Molecular mechanism for silencing virally transduced genes involves histone deacetylation and chromatin condensation

Virally transduced genes are often silenced after integration into the host genome. Chromatin immunoprecipitation and nuclease sensitivity experiments now demonstrate that silencing of the transgene is characterized by deacetylation of histone H4 lysines and chromatin condensation. Trichostatin A treatment results in dramatic reactivation of gene expression that is preceded by histone acetylation and chromatin decondensation. Analysis of individual histone H4 lysines demonstrate that chromatin domain opening is coincident with rapid acetylation of histone H4 K5, K12, and K16 and that maintenance of the open domain is correlated with acetylation of histone H4 K8. Removal of trichostatin A results in rapid deacetylation of histone H4 K8, chromatin condensation, and transcription silencing. The results suggest that deacetylation of histone H4 lysines and coincident chromatin condensation are critically involved in the silencing of virally transduced genes.

Enhanced transgene expression and effective in vivo antitumor immune responses initiated by dendritic progenitors transfected with a nonviral T7 vector expressing a model tumor antigen

Genetic education of dendritic cells (DCs) with tumor-associated antigens is an encouraging development in DC-mediated tumor immunotherapy. In this study, to increase the transgene expression by DCs using nonviral vectors, a cytoplasmic T7 vector (T7T7/T7Luc) was used to transfect bone marrow-derived DCs with the firefly luciferase gene as a reporter and as a model tumor antigen. As a result, the luciferase activity of T7T7/T7Luc-transfected DCs was more than four times greater than that of DCs transfected with pCMVLuc, a commonly used nonviral vector. Furthermore, the luciferase activity was increased three times more when dendritic progenitor cells rather than mature DCs were transfected. In vivo tumor studies showed that T7T7/T7Luc-transfected DCs, which express high levels of luciferase (model tumor antigen), stimulated a stronger immune response than did pCMVLuc-transfected DCs, which express relatively low levels of luciferase, as indicated by the cytotoxic T lymphocyte assay. T7T7/T7Luc transfected DCs, when injected into recipient mice, evoked an antigen-specific immune response that can effectively eradicate implanted metastasis and prevent new tumor development by murine melanoma cells genetically modified to express luciferase. Therefore, the T7 system is a powerful nonviral vector that can be used to genetically educate DCs with tumor-associated antigens for tumor immunotherapy.

Effect of Toosendanin on acetylcholine level of rat brain, a microdialysis study

The effect of prejunctional blocker Toosendanin (TSN) on acetylcholine (ACh) level in striatum and parietal cortex was investigated by means of method of brain dialysis coupled with microbore high-performance liquid chromatograph (HPLC)-electrochemical detection (ECD) with enzyme immobilized post-column at freely moving rats. The results are as follows: (1) TSN inhibits high K+ (100 mM)-induced ACh release from the mentioned two regions of brain, completely and irreversibly. (2) Before the inhibition, there appears a transient rise of ACh level. (3) This rise of ACh level can be blocked by TTX. (4) Calcium is necessary for the onset of this rise, but not for that of the sustained decrease of ACh level. These results indicate that the effect of TSN on central cholinergic synapses is similar to that of neuromuscular junction, namely, its blocking action is always preceded by a Ca(2+)-dependent facilitatory phase with result of a TSN-induced transient rise of ACh, but the sustained decline and final blockade of ACh release are Ca(2+)-independent.

A human prolactin antagonist, hPRL-G129R, inhibits breast cancer cell proliferation through induction of apoptosis

