猪卵泡抑素基因接拼形式克隆、表达及分析

猪卵泡抑素基因（Follistatin,FS）具有调控动物生殖活动和肌肉生长的生物功能,但对猪的研究报道很少。本研究克隆了猪卵泡抑素基因两种接拼形式、比较分析其蛋白结构特征、进化关系和组织表达特性。研究结果表明,通过两对引物成功克隆了猪卵泡抑素基因的1045bp（FS—L）和964bp（FS-L）的两种接拼形式;与Genbank中的序列比对表明FS-L和FS-L的CDS序列与人、牛、家鼠、沟鼠、斑马鱼的卵泡抑素基因序列相似性在80％以上。对两种蛋白质结构域的比较发现,FS-L蛋白相比FS-L蛋白而言缺失了一个FS结构域。同源性分析表明,猪与牛的亲缘关系较近,与人、小鼠、沟鼠和斑马鱼的关系相对较远。组织表达分析表明,两种拼接形式在梅山猪不同组织中的表达存在差异,FS-L基因在梅山猪肌肉及生殖系统等组织中均有表达,而FS-L基因则主要在生殖系统中表达。表明FS-L在肌肉生长中发挥作用,而FS-L主要调控动物的生殖功能。     

Expression and purification of the recombinant porcine NK-lysin in Pichia pastoris and observation of anticancer activity in vitro

Natural killer (NK)-lysin, a broad-spectrum antimicrobial peptide, has antitumor and antibactericidal activities against both gram-positive and gram-negative bacteria. In this study the recombinant porcine NK-lysin was expressed and purified in the Pichia pastoris system, and then 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide was used to assess its anticancer activity in vitro. The results showed that the recombinant porcine NK-lysin possesses potent antitumor activity against the human hepatocellular carcinoma cell line SMMC-7721 in a time- and dose-dependent manner, but has negligible hemolysis activity against human erythrocytes. Scanning electronic microscopy was used to directly observe the ultrastructure of SMMC-7721 cells treated with NK-lysin; untreated cells showed lamellipodia and filopodia scattered with the cell surface, with good cell–cell contacts among neighboring cells. In contrast, treated tumor cells exhibited marked alterations in cell morphology, and cell–cell contacts disappeared among neighboring cells. Compared with the untreated tumor cells, the tumor cells treated with NK-lysin for 12 and 24 hr were suppressed for the expression of fascin 1. Thus, the recombinant porcine NK-lysin potentially could be developed as a therapeutic agent for inhibiting tumor growth.     

Characterization of a porcine intestinal epithelial cell line for in vitro studies of microbial pathogenesis in swine

In vitro studies on the pathogenesis in swine have been hampered by the lack of relevant porcine cell lines. Since many bacterial infections are swine-specific, studies on pathogenic mechanisms require appropriate cell lines of porcine origin. We have characterized the permanent porcine intestinal epithelial cell line, IPEC-J2, using a variety of methods in order to assess the usefulness of this cell line as an in vitro infection model. Electron microscopic analyses and histochemical staining revealed the cells to be enterocyte-like with microvilli, tight junctions and glycocalyx-bound mucin. The functional integrity of monolayers was determined by transepithelial electrical resistance (TEER) measurements. Both commensal bacteria and important bacterial pathogens were chosen for study based on their principally different infection mechanisms: obligate extracellular Escherichia coli, facultative intracellular Salmonella and obligate intracellular Chlamydia. We determined the colonization and proliferation of the bacteria on and within the host cells and monitored the host cell response. We verified the expression of mRNAs encoding the cytokines IL-1α, −6, −7, −8, −18, TNF-α and GM-CSF, but not TGF-β or MCP-1. IL-8 protein expression was enhanced by Salmonella invasion. We conclude that the IPEC-J2 cell line provides a relevant in vitro model system for porcine intestinal pathogen–host cell interactions.     

