Prevention of acetaminophen-induced cataract by a combination of diallyl disulfide and N-acetylcysteine

Injection of acetaminophen (APAP) (350 mg/kg body weight) into C57BL/6 mice in which cytochrome P450 (CYP) 1A1/1A2 had been induced produced acute cataract and other ocular tissue damage. Treatment of APAP-injected mice with one of the major organosulfides in garlic oil, diallyl disulfide (DADS) (200 mg/kg body weight), prevented cataract development and prolonged survival time. N-acetyl L-cysteine (NAC) (500 mg/kg body weight), a prodrug that stimulates glutathione synthesis, also prolonged survival time but was effective only weakly to prevent cataract formation. A combination of DADS and NAC completely prevented cataractogenesis, and all of the treated animals survived APAP toxicity. Neither DADS nor NAC inhibited CYP 1A1/1A2 induction as determined by their effect on the induction of hepatic microsomal ethoxyresorufin O-dealkylase (ERD) activity. However, in the in vitro enzyme assay, DADS, but not NAC, was a potent inhibitor of ERD activity (IC50 = 3.5 mM). Treatment with DADS or NAC slowed but did not stop the decrease of hepatic glutathione (GSH) content. At 4 hours after APAP injection, hepatic GSH began to increase only when DADS and NAC were administered together. These results suggest that the protective effect of DADS is due to its inhibition of biotransformation of APAP to the reactive metabolite N-acetyl-p-benzoquinone imine (NAPQI) by CYP 1A1/1A2 enzymes and that NAC provides protection by increasing cellular cysteine level and GSH synthesis, thus facilitating detoxification of NAPQI by glutathione conjugation. Assay of plasma glutamate-pyruvate transaminase activity, an indicator of liver necrosis, showed that treatment with DADS and NAC together effectively protected the liver. Therefore, the decrease of GSH as much as 30% of normal concentration, by itself, is not responsible for liver damage. The primary cause of hepatic necrosis is rapid accumulation of NAPQI.

Overexpression of lactate dehydrogenase A attenuates glucose-induced insulin secretion in stable MIN-6 beta-cell lines

Since islet beta-cells express little L-lactate dehydrogenase (LDH) activity, we have examined the effects on these cells of LDH overexpression. In mock-transfected MIN6 beta-cells, LDH activity was 38 nmol/min/mg protein, and 30 mM glucose stimulated secretion 10.4-fold. In two MIN6 cell clones stably overexpressing human LDH-A cDNA, insulin secretion was stimulated only 2.7- and 2.1-fold by high glucose. K+-stimulated insulin secretion was unaffected, and leucine stimulation enhanced, by LDH-A overexpression. LDH-A-overexpressing clones displayed unaltered activities of hexokinase, glucokinase, and malate dehydrogenase, slightly elevated plasma membrane lactate transport activity, and lowered insulin content. Low LDH activity would therefore appear important in beta-cell glucose sensing.

Secretory-granule dynamics visualized in vivo with a phogrin-green fluorescent protein chimaera

To image the behaviour in real time of single secretory granules in neuroendocrine cells we have expressed cDNA encoding a fusion construct between the dense-core secretory-granule-membrane glycoprotein, phogrin (phosphatase on the granule of insulinoma cells), and enhanced green fluorescent protein (EGFP). Expressed in INS-1 beta-cells and pheochromocytoma PC12 cells, the chimaera was localized efficiently (up to 95%) to dense-core secretory granules (diameter 200-1000 nm), identified by co-immunolocalization with anti-(pro-)insulin antibodies in INS-1 cells and dopamine beta-hydroxylase in PC12 cells. Using laser-scanning confocal microscopy and digital image analysis, we have used this chimaera to monitor the effects of secretagogues on the dynamics of secretory granules in single living cells. In unstimulated INS-1 beta-cells, granule movement was confined to oscillatory movement (dithering) with period of oscillation 5-10 s and mean displacement <1 microm. Both elevated glucose concentrations (30 mM), and depolarization of the plasma membrane with K+, provoked large (5-10 microm) saltatory excursions of granules across the cell, which were never observed in cells maintained at low glucose concentration. By contrast, long excursions of granules occurred in PC12 cells without stimulation, and occurred predominantly from the cell body towards the cell periphery and neurite extensions. Purinergic-receptor activation with ATP provoked granule movement towards the membrane of PC12 cells, resulting in the transfer of fluorescence to the plasma membrane consistent with fusion of the granule and diffusion of the chimaera in the plasma membrane. These results illustrate the potential use of phogrin-EGFP chimeras in the study of secretory-granule dynamics, the regulation of granule-cytoskeletal interactions and the trafficking of a granule-specific transmembrane protein during the cycle of exocytosis and endocytosis.

