Search

Keiji Hirai, Junki Morino, Saori Minato, Shohei Kaneko, Katsunori Yanai, Yuko Mutsuyoshi, Hiroki Ishii, Momoko Matsuyama, Taisuke Kitano, Akinori Aomatsu, Haruhisa Miyazawa, Kiyonori Ito, Yuichiro Ueda, Susumu Ookawara, Yoshiyuki Morishita Division of Nephrology, First Department of Integrated Medicine, Saitama Medical Center, Jichi Medical University, Saitama, JapanCorrespondence: Keiji HiraiDivision of Nephrology, First Department of Integrated Medicine, Saitama Medical Center, Jichi Medical University, 1-847 Amanuma-cho, Omiya-ku, Saitama-shi, Saitama-ken 330-8503, JapanTel +81-48-647-2111Fax +81-48-647-6831Email keijihirai@kfy.biglobe.ne.jpPurpose: The objective of this study was to determine factors associated with the change in carotid maximum intima-media thickness (IMT), an established surrogate marker of atherosclerosis, in moderate-to-advanced stage chronic kidney disease (CKD) patients.Methods: In total, 130 moderate-to-advanced stage CKD patients (mean age: 67.6 ± 11.0 years old; 91 men and 39 women) were included in this retrospective, single-center, observational study. Relationships between the change in carotid maximum IMT and clinical and laboratory data were analyzed by using multivariate linear regression analyses.Results: Mean observation period was 2.9 ± 1.6 years. Mean carotid maximum IMT at baseline was 2.2 ± 1.0 mm, and the annual change in carotid maximum IMT was 0.06 ± 0.22 mm/year. Low-density lipoprotein (LDL)-cholesterol (β = 0.173, p < 0.05) and annual change in triglyceride (β = 0.175, p < 0.05) independently correlated with the annual change in carotid maximum IMT.Conclusion: Increases in LDL-cholesterol and triglyceride were associated with the rate of progression of carotid maximum IMT in moderate-to-advanced stage CKD patients.Keywords: atherosclerosis, carotid maximum intima-media thickness, chronic kidney disease

Saori Minato, Keiji Hirai, Junki Morino, Shohei Kaneko, Katsunori Yanai, Yuko Mutsuyoshi, Hiroki Ishii, Momoko Matsuyama, Taisuke Kitano, Mitsutoshi Shindo, Akinori Aomatsu, Haruhisa Miyazawa, Kiyonori Ito, Yuichiro Ueda, Taro Hoshino, Susumu Ookawara, Yoshiyuki Morishita Division of Nephrology, First Department of Integrated Medicine, Saitama Medical Center, Jichi Medical University, Saitama, JapanCorrespondence: Keiji HiraiDivision of Nephrology, First Department of Integrated Medicine, Saitama Medical Center, Jichi Medical University, 1-847 Amanuma-cho, Omiya-ku, Saitama, Saitama 330-8503, JapanTel +81-48-647-2111Fax +81-48-647-6831Email keijihirai@kfy.biglobe.ne.jpAim: The aim of this study was to investigate different intensities of uremic pruritus in the daytime and nighttime, as well as contributing factors, in patients undergoing peritoneal dialysis (PD).Methods: A total of 46 patients (31 males, 15 females) with a mean age of 59.4± 14.7 years and mean PD vintage of 29.2± 25.2 months were enrolled in this single-center, prospective, cross-sectional study. The intensity of uremic pruritus in the daytime and nighttime was assessed using a visual analog scale (VAS). The relationships between intensity and various clinical and laboratory parameters were analyzed using multiple linear regression analyses.Results: The most common site of uremic pruritus was on the back (70%), followed by lower limbs (67%), chest and abdomen (59%), upper limbs (28%), and head and neck (22%). Mean VAS scores were higher in the nighttime compared with the daytime (4.5± 3.3 vs. 3.5± 2.7, P=0.02). Only male sex was correlated with higher uremic pruritus intensity in the daytime (standard coefficient [β]=0.310, P=0.036). PD vintage (β=0.415, P=0.004) and topical medicines, including moisturizer and topical corticosteroid use (β=0.345, P=0.019), were independently correlated with higher uremic pruritus intensity in the nighttime.Conclusion: Uremic pruritus intensity was greater in the nighttime than in the daytime in PD patients. Male sex was associated with higher uremic pruritus intensity in the daytime, whereas PD vintage and topical medicine use were associated with higher uremic pruritus intensity in the nighttime.Keywords: uremic pruritus, peritoneal dialysis &nbsp

