Genes of the sbo-alb locus of Bacillus subtilis are required for production of the antilisterial bacteriocin subtilosin

Bacillus subtilis JH642 and a wild strain of B. subtilis called 22a both produce an antilisterial peptide that can be purified by anion-exchange and gel filtration chromatography. Amino acid analysis confirmed that the substance was the cyclic bacteriocin subtilosin. A mutant defective in production of the substance was isolated from a plasmid gene disruption library. The plasmid insertion conferring the antilisterial-peptide-negative phenotype was located in a seven-gene operon (alb, for antilisterial bacteriocin) residing immediately downstream from the sbo gene, which encodes the precursor of subtilosin. An insertion mutation in the sbo gene also conferred loss of antilisterial activity. Comparison of the presubtilosin and mature subtilosin sequences suggested that certain residues undergo unusual posttranslational modifications unlike those occurring during the synthesis of class I (lantibiotic) or some class II bacteriocins. The putative products of the genes of the operon identified show similarities to peptidases and transport proteins that may function in processing and export. Two alb gene products resemble proteins that function in pyrroloquinoline quinone biosynthesis. The use of lacZ-alb and lacZ-sbo gene fusions, along with primer extension analysis, revealed that the sbo-alb genes are transcribed from a major promoter, residing upstream of sbo, that is very likely utilized by the sigma(A) form of RNA polymerase. The sbo and alb genes are negatively regulated by the global transition state regulator AbrB and are also under positive autoregulation that is not mediated by the subtilosin peptide but instead requires one or more of the alb gene products.

Thermolysis of vic-dihydroxybacteriochlorins: a new approach for the synthesis of chlorin-chlorin and chlorin-porphyrin dimers

[formula: see text] A novel approach for the preparation of symmetrical (chlorin-chlorin), and unsymmetrical (chlorin-porphyrin) dimers joined with carbon-carbon linkages as models to study the "intramolecular" charge transfer is discussed.

Changes in blood pressure, body mass index, and salt consumption in a Chinese population

BACKGROUND

The prevalence of hypertension among the population of Tianjin is one of the highest in China. We attempted to assess the changes in blood pressure, body mass index, and salt consumption in Tianjin from 1989 to 1996.

METHODS

Two independent cross-sectional population surveys with the representative samples of 14,046 persons in 1989 and 2,000 persons in 1996 were carried out in Tianjin. A salt surveillance system was established with four salt consumption surveys (in 1992, 1993, 1994, and 1996) to estimate the changes in salt consumption at the household level.

RESULTS

From 1989 to 1996, the prevalence of hypertension and obesity decreased among people aged 45-64 years in both genders. Mean systolic blood pressure decreased significantly in women and leveled off in men. Diastolic blood pressure increased significantly. Body mass index remained unchanged. The unfavorable trends were mainly attributable to the negative changes in younger people (15-34 years) in both genders. There were no changes in salt consumption between 1992 and 1996 at the house level.

CONCLUSIONS

There was a favorable development in prevalence of hypertension and obesity among individuals in the age group of 45-64 years in the study population. Health education needs to pay more attention to young people.

[Study of relative factors which influenced the embolic level of microspheres in the hamster lingual carcinoma]

OBJECTIVE

To study the relative factors which influence the embolic level of microspheres in the hamster lingual carcinoma.

METHODS

Micropicture analysis instrument was used to measure the embolic level of microspheres which were poured through ascending aorta.

RESULTS

The optimum pressure of embolization was 30 kPa. The embolic level approached to remote site of the lingual artery as tongue cancer developed. In early invasive cancer period, the embolic level of microspheres was at arteriole level where microspheres block "the total values" which controlled the tumor microcirculation. The optimum embolic result and less offshoot microcirculation were obtained at this time. When in later period, microspheres mainly embolized the meta-arteriole. As the microvessels dilated, the dose of microspheres must be increased to get the best embolic result.

CONCLUSION

The experimental data for clinical choice of optimum pouring pressure, optimum opportunity and optimum cases.

Absolute quantitation of specific mRNAs in cell and tissue samples by comparative PCR

A comparative PCR assay, for the absolute quantitation of specific mRNAs in cell and tissue samples, has been designed to overcome problems with previous techniques. cDNAs made from the RNAs are co-amplified with "competitor" plasmid templates under conditions in which reagents are not limiting at the equivalence point, thereby preventing competition between target and competitor templates and distinguishing the assay from competitive PCR assays. The cDNAs are serially diluted, and competitor templates concentrations are kept constant, rather than vice versa, as occurs in competitive PCR assays. Products from target and competitor templates are resolved by electrophoresis and measured by phosphorescent or fluorescent imagery. Both products are measured to minimize errors in the competitor:target ratio. A synthetic external standard RNA is included in the tissue lysis solution and co-purified with endogenous mRNAs, thereby being subjected to identical losses of yield during subsequent procedures. The determination of the number of copies of external standard cDNA allows inefficiencies of RNA extraction and cDNA synthesis to be taken into account. Standard concentrations of plasmids containing the endogenous target sequences are also measured, so that corrections can be made for discrepancies due to unequal amplification of target and competitor sequences. These corrections, together with the use of an external standard and the PCR conditions chosen, allow for the accurate, specific and sensitive determination of the absolute number of mRNA copies in a sample.

Isolation, partial purification and characterization of a bacteriocin produced by a newly isolated Bacillus subtilis strain

A wild type micro-organism producing antibacterial substances has been isolated from a Chinese fermented soybean seasoning and identified as Bacillus subtilis. A crude antibacterial preparation (CABP) was obtained by ammonium sulphate precipitation. Isoelectric focusing assay revealed at least four antimicrobial components in the CABP. However, in SDS-PAGE analysis, only one peptide band displayed antimicrobial activity against pathogenic Bacillus cereus and Listeria monocytogenes. This inhibitory peptide had a molecular weight of approximately 3.4 kDa and a pI value of approximately 4.7. Results of this study suggest that at least one antimicrobial substance produced by this wild type strain of B. subtilis may be a new bacteriocin. Its sensitivity to gastric peptidases and activity against the food-borne pathogens make this bacteriocin potentially useful as an antimicrobial agent in foods.