Histochemical and immunohistochemical studies of distribution of acetylcholinesterase-positive fibers and peptidergic terminals in the nasal mucosa of rats

OBJECTIVE

To further investigate the mechanism of nasal secretion closely related to the innervation patterns in nasal mucosa with emphasis on the acetylcholinesterase (AChE)-positive fibers and peptidergic terminals in nasal mucosa as well as trigeminal ganglion (TG) cells.

METHODS

Histochemical demonstration of AChE-positive fibers, immunohistochemical study of the distribution patterns of multiple peptidergic terminals, double labelling of AChE and substance P (SP) and somatostatin (SOM) mRNA in situ hybridization were carried out in nasal mucosa and trigeminal ganglion (TG) in rats.

RESULTS

AChE-positive terminals were mainly distributed in the mid to posterior one third of septal nasal mucosa, with greater staining density on the walls of small vessels and glands. There were fewer such terminals in turbinate mucosa. Tachykinins-ergic terminals, including substance P (SP)-, neurokinin A (NKA)-, neurokinin B (NKB)- and calcitonin gene-related peptide (CGRP)-ergic terminals, had an extensive localizations in nasal mucosa, involving the following areas: between epithelial cells, submucosa, the walls of small vessels, glands and venous sinusoids in both septal and turbinate nasal mucosa. Septal mucosa had the greater density. There were overlaps in the distribution of these peptidergic terminals. There were also vasoactive intestinal peptide (VIP)-, neuropeptide Y (NPY)- and galanin (GAL)-ergic terminals in nasal mucosa. But no neurotensin (NT)- and somatostatin (SOM)-ergic terminals were found. In situ hybridization revealed SOMmRNA expression in TG cells. AChE and nine neuropeptides existed in the cytoplasms of TG cells. Besides, AChE and SP could exist simultaneously in cytoplasms of TG cells.

CONCLUSIONS

AChE-positive (corresponding to parasympathetic nerves) and peptidergic terminals have different distribution patterns in the nasal mucosa of rats, although an overlap does exist, indicative of their different physiological effects on the regulation of nasal secretion and other functions; AChE and multiple neuropeptides in the cytoplasm of TG cells might play a role in modulating the nasal secretion in response to stimuli in the nasal mucosa.

[Immunohistochemical study on three peptidergic terminals in nasal mucosa in a rat AR model]

To study the density alterations of three peptidergic terminals in nasal mucosa of allergic rhinitis (AR), an exhaustive immunohistochemical sutdy on the changes of substance P (SP), neurokinin A (NKA) and neurokinin B (NKB) in nasal mucosa was carried out in a toluene-2, 4-isocyanate (TDI)-induced rat AR model. The densities of all three tachykininergic terminals in nasal mucosa were significantly increased (P < 0.01) in experimental group as compared with control group. Increased staining, thickening of peptidergic terminals as well as enlargement of varicosities were observed. The increased densities of three tachykininergic terminals (SP, NKA and NKB) in nasal mucosa in rat AR model indicates that tachykinins play an important role in the pathogenesis of AR.

