Functional expression of Fas and Fas ligand on human intestinal intraepithelial lymphocytes

Intestinal intraepithelial lymphocytes (IEL) constitute the first lymphoid compartment to encounter dietary antigens and intestinal pathogens. IEL are proposed to be involved in the defence against bacterial and viral invasion and to play an important role in mucosal immunity. Fas (CD95/APO-1) is a surface receptor that induces apoptotic cell death upon ligation with Fas ligand (FasL). The aim of this study was to examine the expression and function of Fas and FasL on freshly isolated normal human colonic IEL. The expression and function of Fas and FasL on IEL isolated from 40 normal colonic specimens were examined by flow cytometry, reverse transcriptase-polymerase chain reaction, immunohistochemistry, and DNA-release cytotoxicity assay. Virtually all CD3+ IEL (95.2 +/- 4.3%) expressed Fas and were sensitive to agonistic anti-Fas antibody, whereas only 56.6 +/- 8.4% of peripheral T lymphocytes expressed Fas and were resistant to the antibody. We also detected FasL mRNA and protein (40.1 +/- 4.2%) on IEL, and found that IEL exerted FasL-mediated cytotoxicity against Fas-expressing target cells. These findings suggest that human IEL are activated in situ but are tightly regulated by the constitutive expression of functional Fas and FasL to maintain homeostasis of the mucosal immune system.

The protein phosphatase inhibitors, okadaic acid and calyculin A, induce apoptosis in human submandibular gland ductal cell line HSG cells

OBJECTIVE

To investigate a possible relationship between protein phosphorylation or dephosphorylation status and apoptosis in salivary gland cells, we examined the effects of okadaic acid and calyculin A, the protein phosphatase inhibitors, on cultured human submandibular gland ductal cell line, HSG cells.

METHODS

HSG cells at subconfluent stages were exposed to varying concentrations of okadaic acid or calyculin A. Apoptoses were analysed in HSG cells by phase-contrast microscopy, WST-1 cytotoxicity assay, Hoechst 33342 staining, and DNA ladder formation.

RESULT

Both okadaic acid and calyculin A induced cell death in HSG cells in a dose-dependent fashion. Marked nuclear condensation and fragmentation of chromatin was observed in HSG cells. DNA ladder formation was also detected in HSG cells by treatment with okadaic acid or calyculin A. The induced DNA ladder formation was dose-dependent with maximal effect at concentrations of 50 nM okadaic acid and 2 nM calyculin A, respectively, and were time-dependent from 14 h to 48 h. To further determine if new gene transcription and protein synthesis regulate okadaic acid-induced apoptosis in HSG cells, the cells were treated with cycloheximide or actinomycin D in the presence of 20 nM okadaic acid. Neither inhibitor protected the cells against okadaic acid-induced apoptosis.

CONCLUSION

Based on the known selectivity of okadaic acid and calyculin A, our results indicate that the pathway of the apoptosis in the cultured salivary gland cells is regulated by protein phosphatase type 1 or type 2A. Our results also suggest that new protein synthesis and/or mRNA expression are not involved in okadaic acid-induced apoptosis in HSG cells.

Differential involvement of the CD95 (Fas/APO-1) receptor/ligand system on apoptosis induced by the wild-type p53 gene transfer in human cancer cells

The CD95 (Fas/APO-1) system regulates a number of physiological and pathological processes of cell death. The ligand for CD95 induces apoptosis in sensitive target cells by interacting with a transmembrane cell surface CD95 receptor. We previously reported that the recombinant adenovirus-mediated transfer of the wild-type p53 gene caused apoptotic cell death in a variety of human cancer cells. To better understand the mechanism responsible for this cell death signaling, we have investigated the potential involvement of the CD95 receptor/ligand system in p53-mediated apoptosis. The transient expression of the wild-type p53 gene upregulated the CD95 ligand mRNA as well as protein expression in H1299 human lung cancer cells deficient for p53 and in DLD-1 and SW620 human colon cancer cells with mutated p53, all of which constitutively expressed CD95 receptor as shown by a flow cytometric analysis, and induced rapid apoptotic cell death as early as 24 h after gene transfer. However, the sensitivity to the cytolytic effect of agonistic anti-CD95 antibody (CH11) varied among these cell lines: CH11 induced apoptosis in H1299 cells, but not in DLD-1 and SW620 cells despite their abundant CD95 receptor expression, suggesting that the CD95 receptors on DLD-1 and SW620 cells might be inactivated. In addition, an antagonistic anti-CD95 ligand antibody (4H9) that interfered with the CD95-receptor-ligand interaction partially reduced the apoptosis induced by the wild-type p53 gene transfer in H1299 cells, whereas apoptosis of DLD-1 and SW620 cells occurred in the presence of 4H9. Taken together, these findings led us to conclude that the CD95 receptor/ligand system is differentially involved in p53-mediated apoptosis, suggesting that the restoration of the wild-type p53 function may mediate apoptosis through CD95 receptor/ligand interactions as well as an alternative pathway.

