Human papillomavirus related oropharyngeal cancer: identifying and quantifying topics of patient interest.

OBJECTIVE: As the incidence of human papillomavirus related oropharyngeal cancer continues to rise, it is increasingly important for public understanding to keep pace. This study aimed to identify areas of patient interest and concern regarding human papillomavirus and oropharyngeal cancer. METHOD: This study was a retrospective survey of search queries containing the keywords 'HPV cancer' between September 2015 and March 2021. RESULTS: There was 3.5-fold more interest in human papillomavirus related oropharyngeal cancer (15 800 searches per month) compared with human papillomavirus related cervical cancer (4500 searches per month). Among searches referencing cancer appearance, 96.8 per cent pertained to the head and neck region (3050 searches per month). Among vaccination searches, 16 of 47 (34.0 per cent; 600 searches per month) referenced human papillomavirus vaccines as being a cause of cancer rather than preventing cancer. CONCLUSION: The vast majority of online searches into human papillomavirus cancer pertain to the oropharynx. There are relatively few search queries on the topic of vaccination preventing human papillomavirus associated oropharyngeal cancer, which highlights the continued importance of patient education and awareness campaigns.

Clinical practice guidelines on nutrition management in head and neck cancer: a systematic quality appraisal using the Appraisal of Guidelines for Research and Evaluation 2nd edition instrument.

OBJECTIVE: Several guidelines have been produced for the management of nutrition in patients with head and neck cancer. However, no systematic evaluation of the quality of these guidelines has been performed to date. METHOD: A comprehensive search was conducted up to August 2020. The quality of guidelines was assessed by four independent reviewers using the Appraisal of Guidelines for Research and Evaluation, 2nd edition. RESULTS: Nine guidelines were assessed for critical evaluation. Only two guidelines were classified as 'high quality'. The 'scope and purpose' domain achieved the highest mean score (75.5 ± 17.0 per cent), and the lowest domain mean score was 'applicability' (37.6 ± 23.0 per cent). CONCLUSION: These findings highlight the variability in the methodological quality of guidelines for the management of nutrition in head and neck cancer. These results may help to improve the reporting of future guidelines and guide the selection for use in clinical practice.

A critical appraisal of clinical practice guidelines for the diagnosis and management of benign paroxysmal positional vertigo.

BACKGROUND: Delays in the diagnosis and therapy of benign paroxysmal positional vertigo can greatly impact quality of life and increase healthcare costs for patients. This study aimed to appraise the quality of clinical practice guidelines for the diagnosis and management of benign paroxysmal positional vertigo. METHODS: A comprehensive database search of clinical practice guidelines was completed up to 30 October 2021. Four independent reviewers used the Appraisal of Guidelines for Research and Evaluation II instrument in the quality appraisal. RESULTS: The highest score was in 'clarity and presentation' (58.33 ± 22.7). The lowest score was in 'applicability' (13.96 ± 30.1). Overall, four clinical practice guidelines were 'low quality' and only one guideline was 'high quality'. CONCLUSION: This review identified a significant lack of quality in clinical practice guideline development for benign paroxysmal positional vertigo, highlighting the need for a more rigorous approach for future guideline development.

What has the National Cancer Database taught us about oral cavity squamous cell carcinoma?

The wealth of data in the National Cancer Database (NCDB) has allowed numerous studies investigating patient, disease, and treatment-related factors in oral cavity squamous cell carcinoma (OCSCC); however, to date, no summation of these studies has been performed. The aim of this study was to provide a concise review of the NCDB studies on OCSCC, with the hopes of providing a framework for future, novel studies aimed at enhancing our understanding of clinical parameters related to OCSCC. Two databases were searched, and 27 studies published between 2002 and 2020 were included. The average sample size was 13,776 patients (range 356-50,896 patients). Four areas of research focus were identified: demographic and socioeconomic status, diagnosis, prognosis, and treatment. This review highlights the impact of age, sex, ethnicity, and socioeconomic status on the prognosis and management of OCSCC, describes the prognostic factors, and details the modalities and indications for neck dissection and adjuvant therapy in OCSCC. In conclusion, the NCDB is a very valuable resource for clinicians and researchers involved in the management of OCSCC, offering an incomparable perspective on a large dataset of patients. Future developments regarding hospital information management, review of data accuracy and completeness, and wider accessibility will help clinicians to improve the care of patients affected by OCSCC.

