Carboxy terminal region of a chloroplast DNA polymerase accessory factor stimulates DNA polymerase activity

p43, a glycoprotein of pea chloroplast (ct), acts as an accessory protein of pea chloroplast DNA polymerase. p43 binds to DNA, binds to ct-DNA polymerase and stimulates the ct-DNA polymerase activity. In the work presented here, the C-terminal domain of p43 (p22) has been overexpressed in E. coli. South Western analysis reveals that the recombinant p22 lacks in DNA binding activity. However, the recombinant p22 can form complex with the pea ct-DNA polymerase quite efficiently and stimulates the DNA polymerase activity to a greater extent than the native p43. Thus the DNA binding domain of p43 appears to be spatially separate from the domain responsible for the DNA polymerase accessory activity. The DNA binding domain is also highly O-glycosylated and loss of glycosylation of p43 leads to enhanced DNA binding as well as repression of ct-DNA polymerase activity. These findings allow us to propose a model to explain how glycosylation of p43 helps ct-DNA polymerase latch onto the DNA template for enhanced processivity. The predictive components of the model have been discussed.

Groundwater arsenic contamination in Bangladesh and West Bengal, India

Nine districts in West Bengal, India, and 42 districts in Bangladesh have arsenic levels in groundwater above the World Health Organization maximum permissible limit of 50 microg/L. The area and population of the 42 districts in Bangladesh and the 9 districts in West Bengal are 92,106 km(2) and 79.9 million and 38,865 km(2) and 42.7 million, respectively. In our preliminary study, we have identified 985 arsenic-affected villages in 69 police stations/blocks of nine arsenic-affected districts in West Bengal. In Bangladesh, we have identified 492 affected villages in 141 police stations/blocks of 42 affected districts. To date, we have collected 10,991 water samples from 42 arsenic-affected districts in Bangladesh for analysis, 58,166 water samples from nine arsenic-affected districts in West Bengal. Of the water samples that we analyzed, 59 and 34%, respectively, contained arsenic levels above 50 microg/L. Thousands of hair, nail, and urine samples from people living in arsenic-affected villages have been analyzed to date; Bangladesh and West Bengal, 93 and 77% samples, on an average, contained arsenic above the normal/toxic level. We surveyed 27 of 42 districts in Bangladesh for arsenic patients; we identified patients with arsenical skin lesions in 25 districts. In West Bengal, we identified patients with lesions in seven of nine districts. We examined people from the affected villages at random for arsenical dermatologic features (11,180 and 29,035 from Bangladesh and West Bengal, respectively); 24.47 and 15.02% of those examined, respectively, had skin lesions. After 10 years of study in West Bengal and 5 in Bangladesh, we feel that we have seen only the tip of iceberg.

Groundwater arsenic contamination in Bangladesh and West Bengal, India

Nine districts in West Bengal, India, and 42 districts in Bangladesh have arsenic levels in groundwater above the World Health Organization maximum permissible limit of 50 microg/L. The area and population of the 42 districts in Bangladesh and the 9 districts in West Bengal are 92,106 km(2) and 79.9 million and 38,865 km(2) and 42.7 million, respectively. In our preliminary study, we have identified 985 arsenic-affected villages in 69 police stations/blocks of nine arsenic-affected districts in West Bengal. In Bangladesh, we have identified 492 affected villages in 141 police stations/blocks of 42 affected districts. To date, we have collected 10,991 water samples from 42 arsenic-affected districts in Bangladesh for analysis, 58,166 water samples from nine arsenic-affected districts in West Bengal. Of the water samples that we analyzed, 59 and 34%, respectively, contained arsenic levels above 50 microg/L. Thousands of hair, nail, and urine samples from people living in arsenic-affected villages have been analyzed to date; Bangladesh and West Bengal, 93 and 77% samples, on an average, contained arsenic above the normal/toxic level. We surveyed 27 of 42 districts in Bangladesh for arsenic patients; we identified patients with arsenical skin lesions in 25 districts. In West Bengal, we identified patients with lesions in seven of nine districts. We examined people from the affected villages at random for arsenical dermatologic features (11,180 and 29,035 from Bangladesh and West Bengal, respectively); 24.47 and 15.02% of those examined, respectively, had skin lesions. After 10 years of study in West Bengal and 5 in Bangladesh, we feel that we have seen only the tip of iceberg.

Short-acting general anaesthesia facilitates therapeutic ERCP in frail elderly patients with benign extra-hepatic biliary disease

AIMS AND OBJECTIVES

To ascertain whether therapeutic endoscopic retrograde cholangiopancreatography (ERCP) for benign biliary disease in frail elderly patients with comorbid conditions can be safely undertaken in a district general hospital, and whether the procedure is facilitated by the use of short-acting general anaesthesia.

SETTING

District general hospital in South East England.

DESIGN OF STUDY

Clinical study of 25 consecutive patients with benign biliary disease.

METHODS

Describes the process of bile duct clearance by therapeutic ERCP under short-acting general anaesthesia in 25 patients with co-morbidity aged > or = 80 years and gives details of the general anaesthesia and monitoring.

