Fiber spin-profile designs for producing fibers with low polarization mode dispersion

Using coupled-mode theory, we develop a theoretical model to analyze the effects of fiber spin profiles on polarization mode dispersion (PMD). Constant, sinusoidal, and frequency-modulated spin profiles are examined, and phase-matching conditions are analyzed. Our analysis shows that PMD can be reduced effectively by use of frequency-modulated spin profiles.

Non-destructive analysis of the conformational changes in human lens lipid and protein structures of the immature cataracts associated with glaucoma

Previous study has supposed a possible mechanism of exacerbating cataract formation in cataractous human lens capsules induced by hypertension or glaucoma. To clarify the glaucoma-induced cataract formation of the eyes lens, changes in the human lens lipid and protein structures of immature cataractous patients with or without glaucoma were investigated. Two normal lenses, ten immature cataractous lenses without any complication and four immature cataractous lenses with glaucoma were used after surgical operation. Each de-capsulated human lens sample was sliced with a number 15 surgical blade. The intact nuclear lens regions were used for non-destructive analysis. The lens lipid and protein structures, as well as compositions of these lens samples, were determined using a Fourier transform infrared (FTIR) microspectroscopy with second-derivative, de-convolution and curve-fitting methods. The results indicate that the IR spectrum of glaucomatous lenses appeared as a shoulder only at 2853 cm-1, thus the composition of the symmetric CH2 stretching band at 2853 (2852) cm-1 decreased more significantly in glaucomatous lens to only one half of that in normal and immature cataractous lenses. The composition of the asymmetric CH3 stretching band at 2965 cm-1 for normal lens decreases markedly from 32 to 20% for immature cataractous lenses with or without glaucoma. The compositional ratio of component at 2965 cm-1 to component at 2928 (2930) cm-1 for normal lenses was about 0.702, and that ratio for cataractous lenses without glaucoma was 0.382 but for glaucomatous lenses was 0.377. The maximum peak position of amide I band for IR spectra of the normal lens, immature cataractous lenses without complications or glaucomatous lenses appeared respectively at 1632, 1630 or 1622 cm-1, assigned to beta sheet structure. A marked difference in peak intensity of amide I band for the normal lenses and immature cataractous human lenses with or without glaucoma was observed. The peak intensity ratio of amide I/amide II (1632/1545 cm-1) for normal lenses was in the range of 2.20-2.33, whereas in the spectra of immature cataractous lenses without glaucoma this ratio (1630/1545 cm-1) was 1.28-1.41 but was 1.04-1.13 for glaucomatous lens in the intensity ratio of 1622/1545 cm-1. The intensity of the glycogen bands in the wavenumber region 1135-1076 and 1069-1032 cm-1 was found to increase for the immature cataractous lenses with or without glaucoma, as compared with the normal ones. The peaks ranging from 1633 to 1610 cm-1 assigned to beta-sheet structure also exhibited a pronounced compositional difference, particularly in glaucomatous lenses. The human lens lipid and protein secondary structures were more affected by glaucoma. Higher protein side chains and reduced lipid content contributed predominantly to the CH stretching vibrations of normal lens structure, whereas high lipid content and less protein side chains dominated the CH stretching vibrations of cataractous lenses with or without glaucoma. Decrease alpha-helix and random coil structures but enhanced beta-sheet structure in the immature cataractous human lens induced by glaucoma might result from the formation of intermolecular hydrogen-bonding insoluble protein aggregates that modify the secondary structure of protein in lenses.

Thermal stability and reversibility of secondary conformation of alpha-crystallin membrane during repeated heating processes

