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Biomedical subjects

Ramesh Murthy

Publications and source records attributed to Ramesh Murthy.

10 recordsLinked to original sources
PubMed2006

Relationships between microbial community structure and soil processes under elevated atmospheric carbon dioxide.

There is little current understanding of the relationship between soil microbial community composition and soil processes rates, nor of the effect climate change and elevated CO(2) will have on microbial communities and their functioning. Using the eastern cottonwood (Populus deltoides) plantation at the Biosphere 2 Laboratory, we studied the relationships between microbial community structure and process rates, and the effects of elevated atmospheric CO(2) on microbial biomass, activity, and community structure. Soils were sampled from three treatments (400, 800, and 1200 ppm CO(2)), a variety of microbial biomass and activity parameters were measured, and the bacterial community was described by 16S rRNA libraries. Glucose substrate-induced respiration (SIR) was significantly higher in the 1200 ppm CO(2) treatment. There were also a variety of complex, nonlinear responses to elevated CO(2). There was no consistent effect of elevated CO(2) on bacterial diversity; however, there was extensive variation in microbial community structure within the plantation. The southern ends of the 800 and 1200 ppm CO(2) bays were dominated by beta-Proteobacteria, and had higher fungal biomass, whereas the other areas contained more alpha-Proteobacteria and Acidobacteria. A number of soil process rates, including salicylate, glutamate, and glycine substrate-induced respiration and proteolysis, were significantly related to the relative abundance of the three most frequent bacterial taxa, and to fungal biomass. Overall, variation in microbial activity was better explained by microbial community composition than by CO(2) treatment. However, the altered diversity and activity in the southern bays of the two high CO(2) treatments could indicate an interaction between CO(2) and light.

Biodiversity↗
PubMed2005

The interacting effects of elevated atmospheric CO2 concentration, drought and leaf-to-air vapour pressure deficit on ecosystem isoprene fluxes.

Isoprene is the most abundant biogenic hydrocarbon released from vegetation and it plays a major role in tropospheric chemistry. Because of its link to climate change, there is interest in understanding the relationship between CO2, water availability and isoprene emission. We explored the effect of atmospheric elevated CO2 concentration and its interaction with vapour pressure deficit (VPD) and water stress, on gross isoprene production (GIP) and net ecosystem exchange of CO2 (NEE) in two Populus deltoides plantations grown at ambient and elevated atmospheric CO2 concentration in the Biosphere 2 Laboratory facility. Although GIP and NEE showed a similar response to light and temperature, their responses to CO2 and VPD were opposite; NEE was stimulated by elevated CO2 and depressed by high VPD, while GIP was inhibited by elevated CO2 and stimulated by high VPD. The difference in response between isoprene production and photosynthesis was also evident during water stress. GIP was stimulated in the short term and declined only when the stress was severe, whereas NEE started to decrease from the beginning of the experiment. This contrasting response led the carbon lost as isoprene in both the ambient and the elevated CO2 treatments to increase as water stress progressed. Our results suggest that water limitation can override the inhibitory effect of elevated CO2 leading to increased global isoprene emissions in a climate change scenario with warmer and drier climate.

Atmosphere↗
PubMed2005

Ocular surface squamous neoplasia in Papillon-Lefevre syndrome.

PURPOSE: To report the occurrence of ocular surface squamous neoplasia (OSSN) in a patient with Papillon-Lefevre syndrome. DESIGN: Interventional case report. METHODS: A 14-year-old boy presented with a progressively growing limbal lesion in the right eye for 2 months. He had associated erythematous scaly lesions on the elbows, knees, and feet with periodontosis suggestive of Papillon-Lefevre syndrome. An excision biopsy of the limbal tumor and a skin biopsy was performed. RESULTS: The limbal tumor showed features of carcinoma in situ with clear margins. The skin biopsy showed epidermal hyperplasia and hyperkeratosis with perivascular infiltrates, consistent with Papillon-Lefevre syndrome. CONCLUSIONS: Ocular surface squamous neoplasia may occur in patients with Papillon-Lefevre syndrome, an association that to the best of our knowledge has not been previously reported.

Adolescent↗
PubMed2005

Polycystic echinococcosis of the orbit.

PURPOSE: To report a case of polycystic echinococcosis of the orbit caused by Echinococcus oligarthrus. DESIGN: Interventional case report. METHODS: A 14-year-old girl presented with a massive proptosis of the right eye of 9 years duration and loss of vision. The eye was phthisic, and a cystic mass was palpable. Computed tomography scan showed closely packed multiple orbital cysts with destruction of the medial orbital wall. Surgical exploration was performed. RESULTS: The phthisic eye was enucleated. Dissection of the outer fibrous capsule yielded approximately 30 intact translucent white cysts of various sizes that were suggestive of polycystic echinococcosis. The diagnosis of echinococcosis was confirmed on histopathologic evaluation. The specific diagnosis of E oligarthrus was made on the basis of the presence of straight-backed hooks and central guards. CONCLUSION: Polycystic echinococcosis of the orbit caused by E oligarthrus is rare. It may be an entirely new entity or hitherto unrecognized form of orbital echinococcosis.