Megalin (gp330) is an endocytic receptor for thyroglobulin on cultured fisher rat thyroid cells

We recently reported that megalin (gp330), an endocytic receptor found on the apical surface of thyroid cells, binds thyroglobulin (Tg) with high affinity in solid phase assays. Megalin-bound Tg was releasable by heparin. Here we show that Fisher rat thyroid (FRTL-5) cells, a differentiated rat thyroid cell line, can bind and endocytose Tg via megalin. We first demonstrated that FRTL-5 cells express megalin in a thyroid-stimulating hormone-dependent manner. Evidence of Tg binding to megalin on FRTL-5 cells and on an immortalized rat renal proximal tubule cell line (IRPT cells), was obtained by incubating the cells with 125I-Tg, followed by chemical cross-linking and immunoprecipitation of 125I-Tg with antibodies against megalin. To investigate cell binding further, we developed an assay in which cells were incubated with unlabeled Tg at 4 degrees C, followed by incubation with heparin, which released almost all of the cell-bound Tg into the medium. In solid phase experiments designed to illuminate the mechanism of heparin release, we demonstrated that Tg is a heparin-binding protein, as are several megalin ligands. The amount of Tg released by heparin from FRTL-5 and IRPT cells, measured by enzyme-linked immunosorbent assay (ELISA), was markedly reduced by two megalin competitors, receptor-associated protein (RAP) and 1H2 (monoclonal antibody against megalin), indicating that much of the Tg released by heparin had been bound to megalin ( approximately 60-80%). The amount inhibited by RAP was considered to represent specific binding to megalin, which was saturable and of high affinity (Kd approximately 11.2 nM). Tg endocytosis by FRTL-5 and IRPT cells was demonstrated in experiments in which cells were incubated with unlabeled Tg at 37 degrees C, followed by heparin to remove cell-bound Tg. The amount of Tg internalized (measured by ELISA in the cell lysates) was reduced by RAP and 1H2, indicating that Tg endocytosis is partially mediated by megalin.

[Histopathologically observational study of cartilage-mucosa on the eustachian tube isthmus of temporal bone with otitis media]

OBJECTIVE

To explore the influence of inflammatory pathology change of otitis media upon cartilage-mucosa at the eustachian tube isthmus (ETI).

METHOD

The cartilage-mucosa at ETI and bone-mucosa on the tympanic promontory of 32 temporal bones with otitis media were observated histopathologiclly in comparison with 50 normal temporal bones under light microscopy.

RESULT

The eustachian tube isthmus in all the 32 temporal bone with otitis media and in 50 normal temporal bone were unblocked. The thick-measures and pathology observations of the cartilage-mucosa on ETI in the temporal bones with otitis media revealed there was no obviously inflammatory change and no significantly difference in comparison with the normal control group. But there was obviously inflammatory pathologic change on the bone-mucosa of tympanic promomtory of temporal bone with otitis media. The demarcation line of completely different inflammatory reaction in middle ear cleft was exactly at the connective line between cartilage and bone of eustachian tube.

CONCLUSION

With the specifically histologic structure, the cartilage-mucosa on eustachian tube is possessed of very strong function of natural defence for inflammatory desease, and it almost is impossible to lead to obstruction of eustachian tube by inflammatory influence upon the cartilage-mucosa.

Association of specific DNA binding and transcriptional repression with the transforming and myogenic activities of c-Ski

The ski oncogene encodes a transcription factor that induces both transformation and muscle differentiation in avian fibroblasts. The first 304 amino acids of chicken Ski, the transformation domain, are both necessary and sufficient to mediate these biological activities. Ski's biological duality is mirrored by its transcriptional activities: it coactivates or corepresses transcription depending on its interactions with other transcription factors. Ski represses transcription through specific binding to GTCTAGAC (GTCT element) but it possesses a transferable repression activity that can function independently of this DNA element. In this study, we locate this repression domain to the NH2-terminal two-thirds and the GTCT binding region to the COOH-terminal one-third of Ski's transformation domain. Mutations in the transformation domain of c-Ski reveal a strong correlation between GTCT-mediated transcriptional repression and the biological activities of transformation and myogenesis. We also show that a dimerization domain located at the COOH terminal end of the Ski protein increases its transforming activity and its binding to GTCTAGAC.

Stereoselective total synthesis of (3R,8S)-falcarindiol, a common polyacetylenic compound from umbellifers

The first stereoselective total synthesis of (3R,8S)-falcarindiol (1) from L-tartaric acid and D-xylose is reported, via the Cadiot-Chodkiczwicz reaction, to couple 1-bromoalkyne (2) with 3(R)-(tert-butyldiphenylsilyloxy)-1-penten-4-yne (3).

Heterodimers of the SnoN and Ski oncoproteins form preferentially over homodimers and are more potent transforming agents

sno is a member of the ski oncogene family and shares ski 's ability to transform avian fibroblasts and induce muscle differentiation. Ski and SnoN are transcription factors that form both homodimers and heterodimers. They recognize a specific DNA binding site (GTCTAGAC) through which they repress transcription. Efficient homodimerization of Ski, mediated by a bipartite C-terminal domain consisting of five tandem repeats (TR) and a leucine zipper (LZ), correlates with efficient DNA binding and cellular transformation. The present study assesses the role of SnoN homodimerization and SnoN:Ski heterodimerization in the activities of these proteins. Unlike Ski, efficient homodimerization by SnoN is shown to require an upstream region of the protein in addition to the TR/LZ domain. Deletion of the TR/LZ from SnoN decreases its activity in transcriptional repression and cellular transformation. When co-expressed in vitro, c-Ski and SnoN preferentially form heterodimers. In vivo, they form heterodimers that bind the GTCTAGAC element. Tethered Ski:Sno hetero-dimers that lack TR/LZ domains are more active than either their monomeric counterparts, tethered Ski:Ski homodimers or full-length SnoN and c-Ski. This work demonstrates, for the first time, the differences between dimer formation by Ski and SnoN and underscores the importance of dimerization in their activity.

[Cloning and sequence characterization of heavy chain variable region gene from hybridoma cells secreting MAB against VEGF]

OBJECTIVE

To clone the variable region of heavy chain (VH) gene from hybridoma secreting monoclonal antibody against human vasoendothelial growth factor (VEGF) for construction of recombinant antibody (scFv).

