甲亢甲低患者肝纤维化指标检测的临床意义分析

目的：探讨甲状腺功能亢进（甲亢）、甲状腺功能减低（甲低）与肝纤维化指标的关系及其可能的机制。方法：采用放射免疫分析法（R1A）检测57例甲亢患者、43例甲低患者、39例甲亢治疗后甲状腺激素正常者和50例健康成人的血清Ⅳ型胶原（1V-C）、Ⅲ型前胶原（PCⅢ）、透明质酸（HA）、层粘连蛋白（LN）、T3、T4、FT3、FT4、TSH、TGA、TMA含量。结果：甲亢患者组血清中1V-C、PCⅢ含量比正常对照组及甲低患者组显著性增高（P〈0.05）;治疗后甲状腺激素下降,1V-C、PCⅢ含量也随之下降（与治疗前比较P〈0.01）;HA、LN在四组中无显著性差异（P〉0.05）,在甲亢治疗前后无显著性差异（P〉0.05）。各项肝纤维化指标与TGA、TMA的阳性率无关。结论：甲亢患者可有不同程度的肝功能损害,血清中甲状腺激素水平增高时,1V-C、PCⅢ水平也增高,在用1V-C、PCⅢ判断肝纤维化时应注意有无甲状腺疾病特别是甲亢。未发现HA、LN含量与甲状腺激素水平的关系。     

Structure–activity relationships of antitubercular salicylanilides consistent with disruption of the proton gradient via proton shuttling

A series of salicylanilides was synthesized based on a high-throughput screening hit against Mycobacterium tuberculosis. A free phenolic hydroxyl on the salicylic acid moeity is required for activity, and the structure–activity relationship of the aniline ring is largely driven by the presence of electron withdrawing groups. We synthesized 94 analogs exploring substitutions of both rings and the linker region in this series and we have identified multiple compounds with low micromolar potency. Unfortunately, cytotoxicity in a murine macrophage cell line trends with antimicrobial activity, suggesting a similar mechanism of action. We propose that salicylanilides function as proton shuttles that kill cells by destroying the cellular proton gradient, limiting their utility as potential therapeutics.     

Characterization of the mechanical behavior of the optic nerve sheath and its role in spaceflight-induced ophthalmic changes

Visual impairment and intracranial pressure (VIIP) syndrome is characterized by a number of permanent ophthalmic changes, including loss of visual function. It occurs in some astronauts during long-duration spaceflight missions. Thus, understanding the pathophysiology of VIIP is currently a major priority in space medicine research. It is hypothesized that maladaptive remodeling of the optic nerve sheath (ONS), in response to microgravity-induced elevations in intracranial pressure (ICP), contributes to VIIP. However, little is known about ONS biomechanics. In this study, we developed a custom mechanical testing system that allowed for unconfined lengthening, twisting, and circumferential distension of the porcine ONS during inflation and axial loading. Data were fit to a four-fiber family constitutive equation to extract material and structural parameters. Inflation testing showed a characteristic “cross-over point” in the pressure–diameter curves under different axial loads in all samples that were tested; the cross-over pressure was \(10.3 \pm 0.95\) mmHg (\(\hbox {mean} \pm \hbox {SEM}\)). Large sample-to-sample variations were observed in the circumferential strain, while only modest variations were observed in the circumferential stress. Multiphoton microscopy revealed that the collagen fibers of the ONS were primarily oriented axially when the tissue was loaded. The existence of this cross-over behavior is expected to be neuroprotective, as it would avoid optic nerve compression during routine changes in gaze angle, so long as ICP was within the normal range. Including these observations into computational models of VIIP will help provide insight into the pathophysiology of VIIP and could help identify risk factors and potential interventions.     

