Phytoremediation ability and selected genetic transcription in Hydrocotyle umbellata-under cadmium stress

Cadmium (Cd) is the most toxic element which may cause serious consequences to microbial communities, animals, and plants. The use of green technologies like phytoremediation employs plants with high biomass and metal tolerance to extract toxic metals from their rooting zones. In the present work, Hydrocotyle umbellata was exposed to five Cd concentrations (2, 4, 6, 8, and 10 µmol) in triplicates to judge its phytoextraction ability. Effects of metal exposure on chlorophyll (Chl), bio-concentration factor (BCF), translocation factor (TF), and electrolyte leakage (EL) were analyzed after 10 days of treatment. Metal-responding genes were also observed through transcriptomic analysis. Roots were the primary organs for cadmium accumulation followed by stolon and leaves. There was an increase in EL. Plants showed various symptoms under increasing metal stress namely, chlorosis, browning of the leaf margins, burn-like areas on the leaves, and stunted growth, suggesting a positive relationship between EL, and programmed cell death (PCD). Metal-responsive genes, including glutathione, expansin, and cystatin were equally expressed. The phytoextraction capacity and adaptability of H. umbellata L. against Cd metal stress was also demonstrated by BCF more than 1 and TF less than 1.

Ulnar nerve morphology on magnetic resonance imaging predicts nerve recovery after surgery for cubital tunnel syndrome

Magnetic resonance imaging (MRI) can evaluate nerve morphology in cubital tunnel syndrome (CuTS), but its value in predicting surgical outcome is unclear. The purpose of this study was to determine whether ulnar nerve morphology on MRI correlated with outcome after CuTS surgery. We reviewed 40 patients who had preoperative MRI and electrodiagnostic (EDX) examinations for CuTS and outcome evaluation 6 months and 2 years postoperatively. Using MRI, ulnar nerve cross-sectional area (UNCSA), changes in signal intensity, and any space-occupying lesion were evaluated. Other factors assessed were age, symptom duration and severity, type-2 diabetes and EDX parameters. Factors associated with unfavorable surgical outcome were identified. At 6 months postoperatively, 12 patients (30%) had excellent, 19 (47.5%) good, 8 (20%) fair and 1 (2.5%) poor results on modified Wilson-Krout criteria. On univariate analysis, unfavorable outcomes were associated with increased UNCSA, space-occupying lesion, and decreased motor nerve conduction velocity (mNCV), and on multivariate analysis with increased UNCSA 1 cm distal from the epicondyle only (model 1) or increased UNCSA 1 cm proximal from the epicondyle and decreased mNCV (model 2). At 2 years, 15 patients (37.5%) had excellent, 21 (52.5%) good, 3 (7.5%) fair and 1 (2.5%) poor results, and no factors correlated with unfavorable outcome. Increased UNCSA on MRI was associated with unfavorable outcome at 6 months but not at 2 years. This study suggests that morphologic ulnar nerve changes can predict delayed nerve recovery after surgery for CuTS.

Pharmacological inhibition of poly(ADP-ribose) polymerase (PARP) activity in PARP-1 silenced tumour cells increases chemosensitivity to temozolomide and to a N3-adenine selective methylating agent

We recently demonstrated that poly(ADP-ribose) polymerase (PARP)-1 is involved in angiogenesis and tumour aggressiveness. In this study we have compared the influence of abrogation of PARP-1 expression by stable gene silencing to that of the pharmacological inhibition of cellular PARP activity using PARP-1/-2 inhibitors on the chemosensitivity of tumour cells to the wide spectrum methylating agent temozolomide (TMZ) and to the N3-adenine selective methylating agent {1-methyl-4-[1-methyl-4-(3-methoxysulfonylpropanamido)pyrrole-2-carboxamido]-pyrrole-2-carboxamido}propane (Me-Lex). Silencing of PARP-1 in melanoma or cervical carcinoma lines enhanced in vitro sensitivity to TMZ and Me- Lex, and induced a higher level of cell accumulation at the G2/M phase of cell cycle with respect to controls. GPI 15427, which inhibits both PARP-1 and PARP-2, increased sensitivity to TMZ and Me-Lex both in PARP-1-proficient and - deficient cells. However, it induced different cell cycle modulations depending on PARP-1 expression, provoking a G2/M arrest only in PARP-1 silenced cells. Treatment of PARP-1 silenced cells with TMZ or Me-Lex resulted in a more extensive phosphorylation of Chk-1 and p53 as compared to PARP-1 proficient cells. The combination of the methylating agents with GPI 15427 increased Chk-1 and p53 phosphorylation both in PARP-1 proficient or deficient cells. When mice challenged with PARP-1 silenced melanoma cells were treated with the TMZ and PARP inhibitor combination there was an additional reduction in tumour growth with respect to treatment with TMZ alone. These results suggest the involvement of PARP-2 or other PARPs, in the repair of DNA damage provoked by methylating agents, highlighting the importance of targeting both PARP-1 and PARP-2 for cancer therapy.

Abrogation of DNA vector-based RNAi during apoptosis in mammalian cells due to caspase-mediated cleavage and inactivation of Dicer-1

RNA interference (RNAi) is used as a reverse-genetic tool to examine functions of a gene in different cellular processes including apoptosis. As key cellular proteins are inactivated during apoptosis, and as RNAi requires cooperation of many cellular proteins, we examined whether DNA vector-based RNAi would continue to function during apoptosis. The short hairpin RNA transcribed from the DNA vector is processed by Dicer-1 to form small interfering RNA that is incorporated in the RNA-induced silencing complex (RISC) to guide a sequence-specific silencing of the target mRNA. We report here that DNA vector-based RNAi of three different genes, namely poly(ADP-ribose) polymerase-1, p14(ARF) and lamin A/C are abrogated during apoptosis. The failure of DNA vector-based RNAi was not at the level of Ago-2 or RISC-mediated step of RNAi but due to catalytic inactivation of Dicer-1 on specific cleavage at the STTD(1476) and CGVD(1538) sites within its RNase IIIa domain. Using multiple approaches, caspase-3 was identified as the major caspase responsible for the cleavage and inactivation of Dicer-1. As Dicer-1 is also the common endonuclease required for formation of microRNA (miRNA) in mammalian cells, we observed decreased levels of mature forms of miR-16, miR-21 and let-7a. Our results suggest a role for apoptotic cleavage and inactivation of Dicer-1 in controlling apoptotic events through altered availability of miRNA.

