Enhanced kinetics and free-volume universality in dense aggregating systems

Aggregation kinetics and cluster-size distributions are studied with off-lattice, diffusion-limited cluster-cluster simulations. With increased cluster crowding (occurring at late times) as measured by the normalized free volume, Omega, both the kinetics speeds up and the size distribution broadens. The exponents characterizing each, z and lambda, respectively, are found to be universal functions of Omega. Moreover, the relation z=(1-lambda)(-1) continues to hold up to omega=0 (the ideal gel point), implying mean-field kinetics still applies despite the crowding.

Change in distribution & antifungal susceptibility of Candida species isolated from candidaemia cases in a tertiary care centre during 1996-2000

BACKGROUND & OBJECTIVES

As a marked increase in the number of patients with candidaemia was reported in the first half (1991-1995) of the last decade at the Postgraduate Institute of Medical Education & Research, Chandigarh, India, the present study was aimed at determining further change if any, in the incidence and distribution of Candida species and their antifungal resistance pattern during the second half (1996-2000) of the same decade.

METHODS

The patients with candidaemia were studied to determine the frequency of candidaemia and Candida species isolated during 1996-2000. One hundred Candida strains other than Pichia anomala (C. pelliculosa) were randomly selected from those isolates to evaluate antifungal susceptibility pattern against amphotericin B, 5-fluorocytosine, ketoconazole, fluconazole and itraconazole. The results were compared with our previous study.

RESULTS

An increase in the number of patients with candidaemia was observed during 1996 (538) and 1997 (421) compared to 1998-2000 due to P. anomala outbreak. With the control of the outbreak, a substantial decrease in the incidence of candidaemia was observed from 1998 (251 in 1998, 122 in 1999 and 165 in 2000). A higher isolation of non-C. albicans Candida species (89.8%) was observed, with C. tropicalis being the most common (541, 36.1%) agent. No major change in the isolation rate of other non-C. albicans Candida species (C. guilliermondii, C. krusei, C. glabrata and C. parapsilosis) was observed. An emergence of resistance to amphotericin B in 15.4 per cent C. albicans, 8.1 per cent C. tropicalis and 33.3 per cent C. krusei strains was observed. An increase in resistance to ketoconazole (from 0% to 13%) and 5-fluorocytosine (from 1% to 8%) and a decrease to fluconazole (from 13% to 6%) were observed. Resistance to itraconazole was observed in 17 per cent of Candida strains by broth macro-dilution method.

INTERPRETATION & CONCLUSION

A change in the isolation of Candida species was observed i.e. in the incidence and isolation of non-C. albicans Candida species. Emergence of resistance to amphotericin B and increase of resistance to most other antifungals are cause for concern.

Mannan antigen detection in the diagnosis of patients with invasive candidiasis

BACKGROUND & OBJECTIVES

With the increase in the incidence of invasive candidiasis (IC) in recent years, there is a need to improve the sensitivity of diagnosis. A conventional technique like blood culture is positive in nearly 50 per cent of cases. To improve the diagnostic efficiency in invasive candidiasis mannan antigen detection holds promise. Hence mannan antigen detection was evaluated in patients with suspected invasive candidiasis in the Paediatric Intensive Care Unit (PICU).

METHODS

A prospective study, involving 186 consecutive patients admitted to the PICU of the Advanced Paediatric Center at the Postgraduate Institute of Medical Education and Research (PGIMER), Chandigarh between March 1999 and November 1999 were followed up for possible invasive candidiasis. Sixty five children clinically suspected to have sepsis and at risk for developing IC and or who stayed in the hospital more than 5 days were further evaluated for the diagnosis of IC by collecting two blood culture samples 48 h apart and by mannan antigen and anti-mannan antibody detection. Both antigen and antibody were detected by in-house standardized techniques: antibody by whole cell agglutination (WCA) and antigen by sandwich enzyme linked immunosorbent assay (ELISA).

RESULTS

Twenty of 65 patients (30.7%) were positive by blood culture. Mannan antigen was positive in all 20 patients and significant anti-mannan antibody titre (> or = 128) was present in 12 (60%) patients. Mannan antigen was detected in 15 more patients, who were negative for isolation of Candida from blood. Twelve of these patients had febrile episode not responding to antibacterial therapy but responding to fluconazole/itraconazole therapy indicating that the patients possibly had IC. Mannan concentration was also found to be significantly higher in the patients with Candida isolated from blood.