METHODS

One step method was used to extract total RNA and degeneration primer was used to amplify the cDNAs by retropolymerase chain reaction (RT-PCR), then the products were inserted to T-vector and its sequence was analysed.

RESULTS

The VH gene contained 369 base pairs encoding 123 amine acid resides. Analysis of the nucleotide sequence of the light chain variable region revealed that the VH sequence was 87% identical to the sequence present in mouse Ig VH region.

CONCLUSION

The VH gene was 369 bp. According to Kabat classification, the VH gene belonging to mouse kappa light chains subgroup I (A), resulting from VH-D-JH4 rearrangment.

[Design and synthesizing of human vascular endothelial growth factor (VEGF) peptide]

OBJECTIVE

To predict continuous epitopes of VEGF using synthetic peptide of VEGF as antigen to produce anti-VEGF-peptide monoclonal antibody.

METHODS

According to amino sequence of VEGF189, antigen index program and Goldkey soft were used to predict VEGF epitopes, and the peptide containing one of predicted epitopes was synthesized by 430A Peptide Synthesizer.

RESULTS

The NH2-terminal 1-26 amino acid sequence of VEGF was determined as synthetic peptide and synthesized.

CONCLUSION

The predicted epitope of VEGF was synthesized, which provided an effective method when lacking of VEGF.

[Study on the action force of dimerization of cobalt tetrasulfonate Ph-thalocyanine in aqueous solotion]

The dimerization of cobalt tetrasulfonate phthalocyanine (CoTSPc) was studied in the microemulsion, micelles and aqueous alcoholic solutions. The coordination reaction for the formation of complexes CoTSPc (L), which was formed by cobalt tetrasulfonate phthalocyanine (CoTSPc) plus ligand L(L = NH3, CN-, en), was also studied. The reaction kinetics was discussed and the stability constant K of CoTSPc(L)2 was also calculated from absorbance measurement.

Study on the metastatic mechanisms of human giant-cell lung carcinoma comparison between the strains C and D

The biologic characteristics of the two human giant-cell lung carcinoma strains with high (strain D) and low metastatic potential (strain C) were studied, including karyotype of chromosome, intracellular free calcium ([Ca2+]i), morphologic changes of cell surface and the expression of nm23-H1, p53, ras, c-myc, c-erbB2, bcl-2 genes and PCNA. The correlation between different biologic features and the metastatic potential of the two strains was analyzed. We found: 1) Both strains had the karyotypic abnormality of -13, -14, -15, +20, +21 with seven same marker chromosomes. Only strain D had the karyotypic abnormality of +7, -17, -18, +X, 7p+; 2) [Ca2+]i of the strain C (984.7 +/- 573.8) and D (517.6 +/- 216.6) was significantly different (p < 0.05). The amplitude of intracellular calcium oscillations of strain C was lower than the one of strain D; 3) strain C had more villous-like protrusions on the cell surface, whereas strain D had more bubble-like protrusions; 4) The expression of nm23-H1 and p53 protein of strain C was all higher than that of strain D. The expression of PCNA of strain C was lower than strain D; 5) nm23-H1 mRNA levels of strain C was lower than that of strain D. We consider that the karyotype of chromosomes, intracellular free calcium, the structure of cell membrane and the expression of nm23-H1 gene, p53 gene, PCNA could be closely related to the metastatic potential of human giant-cell lung carcinoma. They could be used as the sign for judging whether the tumor will metastasize in clinical practice as well as in judging the prognoses of patients.

[Retinal detachment after intraocular lens implantation]

OBJECTIVE

To study the specificity of retinal detachment after intraocular lens implantation.

METHODS

The specialty of this type of retinal detachment through the clinical observation of 44 eyes of 42 cases from 1991 to 1996 was analyzed.

RESULTS

The retinal detachment after intraocular lens implantation is more severe than others. It is more difficult to find a hole or holes because posterior capsular opacification and the implanted intraocular lens interfere with the careful search. The retinal detachment may develop into a complicated one. Its cure rate was 80.0% in the immediate postoperative period.

CONCLUSION

The retinal injury during intraocular lens implantation should be avoided. As the retinal detachment occurs after the implantation, a more careful search and a earlier scleral buckling or/and vitrectomy should be done.

Epithelial cells up-regulate matrix metalloproteinases in cells within the same mammary carcinoma that have undergone an epithelial-mesenchymal transition

A metastatic rat mammary carcinoma cell line, BC1, contains cells that have retained epithelial differentiation characteristics and metaplastic cells that have undergone an epithelial-mesenchymal transition. These two subpopulations cooperate to degrade collagen. We have used novel PCR assays to quantitate, for the first time, absolute levels of the mRNAs encoding matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) in cell and tumor samples. BC1 tumors expressed high levels of the collagenase-3, TIMP-2, stromelysin-1, and gelatinase B genes and low levels of the stromelysin-2 and TIMP-1 genes. This pattern of expression was repeated in cultures of BC1 and cultures containing mixed clones of epithelial cells and metaplastic cells. In both BC1 and the biclonal cultures, metaplastic cells were the main source of collagenase-3, stromelysin-1 and stromelysin-2, whereas TIMPs were equally distributed and epithelial cells were the main source of gelatinase B. High levels of all four MMP mRNAs in metaplastic cells were dependent on coculture with epithelial cells, suggesting the production of an inducing factor by the epithelial cells. In contrast, gelatinase B mRNA was produced at a high level by epithelial cells in the absence of metaplastic cells. TIMP-2 mRNA was abundant in both subpopulations grown alone and did not change substantially upon coculture. Thus, the interclonal cooperativity to degrade collagen in BC1 cells required the induction of MMPs in metaplastic cells by epithelial cells. Interclonal cooperativity may be important to the progression of neoplastic tumors, a feature of which is phenotypic heterogeneity.

