First report of detection of IgA anti-Acanthamoeba antibodies among Saudi population and amoeba isolation from their surroundings

Acanthamoeba is an opportunistic protozoan pathogen which is found in diverse environment worldwide. Being ubiquitous nature of this amoeba we come across it in our daily life. Acanthamoeba species are recognized as human pathogens; that may cause blinding keratitis and rare but fatal granulomatous encephalitis involving central nervous system. To date, there is not a single report in literature demonstrating anti-Acanthamoeba antibodies among the Saudi population, and thus aim of the present study. Using ELISA, we identified the antibody level in the local population. Our results represent the secretory IgA antiAcanthamoeba in mucosal secretions from 133 individuals aged 15-60 years. The antiAcanthamoeba antibody prevalence rate was > 80%, and no considerable differences were observed between prevalence in males (80.28%) and that in females (80.64%). In addition, environmental sources (soil and water) from the environment of the participants in our study were evaluated for amoeba incidence. The amoeba was identified by morphological characteristics of cysts or trophozoites on non-nutrient agar plates grown with E. coli. Overall, 58.75% of samples from water and 32.85% of those from soil were culture positive for outgrowth of amoeba on non-nutrient agar plates. Furthermore, PCR was carried out with genus-specific primers to confirm the presence of Acanthamoeba DNA. Our results revealed that about 68% of cultures from water and 43% of those from soil were successfully amplified and proved to be amoeba DNA. Interestingly, a few samples yielded more than one product, which suggests that some other amoebic species may be present in the same sample (MAC-W1 and MADW1). To the best of our knowledge, we described for the first time the amoeba isolation from the participant's close environment and antibodies level among Saudi population. Our future studies will be focused on additional molecular characterization of isolated amoeba and their pathogenic potential which could be a possible threat for the community.

The Additive Effects of Midazolam in Sub Arachnoid Block in Elective Caesarian Section: A Randomized Control Trial

The incidence of visceral pain among caesarean section can be as high as 50% in sub arachnoid block (SAB) in spite adequate sensory block, which requires conversion to general anesthesia. Different types of adjuvant have been used to augment the effect of local anesthetics but their use is limited due to adverse effects. The effect of intrathecal midazolam along with hyperbaric bupivacaine in sub arachnoid block is less known. So this randomized, double blind study was conducted to evaluate the additive effect of 0.4ml midazolam to 0.5% 3ml bupivacaine on sub arachnoid block in scheduled elective caesarean section. This study demonstrated that the addition of intrathecal 0.4ml midazolam to spinal 0.5% bupivacaine kept all the characteristics of block unaffected, furthermore pain score VAS 3.4±1.3 in Group A and 1.8±1.22 in Group B which is statistically significant, the requirement of intraoperative analgesia and also increased the duration of postoperative analgesia that is 130.3±5.4 minute in Group A, 265.1±3.6 minute in Group B and also statistically significant. Therefore addition of 2.0mg midazolam with 0.5% bupivacaine significantly reduces the VAS score, reduces the intraoperative visceral pain and need of analgesia.

Proximate composition, sensory evaluation and microbial quality of a dairy product (Special Kheersa) formulated with psyllium husk and malta peel powder

The research study was conducted to develop a suitable formulation of dairy products (Special Kheersa) using fresh cow milk with sugar and other ingredients such as psyllium husk, bread crumb, and malta peel powder in different proportions. Among four types of formulation, no psyllium husk and malta peel powder were used in Formulation (F1), but in Formulation (F2) 1.5 g psyllium husk and 30 g malta peel powder, Formulation (F3) 2.5 g psyllium husk and 30 g malta peel powder, Formulation (F4) 5 g psyllium husks and 30 g malta peel powder were used respectively. This study also assessed the proximate composition, sensory attributes and microbial quality of the Special Kheersa formulated with psyllium husk and malta peel powder. The results of the proximate analysis showed a significant difference (p<0.05) in all parameters. Special Kheersa prepared with 2.5 g of psyllium husk and 30 g of malta peel powder showed the maximum sensory score. Total viable count, Coliform, E. coli and Salmonella count of the Special Kheersa were determined after 0, 24, 48 and 72 hrs of its preparation. The formulated Special Kheersa is nutritionally acceptable like commercially available kheer and sufficient to meet the nutritional requirements as a dessert item.

Formulation and quality evaluation of instant mango drink powder

The study was conducted to develop a healthy instant mango drink powder and to compare its nutritional facts with commercially available mango drink powder. For this purpose, ripe Amropali mangoes were collected from a local source. After drying the mango pulp in a cabinet dryer, three formulations were prepared to compare with a locally available commercial brand mango drink powder. In this study, moisture, ash, protein, fat, carbohydrate, and energy contents were ranged from 0.2 to 4.6%, 0.4 to 2.6%, 0.7 to 2.2%, 0.6 to 0.9%, 89.5 to 97.8% and 375.4 to 400.5 kcal/100 g, respectively. The crude fiber was not found in any of the instant mango drink powder. Among the bioactive compounds, the flavonoid content in the commercial brand was higher than other formulated mango drink powder. In contrast, total anthocyanin content and total phenolic content values of all formulated instant mango drinks were higher than the commercial brand. Potassium, Magnesium, Chloride, Phosphorus, and Vitamin C were higher in formulated powder than the commercial preparation, but sodium, calcium, and iron contents were higher in the commercial mango drink powder. Antioxidant capacity was also found to be significantly higher in our formulated powder than that of commercial preparation. From the sensory and microbiological point of view, our formulated instant mango drink powder exhibited significant acceptability and stability. So, the formulated instant mango drink powder appears to be nutritionally and tastefully as acceptable as commercially available instant mango drink powders and able to meet day-to-day nutritional requirements as a supplement.

