Purkinje cell degeneration in mice lacking the xeroderma pigmentosum group G gene

Laboratory mice carrying the nonfunctional xeroderma pigmentosum group G gene (the mouse counterpart of the human XPG gene) alleles have been generated by using gene-targeting and embryonic stem cell technology. Homozygote animals of this autosomal recessive disease exhibited signs and symptoms, such as postnatal growth retardation, reduced levels of activity, progressive ataxia and premature death, similar to the clinical manifestations of Cockayne syndrome (CS). Histological analysis of the cerebellum revealed multiple pyknotic cells in the Purkinje cell layer of the xpg homozygotes, which had atrophic cell bodies and shrunken nuclei. Further examination by an immunohistochemistry for calbindin-D 28k (CaBP) showed that a large number of immunoreactive Purkinje cells were atrophic and their dendritic trees were smaller and shorter than in wild-type littermates. These results indicated a marked degeneration of Purkinje cells in the xpg mutant cerebellum. Study by in situ detection of DNA fragmentation in the cerebellar cortex demonstrated that some deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin in situ nick labeling (TUNEL)-positive cells appeared in the granule layer of the mutant mice, but few cell deaths were confirmed in the Purkinje layer. These results suggested Purkinje cell degeneration in the mutant cerebellum was underway, in which much Purkinje cell death had not appeared, and the appearance of some abnormal cerebellar symptoms in the xpg-deficient mice was not only due to a marked Purkinje cell degeneration, but also to damage of other cells.

[Le Duc-Camey procedure as a method of ureteroileal implantation on augmentation cystoplasty in patients with myelodysplasia]

PURPOSE

We investigated the results of Le Duc-Camey procedure as a method of ureteroileal implantation on augmentation cystoplasty in patients with myelodysplasia.

MATERIALS AND METHODS

A total of 14 patients (25 renal units) underwent ureteroileal implantation with Le Duc-Camey procedure on augmentation cystoplasty. The possible causes of complications concerning ureteroileal implantation that developed during the postoperative observation were classified as preoperative factors and postoperative factors.: The preoperative factors were the causative disease required ureteroneostomy, the grade of preoperative VUR, and the ureteral diameter at the anastomosis with the ileum.: The postoperative factors were the volume, and the compliance of the urinary bladder, and the maximum intravesical pressureled by the peristalsis of the utilized intestine.

RESULTS

With the mean observation period of 31.6 months, no complications developed but VUR observed in 4 renal units of 4 patients. The patients with VUR had a larger ureteral diameter at the anastomosis site to the ileum among the preoperative factors and a significantly larger maximum intravesical pressure led by the intestinal peristalsis among the postoperative factors when compared with the patients without VUR.

CONCLUSION

Regarding ureteroileal implantation with Le Duc-Camey procedure on augmentation cystoplasty in patients with myelodysplasia. It seems necessary to consider some countermeasures for the dilated ureters and for the unexpected 2 elevation of intravesical pressure due to the peristalsis of the utilized intestine.

Dimerization and nuclear localization of ku proteins

Ku, a heterodimer of Ku70 and Ku80, plays a key role in multiple nuclear processes, e.g. DNA repair, chromosome maintenance, and transcription regulation. Heterodimerization is essential for Ku-dependent DNA repair in vivo, although its role is poorly understood. Some lines of evidence suggest that heterodimerization is required for the stabilization of Ku70 and Ku80. Here we show that the heterodimerization of these Ku subunits is important for their nuclear entry. When transfected into Ku-deficient xrs-6 cells, exogenous Ku70 and Ku80 tagged with green fluorescent protein accumulated into the nucleus, whereas each nuclear localization signal (NLS)-dysfunctional mutant was undetectable in the nucleus, supporting the idea that each Ku can translocate to the nucleus through its own NLS. On the other hand, the nuclear accumulation of each NLS-dysfunctional mutant was markedly enhanced by the presence of an exogenous wild-type counterpart. In Ku-expressing HeLa cells, each NLS-dysfunctional mutant, as well as wild-type Ku70 and Ku80, was still detectable in the nucleus, whereas the double mutant of each Ku subunit with decreased functions of both nuclear targeting and dimerization was undetectable in the nucleus. Our results indicate that each Ku subunit can translocate to the nucleus not only through its own NLS but also through heterodimerization with each other.