MUC1 mucin mRNA expression in stage I lung adenocarcinoma and its association with early recurrence

BACKGROUND

MUC1 is a membrane-bound mucin with an extensively O-glycosylated core protein and is developmentally regulated and aberrantly expressed by carcinomas. A high level of MUC1 mucin expression and secretion is associated with high metastatic potential and a poor prognosis. We studied the expression of MUC1 messenger ribonucleic acid (mRNA) in stage I lung adenocarcinoma by reverse transcriptase-polymerase chain reaction and examined its correlation with early recurrence.

METHODS

The expression of MUC1 mRNA, in surgical specimens from 33 patients with stage I lung adenocarcinoma was determined by reverse transcriptase-polymerase chain reaction. The MUC1 and beta-actin sequences were subsequently coamplified to analyze the semiquantitative determination by polymerase chain reaction. The ratio of MUC1 to beta-actin product was used for further analysis.

RESULTS

An analysis of the disease-free survival (median follow-up, 33.4 months) revealed that a high expression of MUC1 was associated with early recurrence (p = 0.0191). Six of the 33 patients had recurrence within 2 years after operation. The recurrence sites suggested hematogenic metastasis.

CONCLUSIONS

Our results indicate that MUC1 mRNA level may be useful as a marker of early recurrence in stage I lung adenocarcinoma.

Extracts of Actinobacillus actinomycetemcomitans induce apoptotic cell death in human osteoblastic MG63 cells

Whether an extracellular component of periodontal-disease-causing bacteria induces apoptotic cell death in bone-related cells is unknown. To study the effects on osteoblasts of extracts obtained from sonicated Actinobacillus actinomycetemcomitans and Prevotella intermedia, we cultured human osteoblastic cell lines MG63 and Saos-2 cells and mouse osteoblastic cell line MC3T3-E1 cells in the presence of such extracts. The addition of the extracts from Actinobacillus actinomycetemcomitans induced cell death in MG63 cells in a dose- and time-dependent fashion over the concentration range of 0.1 to 10 microg/mL. By contrast, the extracts from Prevotella intermedia did not induce cell death in these cells, even in the presence of 10 microg/mL protein. By using the Hoechst 33342 staining technique, we observed marked nuclear condensation and fragmentation of chromatin in MG63 cells treated with the extracts of Actinobacillus actinomycetemcomitans. DNA ladder formation, a hallmark of apoptosis, also was detected in MG63 cells treated with extracts from Actinobacillus actinomycetemcomitans. In MG63 cells, DNA ladder formation was dose-dependent, with a maximal effect at a concentration of 10 microg/mL, and time-dependent, from 12 to 48 hrs. However, the extracts from Prevotella intermedia did not induce DNA fragmentation in MG63, Saos-2, or MC3T3-E1 cells. The extracts from Actinobacillus actinomycetemcomitans did not induce cell death and DNA fragmentation in Saos-2 and MC3T3-E1 cells. Sonicated extracts of Actinobacillus actinomycetemcomitans that had been treated with heat and trypsin did not induce DNA ladder formation in MG63 cells, suggesting that the apoptosis-inducing factors are proteinaceous. Cycloheximide prevented the Actinobacillus actinomycetemcomitans-induced DNA ladder formation in MG63 cells in a dose-dependent fashion, suggesting that new gene transcription and protein synthesis are regulated for Actinobacillus actinomycetemcomitans-induced apoptosis in MG63 cells. Our results indicate that apoptosis in alveolar bone cells induced by Actinobacillus actinomycetemcomitans plays an important role in periodontal diseases.

