GSTT1 and GSTM1 gene deletions are not associated with hepatotoxicity caused by antitubercular drugs

BACKGROUND AND OBJECTIVE

Susceptibility to antitubercular drug (ATD)-induced hepatotoxicity may be genetically mediated, with variant alleles of genes such as N-acetyltransferase (NAT2) and CYP2E1 reported as risk factors. Two studies of Asian populations have reported that GSTM1*0 ⁄ *0 (null) genotype was a likely predictor of hepatotoxicity, whereas another of a Caucasian population implicated GSTT1*0 ⁄ *0. We undertook a prospective case-control study to investigate whether GSTM*0 ⁄ *0 and GSTT1*0 ⁄ *0 were risk factors for ATD-induced hepatotoxicity.

METHODS

Pulmonary tuberculosis patients on isoniazid, rifampicin and pyrazinamide who developed hepatotoxicity using defined criteria were prospectively identified. These cases were then matched with at least one control subject on the same drugs but without hepatotoxicity. Genotyping for GSTM1 and GSTT1 was performed by multiplex PCR on genomic DNA. The odds ratios for the frequency of specific GSTM1 and GSTT1 homozygotes in the case and control subjects were calculated to test for association between the genotypes and hepatotoxicity.

RESULTS AND DISCUSSION

Hundred and fifty-one subjects (51 cases, 100 controls) were enrolled. Odds ratio for GSTM1 null genotype was 1.00 (95% CI 0.51-1.97) and GSTT1 null was 2.02 (95% CI 0.39-10.39), respectively, showing that these genotypes are not associated with hepatotoxicity.

CONCLUSION

GSTM1 *0 ⁄ *0 or GSTT1 *0 ⁄ *0 or both null genotypes, do not appear to be associated with ATD-induced hepatotoxicity in our Indian population.

Size-induced metallic state in nanoparticles of ferromagnetic insulating Nd0.8Sr0.2MnO3

A detailed investigation of the electronic- and magneto-transport properties of Nd(0.8)Sr(0.2)MnO(3) with the variation of grain size (down to 42 nm) is presented here. Interestingly, we observe that the ferromagnetic insulating state is suppressed and a metallic state is stabilized as the grain size of the sample is reduced. As a result, a metal-insulator transition is observed in this low doped manganite which is insulating in nature in its bulk form. Destabilization of polaronic order in the ferromagnetic insulating state due to enhanced surface disorder on grain size reduction is attributed to this effect. A phenomenological model is proposed to represent the concept of destabilization of polaron formation in the surface region of the nanograins. Resistivity and magnetoresistance data are carefully analysed employing different suitable models. Electrical third harmonic resistance is measured to directly probe the electrical nonlinearity in the samples.

Mediastinal hydatid disease: an unusual presentation

Hydatid disease is a significant health problem in endemic areas. While occurrence of the cysts in the liver and lung is common, mediastinal localisation is extremely rare. We report the case of a 35-year-old male who presented with a painless swelling on the right side of the neck and features of superior vena caval obstruction. Chest radiography and computed tomography (CT) suggested a cyst in the right upper lobe, extending into the right supraclavicular region as well as another cyst in the left lung. Thoracotomy revealed that the right-sided cyst was actually mediastinal in location and had herniated through the thoracic inlet compressing the superior vena cava (SVC). Both cysts were removed in two separate operations and symptoms of SVC compression subsided after removal of the right-sided cyst. Histopathology was consistent with a hydatid disease.

CHARMM general force field: A force field for drug-like molecules compatible with the CHARMM all-atom additive biological force fields

The widely used CHARMM additive all-atom force field includes parameters for proteins, nucleic acids, lipids, and carbohydrates. In the present article, an extension of the CHARMM force field to drug-like molecules is presented. The resulting CHARMM General Force Field (CGenFF) covers a wide range of chemical groups present in biomolecules and drug-like molecules, including a large number of heterocyclic scaffolds. The parametrization philosophy behind the force field focuses on quality at the expense of transferability, with the implementation concentrating on an extensible force field. Statistics related to the quality of the parametrization with a focus on experimental validation are presented. Additionally, the parametrization procedure, described fully in the present article in the context of the model systems, pyrrolidine, and 3-phenoxymethylpyrrolidine will allow users to readily extend the force field to chemical groups that are not explicitly covered in the force field as well as add functional groups to and link together molecules already available in the force field. CGenFF thus makes it possible to perform "all-CHARMM" simulations on drug-target interactions thereby extending the utility of CHARMM force fields to medicinally relevant systems.