Microgravity alters the physiological characteristics of Escherichia coli O157:H7 ATCC 35150, ATCC 43889, and ATCC 43895 under different nutrient conditions

The aim of this study is to provide understanding of microgravity effects on important food-borne bacteria, Escherichia coli O157:H7 ATCC 35150, ATCC 43889, and ATCC 43895, cultured in nutrient-rich or minimal medium. Physiological characteristics, such as growth (measured by optical density and plating), cell morphology, and pH, were monitored under low-shear modeled microgravity (LSMMG; space conditions) and normal gravity (NG; Earth conditions). In nutrient-rich medium, all strains except ATCC 35150 showed significantly higher optical density after 6 h of culture under LSMMG conditions than under NG conditions (P < 0.05). LSMMG-cultured cells were approximately 1.8 times larger than NG-cultured cells at 24 h; therefore, it was assumed that the increase in optical density was due to the size of individual cells rather than an increase in the cell population. The higher pH of the NG cultures relative to that of the LSMMG cultures suggests that nitrogen metabolism was slower in the latter. After 24 h of culturing in minimal media, LSMMG-cultured cells had an optical density 1.3 times higher than that of NG-cultured cells; thus, the higher optical density in the LSMMG cultures may be due to an increase in both cell size and number. Since bacteria actively grew under LSMMG conditions in minimal medium despite the lower pH, it is of some concern that LSMMG-cultured E. coli O157:H7 may be able to adapt well to acidic environments. These changes may be caused by changes in nutrient metabolism under LSMMG conditions, although this needs to be demonstrated in future studies.

Neuroprotective effects of rosmarinic acid on ciguatoxin in primary human neurons

Ciguatoxin (CTX), is a toxic compound produced by microalgae (dinoflagellate) Gambierdiscus spp., and is bio-accumulated and bio-transformed through the marine food chain causing neurological deficits. To determine the mechanism of CTX-mediated cytotoxicity in human neurons, we measured extracellular lactate dehydrogenase (LDH) activity, intracellular levels of nicotinamide adenine dinucleotide (NAD(+)) and H2AX phosphorylation at serine 139 as a measure for DNA damage in primary cultures of human neurons treated with Pacific (P)-CTX-1B and P-CTX-3C. We found these marine toxins can induce a time and dose-dependent increase in extracellular LDH activity, with a concomitant decline in intracellular NAD(+) levels and increased DNA damage at the concentration range of 5-200 nM. We also showed that pre- and post-treatment with rosmarinic acid (RA), the active constituent of the Heliotropium foertherianum (Boraginaceae) can attenuate CTX-mediated neurotoxicity. These results further highlight the potential of RA in the treatment of CTX-induced neurological deficits.

Laparoscopic findings of subfertile women attended in a tertiary level care centre

This retrospective study was done in the Obstetrics and Gynaecology Department of Bangladesh Medical College hospital during the period of July 2003 to June 2004 in the women suffering from primary and secondary subfertility, who underwent laparoscopy. The aim of this study was to see the laparoscopic findings of internal genitalia and other pelvic structures in subfertile women. The study group comprises 55 cases of which 67.37% of primary and 32.73% were of secondary subfertility. Both the ovaries were normal looking in 41.81% cases. Endometriosis was present in 5.45% of both the ovaries. Corpus luteum was seen in 20% cases on right ovary and in 27.27% cases on left ovary. Laparoscopy shows normal looking fallopian tube in 65.45% cases in right side and 61.81% cases in the left side. Right sided tubal block was in 5.46% and 9.10 % in the left side. Both the tubes were patent in 81.6% cases.

Rodent p53 suppresses the transforming activity of the activated Neu oncogene by modulating the Basal promoter activity of Neu

The rat neu oncogene encodes a dominant transforming oncogene. The mouse wild-type p53 suppresses the transforming activity of the neu oncogene while different p53 mutants demonstrate varying ability to repress neu-induced transformation. Suppression of neu-transforming activity is due to inhibition of transcription. Deletion analysis of the rat neu promoter shows that p53 represses the basal promoter activity of neu. Therefore, rodent p53 suppresses the transforming potential of neu by inhibiting transcription from the basal promoter of neu.

Crystal structure of ChrR--a quinone reductase with the capacity to reduce chromate

The Escherichia coli ChrR enzyme is an obligatory two-electron quinone reductase that has many applications, such as in chromate bioremediation. Its crystal structure, solved at 2.2 Å resolution, shows that it belongs to the flavodoxin superfamily in which flavin mononucleotide (FMN) is firmly anchored to the protein. ChrR crystallized as a tetramer, and size exclusion chromatography showed that this is the oligomeric form that catalyzes chromate reduction. Within the tetramer, the dimers interact by a pair of two hydrogen bond networks, each involving Tyr128 and Glu146 of one dimer and Arg125 and Tyr85 of the other; the latter extends to one of the redox FMN cofactors. Changes in each of these amino acids enhanced chromate reductase activity of the enzyme, showing that this network is centrally involved in chromate reduction.

Melanotic neuroectodermal tumour of infancy

Melanotic neuroectodermal tumour in infancy is rare, mainly benign with little tendency to recur after excision or effective curettage. This pigmented neoplasm of neural crest origin occurring in infants before 1 year of age. The most common site of occurrence is the anterior maxillary alveolar ridge (70%), following by the skull, brain and mandible. The genital organ is the most frequent extra cranial site. We report a 6 months old male baby with a similar tumour arising from right half of cheek involving the maxilla. We diagnosed the case after histological report. We remove the tumour through a sub-labial incision. The mass was blackish in colour, and was mobilized from all side including from the maxillary sinuses. The author thought that this should be reported for improving the clinical awareness and treatment of pigmented soft tissue mass in children. Almost one year follow up of the patients showed no recurrence.

