CD exciton chirality method for determination of the absolute configuration of beta-hydroxy-alpha-amino acid derivatives

The absolute configuration of beta-hydroxy-alpha-amino acids was studied by CD exciton chirality method using 7-diethylaminocoumarin-3-carboxylate as a red-shifted chromophore. The CD spectra of bischromophoric derivatives of (S)-serine and (2S,3R)-threonine methyl esters (2 and 7) were compared with those of acyclic vic-aminoalcohols and diols (3--6 and 8--9). This study indicates that the polar carboxylate group of beta-hydroxy-alpha-amino acids makes them a unique subclass of vic-aminoalcohols. By combining the data of CD and NMR coupling constants, we are able to correlate their preferred conformer B and positive CD to the corresponding absolute configuration.

Use of bacterially expressed EBNA-1 protein cloned from a nasopharyngeal carcinoma (NPC) biopsy as a screening test for NPC patients

EBV serological tests have been used for many years as accessory diagnostic predictors of nasopharyngeal carcinoma (NPC). To increase the sensitivity and specificity of the NPC detection rate, a novel enzyme-linked immunosorbent assay (ELISA) was established using a bacterially-expressed GST-EBNA-1 protein, containing the EBNA-1 sequence cloned from an NPC patient. Serum samples were collected from age- and gender-matched patients with NPC, community control subjects and hospital control patients and tested using this ELISA. The positivity rates were 78.7% (247/314) in NPC, 11.5% (28/244) in hospital controls and 3.8% (10/263) in the community control group. These serum samples were also tested for IgA anti-VCA antibodies and their ability to neutralize EBV DNase and the sensitivities of the anti-VCA antibody and DNase-neutralization tests also were analyzed. The optimum combination is VCA plus EBNA-1, which can identify 92.5% (287/310) of NPC patients, and shows a specificity of 92.7% (242/261) for normal individuals.

Reproductive outcomes and infant health in adolescent pregnancy in Taichung city

The study aimed at determining the reproductive outcomes, caregiving condition, and children's growth and development compared to those born to adult mothers. All adolescent mothers ages less than 20 years and their first born infants matched with adults mothers aged 20-29 years and their first born infants at the same neighborhoods in Taichung city in 1997 were included in this study. The results showed that there is no significant difference between children of adolescent mothers and of adult mothers in terms of the prevalence of prematurity and congenital diseases, but the children of teenage mothers have a significantly higher prevalence of low birth weight (adjusted odds ratio = 1.61, 95% CI = 1.21-2.80) than those of compared mothers. Multiple logistic regression was used to find out the risk factors for low birth weight, and found that maternal weight gain and hospitalization or not during pregnancies in mothers are significant risk factors for low birth weight. We can not find difference between the two groups in caregiving condition, such as breast feeding duration, accidental injury, diseases necessitating admission, and vaccination rates. Also there is no difference in the rate of failure to thrive or delayed developmental milestones. A long-term follow-up study on the prognosis for the adolescent mothers and their children is recommended.

Identification and cellular localization of human PFTAIRE1

We isolated a novel member of putative Cdc2-related serine/threonine protein kinases from a Hela cell cDNA library. The cDNA encodes a protein of 469 amino acids, sharing 95% identities with the mouse PFTAIRE1 throughout the entire protein sequence. This gene was designated human PFTAIRE1. The gene was located at human chromosome 7q21.13 with radiation hybrid polyermase chain reaction (RH-PCR) analysis. By Northern blotting analysis, an approximately 6 kb transcript is detected with varied levels of expression of the hPFTAIRE1 in 16 human tissues. The hPFTAIRE1 was highly expressed in brain, pancreas, kidney, heart, testis and ovary. The transcript was also detected at lower level in other tissues, except in spleen and thymus where the transcript was hardly detected. The protein was fused to the C-terminus of a green fluorescent protein (GFP) and ectopically expressed in Hela cells. The florescence microscope results indicated that the hPFTAIRE1 exhibits cytoplasmic distribution.