Chemical, biochemical, and biological impact of untreated domestic sewage water use on Vertisol and its consequences on wheat (Triticum aestivum) productivity

In the peri-urban areas of central India, sewage water is a valuable resource for agricultural production. In this study, impact of domestic sewage water irrigation for 5 years on Vertisol with no previous history of sewage irrigation was investigated in an ongoing field experiment at Bhopal (India) under subtropical monsoon type climate. The wheat (Triticum aestivum) crop was grown during post-rainy winter season with 30 cm of irrigation (groundwater or sewage water) and four nutrient treatments (T(1), 0; T(2), 100%; T(3), 50%; and T(4), 50% of general recommended doses of NPK + FYM at 10 Mg/ha). Results showed that sewage irrigation of about 150 cm over a period of 5 years resulted significant increases in salinity as well as available fractions of N, P, K, and micronutrients, viz., Zn, Fe, and Mn in soils. Carbon and phosphorus applied through sewage water were accumulated more in subsoil layer compared to topmost plough layer. Soil microbiological activity, as indicated by soil respiration, microbial biomass C, as well as dehydrogenase enzyme activity was higher in sewage water-irrigated soils. There was also significant increase in fungal and actinomycetes as well as total coliform population in such soils. Nutrients supplied through sewage water were not able to raise the productivity of wheat to the level that obtained through fertilizers at the recommended level which indicated that additional nutrients through fertilizers are required to obtain higher productivity of wheat under sewage farming. Protein and Zn content in wheat grains were more when the crop was grown with sewage irrigation. Overall results show that except for increase in coliform population, short duration (5 years) of municipal sewage water irrigation did not have any appreciable harmful effect on soil quality as well as crop productivity; rather, it proved beneficial in improving soil fertility, wheat productivity, and produce quality.

Isolation, molecular characterization and growth-promotion activities of a cold tolerant bacterium Pseudomonas sp. NARs9 (MTCC9002) from the Indian Himalayas

A bacterium that grows and expresses plant growth promotion traits at 4 degrees C was isolated from the rhizospheric soil of Amaranth, cultivated at a high altitude location in the North Western Indian Himalayas. The isolate was Gram negative and the cells appeared as rods (2.91 x 0.71 microm in size). It grew at temperatures ranging from 4 to 30 degrees C, with a growth optimum at 28 degrees C. It exhibited tolerance to a wide pH range (5-10; optimum 8.0) and salt concentrations up to 6% (wt/vol). Although it was sensitive to Rifampicin (R 20 microg mi-1), Gentamicin (G 3 microg mi-1), and Streptomycin (S 5 microg mi-1), it showed resistance to higher concentrations of Ampicillin (A 500 microg mi-1), Penicillin (P 300 microg mi-1), Polymixin B sulphate (Pb 100 microg mi-1) and Chloramphenicol (C 200 microg mi-1). The 16S rRNA sequence analysis revealed maximum identity with Pseudomonas lurida. The bacterium produced indole Acetic Acid (IAA) and solubilizes phosphate at 4, 15 and 28 degrees C. It also retained its ability to produce rhamnolipids and siderophores at 15 degrees C. Seed bacterization with the isolate enhanced the germination, shoot and root lengths of thirty-day-old wheat seedlings by 19.2, 30.0 & 22.9% respectively, as compared to the un-inoculated controls.

Growth promotion of wheat seedlings by Exiguobacterium acetylicum 1P (MTCC 8707) a cold tolerant bacterial strain from the Uttarakhand Himalayas

Exiguobacterium acetylicum strain 1P (MTCC 8707) is a gram-positive, rod-shaped, yellow pigmented bacterium isolated from soil on nutrient agar plates at 4°C. The identity of the bacterium was arrived on the basis of the biochemical characterization, BIOLOG sugar utilization pattern and sequencing of the 16S rRNA gene. It grew at temperatures ranging from 4 to 42°C, with temperature optima at 30°C. It expressed multiple plant growth promotion attributes such as phosphate solubilization, indole acetic acid (IAA), siderophore and hydrogen cyanide (HCN) production, differentially at suboptimal growth temperatures (15 and 4°C). At 15°C it solubilized phosphate (21.1 μg of P ml(-1) day(-1)), and produced IAA (14.9 μg ml(-1) day(-1)) in tryptophan amended media. Qualitative detection of siderophore production and HCN were possible at 15°C. At 4°C it retained all the plant growth promotion attributes. Seed bacterization with the isolate, positively influenced the growth and nutrient uptake parameters of wheat seedlings in glass house studies at suboptimal cold growing temperatures.

