Irradiation influence on the phenoloxidase pathway and an anti-oxidant defense mechanism in Spodoptera litura (Lepidoptera: Noctuidae) and its implication in radio-genetic 'F 1 sterility' and biorational pest suppression tactics

The present study was conducted to appraise the ontogenic radio-sensitivity of a serious tropical pest, Spodoptera litura (Fabr.). The molecular responses pertaining to the phenoloxidase (PO) pathway and an anti-oxidant defense mechanism were evaluated in order to understand its implication in pest control at pre-harvest and post-harvest intervals. Irradiation exhibited an inverse relationship with age with respect to impact on developmental and transcriptional responses. Transcript abundance of PO cascade enzymes, prophenoloxidase (slppo-2), its activating enzyme (slppae-1) and free-radical scavenging enzymes, superoxide dismutase (slsod) and catalase (slcat) was evaluated upon gamma irradiation alone and the dual-stress of radiation plus microbial challenge. The slppo-2, slppae-1, slsod and slcat transcripts were significantly up-regulated in F 1 L6 larvae (6th-instar) resulting from 100 Gy sub-sterilized male adults and unirradiated female moths. The extent of upregulation was relatively higher in comparison with L6 survivors (6th-instar larvae) developed from irradiated neonates (L1) treated with 100 Gy. Upon Photorhabdus challenge, the transcripts were down-regulated in irradiated L1 suggesting increased larval susceptibility to bacterial infections. Radioresistance increased with the age of the insect, and molecular responses (transcript abundance) of insect defense mechanism were less influenced when older age (F 1 progeny) were irradiated. These findings will help to optimize the gamma dose to be employed in inherited sterility technique for (pre-harvest) pest suppression and (post-harvest) phytosanitation and quarantine, and suggest compatible integration of biorational tactics including nuclear technology.

Schwannoma of the nasal septum

Schwannomas of the nasal cavity and paranasal sinuses are very rare. We report the case of a 54-year-old woman with a schwannoma arising from the nasal septum. We discuss the clinical presentation, differential diagnosis, imaging characteristics and treatment of this rarely encountered lesion.

Selective surgicel packing for the treatment of posterior epistaxis

Rod lens endoscopes provide residents in otolaryngology a means of more accurately identifying the site of bleeding and, when possible, cauterizing the bleeding vessel. Identification of a posterior bleeding point is often difficult and sometimes impossible. Intranasal manipulation for electrocautery is painful, may require general anesthesia, and is associated with complications. We describe a pilot study designed to evaluate selectively packing the bleeding site with Surgicel (oxidized cellulose) to control the hemorrhage without packing the nasal cavity and to reduce patient morbidity and length of stay in the hospital. We describe the technique and present the results of treating 8 patients admitted with acute posterior epistaxis over a 10-month period in 1995-1996.

Selective Surgicel Packing for the Treatment of Posterior Epistaxis

Rod lens endoscopes provide residents in otolaryngology a means of more accurately identifying the site of bleeding and, when possible, cauterizing the bleeding vessel. Identification of a posterior bleeding point is often difficult and sometimes impossible. Intranasal manipulation for electrocautery is painful, may require general anesthesia, and is associated with complications. We describe a pilot study designed to evaluate selectively packing the bleeding site with Surgicel (oxidized cellulose) to control the hemorrhage without packing the nasal cavity and to reduce patient morbidity and length of stay in the hospital. We describe the technique and present the results of treating 8 patients admitted with acute posterior epistaxis over a 10-month period in 1995–1996.

A simple and rapid Agrobacterium-mediated transformation protocol for cotton (Gossypium hirsutum L.): embryogenic calli as a source to generate large numbers of transgenic plants

A protocol is presented for efficient transformation and regeneration of cotton. Embryogenic calli co-cultivated with Agrobacterium carrying cry1Ia5 gene were cultured under dehydration stress and antibiotic selection for 3-6 weeks to generate several transgenic embryos. An average of 75 globular embryo clusters were observed on selection plates and these embryos were cultured on multiplication medium followed by development of cotyledonary embryos on embryo maturation medium to obtain an average of 12 plants per Petri plate of co-cultivated callus. About 83% of these plants have been confirmed to be transgenic by Southern blot analysis. An efficiency of ten kanamycin-resistant plants per Petri plate of co-cultivated embryogenic callus was obtained. The simplicity of the procedure and the efficiency of the initial material allow transformation of any variety where a single regenerating embryogenic callus line can be obtained. In addition, multiple transformations can be performed either simultaneously or sequentially. The method is extremely simple, reliable, efficient, and much less laborious than any other existing method for cotton transformation.

Relocating expression of vegetative insecticidal protein into mother cell of Bacillus thuringiensis

Vegetative insecticidal protein (VIP) is a class of insecticidal proteins produced by some strains of Bacillus thuringiensis during the vegetative stage of their growth. Unlike delta-endotoxins which are produced as parasporal inclusion bodies within the cell during sporulation, VIP is secreted into the culture medium. Here we report the relocation of the expression of VIP into the mother cell compartment in a manner similar to well-characterized Cry proteins. Relocation of VIP is directed to mother cell by placing its synthesis under sporulation-dependent promoters, BtI and BtII. The insertion of cry preferred transcription termination sequence at the 3(') region and a STAB-SD sequence at the 5(') region of the gene provided stability to the vip transcript and enhanced its yield. The demonstrated expression of VIP within the cells in the form of inclusion bodies would facilitate development of a suitable formulation for the application of this class of insecticidal proteins in the field.

High-frequency somatic embryo production and maturation into normal plants in cotton (Gossypium hirsutum) through metabolic stress

A highly efficient somatic embryo production and maturation procedure has been developed to regenerate plantlets from cotton ( Gossypium hirsutum). This procedure involves the acceleration of differentiation through manipulations of nutrient and microenvironment conditions. Embryogenic calli, initiated from hypocotyls or cotyledonary leaf sections on MS medium containing 0.1 mg/l 2,4 dichlorophenoxyacetic acid, 0.5 mg/l kinetin, and 3% maltose produced globular-stage somatic embryos when transferred to hormone-free MS medium supplemented with high concentrations of nitrate. Subculture of globular embryos on hormone-free MS medium led to the development of torpedo- and cotyledonary-stage at a low frequency (two to four per plate) with the majority of embryos lacking further growth or entering into the dedifferentiation stage. Significant improvement in embryogenesis (two- to threefold) was achieved when calli were cultured on 1/5-strength MS medium irrespective of stress treatment. However, the frequency of globular embryos developing into normal plantlets improved considerably (20-24 per plate) when cultured on filter paper placed on MS medium. In this procedure, about 33% of globular embryos not only developed into the cotyledonary stage but rooted simultaneously, eliminating a separate rooting step. More than 70% of cotyledonary embryos developed into normal plantlets when cultured on full- strength MS medium containing 0.05 mg/l gibberellic acid.

