Proceedings of the Association of American Physicians最新文献

We investigated the regulation, secretion, and surface expression of the low-affinity FcepsilonRII receptor (CD23) in eosinophils isolated from human blood using multiple monoclonal antibodies (mAbs) directed at different epitopes of human CD23. Substantial surface expression of CD23 was not demonstrated in the resting state. Mean fluorescence intensity (MFI) measured by flow cytometry was 7. 1 +/- 0.8 for 9P25 mAb (p = NS) and 15.7 +/- 3.8 for BU38 mAb (p <. 04) versus 5.3 +/- 1.0 for IgG1 isotype control Ab. By contrast, MFI using BU38 mAb was 154 +/- 18 for JY-B lymphocytes (p <.0001 versus eosinophils). Despite weak surface expression, eosinophil permeabilization demonstrated substantial intracellular expression of CD23; MFI was 33.6 +/- 5.2 for 9P25 mAb versus 4.4 +/- 0.43 for IgG control (p <.001). Western blot analysis using both positive and negative controls demonstrated immunological identity with CD23 on JY-B lymphocytes. Activation of eosinophils caused rapid translocation of CD23 to the surface membrane (160 +/- 33 MFI; p <. 005), which was maximal within 30 sec. Secretory CD23 was detected within the perfusate also at 30 sec and was fully reinternalized at 10 min. This is the first demonstration of the presence of intracellular CD23 in human eosinophils. Our data indicate that eosinophils rarely express CD23 on their surface but are capable of transient high-level expression and secretion with rapid reuptake of intracellular stores of CD23.

We have performed the first prenatal assessment of clinical phenotype in a family affected by Ehlers-Danlos syndrome type VI (EDS VI), an inherited collagen disorder, by screening the fetal DNA for mutations in the lysyl hydroxylase (LH) gene. We have previously reported that the affected child in this family is compound heterozygous for mutations in the LH gene. One allele has a paternally inherited C1557 to G change that codes for a premature stop codon (Y511X) in exon 14 and the other allele has a deletion of exon 5 that results from a maternally inherited mutation in the consensus donor splice site of intron 5. To perform the prenatal diagnosis, we sequenced genomic DNA isolated from cultured chorionic villus cells at 10 weeks of gestation. One allele had the maternally inherited gt --> at splice-site mutation in exon 5, and the other paternally inherited allele was normal. As EDS VI is a recessive disorder, we predicted that although a carrier, the baby should be unaffected. This conclusion, which was supported by a normal level of LH activity in the chorionic villus cells, was confirmed by the birth of a healthy unaffected baby.

Cancer is a leading cause of morbidity and mortality in the United States and other developed countries. In searching for preventive strategies against this disease, researchers have postulated that antioxidant vitamins may play a role in preventing cancer since several plausible biological mechanisms exist. This article reviews the epidemiological evidence for a role of antioxidant vitamins (in particular, beta-carotene, vitamin E, and vitamin C) in the development of cancer. Observational studies provide fairly consistent data for an inverse association between high intake of antioxidant vitamins, especially beta-carotene and vitamin C, and cancer risk. However, randomized trials generally have not supported the hypothesis. Several explanations for these inconsistent findings are possible. These include: 1) confounding by other healthy dietary and nondietary habits in observational studies; 2) the protective role of a combination of many different nutrients present in fruits and vegetables, rather than the single nutrient or combination of two nutrients that most trials have tested; 3) inadequate duration of follow-up in most randomized trials; and 4) heterogeneity of the populations studied. Reliable epidemiological evidence regarding whether antioxidant vitamins play a role in preventing cancer will have to come from both observational studies and randomized trials since these different study designs each have unique strengths and limitations. Based on the available evidence, it seems prudent to advocate a diet rich in fruits and vegetables, rather than the consumption of specific antioxidant vitamin supplements, in order to decrease the risk of developing cancer.

Basic research studies suggest that oxidative mechanisms may play an important role in the pathogenesis of cataract and age-related macular degeneration, the two most important causes of visual impairment in older adults. These findings raise the possibility that vitamins and trace minerals with antioxidant properties can be of benefit in preventing the onset or progression of disabling eye disease. Results from observational epidemiological studies in humans, however, are inconclusive. Although findings from several studies, primarily cross-sectional and case-control, are generally compatible with a possible protective role for micronutrients in disease development, the data for specific nutrients or specific disease types are inconsistent. The imprecision of dietary exposure data and the likely effects of uncontrolled confounding further limit these observational studies. Well-designed, large-scale, randomized trials are required to evaluate definitively the potentially important benefit of vitamin supplementation in eye disease.