Congenital muscular torticollis: experience of 14 cases

Congenital Muscular Torticollis (CMT) is a postural deformity of head and neck detected at birth or shortly after birth, primarily resulting from unilateral shortening of Sternocleidomastoid Muscle (SCM). In neonates and infants, patient may cure conservatively by physiotherapy but surgery is the treatment of choice for children and adolescents. There are various techniques of surgery. Here we show our experience regarding management of congenital muscular torticollis. In the present retrospective case series, fourteen patients of congenital muscular torticollis were treated. The cases were enrolled between Nov' 2005 to Oct' 2007 in Bangabandhu Sheikh Mujib Medical University, Gonosasthaya Somaj Vittik Medical College Hospital, Dhaka and different private clinics of Dhaka city of Bangladesh. Neonates and infants were treated conservatively with physiotherapy and others treated surgically by transection of both sternal and clavicular head of SCM under general anesthesia. Operated patients were released on following post operative day with advised to do physiotherapy. Patients age range from 7 days to 15 years of which ten were female and four male. SCM was shortened in all cases (8 on right side and 6 on left side). Eleven were female and three male. Of 14 patients, 2 neonates, 7 infants and 5 were more than 1 year age. There was no associated anomaly. Out of 9 neonates and infants 8 cured conservatively with physiotherapy and another one significantly improved. Six were treated surgically including one failed physiotherapy. Post operative period was uneventful and there was no complication. Results were evaluated clinically and comments of peers. Most of the patient of congenital muscular torticollis can be treated conservatively during infancy. Division of both sternal and clavicular head of SCM is easy and safe surgical technique for the treatment of CMT of older children and adolescents.

Role of nitric oxide in Salmonella typhimurium-mediated cancer cell killing

Background

Bacterial targeting of tumours is an important anti-cancer strategy. We previously showed that strain SL7838 of Salmonella typhimurium targets and kills cancer cells. Whether NO generation by the bacteria has a role in SL7838 lethality to cancer cells is explored. This bacterium has the mechanism for generating NO, but also for decomposing it.

Methods

Mechanism underlying Salmonella typhimurium tumour therapy was investigated through in vitro and in vivo studies. NO measurements were conducted either by chemical assays (in vitro) or using Biosensors (in vivo). Cancer cells cytotoxic assay were done by using MTS. Bacterial cell survival and tumour burden were determined using molecular imaging techniques.

Results

SL7838 generated nitric oxide (NO) in anaerobic cell suspensions, inside infected cancer cells in vitro and in implanted 4T1 tumours in live mice, the last, as measured using microsensors. Thus, under these conditions, the NO generating pathway is more active than the decomposition pathway. The latter was eliminated, in strain SL7842, by the deletion of hmp- and norV genes, making SL7842 more proficient at generating NO than SL7838. SL7842 killed cancer cells more effectively than SL7838 in vitro, and this was dependent on nitrate availability. This strain was also ca. 100% more effective in treating implanted 4T1 mouse tumours than SL7838.

Conclusions

NO generation capability is important in the killing of cancer cells by Salmonella strains.

Visualizing implanted tumors in mice with magnetic resonance imaging using magnetotactic bacteria

PURPOSE

To determine if magnetotactic bacteria can target tumors in mice and provide positive contrast for visualization using magnetic resonance imaging.

EXPERIMENTAL DESIGN

The ability of the magnetotactic bacterium, Magnetospirillum magneticum AMB-1 (referred to from here as AMB-1), to confer positive magnetic resonance imaging contrast was determined in vitro and in vivo. For the latter studies, AMB-1 were injected either i.t. or i.v. Bacterial growth conditions were manipulated to produce small (approximately 25-nm diameter) magnetite particles, which were observed using transmission electron microscopy. Tumor targeting was confirmed using 64Cu-labeled bacteria and positron emission tomography and by determination of viable cell counts recovered from different organs and the tumor.

RESULTS

We show that AMB-1 bacteria with small magnetite particles generate T1-weighted positive contrast, enhancing in vivo visualization by magnetic resonance imaging. Following i.v. injection of 64Cu-labeled AMB-1, positron emission tomography imaging revealed increasing colonization of tumors and decreasing infection of organs after 4 hours. Viable cell counts showed that, by day 6, the bacteria had colonized tumors but were cleared completely from other organs. Magnetic resonance imaging showed a 1.22-fold (P = 0.003) increased positive contrast in tumors on day 2 and a 1.39-fold increase (P = 0.0007) on day 6.

CONCLUSION

Magnetotactic bacteria can produce positive magnetic resonance imaging contrast and colonize mouse tumor xenografts, providing a potential tool for improved magnetic resonance imaging visualization in preclinical and translational studies to track cancer.

Demonstration and partial characterization of ecto-ATPase in Balamuthia mandrillaris and its possible role in the host-cell interactions

AIMS

To investigate the presence and partial characterization of ecto-ATPase in Balamuthia mandrillaris.

METHODS AND RESULTS

In vitro assays were used to demonstrate that live B. mandrillaris hydrolyses extracellular AtP. Using nondenaturing polyacrylamide gel electrophoresis, B. mandrillaris exhibited a single ecto-ATPase band of molecular mass of more than 545 kDa. This ecto-ATPase was insensitive to ouabain, levamisole, sodium azide and sodium orthovanadate but stimulated by MgCl2. The ecto-ATPase was heat stable, but labile to detergent, sodium dodecyl sulphate. Suramin, an antagonist of P2 purinoreceptors and an inhibitor of some ecto-ATPases, inhibited B. mandrillaris binding to and cytotoxicity of HBMEC (human brain microvascular endothelial cello), in vitro.

CONCLUSIONS

For the first time, we describe that live B. mandrillaris hydrolyses extracellular ATP and exhibits a > 545kDa ecto-ATPase.

SIGNIFICANCE AND IMPACT OF THE STUDY

This surface enzyme may play a role in the salvage of purines from the extracellular medium and may be important for the pathogenesis of B. mandrillaris.