Reflectance FT-IR/DSC microspectroscopy was first used to study the structural conformation of alpha-crystallin membranes in the heating-cooling-reheating cycle. The thermotropic transition and the changes in secondary structure of alpha-crystallin membrane during heating and reheating processes were investigated. A thermal transition ranging between 50 and 70 degrees C with a midpoint at 60 degrees C for the alpha-crystallin membrane was easily obtained from the three-dimensional plots of the reflectance FT-IR spectra as a function of temperature. The secondary structural components of the alpha-crystallin membrane were modified step-by-step with the increase of temperature from 25 to 120 degrees C, but restored to original values after cooling to 25 degrees C. During the heating process, the compositions of the alpha-helix, random coil and beta-sheet structure decreased with temperature, but the content of the beta-turn structure increased, however, all of them were restored after cooling. The absence of significant alteration in the secondary structures for the alpha-crystallin membrane before and after the first-heating process strongly suggests the high thermal stability and reversibility of alpha-crystallin. Interestingly, the thermal behavior of the first-heated alpha-crystallin membrane during the reheating process exhibited a unique thermal behavior with two transitional temperatures at 35-50 and 55-70 degrees C. The reflectance FT-IR/DSC microscopic data indicated that alpha-crystallin in the membrane state had higher thermal stability and reversibility.

Integrality of benign prostatic hyperplasia tissues after transurethral thermotherapy evidenced by transmittance fourier transform infrared spectroscopy combined with thermal analyzer

Transmittance Fourier transform infrared microspectroscopy combined with differential scanning calorimetry was used to simulate the clinically transurethral thermotherapy of benign prostatic hyperplasia (BPH) by in vitro isothermal determination. The simulative study to the thermotherapy of epithelium or stroma in BPH tissue was performed at 47 degrees C for 3 h, like clinical therapy. Whether thermal treatment can induce changes in the secondary structure of epithelium or stroma in BPH tissue was investigated. The results indicate that the epithelium and stroma in BPH tissue had different protein secondary structures, due to the different compositions of the epithelium and stroma. No significant change was evidenced in secondary structure for each sample either before or after isothermal study, suggesting the integrality and safety of BPH thermotherapy in a 47 degrees C for 3 h treatment course.

Assessment of protein conformation in human benign and malignant astrocytomas by reflectance Fourier transform infrared microspectroscopy

The secondary structure and composition of protein in the tissues of benign and malignant astrocytomas were determined by reflectance Fourier-transform infrared (FT-IR) microspectroscopy. The peak maximum of IR spectra of the tissues from recurrent malignant astrocytoma markedly appeared at higher frequency (1655 or 1663 cm(-1)), which was significantly different from that of the tissues from benign astrocytoma at 1651 cm(-1) and tissues from malignant astrocytoma at 1652 cm(-1). Malignant astrocytoma indicated slightly different compositions in the protein secondary structure from benign astrocytoma. However, a significant increase in beta-turn structure but a marked decrease in beta-sheet and random coil structures were observed in the protein secondary structure of the recurrent malignant astrocytoma. The phenomenon was more pronounced in recurrent malignant astrocytoma pretreated with radiation and chemotherapy. The rapid cell proliferation and cell differentiation of malignant astrocytoma with or without recurrence might be the possible explanations for the different compositions of protein conformational structures.

The human HNRPD locus maps to 4q21 and encodes a highly conserved protein

The hnRNP D protein interacts with nucleic acids both in vivo and in vitro. Like many other proteins that interact with RNA, it contains RBD (or "RRM") domains and arg-gly-gly (RGG) motifs. We have examined the organization and localization of the human and murine genes that encode the hnRNP D protein. Comparison of the predicted sequences of the hnRNP D proteins in human and mouse shows that they are 96.9% identical (98.9% similar). This very high level of conservation suggests a critical function for hnRNP D. Sequence analysis of the human HNRPD gene shows that the protein is encoded by eight exons and that two additional exons specify sequences in the 3' UTR. Use of two of the coding exons is determined by alternative splicing of the HNRPD mRNA. The human HNRPD gene maps to 4q21. The mouse Hnrpd gene maps to the F region of chromosome 3, which is syntenic with the human 4q21 region.

Suspected malignant hyperthermia during isoflurane anesthesia--a case report

We present a patient with thyroid cancer, who developed respiratory acidosis, tachycardia and hyperthermia during isoflurane anesthesia. Malignant hyperthermia was suspected on the basis of clinical manifestation and laboratory finding. With early diagnosis and treatment the patient survived the episode.