Adolescent↗
PubMed2005

Neoadjuvant chemotherapy in the management of sebaceous gland carcinoma of the eyelid with regional lymph node metastasis.

A 55-year-old Asian Indian woman who had recurrent sebaceous gland carcinoma of the left lower eyelid with orbital extension and regional lymph node metastasis was treated with neoadjuvant chemotherapy, using a combination of carboplatin and 5-fluorouracil. Eyelid-sparing orbital exenteration was performed after 3 cycles of chemotherapy, followed by radiotherapy to the regional lymph nodes. Subsequently, 3 cycles of adjuvant chemotherapy were administered. Significant eyelid and orbital tumor volume reduction was achieved with neoadjuvant chemotherapy, making eyelid-sparing orbital exenteration possible. Chemotherapy also spared the patient from radical neck dissection. The patient had limited morbidity and was free of local, regional, and systemic disease at 26 months of follow-up.

Adenocarcinoma, Sebaceous↗
PubMed2004

Interactive effects of paraoxon and pyridostigmine on blood-brain barrier integrity and cholinergic toxicity.

The effect of the organophosphorous insecticide paraoxon on the integrity of the blood-brain barrier (BBB) and permeability of pyridostigmine (PYR), a peripheral inhibitor of cholinesterase activity, was examined in Long Evans rats. The integrity of the BBB was examined by measuring the number of capillaries leaking horseradish peroxidase, which was injected into the heart. Treatment with paraoxon at 100 microg/kg, intramuscularly, resulted in a 3- to 4-fold increase in the number of leaky capillaries in young rats (25 to 30 days old) but not in older rats (90 days old). Interestingly, young rats treated with PYR (30 mg/kg, po) 50 min before treatment with paraoxon showed an inhibited effect of paraoxon on the BBB. Furthermore, no increase in the degree of inhibition of acetylcholinesterase activity was observed in young rats treated with PYR before paraoxon compared with young rats treated with paraoxon alone. Cholinergic toxicity, as assessed by changes in behavior, was not observed in young rats treated with paraoxon alone; but, slight signs of cholinergic toxicity were observed in rats treated with PYR. Young rats treated with both PYR and paraoxon did not exhibit more extensive signs of toxicity than rats treated with paraoxon alone or PYR alone. The results indicate that treatment with paraoxon can compromise BBB permeability at dosages that do not induce cholinergic toxicity, but only in young rats. Also, PYR pre-exposure appears to protect the BBB from the paraoxon-induced alterations.

Age Factors↗
PubMed2004

Growth CO2 concentration modifies the transpiration response of Populus deltoides to drought and vapor pressure deficit.

Cottonwood (Populus deltoides Bartr. ex Marsh.) trees grown for 9 months in elevated carbon dioxide concentration ([CO2]) showed significant increases in height, leaf area and basal diameter relative to trees in a near-ambient [CO2] control treatment. Sample trees in the CO2 treatments were subjected to high and low atmospheric vapor pressure deficits (VPD) over a 5-week period at both high and low soil water contents (SWC). During these periods, transpiration rates at both the leaf and canopy levels were calculated based on sap flow measurements and leaf-to-sapwood area ratios. Leaf-level transpiration rates were approximately equivalent across [CO2] treatments when soil water was not limiting. In contrast, during drought stress, canopy-level transpiration rates were approximately equivalent across [CO2] treatments, indicating that leaf-level fluxes during drought stress were reduced in elevated [CO2] by a factor equal to the leaf area ratio of the two canopies. The shift from equivalent leaf-level transpiration to equivalent canopy-level transpiration with increasing drought stress suggests maximum water use rates were controlled primarily by atmospheric demand at high SWC and by soil water availability at low SWC. Changes in VPD had less effect on transpiration than changes in SWC for trees in both CO2 treatments. Transpiration rates of trees in both CO2 treatments reached maximum values at a VPD of about 2.0 kPa at high SWC, but leveled off and decreased slightly in both canopies as VPD increased above this value. At low SWC, increasing VPD from approximately 1.4 to 2.5 kPa caused transpiration rates to decline slightly in the canopies of trees in both treatments, with significant (P = 0.004) decreases occurring in trees in the near-ambient [CO2] treatment. The transpiration responses at high VPD in the presence of high SWC and throughout the low SWC treatment suggest some hydraulic limitations to water use occurred. Comparisons of midday leaf water potentials of trees in both CO2 treatments support this conclusion.

Carbon Dioxide↗