Assessment of YouTube as an educational tool in teaching thyroidectomy and parathyroidectomy.

OBJECTIVE: YouTube has become the preferred resource for trainees to learn and prepare for surgical cases. This study evaluated the educational quality of YouTube videos detailing thyroidectomy and parathyroidectomy. METHOD: YouTube was systematically searched using 11 terms related to thyroidectomy and parathyroidectomy. Four independent clinical reviewers assessed the videos using Laparoscopic Surgery Video Educational Guidelines as well as modified Laparoscopic Surgery Video Educational Guidelines subgroup tools. RESULTS: Sixty-five videos were identified and evaluated. Overall Laparoscopic Surgery Video Educational Guidelines score was 8.58 ± 3.85 (mean subgroup score, 5.67 ± 2.40). Twenty-eight of 65, 25 of 65 and 12 of 65 videos were deemed medium, low and high quality, respectively. Inter-rater reliability was good for both attending surgeons and residents. Presence of audio or visual commentary had a positive correlation with total Laparoscopic Surgery Video Educational Guidelines scores (R2=0.38). Videos produced by otolaryngologists and US-based physicians scored higher on total scores compared to non-otolaryngology and non-US based physicians. CONCLUSION: Some YouTube videos on thyroidectomy and parathyroidectomy exhibit high educational value. Future efforts should increase the number of high-quality YouTube videos containing both audio and visual commentary or create an online repository of videos for medical students and residents to augment their surgical training.

Biolistic Transformation of Cotton Zygotic Embryo Meristem.

Biolistic transformation of cotton (Gossypium hirsutum L.) meristems, isolated from mature seed, is detailed in this report. A commercially available, helium-driven biolistic device (Bio-Rad PDS1000/He ) was used to bombard gold particles coated with a marker gene (uidA or "GUS") into the shoot meristem. The penetration of gold particles was dependent on bombardment parameters, and it was mostly one- to two-cell layers deep. Stable transformation of epidermal L1 layer was consistently observed in approximately 5% of the seedlings. Germ line transformation was observed in up to 0.71% of bombarded meristems by several laboratories. Using this method identification of germ line transformation is laborious and time-consuming. However, the protocol described here represents a simple and efficient method for generating germ line transformation events. In addition, this procedure offers a quick method to evaluate gene constructs in cotton tissues (embryos, cotyledons, leaf) especially fibers which originate as single cells from the maternal epidermis layer.

Biolistic Transformation of Cotton Embryogenic Cell Suspension Cultures.

Genetic transformation of cotton (Gossypium hirsutum L.) is highly dependent on the ability to regenerate fertile plants from transgenic cells through somatic embryogenesis. Induction of embryogenic cell cultures is genotype-dependent. However, once embryogenic cell cultures are available, they can be effectively used for transformation by Agrobacterium or biolistic bombardment methods. Here I describe a detailed procedure to transform cotton embryogenic cell suspension cultures by biolistic bombardment. A commercially available, helium-driven biolistic device (Bio-Rad PDS1000/He) was used to bombard gold particles coated with plasmid DNA (for visual identification of transformed cells and/or selection) into embryogenic cells. Stable transformation at a high frequency (up to 4% of the transiently expressing cells) is possible. Regeneration of fertile transgenic plants from embryogenic cells takes only about 2 months. Another advantage of the embryogenic cell suspension cultures is that they are amenable for cryopreservation and long-term storage. It is highly preferable to transform commercial varieties of choice than obsolete varieties to avoid genetic drug due to backcrossing.

Medialisation thyroplasty with tensor fascia lata: a novel approach for reducing post-thyroplasty complications.

