Need for enrichment of lutetium isotope and design of a laser based separator module

Lutetium-177 radio-pharmaceutical has become an important theranostic candidate in cancer treatment. Its availability from bench-to-bed requires strategic implementation of isotope-enrichment, neutron-irradiation and radio-chemical techniques. In this paper, the need for enrichment of lutetium-176 is emphasized by estimating specific activity of lutetium-177 as a function of enrichment percentage for typical neutron flux available at Dhruva reactor, India. A novel Atomic Vapour Laser Isotope Separation (AVLIS) module for lutetium-176 enrichment is designed to meet the above requirement. The paper documents its characteristics and production estimates. The design is carried out after critical assessment and evaluation of available AVLIS-infrastructure in the country. Outline of lutetium-177 enrichment, capable of producing non-carrier-added lutetium is also provided. This work concludes that India has taken a step forward towards self-reliance (Atmanirbhar Bharat) in securing the supply chain of lutetium-177.

Randomized control trial evaluating the use of a shared decision-making aid for older ventral hernia patients in the Geriatric Assessment and Medical Preoperative Screening (GrAMPS) Program

PURPOSE

Shared decision making (SDM) is ideally suited to abdominal wall surgery in older adults given the breadth of decision making required by the hernia surgeon and the impact on quality of life (QOL) by various treatment options. Given the paucity of literature surrounding SDM in hernia patients, the feasibility of a novel, formalized SDM aid/tool was evaluated in a pilot randomized trial.

METHODS

Patients 60 years or older with a diagnosed ventral hernia were prospectively randomized at an academic hernia center. In the experimental arm, a novel SDM tool, based on the SHARE Approach, guided the consultation. Previously validated SDM assessments and patient's hernia knowledge retention was measured.

RESULTS

Eighteen (18) patients were randomized (9 control and 9 experimental). Cohorts were well matched in age (p = 0.51), comorbidities (Charlson Comorbidity Score: p = 0.43) and frailty (mFI-11: p = 0.19; Risk Analysis Index: p = 0.33). Consultation time was 11 min longer in the experimental cohort (p < 0.01). There was a trend towards better Decisional Conflict Scores in the experimental group (p = 0.25) and the experimental cohort had improved post-visit retained hernia knowledge (p < 0.01). All patients in the experimental arm (100%) enjoyed working through the SDM aid/tool and felt it was a worthwhile exercise.

CONCLUSION

Incorporating a formalized SDM tool into a busy hernia surgical practice is feasible and well received by patients. In addition, early results suggest it improves retention of basic hernia knowledge and may reduce patient's decisional conflict. Next steps include condensing the SDM tool to enhance efficiency within the clinic and beginning a large, randomized control trial.

Artificial intelligence in cancer diagnostics and therapy: current perspectives

Artificial intelligence (AI) has found its way into every sphere of human life including the field of medicine. Detection of cancer might be AI's most altruistic and convoluted challenge to date in the field of medicine. Embedding AI into various aspects of cancer diagnostics would be of immense use in dealing with the tedious, repetitive, time-consuming job of lesion detection, remove opportunities for human error, and cut costs and time. This would be of great value in cancer screening programs. By using AI algorithms, data from digital images from radiology and pathology that are imperceptible to the human eye can be identified (radiomics and pathomics). Correlating radiomics and pathomics with clinico-demographic-therapy-morbidity-mortality profiles will lead to a greater understanding of cancers. Specific imaging phenotypes have been found to be associated with specific gene-determined molecular pathways involved in cancer pathogenesis (radiogenomics). All these developments would not only help to personalize oncologic practice but also lead to the development of new imaging biomarkers. AI algorithms in oncoimaging and oncopathology will broadly have the following uses: cancer screening (detection of lesions), characterization and grading of tumors, and clinical decision-making and prognostication. However, AI cannot be a foolproof panacea nor can it supplant the role of humans. It can however be a powerful and useful complement to human insights and deeper understanding. Multiple issues like standardization, validity, ethics, privacy, finances, legal liability, training, accreditation, etc., need to be overcome before the vast potential of AI in diagnostic oncology can be fully harnessed.