Effects of chromophore dissociation on the optical properties of rare-Earth-doped polymers

The observed dissociation of tetrakis rare-earth chromophores in rare-earth-doped organic polymers is reported, and a time-resolved spectroscopic technique is presented to determine quantitatively the fractional concentrations of different chromophore species in various solvents. Based on this technique, the equilibrium constants of tetrakis rare-earth chromophores in rare-earth-doped polymers are determined. Thus, the equilibrium constants for tetrakis rare-earth compounds of benzoyltrifluoroacetonate (BTF), for example, Sm(BTF)(4)P and Eu(BTF)(4)P in methyl methacrylate monomer, are K = 4.7 ? 0.5 x 10(-4) M and K = 1.2 ? 0.5 x 10(-4) M, respectively. In contrast, the tetrakis rare-earth compounds of hexafluoroacetylacetonate (HFA), for example, Sm(HFA)(4)Net(4) and Eu(HFA)(4)Net(4), are quite stable and show no evidence of dissociation. We further characterize the dissociation of several chromophore systems and discuss the influence such dissociation has on overall optical performance. The results enable determination of optimal doping concentrations as well as preferred rare-earth chromophore preparation and doped polymer fabrication procedures.

A study of retentive filler and its use in dentistry

OBJECTIVE

The purpose of this study was to develop a fine compound inorganic filler with special surface microstructure (called retentive filler or RF) and to investigate its use in composite resin and synthetic resin teeth.

METHODS

Barium silicate glass and fine silicon dioxide or barium silicate glass were mixed and sintered, then dispersed and classified by sedimentation. The surface microstructure and the particle size distribution of retentive filler were surveyed, and the mechanical properties of the composite resin and the resin tooth material reinforced with RF were tested.

RESULTS

Scanning electron microscopy showed that the surface of RF particles is distinguished for its retentive contour microstructure. The particle size of RF is smaller than 3 microns. The mechanical properties of composite resin reinforced with RF are better than that of composites containing normal fillers, and the wear resistance of the resin tooth material containing RF is better than that of normal synthetic resin.

CONCLUSIONS

The RF can be successfully prepared by the technological process in this study. Because of the special surface microstructure, RF has a good bonding to the resin matrix. The testing results suggest that it is feasible to improve the mechanical properties, especially the wear resistance of the composite resin and resin teeth, by using retentive filler.

[The choice of methods of intraocular lens implantation in traumatic cataract in the absence of capsular and zonular support]

OBJECTIVE

To study the choice between the methods of anterior chamber intraocular lens (AC-IOL) implantation and posterior chamber IOL suture fixation in traumatic cataract without posterior capsular support.

METHODS

The study included 86 cases (86 eyes) with traumatic cataract. A new flexible open-loop one piece PMMA IOL was implanted in the AC-IOL group of 56 cases (56 eyes); fixation of a C-loop one piece PMMA IOL at ciliary sulcus with two sutures was performed on 30 cases (30 eyes) in the posterior chamber IOL (PC-IOL) group.

RESULTS

The follow-up period was 1 - 42 months. The visual acuity 0.5 or better was in 71.4% (40/56) in AC-IOL group, in 90.0% (27/30) in PC-IOL group; 1.0 or better was in 39.3% (22/56) in AC-IOL group, in 46.7% (14/30) in PC-IOL group.

CONCLUSION

Both AC-IOL implantation and PC-IOL suture fixation are the remedy methods when the PC-IOL intracapsular implantation is unsuccessful. The AC-IOL is suitable for old persons with good anterior segment (cornea, iris and the angle of anterior chamber) and poor posterior segment (vitreous, retina) situations, while the PC-IOL suture fixation is suitable for the young with relatively poor anterior segment and good posterior segment conditions.

[Determination of taurine in foods by high performance liquid chromatography]

Taurine (2-aminoethanesulfonic acid) was quantitated by reversed-phase liquid chromatography on a C18 resolve column (ZOBAX ODS) using a mobile phase of methyl alcohol-phosphate buffer (pH = 4.9). L-glutamine was used as the internal standard. Before separation, the sample was extracted with 0.2 mol/L sulfosalicylic acid solution and cleaned up with dual ion exchange column chromatography. The amino acid was derived with o-phthalaldehyde to form an amino acid adduct which was monitored at 340 nm by UV detector. The HPLC method for taurine analysis in foods showed the precision (relative standard deviation) is better than 5%. The recoveries are more than 95% and the detection limit is 12 ng of taurine.

[Compositional analysis of two metal crowns and its cements unearthed from a Ming Dynasty grave in China by SEM]

OBJECTIVE

To investigate the prosthodontic level of our country in Ming Dynasty (from A. D. 1368 to A. D. 1644) and provide our courtry's history of stomatological development with some details.

METHODS

By means of range estimation and SEM, the structure and shape of the metal crowns on the two human teeth which were unearthed from a Ming Dynasty grave, numbered 0754/0046 and stored in Wujin museum of Jiangsu province, as well as the compositions of the crowns and its cements were examined and analysed preliminarily.

RESULTS

The two teeth looked like upper anterior teeth and no marks of preparations were observed. The golden-yellow metal crowns might have been hammered and welded into shape. The spectrum analysis of SEM showed the crowns were made from gold-copper alloy and the cements contains Zinc.

CONCLUSION

The defects of teeth could have been restored with extra-hard gold-copper alloy and cement luting materials during A. D. 1500-1600 in China.

[Effect of taixian tablet on hamster buccal pouch carcinogenesis]

Eighty syrian hamsters were divided into 4 equal groups. The right buccal pouches of hamsters in group I and group II were painted three times weekly with 0.5% DMBA dissolved in acetone, but the hamsters in group I received 0.45 g Taixian tablet daily by mouth. The animals in group III only received 0.45 g Taixian tablet daily and group IV was control group. After 9, 12 weeks, animals were killed with their pouches excised, and tumors were counted and measured. The results showed; 1. Comparing with group II, the malignant rate of group I was lower after 9 weeks and the tumor volume was smaller after 12 weeks (P < 0.01); 2. It was found histologically many inflammatory cells locating in the epithelial layer and lamina propria of group I after 9 weeks, while only a few inflammatory cells in group II. The high differentiated squamous cell carcinoma could be seen in group I and group II after 12 weeks, but no abnormal changes in cervical lymphnodes and organs (lung, liver, spleen, et al) of all animals in 4 groups. It suggests that Taixian tablet can restrain the development of oral carcinogenesis.

[The effect of internal irradiotherapy with 32P glass microspheres on tumor vasculature in mouse sarcoma 180]

In order to investigate the effect of internal irradiotherapy on tumor microvasculature, the vascular changes of tumor S180 following internal irradiotherapy with 32P glass microspheres were observed microscopically with vessel casts of resin perfusion and ink perfusion. The results showed that the microvessels expanded with the endothelial cells swelling and the amount of microvessels and new vessels decreased, which led to peritumoral vascular density descended. It suggests that internal irradiotherapy destroying the tumor microvasculature as external irradiation is an important influence on the efficiency of internal irradiotherapy.