Nuclear Rad51 foci induced by DNA damage are distinct from Rad51 foci associated with B cell activation and recombination

Lipopolysaccharide (LPS) is a B cell mitogen which can stimulate murine primary B cells to proliferate and carry out immunoglobulin heavy chain class switch recombination. LPS can also function as an endotoxin, which may cause DNA damage and apoptosis in certain types of cells. We have previously reported that LPS-activated primary murine B cells contain nuclear foci that stain brightly with anti-Rad51 antibodies (Li et al. (1996) Proc. Natl. Acad. Sci. USA 93, 10222-10227). We have now analyzed Rad51 nuclear foci induced in both primary and immortalized B cells by treatment with the DNA damaging agent, methyl methanesulfonate (MMS). We have found that, in LPS-cultured primary B cells, MMS treatment increases the fraction of cells containing Rad51 foci and induces formation of a very high number of foci per cell. The foci induced by MMS treatment are small, punctate, and numerous; in contrast, the foci induced by LPS activation are large, brightly staining, and relatively few in number. In LPS-cultured primary B cells, Rad51 relocalizes during the cell cycle, and large, brightly staining nuclear foci are present in only restricted stages of the cell cycle. Rad51 foci similar to those present in LPS-activated primary B cells are also observed in immortalized B cells lines cultured in the absence of LPS. These foci are unaltered in number or appearance by culture with LPS, but treatment of immortalized B cell lines with MMS induces foci which are small and punctate in staining, like those induced by MMS in primary B cells. These data show that distinctive Rad51 foci are induced by DNA damaging agents and cell activation and that the response to DNA damage may involve pathways distinct from those associated with B cell activation and switch recombination.

Infra-red (ATR/FT) spectroscopic study on the conformational structure of the isolated human gastric mucus pretreated with ethanol

In order to investigate the conformational structure of isolated human gastric mucus gel pretreated with or without ethanol, gel samples were determined by attenuated total reflection/Fourier transform-infra-red (ATR/FT-IR) microspectroscopy. The result indicates that the secondary structure-dependent amide I band and the glycoprotein region were significantly different in the gastric mucus gels pretreated with and without 40% ethanol. The structural composition of beta-sheet structure (1640-1600 cm-1) increased from 38.48 to 55.08% (+16.6%) after 6-hour pretreatment with 40% ethanol, but the beta-turn structure, (1660-1700 cm-1) decreased from 41.38 to 24.29% (-17.05%). The peak area ranging from 1180 to 1000 cm-1, assigned to the glycoprotein region, was also different after pretreatment with ethanol for 6 h. The higher peak area of the carbohydrate band was obtained in the frequency region between 1000 and 1040 cm-1 and 1100 and 1180 cm-1 for mucus gel pretreated with 40% ethanol. However, the peak area ranging from 1100 to 1040 cm-1 mainly due to the symmetric phosphate stretching mode of proteins was somewhat lower for the ethanol-pretreated mucus gel than the native mucus gel. This result strongly reveals that ethanol significantly modified the conformational structure of proteins and carbohydrates of gastric mucus gel. We propose that the dehydration and interference of hydrophobic interactions in the isolated mucus gel after pretreatment with ethanol might be responsible for this conformational change.

Fourier transform infrared spectral evidences for protein conformational changes in immature cataractous human lens capsules accelerated by myopia and/or systemic hypertension

The possible changes in protein structures of the cataractous human lens capsules of the immature patients with myopia and/or systemic hypertension have been investigated using Fourier transform infrared (FT-IR) microspectroscopy. Second-derivative and deconvolution methods have been applied to obtain the position of the overlapping components of the amide I band and assign them to different secondary structures. Changes in the protein secondary structure and composition of amide I band were estimated quantitatively from Fourier self-deconvolution and curve fitting algorithms. The results indicate that myopia and/or systemic hypertension were found to significantly modify the protein secondary structure of the cataractous human lens capsules to increase the beta-type structure and random coil and decrease the alpha-helix structure. Myopia-induced conformational change in triple helix structure was more pronounced. In conclusion, myopia and/or systemic hypertension seem to modify the conformation of the protein structures in cataractous human lens capsule to change ionic permeation through lens capsule to accelerate the cataract formation of senile patients.