[Distribution of substance P receptors in rat nasal mucosa of allergic rhinitis]

OBJECTIVE

To explore the potential role of substance P receptor (SPR) in the initiation and development of allergic rhinitis (AR).

METHODS

Twenty healthy rats were randomly divided into two groups. A model of allergic rhinitis in rat was established by using ovalbumin intraperitoneal immunization and nasal antigen challenge. The nasal mucosa obtained from seven out of ten AR models as well as ten normal controls were studied routinely by HE and immunohistochemical staining to observe the distribution and changes of SPR.

RESULTS

The study showed that immunoreactivity to SPR was present both on the surface and in the cytoplasm of epithelial cells, eosinophils, glandular cells and its ducts, mast cells, plasmocyte and other monocytes. During nasal hypersensitiveness, the staining density and the positive staining cells increased significantly as compared with those in normal controls.

CONCLUSION

The increase of SPR in nasal mucosa in rat AR model indicates that SPR might play a critical role in the development of AR.

Characterisation and partial purification of cellular factors interacting with a negative element on human papillomavirus type 1 late mRNAs

We have previously identified and characterized an AU-rich inhibitory RNA element located in the 3' untranslated region on late human papillomavirus type 1 (HPV-1) mRNAs. This sequence is active in the absence of virus proteins and interacts specifically with cellular proteins, which presumably mediate the inhibitory activity. Here we have characterized and partially purified five proteins (80-, 52-, 46-, 44-, and 38-kDa) that interact independently and specifically with an AU-rich inhibitory sequence on HPV-1 late mRNAs. Dephosphorylation of the proteins resulted in loss of RNA binding activity. Proteins similar to the 38-, 44-, and 46-kDa proteins were detected also in murine epithelial cells, whereas proteins corresponding to the 80- and 52-kDa proteins were not. Since the inhibitory HPV-1 sequence is active in murine epithelial cells, the results suggested a role for the 38-, 41, and the 46-kDa proteins in the regulation of HPV-1 late gene expression.

High-resolution imaging at the cellular and subcellular levels in flattened whole mounts of early zebrafish embryos

We describe a rapid and sensitive method for high-resolution imaging at the cellular and subcellular levels in the whole-mount zebrafish embryo. The procedure involves fixing and staining the embryo, followed by deyolking and flattening it under a cover slip, to produce a planar mount that is 20 to 100 microns thick. Such a flattened whole mount allows imaging with a spatial resolution of approximately 500 nm in the x-y plane and does not require the use of embedding, sectioning, confocal microscopy, or computational deblurring procedures. We can resolve all individual nuclei and chromosome sets in the embryo, up to the late gastrula stage (10,000 cell stage). In addition, older embryos (through the segmentation stage) can also be examined, with the preservation of significant morphological detail. Because of its ability to resolve subcellular detail, the flattened whole-mount method can provide significant biological information beyond what can be obtained from conventional (three-dimensional) whole mounts. We have used the flattened whole-mount method to study subcellular events related to progression through the cell cycle or to apoptosis, in cells of the early zebrafish embryo. A specific DNA-binding dye (Hoechst 33258) or an antibody against a chromosomal protein (histone H1) was used to stain the nuclei of individual cells in the embryo. This allowed us to determine the spatial positions of all the individual cells, and also their stages in the cell cycle. A terminal transferase (TUNEL) assay was used to detect apoptotic cells. This combination of specific stains allowed us to study the behaviors of groups of cells in situ, within the developing zebrafish embryo.

[Engineered glutamic acid decarboxylase fusion protein in diagnosis of type I diabetes mellitus]

OBJECTIVE

To get recombinant GAD 65 proteins which have immunogenicity by the method of gene engineering so that the recombinant protein can be used for early diagnosis in type I diabetes mellitus.

METHOD

We amplified the complete fragment encoding GAD65 gene by PCR, and expressed its protein in E. coli. DH5 alpha after inserting it in the vector and determining its nucleotide sequence. Consequentially, we attempted to prove the immunogenicity of expresion products and construct a method for detecting antibodies against GAD65 in Diabetic serum.