Identification of stress-responsive genes in Streptococcus mutans by differential display reverse transcription-PCR

Streptococcus mutans, which causes dental caries in the human oral cavity and occasionally causes infective endocarditis in the heart, withstands adverse environmental stress through diverse alterations in protein synthesis. Differential gene expression in response to environmental stress was analyzed by RNA fingerprinting using arbitrarily primed PCR with a panel of 11mer primers designed for differential display in Enterobacteriaceae. Dot and Northern blot hybridization confirmed that the transcription of several genes was up- or down-regulated following exposure to acid shock from pH 7.5 to 5.5. RNA of a gene designated AP-185 (acid-stress protein) was induced specifically by acid treatment, while RNA of GSP-781 (general-stress protein) was up-regulated significantly when bacteria were exposed to high osmolarity and temperature, as well as low pH. The deduced amino acid sequence of AP-185 shares homology (78% identity) with branched-chain amino acid aminotransferase. Cloning and sequence analysis of GSP-781 revealed a potential secreted protein of a molecular mass of about 43 kDa and with a pI predicted to be 5.5. Transcriptional levels of another gene, designated AR-186 (acid-repressed protein), which encodes putative aconitase, were repressed by acid treatment but were enhanced by plasma or serum components. Analogous results were identified in icd and citZ genes, and repression of these genes, along with AR-186, was also observed when they were exposed to high osmolarity and temperature. These results indicate that differential regulation of specific genes at the transcriptional level is triggered by different stress and that genes responsible for glutamate biosynthesis in the citrate pathway are coordinately regulated during the stress response of S. mutans.

[Soft tissue profile changes after maxillary protraction in complete unilateral cleft lip and palate patients]

OBJECTIVE

The purpose is to evaluate the soft tissue profile changes in patients with complete unilateral cleft lip and palate treated after maxillary protraction.

METHODS

12 patients with complete unilateral cleft lip and palate were treated using maxillary protraction. Lateral cephalometric films were taken before and after treatment. Soft tissue profile changes were evaluated by comparing the difference of soft tissue landmarks between two films.

RESULTS

After maxillary protraction, the convex of nose (S-Ns-PRN) increased significantly (P<0.001), the convex of maxillary soft tissue was increased by 3.8 degree (P<0.01). The convex of middle face changed significantly (P<0.01). In mandible angle S-Ns-SM was decreased one degree (P>0.05). Vertically, there was no significant difference in upper face height (P>0.05). Total face height increased significantly (P<0.01).

CONCLUSION

After treatment of maxillary protraction, the soft tissue profile in patients with complete cleft lip and palate improved significantly.

Phase signal coupling induced n:m phase synchronization in drive-response oscillators

We have studied phase synchronization between two identical Rössler oscillators connected in the drive-response configuration by a single phase signal. Before the transition to phase synchronization, the distribution of the time interval between consecutive 2pi jumps shows several sharp peaks. With a strong phase signal coupling, the n:m phase synchronization between the oscillators can be achieved. For the n (not equal) m phase synchronizing state, some values of coupling strength result in a phenomenon characterized by a reduction in the mean amplitude of the response termed amplitude reduction. In these regions, the mean rotation speed of the response remains approximately constant while the locking ratio n:m varies.

Domain specific monoclonal anti-factor VIII antibodies generated by inclusion body-renatured factor VIII peptides

Production of monoclonal anti-factor VIII (FVIII) antibodies was hampered by the availability of FVIII proteins devoid of albumin and the von Willebrand factor (vWF). We showed a successful way to generate domain specific anti-FVIII antibodies by using a series of Escherichia coli expressed FVIII fusion peptides. A total of eight fusion peptides were synthesized to cover almost the entire coding region of FVIII. All except one of the fusion peptides were insoluble and became aggregated as inclusion bodies. Purification and refolding of the peptides were accomplished by solublizing them with denaturants and dialyzing them in appropriate buffers, this being followed by chromatography of the refolded fractions on a metal-ion chelating column. These purified FVIII fusion peptides were used individually or as a pool to immunize mice and generate antibodies. Three monoclonal antibodies, D2, E6 and B12, were obtained. D2 recognizes a region (residues 1680-1703) of the light chain of FVIII, E6 recognizes a fragment (residues 744-1021) in the heavy chain, and B12, the A1 domain (residues 89-326). Both D2 and B12 inhibited >80% FVIII function. The affinities (k(A)) of the antibodies for FVIII were 1.62x10(7) M(-1) for D2 and 2.2x10(8) M(-1) for E6. Although B12 is inhibitory, it did not show a strong binding affinity with FVIII. The specificity of D2 and E6 for FVIII was demonstrated by immunoprecipitation of the FVIII protein in full-length recombinant FVIII (rFVIII) supplemented FVIII-deficient plasma, but not in FVIII-deficient plasma alone. An enzyme-linked immunosorbant assay (ELISA) using D2 or E6 was designed to detect plasma FVIII. The system may be useful in monitoring FVIII in cultured supernatants and in mouse models for gene therapy experiments.