Spermatheca Gland Extract of Snail (Telescopium telescopium) Has Wound Healing Potential: An Experimental Study in Rabbits

The effects of spermatheca gland extract of snail ( Telescopium telescopium) to promote wound healing were studied in an animal model. The spermatheca gland extract of the snail was used as a topical medicament to treat experimentally created full thickness wounds in 12 rabbits ( Oryctologous cuniculus). Wound healing was assessed on the basis of physical, histomorphological, and histochemical changes on days 0, 3, 7, and 14. Statistically significant differences were observed between the groups in all measured parameters. These exciting findings suggest that the data should be further tested in animal models to better understand the potential for wound healing in the spermatheca gland extract of the marine snail.

Neutron reflectivity study of the complexation of DNA with lipids and surfactants at the surface of water

Complexation of lipids and surfactants with short DNA fragments at the air-water interface has been studied by neutron reflectivity. Complexation with zwitterionic lipids occurs in the presence of divalent cations, and ion specificity has been demonstrated (binding is less effective with Ba2+ than with Mg2+ or Ca2+). One and two DNA layers have been observed for dilute and more compact lipid monolayers, respectively. Two DNA layers have also been found with the soluble cationic surfactant dodecyltrimethylammonium bromide (DTAB), except close to the precipitation boundary. This result is opposite to that found in ellipsometry where very thick layers are found in this region. It is possible that the ellipsometry signal is due to highly hydrated bulk complexes adsorbing at the surface, not seen by neutrons because of unfavorable contrast conditions. Long DNA was found to be less keen to form surface complexes than short DNA fragments.

Percutaneous treatment of bifurcation coronary stenosis: a long-term follow-up

BACKGROUND

The treatment of bifurcation coronary stenosis involved several techniques in the last few years, with the use of one stent, two stents, kissing balloon, crush stenting. Basic objective was to reduce MACE rate and improve event-free survival.

OBJECTIVE

To examine the performance of some techniques of stent placement adopted in the last few years by evaluating MACE (major adverse cardiac events) and TLR (target lesion revascularization).

METHODS

Between 1999 and 2003, 74 consecutive patients with bifurcation lesions were treated with either stenting two vessels (type A, n = 8) or single vessels (type B, n = 66) and were followed for 30 days, 6 months, with a mean follow-up of 23 months for clinically driven MACE and TLR. RESULTS, The mean reference diameters of the main and side branches were 2.97 +/- 0.27 mm and 2.28 +/- 0.49 mm, respectively. The side branch was stented in 11% cases. Less than 30% residual stenosis in the main branch was achieved in 100% cases, <50% in the side branch in 94.5% of the cases. In-hospital major adverse cardiac events were non-Q-wave MI in 5% patients. During follow-up, death was 1.35%, subacute stent thrombosis (SAT) was 4%, and TLR (CABG) was 10.8%. Multivariate analysis showed type 1 lesion, and STEMI was associated with more MACE than others. There was 4.35-fold greater odds of MACE, associated with stenting both vessels in bifurcation lesion. CONCLUSION, Stenting of the main branch along with kissing balloon dilatation or provisional stenting of the side branch is a safe and effective treatment of coronary bifurcation lesions with acceptable TLR rates.

Relaxation of bimolecular layer films on water surfaces

Ferric stearate, a three-tailed amphiphile, forms bimolecular layers on water surfaces. Molecules in the lower layer are in an "asymmetric" configuration, Fe-containing heads touching water and three hydrocarbon tails in air, while molecules in the upper layer are in a "symmetric" configuration, in pairs of "Y and inverted Y" disposition of tails about the Fe-bearing head. Pressure relaxation at constant area (pi- t curves) and area relaxation at constant pressure ( A- t curves) of this bimolecular layer can be modeled as a sum of three exponential decay terms with distinct time constants and weight factors. Relating the long-term decay with desorption of the total film thus indicates a remarkable long-term stability of the bimolecular layer film. An X-ray reflectivity study of the bimolecular films deposited horizontally on Si(001) at various conditions of relaxation shows no further growth along the vertical of any other layer. Under pressure relaxation molecules are transferred from the upper layer to the lower layer with a change from symmetric to asymmetric configuration, while under area relaxation the transfer is from the lower layer to the upper layer with a configurational change from symmetric to asymmetric.

