Antitumour activities of levans produced by Zymomonas mobilis strains

Levans produced by four Zymomonas mobilis strains showed antitumour activity against sarcoma 180 and Ehrlich carcinoma in Swiss albino mice. Levans from two strains (ZAP and CP4) had the highest effects. NMR analysis showed that the polymers were composed only of fructose units. The results suggested that the antineoplasic effect is associated to the polysaccharide molecular weight and that a particular molecular weight range may be responsible for this effect.     

An overview of malaria transmission from the perspective of Amazon Anopheles vectors

In the Americas, areas with a high risk of malaria transmission are mainly located in the Amazon Forest, which extends across nine countries. One keystone step to understanding the Plasmodium life cycle in Anopheles species from the Amazon Region is to obtain experimentally infected mosquito vectors. Several attempts to colonise Ano- pheles species have been conducted, but with only short-lived success or no success at all. In this review, we review the literature on malaria transmission from the perspective of its Amazon vectors. Currently, it is possible to develop experimental Plasmodium vivax infection of the colonised and field-captured vectors in laboratories located close to Amazonian endemic areas. We are also reviewing studies related to the immune response to P. vivax infection of Anopheles aquasalis, a coastal mosquito species. Finally, we discuss the importance of the modulation of Plasmodium infection by the vector microbiota and also consider the anopheline genomes. The establishment of experimental mosquito infections with Plasmodium falciparum, Plasmodium yoelii and Plasmodium berghei parasites that could provide interesting models for studying malaria in the Amazonian scenario is important. Understanding the molecular mechanisms involved in the development of the parasites in New World vectors is crucial in order to better determine the interaction process and vectorial competence.     

Physiological methods to study biofilm disinfection

This report reviews the development of a rapidin situ approach to study the physiological responses of bacteria within biofilms to disinfectants. One method utilized direct viable counts (DVC) to assess the disinfection efficacy when thin biofilms were exposed to chlorine or monochloramine. Results obtained using the DVC method were one log higher than plate count (PC) estimates of the surviving population after disinfection. Other methods incorporated the use of fluorogenic stains, a cryotomy technique to yield thin (5-m) sections of biofilm communities and examination by fluorescence microscopy. The fluorogenic stains used in this approach included 5-cyano-2,3-ditolyl tetrazolium chloride (CTC), which indicates cellular electron transport activity and Rhodamine 123, which responds specifically to proton motive force. The use of these stains allowed the microscopic discrimination of physiologically active bacteria as well as heterogeneities of active cells within thicker biofilms. The results of experiments using these techniques with pure culture and binary population biofilms on stainless steel coupons indicated biocidal activity of chlorine-based disinfectants occurred initially at the bulk-fluid interface of the communities and progressed toward the substratum. This approach provided a unique opportunity to describe the spatial response of bacteria within biofilms to antimicrobial agents and address mechanisms explaining their comparative resistance to disinfection in a way that has not been possible using traditional approaches. Results obtained using this alternative approach were also consistently higher than PC data following disinfection. These observations suggest that traditional methods involving biofilm removal and bacterial enumeration by colony formation overestimate biocide efficacy. Hence the alternative approach described here more accurately indicates the ability of bacteria surviving disinfection to recover and grow as well as demonstrate spatial heterogeneities in cellular physiological activities within biofilms.     

Regional differences in the force-frequency relation of human left ventricular myocardium in mitral regurgitation: implications for ventricular shape

