Effects of oral administration of aflatoxin B1 and fumonisin B1 in rabbits (Oryctolagus cuniculus)

The effects of prolonged oral administration (21 days) of fumonisin B₁ (FB₁) and aflatoxin B₁ (AFB₁) were studied in male New Zealand rabbits by clinical, pathological, biochemical and sphingolipid analyses. Twenty-four animals were randomly divided into the following four experimental groups: (A) 0 mg FB₁ + 0 μg AFB₁/(kg body weight (bw) day) (control); (B) 0 mg FB₁ + 30 μg AFB₁/(kg bw day); (C) 1.5 mg FB₁/(kg bw day) + 30 μg AFB₁/(kg bw day); (D) 1.5 mg FB₁/(kg bw day) + 0 μg AFB₁. Animals from group B and principally from group C presented clinical signs of intoxication. Rabbits from group C presented a lower body weight gain than controls. Differences were observed between intoxicated rabbits and controls with respect to absolute and relative liver and kidney weight, hepatic function, serum urea and creatinine levels and Sa/So ratio. The most frequent hepatic and renal injuries were vacuolar degeneration of the liver and kidney as shown by the histopathological and serum biochemical results. Combined administration of AFB₁ and FB₁ resulted in synergistic toxic effects both in the liver and in the kidney, but hepatic injuries were more marked.     

Lysophosphatidic Acid Sensitises Ca Influx through Mechanosensitive Ion Channels in Cultured Lens Epithelial Cells

We investigated the effect of lysophosphatidic acid (LPA), a bioactive phospholipid, on the response in cytosolic free Ca²⁺ concentration ([Ca²⁺]_i) to mechanical stress in cultured bovine lens epithelial cells. Spritzing of bath solution onto cells as mechanical stress caused marked increase in [Ca²⁺]_i in the presence of LPA and this increase was concentration-dependent (1–10 μM), whereas neither addition of LPA alone nor the mechanical stress in the absence of LPA affected [Ca²⁺]_i. The mechanical stress-induced increase in [Ca²⁺]_i in the presence of LPA was inhibited by removing extracellular Ca²⁺ or by addition of Gd³⁺, a blocker of mechanosensitive cation channels, but not by nicardipine, thapsigargin, an inhibitor of endoplasmic reticulum-ATPase pump, or U73122, a phospholipase C inhibitor. These results show that LPA sensitises Ca²⁺ influx through cation-selective mechanosensitive channels, but does not sensitise Ca²⁺ release from intracellular stores, triggered by changes in mechanical stress. On the other hand, phosphatidic acid had less of a sensitising effect than LPA, and neither lysophosphatidylcholine nor chlorpromazine had any effect. Also Ca²⁺ mobilising agonists, ATP, histamine and carbachol, did not sensitise Ca²⁺ response to the mechanical stress. These results show that LPA sensitises mechanoreceptor-linked response in lens epithelial cells, suggesting that it plays a role in the development of cataracts due to increases in [Ca²⁺]_i induced by mechanical stress.     

Estrogen metabolism and formation of estrogen-DNA adducts in estradiol-treated MCF-10F cells. The effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin induction and catechol-O-methyltransferase inhibition

Formation of estrogen metabolites that react with DNA is thought to be a mechanism of cancer initiation by estrogens. The estrogens estrone (E₁) and estradiol (E₂) can form catechol estrogen (CE) metabolites, catechol estrogen quinones [E₁(E₂)-3,4-Q], which react with DNA to form predominantly depurinating adducts. This may lead to mutations that initiate cancer. Catechol-O-methyltransferase (COMT) catalyzes an inactivation (protective) pathway for CE. This study investigated the effect of inhibiting COMT activity on the levels of depurinating 4-OHE₁(E₂)-1-N3Ade and 4-OHE₁(E₂)-1-N7Gua adducts in human breast epithelial cells. MCF-10F cells were treated with TCDD, a cytochrome P450 inducer, then with E₂ and Ro41-0960, a COMT inhibitor. Estrogen metabolites and depurinating DNA adducts in culture medium were analyzed by HPLC with electrochemical detection. Pre-treatment of cells with TCDD increased E₂ metabolism to 4-OHE₁(E₂) and 4-OCH₃E₁(E₂). Inclusion of Ro41-0960 and E₂ in the medium blocked formation of methoxy CE, and depurinating adducts were observed. With Ro41-0960, more adducts were detected in MCF-10F cells exposed to 1 μM E₂, whereas without the inhibitor, no increases in adducts were detected with E₂ ≤ 10 μM. We conclude that low COMT activity and increased formation of depurinating adducts can be critical factors leading to initiation of breast cancer.     