Inhibition of cellular proliferation by the Wilms tumor suppressor WT1 requires association with the inducible chaperone Hsp70

The Wilms tumor suppressor WT1 encodes a zinc finger transcription factor that is expressed in glomerular podocytes during a narrow window in kidney development. By immunoprecipitation and protein microsequencing analysis, we have identified a major cellular protein associated with endogenous WT1 to be the inducible chaperone Hsp70. WT1 and Hsp70 are physically associated in embryonic rat kidney cells, in primary Wilms tumor specimens and in cultured cells with inducible expression of WT1. Colocalization of WT1 and Hsp70 is evident within podocytes of the developing kidney, and Hsp70 is recruited to the characteristic subnuclear clusters that contain WT1. The amino-terminal transactivation domain of WT1 is required for binding to Hsp70, and expression of that domain itself is sufficient to induce expression of Hsp70 through the heat shock element (HSE). Substitution of a heterologous Hsp70-binding domain derived from human DNAJ is sufficient to restore the functional properties of a WT1 protein with an amino-terminal deletion, an effect that is abrogated by a point mutation in DNAJ that reduces binding to Hsp70. These observations indicate that Hsp70 is an important cofactor for the function of WT1, and suggest a potential role for this chaperone during kidney differentiation.

Megalin (gp330): a putative endocytic receptor for thyroglobulin (Tg)

Megalin (gp330) is a large glycoprotein receptor found mainly on a group of absorptive epithelial cells, including renal proximal tubule, epididymal and thyroid cells. Megalin has been shown to bind multiple, unrelated ligands, mainly in vitro, and to mediate endocytosis of ligandsin cultured cells. However, physiologic ligands of megalin are largely unknown. In the present study we have demonstrated that purified rat megalin binds rat thyroglobulin (Tg) in solid phase assays, with anestimated Kd of 9.2+/-0.6 nM. Binding was calcium dependent and was almost completely inhibited by excess Tg, by three megalin ligands - lactoferrin, lipoprotein lipase and apolipoprotein J- and by the receptor associated protein (RAP), which inhibits binding of all megalin ligands. Three anti-megalin antibodies partially inhibited Tg binding to megalin. 125I labeled Tg bound to megalin was released by EDTA and heparin; the released product was shown by SDS-PAGE and autoradiography to be 660 kD (dimeric) Tg. However, an immunoblotting experiment showed binding of megalin both to monomeric (330 kD) and dimeric Tg. We propose that megalin, which is known to mediate ligand endocytosis and is found on the apical surface of thyrocytes, may participate in the endocytosis of Tg from the colloid, a process that is required for hormone release from Tg.

Immortalized rat proximal tubule cells produce membrane bound and soluble megalin

Megalin (gp330), a glycoprotein receptor found on renal proximal tubule cells and several other epithelial cells, is deduced to be a type I integral membrane protein, but may also exist as a cell surface form lacking a cytoplasmic domain. Furthermore, soluble megalin products have been detected in urine, and in culture medium of a rat yolk sac carcinoma cell line, combined with receptor associated protein (RAP). Permanent renal cell lines expressing megalin were unavailable until the recent description of two immortalized rat proximal tubule cell lines (IRPTC). The present study demonstrated megalin on IRPTC surface by immunofluorescence, without surface staining for RAP, which was, however, readily detected within cells. Antibodies to ectodomain megalin epitopes immunoprecipitated megalin products both from cell lysates and culture medium, whereas antibodies to cytoplasmic domain epitopes precipitated megalin only from lysates. Western blots showed two major megalin products in medium, a prominent band at approximately 200 kDa, and a fainter band above 400 kDa, slightly below intact megalin in cell lysates. Anti-receptor associated protein antibodies immunoprecipitated megalin from IRPTC lysates, but not from media. We propose that portions of megalin are spontaneously produced by IRPTC, probably either by cleavage in the ectodomain or release of forms lacking a cytoplasmic domain.

[A stereological study of the remaining parotid gland of rat after duct-preserved partial parotidectomy]

The remaining parotid glands of rats after duct-preserved partial parotidectomy were sectioned and examined randomly by stereological methods which determine acinararea and proportional volumes (PV) of the component tissues. The volume of the remaining glands were measured at the same time. Results showed that: 1. there were no difference of the above quota 1-3 days after the operation (P > 0.05); 2. 1-2 weeks after the operation, the gland volume decreased (P < 0.05) with the PV of acini decreasing (P < 0.05); 3. 4-7 weeks after the operation, the acinar area increased (P < 0.05), the PV of acini and gland volume regained (P > 0.05). All the results indicate, with the duct preserved, the remaining parotid glands after partial parotidectomy do have the regenerating ability and significant function.

[Molecular biological evidence for the genetic stability of in vivo passaged doxorubicin resistant cell line S-180R]

OBJECTIVE

To assess the genetic stability of doxorubicin resistant sarcoma 180 cell line(S-180R) after in vivo passages.

METHODS

Flow cytometry, Southern blot, Northern blot and RT-PCR were used to examine genes and molecules related to drug resistance.

RESULTS

The drug-efflux of S-180R was nearly 100-fold as high as that of the parental cells. The ratio of half peak width to peak height was 0.23 as compared to 0.56 measured two years before when the S-180R cell line was initially established. The mdr-1 gene was significantly amplified and transcribed while the transcription of topoisomerase II alpha gene was decreased. However there was no increase in mRNA expression of the multidrug resistance associated protein(MRP).

CONCLUSION

Compared with the initially established S-180R, its resistance to doxorubicin is not only maintained but in fact has been increased since in vivo passage for 2 years. The major mechanism is amplification and over-expression of mdr-1 gene, but decreased topoisomerase II alpha also contributes. S-180R is an ideal experimental model for the study of doxorubicin resistance and its reversion.

