The effect of pH on Marinobacter hydrocarbonoclasticus denitrification pathway and nitrous oxide reductase

Increasing atmospheric concentration of N₂O has been a concern, as it is a potent greenhouse gas and promotes ozone layer destruction. In the N-cycle, release of N₂O is boosted upon a drop of pH in the environment. Here, Marinobacter hydrocarbonoclasticus was grown in batch mode in the presence of nitrate, to study the effect of pH in the denitrification pathway by gene expression profiling, quantification of nitrate and nitrite, and evaluating the ability of whole cells to reduce NO and N₂O. At pH 6.5, accumulation of nitrite in the medium occurs and the cells were unable to reduce N₂O. In addition, the biochemical properties of N₂O reductase isolated from cells grown at pH 6.5, 7.5 and 8.5 were compared for the first time. The amount of this enzyme at acidic pH was lower than that at pH 7.5 and 8.5, pinpointing to a post-transcriptional regulation, though pH did not affect gene expression of N₂O reductase accessory genes. N₂O reductase isolated from cells grown at pH 6.5 has its catalytic center mainly as CuZ(4Cu1S), while that from cells grown at pH 7.5 or 8.5 has it as CuZ(4Cu2S). This study evidences that an in vivo secondary level of regulation is required to maintain N₂O reductase in an active state.

Anaesthetic management of intracranial hypertension and pregnancy. A case report

Hydrocephalus is an active distension of the ventricular system of the brain. The improved survival rates of patients with neurosurgical pathology is accompanied by a greater number of non-neurosurgical procedures in patients who have therapeutic neurosurgical devices. The real incidence of pregnancy in patients with obstructive hydrocephalus controlled with ventriculoperitoneal shunt (VPS) is unclear. We present a case of a pregnant 34-year-old female with a VPS for obstructive hydrocephalus. Due to VPS obstruction secondary to uterus volume, she presented several episodes of neurological impairment during pregnancy. An elective caesarean section (C-section) and VPS review were planned for the same operative time. This rare case reflects the challenge that the anaesthesiologist has to face in order to provide the best and simultaneous management of the wellbeing of the mother, the mother's brain and the foetus.

Proton-coupled electron transfer mechanisms of the copper centres of nitrous oxide reductase from Marinobacter hydrocarbonoclasticus - An electrochemical study

Reduction of N₂O to N₂ is catalysed by nitrous oxide reductase in the last step of the denitrification pathway. This multicopper enzyme has an electron transferring centre, CuA, and a tetranuclear copper-sulfide catalytic centre, "CuZ", which exists as CuZ*(4Cu1S) or CuZ(4Cu2S). The redox behaviour of these metal centres in Marinobacter hydrocarbonoclasticus nitrous oxide reductase was investigated by potentiometry and for the first time by direct electrochemistry. The reduction potential of CuA and CuZ(4Cu2S) was estimated by potentiometry to be +275 ± 5 mV and +65 ± 5 mV vs SHE, respectively, at pH 7.6. A proton-coupled electron transfer mechanism governs CuZ(4Cu2S) reduction potential, due to the protonation/deprotonation of Lys397 with a pK_ox of 6.0 ± 0.1 and a pK_red of 9.2 ± 0.1. The reduction potential of CuA, in enzyme samples with CuZ*(4Cu1S), is controlled by protonation of the coordinating histidine residues in a two-proton coupled electron transfer process. In the cyclic voltammograms, two redox pairs were identified corresponding to CuA and CuZ(4Cu2S), with no additional signals being detected that could be attributed to CuZ*(4Cu1S). However, an enhanced cathodic signal for the activated enzyme was observed under turnover conditions, which is explained by the binding of nitrous oxide to CuZ⁰(4Cu1S), an intermediate species in the catalytic cycle.