RESULTS

Twenty-two patients had their bile ducts successfully cleared locally and one patient was stented for a benign biliary stricture. The ampullae of two other patients were lying within diverticula, which hindered cannulation and only pancreatograms were obtained; one of the patients had a successful bile duct clearance at a tertiary centre, the other refused further intervention. Complications (melaena, bronchopneumonia and a Clostridium difficile infection) occurred in two patients (8%). There was no morbidity associated with the anaesthesia, and no mortality occurred within 30 days of the procedure.

CONCLUSIONS

Bile duct clearance by therapeutic ERCP can be safely carried out in frail elderly patients in a district general hospital and the process is facilitated by the use of short-acting general anaesthesia. The importance of optimizing the patient's condition before ERCP, and not overfilling the pancreatic duct, is highlighted.

Pea chloroplast FtsZ can form multimers and correct the thermosensitive defect of an Escherichia coli ftsZ mutant

This paper reports the isolation and characterization of a cDNA encoding the FtsZ protein of pea. The protein is synthesised as a precursor molecule of 423 amino acids with a molecular mass of 44 kDa. When translated in vitro, the protein is translocated efficiently into isolated, intact pea chloroplasts, demonstrating that the protein is localised in the chloroplast. Pea FtsZ synthesised in vitro formed multimers in a calcium-dependent manner. The pea cDNA complemented the thermosensitive defect of an E. coli ftsZ mutant in vivo and converted the filamentous phenotype of the E. coli mutant into the normal wild-type morphology at 42 degrees C. However, pea FtsZ mutants that were defective in multimerisation in vitro failed to correct the phenotype of the E. coli ftsZ mutant in vivo. The pea ftsZ transcripts were abundantly present in the young leaves, but barely detectable in roots and stems and undetectable in older leaves. Light stimulated transcription of the gene significantly in young and dark-grown leaves. This study strongly suggests that the division mechanisms used by chloroplasts and bacteria show considerable similarity.

Cytosine arabinoside (ara-C) resistance confers cross-resistance or collateral sensitivity to other classes of anti-leukemic drugs

The major limitation of treatment with antimetabolite drugs is that they produce resistant clones both in vitro and in patients who either do not respond to treatment or relapse soon after response has been documented. To better understand the phenomenon of cross-resistance, we developed seven CEM/ara-C-resistant leukemic clones from the CEM/0 (wt) cell line. These clones ranged from 4- to 3.5 x 10(8)-fold more resistant to ara-C than the wt CEM/0 cell line. Using this model, we determined IC50 concentrations to several chemotherapeutic agents and gamma radiation, and we also studied pro- (p53) and anti-apoptotic (bcl-2) proteins, as well as P-glycoprotein (P-gp) and multidrug resistance related protein (MRP). The cell viability assays showed that these clones were cross-resistant to 6-thioguanine (6-TG) or 6-mercaptoguanosine (6-TGuo) from 1.1- to 8.8-fold with ara-C; cross-resistance to vincristine (VCR) was from 200- to 1 x 10(4)-fold with ara-C. Taxotere (TXR) showed cross-resistance with ara-C from 1.39- to 3.03 x 10(3)-fold; dexamethasone (DEX) also showed a significant degree of cross-resistance from 27.4- to 3.87 x 10(7)-fold. Gamma radiation treatments from 0.77 Gy to 12.3 Gy showed a radiation dose-dependent cross-resistance with ara-C from 1.43- to 2.93-fold. Idarubicin was collaterally sensitive with ara-C from 4.6- to 1 x 10(9)-fold in these cell lines. The CEM/ara-C/G resistant cell line was 3-fold more sensitive to 6-TG or VCR than CEM/0 (wt), and 5-fold more sensitive to 6-TGuo. This cell clone expressed p53 and did not overexpress bcl-2 protein. All of the cell lines studied, CEM/0 (wt) and the ara-C resistant clones, showed functional p53 protein. The cell treatment with 0.1, 1 and 10 microM ara-C for 48 hours showed increased p53 protein expression in most of these lines. No increase in bcl-2 protein expression was seen in the wt cell line after ara-C treatment for 48 hours. Three cell lines resistant to ara-C (CEM/ara-C/B, CEM/ara-C/D and CEM/ara-C/I) showed an important increased expression of bcl-2 protein after treatment with 1 microM ara-C, but not after 10 microM. This alteration may lead to resistance to apoptosis and enhanced cell survival. The ratio of bcl-2 to p53 was increased significantly in these three clones, thus favoring an anti-apoptotic drive. All of the cell lines examined were negative for MRP expression and only two, CEM/ara-C/B and CEM/ara-C/J, were positive for MRP functional activity. However, three ara-C resistant cell clones, CEM/ara-C/7A, CEM/ara-C/B and CEM/ara-C/G, were positive for P-gp expression and functional activity. It is apparent that selection for ara-C resistance confers cross-resistance to many other classes of drugs and gamma radiation, probably due to bcl-2 protein overexpression or P-gp and MRP expression, as independent mechanisms.