Suppression of apoptosis in hepatocytes by fructose-modified dendrimers

By immobilizing fructose-modified dendrimers on a polystyrene culture plate, the number of initially adhered hepatocytes on it was increased. Moreover, increasing the number of generations of fructose-modified dendrimer (fructose-dendrimer) increased the number. Urea synthesis per unit area also was increased, corresponding to the increase in the number of initially adhered hepatocytes. This result suggests that the fructose-dendrimers do not cause a decline in cell function. On the other hand, apoptosis of hepatocytes occurs during cultivation, and results in a decrease in the number of adhered cells and a decline in cell function. Fructose-dendrimers were found to suppress apoptosis of hepatocytes. This characteristic is considered to be responsible for the increase in the number of initially adhered hepatocytes without a decline in cell function. Fructose-dendrimers are shown to be very suitable scaffolds for use in a high-performance bioartificial liver support system.

Genetic polymorphisms of CC chemokine receptor 3 in Japanese and British asthmatics

Whole genome scan analyses have revealed that chromosomal region 3p21-24, which contains a gene cluster of CC chemokine receptors such as CCR3, is possibly linked to asthma. Because CCR3 ligands play a pivotal role in the selective recruitment and activation of inflammatory cells in the asthmatic airway, the authors examined whether there is any association between asthma and the CCR3 gene polymorphisms. Three polymorphisms were identified using the single stranded conformational polymorphism method in Japanese (Asian) and British (Caucasian) subjects; one silent mutation T51C and two missense mutations G824A and T971C. These polymorphisms were examined in 391 Japanese subjects (210 asthmatics and 181 nonasthmatic controls) and 234 British subjects (142 asthmatics and 92 nonasthmatic controls). Asthma diagnosis was based on episodic symptoms, documented wheeze, and the presence of reversible airflow limitation. CCR3 T51C demonstrated a significant association with the diagnosis of asthma in the British population (odds ratio 2.35, p<0.01), but not in the Japanese population. Multiple logistic regression analysis also showed that CCR3 T51C was associated with asthma (odds ratio 2.83, p < 0.02), independent of atopic phenotypes such as high levels of total or house dust mite-specific immunoglobulin-E in serum. In conclusion, a significant association between asthma and CCR3 T51C polymorphism localized on chromosome 3p21 was found.

Ku70 can translocate to the nucleus independent of Ku80 translocation and DNA-PK autophosphorylation

Ku plays an important role in multiple nuclear processes, e.g., DNA repair, chromosome maintenance, and transcriptional regulation. Although some evidence suggests that the nuclear translocation of Ku plays a key role in regulating the function of Ku, the mechanism is poorly understood. Using the site-directed mutagenesis technique, we demonstrate here that Ku70 can translocate to the nucleus without heterodimerization with Ku80. The nuclear accumulation of Ku70 mutants of the nuclear localization signal, which retained their binding ability with Ku80, was diminished. On the other hand, Ku70 mutants which lacked the ability to bind with Ku80 could translocate to the nuclei. Human Ku70, when transfected, accumulated within the nuclei of hamster xrs-6 cells which had undetectable DNA-PK activity and Ku80. Ku70 and Ku80 mutants of DNA-PK phosphorylation sites showed normal heterodimerization and nuclear translocation. These findings also support the idea that Ku70 can translocate to the nucleus independent of DNA-PK autophosphorylation.

Antioxidative activity of (-)-epigallocatechin-3-(3''-O-methyl)gallate isolated from fresh tea leaf and preliminary results on its biological activity

Antioxidative activity of (-)-epigallocatechin-3-(3''-O-methyl)gallate (catechin e) was examined. Catechin e showed a strong antioxidative activity. A preliminary test using rat cancer cells suggests that catechin e also has a strong cytotoxic activity. Among tested catechins, only catechin e has strong activity for both.