Toxicity analysis of N- and C-terminus-deleted vegetative insecticidal protein from Bacillus thuringiensis

A vegetative insecticidal protein (VIP)-encoding gene from a local isolate of Bacillus thuringiensis has been cloned, sequenced, and expressed in Escherichia coli. The expressed protein shows insecticidal activity against several lepidopteran pests but is ineffective against Agrotis ipsilon. Comparison of the amino acid sequence with those of reported VIPs revealed a few differences. Analysis of insecticidal activity with N- and C-terminus deletion mutants suggests a differential mode of action of VIP against different pests.

Secretion of dopamine and norepinephrine in hypophyseal portal blood and prolactin in peripheral blood of Holstein cattle

The objective was to test the hypothesis that dopamine regulates prolactin (PRL) secretion by determining acute changes in catecholamine concentrations in hypophyseal portal blood of cattle, and their relation to peripheral blood concentration of PRL in hypophyseal stalk-transected (HST) and sham-operated controls (SOC). Holstein heifers (606 +/- 21 kg BW; mean +/- SE) were subjected to neurosurgery for 8 h to collect hypophyseal portal blood with a stainless steel cannula designed with a cuff placed under the pituitary stalk and peripheral blood via a jugular vein catheter. PRL plasma concentration was measured by radioimmunoassay, and dopamine and norepinephrine in portal plasma by radioenzymatic assay. During anesthesia before HST or SOC, PRL plasma concentration ranged from 20-40 ng/ml throughout 255 min. PRL abruptly increased and remained above 90 ng/ml after HST compared with a steady decrease to <20 ng/ml in SOC heifers throughout 440 min. Within 5 min after severing the hypophyseal stalk, dopamine in portal blood (>8 ng/ml) was significantly increased (P < 0.05) compared with peripheral blood (<2 ng/ml). Norepinephrine concentration in portal blood was significantly greater (P < 0.05) than in peripheral blood during the first 60 min. The sustained high PRL level in peripheral plasma after severing the hypophyseal stalk stimulated hypothalamic dopamine secretion from hypophyseal portal vessels during the prolonged period of blood collection. Norepinephrine concentration in these cattle was greater in hypophyseal portal than in peripheral blood, implicating both an important hypothalamic source of the catecholamine as well as an adrenal gland contribution during anesthesia.

Phylogenetic analysis of gram-positive bacteria based on grpE, encoded by the dnaK operon

The dnaK operon in gram-positive bacteria includes grpE, dnaJ and, in some members, hrcA as well. Both DnaK and DnaJ have been utilized for constructing phylogenetic relationships among various organisms. Multiple copies exist for dnaK and dnaJ genes in some bacterial genera, as opposed to a single gene copy for grpE and for hrcA, according to the currently available data. Here, we present a partial protein-based phylogenetic tree for gram-positive bacteria, derived by using the amino acid sequence identity of GrpE; the results are compared with the phylogenetic trees generated from 5S rRNA, 16S rRNA, dnaK and dnaJ sequences. Our results indicate three main groupings: two are within low-G+C DNA gram-positive bacteria comprising Bacillus species and Staphylococcus aureus on the one hand and Streptococcus species/Lactococcus lactis/Enterococcus faecalis/Lactobacillus sakei on the other hand; the Mycobacterium species and Streptomyces coelicolor, belonging to the high-G+C DNA gram-positive bacteria, form the third cluster. This hierarchical arrangement is in close agreement with that obtained with 16S rRNA and DnaK sequences but not DnaJ-based phylogeny.

Molecular cloning of the dnaK gene region from Bacillus sphaericus in the context of genomic comparisons

The dnaK gene region of Bacillus sphaericus was cloned as a 3.8 kb HindIII fragment and an overlapping 1.7 kb EcoRI fragment by using an internal B. sphaericus specific dnaK gene probe generated by polymerase chain reaction (PCR). Complete DNA sequencing of the two fragments revealed three complete open reading frames (ORFs). These ORFs exhibited a high degree of identity to the grpE dnaK, and dnaJ heat shock genes from other gram-positive bacteria. The order of the genes was found to be grpE-dnaK-dnaJ. Additionally, the 5'-end and 3'-end contained amino acid sequences that were homologous to the C-terminal sequence of the hrcA gene and the N-terminal sequence of ORF35 (yqeT), respectively, from Bacillus subtilis. The entire hrcA gene from B. sphaericus was then isolated by high-fidelity PCR and completely sequenced. A transcription stop site is located between the dnaK and dnaJ genes but not after the dnaJ gene. Consistent with this observation, the dnaJ gene is immediately followed by an ORF that shows a high degree of identity to ORF35 from B. subtilis, Staphylococcus aureus, and Clostridium acetobutylicum. The presence of ORF35 is not indicated in other genera representing the gram-positive bacteria. The amino acid sequence of ORF35 exhibited nearly 30% identity with the methyltransferase for large subunit ribosomal protein L11 from gram-negative Proteobacteria and the related protein from cyanobacteria, other gram-negative bacteria, and Archaea, suggesting the presence of the gene for this protein in the common ancestor of Bacteria and Archaea. The absence of the ORF35 gene in Mycobacterium tuberculosis and other gram-positive bacteria indicates that the loss of this gene must have occurred in an ancestor of other gram-positive bacteria following their divergence from the ancestor of Bacillus/Clostridium/staphylococcus lineage.

A protein-based phylogenetic tree for gram-positive bacteria derived from hrcA, a unique heat-shock regulatory gene

The dnaK operon from Bacillus subtilis and other Gram-positive bacteria with low G + C DNA content contains additional heat-shock genes, including hrcA. The hrcA gene encodes a transcription factor that negatively regulates heat-shock genes and is uniformly present in all Gram-positive bacteria studied to date. An hrcA homologue is also present in Synechocystis species, Leptospira interrogans, Chlamydia trachomatis, Caulobacter crescentus and Methanococcus jannaschii, organisms that diverged early on from the common ancestor of all Gram-positive bacteria and Proteobacteria, according to 16S rRNA phylogeny. A partial, protein-based phylogenetic tree, derived using amino acid sequence homology of hrcA proteins from Gram-positive bacteria, is presented here, and the results are compared with the phylogenetic trees generated from 16S rRNA, dnaK and dnaJ sequences. The location of the hrcA gene and the genome organization of the dnaK operon support the division of all Gram-positive bacteria into three major groups: one group contains high-G + C Gram-positive bacteria, and two others contain low-G + C Gram-positive bacteria. Among the Gram-positive bacteria with low G + C DNA content, the results indicate that there is a close phylogenetic relationship between Bacillus species and Clostridium species on the one hand and between Lactococcus lactis and Streptococcus mutans on the other. Streptomyces and Mycobacterium species also exhibited a close relationship. A hierarchical arrangement of Gram-positive bacteria based on HrcA sequences is proposed as an additional refinement of the phylogenetic relationships within this important bacterial group.