[Analysis of the relations between Toynbee phenomenon and middle ear pressure]

This paper studied the relations between the middle ear pressure, the opening duration of eustachian tube (ET), and the duration of nasopharyngeal pressure phase during Toynbee maneuver by sonotubometry, tympanometry and nasopharynx manometry. The mucociliary clearance of ET in Toynbee maneuver was also studied by Saccharin method. The results showed that negative middle ear pressure induced by Toynbee maneuver was related to prolonged opening duration of ET and duration of negative pressure in nasopharynx and lower opening pressure of ET. This phenomenon was often shown on the patients with nasal obstruction, and reduced ET mucociliary clearance. The Toynbee phenomenon indicates a closing failure of the ET, clinically, this situation needs to be prevented and resolved in a timely manner.

High affinity dimerization by Ski involves parallel pairing of a novel bipartite alpha-helical domain

c-Ski protein possesses a C-terminal dimerization domain that was deleted during the generation of v-ski, and has been implicated in the increased potency of c-ski in cellular transformation compared with the viral gene. The domain is predicted to consist of an extended alpha-helical segment made up of two motifs: a tandem repeat (TR) consisting of five imperfect repeats of 25 residues each and a leucine zipper (LZ) consisting of six heptad repeats. We have examined the structure and dimerization of TR or LZ individually or the entire TR-LZ domain. Using a quenched chemical cross-linking method, we show that the TR dimerizes with moderate efficiency (Kd = 4 x 10(-6) M), whereas LZ dimerizes poorly (Kd > 2 x 10(-5) M). However, the entire TR-LZ domain dimerizes efficiently (Kd = 2 x 10(-8) M), showing a cooperative effect of the two motifs. CD analyses indicate that all three proteins contain predominantly alpha-helices. Limited proteolysis of the TR-LZ dimer indicates that the two helical motifs are linked by a small loop. Interchain disulfide bond formation indicates that both the LZ and TR helices are oriented in parallel. We propose a model for the dimer interface in the TR region consisting of discontinuous clusters of hydrophobic residues forming "leucine buttons."

DNA binding and transcriptional activation by the Ski oncoprotein mediated by interaction with NFI

The Ski oncoprotein has been found to bind non-specifically to DNA in association with unindentified nuclear factors. In addition, Ski has been shown to activate transcription of muscle-specific and viral promoters/enhancers. The present study was undertaken to identify Ski's DNA binding and transcriptional activation partners by identifying specific DNA binding sites. We used nuclear extracts from a v-Ski-transduced mouse L-cell line and selected Ski-bound sequences from a pool of degenerate oligonucleotides with anti-Ski monoclonal antibodies. Two sequences were identified by this technique. The first (TGGC/ANNNNNT/GCCAA) is the previously identified binding site of the nuclear factor I (NFI) family of transcription factors. The second (TCCCNNGGGA) is the binding site of Olf-1/EBF. By electophoretic mobility shift assays we find that Ski is a component of one or more NFI complexes but we fail to detect Ski in Olf-1/EBF complexes. We show that Ski binds NFI proteins and activates transcription of NFI reporters, but only in the presence of NFI. We also find that homodimerization of Ski is essential for co-activation with NFI. However, the C-terminal dimerization domain of c-Ski, which is missing in v-Ski, can be substituted by the leucine zipper domain of GCN4.

Magnesium status and risk of coronary artery disease in rural and urban populations with variable magnesium consumption

This survey was conducted to determine the association between amount of magnesium intake and prevalence of coronary artery disease (CAD) and coronary risk factors in north India. There were 3575 subjects aged 25-64 years including 1769 rural (894 men, 875 women) and 1806 urban (904 men, 902 women) subjects. The survey methods were questionnaires for 7-day food intake record, physical examination and electrocardiography using World Health Organization criteria. The overall prevalence of CAD was three-fold greater in urban compared to rural subjects (9.0 vs 3.3 per cent, p < 0.001). The prevalence of CAD was significantly higher among subjects consuming lower dietary magnesium. Lower magnesium status was inversely associated with risk of CAD in both rural and urban subjects in both sexes. Among subjects with low magnesium status, there was a higher prevalence of hypertension, hypercholesterolemia and diabetes mellitus showing a significant increasing trend with decrease in magnesium status. Multivariate logistic regression analysis after pooling of data from rural and urban subjects and after adjustment of age showed that magnesium intake had an inverse association with prevalence of CAD. Serum magnesium (odds ratio: men 1.14, women 1.05), dietary magnesium (men 1.21, women 1.12), serum cholesterol (men 1.15, women 1.15), blood pressure (1.26 men, women 1.21), diabetes mellitus (men 1.20, women 1.18) in both sexes and smoking in men (1.05) were significant risk factors of CAD. Lower consumption of dietary magnesium and low serum Mg level in north India have a higher prevalence of CAD and of the coronary risk factors hypertension, hypercholesterolemia and diabetes mellitus. It is possible that increased intake of magnesium to about 500 mg/day may be of benefit in the prevention of CAD.

Synthesis, photophysical properties, in vivo photosensitizing efficacy, and human serum albumin binding properties of some novel bacteriochlorins

The synthesis, photophysical characteristics, in vivo photosensitizing efficacy, human serum albumin (HSA) binding properties, and skin phototoxicity of some stable bacteriochlorins were investigated. The novel bacteriochlorins, obtained from chlorophyll-a, have long-wavelength absorptions in the range lambda max = 734-758 nm. Preferential migration of ethyl over methyl substituents among ketobacteriochlorins obtained in the pinacol-pinacolone rearrangements of vic-dihydroxybacteriochlorins was confirmed by NOE studies. The bacteriochlorins show relatively low fluorescence quantum yields. Among all the bacteriochlorins the triplet states were quenched by ground state molecular oxygen in a relatively similar manner, yielding comparable singlet oxygen quantum yields. In preliminary in vivo studies (DBA/2 mice, transplanted with SMT/F tumors), ketobacteriochlorins were found to be more photodynamically active than the related vic-dihydroxy analogues. Replacement of the methyl ester functionalities with di-tert-butylaspartic acids enhanced the in vivo efficacy. Site specific human serum albumin (HSA) binding studies indicated a direct correlation between the ability of the compound to bind to the diazepam binding site (albumin site II) and the in vivo photosensitizing efficacy.