Elevated F2-isoprostanes in thalassemic patients

This study was aimed at investigating oxidative stress in thalassemic patients by measurement of the oxidative damage biomarker, F₂-isoprostanes (F₂-IsoPs), using gas chromatography-mass spectrometry. The results showed that the mean value of urinary F₂-IsoPs, normalized with creatinine, in the thalassemic group was significantly higher than that from healthy subjects (3.38 ± 2.15 ng/mg creatinine vs 0.86 ± 0.55 ng/mg creatinine, respectively), and the mean value of plasma total F₂-IsoPs in the thalassemic group was also significantly higher than that from healthy subjects (0.39 ± 0.15 ng/ml vs 0.18 ± 0.03 ng/ml, respectively). Serum ferritin, erythrocyte superoxide dismutase (SOD), glutathione peroxidase, glutathione, and TBARS levels after treatment of erythrocytes with H₂O₂ were also investigated, and serum ferritin and erythrocyte SOD levels were significantly higher in thalassemic patients. Our findings are consistent with oxidative stress in thalassemia patients.     

重组水蛭素的突变及突变体部分性质研究

以基因突变结合动力学分析的方法研究了水蛭素空间结构及其与凝血酶的相互作用．采用基因定点突变和随机突变的方法得到两个重组水蛭素突变体,并从抗酰胺水解活性,抗凝血酶活力和稳定性三个方面,比较研究了重组水蛭素ｒＨＶ２中４７位和１１位两个氨基酸残基对其稳定性和抑制能力的影响．将ｒＨＶ２中Ｇｌｎ１１和Ａｓｎ４７分别突变为Ｈｉｓ１１和Ｌｙｓ４７后,ｒＨＶ２－Ｈ１１生物活力降低３０％,ｒＨＶ２－Ｋ４７生物活力提高６１％．测定抑制常数Ｋｉ表明,ｒＨＶ２－Ｈ１１突变体Ｋｉ值升高１４倍,ｒＨＶ２－Ｋ４７突变体Ｋｉ值降低１４倍,两个突变体的热稳定性均有所增强,ｒＨＶ２－Ｈ１１在酸性和碱性条件的稳定性降低．分析实验结果,可以认为：①４７位的Ｌｙｓ可能是通过氢键和静电两种作用力同时影响着水蛭素的三维结构和其与凝血酶的结合．②１１位氨基酸可能是水蛭素分子中另一个重要位点．     

Actions of endothelin-1 on prostaglandin production by gestational tissues

Endothelin-1 (10⁻¹¹M-10⁻⁷M) was incubated with human umbilical vein endothelial cells and cells derived from amnion and decidua and prostaglandin production was determined. The rates of biosynthesis of 6-keto-prostaglandin F₁ (6-keto-PGF₁) and prostaglandin E₂ (PGE₂) by endothelial cells were increased significantly by treatment with endothelin-1. Amnion cell PGE₂ production was reduced significantly by endothelin-1 treatment whereas decidual PGE₂ and prostaglandin F₂ production was unaffected by this treatment. Thus, it is possible that endothelins may play a part in the regulation of uteroplacental hemodynamics and the mechanisms of parturition.     

