An Automated Self‐Similarity Analysis of the Pulmonary Tree of the Sprague–Dawley Rat

We present the results of an automated analysis of the morphometry of the pulmonary airway trees of the Sprague–Dawley rat. Our work is motivated by a need to inform lower‐dimensional mathematical models to prescribe realistic boundary conditions for multiscale hybrid models of rat lung mechanics. Silicone casts were made from three age‐matched, male Sprague–Dawley rats, immersed in a gel containing a contrast agent and subsequently imaged with magnetic resonance (MR). From a segmentation of this data, we extracted a connected graph, representing the airway centerline. Segment statistics (lengths and diameters) were derived from this graph. To validate this MR imaging/digital analysis method, airway segment measurements were compared with nearly 1,000 measurements collected by hand using an optical microscope from one of the rat lung casts. To evaluate the reproducibility of the MR imaging/digital analysis method, two lung casts were each imaged three times with randomized orientations in the MR bore. Diameters and lengths of randomly selected airways were compared among each of the repeated imaging datasets to estimate the variability. Finally, we analyzed the morphometry of the airway tree by assembling individual airway segments into structures that span multiple generations, which we call branches. We show that branches not segments are the fundamental repeating unit in the rat lung and develop simple mathematical relationships describing these structures for the entire lung. Our analysis shows that airway diameters and lengths have both a deterministic and stochastic character. Anat Rec, 2008. © 2008 Wiley‐Liss, Inc.     

Synthesis and antimicrobial activities of N-chloroacetyl-2,6-diarylpiperidin-4-ones

An array of new N-chloroacetyl-2,6-diarylpiperidin-4-ones has been synthesised and their antibacterial activity against Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa, and Salmonella typhi, and antifungal activity against Cryptococcus neoformans, Candida albicans, Rhizopus sp., Aspergillus flavus, and Aspergillus niger examined. Compounds 14 against P. aeruginosa, 15 against S. typhi, 16 against S. aureus, and 19 against B. subtilis showed marked antibacterial activity. Similarly, compounds 15 and 19 against A. niger and 19 against A. flavus exerted significant antifungal activities.     

Host immune response to Plasmodium.

Malaria is the most widely spread infectious disease of man affecting almost half of the world's population. Control of malaria remains one of the world's biggest health challenges. Development of vaccines has been considered a valid and necessary complement to control malaria in addition to the control measures of the vectors. The Plasmodium parasites that cause the disease have many stages in their cycle, each with distinct morphology and antigenicity. Understanding the activation, interaction and effector function of the different components of the immune system in relation to target antigens on different stages of malaria parasites is necessary to achieve complete protection by vaccination.     

Longitudinal studies in South Indian villages on Japanese encephalitis virus infection in mosquitoes and seroconversion in goats

Japanese encephalitis (JE) is endemic in Cuddalore district, Tamil Nadu, where Culex tritaeniorhynchus Giles was the major vector. We screened 45 100 adult female Cx. tritaeniorhynchus (902 pools) by enzyme-linked immunosorbent assay and isolated and confirmed JE virus (JEV) by using an insect bioassay system. We had 69 isolates of which 62 (90%) were identified as JEV. The average vector abundance per man hour for Cx. tritaeniorhynchus was 324.5 per month for the period June 1998-May 2000. The average minimum infection rate (MIR) per month in Cx. tritaeniorhynchus was 1.4 (range 0.0-5.6). Every year, a new batch of goats, 20 in the first year and 31 in the second year, born during the non-JE transmission period (January-June), aged <6 months and negative for haemagglutination inhibition (HI) antibodies were procured and placed in the villages as sentinels. Fortnightly, blood specimens were collected from these goats and tested for JE antibodies by HI test. Seroconversions (SCs) were recorded in 14 goats (70%) in the first year and 23 goats (74%) in the second year. JE HI antibody titres in goats were low (1:10-1:80) and these levels declined to undetectable levels in about 4 weeks following SCs. The time sequence of events indicated that four of five peaks of MIR in mosquitoes were followed 1-3 months later by peaks in the proportion of seroconverted goats. We suggest the screening of goats and cattle as a more feasible tool to stratify areas according to JE infection risk to the human population through the regular health system rather than screening mosquitoes using monoclonal antibodies, which is possible only in specialized laboratories.     