CNOB/ChrR6, a new prodrug enzyme cancer chemotherapy

We report the discovery of a new prodrug, 6-chloro-9-nitro-5-oxo-5H-benzo(a)phenoxazine (CNOB). This prodrug is efficiently activated by ChrR6, the highly active prodrug activating bacterial enzyme we have previously developed. The CNOB/ChrR6 therapy was effective in killing several cancer cell lines in vitro. It also efficiently treated tumors in mice with up to 40% complete remission. 9-Amino-6-chloro-5H-benzo(a)phenoxazine-5-one (MCHB) was the only product of CNOB reduction by ChrR6. MCHB binds DNA; at nonlethal concentration, it causes cell accumulation in the S phase, and at lethal dose, it induces cell surface Annexin V and caspase-3 and caspase-9 activities. Further, MCHB colocalizes with mitochondria and disrupts their electrochemical potential. Thus, killing by CNOB involves MCHB, which likely induces apoptosis through the mitochondrial pathway. An attractive feature of the CNOB/ChrR6 regimen is that its toxic product, MCHB, is fluorescent. This feature proved helpful in in vitro studies because simple fluorescence measurements provided information on the kinetics of CNOB activation within the cells, MCHB killing mechanism, its generally efficient bystander effect in cells and cell spheroids, and its biodistribution. The emission wavelength of MCHB also permitted its visualization in live animals, allowing noninvasive qualitative imaging of MCHB in mice and the tumor microenvironment. This feature may simplify exploration of barriers to the penetration of MCHB in tumors and their amelioration.

Role of the rapA gene in controlling antibiotic resistance of Escherichia coli biofilms

By using a high-throughput screening method, a mutant of a uropathogenic Escherichia coli strain affected in the rapA gene was isolated. The mutant formed normal-architecture biofilms but showed decreased penicillin G resistance, although the mutation did not affect planktonic cell resistance. Transcriptome analysis showed that 22 genes were down-regulated in the mutant biofilm. One of these genes was yhcQ, which encodes a putative multidrug resistance pump. Mutants with mutations in this gene also formed biofilms with decreased resistance, although the effect was less pronounced than that of the rapA mutation. Thus, an additional mechanism(s) controlled by a rapA-regulated gene(s) was involved in wild-type biofilm resistance. The search for this mechanism was guided by the fact that another down-regulated gene in rapA biofilms, yeeZ, is suspected to be involved in extra cell wall-related functions. A comparison of the biofilm matrix of the wild-type and rapA strains revealed decreased polysaccharide quantities and coverage in the mutant biofilms. Furthermore, the (fluorescent) functional penicillin G homologue Bocillin FL penetrated the mutant biofilms more readily. The results strongly suggest a dual mechanism for the wild-type biofilm penicillin G resistance, retarded penetration, and effective efflux. The results of studies with an E. coli K-12 strain pointed to the same conclusion. Since efflux and penetration can be general resistance mechanisms, tests were conducted with other antibiotics. The rapA biofilm was also more sensitive to norfloxacin, chloramphenicol, and gentamicin.

Evaluation of gemcitabine versus cisplatinum as an adjunct to radiotherapy in locally advanced carcinoma uterine cervix

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Background: Locally advanced carcinoma cervix patients are treated by a combination of external beam radiation and brachytherapy. Concurrent chemo-radiotherapy has been an active area of investigation in such patients. In this present study, we have compared two chemotherapy drugs- cisplatinum vs gemcitabine along with radiotherapy in loco-regionally advanced carcinoma cervix with the purpose of evaluating loco-regional disease control and tolerability of these combinations. Methods: This study was undertaken on 65 biopsy-proven patients with stage IIb- IIIb carcinoma cervix. All patients were treated with 50 Gy of external beam radiation with 2 Gy per fraction, 5 days a week followed by intra-cavitary radiotherapy (ICRT). Dose of ICRT delivered by high dose rate brachytherapy was 18 Gy by either of the two schedules, viz. 3 fractions of 6 Gy at weekly interval or 2 fractions of 9 Gy each at one week apart. The concurrent chemotherapy was either inj. Cisplatinum 35 mg/m2 IVI weekly (control group), or inj. gemcitabine 150 mg/m2 IVI weekly (Study group). Results: A total of 65 age and stage matched patients were recruited in the two arms of the study. We analyzed sixty patients who completed the above treatment protocol with 32 patients in control group and 28 in study group. Eighty-nine percent patients in study group had complete response (CR) to the above combination treatment vs. 72% CR in control arm (p< 0.05). However, overall response rate (CR+ PR) was similar in both the groups (96% in study group vs. 100% in control group). No patient in both the groups had grade IV skin reaction with only one patient in study group developing grade III skin toxicity. Grade III gastrointestinal (GI) toxicity was higher in study group as compared to controls (14% vs. 3%) with none of the patients experiencing grade IV GI toxicity. No other significant toxicity was encountered in this study. Conclusions: We can conclude that synchronous chemo-radiotherapy using either gemcitabine or cisplatinum as radiation sensitizer is feasible in locally advanced carcinoma cervix with similar overall response rate and acute toxicity profile with a significantly higher complete response rate when gemcitabine is used as a chemotherapeutic drug.

No significant financial relationships to disclose.

What leads from dead-end?

The 129 mouse strain develops congenital testicular germ cell tumors (TGCTs) at a low frequency. TGCTs in mice resemble the testicular tumors (teratomas) that occur in human infants. The genes that cause these tumors in 129 have not been identified. The defect at the Ter locus increases TGCT incidence such that 94% of 129-Ter/Ter males develop TGCTs. The primary effect of the Ter mutation is progressive loss of primordial germ cells (PGCs) during embryonic development. This results in sterility in adult Ter/Ter mice on all mouse strain backgrounds. However, on the 129 background, Ter causes tumor development in addition to sterility. Therefore, Ter acts as a modifier of 129-derived TGCT susceptibility genes. Ter was identified to be a mutation that inactivates the Dead-end1 (Dnd1) gene. In this perspective, I discuss the possible areas of future investigations to elucidate the mechanism of TGCT development due to Dnd1 inactivation.

