Exonic splicing enhancer motif recognized by human SC35 under splicing conditions

Exonic splicing enhancers (ESEs) are important cis elements required for exon inclusion. Using an in vitro functional selection and amplification procedure, we have identified a novel ESE motif recognized by the human SR protein SC35 under splicing conditions. The selected sequences are functional and specific: they promote splicing in nuclear extract or in S100 extract complemented by SC35 but not by SF2/ASF. They can also function in a different exonic context from the one used for the selection procedure. The selected sequences share one or two close matches to a short and highly degenerate octamer consensus, GRYYcSYR. A score matrix was generated from the selected sequences according to the nucleotide frequency at each position of their best match to the consensus motif. The SC35 score matrix, along with our previously reported SF2/ASF score matrix, was used to search the sequences of two well-characterized splicing substrates derived from the mouse immunoglobulin M (IgM) and human immunodeficiency virus tat genes. Multiple SC35 high-score motifs, but only two widely separated SF2/ASF motifs, were found in the IgM C4 exon, which can be spliced in S100 extract complemented by SC35. In contrast, multiple high-score motifs for both SF2/ASF and SC35 were found in a variant of the Tat T3 exon (lacking an SC35-specific silencer) whose splicing can be complemented by either SF2/ASF or SC35. The motif score matrix can help locate SC35-specific enhancers in natural exon sequences.

Evidence for the function of an exonic splicing enhancer after the first catalytic step of pre-mRNA splicing

Exonic splicing enhancers (ESEs) activate pre-mRNA splicing by promoting the use of the flanking splice sites. They are recognized by members of the serine/arginine-rich (SR) family of proteins, such as splicing factor 2/alternative splicing factor (SF2/ASF), which recruit basal splicing factors to form the initial complexes during spliceosome assembly. The in vitro splicing kinetics of an ESE-dependent IgM pre-mRNA suggested that an SF2/ASF-specific ESE has additional functions later in the splicing reaction, after the completion of the first catalytic step. A bimolecular exon ligation assay, which physically uncouples the first and second catalytic steps of splicing in a trans-splicing reaction, was adapted to test the function of the ESE after the first step. A 3' exon containing the SF2/ASF-specific ESE underwent bimolecular exon ligation, whereas 3' exons without the ESE or with control sequences did not. The ESE-dependent trans-splicing reaction occurred after inactivation of U1 or U2 small nuclear ribonucleoprotein particles, compatible with a functional assay for events after the first step of splicing. The ESE-dependent step appears to take place before the ATP-independent part of the second catalytic step. Bimolecular exon ligation also occurred in an S100 cytosolic extract, requiring both the SF2/ASF-dependent ESE and complementation with SF2/ASF. These data suggest that some ESEs can act late in the splicing reaction, together with appropriate SR proteins, to enhance the second catalytic step of splicing.

Nocistatin reverses the effect of orphanin FQ/nociceptin in antagonizing morphine analgesia

Nocistatin is a recently characterized neuropeptide derived from the preprohormone containing nociceptin (Orphanin FQ, OFQ). Nocistatin was reported to antagonize OFQ induced allodynia, hyperalgesia and prostaglandin E2-elicited pain responses. The aim of the present study was to determine whether nocistatin, injected intracerebroventricularly (i.c.v.), would reverse the anti-morphine effect of OFQ in rats using the tail-flick latency (TFL) as the nociceptive index. I.c.v. injection of nocistatin at doses of 0.005, 0.05, 0.5, 5, 50, and 500 ng produced no significant changes in the basal TFL, nor did it affect morphine analgesia. However, it significantly reversed the antagonistic effect of OFQ on morphine analgesia when co-injected i.c.v. at doses of 0.05, 0.5, 5, 50 and 500 ng per rat with OFQ. The dose-response curve was bell-shaped and the most effective dose was 0.5 ng. The results suggest that nocistatin can reverse the anti-morphine effect of OFQ in rat brain.

[Repeated 100 Hz TENS for the treatment of chronic inflammatory pain in rats: optimal parameters and possible neuro-chemical mechanisms]

AIMS

To establish a reliable animal model of chronic arthritic inflammatory pain, to find the optimal parameters and appropriate intervals of repeated 100 Hz transcutaneous electrical nerve stimulation (TENS) for the treatment of the chronic arthritic pain, and to explore the possible central neurochemical mechanisms.