Isolation and characterisation of the cDNA encoding a glycosylated accessory protein of pea chloroplast DNA polymerase

The cDNA encoding p43, a DNA binding protein from pea chloroplasts (ct) that binds to cognate DNA polymerase and stimulates the polymerase activity, has been cloned and characterised. The characteristic sequence motifs of hydroxyproline-rich glyco-proteins (HRGP) are present in the cDNA corres-ponding to the N-terminal domain of the mature p43. The protein was found to be highly O-arabinosylated. Chemically deglycosylated p43 (i.e. p29) retains its binding to both DNA and pea ct-DNA polymerase but fails to stimulate the DNA polymerase activity. The mature p43 is synthesised as a pre-p43 protein containing a 59 amino acid long transit peptide which undergoes stromal cleavage as evidenced from the post-translational in vitro import of the precursor protein into the isolated intact pea chloroplasts. Surprisingly, p43 is found only in pea chloroplasts. The unique features present in the cloned cDNA indicate that p43 is a novel member of the HRGP family of proteins. Besides p43, no other DNA-polymerase accessory protein with O-glycosylation has been reported yet.

Suppression of pea nuclear topoisomerase I enzyme activity by pea PCNA

Proliferating cell nuclear antigen (PCNA), a highly conserved DNA polymerase accessory protein of eukary- otic kingdom, has not been studied thoroughly in bio- chemical terms in plants. We describe the isolation of the cDNA encoding PCNA from the pea cDNA library using the PCR approach. The cDNA was used for expression of pea PCNA in bacteria as a fusion protein (GST.PCNA) with the GST tag at the amino terminal end. The GST.PCNA stimulated the partially purified pea DNA polymerases approximately 30-fold. The stimulation was due to the oligomeric form of GST.PCNA. The pea PCNA interacted with the recombinant type I pea topoiso- merase as well as the native pea nuclear topoisomerase I and repressed the DNA relaxation activities. However, the DNA binding activity of Topo I remained undisturbed in the presence of high amounts of PCNA, thereby signify- ing that the catalysis of Topo I was probably affected by PCNA.

Flixotide Nebules: new for chronic severe asthma

Allen & Hanburys recently launched Flixotide Nebules for prophylactic management of severe chronic asthma in patients requiring high-dose inhaled or oral corticosteroid therapy.

Increased p21/WAF-1 and p53 protein levels following sequential three drug combination regimen of fludarabine, cytarabine and docetaxel induces apoptosis in human leukemia cells

Combinations of nucleoside analog drugs, such as F-araA and ara-C, combined with Topoisomerase II inhibitors, such as anthracyclines, are synergistic against human leukemic T-cells and induce apoptotic cell death. Similarly, nucleoside analog drugs followed by mitotic inhibitors also have a synergistic effect. Sequence specific combinations of F-araA followed by ara-C and Taxotere (docetaxel) in CEM/0 cells showed a 2- to 3-fold synergism over the two drug (F-araA + ara-C) combinations and 2- to 4-fold synergism over Taxotere alone. This synergism was evident due to enhanced cellular apoptosis. In the CEM/ara-C/7A cell line, which is partially resistant to ara-C, the synergy observed with the triple drug combination was 9-fold greater than the F-araA plus araC combination, and 3-fold greater than Taxotere alone, making this three-drug regimen collaterally sensitive to ara-C. This study describes the mechanisms of the synergistic effect in regards to apoptosis achieved by three-drug regimens comprised of two nucleoside analog drugs and a mitotic inhibitor in comparison with the combination of two nucleotide analog drugs. The study also demonstrates that the possible biochemical mechanism of cellular toxicity and drug synergism is attributed to induction of apoptosis following drug treatment and the onset of the apoptotic cascade is primarily regulated by p21/WAF-I, which is transcriptionally activated by p53 following DNA damage. The anti-apoptotic protein, bcl-2, seemed to have no effect in inhibiting apoptosis following treatment with the two or three drug regimens in this in vitro leukemia model. The three-drug combination induced greater cellular apoptosis than the two-drug combination or Taxotere monotherapy. We conclude that the greater drug synergism observed in human leukemic cells, sensitive or resistant to ara-C, by Fludarabine + ara-C + Taxotere can be explained by the greater oligonucleosomal DNA fragmentation indicative of increased cellular apoptosis. The mechanism of this increased cytotoxic action is due to the upregulation of p53 and p21/WAF-1 with a down regulation of bcl-2. These studies are encouraging, and testing this three drug regimen in a clinical setting may result in improved antileukemic therapies.

Review of pneumococcal endocarditis in adults in the penicillin era

Streptococcus pneumoniae is an infrequent cause of infectious endocarditis in adults. In the past 2 years, however, we have encountered several cases at our institution, and additional cases have been reported in the literature. This infection typically follows pneumonia in the setting of chronic alcoholism and may additionally be complicated by meningitis. Less commonly, pneumococcal endocarditis occurs in other hosts or follows primary infection at other extrapulmonary sites. In such cases, the diagnosis may be initially missed, with a resultant delay in institution of appropriate therapy. Moreover, there are controversies regarding the optimal therapy for infections of this nature in the era of penicillin resistance. Since a comprehensive review of this topic has not been published since 1990, we reviewed cases of pneumococcal endocarditis in the penicillin era, with particular attention to disease recognition, the role of echocardiography, and the dilemmas surrounding medical and surgical therapeutic interventions.