Human breast cancer is the predominant malignancy and the leading cause of cancer death in women from Western societies. The cause of breast cancer is still unknown. Recently, the association between human prolactin (hPRL) activity and breast cancer has been reemphasized. Biologically active hPRL has been found to be produced locally by breast cancer cells that contain high levels of PRL receptor. A high incidence of mammary tumor growth has also been found in transgenic mice overexpressing lactogenic hormones. More importantly, it has been demonstrated that the receptors for sex steroids and PRL are coexpressed and cross-regulated. In this study, we report that we have designed and produced a hPRL antagonist, hPRL-G129R. By using cell proliferation assays, we have demonstrated that: (a) hPRL and E2 exhibited an additive stimulatory effect on human breast cancer cell (T-47D) proliferation; (b) hPRL-G129R possessed an inhibitory effect on T-47D cell proliferation; and (c) when antiestrogen (4-OH-tamoxifen) and anti-PRL (hPRL-G129R) agents were added together, an additive inhibitory effect was observed. We further investigated the mechanism of the inhibitory effects of hPRL-G129R in four hPRLR positive breast cancer cell lines. We report that hPRL-G129R is able to induce apoptosis in all four cell lines in a dose-dependent manner as determined by the Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay. The apoptosis is induced within 2 h of treatment at a dose as low as 50 ng/ml. We hope that the hPRL antagonist could be used to improve the outcome of human breast cancer therapy in the near future.

Impact of peritoneal membrane transport on technique failure and patient survival in a population on automated peritoneal dialysis

The peritoneal equilibration test (PET) is well established as a tool for classifying patients as low (L), low average (LA), high average (HA), or high (H) peritoneal transporters. We performed this retrospective 6 year cohort survey to evaluate the impact of different types of PET results on technique survival and patient survival on automated peritoneal dialysis (APD) therapy. From March 1992 to May 1998, 50 patients (20 men, 30 women) receiving APD were enrolled. The mean follow-up period was 25.2 +/- 9.2 months. Basic data and PET results of each patient at the initiation of APD therapy were retrospectively obtained for analysis. Adequacy of dialysis was estimated by measurement of total weekly urea clearance (Kt) normalized to total body water (V) and total weekly creatinine clearance (Ccr) per 1.73 m2 body surface area. The clinical outcomes evaluated were technique survival and patient survival. For statistical analyses we used the Kruskal-Wallis test, Friedman test, Kaplan-Meier life table analysis, and Cox's proportional hazards regression model. There were no differences in age, gender, prevalence of diabetes mellitus (DM), duration of APD, or the initial value of serum albumin between the four subgroups (H, HA, LA, and L). There were 11 (22%) deaths and 8 (16%) technique failures. The 2 year patient survival probability was significantly higher (100%) in the L subgroup than in the LA (62.6%), HA (48.4%), or H (46.2%) subgroups. Patients with DM had a lower patient survival rate than patients without DM; however, there was no statistical significance in technique survival rate between them. Diabetes mellitus (RR = 2.898) and the final albumin value (RR = 0.2099 per increase of 1 gm/dl) had a significant influence on patient survival. By stepwise regression analysis of final serum albumin levels, we found that patients with lower serum albumin values (< or = 3.0 gm/dl vs. >3.0 gm/dl) had a significantly lower probability of patient survival (p = 0.0156). We conclusively demonstrate four important findings in this work: 1) patients with H peritoneal transport had a lower probability of patient survival, but not a decreased rate of technique survival; 2) patients with L peritoneal transport can tolerate APD well; 3) there was no significant difference in technique survival rate between the different PET subgroups; and 4) DM and a lower serum albumin, implicating malnutrition, may contribute to the lower probability of patient survival among H peritoneal transporters.

On-line derivatization for continuous and automatic monitoring of brain extracellular glutamate levels in anesthetized rats: a microdialysis study

Glutamate is an important excitatory amino acid in central nervous system. We developed a method for in vivo, continuous and automatic monitoring of brain extracellular glutamate, as well as other amino acids in anesthetized rat. This method involves the use of microdialysis perfusion technique and a high-performance liquid chromatography system equipped with a fluorescence detector. The microdialysate (perfused at a flow-rate of 1 microl/min) was on-line derivatized with o-phthaldehyde (perfused at 2 microl/min) through a mixing tee prior to the injection onto the HPLC column. The efficiency of this on-line derivatization was equivalent to that performed with an off-line manner. The effect of cerebral ischemia (2 h) and reperfusion (2 h) in brain cortex of anesthetized rats was monitored using this method. In addition to glutamate, extracellular concentrations of other amino acids, such as aspartate, glutamine, glycine, taurine and gamma-aminobutyric acid, were also simultaneously monitored with this on-line method. Since monitoring of extracellular amino acids by microdialysis perfusion is intensively used in neuroscience investigations, this simple and convenient method would be useful in the future applications.

