[Regulatory effect of lingqi anshen liquor on erythrocyte immune function and antioxidation in immunosuppressed mice]

The regulatory effect of Lingqi Anshen Liquor (LQASL) on erythrocyte immune function and antioxidation in cyclophosphamide induced immunosuppressed model mice was observed. After given LQASL for 7 days, the results showed that it could antagonize the inhibitory action of cyclophosphamide significantly, demonstrated by raising the level of superoxide dismutase activity, erythrocyte immune adhesive enhance factor and erythrocyte C3b receptor rosette forming rate, lowering the serum malondialdehyde, erythrocyte adhesive inhibitory factor and erythrocyte immunocomplex rosette forming rate. It suggested that LQASL can regulate the erythrocyte immune function and antagonize the injury of oxygen free radical in immunosuppressed mice.

Nuclear matrix proteins as structural and functional components of the mitotic apparatus

The eukaryotic nucleus is a membrane-enclosed compartment containing the genome and associated organelles supported by a complex matrix of nonhistone proteins. Identified as the nuclear matrix, this component maintains spatial order and provides the structural framework needed for DNA replication, RNA synthesis and processing, nuclear transport, and steroid hormone action. During mitosis, the nucleoskeleton and associated chromatin is efficiently dismantled, packaged, partitioned, and subsequently reassembled into daughter nuclei. The dramatic dissolution of the nucleus is accompanied by the assembly of a mitotic apparatus required to facilitate the complex events associated with nuclear division. Until recently, little was known about the fate or disposition of nuclear matrix proteins during mitosis. The availability of specific molecular probes and imaging techniques, including confocal microscopy and improved immunoelectron microscopy using resinless sections and related procedures, has enabled investigators to identify and map the distribution of nuclear matrix proteins throughout the cell cycle. This chapter will review the structure, function, and distribution of the protein NuMA (nuclear matrix mitotic apparatus) and other nuclear matrix proteins that depart the nucleus during the interphase/mitosis transition to become structural and functional components within specific domains of the mitotic apparatus.

Muscle fibre type and dimension in genetically obese and lean Zucker rats

Skeletal muscle structure and morphology may be altered in obesity. To study this further, muscles from six genetically obese (fa/fa) and six normal male rats were examined at 15 weeks of age. The gluteus medius, vastus lateralis and rectus abdominis muscles were dissected out and stained for histochemical fibre typing. In addition the fibre cross-sectional area was measured on a graphic tablet. The proportion of fast-twitch fibres was larger in the vastus lateralis and rectus abdominis muscles of the obese rats (P < 0.01); no difference was seen for the gluteus medius muscle. For the normal rats the cross-sectional area of the fast-twitch fibres was 2-3 times larger than the area of slow-twitch fibres in the same muscle. The cross-sectional area of the fast-twitch fibres in the obese rats was 40-47% less than in the control animals (P < 0.003), while no difference between the two groups was found for the slow-twitch fibre area. The data thus suggest that in the genetically obese rats the development of fast-twitch fibres was primarily affected. Moreover, in these animals some muscles may be more affected than others.

The C terminus of mitosin is essential for its nuclear localization, centromere/kinetochore targeting, and dimerization

Mitosin is a novel 350-kDa nuclear phosphoprotein that dramatically relocates from the evenly nuclear distribution in S phase to the centromere/kinetochore and mitotic apparatus in M phase. The dynamic relocalization of mitosin is accompanied by the phosphorylation of itself, suggesting that mitosin plays a role in mitotic progression. The molecular basis of nuclear localization and targeting of mitosin to the centromere/kinetochore were characterized using a set of epitope-tagged deletion mutants. The data indicate that the extreme C terminus (amino acids 2,487-3,113) of mitosin has both an independent centromere/kinetochore targeting domain and an unusually spaced bipartite nuclear localization signal. Moreover, the same centromere/kinetochore targeting domain was shown to be essential for the ability of mitosin to bind to itself or other putative mitosin-associated proteins through use of the yeast two-hybrid system. These results suggest that the C terminus of the mitosin is essential for its role in influencing cell cycle progression.

