Combinatorial Ligand Assisted Simultaneous Control of Axial and Central Chirality in Highly Stereoselective C-H Allylation

The significance of stereoselective C-H bond functionalization thrives on its direct application potential to pharmaceuticals or complex chiral molecule synthesis. Complication arises when there are multiple stereogenic elements such as a center and an axis of chirality to control. Over the years cooperative assistance of multiple chiral ligands has been applied to control only chiral centers. In this work, we harness the essence of cooperative ligand approach to control two different stereogenic elements in the same molecule by atroposelective allylation to synthesize axially chiral biaryls from its racemic precursor. The crucial roles played by chiral phosphoric acid and chiral amino acid ligand in concert helped us to obtain one major stereoisomer out of four distinct possibilities.

Simplifying the Synthesis of Nonproteinogenic Amino Acids via Palladium-Catalyzed δ-Methyl C-H Olefination of Aliphatic Amines and Amino Acids

Transition metal-catalyzed directing group assisted C-H functionalizations provide a straightforward access to a wide variety of nonproteinogenic amino acids. While altering the side chain of an existing natural amino acids is one way, introducing a functional group to an aliphatic amine to synthesize versatile unnatural amino acids is another exciting avenue. In this work, we explore both the possibilities by the palladium-catalyzed δ-C(sp³)-H olefination of aliphatic amines and amino acids. A diverse substrate scope including sequential difunctionalizations followed by post synthetic transformations were achieved to understand the applicability of the current protocol. An in-depth mechanistic study was carried out to learn the mode of the reaction pathway.

Expanding chemical space by para-C-H arylation of arenes

Biaryl scaffolds are privileged templates used in the discovery and design of therapeutics with high affinity and specificity for a broad range of protein targets. Biaryls are found in the structures of therapeutics, including antibiotics, anti-inflammatory, analgesic, neurological and antihypertensive drugs. However, existing synthetic routes to biphenyls rely on traditional coupling approaches that require both arenes to be prefunctionalized with halides or pseudohalides with the desired regiochemistry. Therefore, the coupling of drug fragments may be challenging via conventional approaches. As an attractive alternative, directed C−H activation has the potential to be a versatile tool to form para-substituted biphenyl motifs selectively. However, existing C–H arylation protocols are not suitable for drug entities as they are hindered by catalyst deactivation by polar and delicate functionalities present alongside the instability of macrocyclic intermediates required for para-C−H activation. To address this challenge, we have developed a robust catalytic system that displays unique efficacy towards para-arylation of highly functionalized substrates such as drug entities, giving access to structurally diversified biaryl scaffolds. This diversification process provides access to an expanded chemical space for further exploration in drug discovery. Further, the applicability of the transformation is realized through the synthesis of drug molecules bearing a biphenyl fragment. Computational and experimental mechanistic studies further provide insight into the catalytic cycle operative in this versatile C−H arylation protocol.

Biaryls are privileged structural motif used in the discovery and design of therapeutics with high affinity and specificity for a broad range of protein targets. Herein, the authors develop a robust strategy for para-C–H arylation of arenes with a range of (het)aryl iodides, including bioactive molecules.

Pd-catalysed C-H functionalisation of free carboxylic acids

Pd-catalysed C-H functionalisation of free carboxylic acids has drawn significant attention over the last few years due to the predominance of carboxylic acid moieties in pharmaceuticals and agrochemicals. But their coordinating ability was overlooked and masked by exogenous directing groups for a long time. Even other crucial roles of carboxylic acids as additives and steric inducers that directly influence the mode of a reaction have been widely neglected. This review aims to embrace all of the diverse aspects of carboxylic acids except additive and steric effects by concisely and systematically describing their versatile role in Pd-catalysed proximal and distal C-H activation reactions that could be implemented in the pharmaceutical and agrochemical industries. In addition, the mechanistic perspectives along with several recent strategies developed in the last few years discussed here will serve as educational resources for future research.

