Expression of heme oxygenase and inducible nitric oxide synthase mRNA in human brain tumors

Heme oxygenase-1, a key enzyme in heme catabolism, and inducible nitric oxide synthase (iNOS) are responsible for production of carbon monoxide and nitric oxide (NO), respectively. Expression of each enzyme has been shown to be modulated by heme and NO, raising a possibility for the coordinated regulation of the two enzymes. We therefore analyzed the expression levels of both mRNA in humans using brain tumors. Either heme oxygenase-1 or iNOS mRNA was expressed at higher levels in brain tumors compared to the brain tissue, but their expression levels were not apparently correlated. In the brain tumor cell lines, treatment with cytokines increased the expression of iNOS mRNA but not heme oxygenase-1 mRNA, whereas treatment with an NO donor increased the expression of heme oxygenase-1 mRNA but not iNOS mRNA. These results suggest the separate regulation of expression of both enzyme mRNA in humans.

An improved quantitative RT-PCR fluorescent method for analysis of gene transcripts in the STS-65 space shuttle experiment

We describe a reverse transcription polymerase chain reaction (RT-PCR) technique using fluorescent dUTP to examine changes in mRNA level in samples. In this procedure, the amplified product is identified by the fluorescent detection system in an automated DNA sequencer, and if the MW of the DNA/RNA or the fluorescent dye is different, several samples can be analyzed in a single lane. The basis for this technique is similar to that of radiolabeled methods, and we applied this technique for the comparison of the expression level of the rat c-myc gene in osteoblasts exposed to microgravity and unit gravity conditions. Using the fluorescent- and radiolabeled methods, the level of rat c-myc mRNA were compared quantitatively and the results demonstrated that the c-myc expression level was not altered by microgravity. Therefore, this fluorescent RT-PCR technique is useful for gene expression analysis particularly when the samples are limited, such as in space flight experiments. The method also allows for rapid assessment of mRNA changes in many samples simultaneously.

Microgravity induces prostaglandin E2 and interleukin-6 production in normal rat osteoblasts: role in bone demineralization

It has been suggested that microgravity alters bone metabolism. Evidence for this phenomenon includes the negative calcium balance and decreased bone density in astronauts, as well as, inhibition of bone formation in rats flown for 2 to 3 weeks. However, the specific mechanisms that modulate these changes in microgravity are unknown. The purpose of this study was to clarify the mechanism of microgravity-induced bone demineralization using normal rat osteoblasts obtained from femur marrow cultures. The osteoblasts were cultured for 5 days during a Shuttle-Spacelab flight (STS-65). After collection of the culture medium, the cellular DNA and RNA were fixed on board. Enzyme-immunoassay of the culture medium for prostaglandin E2 (PGE2) indicated that microgravity induced a 4.5- to 136-fold increase in flight samples as compared to the ground control cultures. This increase of PGE2 production was consistent with a 3.3- to 9.5-fold elevation of inducible prostaglandin G/H synthase-2 (PGHS-2) mRNA, quantitated by reverse transcription-polymerase chain reaction (RT-PCR). The mRNA induction for the constitutive isozyme PGHS-1 was less than that for PGHS-2. The interleukin-6 (IL-6) mRNA was also increased (6.4- to 9.3-fold) in microgravity as compared to the ground controls. Since PGE2 and IL-6 are both known to play a role in osteoclast formation and bone resorption, these data provide molecular mechanisms that contribute to our understanding of microgravity-induced alterations in the bone resorption process.

Regulation of p16CDKN2 expression and its implications for cell immortalization and senescence

p16CDKN2 specifically binds to and inhibits the cyclin-dependent kinases CDK4 and CDK6, which function as regulators of cell cycle progression in G1 by contributing to the phosphorylation of the retinoblastoma protein (pRB). Human cell lines lacking functional pRB contain high levels of p16 RNA and protein, suggesting a negative feedback loop by which pRB might regulate p16 expression in late G1. By a combination of nuclear run-on assays and promoter analyses in human fibroblasts expressing a temperature-sensitive simian virus 40 T antigen, we show that p16 transcription is affected by the status of pRB and define a region in the p16 promoter that is required for this response. However, the effect is not sufficient to account for the differences in p16 RNA levels between pRB-positive and -negative cells. Moreover, p16 RNA is extremely stable, and the levels do not change appreciably during the cell cycle. Primary human fibroblasts express very low levels of p16, but the RNA and protein accumulate in late-passage, senescent cells. The apparent overexpression of p16 in pRB-negative cell lines is therefore caused by at least two factors: loss of repression by pRB and an increase in the number of population doublings.

Clinical evaluation of a five-zone refractive multifocal intraocular lens

PURPOSE

To evaluate the clinical performance of a five-zone refractive multifocal intraocular lens (AMO, model MPC-25NB, Array).

METHODS

We performed a retrospective clinical trial of 31 cataract patients (mean age 64.3 years). The parameters studied were intraoperative and postoperative complications, distance and near visual acuity, spectacle use, decreased number of corneal endothelial cells, contrast sensitivity, percentage of glare disability, near binocular vision, and depth of focus.

RESULTS

Intraoperatively, iris damage occurred in two eyes (4.2%), vitreous loss in one eye (2.1%), and consecutive rupture of Zinn's zonule and vitreous in one eye (2.1%). Postoperatively, posterior capsule opacification was observed in two eyes (4.2%), temporary intraocular pressure increase in one eye (2.1%), and cystoid macular edema in one eye (2.1%). Uncorrected distance visual acuity of 20/40 or better was achieved by 34 of 37 eyes (91.9%) with less than 1.5 diopters of preoperative keratometric astigmatism; best corrected distance acuity of 20/20 or better was achieved by 41 of 45 eyes (91.1%). Near visual acuity with distance correction of 20/40 or better was achieved by 29 of 43 eyes (67.4%). These data were compared retrospectively with data from control patients who received monofocal lenses, and no significant differences in the decreased number of corneal endothelial cells were found. Mean contrast sensitivities were within normal range for all spatial frequencies. Percentage of glare disability and near binocular vision were within normal limits.

