Multiplexed fluidic circuit board for controlled perfusion of 3D blood vessels-on-a-chip

Three-dimensional (3D) blood vessels-on-a-chip (VoC) models integrate the biological complexity of vessel walls with dynamic microenvironmental cues, such as wall shear stress (WSS) and circumferential strain (CS). However, these parameters are difficult to control and are often poorly reproducible due to the high intrinsic diameter variation of individual 3D-VoCs. As a result, the throughput of current 3D systems is one-channel-at-a-time. Here, we developed a fluidic circuit board (FCB) for simultaneous perfusion of up to twelve 3D-VoCs using a single set of control parameters. By designing the internal hydraulic resistances in the FCB appropriately, it was possible to provide a pre-set WSS to all connected 3D-VoCs, despite significant variation in lumen diameters. Using this FCB, we found that variation of CS or WSS induce morphological changes to human induced pluripotent stem cell (hiPSC)-derived endothelial cells (ECs) and conclude that control of these parameters using a FCB is necessary to study 3D-VOCs.

Pressure-Driven Perfusion System to Control, Multiplex and Recirculate Cell Culture Medium for Organs-on-Chips

Organ-on-chip (OoC) devices are increasingly used to mimic the tissue microenvironment of cells in intact organs. This includes microchannels to mimic, for example, fluidic flow through blood vessels. Present methods for controlling microfluidic flow in these systems rely on gravity, rocker systems or external pressure pumps. For many purposes, pressure pumps give the most consistent flow profiles, but they are not well-suited for high throughput as might be required for testing drug responses. Here, we describe a method which allows for multiplexing of microfluidic channels in OoC devices plus the accompanying custom software necessary to run the system. Moreover, we show the approach is also suitable for recirculation of culture medium, an essential cost consideration when expensive culture reagents are used and are not "spent" through uptake by the cells during transient unidirectional flow.

Can physiological stimulation prior to ileostomy closure reduce postoperative ileus? A prospective multicenter pilot study

BACKGROUND

The aim of this study was to assess the impact of ileostomy closure following preoperative physiological stimulation (PPS) on postoperative ileus (POI) in patients with loop ileostomy after low anterior resection for rectal cancer.

METHODS

Patients who underwent ileostomy closure between January 2017 and February 2020 in two tertiary referral centers were prospectively included. PPS stimulation was compared to standard treatment. Stimulation was carried out daily during the 15 days prior to ileostomy closure by the patient's self-instillation of 200 ml of fecal contents from the ileostomy bag via the efferent loop, using a rectal catheter. Standard treatment (ST) consisted of observation. Outcomes measures were POI, morbidity, stimulation feasibility, and predictors to ileus.

RESULTS

A total of 58 patients were included [42 males and 16 females, median age 67 (43-85) years]. PPS was used in 24 patients, who completed the entire stimulation process, and ST in 34 patients. No differences in preoperative factors were found between the two groups. POI was significantly lower in the PPS group (4.2%) vs the ST group (32.4%); p < 0.01, OR: 0.05 (CI 95% 0.01-0.65). The PPS group had a shorter time to restoration of bowel function (1 day vs 3 days) p = 0.02 and a shorter time to tolerance of liquids (1 day vs 2 days), p = 0.04. Age (p = 0.01), open approach at index surgery, p = 0.03, adjuvant capecitabine (p = 0.01). and previous abdominal surgeries (p = 0.02) were associated with POI in the multivariate analysis. C-reactive-protein values on the 3rd (p = 0.02) and 5th (p < 0.01) postoperative day were also associated with POI.

CONCLUSIONS

PPS for patients who underwent ileostomy closure after low anterior resection for rectal cancer is feasible and might reduce POI.

