成纤维细胞的力学生物学(下)

一、肌腱内成纤维细胞的力学生物学反应 肌腱内的成纤维细胞可以合成胶原蛋白及其他一些大分子。成纤维细胞可以将这些分子排列成组织性较高的单元，并使纤维的方向与张力方向平行。无论是培养的肌腱还是独立的成纤维细胞都可以对力做出相应的反应。     

Gas permeation through two side-chain liquid-crystalline polyacrylate-based membranes containing 4-methoxyphenyl 4-hexyloxybenzoate or 4-cyanophenyl 4-hexyloxybenzoate mesogenic side groups

Two kinds of side-chain liquid-crystalline (LC) polymers with different side-chain mesogenic end groups were synthesized. The laminated membrane was prepared by sandwiching the side-chain LC polymer between two porous polypropene (Celgard) films. Permeation properties for O₂, N₂, CO₂ and CH₄ through the laminated side-chain LC polymer-based membranes were measured using a gas-chromatographic method at several temperatures corresponding to the stability range of the different phases of the side-chain LC polymers. The gas permeation behaviour depends strongly on the state of the side-chain LC polymer. The activation energy for permeation depends on the state, too. The plot of separation factor P/P versus P exhibits an unusual behaviour. P/P increases with P when the temperature rises and the phase of the side-chain LC Polymer changes from the glassy state to the liquid-crystalline state. The magnitude of gas permeability coefficients for the laminated membranes is rather low compared to those of some common polymers. The low gas permeability seems to originate from the low gas solubility rather than from the low gas diffusivity in the laminated side-chain LC polymer membrane.     

Elastase activity in granulomatous inflammation in experimental murine leprosy

Proteolytic activity for [3H]elastin, pyro-Glu-Pro-Val-pNA(S-2484), and Suc-(Ala)3-pNA(AAApNA) was demonstrated in the bound fraction extracted with 2 M KSCN + 0.1% Triton X-100 from hypersensitivity-type murine lepromas in C57BL/6N mice, while elastase-inhibitor activity was separately observed in the soluble fraction extracted with a Tris-saline buffer. Sephacryl S-200 gel chromatography showed a peak of elastolytic activity with approximately 20,000 in molecular weight. The following DEAE-Sepharose chromatography demonstrated three fractions of elastolytic activity (E-I, II, III). The inhibitory profile showed that E-I is a thiol proteinase, while E-II and E-III belong to serine proteinase-type elastases. Both E-II and E-III showed different properties with neutrophil elastase or elastase secreted from cultured macrophages, but identical characteristics to membrane bound-type elastase of monocytes. A lower level of elastolytic activity was detected in the bound fraction of nonhypersensitivity-type murine lepromas in CBA/N mice, suggesting a more involvement of membrane bound-type elastase from monocytes/macrophages during the tissue remodelings of hypersensitivity-type granulomas.     

Glutaraldehyde-treated bioprosthetic substitute for rabbit Achilles tendon

The biomechanical properties and histocompatibility of a glutaraldehyde-treated xenograft were examined after implanting it in 27 rabbits. This xenograft was used as an Achilles tendon substitute placed in vivo for 2 to 48 wk. The specimens were then subjected to mechanical strength testing using a specially constructed tensioning device. The contralateral Achilles tendon was used as the reference baseline. Mechanical testing showed that the strength of the implanted graft increased to 33.5% of the normal side at week 10 and to 79.5% at week 14. The host generated a fibrous cord around the xenograft, linking the two ends of the Achilles tendon. Light and electron microscopic examination showed fibroblastic infiltration of varying magnitude in all specimens but no statistical correlation between degree of infiltration and duration of implantation was found. Also, there was no histological evidence of immunological rejection within the 48 wk of study.     

Coexpression of galanin and adrenocorticotropic hormone in human pituitary and pituitary adenomas.