CONCLUSIONS

Eyes implanted with the five-zone refractive multifocal lens showed better near visual acuity than control eyes and compared favorably in other aspects of visual function, indicating that these lenses are effective and safe.

Lens epithelial cell migration onto the posterior capsule in vitro

PURPOSE

To investigate lens epithelial cell (LEC) proliferation on the posterior capsule in an in vitro model.

SETTING

Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan.

METHODS

We cultured the cells remaining on the postoperative capsular bag and expanded the capsule with an open poly(methyl methacrylate) ring to simulate actual postoperative conditions. Using human and rabbit cadaver eyes, we monitored the migration and proliferation of LECs onto the postoperative capsular bag by time-lapse videomicroscopy.

RESULTS

The remaining viable cells migrated onto the posterior capsule through the equator and directly from the anterior capsule. The cells typically proliferated in a monolayer because of contact inhibition of cell movement and division, but they proliferated in a multilayer at some regions where nonviable cells had accumulated and there were capsular folds.

CONCLUSION

A means to block both routes of cell expansion must be developed to prevent LEC migration onto the posterior capsule.

Lens epithelial cell proliferation onto the intraocular lens optic in vitro

PURPOSE

To determine how lens epithelial cells (LECs) proliferate onto an intraocular lens (IOL) after extracapsular cataract surgery.

SETTING

Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan.

METHODS

We cultured the capsular bags retaining LECs of eight human eye-bank eyes and six rabbit eyes that had had extracapsular lens extraction with in-the-bag implantation of a poly(methyl methacrylate) (PMMA) IOL and a PMMA ring. Cell proliferation onto the IOL optic was monitored by a time-lapse video system.

RESULTS

Cells proliferated onto the IOL optic via the anterior capsulotomy margin, the inner surface of the anterior capsule, and the posterior capsule. They formed cell sheets similar to the membranes observed in clinical cases.

CONCLUSIONS

Since the cells proliferated from the anterior capsule as well as from the posterior capsule onto the IOL optic, the membranes observed clinically on the IOL optic may be LEC sheets.

The helix-loop-helix protein Id-1 and a retinoblastoma protein binding mutant of SV40 T antigen synergize to reactivate DNA synthesis in senescent human fibroblasts

Normal somatic cells of higher organisms do not divide indefinitely. After a finite number of divisions, normal cells irreversibly cease proliferation by a process termed replicative or cellular senescence. Replicative senescence is controlled by multiple, dominant-acting genes about which very little is known. The only genes known to reactivate DNA synthesis in senescent cells are viral oncogenes encoding proteins that bind and inactivate the p53 and retinoblastoma (pRb) tumor suppressor proteins. SV40 T antigen is the best studied of these viral oncoproteins. T[K1] is a T antigen point mutant that selectively is defective in binding pRb and the pRb-related proteins p107 and p130. We show that T[K1] stimulated quiescent human fibroblasts to synthesize DNA nearly as well as wild-type T but was incapable of stimulating senescent cells. We tested several growth regulatory genes that are repressed in senescent cells for ability to restore activity to T[K1]. These included c-fos, c-jun, Id-1, Id-2, E2F-1, and cdc2. Only the helix-loop-helix (HLH) protein, Id-1, restored the ability of T[K1] to reactivate DNA synthesis in senescent cells. This activity of Id-1 was not shared by Id-2, a related protein, and depended on an intact HLH domain. It did not appear that Id-1 interacted directly with pRb or p107. Constitutive Id-1 expression failed to rescue proliferating cells from growth inhibition by pRb, p107, or p130, and failed to interact with pRb in the yeast two hybrid system. Because Id proteins negatively regulate basic-HLH (bHLH) transcription factors, we suggest that senescent cells express one or more bHLH factor that cooperates with pRb, or pRb-related proteins, to suppress proliferation.

Induction of anti-tumor immunity by mouse tumor cells transfected with mouse interleukin-12 gene

Interleukin-12 (IL-12) is a heterodimeric cytokine. In order to transduce both cDNAs for p35 and p40 of IL-12 in the tumor cells, a polycistronic retroviral vector was constructed by inserting the internal ribosome entry site gene of encephalomyocarditis virus between two cDNAs. On the other hand, two cDNAs were sequentially transfected in the tumor cells. Both polycistronic gene transfectants and double transfectants produced biologically active mouse IL-12. IL-12-expressing tumor cells were all rejected in syngeneic mice, and induced cytotoxic T lymphocyte activity. The capacity to induce anti-tumor memory may depend on the amount of IL-12 produced by the transfectants, because the relatively higher IL-12 producer tumor cell line induced the anti-tumor memory in the rejected mice, but the lower producer did not.