Increased toxicity of modified mosquitocidal binary toxins of Bacillus sphaericus expressed in Escherichia coli

The binary mosquitocidal genes of 51-kDa and 42-kDa proteins isolated from Bacillus sphaericus 1593 have been expressed at moderate levels in Escherichia coli employing the pQE expression system. The expressed proteins are readily visible in Coomassie blue-stained protein gels. The recombinant E. coli cells expressing toxic proteins were toxic towards Culex larvae. During the assembly of crystals in B. sphaericus, the 42-kDa toxin is first cleaved at the N-terminal end by a specific B. sphaericus protease. To express the toxins in E. coli the B. sphaericus specific protease-recognition site was deleted at the N-terminal end of the 42-kDa toxin, thereby mimicking the structure of the toxin as present in the crystal. This modification resulted in a twofold increase in the toxicity of the E. coli cells expressing the modified 42-kDa toxin as a constituent of the binary toxin. Our results demonstrate the utility of this modification for heterologous expression of the binary toxin genes from B. sphaericus.

Phage display of Bacillus thuringiensis CryIA(a) insecticidal toxin

The display of proteins or peptides on the surface of filamentous phages or phagemids has been shown to be a very powerful technology for the rescue of specific binders from large combinatorial libraries, as well as to select derivatives of known proteins with altered binding properties. The Bacillus thuringiensis (Bt) crystal proteins are a large family of insecticidal toxins which bind to receptors found on the brush border of larval midgut cells, different crystal toxins having different larval specificities. Here we describe the display of different CryIA(a) toxin regions on the surface of phagemids using the display vector pHEN1, the purpose being the identification of toxin sequences suitable for mutagenesis and selection using phage display. We show that CryIA(a) domain II, in which the receptor binding activity is located, is efficiently displayed as well as being secreted as soluble protein into the periplasm of bacterial cell. This forms the basis of a simple means for the modification of toxin specificity and the selection of toxin proteins with novel or expanded host ranges.

Evidence for the shikimate-3-phosphate interacting site in the N-terminal domain of 5-enolpyruvyl shikimate-3-phosphate synthase of Bacillus subtilis

The role of basic amino acid residues that are highly conserved in the N-terminal domain of 5-enolpyruvyl shikimate-3-phosphate synthase (EPSPs) in the binding of the substrate, shikimate-3-phosphate, has been assessed. Lys 19 and Arg 24 in the Bacillus subtilis EPSPs were substituted by glutamic acid and aspartic acid residues respectively by site-directed mutagenesis. Native and the mutant proteins were expressed using a two-vector system and the expressed proteins were purified to near homogeniety. The replacement of either Lys 19 or Arg 24 with a negatively charged residue nearly completely abolished the enzyme activity. The kinetic characterization of the purified wild type and the mutant proteins revealed that the substitution of positively charged residues in the N-terminal domain (K19 and R24) results in reduced affinity for shikimate-3-phosphate (S3P). The results suggest the involvement of these residues in the binding of S3P during enzyme catalysis.

Alport's syndrome--a case report

Alport's syndrome (hereditary nephritis with deafness), is an uncommon disease and is seen very infrequently in India. We report a fatal case in a young girl with characteristic ultrastructural changes in the kidney thus emphasising the exception noted in the observation that females have a better prognosis compared to males.

Point mutation of a conserved arginine (104) to lysine introduces hypersensitivity to inhibition by glyphosate in the 5-enolpyruvylshikimate-3-phosphate synthase of Bacillus subtilis

The role of a conserved arginine (R104) in the putative phosphoenol pyruvate binding region of 5-enolpyruvyl shikimate-3-phosphate synthase of Bacillus subtilis has been investigated. Employing site directed mutagenesis arginine was substituted by lysine or glutamine. Native and mutant proteins were expressed and purified to near homogeneity. Estimation of Michaelis and inhibitor constants of the native and mutant proteins exhibited altered substrate-inhibitor binding mode and constants. Mutation R104K hypersensitized the enzyme reaction to inhibition by glyphosate. The role of R104 in discriminating between glyphosate and phosphoenol pyruvate is discussed.

5-Enolpyruvylshikimate-3-phosphate synthase of Bacillus subtilis is an allosteric enzyme. Analysis of Arg24-->Asp, Pro105-->Ser and His385-->Lys mutations suggests a hidden phosphoenolpyruvate-binding site

5-Enolpyruvylshikimate-3-phosphate synthase of Bacillus subtilis has been cloned, expressed and purified to near homogeneity. Clustal alignment of the amino acid sequences from different bacteria revealed several conserved residues located in the N-terminal, middle and C-terminal domains. The role of conserved Arg24, Pro105, and His385 residues has been examined by site-directed mutagenesis. Steady-state kinetic analysis of the native synthase exhibited allosteric behaviour, a feature thought to be unique amongst bacterial and plant 5-enolpyruvylshikimate-3-phosphate synthase enzymes investigated so far. Both substrates, phosphoenolpyruvate (P-pyruvate) and shikimate 3-phosphate have multiple interaction sites. There are two sites for P-pyruvate binding, catalytic and non-catalytic. Glyphosate (N-phosphonomethyl glycine) competes for binding at the catalytic site and does not interact at the secondary site. Glyphosate in the absence of ammonium ions increases cooperativity of P-pyruvate binding and favors dimerization of the enzyme through an interaction between P-pyruvate-binding sites. The ammonium-ion-activated 5-enolpyruvylshikimate-3-phosphate synthase displays no cooperativity with respect to P-pyruvate. Absence of ammonium ions decreases affinity for substrates and introduces cooperativity. Cooperativity was also introduced in the enzyme by point mutations, Arg24-->Asp and His385-->Lys. The latter mutant of the native enzyme exists as a dimer and aggregates to a tetrameric form in the presence of glyphosate. The occurrence of multimeric forms of the synthase has been demonstrated by staining for the enzyme activity on the native gel and by resolving purified enzyme preparations on a sucrose density gradient. A model describing the alteration in the aggregation status of the enzyme by the inhibitor, activator and the substrates has been proposed.

