Characterization of bacteria degrading 3-hydroxy palmitic acid methyl ester (3OH-PAME), a quorum sensing molecule of Ralstonia solanacearum.

UNLABELLED: Bacterial wilt pathogen Ralstonia solanacearum causes severe crop loss of eggplant, which is of economic importance in India. 3-hydroxy palmitic acid methyl ester (3OH-PAME) is the main quorum sensing molecule governing the expression of virulence factors in R. solanacearum. Ability of 164 bacterial isolates from the xylem of eggplant (Solanum melongena L.), chilli pepper (Capsicum annuum L.) and wild eggplant (Solanum torvum Sw.) to degrade 3OH-PAME was tested by disc diffusion assay. Enzymatic degradation of 3OH-PAME by five bacteria was confirmed by High-Performance Liquid Chromatography-Mass Spectrometry analysis. 3OH-PAME degrading bacteria were identified as Stenotrophomonas maltophilia, Pseudomonas aeruginosa and Rhodococcus corynebacterioides. 3OH-PAME degrading bacteria reduced the expression of virulence factors (exopolysaccharides and endoglucanase) of R. solanacearum in vitro and reduced wilt incidence in eggplant seedlings under greenhouse conditions. Isolates with quorum quenching activity successfully re-colonized eggplant seedlings. Quorum quenching bacteria produced antagonistic compounds, which may act synergistically with quorum quenching in reducing bacterial wilt in eggplant. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report on endophytic bacteria of class Gammaproteobacteria and phylum Actinobacteria having 3OH-PAME degrading activity. This study demonstrates the potential use of endophytic bacteria as quorum quenching biocontrol agents for management of bacterial wilt in eggplant.

Development of a landfill model to prioritize design and operating objectives.

The application of scientifically based decision making tools to help address solid waste management issues dates back to the early 1960s. Researchers continue to use operations research tools to help optimize landfill design and operating parameters. This paper discusses the application of another type of decision making tool, the analytical hierarchy process (AHP), to address priority ranking for a number of landfill engineering design and operating objectives in developing and developed countries. In this application, the AHP is used to rank, and prioritize, economic, environmental, health and safety, legislative and public perception objectives for landfill design and operations specific to landfill distance from a community, and precipitation levels. Results from a global survey using the Delphi process are included, with a discussion on the survey's impact on the objective rankings relative to community proximity and precipitation. The Delphi process worked extremely well, and was an excellent tool to use in this application. The initial results from the objective rankings show promise in the development of an integrated model for landfill design and operation.

An investigation into solvent extraction of pcbs from weathered soils.

Laboratory investigations were conducted to study the efficiency of extraction of polychlorinated biphenyls (PCBs) from weathered soils by polar organic solvents i.e. acetone, isopropanol (IPA) and methanol that were chosen for lower hazard and for penetration in wet soil. The impacts of hydrogen peroxide pretreatment, soil-solvent ratio and number of extraction cycles on PCBs extraction efficiency were investigated. The pretreatment of soil with hydrogen peroxide (H2O2) prior to extraction improved PCB extraction efficiency. An enhancement in extraction efficiencies was also observed with an increasing number of extraction cycles and at lower soil-solvent ratio. All three solvents could recover Aroclor 1254 (> 73%) from the weathered soils with multicycle extractions.

Effect of wetting and drying and dilution on moisture migration through oil contaminated hydrophobic soils.

Hydrophobic soils display resistance to wetting and frequently do not hold water to support good plant growth. A laboratory investigation was conducted to study moisture movement through hydrophobic soils. Test results indicated that hydrophobic soils have a critical moisture content beyond which they behave as wettable or hydrophilic soils. Soil hydrophobicity decreased and water infiltration increased when the soil was subjected to an increasing number of wetting and drying cycles. The effect of diluting hydrophobic soil with hydrophilic soil on water infiltration was also studied. The results indicated that water infiltration into soil becomes more rapid and uniform as the mass fraction of hydrophilic soil is increased in the mix. Water infiltration was observed even in hydrophobic-hydrophilic soil mixtures classified as severely water-repellent by commonly used arbitrary ordinal scales.

Choroid plexus papillomas of the cerebellopontine angle.