BACKGROUND: Medialisation thyroplasty is considered the 'gold standard' treatment for unilateral vocal fold paralysis, enabling improvement of voice and swallowing function, and preventing life-threatening aspiration events. The most commonly used laryngeal implants induce some degree of local tissue inflammatory response, and carry the risk of immediate or delayed implant extrusion. METHODS: This paper describes a novel approach for medialisation thyroplasty. Specifically, it utilises a ribbon of autologous tensor fascia lata harvested at the time of surgery. This is layered within the paraglottic space in a manner similar to Gore-Tex thyroplasty. RESULTS: Thus far, this method has been accomplished in two patients with unilateral vocal fold paralysis, who also received prior radiotherapy to the head and neck. CONCLUSION: Given the increased risk of post-operative wound breakdown and infection in irradiated patients, it is suggested that this new approach will lead to improved outcomes, and a decrease in complications such as extrusion or wound infection, particularly in this patient population.

Increased excitability and excitatory synaptic transmission during in vitro ischemia in the neonatal mouse hippocampus.

OBJECTIVE: The present study tested the hypothesis that exposure to in vitro hypoxia-ischemia alters membrane properties and excitability as well as excitatory synaptic transmission of CA1 pyramidal neurons in the neonatal mouse. METHODS: Experiments were conducted in hippocampal slices in P7-P9 C57Bl/6 mice using whole-cell patch clamp in current- and voltage-clamp mode. Passive membrane potential (Vm), input resistance (Rin) and active (action potential (AP) threshold and amplitude) membrane properties of CA1 pyramidal neurons were assessed at baseline, during 10 min in vitro ischemia (oxygen-glucose deprivation (OGD)) and during reoxygenation. Spontaneous and miniature excitatory post-synaptic currents (s and mEPSCs) were studied under similar conditions. RESULTS: OGD caused significant depolarization of CA1 pyramidal neurons as well as decrease in AP threshold and increase in AP amplitude. These changes were blocked by the application of tetrodotoxin (TTX), indicating Na(+) channels' involvement. Following 10 min of reoxygenation, significant membrane hyperpolarization was noted and it was associated with a decrease in Rin. AP threshold and amplitude returned to baseline during that stage. sEPSC and mEPSC frequency increased during both OGD and reoxygenation but their amplitude remained unchanged. Additionally, we found that OGD decreases Ih (hyperpolarization activated current) in CA1 neurons from neonatal mice and this effect persists during reoxygenation. SIGNIFICANCE: These results indicate that in vitro ischemia leads to changes in membrane excitability mediated by sodium and potassium channels. Further, it results in enhanced neurotransmitter release from presynaptic terminals. These changes are likely to represent one of the mechanisms of hypoxia/ischemia-mediated seizures in the neonatal period.

Effect of curcumin analog on gamma-radiation-induced cellular changes in primary culture of isolated rat hepatocytes in vitro.

The present study was aimed to evaluate the radioprotective effect of curcumin analog, on gamma-radiation-induced toxicity in primary cultures of isolated rat hepatocytes. Hepatocytes were isolated from the liver of rats by collagenase perfusion. The DNA damage was analysed by single cell gel electrophoresis (comet assay). An increase in the severity of DNA damage was observed with the increase in gamma-radiation dose at 1-4 Gy in cultured rat hepatocytes. The levels of lipid peroxidative indices like thiobarbituric acid reactive substances (TBARSs) were increased significantly, whereas the levels of reduced glutathione (GSH) and antioxidant enzymes were significantly decreased in gamma-irradiated groups. The maximum damage to hepatocytes was observed at 4Gy gamma-irradiation. Pretreatment with different concentrations of curcumin analog (1.38, 6.91 and 13.82 microM) shows a significant decrease in the levels of TBARS and DNA damage. Pretreatment with curcumin analog prevents the loss of enzymic and non-enzymic antioxidants like GSH upon gamma-irradiation. The maximum protection of hepatocytes was observed at 6.91 microM of curcumin analog pretreatment. Thus, our result shows that pretreatment with curcumin analog protects the hepatocytes against gamma-radiation-induced cellular damage.

Synthesis and spectral characterization of antifungal sensitive schiff base transition metal complexes.