Aneurysm-on-a-Chip: Setting Flow Parameters for Microfluidic Endothelial Cultures Based on Computational Fluid Dynamics Modeling of Intracranial Aneurysms

Intracranial aneurysms are pouch-like extrusions from the vessels at the base of the brain which can rupture and cause a subarachnoid hemorrhage. The pathophysiological mechanism of aneurysm formation is thought to be a consequence of blood flow (hemodynamic) induced changes on the endothelium. In this study, the results of a personalized aneurysm-on-a-chip model using patient-specific flow parameters and patient-specific cells are presented. CT imaging was used to calculate CFD parameters using an immersed boundary method. A microfluidic device either cultured with human umbilical vein endothelial cells (HUVECs) or human induced pluripotent stem cell-derived endothelial cells (hiPSC-EC) was used. Both types of endothelial cells were exposed for 24 h to either 0.03 Pa or 1.5 Pa shear stress, corresponding to regions of low shear and high shear in the computational aneurysm model, respectively. As a control, both cell types were also cultured under static conditions for 24 h as a control. Both HUVEC and hiPSC-EC cultures presented as confluent monolayers with no particular cell alignment in static or low shear conditions. Under high shear conditions HUVEC elongated and aligned in the direction of the flow. HiPSC-EC exhibited reduced cell numbers, monolayer gap formation and cells with aberrant, spread-out morphology. Future research should focus on hiPSC-EC stabilization to allow personalized intracranial aneurysm models.

Fluidic circuit board with modular sensor and valves enables stand-alone, tubeless microfluidic flow control in organs-on-chips

Organs-on-chips are a unique class of microfluidic in vitro cell culture models, in which the in vivo tissue microenvironment is mimicked. Unfortunately, their widespread use is hampered by their operation complexity and incompatibility with end-user research settings. To address these issues, many commercial and non-commercial platforms have been developed for semi-automated culture of organs-on-chips. However, these organ-on-chip culture platforms each represent a closed ecosystem, with very little opportunity to interchange and integrate components from different platforms or to develop new ones. The translational organ-on-chip platform (TOP) is a multi-institutional effort to develop an open platform for automated organ-on-chip culture and integration of components from various developers. Central to TOP is the fluidic circuit board (FCB), a microfluidic plate with the form factor of a typical well plate. The FCB enables microfluidic control of multiple components like sensors or organ-on-chip devices through an interface based on openly available standards. Here, we report an FCB to integrate commercial and in-house developed components forming a stand-alone flow control system for organs-on-chips. The control system is able to achieve constant and pulsatile flow recirculation through a connected organ-on-chip device. We demonstrate that this system is able to automatically perfuse a heart-on-chip device containing co-cultures of cardiac tissues derived from human pluripotent stem cell-derived cardiomyocytes and monolayers of endothelial cells for five days. Altogether, we conclude that open technology platforms allow the integration of components from different sources to form functional and fit-for-purpose organ-on-chip systems. We anticipate that open platforms will play a central role in catalyzing and maturing further technological development of organ-on-chip culture systems.

Organ-on-a-chip technology: a novel approach to investigate cardiovascular diseases

The development of organs-on-chip (OoC) has revolutionized in vitro cell-culture experiments by allowing a better mimicry of human physiology and pathophysiology that has consequently led researchers to gain more meaningful insights into disease mechanisms. Several models of hearts-on-chips and vessels-on-chips have been demonstrated to recapitulate fundamental aspects of the human cardiovascular system in the recent past. These 2D and 3D systems include synchronized beating cardiomyocytes in hearts-on-chips and vessels-on-chips with layer-based structures and the inclusion of physiological and pathological shear stress conditions. The opportunities to discover novel targets and to perform drug testing with chip-based platforms have substantially enhanced, thanks to the utilization of patient-derived cells and precise control of their microenvironment. These organ models will provide an important asset for future approaches to personalized cardiovascular medicine and improved patient care. However, certain technical and biological challenges remain, making the global utilization of OoCs to tackle unanswered questions in cardiovascular science still rather challenging. This review article aims to introduce and summarize published work on hearts- and vessels-on chips but also to provide an outlook and perspective on how these advanced in vitro systems can be used to tailor disease models with patient-specific characteristics.