[Knocking out of CEK2 and CSK1 affect the phenotype of Candida albicans]

We have cloned two novel mitogen-activated protein kinase (MAPK) genes CEK2 and CSK1 from Candida albicans strain SC5314. The heterozygous and homozygous cek 2 and csk 1 mutants were obtained by homologous recombination. The cek2 and csk1 null mutant strains CAJ3 and CAJ6 grew as wrinkled clonis on solid YPD medium. Expression of CEK2 gene in strain CAF3-1 repressed the filamentous growth of the strain weakly. Two-hybrid results showed Cek2 and Csk1 could not interact with Cph1 and Hst7 directly. Cek2 and Csk1 might cooperate with the filamentous transcriptional repressor Tup1.

Human T-cell responses to the glucosyltransferases of Streptococcus mutans

We previously reported differential humoral responses to glucosyltransferases (GTFs), with significantly higher saliva and serum antibody levels to GtfD than to GtfB or GtfC. To test the hypothesis that cellular immune responses to these molecules also may differ, peripheral blood mononuclear cell (PBMC) and T-cell proliferative responses in young adults and children with distinct genetic backgrounds were determined using purified recombinant GtfC and GtfD. PBMCs from all of the volunteers responded to GtfC and -D, but responses were directed predominantly towards GtfD and were major histocompatibility class II antigen dependent. A predominant T-cell response to GtfD, over GtfC, was detectable at various antigen concentrations ranging from 1 to 20 microg/ml and correlated with the differential serum immunoglobulin G (IgG) and salivary IgA antibody responses to the GTFs. Therefore, in naturally sensitized humans, Streptococcus mutans GTFs stimulate differential humoral and cellular immune responses, with the secreted form of GtfD eliciting a stronger response than the cell wall-associated form of GtfC.

Endogenous production of protoporphyrin IX induced by 5-aminolevulinic acid in leukemia cells

AIM

To explore the photosensitization of 5-aminolevulinic acid (ALA) in myeloid leukemia cell line.

METHODS

Using the technique of fluorescence spectra, the A LA induced protoporphyrin IX (Pp IX) was measured in myeloid leukemia JCS cells. Cofocal laser scanning microscopy (CLSM) combined with fluorescence organelle probe was used to detect the localization of Pp IX in JCS cells at the subcellular levels. MTT assay was used to measure the cell survival after light irradiation.

RESULTS

ALA successfully produced endogenous PpI X in leukemia JCS cells. PpIX was observed to be distributed in the cytoplasm and mitochondria was exhibited as the one of binding sites of PpIX. As a photosensitizer, PpIX initiated photodynamic reaction after light irradiation and effectively photodamaged leukemia cells.

CONCLUSION

ALA-based photosensitization could be used for inactivation of leukemia cells.

Specific alterations of U1-C protein or U1 small nuclear RNA can eliminate the requirement of Prp28p, an essential DEAD box splicing factor

While some members of the ubiquitous DExD/H box family of proteins have RNA helicase activity in vitro, their roles in vivo remain virtually unknown. Here, we show that the function of an otherwise essential DEAD box protein, Prp28p, can be bypassed by mutations that alter either the protein U1-C or the U1 small nuclear RNA. Further analysis suggests that the conserved L13 residue in the U1-C protein makes specific contact to stabilize the U1 snRNA/5' splice site duplex in the prespliceosome, and that Prp28p functions to counteract the stabilizing effect of the U1-C protein, thereby promoting the dissociation of the U1 small nuclear ribonucleoprotein particle from the 5' splice site. Thus, in addition to unwinding RNA, the DExD/H box proteins may affect RNA-RNA rearrangements by antagonizing specific RNA-stabilizing proteins.

[Correlation between the changes of soft and hard tissue after advanced Lefort I osteotomy in patients with cleft lip and palate]

OBJECTIVE

The purpose is to evaluate the correlation between the changes of soft and hard tissue after advanced Lefort I osteotomy in patients with complete unilateral cleft lip and palate.

METHODS

Lateral cephalometric films were taken from before and after operation. The same landmarks in two films were compared horizontally and vertically. The correlation ratio between changes of soft and hard tissue were analysed statistically.