New N2O2 donor type Schiff base has been designed and synthesized by condensing acetoacetanilido-4-aminoantipyrine with 2-aminobenzoic acid in ethanol. Solid metal complexes of the Schiff base with Cu(II), Ni(II), Co(II), Mn(II), Zn(II), VO(IV), Hg(II) and Cd(II) metal ions were synthesized and characterized by elemental analyses, magnetic susceptibility, molar conduction, fast atom bombardment (FAB) mass, IR, UV-Vis, and (1)H NMR spectral studies. The data show that the complexes have the composition of ML type. The UV-Vis. and magnetic susceptibility data of the complexes suggest a square-planar geometry around the central metal ion except VO(IV) complex which has square-pyramidal geometry. The in vitro antifungal activities of the compounds were tested against fungi such as Aspergillus niger, Aspergillus flavus, Rhizopus stolonifer, Candida albicans, Rhizoctonia bataicola and Trichoderma harizanum. All the metal complexes showed stronger antifungal activities than the free ligand. The minimum inhibitory concentrations (MIC) of the metal complexes were found in the range of 10~31 µg/ml.

Identification of a Maize Kernel Pathogenesis-Related Protein and Evidence for Its Involvement in Resistance to Aspergillus flavus Infection and Aflatoxin Production.

ABSTRACT Aflatoxins are carcinogens produced by Aspergillus flavus and A. parasiticus during infection of susceptible crops such as maize. Several aflatoxin-resistant maize genotypes have been identified and kernel proteins have been suggested to play an important role in resistance. In the present study, one protein (#717), which was expressed fivefold higher in three resistant lines compared with three susceptible ones, was identified using proteomics. This protein was sequenced and identified as a pathogenesis-related protein (PR-10) based on its sequence homology. To assess the involvement of this PR-10 protein (ZmPR-10) in host resistance of maize against fungal infection and aflatoxin production, the corresponding cDNA (pr-10) was cloned. It encodes a protein of 160 amino acids with a predicted molecular mass of 16.9 kDa and an iso-electric point of 5.38. The expression of pr-10 during kernel development increased fivefold between 7 and 22 days after pollination, and was induced upon A. flavus infection in the resistant but not in the susceptible genotype. The ZmPR-10 overexpressed in Escherichia coli exhibited a ribonucleolytic and antifungal activities. Leaf extracts of transgenic tobacco plants expressing maize pr-10 also demonstrated RNase activity and inhibited the growth of A. flavus. This evidence suggests that ZmPR-10 plays a role in kernel resistance by inhibiting fungal growth of A. flavus.

Prevention of preharvest aflatoxin contamination through genetic engineering of crops.

Current practices on prevention of aflatoxin contamination of crop species include time consuming, expensive agronomic practices. Of all the methods available to-date, conventional breeding and/or genetic engineering to develop host plant-based resistance to aflatoxin-producing fungi appear to be valuable for several reasons. However, breeding for disease-resistant crops is very time consuming, especially in tree crops, and does not lend itself ready to combat the evolution of new virulent fungal races. Moreover, availability of known genotypes with natural resistance to mycotoxin-producing fungi is a prerequisite for the successful breeding program. While it is possible to identify a few genotypes of corn or peanuts that are naturally resistant toAspergillus we do not know whether these antifungal factors are specific toA. flavus. In crops like cotton, there are no known naturally resistant varieties toAspergillus. Availability of transgenic varieties with antifungal traits is extremely valuable as a breeding tool. Several antifungal proteins and peptides are available for genetic engineering of susceptible crop species, thanks to the availability of efficient modern tools to understand and evaluate protein interactions by proteomics of host, and genomics and field ecology of the fungus. Transgenic approaches are being undertaken in several industry and academic laboratories to prevent invasion byAspergillus fungi or to prevent biosynthesis of aflatoxin. Recent trends in reducing aflatoxin contamination through genetic engineering of cultivated crop species with antifungal proteins are summarized in this report.

Chemoprevention of colon cancer by a synthetic curcumin analog involves amelioration of oxidative stress.