Drug permeation through the three layers of the human nail plate

The in-vitro permeation characteristics of a water soluble model drug, 5-fluorouracil, and a poorly water soluble model drug, flurbiprofen, were investigated through three layers of the human nail plate (namely, the dorsal, intermediate and ventral nail plates), using a modified side-by-side diffusion cell. The dorsal-filed nail plate, the ventral-filed nail plate and the dorsal-and-ventral-filed nail plate were prepared to known thicknesses and then used with the full-thickness nail plate to investigate the permeation characteristics of each single layer. Most of the lipids in the human nail plate were found in the dorsal and ventral layers. The rank orders of the permeation fluxes for 5-fluorouracil and flurbiprofen were both: dorsal-and-ventral-filed nail plate > dorsal-filed nail plate > ventral-filed nail plate > full-thickness nail plate. With respect to 5-fluorouracil permeation through each single layer, the permeability coefficient of the intermediate layer was higher than those of other single layers. However in the case of flurbiprofen, the permeability coefficient of the ventral layer was higher than other single layers. The diffusion coefficients of 5-fluorouracil and flurbiprofen in the dorsal layer were the lowest of any single layer. The drug concentration in each layer was estimated using each respective permeation parameter. The drug concentration in the nail plate was observed to be dependent on the solubility and the flux of the drug. From these findings, we suggest that the human nail plate behaves like a hydrophilic gel membrane rather than a lipophilic partition membrane and that the upper layer functions as the main nail barrier to drug permeation through its low diffusivity against the drugs.

Dental treatment of a prospective recipient of a liver transplant: a case report

A protocol to treat a carious condition in a young girl scheduled to receive a liver transplantation is described. Teeth with serious caries were filled with amalgam. Those teeth with pulp exposure were extracted. To stop bleeding, sutures and a surgical splint with a periodontal pack were used. All procedures were performed as rapidly as possible to minimize stress. Antibiotics were used sparingly. By improving the oral health of transplant recipients, the chances that the transplanted liver will become infected are much reduced, increasing the likelihood of a successful surgical outcome.

Structure determination of rubredoxin from Desulfovibrio vulgaris Miyazaki F in two crystal forms

The structures of two crystal forms (form I, P3221, a = b = 43.7, c = 50.7 A; form II, P21, a = 27.3, b = 44.9, c = 51.2 A and beta = 90. 6 degrees ) of the rubredoxin from Desulfovibrio vulgaris Miyazaki F have been solved by the molecular-replacement method. Form I has been refined at a resolution of 2.0 A to an R value of 20.8% and includes 32 water molecules. Form II includes 86 water molecules and has been refined at 1.9 A resolution to an R value of 17.5%. In form II, there are three molecules in the asymmetric unit with the molecules related by a non-crystallographic 32 symmetry axis. In both crystal forms, it was found that only a few residues effectively participate in the formation of intermolecular contacts along both the crystallographic (form I) and the non-crystallographic (form II) 32 axes. The crystal structure of the form II crystal is compared with those of other rubredoxin molecules from anaerobic bacteria. From this comparison, a similarity in the core region, which is composed of aromatic residues and includes the active centre, has been revealed.

A generational comparison of changes in mandibular third molars

Due to recent increases in the number of cases of embedded mandibular third molars, the Department of Dental Radiology, Kyushu Dental College decided to investigate generational differences in their occurrence. For the purpose of investigation, 670 panoramic radiographs, obtained from two different generations (1970s and 1999s) of Kyushu Dental College students, wer used. There were significant statistical differences in the angle of eruption of the third molar between the 1970s and 1990s groups. The mandibular third molars in the 1990s group were growing at an abnormal angle (P < 0.05) and were closer to the mandibular canal (P < 0.05) than those in the 1970s group.

A low-resolution structure of rice dwarf virus determined by ab initio phasing

Rice dwarf virus crystals belong to space group I222 with cell parameters a = 770 (2), b = 795 (5), c = 814 (5) A and alpha = beta = gamma = 90 degrees. The unit cell of the crystal contains two viruses at the origin and body-centred positions. Using data synthesized from a rice dwarf virus model crystal in the space group I222, the possibility of ab initio phasing was thoroughly examined. The centric nature of the initial phases was unexpectedly broken by extensive iteration of the non-crystallographic symmetry averaging. The structure of rice dwarf virus was then solved with ab initio phasing up to 20 A resolution. The triangulation number determined by the present study is T = 13, which is different from the triangulation number, T = 9, previously determined by electron microscopy [Uyeda & Shikata (1982). Ann. Phytopathol. Soc. Jpn, 48, 295-300].