Congenital hypothyroidism with multiple ovarian cysts

A case of ectopic thyroid with congenital hypothyroidism presenting with bilateral multicystic ovaries without marked precocious puberty is reported. The cystic ovaries disappeared dramatically after thyroid hormone therapy.

CONCLUSION

When ovarian cysts are found in prepubescent females, the possibility of associated hypothyroidism should be considered.

Maximum grip strength in normal subjects from 20 to 64 years of age

The purposes of this study were to develop normative maximum grip strength (GRIP) data for men and women aged 20 to 64 years, separated into nine five-year age groups, and to develop prediction equations for GRIP using gender, age, height, weight, and hand dominance. A total of 1,182 volunteers (553 men and 629 women) participated in the study. Maximum hand grips were obtained using the Jamar dynamometer with standardized positioning and instructions. The hand to be tested first was chosen randomly. Each hand was then tested alternately. Three trials were performed on each hand. The highest GRIP for each hand was used for analysis. Two-way analyses of variance showed significant differences between the right and left hands and across the age groups for both genders. Follow-up analyses showed that significant decreases occurred between the age groups of 50-54 and 55-59 years in men and between the age groups of 50-54 and 60-64 years in women. The data also indicated that right and left GRIPs were highly correlated with each other (r = 0.93). Gender, height, and weight moderately correlated with both GRIPS (r = 0.52-0.73. Age correlated weakly with both GRIPs (r = -0.17). If either the right or the left GRIP was known, the other GRIP could be predicted easily from the known GRIP, with 87% of variance accounted for. Without the knowledge of the other GRIP, either GRIP could be predicted through gender, height, weight, age, and hand dominance, with 61% to 62% of the explained variance. The norms and prediction equations of GRIP developed in this study for men and women aged 20 to 64 years will help clinicians with decision making regarding grip strength.

Alpha-tocopherol acetate significantly suppressed the increase in heart interstitial 8-hydroxydeoxyguanosine following myocardial ischemia and reperfusion in anesthetized rats

The effect of alpha-tocopherol acetate, an aqueous form of alpha-tocopherol, on the increase in heart interstitial 8-hydroxydeoxyguanosine (8-OH-dG) levels following myocardial ischemia/reperfusion was investigated. A microdialysis probe was implanted in the left ventricular interstitial space of anesthetized rat hearts. Myocardial ischemia was induced by ligating the left anterior descending coronary artery. Levels of 8-OH-dG in microdialysates were analyzed via an on-line high-performance liquid chromatography system equipped with an electrochemical detector. The 8-OH-dG levels significantly increased (maximum 3.6-fold of increase relative to basal value) during the 60-min reperfusion stage following a 20 min ischemia. Administration of alpha-tocopherol acetate (20 mg/kg, intravenous, bolus) at 3 min prior to onset of reperfusion, significantly suppressed the reperfusion-induced increase in 8-OH-dG levels. These results suggested that one of the possible protective effect of alpha-tocopherol acetate was to reduce oxidative DNA damage during in myocardial ischemia and reperfusion.

Microcalorimetric Studies of the Interactions of Lysozyme with Immobilized Metal Ions: Effects of Ion, pH Value, and Salt Concentration