Dome formation by oral epithelia in vitro

Summary Multicellular, cystic structures, termed domes, have been described previously in epithelia cultured from various tissues that have a known transport or secretory function in vivo and in vitro. We report for the first time dome formation in cells cultured from “covering” and “rest” epithelia of oral tissues: porcine gingival and alveolar mucosa epithelium and epithelial rests of Malassez. As demonstrated by light- and electron microscopy, the morphology of the domes varied with the location of their lumen and the number of cells or cell layers involved in their structure. Sequential observations using phase contrast microscopy and time lapse cinematography of living cultures showed that the domes were dynamic structures with expansion-collapse cycles of between 30 min and 17 h duration. Dome formation in oral epithelia was stimulated by dibutyryl cyclic AMP (dbcAMP, 10⁻³ to 10⁻⁶ M) and abolished by ouabain (10⁻¹⁰ M), an inhibitor of sodium transport. The morphological features and the dynamic nature of domes found in oral epithelia, and their dbcAMP and ouabain responsiveness are similar to those demonstrated previously in several other epithelia that have a known transport function in vivo and in vitro. Such fluid transport is not thought to be a property of oral epithelia in vivo. Our data, however, suggest a similar function of these epithelia cultured in vitro, and perhaps in pathological cyst formation in vivo.     

Cloning, sequencing, and expression of the gene encoding the porcine alpha 2-adrenergic receptor. Allosteric modulation by Na+, H+, and amiloride analogs

The gene for an alpha 2-adrenergic receptor has been cloned from a porcine genomic library, using as a probe a 0.95-kilobase Pst fragment of the gene for the human platelet alpha 2-adrenergic receptor. The identity of the cloned porcine gene was confirmed initially on the basis of partial amino acid sequence information obtained following cyanogen bromide digestion of homogeneous preparations of porcine brain alpha 2-adrenergic receptors. The deduced amino acid sequence for the porcine receptor, when compared to other members of the family of guanine nucleotide-binding protein-coupled receptors, shares the same overall structural characteristics and most closely resembles the human platelet C10 alpha 2-adrenergic receptor (greater than 93% homology). The putative porcine alpha 2-receptor gene was expressed in the COS-M6 cell line. Transfected cells display saturable [3H]yohimbine binding. The KD for [3H]yohimbine, determined in digitonin-solubilized preparations, is 5.8 nM. The selectivity of agonists and antagonists in competing for [3H]yohimbine binding to membranes prepared from the transfected cells is characteristic of the alpha 2A subtype of adrenergic receptors. The porcine alpha 2-receptor also was expressed permanently in LLC-PK1 porcine kidney cells at a level of 100 pmol/mg protein. The alpha 2-agonist UK14304 is able to attenuate forskolin or vasopressin-stimulated cAMP accumulation by at least 50% in these cells. Allosteric modulation of [3H] yohimbine binding by Na+, H+, and 5-amino-substituted analogs of amiloride also was demonstrated for the alpha 2-receptor expressed in COS-M6 cells. Moreover, these modulatory effects were quantitatively similar to those observed for homogeneous preparations of the alpha 2-receptor purified from porcine brain cortex. Retention of the effects of cations and amiloride analogs in transiently expressed alpha 2-receptors supports the interpretation that the allosteric sites for these agents reside in the alpha 2-receptor molecule itself.     

Cytochrome P450 expression profile of the PICM-19H pig liver cell line: potential application to rapid liver toxicity assays