Three-dimensional structural analysis of recombinant rotavirus-like particles with intact and amino-terminal-deleted VP2: implications for the architecture of the VP2 capsid layer

Rotaviruses are the leading cause of severe infantile gastroenteritis worldwide. These viruses are large, complex icosahedral particles consisting of three concentric capsid layers enclosing a genome of eleven segments of double-stranded RNA (dsRNA). The amino terminus of the innermost capsid protein VP2 possesses a nonspecific single-stranded RNA and dsRNA binding activity, and the amino terminus is also essential for the incorporation of the polymerase enzyme VP1 and guanylyltransferase VP3 into the core of the virion. Biochemical and structural studies have suggested that VP2, and especially the amino terminus, appears to act as a scaffold for proper assembly of the components of the viral core. To locate the amino terminus of VP2 within the core, we have used electron cryomicroscopy and image reconstruction to determine the three-dimensional structures of recombinant virus-like particles that contain either full-length or amino-terminal-deleted forms of VP2 coexpressed with the intermediate capsid protein VP6. A comparison of these structures indicates two significant changes along the inner surface of VP2 in the structure lacking the amino terminus: a loss of mass adjacent to the fivefold axes and a redistribution of mass along the fivefold axes. Examination of the VP2 layer suggests that the proteins are arranged as dimers of 120 quasi-equivalent molecules, with each dimer extending between neighboring fivefold axes. Our results indicate that the amino termini of both quasi-equivalent VP2 molecules are located near the icosahedral vertices.

The effects of aging and neurodegeneration on apoptosis-associated DNA fragmentation and the benefits of nicotinamide

In this work, the tertiary butylhydroperoxide- (t-BuOOH) treated mouse was used as a model to study the oxidative stress that is associated with various neurodegenerative diseases. DNA was found to be an early target of t-BuOOH attack. Necrosis was associated with extensive DNA fragmentation that occurred in almost all regions of the brain within 20 min following intracerebroventricular (icv) injection of 109.7 mg/kg t-BuOOH. Apoptosis was associated with high levels of DNA fragmentation that was observed at 48 h after icv administration of 21.9 mg/kg t-BuOOH. Susceptibility to DNA damage was found to be age-dependent, since 24-mo-old mice exhibited consistently higher and more pervasive DNA damage than 8 mo-old-mice. Extensive DNA damage was seen in various brain regions in patients with Alzheimer disease (AD) and with both Alzheimer and Parkinson disease (AD-PD). These results directly implicate DNA damage in neurodegeneration. The DNA fragmentation ob-served can lead to both apoptosis and necrosis, as suggested by gel electrophoresis. Nicotinamide, a precursor of NAD in the brain, was able to prevent DNA fragmentation induced by low-dose t-BuOOH, when coadministered with the toxin.

Increased brain NAD prevents neuronal apoptosis in vivo

Apoptosis is a characteristic form of cell death which has been implicated in neurodegeneration. In this study we document the induction of apoptosis and DNA fragmentation in vivo by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a neurotoxin. MPTP selectively damages dopaminergic neurons in the substantia nigra of the midbrain. It is a potent inducer of oxygen radicals. Nicotinamide, a precursor of NAD, is able to block the apoptosis induced by MPTP. Nicotinamide also quenches some of the radicals formed by xanthine oxidase. Nicotinamide may be of interest in the treatment of neurodegeneration.

Prevention of radiation induced taste aversion in rats

Diltiazem, a calcium channel blocker, and a cardiovascular therapeutic agent offers significant protection to mice against lethal dose of ionizing radiation. Considering the potential efficacy of diltiazem as a radioprotector for human use, it was deemed necessary to investigate its influence on radiation-induced behavioural changes like nausea, vomiting, learning, memory and performance. In the present studies, conditioned taste aversion (CTA) test based on consumption of saccharin solution, was used as a marker of behavioural changes. Significant CTA (97 +/- 2%) was observed in rats irradiated with Co-60 gamma rays (absorbed dose 1 Gy). Administration of diltiazem at doses greater than 10 mg/kg, body wt, evoked CTA in a dose-dependent manner and that was found to be further aggravated on irradiation. At a lower dose of 5 mg/kg, body wt, diltiazem did not evoke CTA and protected against radiation induced aversion significantly (62 +/- 3%). The results suggest that diltiazem at concentrations lower than 10 mg/kg, body wt, in rats may be useful in preventing radiation induced behavioural changes. This observation could be of particular significance in clinical radiotherapy where radiation induced nausea and vomiting are of great concern.