Phenomenological Constraints on the Transport Properties of QCD Matter with Data-Driven Model Averaging

Using combined data from the Relativistic Heavy Ion and Large Hadron Colliders, we constrain the shear and bulk viscosities of quark-gluon plasma (QGP) at temperatures of ∼150-350  MeV. We use Bayesian inference to translate experimental and theoretical uncertainties into probabilistic constraints for the viscosities. With Bayesian model averaging we propagate an estimate of the model uncertainty generated by the transition from hydrodynamics to hadron transport in the plasma's final evolution stage, providing the most reliable phenomenological constraints to date on the QGP viscosities.

Recurrent aplastic anemia with donor-type aplasia: A rare occurrence in the Indian subcontinent

Donor-type aplasia (DTA) is a condition where an individual continues to be aplastic even after a successful engraftment of a hematopoeitic stem cell transplant with a majority of donor type cells in the bone marrow. This entity has been seen with varying frequency around the world, especially in Southeast Asia. However, its incidence in the Indian subcontinent remains fairly low. Here is a case of a 17-year-old child with DTA who had a 89% population of donor cells after a successful transplant and presented with recurrent severe aplastic anemia later. The patient eventually succumbed to his condition before a second transplant could be performed. The awareness about the seriousness of this relatively rare condition, therefore, needs to be emphasized.

An autopsy series of an oft-missed ante-mortem diagnosis: hemophagocytic lymphohistiocytosis

Hemophagocytic lymphohistiocytosis (HLH) is a rare and potentially fatal syndrome resulting from a hyperactivated immune system. Diverse patient profiles and clinical presentations often result in misdiagnosis. This article describes the varied clinical presentations and autopsy findings in three patients with this entity. The etiopathogenesis of HLH, its disparate and confounding clinical features, the diagnostic criteria, and management principles are also briefly reviewed.

Uncommon affliction of a common disease - primary tuberculosis of thyroid gland

Tuberculosis (TB) continues to be a major public health problem in India. With an annual incidence rate of 2.8 million new cases, India accounts for a quarter of the global TB burden. Primary thyroid TB still remains a rare entity even in this era of global TB pandemic. Here we discuss a case of primary thyroid TB in a 22-year-old immunocompetent male patient presenting with a thyroid swelling followed by non-healing sinus tract after fine-needle aspiration cytology (FNAC) procedure. TB is a known common cause for development of chronic sinuses and ulcers. However, the primary involvement of thyroid gland along with formation of non-healing sinus tract post FNAC make it a most unusual case posing a diagnostic challenge to the unsuspecting physician.

Kimura disease with nephrotic syndrome in a child- A rare association

Lymphadenopathy along with various systemic manifestations is commonly encountered in pediatric patients, tuberculosis being the commonest etiology. Occasional patients may present a diagnostic conundrum. Here, the authors report an unusual manifestation of Kimura disease (KD) presenting as nephrotic syndrome associated with mesenteric lymphadenitis in an 11-year-old male child. KD is a chronic inflammatory disorder of unknown etiology. It typically affects young adult males in the age range of 27-40 years and usually presents as painless itchy nodular masses in the head and neck region. The involvement of mesenteric lymph nodes along with a very young age of presentation makes it a rare case, posing a diagnostic challenge for the unsuspecting physician.

Double-positive in triple-negative? How significant is basal cytokeratin expression in breast cancer?

Background

Basal-like breast cancer has an unfavorable prognosis. Immunohistochemically, they are predominantly estrogen receptor (ER), progesterone receptor (PR) and CerbB2 receptor (HER2)-negative, show expression of Cytokeratins (CKs) 5/6, CK14, CK 17 and P-cadherin and are associated with germline BRCA1 mutations. Immunohistochemistry (IHC) is an easily available and relatively inexpensive technique that can detect this cancer subtype, and patients can benefit from aggressive management protocols. The aim of this study was to evaluate the expression of CK 5/6 and CK14 in breast cancer and its correlation with age, tumor grade, tumor size, histomorphological pattern, nodal status, ER, PR, HER2/neu, and Ki-67 index.