The bacterial MrpORP is a novel Mrp/NBP35 protein involved in iron-sulfur biogenesis

Despite recent advances in understanding the biogenesis of iron-sulfur (Fe-S) proteins, most studies focused on aerobic bacteria as model organisms. Accordingly, multiple players have been proposed to participate in the Fe-S delivery step to apo-target proteins, but critical gaps exist in the knowledge of Fe-S proteins biogenesis in anaerobic organisms. Mrp/NBP35 ATP-binding proteins are a subclass of the soluble P-loop containing nucleoside triphosphate hydrolase superfamily (P-loop NTPase) known to bind and transfer Fe-S clusters in vitro. Here, we report investigations of a novel atypical two-domain Mrp/NBP35 ATP-binding protein named Mrp_ORP associating a P-loop NTPase domain with a dinitrogenase iron-molybdenum cofactor biosynthesis domain (Di-Nase). Characterization of full length Mrp_ORP, as well as of its two domains, showed that both domains bind Fe-S clusters. We provide in vitro evidence that the P-loop NTPase domain of the Mrp_ORP can efficiently transfer its Fe-S cluster to apo-target proteins of the ORange Protein (ORP) complex, suggesting that this novel protein is involved in the maturation of these Fe-S proteins. Last, we showed for the first time, by fluorescence microscopy imaging a polar localization of a Mrp/NBP35 protein.

Genomic organization, gene expression and activity profile of Marinobacter hydrocarbonoclasticus denitrification enzymes

Background

Denitrification is one of the main pathways of the N-cycle, during which nitrate is converted to dinitrogen gas, in four consecutive reactions that are each catalyzed by a different metalloenzyme. One of the intermediate metabolites is nitrous oxide, which has a global warming impact greater then carbon dioxide and which atmospheric concentration has been increasing in the last years. The four denitrification enzymes have been isolated and biochemically characterized from Marinobacter hydrocarbonoclasticus in our lab.

Methods

Bioinformatic analysis of the M. hydrocarbonoclasticus genome to identify the genes involved in the denitrification pathway. The relative gene expression of the gene encoding the catalytic subunits of those enzymes was analyzed during the growth under microoxic conditions. The consumption of nitrate and nitrite, and the reduction of nitric oxide and nitrous oxide by whole-cells was monitored during anoxic and microoxic growth in the presence of 10 mM sodium nitrate at pH 7.5.

Results

The bioinformatic analysis shows that genes encoding the enzymes and accessory factors required for each step of the denitrification pathway are clustered together. An unusual feature is the co-existence of genes encoding a q- and a c-type nitric oxide reductase, with only the latter being transcribed at similar levels as the ones encoding the catalytic subunits of the other denitrifying enzymes, when cells are grown in the presence of nitrate under microoxic conditions. Using either a batch- or a closed system, nitrate is completely consumed in the beginning of the growth, with transient formation of nitrite, and whole-cells can reduce nitric oxide and nitrous oxide from mid-exponential phase until being collected (time-point 50 h).

Discussion

M. hydrocarbonoclasticus cells can reduce nitric and nitrous oxide in vivo, indicating that the four denitrification steps are active. Gene expression profile together with promoter regions analysis indicates the involvement of a cascade regulatory mechanism triggered by FNR-type in response to low oxygen tension, with nitric oxide and nitrate as secondary effectors, through DNR and NarXL, respectively. This global characterization of the denitrification pathway of a strict marine bacterium, contributes to the understanding of the N-cycle and nitrous oxide release in marine environments.