Application of magnetic resonance (MR) imaging for the development and validation of computational fluid dynamic (CFD) models of the rat respiratory system

Computational fluid dynamic (CFD) models of the respiratory system provide a quantitative basis for extrapolating the localized dose of inhaled materials and improving human health risk assessments based upon inhalation studies conducted in animals. Nevertheless, model development and validation have historically been tedious and time-consuming tasks. In recognition of this, we previously reported on the use of proton (1H) magnetic resonance (MR) imaging for visualizing nasal-sinus passages in the rat, and for speeding computational mesh generation. Here, the generation and refinement of meshes for rat nasal airways are described in more detail and simulated airflows are presented. To extend the CFD models to the complete respiratory tract, three-dimensional (3D) 1H MR imaging of rat pulmonary casts was also utilized to construct pulmonary airway meshes using procedures developed for the nasal airways. Furthermore, the feasibility of validating CFD predictions with MR was tested by imaging hyperpolarized 3He gas at physiological flow rates in a straight pipe with a diameter comparable to the rat trachea. Results from these diverse studies highlight the potential utility of MR imaging not only for speeding CFD development but also possibly for model validation.     

Synthesis, stereochemistry, and antimicrobial evaluation of substituted piperidin-4-one oxime ethers

In a wide search program toward new and efficient antimicrobial agents, a series of substituted piperidin-4-one oxime ethers (5a-5k) was synthesized and tested for their in vitro antibacterial and antifungal activities. Also, the structures of these oxime ethers and their relative stereochemistries have been investigated by nuclear magnetic resonance spectroscopy. In all the oxime ethers synthesized, the orientation of the N-O bond of the oxime ether moiety syn to C-5 (E-isomer) was deduced based on (1)H NMR and (13)C NMR spectra. It was found that the sterically less hindered compounds, either C-3 (H) and C-5 (H)- or C-3 (Me) and C-5 (H) -substituted ones 5a, 5c, 5d, 5f, 5g, 5i and 5j prefer chair conformation, whereas the sterically more hindered C-3 (Me) and C-5 (Me) -substituted ones 5b, 5e, 5h, and 5k prefer twist-boat conformation. Among the oxime ethers tested, 1,3,5-trimethyl-2,6-diphenylpiperidin-4-one O-(2-chlorophenylmethyl)oxime (5h) exhibited good antibacterial property against Bacillus subtilis, with minimum inhibitory concentration (MIC) closer to that of reference drug, streptomycin. Compounds, 1,3-dimethyl-2,6-diphenylpiperidin-4-one O-(2-chlorophenylmethyl)oxime (5g) and 1,3-dimethyl-2,6-diphenylpiperidin-4-one O-(2-bromophenylmethyl)oxime (5j) showed potent antifungal activity against Aspergillus flavus and Candida-51, respectively. The later compound 5j is more active than the reference drug while the activity of the former one 5g is similar to that of the reference drug, amphotericin B in terms of MIC. The present results may be used as key steps for the construction of novel chemical entities with better pharmacological profiles than standard drugs.     

Aggregatibacter actinomycetemcomitans as an Early Colonizer of Oral Tissues: Epithelium as a Reservoir?