Control of blood pressure and lifestyle-related risk factors in elderly Japanese hypertensive subjects

The aim of this study was to analyze the treatment of elderly hypertensive patients by Japanese physicians specializing in hypertension. We enrolled 939 patients with hypertension who were treated in the outpatient clinics of 11 hospitals in 1995; 793 of these patients (388 men and 405 women; mean age, 66.6+/-9.0 years) received follow-up examinations in 1996, and the data on these patients was used for the present analysis. Blood pressure (BP), body mass index, lifestyle, and laboratory data were analyzed in all patients. The average BP was 143+/-16/81+/-10 mmHg in 1995 and 142+/-15/80+/-10 mmHg in 1996. The patients whose baseline BP was at the level of Grade 2 or 3 in the WHO-ISH classification (n=117) were characterized by a higher women-to-men ratio, higher age, a higher serum total cholesterol concentration, and higher QRS voltage. In these patients, from 1995 to 1996, the average BP significantly decreased, whereas fasting plasma glucose, serum total cholesterol and serum creatinine concentrations showed only negligible changes. In 220 patients (28%), BP was <140/<90 mmHg at both the initial and the follow-up examinations, whereas 351 patients (44%) were hypertensive in both 1995 and 1996. Thirty-three percent of the patients were smokers. More smokers than nonsmokers had had prior cardiovascular events, diabetes mellitus, or overt proteinuria. In conclusion, the average BP level among the patients treated by Japanese physicians specializing in hypertension was somewhat higher than that recommended by WHO-ISH Guidelines (1999). Patient education to control lifestyle-related risk factors, particularly to stop smoking, should be emphasized.

Primary pulmonary hypertension with central sleep apnea: sudden death after bilevel positive airway pressure therapy

An obese 23-year-old man with sleep-disordered breathing and primary pulmonary hypertension (PPH) had been administered oral beraprost sodium, anticoagulant warfarin, and home oxygen therapy, at another hospital as treatment for the PPH, but he had not experienced any symptomatic improvement. The patient had a body mass index of 32.4kg/m2, and complained of fatigue, shortness of breath on exertion, excessive daytime sleepiness, and snoring. Arterial blood gas analysis showed a PaO2 and a PaCO2 of 70.9 and 31.2mmHg, respectively. A polysomnographic study revealed central sleep apnea with an apnea-hypopnea index (AHI) of 29.7episodes/h. The patient showed improvement of daytime sleepiness after starting nocturnal nasal bilevel positive airway pressure (BiPAP) therapy for the central sleep apnea, but his pulmonary hypertension, measured in the daytime, worsened. The patient died suddenly while walking to the bathroom in the morning 1 month after initiation of BiPAP therapy. It is necessary to consider the possibility of sudden death when nasal BiPAP therapy is given to a PPH patient with central sleep apnea.

[Telemedicine and lifestyle modifications in obstructive sleep apnea patients]

The recent advent of information technology(IT) has led to the application of telemedicine to the diagnosis of sleep-disordered breathing(SDB) such as obstructive sleep apnea(OSA). Trials with automatic SDB analyzers(Night Watch and Alice 4) are investigating the use of home SDB testing via telephone circuits or the internet, home continuous positive airway pressure(CPAP) titration via remote-control, and super-remote polysomnographic monitoring using the time difference between Japan and the United States. In 1994, we developed a computer-controlled lifestyle improvement support system(AILIFE) using a telephone circuit. The support system is expected to heighten the effectiveness of treatments for OSA with CPAP, prosthetic mandibular advancement, or uvulopalatopharyngoplasty by improving the lifestyle of OSA patients through the provision of home-based guidance on nutrition and exercise via telecare.

[Sleep apnea syndrome (SAS) and ischemic heart disease (IHD)]

Several epidemiological studies have suggested that sleep-disordered breathing is a risk factor for cardiovascular disease, particularly hypertension, stroke and IHD. The relative risk for IHD among obstructive SAS(OSAS) patients is 1.2 to 6.9 higher compared with the general population. The prevalence of SAS with an apnea-hypopnea index(AHI) of 10 and over was 35 to 40% in IHD, while 23.8% of SAS patients had IHD. These evidence suggests that IHD is an important prognostic factor in SAS patients. Characteristic pathophysiological conditions such as sleep apnea-induced hypoxemia and sympathetic activation may play an important role in the genesis of nocturnal angina pectoris. Most patients with OSAS are obese, and the complication of non-insulin dependent diabetes mellitus is quite a few. Insulin resistance is also attracting great attention as a cause of the cardiovascular complication of SAS.