Galanin is a neuropeptide that regulates the secretion of several pituitary hormones, including prolactin (PRL) and growth hormone (GH). Galaninlike immunoreactivity (Gal-IR) and galanin mRNA in the rat anterior pituitary is cell lineage specific, with predominant expression in lactotrophs and somatotrophs. The authors examined the cellular distribution of human Gal-IR in seven normal postmortem pituitaries and 62 pituitary tumors by immunoperoxidase staining. In contrast to the rat, Gal-IR in human anterior pituitaries was present in corticotrophs scattered throughout the gland, but not in lactotrophs, somatotrophs, thyrotrophs, or gonadotrophs. Distinct Gal-IR also was present in hyperplastic and neoplastic corticotrophs in 19 of 22 patients with Cushing's disease. In noncorticotroph cell tumors, unequivocal Gal-IR was present in 5 of 11 GH-secreting tumors associated with clinical acromegaly, 9 of 18 nonfunctioning pituitary adenomas, and 2 of 14 prolactinomas. Of these galanin-positive tumors, four of the five GH-secreting adenomas, six of the nine nonfunctioning adenomas, and both of the prolactinomas also contained adrenocorticotropic hormone immunoreactivity (ACTH-IR). Immunostaining and in situ hybridization on adjacent sections using an 35S-labeled probe complementary to human galanin mRNA demonstrated predominant galanin expression in normal corticotrophs. Immunoelectron microscopy confirmed the presence of Gal-IR in pituitary cells characteristic of corticotrophs in both normal and neoplastic pituitaries. Thus, as in the rat, galanin gene expression in the human pituitary is cell-type specific. Unlike the rat, however, human galanin gene expression is restricted to the corticotroph lineage. Studies of tumors confirmed the observed coexpression of galanin and adrenocorticotropic hormone. The divergent cell type specificity of galanin production in human and rat pituitaries reflects different patterns of gene activation in these two species. In addition, these results suggest that galanin in the human pituitary may participate locally in the regulation of the hypothalamic-pituitary-adrenal axis.     

Antimicrobial susceptibility testing of aquatic bacteria: quality control disk diffusion ranges for Escherichia coli ATCC 25922 and Aeromonas salmonicida subsp. salmonicida ATCC 33658 at 22 and 28 degrees C

Quality control (QC) ranges for disk diffusion susceptibility testing of aquatic bacterial isolates were proposed as a result of a multilaboratory study conducted according to procedures established by the National Committee for Clinical Laboratory Standards (NCCLS). Ranges were proposed for Escherichia coli ATCC 25922 and Aeromonas salmonicida subsp. salmonicida ATCC 33658 at 22 and 28 degrees C for nine different antimicrobial agents (ampicillin, enrofloxacin, erythromycin, florfenicol, gentamicin, oxolinic acid, oxytetracycline, ormetoprim-sulfadimethoxine, and trimethoprim-sulfamethoxazole). All tests were conducted on standard Mueller-Hinton agar. With >/=95% of all data points fitting within the proposed QC ranges, the results from this study comply with NCCLS guidelines and have been accepted by the NCCLS Subcommittee for Veterinary Antimicrobial Susceptibility Testing. These QC guidelines will permit greater accuracy in interpreting results and, for the first time, the ability to reliably compare susceptibility test data between aquatic animal disease diagnostic laboratories.     

Drosophila awd, the homolog of human nm23, regulates FGF receptor levels and functions synergistically with shi/dynamin during tracheal development

Human nm23 has been implicated in suppression of metastasis in various cancers, but the underlying mechanism of such activity has not been fully understood. Using Drosophila tracheal system as a genetic model, we examined the function of the Drosophila homolog of nm23, the awd gene, in cell migration. We show that loss of Drosophila awd results in dysregulated tracheal cell motility. This phenotype can be suppressed by reducing the dosage of the chemotactic FGF receptor (FGFR) homolog, breathless (btl), indicating that btl and awd are functionally antagonists. In addition, mutants of shi/dynamin show similar tracheal phenotypes as in awd and exacerbate those in awd mutant, suggesting defects in vesicle-mediated turnover of FGFR in the awd mutant. Consistent with this, Btl-GFP chimera expressed from a cognate btl promoter-driven system accumulate at high levels on tracheal cell membrane of awd mutants as well as in awd RNA duplex-treated cultured cells. Thus, we propose that awd regulates tracheal cell motility by modulating the FGFR levels, through a dynamin-mediated pathway.     