Background-minimized cassette mutagenesis by PCR using cassette-specific selection markers: a useful general approach for studying structure-function relationships of multisubstrate enzymes

An efficient protocol, termed background-minimized cassette mutagenesis (BMCM) by PCR, has been developed for multiple mutagenesis of DNA. This method uses suitable extension primers for incorporating various mutation(s) and is not limited by either the nature of the mutation or the size and spatial location of mutational loci. Minimization of the wild type background clone and mutant selection at very high frequency were easily achieved through a two-step process. First, a deletion of a unique restriction site within the cassette was introduced through additional silent mutation(s). Then, the recombinant clones were digested with the corresponding enzyme followed by transformation when selective linearization of wild-type clone led to its near total removal leaving the mutant clones as the only practicable transformants. Because it is generally possible to design several such cassette-specific unique background minimization markers for any gene, for multiple mutagenesis involving distally located portions of the gene the present protocol is superior to other currently available methods. The efficiency of BMCM-PCR has been demonstrated here by using the multisubstrate enzyme 5-enolpyruvyl-shikimate-3-phosphate synthase (EPSPs) of Bacillus subtilis as a model system. Three different sets of cassettes of varying sizes were generated to encompass the three putative active/binding regions in the beginning, middle, and the end of the gene encoding EPSPs. Very high efficiency of mutation incorporation and selection were obtained in all cases. Furthermore, by taking advantage of the unique cassette-specific background elimination markers, it was possible to generate a nested set of double and/or triple mutants. The mutant enzymes were overexpressed in Escherichia coli and purified to near homogeneity.(ABSTRACT TRUNCATED AT 250 WORDS)

Recombinant enrichment by exploitation of restriction sites with interrupted palindromes: design, synthesis and incorporation of zero-background linkers in cloning and expression vectors

A universal approach for improving the efficiency of cloning through a selective enrichment of recombinants has been developed. This was achieved by using novel polylinkers or multiple cloning sites (MCS) termed zero-background linkers (ZBL). These MCS have short-cutter site(s) incorporated in the wobble portion of the recognition sequence of the long-cutter(s) in such a fashion that cloning at the short-cutter site disrupts the continuity of the long-cutter-specific sequence. Consequently, digestion of the ligation mixture with the long-cutter, prior to transformation, essentially eliminates the insert negative clones from transformants. The usefulness of such background removal has been illustrated through the design and synthesis of a model ZBL molecule and then its incorporation into various popular cloning and expression vectors. We demonstrate that replacement of the residing MCS of a vector with ZBL leads to enhanced cloning efficiency, as evidenced by the marked increase in the ratio of recombinants to non-recombinants. Such vector improvement is nearly universal as zero backgrounding is an add-on feature and can be adapted to practically any vector system, without having to alter the essential features of the parent vectors.

Further studies on central actions of nitroglycerin and lack of evidence for nitroglycerin interacting on [3H]clonidine binding sites in cortex membranes

Decerebration and transection of the spinal cord totally abolished the hypotensive and tachycardiac responses to i.c.v injection of nitroglycerin (NTG) and reduced the tachycardia induced by i.v. injection of the drug. The hypotensive responses to i.v. injection of sodium nitroprusside were not altered by decerebration. Microinjection of NTG (0.1-1.0 nmol) into anterior hypothalamic medial preoptic area (AH/POA) produced dose-dependent decreases in mean arterial pressure and heart rate, but minimal responses were induced when the same doses of NTG were injected into the rostral ventrolateral medulla. Pretreatment with rauwolscine (2.5 nmol), injected into the AH/POAs, antagonized the depressor responses to NTG when it was administered into the areas or given i.v. However, rauwolscine did not alter the depressor responses induced by i.v. sodium nitroprusside. Prazosin (1.5 nmol) in the AH/POA did not alter the bradycardic effects induced by microinjection of NTG into the areas. (minus)-Epinephrine significantly interacted with alpha-2 adrenoceptor binding sites, but serotonin and NTG did not interact with [3H] clonidine binding sites in cortex membranes. Results suggest that cardiovascular responses after i.v. injection of NTG involve central and peripheral component. AH/POA is one of the central sites involved in the depressor effects of NTG. NTG-induced modulation of noradrenergic transmission appears to stimulate alpha-2 adrenoceptors in the central nervous system, but the drug does not involve direct interaction with alpha-2 adrenoceptors. Hypotensive effects of sodium nitroprusside result from its action at peripheral sites.

Structure-activity studies on a potent antagonist to organophosphate-induced toxicity

Molecular modifications have been made on a highly potent, active antagonist to organophosphate-induced toxicity, 4,4'-bis[1,3-dioxan-2-ylmethyl)methylamino]acetyl]biphenyl dimethobromide (1). Stepwise removal of the oxygen atoms from the dioxane rings, as well as changing the position of attachment of substituents on the 1,3-dioxane rings and decreasing the ring size from six-membered to five-membered caused drastic or complete loss of pharmacological effect. Partial structures of 1 were all inactive. Thus, the structure of 1 seems to be remarkably specific. Additional pharmacological data are reported for 1.

Ca2(+)-dependent, ATP-induced conversion of the [3H]hemicholinium-3 binding sites from high- to low-affinity states in rat striatum: effect of protein kinase inhibitors on this affinity conversion and synaptosomal choline transport

Tritium-labeled hemicholinium-3 ([3H]HC-3) was used to characterize the sodium-dependent high-affinity choline carrier sites in rat striatal preparations. In an earlier study, we had shown that [3H]HC-3 labels choline carrier sites with high and low affinities and had suggested that the low-affinity sites represent "functional" carrier sites. The objective of the present study was to examine the mechanisms involved in the regulation of the two affinity states of [3H]HC-3 binding. Here, we demonstrate that these two affinity states are totally interconvertible; addition of 0.1 mM ATP in the binding assay medium quantitatively converted all the binding sites to the low-affinity state, whereas addition of 1 mM beta,gamma-methylene 5'-ATP quantitatively converted all the binding sites to the high-affinity state. Preincubation of the tissue (for 15 min at 37 degrees C) before the binding assay also converted the binding sites to the high-affinity state, whereas supplementation of the assay medium with ATP (0.5 mM) again induced expression of the low-affinity state of the binding sites. This effect of ATP was found to be selective for this nucleotide. Neither ADP (1 mM) nor cyclic AMP could mimic such an effect. Other nucleotide triphosphates--CTP (0.5 mM) and GTP (0.5 mM)--also could not substitute for ATP. GTP, however, caused nearly a 35% reduction in the number of binding sites, accompanying a loss of the low-affinity component of binding. This effect of GTP was also shared by 5'-guanylylimidodiphosphate but not by GDP or cyclic GMP. This ATP-dependent low-affinity conversion of [3H]HC-3 binding sites requires divalent metal ions.(ABSTRACT TRUNCATED AT 250 WORDS)

Critical evaluation of Per-Lee tubes in children

A retrospective view of 37 Per-Lee tubes inserted into 29 patients over a period of four years. At the time of review all the tubes were in situ but eleven had to be removed due to recurrent otorrhoea or perforations causing increasing deafness particularly in children. Per-Lee tubes are not suitable for long-term ventilation of the middle ear cavity in children.