Methods

Fifty treatment-naїve patients of breast carcinoma who underwent surgery constituted the study group. No core cut biopsy specimens were considered. Histopathological examination along with IHC was performed for CK5/6, CK14, ER, PR, HER2/neu, and Ki-67. Comparison between the expression of CK5/6 and CK14 with age, tumor size, tumor grade, histological subtype, nodal status, ER, PR, HER2/neu, and Ki-67 expression was performed using SPSS 20 version software.

Results

Twenty-six percent of cases showed expression of CK5/6 and CK14. CK5/6 and CK14 expression correlated strongly with ER/PR negativity, young age, and Ki-67 proliferative index greater than 15%. No significant association with HER2/neu negativity was demonstrated. Contrasting results were obtained between CK5/6 and CK14 expression with respect to tumor grade and lymph node status.

Conclusion

IHC can be used to identify patients with basal phenotype breast cancer with good sensitivity and specificity, and such patients can benefit from aggressive management.

Taming Alzheimer's disease: New perspectives, newer horizons

Alzheimer's disease (AD) is the leading cause of dementia. However, current therapies do not prevent progression of the disease. New research into the pathogenesis of the disease has brought about a greater understanding of the "amyloid cascade" and associated receptor abnormalities, the role of genetic factors, and revealed that the disease process commences 10 to 20 years prior to the appearance of clinical signs. This greater understanding of the disease has prompted development of novel disease-modifying therapies (DMTs) which may prevent onset or delay progression of the disease. Using genetic biomarkers like apolipoprotein E (ApoE) ε4, biochemical biomarkers like cerebrospinal fluid (CSF) amyloid and tau proteins, and imaging biomarkers like magnetic resonance imaging (MRI) and positron emission tomography (PET), it is now possible to detect preclinical AD and also monitor its progression in asymptomatic people. These biomarkers can be used in the selection of high-risk populations for clinical trials and also to monitor the efficacy and side-effects of DMT. To validate and standardize these biomarkers and select the most reliable, repeatable, easily available, cost-effective and complementary options is the challenge ahead.

The use of Vicryl mesh in a porcine model to assess its safety as an adjunct to posterior fascial closure during retromuscular mesh placement

BACKGROUND

Posterior component separation has become a common approach to complex abdominal wall reconstructions. This technique includes creation of an extraperitoneal retromuscular space for subsequent large synthetic mesh reinforcement. In certain cases, when complete restoration of "posterior" layer is precluded by significant tissue loss/damage, one proposed strategy is to replace the posterior fascia with an absorbable synthetic polyglactin (Vicryl) mesh. However, the safety of this strategy to prevent mesh-related visceral complication is unknown. Herein, we aimed to characterize mesh-viscera adhesion profiles and host tissue response of synthetic mesh either exposed directly to the viscera, or protected with Vicryl mesh.

METHODS

Using adult Yorkshire pigs, 5 × 5 cm pieces of mesh were secured to the intact peritoneum in each of the four quadrants (n = 6 pigs, 24 mesh samples). The study groups were Vicryl (V), Marlex (M), Softmesh (S), Marlex + Vicryl construct (MV), Softmesh + Vicryl construct (SV). The self-made composite meshes were then implanted with the Vicryl side facing the exposed viscera. The pigs were survived for 60 days. At necropsy, grossly, the extent and tenacity of visceral adhesions were evaluated using established scales. Histologically, all specimens for fibrous encapsulation on the visceral surface of the mesh were reviewed by an experienced pathologist blind to meshes used.

RESULTS

At necropsy, all Vicryl meshes were completely resorbed. The mean adhesion and tenacity scores for M and MV were 1.8 and 1.1 (P > 0.05), 2.0 and 1.5 (P > 0.05), respectively; while the mean adhesion extent scores and tenacity scores for S and SV were 2.0 and 1.2 (P > 0.05), 2.0 and 1.7 (P > 0.05). No significant difference in adhesion extent and tenacity was observed between Synthetic and Vicryl composite mesh groups. Histologically, Marlex + Vicryl mesh and Softmesh + Vicryl mesh constructs had thicker fibrous capsules than the corresponding unprotected Marlex and Soft mesh implants. Furthermore, visceral adhesions in the composite groups were noted to be to the fibrous capsule and not synthetic mesh itself.