Keiji Hirai, Junki Morino, Saori Minato, Shohei Kaneko, Katsunori Yanai, Yuko Mutsuyoshi, Hiroki Ishii, Momoko Matsuyama, Taisuke Kitano, Mitsutoshi Shindo, Akinori Aomatsu, Haruhisa Miyazawa, Kiyonori Ito, Yuichiro Ueda, Susumu Ookawara, Yoshiyuki Morishita Division of Nephrology, First Department of Integrated Medicine, Saitama Medical Center, Jichi Medical University, Saitama, JapanCorrespondence: Keiji HiraiDivision of Nephrology, First Department of Integrated Medicine, Saitama Medical Center, Jichi Medical University, 1-847 Amanuma-Cho, Omiya-Ku, Saitama City, Saitama 330-8503, JapanTel +81-48-647-2111Fax +81-48-647-6831Email keijihirai@kfy.biglobe.ne.jpIntroduction and Objectives: We investigated the efficacy and safety of sodium-glucose cotransporter-2 (SGLT-2) inhibitors as an add-on therapy in patients with advanced-stage diabetic kidney disease taking renin-angiotensin system (RAS) blockers.Materials and Methods: Changes in glycated hemoglobin (HbA1c), urine protein-to-creatinine ratio (UACR), body weight, systolic blood pressure, and annual change in estimated glomerular filtration rate (eGFR) were retrospectively analyzed in 20 patients after 12 months of SGLT-2 inhibitor administration (mean eGFR: 22.8 ± 9.7 mL/min/1.73 m2). All patients had advanced-stage diabetic kidney disease and were taking RAS blockers. Twenty patients matched with similar propensity scores who were not taking SGLT-2 inhibitors served as the control group.Results: The annual change in eGFR improved significantly from − 8.6 ± 12.5 mL/min/1.73 m2/year to − 2.6 ± 5.0 mL/min/1.73 m2/year after 12 months by SGLT-2 inhibitor administration (p < 0.05), but did not change in the control group. Other clinical parameters, such as HbA1c, UACR, body weight, blood pressure, serum lipids, and electrolytes did not change in either group. No adverse effects were observed by taking SGLT-2 inhibitors.Conclusion: Using SGLT-2 inhibitors as an add-on therapy may have beneficial effects on renal function in patients with advanced-stage diabetic kidney disease taking RAS blockers without any adverse effects.Keywords: advanced-stage diabetic kidney disease, renin-angiotensin system blocker, sodium-glucose cotransporter-2 inhibitor

Tritium (T) distributions in divertor tiles retrieved from the JET-ITER Like Wall (ILW) after the 1st (2011–2012) and 2nd (2013–2014) experimental campaigns were examined by measuring energy spectra of X-rays induced by β-rays from T. Disk specimens cored from the W-coated CFC divertor tiles (Tiles 1, 4, 6, 7 and 8) were analysed using a silicon-drift detector (SDD) equipped with an ultra-thin window (70 nm-thick Si3N4) at QST, Rokkasho. Analysis using a SDD with a conventional window (8 μm-thick Be) was performed at VTT. The former SDD was used to detect characteristic X-rays of Be together with those of W, while the latter was more suitable for non-destructive depth profiling by analysing X-ray energy spectra. A majority of T currently present in the JET vacuum vessel is produced by DD fusion reactions [D + D → T (1.01 MeV) + H (3.03 MeV)]. Therefore, T is present as a minor isotope of hydrogen in the vessel. A part of T produced is implanted into the tiles at high energy (~MeV), while a remaining part of T is thermalized in the plasma. Strong peaks of Be KαX-rays were observed for the horizontal and upper vertical parts of Tile 1 due to heavy co-deposition of T with Be eroded from the main chamber wall. Intensity of Be KαX-rays was below detection limit for other tiles because of far smaller thickness or absence of Be deposition layer. In contrast, the intensity of W MαX-rays was almost uniform though it was somewhat high at the positions close to the main plasma (the horizontal parts of Tiles 1 and 8). Depth profile analyses showed that T penetrated into depths up to 0.5–4 μm. These observations indicated the implantation of high energy T into the W layers. Exceptionally high intensity of X-rays (and also γ-rays) was observed at the shadowed region of Tile 4, though thermal desorption spectrometry showed relatively small D retention in this region. The mechanisms underlying this exceptional T accumulation will be discussed in the presentation by taking account of the results of microstructural analysis., 16th International Conference on Plasma-Facing Materials and Components for Fusion Applications (PFMC-16)