Facilitating implementation of organs-on-chips by open platform technology

Organ-on-chip (OoC) and multi-organs-on-chip (MOoC) systems have the potential to play an important role in drug discovery, disease modeling, and personalized medicine. However, most devices developed in academic labs remain at a proof-of-concept level and do not yet offer the ease-of-use, manufacturability, and throughput that are needed for widespread application. Commercially available OoC are easier to use but often lack the level of complexity of the latest devices in academia. Furthermore, researchers who want to combine different chips into MOoC systems are limited to one supplier, since commercial systems are not compatible with each other. Given these limitations, the implementation of standards in the design and operation of OoCs would strongly facilitate their acceptance by users. Importantly, the implementation of such standards must be carried out by many participants from both industry and academia to ensure a widespread acceptance and adoption. This means that standards must also leave room for proprietary technology development next to promoting interchangeability. An open platform with standardized interfacing and user-friendly operation can fulfill these requirements. In this Perspective article, the concept of an open platform for OoCs is defined from a technical perspective. Moreover, we discuss the importance of involving different stakeholders in the development, manufacturing, and application of such an open platform.

Combination of white matter hyperintensities and Aβ burden is related to cognitive composites domain scores in subjective cognitive decline: the FACEHBI cohort

BACKGROUND

To explore whether the combination of white matter hyperintensities (WMHs) and amyloid-beta (Aβ) deposition is associated with worse cognitive performance on cognitive composites (CCs) domain scores in individuals with subjective cognitive decline (SCD).

METHODS

Two hundred participants from the FACEHBI cohort underwent structural magnetic resonance imaging (MRI), 18F-florbetaben positron emission tomography (FBB-PET), and neuropsychological assessment. WMHs were addressed through the Fazekas scale, the Age-Related White Matter Changes (ARWMC) scale, and the FreeSurfer pipeline. Eight CCs domain scores were created using the principal component analysis (PCA). Age, sex, education, and apolipoprotein E (APOE) were used as adjusting variables.

RESULTS

Adjusted multiple linear regression models showed that FreeSurfer (B - .245; 95% CI - .1.676, - .393, p = .016) and β burden (SUVR) (B - .180; 95% CI - 2.140, - .292; p = .070) were associated with face-name associative memory CCs domain score, although the latest one was not statistically significant after correction for multiple testing (p = .070). There was non-significant interaction of these two factors on this same CCs domain score (p = .54). However, its cumulative effects on face-name associative performance indicated that those individuals with either higher WMH load or higher Aβ burden showed the worst performance on the face-name associative memory CCs domain score.

CONCLUSIONS

Our results suggest that increased WMH load and increased Aβ are independently associated with poorer episodic memory performance in SCD individuals, indicating a cumulative effect of the combination of these two pathological conditions in promoting lower cognitive performance, an aspect that could help in terms of treatment and prevention.

Correlations between plasma and PET beta-amyloid levels in individuals with subjective cognitive decline: the Fundació ACE Healthy Brain Initiative (FACEHBI)

BACKGROUND

Peripheral biomarkers that identify individuals at risk of developing Alzheimer's disease (AD) or predicting high amyloid beta (Aβ) brain burden would be highly valuable. To facilitate clinical trials of disease-modifying therapies, plasma concentrations of Aβ species are good candidates for peripheral AD biomarkers, but studies to date have generated conflicting results.

METHODS

The Fundació ACE Healthy Brain Initiative (FACEHBI) study uses a convenience sample of 200 individuals diagnosed with subjective cognitive decline (SCD) at the Fundació ACE (Barcelona, Spain) who underwent amyloid florbetaben(18F) (FBB) positron emission tomography (PET) brain imaging. Baseline plasma samples from FACEHBI subjects (aged 65.9 ± 7.2 years) were analyzed using the ABtest (Araclon Biotech). This test directly determines the free plasma (FP) and total plasma (TP) levels of Aβ40 and Aβ42 peptides. The association between Aβ40 and Aβ42 plasma levels and FBB-PET global standardized uptake value ratio (SUVR) was determined using correlations and linear regression-based methods. The effect of the APOE genotype on plasma Aβ levels and FBB-PET was also assessed. Finally, various models including different combinations of demographics, genetics, and Aβ plasma levels were constructed using logistic regression and area under the receiver operating characteristic curve (AUROC) analyses to evaluate their ability for discriminating which subjects presented brain amyloidosis.