A 43 kDa DNA binding protein from the pea chloroplast interacts with and stimulates the cognate DNA polymerase

A DNA binding protein with DNA polymerase 'accessory activity' has been identified and purified to apparent homogeneity from pea chloroplasts. This protein consists of a single subunit of 43 kDa and binds to DNA regardless of its base sequence and topology. It increases cognate DNA polymerase-primase activity in a dose dependent manner. Using solid phase protein-protein interaction trapping and co-immunoprecipitation techniques, the purified protein was found to associate with the chloroplast DNA polymerase. The chloroplast DNA polymerase also binds directly to the radioiodinated 43 kDa protein. The specific interaction between 43 kDa protein and chloroplast DNA polymerase results in the synthesis of longer DNA chains. The 43 kDa protein, present abundantly in the pea chloroplast, appears to increase processivity of the chloroplast DNA polymerase and may play an important role in the replication of pea chloroplast DNA.

Apoptosis and oxidative stress in the aging brain

DNA is a primary site of damage during oxidative stress in the brain. DNA fragmentation occurs within minutes of induction of oxidative stress. This DNA fragmentation probably results from the attack of free radicals on DNA and from the activation of endonucleases. Oxidative stress was induced by intracerebroventricular injection of t-butylhydroperoxide. This results in a very rapid flux of t-butylhydroperoxide, which is cleared from the brain within minutes. This flux of t-butylhydroperoxide results in the formation of hydroxyl radical in the brain and probably in the nuclei of brain cells. Necrosis results from extensive DNA fragmentation caused by massive oxidative stress. Cresyl violet stained brain sections demonstrated necrosis in many brain regions. In addition, previous electron microscopy studies showed degradation of cellular nuclei caused by tBuOOH toxicity. Low doses of t-butylhydroperoxide can induce apoptosis, which is a delayed form of cell death. Apoptosis was found in brains stained to visualize apoptotic DNA fragments. Experiments performed in mice aged 2, 8 or 24 months will be discussed. We have also found that apoptosis and DNA fragmentation can be prevented by pretreating mice with the vitamin micotinamide. Nicotinamide is a precursor for NAD. DNA repair requires high levels of NAD in the nucleus for the activity of poly(ADP-ribose) polymerase. Oxidative stress in the brain produces both necrosis and apoptosis, probably as the result of DNA fragmentation. Senescence is associated with an increase in the production of DNA fragments during brain oxidative stress, which probably leads to more necrosis and apoptosis than in younger mice.

Mode of action of three structurally different hypoglycemic agents: a comparative study

The mechanism of dose-dependent hypoglycemic effect, the margin of safety and ED50 of three structurally unrelated compounds, tolbutamide (TB), centpiperalone (CP) and a swerchirin-containing fraction (SWI) from the plant Swertia chirayita, were investigated in experimental models. After a single oral administration of TB, CP and SWI to groups of normal and streptozotocin (STZ)-induced mild and severe diabetic rats, the blood sugar lowering effect and ED50 of the agents were determined. Plasma Immuno Reactive Insulin (IRI) levels and the degree of islet beta cell degranulation were assayed using RIA and histochemical staining, respectively, in normal rats treated with the agents. The percent blood sugar lowering, increase in IRI levels and beta cell degranulation were highest in CP treated normal rats (69, 124 and 75%, respectively). In addition, CP was the only agent found active in STZ-induced severely diabetic rats (P < 0.01). In STZ-mild diabetic rats, however, TB was more effective than CP and SWI. By analysis of data using Anova method, it is concluded that CP is more effective than SWI (P < 0.01) and TB. However, SWI an impure natural product showed better blood sugar lowering than tolbutamide which is a drug in use.

Nicotinamide as a precursor for NAD+ prevents apoptosis in the mouse brain induced by tertiary-butylhydroperoxide

The vitamin nicotinamide can protect against oxidative stress-induced apoptosis in the brain when used as a precursor for nicotinamide adenine dinucleotide (NAD+). The intracerebroventricular administration of tertiary-butylhydroperoxide (t-buOOH) to mice was used to simulate physiologic oxidative stress and apoptosis which may occur in some neurodegenerative conditions. t-buOOH produced characteristic apoptotic nuclear degeneration in neurons with extensive fragmentation of DNA. In this report we show that the elevation of NAD+ by nicotinamide prevents DNA fragmentation during apoptosis or necrosis in the brain as stimulated by t-buOOH administration. NAD+ levels can be increased by 50% in the brain. This may prevent the critical depletion of NAD+ by poly(ADP-ribose) polymerase (PARP) and provide additional substrate during the repair of DNA. Nicotinamide may be of particular interest in the treatment of neurodegeneration.

Parenteral ciprofloxacin in persistent diarrhoea in children

In a controlled trial of 30 cases of persistent diarrhoea in infants, ciprofloxacin was used parenterally for systemic antibiotic therapy. Group A cases (15 in number) were treated with parenteral ciprofloxacin and group B control cases (remaining 15) were treated with parenteral ampicillin and chloramphenicol or ampicillin/amikacin along with treatment of dehydration and malnutrition. All group A cases had excellent response and 9 infants of group B had no response up to day 4. After stopping all other drugs and with parenteral ciprofloxacin they responded favourably. Follow-up of all the cases was done regularly every 2 weeks for 6 months after discharge. No toxicity of ciprofloxacin was noted.