Liver in vitro models are needed to replace animal models for rapid assessment of drug biotransformation and toxicity. The PICM-19 pig liver stem cell line may fulfill this need since these cells have activities associated with xenobiotic phase I and II metabolism lacking in other liver cell lines. The objective of this study was to characterize phase I and II metabolic functions of a PICM-19 derivative cell line, PICM-19H, compared to the tumor-derived human HepG2 C3A cell line and primary cultures of adult porcine hepatocytes. Following exposure of PICM-19H cells to either 3-methylcholanthrene, rifampicin or phenobarbital, the induced activities of cytochrome P450 (CYP450) isozymes CYP-1A, -2, and-3A were assessed. Relative to adult porcine hepatocytes, PICM-19H cells exhibited 30% and 43%, respectively, of CYP1A and 3A activities, while HepG2 C3A cells exhibited 7% and 0% of those activities. Fluorescent metabolites were extensively conjugated, i.e., 52% and 96% of CYP450-1A and-3A metabolites were released from medium samples following treatment with β-glucuronidase/arylsulfatase. Rifampicin induction of CYP450 isozyme activities was confirmed by conversion of testosterone to 6β-OH-, 2α-OH- and 2β-OH-testosterone, as determined by mass spectrometry. Susceptibility of PICM-19H cells to acetaminophen toxicity was determined; CD₅₀ was calculated to be 14.9 ± 0.9 mM. Toxicity and bioactivation of aflatoxin B1 was determined in 3-methylcholanthrene-treated cultures and untreated controls; CD₅₀ were 1.59 μM and 31 μM, respectively. These results demonstrate the potential use of PICM-19H cells in drug biotransformation and toxicity testing and further support their use in extracorporeal artificial liver device technology.     

Characterization of a porcine lung epithelial cell line suitable for influenza virus studies

We established a porcine lung epithelial cell line designated St. Jude porcine lung cells (SJPL) and demonstrated that all tested influenza A and B viruses replicated in this cell line. The infectivity titers of most viruses in SJPL cells were comparable to or better than those in MDCK cells. The propagation of influenza viruses from clinical samples in SJPL cells did not lead to antigenic changes in the hemagglutinin molecule. The numbers of both Sia2-3Gal and Sia2-6Gal receptors on SJPL cells were greater than those on MDCK cells. Influenza virus infection of SJPL cells did not lead to apoptosis, as did infection of MDCK cells. No porcine endogenous retrovirus was detected in SJPL cells, and in contrast to MDCK cells, SJPL cells did not cause tumors in nude mice.     

Porcine Pluripotent Stem Cells Derived from IVF Embryos Contribute to Chimeric Development In Vivo

Although the pig is considered an important model of human disease and an ideal animal for the preclinical testing of cell transplantation, the utility of this model has been hampered by a lack of genuine porcine embryonic stem cells. Here, we derived a porcine pluripotent stem cell (pPSC) line from day 5.5 blastocysts in a newly developed culture system based on MXV medium and a 5% oxygen atmosphere. The pPSCs had been passaged more than 75 times over two years, and the morphology of the colony was similar to that of human embryonic stem cells. Characterization and assessment showed that the pPSCs were alkaline phosphatase (AKP) positive, possessed normal karyotypes and expressed classic pluripotent markers, including OCT4, SOX2 and NANOG. In vitro differentiation through embryonic body formation and in vivo differentiation via teratoma formation in nude mice demonstrated that the pPSCs could differentiate into cells of the three germ layers. The pPSCs transfected with fuw-DsRed (pPSC-FDs) could be passaged with a stable expression of both DsRed and pluripotent markers. Notably, when pPSC-FDs were used as donor cells for somatic nuclear transfer, 11.52% of the reconstructed embryos developed into blastocysts, which was not significantly different from that of the reconstructed embryos derived from porcine embryonic fibroblasts. When pPSC-FDs were injected into day 4.5 blastocysts, they became involved in the in vitro embryonic development and contributed to the viscera of foetuses at day 50 of pregnancy as well as the developed placenta after the chimeric blastocysts were transferred into recipients. These findings indicated that the pPSCs were porcine pluripotent cells; that this would be a useful cell line for porcine genetic engineering and a valuable cell line for clarifying the molecular mechanism of pluripotency regulation in pigs.     