RESULTS

FBB-PET global SUVR correlated weakly but significantly with Aβ42/40 plasma ratios. For TP42/40, this observation persisted after controlling for age and APOE ε4 allele carrier status (R2 = 0.193, p = 1.01E-09). The ROC curve demonstrated that plasma Aβ measurements are not superior to APOE and age in combination in predicting brain amyloidosis. It is noteworthy that using a simple preselection tool (the TP42/40 ratio with an empirical cut-off value of 0.08) optimizes the sensitivity and reduces the number of individuals subjected to Aβ FBB-PET scanners to 52.8%. No significant dependency was observed between APOE genotype and plasma Aβ measurements (p value for interaction = 0.105).

CONCLUSION

Brain and plasma Aβ levels are partially correlated in individuals diagnosed with SCD. Aβ plasma measurements, particularly the TP42/40 ratio, could generate a new recruitment strategy independent of the APOE genotype that would improve identification of SCD subjects with brain amyloidosis and reduce the rate of screening failures in preclinical AD studies. Independent replication of these findings is warranted.

FACEHBI: A Prospective Study of Risk Factors, Biomarkers and Cognition in a Cohort of Individuals with Subjective Cognitive Decline. Study Rationale and Research Protocols

BACKGROUND

Long-term longitudinal studies with multimodal biomarkers are needed to delve into the knowledge of preclinical AD. Subjective cognitive decline has been proposed as a risk factor for the development of cognitive impairment. Thus, including individuals with SCD in observational studies may be a cost-effective strategy to increase the prevalence of preclinical AD in the sample.

OBJECTIVES

To describe the rationale, research protocols and baseline characteristics of participants in the Fundació ACE Healthy Brain Initiative (FACEHBI).

DESIGN

FACEHBI is a clinical trial (EudraCT: 2014-000798-38) embedded within a long-term observational study of individuals with SCD.

SETTING

Participants have been recruited at the memory clinic of Fundació ACE (Barcelona) from two different sources: patients referred by a general practitioner and individuals from an Open House Initiative.

PARTICIPANTS

200 individuals diagnosed with SCD with a strictly normal performance in a comprehensive neuropsychological battery.

MEASUREMENTS

Individuals will undergo an extensive neuropsychological protocol, risk factor assessment and a set of multimodal biomarkers including florbetaben PET, structural and functional MRI, diffusion tensor imaging, determination of amyloid species in plasma and neurophthalmologic assessment with optical coherence tomography.

RESULTS

Two hundred individuals have been recruited in 15 months. Mean age was 65.9 years; mean MMSE was 29.2 with a mean of 14.8 years of education.

CONCLUSIONS

FACEHBI is a long-term study of cognition, biomarkers and lifestyle that has been designed upon an innovative symptom-based approach using SCD as target population. It will shed light on the pathophysiology of preclinical AD and the role of SCD as a risk marker for the development of cognitive impairment.

Effect of Sildenafil on Pre-Eclampsia-Like Mouse Model Induced By L-Name

N(omega)-nitro-L-arginine methyl ester (L-NAME) decreases the vasodilator effect of nitric oxide (NO) and induces pre-eclampsia in mouse. Sildenafil inhibits the degradation of nitric oxide and increases vasodilation. This study aimed to determine the effects of sildenafil citrate on angiogenesis and oxidative stress at the maternal foetal interface on pre-eclampsia-like mouse model induced by L-NAME. Twenty pregnant mice were divided into four groups: (i) vehicle control; (ii) L-NAME; (iii) sildenafil; (4) L-NAME+sildenafil. L-NAME was administered from day 7 of pregnancy and sildenafil from day 8 until day 16; animals were euthanized on day 17. Placental and foetal sizes and weights were measured; lipid peroxide levels and catalase activity in placental homogenates were determined, and placental vascular endothelia were identified by lectin-histochemistry using BSA-I lectin. Western blot analysis was used to determine VEGF expression in placental homogenates. No changes were seen in placental and foetal development in mice with normal pregnancies treated with sildenafil. Treatments with L-NAME reduced significantly the placental weight and average height and decreased the percentage of the endothelial surface. These alterations may be mediated by the reduction of NO levels in trophoblastic cells, due to the inhibitory effect of L-NAME on nitric oxide synthase (NOS) synthesis. This effect was offset by the treatment with sildenafil, with an increase in the percentage of the endothelial surface. In conclusion, our results indicate that treatment with sildenafil on pre-eclampsia mouse model can be used without adverse effects on the concept and its use in the treatment of pre-eclampsia is promising.