Spectroscopic Definition of the CuZ° Intermediate in Turnover of Nitrous Oxide Reductase and Molecular Insight into the Catalytic Mechanism

Spectroscopic methods and density functional theory (DFT) calculations are used to determine the geometric and electronic structure of Cu_Z°, an intermediate form of the Cu₄S active site of nitrous oxide reductase (N₂OR) that is observed in single turnover of fully reduced N₂OR with N₂O. Electron paramagnetic resonance (EPR), absorption, and magnetic circular dichroism (MCD) spectroscopies show that Cu_Z° is a 1-hole (i.e., 3Cu^ICu^II) state with spin density delocalized evenly over Cu_I and Cu_IV. Resonance Raman spectroscopy shows two Cu-S vibrations at 425 and 413 cm^-1, the latter with a -3 cm^-1 O¹⁸ solvent isotope shift. DFT calculations correlated to these spectral features show that Cu_Z° has a terminal hydroxide ligand coordinated to Cu_IV, stabilized by a hydrogen bond to a nearby lysine residue. Cu_Z° can be reduced via electron transfer from Cu_A using a physiologically relevant reductant. We obtain a lower limit on the rate of this intramolecular electron transfer (IET) that is >10⁴ faster than the unobserved IET in the resting state, showing that Cu_Z° is the catalytically relevant oxidized form of N₂OR. Terminal hydroxide coordination to Cu_IV in the Cu_Z° intermediate yields insight into the nature of N₂O binding and reduction, specifying a molecular mechanism in which N₂O coordinates in a μ-1,3 fashion to the fully reduced state, with hydrogen bonding from Lys397, and two electrons are transferred from the fully reduced μ₄S^2- bridged tetranuclear copper cluster to N₂O via a single Cu atom to accomplish N-O bond cleavage.

TLR9 re-expression in cancer cells extends the S-phase and stabilizes p16(INK4a) protein expression

Toll-like receptor 9 (TLR9) recognizes bacterial, viral or cell damage-associated DNA, which initiates innate immune responses. We have previously shown that TLR9 expression is downregulated in several viral induced cancers including HPV16-induced cervical neoplasia. Findings supported that downregulation of TLR9 expression is involved in loss of anti-viral innate immunity allowing an efficient viral replication. Here we investigated the role of TLR9 in altering the growth of transformed epithelial cells. Re-introducing TLR9 under the control of an exogenous promoter in cervical or head and neck cancer patient-derived cells reduced cell proliferation, colony formation and prevented independent growth of cells under soft agar. Neither TLR3, 7, nor the TLR adapter protein MyD88 expression had any effect on cell proliferation, indicating that TLR9 has a unique role in controlling cell growth. The reduction of cell growth was not due to apoptosis or necrosis, yet we observed that cells expressing TLR9 were slower in entering the S-phase of the cell cycle. Microarray-based gene expression profiling analysis highlighted a strong interferon (IFN) signature in TLR9-expressing head and neck cancer cells, with an increase in IFN-type I and IL-29 expression (IFN-type III), yet neither IFN-type I nor IL-29 production was responsible for the block in cell growth. We observed that the protein half-life of p16(INK4a) was increased in TLR9-expressing cells. Taken together, these data show for the first time that TLR9 affects the cell cycle by regulating p16(INK4a) post-translational modifications and highlights the role of TLR9 in the events that lead to carcinogenesis.

Diagnóstico y tratamiento de las lesiones benignas de la mama en el embarazo

OBJECTIVES

To retrospectively study the diagnosis and treatment of benign breast disease during pregnancy and breastfeeding at our department. To review the relevant literature.

MATERIALS AND METHODS

From January 2001 to March 2005, a total of 91 pregnant or breastfeeding women (age range: 23-36 years) were diagnosed with benign breast pathology. All patients presented with palpable nodules or inflammatory symptoms. Ultrasound-guided fine-needle cytology was performed in all cases and percutaneous core biopsy was considered necessary in three cases. Abscesses were drained when present. Patients provided their informed consent before all procedures.

RESULTS

Tumors were detected in 28 cases (30%): fibroadenomas (n = 12), lactating adenomas (n = 9), galactoceles (n = 5), and papillomas (n = 2). Conservative treatment with ultrasound follow-up was employed in all cases except one, which required surgical treatment in the third trimester. On 63 occasions (70%), the pathology was inflammatory, including abscesses in 24 cases (38%); abscesses were drained using fine-needle aspiration (n = 16) or pig-tail catheter (n = 3), according to protocol, depending on the size of the abscess (less than or greater than 3 cm). In 5 cases the abscesses were drained surgically.