The modulating effects of a bisdemethoxycurcumin analog (BDMC-A) on 1,2-dimethylhydrazine (DMH)-induced oxidative stress during colon carcinogenesis was investigated in male Wistar rats. The effects were compared with those of curcumin, a known anticarcinogen. All the animals given a weekly subcutaneous injection of DMH (20 mg/kg body wt.) for 15 weeks developed colon tumors. The colon and intestine administered DMH showed a decrease in lipid peroxidation with a concomitant increase in the activities of GSH-dependent enzymes (glutathione peroxidase, glutathione S-transferase) when compared to untreated control rats. In groups of animals given DMH and BDMC-A no tumors were observed, and the lipid peroxidation as well as the GSH-dependent enzymes showed a pattern similar to that of untreated control rats. We speculate that BDMC-A modulates DMH-induced oxidative stress and offers chemoprevention against colon carcinogenesis, and the modulatory effect is comparable with that of curcumin. Thus, lipid peroxidation and antioxidant status together could be used as markers of colon cancer chemoprevention by BDMC-A.

Protective Role of a Novel Curcuminoid on Alcohol and PUFA-Induced Hyperlipidemia.

Alcohol use is contributing to an unprecedented decline in life expectancy. It induces hyperlipidemia when taken at higher concentrations. Alcoholics usually after a heavy binge of alcohols take fried food items normally made up of polyunsaturated fatty acids (PUFAs). The combined ingestion of alcohol and PUFAs is considered to be dangerous and known to result in hyperlipidemic conditions. Previous studies have shown that curcumin, an active principle of turmeric (Curcuma longa), has antihyperlipidemic properties. So in the present work we have synthesized an analog of curcumin and tested the protective role of that synthetic curcuminoid on alcohol and thermally oxidized sunflower oil-induced hyperlipidemia. Male Albino rats of Wistar strain were used for the experimental study. Antihyperlipidemic activity of the synthetic curcuminoid was evaluated by analyzing the levels of lipids (cholesterol, triglycerides [TGs], phospholipids [PLs], and free fatty acids [FFAs]) in different tissues and histopathological changes in the liver. The results showed that the levels of cholesterol, TGs, and FFAs were increased significantly in alcohol, thermally oxidized sunflower oil (Delta PUFA), and alcohol + Delta PUFAs treated groups. Administration of synthetic curcuminoid effectively reduced these levels. The phospholipid (PL) levels, which were decreased in the liver and kidney and increased in the heart in the alcohol, Delta PUFA, and alcohol + Delta PUFA groups, were positively modulated by treatment with synthetic curcuminoid (CA). Our histopathological observations were also in correlation with the biochemical parameters. From the results obtained, we could conclude that the synthetic curcuminoid effectively protects the system against alcohol and Delta PUFA-induced hyperlipidemia and may become an effective therapeutic agent for the treatment of hyperlipidemia.

Anticarcinogenic effect of bis-1,7-(2-hydroxyphenyl)-hepta-1,6-diene-3,5-dione a curcumin analog on DMH-induced colon cancer model.

