Agrobacterium-mediated direct transformation of wheat mature embryos through organogenesis

Transgenic plant production in monocotyledonous species has primarily relied on embryogenic callus induction from both immature and mature embryos as the pathway for plant regeneration. We have efficiently regenerated fertile transgenic wheat plants through organogenesis after Agrobacterium-mediated direct transformation of mechanically isolated mature embryos from field-grown seed. Centrifugation of the mature embryos in the presence of Agrobacterium was found to be essential for efficient T-DNA delivery to the relevant regenerable cells. The inoculated mature embryos formed multiple buds/shoots on high-cytokinin medium, which directly regenerated into transgenic shoots on hormone-free medium containing glyphosate for selection. Rooted transgenic plantlets were obtained within 10-12 weeks after inoculation. Further optimization of this transformation protocol resulted in significant reduction of chimeric plants to below 5%, as indicated by leaf GUS staining and T1 transgene segregation analysis. Direct transformation of wheat mature embryos has substantial advantages over traditional immature embryo-based transformation systems, including long-term storability of the mature dry explants, scalability, and greatly improved flexibility and consistency in transformation experiments.

Commercial scale genetic transformation of mature seed embryo explants in maize

A novel, efficient maize genetic transformation system was developed using Agrobacterium-mediated transformation of embryo explants from mature seeds. Seeds from field grown plants were sterilized and crushed to isolate embryo explants consisting of the coleoptile, leaf primordia, and shoot apical meristem which were then purified from the ground seed bulk preparation. The infection of relevant tissues of seed embryo explants (SEEs) by Agrobacterium was improved by the centrifugation of the explants. Transgenic plants were obtained by multiple bud induction on high cytokinin media, followed by plant regeneration on hormone-free medium. Three different selectable markers (cp4 epsps, aadA, and nptII) were successfully used for producing transgenic plants. Stable integration of transgenes in the maize genome was demonstrated by molecular analyses and germline transmission of the inserted transgenes to the next generation was confirmed by pollen segregation and progeny analysis. Phenotypic evidence for chimeric transgenic tissue was frequently observed in initial experiments but was significantly reduced by including a second bud induction step with optimized cytokinin concentration. Additional improvements, including culturing explants at an elevated temperature during bud induction led to the development of a revolutionary system for efficient transgenic plant production and genome editing. To our knowledge, this is the first report of successful transgenic plant regeneration through Agrobacterium-mediated transformation of maize mature SEEs. This system starts with mature seed that can be produced in large volumes and the SEEs explants are storable. It has significant advantages in terms of scalability and flexibility over methods that rely on immature explants.

Quality of root fillings performed with two root filling techniques. An in vitro study using micro-CT

Objective.

The aim of this study was to compare the presence of voids in root fillings performed in oval and ribbon-shaped canals with two root filling techniques, lateral compaction technique (LCT) or hybrid technique (HT), a combination of a gutta-percha masterpoint and thermoplastic gutta-percha. Furthermore, the obturation time for the two techniques was evaluated.

Materials and methods.

Sixty-seven roots with oval and ribbon-shaped canals were prepared using Profile Ni-Ti rotary files. After preparation, the roots were randomly allocated to two groups according to root filling technique. All roots were filled with AH plus and gutta-percha. Group 1 was filled using LCT (n = 34) and group 2 was filled using HT (n = 33). The obturation time was measured in 30 cases evenly distributed between the two techniques. Voids in relation to the root canal fillings were assessed using cross-section images from Micro-computed Tomography scans.

Results.

All root canal fillings had voids. Permutation test showed no statistically significant difference between the two root filling techniques in relation to presence of voids (p = 0.092). A statistically significant difference in obturation time between the two techniques was found (p < 0.001).

Conclusion.

The present study found no statistically significant difference in percentage of voids between two root filling techniques. A 40% reduction in obturation time was found for the HT compared to the LCT.