Correlation between site II-specific human serum albumin (HSA) binding affinity and murine in vivo photosensitizing efficacy of some Photofrin components

Human serum albumin (HSA) is one of the key components in human blood that may influence drug distribution. As such, it is important to know the affinity of any drug for albumin. Previously, Photofrin, a mixture of monomeric, dimeric and oligomeric porphyrins, has been subjected to HSA binding studies. However, due to its complex nature, binding studies on Photofrin or other hematoporphyrin derivatives with HSA are inconclusive. In this report, the binding properties of some components (dimers and trimers) of Photofrin and the relationship between murine photosensitizing efficacy and those binding properties were investigated. The interaction of these porphyrins with HSA was investigated by direct ultrafiltration and fluorescent titration techniques with fluorescent probes such as dansyl-L-proline (DP), which is known to interact selectively with site II on HSA. Porphyrins also were tested for antitumor activity in a mouse model following intravenous administration and exposure to laser light. Together, the results suggest that the photosensitizers that were preferentially bound to site II of HSA were most effective at controlling murine tumor regrowth.

Identification of a core functional and structural domain of the v-Ski oncoprotein responsible for both transformation and myogenesis

The v-ski oncogene promotes cellular transformation and myogenic differentiation. In quail embryo fibroblasts the two properties are displayed simultaneously and terminal muscle differentiation occurs only among cells already transformed by v-ski. To understand how the two phenotypes are derived from a single gene, we have undertaken to identify functionally important regions in v-ski and to test whether these regions can promote one phenotype without the other. We have generated both random and targeted mutations in v-ski and evaluated the effects of these mutations on expression, intracellular location, transformation, and myogenesis. Among a total of 26 mutants analysed, we have not found complete separation of the myogenic and transforming properties. Mutations in the region of v-Ski encoded by exon 1 of c-ski frequently abolish both its transformation and muscle differentiation activities, whereas mutations outside of this region are always tolerated. When expressed in cells from a minigene containing only the exon 1 sequence, the protein displays the transforming and myogenic activities similar to v-Ski. These results argue that the amino acid sequence encoded by exon 1 contains the core functional domain of the oncoprotein. To determine whether this functional domain has a structural counterpart, we have fragmented the v-Ski protein by limited proteolysis and found a single proteolytically stable domain spanning the entire exon 1-encoded region. Physical studies of the polypeptide encoded by exon 1 confirms that it folds into a compact, globular protein. The finding that both the transforming and myogenic properties of v-Ski are inseparable by mutation and are contained in a single domain suggests that they are derived from the same function.

Determination of rate and equilibrium constants for the reactions between electron transfer mediators and proteins by linear sweep voltammetry

Redox proteins undergo measurable charge transfer at electrodes only under special circumstances, while they readily take part in electron transfer reactions with mediators in solution. Advantage was taken of the latter fact to develop a new method to study the kinetics and equilibria of protein-mediator electron transfer reactions. It was shown that rate and equilibrium constants for the electron exchange between electron transfer mediator and the protein can be obtained from the analysis of the perturbation of the linear sweep voltammetry (LSV) response of the mediator due to the presence of the protein. The experiments were carried out under conditions where the protein does not interact with the electrode. Theoretical data obtained by digital simulation are presented to show the conditions under which rate and equilibrium constants are accessible by the LSV technique. The electron transfer reactions between ferri- and ferrocytochrome c and N,N,N',N'-tetramethylphenylenediamine and the corresponding radical cation in phosphate-buffered saline (0.04 M phosphate, pH 7.4, 0.1 M NaCl) buffer were selected to demonstrate the technique. These studies resulted in an equilibrium constant equal to 1.0 and forward and reverse rate constants equal to 1.6 x 10(4) M-1 s-1. The data available from this method include forward and reverse rate constants for electron transfer and the formal potential for the protein redox couple.

[Drug resistance mechanism of doxorubicin-resistant human gastric cancer cells BGC-823/DOX]

To further investigate drug resistance mechanism of BGC-823/DOX, we analysed the amplication, transcription and overexpression of genes associated with drug resistance by Southern blot, RT-PCR, immunohisto clogical assay and the concentration of Doxorubicin in the cells by flow cytometry. The results showed that parent cells of BGC-823 were cell line with intrinsic drug resistance similar to the gastrointestinal tumors. Multidrug resistance was the main mechanism of drug resistance in BGC-823/DOX. There was a significant difference between the doxorubicin-resistant cells line from parent cells with intrinsic drug resistance and from parent cells without intrinsic drug resistance in drug resistance.

[Evaluation of oral glucose tolerance test in the assessment of reserved function of liver for patients with hepatocellular carcinoma]

The aim of this study was to evaluate oral glucose tolerance test(OGTT)in the assessment of reserved function of liver for predicting the tolerability of patients to hepatectomy and hence provided a criteria for selecting the candidates for undergoing hepatectomy, since the majority of hepatocellular carcinoma (HCC) patients were associated with posthepatitis cirrhosis. The preoperative and postoperative OGTT and liver biopsy for pathological investigation were carried out in 62 cases of hepatecomized patients and 49 cases of unresected patients for comparison. The results revealed that the patients whose preoperative OGTT curve was of P type recovered uneventfully after hepatectomy, but those whose curve was of L type of tolerated poorly to hepatectomy and were liable to postoperative hepatic failure and complications. The severity of cirrbosis in those poor risk patients fell to C III or C IV histological degree. 29 patients with intermediate feature of OGTT curve between P type and L type, i.e. I type underwent regional vascular occlusion at hepatic hilus as hepatectomy, and infusion of Danshen extract solution before vascular occlusion to prevent hepatocytes from reperfusion injury. Of them, 20 recovered uneventfully, 8 suffered from complications such as ascites and/or juandice, and 1 died within 1 month after operation. The followup study showed that the survival time of patients with P type OGTT curve was longer than that of I type, and the latter was longer than that of L type. The pattern of OGTT curve could change from preoperative P type to postoperative L type, depending on the severity of vascular interruption of liver and the ischemic injury to hepatocytic mass in operation.

[Establishment and characterization of doxorubicin-resistant BGC-823/DOX of human gastric cancer cell line]

To study drug resistance mechanism of gastrointestinal tumor, doxorubicin resistant cell line of human gastric cancer, we developed BGC-823/DOX, by increasing doses of doxorubicin. We completed chromosomal analysis, double time of cell grow, cell cycle distributions, drug resistance and cross-resistance, and studied reversing drug resistance. The results showed that chromosome of BGC-823/DOX was subtriploid karyotype. Cell morphology, double time, cell cycle distributions were different from its parent cells and 6.35 times more resistant to cytotoxic action of doxorubicin, cross-resistant to VP-16. Verapamil showed modified effect on doxorubicin resistance. BGC-823/DOX with doxorubicin resistance has many characteristics of gastrointestinal tumors.