The preemptive effect of pre-incisional bupivacaine infiltration on postoperative analgesia following lower abdominal surgery under epidural anesthesia

BACKGROUND

In attempts to reduce central sensitization after tissue injury, the concept of preemptive analgesia has evolved. The aim of the present study was to evaluate the preemptive effect of pre-incisional infiltration of the surgical area with bupivacaine on pain following lower abdominal surgery under epidural anesthesia.

METHODS

Sixty female patients scheduled for lower abdominal surgery under epidural anesthesia with bupivacaine were randomly divided into two Groups (n = 30, each). Five minutes before surgical incision, patients in Group 1 received subcutaneous infiltration of the proposed surgical area with 30 ml of 0.125% bupivacaine (with 1/200,000 epinephrine), while those in Group 2 received 30 ml of isotonic saline (with 1/200,000 epinephrine) infiltration. Postoperatively, pain was assessed for 48 h by a visual analogue scale of pain at rest, during cough and by cumulative morphine doses (self-administered by patient-controlled analgesia).

RESULTS

The pain score at rest was significantly lower in Group 1 than in Group 2 from the 6th h to the 24th h postoperatively. The cough-associated pain score was lower in Group 1 than in Group 2 from the 6th h to the 28th h postoperatively. Furthermore, Group 1 consumed less morphine than did Group 2 from the 6th h to the 24th h postoperatively.

CONCLUSIONS

The results indicate that pre-incisional infiltration of surgical area with bupivacaine markedly decreases the intensity of pain following lower abdominal surgery under epidural anesthesia.

Nucleolin is one component of the B cell-specific transcription factor and switch region binding protein, LR1

LR1 is a B cell-specific, sequence-specific DNA binding activity that regulates transcription in activated B cells. LR1 also binds Ig heavy chain switch region sequences and may function in class switch recombination. LR1 contains two polypeptides, of 106 kDa and 45 kDa, and here we report that the 106-kDa component of LR1 is nucleolin. This identification, initially made by microsequence analysis, was verified by showing that (i) LR1-DNA binding activity increased in B cells transfected with a nucleolin cDNA expression construct; (ii) LR1-DNA binding activity was recognized by antibodies raised against recombinant human nucleolin; and (iii) in B cells transfected with epitope-tagged nucleolin expression constructs, the LR1-DNA complex was recognized by the anti-tag antibody. Nucleolin is an abundant nucleolar protein which is believed to play a role in rDNA transcription or organization, or rRNA processing. Homology between nucleolin and histone H1 suggests that nucleolin may alter DNA organization in response to cell cycle controls, and the nucleolin component of LR1 may therefore function to organize switch regions before, during, or after switch recombination. The demonstration that nucleolin is a component of a B cell-specific complex that binds switch region sequences suggests that the G-rich switch regions may have evolved from rDNA.

Developmental specificity of immunoglobulin heavy chain switch region recombination activities

To understand the regulation of enzymes that carry out immunoglobulin heavy chain class switch recombination, we have assayed recombination of extrachromosomal substrates carrying switch region sequences in cell lines representing different stages of lymphoid cell development. Both pre-B and mature B cell lines supported switch substrate recombination, but B cell lines derived from later stages of cell development did not. Recombination did not occur in an erythroid or a macrophage line. Most recombination junctions in the substrates recovered from transfection of pre-B and B cells mapped to heterogeneous sites within the S mu and Sgamma regions, as do chromosomal switch junctions. Some recombination did occur in T cell lines, but most recombination junctions involved an upstream promoter and did not map preferentially to S regions. Culture of the pre-B cell lines PD31 and 70Z/3 with LPS increased recombination two-fold, to levels approaching those observed in LPS-cultured primary B cells. These results show that the full complement of factors necessary for switch recombination is present only in cells representing a limited spectrum of B cell development and that LPS, which can activate resting splenic B cells to carry out chromosomal recombination, can also stimulate recombination activity in immortalized pre-B cell lines.