Beware the steroid responsive nature of a pyrexial illness

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Nuclear disintegration in chicken peritoneal macrophages exposed to fumonisin B1 from Indian maize

The effects of fumonisin B1 (FB1) on the morphology of chicken peritoneal macrophages were studied. It was found that FB1-exposure caused nuclear disintegrations in peritoneal macrophages. The number of macrophages experiencing nuclear disintegration increased with the rise in the dose of FB1 from 6 to 18 micrograms ml-1. The finding implies that dietary intake of FB1 may damage the macrophages in consumers rendering the latter susceptible to infection.

Left ventricular mass estimation by echocardiography: is it clinically useful?

Echocardiographic determination of left ventricular mass provides prognostic information that is independent of blood pressure. This prognostic information has a graded and continuous relationship with outcome, and is independent of traditional risk factors. This article addresses the prognostic and clinical utility of echocardiography for detection of left ventricular mass. Recommendations will be offered regarding the use of echocardiography for screening in select individuals.

Microbial production of L-tyrosine: a review

Microbial production of L-tyrosine by direct fermentation and by enzymatic methods has been reviewed. Achievements in this regard made through recombinant DNA techniques have also been included. The review also includes biosynthesis and regulation of tyrosine.

Apoptosis and DNA fragmentation as induced by tertiary butylhydroperoxide in the brain

In this study, the effect of intracerebroventricular administration of the free radical generator, tertiary butylhydroperoxide, on DNA, was quantitated. Previous studies had established DNA as a very important site of free radical attack. The purpose of the study was to detect whether DNA was one of the primary targets of the toxin as well as to detect any apoptosis that may have been induced by the toxin. The DNA fragmentation assay clearly showed DNA damage within 20 min of administration of 109.7 mg/kg t-BuOOH almost in all brain regions in both 2-month and 8-month-old C57BL/6 mice. In Situ Apoptosis Detection assay, where brain sections were stained with Apoptag, demonstrated that t-BuOOH induces apoptosis in many brain regions. Electron microscopy was done to show nuclear damage and DNA fragments appearing in the cytoplasm. Cresyl violet staining was done to show that while low dose (21.9 mg/kg) t-BuOOH induces apoptosis, it may also induce necrosis in other cells of the same brain region. Thus, from this study we can conclude that DNA may be one of the primary target sites of free radical attack in the brain, and results in both necrosis and apoptosis. This can have a profound effect on neurodegeneration.

Characterisation and mode of in vitro replication of pea chloroplast OriA sequences

A partially purified replicative system of pea chloroplast that replicates recombinant DNAs containing pea chloroplast origin sequences has been characterised. Polymerisation by this system is very fast and insensitive to chain terminators like dideoxynucleotides, arabinosylcytosine 5'-triphosphate, etc. Both strands of template DNA are synthesized and single-stranded DNA templates undergo more than one round of replication. When sequences of either of the two chloroplast origins of replication (OriA or OriB) are used as templates, the replicative intermediates are found to have sigma structures. Electron microscopic analysis of the sigma structures restricted with various enzymes reveals that the initiation site of in vitro replication maps near the displacement-loop regions where replication initiates also in vivo. Although the observed replication initiation in the OriA recombinant template is chloroplast-DNA-specific, the mode of replication is different from that observed in vivo with intact ctDNA. However, when the template DNA contains both the OriA and OriB sequences, the in vitro replication proceeds in the theta mode, the mode of replication usually observed in vivo.

Purification and characterization of a eukaryotic type 1 topoisomerase from pea chloroplast

A 69-kDa protein with topoisomerase I activity has been homogeneously purified from the chloroplasts of pea leaves. The topoisomerase properties are detected in crude lysate of pea chloroplasts using the technique of transferring 32P radioactivity from the 32P-labeled DNA to the protein. The purified enzyme relaxes both positive and negative supercoils in topological steps of unity without requiring magnesium ions. The enzyme is sensitive to topoisomerase I-specific inhibitors like camptothecin and berenil, and unaffected by reagents like novobiocin and doxorubicin at the topoisomerase II-inhibitory dosage. In the presence of the enzyme, supercoiled DNA is nicked, and the 3'-phosphoryl end of the nick becomes covalently linked with the enzyme. A tyrosine residue of the enzyme is responsible for the covalent linkage. Rabbit antiserum raised against the 16-mer peptide spanning the active residues of human topoisomerase I recognizes the 69-kDa protein within the crude lysate of pea chloroplasts as does the antiserum to the purified 69-kDa protein. From the enzymatic characteristics, the protein has been classified as a eukaryotic type I topoisomerase.

Denatured supercoiled DNA--structural and biological activity

Supercoiled DNA on treatment with NaOH followed by neutralization produces a condensed structure (form Id). This structure does not split into topoisomers when run on long gel in presence of intercalating agents and the migration of this form does not change appreciably in presence or absence of ethidium bromide. Relaxation of form Id by topoisomerase I from pea chloroplast is facilitated more than form I. Single-stranded binding (SSB) protein binds more to form Id as evidenced from gel retardation study. Hydroxyl radical nicking is facilitated in this form. Compared to form I, this form produces half the number of transformants, but adsorption and penetration remain almost same in both the forms. Post-transformational growth using 32P labelled form I and form Id showed greater amount of degradation in form Id.

