Biomedical subjects
Publications and source records attributed to J J Menn.
The authors introduce a unique and clinically oriented technique for evaluation of hallux abducto valgus deformity and its operative correction. A new concept in the application of the Austin osteotomy is also presented.
New approaches to the development of insect control agents have been revealed through the molecular description of neuropeptides, their biogenesis, action, and degradation. Prerequisite to the exploitation of a neuropeptide as a lead to control agent development is a thorough understanding of the biochemistry of the neuropeptide and appreciation of its physiological impact. Reliable bioassays must be coupled with advanced biochemical and molecular genetic technologies to overcome limitations imposed by the typically low endogenous levels of individual neuropeptides. Purification, amino acid sequencing, and gene cloning provide the molecular tools necessary for studies on neuropeptide synthesis, processing, secretion, receptor binding, and inactivation. Each of these areas consists of a number of amino acid sequence-, and enzyme-dependent steps which may be considered as targets for the development of highly specific control agents. These agents will include antagonist and superagonists, peptidomimetics, recombinant peptides delivered through the baculovirus technology, receptor blockers, and enzyme inhibitors.
Sex pheromone production in females of many species of moths is controlled by a pheromone biosynthesis activating neuropeptide (PBAN), PBAN from Helicoverpa zea (Hez-PBAN) is a 33 amino acid peptide produced in the suboesophageal ganglion of both female and male moths. PBAN-like activity is widespread among Lepidoptera and is also reported from a cockroach and a grasshopper. The C-terminal pentapeptide of Hez-PBAN represents the minimum sequence with pheromonotropic activity. Another pentapeptide fragment of the molecule also has high pheromonotropic activity. Presence of PBAN-like immunoreactivity and biological activity in the corpora cardiaca suggests that it is the possible site of PBAN release. There is evidence that PBAN action on pheromone gland is mediated by a second messenger. Several possible sites of action for PBAN have been suggested in the biosynthetic pathway of pheromones. The gene for Hez-PBAN has been cloned and sequenced. Cloning of a synthetic PBAN gene into a baculovirus has been attempted. Studies to isolate and identify the receptors for PBAN as well as the metabolic fate of PBAN have been initiated.
Synthetic agricultural chemicals will continue to be the major component in protecting food and fiber crops from attack by insects, fungi, and weeds. This trend will most likely continue through the end of this century and possibly beyond. The discovery and introduction of potent new pesticides such as the sulfonylurea and imidazolinone herbicides and synthetic pyrethroid insecticides have demonstrated that excellent weed and insect control can be achieved with minute amounts of chemical per treated unit area in comparison to older chemicals. In some instances, these reductions approached two orders of magnitude. Further improvements in delivery systems and formulations have also contributed to reductions in the chemical load in the environment. However, increased regulatory demands; environmental concerns; developing resistance in key pests; increasing costs of research, development, manufacturing, and selling; and even a smaller number of basic producers, all in concert impact heavily on future developments in chemical pesticides. We can expect also that, within the next decade, there will be an increasing number of introductions of biological pesticides, including microbials and biochemicals derived from microbiological sources. These new products--including mycoherbicides, mycofungicides, and biological insecticides--are expected to become prominent control measures in the intermediate time span (10-20 years), to be supplemented in the long-term by products and transgenic plants derived from recombinant DNA technology.
Fibroepithelial polyps usually present as small, benign dermal growths known as skin tags. The incidence of this lesion in the foot has not been precisely determined. An unusual case and a literature review were presented.
1. Molinate sulphoxide, an oxidation metabolite of molinate, is cleaved in vitro by Japanese carp liver cytosol fraction, indicating the presence of GSH-S-transferase activity, since cleavage of the sulphoxide is dependent on the amount of supernatant protein and GSH in the assay medium. 2. Molinate mercapturate was identified as a major metabolite recovered from bile of carp treated with molinate. 3. The structure of the mercapturate was established by co-chromatography with an authentic standard in three t.l.c. systems and by mass spectrometry.
Pesticide chemicals are an important component of modern agriculture. Through their use, plants and animals are exposed to pesticides directly and indirectly from transport through soil, water, and other environmental components. Pesticide chemicals which are absorbed by plants and animals undergo extensive biotransformation. Lipophilic compounds are converted to polar metabolites through a variety of microsomal and extramicrosomal reactions in plants and animals. Generally, biotransformations are qualitatively similar in both systems. However, there are important quantitative rate differences in metabolism which often determine the balance between activation and deactivation of a pesticide. Furthermore, there are qualitative differences in conjugative mechanisms in plants and animals. Animals through an efficient excretory system eliminate transformation products via the urine and feces. Since efficient excretory systems are absent in plants, terminal degradation products are stored as conjugates and/or derivatives which may be incorporated into the plants themselves. Metabolic transformations of selected pesticides illustrating various types of reactions in plants and animals are discussed.
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Carbophenothion sulfoxide, an oxidative metabolite of carbophenothion, is reduced to carbophenothion in the living rat and by an in vitro system containing rat liver enzyme, reduced nicotinamide adenine dinucleotide phosphate, and flavin adenine dinu cleotide phosphate. Reduction of sulfoxides, formed metabolicially from certain commercial organophosphorus insecticides, may be important in ameliorating the toxicity of these compounds.
Rat metabolism studies were conducted with three organophosphorus ester insecticides: [phenyl- or ethoxy-14C]Dyfonate, O-ethyl S-phenyl ethylphosphonodithioate; [phenyl-14C]Trithion, S-[(4-chlorophenylthio)methyl]O,O-diethylphosphorodithioate; and [phenyl-14C]R-14805, 4-[O,0-diethyl phosphorothioyl)]-acetophenoneoxime-N'-methylcarbamate. Compounds were administered orally to rats at 2 to 8 mg/kg, and biotransformation pathways were established from identified metabolites. Metabolites were isolated from O-96 hr urine and identified by using one or more methods including thin-layer chromatography, radio-gas-liquid chromatography, mass spectrometry, and nuclear magnetic resonance. Each of these model insecticides displayed a distinct bioactivation and detoxification pathway. Conversion to potent acetylcholinesterase inhibitors resulted from desulfuration of Dyfonate, desulfuration and thioether oxidation of Trithion, and desulfuration and a variety of modifications of the leaving group of R-14805. The compounds were deactivated primarily via cleavage of an organophosphorus ester group. All three compounds and their metabolites were rapidly excreted primarily in urine without any bioaccumulation in tissues.
Chemicals which interfere with the growth and development of insects (morphogenetic agents) have been receiving major attention as potential means of selective insect control. Major advances in this field resulted from the identification of Juvenile Hormones -1, -2, and -3, and the discovery that various terpenoid and sesquiterpenoid derivatives were more potent morphogenetic agents than the three known Juvenile Hormones. Several highly active compounds have emerged from these research programs. Their field performance, problems, and prospects in selective insect control are considered here.
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