The distribution of fitness effects of spontaneous mutations in Chlamydomonas reinhardtii inferred using frequency changes under experimental evolution

The distribution of fitness effects (DFE) for new mutations is fundamental for many aspects of population and quantitative genetics. In this study, we have inferred the DFE in the single-celled alga Chlamydomonas reinhardtii by estimating changes in the frequencies of 254 spontaneous mutations under experimental evolution and equating the frequency changes of linked mutations with their selection coefficients. We generated seven populations of recombinant haplotypes by crossing seven independently derived mutation accumulation lines carrying an average of 36 mutations in the haploid state to a mutation-free strain of the same genotype. We then allowed the populations to evolve under natural selection in the laboratory by serial transfer in liquid culture. We observed substantial and repeatable changes in the frequencies of many groups of linked mutations, and, surprisingly, as many mutations were observed to increase as decrease in frequency. Mutation frequencies were highly repeatable among replicates, suggesting that selection was the cause of the observed allele frequency changes. We developed a Bayesian Monte Carlo Markov Chain method to infer the DFE. This computes the likelihood of the observed distribution of changes of frequency, and obtains the posterior distribution of the selective effects of individual mutations, while assuming a two-sided gamma distribution of effects. We infer that the DFE is a highly leptokurtic distribution, and that approximately equal proportions of mutations have positive and negative effects on fitness. This result is consistent with what we have observed in previous work on a different C. reinhardtii strain, and suggests that a high fraction of new spontaneously arisen mutations are advantageous in a simple laboratory environment.     

Annexin-V imaging for noninvasive detection of cardiac allograft rejection.

Heart transplant rejection is characterized pathologically by myocyte necrosis and apoptosis associated with interstitial mononuclear cell infiltration. Any one of these components can be targeted for noninvasive detection of transplant rejection. During apoptotic cell death, phosphatidylserine, a phospholipid that is normally confined to the inner leaflet of cell membrane bilayer, gets exteriorized. Technetium-99m-labeled annexin-V, an endogenous protein that has high affinity for binding to phosphatidylserine, has been administered intravenously for noninvasive identification of apoptotic cell death. In the present study of 18 cardiac allograft recipients, 13 patients had negative and five had positive myocardial uptake of annexin. These latter five demonstrated at least moderate transplant rejection and caspase-3 staining, suggesting apoptosis in their biopsy specimens. This study reveals the clinical feasibility and safety of annexin-V imaging for noninvasive detection of transplant rejection by targeting cell membrane phospholipid alterations that are commonly associated with the process of apoptosis.     

Vascular Streak Dieback of cacao in Southeast Asia and Melanesia: in planta detection of the pathogen and a new taxonomy

Vascular Streak Dieback (VSD) disease of cacao (Theobroma cacao) in Southeast Asia and Melanesia is caused by a basidiomycete (Ceratobasidiales) fungus Oncobasidium theobromae (syn. =Thanatephorus theobromae). The most characteristic symptoms of the disease are green-spotted leaf chlorosis or, commonly since about 2004, necrotic blotches, followed by senescence of leaves beginning on the second or third flush behind the shoot apex, and blackening of infected xylem in the vascular traces at the leaf scars resulting from the abscission of infected leaves. Eventually the shoot apex is killed and infected branches die. In susceptible cacao the fungus may grow through the xylem down into the main stem and kill a mature cacao tree. Infections in the stem of young plants prior to the formation of the first 3-4 lateral branches usually kill the plant. Basidiospores released from corticioid basidiomata developed on leaf scars or along cracks in the main vein of infected leaves infect young leaves. The pathogen commonly infects cacao but there are rare reports from avocado. As both crops are introduced to the region, the pathogen is suspected to occur asymptomatically in native vegetation. The pathogen is readily isolated but cultures cannot be maintained. In this study, DNA was extracted from pure cultures of O. theobromae obtained from infected cacao plants sampled from Indonesia. The internal transcribed spacer region (ITS), consisting of ITS1, 5.8S ribosomal RNA and ITS2, and a portion of nuclear large subunit (LSU) were sequenced. Phylogenetic analysis of ITS sequences placed O. theobromae sister to Ceratobasidium anastomosis groups AG-A, AG-Bo, and AG-K with high posterior probability. Therefore the new combination Ceratobasidium theobromae is proposed. A PCR-based protocol was developed to detect and identify C. theobromae in plant tissue of cacao enabling early detection of the pathogen in plants. A second species of Ceratobasidium, Ceratobasidium ramicola, identified through ITS sequence analysis, was isolated from VSD-affected cacao plants in Java, and is widespread in diseased cacao collected from Indonesia.     