Hemicholinium-3 congeners as potential antagonists to organophosphate-induced toxicity

A series of congeners of hemicholinium-3, in which the 1,4-oxazinium rings of hemicholinium are replaced by pyrrolidine, piperidine, 1,3-dioxane, or 1,4-oxazine rings, is described. Several of the target compounds produced blockade of neuromuscular transmission in the rabbit, and three heterocyclic derivatives, 10, 11, and 13, significantly antagonized paraoxon-induced lethality in mice. 1,3-Dioxane derivative 11 was an extremely potent antagonist of paraoxon-induced toxicity in mice, compared with prototypical protective agents physostigmine and pyridostigmine. Compound 11 exhibited a much more favorable therapeutic ratio than the reference drugs. The mechanism of action of 11 has not been elucidated, although it is concluded that it differs from that of hemicholinium-3 (inhibition of high-affinity, sodium-dependent uptake of choline into nerve terminals).

Exploitation of the broad specificity of the membrane-bound isoenzyme of lactate dehydrogenase for direct selection of null mutants in Neisseria gonorrhoeae

Lactic acid is readily utilized as a carbon and energy source by Neisseria gonorrhoeae. The oxidation of lactate is coupled to electron transport via a membrane-bound lactate dehydrogenase (iLDH) which is independent of pyridine nucleotide. The broad substrate specificity of iLDH endows N. gonorrhoeae with the novel ability to convert phenyllactate to L-phenylalanine via phenylpyruvate. N. gonorrhoeae ATCC 27628 typifies a class of clinical isolate whose growth is inhibited by phenylpyruvate (or L-phenylalanine). Exploiting resistance to growth inhibition by phenyllactate as a strategy of positive selection, mutant derivatives of strain ATCC 27628 lacking iLDH activity were readily obtained. These mutants are incapable of oxidizing phenyllactate, and lack the parent-strain ability to reduce c-type cytochromes in the presence of lactate, phenyllactate or 4-hydroxyphenyllactate. They retain, however, a cytoplasmic NAD(+)-linked lactate dehydrogenase (nLDH). Since the mutants retained the ability to grow on lactate as a sole source of carbon, nLDH presumably can function in an opposite-to-normal physiological direction in the absence of iLDH. This would explain the failure to isolate iLDH-deficient mutants by selection for inability to grow on lactate.

Introduction of a putative dopaminergic prodrug moiety into a 6,7-substitution pattern characteristic of certain 2-aminotetralin dopaminergic agonists

On the basis of the premise that the dopaminergic agonist profile of 2-(di-n-propylamino)-5-hydroxy-6-methyltetralin (1a) is due to in vivo oxidation of the 6-methyl moiety and that 1a may represent a novel prodrug strategy, the vicinal methyl-hydroxyl substitution pattern was incorporated into the 6- and 7-positions of 2-(di-n-propylamino)tetralin to give the 6-methyl-7-hydroxy and 6-hydroxy-7-methyl isomers 8 and 9, respectively. A multistep synthetic approach was devised which permitted preparation of target molecules 8 and 9. Pharmacological data revealed that both target compounds exhibit modest dopamine-like effects in the cardioaccelerator nerve assay in the cat, but neither appeared to be metabolically activated as was the case with 1a. The effects of 9 (but not of 8) were antagonized by pretreatment with haloperidol. Thus, the 5-hydroxy-6-methyl substitution pattern in the 2-aminotetralins remains unique as a dopaminergic agonist prodrug structure.

5-HT1A-receptor antagonism: N-alkyl derivatives of (R)-(-)-8,11-dimethoxynoraporphine

Prompted by previous findings that a p-dimethoxy substitution pattern on an aromatic ring permits retention of dopaminergic agonist effects in certain ring systems, catechol derivatives of which are potent dopaminergic agonists, an 8,11-dimethoxy substitution pattern was introduced into the aporphine ring in place of the 10,11-dihydroxy moiety in apomorphine. Acid-catalyzed rearrangement of an appropriate morphine derivative provided the aporphine ring system with retention of the stereochemical integrity of the 6a asymmetric center. The hydroxyl group at position 10 was removed by catalytic hydrogenolysis of its phenyltetrazoyl ether. The methyl ether of the resulting 11-hydroxyaporphine was iodinated in high yield at position 8 with trifluoroacetyl hypiodite. This is the first account of synthesis of an iodinated aporphine derivative. The 8-iodo substituent was replaced with methoxyl by reaction with sodium methoxide and cuprous iodide. Neither the N-methyl target compound 7 nor the N-n-propyl derivative 8 demonstrated dopaminergic nor serotonergic agonism. However, 7 exhibited receptor-binding characteristics and other pharmacological properties suggesting that it may be a 5-HT1A receptor antagonist.

The biochemical basis for growth inhibition by L-phenylalanine in Neisseria gonorrhoeae

Clinical isolates of Neisseria gonorrhoeae are commonly subject to growth inhibition by phenylpyruvate or by L-phenylalanine. A blockade of tyrosine biosynthesis is indicated since inhibition is reversed by either L-tyrosine or 4-hydroxyphenylpyruvate. Phenylalanine-resistant (PheR) and phenylalanine-sensitive (PheS) isolates both have a single 3-deoxy-D-arabino-heptulosonate 7-phosphate (DAHP) synthase that is partially inhibited by L-phenylalanine (80%). However, PheS and PheR isolates differ in that the ratio of phenylpyruvate aminotransferase to 4-hydroxyphenylpyruvate aminotransferase is distinctly greater in PheS isolates than in PheR isolates. A mechanism for growth inhibition is proposed in which phenylalanine exerts two interactive effects. (i) Phenylalanine decreases precursor flow to 4-hydroxyphenylpyruvate through its controlling effect upon DAHP synthase; and (ii) phenylalanine is largely transaminated to phenylpyruvate, which saturates both aminotransferases, preventing transamination of an already limited supply of 4-hydroxyphenylpyruvate to L-tyrosine.