Increase in expression levels of interferon-inducible genes in senescent human diploid fibroblasts and in SV40-transformed human fibroblasts with extended lifespan

The normal human fibroblast line, TIG-3 which senesces at around 80 population doubling levels (PDLs), expressed interferon (IFN)-inducible genes such as 6-16, 2', 5'-oligoadenylate synthetase (2,5-A) and HLA B7 near the end of the proliferative lifespan. Other normal fibroblast line such as MRC-5 also expressed IFN-inducible genes when senesced. Clones transformed with SV40 T-antigen, which extended their proliferative lifespan by about 20-30 PDLs, also expressed IFN-inducible genes during their extended life. Anti-IFN-beta antibodies added in culture medium repressed the expression of IFN-inducible gene in both normal senescent and life-extended SV40-transformed cells. IFN-beta repressed DNA synthesis in normal TIG-3 and induced IFN-inducible genes in both normal and SV40-transformed TIG-3. Conditioned medium recovered from life-extended SV40-transformed cells contained IFN-beta, but not IFN-alpha, IFN-gamma or TNF-alpha and possessed an activity that inhibited DNA synthesis of young TIG-3. Addition of anti-IFN-beta antibodies into the medium enhanced the serum-induced DNA synthesis of near senescent (91% lifespan completed) TIG-3, while it neither induced DNA synthesis in fully senescent TIG-3 nor extended the proliferative lifespan of TIG-3. These results suggest that normal and SV40-transformed human fibroblasts increase expression of IFN-beta with increasing proliferative age especially near the end of their lifespan resulting in induction of IFN-inducible genes and possibly in growth repression.

Suppression of mammary epithelial cell differentiation by the helix-loop-helix protein Id-1

Cell proliferation and differentiation are precisely coordinated during the development and maturation of the mammary gland, and this balance invariably is disrupted during carcinogenesis. Little is known about the cell-specific transcription factors that regulate these processes in the mammary gland. The mouse mammary epithelial cell line SCp2 grows well under standard culture conditions but arrests growth, forms alveolus-like structures, and expresses beta-casein, a differentiation marker, 4 to 5 days after exposure to basement membrane and lactogenic hormones (differentiation signals). We show that this differentiation entails a marked decline in the expression of Id-1, a helix-loop-helix (HLH) protein that inactivates basic HLH transcription factors in other cell types. SCp2 cells stably transfected with an Id-1 expression vector grew more rapidly than control cells under standard conditions, but in response to differentiation signals, they arrested growth and formed three-dimensional structures similar to those of control cells. Id-1-expressing cells did not, however, express beta-casein. Moreover, 8 to 10 days after receiving differentiation signals, they lost three-dimensional organization, invaded the basement membrane, and then resumed growth. SCp2 cells expressing an Id-1 antisense vector grew more slowly than controls; in response to differentiation signals, they remained stably growth arrested and fully differentiated, as did control cells. We suggest that Id-1 renders cells refractory to differentiation signals and receptive to growth signals by inactivating one or more basic HLH proteins that coordinate growth and differentiation in the mammary epithelium.

Postoperative membranous proliferation from the anterior capsulotomy margin onto the intraocular lens optic

We performed slitlamp microscopy and specular microscopy in 15 patients who had cataract surgery to determine the clinical course of postoperative membranous proliferation from the anterior capsulotomy margin onto the intraocular lens optic. Membranous proliferation observed in 11 of the 15 eyes eventually resolved in 10 eyes. We speculate that lens epithelial cells were the origin of the membrane.

Contrast visual acuities in cataract patients. III. Changes of contrast acuity profiles in normal and pathological eyes

We compared pre- and postoperative visual acuities in 45 cataract patients without ocular pathology except lens opacity (group 1) and 20 patients with ocular pathologies and lens opacity (group 2) using Variable Contrast Visual Acuity Charts. Charts 1 and 4 have 90% contrast; chart 4 has white optotypes on a black background (reverse polarity), charts 2 and 3 have 15% and 2.5% contrast, respectively. The mean preoperative visual acuities of groups 1 and 2 measured with the high-contrast Landolt optotypes ranged from 0.02-0.80 and 0.22-0.40, respectively. Visual acuity improvements between the pre- and postoperative periods ranged from 1.37-1.61 and 0.52-1.24 octaves in groups 1 and 2, respectively, with the different charts. Visual acuity improvement was poorest with chart 3. The group 1 mean preoperative visual acuity measured with chart 2 was 1.11 octaves lower than with chart 1. In group 2, the visual acuity reduction was 1.81 octaves. The relation between the visual acuities measured with the high-contrast intermediate-contrast optotypes are important for predicting postoperative visual acuity improvement. An abnormal contrast acuity profile may indicate the presence of additional ocular pathologies.

Regulation of two E2F-related genes in presenescent and senescent human fibroblasts

Several mammalian genes expressed in late G1 are positively regulated by E2F, a heterodimeric transcription factor. Genes encoding two E2F proteins, E2F-1 and DP-1, were regulated differently during the cell cycle and replicative senescence of normal human fibroblasts. In presenescent cells, E2F-1 mRNA was cell-cycle regulated, appearing a few hours before S phase. By contrast, DP-1 mRNA was constitutively expressed, independent of position in the cell cycle. After a finite number of divisions, normal cells enter a state of irreversible growth arrest termed senescence. Many genes remain mitogen-inducible in senescent cells; there are, however, exceptions, including several late G1 genes potentially regulated by E2F. Senescent cells expressed DP-1 at the presenescent level, but did not express E2F-1 mRNA. Senescent cells were also markedly deficient in E2F binding activity associated with the dihydrofolate reductase promoter. E2F-1 and DP-1 expression vectors only weakly induced DNA synthesis in quiescent or senescent human cells and immortal murine NIH3T3 cells, although the E2F-1 vector stimulated DNA synthesis in immortal murine A31 cells, and transactivated E2F-responsive promoters in NIH3T3 cells. The results suggest that senescent cells may fail to express late G1 genes due to repression of E2F-1, leading to a deficiency of E2F activity. Furthermore, although E2F-1 stimulates DNA synthesis in some cells, other cells, including normal human fibroblasts, require additional factors.