CONCLUSION

Utilization of the absorbable polyglactin (Vicryl) mesh as a separating layer between a synthetic mesh and intestines, did not reduce adhesions across various mesh types and composites. Histologically, however, a thick fibrous capsule replaced the Vicryl mesh and may be an important layer to prevent intestinal erosion into retromuscular synthetic meshes.

Note: Design principles of a linear array multi-channel effusive metal-vapor atom source

Atomic beams can easily be produced by allowing atoms to effuse through a channel. In an earlier investigation [A. Majumder et al., Vacuum 83, 989 (2009)], we had designed, fabricated, and characterized an effusive metal-vapor source using collinear-array of multi-channel. In this note, we describe the theoretical basis of designing the source. Atom density in atomic beam has been estimated using a set of analytical expressions for long-channel operated in transparent mode. Parametric studies on aspect ratio of channel, inter-channel separation, beam width, and vertical distance from the source are carried out. They are useful in providing physical picture and optimizing design parameters.

Peripheral neuropathy in diabetes

Peripheral neuropathy is common complication of diabetes. The prevalence of peripheral neuropathy among diabetic patients on the basis of loss of vibration sensation had been studied. Detailed clinical history of each patient including age, gender, duration of diabetes, foot ulcer and biothesiometry was recorded in 211 diabetic patients between 20 and 80 years of age. It was observed that all patients under 30 years age (n = 8) felt vibration below 15 volts (no risk zone); 77% (24 out of 31) of the patients in the age group of 30-39 years were in the no risk zone, and 23% (n = 7) had mild peripheral neuropathy. Sixty per cent of the patients between 40 and 50 years (n = 44) were in the no risk zone, while 32% (n = 24) had mild peripheral neuropathy, 5% (n = 4) had moderate neuropathy and 3% (n = 2) had severe peripheral neuropathy. Amongst patients above 50 years of age, 31% (n = 31) were in no risk zone, 34% (n = 34) had mild peripheral neuropathy, 22% (n = 20) had moderate peripheral neuropathy and 13% (n = 13) had severe peripheral neuropathy. Of the patients with diabetes for less than 5 years, 58% had no neuropathy, and only 3% had severe neuropathy. Of the patients with diabetes for 5 to 15 years, 50% had no neuropathy, 30% had mild, and 10% had severe peripheral neuropathy. When patients with diabetes for over 15 years were studied, only 6% had no neuropathy and 19% had severe peripheral neuropathy. The study re-establishes that the severity of peripheral neuropathy increases with age and vibration perception decreses progressively with increased duration of diabetes. Vibration perception threshold testing helps to identify the high risk subjects who require special counselling and education to protect their feet.

Suppression of the high-p(T) charged-hadron R(AA) at the LHC

We present a parameter-free postdiction of the high-p(T) charged-hadron nuclear modification factor (R(AA)) in two centralities, measured by the CMS Collaboration in Pb-Pb collisions at the LHC. The evolution of the bulk medium is modeled using viscous fluid dynamics, with parameters adjusted to describe the soft hadron yields and elliptic flow. Assuming the dominance of radiative energy loss, we compute the medium modification of the R(AA) using a perturbative QCD-based formalism, the higher twist scheme. The transverse momentum diffusion coefficient q[over ^] is assumed to scale with the entropy density and is normalized by fitting the R(AA) in the most central Au-Au collisions at the Relativistic Heavy-Ion Collider. This setup is validated in noncentral Au-Au collisions at the Relativistic Heavy-Ion Collider and then extrapolated to Pb-Pb collisions at the LHC, keeping the relation between q[over ^] and entropy density unchanged. We obtain a satisfactory description of the CMS R(AA) over the p(T) range from 10 to 100 GeV.

Primary squamous cell carcinoma of kidney - a case report of unusual local recurrence with literature review

Primary squamous cell carcinoma of the kidney is a rare clinical entity. Primary squamous cell carcinoma is more frequently reported in urinary bladder and male urethra than in kidney. Primary renal squamous cell carcinoma (RSCC) accounts for less than 5% of urothelial tumours in urinary system. Very few cases of primary squamous cell carcinoma of kidney have been reported in the world literature. Only forty-six cases over forty four years had been reported from Mayo Clinic. These neoplasms are highly aggressive and locally advanced or metastatic at the time of presentation. Here we report such a case of primary squamous cell  carcinoma of kidney in a 50-year-old lady at a locally recurrent stage with fistulous tract formation.  Palliative radiotherapy came out to be a good clinical modality even in locally recurrent stage in this patient. DOI: http://dx.doi.org/10.3329/bjms.v11i3.11734 Bangladesh Journal of Medical Science Vol. 11 No. 03 July’12

Is immediate postoperative CA15.3 assay a predictive marker of early postoperative recurrence of carcinoma breast?