Adrenal response of male rats exposed to prenatal stress and early postnatal stimulation

Stress in pregnant rats caused by chronic immobilization alters the pattern of secretion of corticosterone and modifies the hypothalamic-pituitary-adrenal axis (HPA) of the fetus. Early postnatal handling, however, may reverse the effects of increased secretion of corticosterone. We investigated the effects of prenatal stress and postnatal handling on the activity of the HPA axis of male offspring of stressed female rats. Male 90-day-old rats from four groups were investigated: prenatally stressed animals without postnatal handling, prenatally stressed animals with postnatal handling, unstressed control animals with postnatal handling, and unstressed control animals without postnatal handling. After sacrifice, the adrenal glands were weighed to determine the adrenal-somatic index. Apoptosis was evaluated by TUNEL assay and active caspase-3 expression. We found that the adrenal gland cortex:medulla ratio increased in animals with prenatal stress and that eventually the stress caused apoptosis. Handling newborns to simulate maternal activity ameliorated some of the negative effects of prenatal stress.

[Roux-en-Y gastric bypass for treatment of patients with DM type 2 and BMI of 30 to 35 Kg/m²]

BACKGROUND

The incidence of obesity and its most feared comorbidity, diabetes mellitus type 2, is increasing and there would not seem to be any medical treatment to help control these pandemics. However, there is a bariatric surgery technique, the Roux-en-Y Gastric Bypass (RYGB), which is safe and not only helps control excess weight, but produces encouraging results in the control and remission of diabetes.

METHODS

We present 15 selected patients with a BMI between 30 and 35 kg/mt² and diabetes type 2 who underwent a laparoscopic RYGB with of one-year follow-up.

RESULTS

A total of 14 women and one man were operated with the following average values: age: 37 years, weight: 88.3 kg, BMI: 32.8 kg/mt², blood glucose: 120 ± 38.8 mg%, HbA1c: 7.6 ± 0.73. Forty percent (40%) suffered from high blood pressure and 33.3% were dyslipidemic. Average surgical time was 75 minutes, hospital length of stay was two days, and there was a low rate of complications and no mortality. Diabetes remission was achieved in 93% of cases with significant drops in blood glucose and HbA1c (p ≤ 0.05 and p ≤ 0.001 respectively), dyslipidemia was 100% controlled and hypertension was 83.3% controlled.

CONCLUSIONS

RYGB in selected patients with obesity type 1 and diabetes mellitus type 2 is a safe and effective technique for metabolic control and obesity control.

Changes in ruminal microbiota due to rumen content processing and incubation in single-flow continuous-culture fermenters

The aim of this study was to investigate the impact of rumen content manipulation and its incubation in an in vitro system on the abundance of some microbial groups and the bacterial diversity of goat rumens. Animals and single-flow continuous-culture fermenters were fed diets differing in forage to concentrate ratio (70 : 30; LC and 30 : 70; HC). Rumen contents were sampled after animals’ adaptation to the experimental diets, processed for inoculum preparation and inoculated into fermenters. Fermenter contents were sampled 1 and 7 days after inoculation. Total bacteria, Fibrobacter succinogenes, fungi and methanogen abundances were lower in the fermenter than in goat rumens, but no differences were found for Ruminococcus flavefaciens. The abundances of all these microorganisms were similar at 1 and 7 days of rumen content incubation in fermenters. Bacterial species richness did not change due to rumen content processing or the in vitro incubation. Shannon–Wiener index and Pielou evenness were lower in the fermenter than in rumen only when the enzyme HaeIII was used in terminal-restriction fragment length polymorphism analysis. Non-metric multidimensional scaling analysis, both in denaturing gradient gel electrophoresis and terminal-restriction fragment length polymorphism, showed a segregation of in vivo and in vitro samples, but no trends of grouping for fermenter samples was observed. The HC diet promoted higher abundance of total bacteria than LC in rumen but not in fermenters. Diet only had an effect on bacterial diversity when the enzyme HaeIII was considered. Rumen content processing and incubation in fermenters caused an important decline of the studied ruminal microbial groups although bacterial community structure and diversity did not significantly change.