Preparation of a subtractive cDNA library enriched in cDNAs which expressed at a high level in cultured senescent human fibroblasts

Subtracted cDNA library was prepared by subtracting [cDNA from young growing SV40-transformed human fibroblasts] from [cDNA from growing SV40-transformed fibroblasts in extended lifespan]. Isolated cDNA clones which expressed at high level in life-extended transformed cells also expressed at high level in normal senescent fibroblasts but did at low level in growing and growth-arrested young cells. Neither fibronectin nor procollagen cDNA was isolated. This cDNA library is useful for isolation of senescent-specific cDNA species which express at high level in normal senescent cells but at low level in growing and growth-arrested young cells, avoiding growth-arrest-specific cDNAs.

Id-related genes encoding helix-loop-helix proteins are required for G1 progression and are repressed in senescent human fibroblasts

Three complete cDNA clones encoding Id-related helix-loop-helix (HLH) proteins lacking a basic region were isolated from a pcD2 cDNA expression library prepared from TIG-3 human diploid fibroblasts (HDF). Of these cDNAs (Id-1H, Id-1H', and Id-2H), two (Id-1H and Id-1H') appeared to be derived by alternative RNA splicing. Id-1H and Id-2H seem to be human homologues of mouse Id-1 and Id-2, respectively, and have potential to encode 154 and 135 amino acid proteins. The Id-1H and Id-2H mRNAs were barely detectable in quiescent early passage HDF; serum coordinately induced both mRNAs, with two peaks of expression, in early and late in G1. Antisense oligomers complementary to Id-1H and Id-2H mRNA prevented early passage HDF from entering the S phase of the cell cycle. The treatment of serum-stimulated early passage cells with the antisense Id-1H oligomer completely abolished Id-1H. In senescent cells, serum barely induced the Id-1H and Id-2H mRNAs, although the levels of c-myc expression induced were similar in early passage and senescent cells. The expression levels of these Id genes vary among immortal human cell lines. Both genes were overexpressed in VA4 SV40-transformed lung fibroblasts and EJ-1 bladder carcinoma cells, while these genes were expressed at a very low level in SVts8 cells derived from SV40 tsA-transformed TIG-3 cells. SVts8 cells may acquire some function redundant to Id proteins. HT1080 fibrosarcoma cells expressed the Id-1H gene but not the Id-2H gene, suggesting these Id genes may subserve redundant functions.

Review of laser treatment at Keio University Eye Clinic

Between 1978 and 1992, 5310 eyes in 4317 cases were treated by laser photocoagulation at our clinic. Argon, krypton and dye lasers with slit lamp microscope were used 7556 times for 4446 eyes. Main indications included diabetic retinopathy, retinal vein occlusion, retinal break and glaucoma. For treatment of these diseases, argon blue-green and green laser were chosen in majority of cases. Macular diseases were treated most frequently by krypton laser. Endophotocoagulation by argon laser during vitreous surgery was performed in 399 eyes mainly with diabetic retinopathy, retinal detachment and retinal vein occlusion for 7 years. Treatment by Nd: YAG laser was done in 465 eyes for 5 years and more than 90% of cases were performed capsulotomy for after-cataract. Numbers of cases treated by any kinds of laser is increasing with the years.

Identification of a universal B cell epitope on DNA topoisomerase I, an autoantigen associated with scleroderma

OBJECTIVE

To investigate the distribution of B cell autoepitopes of human DNA topoisomerase I (topo I), an autoantigen associated with scleroderma.

METHODS

A complementary DNA clone, T1B, was used to produce recombinant proteins of topo I as beta-galactosidase fusion proteins. Immunoreactivity to these fusion proteins was then tested in 35 anti-topo I-positive sera from patients with scleroderma, by immunoblotting, enzyme-linked immunosorbent assay, and double immunodiffusion.

RESULTS

One epitope was found to be universally recognized by all sera tested. Thirty-two of the samples recognized multiple antigenic regions, but sera from the remaining 3 patients recognized only this universal epitope, and in longitudinal studies of 1 of these 3 patients, the serum recognized only this epitope for more than 2 years, even though multiple, potent, antigenic regions were found on topo I.

CONCLUSION

Recognition of multiple epitopes in most patients suggests that the topo I molecule itself would drive the autoimmunity on topo I. However, antigen-driven autoimmunity could not explain the production of the monoreactive anti-topo I antibody seen in the 3 patients. We thus hypothesize that there is a process whereby recognition of the universal epitope by cross-reaction develops into antigen-driven autoimmunity.

DNA-DNA subtractive cDNA cloning using oligo(dT)30-Latex and PCR: identification of cellular genes which are overexpressed in senescent human diploid fibroblasts

We previously reported an efficient method for subtractive cDNA cloning using oligo(dT)30-Latex and polymerase chain reaction (PCR) (E. Hara et al., Nucleic Acids Res. 19, 7097-7104, 1991). The subtraction was performed by hybridization between mRNA of cell type B and the cDNA made from mRNA of cell type A using an oligo(dT)30 primer covalently linked to Latex particles in an Eppendorf tube. The mRNA common to both types of cells could be removed by a brief centrifugation. In the present paper, the method was improved by using the sense strand DNA instead of mRNA for hybridization to cDNA covalently linked to the particles to minimize mRNA degradation and by optimizing the hybridization condition. The sense strand DNA was made from cDNA-oligo(dT)30-Latex by asymmetric PCR. Using the improved method, a subtractive cDNA library with longer cDNA inserts was successfully constructed with higher probability than the original method.