Effect of growth factors on in vitro development of caprine preantral follicle oocytes

The objective of this work was to examine the effect of various growth factors including epidermal growth factor (EGF) and insulin-like growth factor-I (IGF-I), either individually or in association, in the presence of follicle stimulating hormone (FSH) on the in vitro growth and viability of caprine preantral follicle oocytes. Preantral follicles were disassociated enzymatically and mechanically from prepuberal caprine ovaries after the animals were anesthetically ovariectomized. In experiment, caprine preantral follicles in groups 1–4 were cultured in growth culture medium, growth culture medium + EGF, growth culture medium + IGF-I and growth culture medium + IGF-I + EGF, respectively, for 9 days. The results indicated that EGF (50 mg/l) increased the survival rate of oocytes, but decreased the growth rate of oocytes; IGF-I (100 mg/l) effectively maintained the survival of oocytes and stimulated their growth; IGF-I (100 mg/l) and EGF (50 mg/l) in combination produced a higher effect on both of the survival and the growth rate of oocytes than IGF-I or EGF alone. Conclusively, the growth factors can effectively maintain the survival of caprine preantral follicle oocytes and regulated their growth in culture. EGF and IGF-I in association could synergically meliorate the culture system of caprine preantral follicle oocytes.     

Mycobacterium avium enters intestinal epithelial cells through the apical membrane, but not by the basolateral surface, activates small GTPase Rho and, once within epithelial cells, expresses an invasive phenotype

Mycobacterium avium is a common pathogen in AIDS patients that is primarily (but not exclusively) acquired through the gastrointestinal tract, leading to the development of bacteraemia and disseminated disease. To cause infection through the gut, binding and invasion of the intestinal epithelial barrier are required. To characterize this process further, we determined the cell surface(s) (basolateral vs. apical membrane) that M. avium interacts with in intestinal mucosal cells in vitro . The level of binding and invasion of both HT-29 and Caco-2 intestinal cell monolayers by M. avium were similar when the assay was performed with control medium in the presence of Ca²⁺ (when only the apical surface was exposed), with Ca²⁺-depleted medium or with Ca²⁺-depleted medium + 1 mM EGTA (exposure of both apical and basolateral membranes), suggesting that the bacterium enters the apical surface of the epithelial lining. These observations were confirmed by assays in a transwell system and by using fluorescent microscopy. Real-time video microscopy showed that M. avium entry was not associated with membrane ruffling and the use of pharmacological inhibitors of the small GTPases demonstrated that M. avium invasion is dependent on the activation of the small GTPases Rho, but not on Rac or Cdc42. Passage of M. avium through HT-29 cells led to a phenotypic change (intracellular growth; IG) that was associated with a significantly greater (between five- and ninefold) ability to bind to and invade new monolayers of epithelial cells or macrophages when compared with the invasion by M. avium grown on agar (extracellular growth; EG). IG phenotype invasion of HT-29 cells also takes place only by the apical surface. M. avium enters intestinal epithelial cells by the apical surface and, once within the cells, changes phenotype, becoming more invasive towards both macrophages and other epithelial cells.     

Uncoupler-reversible inhibition of mitochondrial ATPase by metal chelates of bathophenanthroline. II. comparison with other inhibitors

(1) Trisbathophenanthroline-Fe²⁺(BPh₃Fe²⁺) alters the hyperbolic relationship between concentration of ATP and reaction velocity of F₁-ATPase to sigmoidal, with a simultaneous decrease in maximal velocity. (2) BPh₃Fe²⁺ binds to the β-subunit of F₁ and competes with the binding of aurovertin. The reversal of this effect by uncouplers in enhanced by ADP and diminished by ATP. BPh₃Fe²⁺ also changes the hyperbolic concentration dependence of aurovertin binding to sigmoidal. (3) BPh₃Fe²⁺ stabilizes F₁ against cold inactivation and cold dissociation in an uncoupler-reversible manner. (4) BPh₃Fe²⁺ efficiently protects F₁ against the light-induced inactivation occurring in the presence of Rose Bengal, and the effect is reversed by uncouplers. (5) The results are discussed in relation to the reaction mechanism of F₁-ATPase and other enzymes catalyzing the reversible hydrolysis of pyrophosphate bonds.     