The effect of ALA and radiation on porphyrin/heme biosynthesis in endothelial cells

To study porphyrin biosynthesis in human microvascular endothelial cells, HMEC-1 cells, a transformed human microvascular endothelial cell line, were incubated with 5-aminolevulinic acid (ALA), the precursor of endogenous porphyrins, and porphyrin accumulation was measured spectro-fluorometrically. The HMEC-1 cells accumulated porphyrin in a concentration-related and a time-dependent fashion. Protoporphyrin was the predominant porphyrin accumulated in the cells. The effect of light on protoporphyrin accumulation was evaluated by exposing the ALA-loaded HMEC-1 cells to ultraviolet-A (UVA) and blue light, followed by another incubation with ALA for 2-24 h. Enhancement of protoporphyrin accumulation in irradiated HMEC-1 cells was observed 2-24 h after irradiation, which was associated with a decrease in ferrochelatase protein and activity. Porphyrin accumulation from ALA after irradiation was significantly decreased when catalase (750-3000 U/mL, 29.3-44.3% suppression) or superoxide dismutase (270 U/mL, 36.4% suppression) was present during irradiation. These data demonstrate that HMEC-1 cells were capable of porphyrin biosynthesis, and that exposure of protoporphyrin-containing HMEC-1 cells to UVA and blue light, which includes the Soret band spectrum, decreased the ferrochelatase activity and its protein. These changes were mediated, at least in part, by reactive oxygen species.

The effect of porphyrin and radiation on ferrochelatase and 5-aminolevulinic acid synthase in epidermal cells

The effects of ultraviolet A (UVA) and blue light on ferrochelatase protein, and its mRNA level, in 5-aminolevulinic acid (ALA)-loaded A431 cells was evaluated. Western blot analysis of ferrochelatase protein showed a protein band of 43 kDa. There was a decrease in the protein concentration 24 h and 48 h after irradiation of these cells. In contrast, as judged by Northern blot analysis, there was no change in ferrochelatase mRNA level. Measurement of ALA synthase activity showed an ALA dose-dependent but radiation-independent decrease of enzyme activity, suggesting an end-product feedback inhibition. Since reactive oxygen species generated by porphyrin-induced photochemical reaction may be involved in the decrease in ferrochelatase protein, the effect of scavengers of reactive oxygen species was evaluated by measuring porphyrin accumulation in irradiated, ALA-loaded A431 cells. Porphyrin accumulation was significantly decreased in the presence of singlet oxygen scavenger sodium azide (0.05 mM, 40.6% suppression) or hydroxyl radical scavenger mannitol (5.0 mM, 45.0% suppression). These data suggest that the photochemical reaction induced by porphyrin and irradiation resulted in a decrease in ferrochelatase protein content, but had no effect on ferrochelatase mRNA level nor on ALA synthase activity. The decrease in protein was partly mediated by the reactive oxygen species.

The nature and origins of acid summer haze air pollution in metropolitan Toronto, Ontario

During July and August of 1986, 1987, and 1988, a field study was conducted of ambient acidic aerosol levels in Toronto, Ontario. Fine particle mass (da < 2.5 microns) samples were collected twice daily at a central-city site for the determination of particulate-phase strong acidity (H+) and sulfate (SO4 =). Two additional H(+)-monitoring sites were concurrently operated during the summers of 1986 and 1987 to examine the spatial variability of H+ within the metropolitan area. During the summer of 1986, a quasi-continuous total sulfate/sulfuric acid analyzer was also deployed to allow a determination of the chemical form of H+. Results indicate that acid aerosol episodes (H+ > or = 100 nmole/m3) did occur in this city during the summer months, and that H+ peaks were well correlated with sulfate peaks. Virtually all of the H+ was found to be present as ammonium bisulfate (NH4HSO4). While H+ concentrations were highly correlated among the three monitoring sites (r = 0.9), the highest H+/SO4 = ratios prevailed during SO4 = episode periods and at the least urbanized site. This latter trend was apparently due to greater neutralization of H+ by local ammonia at the more urbanized sites. Comparisons of day vs night H+/SO4 = ratios, an examination of air mass back-trajectories, and contemporaneous H+ measurements at surrounding sites collectively indicated that transported regional haze air pollution from the United States is a major contributor to the H+ events recorded within Toronto.