Hexafluoroisopropanol: the magical solvent for Pd-catalyzed C-H activation

Among numerous solvents available for chemical transformations, 1,1,1,3,3,3-hexafluoro-2-propanol (popularly known as HFIP) has attracted enough attention of the scientific community in recent years. Several unique features of HFIP compared to its non-fluoro analogue isopropanol have helped this solvent to make a difference in various subdomains of organic chemistry. One such area is transition metal-catalyzed C-H bond functionalization reactions. While, on one side, HFIP is emerging as a green and sustainable deep eutectic solvent (DES), on the other side, a major proportion of Pd-catalyzed C-H functionalization is heavily relying on this solvent. In particular, for distal aromatic C-H functionalizations, the exceptional impact of HFIP to elevate the yield and selectivity has made this solvent irreplaceable. Recent research studies have also highlighted the H-bond-donating ability of HFIP to enhance the chiral induction in Pd-catalyzed atroposelective C-H activation. This perspective aims to portray different shades of HFIP as a magical solvent in Pd-catalyzed C-H functionalization reactions.

Para-Selective Cyanation of Arenes by H-Bonded Template

The significance of site selective functionalization stands upon the superior selectivity, easy synthesis and diverse product utility. In this work, we demonstrate the para-selective introduction of versatile nitrile moiety, enabled by a detachable and reusable H-bonded auxiliary. The methodology holds its efficiency irrespective of substrate electronic bias. The conspicuous shift in the step energetics was probed by both experimental and computational mechanistic tools, which heralds the inception of para-deuteration. The synthetic impact of the methodology was highlighted with reusability of directing group and post synthetic modifications.

Role of hexafluoroisopropanol in C–H activation

HFIP has developed immense importance in the C–H functionalization methodology. Both the reactivity and selectivity have been vastly improved using HFIP whose H-bonding to the substrate facilitates and accelerates C–H activation. This review summarizes the chronological development of the evolution of HFIP in C–H activation along with important mechanistic details.

Correction: Role of hexafluoroisopropanol in C–H activation

Correction for ‘Role of hexafluoroisopropanol in C–H activation’ by Soumya Kumar Sinha et al., React. Chem. Eng., 2019, 4, 244–253.

H-bonded reusable template assisted para-selective ketonisation using soft electrophilic vinyl ethers

In nature, enzymatic pathways generate C_aryl−C(O) bonds in a site-selective fashion. Synthetically, C_aryl−C(O) bonds are synthesised in organometallic reactions using prefunctionalized substrate materials. Electrophilic routes are largely limited to electron-rich systems, non-polar medium, and multiple product formations with a limited scope of general application. Herein we disclose a directed para-selective ketonisation technique of arenes, overriding electronic bias and structural congestion, in the presence of a polar protic solvent. The concept of hard–soft interaction along with in situ activation techniques is utilised to suppress the competitive routes. Mechanistic pathways are investigated both experimentally and computationally to establish the hypothesis. Synthetic utility of the protocol is highlighted in formal synthesis of drugs, drug cores, and bioactive molecules.

Electrophilic acylation of arenes is largely limited to electron rich systems, non-polar medium and often displays moderate selectivity. Here, the authors show a directed para-selective ketonisation of arenes, overriding electronic bias and structural congestion, and apply it to the synthesis of bioactive compounds.

Combining transition metals and transient directing groups for C–H functionalizations

In the domain of synthetic chemistry, C–H bond activation has always remained in the spotlight for researchers over the last few decades. Although different strategies have been employed to chemically trigger unactivated C–H bonds, transition metal catalyzed directing group (DG) aided C–H bond activation is the most explored pathway of all because of its ability to perform diverse site selective functional metamorphosis. Despite its popularity, tedious synthetic methodology requiring additional steps for the installation and removal of DGs from the target substrate diminishes its efficacy. However, replacement of directing groups by transient directing groups (tDGs) reduces the hurdle to a greater extent without compromising the product yield and selectivity. In this report we have depicted the intense journey of transient directing groups with three (Rh, Ru, and Pd) prevalent second row transition metals.

This review is about the momentous evolution of transient directing group assisted C–H functionalizations promoted by three major second row transition metals.

Co-existence of psoriasis and melanoma in a large urban academic centre population: a cross-sectional retrospective study

BACKGROUND

Psoriasis has been linked to increased malignancy risk, particularly lympho-haematopoietic and non-melanoma skin cancers; however, its association with cutaneous melanoma remains unclear.

OBJECTIVE

The aim of this study was to determine if there is an association between melanoma and psoriasis in a large, urban academic population through an electronic medical record database.