Sphericalization of the left ventricular (LV) chamber shape in patients with mitral regurgitation (MR) contributes to increased LV wall stress and energy consumption. On the basis of previous observations, we hypothesized the existence of regional differences in the force-frequency relation (FFR) within the LV that may contribute to its shape. Accordingly, in the present study, we assessed regional variation in the FFR in patients undergoing surgery for chronic, nonischemic MR with class II-III heart failure symptoms and related our findings to the in vivo LV shape. FFRs (steady-state isometric twitches, 0.2-3.4 Hz, 37 degrees C) were evaluated in MR myocardium from the LV subepicardial free wall (MR-FW) and papillary muscle (MR-PM) and from the subepicardial free wall in coronary artery bypass graft patients with normal LV contraction patterns [nonfailing (NF)]. Ascending slope, optimal stimulation frequency, and maximal twitch tension of the FFR were depressed in MR-FW and MR-PM compared with NF (P < 0.05). FFR depression was greater in MR-PM than in MR-FW. Between 107 and 134 beats/min, twitch tension became weaker in MR-PM, whereas it increased in MR-FW. Elevation of intracellular cAMP with forskolin eliminated FFR depression in MR-FW but not in MR-PM. MR-PM also had a 35% lower myosin heavy chain content and slowed twitch kinetics. In MR patients, the echocardiographic end-diastolic LV shape (end-diastolic eccentricity index = long axis/short axis) correlated with the ratio of ascending FFR slopes such that the end-diastolic eccentricity index increased 10% per 15% increase in slope ratio (r = 0.88, P = 0.01). These regional differences in the frequency dependence of contractility between the free wall and papillary myocardium may contribute to changes in LV shape in MR as well as during exercise.     

Retroviral transfer of the p16INK4a cDNA inhibits C6 glioma formation in Wistar rats

BACKGROUND: The p16INK4A gene product halts cell proliferation by preventing phosphorylation of the Rb protein. The p16INK4a gene is often deleted in human glioblastoma multiforme, contributing to unchecked Rb phosphorylation and rapid cell division. We show here that transduction of the human p16INK4a cDNA using the pCL retroviral system is an efficient means of stopping the proliferation of the rat-derrived glioma cell line, C6, both in tissue culture and in an animal model. C6 cells were transduced with pCL retrovirus encoding the p16INK4a, p53, or Rb genes. These cells were analyzed by a colony formation assay. Expression of p16INK4a was confirmed by immunohistochemistry and Western blot analysis. The altered morphology of the p16-expressing cells was further characterized by the senescence-associated beta-galactosidase assay. C6 cells infected ex vivo were implanted by stereotaxic injection in order to assess tumor formation. RESULTS: The p16INK4a gene arrested C6 cells more efficiently than either p53 or Rb. Continued studies with the p16INK4a gene revealed that a large portion of infected cells expressed the p16INK4a protein and the morphology of these cells was altered. The enlarged, flat, and bi-polar shape indicated a senescence-like state, confirmed by the senescence-associated beta-galactosidase assay. The animal model revealed that cells infected with the pCLp16 virus did not form tumors. CONCLUSION: Our results show that retrovirus mediated transfer of p16INK4a halts glioma formation in a rat model. These results corroborate the idea that retrovirus-mediated transfer of the p16INK4a gene may be an effective means to arrest human glioma and glioblastoma.     

The effects of aging on the intimal region of the human saphenous vein: insights from multimodal microscopy and quantitative image analysis

We hypothesized that structural remodeling associated with advancing age occurs in human saphenous veins. To address this hypothesis, we have identified structural remodeling in human saphenous veins by applying histochemistry, fluorescence staining and quantitative image analysis to specifically assess intimal area, intimal cellularity and intimal collagen content and organization. Saphenous veins were collected from patients undergoing coronary artery bypass graft surgery. Area measurements and cellularity were quantified using the image analysis software Stereo Investigator, employing planimetry and counting frames, respectively. Collagen content and organization were quantified in MetaMorph image analysis software based on measurements of color (hue, saturation, and intensity) from polarized light images. Intimal area and cellularity showed no statistically significant increases with age; in contrast, total collagen content showed a significant decrease with advancing age. Furthermore, collagen fiber types also demonstrated a statistically significant alteration with age; increases in age resulted in decreases in larger collagen fibers. No significant changes in small collagen fibers were identified. These results raise the possibility that age-associated structural alterations in total collagen content, specifically collagen fiber size, could be a factor in the etiology of age-associated venous diseases.     