Nuclear-mitotic apparatus protein: a structural protein interface between the nucleoskeleton and RNA splicing

Vertebrate splicing factors are localized to discrete domains within the nuclei of somatic cells. The mechanism whereby such nuclear domains, identified as speckles by immunofluorescence microscopy, are generated is unclear. Recent studies suggest that the spatial order within the nucleus is maintained by nuclear matrix factors. Here we show that a protein in the nuclear matrix and mitotic apparatus [nuclear-mitotic apparatus protein, NuMA; Lydersen, B. & Pettijohn, D. (1980) Cell 22, 489-499] colocalizes with splicing factors in interphase nuclei and is associated with small nuclear ribonucleoproteins in a complex immunoprecipitated from HeLa extract with small nuclear ribonucleoprotein antibodies. Moreover, NuMA associates with splicing complexes that are reconstituted in vitro using wild-type pre-mRNA, but not with nonspecific RNA. Cumulatively, these observations suggest a function of NuMA or NuMA-like proteins in interphase cells in providing a bridge between RNA processing and the nucleoskeleton.

Effect of porphyrin and irradiation on heme biosynthetic pathway in endothelial cells

To study porphyrin biosynthesis in human umbilical vein endothelial cells (EC), cultured EC were incubated with delta-aminolevulinic acid (ALA), the precursor of porphyrin synthesis, and porphyrins generated were measured spectrofluorometrically. EC accumulated porphyrins in an incubation time-dependent and ALA dose-dependent fashion. Porphyrin accumulation was enhanced by CaMg EDTA, a ferrochelatase inhibitor, suggesting the participation of ferrochelatase. The effect of porphyrin and irradiation on porphyrin accumulation was evaluated by exposing porphyrin-containing EC to the UVA and blue light, followed by incubation with ALA for 2-48 h. Decreased porphyrin accumulation 2-48 h after the irradiation was noted at all the time-points examined. However, no alteration of ferrochelatase activity was observed, suggesting that the decrease in porphyrin levels was due to suppression of the activity of the other enzymes in the earlier steps of the heme biosynthetic pathway.

Localization of NuMA protein isoforms in the nuclear matrix of mammalian cells

Using a monoclonal antibody 2D3 generated against a kinetochore-enriched human chromosome preparation, we identified a high molecular mass protein with nuclear staining in interphase and polar staining of the pericentriolar region in the mitotic spindle. Initially termed centrophilin, this protein associates with the minus-ends of spindle microtubules (MT) and appears to be important in spindle organization [Tousson et al., 1991: J. Cell Biol. 112:427-440]. Comparison of a partial cDNA sequence obtained for centrophilin with the full length cDNA sequence of nuclear mitotic apparatus protein (NuMA) [Compton et al., 1992: J. Cell Biol. 116:1395-1408; Yang et al., 1992: J. Cell Biol. 116:1303-1317] has indicated that NuMA and centrophilin are the same protein. Using a polyclonal NuMA antibody, we have provided further evidence that NuMA exists as isoforms as shown by peptide mapping and immunoblots. Sequential fractionation experiments along with immunofluorescence, immunoblotting, and EM immunogold labeling have demonstrated that NuMA isoforms are novel components of nuclear core filaments. Thus, NuMA, a long coiled-coil protein, appears to have dual functions in interphase and mitosis during the cell cycle. In interphase, NuMA likely plays a structural role in the nucleoskeleton that may be important in nuclear organization and functions, whereas in mitosis, NuMA appears to be associated with spindle MT organization and chromosome positioning.

Hepatic nuclear ploidy distribution of dietary-restricted mice

Hepatic parenchymal cells in most adult mammals are polyploid, with most of the cells in the quiescent or low-proliferation state. Polyploidization has been related to carcinogenesis and aging, and both end points are significantly affected by dietary restriction (DR). Direct measures of hepatic nuclear polyploidization in DR B6C3F1 mice have not been examined. We examined the effect of DR on distributions of nuclear ploidy in both sexes and on different age groups of B6C3F1 mice. Differences between young and old male mice and between old male and female mice were also compared. Hepatic nuclear ploidy values were measured by flow cytometry. The DNA histograms were analyzed for the percentage of nuclei having different classes of DNA content by gating channels between the areas under the peaks of diploid, tetraploid, and octaploid. The results indicate that 1 or 26 months of DR started at 4 months of age did not alter hepatic nuclear ploidy distributions in young and old mice. Our data suggest that in the male mouse, polyploidization is established by 5 months of age for hepatic nuclei and that ploidy classes are affected by sex at 30 months of age. For females, effects in the octaploid nuclei are seen as a result of DR.