THE RESULTS

(1) Injection of water-in-oil type complete Freund's adjuvant into the tibio-tarsal joint of the rat produced a reliable, reproducible monoarthritic model. (2) The interval between 2 sessions of stimulations and the intensity of stimulation were important factors determining the therapeutic effects of repeated 100 Hz TENS on both acute and stable period of monoarthritis. (a) For acute period of monoarthritis, the optimal frequency is twice a week, while in the stable period, once a week seems better. (b) The effects of TENS in three intensities: the weaker stimulation was found to produce better results. (3) In the period from 2 to 9 weeks, the levels of spinal release of SP-ir in the TENS group were lower than the control group. This may constitute one of the possible neuro-chemical mechanisms underlying the therapeutic effects of multiple TENS treatment. (4) In both acute and stable period of adjuvant-induced monoarthritis, intrathecal microinjection of Nor-BNI produced dose-dependent increase of arthritic flexion pain scores (i.e. hyperalgesia), suggesting that spinal dynorphin/kappa system plays a role in suppressing arthritic pain.

A reproducible, simple, and sensitive high-performance capillary electrophoresis method for simultaneous determination of capreomycin, ofloxacin and pasiniazide in urine

Separation and determination of capreomycin (Cp), ofloxacin (Oflx) and pasiniazide (Ipa) in urine by high-performance capillary electrophoresis (HPCE) with 280 nm detection have been studied systematically. The calibration lines were linear in the range of 0.5 approximately 50 mg 1(-1), and the detection limits (S/N = 3) were 0.15, 0.20 and 0.10 mg 1(-1) for Cp, Oflx and Ipa, respectively. The recoveries for these materials from urine were higher than 93.5%. The accuracy and intra- and inter- day reproducibility of Cp, Oflx and Ipa were determined with satisfactory results. This method was successfully used for determining Cp. Oflx and Ipa in human urine.

Identification of functional exonic splicing enhancer motifs recognized by individual SR proteins

Using an in vitro randomization and functional selection procedure, we have identified three novel classes of exonic splicing enhancers (ESEs) recognized by human SF2/ASF, SRp40, and SRp55, respectively. These ESEs are functional in splicing and are highly specific. For SF2/ASF and SRp55, in most cases, only the cognate SR protein can efficiently recognize an ESE and activate splicing. In contrast, the SRp40-selected ESEs can function with either SRp40 or SRp55, but not with SF2/ASF. UV cross-linking/competition and immunoprecipitation experiments showed that SR proteins recognize their cognate ESEs in nuclear extract by direct and specific binding. A motif search algorithm was used to derive consensus sequences for ESEs recognized by these SR proteins. Each SR protein yielded a distinct 5- to 7-nucleotide degenerate consensus. These three consensus sequences occur at higher frequencies in exons than in introns and may thus help define exon-intron boundaries. They occur in clusters within regions corresponding to naturally occurring, mapped ESEs. We conclude that a remarkably diverse set of sequences can function as ESEs. The degeneracy of these motifs is consistent with the fact that exonic enhancers evolved within extremely diverse protein coding sequences and are recognized by a small number of SR proteins that bind RNA with limited sequence specificity.

Comparison of high-performance capillary electrophoresis and liquid chromatography on analysis of zinc 5-aminosalicylate dihydrate and related materials

Separation and determination of zinc 5-aminosalicylate dihydrate (ZASA) and related materials by high-performance capillary electrophoresis (HPCE) and liquid chromatography (HPLC) have been studied systematically. The R.S.D. of peak time and area and detection limits of materials were lower in HPLC compared to HPCE. HPCE and HPLC were used for determining ZASA and related materials in crude and treated ZASA using acid and heat, and similar results with both techniques showed the principal impurities in the crude ZASA were 5-aminosalicylic acid (ASA) and salicylic acid (SA), the compounds from ZASA decomposing under conditions of acid and heat were ASA, p-aminophenol and 5-benzeneazosalicylic acid.

Comparison of high performance capillary electrophoresis and liquid chromatography for the determination of acyclovir and guanine in pharmaceuticals and urine

High-performance capillary electrophoresis (HPCE) and high-performance liquid chromatography (HPLC) were developed and applied to the determination of acyclovir (ACV) and guanine (G) in pharmaceuticals. The comparison study showed that two methods gave comparable results in linear range, recovery and reproducibility. HPCE was used for the determination of ACV and G in urine; the recovery was better than 81.3% and the RSD was less than 4.4%.

Mapping of branchpoint nucleotides in mutant pre-mRNAs expressed in plant cells

Pre-mRNA encoding rubisco activase in the Arabidopsis thaliana mutant rca contains a GU to AU change at the 5' splice site of intron 3 and this mutation results in accumulation of splicing intermediates bearing an incompletely processed intron. It has been demonstrated that one of the intermediates contains intron 3 in the form of a lariat and the branchpoint nucleotide has been mapped to the A residue at position -32 forming part of the sequence UUGAU. Analysis of a similar GU to AU 5' splice site mutation, present in a synthetic pre-mRNA context expressed in transfected protoplasts of Nicotiana plumbaginifolia, also suggests formation of lariats with branching occurring at A-31. A small fraction (approximately 10%) of this mutant pre-mRNA also underwent the second step of splicing. In addition to the consensus AG, an AU dinucleotide was used as splicing acceptor.