METHODS

We searched our institution's electronic medical record database (EDW-Electronic Data Warehouse) from 1/2001 to 11/2013. Subjects were identified by ICD-9 codes. Melanoma diagnosis was included only if documented at least 1 month after the psoriasis diagnosis was documented. Odds ratio (OR) was obtained for association between cutaneous melanoma and psoriasis. The OR was then adjusted for phototherapy and age. To minimize detection bias, we also obtained the OR for association between cutaneous melanoma and atopic dermatitis.

RESULTS

We identified 10 947 patients with psoriasis, 64 of whom had a subsequent diagnosis of cutaneous melanoma. We detected a significant association between melanoma and psoriasis (OR = 1.77; 95%CI 1.38-2.26; P < 0.0001; total n = 1 525 252). After adjusting for phototherapy and age, a statistically significant association between melanoma and psoriasis remained detectable (OR = 1.9; 95%CI 1.55-2.55; P < 0.0001 and OR = 1.64; 95%CI 1.17-2.26; P = 0.003 respectively). The OR for melanoma with atopic dermatitis in the same patient database showed a statistically significant inverse association between the two diseases (OR = 0.35; 95%CI 0.16-0.73; P = 0.005).

CONCLUSION

Our findings show a statistically significant association between psoriasis and melanoma. After adjusting the OR for phototherapy and age, a statistically significant association remained. Further investigations exploring these associations are warranted in order to establish the relative risk for melanoma in psoriasis patients.

Umbilical Myiasis in a Newborn: a case report

Myiasis is an infection of live mammalian tissue by the larval forms of dipteran flies, usually infects domestic and wild animal but human may be affected sometimes. Although adult cases have been reported, neonatal myiasis is a rare condition. Umbilical myiasis is very rare in newborns with few reported cases in the literature. In this article we are reporting an eight day old female neonate from urban slum area in West Bengal (India) presented with umbilical myiasis and omphalitis. She was infected with Chrysomya spp. larvae, was clinically well. Journal of College of Medical Sciences-Nepal, 2012, Vol-8, No-4, 42-45 DOI: http://dx.doi.org/10.3126/jcmsn.v8i4.8700  

A note on two-sample tests for comparing intra-individual genetic sequence diversity between populations

Gilbert, Rossini, and Shankarappa (2005, Biometrics 61, 106-117) present four U-statistic based tests to compare genetic diversity between different samples. The proposed tests improved upon previously used methods by accounting for the correlations in the data. We find, however, that the same correlations introduce an unacceptable bias in the sample estimators used for the variance and covariance of the inter-sequence genetic distances for modest sample sizes. Here, we compute unbiased estimators for these and test the resulting improvement using simulated data. We also show that, contrary to the claims in Gilbert et al., it is not always possible to apply the Welch-Satterthwaite approximate t-test, and we provide explicit formulas for the degrees of freedom to be used when, on the other hand, such approximation is indeed possible.

Long term effect of monosodium glutamate in liver of albino mice after neo-natal exposure

Mono Sodium Glutamate (MSG) is a naturally occurring excitatory neurotransmitter. It is extensively used as a food additive and flavoring agent for its UMAMI taste. Simultaneously it is being implicated for varied pathological condition like obesity, gonadal dysfunction, learning difficulty etc. It produces oxygen derived free radicals and metabolized in liver. Neonate mice are sensitive and suffer from adverse effects. Present work was undertaken to study the long term effects on histology of liver following MSG injection in neonates. The changes in the liver parenchyma of 75 days old mice showed variable changes. Areas around central vein were most affected. The liver cords were disrupted, dilated sinusoids, prominent Kupffer cells with accumulation of particulate matter.There were inflammatory cells around central vein. The hepatocyte cell membrane were disrupted, cytoplasm vacuolated, nucleus were pyknotic. Even the normal looking cells showed depletion of PAS +ve material in the cytoplasm.The long term effect on histology showed moderate and patchy hepatocellular damage.