Effect of UVA and blue light on porphyrin biosynthesis in epidermal cells

To study porphyrin biosynthesis in normal human keratinocytes and A431 cells derived from human epidermoid carcinoma, cultured cells were incubated with delta-aminolevulinic acid (ALA), the precursor of porphyrin synthesis, and accumulation of porphyrins was measured spectrofluorometrically. Both human keratinocytes and A431 cells accumulated porphyrins in a time-dependent and a dose-dependent fashion. Protoporphyrin was the predominant porphyrin accumulated by both cell types. Porphyrin accumulation was enhanced by Ca Mg ethylenediaminetetraacetic acid, a ferrochelatase inhibitor, and the enhancement was reversed by the addition of iron, suggesting the utilization of iron by ferrochelatase. The effect of light on porphyrin accumulation was evaluated by exposing the ALA-loaded A431 cells to ultraviolet-A (UVA) and blue light radiation, followed by continued incubation with ALA for 2-48 h. There was an enhancement of porphyrin accumulation 2-48 h after the radiation as compared with nonirradiated controls. Consistent with this finding, ferrochelatase activity decreased in these cells at 24 h and 48 h. These data demonstrate that human keratinocytes and A431 cells are capable of porphyrin biosynthesis, and that exposure of porphyrin-containing A431 cells to light, which includes the Soret band spectrum, decreases the ferrochelatase activity, which is responsible, at least in part, for the further increase in porphyrin level.

Porphyrin synthesis by murine epidermal cells

Incubation of murine epidermal cells with delta-aminolevulinic acid (ALA) resulted in a dose- and time-dependent accumulation of porphyrins, predominantly of protoporphyrin. Porphyrin accumulation decreased in the presence of iron, and the iron-mediated decrease was partially reversed by CaMg EDTA (1.25-10.0 mM), suggesting that there is functionally active ferrochelatase in these cells. This study suggests that these cells may be a useful model for the study of cutaneous porphyrin metabolism involving ferrochelatase activity.

Assessment of an extracorporeal liver assist device in anhepatic dogs

We have used an anhepatic dog model to demonstrate the efficacy of a bioartificial liver assist device. Six dogs underwent total hepatectomy. Three received only medical care (controls) while the remainder were connected to an extracorporeal liver assist device (ELAD). The control dogs failed to regain consciousness after anesthesia although all lived 4-5 h postoperatively. Plasma ammonia concentration increased by an average of 250 mumol/L between the end of surgery and the demise of the animals. The treated dogs lived 3-12.5 h, and 2 of them required repeated doses of thiamylal sodium to maintain sedation. Plasma ammonia concentration was unchanged after connection to the ELAD except in the longest survivor, whose ammonia began to rise after 8 h on the ELAD. The short survival in the other 2 treated dogs was the result of uncontrolled intraabdominal bleeding. This device is capable of replacing the metabolic function of the liver, and might provide hepatic support in patients awaiting transplantation or in fulminant hepatic failure.

Stimulation of thymidine kinase activity in baculovirus infected cells is not due to a virus-coded enzyme

A polyhedrin-positive recombinant autographa californica nuclear polyhedrosis virus (AcNPV) carrying a herpes simplex virus thymidine kinase gene under the control of the SynXIV promoter, a fusion of synthetic and linker-modified polyhedrin promoters, has been constructed. When this recombinant baculovirus was used to infect a variant of Spodoptera frugiperda cells deficient in thymidine kinase (TK-), a high level of TK activity was detected. These results, in conjunction with the demonstration that AcNPV could replicate in TK- S. frugiperda cells and no TK activity was found throughout infection, imply that the wild type virus-stimulated TK activity observed in S. frugiperda (TK+) cells is not contributed by a virus-coded enzyme.