Energy spectra of β-ray induced x-rays from divertor tiles used in ITER-like wall campaigns of the Joint European Torus were measured to examine tritium (T) penetration into tungsten (W) layers. The penetration depth of T evaluated from the intensity ratio of W(Lα) x-rays to W(Mα) x-rays showed clear correlation with poloidal position; the penetration depth at the upper divertor region reached several micrometers, while that at the lower divertor region was less than 500 nm. The deep penetration at the upper part was ascribed to the implantation of high energy T produced by DD fusion reactions. The poloidal distribution of total x-ray intensity indicated higher T retention in the inboard side than the outboard side of the divertor region.

Peroxisome proliferator activator-receptor (PPAR)-gamma is a ligand-activated transcriptional factor belonging to a steroid receptor superfamily. PPAR-gamma plays a role in both adipocyte differentiation and carcinogenesis. Up-date, PPAR-gamma is expressed in various cancer tissues, and PPAR-gamma ligand induces growth arrest of these cancer cells. In this study, we examined the expression of PPAR-gamma in human urological cancer (including renal cell carcinoma, bladder tumor, prostate cancer and testicular cancer) by RT-PCR and immunohistochemistry, and we also examined the effect of PPAR-gamma ligand in these cells by MTT assay, flow cytometry and hoechest staining. PPAR-gamma expression was significantly more extensive and intense in malignant tissues than in normal tissues. PPAR-gamma ligand induced the reduction of malignant cell viability through early apoptosis. These results demonstrated that generated PPAR-gamma in urological cancer cells may play an important role in carcinogensis and become a new target therapy in the treatment of urological cancer.

Mutsushi Matsuyama,1,2 Kazuo Kato,3 Seiichi Goto,4 Suzuko Moritani,5 Kazuhiro Sentani,6 Makoto Kuroda7 1Clinical Laboratory, Hekinan Municipal Hospital, Hekinan, Aichi, 2Department of Cell Biology and Anatomy, Fujita Health University School of Medicine, Toyoake, Aichi, 3Clinical Laboratory, Rousai Hospital, Nagoya, Aichi, 4Department of Internal Medicine, Hekinan Municipal Hospital, Hekinan, Aichi, 5Department of Advanced Diagnosis, Division of Pathology, National Hospital Organization, Nagoya Medical Center, Nagoya, Aichi, 6Department of Molecular Pathology, Hiroshima University Graduate School of Biomedical Sciences, Hiroshima, 7Department of Diagnostic Pathology, Fujita Health University School of Medicine, Toyoake, Aichi, Japan Abstract: An 80-year-old man had severe lumbago that was diagnosed as multiple myeloma. He was treated with melphalan, prednisone, and zoledronic acid, with a good response. However, he had severe anemia, and endoscopic examination revealed gastric cancer. He died 3 months later. Autopsy revealed verrucous gastric cancer consisting of numerous polypoid mucosal excrescences that had metastasized to the gallbladder and urinary bladder, showing similar polypoid mucosal lesions. The cancer consisted of poorly differentiated cells (about 85%) and signet ring cells (15%) in the stomach. The cancerous tissue was not associated with a desmoplastic reaction, and the signet ring cells showed a positive reaction to cytokeratin 7 and regenerating islet-derived family member 4 antibodies. The cancer cells had a propensity to proliferate on the mucosal surface of the stomach, gallbladder, and urinary bladder. Keywords: warty gastric cancer, polypoid metastases, signet ring cells, cytokeratin 7, regenerating islet-derived family member 4

The correlation between the intensity of X-rays induced by β-rays of tritium and the total pressure of hydrogen isotope mixtures was examined in a pressure range from 10-1 to 105 Pa by using three different tritium gases, i.e., pure T2, D2-1%T2 and H2-1%T2 mixtures. It was found that linear pressure dependence was obtained up to a few kPa for all of the measured gases by taking dead time of the X-ray detector into account. Above this pressure, however, downward deviation from the linear relation appeared. It was revealed that the effect of self-absorption of β-rays on the pressure dependence was not negligibly small, because the ratios of the counting rates corrected by dead time to total pressure, i.e., specific counting rates, could not be reproduced by a simple exponential function using the absorption coefficients of hydrogen isotopes as variables. The results suggested that an additional factor such as contribution of an X-ray formation on the surfaces of a measuring cell must be taken into consideration in changing in the specific counting rates.