Analysis of novel soluble chromate and uranyl reductases and generation of an improved enzyme by directed evolution

Most polluted sites contain mixed waste. This is especially true of the U.S. Department of Energy (DOE) waste sites which hold a complex mixture of heavy metals, radionuclides, and organic solvents. In such environments enzymes that can remediate multiple pollutants are advantageous. We report here evolution of an enzyme, ChrR6 (formerly referred to as Y6), which shows a markedly enhanced capacity for remediating two of the most serious and prevalent DOE contaminants, chromate and uranyl. ChrR6 is a soluble enzyme and reduces chromate and uranyl intracellularly. Thus, the reduced product is at least partially sequestered and nucleated, minimizing the chances of reoxidation. Only one amino acid change, (Tyr)128(Asn), was responsible for the observed improvement. We show here that ChrR6 makes Pseudomonas putida and Escherichia coli more efficient agents for bioremediation if the cellular permeability barrier to the metals is decreased.

Escherichia coli biofilms formed under low-shear modeled microgravity in a ground-based system

Bacterial biofilms cause chronic diseases that are difficult to control. Since biofilm formation in space is well documented and planktonic cells become more resistant and virulent under modeled microgravity, it is important to determine the effect of this gravity condition on biofilms. Inclusion of glass microcarrier beads of appropriate dimensions and density with medium and inoculum, in vessels specially designed to permit ground-based investigations into aspects of low-shear modeled microgravity (LSMMG), facilitated these studies. Mathematical modeling of microcarrier behavior based on experimental conditions demonstrated that they satisfied the criteria for LSMMG conditions. Experimental observations confirmed that the microcarrier trajectory in the LSMMG vessel concurred with the predicted model. At 24 h, the LSMMG Escherichia coli biofilms were thicker than their normal-gravity counterparts and exhibited increased resistance to the general stressors salt and ethanol and to two antibiotics (penicillin and chloramphenicol). Biofilms of a mutant of E. coli, deficient in sigma(s), were impaired in developing LSMMG-conferred resistance to the general stressors but not to the antibiotics, indicating two separate pathways of LSMMG-conferred resistance.

Effect of chromate stress on Escherichia coli K-12

The nature of the stress experienced by Escherichia coli K-12 exposed to chromate, and mechanisms that may enable cells to withstand this stress, were examined. Cells that had been preadapted by overnight growth in the presence of chromate were less stressed than nonadapted controls. Within 3 h of chromate exposure, the latter ceased growth and exhibited extreme filamentous morphology; by 5 h there was partial recovery with restoration of relatively normal cell morphology. In contrast, preadapted cells were less drastically affected in their morphology and growth. Cellular oxidative stress, as monitored by use of an H2O2-responsive fluorescent dye, was most severe in the nonadapted cells at 3 h postinoculation, lower in the partially recovered cells at 5 h postinoculation, and lower still in the preadapted cells. Chromate exposure depleted cellular levels of reduced glutathione and other free thiols to a greater extent in nonadapted than preadapted cells. In both cell types, the SOS response was activated, and levels of proteins such as SodB and CysK, which can counter oxidative stress, were increased. Some mutants missing antioxidant proteins (SodB, CysK, YieF, or KatE) were more sensitive to chromate. Thus, oxidative stress plays a major role in chromate toxicity in vivo, and cellular defense against this toxicity involves activation of antioxidant mechanisms. As bacterial chromate bioremediation is limited by the toxicity of chromate, minimizing oxidative stress during bacterial chromate reduction and bolstering the capacity of these organisms to deal with this stress will improve their effectiveness in chromate bioremediation.

New enzyme for reductive cancer chemotherapy, YieF, and its improvement by directed evolution

Reductive prodrugs, mitomycin C and 5-aziridinyl-2,4-dinitrobenzamide (CB 1954), are nontoxic in their native form but become highly toxic upon reduction. Their effectiveness in cancer chemotherapy can be enhanced by delivering to tumors enzymes with improved prodrug reduction kinetics. We report the discovery of a new prodrug-reducing enzyme, YieF, from Escherichia coli, and the improvement of its kinetics for reducing mitomycin C and CB 1954. A YieF-derived enzyme, Y6, killed HeLa spinner cells with >or=5-fold efficiency than the wild-type enzymes, YieF and NfsA, at a variety of drug and enzyme concentrations and incubation times. With adhered HeLa cells and Salmonella typhimurium SL 7838 bacteria as enzyme delivery vehicle, at least an order of magnitude less of Y6-producing bacteria were required to kill >90% of tumor cells compared with bacteria expressing the wild-type enzymes, which at a comparable level killed < 5% of the cells. Thus, Y6 is a promising enzyme for use in cancer chemotherapy, and Salmonella strain SL 7838, which specifically targets tumors, may be used to deliver the prodrug-activating enzymes to tumors.

ChrR, a Soluble Quinone Reductase of Pseudomonas putida That Defends against H2O2

Most bacteria contain soluble quinone-reducing flavoenzymes. However, no biological benefit for this activity has previously been demonstrated. ChrR of Pseudomonas putida is one such enzyme that has also been characterized as a chromate reductase; yet we propose that it is the quinone-reducing activity of ChrR that has the greatest biological significance. ChrR reduces quinones by simultaneous two-electron transfer, avoiding formation of highly reactive semiquinone intermediates and producing quinols that promote tolerance of H(2)O(2). Expression of chrR was induced by H(2)O(2), and levels of chrR expression in overexpressing, wild type, and knock-out mutant strains correlated with the H(2)O(2) tolerance and scavenging ability of each strain. The chrR expression level also correlated with intracellular H(2)O(2) levels as measured by protein carbonylation assays and fluorescence-activated cell scanning analysis with the H(2)O(2)-responsive dye H(2)DCFDA. Thus, enhancing the activity of ChrR in a chromate-remediating bacterial strain may not only increase the rate of chromate transformation, it may also augment the capacity of these cells to withstand the unavoidable production of H(2)O(2) that accompanies chromate reduction.