Protein phosphorylation required for the formation of E2F complexes regulates N-myc transcription during differentiation of human embryonal carcinoma cells

The human embryonal carcinoma (EC) cell line NEC14 can be induced to differentiate morphologically by the addition of 10(-2) M N,N'-hexamethylene-bis-acetamide (HMBA). The N-myc gene is expressed at a high level in the undifferentiated cells, but the level decreased steeply after 12-24 h HMBA treatment, returning to its original level after 48 h. The alteration in the N-myc level was well correlated with the formation of complexes with the E2F motif in the N-myc promoter region, and no complex was formed with cell extracts prepared from cells treated with HMBA for 12-24 h. The absence of E2F complexes during this period was caused by an inhibitor generated by a phosphatase reaction. Treatment of the 12-h extract with a cyclic AMP-dependent protein kinase resulted in the formation of E2F complexes, and treatment of the undifferentiated (0 h) and 48-h extracts with a calf intestinal phosphatase abolished complex formation completely. An inhibitor generated by the 0-h extract after treatment with a phosphatase inhibited E2F complex formation by the untreated 0-h extract in the presence of phosphatase inhibitors, okadaic acid and sodium vanadate. One of the two E2F complexes in the undifferentiated cells contained cyclin A, but the complex with similar mobility, formed after the transient decrease in the N-myc level, did not.

[Quantitative cytochemical analysis of T1 breast cancer]

The authors attempted to estimate the relationship between three biological parameters (nuclear DNA content, PCNA (proliferating cell nuclear antigen)/cyclin, HER-2/neu oncoprotein) and lymph node metastasis. We evaluated 37 breast cancers which were less than 2 cm in maximum dimension. Quantitative analysis was performed using a CAS 200 Image Analysis System, after Feulgen staining and immunochemical staining using anti-PCNA/cyclin monoclonal antibody and anti-HER-2/neu oncoprotein polyclonal antibody. In lymph node-negative cases 20.0% were aneuploid, while in lymph node-positive cases 58.8% were aneuploid. A total of 20.0% lymph node-negative cases were in the high proliferation group, as opposed to 52.9% of lymph node-positive cases. This analysis revealed a significant relationship between cell proliferation and lymph node metastasis. Analysis of the expression of HER-2/neu oncoprotein revealed no significant relationship between overexpression of HER-2/neu oncoprotein and lymph node metastasis, but the expression of HER-2/neu oncoprotein was significantly related to a shorter relapse-free survival.

Mechanism of induction of cellular DNA synthesis by the adenovirus E1A 12S cDNA product

The mechanism of induction of DNA synthesis in quiescent rat 3Y1 cells by the adenovirus E1A gene was investigated using the 3Y1 derivative cell lines g12-21, gn12RB1, and gn12RB2. The g12-21 cells express the E1A 12S cDNA and the latter two cells express both the E1A 12S cDNA and the human retinoblastoma susceptibility (Rb) gene at different levels in response to dexamethasone (dex). The cDNA sequences of E1A-inducible cell cycle-dependent genes, clone 3 and clone 16, were isolated by differential screening of a cDNA library constructed from dex-treated g12-21 cells. The quiescent 3Y1 cells induced c-fos and c-myc expression within 2 h after serum stimulation and expressed clone 16 and clone 3 transiently at around 8 h before the onset of DNA synthesis (10 h). In contrast, the quiescent g12-21 cells treated with dex expressed a high level of E1A at 6 to 8 h after treatment and expressed clone 16 and clone 3 at around 8 h without stimulation of c-fos and c-myc expression, suggesting that E1A bypasses the cell cycle early in G1. The half-maximal rate of DNA synthesis was reached in a much shorter time in dex-treated g12-21 cells (12 h) than in serum-treated 3Y1 cells (18 h), suggesting that E1A also bypasses the cell cycle at the G1/S boundary. The gn12RB1 and gn12RB2 cells were unable to induce DNA synthesis in response to dex presumably due to lower levels of E1A expression, although gn12RB2 but not gn12RB1 cells could express clone 16 and clone 3. These results suggest that the level of E1A required for bypass at the G1/S boundary is higher than that required early in G1.

Subtractive cDNA cloning using oligo(dT)30-latex and PCR: isolation of cDNA clones specific to undifferentiated human embryonal carcinoma cells

The human embryonal carcinoma cell line NEC14 can be induced to differentiate by the addition of 10(-2)M N,N'-hexamethylene-bis-acetamide (HMBA). A subtractive cDNA library specific to undifferentiated NEC14 cells was constructed using oligo(dT)30-Latex and polymerase chain reaction (PCR). The method was designed to improve the efficiency of subtraction and the enrichment of cDNA clones corresponding to low abundance mRNAs. The single strand of cDNA was made from mRNA prepared from the HMBA-treated NEC14 cells using an oligo(dT)30 primer covalently linked to Latex particles. After removal of the mRNA template by heat-denaturation and centrifugation, the subtractive hybridization was carried out between the cDNA-oligo(dT)30-Latex and mRNA from untreated NEC14 cells. Unhybridized mRNA collected by centrifugation was hybridized repeatedly to the cDNA-oligo(dT)30-Latex and subtractive mRNA was converted to cDNA. The subtractive cDNA was then amplified by PCR and cloned into pBluescript II KS-. The cDNA library thus constructed consisted of approximately 10,000 independent clones with cDNA inserts of 1.7 Kb on average. Differential hybridization of these transformants indicated that approximately 3% of them contained cDNA inserts specific to the undifferentiated EC cells, some of which were derived from low abundance mRNAs.

Cooperative effect of antisense-Rb and antisense-p53 oligomers on the extension of life span in human diploid fibroblasts, TIG-1

Normal human diploid fibroblasts, TIG-1, which have a replicative life span of about 62 population doublings (PD), tended to senesce after about 50 PD with a gradual decrease in sensitivity to serum. Treatment of TIG-1 cells with the antisense-Rb oligomer, which completely depleted the retinoblastoma susceptibility gene product (RB), extended life span by about 10 PD. Treatment with the antisense-p53 oligomer alone had no effect; however, cotreatment with the antisense-Rb oligomer further potentiated the extension and the increased sensitivity to serum caused by the antisense-Rb oligomer alone, suggesting that p53 and RB function in separate, yet complementary pathways in signal transduction to senescence. The c-fos expression, which is presumed to be regulated negatively by RB, was not stimulated in partially senescent TIG-1 cells by treatment with the antisense-Rb oligomer.