INTERPRETATION & CONCLUSION

Thus, the present study confirms the earlier claim that mannan antigen detection possibly improves the diagnostic efficiency of IC.

Anisotropic ordering in sheared binary fluids with viscous asymmetry: experiment and computer simulation

Optical measurements of the structure and morphology of phase-separating polymer blend under simple shear flow have been performed and the results are compared with computer simulations of sheared phase-separating binary mixtures with viscous asymmetry in the fluid components. Information about the structure is obtained from the two-point composition correlation function. Both experiment and simulation suggest subtle differences in the shear response depending on whether the more viscous phase is dispersed or continuous. Measurements of the string width along the neutral direction suggest power-law decay in the shear rate with an exponent of 1/3 when the more viscous phase is dispersed. The simulations suggest that the mean string width, measured along the velocity-gradient direction in the two-dimensional model calculation, exhibits power-law decay in the shear rate with an exponent of 1/3 independent of which phase is dispersed.

Generalized lymphadenopathy caused by Trichosporon asahii in a patient with Job's syndrome

Of the six species of Trichosporon known to cause human infections, T. asahii is the main agent of invasive trichosporonosis. We describe an unusual case of generalized lymphadenopathy due to T, asahii in a 10-year-old boy with Job's syndrome (markedly elevated IgE with eosinophilia). The diagnosis was based on the presence of blastic conidia and hyphal elements breaking into arthroconidia in biopsied tissue of the cervical lymph node and isolation of the causal agent T, asahii in pure culture. The patient responded initially to amphotericin B therapy, but the infection recurred within 4 weeks and did not respond to therapy of liposomal amphotericin B and 5-fluorocytosine for 10 days. The patient left the hospital against medical advice.

Fungal endophthalmitis following cataract surgery: clinical presentation, microbiological spectrum, and outcome

PURPOSE

To determine the clinical presentation, microbiological spectrum, and outcome in cases of fungal endophthalmitis following cataract surgery.

DESIGN

Observational case series.

METHODS

SETTING

Tertiary referral hospital.

PATIENTS

Retrospective analysis of 27 cases of smear- and culture-proven fungal endophthalmitis.

INTERVENTION

Pars plana vitrectomy in 18 eyes, where the corneal condition did not preclude the same. All eyes received intravitreal amphotericin B and dexamethasone along with systemic antifungal agents.

MAIN OUTCOME MEASURES

Functional success: Final visual acuity of 3/60 or better with attached retina. Anatomical success: Final visual acuity of better than light perception with preserved anatomy of globe.

RESULTS

The majority of the eyes (22 of the 27) had early onset and diffuse presentation (that is, anterior segment as well as posterior vitreous exudates). Substantial corneal involvement was seen in 14 eyes (51.85%). Aspergillus sp. was the most common isolate. Multivariate analysis using forward stepwise logistic regression showed corneal involvement as the single most important risk factor in determining final visual outcome (P =.0429).

CONCLUSIONS

Early onset and diffuse presentation, which mimics bacterial endophthalmitis, stresses the importance of both bacterial and fungal cultures from intraocular fluids to reach a diagnosis apart from the clinical judgment. Corneal involvement was the most important predictor of outcome in cases of fungal endophthalmitis.

Detection of an mRNA polymorphism by differential display

Differential Display (DD) technology was utilized to compare programs of gene expression in primary cultures of human skin fibroblasts from normal volunteers and patients diagnosed with melancholic depression. Polymorphic transcripts of a single gene differing by one tandem repeat sequence of four nucleotides (TGAT) in the 3' noncoding region were detected.

Spaceflight and clinorotation cause cytoskeleton and mitochondria changes and increases in apoptosis in cultured cells

The cytoskeleton is a complex network of fibers that is sensitive to environmental factors including microgravity and altered gravitational forces. Cellular functions such as transport of cell organelles depend on cytoskeletal integrity; regulation of cytoskeletal activity plays a role in cell maintenance, cell division, and apoptosis. Here we report cytoskeletal and mitochondria alterations in cultured human lymphocyte (Jurkat) cells after exposure to spaceflight and in insect cells of Drosophila melanogaster (Schneider S-1) after exposure to conditions created by clinostat rotation. Jurkat cells were flown on the space shuttle in Biorack cassettes while Schneider S-1 cells were exposed to altered gravity forces as produced by clinostat rotation. The effects of both treatments were similar in the different cell types. Fifty percent of cells displayed effects on the microtubule network in both cell lines. Under these experimental conditions mitochondria clustering and morphological alterations of mitochondrial cristae was observed to various degrees after 4 and 48 hours of culture. Jurkat cells underwent cell divisions during exposure to spaceflight but a large number of apoptotic cells was also observed. Similar results were obtained in Schneider S-1 cells cultured under clinostat rotation. Both cell lines displayed mitochondria abnormalities and mitochondria clustering toward one side of the cells which is interpreted to be the result of microtubule disruption and failure of mitochondria transport along microtubules. The number of mitochondria was increased in cells exposed to altered gravity while cristae morphology was severely affected indicating altered mitochondria function. These results show that spaceflight as well as altered gravity produced by clinostat rotation affects microtubule and mitochondria organization and results in increases in apoptosis. Grant numbers: NAG 10-0224, NAG2-985.