Selenite cataracts: Activation of endoplasmic reticulum stress and loss of Nrf2/Keap1-dependent stress protection

Cataract-induced by sodium selenite in suckling rats is one of the suitable animal models to study the basic mechanism of human cataract formation. The aim of this present investigation is to study the endoplasmic reticulum (ER) stress-mediated activation of unfolded protein response (UPR), overproduction of reactive oxygen species (ROS), and suppression of Nrf2/Keap1-dependent antioxidant protection through endoplasmic reticulum-associated degradation (ERAD) pathway and Keap1 promoter DNA demethylation in human lens epithelial cells (HLECs) treated with sodium selenite. Lenses enucleated from sodium selenite injected rats generated overproduction of ROS in lens epithelial cells and newly formed lens fiber cells resulting in massive lens epithelial cells death after 1–5 days. All these lenses developed nuclear cataracts after 4–5 days. Sodium selenite treated HLECs induced ER stress and activated the UPR leading to release of Ca^2 + from ER, ROS overproduction and finally HLECs death. Sodium selenite also activated the mRNA expressions of passive DNA demethylation pathway enzymes such as Dnmt1, Dnmt3a, and Dnmt3b, and active DNA demethylation pathway enzyme, Tet1 leading to DNA demethylation in the Keap1 promoter of HLECs. This demethylated Keap1 promoter results in overexpression of Keap1 mRNA and protein. Overexpression Keap1 protein suppresses the Nrf2 protein through ERAD leading to suppression of Nrf2/Keap1 dependent antioxidant protection in the HLECs treated with sodium selenite. As an outcome, the cellular redox status is altered towards lens oxidation and results in cataract formation.     

In vivo relevance for photoprotection by the vitamin D rapid response pathway

Vitamin D is produced by exposure of 7-dehydrocholesterol in the skin to UV irradiation (UVR) and further converted in the skin to the biologically active metabolite, 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) and other compounds. UVR also results in DNA damage producing cyclobutane pyrimidine dimers (CPD). We previously reported that 1,25(OH)₂D₃ at picomolar concentrations, protects human skin cells from UVR-induced apoptosis, and decreases CPD in surviving cells. 1,25(OH)₂D₃ has been shown to generate biological responses via two pathways—the classical steroid receptor/genomic pathway or a rapid, non-genomic pathway mediated by a putative membrane receptor. Whether the rapid response pathway is physiologically relevant is unclear. A cis-locked, rapid-acting agonist 1,25(OH)₂lumisterol₃ (JN), entirely mimicked the actions of 1,25(OH)₂D₃ to reduce fibroblast and keratinocyte loss and CPD damage after UVR. The effects of 1,25(OH)₂D₃ were abolished by a rapid-acting antagonist, but not by a genomic antagonist. Skh:hr1 mice exposed to three times the minimal erythemal dose of solar-simulated UVR and treated topically with 1,25(OH)₂D₃ or JN immediately after UVR showed reduction in UVR-induced UVR-induced sunburn cells (p < 0.01 and <0.05, respectively), CPD (p < 0.01 for both) and immunosuppression (p < 0.001 for both) compared with vehicle-treated mice. These results show for the first time an in vivo biological response mediated by a rapid-acting analog of the vitamin D system. The data support the hypothesis that 1,25(OH)₂D₃ exerts its photoprotective effects via the rapid pathway and raise the possibility that other D compounds produced in skin may contribute to the photoprotective effects.     

Production and Characterization of Hirudin Variant-1 by SUMO Fusion Technology in E. coli