RESULT

The sequence analysis showed that the amplified fragments contained 1758 bp, encoded 585 amino acid, and had been correctly inserted into pGEX-3X vector. The recombinant proteins expressed in E. Coli. DH5 alpha had immunogenicity and could be used to detect agtibodies against GAD65 in diabetic serum.

CONCLUSION

We have got recombinant GAD65 proteins which have immunogenicity and have used them to detect preliminarily antibodies against GAD65 in diabetic serum.

Dependence of mammalian putrescine and spermidine transport on plasma-membrane potential: identification of an amiloride binding site on the putrescine carrier

The mechanism of mammalian polyamine transport is poorly understood. We have investigated the role of plasma-membrane potential (DeltaPsipm) in putrescine and spermidine uptake in ZR-75-1 human breast cancer cells. The rate of [3H]putrescine and [3H]spermidine uptake was inversely correlated to extracellular [K+] ([K+]o) and to DeltaPsipm, as determined by the accumulation of [3H]tetraphenylphosphonium bromide (TPP). Inward transport was unaffected by a selective decrease in mitochondrial potential (DeltaPsimit) induced by valinomycin at low [K+]o, but was reduced by approximately 60% by the rheogenic protonophore carbonylcyanide m-chlorophenylhydrazone (CCCP), which rapidly (<=15 min) collapsed both DeltaPsipm and DeltaPsimit. Plasma-membrane depolarization by high [K+]o or CCCP did not enhance putrescine efflux in cells pre-loaded with [3H]putrescine, suggesting that decreased uptake caused by these agents did not result from a higher excretion rate. On the other hand, the electroneutral K+/H+ exchanger nigericin (10 microM) co-operatively depressed -3H-TPP, [3H]putrescine and [3H]spermidine uptake in the presence of ouabain. Suppression of putrescine uptake by nigericin+ouabain was Na+-dependent, suggesting that plasma-membrane repolarization by the electrogenic Na+ pump was required upon acidification induced by nigericin, due to the activation of the Na+/H+ antiporter. The sole addition of 5-N, N-hexamethylene amiloride, a potent inhibitor of the Na+/H+ antiporter, strongly inhibited putrescine uptake in a competitive fashion -Ki 4.0+/-0.9 (S.D.) microM-, while being a weaker antagonist of spermidine uptake. The potency of a series of amiloride analogues to inhibit putrescine uptake was clearly different from that of the Na+/H+ antiporter, and resembled that noted for Na+ co-transport proteins. These data demonstrate that putrescine and spermidine influx is mainly unidirectional and strictly depends on DeltaPsipm, but not DeltaPsimit. This report also provides first evidence for a high-affinity amiloride-binding site on the putrescine carrier, which provides new insight into the biochemical properties of this transporter.

Plant homologue of human excision repair gene ERCC1 points to conservation of DNA repair mechanisms

Nucleotide excision repair (NER), a highly versatile DNA repair mechanism, is capable of removing various types of DNA damage including those induced by UV radiation and chemical mutagens. NER has been well characterized in yeast and mammalian systems but its presence in plants has not been reported. Here it is reported that a plant gene isolated from male germline cells of lily (Lilium longiflorum) shows a striking amino acid sequence similarity to the DNA excision repair proteins human ERCC1 and yeast RAD10. Homologous genes are also shown to be present in a number of taxonomically diverse plant genera tested, suggesting that this gene may have a conserved function in plants. The protein encoded by this gene is able to correct significantly the sensitivity to the cross-linking agent mitomycin C in ERCC1-deficient Chinese hamster ovary (CHO) cells. These findings suggest that the NER mechanism is conserved in yeast, animals and higher plants.