A clearance model of inhaled man-made fibers in rat lungs

A clearance model of inhaled man-made fibers (MMFs) was developed, and the calculated fiber numbers and dimensions were compared with the experimental ones using a glass fiber (GF), ceramic fiber (RF1) and two potassium octatitanate whiskers (PT1, TW). If the translocation rate by macrophages is constant and the effect of dissolution and disintegration can be ignored, the fiber number is expected to decrease exponentially with time. In the experimental study, however, the fiber number did not always decrease exponentially. In the case of RF1, the fiber number decreased almost exponentially and the diameter decreased linearly with the time. The clearance rate constant of GF during 3 to 6 months after the end of one-month exposure was greater than that during 1 to 3 months. On the contrary, the clearance rate constants of PT1 and TW during 1 to 6 months were greater than next six months. The diameter and the length of GF did not change significantly. The fiber length of PT1 tends to become longer with time although the diameter did not change significantly. Our theoretical model gives a satisfactory fit to these experimental results.

Detection of Escherichia coli O157:H7 from Musca domestica (Diptera: Muscidae) at a cattle farm in Japan

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 was isolated for the first time from Musca domestica L. A total of 310 fly samples was collected from 4 different farms in Obihiro-City, Hokkaido, in the summer and autumn of 1997;5 samples carried E. coli serotype O157:H7. Using ELISA and Vero cell cytotoxicity assay, 3 isolates from 1 cattle farm produced both active Shiga-toxin type 1 (Stx1) and 2 (Stx2). These isolates also carried hemolysin and eaeA genes and harbored the 90-kb virulence plasmid of EHEC O157:H7. Based on plasmid profiles, antibiotic patterns, polymerase chain reaction (PCR)-based DNA finger printing analysis using random amplified polymorphic DNA, pulsed field gel electrophoresis analysis, and DNA sequences of stx1 and stx2, all 3 isolates from fly samples were identical. These results indicate that the house fly is capable of carrying the toxigenic EHEC O157:H7 involved in human disease.

Inhibitors of protein synthesis and RNA synthesis protect against okadaic acid-induced apoptosis in human osteosarcoma cell line MG63 cells but not in Saos-2 cells

In a previous study, we demonstrated that the protein phosphatase inhibitors, okadaic acid and calyculin A, induced apoptosis in human osteosarcoma cell lines, Saos-2 and MG63 cells. In the present study, to determine if new gene transcription and protein synthesis are required for okadaic acid-induced apoptosis in Saos-2 and MG63 cells, the cells were treated for 48h with varying concentrations of the inhibitors of protein or RNA synthesis, i.e., cycloheximide, actinomycin D, and puromycin, in the presence of a fixed dose of okadaic acid. All these reagents in different concentrations prevented the okadaic acid-induced apoptosis in MG63 cells in a dose-dependent fashion. The same concentrations of cycloheximide, actinomycin D, or puromycin alone did not induce any apoptotic features in MG63 cells. However, not all the aforementioned reagents affected okadaic acid-induced apoptosis in Saos-2 cells. Okadaic acid-induced and cycloheximide-prevented apoptosis was shown by phase-contrast microscopy, WST-1 assay, direct visualization of nuclear condensation and fragmentation of chromatin, and the characteristic DNA ladder formation on agarose gel electrophoresis. The present results indicate that the induction of new cell death genes and ongoing protein synthesis may have a role in okadaic acid-induced apoptosis in MG63 cells and that such proteins are not required in Saos-2 cells.

A novel panoramic machine for photofluorography

OBJECTIVE

To describe the main features of a prototype panoramic X-ray machine modified for photofluorography.

METHODS

The prototype PTM 2001 (Asahi Roentgen, Kyoto, Japan) consists of a conventional panoramic machine with a modified X-ray generator and incorporating a 9-inch image intensifier and a photofluorographic camera.

RESULTS

The photofluorographic panoramic radiograph is reduced in size by 60% compared with conventional images. Using 10 cm x 45.7 m photoradiographic film 250 panoramic images can be continuously obtained. Examination time is shorter since cassette changes are not necessary. The radiation dose-in-air, measured in front of the secondary collimator, is 174 muGy.

CONCLUSIONS

The advantages of the photofluorographic panoramic radiography include cost economy, shorter examination time and lower radiation exposure.