Interaction of nuclear factors with the regulatory region of the N-myc gene during differentiation of human embryonal carcinoma cells

The human embryonal carcinoma cell line, NEC14, can be induced to differentiate by the addition of 10(-2) M N,N'-hexamethylene-bis-acetamide (HMBA). During the early stage of HMBA-induced differentiation, the level of N-myc expression decreased steeply and transiently, and then quickly returned to its original level after reaching a minimal level at 18 h after addition of HMBA. Nuclear run-on experiments indicated that this transient decrease is regulated at the transcription start point. To investigate the mechanism of this down-regulation, the 5'-flanking region of the human N-myc gene was cloned and sequenced. Computer analysis of the sequence revealed high homology with the 5'-flanking region of the mouse N-myc gene, especially (greater than 80%) in the region of nt positions -1777 to -1732, nt positions -763 to -501 and nt positions -260 to + 1. The patterns of protein binding to the upstream region during the early stage of NEC14 cell differentiation were analyzed by gel retardation assay. The DNA fragments VIII and X, containing the sequences of nt positions -1437 to -1237 and nt positions -1863 to -1710, respectively, formed the DNA-protein complexes which were greatly reduced in quantity in the cell extract prepared 18 h after the addition of HMBA. This reduction, however, was not observed with an extract similarly prepared from the NEC14 derivative cell line, H10, expressing the N-myc gene constitutively. These results suggest a causal connection between the complex formation and the high-level transcription of the N-myc gene.

A transient decrease in N-myc expression and its biological role during differentiation of human embryonal carcinoma cells

The human embryonal carcinoma (EC) cell line, NEC14 can be induced to morphologically differentiate by the addition of 10(-2) M N,N'-hexamethylene-bis-acetamide (HMBA) in vitro. The expression of several cellular oncogenes (c-onc) in NEC14 cells was examined after induction of differentiation by HMBA. The level of N-myc expression was the highest in undifferentiated cells but decreased transiently to less than 1/10 of the original level shortly after the induction of differentiation. To investigate the role of the transient decrease in N-myc level on NEC14 cell differentiation, a chimeric human N-myc gene in which transcription is initiated at the human beta-actin gene promoter was constructed and introduced into NEC14 cells. Several transformants expressing the exogenous N-myc gene constitutively were established. These transformants showed 10- to 70-fold increases in plating efficiency and shorter population doubling times as compared with the parental NEC14 cells. The transformants were hard to induce, spontaneously differentiated cells on the periphery of cell clusters in culture, unlike parental NEC14 cells, and took longer for HMBA-induced morphological differentiation. The populations of the cells expressing HLA and SSEA-1 antigens increased from 10%-20% to nearly 100% in NEC14 cells after the induction of differentiation, while the populations expressing these antigens increased only to 50%-60% in one of the transformants, S11. The transformants gained an increased tumorigenic potential in nude mice, and the tumors produced consisted exclusively of EC stem cells. These results suggest that the additional expression of the exogenous N-myc gene (increased about two-fold) confers the more transformed state on the cells.

Drug-induction decreases the mobility of cytochrome P-450 in rat liver microsomes: protein rotation study

Effect of drug-induction on the rotation of cytochrome P-450 and on lipid fluidity in rat liver microsomes was examined. Rotational diffusion of cytochrome P-450 was examined by observing the decay of absorption anisotropy, r(t), after photolysis of the heme.CO complex by a vertically polarized laser flash. Analysis of r(t) was based on a "rotation-about-membrane normal" model. Microsomal lipid fluidity was measured by observing fluorescence anisotropy of DPH incorporated in the lipid bilayer. The absorption anisotropy decayed within 2 ms to a time-independent value. Rotational diffusion of cytochrome P-450 was dependent on the drug-induction with PB, MC, and PCB when compared with non-induced CON-microsomes. The observed values for the normalized time-independent anisotropy r(infinity)/r(0) are r(infinity)/r(0) = 0.41 (CON-microsomes), 0.54 (PB-microsomes), 0.52 (MC-microsomes), and 0.57 (PCB-microsomes). The average rotational relaxation time phi = 580-690 microseconds was almost unchanged over all microsomes presently examined. A significantly high value of r(infinity)/r(0) = 0.41-0.57 implies the co-existence of mobile and immobile populations of cytochrome P-450. Based on the assumption that the heme tilts about 55 degrees from the membrane plane for all species of P-450s besides P-450PB, 59% (CON-microsomes), 46% (PB-microsomes), 48% (MC-microsomes), and 43% (PCB-microsomes), respectively, of the cytochrome P-450 in microsomes is calculated to be mobile. Upon drug-induction the microsomal membrane was fluidized to some extent as judged by the steady-state fluorescence anisotropy of 0.156 for CON-microsomes and 0.139-0.148 for drug-induced microsomes.(ABSTRACT TRUNCATED AT 250 WORDS)

[Immunohistochemical Study of 3-methylcholanthrene inducible cytochrome P-450 in the stomach and liver--a guide of postoperative chemotherapy in gastric cancer]

Immunohistochemical determination of 3-methylcholanthrene (MC) inducible cytochrome P-450 (MC-P-450) was investigated in rat and human tissue, and its clinical availability was discussed. Induced by MC, MC-P-450 in rat liver and stomach was well stained immunohistochemically, showing clear contrast against control without induction. The staining intensity in the tissue was correlated with the amount of tissue MC-P-450 which was determined previously by electrophoretical and biochemical technics. By the same immunohistochemical method MC-P-450 in human liver and stomach was also detectable. The staining grade of MC-P-450 in human liver and stomach was different from each person. However, its intensities in liver and stomach in the same individual showed clear correlation with p less than 0.02. Since MC-P-450 in liver plays a major role in drug metabolism, the proof of correlation between staining degree of the resected stomach and hepatic tissue would provide useful clue in gastric cancer for postoperative administration of masked compounds activated by MC-P-450.