Relative changes in phosphatase activities as influenced by source and application rate of organic composts in field crops

Potential impact of different levels and sources of organic composts on activities of phosphatases (acid and alkaline phosphatase, phosphodiesterase, and inorganic pyrophosphatase) was studied after three years of continuous application. Enzyme activities were compared with microbial biomass P and available P. Experimental plots were divided based on the organic source into three groups: those receiving farmyard manure (FYM), vermicompost (VC) and Lantana compost (LC). Microbial biomass P (11.7 g kg(-1) soil), available P (24.0 g kg(-1) soil) and acid phosphatase (1.3 mg g(-1) p-NP g(-1) soil h(-1)) was highest in highest dose of VC. Acid phosphatase activity was high in all plots, including those where microbial biomass P levels were low. Most of the phosphatase activities were significantly correlated with available P in FYM and VC. These relationships were negative for LC treatments. Results showed that application of earthworm casts is helpful in faster transformation of organic P by facilitating better environment to microbes and plant roots.

Isolation and characterization of nonrhizobial plant growth promoting bacteria from nodules of Kudzu (Pueraria thunbergiana) and their effect on wheat seedling growth

The leguminous vine Kudzu (Pueraria thunbergiana) is an introduction into the N. W. Himalayan region of India. Despite its value as a fodder and cover crop, little is known about the nature of the nodule microflora. In an attempt to study the nodule bacteria, we isolated and characterized three nonrhizobial plant growth promoting bacteria from surface sterilized nodules of Kudzu. Based on the sequencing of the 16 S r RNA gene, the isolates were designated as Bacillus thuringiensis KR-1, Enterobacter asburiae KR-3, and Serratia marcescens KR-4. Crystalline bodies were detected in the isolate KR-1, confirming its identity as B. thuringiensis. Under in vitro conditions, all three isolates were found to produce indole acetic acid. Other plant growth promotion attributes such as P solubilization, hydrogen cyanide production, and ammonia production varied among the isolates. All of the three isolates promoted growth and positively influenced nutrient uptake parameters of wheat seedlings.

A 5-year audit of rhinology procedures carried out in a district general hospital

INTRODUCTION

Although there has been many studies quoting ENT and rhinology complications, there have been none looking at the complication rates of one department with a single specialist rhinologist over a 5-year period.

PATIENTS AND METHODS

Over a 5-year period between 1998 and 2002, the number of operative procedures undertaken in the ENT department in a busy district general hospital was collected in a prospective manner.

RESULTS

A total of 10,768 ENT procedures were undertaken in the department which comprised four consultants and associated junior staff (SpRs/SASs/SHOs); 2507 of these procedures were rhinology cases. There were 39 recorded complications following nasal surgery, giving an overall rhinology complication rate of 1.56%. This included 12 postoperative nose bleeds (0.48%), 5 cases of infection following septal surgery (0.56%), 7 cases of septal perforation (0.75%) and various minor functional endoscopic sinus surgery (FESS) complications (2.17%). These figures are either below or within the quoted literature rates. There were no major complications or deaths recorded following nasal surgery.

CONCLUSIONS

These results compare favourably with those of other studies.

Inhibitory activity of pine needle tannin extracts on some agriculturally resourceful microbes

Crude extracts of water and solvent extractable tannin fractions from pine needles were found to contain tannin concentrations of 10.15% and 13.15% tannic acid equivalents respectively. Thin Layer Chromatography revealed the presence of four distinct phenolic compounds, amongst which two were tannic acid like compounds. Both the extracts were found to be inhibitory to several microbes of agricultural importance. Amongst the bacterial strains studied, Azotobacter sp (VL-A2) was able to tolerate upto 1000 ppm of crude tannin concentration without any growth inhibition. While growth of Rhizobium (VL-R1) and Bacillus halodurans (MTCC 7181) was inhibited by crude tannin concentrations of 50 and 100 ppm respectively of both water and solvent extracted tannins. Among the fungal genera, Pleurotus djamor was found to tolerate up to 10000 ppm of crude tannins, while Trichoderma virescens (MTCC 6321) and T. reesii could tolerate up to 3000 ppm of both water extractable and acetone extractable crude tannins without any growth inhibition.