Neurobehavioural study of subchronic administration of oxydemeton-methyl (insecticide and acaricide) in rats

Oxydemeton-methyl, an organophosphate insecticide and acaricide produced decrease in the exploratory behaviour and prolongation of barbitone sodium induced hypnosis in rats after intermittent aerosol spray inhalational exposure, for 1/2 hour daily for 7 consecutive days, compared to the saline control group. Further, ED50 +/- SEM value for haloperidol induced catalepsy, CD50 +/- SEM value for pentylenetetrazole induced seizure and CI50 +/- SEM value for electroshock (i.e. the dose of haloperidol, PTZ and intensity of electroshock producing catalepsy or positive seizure response in 50% of rats) were significantly decreased after 7 days exposure to oxydemeton-methyl compared to that of saline control group. The study has established the central nervous system depressant effect, extrapyramidal effect and proconvulsant potential of oxydemeton-methyl which is widely used by the agricultural workers in the form of field spray.

Training medical myocologists in developing countries

Although there has over recent years been a marked rise in the incidence of serious fungal infections, many of which are prevalent in developing countries, few facilities exist for diagnosis and research in medical mycology. In most countries, medical mycology is not taught adequately to medical students and consequently there is little awareness of the importance of fungal infections. Model teaching programmes need to be developed. Practical knowledge of mycoses, their diagnosis and treatment and also basic mycology can be disseminated through well-constructed courses and workshops. Formalized training in mycology research also needs to be introduced. To achieve all of this, expertise and additional resources need to be made available. In this regard, ISHAM can and should help.

In vitro susceptibility pattern of Sporothrix schenckii strains isolated from three centers in India

BACKGROUND & OBJECTIVES

With the availability of more number of antifungal agents in recent years, drugs other than saturated solution of potassium iodide (SSKI) are being increasingly used to treat sporotrichosis. It was therefore considered pertinent to evaluate in vitro antifungal susceptibility pattern of Sporothrix schenckii strains isolated at three centers in India against five commonly used antifungal agents.

METHODS

Agar dilution method was used to evaluate 50 clinical isolates (25 from north, 17 from east and 8 from south India) both in its yeast and mycelial forms against amphotericin-B, 5-fluorocytosine, ketoconazole, fluconazole and itraconazole.

RESULTS

No resistance was observed in the yeast form of S. schenckii against amphotericin B and azoles. However, 54 per cent strains in the yeast form were resistant to 5-fluorocytosine. None of the strains was susceptible to amphotericin B and ketoconazole, 56 and 10 per cent strains in the mycelial form were susceptible to itraconazole and fluconazole respectively. No significant difference was observed in the antifungal susceptibility pattern among the strains isolated from these three regions in India.

INTERPRETATION & CONCLUSION

Clinical isolates of S. schenckii from three regions of India had a more or less uniform antifungal susceptibility pattern. Itraconazole had the best in vitro susceptibility results against the clinical isolates of S. schenckii and has the potential to replace SSKI.

Outbreak of Pichia anomala infection in the pediatric service of a tertiary-care center in Northern India

An outbreak of nosocomial fungemia due to the unusual yeast, Pichia anomala occurred in the pediatric wards of our hospital over a period of 23 months (April 1996 to February 1998). A total of 379 neonates and children (4.2% admissions) were infected. The probable index case was admitted to the pediatric emergency ward, with subsequent transmission to the premature nursery, pediatric intensive care units, and other children wards. Carriage on the hands of health care personnel was likely to be responsible for dissemination of the fungus. The outbreak could only be controlled after a health education campaign to improve hand-washing practices was instituted and after nystatin-fluconazole prophylaxis to all premature neonates and high-risk infants was introduced. In a case-control study, we identified a lower gestational age, a very low birth weight (<1,500 g), and a longer duration of hospital stay as significant risk factors associated with P. anomala fungemia in premature neonates. We conducted a culture prevalence survey of 50 consecutive premature neonates and found that 28% were colonized with P. anomala at a skin or mucosal site on the date of delivery and that 20% of these neonates subsequently developed P. anomala fungemia. We performed multilocus enzyme electrophoresis on 40 P. anomala outbreak isolates (including patient and health care workers' hand isolates), and the results suggested that these isolates were identical. Our study highlights the importance of P. anomala as an emerging nosocomial fungal pathogen.