Parameters affecting the efficient delivery of mesoporous silica nanoparticle materials and gold nanorods into plant tissues by the biolistic method

Applying nanotechnology to plant science requires efficient systems for the delivery of nanoparticles (NPs) to plant cells and tissues. The presence of a cell wall in plant cells makes it challenging to extend the NP delivery methods available for animal research. In this work, research is presented which establishes an efficient NP delivery system for plant tissues using the biolistic method. It is shown that the biolistic delivery of mesoporous silica nanoparticle (MSN) materials can be improved by increasing the density of MSNs through gold plating. Additionally, a DNA-coating protocol is used based on calcium chloride and spermidine for MSN and gold nanorods to enhance the NP-mediated DNA delivery. Furthermore, the drastic improvement of NP delivery is demonstrated when the particles are combined with 0.6 μm gold particles during bombardment. The methodology described provides a system for the efficient delivery of NPs into plant cells using the biolistic method.

Utilizing protein-lean coproducts from corn containing recombinant pharmaceutical proteins for ethanol production

Protein-lean fractions of corn (maize) containing recombinant (r) pharmaceutical proteins were evaluated as a potential feedstock to produce fuel ethanol. The levels of residual r-proteins in the coproduct, distillers dry grains with solubles (DDGS), were determined. Transgenic corn lines containing recombinant green fluorescence protein (r-GFP) and a recombinant subunit vaccine of Escherichia coli enterotoxin (r-LTB), primarily expressed in endosperm, and another two corn lines containing recombinant human collagen (r-CIα1) and r-GFP, primarily expressed in germ, were used as model systems. The kernels were either ground and used for fermentation or dry fractionated to recover germ-rich fractions prior to grinding for fermentation. The finished beers of whole ground kernels and r-protein-spent endosperm solids contained 127-139 and 138-155 g/L ethanol concentrations, respectively. The ethanol levels did not differ among transgenic and normal corn feedstocks, indicating the residual r-proteins did not negatively affect ethanol production. r-Protein extraction and germ removal also did not negatively affect fermentation of the remaining mass. Most r-proteins were inactivated during the mashing process used to prepare corn for fermentation. No functionally active r-GFP or r-LTB proteins were found after fermentation of the r-protein-spent solids; however, a small quantity of residual r-CIα1 was detected in DDGS, indicating that the safety of DDGS produced from transgenic grain for r-protein production needs to be evaluated for each event. Protease treatment during fermentation completely hydrolyzed the residual r-CIα1, and no residual r-proteins were detectable in DDGS.

Wet-milling transgenic maize seed for fraction enrichment of recombinant subunit vaccine

The production of recombinant proteins in plants continues to be of great interest for prospective large-scale manufacturing of industrial enzymes, nutrition products, and vaccines. This work describes fractionation by wet-milling of transgenic maize expressing the B subunit of the heat-labile enterotoxin of Escherichia coli (LT-B), a potent immunogen and candidate for oral vaccine and vaccine components. The LT-B gene was directed to express in seed by an endosperm specific promoter. Two steeping treatments, traditional steeping (TS, 0.2% SO(2) + 0.5% lactic acid) and water steeping (WS, water only), were evaluated to determine effects on recovery of functional LT-B in wet-milled fractions. The overall recovery of the LT-B protein from WS treatment was 1.5-fold greater than that from TS treatment. In both steeping types, LT-B was distributed similarly among the fractions, resulting in enrichment of functional LT-B in fine fiber, coarse fiber and pericarp fractions by concentration factors of 1.5 to 8 relative to the whole kernels on a per-mass basis. Combined with endosperm-specific expression and secretory pathway targeting, wet-milling enables enrichment of high-value recombinant proteins in low-value fractions, such as the fine fiber, and co-utilization of remaining fractions in alternative industrial applications.