We conducted an 18-month, placebo-controlled, double-blind study to evaluate cladribine in the treatment of 52 patients with relapsing-remitting multiple sclerosis. Patients received either placebo or cladribine 0.07 mg/kg/day by subcutaneous injection for 5 consecutive days as six monthly courses for a total cumulative dose of 2.1 mg/kg. Analysis of results revealed a statistically significant favorable effect of cladribine on the joint frequency and severity of relapses and magnetic resonance imaging (MRI) findings. MRI-enhancing lesions were completely suppressed in the cladribine patients by the sixth month of treatment. Mild segmental herpes zoster occurred in two cladribine-treated patients and one patient receiving placebo. Otherwise, there were no side effects or adverse events. We conclude that cladribine shows promise as a treatment for relapsing-remitting multiple sclerosis.

We compared internalization of three radioiodinated octreotide (OCT) somatostatin (SS) analogs-[125I-Tyr3]OCT, [DTPA degrees, 125I-Tyr3]OCT, and [DOTA degrees,125I-Tyr3]OCT-by somatostatin receptor (SSR)-positive mouse AtT20 pituitary tumor cells and human insulinoma cells. The three SS analogs were internalized in a specific, time-dependent manner. Internalization was significantly inhibited by pertussis toxin (100 microg/l) by 38%, 43%, and 31%, and by an inhibitor of receptor-mediated endocytosis (phenyl arsine oxide; 10 microM) by 98%, 94%, and 92%, respectively. Binding affinities of the three radioligands were comparable (0.2, 0.2, and 0.3 nM, respectively). However, [DOTA degrees,125I-Tyr3]OCT was internalized in a five-fold higher amount in comparison with the two other radioligands. A comparably high uptake of [DOTA degrees, 125I-Tyr3]OCT was found in SSR-positive organs (pituitary, pancreas, and adrenals) in vivo in rats (a ten-fold, five-fold, and eight-fold higher uptake 4 hr post injection, respectively, compared with the two other radioligands). This resulted in very high target-background ratios for [DOTA degrees,125I-Tyr3]OCT 4 hr post injection amounting to 274, 566, and 623 in the pituitary, adrenals, and pancreas, respectively. Both in vivo and in vitro there was a rapid dissociation of radioactivity from the SSR-positive cells. Main conclusions are that: 1) coupling of chelating groups like DTPA or DOTA to the SS analog [Tyr3]OCT does not prevent the internalization of OCT after binding to SSRs; 2) [DOTA degrees, 125I-Tyr3]OCT is internalized in a significantly higher amount by AtT20 and human insulinoma cells and in vivo in rats in SSR-positive organs, in comparison with [DTPA degrees,125I-Tyr3]OCT and [125I-Tyr3]OCT; and 3) the very high target-background ratios in vivo make radioiodinated [DOTA degrees,Tyr3]OCT a very suitable ligand for SSR-targeted radioguided surgery of SSR-positive human neuroendocrine tumors.

Osteoclast activity is inhibited by elevated [Ca2+]o; however, the underlying molecular mechanism is unknown. We used the human osteoclast-like cells GCT23 to elucidate their cation-sensing properties. Cells responded to elevated [Ca2+]o with rapid concentration-dependent [Ca2+]i transients (EC50 = 7.8 mm, time to peak 44 +/- 4 sec) that were due to release from intracellular stores, followed by Ca2+ influx across the plasma membrane. Ca2+ store depletion by thapsigargin, endothelin-1, or bradykinin activated calcium entry pathways. Cells responded similarly to Ni2+ and Cd2+ with albeit slower kinetics (EC50 <10 microm and <100 microm, times to peak 140 +/- 25 sec and 150 +/- 24 sec, respectively). The three cations stimulated inositol phosphate production (two-fold, p <.02) similar to bradykinin (2.5-fold, p <. 002), which activates a phospholipase C (PLC)-coupled receptor in GCT23 cells. The cells did not respond to 0.1-1 mM Gd3+ or neomycin B, indicating that the parathyroid calcium receptor (PCaR) is not functionally expressed. In confirmation, PCaR could not be detected by reverse transcriptase polymerase chain reaction in GCT23 cells and in mouse osteoclasts, and the calcimimetic compound NPS R-568 failed to produce the left shift of the concentration-response curve characteristic for PCaR. Our data demonstrate for the first time that cation sensing by osteoclast-like GCT23 cells is mediated by a PLC-coupled receptor that is not identical to PCaR.