Possible mechanism of exacerbating cataract formation in cataractous human lens capsules induced by systemic hypertension or glaucoma

To clarify the role of the lens capsule in cataract formation, changes in the protein conformational structure of immature cataractous lens capsules from patients with systemic hypertension or glaucoma have been investigated, as compared to normal lens capsules. The protein secondary structure and composition of these capsular samples were determined using Fourier transform infrared microspectroscopy with second-derivative, deconvolution and curve-fitting methods. We found that the composition of both random coil and beta-type (beta-sheet and beta-turn) structures in the immature cataractous human lens capsules was increasingly induced by systemic hypertension or glaucoma, but alpha-helix content clearly decreased, leading to the alteration of protein conformational structures in lens capsules. A possible pathway of cataract formation exacerbated by systemic hypertension or glaucoma is discussed. According to the results, we propose that systemic hypertension or glaucoma induce changes in the protein conformational structures of the lens capsule, then cause alteration of membrane transport and permeability for ions, and finally increase intraocular pressure, resulting in the exacerbation of cataract formation. The effect on the conformational structure of cataractous human lens capsules is more pronounced for systemic hypertension than for glaucoma. The present study implies that systemic hypertension or glaucoma can exacerbate cataract formation in senile patients by modifying the protein secondary structures in the lens capsule.

Rad51 expression and localization in B cells carrying out class switch recombination

Rad51 is a highly conserved eukaryotic homolog of the prokaryotic recombination protein RecA, which has been shown to function in both recombinational repair of DNA damage and meiotic recombination in yeast. In primary murine B cells cultured with lipopolysaccharide (LPS) to stimulate heavy chain class switch recombination, Rad51 protein levels are dramatically induced. Immunofluorescent microscopy shows that anti-Rad51 antibodies stain foci that are localized within the nuclei of switching B cells. Immunohistochemical analysis of splenic sections shows that clusters of cells that stain brightly with anti-Rad51 antibodies are evident within several days after primary immunization and that Rad51 staining in vivo is confined to B cells that are switching from expression of IgM to IgG antibodies. Following switch recombination, B cells populate splenic germinal centers, where somatic hypermutation and clonal proliferation occur. Germinal center B cells are not stained by anti-Rad51 antibodies. Rad51 expression is therefore not coincident with somatic hypermutation, nor does Rad51 expression correlate simply with cell proliferation. These data suggest that Rad51, or a highly related member of the conserved RecA family, may function in class switch recombination.

Outcomes after detection of metastatic carcinoma of the colon and rectum in a national hospital system

BACKGROUND

Selected institutions have reported good results with resection for metastatic carcinoma of the colon and rectum, but the number of patients and the expenses required to identify the resectable metastases are unknown.

STUDY DESIGN

A retrospective survival analysis was performed using computerized files of the United States Department of Veterans Affairs hospitals from 1988 to 1992, complete through December 1994. Survival was calculated from diagnosis or resection until death. Patients without a death record were assumed to be alive.

RESULTS

In all, 22,715 patients underwent colectomy for carcinoma, and 12,150 presented with metastatic carcinoma of the colon and rectum, of which 6,607 had hepatic and 2,659 had pulmonary metastases. Only 2,040 patients with hepatic (and 514 with pulmonary metastases had no prior or other metastatic sites. Of the patients with hepatic metastases, 887 had a computed tomography (CT) scan or liver biopsy, or both, for diagnosis; 133 hepatic and 76 pulmonary resections were done. The projected five-year survival rate after hepatic resection was 26 percent, mean survival was 31 months, and the 30-day mortality rate was 4 percent. After pulmonary resection, results were similar: 36 percent, 38 months, and 3 percent, respectively. The 887 patients with hepatic metastases documented by CT scan or biopsy results has a mean survival of 11 months, and less than 2 percent were alive or unavailable for follow-up examination at analysis. Estimated surveillance costs alone averaged $1.3 million per life saved by resection, or $203,000 per year of added life.

CONCLUSIONS

Resection of isolated colorectal metastases produced 70 five-year survivors (hepatic, n=42, pulmonary, n=28) and accounted for 446 additional years of patient life over that expected without resection.

Fully planar proton-exchanged lithium niobate waveguides with grating taps

A two-step proton-exchange process to produce waveguides and gratings in lithium niobate is described. In both steps, mixtures of lithium benzoate and benzoic acid are used. The fabricated components are characterized at 0.633 and 0.422 µm. In particular, we observe that the light intensity diffracted into the air by the grating is ~0.5% of that in the waveguide.