Biodegradation of phenol by native microorganisms isolated from coke processing wastewater

The present investigation was undertaken to assess the biodegradation of phenol by native bacteria strains isolated from coke oven processing wastewater. The strains were designated ESDSPB1, ESDSPB2 and ESDSPB3 and examined for colony morphology Gram stain characters and biochemical tests. Phenol degrading performance of all the strains was evaluated initially. One of the strains namely ESDSPB2 was found to be highly effective for the removal of phenol, which was used as sole carbon and energy source. From an initial concentration of 200 mg I(-1) it degraded to 79.84 +/- 1.23 mg l(-1). In turn the effect of temperature (20 to 45 degrees C), pH (5-10) and glucose concentration (0, 0.25 and 0.5%) on the rate of phenol degradation by that particular strain was investigated. Observations revealed that the rate of phenol biodegradation was significantly affected by pH, temperature of incubation and glucose concentration. The optimal conditions for phenol removal were found to be pH of 7 (84.63% removal), temperature, 30 degrees C (76.69% removal) and 0.25% supplemented glucose level (97.88% removal). The main significance of the study is the utilization of native bacterial strains from the waste water itself having potential of bioremediation.

Isolation and characterization of high quality DNA from marine benthic macroalgae

The isolation of high quality DNA is essential for many molecular biology applications including polymerase chain reaction (PCR) and endonuclease restriction digestion based techniques. An easy and inexpensive protocol has been developed for extracting genomic DNA from seven species of algae viz. Lola capillaries, Enteromorpha intestinalis, Ulva lactuca and Rhizoclonium sp belonging to Chlorophyceae, Catenella nipae, Polysiphonia mollis belonging to Rhodophyceae and Dictyota ceylanica belonging to Phaeophyceae group were collected from the coastal regions of Sunderban delta in West Bengal, India dominantly growing on mud flats, bark of different mangrove trees, pneumatophores, stilt roots, concrete surfaces, wooden and bamboo poles, sides of the boats and other water vehicles inundated during high tides. The DNA was found suitable for restriction endonuclease digestion and PCR amplification with randomely amplified polymorphic DNA (RAPD) primers. The A260/A280 ratio of 1.15 0.14 to 1.94 indicated little contamination from proteins and polysaccharides. The PCR amplification with RAPD primers showed its suitability in PCR based techniques and the restriction digestion with Eco RV confirmed its suitability for hybridization based techniques. The protocol is equally good for isolating DNA from both fresh as well as preserved materials.

Primary electron-transfer dynamics in 2-phenylindole-9-cyanoanthracene system. A comparative study with 2-methylindole

Electrochemical measurements by cyclic voltammetry predict the possibility of occurrence of photoinduced electron-transfer (PET) reactions between the ground state of 2-phenylindole (2PI) (electron donor) and the excited singlet of 9-cyanoanthracene (9CNA) molecule acting as an electron acceptor. However, 2PI should be expected to behave as a relatively weaker electron donating agent than the structurally related donor 2-methylindole (2MI) as it possesses higher oxidation potential value. Both steady-state and time-resolved spectroscopic measurements in the polar acetonitrile (ACN) and ethanol (EtOH) solvents show that the fluorescence quenching phenomenon of 9CNA in presence of 2PI is primarily due to the involvement of dynamic process which in high probability should be PET. Nevertheless, in less polar tetrahydrofuran (THF) medium, the quenching of 9CNA results from the combined effect of dynamic and static modes. The transient absorption spectra, measured by using nanosecond laser flash photolysis, of 9CNA in presence of 2PI exhibit the signature of the bands of the anionic species of 9CNA, cation of the donor 2PI and the contact neutral radical. Observations of the transient absorption at the different delays infer that ion-recombination mechanism is responsible for production of the monomeric triplets of both 9CNA and 2PI. From the transient absorption decays in ACN medium, it has been demonstrated that the diffusional separation of ions from geminate ion-pair is facilitated in the case of 2MI-9CNA pair whereas for 2PI-9CNA system the energy wasting charge recombination dominates over the process of charge dissociation. From the above observations, the possibility of developing much potential photosynthetic model compounds with the donor 2MI, rather than with the other donor 2PI molecule has been hinted.