The broad-specificity, membrane-bound lactate dehydrogenase of Neisseria gonorrhoeae: ties to aromatic metabolism

Neisseria gonorrhoeae can convert phenyllactate (PL) to phenylalanine and 4-hydroxyphenyllactate (HPL) to tyrosine. This was demonstrated by nutritional and physiological approaches. The enzymic basis for this unusual ability was shown to be the broad specificity of a particulate, unidirectional, pyridine-nucleotide-independent lactate dehydrogenase. This enzyme, denoted [iLDH], has been implicated in a pathogenic mechanism whereby host-derived lactate is linked to increased gonococcal oxygen consumption and electron transport. A similar role for HPL, a metabolite available in human host tissues, may provide a selective basis to explain evolution of broadened [iLDH] specificity in Neisseria. The interplay between aromatic metabolism and [iLDH] suggests new approaches for manipulating the host-pathogen relationship.

Alterations in acetylcholine metabolism in rat striatal slices by a 4-methyl piperidine analog of hemicholinium-3

The in vitro effects of a tertiary amine, 4-methyl piperidine analog of hemicholinium-3 (A-4), were investigated on acetylcholine (ACh) metabolism in rat striatal slices. Rat striatal slices were incubated in the presence of 1.0 microM [3H]-choline in the presence or absence of 0.1 mM A-4. High pressure liquid chromatography with electrochemical detection was utilized to separate and measure total and [3H]-labeled ACh and choline. The effects of A-4 on [3H]-choline uptake, ACh and choline content, ACh release, and specific activity of ACh and choline tissue pools were investigated. Results indicated that A-4 inhibited the uptake of [3H]-choline into the striatal slices. Addition of 0.1 mM A-4 also produced a significant reduction in ACh content and ACh release and reduced the specific activity of the tissue choline and ACh pools. The effects of A-4 were more prominent upon immediate incubation than after a 60-min preincubation. These studies demonstrate that the pharmacological effects exhibited by A-4 are consistent with inhibition of choline uptake, with subsequent reduction in ACh synthesis and release.

Role of the carbon source in regulating chloramphenicol production by Streptomyces venezuelae: studies in batch and continuous cultures

Both carbon- and nitrogen-limited media that supported a biphasic pattern of growth and chloramphenicol biosynthesis were devised for batch cultures of Streptomyces venezuelae. Where onset of the idiophase was associated with nitrogen depletion, a sharp peak of arylamine synthetase activity coincided with the onset of antibiotic production. The specific activity of the enzyme was highest when the carbon source in the medium was also near depletion at the trophophase-idiophase boundary. In media providing a substantial excess of carbon source through the idiophase, the peak specific activity was reduced by 75%, although the timing of enzyme synthesis was unaltered. Moreover, chemostat cultures in which the growth rate was limited by the glucose concentration in the input medium failed to show a decrease in specific production of chloramphenicol as the steady-state intracellular glucose concentration was increased. The results suggest that a form of "carbon catabolite repression" regulates synthesis of chloramphenicol biosynthetic enzymes during a trophophase-idiophase transition induced by nitrogen starvation. However, this regulatory mechanism does not establish the timing of antibiotic biosynthesis and does not function during nitrogen-sufficient growth in the presence of excess glucose.

Structure-activity relationship studies of hemicholinium (HC-3) congeners

In a continuing investigation of structural requirements for hemicholinium-like activity (inhibition of neuromuscular transmission due to inhibition of uptake of choline into nerve terminals), some additional molecular modifications of hemicholinium ("HC-3"; structure 1) were made. The target compounds were prepared by standard one- or two-step sequences. Noncyclic acetal moieties in general permitted retention of pharmacological activity, as did concomitant replacement of the central biphenyl "spacer" by other bulky cyclic groupings and replacement of the oxazinium rings by piperidine or 4-methylpiperidine. However, these modifications generally produced compounds of a lower potency. Replacement of the biphenyl moiety of HC-3 with polyakylene chains permitted retention of a considerable degree of activity. In these target compounds, the two quaternary nitrogens can exist the same distance apart (approximately 14 A) as in the hemicholinium molecule. The ditertiary amino congener of a pharmacologically active bis-quaternary oxazinium compound was almost completely inactive. To date, only one tertiary amine has been found which displays a significant degree of hemicholinium-like activity.

Methylpiperidine analog of hemicholinium-3: a selective, high affinity non-competitive inhibitor of sodium dependent choline uptake system

The potency of hemicholinium-3 (HC-3) and its analogs to inhibit sodium dependent high affinity choline uptake were evaluated in rat striatal synaptosomal preparation. Hemicholinium-3 inhibited sodium dependent high affinity choline uptake (IC50 = 18 nM) while the half molecule of HC-3, HC-15, was inactive. The order of potency for choline uptake inhibition of piperidine substituted HC-3 molecule was as follows: 4-methylpiperidine (A-5 and CA-5) much greater than HC-3 much greater than unsubstituted piperidines (CA-1 and A-1) much greater than 2- or 3-methylpiperidine (A-2 and A-3) and 4-hydroxypiperidine (A-7). The tertiary amine derivative of 4-methylpiperidine substituted HC-3 (A-4) was nearly 10-fold less potent than its corresponding quaternary derivative (A-5). Choline uptake was inhibited competitively by HC-3 and non-competitively by A-5. The inhibition of choline uptake by A-5 was readily reversible by washing. A-5 did not inhibit the uptake of dopamine and gamma-aminobutyric acid. These findings suggest that the N-methyl,4-methylpiperidine analog of HC-3 (A-5) is the most potent of all known inhibitors of sodium dependent high affinity choline uptake and that the inhibition of choline uptake by this compound is mediated through a mechanism distinct from a simple competitive one.