Polarization dependence of grating-assisted waveguide Bragg reflectors

Polarization dependence of grating-assisted waveguide Bragg reflectors is studied theoretically by use of a vectorial coupled-mode theory based on the ideal mode expansion. A criterion for choosing ideal waveguides is proposed. Experimental results obtained from an ion-exchanged waveguide with an etched grating agree well with the theory.

Nucleotide sequence of the Buzura suppressaria single nucleocapsid nuclear polyhedrosis virus polyhedrin gene

A portion of the genome of the Buzura suppressaria (Lepidoptera) single nucleocapsid nuclear polyhedrosis virus (BsSNPV) containing the polyhedrin gene was sequenced. An open reading frame of 738 nucleotides encoded a protein of 246 amino acids and represented the polyhedrin gene. A conserved TAAG motif, associated with transcriptional start sites in other polyhedrin genes, was identified 51 nucleotides upstream of the BsSNPV polyhedrin gene. A putative polyadenylation signal, AATAAA, was found immediately downstream of the polypeptide termination codon. Comparison of the amino acid sequence of BsSNPV polyhedrin with other NPV polyhedrins and granulosis virus granulins showed that the BsSNPV polyhedrin was most closely related to the polyhedrin of Orgyia pseudotsugata (Lepidoptera) SNPV and most distantly related to the polyhedrin of Neodiprion sertifer (Hymenoptera) SNPV.

Uncorrected SCE levels of Bloom syndrome cells by cell hybridization with malignant cells with 14q32 structural abnormalities

Because 14q markers were frequently observed in lymphoid malignancies, we have done cell hybridization between Bloom syndrome (BS) cell lines and various malignant cell lines with and without 14q abnormalities, and noticed that BS cell hybrids which had been fused with cell lines involving 14q32 abnormalities did not decrease high SCE values in BS cells, as was observed in those of hybrids between homozygote BS. A constant fragile site was observed at 14q23 in bromodeoxyuridine (BrdU)-labeled hetero and homo BS cells. We considered the possible linkage of BrdU-induced fragility and SCE in BS cells.

Human papillomavirus, human cytomegalovirus and oncogene C-myc in cervical carcinoma and cervicitis

HPV-16 and HCMV DNA homologous sequence and the status of cellular oncogene C-myc DNA were examined in uterine cervical diseases with dot blot hybridization and Southern hybridization. The results showed a positive rate of 70.8% in HPV-16 and 38.7% in HCMV in cervical carcinoma, and that of 36.7% in HPV-16 and 16.7% in HCMV in cervicitis. C-myc DNA was widely detectable in uterine cervical carcinoma, but the manifestation of translocation, deletion or overexpression in cervical carcinoma was frequent. The value of these findings in the development of cervical carcinoma is discussed.

Inhibition of neutrophil priming and tyrosyl phosphorylation by cepharanthine, a nonsteroidal antiinflammatory drug

Receptor-mediated superoxide (O2.-)-generation and tyrosyl phosphorylation of neutrophil proteins, such as 58, 65, 84, 108 and 115 kDa, were enhanced by priming cells with granulocyte colony stimulating factor (G-CSF) [Akimura, K. et al. Arch. Biochem. Biophys. 298: 703-709, 1992]. To elucidate the possible involvement of tyrosyl phosphorylation of neutrophil proteins in the enhancing mechanism of O2.- generation, the effect of cepharanthine, a biscoclaurine alkaloid that inhibits phorbol 12-myristate 13-acetate (PMA)- and receptor-mediated O2.- generation, on the priming of human peripheral neutrophils (HPPMN) was studied. Both enhancement of formyl-methionyl-leucyl- phenylalanine (FMLP)-mediated O2.- generation and tyrosyl phosphorylation of some neutrophil proteins, i.e., 115, 108 and 84 kDa proteins, by HHPMN after treatment with G-CSF were strongly inhibited by cepharanthine in a concentration- and treatment-time-dependent manner. In contrast, inhibition of PMA-mediated O2.- generation by cepharanthine was weak and independent of treatment time. These results suggest that cepharanthine might inhibit the priming step of neutrophil activation concomitantly with its inhibition of the tyrosyl phosphorylation of some neutrophil proteins that might underlie the mechanism for priming of neutrophils with G-CSF.