Role and Regulation of σ s in General Resistance Conferred by Low-Shear Simulated Microgravity in Escherichia coli

Life on Earth evolved in the presence of gravity, and thus it is of interest from the perspective of space exploration to determine if diminished gravity affects biological processes. Cultivation of Escherichia coli under low-shear simulated microgravity (SMG) conditions resulted in enhanced stress resistance in both exponential- and stationary-phase cells, making the latter superresistant. Given that microgravity of space and SMG also compromise human immune response, this phenomenon constitutes a potential threat to astronauts. As low-shear environments are encountered by pathogens on Earth as well, SMG-conferred resistance is also relevant to controlling infectious disease on this planet. The SMG effect resembles the general stress response on Earth, which makes bacteria resistant to multiple stresses; this response is σ s dependent, irrespective of the growth phase. However, SMG-induced increased resistance was dependent on σ s only in stationary phase, being independent of this sigma factor in exponential phase. σ s concentration was some 30% lower in exponential-phase SMG cells than in normal gravity cells but was twofold higher in stationary-phase SMG cells. While SMG affected σ s synthesis at all levels of control, the main reasons for the differential effect of this gravity condition on σ s levels were that it rendered the sigma protein less stable in exponential phase and increased rpoS mRNA translational efficiency. Since σ s regulatory processes are influenced by mRNA and protein-folding patterns, the data suggest that SMG may affect these configurations.

Mechanism of chromate reduction by the Escherichia coli protein, NfsA, and the role of different chromate reductases in minimizing oxidative stress during chromate reduction

Chromate [Cr(VI)] is a serious environmental pollutant, which is amenable to bacterial bioremediation. NfsA, the major oxygen-insensitive nitroreductase of Escherichia coli, is a flavoprotein that is able to reduce chromate to less soluble and less toxic Cr(III). We show that this process involves single-electron transfer, giving rise to a flavin semiquinone form of NfsA and Cr(V) as intermediates, which redox cycle, generating more reactive oxygen species (ROS) than a divalent chromate reducer, YieF. However, NfsA generates less ROS than a known one-electron chromate reducer, lipoyl dehydrogenase (LpDH), suggesting that NfsA employs a mixture of uni- and di-valent electron transfer steps. The presence of YieF, ChrR (another chromate reductase we previously characterized), or NfsA in an LpDH-catalysed chromate reduction reaction decreased ROS generation by c. 65, 40, or 20%, respectively, suggesting that these enzymes can pre-empt ROS generation by LpDH. We previously showed that ChrR protects Pseudomonas putida against chromate toxicity; here we show that NfsA or YieF overproduction can also increase the tolerance of E. coli to this compound.

Chromate-reducing properties of soluble flavoproteins from Pseudomonas putida and Escherichia coli

Cr(VI) (chromate) is a toxic, soluble environmental contaminant. Bacteria can reduce chromate to the insoluble and less toxic Cr(III), and thus chromate bioremediation is of interest. Genetic and protein engineering of suitable enzymes can improve bacterial bioremediation. Many bacterial enzymes catalyze one-electron reduction of chromate, generating Cr(V), which redox cycles, generating excessive reactive oxygen species (ROS). Such enzymes are not appropriate for bioremediation, as they harm the bacteria and their primary end product is not Cr(III). In this work, the chromate reductase activities of two electrophoretically pure soluble bacterial flavoproteins--ChrR (from Pseudomonas putida) and YieF (from Escherichia coli)-were examined. Both are dimers and reduce chromate efficiently to Cr(III) (kcat/Km = approximately 2 x 10(4) M(-1) x s(-1)). The ChrR dimer generated a flavin semiquinone during chromate reduction and transferred >25% of the NADH electrons to ROS. However, the semiquinone was formed transiently and ROS diminished with time. Thus, ChrR probably generates Cr(V), but only transiently. Studies with mutants showed that ChrR protects against chromate toxicity; this is possibly because it preempts chromate reduction by the cellular one-electron reducers, thereby minimizing ROS generation. ChrR is thus a suitable enzyme for further studies. During chromate reduction by YieF, no flavin semiquinone was generated and only 25% of the NADH electrons were transferred to ROS. The YieF dimer may therefore be an obligatory four-electron chromate reducer which in one step transfers three electrons to chromate and one to molecular oxygen. As a mutant lacking this enzyme could not be obtained, the role of YieF in chromate protection could not be directly explored. The results nevertheless suggest that YieF may be an even more suitable candidate for further studies than ChrR.

Tetracycline rapidly reaches all the constituent cells of uropathogenic Escherichia coli biofilms

We have developed a method for visualizing Escherichia coli cells that are exposed to tetracycline in a biofilm, based on a previous report that liposomes containing the E. coli TetR(B) protein fluoresce when exposed to this antibiotic. By our method, cells devoid of TetR(B) also exhibited tetracycline-dependent fluorescence. At 50 microg of tetracycline ml(-1), planktonic cells of a uropathogenic E. coli (UPEC) strain developed maximal fluorescence after 7.5 to 10 min of exposure. A similar behavior was exhibited by cells in a 24- or 48-h UPEC biofilm, as examined by confocal laser microscopy, regardless of whether they lined empty spaces or occupied densely packed regions. Further, a comparison of phase-contrast and fluorescent images of corresponding biofilm zones showed that all the cells fluoresced. Thus, all the biofilm cells were exposed to tetracycline and there were no pockets within the biofilm where the antibiotic failed to reach. It also appeared unlikely that niches of reduced exposure to the antibiotic existed within the biofilms.