Ten years' experience in zygomycosis at a tertiary care centre in India

OBJECTIVE

To define the spectrum of zygomycosis due to mucorales in an Indian scenario.

METHODS

One-hundred and twenty-nine patients with zygomycosis due to mucorales diagnosed at the Postgraduate Institute of Medical Education and Research, Chandigarh, India during 1990-99, were retrospectively analysed regarding the sites of involvement, underlying disease, species of fungi isolated and outcome of therapy.

RESULTS

Higher prevalence rate (19.4%) was observed in 1999. Rhino-orbito-cerebral type (44.2%) was the commonest presentation followed by cutaneous (15.5%) and renal (14.0%) involvement. Disseminated zygomycosis was seen in 11.6% patients. Pulmonary and gastrointestinal zygomycosis were diagnosed in 10.1% and 4.7% patients, respectively. Uncontrolled diabetes mellitus (in 50% of cases) was the significant risk factor in rhino-orbito-cerebral type [odds ratio (OR), 9.3; P<or=0.001) and breach of skin (in 40% cases) in cutaneous zygomycosis (OR, 6.9; P<or=0.01). However, a considerable number of 22 (22.9%) patients were apparently healthy hosts in this series. Forty-five patients (34.9%) of this series were diagnosed only at post-mortem. Among 47 patients where culture was attempted, mucorales were isolated from 25 patients with Rhizopus arrhizus (11 patients) and Apophysomyces elegans (eight patients) as the predominant isolates. Adequate therapy could be provided in 33 patients. A combination of aggressive surgical debridement of necrotic tissue and amphotericin-B was found to be the best treatment protocol as 81.3% patients treated with surgical debridement and amphotericin-B were cured, compared with 46.7% patients treated with amphotericin-B alone.

CONCLUSION

The study highlights the importance of increased awareness for early diagnosis of zygomycosis and aggressive management. The large number of cases in apparently healthy hosts and increased isolation of A. elegans in the present series are important characteristics of this disease in India and requires further evaluation.

Binding of a denatured heme protein and ATP to erythroid spectrin

Spectrin is a large, worm-like cytoskeletal protein that is abundant in all cell types. The denatured heme enzyme, horseradish peroxidase showed significant decrease in the reactivation yield, after 30 min of refolding, in presence of increasing concentrations of spectrin from that in the absence. This indicated that spectrin could bind denatured HRP and inhibit their refolding. In presence of 1 mM ATP and 10 mM MgCl(2) the spectrin binding of denatured HRP is abolished. This activity of decreasing the reactivation yield was found to be ATP-dependent and the denatured enzyme after 30 min refolding in the presence of spectrin, pretreated with Mg/ATP, showed about 40% increase in the reactivation yield compared to the same in absence of spectrin. Fluorescence spectroscopic studies indicated binding of ATP to native spectrin showing concentration-dependent quenching of tryptophan fluorescence by ATP. The apparent dissociation constant of binding of ATP to spectrin was estimated to be 1.1 mM. A high affinity binding of spectrin with denatured HRP has been characterized (K(d) = 16 nM). Since these properties are similar to those of established molecular chaperone proteins, these data indicate that spectrin might have a chaperone-like function in erythrocytes.

Effect of cholesterol on interaction of dibucaine with phospholipid vesicles: a fluorescence study