Irradiation of protoporphyric mice induces down-regulation of epidermal eicosanoid metabolism

This study investigated the effect of radiation on clinical and histologic changes, and on cutaneous eicosanoid metabolism, in Skh:HR-1 hairless albino mice rendered protoporphyric by the administration of collidine. At 0.1-18 h after exposure to 12 kJ/m2 of 396-406 nm irradiation, thicknesses of back skin and ears were measured, and histologic changes were evaluated by using hematoxylin and eosin (H-E) and Giemsa's stains. Activities of eicosanoid-metabolizing enzymes in epidermal and dermal homogenates were assessed by incubating the tissue homogenates with 3H-AA, followed by quantitation of the eicosanoids generated by radio-TLC. In irradiated protoporphyric mice, an increase of back-skin thickness was noted at 0.1 h, reaching a peak at 18 h, whereas maximal increase in ear thickness was observed at 12 h. Histologic changes included dermal edema, increased mast cell degranulation, and mononuclear cells in the dermis. In these irradiated protoporphyric animals, generations of 6 keto-PGF1a, PGF2a, PGE2, PGD2, and HETE by epidermal eicosanoid-metabolizing enzymes were markedly suppressed at all the timepoints studied. Dermal eicosanoid-metabolizing enzymes of irradiated protoporphyric mice generated increased amounts of PGE2 and HETE at 18 h, probably reflecting the presence of dermal cellular infiltrates. The suppression of the activities of epidermal eicosanoid-metabolizing enzymes was prevented by intraperitoneal injection of WR-2721, a sulfhydryl group generator, prior to irradiation, suggesting that the suppression was secondary to photo-oxidative damage of the enzymes during the in vivo phototoxic response. These results suggest that the effect of protoporphyrin and radiation on cutaneous eicosanoid metabolism in this animal model in vivo is that of a down regulation of the activities of epidermal eicosanoid-metabolizing enzymes.

C5a, cutaneous mast cells, and inflammation: in vitro and in vivo studies in a murine model

To evaluate further the interactions of C5a and mast cells in cutaneous inflammation, the ability of human native C5a (nC5a) (10 to 500 ng/ml) and human recombinant C5a (rC5a) (10 ng/ml to 100 ng/ml) to induce histamine release from purified BALB/c cutaneous mast cells (CMC) and peritoneal mast cells (PMC) was analyzed. It was found that nC5a induced histamine release from CMC but not from PMC, with a maximal net release at 250 ng/ml nC5a (22.8 +/- 2.6%). Kinetic experiments demonstrated that nC5a-induced maximal net histamine release occurred 5 min after the presentation of this stimulus (25.8 +/- 6.0%). Using rC5a and CMC, dose-response studies indicated a maximal net release of 7.0 +/- 1.7% at rC5a of 10 ng/ml, and kinetic studies showed a maximal net release at 5 min of incubation (12.9 +/- 1.6%). Release induced by rC5a was calcium-dependent, and peaked at 30 degrees C. These results indicate that functional heterogeneity exists between the CMC and the PMC of BALB/c mice, that C5a is a relevant stimulus for characterization of this heterogeneity, and that CMC from these animals can serve as a convenient in vitro model for the study of human C5a-mast cell interactions. In vivo, injections of nC5a (25-100 ng) and rC5a (25-100 ng) into the skin of BALB/c mice induced an increase in cutaneous vasopermeability, as assessed by the extravasation of intravenously injected 125I-bovine serum albumin. nC5a induced a dose-dependent increase in vasopermeability, whereas alterations induced by rC5a plateaued at 50 ng. The C5a-induced vasopermeability was markedly enhanced in animals that had been previously treated with an inhibitor of serum carboxypeptidase, which converts C5a to the less potent derivative, C5a des Arg. These findings suggest that carboxypeptidase plays an important role in vivo in the modulation of C5a-induced cutaneous inflammation in murine skin.

Effects of single- and multiday ozone exposures on respiratory function in active normal children

Ventilatory function was measured twice daily on 46 healthy children aged 8-14 years on at least 7 days for each child during a 4-week period at a northwestern New Jersey residential summer camp in 1988. The highest 1-hr O3 concentration was 150 ppb, while the highest 12-hr H+ concentration (as H2SO4) was 18.6 micrograms/m3. The highest temperature-humidity index was 81 degrees F. The regressions of FVC, FEV1, FEF25-75, and PEFR on O3 in the hour preceding the afternoon function measurements yielded slopes essentially the same as those measured on other children at the same camp in 1984. Regressions of the changes in function between the late morning and late afternoon function measurements on average O3 concentration between them produced significant, but somewhat smaller effects, while regressions of morning function on O3 during the previous day indicated small but still significant effects. There were no significant correlations with other measured environmental variables including H+. Based on the results of this study and similar previous studies, we conclude that O3 exposures in ambient air produce greater lung function deficits in active young people in natural settings then does pure O3 in controlled chamber exposure studies because of: (1) longer exposures; (2) potentiation by other factors in the ambient exposures; (3) the persistence of effects from prior day's exposures; and (4) the persistence of a transient response associated with the daily peak of exposure. It follows that projections of likely effects in the real world from controlled chamber exposure studies should either have a large margin of safety, or the judgment of the extent of effects likely to occur among populations should be based directly on the effects observed in field studies.