Regulation of poly(ADP-ribose) polymerase-1 functions by leukocyte elastase inhibitor/LEI-derived DNase II during caspase-independent apoptosis

Poly(ADP-ribose) polymerase-1 (PARP-1) is an important regulator of apoptosis. Its over-activation at the onset of apoptosis can inhibit the action of apoptotic endonucleases like caspase-activated DNase and DNAS1L3. Therefore, controlled PARP-1 proteolysis during caspase-dependent apoptosis is considered essential to promote DNA degradation. Yet, little is known about the interplay of PARP-1 and endonucleases that operate during caspase-independent cell death. Here we show that in the long-term cultured HeLa cells which undergo caspase-independent death, PARP-1 co-immunoprecipitates with leukocyte elastase inhibitor-derived DNase II (L-DNase II), an acid DNase implicated in this death pathway and activated by serine proteases. Our results indicate that, despite having putative poly(ADP-ribose)-acceptor sites, LEI/L-DNase II is neither significantly poly(ADP-ribosyl)ated nor inhibited by PARP-1 during caspase-independent apoptosis. Unexpectedly, caspase-independent apoptosis induced by hexa-methylene amiloride, LEI/L-DNase II can activate PARP-1 and promote its auto-poly(ADP-ribosyl)ation, thus inhibiting PARP-1 activity. Moreover, overexpression of LEI blocks the pro-survival effect of PARP-1 in this model of cell death. Our results provide the original evidence for a new mechanism of PARP-1 activity regulation in the caspase-independent death pathway involving LEI/L-DNase II.

Niacin deficiency in rats increases the severity of ethylnitrosourea-induced anemia and leukopenia

Many chemotherapeutic agents function by damaging the DNA of rapidly dividing cells, leading to side effects in the bone marrow, including anemia and leukopenia during chemotherapy and the development of secondary leukemias in the years following recovery from the original disease. We have created an animal model of alkylation-based chemotherapy, in nontumor-bearing rats, to investigate the effect of niacin deficiency on the side effects of chemotherapy [2 x 2 design, niacin-deficient (ND) vs. pair-fed (PF) control, and ethylnitrosourea (ENU) vs. vehicle control (C)]. Weanling Long-Evans rats were fed ND diet or PF niacin replete diet for 4 wk. ENU or C treatment started after 1 wk of feeding and consisted of 12 doses delivered by gavage, every other day. At 4 wk postweaning, niacin deficiency and ENU treatment ended, the rats were fed a high-quality control diet (AIN-93M) and the recovery of blood variables was monitored. ND alone decreased growth rate and caused anemia and neutrophilia. ENU treatment alone caused anemia, lymphopenia, neutropenia and an increase in circulating reticulocytes. In combination, ND and ENU treatment synergistically decreased hematocrit. ND prevented the ENU-induced increase in reticulocyte numbers observed in control rats. ND also increased the severity of ENU-induced lymphopenia. A combination of ND and ENU abolished the neutrophilia caused by ND alone. In summary, ND significantly increased the susceptibility of young Long-Evans rats to ENU-induced bone marrow suppression, suggesting that niacin-deficient cancer patients may benefit from supplementation.

Survival and proliferation of cells expressing caspase-uncleavable Poly(ADP-ribose) polymerase in response to death-inducing DNA damage by an alkylating agent

To determine whether caspase-3-induced cleavage of poly(ADP-ribose) polymerase (PARP), a DNA damage-sensitive enzyme, alters the balance between survival and death of the cells following DNA damage, we created stable cell lines that express either caspase-uncleavable mutant or wild type PARP in the background of PARP (-/-) fibroblasts. The survival and apoptotic responses of these cells were compared after exposure to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), a DNA-damaging agent that activates PARP, or to tumor necrosis factor-alpha, which causes apoptosis without initial DNA damage. In response to MNNG, the cells with caspase-uncleavable PARP were very resistant to loss of viability or induction of apoptosis. Most significantly, approximately 25% of these cells survived and retained clonogenicity at a level of DNA damage that eliminated the cells with wild type PARP or PARP (-/-) cells. Expression of caspase-uncleavable PARP could not protect the cells from death induced by tumor necrosis factor, although there was a slower progression of apoptotic events in these cells. Therefore, one of the functions for cleavage of PARP during apoptosis induced by alkylating agents is to prevent survival of the extensively damaged cells.

Niacin deficiency increases the sensitivity of rats to the short and long term effects of ethylnitrosourea treatment

Most chemotherapy agents function by causing damage to the DNA of rapidly dividing cells, such as those in the bone marrow, leading to anemia and leukopenia during chemotherapy and the development of secondary leukemias in the years following recovery from the original disease. We created an animal model of nitrosourea-based chemotherapy using ethylnitrosourea (ENU) to investigate the effect of niacin deficiency on the side effects of chemotherapy. Weanling Long-Evans rats were fed diets containing various levels of niacin for a period of 4 weeks. ENU treatment started after 1 week of feeding and consisted of 12 doses delivered by gavage, every other day. Cancer incidence was also monitored in the following months. ENU treatment caused many of the acute symptoms seen in human chemotherapy patients, including anemia and neutropenia. Niacin deficiency (ND) had several interesting effects, alone and in combination with ENU. Niacin deficiency alone caused a modest anemia, while in combination with ENU it induced a severe anemia. Niacin deficiency alone caused a 4-fold increase in circulating neutrophil numbers, and this population was drastically reduced by ENU-treatment. In the long term, macin deficiency caused an increased incidence of cancer, especially chronic granulocytic leukemias.

SAPK2/p38-dependent F-actin reorganization regulates early membrane blebbing during stress-induced apoptosis

In endothelial cells, H2O2 induces the rapid formation of focal adhesion complexes at the ventral face of the cells and a major reorganization of the actin cytoskeleton into dense transcytoplasmic stress fibers. This change in actin dynamics results from the activation of the mitogen-activated protein (MAP) kinase stress-activated protein kinase-2/p38 (SAPK2/p38), which, via MAP kinase-activated protein (MAPKAP) kinase-2/3, leads to the phosphorylation of the actin polymerization modulator heat shock protein of 27 kD (HSP27). Here we show that the concomitant activation of the extracellular signal-regulated kinase (ERK) MAP kinase pathway by H2O2 accomplishes an essential survival function during this process. When the activation of ERK was blocked with PD098059, the focal adhesion complexes formed under the plasma membrane, and the actin polymerization activity led to a rapid and intense membrane blebbing. The blebs were delimited by a thin F-actin ring and contained enhanced levels of HSP27. Later, the cells displayed hallmarks of apoptosis, such as DEVD protease activities and internucleosomal DNA fragmentation. Bleb formation but not apoptosis was blocked by extremely low concentrations of the actin polymerization inhibitor cytochalasin D or by the SAPK2 inhibitor SB203580, indicating that the two processes are not in the same linear cascade. The role of HSP27 in mediating membrane blebbing was assessed in fibroblastic cells. In control fibroblasts expressing a low level of endogenous HSP27 or in fibroblasts expressing a high level of a nonphosphorylatable HSP27, H2O2 did not induce F-actin accumulation, nor did it generate membrane blebbing activity in the presence or absence of PD098059. In contrast, in fibroblasts that expressed wild-type HSP27 to a level similar to that found in endothelial cells, H2O2 induced accumulation of F-actin and caused bleb formation when the ERK pathway was inhibited. Cis-platinum, which activated SAPK2 but induced little ERK activity, also induced membrane blebbing that was dependent on the expression of HSP27. In these cells, membrane blebbing was not followed by caspase activation or DNA fragmentation. We conclude that the HSP27-dependent actin polymerization-generating activity of SAPK2 associated with a misassembly of the focal adhesions is responsible for induction of membrane blebbing by stressing agents.