The cardinal clinical manifestations of major depression with melancholic features include sustained anxiety and dread for the future as well as evidence of physiological hyperarousal (e.g., sustained hyperactivity of the two principal effectors of the stress response, the corticotropin-releasing-hormone, or CRH, system, and the locus ceruleus-norepinephrine, or LC-NE, system). Sustained stress system activation in melancholic depression is thought to confer both behavioral arousal as well as the hypercortisolism, sympathetic nervous system activation, and inhibition of programs for growth and reproduction that consistently occur in this disorder. Data also suggest that activation of the CRH and LC systems in melancholia are involved in the long-term medical consequences of depression such as premature coronary artery disease and osteoporosis, the two-three-fold preponderance of females in the incidence of major depression, and the mechanism of action of antidepressant drugs. In addition, recent data reveal important bidirectional interactions between stress-system hormonal factors in depression and neural substrates implicated in many discrete behavioral alterations in depression (e.g., the medial prefrontal cortex, important in shifting affect based on internal and external cues, the mesolimbic dopaminergic reward system, and the amygdala fear system). We have also advanced data indicating that the hypersomnia, hyperphagia, lethargy, fatigue, and relative apathy of the syndrome of atypical depression are associated with concomitant hypofunctioning of the CRH and LC-NE systems. These data indicate the need for an entirely different therapeutic strategy than that used in melancholia for the treatment of atypical depression, and they suggest that this subtype of major depression will be associated with its own unique repertoire of long-term medical consequences.

The hypothesis that antioxidant vitamins might reduce cardiovascular disease risk is based on a large body of both basic and human epidemiological research. One of the most consistent findings in dietary research is that those who consume higher amounts of fruits and vegetables have lower rates of heart disease and stroke as well as cancer. Recent attention has focused on the antioxidant content of fruits and vegetables as a possible explanation for the apparent protective effects. Basic research provides a plausible mechanism by which antioxidants might reduce the risk of atherosclerosis. A large number of descriptive, case-control, and cohort studies provide data suggesting that consumption of antioxidant vitamins is associated with reduced risks of cardiovascular disease. These data raise the question of a possible role of antioxidants, such as vitamins C and E and beta-carotene, in the primary prevention of cardiovascular disease, but they do not provide a definitive answer. Randomized trial data will be essential in fully assessing whether or not there is a causal effect of antioxidants in reducing the risk of cardiovascular disease. Results from several large-scale randomized trials of antioxidant supplements are now available, and additional trial data should be forthcoming in the near future, which will better define the role of antioxidants in the primary and secondary prevention of atherosclerotic disease. At this point, antioxidants represent a possible but as yet unproven means to reduce the risk of cardiovascular disease.

Type 1 diabetes is an autoimmune disease characterized by immune-mediated destruction of the pancreatic beta cells. Insulin autoantibodies (IAAs) develop in many subjects at high risk for developing type 1 diabetes prior to onset of clinical disease and exposure to exogenous insulin, whereas insulin antibodies (IAs) commonly develop in patients treated with exogenous insulin. To investigate whether the binding characteristics of IAA and IA are similar, we measured eight different binding characteristics of IAAs from 19 insulin-naive first-degree relatives of type 1 diabetes patients and compared these to the binding characteristics of IAs from 19 type 1 diabetes patients treated with exogenous insulin. IAA and IA samples were matched for percentage insulin binding. Scatchard analysis revealed that IAAs have a two-slope representation similar to IAs-that is, two populations of antibodies, a high-affinity low-capacity population and a low-affinity high-capacity population. Binding properties of the two respective populations were found to be similar for IAAs and IAs. Sipps' equation was used to generate a Hill plot and produce an index of heterogeneity, which showed further similarity between IAAs and IAs. These results suggest that the IAAs found in subjects at increased risk for type 1 diabetes, like IAs, are likely to be polyclonal in nature. The similarities between IAAs and IAs support the hypothesis that both are induced by insulin presentation to the immune system.