Discovery of ritonavir, a potent inhibitor of HIV protease with high oral bioavailability and clinical efficacy

The structure-activity studies leading to the potent and clinically efficacious HIV protease inhibitor ritonavir are described. Beginning with the moderately potent and orally bioavailable inhibitor A-80987, systematic investigation of peripheral (P3 and P2') heterocyclic groups designed to decrease the rate of hepatic metabolism provided analogues with improved pharmacokinetic properties after oral dosing in rats. Replacement of pyridyl groups with thiazoles provided increased chemical stability toward oxidation while maintaining sufficient aqueous solubility for oral absorption. Optimization of hydrophobic interactions with the HIV protease active site produced ritonavir, with excellent in vitro potency (EC50 = 0.02 microM) and high and sustained plasma concentrations after oral administration in four species. Details of the discovery and preclinical development of ritonavir are described.

Discovery of ritonavir, a potent inhibitor of HIV protease with high oral bioavailability and clinical efficacy

The structure-activity studies leading to the potent and clinically efficacious HIV protease inhibitor ritonavir are described. Beginning with the moderately potent and orally bioavailable inhibitor A-80987, systematic investigation of peripheral (P3 and P2') heterocyclic groups designed to decrease the rate of hepatic metabolism provided analogues with improved pharmacokinetic properties after oral dosing in rats. Replacement of pyridyl groups with thiazoles provided increased chemical stability toward oxidation while maintaining sufficient aqueous solubility for oral absorption. Optimization of hydrophobic interactions with the HIV protease active site produced ritonavir, with excellent in vitro potency (EC50 = 0.02 microM) and high and sustained plasma concentrations after oral administration in four species. Details of the discovery and preclinical development of ritonavir are described.

Temperature-induced expression of yeast FKS2 is under the dual control of protein kinase C and calcineurin

FKS1 and FKS2 are alternative subunits of the glucan synthase complex, which is responsible for synthesizing 1,3-beta-glucan chains, the major structural polymer of the Saccharomyces cerevisiae cell wall. Expression of FKS1 predominates during growth under optimal conditions. In contrast, FKS2 expression is induced by mating pheromone, high extracellular [Ca2+], growth on poor carbon sources, or in an fks1 mutant. Induction of FKS2 expression in response to pheromone, CaCl2, or loss of FKS1 function requires the Ca2+/calmodulin-dependent protein phosphatase calcineurin. Therefore, a double mutant in calcineurin (CNB1) and FKS1 is inviable due to a deficiency in FKS2 expression. To identify novel regulators of FKS2 expression, we isolated genes whose overexpression obviates the calcineurin requirement for viability of an fks1 mutant. Two components of the cell integrity signaling pathway controlled by the RHO1 G protein (MKK1 and RLM1) were identified through this screen. This signaling pathway is activated during growth at moderately high temperatures. We demonstrate that calcineurin and the cell integrity pathway function in parallel, through separable promoter elements, to induce FKS2 expression during growth at 39 degrees C. Because RHO1 also serves as a regulatory subunit of the glucan synthase, our results define a regulatory circuit through which RHO1 controls both the activity of this enzyme complex and the expression of at least one of its components. We show also that FKS2 induction during growth on poor carbon sources is a response to glucose depletion and is under the control of the SNF1 protein kinase and the MIG1 transcriptional repressor. Finally, we show that FKS2 expression is induced as cells enter stationary phase through a SNF1-, calcineurin-, and cell integrity signaling-independent pathway.

[Clinical analysis of Doppler waveform in arterial occlusive disease in the lower limbs]

OBJECTIVE

In order increase the diagnostic standard of Doppler ultrasound to arterial occlusive disease in the lower limbs.

METHODS

120 normal lower limbs and 66 lower limbs with arterial occlusive disease were measured by directional Doppler blood velocity detector in different segments. The peak forward velocity(PFV), peak reverse velocity(PRV), acceleration time(AT), and deceleration time(DT) were determined and compared.