CONCLUSIONS

The most common benign breast pathology during pregnancy is inflammatory and is satisfactorily managed with antibiotics and percutaneous drainage with good esthetic results. Ultrasound is the diagnostic technique of choice, together with cytology; percutaneous biopsy is only performed in uncertain cases to minimize the risk of fistulas. Management of tumors after histological confirmation should be conservative with close follow-up. These tumors cause no problems for the child, the mother, or breastfeeding.

A cavernous haemangioma of breast in male: radiological-pathological correlation

Vascular tumours of the breast are especially rare in men, and a majority of them are angiosarcomas. In fact, we found only four cases of haemangioma in males in the literature. We present a case of cavernous haemangioma in a male aged 48 years, and which commenced as a palpable mass. We performed differential diagnosis and radiological-pathological correlation. We established the correct classification of this case histologically, and decided on the definitive therapeutic approach.

Mammary tuberculosis: percutaneous treatment of a mammary tuberculous abscess

It is currently very rare to find mammary involvement in cases of tuberculosis, in either primary or secondary form. Diagnosis is classically clinical and microbiological, and the basic techniques used in imaging diagnosis are mammography and ultrasound. Computed tomography may define the involvement of the thoracic wall in those cases which present as mammary masses adhering to deep levels, and is also able to evaluate accompanying pulmonary disease, if it is present. Traditionally, treatment has consisted of quadrantectomy and specific antibiotic therapy. We present a case of tuberculous mammary abscess secondary to pulmonary disease, which was treated by percutaneous drainage controlled by CT and specific antibiotic therapy. We revise the diagnosis, differential diagnosis and treatment of mammary tuberculosis.

Conception control by vaginal administration of pills containing ethinyl estradiol and dl-norgestrel

One hundred twenty-four women of reproductive age have used vaginal pills containing 50 micrograms dl-norgestrel and 35 micrograms ethinyl estradiol to prevent conception for periods ranging from 6 to 20 months. One thousand four hundred thirty-eight woman-months were recorded. No pregnancies occurred. Cycle control was good. Bleeding usually lasted 3 to 5 days, and the interval between withdrawal bleeding events was 26 to 30 days in 86% of the cycles. Amenorrhea, breakthrough bleeding, and spotting occurred rarely. The continuation rate at 1 year was 64%.

Ovulation inhibition following vaginal administration of pills containing norethindrone and mestranol

Plasma levels of estradiol and progesterone were investigated in women using daily vaginal pills containing 1 mg norethindrone and 50 mcg mestranol. Of 13 treatment cycles in ten women using one vaginal pill daily, six were ovulatory and seven anovulatory. All 12 cycles in ten women using two vaginal pills daily were anovulatory.

Heart rate and avoidance conditioned activity in rats

In accordance with the determination of base-line heart rate and running in an activity wheel, 14 Long-Evans male rats were given ten 30 minute sessions of Immobile-Avoid conditioning followed by 30 minute sessions of Active-Avoid conditioning. Control Ss were yoked to the experimental Ss. Experimental Ss made significantly fewer responses in the immobile-avoid period and significantly more responses in the active-avoid period than did the yoked control Ss. Heart rate was correlated with skeletal activity both for experimental and control Ss. For experimental Ss, low heart rate was concomitant with a low amount of activity in the immobile-avoid peroid and high heart rate was concomitant with greater skeletal activity in the active-avoid period. These results support the position that heart rate is secondary to responses of the somatic-motor system and that heart rate during immobile-avoid or active avoid conditioning is more closely related to the level of somatic-motor activity than to the emotional stress which purportedly motivates instrumental avoidance behavior.