Use of multivariate statistical methods to identify immunochemical cross‐reactants

Quantitative competition immunoassays with appropriate combinations of antibodies give consistent dose‐response patterns which may be used to identify and estimate amounts of cross‐reacting compounds. Previously reported methods of analyzing cross‐reaction patterns include multiple regression, principal components analysis and minimum estimates of variance (MEV). Four other techniques which are preferable in theory have been surveyed: discriminant analysis (DA), maximum likelihood estimates (MLE), classification and regression trees (CART), and computational neural networks (NN). MLE and simple back‐propagation neural networks can estimate the concentration, as well as the identity, of individual compounds. These four methods worked well with unfitted, unscaled data from monoclonal assays of triazines, phenylureas and avermectins. Immunoassays must be properly designed to provide adequate data for pattern recognition. Cross‐reactivity pattern analysis will make multi‐analyte, multi‐antibody immunoassays feasible for many applications in toxicology and hazard assessment.     

Molecular characterization of severe α-Thalassemias causing hydrops fetalis in Taiwan

α-Thalassemia hydrops fetalis is a common disorder in Taiwan. The condition causes perinatal death and many maternal obstetrical complications. In order to determine the molecular defects of this condition in Chinese, 87 unrelated families with this disorder were collected in the past 4 years. The molecular defects were studied by Southern blotting and DNA hybridization with φζ1-globin gene and LO (a 0.4 kb BamHI/EcoRI fragment in the 5′ flanking region of the ζ2-globin gene) probes. Eighty-one (93.1%) fetuses had homozygous Southeast Asian deletion (– –^SEA/– –^SEA). Five (5.7%) fetuses were compound heterozygotes for the Southeast Asian deletion and Thailand deletion (– –^SEA/– –^THAI). The remaining fetus was a compound heterozygote for the Southeast Asian deletion and an uncharacterized nondeletional defect (– –^SEA/(αα)Th). The molecular defects of α-thalassemia hydrops fetalis in Chinese are heterogeneous. This fact has important implications for genetic counseling and prenatal diagnosis.     

Alterations in the genomes of avian sarcoma viruses

We have identified polypeptides specific to region Elb (map position [mp] 4.6–112) of adenovirus 2 (Ad2) that are synthesized in six lines of Ad-transformed rat or human cells (F17, F4, T2C4, 8617, 5RK clone I, 293), and in Ad2 early infected KB cells. [³⁵S]Methionine-labeled polypeptides were immunoprecipitated using antisera against F17 cells, an Ad2-transformed rat cell line that retains only El. To determine whether they are viral coded, these polypeptides were compared by tryptic peptide mapping with polypeptides translated in vitro from Ela-specific mRNA (mp 1.3–4.5) and Elb-specific mRNA. Polypeptides of 19,000 daltons early infected KB cells. The 19K, 20K, and 53K could be translated from Elb-specific mRNA and thus are coded by Elb. The 19K was precipitated from all transformed cell lines, the 20K was immunoprecipitated from F4, 8617, and T2C4 cells, and the 53K was immunoprecipitated from F4, 8617, T2C4, and 293 cells. These results suggest that the 19K, and perhaps the 20K and 53K, may be important in adenovirus-induced cell transformation. The 20K and 53K share methionine-containing tryptic peptides with each other, but not with the 19K. These results, together with the Ad2 Elb DNA sequence (T. Gingeras and R. Roberts, personal communication), suggest that 19K is translated in a different reading frame from 53K and 20K.