Enamel protein and collagen production by cells subcultured from porcine tooth bud explants

Fibroblast (F) and epithelial (E) cells were obtained as primary outgrowths from explants of fetal porcine maxillary molars and subcultured up to four passages in monolayers enriched with either cell type. Histology of a tooth bud after 1 day in culture showed intact odontogenic E cell layers which were the probable source of the E cell outgrowths. After 2 months in culture, the fourth passage E cells demonstrated morphological differentiation by an alteration in cell packing and the formation of domes and nodules, when E and F cells were cocultured. Occasionally the nodules grew to considerable size, indicating the potential of these cells to aggregate and reorganize into odontogenic tissues even on culture dishes. The cells were characterized in monolayer culture by immunocytochemical staining. Laminin and type IV collagen staining was distributed diffusely throughout the culture, whereas type I collagen and osteonectin staining was predominantly localized in the F cells. Radiolabelled proteins from both E and F cell media produced similar collagen patterns (95% type I, 4% type V, 1% other), except that the F cells appeared to produce active collagenase. In addition, the E cells produced two radiolabelled proteins (relative masses of 50,000 and 53,000) that reacted with an affinity-purified antibody directed against porcine amelogenin. These experiments show that cells subcultured from tooth buds and grown in monolayer cultures can be used to study tooth organogenesis in vitro, as well as enamel protein biosynthesis.     

Establishment of a novel ovine kidney cell line for isolation and propagation of viruses infecting domestic cloven-hoofed animal species

A sheep kidney-derived cell line, FLK-N3, was successfully established after serial (>100) passages. Persistent infection of this cell line with viruses and mycoplasma was not detected. The cells grew well and showed susceptibility to a wide variety of viruses derived from ovine, bovine, and porcine species, including orf virus, maedi visna virus, bovine herpesvirus 1, bovine parainfluenza virus 3, bovine viral diarrhea viruses 1 and 2, bovine coronavirus, bovine respiratory syncytial virus, bovine enterovirus, suid herpesvirus 1, and porcine enterovirus. These results suggest that the FLK-N3 cell line could be useful for isolation and propagation of viruses that affect cloven-hoofed animals.     

Development and characterization of a new epithelial cell line PSF from caudal fin of Green chromide, <Emphasis Type="Italic">Etroplus suratensis</Emphasis> (Bloch, 1790)

A new cell line [pearlspot fin (PSF)] has been developed from caudal fin of Etroplus suratensis, a brackish/freshwater fish cultivated in India. The cell line was maintained in Leibovitz’s L-15 supplemented with 10% fetal bovine serum (FBS). The PSF cell line consisted predominantly of epithelial-like cells. The cells were able to grow at temperatures between 25°C and 32°C with optimum temperature of 28°C. The growth rate of PSF cells increased as the FBS proportion increased from 2% to 20% at 28°C with optimum growth at the concentration of 10% FBS. One marine fish virus (fish nodavirus) was tested on this cell line and found not susceptible. After confluency, the cells were subcultured with a split ratio of 1:2. The cells showed epithelial-like morphology and reached confluency on the third d after subculture. Polymerase chain reaction amplification of mitochondrial 16S rRNA and COI indicated identity of this cell line with those reported from this fish species, confirming that the cell line was of pearlspot origin. The cells were successfully cryopreserved and revived at the tenth, 25th, and 35th passages. The bacterial extracellular products from Vibrio cholerae MTCC 3904 were found to be toxic to PSF. Karyotyping analysis indicated that the modal chromosome number was 48.     

Dome formation in the human colon carcinoma cell line Caco-2 in culture. Influence of ouabain and permeable supports

We studied formation of domes in cell monolayers of the human colon carcinoma cell line Caco-2 which has been shown to exhibit signs of enterocytic differentiation and transport properties. After a 24 hr incubation with 4 X 10(-8) M ouabain, the number of domes seen on Caco-2 cell monolayers grown on plastic dishes was not significantly altered. After a 90 min preincubation with ouabain, 86rubidium uptake by Caco-2 cells was inhibited by ouabain, indicating that the cells have an ouabain-sensitive Na+, K+-ATPase, while dome formation was unaffected by ouabain. Domes were observed in Caco-2 cell monolayers grown on Nuclepore filters when the pore size was 0.015 micron but not when it was 0.030 micron. Our results suggest that dome formation in the Caco-2 cell line could be independent of Na+, K+-ATPase activity and might be due to accumulation of molecules having an effective hydrodynamic radius comprised between 0.015 and 0.030 micron.     