Reusability of entrapped cells of Pseudomonas diminuta for production of 7-aminocephalosporanic acid

Entrapped cells of P. diminuta were used for the production of 7-aminocephalosporanic acid (7-ACA), a key intermediate required for the production of most of the clinically used cephalosporin derivatives, i.e., semisynthetic cephalosporins. The repeated batch production of 7-ACA with entrapped cells of P. diminuta in different carriers were carried out for six cycles at optimal conditions. It was found that 33% , 38%, and 47% of activity was lost with chitosan, gelatin, and agar, respectively as immobilizing supports after the sixth cycle of operation.

Invasive aspergillosis localised to the colon presenting as toxic megacolon

Primary gut involvement by Aspergillus is an exceedingly rare and often a fatal complication of intensive chemotherapy in patients with acute leukaemia. We report a 46-yr-old patient with granulocytic sarcoma of the testis. He received acute myeloid leukaemia type treatment with ADE chemotherapy (Cytosine Arabinoside, Daunorubicin and Etoposide). While neutropenic he presented with pyrexia, abdominal pain and massive abdominal distention. He was treated with intravenous antibiotics and antifungals according to our usual institutional protocol without any response. He was found to have toxic megacolon on plain X-ray and subsequently underwent total colectomy and ileostomy. The colon histology showed Aspergillus fungal hyphae infiltrating the bowel wall. There was no any evidence of pulmonary, hepatic, splenic or renal lesions on the computerised tomography scan. Following colectomy, he was treated with 2 wk of antifungal treatment. He recovered well and was discharged home. The increased awareness, high degree of clinical suspicion of unusual presentation and early surgical intervention with aggressive antifungal treatment, has a key role in the management of these rare and often fatal cases.

A young male with paraplegia, massive cervical adenopathy and nondiagnostic biopsy specimens

An 18-year-old man presenting with paraplegia due to spinal epidural infiltration at D6-D7 underwent laminectomy and spinal decompression followed by near-complete resolution of neurological symptoms; but this resolution was followed by progressively enlarging cervical lymph nodes. Leucocytosis, an elevated erythrocyte sedimentation rate, a marked polyclonal hypergammaglobulinemia and a moderate hepatosplenomegaly were found. The diagnosis of sinus histiocytosis with massive lymphadenopathy (SHML), also known as Rosai-Dorfman disease was established histologically by lymph node biopsy about 2 years after presentation.

A study on blood eosinophil level and ventilatory pulmonary function of the workers exposed to storage grain dust

The workers engaged in storage grain handling are exposed to storage grain dust and suffer from different respiratory symptoms like, cough wheezing, chest tightness, eye and nasal irritations. It has been reported abroad and the present study results noted that the grain handlers have allergic symptoms like redness of eyes, itching, sneezing, skin rash, breathlessness and decrement of pulmonary function test values. According to their nature of job, the workers of storage grain godowns were divided into four categories i.e., load handling worker (LHW), ancillary, quality control and depot administration workers. The pulmonary function tests (PFT) and the differential count of leucocytes were carried out among the workers by standard technique. Decrement of pulmonary function test values was noted with the increment of blood eosinophil level.

The PFT results were presented according to the blood eosinophil level. The decrement of mean PFT values were noticed as the blood level of eosinophil gradually increased from, up to -4%, >4-10% and above 10%. The maximum numbers of workers in different job categories are belonged to >4 -10% of eosinophil level. The percentage figure of workers in different departments were LHW 48.38%, (n=45), ancillary 38.88%, (n=7), quality control 54.54% (n=6) and depot administration workers 47.05% (n=16) are belonged to that range. Among the total workers the higher figure was found >4-10% ranges 47.43% (n=74) workers. The allergic manifestations like redness, itchiness and watering of eyes, sneezing, cough, breathless etc. are reported. These workers have blood eosinophil level and low pulmonary function test values. The respiratory impairments among the workers are restrictive, obstructive and combined restrictive and obstructive type.