This study extends previous research on the interaction of biomaterials with immobilized Cu(II) by isothermal titration calorimetry (ITC) on Fe(III). The difference of the binding behavior of protein with that of the immobilized metal ions is also discussed. For the immobilized Fe(III), ITC results show that the adsorption enthalpy at a constant pH value decreased as the NaCl concentration increased and also decreased with the pH values at constant NaCl concentrations. The adsorption enthalpy become negative under higher pH values or higher salt concentrations indicating the adsorption process is partly driven by the enthalpy. The enthalpy of lysozyme with Fe(III) is higher than that with Cu(II) implying that the heat required for the dehydration of Cu(II) is lower than for the dehydration of Fe(III) and/or that the heat generated from the formation of the coordination with Cu(II) is higher than with Fe(III). In addition, the comparison of different immobilized metal ions corresponding to the equilibrium binding affinity suggests that the binding force of lysozyme with Cu(II) is higher than with Fe(III). This study presents the chemical differences between the binding affinity and the adsorption enthalpy of lysozyme interacting with the immobilized metal ions. The binding and thermodynamic data presented in this study elucidate the mechanism and process of lysozyme binding with immobilized metal ions. In addition, the thermodynamic characteristic functions provide valuable information enabling a more thorough understanding of protein adsorption at the immobilized metal ion affinity surface. Copyright 1999 Academic Press.

Trichostatin A up-regulates human papillomavirus type 11 upstream regulatory region-E6 promoter activity in undifferentiated primary human keratinocytes

Human papillomavirus (HPV) gene expression in squamous epithelia is differentiation dependent in benign patient lesions and in organotypic raft cultures of primary human keratinocytes (PHKs). Using the lacZ reporter in raft cultures, we previously showed that this transcriptional regulation of the HPV type 11 (HPV-11) enhancer-promoter located in the upstream regulatory region (URR) appears to have resulted from coordination between the transcription transactivators AP1, Oct1, and Sp1 in differentiated upper strata and the repressor C/EBP in proliferating basal cells. We report here that trichostatin A, a specific inhibitor of histone deacetylase, dramatically stimulated reporter gene activity from the wild-type HPV-11 URR or the C/EBP mutation in PHKs grown in undifferentiated submerged cultures. In epithelial raft cultures, up-regulation occurred predominantly in basal and parabasal strata; this effect was promoter specific, as expression of the lacZ reporter gene driven by the murine leukemia virus long terminal repeat (LTR), the keratin 14 promoter, or the involucrin promoter was not altered, nor was expression of endogenous keratin 10 and profilaggrin affected. However, the responses were not cell type or species specific, as identical results were observed for both HPV-11 URR-lacZ and LTR-lacZ in murine retrovirus producer cell lines of fibroblast origin.

Expression of tissue-type and urokinase-type plasminogen activator activities in chronic venous leg ulcers

BACKGROUND

Chronic wounds have been shown to exhibit elevated levels of several classes of proteinases. Plasminogen activators (PAs) are proteinases which play a major role in the biological processes involved in wound healing and abnormalities in PAs may play a role in the pathology associated with chronic wounds. Here, we investigated the expression of tPA and uPA activities in chronic venous ulcer biopsies.

PATIENTS AND METHODS

In 22 patients with chronic venous leg ulcers, punch biopsies were taken from the ulcer base, ulcer margin and uninvolved skin from the thigh of the affected limb and PA activities were assessed using in situ histological zymography.

RESULTS

tPA is the main PA activity in uninvolved skin but was reduced in ulcer margin skin and venous leg ulcer tissue compared to normal skin. uPA activity appeared throughout the ulcer margin skin but was at low levels in normal skin. Ulcer base tissue appeared to exhibit a plasminogen-independent proteinase activity not seen in normal or ulcer margin skin.

CONCLUSION

PA activities are altered in and around chronic venous leg ulcers and their distribution suggests that blood vessels in CVI may be damaged and that the tissue is in an inflamed state.

Effects of glucocorticoids on maturation of pig oocytes and their subsequent fertilizing capacity in vitro