Cellular responses to DNA damage in the absence of Poly(ADP-ribose) polymerase

Poly(ADP-ribose) polymerase (PARP) is a nuclear enzyme which is catalytically activated by DNA strand interruptions. The involvement of PARP has been implicated in different cellular responses to genotoxic damage, including cell survival, DNA repair, transformation, and cell death. However, the exact contribution of PARP polypeptide or its enzymatic product has remained ill defined. Recent studies with two different PARP knock out mice have demonstrated the beneficial role of PARP in maintaining genomic integrity and in survival responses after exposure to whole body gamma-irradiation. Other studies have demonstrated the instrumental role of PARP in death of the neuronal cells after ischemia-reperfusion injury. The recombination inhibiting function of PARP at DNA strand breaks was more evident in a model system deficient in activities of two major DNA strand break binding proteins, PARP and DNA-dependent protein kinase. The present review summarizes similarities and differences obtained with the two PARP knock out mice and reanalyzes the role of PARP in various cellular responses to DNA damage.

Cleavage of poly(ADP-ribose) polymerase: a sensitive parameter to study cell death

Proteases play a crucial role in apoptosis or programmed cell death. The aim of this review is to highlight the purpose for which these proteases are activated, i.e., to specifically cleave a select subset of cellular proteins at an appropriate time during cell death. Poly(ADP-ribose) polymerase (PARP), a nuclear protein implicated in DNA repair, is one of the earliest proteins targeted for a specific cleavage to the signature 89-kDa fragment during apoptosis. Characterization of the apoptotic cleavage of PARP and other target proteins helped in understanding the role of cysteine aspartic acid specific proteases (caspases) in the apoptotic process. We have recently identified that in some models of cell death, the cleavage pattern for PARP is different from production of the signature 89-kDa fragment. Necrotic death of HL-60 cells and apoptotic death of Jurkat cells mediated by granzyme B and perforin were accompanied by distinct additional fragments, suggesting cleavage of PARP at other sites by caspases or other death proteases. This review summarizes how detection and characterization of PARP cleavage could serve as a sensitive parameter for identification of different types of cell death and as a marker for activation of different death proteases. The putative biological functions for early cleavage of PARP in apoptosis are also discussed.

6-Aminonicotinamide sensitizes human tumor cell lines to cisplatin

The nicotinamide analogue 6-aminonicotinamide (6AN) is presently undergoing evaluation as a potential modulator of the action of various antineoplastic treatments. Most previous studies of this agent have focused on a three-drug regimen of chemical modulators that includes 6AN. In the present study, the effect of single-agent 6AN on the efficacy of selected antineoplastic drugs was assessed in vitro. Colony-forming assays using human tumor cell lines demonstrated that pretreatment with 30-250 microM 6AN for 18 h resulted in increased sensitivity to the DNA cross-linking agent cisplatin, with 6-, 11-, and 17-fold decreases in the cisplatin dose that diminishes colony formation by 90% being observed in K562 leukemia cells, A549 non-small cell lung cancer cells, and T98G glioblastoma cells, respectively. Morphological examination revealed increased numbers of apoptotic cells after treatment with 6AN and cisplatin compared to cisplatin alone. 6AN also sensitized cells to melphalan and nitrogen mustard but not to chlorambucil, 4-hydroperoxycyclophosphamide, etoposide, or daunorubicin. In additional studies undertaken to elucidate the mechanism underlying the sensitization to cisplatin, atomic absorption spectroscopy revealed that 6AN had no effect on the rate of removal of platinum (Pt) adducts from DNA. Instead, 6AN treatment was accompanied by an increase in Pt-DNA adducts that paralleled the degree of sensitization. This effect was not attributable to 6AN-induced decreases in glutathione or NAD+, because other agents that depleted these detoxification cofactors (buthionine sulfoximine and 3-acetylpyridine, respectively) did not increase Pt-DNA adducts. On the contrary, 6AN treatment increased cellular accumulation of cisplatin. Further experiments revealed that 6AN was metabolized to 6-aminonicotinamide adenine dinucleotide (6ANAD+). Concurrent administration of nicotinamide and 6AN had minimal effect on cellular 6AN accumulation but abolished the formation of 6ANAD+, the increase in Pt-DNA adducts, and the sensitizing effect of 6AN in clonogenic assays. These observations identify 6AN as a potential modulator of cisplatin sensitivity and suggest that the 6AN metabolite 6ANAD+ exerts this effect by increasing cisplatin accumulation and subsequent formation of Pt-DNA adducts.

Characterization of anti-peptide antibodies directed towards the automodification domain and apoptotic fragment of poly (ADP-ribose) polymerase

Poly(ADP-ribose) polymerase (PARP; EC 2.4.2.30) is a highly conserved nuclear enzyme present in higher eukaryotes. PARP is activated following DNA damage, is implicated in DNA repair, and its proteolysis has been shown to be an early marker of programmed cell death or apoptosis. In order to better understand the role of PARP in apoptosis and DNA repair and also to study PARP automodification, we have developed anti-peptide sera directed against four peptides from the conserved automodification domain of PARP. Four peptides were synthesized according to the four branched Multiple Antigenic Peptide (MAP) system and injected into rabbits. Immune sera were titrated by ELISA and analysed in Western blotting experiments on cell lines. The sera were also analysed for their capacity to inhibit PARP activity in an in vitro assay. Of the eight sera developed (two for each peptide), a serum directed against a peptide localized at the C-terminal part of the automodification domain of PARP (#422) appeared to be the best antibody to detect PARP from different species. All antipeptide antibodies were efficient in detecting the apoptotic fragment of PARP during programmed cell death in HL-60 apoptotic cells. None of the serum alone was able to completely inhibit PARP activity but combinations of the sera could significantly reduce automodification of PARP consistent with the localization of half of the automodification sites on bovine PARP. Sera were also used to map proteolysed purified PARP and to immunoprecipitate purified bovine PARP.