Sleep apnea syndrome in patients with pulmonary thromboembolism

Seven patients (one man and six women) with a diagnosis of pulmonary thromboembolism (PTE) were examined by polysomnography in order to clarify the relationship between sleep-related breathing disorders and PTE. In the chronic stage of PTE, sleep apnea syndrome (SAS) was recognized in two patients (a man and a woman) among the subjects. Four of the five patients without SAS showed nocturnal hypoxemia. The female predominance was different from ordinary SAS without the disease background of PTE even though PTE is accompanied by hypoxemia and pulmonary hypertension like SAS. A pathophysiological relationship between PTE and SAS was not found in this study.

Longitudinal follow-up study of smoking-induced lung density changes by high-resolution computed tomography

To evaluate the ability of high-resolution computed tomography (HRCT) to detect longitudinal changes in structural abnormalities caused by smoking, HRCT and pulmonary function tests were used to examine nonsmokers, current smokers, and past smokers annually for 5 yr. Inspiratory HRCT was taken for the upper, middle, and lower lung fields, while expiratory images were obtained for the upper and lower lung fields only. We estimated the three quantitative CT parameters including MLD (mean CT value), HIST (CT value with the most frequent appearance), and %LAA (relative area of low attenuation with CT values less than -912 HU). Most of the pulmonary function tests, excepting FEV(1), did not change annually, whereas many of the inspiratory HRCT parameters did. In nonsmokers, only %LAA in the middle or lower lung fields exhibited an annual increase. In current smokers, %LAA in the upper lung field was augmented, while inspiratory MLD or HIST in the middle or lower lung field became more positive. In past smokers, %LAA in any lung field examined increased. The annual change in %LAA in the upper lung field was larger for past smokers than nonsmokers, with little difference between past and current smokers. Expiratory CT parameters showed few annual changes in all groups. In conclusion, (1) aging increases airspace abnormalities, mainly in the lower lung field; (2) although continuous smoking worsens airspace abnormalities mainly in the upper portion of the lung, this trend does not seem to slow down even after smoking cessation; and (3) inspiratory HRCT images are superior to expiratory images for longitudinal estimation of structural abnormalities caused by aging and smoking.

Immobilization of ligand-modified polyamidoamine dendrimer for cultivation of hepatoma cells

Cationic polyamidoamine dendrimers are known to be highly branched cascade polymers. The core part of these polymers, tris(2-aminoethyl)amine, was immobilized onto polystyrene plates to which animal cells do not adhere. using photoreactive 4-(3-trifluoromethylazirino) benzoyl-N-succinimide (TDBA-OSu). Cells of a rat hepatoma cell line, H4-II-E-C3, adhered to a surface immobilized with a first-generation dendrimer probably through interactions between the terminal amino groups of the dendrimer and the cell membranes. The adhered cells were viable, could proliferate, and exhibited urea synthetic activity. The modification of the terminal amino groups with fructose increased the final number of cells obtained after 5 days of cultivation. Multigeneration dendrimers were prepared by repeated linkage of tris(2-aminoethyl)amine with the amino groups. Theoretically, the number of terminal amino groups available for ligand modification is twice as much for each generation of dendrimer growth. Cells cultivated on multigeneration fructose-modified dendrimers exhibited enhanced urea synthetic activity. The use of ligand-modified dendrimers is, therefore, considered to be very promising for the construction of bioartificial organs based on cultivation of the animal cells.