Hirudin is the most potent non-covalent inhibitor of thrombin. Several expression systems have been used to produce recombinant hirudin for pharmaceutical purposes. However, high expression of active hirudin in Escherichia coli cytoplasm has not been successful owing to the fact that heterogenetic small peptide is easily degraded in the cell. To solve this problem, we constructed a recombinant form of the hirudin variant-1 (HV1) as a fusion protein with the small ubiquitin-related modifier gene (SUMO) by use of over-lap PCR. The fusion gene His₆-SUMO-HV1 was highly expressed in E. coli BL21 (DE3) in which the SUMO-HV1 accounts for over 30% of the soluble fraction. The fusion protein was purified by Ni?CNTA affinity chromatography and cleaved by a SUMO-specific protease Ulp1 to release the HV1 with natural N-terminal. The recombinant HV1 (rHV1) was further purified by Ni?CNTA affinity chromatography and then by Q anion-exchange chromatography. N-terminal sequencing result demonstrated the purified rHV1 had the same N-terminal sequence as the native hirudin. MALDI-TOF/MS analysis indicated that the molecular weight of the purified rHV1 protein was 6939.161 Da, which was similar to the theoretical molecular weight of rHV1 6,944 Da. The Chromozym TH assay result showed that the anti-thrombin activity of purified rHV1 was 8,800 ATU/mg and comparable to the specific activity of native hirudin.     

Estrone sulfate (E1S), a prognosis marker for tumor aggressiveness in prostate cancer (PCa)

Seeking insight into the possible role of estrogens in prostate cancer (PCa) evolution, we assayed serum E₂, estrone (E₁), and estrone sulfate (E₁S) in 349 PCa and 100 benign prostatic hyperplasia (BPH) patients, and in 208 control subjects in the same age range (50–74 years).

E₁ (pmol/L ± S.D.) and E₁S (nmol/L ± S.D.) in the PCa and BPH patients (respectively 126.1 ± 66.1 and 2.82 ± 1.78, and 127.8 ± 56.4 and 2.78 ± 2.12) were significantly higher than in the controls (113.8 ± 47.6 and 2.11 ± 0.96). E₂ was not significantly different among the PCa, BPH, and control groups. These assays were also carried out in PCa patients after partition by prognosis (PSA, Gleason score (GS), histological stage, and surgical margins (SM)). Significantly higher E₁S levels were found in PCa with: PSA > 10 ng/L (3.05 ± 1.92) versus PSA ≤ 10 ng/mL (2.60 ± 1.55), stage pT3-T4 (2.99 ± 1.80) versus pT2 (2.58 ± 1.58), and positive (3.26 ± 1.95) versus negative margins (2.52 ± 1.48). E₁ was higher in poor- than in better-prognosis PCa. E₂ was significantly higher in PCa with GS ≥ 4 + 3 (109.5 ± 43.8) versus GS ≤ 3 + 4 (100.6 ± 36.5) and increased significantly when GS increased from 3 + 3 to 4 + 4. Estrogens, especially E₁S appeared to be possible markers of PCa progression.

Attempting to identify potential sources of E₂ in PCa according to prognosis, as well as in BPH, we found a significant correlation coefficient between E₁S and E₂ (0.266–0.347) in poor-prognosis PCa and no correlation in BPH (0.026) and better-prognosis PCa (0.013–0.104).

It is as though during progression of PCa from good to poor prognosis there were a shift in the E₁ to E₂ metabolic pathway from predominantly oxidative to predominantly reductive.     

Synthesis, structure and biological activities of cobalt(II) and zinc(II) coordination compounds with 2-benzimidazole derivatives

In this work we present the synthesis, structural and spectroscopic characterisation of a series of cobalt(II) and zinc(II) coordination compounds with benzimidazole (bz) and its 2-benzimidazole derivatives: 2-aminobenzimidazole (2ab), albendazole (abz) and tris(2-benzimidazolylmethyl)amine (ntb). The compounds were evaluated for their in vitro antimicrobial activity against Staphylococcus aureus, Micrococcus luteus, Salmonella typhi, Pseudomonas aeruginosa, Escherichia coli and Proteus vulgaris. Their cytotoxic activity was also evaluated using human cancer lines, HeLa, HCT-15 and SKLU-1. The halide tetrahedral compounds [Co(bz)₂Br₂] 3, [Zn(2ab)₂Cl₂] · 0.5H₂O 11, [Co(abz)Cl₂(H₂O)] · 3H₂O 14, [Co(abz)Br₂(H₂O)] 15, [Zn(abz)Cl₂(H₂O)] · 3H₂O 17 and [Zn(abz)Br₂(H₂O)] · H₂O 18 displayed similar minimal inhibition concentration (MIC) values against Micrococcus luteus and Escherichia coli, comparable to those of amoxicillin and chloramphenicol. Additionally, 11 showed a wide range of activity towards Gram(+) and Gram(−) microorganisms. The tetradentate ntb and its trigonal bipyramidal cobalt(II) and zinc(II) compounds were active, regardless of the anion present in the complex. Compound [Co(abz)Cl₂(H₂O)] · 3H₂O 14 showed promising activity in HeLa cells, while [Co(ntb)Br]Br · H₂O 21 inhibited Hela and HCT-15 cell lines.     