Different cleavage pattern for poly(ADP-ribose) polymerase during necrosis and apoptosis in HL-60 cells

Human promyelomonocytic leukemia cells HL-60 were treated with etoposide or cytochalasin B to induce apoptosis or necrosis, respectively. We report here that during necrosis, the DNA-repair associated nuclear enzyme poly(ADP-ribose) polymerase (PARP) was degraded differently from that observed during apoptosis. While apoptotic HL-60 cells exhibit only the signature 89 kDa fragment of PARP, necrosis of these cells was accompanied by formation of major fragments at MWr approximately 89 and 50 kDa and minor fragments at approximately 40 and 35 kDa. The necrosis-specific degradation of PARP was coincident with other changes detected by flow cytometric analysis, but earlier than the extensive degradation of DNA. Therefore, the unique necrotic degradation of PARP could be used as a sensitive indicator for necrotic death of cells.

Effect of serum subfractions from peritoneal dialysis patients on Hep-G2 cell apolipoprotein A-I and B metabolism

We previously showed that uremic serum subfractions isolated from hemodialysis (HD) patients inhibited the production of apolipoprotein (apo) A-I by human hepatoblastoma cells, Hep-G2. Because of the reported differences in atherogenic cardiovascular mortality between HD and peritoneal dialysis (PD) patients, we examined the effect of similar subfractions from PD patients on apo A-I and apo B synthesis. After obtaining informed consent, serum samples from five normal subjects and nine stable PD patients were applied to Sephadex G-25 columns to obtain the serum subfractions used in the various experiments. Sephadex G-25 chromatograms of PD sera showed a broad peak from fractions 30 through 60 (molecular wt 500 to 2000 Da). Control serum showed no peak in this region. PD serum subfractions decreased apo A-I synthesis, secretion, and apo A-I mRNA expression by Hep-G2 cells when compared to subfractions from control subjects. Cholesterol efflux studies showed that conditioned media obtained from Hep-G2 cells incubated with PD serum subfractions inhibited cholesterol efflux from fibroblasts, suggesting a biologically-significant decrease in apo A-I synthesis. PD serum subfractions increased protein synthesis and mRNA expressions of apo B by Hep-G2 cells. Therefore, serum subfractions obtained from PD patients decreased apo A-I and increased apo B synthesis, findings consistent with their serum lipoprotein profiles suggesting that a biologically-active component in these subfractions could contribute to the risk of atherogenic cardiovascular disease in PD.

New paradigm for lymphocyte granule-mediated cytotoxicity. Target cells bind and internalize granzyme B, but an endosomolytic agent is necessary for cytosolic delivery and subsequent apoptosis

Lymphocyte granule-mediated apoptosis is postulated to entail the formation of membrane pores by perforin. Then soluble granzyme reaches the cytosol either through these pores or by reparative pinocytosis. We demonstrate here that Jurkat cells bind and internalize granzyme B via high affinity binding sites without toxic consequence. Apoptosis occurs, however, if sublytic perforin is added to targets washed free of soluble granzyme B. We suggest that granule-mediated apoptosis mimics viral strategies for cellular entry. Accordingly, co-internalization of granzyme B with adenovirus, a virus that escapes endosomes to reach the cytosol, also induced apoptosis. Poly(ADP-ribose) polymerase cleavage and processing of CPP32, ICE-LAP3, and Mch2 were detected at 30 min, while cytosolic acidification and DNA fragmentation occurred at 60 min. Annexin V binding and membrane permeabilization arose at 4 h. The concurrent activation of the Ced-3 proteases differed from the rate at which each cysteine protease is cleaved in vitro by granzyme B. Thus, granzyme B may not directly process these proteases in whole cells but rather may function by activating a more proximal enzyme. These results indicate that adenovirus-mediated delivery of granzyme B is suitable for elucidating biochemical events that accompany granule-mediated apoptosis.

Granzyme B/perforin-mediated apoptosis of Jurkat cells results in cleavage of poly(ADP-ribose) polymerase to the 89-kDa apoptotic fragment and less abundant 64-kDa fragment

Cytotoxic lymphocytes utilize granule associated serine proteases (granzymes) and perforin to induce apoptosis. Although the importance of granzyme B has been established by gene ablation experiments, biochemical events initiated by the granzyme remain enigmatic. We show here that exposure of Jurkat cells to granzyme B and perforin results in cleavage of poly(ADP-ribose) polymerase to an apoptotic 89 kDa fragment and to lesser amounts of a 64 kDa fragment. The 64 kDa fragment is produced directly by granzyme B while the 89 kDa fragment is presumably generated by activated ICE/Ced-3 proteases. Establishing the intracellular function of GrB in the apoptotic response, these results indicate that granzyme B enters perforin treated targets activating the ICE/Ced-3 family proteases which then cleave poly(ADP-ribose) polymerase to its apoptotic fragment. Intracellular granzyme B appears to be translocated to the nucleus where the protease directly cleaves poly(ADP-ribose) polymerase.

Complete inhibition of poly(ADP-ribose) polymerase activity prevents the recovery of C3H10T1/2 cells from oxidative stress

Activation of the poly(ADP-ribose) polymerase after oxidative damage is implicated in different responses of the cells, for example, cell recovery after sublethal damage or cell death after lethal damage. However, the extent and mechanism of involvement of the enzyme in these two processes appear to be different. Inhibitors of this polymerase, such as benzamides, which do not completely inhibit PARP have been shown to protect the cells from killing by massive oxidant damage, could neither reduce the cellular recovery after mild oxidant damage nor completely inhibit DNA repair in vitro. We report here that 1,5-dihydroxyisoquinoline, which was earlier shown to be a strong inhibitor of this polymerase in vitro, is also its potent inhibitor in vivo. Using sensitive techniques for measuring low levels of cellular poly(ADP-ribose) polymer, we show that this inhibitor can completely abolish oxidant-induced activation of the polymerase in C3H10T1/2 cells. We show that only a minor fraction of the poly(ADP-ribose) polymerase activity is sufficient in cellular recovery after sublethal oxidant damage. We also demonstrate that cells are unable to recover from oxidant damage in the complete absence of polymerase activity.

Elevated plasma lipoprotein(a) levels and hypoalbuminemia in peritoneal dialysis patients

Plasma lipoprotein(a), Lp(a), is strongly and independently associated with atherosclerosis, and levels are elevated in hemodialysis (HD) patients and in some studies of those on peritoneal dialysis (PD). We hypothesized that protein losses and hypoalbuminemia could stimulate hepatic Lp(a) synthesis, and this effect would be accentuated in PD patients with malnutrition. The PD subjects (n = 24) had higher plasma Lp(a) levels than those (n = 10) on HD (median 34.4 vs 21.0 mg/dl, p < 0.05), and values exceed normal in 62.5% vs 20% of the subjects (p < 0.03), respectively. The serum albumin levels inversely correlated with concentrations of Lp(a) and apolipoprotein B, as well as the apolipoprotein B/AI ratio. In conclusion, plasma Lp(a) concentrations are frequently elevated in PD as well as HD patients. Measuring Lp(a) levels is useful in identifying patients at increased atherogenic risk, which may not be reflected in routine lipid profiles. The negative correlation between plasma Lp(a) and albumin levels suggests that the latter may be linked pathophysiologically to hepatic Lp(a) production. The association of hypoalbuminemia with higher Lp(a) values is of particular concern because malnutrition frequently occurs in PD patients.