Blood and hepatic glutathione in linamarin fed rats

Female Sprague Dawley rats were fed 5 mg linamarin daily for 10 days. Reduced glutathione (GSH) levels in blood and liver of experimental rats were analysed. The results showed an increase of 45% and 33% glutathione levels in blood and liver respectively in experimental rats. This alteration in glutathione levels could be most likely either due to increased hepatic biosynthesis or as a consequence of decreased peripheral utilization which might be appreciated due to hypothyroidal status induced by linamarin feeding.

Destruction of phagocytosis-suppressing activity of aflatoxin B1 by ozone

The impact of ozone on the immunity-impairing activity of aflatoxin B1 (AFB1) was studied. Phagocytosis by rat peritoneal macrophages, which was found to be suppressed in the presence of AFB1, remained unimpaired when the applied AFB1 was pretreated with ozone (1.2 mg l-1) for 6 min at a flow rate of 40 ml min-1. Hence, application of ozone on AFB1-contaminated foodcrops seems to be a promising preventive measure against any adverse immunological disorder in consumers.

Biochemical activities of denatured covalently closed circular duplex DNA

Covalently closed circular duplex DNA when exposed to high alkaline pH followed by neutralization yields a collapsed state structure (form I(d)) that can undergo transition to form I and was susceptible to S1 nuclease. Form I(d), in spite of its compact structure, admits specific cleavage by restriction enzymes over its entire genome. When used in a semi-in vitro replication complex, form I(d) gave significantly better template activity, and undergoes better primer extension in in vitro using Klenow. Thus form I(d) having a compact shape can behave as a better substrate in a few key enzymatic reactions.

Mechanism of blood sugar lowering by a swerchirin-containing hexane fraction (SWI) of Swertia chirayita

Mechanism of blood sugar lowering by the crude/impure swerchirin (SWI) isolated from the hexane fraction of Swertia chirayita was investigated. Single oral administration of SWI (50 mg/kg, body wt) to fed CF rats induced about 60% (max.) fall in blood glucose by 7 hr post-treatment. This was associated with marked depletion of aldehyde-fuchsin stained beta-granules and immunostained insulin in the pancreatic islets. In vitro, glucose uptake and glycogen synthesis by muscle (diaphragm) was significantly enhanced by the serum of SWI-treated rat. At 100, 10 and 1 microM final concentration, SWI greatly enhanced glucose (16.7 mM)-stimulated insulin release from isolated islets. It is therefore concluded that SWI lowers blood glucose level by stimulating insulin release from islets of Langerhans.

Swerchirin induced blood sugar lowering of streptozotocin treated hyperglycemic rats

Effect of Swerchirin (1:8 dihydroxy 3:5 dimethoxy xanthone) isolated from hexane fraction of Swertia chirayita on the blood sugar level of healthy and streptozotocin treated rats was studied. Streptozotocin was administered in citrate buffer (pH-4.5) intravenously / 35 and 65 mg/kg body wt to Charles Foster strain albino rats. Swerchirin (50 mg/kg, po) suspended in gum acacia was fed through cannula to the above rats and to a group of healthy rats. Blood sugar estimated at 0, 1, 3 and 7 hr after, indicated a very significant lowering in healthy and streptozotocin (35 mg/kg iv) but not in streptozotocin (65 mg/kg) treated rats.

Hypoglycemic effect of swerchirin from the hexane fraction of Swertia chirayita

A xanthone was isolated from the hexane fraction of the Swertia chirayita plant and identified as 1,8-dihydroxy-3,5-dimethoxyxanthone (swerchirin). It has a very significant blood sugar lowering effect in fasted, fed, glucose loaded, and tolbutamide pretreated albino rat models. The ED50 for 40% blood sugar lowering in CF male albino rats (body weight 140-165 g) is 23.1 mg/kg/oral. The possibility of its application in clinical therapy for diabetes mellitus needs exploration.

Hypoglycemic activity of Swertia chirayita (Roxb ex Flem) Karst

Hexane fraction of S. chirayita (250 mg/kg body wt.) induced significant fall in blood sugar and significant increase in plasma IRI simultaneously after single oral administration without influencing liver glycogen concentration in albino rats. On the other hand, daily administration for 28 days resulted in significant lowering of blood sugar and increase in plasma IRI along with a significant rise in liver glycogen. Intestinal absorption of glucose was not inhibited by hexane fraction. It is suggested that hexane fraction of S. chirayita possibly acts through its insulin releasing effect.

Potassium induced insulin release from isolated islet of Langerhans of albino rats

The secretory effect of Potassium (K+) on endocrine pancreas was studied using collagenase digested isolated islets of Langerhans. Isolated islets of Langerhans incubated in KRB containing 5 15, 30 and 45 mM, quantity of additional K ions caused the release of insulin from beta-cells (significant release of insulin, P less than 0.01, at 15, 30 and 45 mM K+ in presence of 2.8 mM glucose and at 30 mM K in presence of 16.7 mM glucose). But lysosomal AP and CB enzymes did not record proportionate change. Thus a definite stimulation in the release of insulin without significant change in AP and CB were seen.