Non-radiative depletion of the excited electronic states of 9-cyanoanthracene in presence of tetrahydronaphthols

Both steady state and time resolved spectroscopic measurements reveal that the prime process involved in quenching mechanism of the lowest excited singlet (S1) and triplet (T1) states of the well known electron acceptor 9-Cyanoanthracene (9CNA) in presence of 5,6,7,8-tetrahydro-1-naphthol (TH1N) or 5,6,7,8-tetrahydro-2-naphthol (TH2N) is H-bonding interaction. It has been confirmed that the fluorescence of 9CNA is not at all affected in presence of 5,6,7,8-tetrahydro-2-methoxy naphthalene (TH2MN) both in non-polar n-heptane (NH) and highly polar acetonitrile (ACN) media. This indicates that the H-bonding interaction is crucial for the occurrence of the quenching phenomenon observed in the present investigations with TH1N (or TH2N) donors and 9CNA acceptor. In ACN solvent both contact ion-pair (CIP) and solvent-separated (or dissociated) ions are formed due to intermolecular H-bonding interactions in the excited electronic states (both singlet and triplet). In NH environment due to stronger H-bonding interactions, the large proton shift within excited charge transfer (CT) or ion-pair complex, 1 or 3(D+-H...A-), causes the formation of the neutral radical, 3(D+H-A)*, due to the complete detachment of the H-atom. It is hinted that both TH1N and TH2N due to their excellent H-bonding ability could be used as antioxidants.

Preferential association of the heat-stable enterotoxin gene (stn) with environmental strains of Vibrio cholerae belonging to the O14 serogroup

Toxigenic Vibrio cholerae O1 and O139 serogroups have the capacity of causing epidemic and pandemic cholera but are infrequently found in the environment. The other serogroups are abundant in aquatic environments but do not possess the virulence genes necessary for causing the disease. Of the 559 environmental strains of V. cholerae, collected during different periods from environmental samples in Calcutta, 9 (1.6%) harboured the heat-stable enterotoxin gene (stn). Six of the 9 strains belonged to the O14 serogroup. Thus, V. cholerae strains carrying the stn gene revealed preferential association with the O14 serogroup. Three of the six strains harboured the tcpA gene of the E1 Tor type, which is an unusual feature among environmental V. cholerae strains. A strain that possessed the E1 Tor type tcpA also had the CTX prophage. Pulsed field gel electrophoresis (PFGE) revealed that the stn gene positive O14 strains of V. cholerae were not clonal.

Side bias and accidents: are they related?

This study purports to examine the role of different forms of side bias, handedness, footedness, eyedness, and earedness, in eliciting accident-proneness in individuals. A representative sample (N = 150) was administered a Side Bias Questionnaire (Handedness: 22 items, footedness: 5 items, eyedness: 5 items, earedness: 5 items) to ascertain their preferential bias. The questionnaire also required subjects to report the number of accidents committed during their lifetime while performing activities like sports, driving, household work, etc., that required attention of medical professionals. Regression analysis of data indicated that accident-prone behavior was significantly predicted from handedness. Analysis of variance, 3 (Accident groups: low, moderate, high) x 4 (Side bias: hand, foot, eye, ear), indicated that 'mixed' handers committed more accidents as compared with clear handers. The other forms of side bias, foot, ear, and eye were unrelated to frequency of accidents.

Using human immunodeficiency virus type 1 sequences to infer historical features of the acquired immune deficiency syndrome epidemic and human immunodeficiency virus evolution

In earlier work, human immunodeficiency virus type 1 (HIV-1) sequences were analysed to estimate the timing of the ancestral sequence of the main group of HIV-1, the virus that is responsible for the acquired immune deficiency syndrome pandemic, yielding a best estimate of 1931 (95% confidence interval of 1915-1941). That work will be briefly reviewed, outlining how phylogenetic tools were extended to incorporate improved evolutionary models, how the molecular clock model was adapted to incorporate variable periods of latency, and how the approach was validated by correctly estimating the timing of two historically documented dates. The advantages, limitations, and assumptions of the approach will be summarized, with particular consideration of the implications of branch length uncertainty and recombination. We have recently undertaken new phylogenetic analysis of an extremely diverse set of human immunodeficiency virus envelope sequences from the Democratic Republic of the Congo (the DRC, formerly Zaire). This analysis both corroborates and extends the conclusions of our original study. Coalescent methods were used to infer the demographic history of the HIV-1 epidemic in the DRC, and the results suggest an increase in the exponential growth rate of the infected population through time.