RESULTS

After operation, the length of upper lip of the patients with CLP increased. The ratio between the movement of upper incisor and upper lip was 0.77 horizontally and 0.67 vertically, respectively.

CONCLUSION

The slope between hard and soft tissue was treated as ratio. It is more significant than the horizontal difference between soft and hard tissue, since correlative factor was contained in the slope.

Elevated expression of thyroid hormone receptor alpha 2 (c-erb A- alpha 2) in nasopharyngeal carcinoma

Differential display was used to identify genes differentially expressed between cultured normal nasal epithelial cells and nasopharyngeal carcinoma (NPC) cell lines. A 130 bp cDNA fragment showing homology with thyroid hormone receptor alpha2 (TR-alpha2 or c-erb A-alpha2) was identified in NPC cell lines. Northern blot analysis using the 130 bp cDNA fragment and a TR-alpha2 specific cDNA containing part of the coding region as probes, we were able to detect a 2.7 kb transcript corresponding to that of TR-alpha2 in NPC cell lines but not in normal nasal epithelial cells. RNA in situ hybridization was used to detect TR-alpha2 expression in clinical biopsies obtained from NPC patients and non-tumour controls. TR-alpha2 mRNA was detected in 1 out of 24 (4.2%) normal nasopharynx epithelium biopsies, in 5 out of 27 (18.5%) primary and 15 out of 24 (62.5%) recurrent tumours. The positive rate of TR-alpha2 expression in recurrent NPC biopsies was significantly higher than that in normal nasopharynx epithelium (P<0.00001). The relevance of the elevated expression of TR-alpha2 in the pathogenesis process of NPC was discussed.

Human peritoneal mesothelial cells produce nitric oxide: induction by cytokines

OBJECTIVE

To investigate the induction of nitric oxide synthase type II (iNOS) in human peritoneal mesothelial cells (HPMC) using cytokines and bacterial lipopolysaccharide (LPS).

DESIGN

Confluent monolayers of HPMC were exposed to cytokines [tumor necrosis factor alpha (TNFalpha), interleukin-1 beta (IL-1beta), interferon gamma (IFNgamma)] or LPS, individually or in various double and triple combinations, for 24-72 hours. Concentrations of nitrate and nitrite in the media were quantified using the Griess reaction and used as indirect indices of nitric oxide (NO) production. The expression of iNOS was assessed using reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blot.

RESULTS

Neither single cytokines nor LPS was able to induce iNOS mRNA or NO production. Both double combinations of TNFalpha + IFNgamma and IL-1beta + IFNgamma were able to induce iNOS mRNA expression, but only TNFalpha + IFNgamma induced significant NO production. The triple combination of TNFalpha + IFNgamma + IL-1beta induced even more NO production than TNFalpha + IFNgamma. There was no constitutive NO synthase type III (eNOS) expression in HPMC.

CONCLUSIONS

Certain combinations of cytokines could stimulate cultured HPMC to produce NO, and HPMC might be a source of intraperitoneal NO production during peritonitis.

Emerging homosexual conduct during hospitalization among chronic schizophrenia patients

OBJECTIVE

The study investigated the emerging homosexual conduct during hospitalization among chronic schizophrenia patients.

METHOD

We interviewed 55 male and 58 female chronic schizophrenic patients to investigate their sexual history before and after admission. Those patients were under 45 years old, without significant deteriorated cognitive function, lived in a homogeneous gender chronic ward and did not demonstrate homosexual behaviour before admission.

RESULTS

Nineteen patients (16.8%) reported having homosexual conducts during hospitalization. Their characteristics were: 1) having sexual experience before admission; 2) with younger age at first sexual experience; and 3) female patients having more sexual partners before admission.

CONCLUSION

A significant proportion of patients need a sexual outlet during long-term hospitalization. Sexual education and counselling are greatly needed.

Elevated topoisomerase I activity in cervical cancer as a target for chemoradiation therapy

OBJECTIVE

The aim of this study was to determine whether the activity of topoisomerase I (topo I), the target of the anti-neoplastic drug camptothecin (CPT), is elevated in cervical cancer and whether CPT can radiosensitize cervical tumors.

METHODS

The topo I activity of 11 normal cervix and 30 cervical carcinoma tumors was assayed by measuring the relaxation of supercoiled DNA. Subconfluent or postconfluent CaSki human cervical carcinoma cells were exposed to CPT (1-5000 ng/ml) and immediately X-irradiated (0-800 cGy). Cell survival was determined by clonogenic assay.