Assessing the impact of composting and vermicomposting on bacterial community size and structure, and microbial functional diversity of an olive-mill waste

The aim of this study was to couple biochemical and molecular methodologies for evaluating the impact of two recycling technologies (composting and vermicomposting) on a toxic organic waste. To do this, six enzyme activities controlling the key metabolic pathways of the breakdown of organic matter, real-time PCR assays targeting 16S rRNA genes, and denaturing gradient gel electrophoresis (DGGE) profiling-sequence analysis of PCR-amplified 16S rRNA fragments have been used to determine the functional diversity, bacterial number, and bacterial community structure, respectively, in a mixture of olive waste and sheep manure, and in the derived compost and vermicompost. Both the recycling technologies were effective in activating the microbial parameters of the toxic waste, the vermicomposting being the best process to produce greater bacterial diversity, greater bacterial numbers and greater functional diversity. Although several identical populations were detected in the processed and non-processed materials, each technology modified the original microbial communities of the waste in a diverse way, indicating the different roles of each one in the bacterial selection.

Effectiveness of autochthonous bacterium and mycorrhizal fungus on Trifolium growth, symbiotic development and soil enzymatic activities in Zn contaminated soil

AIMS

This study investigates how autochthonous micro-organisms [bacterium and/or arbuscular mycorrhizal (AM) fungi] affected plant tolerance to Zn contamination.

METHODS AND RESULTS

Zinc-adapted and -nonadapted Glomus mosseae strains protected the host plant against the detrimental effect of Zn (600 microg g(-1)). Zn-adapted bacteria increased root growth and N, P nutrition in plants colonized by adapted G. mosseae and decreased the specific absorption rate (SAR) of Cd, Cu, Mo or Fe in plants colonized by Zn-nonadapted G. mosseae. Symbiotic structures (nodule number and extraradical mycelium) were best developed in plants colonized by those Zn-adapted isolates that were the most effective in increasing plant Zn tolerance. The bacterium also increased the quantity and quality (metabolic characteristics) of mycorrhizal colonization, with the highest improvement for arbuscular vitality and activity. Inocula also enhanced soil enzymatic activities (dehydrogenase, beta-glucosidase and phosphatase) and indol acetic acid (IAA) accumulation, particularly in the rhizosphere of plants inoculated with Zn-adapted isolates.

CONCLUSIONS

Glomus mosseae strains have a different inherent potential for improving plant growth and nutrition in Zn-contaminated soil. The bacterium increased the potential of mycorrhizal mycelium as inoculum.

SIGNIFICANCE AND IMPACT OF THE STUDY

Mycorrhizal performance, particularly that of the autochthonous strain, was increased by the bacterium and both contributed to better plant growth and establishment in Zn-contaminated soils.

Two bacterial strains isolated from a Zn-polluted soil enhance plant growth and mycorrhizal efficiency under Zn-toxicity

In this study we investigated the interactions among plant, rhizosphere microorganisms and Zn pollution. We tested the influence of two bacterial strains isolated from a Zn-polluted soil on plant growth and on the symbiotic efficiency of native arbuscular mycorrhizal fungi (AMF) under Zn toxicity. The two bacterial strains exhibited Zn tolerance when cultivated under increasing Zn levels in the medium. However, strain B-I showed a higher Zn tolerance than strain B-II at the two highest Zn levels in the medium (75 and 100 mg l(-1) Zn). Molecular identification placed the strain B-I within the genus Brevibacillus. Our results showed that bacterial strain B-I consistently enhanced plant growth, N and P accumulation, as well as nodule number and mycorrhizal infection which demonstrated its plant-growth promoting (PGP) activity. This strain B-I has been shown to produce IAA (3.95 microg ml) and to accumulate 5.6% of Zn from the growing medium. The enhanced growth and nutrition of plants dually inoculated with the AMF and bacterium B-I was observed at three Zn levels assayed. This effect can be related to the stimulation of symbiotic structures (nodules and AMF colonization) and a decreased Zn concentration in plant tissues. The amount of Zn acquired per root weight unit was reduced by each one of these bacterial strains or AMF and particularly by the mixed bacterium-AMF inocula. These mechanisms explain the alleviation of Zn toxicity by selected microorganisms and indicate that metal-adapted bacteria and AMF play a key role enhancing plant growth under soil Zn contamination.