Biochemical properties and function of poly(ADP-ribose) glycohydrolase

We describe here the latest observations on poly(ADP-ribose) glycohydrolase. There is now extensive evidence that this nuclear enzyme is an endo-exoglycosidase which has a key role to perform in the removal of polymers which interact with proteins through covalent and non-covalent interactions. Also, we have developed a zymogram which will permit the isolation of the various isoforms of the glycohydrolase and the eventual cloning of this enzyme. Finally, we have evidence that very short oligomers and even monomers of ADP-ribose covalently bound to proteins can be removed by poly(ADP-ribose) glycohydrolase.

Mode of action of poly(ADP-ribose) glycohydrolase

The turnover of the homopolymer of ADP-ribose, which is known to be involved in many DNA-related functions, is controlled by 2 principal enzymes. Poly(ADP-ribose) polymerase (EC 2.4.2.30) synthesizes the polymer from NAD, and poly(ADP-ribose) glycohydrolase (PARG) is the major enzyme responsible for its catabolism (Thomassin et al. (1992) Biochim. Biophys. Acta 1137, 171-181). In vivo, poly(ADP-ribose) polymers constitute a heterogeneous population of branched polymers attaining sizes of 200-400 residues. They are rapidly degraded by PARG, displaying variable kinetic parameters as a function of polymer size. Several studies have suggested that PARG acts exoglycosidically on its substrate but others observed that it could act endo/exo-glycosidically. We analysed the mode of action of PARG under conditions most suitable for expression of all the activities of PARG, using HPLC purified long free polymer and very pure PARG. We conclusively show that on large free polymers, PARG exhibits endoglycosidic activity along with exoglycosidic activity. This endoglycosidic activity could have a significant role during cellular response to DNA damage.

Poly(ADP-ribose) catabolism in mammalian cells

Poly(ADP-ribose) catabolism is a complex situation involving many proteins and DNA. We have developed an in vitro turnover system where poly(ADP-ribose) metabolism is monitored in presence of different relative amounts of two principal enzymes poly(ADP-ribose) transferase and poly(ADP-ribose) glycohydrolase along with other proteins and DNA. Our current results reviewed here show that the quality of polymer, i.e. chain length and complexity, as well as preference for the nuclear substrate varies depending upon the availability of poly(ADP-ribose) glycohydrolase. These results are interpreted in the light of the recent data implicating poly(ADP-ribose) metabolism in DNA-repair.

Uremic serum subfraction inhibits apolipoprotein A-I production by a human hepatoma cell line

Abnormalities in lipoprotein metabolism are common in uremic patients and may represent an additional risk factor for the development of atherosclerosis. Despite the frequent occurrence of lipoprotein abnormalities, the role of various serum toxins and subfractions that accumulate in uremic patients on lipoprotein metabolism is not clearly understood. This study addressed the role of uremic toxins on lipoprotein metabolism by examining the effect of a 500 to 2,000-d subfraction obtained from the serum of uremic and control subjects on the synthesis of apolipoprotein (apo) A-I in a human hepatoma cell line (Hep-G2). Serum subfractions obtained from uremic patients inhibited apo A-I synthesis and secretion by Hep-G2 cells in a dose-dependent manner as measured by (3H)leucine incorporation into apo A-I, immunoprecipitation, and ELISA. The uremic serum subfraction decreased the mRNA expression for apo A-I in Hep-G2 cells when compared with controls. These observations suggest that a component of uremic serum can have the potential to inhibit hepatic apo A-I synthesis and may adversely influence high-density lipoprotein metabolism, thus increasing the risk for the development of atherosclerotic vascular complications in uremic patients.

Purification of poly(ADP-ribose) glycohydrolase and detection of its isoforms by a zymogram following one- or two-dimensional electrophoresis

Poly(ADP-ribosyl)ation metabolism, a post-translational modification, involves two nuclear enzymes. Poly(ADP-ribose) polymerase (PARP) and poly(ADP-ribose) glycohydrolase (PARG) are responsible for the anabolism and catabolism of poly(ADP-ribose) polymer, respectively. PARG, despite being less abundant than PARP, is a crucial determinant of polymer metabolism which is known to be implicated in DNA repair and other cellular processes. Here, we describe modifications to improve the purification of PARG from calf thymus, in terms of both quantity and quality, which would allow biochemical and immunological studies. We also developed a zymogram to identify functional polypeptides exhibiting PARG activity. Purified and crude enzyme preparations from calf thymus were electrophoresed in two-dimensional gels. Samples were resolved on sodium dodecyl sulfate-polyacrylamide gel electrophoresis containing the polymer substrate in the form of automodified PARP after a nonequilibrium pH gradient electrophoresis. After renaturation of PARG in the gel, four isoforms of activity were clearly detected in the purified enzyme preparation. Even in the crude extract of the tissue, we could observe the major isoform of PARG. This technique will permit a better understanding of poly(ADP-ribose) catabolism and better characterization of PARG isoforms.

Increased blood flow in Broca's area during auditory hallucinations in schizophrenia

Verbal auditory hallucinations are common in schizophrenia but little is known about how they arise. We have used single photon emission tomography (SPET) to measure regional cerebral blood flow with the aim of identifying brain areas that are especially active during auditory hallucinations. We scanned twelve men with schizophrenia while they were experiencing hallucinations. The subjects were rescanned under identical conditions when their hallucinations had resolved (mean 19 weeks later). Blood flow was significantly greater during hallucinations than in the non-hallucinating state in Broca's area (mean count density on SPET 1.18 [SD 0.04] vs 1.13 [0.06]; p < 0.001); flow was also higher during hallucinations in the left anterior cingulate cortex and regions in the left temporal lobe, but these differences did not achieve significance. The increased flow in Broca's area was not accounted for by changes in other clinical variables nor by changes in the dose of neuroleptic drugs. These findings suggest that the production of auditory hallucinations in schizophrenia is associated with increased activity in a network of cortical areas specialised for language.