Ku80 can translocate to the nucleus independent of the translocation of Ku70 using its own nuclear localization signal

Ku antigen is a complex of Ku70 and Ku80 subunits and plays an important role in not only DNA double-strand breaks (DSB) repair and V(D)J recombination, but also in growth regulation. Ku is generally believed to always form and function as heterodimers on the basis of in vitro observations. Here we demonstrate that the localization of Ku80 does not completely coincide with that of Ku70. Ku70 and Ku80 were colocalized in the nucleus in the interphase but not in the late telophase/early G1 phase of the cell cycle. Since the in vivo function of Ku might be partially regulated by the control of its transport, we attempted to investigate the molecular mechanisms underlying the nuclear translocation of Ku. The nuclear translocation of Ku80 started during the late telophase/early G1 phase after the nuclear envelope was formed and this was preceded by the nuclear translocation of Ku70. Furthermore, we found that the Ku80 protein was transported to the nucleus without heterodimerization with Ku70. To understand in detail the mechanism of transport of Ku80, we attempted to identify the nuclear localization signal (NLS) of Ku80 and defined to a region spanning nine amino acid residues (positions 561 - 569). The Ku80 NLS was demonstrated to be mediated to the nuclear rim by two components of PTAC58 and PTAC97. All these findings support the idea that Ku80 can translocate to the nucleus using its own NLS independent of the translocation of Ku70.

Differential subcellular localization of DNA-dependent protein kinase components Ku and DNA-PKcs during mitosis

The Ku protein is a complex of two subunits, Ku70 and Ku80. Ku plays an important role in DNA-PKcs-dependent double-strand break repair and V(D)J recombination, and in growth regulation, which is DNA-PKcs-independent. We studied the expression and the subcellular localization of Ku and DNA-PKcs throughout the cell cycle in several established human cell lines. Using immunofluorescence analysis and confocal laser scanning microscopy, we detected Ku70 and Ku80 in the nuclei in interphase cells. In mitotic cells (1) most of Ku protein was found diffused in the cytoplasm, (2) a fraction was detected at the periphery of condensed chromosomes, (3) no Ku protein was present in the chromosome interior. Association of Ku with isolated chromosomes was also observed. On the other hand, DNA-PKcs was detected in the nucleus in interphase cells and not at the periphery of condensed chromosomes during mitosis. Using indirect immunoprecipitation, we found that throughout the cell cycle, Ku70 and Ku80 were present as heterodimers, some in complex with DNA-PKcs. Our findings suggest that the localization of Ku at the periphery of metaphase chromosomes might be imperative for a novel function of Ku in the G(2)/M phase, which does not require DNA-PKcs.

Obstructive sleep apnoea in a puerperal patient with Hallermann-Streiff syndrome

A 26 yr old puerperal female with Hallermann-Streiff syndrome developed serious obstructive sleep apnoea syndrome during pregnancy. She underwent an elective Caesarean section delivery, but ending the pregnancy did not improve her clinical symptoms. By treating her with nasal continuous positive airway pressure, a worsening of her headaches and glaucoma was prevented. The administration of acetazolamide controlled all of her symptoms. Treatment with nasal ventilation is the best initial approach. It is also important to assure normal oxygenation before pregnancy since the foetus may suffer from the severe deprivation that may occur in these patients.

Factors related to impairment of activities of daily living

OBJECTIVE

We examined the factors related to the impairment of activities of daily living (ADL).

METHODS

ADL was evaluated by using ADL-20, which consists of 20 items from 4 major categories of activities; mobility, self-care, instrumental, and communication. The patients' gender, birth date, clinical diagnosis, past history, life styles, physical findings, laboratory data, and details of therapy were also recorded. Patients A total of 1,163 outpatients aged 50 years or older were included. Data from 1,093 patients were analyzed.

RESULTS

We divided the subjects into two groups; Group I having full marks of ADL-20 (n=582) and group II exhibiting an impairment of ADL (n=511). Multiple logistic analysis revealed that in both sexes age and stroke were common independent factors related to the impairment of ADL. Other factors associated with impairment of ADL were smoking in men and presence of proteinuria in women. The presence of hyperlipidemia was associated with preservation of the ADL in women.

CONCLUSION

The results demonstrated significant associations of smoking in men and the presence of proteinuria in women with the impairment of ADL in elderly Japanese outpatients. There appears to be a sex difference in the risk factors of impairment of ADL.