Serodiagnosis of ascariasis with specific IgG4 antibody and its use in an epidemiological study

In an earlier study Ascaris-specific IgG4 antibody was found to be elevated in cases of ascariasis. However, the usefulness of the elevated levels of this antibody in Ascaris infection as a diagnostic marker has not been well established. In India, in early 1999, blood samples of 83 cases of Ascaris infection, 35 cases of other nematode infection and 53 control subjects (without any helminth infection) were tested for anti-Ascaris IgG4 by ELISA. Further anti-Ascaris IgG4 levels in the blood of Ascaris-infected patients were determined, after eradication of the worms with drugs, at regular intervals to ascertain the duration of elevation of titre of the serological marker following initial infection. This information would indicate the sensitivity of the test as a diagnostic marker for recent infection. Blood samples of 422 rural people were also tested for anti-Ascaris IgG4 titre to ascertain the prevalence of ascariasis in the community. High levels of anti-Ascaris IgG4 antibody (OD 1.246 +/- 0.212) were found in all the 83 Ascaris-infected subjects compared to controls (OD 0.158 +/- 0.047). Anti-Ascaris IgG4 antibody levels of other nematode-infected subjects were comparable to the controls. Anthelmintic treatment of 8 Ascaris-infected subjects caused sequential fall of IgG4 level in their blood, and its titre reached control level within 6 months of deworming. Of 422 individuals from the rural community 229 (54.3%) had significantly high levels of specific IgG4 antibody against Ascaris excretory-secretory antigen, suggesting that they were infested with Ascaris. Thus, this study demonstrated that anti-Ascaris IgG4 antibody is a very sensitive and specific marker for the diagnosis of Ascaris infection. Utilizing this test, a significant number of a rural population could be diagnosed with Ascaris infection in West Bengal, India.

Continuous quantum measurement and the emergence of classical chaos

We formulate the conditions under which the dynamics of a continuously measured quantum system becomes indistinguishable from that of the corresponding classical system. In particular, we demonstrate that even in a classically chaotic system the quantum state vector conditioned by the measurement remains localized and, under these conditions, follows a trajectory characterized by the classical Lyapunov exponent.

Timing the ancestor of the HIV-1 pandemic strains

HIV-1 sequences were analyzed to estimate the timing of the ancestral sequence of the main group of HIV-1, the strains responsible for the AIDS pandemic. Using parallel supercomputers and assuming a constant rate of evolution, we applied maximum-likelihood phylogenetic methods to unprecedented amounts of data for this calculation. We validated our approach by correctly estimating the timing of two historically documented points. Using a comprehensive full-length envelope sequence alignment, we estimated the date of the last common ancestor of the main group of HIV-1 to be 1931 (1915-41). Analysis of a gag gene alignment, subregions of envelope including additional sequences, and a method that relaxed the assumption of a strict molecular clock also supported these results.

Expanding multiple antibiotic resistance among clinical strains of Vibrio cholerae isolated from 1992-7 in Calcutta, India

Antimicrobial susceptibilities of Vibrio cholerae strains isolated from cholera patients admitted to the Infectious Diseases Hospital, Calcutta, India for 6 years were analysed to determine the changing trends; 840 V. cholerae strains isolated in 1992-1997 were included in this study. Among V. cholerae serogoup O1 and O139, ampicillin resistance increased from 1992 (35 and 70%, respectively) to 1997 (both serogroups 100%). Resistance to furazolidone and streptomycin was constantly high among V. cholerae O1 strains with gradual increase in resistance to other drugs such as ciprofloxacin, co-trimoxazole, neomycin and nalidixic acid. V. cholerae O139 strains exhibited susceptibilities to furazolidone and streptomycin comparable with those of O1 strains. However, after initial increase in resistance to chloramphenicol and co-trimoxazole, all the V. cholerae O139 strains became susceptible to these two drugs from 1995 onwards. Both V. cholerae O1 and O139 remained largely susceptible to gentamicin and tetracycline. V. cholerae non-O1, non-O139 strains, in contrast, exhibited high levels of resistance to virtually every class of antimicrobial agents tested in this study especially from 1995. Kruskal-Wallis one-way analysis showed that V. cholerae O1 Ogawa serogroup exhibited significant yearly increase in resistance to nine antibiotics followed by non-O1 non-O139 and O139 strains to six antibiotics and two antibiotics respectively. Interesting observation encountered in this study was the dissipation of some of the resistant patterns commonly found among V. cholerae non-O1 non-O139 or O1 serogroups to the O139 serogroup and vice versa during the succeeding years.