109 páginas, 53 figuras, 5 tablas, The present chapter deals with the estimation of female fecundity in fishes, mostly teleosts. The chapter is organized in three main blocks. The first block is devoted to technical issues of fish fecundity measurements from fixation, preservation and treatment of ovarian material to automatic oocyte counts. The use of certain staining protocols for the identification of follicular types in ovarian whole mounts and of inexpensive equipments in oocyte counting is also described. Because histology still constitutes the most unbiased method for identifying ovarian structures an array of stereological methods for estimating follicular intensity from assumption/model based methods (e.g. Weibel and oocyte packing density (OPD) method) to assumption/model free methods such as the physical disector or the fractionator principle is also provided. The second block is focused on methods used for the estimation of important variables such as batch fecundity (using hydrated oocytes and or previous developmental stages), daily fecundity and spawning fraction, S. Special emphasis is given to the estimation of S; the postovulatory follicle (POF) method is explicitly described together with its most common bias issues related to POF staging and ageing. In addition, methods that are based on imminent spawners, methods for stocks with high S values, and methods based on the assessment of spawning sites are also descibed. The third block incorporates knowledge acquired in the two other blocks to review what is needed to estimate the annual realized fecundity (the ultimate goal of fecundity studies) in determinate and indeterminate fish species. The autodiametric method for estimating potential annual fecundity, and the impacts of fecundity dowregualtion by atresia and of skipped-spawning in determinate spawners are also included. In short, this chapter will offer the reader an overview of all methodological aspects that need to be considered in fish fecundity investigations., COST Action FRESH (FA0601). NAFO Working Group on Reproductive Potential

109 páginas, 53 figuras, 5 tablas The present chapter deals with the estimation of female fecundity in fishes, mostly teleosts. The chapter is organized in three main blocks. The first block is devoted to technical issues of fish fecundity measurements from fixation, preservation and treatment of ovarian material to automatic oocyte counts. The use of certain staining protocols for the identification of follicular types in ovarian whole mounts and of inexpensive equipments in oocyte counting is also described. Because histology still constitutes the most unbiased method for identifying ovarian structures an array of stereological methods for estimating follicular intensity from assumption/model based methods (e.g. Weibel and oocyte packing density (OPD) method) to assumption/model free methods such as the physical disector or the fractionator principle is also provided. The second block is focused on methods used for the estimation of important variables such as batch fecundity (using hydrated oocytes and or previous developmental stages), daily fecundity and spawning fraction, S. Special emphasis is given to the estimation of S; the postovulatory follicle (POF) method is explicitly described together with its most common bias issues related to POF staging and ageing. In addition, methods that are based on imminent spawners, methods for stocks with high S values, and methods based on the assessment of spawning sites are also descibed. The third block incorporates knowledge acquired in the two other blocks to review what is needed to estimate the annual realized fecundity (the ultimate goal of fecundity studies) in determinate and indeterminate fish species. The autodiametric method for estimating potential annual fecundity, and the impacts of fecundity dowregualtion by atresia and of skipped-spawning in determinate spawners are also included. In short, this chapter will offer the reader an overview of all methodological aspects that need to be considered in fish fecundity investigations. COST Action FRESH (FA0601). NAFO Working Group on Reproductive Potential

It has been suggested that a heparin-binding growth factor, midkine (MK), plays an important role incarcinogenesis because of its frequent overexpression in various malignant tumours. To clarify whether or not MK contributes to theearly stage of carcinogenesis, we examined the status of MK mRNA in 20 adenomas with moderate- and severe-grade dysplasia, 28carcinomas and 28 corresponding normal tissues, by means of Northern blotting. The MK expression level was significantly moreelevated in adenomas than in normal tissues P< 0.001, unpaired Student's t -test). A difference wasalso observed between carcinomas and the corresponding normal tissues P< 0.04, paired Student's t-test). Moreover, MK immunostaining was positive in the adenomas with moderate- and severe-grade dysplasia and in the carcinomas,but not in mild-grade dysplasia or in normal tissues. These findings were in line with those on Western blotting. In three patientswith both adenomas with moderate- or severe-grade dysplasia and carcinomas, elevated MK expression was observed in the neoplasticlesions. This is the first report of the association of elevated MK expression with the early stage of carcinogenesis in humans. © 1999 Cancer Research Campaign