Interaction of [3H]spiperone with rat striatal dopamine D-2 receptors: kinetic evidence for antagonist-induced formation of ternary complex

The characteristics of [3H]spiperone interactions with rat striatal dopamine D-2 receptor were investigated. Although the association of [3H]spiperone occurred monoexponentially, the pseudo-first order rate constant of association showed a hyperbolic dependence on ligand concentration. The data were therefore analyzed with the assumption of a two-step binding reaction leading to ligand-induced receptor isomerization. For the first equilibrium, the dissociation constant (KD) was 1.2 nM, while for the second equilibrium, the association and the dissociation rate constants were 71.6 X 10(-3) sec-1 and 0.9 X 10(-3) sec-1, respectively. The dissociation rate constant of the overall binding reaction, as determined by inducing the dissociation of [3H]spiperone from its binding sites by 1 microM (+)-butaclamol, was 0.92 X 10(-3) sec-1. However, the kinetically derived KD (15 pM) of the binding reaction differed significantly from the KD (218 pM) obtained from equilibrium binding experiments. This inconsistency between the two KD values appeared to have arisen from using different receptor concentrations in deriving kinetic and equilibrium data. The KD of the equilibrium binding reaction indeed showed significant variation with the receptor concentrations in an inverse way, implicating the involvement of a third component in the two-step binding reaction to form a high affinity ternary complex rather than a simple ligand induced receptor isomerization. Pretreatment of the membrane with 0.1 mM guanosine 5'-imidodiphosphate [Gpp(NH)p] reduced the affinity of the equilibrium binding reaction to a value (KD = 1.2 nM) which corresponded to the kinetically derived KD of the first step of the binding reaction, indicating the involvement of a guanine nucleotide-binding protein or G protein in inducing the formation of the high affinity ternary complex. The affinity of the binding reaction in Gpp(NH)p-pretreated membranes, however, increased with the duration of incubation, indicating that the ligand receptor complex still can couple with the G protein even in the presence of Gpp(NH)p. Pretreatment of the membrane with pertussis toxin irreversibly decreased the affinity of the binding reaction without significantly affecting the total number of binding sites, implying the involvement of the Gi subclass of G protein in the interaction of [3H]spiperone with D-2 receptors. Inhibition of the [3H]spiperone binding by a dopamine receptor agonist, bromocriptine, also yielded a monophasic dose response curve both in the presence and in the absence of Gpp(NH)p.(ABSTRACT TRUNCATED AT 400 WORDS)

(R)-(-)-10-methyl-11-hydroxyaporphine: a highly selective serotonergic agonist

Prior work in these laboratories identified (+/-)-5-hydroxy-6-methyl-2- (di-n-propylamino)tetralin as a dopaminergic agonist prodrug. The ortho methyl hydroxy aromatic substitution pattern in this molecule has now been incorporated into the aporphine ring system to give a congener of the dopaminergic agonist apomorphine in which the position 10 OH group has been replaced by methyl. Preparation of the target compound involved acid-catalyzed rearrangement of the 3-(1-phenyltetrazolyl) ether of morphine and subsequent molecular modification of the product, the 10-(1-phenyltetrazolyl) ether of (R)-(-)-apomorphine. Surprisingly, the target compound elicited no responses in any assays for effects at dopamine receptors, but rather it displayed pharmacological properties consistent with its being a serotonergic agonist with a high degree of selectivity for 5-HT1A receptors similar to the serotonergic agonist 8-hydroxy-2-(di-n-propylamino)tetralin.

Enzymic basis for leakiness of auxotrophs for phenylalanine in Pseudomonas aeruginosa

The dual enzymic routes for phenylalanine biosynthesis that exist in Pseudomonas aeruginosa complicate the isolation of phenylalanine auxotrophs. Mutants blocked in each of the various phenylalanine-pathway steps are essential for full appreciation of the physiological nature and gene-enzyme relationships of this biochemical system. A leaky phenylalanine-requiring mutant of P. aeruginosa (PAT1051) was found to lack the bifunctional P-protein (chorismate mutase-prephenate dehydratase), but retained the monofunctional isozyme species of chorismate mutase (chorismate mutase-F) as well as cyclohexadienyl dehydratase (components of the arogenate 'overflow' route to phenylalanine). This is the first mutant of P. aeruginosa shown to be deficient in any enzyme specific for phenylalanine synthesis. It is concluded that although the arogenate pathway has the demonstrated potential to overproduce phenylalanine, the substrate levels normally available to the arogenate pathway in the wild-type are inadequate to satisfy the full metabolic demand for phenylalanine.

Role of sympathetic nerves during developing cardiac hypertrophy in Grollman hypertensive rats

Peak left ventricular (LV) function, during rapid volume expansion, and cardiocyte structure were studied in rats with developing cardiac hypertrophy in response to Grollman hypertension (1 kidney, 1 figure 8) after chemical sympathectomy with 6-hydroxydopamine. This form of renovascular hypertension led to the same magnitude of hypertrophy in rats with or without sympathectomy. Indices of peak LV function, measured during acute volume expansion, tended to be normal or slightly higher in hypertensive rats than in controls. Sympathectomy in rats with hypertension significantly improved cardiac and stroke indices while decreasing total peripheral resistance at peak cardiac output. Despite similar magnitudes of LV hypertrophy (LVH) in the two hypertensive groups, cardiocytes in sympathectomized rats had higher mitochondrial volume densities and slightly lower myofibrillar volume densities. After regional sympathectomy of the anterior portion of the LV with phenol, mitochondrial volume density increased by 21% in hypertensive rats with LVH. These data indicate that, during the development of LVH in response to renovascular hypertension, sympathetic nerves do not contribute to the magnitude of LVH but may limit improvement in peak LV performance in response to increased preload. However, sympathetic nerves do play a role in the regulation of mitochondrial and myofibril growth.

Characteristics of [3H]hemicholinium-3 binding to rat striatal membranes: evidence for negative cooperative site-site interactions

The characteristics of [3H]hemicholinium-3 ([3H]HC-3) interactions with rat striatal membranes were investigated. Under the described assay conditions, [3H]-HC-3 binds with a saturable population of membrane binding sites having the following regional distribution: striatum much greater than hippocampus greater than or equal to cerebral cortex greater than cerebellum. The specific binding of [3H]HC-3 showed an obligatory requirement for NaCl; other halide salts of sodium or KCl failed to substitute for NaCl. The Scatchard transformation of saturation isotherm data generated a curvilinear plot with high- and low-affinity components of binding. The dissociation of [3H]HC-3 at infinite dilution was also multiexponential. The dissociation could, however, be accelerated if unlabeled HC-3 was included in the diluting buffer, and this increase in dissociation appeared to be dependent on the concentrations of unlabeled HC-3 used, with the maximal increase demonstrable at 100 nM. The dissociation was also dependent on the fractional saturation of binding sites with labeled HC-3, such that, at higher fractional saturation of binding sites, the overall dissociation was faster and the difference in the dissociation observed between "dilution only" and "dilution + unlabeled HC-3" was reduced. This occupancy-dependent change in dissociation could also be influenced by temperature and pH. Based on the results of these kinetic studies, the steady-state [3H]HC-3 binding data were analyzed for a homogeneous population of binding sites undergoing site-site interactions of the negative cooperative type. Such an analysis yielded a KD of 9.3 nM for the high-affinity state and a KD of 22.8 nM for the low-affinity state of binding sites, with a Bmax of 434 fmol/mg of protein. Competitive binding studies showed that unlabeled HC-3 was most potent in displacing [3H]HC-3, followed by choline. Other drugs known to have little influence on the synaptosomal sodium-dependent high-affinity choline uptake system (SDHACU) had no significant effect on [3H]HC-3 binding sites. Similarities in ionic dependencies, regional distributions, and pharmacological selectivities of [3H]HC-3 binding with synaptosomal SDHACU suggest that [3H]HC-3 selectively labels SDHACU sites located on presynaptic cholinergic neurons in rat CNS. We suggest that the two affinity states of [3H]HC-3 binding sites represent the different "functional" states of the SDHACU system. The binding of HC-3 (or choline) with the high-affinity state of the binding sites induces negative cooperative site-site interactions among the binding sites, resulting in the formation of a low-affinity binding state.(ABSTRACT TRUNCATED AT 400 WORDS)