Vibrio cholerae O139 in Calcutta, 1992-1998: incidence, antibiograms, and genotypes

We report results of surveillance for cholera caused by Vibrio cholerae O139 from September 1992, when it was first identified, to December 1998. V. cholerae O139 dominated as the causative agent of cholera in Calcutta during 1992-93 and 1996- 97, while the O1 strains dominated during the rest of the period. Dramatic shifts in patterns of resistance to cotrimoxazole, neomycin, and streptomycin were observed. Molecular epidemiologic studies showed clonal diversity among the O139 strains and continuous emergence of new epidemic clones, reflected by changes in the structure, organization, and location of the CTX prophages in the V. cholerae O139

Fibrin sealant for treatment of cerebrospinal fluid leaks

OBJECTIVE

Persistent cerebrospinal fluid leaks in the human population are rarely found in otherwise healthy individuals, but occur in patients with comorbid illnesses. These leaks are frequently resistant to dural suturing or closure of the defect site with connective tissue, cartilage, or plastic materials. In this study, fibrin sealant (ViGuard Fibrin Sealant was used to adhere muscle grafts to surgically created dural defects to close cerebrospinal fluid leaks in chinchillas. Histologic evaluation of the defect sites were conducted to assess healing and tissue response in the test and control groups.

METHOD

In 20 chinchillas, after a skin incision, a 6 mm X 6 mm window was created in the right superior bulla exposing the underlying bony tegmen. Using a microcutting burr, a 3 mm X 3 mm area of tegmen was drilled out and the exposed dura was resected to create a large cerebrospinal fluid (CSF) leak. In the control group (n = 10), a small muscle graft from the surrounding tissue was placed into the defect site. In the test group (n = 10), the muscle graft was glued into the defect with ViGuard Fibrin Sealant. Bulla and skin were then closed. All animals were killed at 3 weeks into the experiment, and tissue was harvested for histologic examination.

SETTING

The Department of Otolaryngology, Head and Neck Surgery Research Laboratory. University of Illinois, Chicago.

RESULTS

Three weeks after surgery in the test group the tegmen defects were found to be closed by bone or connective tissue or both. Meninges had regrown, and the underlying brain appeared histologically normal. There was no evidence of CSF leak, toxicity, infection or other deleterious tissue reactions. In the control group, again the meningeal and bony tegmen defects were seen to be closed by connective tissue or bone or both. Brain tissues appeared histologically normal. There was no evidence of CSF leak, toxicity, or other deleterious tissue reactions. One animal of the test group died of unknown causes. On autopsy, no signs of meningitis or encephalitis could be detected and the cause of death was unapparent.

CONCLUSION

Fibrin Sealant, made from pooled donor blood and treated with viral elimination procedures, was found in combination with muscle grafts to securely close induced CSF leaks in the chinchilla model. Inflammation, infection, or toxic reactions were not observed. We believe that ViGuard Fibrin Sealant has stronger bonding power compared with available autologous fibrin tissue adhesives.

Evaluation of pooled fibrin sealant for ear surgery

HYPOTHESIS

This study investigated the bonding strength and tissue toxicity of a commercially prepared dual-virally-inactivated pooled-blood fibrin tissue adhesive (ViGuard-FS; Melville Biologics, Inc., NY, U.S.A.) and compared it with an autologous fibrin tissue adhesive made by the precipitation of fibrinogen using ethanol and freezing (AFTA-E).

METHODS

The bonding strength of FS was optimized by varying the concentrations of fibrinogen and human or bovine thrombin using three different surface media: inorganic (silastic), animal skin, and human dura mater. Furthermore, tissue reactions and duration of fibrin clots were studied by injecting FS into the auricles of rats.

RESULTS

This study showed that optimized FS with human thrombin was superior in bonding strength to AFTA-E on all three surface media, and that FS does not produce any toxic tissue responses when injected into rat auricles. Minimal traces of the adhesive clot could be observed in a few auricles at 35 days after application.

CONCLUSIONS

Because it is made from pooled-donor blood that has been treated with virus elimination procedures, FS is superior to autologous fibrin tissue adhesive in which fibrinogen is precipitated by the ethanol/freezing method. FS has not shown any undesirable tissue reactions when injected into live rat auricles. We believe that these results provide a rationale for further clinical development of ViGuard-FS as a tissue adhesive for otologic surgery.