The F1-ATPase beta-subunit is the putative enterostatin receptor

It has been suggested that the F₁-ATPase β-subunit is the enterostatin receptor. We investigated the binding activity of the purified protein with a labeled antagonist, β-casomorphin_1–7, in the absence and presence of cold enterostatin. ¹²⁵I-β-casomorphin_1–7 weakly binds to the rat F₁-ATPase β-subunit. Binding was promoted by low concentrations of cold enterostatin but displaced by higher concentrations. To study the relationship between binding activity and feeding behavior, we examined the ability of a number of enterostatin analogs to affect β-casomorphin_1–7 binding to the F₁-ATPase β-subunit. Peptides that suppressed food intake promoted β-casomorphin_1–7 binding whereas peptides that stimulated food intake or did not affect the food intake displaced β-casomorphin_1–7 binding. Surface plasmon resonance measurements show that the β-subunit of F₁-ATPase binds immobilized enterostatin with a dissociation constant of 150 nM, where no binding could be detected for the assembled F₁-ATPase complex. Western blot analysis showed the F₁-ATPase β-subunit was present on plasma and mitochondrial membranes of rat liver and amygdala. The data provides evidence that the F₁-ATPase β-subunit is the enterostatin receptor and suggests that enterostatin and β-casomorphin_1–7 bind to distinct sites on the protein.     

Effect of the isoflavone genistein against galactose-induced cataracts in rats

Worldwide, ocular cataracts are a major cause of human blindness. A key goal of cataract-related research is to identify simple, cost-efficient but effective ways to prevent cataract formation or progression. Genistein is a naturally occurring dietary isoflavone with well-documented estrogenic, antioxidant, and protein tyrosine kinase inhibitor activity, which in turn modulates the activity of several enzymes involved in cell signaling and proliferation. Furthermore, many isoflavones have been shown to be potent inhibitors of aldose reductase, which is an important rate-limiting enzyme in the process of cataract induction in the metabolic disease galactosemia. In order to assess the potential for genistein to mitigate cataract formation, we have studied its effects in the animal model of dietary galactose-induced cataracts in adult male rats. Our experimental hypothesis was that dietary genistein would prevent or delay the progression of cataracts induced by high dietary intake of galactose. Our results show that the isoflavone genistein was not able to completely prevent galactose-induced cataract formation, but genistein did delay the progression of cataracts induced by dietary galactose. In addition, we found that dietary galactose decreased concentrations of serum somatostatin, while adding genistein decreased the serum glucose level but increased the serum testosterone level. As an initial inquiry into the mechanisms by which the partial protective effect of genistein could be mediated, we found that genistein increased the expression of connexin (Cx) 43 in the lens but did not affect the expression of soluble guanylyl cyclase (sGC) subunits. This finding suggests that the partial protective effect of genistein on cataract induction appears to be unrelated to sGC but may be mediated by enhanced expression of Cx43 and changed metabolic state.     

Anterior polar cataract and lysosomal alterations in the lens of rats treated with the amphiphilic lipidosis-inducing drugs chloroquine and chlorphentermine.