Breast cancer is still an enigma. Systemic metastasis is an important prognostic factor. Tumour marker can predict occult systemic metastasis. To evaluate the immediate postoperative CA15.3 as predictor of early recurrence, a study was carried out in 48 patients of carcinoma breast in whom immediate postoperative marker level was done. In follow-up, recurrence was noted and relation with tumour size and stage done. Null hypothesis and 't' test were used for analysis. Relation of tumour size with marker is weak but strong relation exists between tumour stage with marker and recurrence with marker. CA15.3 predicts tumour load, can also predict occult residual/occult metastatic disease better than other prognostic markers which only predict tumour behaviour.

Multiphoton ionization and Coulomb explosion of C2H5Br clusters: a mass spectrometric and charge density study

Using time-of-flight mass spectrometry (TOFMS), laser-induced photochemistry of ethyl bromide clusters has been investigated at three different wavelengths (viz. 266, 355 and 532  nm) utilizing nanosecond laser pulses of ~5 × 10(9)  W/cm(2). An interesting finding of the present work is the observation of multiply charged atomic ions of carbon and bromine at 355 and 532  nm, arising from the Coulomb explosion of (C(2)H(5)Br)(n) clusters. At 266  nm, however, the (C(2)H(5)Br)(n) clusters were found to exhibit the usual multiphoton dissociation/ionization behaviour. The TOFMS studies are complemented by measuring the total charge density of the ionized volume at 266, 355 and 532  nm, using the parallel plate method, and the charge densities were found to be ~2 × 10(9), 6 × 10(9) and 2 × 10(11)  charges/cm(3), respectively. The significantly higher charge density and the presence of energetic, multiply charged atomic ions at 532  nm are explained by the higher ponderomotive energy of the 532  nm photon, coupled with the Coulomb stability of the residual multiply charged ethyl bromide clusters generated upon laser irradiation, due to their larger effective cluster size at 532  nm than at 355 and 266  nm.

Energy and momentum deposited into a QCD medium by a jet shower

For a hard parton moving through a dense QCD medium, we compute self-consistently the energy loss and the fraction deposited into the medium due to showering and rescattering of the shower, assuming weak coupling between probe and medium. The same transport coefficients thus determine both the energy loss and its deposition into the medium. This allows a parameter free calculation of the latter once the former are computed or measured. We compute them for a weakly interacting medium. Assuming a short thermalization time for the deposited energy, we determine the medium's hydrodynamical response and obtain a conical pattern that is strongly enhanced by showering.

Use of multiwavelength emission from hollow cathode lamp for measurement of state resolved atom density of metal vapor produced by electron beam evaporation

State resolved atom population of metal vapor having low-lying metastable states departs from equilibrium value. It needs to be experimentally investigated. This paper reports the use of hollow cathode lamp based atomic absorption spectroscopy technique to measure online the state resolved atom density (ground and metastable) of metal vapor in an atomic beam produced by a high power electron gun. In particular, the advantage of availability of multiwavelength emission in hollow cathode lamp is used to determine the atom density in different states. Here, several transitions pertaining to a given state have also been invoked to obtain the mean value of atom density thereby providing an opportunity for in situ averaging. It is observed that at higher source temperatures the atoms from metastable state relax to the ground state. This is ascribed to competing processes of atom-atom and electron-atom collisions. The formation of collision induced virtual source is inferred from measurement of atom density distribution profile along the width of the atomic beam. The total line-of-sight average atom density measured by absorption technique using hollow cathode lamp is compared to that measured by atomic vapor deposition method. The presence of collisions is further supported by determination of beaming exponent by numerically fitting the data.