Nd:MgO:LiNbO(3) waveguide laser and amplifier

We report efficient operation of a channel waveguide laser and a channel waveguide amplifier in Nd:MgO:LiNbO(3). For the laser a cw output power of 2.9 mW was obtained for 23.6 mW of absorbed pump power. The absorbed pump power at threshold was 1.5 mW, and a slope efficiency of 13% was achieved. For the amplifier a small-signal gain of 7.5 dB was achieved for 22 mW of coupled pump power.

A unique human mutant B-lymphoblastoid cell line (ataxia telangiectasia) which exhibits increased sister-chromatid exchange retaining hypersensitivity to neocarzinostatin and bleomycin

Chromosome aberrations and sister-chromatid exchanges (SCEs) were examined in 4 ataxia telangiectasia (AT)-derived B-lymphoblastoid cell lines (B-LCLs) (AT-S, AT-SHI, AT-SHI B13A and AsHa) following treatments with neocarzinostatin (NCS) and bleomycin. All of these cell lines exhibited extremely high frequencies of chromosome aberrations with the NCS and bleomycin treatments. Among them, AsHa, a mutant B-LCL originating from an AT patient, showed high frequencies of SCEs under high bromodeoxyuridine (BrdU) concentrations retaining hypersensitivity to NCS and bleomycin with regard to chromosome aberrations. A clear BrdU dose-dependent increase in SCEs (9.85 SCEs/cell at 40 micrograms/ml, 36.65 SCEs/cell at 100 micrograms/ml on average) in this mutant was observed. When AsHa mutant cells were treated with NCS (0.02 microgram/ml) and/or bleomycin (5.0 micrograms/ml) under 40 micrograms/ml BrdU (minimum BrdU concentration for sister-chromatid differential staining), SCE levels increased from 9.85 (baseline level) to 21.1 with NCS and 20.5 with bleomycin, in a dose-dependent manner. These observations indicate that AsHa is a unique AT-derived mutant cell clone with a high SCE character retaining the original hypersensitivity to bleomycin and NCS.

Bromodeoxyuridine (BrdU) template and thymidine pool effects on high frequencies of sister-chromatid exchange (SCE) in Bloom syndrome cells and a mutant cell line (AsHa) originated from ataxia telangiectasia

The effect of bromodeoxyuridine (BrdU)-substituted DNA template and thymidine (dT) pool on excess sister-chromatid exchanges (SCEs) was studied in Bloom syndrome (BS) cells and an ataxia telangiectasia (AT)-derived mutant cell line (AsHa). When BS endomitotic cells were labeled with low and high (or high and low) BrdU concentrations during S1 and S2, only the BrdU concentration during S1 phase affected the observed SCE. In BS cells about a 10-fold increase in SCEs occurs during or following replication on a BrdU-substituted template (high-high and high-low BrdU labeling) relative to the normal DNA template. SCEs decreased to about half in AsHa cells labeled with various BrdU doses (40, 60, 80 and 100 micrograms/ml) during only S1, compared with those labeled during S1 and S2. Co-cultivation of AsHa and BS cells resulted in a significant reduction in SCE level from 70 to 13-17 in BS cells, lowered the BrdU concentrations necessary for sister-chromatid differential (SCD) staining from 40 to 10 micrograms/ml with normal SCE level and resulted in decreased level of SCEs at high BrdU concentrations (80-100 micrograms/ml) (12-14 SCE) in AsHa cells, compared with the originally increased SCE level (36.65 SCE at 100 micrograms/ml) without co-culture. However, co-cultivation between AsHa and normal cells lowered the BrdU dose necessary for SCD staining from 40 to 30 micrograms/ml; the dT pool possibly balanced at this level, which is clearly higher than that at co-cultivation between AsHa and BS cells. The reason for the very high BrdU doses needed to achieve SCD would seem to be that AsHa cells have high levels of thymidylate (TMP) synthetase, which maintain a large endogenous thymidine pool. This has been confirmed by direct measurement. These findings strongly support that excess and decreased dT pools are closely related to the condition necessary for high SCE induction.