A bacterial signal peptide is functional in plants and directs proteins to the secretory pathway

The Escherichia coli heat-labile enterotoxin B subunit (LT-B) has been used as a model antigen for the production of plant-derived high-valued proteins in maize. LT-B with its native signal peptide (BSP) has been shown to accumulate in starch granules of transgenic maize kernels. To elucidate the targeting properties of the bacterial LT-B protein and BSP in plant systems, the subcellular localization of visual marker green fluorescent protein (GFP) fused to LT-B and various combinations of signal peptides was examined in Arabidopsis protoplasts and transgenic maize. Biochemical analysis indicates that the LT-B::GFP fusion proteins can assemble and fold properly retaining both the antigenicity of LT-B and the fluorescing properties of GFP. Maize kernel fractionation revealed that transgenic lines carrying BSP result in recombinant protein association with fibre and starch fractions. Confocal microscopy analysis indicates that the fusion proteins accumulate in the endomembrane system of plant cells in a signal peptide-dependent fashion. This is the first report providing evidence of the ability of a bacterial signal peptide to target proteins to the plant secretory pathway. The results provide important insights for further understanding the heterologous protein trafficking mechanisms and for developing effective strategies in molecular farming.

Genetic engineering approaches to improve bioethanol production from maize

Biofuels such as bioethanol are becoming a viable alternative to fossil fuels. Utilizing agricultural biomass for the production of biofuel has drawn much interest in many science and engineering disciplines. As one of the major crops, maize offers promise in this regard. Compared to other crops with biofuel potential, maize can provide both starch (seed) and cellulosic (stover) material for bioethanol production. However, the combination of food, feed and fuel in one crop, although appealing, raises concerns related to the land delineation and distribution of maize grown for energy versus food and feed. To avoid this dilemma, the conversion of maize biomass into bioethanol must be improved. Conventional breeding, molecular marker assisted breeding and genetic engineering have already had, and will continue to have, important roles in maize improvement. The rapidly expanding information from genomics and genetics combined with improved genetic engineering technologies offer a wide range of possibilities for enhanced bioethanol production from maize.

A case of resistance to thyroid hormone without mutation in the thyroid hormone receptor beta

BACKGROUND

Resistance to Thyroid Hormone (RTH) is a condition caused by tissue hyposensitivity to the effects of circulating thyroid hormone, and may be misdiagnosed as hyperthyroidism.

AIMS

We report the first case of RTH in an Irish patient highlighting the clinical features and the pathophysiological mechanism underlying the characteristic laboratory abnormalities found in the condition.

METHODS

We describe an isolated case of RTH initially misdiagnosed as hyperthyroidism, and detail the investigations which ultimately led to the correct diagnosis. Genetic screening of the thyroid hormone receptor beta gene was performed.

RESULTS

Thyroid function tests including T3 suppression test and TRH-stimulation test suggested a diagnosis of RTH. Genetic testing failed to demonstrate a mutation in the thyroid hormone receptor.

CONCLUSION

RTH is a rare inherited condition that may be misdiagnosed as hyperthyroidism. The case we describe most likely results from a de novo mutation in an as yet undiscovered gene. RTH should be considered in patients with elevated thyroid hormone levels and normal TSH so that unnecessary and potentially harmful treatment can be avoided.

Survey on porcine trichinellosis in Ecuador

A survey on porcine trichinellosis was organised in Ecuador between 2000 and 2003. Blood samples were taken in slaughterhouses (study 1, n=2000; study 2, n=331) and in a remote village where pigs are free roaming (study 3, n=646) and examined by ELISA using excretory/secretory (E/S) antigens. Seven samples (0.35%) in study 1 and none of the samples of study 2 were serologically positive. Thirty-seven (5.72%) village pigs tested positive by E/S ELISA in study 3. Sero-positive results by the E/S ELISA in study 1 were confirmed by ELISA using beta-tyvelose antigen, and by immunoblot. Muscle samples taken from pigs slaughtered in the abattoir (study 2) and from animals that showed a positive serology in study 3 were examined by trichinoscopy and artificial digestion. These techniques failed to demonstrate the presence of muscle larvae. The results of this survey need confirmation, but suggest that Trichinella is present in Ecuador; however, prevalence and parasite burdens are likely to be very low. The likelihood of detecting trichinellosis are higher in traditional settings than in pigs raised on improved farms.