Environmental conditions, anthropometric parameters and arterial blood pressure

The influence of environmental conditions and anthropometric parameters on arterial blood pressure level was studied in 280 healthy Kashmiri subjects, aged 18-50 years (140 males, 140 females) Men in the age group of 18-20 years had higher blood pressure than women and their systolic blood pressure showed significant correlation with height, weight and skinfold thickness. Females (18-20 years) showed association of diastolic blood pressure with weight, skinfold thickness. Females (18-20) years) showed association of diastolic blood pressure with weight, skinfold thickness and mid-arm circumference. After the age of 20 years females had higher blood pressure than males. Height and weight decreased with age in both the sexes. Skinfold thickness and midarm circumference increased with age in females. A comparison between the present study and those reported from Haryana and Delhi revealed a higher diastolic pressure in Kashmiris.

Effects of ascorbic acid and pyridoxine supplementation on oxalate metabolism in peritoneal dialysis patients

We studied the effect of vitamin C and B6 supplementation on oxalate metabolism in seven patients receiving chronic peritoneal dialysis therapy. The study was divided into three phases, each lasting 4 weeks. Plasma oxalate, total ascorbic acid, and pyridoxal-5'-phosphate (PLP) were measured at the end of each phase. Twenty-four-hour urinary excretion and dialysate removal rates of oxalate were also obtained. At the end of phase I (supplement-free period), plasma oxalate levels were markedly elevated at 47.6 +/- 7.1 mumol/L (437 +/- 66 micrograms/dL) (normal, 3.4 +/- 0.4 mumol/L [30.3 +/- 1.6 micrograms/dL]). Plasma total ascorbic acid levels were 62 +/- 6 mumol/L (1.0 +/- 0.1 mg/dL) (normal, 45 to 57 mumol/L [0.8 to 1.0 mg/dL]), while plasma PLP levels were markedly reduced to 24 +/- 5 nmol/L (normal, 40 to 80 nmol/L). Daily supplements of 0.57 mmol (100 mg) ascorbic acid orally (phase II) resulted in a 19% increase in the plasma oxalate levels to 57.8 +/- 6.1 mumol/L (520 +/- 55 micrograms/dL) (P less than 0.03), with a concomitant 60% increase in the plasma ascorbate levels (91 +/- 6 mumol/L [1.6 +/- 0.1 mg/dL], P less than 0.01). Plasma PLP values remained low. Finally, during phase III (0.57 mmol or 100 mg ascorbic acid plus 59.6 mumol or 10 mg pyridoxine HCI orally daily), plasma oxalate levels declined by 17% to 47.9 +/- 5.2 mumol/L (431 +/- 47 micrograms/dL) (P greater than 0.05 v phase II).(ABSTRACT TRUNCATED AT 250 WORDS)

Modulation of transcription in rat liver nuclei in vitro by a diol epoxide of benzo[a]pyrene

Treatment of isolated rat liver nuclei with 7 beta, 8 alpha-dihydroxy-9 alpha, 10 alpha-epoxy-7,8,9,10- tetrahydrobenzo[a]pyrene, the ultimate carcinogenic metabolite of benzo[a]pyrene, resulted in inhibition of transcription as measured by radioactive precursor incorporation into RNA. The mechanism of inhibition as analyzed by use of different types of inhibitors suggested that the carcinogen acted on both the major components of transcription machinery, that is, the template chromatin and the enzyme RNA polymerases. This action correlates well with the observations made after administration of benzo[a]pyrene to rats.

Action of some retinol derivatives and their provitamins on microsome-catalyzed formation of benzo[a]pyrene-DNA adduct

Several vitamin A compounds have been tested for their ability to suppress formation of DNA adduct by the carcinogen benzo[a]pyrene (B[a]P) in an in vitro reaction catalyzed by rat liver microsomes. Retinol, retinal, 3-dehydroretinol and 3-hydroxyretinol were found to be effective inhibitors of adduct formation. Certain carotenoids that are precursors of these retinoids also displayed considerable inhibitory capacity. Carotenoids and the 3-substituted retinoids appeared to modulate the DNA adduct formation exclusively through their action on microsomal enzymes, since an effective inhibition in each case was observed on the formation of B[a]P-7,8-diol, a proximate carcinogenic metabolite of B[a]P. Unsubstituted retinoids, on the other hand, had marginal effect on enzymes but were found effective in accelerating inactivation of B[a]P-7,8-diol-9,10-epoxide, the ultimate carcinogenic metabolite that binds to DNA.

The effect of some new platinum (II) and palladium (II) coordination complexes on rat hepatic nuclear transcription in vitro

Several new L-amino acid derivatives of 2,2'-bipyridine and 1,10-phenanthroline complexes of platinum (Pt) and palladium (Pd) and a few binuclear 2,2'-bipyridine complexes of these metals were tested for their potential to inhibit rat hepatic nuclear transcription in vitro. Pd complexes were generally more effective inhibitors of transcription than the corresponding Pt complexes. Among Pd-diimine chlorides, the 2,2'-bipyridine complex was nearly 10 times more active than the corresponding 1,10-phenanthroline complex. Both Pt-diimine chlorides, however, showed same level of inhibitory activity. Amino acid derivatives were less inhibitory with respect to the parent metal diimine chlorides except for 1,10-phenanthroline complexes of Pd. For binuclear 2,2'-bipyridine complexes of Pt, the increase in length of linking hydrocarcon chain increased the inhibitory potential of the complex. The mechanism of inhibition of transcription by these metal complexes was sought to be understood by use of actinomycin-D and poly[d(I-C)] to differentiate effect on the two major components of transcription machinery viz. the template and the enzyme. These studies along with studies on reconstituted system of transcription using either pretreated template or enzyme indicate that these metal complexes displayed dual effect on transcription by inhibiting both the template and the enzymes.

Ascorbic acid supplements in patients receiving chronic peritoneal dialysis

Ascorbic acid supplements are commonly prescribed to patients with end-stage renal disease receiving peritoneal dialysis. To establish the need for ascorbic acid supplements, we evaluated seven chronic peritoneal dialysis patients during a supplement-free (phase I) period, and while receiving oral ascorbic acid (0.57 mmol/d [100 mg/d]) (phase II). Because of a proposed interaction with vitamin B6, patients were additionally supplemented with pyridoxine HCl (59.6 mumol/d [10 mg/d]) (phase III). Plasma levels and dialysate removal rates of total ascorbic acid and plasma pyridoxal-5-phosphate (PLP) were measured at the end of each phase. During phase I, plasma ascorbic acid levels (normal, 45 to 57 mumol/L [0.8 to 1.0 mg/dL]) declined slightly from 74 +/- 11 mumol/L (1.3 +/- 0.2 mg/dL) to 62 +/- 11 mumol/L (1.1 +/- 0.2 mg/dL) (P less than 0.02) at the end of the third week, and then remained stable to the end of the fourth week. Plasma ascorbic acid levels were no different in patients with or without residual renal function. With the addition of vitamin C supplements, plasma ascorbic acid levels increased by 45% of the baseline value at the end of phases II (P less than 0.001). The dialysate removal rate of ascorbic acid was 0.28 +/- 0.03 mmol/d (50 +/- 6 mg/d) at the end of phase I, and increased by 57% of the baseline value at the end of phases II (P less than 0.001). However, the peritoneal clearance of ascorbic acid remained unchanged during all phases the study. Pyridoxine depletion or repletion had no effect on plasma ascorbic acid levels (P greater than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Peritoneal catheters: a comparative study of column disc and Tenckhoff catheters