1,2-Dimethylhydrazine (DMH) is a toxic environmental pollutant which was reported also to be a colon-specific carcinogen. This study was performed to study the effect of bis-1,7-(2-hydroxyphenyl)-hepta-1,6-diene-3,5-dione, a bisdemethoxycurcumin analog (BDMC-A) on DMH-induced colon carcinogenesis in male Wistar rats and effects were compared with that of the reference drug, curcumin. Rats were given a weekly subcutaneous injection of DMH (20mg/kg body weight) in the groin, for 15 weeks. After a total experimental period of 32 weeks (including 2 weeks of acclimatization) tumor incidence was 100% in DMH-treated rats. Tumor was identified histologically as adenocarcinoma. Dysplasia, papillary pattern, cellular pleomorphism and carcinomatous glands were also noticed in DMH-treated rats. However, there was no colonic tumor in DMH+BDMC-A- and DMH+curcumin-treated rats but, lymphocyte infiltrations were observed. The levels of total bile acids and cholesterol in 24h fecal samples were significantly lower in DMH administered rats when compared to control rats, while, the excretion of bile acids and cholesterol were significantly increased and was near normal levels in DMH+BDMC-A- and DMH+curcumin-treated rats. In DMH-induced tumor bearing rats the levels of colonic and intestinal cholesterol was significantly increased whereas, the levels of phospholipid was decreased with a concomitant increase in the activities of phospholipase A (PLA) and phospholipase C (PLC), compared to untreated control rats. Intragastric administration of BDMC-A and curcumin to DMH administered rats significantly lowered the cholesterol content and raised the phospholipid content and lowered the activities of PLA and PLC towards near normal values. Our study shows that the protective effect of BDMC-A during DMH-induced colon carcinogenesis may be due to its modulatory effects on (i). histological changes, (ii). bile acids, (iii). cholesterol, and (iv). phospholipid metabolism in the target organ. Absence of histological changes in the colon of rats treated with BDMC-A, shows that long term administration of BDMC-A is nontoxic to experimental animals. Our study suggest that BDMC-A may emerge as a potent anticarcinogenic agent against colon cancer. As both BDMC-A and curcumin are equipotent in inhibiting the DMH-induced colon tumor incidence and normalizing histological changes, it could be concluded that the terminal phenolic group and the conjugated double bonds in the central seven carbon change may be responsible for the beneficial effects.

Protection of pancreatic beta-cell by the potential antioxidant bis-o-hydroxycinnamoyl methane, analogue of natural curcuminoid in experimental diabetes.

PURPOSE: To evaluate the antioxidant defense by bis-o-hydroxycinnamoylmethane, analogue of the naturally occurring curcuminoid bis-demethoxycurcumin in streptozotocin induced diabetes in male Wistar rats and its possible protection of pancreatic beta-cell against gradual loss under diabetic condition. METHODS: Male wistar rats were divided into five groups. Group1 served as control rats. Group2 was control rats treated intragastrically with bis-o-hydroxycinnamoyl methane at a dose of 15 mg/kg body weight for 45 days. Group3, 4 and 5 rats were injected with 40 mg /kg body weight of streptozotocin to induce diabetes. Group4 rats were treated with the drug similar to group2 and group5 rats treated with the reference drug glibenclamide intragastrically for a similar period. After 45 days, the levels of plasma glucose, glycated hemoglobin, enzymic antioxidants (SOD, CAT) and non-enzymic antioxidants Vit C, Vit E was determined. Histopathological sections of the pancreas were examined. RESULTS: The levels of plasma glucose and glycated hemoglobin which were elevated in group3 diabetic rats were reduced after treatment with the drug. The antioxidant levels showed an increase in the case of treated diabetic rats as compared to group3 diabetic rats. The islets were shrunken in group3 diabetic rats in comparison to normal rats. In the treated diabetic rats there was expansion of islets. CONCLUSIONS: The experimental drug bis-o-hydroxycinnamoylmethane enhances the antioxidant defense against reactive oxygen species produced under hyperglycemic conditions and thus protects the pancreatic b -cell against loss and exhibits antidiabetic property.

Bis-1,7-(2-hydroxyphenyl)-hepta-1,6-diene-3,5-dione (a curcumin analog) ameliorates DMH-induced hepatic oxidative stress during colon carcinogenesis.

The protective effect of a curcumin analog [bis-1,7-(2-hydroxyphenyl)-hepta-1,6-diene-3,5-dione] was investigated on hepatic lipid peroxidation (LPO) and antioxidant status during 1,2-dimethylhydrazine-induced colon carcinogenesis in male Wistar rats. The effects were compared with that of curcumin, a known antioxidant and anticarcinogen. Colon cancer was induced by sub-cutaneous injection of DMH at a dosage of 20mg/kg body weight (15 doses, at 1-week intervals). DMH administered rats developed gross tumours in the colon. Enhanced lipid peroxidation in the liver of colon tumour bearing rats was accompanied by a significant decrease in the activities of glutathione peroxidase (GPx), glutathione S-transferase (GST), superoxide dismutase (SOD) and catalase (CAT). Intragastric administration of curcumin (80mg/kg body weight) and curcumin analog (80mg/kg body weight) to DMH-injected rats significantly reduced the number and size of tumour in the colon, lowered lipid peroxidation and enhanced the activities of GPx, GST, SOD and CAT in the liver. We speculate that the curcumin analog used in the present study exerts chemoprevention against cancer development at extrahepatic sites by modulating hepatic biotransformation enzymes and antioxidant status. The effect is comparable with that of curcumin. This shows that the hydroxyl group in the aromatic ring is responsible for the protective effect rather than the methoxy group.