[Effect of transurethral collagen injection for vesicoureteral reflux in patients with spina bifida]

BACKGROUND

The effect of endoscopic injection of collagen was assessed in spina bifida patients with vesicoureteral reflux (VUR).

METHODS

Endoscopic collagen injection was carried out for grade II or worse VUR according to the international classification. Twenty-two ureters were studied in 6 boys and 8 girls (mean: 14.4 years) who were followed up over a period of at least 3 months (mean: 5 months) after surgery they all had a negative preoperative skin test for collagen and were investigated radiologically and urodynamically. Cystograpy was performed 1, 3 and 12 months after surgery and thereafter once a year to detect recurrence of VUR.

RESULTS

Anesthesia was not necessary in 4 patients. No adverse reactions occurred to the injection of collagen. VUR disappeared after 1 and 2 collagen injections in 17 (77%) and 2 (9%) ureters, respectively. The therapeutic effect of the single collagen injection showed no relationship to shape of the ureteral orifice, grade of VUR, compliance of the bladder, and presence of detrusor hyperreflexia.

CONCLUSIONS

Endoscopic treatment of VUR with collagen injection in spina bifida patients is a simple and less invasive method. We obtained satisfactory short-term results by this method. However, since the risk factor of recurrence remains unclear, sufficient investigation of long-term results is important to determine the role of this method in the treatment of VUR in patients with spina bifida.

Cellular source(s) of platelet-activating-factor acetylhydrolase activity in plasma

Platelet activating factor (PAF) is immediately degraded and inactivated in the bloodstream by plasma PAF acetylhydrolase (PAF-AH). Although plasma PAF-AH-like activity was secreted in vitro from various cell types such as macrophages and hepatocytes, the exact cellular source(s) of this enzyme activity in vivo remains unclear. There is a naturally-occurring missense mutation (V279F) in the plasma PAF-AH gene in the Japanese population which results in complete loss of the enzyme activity. We analyzed 52 Japanese who had received an allogeneic bone marrow transplant and maintained donor-derived hematopoiesis. Ten recipients had chimeric plasma PAF-AH genotypes between the donor-derived peripheral blood leukocytes and the recipient-derived epithelial cells of buccal mucosa. Multiple regression analysis demonstrated that PAF-AH activity in plasma depended on the donor's genotype (standardized regression coefficient = 0.68, P < 0.0001), but not on the recipient's genotype (p = 0.48). One recipient who was a V279F homozygote in leukocytes and wild type homozygote in buccal mucosa had undetectable PAF-AH activity in plasma. We conclude that most of the PAF-AH activity in human plasma originates from hematopoietic lineage cells.

The nuclear localization signal of the human Ku70 is a variant bipartite type recognized by the two components of nuclear pore-targeting complex

Ku protein is a complex of two subunits, Ku70 and Ku80. Ku is suspected to participate in both DNA double-strand break repair and transcription. Since both of these processes take place in the cell nucleus, we have been investigating the subcellular localization and nuclear transport of Ku proteins. In the present study, we analyzed the subcellular localization and nuclear localization signal (NLS) of Ku70. Fusion proteins of Ku70 and green fluorescent protein (GFP) transiently expressed in cells were clearly localized in the nuclei of interphase cells. Ku70 staining was distributed throughout both the nucleus and the cytoplasm in late telophase to early G1 phase cells. The NLS of Ku70 was located at the region composed of 18 amino acid residues (positions 539 to 556). This region overlapped with the Ku80-independent DNA-binding domain reported previously. The Ku70 NLS consisted of two basic subregions and a nonbasic intervening region. All the subregions were necessary for complete NLS activity. The amino acids in the nonbasic intervening region of Ku70 might be important for full NLS activity not only to provide sufficient length between the two separated clusters of basic amino acids but also to have an adequate amino acid sequence. All of the basic amino acid residues in the basic subregions were conserved among mammalian and avian homologues, confirming their importance in the nuclear translocation of Ku70. The structure of the Ku70 NLS resembled the consensus of a bipartite-type NLS. The Ku70 NLS was mediated to target to the nuclear rim by two components of the nuclear pore-targeting complex, PTAC58 and PTAC97.