The aim of this study was to assess the possible role of glucocorticoids in the maturation of pig oocytes and their subsequent fertilizing capacity in vitro. Pig cumulus-enclosed oocytes collected from prepubertal gilts were cultured in Waymouth MB752/1 medium supplemented with sodium pyruvate (50 microg/ml), LH (0.5 microg/ml), FSH (0.5 microg/ml), and estradiol-17beta (1 microg/ml) in the presence or absence of cortisol or dexamethasone (DEX) for 24 h; they then were cultured without hormonal supplements in the presence or absence of cortisol or DEX for an additional 16-24 h. Treatment of cumulus-enclosed or denuded oocytes with increasing concentrations of cortisol or DEX for 48 h resulted in a dose-response inhibition of germinal vesicle breakdown (GVB). Increasing duration (12-48 h) of treatment with DEX (10 microg/ml) led to a time-dependent inhibition of GVB, which achieved statistical significance by 12 h. The addition of DEX (10 microg/ml) to maturation medium immediately after culture or at 12 h, 24 h, or 36 h after culture also decreased the percentage of oocytes with GVB. When oocytes were exposed to DEX for 48 h, the maturation rate was reduced. The degree of this reduction was dependent on DEX, and a concentration of DEX higher than 0.1 microg/ml was needed. The inhibitory effect of DEX on the maturation of oocytes was prevented by the glucocorticoid receptor antagonist RU-486. Exposure of oocytes to DEX for 40 h did not prevent sperm penetration, affect the incidence of polyspermy, or decrease the ability of oocytes to form a male pronucleus. The intracellular concentration of glutathione (GSH) in cumulus-enclosed oocytes was 4.4 mM per oocyte. Exposure of oocytes to DEX (0.01-10 microg/ml) had no effect on GSH concentration. These results demonstrate that glucocorticoids directly inhibit the meiotic but not cytoplasmic maturation of pig oocytes in vitro. This inhibitory effect is not mediated through a decrease in the level of intracellular GSH.

Functions of hyaluronan in wound repair

Hyaluronan is a major carbohydrate component of the extracellular matrix and can be found in skin, joints, eyes and most other organs and tissues. It has a simple, repeated disaccharide linear copolymer structure that is completely conserved throughout a large span of the evolutionary tree, indicating a fundamental biological importance. Amongst extracellular matrix molecules, it has unique hygroscopic, rheological and viscoelastic properties. Hyaluronan binds to many other extracellular matrix molecules, binds specifically to cell bodies through cell surface receptors, and has a unique mode of synthesis in which the molecule is extruded immediately into the extracellular space upon formation. Through its complex interactions with matrix components and cells, hyaluronan has multifaceted roles in biology utilizing both its physicochemical and biological properties. These biological roles range from a purely structural function in the extracellular matrix to developmental regulation through effects of cellular behavior via control of the tissue macro- and microenvironments, as well as through direct receptor mediated effects on gene expression. Hyaluronan is also thought to have important biological roles in skin wound healing, by virtue of its presence in high amounts in skin. Hyaluronan content in skin is further elevated transiently in granulation tissue during the wound healing process. In this review, the general physicochemical and biological properties of hyaluronan, and how these properties may be utilized in the various processes of wound healing: inflammation, granulation and reepithelization, are presented.

Wrapper, a novel member of the Ig superfamily, is expressed by midline glia and is required for them to ensheath commissural axons in Drosophila

The midline glia are specialized, nonneuronal cells at the midline of the Drosophila central nervous system (CNS). During development, the midline glia provide guidance cues for extending axons. At the same time, they migrate and help separate the two axon commissures. They then wrap around and ensheath the commissural axons. In many segments, a few of the glia do not enwrap the axons, and these cells die. The wrapper gene encodes a novel member of the immunoglobulin (Ig) superfamily. Wrapper protein is expressed specifically on the surface of midline glia. In wrapper mutant embryos, the midline glia express their normal guidance cues and migrate normally. However, they do not ensheath the commissural axons, and as a result, the glia die. In the absence of Wrapper, the two axon commissures are not properly separated.

Ki67 labelling index correlates with stage and histology but not significantly with prognosis in thymoma

AIMS

There have been several cell kinetic studies of thymoma, but the effectiveness of using Ki67 antibody as a tool to measure proliferative activity in this tumour was rarely evaluated. We carried out an immuno-histochemical study using this antibody to assess the clinicopathological correlation and the prognostic significance of this technique.