Modified dihadron fragmentation functions in hot and nuclear matter

Medium modification of dihadron fragmentation functions due to gluon bremsstrahlung induced by multiple partonic scattering is studied in both deep-inelastic scattering (DIS) off large nuclei and high-energy heavy-ion collisions within the same framework of twist expansion. The modification for dihadrons is found to closely follow that for single hadrons, leading to a weak nuclear suppression of their ratios in DIS experiments. A mild enhancement of the near-side correlation of two high transverse momentum hadrons with increasing centrality is found in heavy-ion collisions due to trigger bias and the rise in parton energy loss with centrality. Successful comparisons between theory and experiment for multihadron observables in both confining and deconfined media offer comprehensive evidence for partonic energy loss as the mechanism of jet modification in dense matter.

Longitudinal broadening of quenched jets in turbulent color fields

The nearside distribution of particles at intermediate transverse momentum, associated with a high momentum trigger hadron produced in a high energy heavy-ion collision, is broadened in rapidity compared with the jet cone. This broadened distribution is thought to contain the energy lost by the progenitor parton of the trigger hadron. We show that the broadening can be explained as the final-state deflection of the gluons radiated from the hard parton inside the medium by soft, transversely oriented, turbulent color fields that arise in the presence of plasma instabilities. The magnitude of the effect is found to grow with medium size and density and diminish with increasing energy of the associated hadron.

Functional characterization and mutation analysis of family 11, Carbohydrate-Binding Module (CtCBM11) of cellulosomal bifunctional cellulase from Clostridium thermocellum

The non-catalytic, family 11 carbohydrate binding module (CtCBM11) belonging to a bifunctional cellulosomal cellulase from Clostridium thermocellum was hyper-expressed in E. coli and functionally characterized. Affinity electrophoresis of CtCBM11 on nondenaturing PAGE containing cellulosic polysaccharides showed binding with β-glucan, lichenan, hydroxyethyl cellulose and carboxymethyl cellulose. In order to elucidate the involvement of conserved aromatic residues Tyr 22, Trp 65 and Tyr 129 in the polysaccharide binding, site-directed mutagenesis was carried out and the residues were changed to alanine. The results of affinity electrophoresis and binding adsorption isotherms showed that of the three mutants Y22A, W65A and Y129A of CtCBM11, two mutants Y22A and Y129A showed no or reduced binding affinity with polysaccharides. These results showed that tyrosine residue 22 and 129 are involved in the polysaccharide binding. These residues are present in the putative binding cleft and play a critical role in the recognition of all the ligands recognized by the protein.

Cherenkov radiation from jets in heavy-ion collisions

The possibility of Cherenkov-like gluon bremsstrahlung in dense matter is studied. We point out that the occurrence of Cherenkov radiation in dense matter is sensitive to the presence of partonic bound states. This is illustrated by a calculation of the dispersion relation of a massless particle in a simple model in which it couples to two different massive resonance states. We further argue that detailed spectroscopy of jet correlations can directly probe the index of refraction of this matter, which in turn will provide information about the mass scale of these partonic bound states.

Baryon-strangeness correlations: a diagnostic of strongly interacting matter

The correlation between baryon number and strangeness elucidates the nature of strongly interacting matter, such as that formed transiently in high-energy nuclear collisions. This diagnostic can be extracted theoretically from lattice QCD calculations and experimentally from event-by-event fluctuations. The analysis of present lattice results above the critical temperature severely limits the presence of qq bound states, thus supporting a picture of independent (quasi)quarks.

Fenofibrate-induced myopathy

Fenofibrate induced myopathy is a rare adverse event. We present a case of muscle pain and quadriparesis following administration of 200mg of fenofibrate for 35 days. Patient gradually improved after stopping the drug. As per our knowledge, this is probably the first case report of fenofibrate induced myopathy from India.