RESULTS

The blood flow velocity of the lower limb arteries was gradually slowed down from the proximal to the distal in the normal group. The ratio of distal to proximal PFA, PRV, AT and DT was less than 1.0. PFV and PRV in the disease group were slower than in the normal group(P < 0.01). AT and DT in the disease group were longer than in the normal group(P < 0.01). It was discovered that the ratio of distal to proximal DT was greater than 1.0 in arterial stenosis(> 50%) or occlusion (collateral artery development).

CONCLUSION

The results were compared those of arteriography. The diagnostic coincidence ratio of Doppler ultrasound for localization was 91%(60/66).

Reversibility of omeprazole-evoked changes in the ultrastructure of ECL cells in the rat stomach

The ECL cells are histamine- and peptide hormone-producing endocrine cells in the rat oxyntic mucosa. They are rich in secretory vesicles and also contain microvesicles and electron-dense granules. They operate under the control of circulating gastrin. In the present study, we examined the ECL-cell ultrastructure after long term treatment with omeprazole, which is known to induce hypergastrinemia, and after withdrawal of the drug. Rats received omeprazole (400 micromol/kg per day, orally) for 16 days and were killed 1, 5, 20, or 40 days after the last dose of the drug. Oxyntic mucosal specimens were processed for electron microscopy. Electron micrographs of ECL-cell profiles were analyzed planimetrically. The ECL-cell profile area increased promptly in response to omeprazole, the secretory vesicles and granules were reduced in number and volume density, the microvesicles were unchanged in number but reduced in volume density, and vacuoles appeared. Within a week after stopping the omeprazole treatment, the numbers and volume densities of secretory vesicles and microvesicles returned to pre-stimulation values. Also, the vacuoles disappeared promptly. The ECL-cell profile area decreased below the pre-stimulation level within five days after stopping treatment, while, in contrast, the granules increased in number and volume density. Somewhat surprisingly, the cell size and the granule compartment did not return to normal until 40 days after stopping treatment.

[Study on distributions of somatostatin in rat nasal mucosa and trigeminal ganglion]

To explore the regulatory mechanism of the release of neuropeptides in nasal mucosa, the distributions of somatostatin (SOM) and SOMmRNA-immunoreactivities (IR) in cryostat sections of rat nasal mucosa and trigeminal ganglion (TG) cells were investigated using immunohistochemistry (ABC technique) and in situ hybridization histochemistry. The recombinant PSP65 plasmid (400 SOMcDNA) in vitro worked as a plate for the preparation of SOMmRNA single strand (cRNA) probe, which was labelled with digoxigenin. The results showed that neither of these two substances reacted positively in nasal mucosa but positive SOM-IR and SOMmRNA-IR signals were definitely seen in TG cells. In contrast with SOM immunohistochemistry, SOMmRNA-IR positive granules tended to be located in the cytoplasm of TG cells, with a clearer background and a higher resolution rate. The significance of SOMmRNA in TG cells was briefly discussed. It was concluded that SOMmRNA in TG cells might be involved in the regulation of the release of neuropeptides in nasal mucosa.

AU-rich mRNA instability elements on human papillomavirus type 1 late mRNAs and c-fos mRNAs interact with the same cellular factors

Expression levels of human papillomavirus type 1 late genes are determined in part by an AU-rich inhibitory sequence in the 3' untranslated region on the late mRNAs. Fine mapping of the AU rich inhibitory sequence revealed that it mapped to a 57 nucleotide sequence, consisting of an AU-rich region containing two AUUUA motifs and a U-rich region containing three UUUUU motifs. An internal deletion showed that the U-rich region was required for inhibition. Point mutations in the AUUUA- and UUUUU-motifs inactivated the inhibitory sequence. Analysis of the stability of mRNAs containing the AU-rich sequence in sense or anti-sense orientation showed that mRNAs containing the AU-rich sequence in sense orientation had reduced half life. Analysis of RNA-protein interactions revealed that binding to the inhibitory sequence of three poly(U) binding proteins (38, 44 and 46 kDa) correlated with inhibition and that the same proteins bind to the AU-rich mRNA instability element in the 3' untranslated region on the human c-fos mRNA. We speculate that the human papillomavirus late mRNAs, produced from several hundred copies of the virus genome present in infected cells, compete with the c-fos mRNAs for destabilizing cellular factors and that this may lead to elevated Fos protein levels in human papillomavirus infected cells.