The cerebellopontine angle (CPA) is a rare site for the growth of choroid plexus papilloma (CPP). The clinicoradiological diagnosis of this tumor in the CPA is difficult because of the nonspecific clinical presentation and radiological features. Five cases of choriod plexus papilloma (3 males, 2 females) operated upon at this center are reviewed. All the cases were operated upon by retromastoid suboccipital craniectomy. As they all presented with a typical CPA syndrome without any distinctive radiological feature, a clinicoradiological diagnosis of CPP could not be reached in any of these. The diagnosis of CPP could only be suspected at the operation table and established on histopathological examination. Two patients developed recurrences at the primary site following surgery. One patient developed recurrence twice despite gross total excision of tumor in each sitting. Subsequently, this patient remained symptom free for a follow-up period of 1 year. Another patient developed recurrence 2 years following surgery, but he died due to septicemia and aspiration pneumonitis. Therefore definitive surgery could not be performed. Radiotherapy was offered to one of the patients having residual mass post operatively, to render her symptom free for a 4 year follow-up. The remaining two patients have also showed progressive improvement in their symptoms following surgery for 4 years on follow-up. Hydrocephalus was a common feature in all the cases preoperatively, but only one required shunt CSF diversion, because of rapid deterioration in visual equity. In all other cases, hydrocephalus was managed conservatively. Surgery remains the main modality of treatment for CPP, both for primary and recurrent tumors, but radiotherapy may have a role in cases of recurrence, which are quite frequent.

Uncommon presentation of medulloblastoma.

INTRODUCTION: Medulloblastoma commonly occurs in children as a midline posterior fossa mass arising from the vermis, which appears as a hyperdense, homogeneously enhancing mass on CT scan and is associated with the clinical profile of posterior fossa syndrome. This unique clinico-radiological pattern is considered 'typical', but then medulloblastomas do not follow the typical clinico-radiological pattern in a significant number of cases. PATIENTS: Out of the 42 cases of medulloblastoma operated on at SGPGIMS from 1988 to 1998, 29 cases were retrospectively and 13 cases were prospectively studied to detect the atypical clinico-radiological features. The typical radiological feature of a hyperdense homogeneously enhancing mass was seen in only 23 of the 42 patients, while 5 patients had hypodense nonenhancing masses, 13 had cystic changes, and 6 patients had calcifications in their tumours. Three patients presented with tumours in a very unusual location, i.e. the cerebellopontine angle cistern. RESULTS: During follow-up, which ranged from a minimum period of 1 year to a maximum of 9 years, patients came back with metastases at very unusual sites. There were 5 cases of metastases in the frontal and subfrontal area (developed between 5 months and 5 years following surgery), and 1 patient developed a cervical intramedullary metastasis. Two patients developed abdominal metastases and ascites 2 years after definitive surgery and ventriculo-peritoneal shunting. Each of these 2 patients, however, had received a full course of craniospinal irradiation following surgery. Thus, we had a number of cases with an unusual clinical, radiological and metastatic pattern.

Medulloblastomas of the cerebellopontine angle.

It is unusual for a medulloblastoma to occur in the cerebellopontine angle (CPA). Four of the total 63 cases of medulloblastoma managed in our department between 1988 to 1998, presented with a mass in the cerebellopontine angle. There were two children amongst these four patients, aged eight and nine years. The other two patients were young adults. Three patients had primary CPA medulloblastoma, while the fourth case had a recurrence in this region, following the excision of the primary vermian tumour. All the four cases were managed by gross total microsurgical excision and craniospinal irradiation. One of the two children, developed subfrontal recurrence after 1 year and 8 months of initial treatment, while the other child developed a large recurrence at primary site, within three months of post-operative irradiation. However, the adult patient developed CPA recurrence and subsequent cervical intramedullary metastasis within two and a half years of diagnosis. These three cases succumbed to their disease, between three months to thirty months of their initial management. However the fourth patient, a 20 years female with desmoplastic variant, was well at two and a half years of follow up.

Extradural meningioma en-plaque of the cervical cord.

A rare case of cervical extradural en-plaque meningothelial meningioma is reported. The magnetic resonance imaging revealed an extradural sheet of tumor encasing the cervical cord from anterior, posterior and right lateral aspects and emerging from the right C3-4 intervertebral foramina. Though a differential diagnosis of lymphoma and tubercular granulation tissue were considered, its isointense intensity patterns on T1 and T2 weighted images and the intratumoral calcification on intrathecal contrast computed tomographic scan suggested a meningioma. At surgery, the lesion was fibrous, avascular and densely adherent to the dura. The radiological features and management options of the lesion are discussed.

Role of histamine release - a possible mechanism of action of intrauterine contraceptive device.

PIP: The histamine content of the endometrium was estimated in 50 women who were wearing an intrauterine device and in 48 control women. Histological examinations were conducted in both groups. The histamine content was higher among IUD users during all phases of the menstrual cycle. Histologically, endometria which had been exposed to the devices showed leucoytic infiltration and hyperestrogenism. A possible mechanism of action of the IUD is proposed, based on these biochemical and histological changes.^ieng