Hydrophobic, hydrophilic, and charged amino acid networks within protein

The native three-dimensional structure of a single protein is determined by the physicochemical nature of its constituent amino acids. The 20 different types of amino acids, depending on their physicochemical properties, can be grouped into three major classes: hydrophobic, hydrophilic, and charged. The anatomy of the weighted and unweighted networks of hydrophobic, hydrophilic, and charged residues separately for a large number of proteins were studied. Results showed that the average degree of the hydrophobic networks has a significantly larger value than that of hydrophilic and charged networks. The average degree of the hydrophilic networks is slightly higher than that of the charged networks. The average strength of the nodes of hydrophobic networks is nearly equal to that of the charged network, whereas that of hydrophilic networks has a smaller value than that of hydrophobic and charged networks. The average strength for each of the three types of networks varies with its degree. The average strength of a node in a charged network increases more sharply than that of the hydrophobic and hydrophilic networks. Each of the three types of networks exhibits the "small-world" property. Our results further indicate that the all-amino-acids networks and hydrophobic networks are of assortative type. Although most of the hydrophilic and charged networks are of the assortative type, few others have the characteristics of disassortative mixing of the nodes. We have further observed that all-amino-acids networks and hydrophobic networks bear the signature of hierarchy, whereas the hydrophilic and charged networks do not have any hierarchical signature.

Diuretics for Ménière's disease or syndrome

BACKGROUND

Ménière's disease is a disorder characterised by hearing loss, tinnitus and disabling vertigo. Diuretics are used to try and reduce the severity and frequency of episodes but there is little evidence behind this treatment.

OBJECTIVES

To assess the effect of diuretic treatment in patients with Ménière's disease.

SEARCH STRATEGY

We searched the Cochrane Ear, Nose and Throat Disorders Group Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 1 2005), MEDLINE (1966 to 2005), EMBASE (1974 to 2005), CINAHL and the metaRegister of Controlled Trials (mRCT) (up to 2005).

SELECTION CRITERIA

Randomised controlled trials of diuretic versus placebo in Ménière's patients.

DATA COLLECTION AND ANALYSIS

One author identified studies which loosely met the inclusion criteria and full texts were retrieved. Two authors independently applied the inclusion criteria. Seven studies were excluded from the review due to inappropriate study design or absence of randomisation.

MAIN RESULTS

There were no trials of high enough quality to meet the standard set for this review.

AUTHORS' CONCLUSIONS

There is insufficient good evidence of the effect of diuretics on vertigo, hearing loss, tinnitus or aural fullness in clearly defined Ménière's disease.

Diuretics for Ménière's disease or syndrome

BACKGROUND

Ménière's disease is a disorder characterised by hearing loss, tinnitus and disabling vertigo. Diuretics are used to try and reduce the severity and frequency of episodes but there is little evidence behind this treatment.

OBJECTIVES

To assess the effect of diuretic treatment in patients with Ménière's disease.

SEARCH STRATEGY

We searched the Cochrane Ear, Nose and Throat Disorders Group Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 1 2005), MEDLINE (1966 to 2005), EMBASE (1974 to 2005), CINAHL and the metaRegister of Controlled Trials (mRCT) (up to 2005).

SELECTION CRITERIA

Randomised controlled trials of diuretic versus placebo in Ménière's patients.

DATA COLLECTION AND ANALYSIS

One author identified studies which loosely met the inclusion criteria and full texts were retrieved. Two authors independently applied the inclusion criteria. Seven studies were excluded from the review due to inappropriate study design or absence of randomisation.

MAIN RESULTS

There were no trials of high enough quality to meet the standard set for this review.

AUTHORS' CONCLUSIONS

There is insufficient good evidence of the effect of diuretics on vertigo, hearing loss, tinnitus or aural fullness in clearly defined Ménière's disease.

Saturable-absorber-based spatial filtering of high-power laser beams

A saturable-absorber-based technique for spatial filtering of high-average-power laser beams is described. For a focused, radially symmetric beam having its highest intensity at the center, this saturable absorber behaves like a soft aperture with gradually increasing attenuation toward the beam edges, thus selectively transmitting the low divergence components that are confined close to the central axis of the propagating laser beam. This technique has been successfully used to reduce the divergence of a high-power, high-repetition-rate, tunable, narrowband, pulsed dye laser. Our results demonstrate how a judicious choice of operating parameters allows spatial filtering to be achieved with the introduction of a minimum absorption loss of the laser beam in the saturable absorber. Following a time-dependent analysis of a rate equation model describing the propagation and interaction of the laser beam with the saturable absorber, we have also obtained theoretical estimates for the extent of spatial filtering. Our theoretical estimates have been found to be in good agreement with our experimental observations.