Multiple cardiovascular risk factors in obstructive sleep apnea syndrome patients and an attempt at lifestyle modification using telemedicine-based education

Severe obstructive sleep apnea syndrome (OSAS) is a typical 'lifestyle-related disease' characterized by a high incidence of cardiovascular risk factors, such as obesity, smoking, hypertriglyceridemia, and diabetes mellitus. Patients with OSAS tend to have eating disorders as a result of efforts to overcome the intolerable sleepiness. Treatment of OSAS should therefore aim to improve the lifestyle through encouraging weight reduction, physical activity increase, and tobacco avoidance, in addition to direct therapy such as continuous positive airway pressure for upper airway obstruction. The telemedicine system we developed was considered to be effective for providing home-based education on nutrition and exercise aimed at correcting multiple risk factors in OSAS patients

Postnatal growth failure, short life span, and early onset of cellular senescence and subsequent immortalization in mice lacking the xeroderma pigmentosum group G gene

The xeroderma pigmentosum group G (XP-G) gene (XPG) encodes a structure-specific DNA endonuclease that functions in nucleotide excision repair (NER). XP-G patients show various symptoms, ranging from mild cutaneous abnormalities to severe dermatological impairments. In some cases, patients exhibit growth failure and life-shortening and neurological dysfunctions, which are characteristics of Cockayne syndrome (CS). The known XPG protein function as the 3' nuclease in NER, however, cannot explain the development of CS in certain XP-G patients. To gain an insight into the functions of the XPG protein, we have generated and examined mice lacking xpg (the mouse counterpart of the human XPG gene) alleles. The xpg-deficient mice exhibited postnatal growth failure and underwent premature death. Since XPA-deficient mice, which are totally defective in NER, do not show such symptoms, our data indicate that XPG performs an additional function(s) besides its role in NER. Our in vitro studies showed that primary embryonic fibroblasts isolated from the xpg-deficient mice underwent premature senescence and exhibited the early onset of immortalization and accumulation of p53.

Effectiveness of polyamidoamine dendrimers modified with tripeptide growth factor, glycyl-l-histidyl-l-lysine, for enhancement of function of hepatoma cells

Cationic polyamidoamine dendrimers are known to be highly branched cascade polymers. Tripeptide growth factor, glycyl-L-histidyl-L-lysine (GHK), was employed as a ligand for activation or attachment of cells from a rat hepatoma cell line, H4-H-E-C3, and immobilized at the terminus of the dendrimer (GHK-dendrimer) to develop a suitable surface for use as a culture substratum in the bioartificial liver support system (BAL). The growth of cells was inhibited by increasing the number of generations of GHK-dendrimers. On the other hand, urea synthesis and lidocaine clearance of the cells adhered on fifth generation GHK-dendrimers were enhanced much more than on first generation GHK-dendrimers. GHK was shown to act as a growth inhibitor and an activator of hepatoma cells. These properties of GHK are advantageous for the utilization of hepatoma cells in BAL. Ligand-modified dendrimers are very promising for the creation of a high-performance substratum for cell culture and high performance bioartificial organs, as well as for high-performance bioartificial liver systems. GHK may have the potential to be a highly useful ligand.

Subcellular localization and protein-protein interaction regions of Ku proteins

The Ku protein is a complex of Ku70 and Ku80 subunits and is capable of binding promoters in a sequence-specific manner, although it remains unclear whether Ku is involved in transcriptional regulation. We examined the subcellular localization and determined the interaction regions of Ku. Our results indicate that heterodimers of Ku70 and Ku80 are localized in the nucleus, and that the stretches from amino acid (aa) 378 to 482 of Ku70 and from aa 374 to 502 of Ku80 are necessary for heterodimerization. These interaction regions do not contain any previously recognized protein-protein interaction motifs. To determine whether Ku contains a potential transcriptional activation domain, we examined N- and C-terminal deletion mutants of Ku70 and Ku80 for their ability to activate transcription in the GAL4-based one-hybrid system. We found that the whole Ku protein had no transcriptional activity, although the N-terminal peptide fragment of Ku70 was capable of activating transcription of the HIS3 and lacZ reporter genes in yeast cells.