Basis for monomer stabilization in Rhodopseudomonas palustris cytochrome c' derived from the crystal structure

The crystal structure of an unusual monomeric cytochrome c' from Rhodopseudomonas palustris (RPCP) has been determined at 2.3 A resolution. RPCP has the four-helix (helices A, B, C and D) bundle structure similar to dimeric cytochromes c'. However the amino acid composition of the surface of helices A and B in RPCP is remarkably different from that of the dimeric cytochromes c'. This surface forms the dimer interface in the latter proteins. RPCP has seven charged residues on this surface contrary to the dimeric cytochromes c', which have only two or three charged groups on the corresponding surface. Moreover, hydrophobic residues on this surface of RPCP are two to three times fewer than in dimeric cytochromes c'. As a result of the difference in amino acid composition, the A-B surface of RPCP is rather hydrophilic compared with dimeric cytochromes c'. We thus suggest that RPCP is monomeric in solution because of the hydrophilic nature of the A-B surface. The amino acid composition of the A-B surface is similar to that of Rhodobacter capsulatus cytochrome c' (RCCP), which is an equilibrium admixture of monomer and dimer. The charge distribution of the A-B surface in RCCP, however, is considerably different from that of RPCP. Due to the difference, RCCP can form dimers by both ionic and hydrophobic interactions. These dimers are quite different from those in proteins which form strong dimers such as in Chromatium vinosum, Rhodospirillum rubrum, Rhodospirillum molischianum and Alcaligenes. Cytochrome c' can be classified into two types. Type 1 cytochromes c' have hydrophobic A-B surfaces and they are globular. The A-B surface of type 2 cytochromes c' is hydrophilic and they take a monomeric or flattened dimeric form.

Enhancing effect of N-acetyl-l-cysteine or 2-mercaptoethanol on the in vitro permeation of 5-fluorouracil or tolnaftate through the human nail plate

The enhancing effects of various vehicles on the in vitro permeation of a hydrophilic model drug, 5-fluorouracil (5-FU), or a lipophilic model drug, tolnaftate (TN), through human nail plates were investigated using a modified side-by-side diffusion cell. Tip pieces from the 5th finger-nail, clipped from healthy volunteers, were used in this permeation study. The swelling and softening properties of the nail pieces were also measured in each vehicle. The weights and stresses of the nail pieces were dramatically changed after immersion in aqueous solvents containing N-acetyl-L-cysteine (AC) or 2-mercaptoethanol (ME). However, no significant change in the physicochemical properties of the nail pieces was found in the lipophilic vehicles. Thus, the water content in the nail plates absorbed from vehicles may relate to their physicochemical properties. Although keratin-softening agents and new skin permeation enhancers did not significantly promote 5-FU permeation compared with water alone, the flux from solvent systems containing AC or ME was substantially higher. In addition, TN permeation from solvents containing AC or ME could be measured, whereas that from other solvents was undetectable. When the AC concentration was increased, the 5-FU permeation and the nail weight increased and the stress of each nail piece decreased. It is concluded from these experimental results that AC and ME may be useful as enhancers for increasing drug permeation through the human nail plate.

Fiber numbers per unit weight of JFM standard reference samples determined with a scanning electron microscope. Japan Fibrous Material

A standard reference 10 sample-set of fibrous minerals were prepared by the Japan Fibrous Material Research Association (JFMRA) under the name of JMF standard reference samples. In this paper, the fiber number per unit weight of JFM standard reference samples was determined with a scanning electron microscope. Fiber numbers per unit weight (f/microgram) and standard deviations observed in this experiment were as follows: glass wool (GW1) 7.0 +/- 0.1 x 10(2), rock wool (RW1) 1.7 +/- 0.2 x 10(3), micro glass fiber (MG1) 6.5 +/- 0.4 x 10(4), refractory ceramic fibers; (RF1) 8.8 +/- 0.7 x 10(3), (RF2) 8.7 +/- 0.8 x 10(3), mullite fibers (RF3) 3.5 +/- 0.7 x 10(3), potassium titanate whisker (PT1) 5.9 +/- 0.3 x 10(5), silicon carbide whisker (SC1) 4.1 +/- 0.4 x 10(5), titanium oxide whisker (rutile) (TO1) 6.4 +/- 0.6 x 10(5), and wollastonite (WO1) 2.4 +/- 0.1 x 10(4). Fiber numbers per unit weight would change in proportion to the cube or cube root of the fiber size if the fibers have the same density and the same aspect ratio. JFM standard reference samples should be used taking into consideration the difference in fiber number per unit weight when users conduct in vitro and/or in vivo (injection) biological experiments using these samples.