Sensitized polygenic trait analysis

Genetic variation in many biological processes and evolutionary adaptations is caused by polygenes--genes that act in combination to affect a particular trait. Despite the recent identification of several polygenes, many remain to be found, suggesting that new experimental and analytical methods are needed to facilitate their discovery. Here we discuss sensitized polygenetic trait analysis, a method that has emerged recently for simplifying the genetic analysis of polygenic traits. The method uses a known single gene mutation in linkage testing crosses to 'sensitize' the analysis. By increasing the frequency of affected individuals in segregating populations, linkages are more readily detected. This method has considerable potential, especially given the increasing variety of mutations that can be used to sensitize the genetic analysis of polygenic traits.

Nuclear localization of EGF receptor and its potential new role as a transcription factor

Epidermal growth factor receptor (EGFR) has been detected in the nucleus in many tissues and cell lines. However, the potential functions of nuclear EGFR have largely been overlooked. Here we demonstrate that nuclear EGFR is strongly correlated with highly proliferating activities of tissues. When EGFR was fused to the GAL4 DNA-binding domain, we found that the carboxy terminus of EGFR contained a strong transactivation domain. Moreover, the receptor complex bound and activated AT-rich consensus-sequence-dependent transcription, including the consensus site in cyclin D1 promoter. By using chromatin immunoprecipitation assays, we further demonstrated that nuclear EGFR associated with promoter region of cyclin D1 in vivo. EGFR might therefore function as a transcription factor to activate genes required for highly proliferating activities.

The EmrR protein represses the Escherichia coli emrRAB multidrug resistance operon by directly binding to its promoter region

EmrR negatively regulates the transcription of the multidrug resistance pump-encoding operon, emrRAB, by binding to its regulatory region. The binding site spans the promoter and the downstream sequence up to the transcriptional start site of the operon. Structurally unrelated drugs that induce the pump interfere with this binding.

Purification to homogeneity and characterization of a novel Pseudomonas putida chromate reductase

Cr(VI) (chromate) is a widespread environmental contaminant. Bacterial chromate reductases can convert soluble and toxic chromate to the insoluble and less toxic Cr(III). Bioremediation can therefore be effective in removing chromate from the environment, especially if the bacterial propensity for such removal is enhanced by genetic and biochemical engineering. To clone the chromate reductase-encoding gene, we purified to homogeneity (>600-fold purification) and characterized a novel soluble chromate reductase from Pseudomonas putida, using ammonium sulfate precipitation (55 to 70%), anion-exchange chromatography (DEAE Sepharose CL-6B), chromatofocusing (Polybuffer exchanger 94), and gel filtration (Superose 12 HR 10/30). The enzyme activity was dependent on NADH or NADPH; the temperature and pH optima for chromate reduction were 80 degrees C and 5, respectively; and the K(m) was 374 microM, with a V(max) of 1.72 micromol/min/mg of protein. Sulfate inhibited the enzyme activity noncompetitively. The reductase activity remained virtually unaltered after 30 min of exposure to 50 degrees C; even exposure to higher temperatures did not immediately inactivate the enzyme. X-ray absorption near-edge-structure spectra showed quantitative conversion of chromate to Cr(III) during the enzyme reaction.

The G-protein FlhF has a role in polar flagellar placement and general stress response induction in Pseudomonas putida

The flhF gene of Pseudomonas putida, which encodes a GTP-binding protein, is part of the flagellar-motility-chemotaxis operon. Its disruption leads to a random flagellar arrangement in the mutant (MK107) and loss of directional motility in contrast to the wild type, which has polar flagella. The return of a normal flhF allele restores polar flagella and normal motility to MK107; its overexpression triples the flagellar number but does not restore directional motility. As FlhF is homologous to the receptor protein of the signal recognition particle (SRP) pathway of membrane protein translocation, this pathway may have a role in polar flagellar placement in P. putida. MK107 is also compromised in the development of the starvation-induced general stress resistance (SGSR) and effective synthesis of several starvation and exponential phase proteins. While somewhat increased protein secretion in MK107 may contribute to its SGSR impairment, the altered protein synthesis pattern also appears to have a role.

A bacterial model system for understanding multi-drug resistance

Mankind stands at the crossroads, recognizing the need for a radical change in bacterial disease management. The development of several antimicrobial agents in the 1940s and 1950s allowed man to gain the upper hand in controlling these diseases. However, the horizon is now clouded by the activation in bacteria of cryptic multi-drug resistance (MDR) genes and the spread of plasmid- and integron-born MDR genes through bacterial populations. Unless remedial measures are taken, nearly all currently available antimicrobial agents are likely to soon lose their efficacies. We briefly review the bacterial MDR phenomenon and focus on a recently emerging family of small multi-drug resistance (SMR) pumps which may provide an ideal model system for understanding the MDR phenomenon in general.

Analysing complex genetic traits with chromosome substitution strains

Many valuable animal models of human disease are known and new models are continually being generated in existing inbred strains,. Some disease models are simple mendelian traits, but most have a polygenic basis. The current approach to identifying quantitative trait loci (QTLs) that underlie such traits is to localize them in crosses, construct congenic strains carrying individual QTLs, and finally map and clone the genes. This process is time-consuming and expensive, requiring the genotyping of large crosses and many generations of breeding. Here we describe a different approach in which a panel of chromosome substitution strains (CSSs) is used for QTL mapping. Each of these strains has a single chromosome from the donor strain substituting for the corresponding chromosome in the host strain. We discuss the construction, applications and advantages of CSSs compared with conventional crosses for detecting and analysing QTLs, including those that have weak phenotypic effects.