Interaction of the local anesthetic dibucaine with small unilamellar vesicles of dimyristoylphosphatidylcholine (DMPC) and dioleoyl phosphatidylcholine (DOPC) containing different mol percents of cholesterol has been studied by fluorescence spectroscopy. Fluorescence measurements on dibucaine in presence of phospholipid vesicles containing various amounts of cholesterol yielded a pattern of variation of wavelength at emission maximum and steady-state anisotropy which indicated that the microenvironment of dibucaine is more polar and flexible in membranes that contain cholesterol than in membranes without cholesterol. Experiments on quenching of fluorescence from membrane-associated dibucaine by potassium iodide showed a marked increase in quenching efficiency as the cholesterol content of the vesicles was increased, demonstrating increased accessibility of the iodide quenchers to dibucaine in the presence of cholesterol, when compared to that in its absence. Total emission intensity decay profiles of dibucaine yielded two lifetime components of approximately 1 ns and approximately 2.8--3.1 ns with mean relative contributions of approximately 25 and approximately 75%, respectively. The mean lifetime in vesicles was 20--30% smaller than in the aqueous medium and showed a moderate variation with cholesterol content. Fluorescence measurements at two different temperatures in DMPC SUVs, one at 33 degrees C, above the phase transition temperature and another at 25 degrees C, around the main phase transition, indicated two different mode of dibucaine localization. At 25 degrees C dibucaine partitioned differentially in presence and absence of cholesterol. However, at 33 degrees C the apparent partition coefficients remained unaltered indicating differences in the microenvironment of dibucaine in presence and absence of cholesterol in the phospholipid membranes.

Sporotrichosis in Manipur: report of two cases

Two cases of lymphocutaneous sporotrichosis are reported from Imphal. Sporothrix schenekii was isolated from pus from the lesion and identity was confirmed by mycelial to yeast conversion at 37 degrees C and mice pathogenicity test. One patient gave history of injury with bone of fermented fish (Ngari). Both the patients were treated successfully with oral administration of potassium iodide. These two cases are the first authentic cases of sporotrichosis from Manipur.

Centrosome alterations induced by formamide cause abnormal spindle pole formations

The formation of the bipolar mitotic apparatus depends on accurate centrosome organization which is crucial for the separation of the genome during cell division. While it has been shown that mutations and overexpression of centrosome proteins (Brinkley and Goepfert, 1998; Pihan et al., 1998) can cause abnormal spindle pole formation, here we report that damages to centrosome structure caused by the chaotropic agent formamide will cause multipolar mitoses upon recovery from the effect when applied at first cell division in sea urchin eggs. Formamide was used as a chemical tool to manipulate centrosome structure and to investigate the effects on microtubule organization. When 1-1.5 m formamide was administered for 30 min at prometaphase of first cell division, microtubules were disassembled and centrosomes compacted into dense spheres around highly condensed chromatin. Upon recovery from formamide, centrosomes decompacted and attempted to form various mitotic organizations. Normal recovery (and attempts of recovery) to bipolarity was possible in five percent of cells treated with 1-1.5 m formamide for 30 min, but abnormal patterns of spindle formation were observed in all other cells, which included mono- (20%), tri (45%), and multipolar (30%) formations organized by mono-, tri-, and multipolar centrosome clusters. When cells were treated with 1.5 m formamide for 90 min, centrosomes became pulverized and fragmented and only monopolar mitotic formations were observed upon recovery. These results are highly reproducible and reveal that abnormalities in centrosome structure can lead to abnormal mitosis which is not caused by mutation or overexpression of centrosome proteins.

Structural perturbation of proteins in low denaturant concentrations

The presence of very low concentrations of the widely used chemical denaturants, guanidinium chloride and urea, induce changes in the tertiary structure of proteins. We have presented results on such changes in four structurally unrelated proteins to show that such structural perturbations are common irrespective of their origin. Data representative of such structural changes are shown for the monomeric globular proteins such as horseradish peroxidase (HRP) from a plant, human serum albumin (HSA) and prothrombin from ovine blood serum, and for the membrane-associated, worm-like elongated protein, spectrin, from ovine erythrocytes. Structural alterations in these proteins were reflected in quenching studies of tryptophan fluorescence using the widely used quencher acrylamide. Stern-Volmer quenching constants measured in presence of the denaturants, even at concentrations below 100 mM, were higher than those measured in absence of the denaturants. Both steady-state and time-resolved fluorescence emission properties of tryptophan and of the extrinsic probe PRODAN were used for monitoring conformational changes in the proteins in presence of different low concentrations of the denaturants. These results are consistent with earlier studies from our laboratory indicating structural perturbations in proteins at the tertiary level, keeping their native-like secondary structure and their biological activity more or less intact.

Evaluating preceptorship arrangements in a paediatric setting

Preceptorship can be a valuable support mechanism for newly qualified nurses. Both preceptors and preceptees need support to ensure effective preceptorship arrangements. Maintaining effective preceptorship arrangements can be challenging for preceptees, preceptors and the organisation. Further research is required to explore the full potential of preceptorship.