Effect of various organic compounds on synthesis of glucoamylase by an isolated strain Penicillium italicum

Yeast extract (0.5%) stimulates the production of glucoamylase and cell synthesis while methylene blue (0.1 mM) activates the synthesis of glucoamylase. Studies on the metabolic changes during fermentation of glucoamylase in a selected medium by P. italicum show that the rate of production of glucoamylase and cellular growth are greatly accelerated between 48 and 168 hr. Rapid growth of cells during this period may account for enhanced utilization of maltose and NH4NO3 from the medium. The acid production remains constant from 48 to 144 hr. Different forms of nitrogen decrease steadily. Although methylene blue stimulates the production of glucoamylase in the broth it has practically no effect on the rate of utilization of amino and total nitrogen from the broth.

Effect of herbicide banvel on rabbit vaginal mucus membrane

Effect of banvel and its active ingredient, dicamba (3,6-dichloro-o-anisic acid) was investigated employing rabbit mucus membrane irritancy test. Inflammatory changes which did not exceed an average score of 2+ were observed in the animals 48 hr after a single intravaginal application of banvel (0.1 ml/rabbit) and dicamba (100 mg/rabbit). Persistent histopathological changes were observed in 1 out of 6 banvel-treated rabbits 15 days post-application. The results suggest that banvel and dicamba are not primary irritants but should nevertheless be employed with caution.

Blood sugar lowering potentiality of selected Cucurbitaceae plants of Indian origin

Using five experimental models, the blood sugar lowering efficacy of eight plants of Cucurbitaceae family has been assessed. The ethanolic extract of Cucumis sativus Linn, Cucumis melo utilissimum Roxb, Cucumis melo Linn, Benincasa hispida Thunb Cogn and Tricosanthes anguina Nees, when administered in 250 mg/kg dose, orally to rats failed to lower blood sugar or to depress the peak value, after glucose load. However, ethanolic extract of Momordica charantia Linn plant and Coccinia indica Whit and Arn root significantly lowered blood sugar in fasted model and depressed the peak value in glucose loaded model. Ethanolic extract of Tricosanthes dioica Roxb plant caused a significant lowering of blood sugar in fasted rats and depressed the peak value in glucose loaded single and longterm fed groups of rats. The ethanolic extract of the aerial part of T. dioica also induced significant depression in the peak values in the glucose loaded models.

Effects of prednisolone and dexamethasone on (pro)insulin biosynthesis and insulin release by rat islets of Langerhans

Administration of either prednisolone or dexamethasone (10 mg/kg body wt/day/oral) to rats for 21 days resulted in inhibition of (pro)insulin biosynthesis and immunoreactive insulin release by isolated islets. A gradual reversal of prednisolone's effect was obtained after exposing islets to increasing glucose concentrations but glucose challenges failed to influence dexamethasone's effect.

Changes in pancreatic beta cell function during growth and reproductive maturity of rats

An attempt has been made to study the changes, if any, in the efficiency of pancreatic beta cell function at different ages using one experimental model. For this, pancreatic islets were isolated from albino rats of 3, 8, 12 and 36 weeks of age and challenged with various concentrations of glucose (11.0, 16.7 and 22.2 mM). Significantly higher rate of glucose stimulated (pro)insulin biosynthesis was seen in the islets from 3 week old rats as compared to the islets obtained from 8, 12 and 36 week rats. On the other hand, immunoreactive insulin release was observed to be highest from islets of 8 week old rats followed by that of 12, 36 and 3 week old ones.

Anti-secretagogue effect of lithium on isolated rat islets of Langerhans

Administration of lithium carbonate solution (50 mg/kg, po, twice daily) to Charles Foster male albino rats for 45 consecutive days caused an intolerance to oral glucose. Inhibition in (pro)insulin biosynthesis followed by a significant fall in immunoreactive insulin release was seen in islets isolated from identically treated rats. As the activities of acid phosphatase and cathepsin B were unaltered, it is possible that the anti-secretagogue effect is sequential to inhibition of (pro)insulin biosynthesis by lithium.

Effect of prolonged administration of cyclosporin A on (pro)insulin biosynthesis and insulin release by rat islets of Langerhans

One group of rats received, an oral dose of 25 mg/kg body weight of Cyclosporin A daily for 21 consecutive days in olive oil, whereas the control group received an equal amount of the vehicle for the same period. On the 22nd day animals selected at random from both the groups were subjected to glucose tolerance (1.5 g/kg body weight/oral). The blood sugar values indicated glucose intolerance in experimental rats compared to vehicle-treated rats. The remaining animals were killed, and the pancreases were separated for islet isolation. After incubation of islets for 3 hr at 37 degrees with different glucose challenges, a highly significant (P less than 0.001) lowering of (pro)insulin biosynthesis, significant decrease in IRI release as well as significant inhibition in activities of acid phosphatase and cathepsin B was seen.