Electrical currents flow out of domes formed by cultured epithelial cells

Domes are localized areas of fluid accumulation between a cultured epithelial cell monolayer and the impermeable substratum on which the cells are cultured in vitro. Dome formation has been documented in a variety of epithelial cell lines that retain their transepithelial transport properties in vitro. However, it is not known whether domes are predominantly areas of specific active transport, or, alternatively, are predominantly areas of relative weak attachment to the culture surface. In the present study we adapted a vibrating microelectrode, which can detect small currents flowing in extracellular fluid, to determine if current was flowing into or out of domes and thereby to determine if domes were specialized areas of active transport. We used alveolar type II cells as the main epithelial cell type because they readily form domes in vitro and because they transport sodium from the apical to the basal surface. We found that electrical current flowed out of domes. The direction of the current was independent of the size of a dome, of the age of an individual dome, and of the number of days in primary culture for alveolar epithelial cells. This current was inhibited by amiloride and ouabain and was dependent on sodium in the medium. We made similar observations (outward current from domes which is blocked by amiloride and by sodium substitution) with domes formed by the Madin-Darby canine kidney cell line. The data support the hypothesis that sodium is transported across the entire monolayer and leaks back mainly through the domes. We conclude that domes in epithelial monolayers are not predominantly special sites of active transport but are more likely simply areas of weak attachment to the substratum.     

Cloning and expression of the porcine myogenin gene

Abstract

Myogenin is a member of the myoD family of myogenic regulatory factors which direct the initiation of myogenesis during skeletal muscle development. Myogenin is responsible for the differentiation of proliferating myoblasts into myotubes and the absence of this factor results in severe muscular deficiency. Using PCR primers designed from mammalian myogenin sequences, a 215 bp PCR product was amplified from porcine genomic DNA and found to be 89.7% homologous to mouse myogenin. A porcine cosmid library was screened with the myogenin PCR probe and a 6.5 kb portion of a cosmid containing the pig myogenin gene was sequenced. The sequence includes 5´ flanking region, the entire protein coding region composed of three exons and two introns and 3´ flanking region. The protein coding region was highly conserved (≥92.5%) with mouse and human myogenin coding regions. Transfection of pig myogenin into C3H10T1/2 cells, a multipotential fibroblast cell line, resulted in 28% myogenic conversion assayed by cell fusion to form multinucleated cells and synthesis of sarcomeric myosin. These results indicate that the cloned myogenin gene was capable of initiating myogenesis in a fibroblast cell line.     

Oxygen‐rich gas domes of microbial origin in the salt crust of the Great Salt Lake,Utah

Abstract

During the summer of 1977, a severe drought throughout the western part of the United States caused the north arm of the Great Salt Lake, Utah, to evaporate to its lowest level in a number of years, resulting in the precipitation of about 99.6% pure sodium chloride. At the extreme north end of the north arm, in the vicinity of Monument Point, low humidity combined with a shallow‐bottom gradient to form a salt crust along the lake margin in which gas‐emitting domes were common. The domes varied in size; each contained a large amount of gas that analysis showed to be 82 to 86% oxygen and 14 to 18% nitrogen, with <0.2% or no methane, and no detectable carbon dioxide. The bottom of the crust of the domes (3 to 4 cm thick) was a bright red color. Microscopic examination of this red zone revealed 3.5 × 10⁴ cells of Dunaliella salina, 2 × 10³ cells of D. viridis and 10⁸ to 10⁹ clumps of red halophilic bacteria per g of salt. Measurements in situ showed sufficient light (34 klx) and temperature (34°C) under the salt to favor the growth of the algae and associated bacteria within the water phase of the crust or in water immediately underneath the crust. Oxygen produced as a result of algal photosynthesis was trapped under the crust until the crust was either eroded by waves or broken under pressure, releasing the gas. The domes were not observed during the summers of 1978 and 1979.     