Random intracellular drift explains the clonal expansion of mitochondrial DNA mutations with age

Human tissues acquire somatic mitochondrial DNA (mtDNA) mutations with age. Very high levels of specific mtDNA mutations accumulate within individual cells, causing a defect of mitochondrial oxidative metabolism. This is a fundamental property of nondividing tissues, but it is not known how it comes about. To explore this problem, we developed a model of mtDNA replication within single human cells. Using this model, we show that relaxed replication of mtDNA alone can lead, through random genetic drift, to the clonal expansion of single mutant events during human life. Significant expansions primarily develop from mutations acquired during a critical period in childhood or early adult life.     

Selection against pathogenic mtDNA mutations in a stem cell population leads to the loss of the 3243A-->G mutation in blood

The mutation 3243A-->G is the most common heteroplasmic pathogenic mitochondrial DNA (mtDNA) mutation in humans, but it is not understood why the proportion of this mutation decreases in blood during life. Changing levels of mtDNA heteroplasmy are fundamentally related to the pathophysiology of the mitochondrial disease and correlate with clinical progression. To understand this process, we simulated the segregation of mtDNA in hematopoietic stem cells and leukocyte precursors. Our observations show that the percentage of mutant mtDNA in blood decreases exponentially over time. This is consistent with the existence of a selective process acting at the stem cell level and explains why the level of mutant mtDNA in blood is almost invariably lower than in nondividing (postmitotic) tissues such as skeletal muscle. By using this approach, we derived a formula from human data to correct for the change in heteroplasmy over time. A comparison of age-corrected blood heteroplasmy levels with skeletal muscle, an embryologically distinct postmitotic tissue, provides independent confirmation of the model. These findings indicate that selection against pathogenic mtDNA mutations occurs in a stem cell population.     

Effects of varying the position of thyroid hormone response elements within the rat growth hormone promoter: implications for positive and negative regulation by 3,5,3'-triiodothyronine

The thyroid hormone response element (T3RE) of the rat GH (rGH) promoter is located at -188 to -165 relative to the mRNA start site (TSS). Similar sites have been identified in other genes regulated by T3. We have investigated some of these T3REs in positions within the rGH promoter to assess the relative influences of DNA-binding site and position on positive and negative regulation by T3. Synthetic oligonucleotides were used with sequences from the rGH T3RE and proposed negative T3REs (nT3RE) from the rat and human alpha-subunit and rat beta TSH genes. The nT3REs were placed in the background of the wild-type rGH promoter in two positions, at -55 and down-stream of the TSS, with up- and down-mutations of the rGH T3RE. Rat GH T3RE elements were placed 700 basepairs up-stream of a basal rGH promoter and some also at the -55 and TSS positions. Constructions were tested in a transient transfection assay in rat pituitary tumor cells. Two copies of the rGHPAL (palindromic T3RE) placed 700 basepairs up-stream of the rGH promoter conferred 10-fold T3 induction. In the -55 position, the rGHPAL increased T3 induction compared to that in controls, whereas a fragment from the rat and human alpha-subunit gene in the same position reduced induction. Negative T3REs from rat beta TSH and human alpha-subunit reduced T3 induction 50% when placed at the TSS position of a rGH promoter containing an up-mutant T3RE. The T3REPAL placed at the same site increased T3 induction.(ABSTRACT TRUNCATED AT 250 WORDS)