Zn(2+) modulation of neuronal transient K(+) current: fast and selective binding to the deactivated channels

Modulation of voltage-dependent transient K(+) currents (A type K(+) or K(A) current) by Zn(2+) was studied in rat hippocampal neurons by the whole-cell patch-clamp technique. It is found that Zn(2+) selectively binds to the resting (deactivated or closed) K(A) channels with a dissociation constant (K(d)) of approximately 3 &mgr;M, whereas the affinity between Zn(2+) and the inactivated K(A) channels is 1000-fold lower. Zn(2+) therefore produces a concentration-dependent shift of the K(A) channel inactivation curve and enhances the K(A) current elicited from relatively positive holding potentials. It is also found that the kinetics of Zn(2+) action are fast enough to compete with the transition rates between different gating states of the channel. The rapid and selective binding of Zn(2+) to the closed K(A) channels keeps the channel in the closed state and explains the ion's concentration-dependent slowing effect on the activation of K(A) current. This in turn accounts for the inhibitory effect of Zn(2+) on the K(A) current elicited from hyperpolarized holding potentials. Because the molecular mechanisms underlying these gating changes are kinetic interactions between the binding-unbinding of Zn(2+) and the intrinsic gating processes of the channel, the shift of the inactivation curve and slowing of K(A) channel activation are quantitatively correlated with ambient Zn(2+) over a wide concentration range without "saturation"; i.e., The effects are already manifest in micromolar Zn(2+), yet are not saturated even in millimolar Zn(2+). Because the physiological concentration of Zn(2+) could vary over a similarly wide range according to neural activities, Zn(2+) may be a faithful physiological "fine tuner," controlling and controlled by neural activities through its effect on the K(A) current.     

A tetravalent dengue nanoparticle stimulates antibody production in mice

Background

Dengue is a major public health problem worldwide, especially in the tropical and subtropical regions of the world. Infection with a single Dengue virus (DENV) serotype causes a mild, self-limiting febrile illness called dengue fever. However, a subset of patients experiencing secondary infection with a different serotype progresses to the severe form of the disease, dengue hemorrhagic fever/dengue shock syndrome. Currently, there are no licensed vaccines or antiviral drugs to prevent or treat dengue infections. Biodegradable nanoparticles coated with proteins represent a promising method for in vivo delivery of vaccines.

Findings

Here, we used a murine model to evaluate the IgG production after administration of inactivated DENV corresponding to all four serotypes adsorbed to bovine serum albumin nanoparticles. This formulation induced a production of anti-DENV IgG antibodies (p < 0.001). However, plaque reduction neutralization assays with the four DENV serotypes revealed that these antibodies have no neutralizing activity in the dilutions tested.

Conclusions

Our results show that while the nanoparticle system induces humoral responses against DENV, further investigation with different DENV antigens will be required to improve immunogenicity, epitope specicity, and functional activity to make this platform a viable option for DENV vaccines.     

Pattern of carbon dioxide production and retention is similar in adult pigs when fed hourly,but not when fed a single meal

Background

The understanding of bicarbonate kinetics and CO₂ retention in the body is necessary to conduct amino acid tracer oxidation studies in both humans and laboratory animals. Significant metabolic activity is associated with eating which can affect bicarbonate steady state kinetics. A study was conducted to assess the impact of feeding regimen on the recovery of labelled bicarbonate and energy expenditure in adult female pigs (sows). Five catheterized sows (235 ± 5 kg) were fed semi-synthetic diets as: a single meal 2 h into the infusion after an overnight fast, or in eight hourly meals starting 2 h before the infusion. Oxygen consumption, CO₂ production and ¹⁴CO₂ recovery (ie fraction not retained) were determined during primed, constant intravenous infusions of NaH¹⁴CO₃.

Results

The ¹⁴CO₂ recovery (%) after fasting (58.1 ± 4.8) was lower than that after single meal feeding (78.8 ± 5.9) or hourly meal feeding (81.0 ± 2.6, P = 0.03). CO₂ production correlated with ¹⁴CO₂ recovery during hourly feeding (r = 0.40, P = 0.01); this relationship was not significant after single meal feeding (P = 0.30), probably due to physical activity-associated CO₂ production.

Conclusions

The correlation of CO₂ retention factors with CO₂ production during hourly feeding suggests that this regimen should be preferred for future amino acid kinetics studies.