Brevibacillus brevis isolated from cadmium- or zinc-contaminated soils improves in vitro spore germination and growth of Glomus mosseae under high Cd or Zn concentrations

In this study we investigated the saprophyte growth of two arbuscular-mycorrhizal fungi (Glomus mosseae isolate) under increasing Cd or Zn levels and the influence of a selected bacterial strain of Brevibacillus brevis. Microorganisms here assayed were isolated from Cd or Zn polluted soils. B. brevis increased the presymbiotic growth (germination rate growth and mycelial development) of Glomus mosseae. Spore germination and mycelial development of both G. mosseae isolate were reduced as much as the amount of Cd or Zn increased in the growth medium. In medium supplemented with 20 microg Cd mL(-1), the spore germination was only 12% after 20 days of incubation, but the coinoculation with B. brevis increased this value to 40% after only 15 days. The addition of 20 microg Cd mL(-1) to the growth medium drastically inhibited hyphal development, but the presence of the bacterium increased hyphal growth of G. mosseae from 195% (without Cd) until 254% (with 20 microg Cd mL(-1)). The corresponding bacterial effect increasing micelial growth ranged from 125% (without Zn) to 232% (200 microg Zn mL(-1)) in the case of G. mosseae isolated from Zn-polluted soil. Mycelial growth under 5 microg Cd mL(-1) (without bacterium) was similarly reduced from that produced at 15 microg Cd mL(-1) in the presence of the bacteria. As well, 50 microg Zn mL(-1) (without bacterium) reduced hyphal growth as much as 200 microg Zn mL(-1) did in the presence of B. brevis. The bacterial effect on the saprophytic growth of G. mosseae in absence of metal may be due to the involvement of indole acetic acid (IAA) produced by these bacteria. The Cd bioaccumulation ability exhibited (76%) by Cd-adapted B. brevis reduced the Cd damage on G. mosseae in Cd-contaminated medium. These capabilities of B. brevis isolates partially alleviate the inhibitory effects of Cd or Zn on the axenic growth of G. mosseae.

Interactive effect of Brevibacillus brevis and Glomus mosseae, both isolated from Cd contaminated soil, on plant growth, physiological mycorrhizal fungal characteristics and soil enzymatic activities in Cd polluted soil

The interaction between two autochthonous microorganisms (Brevibacillus brevis and Glomus mosseae) isolated from Cd amended soil increased plant growth, arbuscular mycorrhizal (AM) colonization and physiological characteristics of the AM infection (measured as SDH or ALP activities). The enhanced plant Cd tolerance after coinoculation with native microorganisms seemed to be a consequence of increased P and K acquisition and, simultaneously, of decreased concentration of Cd, Cr, Mn, Cu, Mo, Fe and Ni in plant tissue. Autochthonous microbial strains were more efficient for nutrient uptake, to immobilize metals and decrease their translocation to the shoot than reference G. mosseae (with or without bacteria). Indole acetic acid produced by B. brevis may be related to its ability for improving root growth, nodule production and AM fungal intra and extraradical development. Dehydrogenase, phosphatase and beta-glucosidase activities, indicative of microbial metabolism and soil fertility, were maximized by the coinoculation of autochthonous microorganisms in cadmium polluted conditions. As a consequence, the use of native microorganisms may result very efficient in bioremediation.

Influence of bacterial strains isolated from lead-polluted soil and their interactions with arbuscular mycorrhizae on the growth of Trifolium pratense L. under lead toxicity

We isolated two bacterial strains from an experimentally lead (Pb)-polluted soil in Hungary, 10 years after soil contamination. These strains represented the two most abundant cultivable bacterial groups in such soil, and we tested their influence on Trifolium pratense L. growth and on the functioning of native mycorrhizal fungi under Pb toxicity in a second Pb-spiked soil. Our results showed that bacterial strain A enhanced plant growth, nitrogen and phosphorus accumulations, nodule formation, and mycorrhizal infection, demonstrating its plant-growth-promoting activity. In addition, strain A decreased the amount of Pb absorbed by plants, when expressed on a root weight basis, because of increased root biomass due to the production of indoleacetic acid. The positive effect of strain A was not only evident after a single inoculation but also in dual inoculation with arbuscular mycorrhizal fungi. Strain A also exhibited higher tolerance than strain B when cultivated under increasing Pb levels in the spiked soil. Molecular identification unambiguously placed strain A within the genus Brevibacillus. We showed that it is important to select the most tolerant and efficient bacterial strain for co-inoculation with arbuscular mycorrhizal fungi to promote effective symbiosis and thus stimulate plant growth under adverse environmental conditions, such as heavy-metal contamination.