METHODS AND RESULTS

Ninety-one cases of thymoma were collected. Double immunostaining with Ki67 and cytokeratin KL-1 antibodies was performed on paraffin sections. Ki67 labelling index (LI) was expressed as a percentage of Ki67 immunopositive nuclei by counting at least 1000 epithelial cells. The LIs were correlated with stages, histological subtypes based on both Lattes-Bernatz and Müller-Hermelink-Kirchner classifications, and length of survival. There were statistically significant differences of LIs between stage I and stage III and between stage I and stage IV tumours. Histologically, statistically significant differences were identified between predominantly epithelial thymoma and every other subtype of the Lattes-Bernatz classification and between well-differentiated thymic carcinoma and medullary or mixed thymomas of the Müller-Hermelink-Kirchner classification. Regarding the prognostic implication of Ki67 LI, although there appeared a trend that patients with tumours of higher LIs had slightly worse survival, the difference was not statistically significant in both univariate and multivariate survival analyses.

CONCLUSIONS

We have demonstrated the proliferative potential in thymoma is associated with stage and histology. However, its clinical usefulness is limited on account of the overlap of LIs and lack of prognostic significance.

alpha2-adrenoceptors modulate NMDA-evoked responses of neurons in superficial and deeper dorsal horn of the medulla

Extracellular single unit recordings were made from neurons in the superficial and deeper dorsal horn of the medulla (trigeminal nucleus caudalis) in 21 male rats anesthetized with urethan. NMDA produced an antagonist-reversible excitation of 46 nociceptive as well as nonnociceptive neurons. Microiontophoretic application of a preferential alpha2-adrenoceptor (alpha2AR) agonist, (2-[2, 6-dichloroaniline]-2-imidazoline) hydrochloride (clonidine), reduced the NMDA-evoked responses of 86% (6/7) of nociceptive-specific (NS) neurons, 82% (9/11) of wide dynamic range (WDR) neurons, and 67% (4/6) of low-threshold (LT) neurons in the superficial dorsal horn. In the deeper dorsal horn, clonidine inhibited the NMDA-evoked responses of 94% (16/17) of NS and WDR neurons and 60% (3/5) of LT neurons. Clonidine facilitated the NMDA-evoked responses in 14% (1/17) of NS, 9% (1/11) of WDR, and 33% (2/6) of LT neurons in the superficial dorsal horn. Idazoxan, an alpha2AR antagonist, reversed the inhibitory effect of clonidine in 90% (9/10) of neurons, whereas prazosin, an alpha1-adrenoceptor antagonist with affinity for alpha2BAR, and alpha2CAR, were ineffective. We suggest that activation of alpha2ARs produces a predominantly inhibitory modulation of the NMDA-evoked responses of nociceptive neurons in the medullary dorsal horn.

A high throughput screen to identify secreted and transmembrane proteins involved in Drosophila embryogenesis

Secreted and transmembrane proteins play an essential role in intercellular communication during the development of multicellular organisms. Because only a small number of these genes have been characterized, we developed a screen for genes encoding extracellular proteins that are differentially expressed during Drosophila embryogenesis. Our approach utilizes a new method for screening large numbers of cDNAs by whole-embryo in situ hybridization. The cDNA library for the screen was prepared from rough endoplasmic reticulum-bound mRNA and is therefore enriched in clones encoding membrane and secreted proteins. To increase the prevalence of rare cDNAs in the library, the library was normalized using a method based on cDNA hybridization to genomic DNA-coated beads. In total, 2,518 individual cDNAs from the normalized library were screened by in situ hybridization, and 917 of these cDNAs represent genes differentially expressed during embryonic development. Sequence analysis of 1,001 cDNAs indicated that 811 represent genes not previously described in Drosophila. Expression pattern photographs and partial DNA sequences have been assembled in a database publicly available at the Berkeley Drosophila Genome Project website (). The identification of a large number of genes encoding proteins involved in cell-cell contact and signaling will advance our knowledge of the mechanisms by which multicellular organisms and their specialized organs develop.