RESULTS

Mean topo I activity in cervical cancer (3.0 +/- 0.06 h(-1)) was significantly greater than in normal cervix tissue (0.29 +/- 0.06 h(-1)). Stage 3 and 4 cervical carcinoma specimens displayed a trend of greater topo I activity (5.88 +/- 3.7 h(-1)) than stage 1 and 2 tumors (2.57 +/- 0.47 h(-1)). No correlation between topo I protein levels and catalytic activity was found. Combined treatment of subconfluent CaSki cells with CPT and ionizing radiation resulted in additive killing of cells. Combined treatment of postconfluent CaSki cells with low doses of radiation (200 and 400 cGy) and 1 or 10 ng/ml CPT for 2 or 48 h produced significant cytotoxicity compared to CPT or radiation alone, which were ineffective at these doses.

CONCLUSIONS

Topo I activity is elevated in cervical cancer compared to normal cervix. The radiosensitivity of noncycling cells within cervical tumors may be increased by simultaneous treatment with low doses of CPT or other topo I inhibitors.

Epstein-barr virus nuclear antigen 2 retards cell growth, induces p21(WAF1) expression, and modulates p53 activity post-translationally

The Epstein-Barr virus (EBV) nuclear antigen 2 (EBNA2) has been shown to be required for promotion of cell-cycle progression in EBV-immortalized B-lymphocytes. However, other studies have indicated that EBNA2 alone, in the absence of other EBV genes, may retard cell growth. To resolve this discrepancy, we investigated the effect of EBNA2 on the growth of various cells, including EBV target nasopharyngeal carcinoma cells, NPC-TW01 and NPC-TW04. We found that EBNA2 could retard cell growth, in stable Vero, HEp-2, and U2OS cell clones expressing EBNA2, and in Vero, 293, NPC-TW01, and NPC-TW04 cells transiently transfected with EBNA2. While investigating the mechanism underlying the growth-retarding function of EBNA2, we found that EBNA2 induced p21(WAF1) expression in these cells. This induction of p21(WAF1) expression was mediated through p53. EBNA2 was found to stimulate p53 to bind to the p53-response element within the p21(WAF1) promoter, possibly by promoting p53 phosphorylation. This enhancement of p53 sequence-specific DNA-binding activity may be the mechanism through which EBNA2 activates the expression of p53-regulated genes, including p21(WAF1) and mdm-2. Together, these studies reveal a possible intrinsic function of EBNA2 in cell-growth regulation and elucidate a novel mechanism by which EBNA2 modulates transcription.

Physical association between the EBV protein EBNA-1 and P32/TAP/hyaluronectin

Epstein-Barr virus (EBV) nuclear antigen-1 (EBNA-1) is a protein expressed constitutively during EBV latency. It is required to support the replication of the EBV genome once per cell cycle via the latent origin of replication, oriP. EBNA-1 also can activate transcription through binding to the family repeats of oriP. We wished to identify candidate cellular protein(s) that may interact with EBNA-1 and mediate these functions. A 32-kd protein was co-immunoprecipitated with EBNA-1 from 293 cells using a monoclonal antibody EBNA.OT1x. The regions of EBNA-1 which interact with this protein were studied using two deletion clones and mapped to EBNA-1 residues 1-102 and 325-357. Deletion of this region was shown previously in a mutant of EBNA-1 which had dominant-negative effects on both DNA replication and transactivation assays. The 32-kd protein was found to react with a polyclonal antiserum against P32/TAP (HIV Tat associated protein), which is known to interact with other RNA binding proteins and the RNA splicing factor SF2. The function of P32 was therefore proposed to involve RNA processing. In addition, this molecule was recently identified as hyaluronectin, which binds hyaluronic acid. Because several reports documented that intracellular hyaluronic acid can potentially affect cell proliferation, the association between EBNA-1 and P32/TAP/hyaluronectin may help the maintenance of episomal viral DNA within proliferating cells.