Symbiotic efficiency of autochthonous arbuscular mycorrhizal fungus (G. mosseae) and Brevibacillus sp. isolated from cadmium polluted soil under increasing cadmium levels

The effect of inoculation with indigenous naturally occurring microorganisms (an arbuscular mycorrhizal (AM) fungus and rhizosphere bacteria) isolated from a Cd polluted soil was assayed on Trifolium repens growing in soil contaminated with a range of Cd. One of the bacterial isolate showed a marked PGPR effect and was identified as a Brevibacillus sp. Mycorrhizal colonization also enhanced Trifolium growth and N, P, Zn and Ni content and the dually inoculated (AM fungus plus Brevibacillus sp.) plants achieved further growth and nutrition and less Cd concentration, particularly at the highest Cd level. Increasing Cd level in the soil decreased Zn and Pb shoot accumulation. Coinoculation of Brevibacillus sp. and AM fungus increased shoot biomass over single mycorrhizal plants by 18% (at 13.6 mg Cd kg(-1)), 26% (at 33.0 mg Cd kg(-1)) and 35% (at 85.1 mg Cd (kg(1)). In contrast, Cd transfer from soil to plants was substantially reduced and at the highest Cd level Brevibacillus sp. lowered this value by 37.5% in AM plants. Increasing Cd level highly reduced plant mycorrhization and nodulation. Strong positive effect of the bacterium on inocula, are important in plant Cd tolerance and development in Cd polluted soils.

Effect of the interaction between pro-leu-gly-NH2 and catecholaminergic drugs on MSH release from rat pituitaries incubated in vitro

The effect of the interaction between Pro-Leu-Gly-NH2 (PLG) and catecholamines on the release of MSH by rat pituitaries glands was studied in vitro. The catecholamines dopamine (DA) and norepinephrine (NE) inhibited the release of alpha-MSH from pituitary glands incubated in vitro. The DA effect appeared at low concentrations while NE was effective in concentrations 20 times greater than DA. These effects were blocked by an alpha-adrenergic blocker agent. On the other hand, epinephrine (E) at the concentrations tested did not modify MSH release. When 50 or 500 ng/ml of DA is added to the medium containing PLG concentrations it strengthened the inhibitory effect of PLG release, whereas the action of NE and PLG was additive; at the highest tested concentration E (5,000 ng/ml) blocked the inhibition of MSH induced by PLG. It is concluded that, whereas the inhibitory release of MSH by catecholamines is mediated by an alpha-adrenergic receptor, the inhibitory effect of PLG is not exerted through a catecholaminergic receptor since its action is not prevented by any of the catecholamine receptor blockers studied. Thus, it seems that specific PLG receptors are present at the pituitary level.

Differences in the release of melanocyte-stimulating hormone in vitro by rat pituitary glands collected at various times during the oestrous cycle

The release of melanocyte-stimulating hormone (MSH) into the medium during incubation and the pituitary tissue content of MSH were measured separately using pituitary glands collected from rats at various stages of the oestrous cycle. The MSH was measured by a biological assay using a synthetic alpha-MSH as standard. The release of MSH was maximal during thepro-oestrous phase and MSH content of the pituitary gland was highest during dioestrus. The influences of the tripeptide Pro-Leu-Gly-NH2, which inhibits MSH secretion in vivo, and of progesterone on the release of MSH in vitro were studied with tissue collected at various phases of the oestrous cycle. Pro-Leu-Gly-NH2 was effective in inhibiting MSH release both at pro-oestrus and oestrus but not at dioestrus. Progesterone overcame this inhibition.