Susceptibility to testicular germ-cell tumours in a 129.MOLF-Chr 19 chromosome substitution strain

The identification of genes that control susceptibility to testicular germ-cell tumours (TGCTs), the most common cancer affecting young men, has been difficult. In laboratory mice, TGCTs arise from primordial germ cells in only the 129 inbred strains, and susceptibility is under multigenic control. The spontaneously arising mutation Ter (ref. 5) on mouse chromosome 18 (Refs 6,7) increases TGCT frequency on a 129/Sv background. We originally used Ter in genetic crosses to identify loci that control tumorigenesis. A genome scan of tumour-bearing progeny from backcrosses between the 129/Sv-Ter/+ and MOLF/Ei strains provided modest evidence that MOLF-derived alleles on chromosome 19 enhance development of bilateral TGCTs (ref. 9). To obtain independent evidence for linkage to the MOLF chromosome, we made an autosomal chromosome substitution strain (CSS; or 'consomic strain') in which chromosome 19 of 129/Sv+/+ was replaced by its MOLF-derived homologue. The unusually high frequency of TGCTs in this CSS (even in the absence of the Ter mutation) provides evidence confirming the genome survey results, identifies linkage for a naturally occurring strain variant allele that confers susceptibility to TGCTs and illustrates the power of CSSs in complex trait analysis.

pH homeostasis in acidophiles

The acidophilic bacteria comprise an environmentally important group that includes pathogens. A fundamental requirement for existence in strongly acidic environments is generation of a large pH gradient (delta pH) to maintain the cytoplasmic pH near neutrality and safeguard the acid-labile cell constituents. These organisms require the capacity to extrude H+ across the thermodynamic barrier imposed by the delta pH. They also need special transport proteins that can function in strongly acidic environments. The quintessential device by which the acidophiles fulfil these requirements by generating a positive-inside membrane potential (delta psi) that mitigates both the force against which H+ must be extruded, as well as the influxing force of protons into the cells. The delta psi is generated through passive as well as active mechanisms. The former constitutes an H+ diffusion as well as a Donnan potential, and the latter involves electrogenic circulation of Cl-, and the operation of an electrogenic H+/K+ (Na+) antiporter.

The Escherichia coli starvation gene cstC is involved in amino acid catabolism

Escherichia coli strains mutant in the starvation gene cstC grow normally in a mineral salts medium but are impaired in utilizing amino acids as nitrogen sources. They are also compromised in starvation survival, where amino acid catabolism is important. The cstC gene encodes a 406-amino-acid protein that closely resembles the E. coli ArgD protein, which is involved in arginine biosynthesis. We postulate that CstC is a counterpart of ArgD in an amino acid catabolic pathway. The cstC upstream region contains several regulatory consensus sequences. Both sigmaS and sigma54 promoters are probably involved in cstC transcription and appear to compete with each other, presumably to match cstC expression to the cellular amino acid catabolic needs.

Theophylline inhibits the production of nitric oxide by peripheral blood mononuclear cells from patients with asthma

BACKGROUND

Nitric oxide (NO), a reactive free radical synthesized from L-arginine by the enzyme NO synthase (NOS), may play a role in many pathophysiologic conditions, including asthma.

OBJECTIVE

The aim of this study was to investigate whether peripheral blood mononuclear cells (PBMCs) from asthmatics would spontaneously produce NO. A second objective was to ascertain whether commonly used asthma medications would modulate the production of NO.

METHODS

PBMCs were isolated from 24 subjects (10 with asthma, 4 with allergic rhinitis and 10 healthy controls) and were incubated either alone or in the presence of an RNA polymerase inhibitor (actinomycin D, 1 microg/mL), a NOS inhibitor (L-NG-nitroarginine methyl ester [L-NAME], 1 mM), and L-NAME plus L-arginine (5 mM). Furthermore, PBMCs were incubated with or without addition of therapeutic concentrations of hydrocortisone (15 microg/mL), theophylline (15 microg/mL), albuterol (15 microg/mL) and ipratropium bromide (12 microg/mL). Culture supernatants were collected and assayed for NO production.

RESULTS

NO production was significantly elevated in asthmatics compared with the control group (1.39+/-0.21 microM versus 0.46+/-0.01 microM; P < .05). L-NAME significantly reduced NO production in asthmatics (0.83+/-0.06 microM; P < .05), an effect completely reversed by L-arginine. Theophylline blocked NO production in asthmatics (1.39+/-0.21 microM to 0.92+/-0.11; P < .05). There was no significant effect with any of the other medications.

CONCLUSION

This study suggests that theophylline may be antiinflammatory by inhibiting the L-arginine-dependent production of NO in patients with asthma.

Testicular teratocarcinogenesis in mice--a review

Spontaneous testicular germ cell tumours in humans and mice are remarkable for their diverse composition. These tumours are usually composed of an extraordinary variety of cell and tissue types including muscle, skin, bone, cartilage, and neuroepithelia. Their diverse composition reflects their origin from totipotent primordial germ cells at about Day 12 of fetal development. Although much is known about the development of these tumours, remarkably little is known about the genetics of the mammalian primordial germ cell lineage or about the genes that control susceptibility to spontaneous testicular germ cell tumours in humans or mice. Conventional genetic analysis of susceptible 129/Sv mice is difficult because of the large number of susceptibility genes and their low penetrance. We are taking advantage of the Ter mutation to simplify the genetic analysis. Various evidence suggests that Ter is neither necessary nor sufficient for tumourigenesis. Instead, Ter acts as a modifier, dramatically increasing tumour incidence from approximately 1% in +/+ males, to approximately 17% in Ter/+ males and approximately 94% in Ter/Ter males. Segregation analysis suggests that Ter increases tumour incidence by requiring some, but perhaps not all, of the 129/Sv-derived susceptibility genes. With standard crosses that segregate for the Ter mutation, identification not only of Ter but also of these 129/Sv-derived susceptibility genes should be possible. In this paper, we review the genetics and development of germ cell tumours in 129/Sv mice, summarize the status of Ter mapping, and provide evidence that different genetic pathways lead to unilateral and bilateral tumours.