mg/m2/d for 5 days) in approximately twofold in excess of that previously reported in children and that the limiting toxic effect is a degenerative neuropathic disorder. We confirm that this drug has definite activity in AML, but the magnitude of this effect needs to be determined in larger numbers of patients who have received less extensive therapy. This agent deserves further evaluation in patients with both AML and acute lymphoblastic leukemia at these higher doses and perhaps as part of a preparative regimen for patients undergoing bone marrow transplantation.     

Small unilateral jaw gap variations: equilibrium changes, co-contractions and joint forces

Summary  After complex prosthetic reconstructions, small differences in vertical distances between the left and right side of the jaw may occur during jaw closing, nevertheless providing bilateral tooth contacts in intercuspation by small deformations of the mandible. Their effects on the co-contraction of the masticatory muscles, the temporomandibular joint reaction forces, and the point of application of the resultant bite force vector in the maxillary occlusion plane – the so-called reduction point – have not been investigated, thus far simultaneously in one sample. The main goal of this study was to investigate variations of these measures in an experimental intercuspation simulated by one anterior and two posterior force transmission points.