Cloning, expression and chromosomal localization of human Ca2+/calmodulin-dependent protein kinase kinase

A human cDNA clone encoding the calcium/calmodulin-dependent protein kinase kinase (CaMKK) was isolated by RT-PCR amplification of the fragment corresponding to the conserved kinase catalytic domain followed by rapid amplification of cDNA ends and cDNA library screening. Compilation of nucleotide sequencing data yielded a consensus cDNA sequence of 1.9 kb with an open reading frame of 1,251 nucleotides in length which translates to a polypeptide of 417 amino acids (47 kd). It showed significant homology to the rat brain CaMKK isozymes. The human CaMKK, which was expressed as a Flag-tagged protein in human non-small cell lung cancer H- 1299 cells followed by immunoprecipitation with anti-Flag antibody, was shown to phosphorylate recombinant human CaMK I in a calcium/CaM-dependent fashion. Northern blot analysis revealed that human CaMKK is ubiquitously expressed, with brain showing the highest level of expression. The CaMKK gene is localized to human chromosome 12. The presence of cDNA clones with divergent 3' terminal sequences suggests a family of CaMKK variants which may arise from alternative splicing.

Association of apolipoprotein E polymorphism with lipoprotein glomerulopathy. Report of 2 cases with a new genotype and comparison of the relative frequencies of apolipoprotein E isoforms in lipoprotein glomerulopathy and in the general population

Two cases of lipoprotein glomerulopathy with a new apolipoprotein E (Apo E) genotype, epsilon3/epsilon4, were diagnosed recently. These 2 cases, together with other cases documented in English literature made a total of 6 common isoforms of Apo E encountered in lipoprotein glomerulopathy. Although the calculated allele frequency of epsilon2 is relatively high in cases with lipoprotein glomerulopathy as compared with that in the general population (39.3 vs. 6.4-11.4%), the gradual emergence of Apo E isoforms other than E2/E3 in lipoprotein glomerulopathy implicates that the genetic susceptibility of certain Apo E isoforms may not be a crucial factor. An alteration in the local environment of glomerular capillaries may be more important in the pathogenesis of lipoprotein glomerulopathy.

Numerical simulation of flow fields in a tube with two branches

In the present study, a numerical calculation procedure based on the finite volume method was employed to simulate flow fields in double-branched tubes. The configuration was a tube with two vertical branches; the two branches were either on the same side or on the opposite side. The study focused on the baseline flow fields and the possible flow interaction between the two branches. The branching ratio and the branch /main tube diameter ratio were fixed in this study. The results showed that when the two branches were on the same side, the low/oscillating shear regions were found on the ventral walls of the branches and on the dorsal wall of the main tube distal to the branches. The flow field proximal to each branch was similar to that in a single-branched tube when the two branches were distant. When the branches were on the opposite side with the staggering distance S=0 (symmetric case), the low/oscillating shear regions were found on the lateral walls of the main tube. As S increased, the interaction between the two branches weakened, the low/oscillating shear regions were found on the lateral walls of the main tube to the side of the second branch. The flow field near the branch was significantly different from that of a single-branched tube. Care should be taken on localization of plaques in multi-branched vessels due to the flow pattern change. The numerical results were qualitatively consistent with what observed experimentally, by other investigators.

The binding characteristics and intracellular localization of temoporfin (mTHPC) in myeloid leukemia cells: phototoxicity and mitochondrial damage

The state of aggregation of the photosensitizer meso-tetrahydroxyphenylchlorin (mTHPC) in both cell free and intracellular environment was elucidated by comparing its absorption and excitation spectra. In methanol, mTHPC existed as monomers and strongly fluoresced. In aqueous solutions such as phosphate-buffered saline (PBS), mTHPC formed nonfluorescent aggregates. Some portion of mTHPC monomerized in the presence of 10% fetal calf serum PBS. In murine myeloid leukemia M1 and WEHI-3B (JCS) cells, cytoplasmic mTHPC were monomeric. By using organelle-specific fluorescent probes, it was found that mTHPC localized preferentially at the mitochondria and the perinuclear region. Photodynamic treatment of mTHPC-sensitized leukemia cells caused rapid appearance of the apoptogenic protein cytochrome c in the cytosol. Results from flow cytometric analysis showed that the release of cytochrome c was especially pronounced in JCS cells, and well correlated with the extent of apoptotic cell death as reported earlier. Electron microscopy revealed the loss of integrity of the mitochondrial membrane and the appearance of chromatin condensation as early as 1 h after light irradiation. We conclude that rapid release of cytochrome c from photodamaged mitochondria is responsible for the mTHPC-induced apoptosis in the myeloid leukemia JCS and M1 cells.