BUF/Mna strain rats spontaneously develop renal glomerular sclerotic lesions (RSL) at a nearly 100% incidence, diagnosed by hyperalbuminuria (greater than 500 mg/dl) and glomerular lesions morphologically resembling one type of human focal glomerular sclerosis (FGS). Genetic segregation of RSL development was studied by crossing the BUF/Mna strain with two other rat strains, WKY/NCrj and ACI/NMs, which were free of RSL. Two autosomal recessive genes in the BUF/Mna rats were found to determine the susceptibility to RSL in both combinations of crosses.

Seven clonal epithelial cell lines from a thymoma of an (ACI/NMs x BUF/Mna)F1 rat and seven clonal epithelial cell lines from an ACI/NMs rat thymus were established in a medium containing 1 microM dexamethasone (DM) and were characterized cytologically. Long-term treatment of DM stabilized the epithelial nature of these epithelial cells irreversibly. The established cell lines showed a polygonal shape, were positively stained with antikeratin antiserum and had tonofilaments and desmosomes. Species of their keratin peptides were the same as those of normal thymic epithelial cells in primary cultures. The cell lines were positively stained with Th-4 monoclonal antibody which preferentially stains the medullary epithelial cells of the thymus, but not with Th-3 which preferentially stains the subcapsular and cortical epithelial cells of the thymus. The cells from the rat thymoma were much larger than those from the normal thymus, as reflected in their primary cultures. No transformed phenotypes, such as high growth rate, high saturation density, anchorage independency, low serum dependency and so on, were found in the cell lines from the thymoma as in the cell lines from the normal thymus by in vitro assays. DNA synthesis of the thymic lymphocytes was stimulated by culturing with a line of rat thymoma with no lectins. Thymic lymphocytes strongly bound on the cell lines from the thymoma and changed the shape of the cells. These cell lines may be useful to investigate the mechanism of thymomagenesis and the interactions between epithelial cells and thymocytes in the rat thymoma.

Spontaneously developing focal and segmental glomerulosclerosis (FGS) in Buffalo/Mna rats was studied. There were no differences in the occurrence of the disease between male and female rats. Plasma macromolecules were detected in the urine samples of 2-month-old rats using sodium dodecyl sulphate polyacrylamide gel electrophoresis. All 4-month-old animals had proteinuria in excess of 30 mg/24 h. At the age of 4 months, sclerotic glomeruli were rarely observed. At the age of 6 months, all animals had a few sclerotic glomeruli in every kidney section examined. Animals which were 22 months old had sclerotic lesions in 37.8-52.1% of the glomeruli. Ultrastructural examination revealed that alterations in epithelial cells, such as effacement of foot processes, vacuolization, and a podocytic membrane-like structure, were found at the age of 2 months. The animals examined were neither uremic nor hypertensive. Our present study showed that female as well as male Buffalo/Mna rats had an earlier onset of the disease than the other strains of rats and that alterations in glomerular epithelial cells were first detected in the early stage of the disease.

N-Propyl N nitrosourea (PNU) is known to be a strong leukemogen, inducing myelogenous leukemia or thymic lymphoma in some strains of rat. The thymic lymphoma-genic effect of PNU has been demonstrated in F344 rats. On the other hand, the BUF/Mna rat has been established as an inbred strain that develops spontaneous thymomas after one year of age. In the present experiment, PNU was continuously administered in drinking water to male and female BUF/Mna rats starting at 5 weeks of age. Thymic lymphomas were induced in all PNU treated rats with an average latent period as short as 14 experimental weeks. These results show the high susceptibility of the BUF/Mna rat to the lymphomagenic activity of PNU. The BUF/Mna rat is an ideal strain for studies on epithelial cell-lymphocyte interaction, not only in the development of thymic lymphomas but also in that of spontaneous thymoma. Karyotypes of twelve primary thymic lymphomas induced by PNU were analyzed for chromosomal abnormalities. Chromosomal abnormalities were often found in chromosomes 11 and 2. In some types of abnormality, dup (llq) and del(2q) were most frequently observed. In addition, trisomy of chromosome 7, on which the c myc gene is mapped, was observed in five lymphomas, and monosomy of chromosomes 20 and X in six and five cases, respectively, though these changes were generally observed in a minor cell population in each case. Acta Pathol Jpn 39: 706-711, 1989.