Two-step transformation of rat 3Y1 cells by the adenovirus E1A and E1B genes

The transformation of rodent cells by the adenovirus E1A and E1B genes was very efficient when these genes were physically linked. When they were cleaved, the transformation became very inefficient. To clarify this difference, the chimeric E1B genes in which either the adenovirus enhancer or the human beta-actin promoter was linked to the 5' side of the E1B gene were introduced into rat 3Y1 cells. The saturation density of these cell lines (eB or APrB) was similar to that of parental 3Y1 cells. When eB or APrB cell lines were supertransfected with the E1A gene, discrete dense foci were developed after 5-6 weeks, while the supertransfection of 3Y1 derivative cell lines, in which the enhancer-unlinked E1B gene was introduced, did not develop any dense foci. Analysis of the E1A and E1B transcripts in these cell lines indicated that the E1B gene is efficiently expressed in the presence of the E1A gene products if the enhancer is linked to the E1B gene and that an increased level of E1B proteins is required for an efficient expression of the E1A gene. These results indicated that E1A and E1B genes in separate pieces of DNA are capable of cooperatively transforming 3Y1 cells if appropriate cis-acting elements are attached and high-level expressions are achieved.

A rapid and efficient cloning method with a solid-phase DNA probe: application for cloning the 5'-flanking region of the gene encoding human fibronectin

A rapid and efficient gene-cloning method was developed using oligodeoxyribonucleotide probes (approx. 30-mer) immobilized by their 5' terminal to the gel (LiChrosphare Si1000; used for high-performance liquid chromatography). The method allowed us to concentrate DNA fragments having a particular base sequence in an eppendorf tube with very high efficiency within 2 h. For example, genomic DNA encoding the human fibronectin gene (fn) was concentrated by this method and cloned into lambda Charon4A vector. Screening of the concentrated genomic DNA library for the 5' region of the human fn gene showed that approx. 30% of 3000 recombinant phages tested were positive clones. Various factors affecting cloning efficiency were investigated.

Diurnal change in digestion and absorption of sucrose in vivo in rats

To clarify the physiological significance of circadian rhythmic changes in the activity of intestinal sucrase, the activity of digestion and absorption of sucrose in vivo were assessed during the daytime and the nighttime in rats fed ad libitum. When the jejunum was perfused at night with a solution containing sucrose in situ, the disappearance rate of sucrose from the lumen was higher than when perfused during the daytime, in parallel with the day/night difference in sucrase activity. The early response of plasma glucose to oral sucrose load in unanesthetized free-moving rats was also greater during the nighttime than the daytime. It was concluded that the digestion and absorption rate of sucrose shows circadian fluctuations under normal physiological conditions.

Molecular cloning and characterization of cellular genes whose expression is repressed by the adenovirus E1a gene products and growth factors in quiescent rat cells

Several cDNA clones of cellular genes, whose expression is repressed by the adenovirus type-12 E1a gene products, were isolated from a rat 3Y1 cell cDNA library by differential plaque hybridization with labeled cDNA probes prepared from 3Y1 and the derivative cell line expressing the E1a gene constitutively. The changes in the levels of these gene transcripts during cell-cycle progression from G0 to G1 to S phase were analyzed with 3Y1 cells and gMA cell lines, derived from 3Y1 cells, in which the expression of the E1a gene or its 13S, 12S cDNA can be switched on by the addition of dexamethasone. Quantitation of the transcripts by Northern-blot hybridizations and by nuclear run-on experiments revealed the following. (i) The level of clone-53 mRNA (which turned out to be the fibronectin (FN)-coding mRNA) is very high in resting gMA cells and decreased rapidly after switching on of the E1a gene or its 13S, or 12S cDNA. (ii) The addition of serum or platelet-derived growth factor to resting 3Y1 cells also resulted in a rapid decrease in the FN mRNA level, but the addition of epidermal growth factor (EGF) had little or no effect. (iii) The level of clone-56 mRNA in gMA cells was not affected by the induction of the E1a gene expression; however, the addition of EGF to resting gMA or 3Y1 cells resulted in a decrease of this mRNA after a 12- to 16-h lag period. Induction of the E1a gene expression in gMA cells treated with EGF shortened the lag period. The addition of serum to resting 3Y1 cells decreased the clone-56 mRNA level without a significant lag period.

Induction of cell cycle progression by adenovirus E1A gene 13S- and 12S-mRNA products in quiescent rat cells

Rat 3Y1 cell lines that express either adenovirus type 12 E1A 13S mRNA or 12S mRNA in response to dexamethasone treatment were established by introduction of recombinant vector DNA containing the E1A 13S- or 12S-mRNA cDNA placed downstream of the hormone-inducible promoter of mouse mammary tumor virus. These cell lines were growth arrested, and the induction of cell cycle progression was analyzed by flow cytometry after switch on of the cDNA by the addition of dexamethasone. The results indicate that the 13S- or 12S-mRNA product alone has the ability to cause progression of the cell cycle at a similar rate. The simultaneous addition of epidermal growth factor accelerated the rate of cell cycle progression in the transition from the G0/G1 phase to the S phase.