A functioning peritoneal access is crucial to the success of peritoneal dialysis. We report retrospective analysis of our experience using 44 Tenckhoff and 23 column disc, double-cuff, catheters in 46 patients receiving peritoneal dialysis. Postoperative care was identical in both groups. Both catheter groups were comparable with regards to age, sex, obesity and prior abdominal surgery. Catheter removal due to drainage failure was significantly greater with the column disc than the Tenckhoff catheters (22% vs 5%, p = 0.04). In addition, 39% of column disc catheters compared to 11% Tenckhoff catheters were removed as a result of therapy resistant peritonitis (p = 0.011). Furthermore, there was a greater incidence of peritonitis with the column disc than with the Tenckhoff catheters at the end of the first year (71% vs 42%, p less than 0.01). There was no difference between the two groups with respect to other complications, such as pericatheter leak, catheter infections, catheter cuff-extrusion or hernia. Our experience indicates that the column disc catheter is associated with higher complication rates and does not offer any advantage over the Tenckhoff catheter.

Incidence of P.T.C. taste sensitivity and threshold in Kashmiri population

Taste sensitivity and threshold of Phenylthiourea (PTC) was determined in 800 individuals of Kashmir who form a distinct ethnic group. Correlation, if any, with age, sex, blood group, pH of Saliva, or smoking habits was investigated. The taste sensitivity of P.T.C. increased with advancing age. The percentage of non-tasters was more in blood group 'B' & 'O'. However, no correlation was observed as far as sex, pH of saliva and smoking habits were concerned.

Peritoneal leucocyte response to bacterial peritonitis in patients receiving peritoneal dialysis

We evaluated the quantitative peritoneal leucocyte response to antibiotic therapy in 25 CAPD patients with 57 episodes of bacterial peritonitis. Eighty-eight percent of the peritonitis episodes were initially treated with a first generation cephalosporin, but results of microbial sensitivity studies led to a change in the initial antibiotic regimen in 23 episodes. Overall, 47/57 (82%) episodes were cured by antibiotic therapy alone (responders), while 10/57 (18%) required removal of the peritoneal catheter as a curative procedure (nonresponder). Neither the duration of symptoms on initial presentation nor the status of being a nonresponder could be related to the baseline peritoneal leucocyte values, either the total (PLC) or polymorphonuclear counts (PMN). Since the baseline PLC and PMN showed a 500-fold variation, subsequent changes were expressed as a percent [PLC (%) and PMN-PLC (%)] of the baseline value. On day 3 of peritonitis, PLC (%) and PMN-PLC (%) were less in responders (26% and 10%) than nonresponders (251% and 254%) (p less than 0.001). Differentiation between responders and nonresponders based on PLC (%) and PMN-PLC (%) was associated with a high degree of sensitivity (90%) and specificity (90%). Similar results were obtained for day 4. These data suggest that the temporal pattern of PLC and PMN, when expressed as a percentage of the baseline value, may be useful in predicting those episodes of peritonitis which require removal of the peritoneal catheter.

Vitamin B6 requirements of patients on chronic peritoneal dialysis

Patients with chronic renal failure often develop vitamin B6 deficiency, which is of clinical concern because the multiorgan system manifestations are similar to those of uremia. Vitamin B6 deficiency in hemodialysis patients has been previously studied, but the need for daily pyridoxine supplementation in patients on chronic peritoneal dialysis (CPD) remains unclear. Therefore, we studied a group of 11 stable patients, nine on CAPD and two CCPD, to test for vitamin B6 deficiency and to establish daily requirements. Adequacy of vitamin B6 nutrition was assessed by measurement of plasma and dialysate effluent total vitamin B6 and pyridoxal 5'-phosphate (PLP), the latter using a very sensitive modification of the tyrosine apodecarboxylase enzyme assay. After four weeks without vitamin B6 supplements on a diet containing 1.3 +/- 0.2 mg vitamin B6/day (7.7 +/- 1.2 mumol/day), all patients had subnormal plasma PLP levels, 16 +/- 3 nmol/liter (nml 40 to 60), seven having a severe deficiency (less than or equal to 20 nmol/liter). Plasma total vitamin B6 levels (which includes non-PLP forms of the vitamin) were normal in all patients at baseline, 116 +/- 29 nmol/liter. Peritoneal losses were small, 8 +/- 2 nmol PLP/day and 545 +/- 61 nmol total vitamin B6/day. Supplementation with 5 mg/day oral pyrodoxine HCl for up to 16 weeks adequately repleted eight patients (65 +/- 7 nmol PLP/L), while three patients required 10 mg/day to achieve normal plasma PLP levels. During three episodes of peritonitis, dialysate losses of PLP did not increase.(ABSTRACT TRUNCATED AT 250 WORDS)

Alteration in hepatic nuclear RNA polymerase activity following benzo[a]pyrene administration in rat

Benzo[a]pyrene was administered intraperitoneally to male Wistar rats as a single dose of 20 mg.kg-1 body weight. Two hours after its administration, livers were excised and the enzyme RNA polymerase was solubilized from purified nuclei. The enzyme was resolved into three forms, polymerase I, II and III by partial purification on DEAE-Sephadex A-25 column. All the three forms of nuclear RNA polymerase were inhibited in response to administration of benzo[a]pyrene. This was evident in terms of total yield as well as specific activity of each enzyme. The inhibition of nuclear transcription following administration of benzo[a]pyrene as observed previously (1) along with the present results on the enzyme inhibition clearly suggest that benzo[a]pyrene acts on both the major components of transcription machinery i.e. the template chromatin and the enzyme RNA polymerases.

Coagulation cascade, fibrinolytic system, antithrombin III, protein C and protein S in patients maintained on continuous ambulatory peritoneal dialysis

We studied the coagulation cascade, fibrinolytic system and naturally occurring anticoagulants in a group of 14 patients with end-stage renal disease maintained on continuous ambulatory peritoneal dialysis (CAPD). The results were compared with those obtained in a group of ten normal volunteers. Plasma procoagulant activities of factors XII, XI, IX, VIII, VII, X and II were significantly greater in the CAPD group as compared to the normal control group. Likewise plasma concentrations of total and free protein S were increased in the CAPD group. Although the mean value for plasma factor V activity in the CAPD group was higher than that found in the control group the difference did not attain statistical significance. In addition plasma fibrinogen concentration and factor VIII-related antigen level were significantly increased in CAPD patients. No significant difference was found between the CAPD patients and the control group with respect to plasma levels of protein C, antithrombin III, plasminogen or alpha 2-antiplasmin. In summary, the results demonstrate a tendency for increased levels of various coagulation factors and protein S in CAPD patients with no significant alterations in the levels of various fibrinolytic and endogenous anticoagulant agents, i.e. antithrombin III and protein C. The clinical significance and the mechanism responsible for the observed changes require further investigation.