Characterization of intronic uridine-rich sequence elements acting as possible targets for nuclear proteins during pre-mRNA splicing in Nicotiana plumbaginifolia

Introns of nuclear pre-mRNAs in dicotyledonous plants, unlike introns in vertebrates or yeast, are distinctly rich in A+U nucleotides and this feature is essential for their processing. In order to define more precisely sequence elements important for intron recognition in plants, we investigated the effects of short insertions, either U-rich or A-rich, on splicing of synthetic introns in transfected protoplast of Nicotiana plumbaginifolia. It was found that insertions of U-rich (sequence UUUUUAU) but not A-rich (AUAAAAA) segments can activate splicing of a GC-rich synthetic infron, and that U-rich segments, or multimers thereof, can function irrespective of the site of insertion within the intron. Insertions of multiple U-rich segments, either at the same or different locations, generally had an additive, stimulatory effect on splicing. Mutational analysis showed that replacement of one or two U residues in the UUUUUAU sequence with A or C residues had only a small effect on splicing, but replacement with G residues was strongly inhibitory. Proteins that interact with fragments of natural and synthetic pre-mRNAs in vitro were identified in nuclear extracts of N.plumbaginifolia by UV cross- linking. The profile of cross-linked plant proteins was considerably less complex than that obtained with a HeLa cell nuclear extract. Two major cross-linkable plant proteins had apparent molecular mass of 50 and 54 kDa and showed affinity for oligouridilates present in synGC introns or for poly(U).

Some altered concentrations of elements in semen of workers exposed to trinitrotoluene

OBJECTIVES

A cross sectional study was performed to find the concentrations of elements contained in the semen of workers exposed to trinitrotoluene (TNT).

SUBJECTS AND METHODS

Semen of exposed workers in two TNT plants located in He-Nan Province in 1992 were examined.

RESULTS

The average TNT concentrations in the workplace, except the packing site, were found to have exceeded the maximal allowable concentration (MAC, 1 mg/m3); skin contaminations of male workers exposed to TNT were higher after a shift than in controls, and correlated with the total blood concentrations of TNT, 4-amino-2, 6-dinitrotoluene (4A), and 2-amino-4, 6-dinitrotoluene (2A). Cu, Zn, Na, Mg, and Se concentrations were significantly decreased, but K, Ca, Co, Mn and Li contents were not significantly changed in the semen of workers exposed to TNT. Compared with the control group, the percentage of liquifying time of semen, the sperm malformation incidence, and viability in the men exposed to TNT were all significantly changed.

CONCLUSIONS

Men exposed to TNT have decreased concentrations of some elements is semen and altered semen physiology.

Effects of secondary structure on pre-mRNA splicing: hairpins sequestering the 5' but not the 3' splice site inhibit intron processing in Nicotiana plumbaginifolia

We have performed a systematic study of the effect of artificial hairpins on pre-mRNA splicing in protoplasts of a dicot plant, Nicotiana plumbaginifolia. Hairpins with a potential to form 18 or 24 bp stems strongly inhibit splicing when they sequester the 5' splice site or are placed in the middle of short introns. However, similar 24 bp hairpins sequestering the 3' splice site do not prevent this site from being used as an acceptor. Utilization of the stem-located 3' site requires that the base of the stem is separated from the upstream 5' splice site by a minimum of approximately 45 nucleotides and that another 'helper' 3' splice site is present downstream of the stem. The results indicate that the spliceosome or factors associated with it may have a potential to unfold secondary structure present in the downstream portion of the intron, prior to or at the step of the 3' splice site selection. The finding that the helper 3' site is required for utilization of the stem-located acceptor confirms and extends previous observations, obtained with HeLa cell in vitro splicing systems, indicating that the 3' splice site may be recognized at least twice during spliceosome assembly.

Enhancement of the intestinal absorption of a cyclosporine derivative by milk fat globule membrane

A cyclosporine derivative, dihydrocyclosporine D, was used for the evaluation of milk fat globule membrane (MFGM) as an emulsifier of lipophilic cyclopeptides. As compared with olive oil formulation, MFGM emulsion significantly enhanced the blood and lymphatic fluid concentrations of the cyclosporine derivative after intraduodenal dosing in rats. Thus, it was suggested that MFGM can be used as an intestinal absorption enhancer of cyclosporines.