Response of superoxide anion production by guinea pig eosinophils to various soluble stimuli: comparison to neutrophils

The effect of various soluble stimuli on the superoxide production by guinea pig eosinophils was studied in comparison to neutrophils. Phorbol myristate acetate, A23187, digitonin, NaF, concanavalin A (Con A), and cytochalasin E stimulated eosinophils and neutrophils to release O2-. The O2- production by these active agents, excluding Con A and cytochalasin E, was much greater in eosinophils than in neutrophils. Formyl-Met-Leu-Phe stimulated the O2- production in neutrophils but not in eosinophils. Neither histamine nor Val/Ala-Gly-Ser-Glu stimulated the O2- production in both types of leukocytes. A23187- or Con A-stimulated O2- production was greatly enhanced by cytochalasin B pretreatment in neutrophils but not in eosinophils. Lineweaver-Burk analysis of NADPH oxidase in particulate fractions showed that eosinophils possessed the same Km values as neutrophils and greater Vmax values than neutrophils, suggesting that eosinophils have a similar, but more active, O2- -generating enzyme system than neutrophils.

[Serum levels and clinical evaluation of CA 19-9 in various diseases]

We evaluated the clinical significance of serum CA 19-9 in various cancers, benign diseases and healthy controls. The percentage of positive cases for CA 19-9 (higher than 37 U/ml) was 83% in pancreas cancer, 78% in biliary tract cancer and 75% in urinary tract cancer. Benign diseases showed a low frequency of positive cases for CA 19-9, and their serum levels of CA 19-9 were low. Benign diseases with high serum levels of CA 19-9 were rarely seen, but they were easy to differentiate from malignant tumors by simultaneous examination of other tumor markers. In cancer patients with high serum levels of CA 19-9, CA 19-9 showed a weak positive correlation to CEA and ferritin.

Immunochemical study on the contributions of two molecular species of microsomal cytochrome P-450 to the metabolism of benzo(a)pyrene by rat liver microsomes

The roles of two species of cytochrome P-450, the major cytochrome P-450 components of liver microsomes of phenobarbital-treated rats (PB-P-450) and 3-methylcholanthrene-treated rats (MC-P-448), were studied in the metabolism of benzo(a)pyrene in rat liver microsomes in vitro. Benzo(a)pyrene was incubated with polychlorinated biphenyl-treated rat liver microsomes, in which PB-P-450 and MC-P-448 constituted about 45 and 24% of the total cytochrome P-450, respectively. Then the metabolites were separated into those soluble in ethyl acetate and in water, and those covalently bound to protein. Using high-pressure liquid chromatography, the ethyl acetate-soluble metabolites were separated into three major groups, phenols, quinones, and dihydrodiols, including peaks of three unknown materials. Addition of anti-MC-P-448 immunoglobulin to the reaction mixture completely inhibited the formation of all ethyl acetate-soluble metabolites. In contrast, anti-PB-P-450 immunoglobulin did not inhibit the formations of 4,5-dihydro-4,5-dihydroxybenzo(a)pyrene and 3-hydroxybenzo(a)pyrene; partially inhibited the formations of 7,8-dihydro-7,8-dihydroxybenzo(a)pyrene, 9, 10-dihydro-9, 10-dihydroxybenzo(a)pyrene, and the three unknown materials; and caused 30 to 40% enhancement of the formations of 9-hydroxy-benzo(a)pyrene and benzo(a)pyrene-3,6-dione and 80% enhancement of that of benzo(a)pyrene-1,6-dione. Antibody against MC-P-448, but not against PB-P-450, also caused 75% inhibition of the formation of water-soluble metabolites and 85% inhibition of formation of benzo(a)pyrene metabolites covalently bound to protein. These results show that MC-P-448 is important in the metabolism of benzo(a)pyrene.

Impaired insulin secretion after oral sucrose and fructose in rats

The effects of sucrose and fructose on responses in plasma glucose and insulin to glucose given orally and/or iv were examined in unanesthetized, unrestrained rats. The plasma insulin response to oral administration of sucrose or a mixture of glucose and fructose was much lower than that to oral glucose despite the fact that plasma glucose responses to these administrations were similar. Oral administration fructose had no effect on the insulin response to iv infusion of glucose. Intravenous infusion of fructose also did not affect the plasma glucose and insulin responses to oral administration of glucose. The inhibitory effect of oral fructose on the insulin response to oral glucose was reversed by oral administration of soybean oil, which is known to stimulate insulin secretion induced by iv glucose. We conclude that the inhibitory effect of fructose on insulin secretion is mediated by some signals generated in the gastrointestinal tract.

A method for studying the enteroinsular axis in unanesthetized and unrestrained rats

A method for studying the enteroinsular axis of rats under conditions comparable to those in experiments on human subjects was developed by chronically implanting an oral tube and two cardiac catheters into rats. These implantations were easy to perform and made it possible to give glucose and other stimulatory agents orally and/or intravenously and to take sequential blood samples without anesthetizing the rats or disturbing their movements. In this way, it was possible to confirm that oral loads of glucose and fat potentiate the insulin response induced by hyperglycemia.

Diurnal changes in plasma glucose and insulin responses to oral glucose load in rats

The plasma glucose and insulin responses to an oral load of glucose were examined in the daytime and at night in unanesthetized and unrestrained rats. In rats that had been fed during the nighttime (2200-0400 h) every day for 2 wk, the plasma glucose and insulin responses were significantly greater (P less than 0.05) at night (2200-2400 h) than in the daytime (1000-1200 h). In rats that had been fed during the daytime (1000-1600 h), the plasma glucose and insulin responses were greater in the daytime than at night (P less than 0.05). It was concluded that the diurnal variations in the plasma glucose and insulin responses to an oral glucose load are closely related to the feeding schedule on which the rats are kept.