Role of conventional ultrasound and color Doppler sonography in the diagnosis of medullary thyroid carcinoma

Early diagnosis of medullary thyroid carcinoma (MTC) can improve long-term prognosis. MTC can be detected at an early stage by calcitonin screening in all patients with thyroid nodules. This approach, however, is controversial due to high costs and a limited specificity of calcitonin. It was the aim of the present study to investigate whether ultrasonography may contribute to the diagnosis of MTC in patients with thyroid nodules. The study included 19 patients with newly diagnosed MTC. Ten patients had sporadic MTC, 7 had multiple endocrine neoplasia (MEN) type 2A, and 2 patients had MEN 2B. In all subjects conventional ultrasound, and in 14 patients color Doppler sonography were performed before primary surgery. For comparison, ultrasound appearance of 139 benign thyroid nodules was evaluated. In conventional ultrasound, MTC in 17/19 (89%) patients were hypoechoic, contained intranodular calcifications, and had no "halo sign". The combination of these criteria were found in only 8/139 (6%) of benign thyroid nodules. Intranodular blood flow was found in 11/14 patients with MTC (79%), perinodular blood flow in 7/14 MTC (50%). In conclusion, conventional ultrasound reveals a combination of hypoechogenicity, intranodular calcifications, and absence of "halo sign" in the vast majority of MTC. Since this sonographic pattern only rarely occurs in benign thyroid nodules, the results indicate that thyroid ultrasound can contribute to the diagnosis of MTC. In addition, the findings may have implications for calcitonin screening in nodular thyroid disease.

Immunogenicity, safety and lot consistency in adults of a chromatographically purified Vero-cell rabies vaccine: a randomized, double-blind trial with human diploid cell rabies vaccine

The immunogenicity and safety of a chromatographically purified rabies vaccine (CPRV) was evaluated using US veterinary medical students. In the first study, 242 healthy adults were enrolled in a randomized, modified double-blind, multicenter trial and received five doses of either CPRV or human diploid cell vaccine (HDCV) by intramuscular injection on days 0, 3, 7, 14, and 28 concurrently with human rabies immunoglobulin in a simulated post-exposure prophylaxis regimen. Post-immunization titers in the CPRV and HDCV groups reached 0.5 IU/ml (the WHO-recommended minimally acceptable titer) or greater in all subjects in both vaccine groups by day 14 and remained above that level through day 90. In the second study, 438 healthy adults were enrolled in a randomized, double-blind, multicenter trial and assigned to receive five doses from one of three lots of CPRV by intramuscular injection on days 0, 3, 7, 14, and 28 in a simulated post-exposure prophylaxis regimen to evaluate lot consistency. Post-immunization titers rapidly increased to over 0.5 IU/ml by day 14 for all subjects and remained above that level through day 42 when the study was terminated. The three lots were considered equivalent. The percentage of subjects with at least one local reaction during the five-dose regimen was slightly lower in the CPRV group than in the HDCV group (P=0.06). The most frequently reported local reaction for all doses of vaccine was pain at the injection site. Headache, myalgia, and malaise were the most frequently reported systemic events. The percentage of subjects with at least one systemic event was significantly lower for CPRV (P=0.0084). No vaccine-related serious adverse reaction was reported in these studies. The results of these studies indicate that CPRV administered intramuscularly to healthy adults is immunogenic and is associated with fewer local and systemic reactions than HDCV.

[Headache in patients with pheochromocytoma. Influence of arterial hypertension]

Headache is an important diagnostic element in pheochromocytoma and it may characterize a body reaction to pathological hormonal oscillations. We observed the pheochromocytoma instability in 20 patients during arterial hypertension and tried to correlate with headache. We found that isolate hypertension is not the only factor in headache pathogenesis. It is possible that changes in catecholamines, adrenomedullin and other neuropeptides may cause some of these symptoms.