[Possibility of lymphatic absorption of epidermal growth factor from intestine]

Epidermal growth factor (EGF) in the milk fat globule membrane (MFGM) emulsion enhanced the absorption of this factor from the intestine, especially to the intestinal lymph. Most of the radioactive EGF administered was degraded to small molecular weight materials. These degraded materials were absorbed and appeared in both the intestinal lymph and portal vein blood. However, a certain portion of EGF, although small, appeared in the lymph maintaining the original molecular mass. The MFGM emulsion used enhanced the lymphatic absorption of intact EGF, suggesting that this dosage form increased the absorption of EGF, protected the degradation of EGF in the intestine or promoted the absorption of intact EGF. The enhancing effect on the absorbed dose percentage of EGF recovered using MFGM emulsion was also observed in the portal vein plasma. However, the effect on the absorption of intact EGF was much larger in the lymph than in the portal vein.

Mapping of T helper cell epitopes by using peptides spanning the 19-kDa protein of Mycobacterium tuberculosis. Evidence for unique and shared epitopes in the stimulation of antibody and delayed-type hypersensitivity responses

In vivo and in vitro T cell responses to overlapping 20-mer peptides that span the entire 19-kDa protein of Mycobacterium tuberculosis have been compared in three different strains of mice. Immunization of the mice with peptides and analysis of specific antibody production is an in vivo assay of Th cell activity. Peptides 1-20 and 61-80 elicited strong IgG1 responses in BALB/cJ, C57BL/10J, and B10.BR mice, indicating that these peptides could stimulate Th cells, possibly of a Th2 phenotype. T cells isolated from peptide-immunized mice were challenged in vitro with peptide, and their proliferative responses were analyzed. T cells from these three strains of mice immunized with peptides 1-20, 61-80, and 76-95 also responded to challenge with specific peptide in vitro. In addition, B10.BR mice and BALB/cJ mice showed antibody and T cell proliferative responses to peptides 136-155 and 145-159, respectively. Thus, in vitro proliferating T cells were found to possess specificities for peptide epitopes that were almost identical to those of the antibody-producing cells. Delayed-type hypersensitivity (DTH) responses to these peptides were also examined in the three strains. Interestingly, the T cells responding in the DTH assay had Ag specificities that were quite different from those identified in the antibody and proliferation assays. These results suggested that DTH Th cells form a separate population from antibody Th and proliferative T cells and these populations of cells were differentially activated, in an Ag-specific manner.

Mapping of T helper cell epitopes by using peptides spanning the 19-kDa protein of Mycobacterium tuberculosis. Evidence for unique and shared epitopes in the stimulation of antibody and delayed-type hypersensitivity responses

In vivo and in vitro T cell responses to overlapping 20-mer peptides that span the entire 19-kDa protein of Mycobacterium tuberculosis have been compared in three different strains of mice. Immunization of the mice with peptides and analysis of specific antibody production is an in vivo assay of Th cell activity. Peptides 1-20 and 61-80 elicited strong IgG1 responses in BALB/cJ, C57BL/10J, and B10.BR mice, indicating that these peptides could stimulate Th cells, possibly of a Th2 phenotype. T cells isolated from peptide-immunized mice were challenged in vitro with peptide, and their proliferative responses were analyzed. T cells from these three strains of mice immunized with peptides 1-20, 61-80, and 76-95 also responded to challenge with specific peptide in vitro. In addition, B10.BR mice and BALB/cJ mice showed antibody and T cell proliferative responses to peptides 136-155 and 145-159, respectively. Thus, in vitro proliferating T cells were found to possess specificities for peptide epitopes that were almost identical to those of the antibody-producing cells. Delayed-type hypersensitivity (DTH) responses to these peptides were also examined in the three strains. Interestingly, the T cells responding in the DTH assay had Ag specificities that were quite different from those identified in the antibody and proliferation assays. These results suggested that DTH Th cells form a separate population from antibody Th and proliferative T cells and these populations of cells were differentially activated, in an Ag-specific manner.

Recombinant human and rat ciliary neurotrophic factors

The human ciliary neurotrophic factor (CNTF) gene was identified and cloned, based on homology with the recently cloned rat cDNA. The gene encodes a protein of 200 amino acids, which shares about 80% sequence identity with rat and rabbit CNTF and, like these homologues, lacks an apparent secretion signal sequence. The human CNTF gene, like the rat gene, appears to contain a single intron separating two protein coding exons. An intronless human CNTF gene was constructed by the use of polymerase chain reactions and introduced into vectors designed for expression of foreign proteins in E. coli. The rat CNTF gene was also introduced into similar vectors. Both the human and rat proteins were expressed at exceptionally high levels, at 20-40% and 60-70% of total protein, respectively. Extraction of the recombinant proteins from inclusion bodies by guanidinium chloride, followed by two column chromatography steps, produced high yields of pure CNTF that supported survival and neurite outgrowth from embryonic chick ciliary neurons in culture. The biological activity of both recombinant proteins was comparable to that of native rat CNTF.