DNA adducts in human nasal mucosa and white blood cells from smokers and non-smokers

The goal of the present study was to measure the levels of DNA adducts in human nasal mucosa cells and in total white blood cells in relation to smoking. DNA was isolated from samples of 20 healthy volunteers (six smokers and 14 non-smokers). The levels of DNA adducts were measured by 32P-postlabelling assay. In smokers the mean DNA adduct levels were 3.3 and 17.0 adducts/10(8) nucleotides in total white blood cells and nasal mucosa cells respectively. The corresponding values in non-smokers were 2.0 and 6.8 adducts/10(8) nucleotides. The mean adduct level was significantly higher in nasal mucosa cells than in total white blood cells both in smokers and non-smokers. The mean adduct levels in smokers' nasal mucosa cells were significantly higher than those in non-smokers. Thus the nasal mucosa cells constituted a sensitive tissue for the determination of cigarette smoking induced DNA adducts. Combining the sensitivity of the 32P-postlabelling assay with the specificity of the nasal mucosa to the airborne chemical exposures, the DNA adduct analysis from human nasal mucosa cells represents a method of choice in the assessment of exposure to airborne carcinogens.

[A new type of intellectualized Y-maze]

This paper describes the hardware and software of an intellectualized Y-maze with a microcomputer, which controls the whole procedure of discrimination learning test for rats or mice. By monitoring the action of the animal with the infrared photoelectrical sensors, its determination is accurate and timing precise. Due to working on the platform of WINDOWS, the interface is friendly and the operation is convenient and simple.

Experimental antitumor activity of the Ce(IV)-mitoxantrone complex and its interaction with deoxyribonucleic acid

The Ce(IV)-mitoxantrone complex exhibits a higher lethality to Ehrlich ascites tumor cells than that of the free drug and shows stronger inhibition ability on the DNA synthesis of the tumor cells. Thus the Ce(IV)-mitoxantrone complex may become a more potent antitumor drug than mitoxantrone. The different interaction model of mitoxantrone and its Ce(IV) complex with DNA were studied by the methods of spectroscopy, electrochemistry, and electrophoresis. Ce(IV) ions chelate with oxygens of the hydroxyl groups at the 1,4 position and the carbonyl function on C-9 and C-10, then intercalate into the base pairs of DNA together. The complexation of Ce(IV) gives rise to more compact binding of mitoxantrone with DNA, and leads to an additional change on the normal conformation and the double-helical structure of DNA; this may be related to the more stronger action of the complex on DNA synthesis and survival of cultured tumor cells.

Response of substance P-immunoreactive nerve fibres in the anterior pituitary to plasma oestrogen levels in the rat

The mammalian anterior pituitary has recently been shown to be innervated by substantial amounts of peptidergic nerve fibres. It has also been found that adrenalectomy increases the amount of calcitonin gene-related peptide-like immunoreactive nerve fibres in the anterior pituitary of the rat, and that stimulation of the nerve fibres in vitro can enhance release of ACTH. In the present study, the density of substance P-like immunoreactive nerve fibres in the anterior pituitary of the rat were examined in relation to variations in plasma oestrogen status. The amount of substance P-like immunoreactive nerve fibres increased significantly (P < 0.001) after ovariectomy, and decreased significantly (P < 0.01) under oestrogen replacement, in a dose-dependent manner. The results suggest the possibility of the direct neural involvement of oestrogen secretion in anterior pituitary regulation, which further substantiates the hypothesis of neural-humoral dual regulation of the mammalian anterior pituitary.