Chronic treatment of rats with the amphipilic drugs chloroquine and chlorphentermine caused prominent anterior polar cataracts in virtually all rats. The basic pathologic changes underlying these cataracts were: (a) degeneration of anterior polar and sutural endings of cortical lens cells and (b) multilayered proliferation and invasion of epithelial cells into the anterior polar cortex. Ultrastructurally cortical lens cells displayed various patterns of degeneration, finally undergoing complete liquification. Liquified lens substance was phagocytosed by invading epithelial cells. Cortical lens cells and epithelial cells contained numerous lipidosis-like (lamellated) inclusions, which possessed cytochemical acid phosphatase activity. The present drug-induced lenticular alterations are interpreted as the direct or indirect consequences of a drug-induced disturbance of polar lipid metabolism in the lens.     

Anticancer activities of a chemically sulfated polysaccharide obtained from Grifola frondosa and its combination with 5-Fluorouracil against human gastric carcinoma cells

Chemically sulfated polysaccharide (S-GAP-P) was derived from water-insoluble polysaccharide of Grifola frondosa mycelia. In this research, we investigated the anticancer effects of S-GAP-P and its combination with 5-fluorouracil (5-FU) on human gastric carcinoma SGC-7901 cells. Results showed that S-GAP-P distinctly inhibited SGC-7901 cells growth in a dose-dependent manner and induced cell apoptosis evidenced by characteristic DNA ladder and sub-G₀/G₁ peak. Furthermore, the combination of S-GAP-P (10–50 μg/ml) with 1 μg/ml 5-FU resulted in a significant inhibition on SGC-7901 cells growth, meaning the beneficial interaction between the two drugs. All these results suggested that S-GAP-P has evident anticancer activity through apoptotic induction and could significantly accelerate the anticancer activity of 5-FU.     

A quantitative study of spermatogonial multiplication and stem cell renewal in the C3H/101 F1 hybrid mouse

In whole mounts of seminiferous tubules of C3H/101 F₁ hybrid mice, spermatogonia were counted in various stages of the epithelial cycle. Furthermore, the total number of Sertoli cells per testis was estimated using the disector method. Subsequently, estimates were made of the total numbers of the different spermatogonial cell populations per testis.

The results of the cell counts indicate that the undifferentiated spermatogonia are actively proliferating from stage XI until stage IV. Three divisions of the undifferentiated spermatogonia are needed to obtain the number of A₁ plus undifferentiated spermatogonia produced each epithelial cycle. Around stage VIII almost two-thirds of the A_pr and all of the A_al spermatogonia differentiate into A₁ spermatogonia. It was estimated that there are 2.5 × 10⁶ differentiating spermatogonia and 3.3 × 10⁵ undifferentiated spermatogonia per testis. There are about 35,000 stem cells per testis, constituting about 0.03% of all germ cells in the testis. It is concluded that the undifferentiated spermatogonia, including the stem cells, actively proliferate during about 50% of the epithelial cycle.     

甲氰菊酯和阿维菌素对柑橘全爪螨的亚致死效应

通过叶碟饲养的方法, 利用生命表技术,研究了甲氰菊酯和阿维菌素亚致死剂量LC₂₀处理柑橘全爪螨若螨后,对试验种群当代(F₀)和后代(F₁、F₂代)生长发育及繁殖的影响.结果表明: 甲氰菊酯LC₂₀处理若螨后,当代雌成螨产卵量显著增加;F₁、F₂代的产卵前期缩短,后代雌性比例增大,且均与对照差异显著;同时,F₁和F₂代种群内禀增长率(r_m)和周限增长率(λ)增大,世代历期(T)和种群加倍时间(Dt)缩短,且F₂代与对照相比差异显著.用阿维菌素LC₂₀处理若螨后,当代种群雌成螨产卵量显著下降; F₁和F₂代的产卵量也显著下降,但后代雌性比例增大,产卵前期显著缩短;F₁和F₂代的种群r_m和λ增大,T和Dt缩短,且F₂代比F₁代更为明显.总体来看,甲氰菊酯和阿维菌素亚致死浓度LC₂₀对柑橘全爪螨的影响并不完全相同,甲氰菊酯能够促进当代种群的发展,而阿维菌素对当代种群有一定的抑制作用;但两种杀螨剂亚致死浓度处理柑橘全爪螨对后代种群都有一定的促进作用.研究结果对柑橘全爪螨综合防治策略的制定有一定的指导意义.