H-2 antigen expression: Loss in vitro,restoration in vivo,and correlation with cell-mediated cytotoxicity in a mouse lymphoma cell line

The susceptibility to cell-mediated cytolysis of cells of the recently developed C57BL/Ka(H-2 ^b ) lymphoma cell line, BL/VL₃, was investigated in allogeneic assays with thymus-dependent lymphocytes (T cells). Compared to EL4, the widely used C57BL/6(H-2 ^b ) lymphoma cell line, BL/VL₃ cells were found to be insensitive to T-cell-mediated lysis as detected by the use of⁵¹Crrelease methods. When used as immunogens in alloreactive combinations with BALB/c(H-2 ^d ) splenocytes as responder cells, BL/VL₃ cells failed to elicit sensitization. Serological tests showed that this cell line had profoundly reduced levels of H-2^b antigens on its surface. When BL/VL₃ cells were reinjected into C57BL/Ka and BALB/c mice, full recovery of H-2^b antigen expression at the cell surface was observed in both syngeneic and allogeneic hosts after only 11 days of in vivo growth. Concomitantly, they acquired the ability to induce cytotoxic responses in allogeneic T cells and became susceptible to their lytic activity. The expression of H-2 antigens on the surface of BL/VL₃ cells is a reversibly modulated function that depends on in vivo growth conditions and is lost in vitro in the absence of immunoselective pressure.     

Human retinal pigment cell culture

Human retinal pigment epithelium (RPE)-derived cell lines were established from RPE-covered choroid tissue fragments, which had been generated by culture on nontissue culture plastic. Two phenotypes were apparent in a given line: (a) a compact cell which formed domes and ultimately melanosomes before being sloughed; and (b) a squamous cell which was often elongated and which bound antibody to human keratins. This latter cell did not become black or form domes. The average number of cell doublings for the 13 lines tested was between 15 and 40 when cultured in a modified Eagle's minimum essential medium containing 10% fetal bovine serum. Cell lines newly established from material that had been in culture for more than 6 months had normal mitotic chromosomes and still developed areas with strongly pigmented cells when refed. Normal human epithelial cell lines of this kind may be useful in studies of cell aging and defining change associated with the development of neural cells from ectoderm.     

Continuous large-scale production of the cytokine CXCL8 from a novel porcine cell line

Cytokine production from two unstimulated porcine cell lines (SL-24 and SK-L) was examined using porcine cytokine detection ELISA kits and RT-PCR. Porcine IL-1 alpha, IL-6, and CXCL8 were detected in all samples examined. In particular, the SL-24 cell line (derived from bone marrow cells of a malignant lymphoma-affected pig), produced large amounts of porcine CXCL8. Flow cytometer analysis showed the cell line to be strongly CD44 positive, and was therefore considered to be of monocyte or macrophage origin. Porcine CXCL8 production was greatest (83.86 +/- 32.33 ng/mL) at six days post-cultivation. The SK-L cell line (derived from porcine kidney) also produced CXCL8, but production was less than 1.5 ng/mL. Porcine CXCL8 from the SL-24 cell line, induced chemotactic activity in porcine neutrophils, while the production of CXCL8 from the SL-24 cell line was inhibited by dexamethasone, which suggests that the mechanism of CXCL8 production is related to an NF-kappaB binding site. The production of CXCL8 from the SL-24 cell line was enhanced by the addition of recombinant porcine IL-15, which is the first reported observation of such CXCL8 production. Cloning of the SL-24 cell line by limited dilution revealed two types of cells present in the starting population. One cell type, designated as long-form cells (LC), produced large amounts of CXCL8, while the other, designated short-form cells (SC), produced small amounts of the cytokine. The LC cells were adapted to grow in serum-free medium in which they produced large amounts of CXCL8. The large-scale production of porcine CXCL8 from the SL-24 cell line will be of value in determining the mechanism of cytokine production and as a source of naturally produced porcine CXCL8.