[Effect of cigarette smoking on lipid peroxidation and antioxidation in rat lens]

The effects of cigarette smoking on lipid peroxidation, the activities of antioxidases, and the level of non-protein sulphydryl group in the rat lenses were investigated. The results showed that compared with the control group, MDA contents were significantly higher, while the wet weight of lenses, the concentration of non-protein sulphydryl group, the activities of superoxide dismutase and glutathione peroxidase were significantly decreased in the smoking rats. This study suggested that cigarette smoking might be involved in the development of cataract.

The effects of voluntary exercise and immobilization on humoral immunity and endocrine responses in rats

This research examined the effect of type of stressor (physical vs. psychological) on humoral immunity and neuroendocrine responses in male and female rats. Eighty adult Sprague-Dawley rats were assigned to one of the four stress conditions (n = 20 animals/group): 1. Voluntary running (high physical/low psychological stress); 2. immobilization (low physical/high psychological stress); 3. mixed stress (running and immobilization); and 4. cage control group. The experimental manipulations were conducted over a 6-week period for 4 h/day. Five weeks after the start of the study, all animals were immunized with 1 ml of a 10% suspension of sheep red blood cells (SRBC) in saline and sacrificed 1 week later. Data analyses revealed no main effect of stress on any of the immune or endocrine parameters. However, strong gender differences emerged within the stress conditions on these physiological parameters. The stressed female rats displayed an enhanced antibody response to SRBC and a higher percentage of peripheral blood lymphocytes than their male counterparts. However, there were no significant differences between the male and female control animals with respect to these variables. Female rats consistently displayed elevated levels of plasma corticosterone and adrenal norepinephrine across all conditions. In addition, female rats displayed heavier relative organ weights (adrenal and spleen). Taken together, the notion of differential immunity with respect to physical or psychological stress is not supported by the present study.

Endothelium-independent relaxation of aortic rings by the nitric oxide synthase inhibitor diphenyleneiodonium

1. The flavoprotein binder diphenyleneiodonium (DPI) is a potent, irreversible inhibitor of nitric oxide synthase (NOS), but produces only a transient pressor response following systemic administration to animals, despite evidence of persistent NOS inhibition. To characterize further the effects of DPI on vascular tone, isometric tension was recorded from rat isolated aortic rings mounted between steel wires in an organ bath. 2. The NOS inhibitor NG-nitro-L-arginine methyl ester (L-NAME, 1 mM) initiated an additional contraction of prostaglandin F2 alpha-preconstricted rings with endothelium which was sustained throughout the period of L-NAME exposure (+234 +/- 39% at 15 min). In contrast, addition of DPI (5 microM) to rings with endothelium produced a transient initial contraction (+111 +/- 27% at 2 min) followed by a more sustained relaxation (-27 +/- 19% at 15 min, P < 0.001 vs L-NAME). 3. The contraction to DPI was also observed in rings without endothelium, was abolished by L-NAME pretreatment, and was unaffected by the alpha-adrenoreceptor inhibitor prazosin. Relaxation in response to DPI was not inhibited by endothelium removal or by pretreatment with either L-NAME or with the ATP-sensitive potassium channel blocker glibenclamide. 4. The endothelium-independent relaxation to DPI was inhibited at 23 degrees C and its time course was delayed by pretreatment with the guanylate cyclase inhibitor methylene blue. 5. Thus, in addition to a transient initial contraction due to NOS inhibition, DPI produces an endothelium-independent, temperature-dependent relaxation which appears in part due to activation of guanylate cyclase. This relaxant effect of DPI may explain the transient nature of its pressor effect in vivo despite sustained NOS inhibition.

[Observation of the invasion of retinoblastoma cells to ocular tissues in vitro]

PURPOSE

To study the invasion of retinoblastoma cells to ocular tissues.

METHODS

The SO-Rb50 cells of retinoblastoma and various ocular tissue cells were co-cultured. The morphological change of the SO-Rb50 cells adherent to ocular tissue cells was observed.

RESULTS

SO-Rb50 cells can adhere to the various ocular tissues. The adherent ability of SO-Rb50 cell to different ocular tissue cells was different. Tumor cells could be adhesive to keratocyte, scleral fibrocyte, the fibrocyte and the melanocyte of iris and choroid, the epithelial cells of lens, and the astrocyte of optic nerve and grow, but can not be adhesive to the corneal epithelial cell and retinal pigment epithelial cell.

CONCLUSIONS

We consider that the interactions of tumor cells with host cells, as with extracellular matrix, also play an important role in the selective growth of organ and tissue of tumor cell metastasis. Retinoblastoma cells can not adhere to retinal pigment epithelial cell, which may serve as a barrier to obstruct the invasion of tumor cell to the choroid. Being adherent to the glial cells of optic nerve, tumor cells grow in flat and the shape of tumor cell changes, which may be the cause of tumor cell migrate rapidly and grow in the brain while the optic nerve was invaded by tumor cells.

Reflectometric frequency-modulation continuous-wave distributed fiber-optic stress sensor with forward coupled beams

A distributed optical-fiber stress sensor whose principle of operation is based on the frequency-modulation continuous-wave technique is reported. The sensor consists of a length of birefringent fiber with a mirror attached to one end, a diode laser, and a p-i-n photodiode detector. The intensity and the location of an applied stress are determined simultaneously by detecting the amplitude and the frequency of the beat signal, which is produced by two forward-coupled mode beams. The system was found to have a reasonable spatial resolution of 0.85 m (rms error) in a sensing range of 100 m. The advantages and limitations of the sensor are also discussed.

Room-temperature green upconversion fluorescence of an Er(3+)-doped laser liquid

Room-temperature green upconversion fluorescence of an Er(3+)-doped POCl(3)-SnCl(4) solution is achieved when the solution is pumped with an 800-nm GaAs laser diode. The upconversion emission at 550 nm is determined to be the result of a two-step absorption process. Numerical analysis reveals that laser systems that employ this erbium-doped laser liquid should be realizable with threshold pump powers as low as 45 mW.