The ontogenic development of lymphoid and non-lymphoid cells in human splenic white pulp was studied histologically with immunoperoxidase technique, together with that of lymphoid cells from fetal liver, bone marrow and thymus by membrane immunofluorescence assay. The primitive white pulp, which appeared as small accumulations of lymphocytes around arterioles at 14 weeks of gestation (g.w.), was mainly composed of B1 antigen-positive B cells. After the appearance of follicular structure accompanied by follicular dendritic cells (FDC) stained with anti-DRC1 antibody at 26 g.w., these perivascular structures of B cells were located in the periphery of the white pulp areas. A large number of B cells composing the perivascular structure had surface IgM (sIgM) and IgD (sIgD) from the earliest stage (14 g.w.), although this type of B cell with mature phenotype was seldom observed in fetal liver or bone marrow at this stage. It was suggested that the spleen is an important site for B-cell maturation from sIg-negative B cells observed in 10-14 g.w. fetal liver, and that FDC are not involved in this development of B cells. The organization of 9.6 antigen-positive T cells around arterioles developed 4 weeks later than that of B cells, at 18 g.w., although 11 g.w. fetal thymocytes already showed a phenotype very similar to that of infants. Interdigitating reticulum cells (IDC) stained with anti-S-100 protein serum appeared from 14 g.w. before the T-cell organization, suggesting that IDC may play an essential role in the homing of T cells.

Dipeptidyl-aminopeptidase IV (DAP-IV) was purified 850 fold with a yield of 16.5% from human kidney cortex. Only two chromatographic procedures of DEAE-cellulose and anti DAP-IV Sepharose were used. The purified enzyme was shown to be homogeneous by polyacrylamide gel electrophoresis in the presence of sodium dodecylsulfate. Among various substrates with the structure of X-Y-p-nitroanilide, Lys-Pro-Gly-Pro- and Arg-Pro-p-nitroanilides were hydrolyzed very fast by DAP-IV. Optimum pH of DAP-IV in human kidney was pH 8.7, Km value for Gly-Pro-pNA was 2.51 +/- 0.01 x 10(-4) M and V max was 66.6 +/- 0.7 mumol/min/mg protein. Diisopropylfluorophosphate completely inhibited DAP-IV at 0.1 mM. However, the enzyme was almost unaffected by N-ethylmaleimide, p-chloromercuribenzoate, iodoacetate, phenylmethylsulfonylfluoride, and several metals. The amino acid composition of DAP-IV purified from human kidney was similar to that of DAP-IV purified from pig kidney, liver and intestine. These results indicate that the properties of DAP-IV purified from human kidney are almost same as those from pig kidney.

A close relationship was assumed between the developments of nephropathy and thymoma in the previous study, in which the effect of introduction of the rat nude gene was studied in high thymoma BUF/Mna rats. In this paper, the effect of neonatal thymectomy on the development of nephropathy was examined to clarify the relationship between these two lesions in BUF/Mna rats. The average amount of urinary protein excreted from sham-operated and thymectomized BUF/Mna rats was 30.8 +/- 17.1 and 40.0 +/- 20.0 mg/day, respectively, and the number of affected glomeruli per 100 glomeruli 4.9 +/- 1.0 and 5.3 +/- 2.0, respectively. There were no significant differences in the urinary protein content, the number of the affected glomeruli, and immunofluorescence findings. In a control group, ACI/NMs rats exhibited 8.9 +/- 2.6 mg/day protein in urine and 0.8 +/- 0.4% affected glomeruli, which were significantly different from that of sham-operated and thymectomized BUF/Mna rats. These results indicate that nephropathy in BUF/Mna rats results neither from thymoma itself nor from the immunological abnormality secondary to it, and suggest that this lesion might be ascribed to a genetic factors.