[Studies on late replication bands of giant panda (Ailuropoda melanoleuca) chromosomes]

Using the cultured giant panda (Ailuropoda melanoleuca) lymphocytes as experimental material, we carried out the terminal marking on the chromosomes which were in replication by adding BrdU (a final concentration: 10 micrograms/ml) about four hours before harvesting the cells. The chromosomes marked by BrdU were proceeded by staining with acridine orange solution (0.05%), irradiated by ultraviolet and counter-stained by Giemsa, we obtained clear chromosomes replication patterns. According to the different replication bands, every chromosome's characteristics in late replication behavior could be identified. In the two X chromosomes of female individual, one X chromosome is obviously much later than the other one. Especially in the large area near centromere on the long arm of late replicating X chromosome. In the male individual, there is also a large area on the long arm of chromosome Y which replicates very late, but the end of long arm of chromosome Y replicates much earlier.

Effects of cyclophosphamide on maturation and subsequent fertilizing capacity of pig oocytes in vitro

This study examines the effects of cyclophosphamide, a widely used anti-cancer agent, on the maturation of pig oocytes and on their subsequent fertilizing capacity in vitro. Pig cumulus-oocyte complexes collected from prepubertal gilts were cultured in Waymouth MB 752/1 medium supplemented with sodium pyruvate (50 micrograms/ml), luteinizing hormone (0.5 microgram/ml), follicle-stimulating hormone (0.5 microgram/ml), and 17 beta-estradiol (1 microgram/ml) in the presence or absence of cyclophosphamide for 24 hr; they then were cultured without hormonal supplements in the presence or absence of cyclophosphamide for an additional 16-24 hr. The breakdown of germinal vesicle (GVBD) and changes in glutathione (GSH) content before in vitro fertilization were assessed. Oocytes containing one polar body and a metaphase plate were regarded as matured. Cytoplasmic maturation as determined by male pronuclear formation following fertilization in vitro was also examined. Treatment of oocytes with increasing concentrations (1-1000 micrograms/ml) of cyclophosphamide for 48 hr resulted in a dose-response inhibition of the rate of maturation, but had no effect on GVBD. Increasing duration (12-48 hr) of treatment with cyclophosphamide (100 micrograms/ml) led to a time-dependent inhibition of nuclear maturation, achieving statistical significance by 24 hr. The addition of cyclophosphamide (100 micrograms/ml) to maturation medium immediately after culture, 12 hr or 24 hr after culture also decreased the percentage of oocytes matured during a 48-h culture period. Exposure of oocytes to cyclophosphamide (100 micrograms/ml) for 40 hr did not prevent sperm penetration, not affect the incidence of polyspermy, or decrease the ability of oocytes to form a male pronucleus at 8 hr after insemination. The concentration of GSH, an important factor for male pronuclear formation, in pig oocytes was determined by an enzymatic cycling assay. The concentration found was 8.15 +/- 1.19 mM per oocyte. Exposure of oocytes to cyclophosphamide (100 micrograms/ml) had no effect on GSH concentration. These results demonstrate that cyclophosphamide directly inhibits the meiotic but not cytoplasmic maturation of pig oocytes in vitro. This inhibitory effect, apparently, is not mediated through a decrease in the level of intracellular glutathione.

Expression of E-cadherin and alpha- and beta-catenins in thymoma

Expression of the cell adhesion molecules including E-cadherin and its cytosolic binding proteins, alpha- and beta-catenins, has been widely studied in a variety of tumours, but not, to date, in thymic epithelial tumours. To observe the expression pattern of these adhesion molecules, immunohistochemical stains for E-cadherin (E-CD) and alpha- and beta-catenins were performed on 89 cases of thymoma which were classified as cortical (57 cases), mixed (18 cases), and medullary (14 cases), based on the classification of Marino and Müller-Hermelink. The majority of cortical thymomas showed diffuse and homogenous membrane immunoreactivity for these molecules (88 per cent for E-CD; 86 per cent for alpha-catenin; 91 per cent for beta-catenin) and the remaining cases showed heterogeneous immunoreactivity, whereas almost all mixed and medullary thymomas revealed decreased expression or were negative. In each histological subtype of thymoma, the expression did not correlate with invasion or with the presence of myasthenia gravis. These results indicate that the expression of E-CD and alpha- and beta-catenins is more closely associated with the histological subtypes of thymoma than with their biological behaviour.