This study examined in vivo and in vitro colonization by Aggregatibacter actinomycetemcomitans, an organism highly associated with aggressive periodontitis. Thirteen volunteers (5 were A. actinomycetemcomitans positive for buccal epithelial cells [BECs] and teeth, 5 were A. actinomycetemcomitans positive for teeth only, and 3 were A. actinomycetemcomitans-negative controls) had two mandibular stents fabricated. Each stent contained 3 removable hydroxyapatite (HA) tooth surrogates. One HA square was removed from a stent at 5 time points over 7 h to assess the transfer of A. actinomycetemcomitans from teeth or BECs to HA. Streptococcus, Actinomyces, A. actinomycetemcomitans, and total anaerobic counts were evaluated on each square over time. In vitro experiments evaluated binding, desorption, transfer, and reattachment of A. actinomycetemcomitans wild-type and mutant strains to BECs and saliva-coated HA (SHA). Streptococcus and Actinomyces formed 80% of the cultivable flora on HA in all subjects. Transfer of A. actinomycetemcomitans to HA was not seen in subjects with A. actinomycetemcomitans on teeth only. All 5 subjects with A. actinomycetemcomitans on BECs showed transfer of A. actinomycetemcomitans to HA. In vitro, A. actinomycetemcomitans desorbed from BECs and transferred to SHA. A. actinomycetemcomitans binding to SHA was irreversible and did not transfer to BECs. The adhesin Aae showed specificity for BECs. Fimbrial mutants showed the greatest reduction in binding to SHA. A. actinomycetemcomitans migrated from BECs to HA in vivo and to SHA in vitro; however, A. actinomycetemcomitans movement from teeth and SHA to BECs did not occur. In vivo, A. actinomycetemcomitans colonized HA within 6 h and thus can be considered an early colonizer. BECs are a likely reservoir for A. actinomycetemcomitans tooth colonization.Aggregatibacter actinomycetemcomitans has frequently been associated with the etiology of localized aggressive periodontitis (LAP) (41). More recently, longitudinal studies of both humans and animals have added to this evidence and made the association between A. actinomycetemcomitans and LAP even more compelling (10, 14). Furthermore, virulence factors associated with A. actinomycetemcomitans and studied on a molecular level appear to be consistent with the pathogenesis described for LAP (11, 12, 17). Taken together, these data suggest that A. actinomycetemcomitans could play an important role in the initiation and progression of LAP.A. actinomycetemcomitans resides in the oral cavity, is a member of the Haemophilus, Actinobacillus, Cardiobacterium, Eikenella, and Kingella (HACEK) group of “pathogenic” microorganisms, and has been found on six continents (21). While population-based data are far from extensive, A. actinomycetemcomitans has been found in a small subset of individuals in the North and South American continents as well as in Europe, with a lower prevalence in Caucasian individuals and a higher prevalence in individuals from Asia and Africa (2, 3, 15, 16, 28, 29). These demographic patterns raise questions as to how and why certain groups of individuals are more prone to A. actinomycetemcomitans colonization. This global distribution could result from infection due to random but more frequent exposure to A. actinomycetemcomitans by individuals or groups of individuals on one continent than on another (21). Alternatively, A. actinomycetemcomitans colonization could be dependent on the specificity of the outer membrane proteins (OMPs) of the infecting bacteria and their interaction and coupling with surface receptors of host cells (1, 37). If exposure is the driving force for attachment, then colonization would occur in a nonspecific fashion and could be dependent upon the level of A. actinomycetemcomitans in the environment. If specificity is the driving force, then one would expect host selection to dictate A. actinomycetemcomitans attachment and that only those bacteria that interact with appropriate tissue receptors would be colonized by A. actinomycetemcomitans (37).Several groups have been working on the identification and characterization of adherence factors that allow A. actinomycetemcomitans to colonize the oral cavity (8, 24, 35). In vitro studies have suggested that soft tissue binding occurs in a specific manner and is mediated by the autotransporter adhesins ApiA and Aae (11, 24, 40). In contrast, binding of A. actinomycetemcomitans to tooth surfaces appears to occur in a nonspecific manner and is dominated by OMPs such as Flp (19, 31). There is no general agreement as to whether tooth or tissue surfaces form the primary site for A. actinomycetemcomitans colonization in the oral cavity (8, 23). In a longitudinal study of LAP, we confirmed reports by others and identified buccal epithelial cells (BECs) as a primary site for A. actinomycetemcomitans colonization in the oral cavities of healthy A. actinomycetemcomitans-positive individuals (10). However, definitive proof showing that buccal cells can seed tooth surfaces is lacking.Because A. actinomycetemcomitans is typically found in the mouth in <20% of the population (41), studying the role of A. actinomycetemcomitans colonization of clean tooth surfaces in the general population has presented a difficult challenge. As a result, studies that have examined the relationship of A. actinomycetemcomitans to early events in the colonization process in humans are rare (26). However, one study of monkeys, though limited in scope, has shown that A. actinomycetemcomitans can colonize teeth within a 5- to 8-h period after tooth cleaning (22). In that study, the main goal was to determine the influence of a carbohydrate diet on Streptococcus mutans colonization of thoroughly cleaned teeth, and identification of A. actinomycetemcomitans on tooth surfaces was discovered by chance. However, because these teeth were cleaned, the likely source of A. actinomycetemcomitans was the primate mucosa (22). Recent studies have shown that A. actinomycetemcomitans can be found in predentate children, suggesting that the mucosa can serve as a potential reservoir for tooth colonization (33).In an effort to help resolve questions related to early tooth and tissue colonization in humans, we explored the possibility of examining the colonization patterns of a number of A. actinomycetemcomitans-positive participants already enrolled in an ongoing longitudinal study (9). Since we had access to these subjects and had knowledge of their carriage of A. actinomycetemcomitans, we felt that we could recruit an appropriate subject population to study A. actinomycetemcomitans colonization of tooth surrogates in vivo (9). Overall, examination of the colonization patterns of A. actinomycetemcomitans can lead to a better understanding of the role of OMPs in A. actinomycetemcomitans binding, which could lead to potentially useful preventive and therapeutic strategies for LAP. The studies we report herein were designed to begin to address the following two important biological questions related to A. actinomycetemcomitans colonization of the oral cavity. Is A. actinomycetemcomitans an early colonizer of hydroxyapatite (HA) tooth surrogate surfaces? Do BECs serve as an effective reservoir for A. actinomycetemcomitans transfer to HA tooth surrogates?