Effects of a magnesium-free dialysate on magnesium metabolism during continuous ambulatory peritoneal dialysis

While the use of magnesium-containing compounds is usually contraindicated in dialysis patients, the risk of toxicity from hypermagnesemia can be reduced by lowering the magnesium concentration in dialysate. We examined the effects of a magnesium-free dialysate on both serum magnesium level and the peritoneal removal rate of magnesium over 12 weeks in 25 stable patients undergoing continuous ambulatory peritoneal dialysis (CAPD). After 2 weeks, the serum magnesium level decreased from 2.2 to 1.9 mg/dL (0.9 to 0.8 mmol/L) (P less than .02) and the peritoneal removal rate increased from 66 to 83 mg/d (2.8 to 3.5 mmol/d) (P less than .05), with both values remaining stable thereafter. There was a strong association between these parameters (r = -0.62, P less than .05), suggesting that the serum magnesium level decreased as a result of the initial increased peritoneal removal rate. For an additional 4-week period, a subgroup of nine patients received magnesium-containing, phosphate binding agents instead of those containing only aluminum. During this phase, serum inorganic phosphorus was well controlled. The serum magnesium level increased only from 1.8 to 2.5 mg/dL (0.7 to 1.0 mmol/L) (P less than .05), due in great part to the concomitant 41% rise in peritoneal magnesium removal from 91 to 128 mg/d (3.8 to 5.3 mmol/d) (P less than .05). No toxicity was noted during the entire 16-week study period, nor did serum calcium change. Thus, serum magnesium levels remained within an acceptable range as magnesium-containing phosphate binders were given through the use of magnesium-free peritoneal dialysate.(ABSTRACT TRUNCATED AT 250 WORDS)

Modulation of transcription in rat liver by benzo[a]pyrene

Single intraperitoneal administration of benzo[a]pyrene (B[a]P) at 20 mg/kg body weight to male Wistar rats caused an early (2 h) inhibition in liver of gross transcription as measured by incorporation of [14C] orotic acid into nuclear RNA. This inhibition was reversed gradually into a partial stimulation at 2-4 days after administration of B[a]P, followed by another period of inhibition at 7 days which persisted up to 14 days. The early reversible inhibition at 2 h was probed further by studies on in vitro transcription using isolated nuclei from treated rats. It was observed that total expression of RNA polymerase activity was only marginally inhibited because, while expression of RNA polymerases II and III showed remarkable inhibition, RNA polymerase I showed stimulation in activity.

Modulation by plant flavonoids and related phenolics of microsome catalyzed adduct formation between benzo[a]pyrene and DNA

Twenty-six flavonoids and related compounds were screened for their ability to modulate microsome mediated covalent adduct formation between [3H]benzo[a]pyrene ([3H]BP) and DNA in vitro. Some of these flavonoids, notably robinetin, quercetin, isorhamnetin and kaempferol were observed to inhibit the adduct formation significantly at very low levels. The unsubstituted flavone and some of the other flavonoids moderately inhibited this adduct formation, while some flavonoids were inactive, viz., most of the isoflavonoids and methylether derivatives of polyhydroxylated flavonoids. Structural features contributory towards the inhibitory activity of flavonoids appeared to be hydroxyl groups in 3 position of C ring, 5,7-positions of A ring and 3',4'- and 5'-positions of B ring. Methylation or glycosylation of hydroxyl group rendered the flavonoid less active or inactive. Flavanones, with saturated 2,3 double bond, were also inactive. Metabolic activation of BP to proximate carcinogen (+/-)-trans-7,8-dihydroxy-7,8-dihydro-BP (BP-7,8-dihydrodiol) was also measured in presence of some of these flavonoids. The extent of inhibition of metabolism by these flavonoids did not correlate with their ability to inhibit the adduct formation. Thus, suppression of metabolism did not appear to be a major contributory factor towards inhibition of adduct formation. The solvolysis in aqueous dioxane of (+/-)-7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydro-BP (BPDE I), the ultimate carcinogen of BP, was accelerated in presence of selected flavonoids. Inactivation of BPDE I, therefore, appeared to be the major mechanism by which some of these flavonoids inhibited the adduct formation between BP and DNA, and this could be the basis for the anti-carcinogenic nature of these flavonoids.

Effect of lead on human semen

Semen qualities were studied in workers with an average age of 30 years and occupationally exposed to lead in a printing press. Another sample with the same average age but not exposed to lead were taken as control subjects. The average lead content in blood and seminal plasma of the exposed group were 42.5 mcg/100 ml and 14.80 mcg/100 ml, respectively. Their sperm counts and percentage of motile sperm were significantly affected. Significantly higher percentages of abnormal spermatozoa were also observed in these semen samples. The levels of seminal acid phosphatase, succinic dehydrogenase, and fructose in them were also significantly found to be low compared with those from the unexposed subjects. Cytochemical study of sperm head DNA in the exposed groups showed a low surface reaction.

Acyclovir pharmacokinetics in a patient on continuous ambulatory peritoneal dialysis

Acyclovir is an effective agent for the treatment of herpes virus infections, however, the pharmacokinetics of the drug are altered in renal failure. We studied this drug in a continuous ambulatory peritoneal dialysis (CAPD) patient who was immunocompromised and had cutaneous herpes infection. The elimination half-life (17.1 hours) was similar to that reported for end-stage renal disease (ESRD) patients, while the volume of the central compartment (29.6 L/1.73 m2), the steady state volume of distribution (68.1 L/1.73 m2), and the total body clearance (48.3 mL/min/1.73 m2) were greater. The mean CAPD clearance was only 4.4 mL/min, with less than 10% of an administered dose being recovered in the 24-hour dialysate. Further studies are needed to establish a dosing regimen for CAPD patients.

Verapamil kinetics during maintenance hemodialysis

The kinetics of verapamil during chronic oral therapy were evaluated in a maintenance hemodialysis patient. The elimination half-lives of verapamil and its major metabolite norverapamil were 3.8 and 15.2 h. The former is shorter, while the latter is similar to that in patients with normal renal function. Hemodialysis did not affect drug half-life, and neither drug could be detected in the dialysate. Our studies suggest that verapamil kinetics are altered in end-stage renal disease and that hemodialysis does not remove significant amounts of the drug or its metabolite.