[Anesthesia for fourteen cases of auto-renal transplantation]

We experienced anesthetic management of 14 cases of auto-renal transplantation. The causative diseases are stenosis (n = 7) and aneurysm of the renal artery (n = 5) as well as renal cancer (n = 2). The mean time intervals for operation, anesthesia, and clamping of the renal artery were 10 h 54 min, 12 h 42 min and 4 h 14 min, respectively. In the patients whose serum creatinine values were above 1 mg.dl-1 within the 3rd postoperative day, time intervals for operation and anesthesia were significantly longer than in the patients whose serum creatinine values remained below 1 mg.dl-1. The water balance in the former patients was significantly positive in comparison with the latter patients. The auto-renal transplantation is a highly invasive surgery so that proper fluid management and sufficient urination seem to be especially important for the perioperative management of patients of this category.

Characteristics of spontaneous erythema appeared in hairless rats

The hairless rat (WBN/Kob-Ht), a dominant mutant rat derived from the Wistar strain, rarely develops spontaneous erythema of a progressive nature on its skin. Erythema was first observed at 8 weeks of age and the incidence at 20 weeks of age was about 4% in both males and females. Histopathologically, erythema was characterised by dermatitis induced by an immunological reaction. Areas of erythema in the skin were decreased by treatment with dexamethasone (1 mg/kg) or ciclosporin (25 or 50 mg/kg). These results suggested that erythema on the hairless rat could be used as an animal model of spontaneous dermatitis.

Possible mechanisms of vascular relaxation induced by pulsed-UV laser

This study was designed to examine the mechanism of vasorelaxation induced by pulsed-UV laser. Luminal diameters of rat femoral arteries were measured prior to and following krypton-fluoride excimer laser irradiation of 248 nm in wavelength. The diameter was enlarged to 1.3 times the preirradiated size at 1 or 10 Hz irradiation when the fluence was over 2.0 mJ/pulse/mm2, while the diameter reached 1.8 times at 100 Hz with a fluence of 0.8 mJ/pulse/mm2. Vasorelaxation by the 100 Hz irradiation was inhibited when the artery was pretreated with methylene blue but was enhanced with superoxide dismutase. Pathological analysis revealed an ablation crater and vacuole formation in the vessel at 1 or 10 Hz irradiation, but these changes were not remarkable in the 100 Hz-exposed sample. These findings suggest that vasorelaxation induced by the pulsed UV irradiation at 1 or 10 Hz results from structural alteration of vascular smooth muscle by the ablation crater or vacuolization. On the other hand, a possible mechanism of vasorelaxation at the 100 Hz irradiation is partially related to nitric oxide.

Diastereoselective two-directional synthesis and cation transport ability of the central tristetrahydrofuranyl unit of meso polyether glabrescol as naturally occurring podand

The diastereoselective synthesis of the central 2,5-linked tristetrahydrofuran (trisTHF) 6 of naturally occurring meso polyether, glabrescol (5), has been achieved in a two-directional manner by the vanadium(V)-catalyzed anti oxidative cyclizations of diol 14. The trisTHF podand 6 and its stereoisomeric analogs 7 and 8 exhibited outstanding cation transport abilities for physiologically important Na+ and K+.

Subcellular localization of protein phosphatase type 1 isotypes in mouse osteoblastic cells

The cytolocalization of protein phosphatase type 1 catalytic subunits in exponentially growing mouse osteoblastic MC3T3-E1 cells was determined. Formaldehyde-fixed and alcohol-permeabilized cultured cells were reacted with the PP1 alpha, PP1 delta, PP1 gamma 1, and PP1 gamma 2 antibodies using immunohistochemical methods. With PP1 alpha antibody intense staining occurred in the nuclei, while with PP1 delta antibody nucleolus-like bodies were intensely stained. PP1 gamma 1 localized in the perinuclear region and in the nucleus of the cultured cells, with the staining reaction of the former being much stronger than that in the latter. An immunoreaction did not occur in the cells interacted with PP1 gamma 2 antibody or with the normal rabbit serum. Proteins were prepared from the exponentially growing cells and subconfluent cells. Cellular fractionation was also done with the exponentially growing cells and proteins were prepared from each fraction. Each protein preparation was subjected to SDS-PAGE followed by Western blot analysis with the antibodies. PP1 alpha recognized the 38 kDa proteins mainly present in the nucleus, whereas PP1 delta interacted with the proteins in the nucleolar fraction whose molecular weight was estimated as 37 kDa. PP1 gamma 1 antibody recognized a band corresponding to an estimated molecular weight of 36 kDa mainly in the cytosolic fraction. PP1 gamma 2 antibody and the normal rabbit serum did not interact with any proteins prepared from the cultured cells. Our observations show that four different isozymes of protein phosphatases occupy distinct compartments in MC3T3-E1 cells. This differential distribution suggests that these isozymes may play different roles in cellular functions.