Mast-cell heterogeneity: functional comparison of purified mouse cutaneous and peritoneal mast cells

To investigate the functional heterogeneity of mouse mast cells, we extracted and purified cutaneous and peritoneal mast cells from 10- to 18-week-old BALB/c mice and compared their responses to secretagogues. Cutaneous mast cells (CMC) were extracted from mouse ears after digestion with hyaluronidase and collagenase in MEM containing 25% fetal calf serum and purified on a discontinuous Percoll gradient. The histamine content of cells obtained from the 30/40% interface was 1.0 +/- 0.1 pg/cell (mean +/- SE), with a mast-cell purity of 68.6 +/- 4.4% and a viability of greater than 93%. Peritoneal mast cells (PMC) were obtained by lavage with modified Tyrode's buffer followed by purification on 22.5% and 3-9% metrizamide gradients. The histamine content of cells was 12.2 +/- 0.8 pg/cell, with a mast-cell purity of 95.9 +/- 0.6% and a viability of greater than 95%. Histamine release induced by A23187 from CMC peaked at 3.0 microM A23187 (19.1 +/- 4.2%), at 3.0 min (22.3 +/- 2.3%), and at 30 degrees C (17.6 +/- 2.6%). In contrast, histamine release from PMC peaked at 8.0 microM of A23187 (49.4 +/- 12.1%) and at 15.0 min (48.5 +/- 12.2%). Release of histamine from PMC was observed at all the temperatures tested from 22 to 45 degrees C. Histamine release from CMC and PMC induced by A23187 was calcium dependent. Histamine release induced by compound 48/80 from CMC peaked at 0.5 micrograms/ml of compound 48/80 (23.0 +/- 7.4%) and at 5.0 min incubation (16.3 +/- 2.0%), whereas release from PMC peaked at 10.0 micrograms/ml (31.9 +/- 2.6%); release from PMC was similar at all the time points examined (1-15 min). Histamine release induced by substance P (SP) from both CMC and PMC peaked at 5.0 microM (18.8 +/- 6.6% and 12.6 +/- 3.7%, respectively); however, the maximal release from CMC occurred at 3.0 min (18.2 +/- 3.2%) and from PMC at 30.0 min (11.4 +/- 2.0%). SP-induced histamine release from CMC was calcium dependent, whereas release from PMC was only partially inhibited by EDTA. This study demonstrated that functional heterogeneity exists between these two populations of mast cells.

[Enhancing effect of danggui injection on immunologic function]

Experiments have shown that Danggui injection enhances phagocytic function of macrophage in normal mice, and antagonizes the immunosuppressive activity of macrophage by cytoxan. The injection may increase the function of B cells and the activity of serum lysozyme, thus increasing the function of humoral immunity and nonspecific immunity.

The late phase of hematoporphyrin derivative-induced phototoxicity in mice: release of histamine and histologic changes

This study was designed to directly examine the role of mast cells and the histologic changes in the late phase (4-48 h) of hematoporphyrin derivative-induced phototoxicity. BALB/c mice were rendered phototoxic by intraperitoneal injection of HpD, followed by exposure to 1.59 kJ/m2 of 396-406 nm radiation. Immediately before radiation, and at 4, 8, 12, 18, 24 and 48 h after radiation, the ear thickness, serum histamine levels and histologic changes of ears were examined. A maximal net increase in ear thickness of 33.5 +/- 0.3 X 10(-2) mm (mean +/- SE) was noted at 12 h, associated with a maximal net increase of serum histamine (43.3 +/- 11.6 ng/ml, mean +/- SE), and a maximal mast cell degranulation. Other histologic changes consisted of mild epidermal spongiosis at 18-24 h, and a predominant neutrophilic infiltrate, which peaked at 24 h (211.6 +/- 0.4 cells/mm2). No significant alteration was observed in control mice. These data indicated that mast cells participate in the late phase of HpD-induced phototoxicity in mice.