[Promotion of intestinal drug absorption by milk fat globule membrane]

A soybean oil emulsion was prepared by using milk fat globule membrane (MFGM) materials as an emulsifier. Its stability and effect on the intestinal absorption of vitamin D3, amphotericin B and kanamycin were studied. The MFGM emulsion was as highly stable as a Tween 80 emulsion. When the MFGM emulsion was sonicated with ultrasonic disrupter, the emulsion became more stable. Quantification of vitamin D3 in the intestinal lymph indicated that the MFGM emulsion enhanced lymphatic absorption of vitamin D3. The recovered percentage of vitamin D3 emulsified with MFGM in the lymph was 1.4 times that by Tween 80, and 2.5 times that of oil-in-water suspension. Statistically significant difference was found among them (p less than 0.05). The volumes of an oil phase in the emulsion affected the absorption of vitamin D3. The recovered percentage of vitamin D3 from the lymph increased with reducing the volume of the oil phase. Sonication of the emulsion did not affect the intestinal drug absorption. Furthermore, the MFGM emulsion had no effect on the intestinal absorption of amphotericin B and kanamycin.

Compatibility between Oncomelania hupensis and different isolates of Schistosoma japonicum in China

Oncomelania hupensis from six localities were used for infection with different isolates of Schistosoma japonicum in the mainland of China, ie Anhui in the east, Hubei in the center, Guangxi in the south, Sichuan in the West, Yunnan in the southwest and Fujian in the southeast. Snails from Anhui and Hubei were readily infected with the local isolate of S. japonicum and cross infection also took place readily between the snails and the schistosomes from these two places. Snails from Sichuan and Yunnan were refractory to infection with schistosome isolates from Hubei and Anhui, but the isolates from Sichuan and Yunnan were able to develop in snails from Hubei and Anhui. Though the Guangxi isolate developed readily in both Anhui and Guangxi snails, the average precercarial period in the former was significantly longer than in the latter. None of the other snails from Sichuan, Yunnan and Fujian became infected. On the other hand, snails from Guangxi infected with Anhui parasites also had a longer precercarial period than that in Anhui snails. Snails from Fujian were readily infected with the isolates from Anhui and Yunnan. The present results suggest that there might be different geographic strains of S. japonicum and their Oncomelania snail hosts in the mainland of China.

[Flow cytometry in analysis of precancerous lesions of the esophagus]

DNA content of the severe dysplasia cells in the esophageal epithelium was quantitatively analysed using flow cytometry and compared with those of the normal, mild dysplasia and cancer cells. The results showed that DNA index of the severe dysplasia cells was 1.27 +/- 0.11 and there was a significant difference between its value and those of the normal (1.0 +/- 0.02), mild dysplasia (1.01 +/- 0.03) and cancer cells (1.73 +/- 0.35). The DNA content of severe dysplasia cells lies between the normal and cancer cells. The hyperplasia degree of the severe dysplasia cells parallels their DNA contents. This study indicates that flow cytometry is a useful supplementary tool for diagnosis of the tumor.

Establishment and biological properties of mouse granulocytic leukemic cell line-L833

A granulocytic leukemic cell line, called L833 has been established through culturing in vitro from mouse bone marrow of transplantable granulocytic leukemia. More than 280 passages have been performed in 3 years. Cell growth has been rapid and stable. Incidence of tumour formation was 100% with various routes of inoculation. The nature of granulocytic leukemia was confirmed by examination of cytology, cytochemistry, pathology and ultrastructural changes. Analysis proved chromosomes to be hypodiploid with model number of 39, loss of chromosomes, and presence of a marker. Besides the chromosomal change as mentioned above, both L883-A and L833-B derived from colonies formed from the L833 cells cultured in semi-solid agar medium, have their own marker. The cell line was sensitive to various types of antitumour agents in varying degrees. It was also sensitive to ionizing radiation. D0 values of L833 and L883-A cells were 98.8 and 104.9 rad, respectively. The results were similar to that of L801. Establishment of this cell line is of important significance for studying leukemia and screening anti-tumour agents, as well as provides a useful direct, economic and precisely quantitative tool for other relative studies.