Effect of osmolytes and chaperone-like action of P-protein on folding of nucleocapsid protein of Chandipura virus

Amino acid sequences of nucleocapsid proteins are mostly conserved among different rhabdoviruses. The protein plays a common functional role in different RNA viruses by enwrapping the viral genomic RNA in an RNase-resistant form. Upon expression of the nucleocapsid protein alone in COS cells and in bacteria, it forms large insoluble aggregates. In this work, we have reported for the first time the full-length cloning of the N gene of Chandipura virus and its expression in Escherichia coli in a soluble monomeric form and purification using nonionic detergents. The biological activity of the soluble recombinant protein has been tested, and it was found to possess efficient RNA-binding ability. The state of aggregation of the recombinant protein was monitored using light scattering. In the absence of nonionic detergents, it formed large aggregates. Aggregation was significantly reduced in the presence of osmolytes such as d-sorbitol. Aggregate formation was suppressed in the presence of another viral product, phosphoprotein P, in a chaperone-like manner. Both the osmolyte and phosphoprotein P also suppressed aggregation to a great extent during refolding from a guanidine hydrochloride-denatured form. The function of the phosphoprotein and osmolyte appears to be synergistic to keep the N-protein in a soluble biologically competent form in virus-infected cells.

A 72-base pair AT-rich DNA sequence element functions as a bacterial gene silencer

We have previously demonstrated that sequential activation of the bacterial ilvIH-leuO-leuABCD gene cluster involves a promoter-relay mechanism. In the current study, we show that the final activation of the leuABCD operon is through a transcriptional derepression mechanism. The leuABCD operon is transcriptionally repressed by the presence of a 318-base pair AT-rich upstream element. LeuO is required for derepressing the repressed leuABCD operon. Deletion analysis of the repressive effect of the 318-bp element has led to the identification of a 72-bp AT-rich (78% A+T) DNA sequence element, AT4, which is capable of silencing a number of unrelated promoters in addition to the leuABCD promoter. AT4-mediated gene silencing is orientation-independent and occurs within a distance of 300 base pairs. Furthermore, an increased gene-silencing effect was observed with a tandemly repeated AT4 dimer. The possible mechanism of AT4-mediated gene silencing in bacteria is discussed.

LeuO expression in response to starvation for branched-chain amino acids

The recently identified role of LeuO in the regulation of transcription has prompted us to search for the specific function(s) of LeuO in bacterial physiology. The cryptic nature of expression of leuO has previously limited such analysis. A conditional leuO expression was found when bacteria enter stationary phase and was shown to be guanosine 3',5'-bispyrophosphate-dependent. Multiple physiological events, including the stringent response, are induced upon the increase of the bacterial stress signal, guanosine 3',5'-bispyrophosphate. In this study, we tested whether LeuO was directly involved in the bacterial stringent response. LeuO was shown to be indispensable for growth resumption following a 2-h growth arrest caused by starvation for branched-chain amino acids in an E. coli K-12 relA1 strain. This result supports a functional role for LeuO in the bacterial stringent response.

ppGpp-dependent leuO expression in bacteria under stress

Despite the known potential transcription regulatory role of leuO gene product, LeuO, the condition when leuO expresses during bacterial growth cycle remains unclear. Mechanistically, leuO expression was shown to be part of promoter relay mechanism, however, the factor(s) responsible for the regulation of leuO expression is not known. Combining Northern and Western results, we demonstrate in the present communication that leuO expression is normally low and enhanced when bacteria are in transition from exponential growth to stationary phase. The stationary phase-associated leuO expression is ppGpp dependent and rpoS (sigma(s) factor) independent.

Antibacterial activity of Litsea glutinosa bark

The methanol extract of the bark of Litsea glutinosa showed antibacterial activity, comparable to chloramphenicol, against all 16 tested microorganisms.

Anomalies in hepatobiliary excretion of technetium-99m-MAG3 preparations

Technetium-99m-MAG3 is accepted as a renal tubular function agent. However, sporadic liver and gall bladder visualisation during its clinical use is clearly a disadvantage. HPLC-purified 99mTc-MAG3 samples exhibited appreciable hepatobiliary uptake (7%), and an elevated level of such uptake was observed in unpurified kit preparations, which was stated to be associated with the excretory property of the radiolabeled kit impurities. To verify this we attempted to quantitate the hepatobiliary uptake of the kit preparations with that of its radiolabeled components. The contribution of each component toward hepatobiliary uptake of the sample was calculated from their abundance in the chelate mixture and the individual biodistribution of the isolated components. However, the anticipated hepatobiliary uptake of different preparations of 99mTc-MAG3 calculated in this way was always lower than that of the experimental value determined directly. Further work is needed to explain the anomaly.