Evaluation of peracid formation as the basis for resistance to infection in plants transformed with haloperoxidase.

Nonheme haloperoxidase (HPO-P) isolated from Pseudomonas pyrrocinia catalyzed the peroxidation of alkyl acids to peracids. Among acids tested as substrates, acetic acid was most readily peroxidized. The reaction product peracetate possessed potent antifungal activity: 50% death (LD(50)) of Aspergillus flavus occurred at 25 microM peracetate. Viability of A. flavus was inhibited by up to 80% by leaf extracts of tobacco plants transformed with the HPO-P gene from P. pyrrocinia compared to viability of fungi exposed to extracts from controls. To elucidate if peracid formation by HPO-P was the basis for antifungal activity in transgenic leaf tissues, lethalities of hydrogen peroxide-acetate-HPO-P combinations against A. flavus were examined in vitro. LD(50) of A. flavus exposed to the combinations occurred at 30 mM acetate when concentrations of hydrogen peroxide and HPO-P were held constant. This value was identical to the LD(50) produced by 30 mM acetate in the absence of hydrogen peroxide-HPO-P and therefore did not account for enhanced antifungal activity in transgenic plants. For clarification, kinetics of the enzymic reaction were examined. According to the concentration of acetate needed for enzyme saturation (K(m) = 250 mM), acetate was lethal prior to its oxidation to peracetate. Results indicate that peracid generation by HPO-P was not the basis for enhanced antifungal activity in transgenic plants expressing the HPO-P gene.

Expression of an antimicrobial peptide via the chloroplast genome to control phytopathogenic bacteria and fungi.

The antimicrobial peptide MSI-99, an analog of magainin 2, was expressed via the chloroplast genome to obtain high levels of expression in transgenic tobacco (Nicotiana tabacum var. Petit Havana) plants. Polymerase chain reaction products and Southern blots confirmed integration of MSI-99 into the chloroplast genome and achievement of homoplasmy, whereas northern blots confirmed transcription. Contrary to previous predictions, accumulation of MSI-99 in transgenic chloroplasts did not affect normal growth and development of the transgenic plants. This may be due to differences in the lipid composition of plastid membranes compared with the membranes of susceptible target microbes. In vitro assays with protein extracts from T(1) and T(2) plants confirmed that MSI-99 was expressed at high levels to provide 88% (T(1)) and 96% (T(2)) inhibition of growth against Pseudomonas syringae pv tabaci, a major plant pathogen. When germinated in the absence of spectinomycin selection, leaf extracts from T(2) generation plants showed 96% inhibition of growth against P. syringae pv tabaci. In addition, leaf extracts from transgenic plants (T(1)) inhibited the growth of pregerminated spores of three fungal species, Aspergillus flavus, Fusarium moniliforme, and Verticillium dahliae, by more than 95% compared with non-transformed control plant extracts. In planta assays with the bacterial pathogen P. syringae pv tabaci resulted in areas of necrosis around the point of inoculation in control leaves, whereas transformed leaves showed no signs of necrosis, demonstrating high-dose release of the peptide at the site of infection by chloroplast lysis. In planta assays with the fungal pathogen, Colletotrichum destructivum, showed necrotic anthracnose lesions in non-transformed control leaves, whereas transformed leaves showed no lesions. Genetically engineering crop plants for disease resistance via the chloroplast genome instead of the nuclear genome is desirable to achieve high levels of expression and to prevent pollen-mediated escape of transgenes.