Periventricular noradrenergic systems are critical for angiotensin-induced drinking and blood pressure responses

Deficits in experimentally induced drinking and pressor responses after administration of 6-hydroxydopamine (6-OHDA) into the lateral cerebral ventricle (LCV) have been reported. Questions have arisen, however, as to whether these effects are due to non-specific actions of the neurotoxin and, if specific, whether the depletion of dopamine (DA) or of norepinephrine (NE) is the critical factor for producing the impairments. In the present report methods to deplete brain catecholamine (CA) differentially were employed in order to test the hypothesis that central 6-OHDA injections act on brain CA substrates per se to produce behavioral and physiological response deficits to angiotensin II (ANG II) challenges. The findings support the interpretation that forebrain dopamine is essential for the mediation of sensorimotor integration involved in response to acute homeostatic stressors. In addition, the outcome identifies an important role for forebrain noradrenergic systems in the mediation of ANG II-elicited drinking and blood pressure responses.

Ornithine transcarbamylase from Mycobacterium smegmatis ATCC 14468: purification, properties, and reaction mechanism

Ornithine transcarbamylase (EC 2.1.3.3) has been purified 980-fold from Mycobacterium smegmatis and has a molecular weight of 116,000. Initial velocity determinations indicated that the reaction proceeds via a sequential kinetic mechanism. The limiting Michaelis constants for carbamyl phosphate (KmA) and ornithine (KmB) and the dissociation constant for carbamyl phosphate (Kia) were found to be 0.20, 0.25, and 0.07 mM, respectively. Ornithine at higher concentrations acted as an uncompetitive inhibitor when carbamyl phosphate was the variable substrate. Phosphate was a competitive inhibitor with carbamyl phosphate as variable substrate and showed noncompetitive or mixed type inhibition when ornithine was the variable substrate. Norvaline acted as a competitive inhibitor with ornithine as variable substrate and as an uncompetitive inhibitor when carbamyl phosphate was the variable substrate. Such inhibitory patterns are characteristic of reactions that proceed via sequential ordered mechanisms. Although the enzyme activity was strongly inhibited by arginine, several arginine analogs had no effect on the enzyme activity. The results suggest that, even though the enzyme from M. smegmatis is unique in the sense that it is feedback inhibited by arginine, the reaction mechanism is similar to the ornithine transcarbamylase isolated from other microorganisms.

p-Dimethoxy-substituted trans-octahydrobenzo[f]- and -[g]quinolines: synthesis and assessment of dopaminergic agonist effects

The N-n-propyl homologues of the title compounds were prepared for further assessment of the ability of the "p-dimethoxy" moiety to confer dopaminergic agonism upon a variety of ring systems. Both the angularly and the linearly annulated trans-benzoquinoline ring derivatives displayed prominent DA2 dopaminergic effects on the peripheral sympathetic nerve terminal and displayed postjunctional dopamine receptor agonist properties in the striatum. It is speculated that the angular octahydrobenzo[f]quinoline derivative (but not the linear octahydrobenzo[g]quinoline derivative) may owe its dopamine-like effects to metabolic activation phenomena. In contrast, the cis-fused isomer of the angularly annulated benzoquinoline was inactive, as was the simple benzene derivative N,N-di-n-propyl-beta-(2,6-dimethoxyphenyl)ethylamine.

Changes in the enzyme activities involved in nitrogen assimilation in Mycobacterium smegmatis under various growth conditions

Glutamate dehydrogenase (aminating) and glutamine synthetase activities were assayed in Mycobacterium smegmatis following growth on various carbon and nitrogen sources. The activities (expressed as nmoles product formed/min/mg crude extract protein) of these two enzymes were higher in crude extracts from glucose-grown cells than in glycerol- or fructose-grown cells. In the presence of succinate, pyruvate, fumarate or acetate in the growth medium, both these enzyme activities were lower than those in citrate-grown cells. The glutamate dehydrogenase (GDH) activity was the same in asparagine and glutamine-grown cells. Ammonium chloride, alanine or glutamic acid, when used as nitrogen source, resulted in low GDH activity as compared to asparagine-grown cells. Glutamine synthetase activity was considerably lower (2-4 fold) when the cells were grown on alanine, glutamine, glutamic acid or ammonium chloride as the nitrogen source than those in asparagine-grown cells. Glutamate and ammonium chloride, when present in the growth medium, repressed both glutamate dehydrogenase and glutamine synthetase, though the degree of repression was small. The results suggest that only a weak transcriptional control operates for these enzyme activities in M. smegmatis.

Assessment of a potential dopaminergic prodrug moiety in several ring systems

The ortho hydroxy/methyl, hydroxy/hydroxymethyl, hydroxy/formyl, and hydroxy/carboxy substitution patterns, some of which confer dopaminergic agonist effects upon 2-aminotetralin ring systems, have been incorporated into beta-phenethylamine, 2-aminoindan, and trans-octahydrobenzo[f]quinoline rings. Certain of the 2-aminoindan derivatives displayed pharmacologic properties consistent with their being dopaminergic agonists. The beta-phenethylamine derivative did not show any significant dopamine-like activity. The 7-hydroxy-8-methyloctahydrobenzo[f]quinoline derivative 4a was a moderately potent, short-acting DA2 receptor antagonist. All of the carboxylic acid derivatives were inert. Of the ortho hydroxy/methyl derivatives, only the 5-hydroxy-6-methyl-2-aminotetralin derivative displayed pharmacological properties consistent with its being a dopaminergic prodrug. It is concluded that 5-hydroxy-6-methyl-2-(di-n-propylamino)tetralin (1a) is structurally unique for a dopaminergic drug.

Nitrogen metabolism in Aspergillus parasiticus NRRL 3240 and A. flavus NRRL 3537 in relation to aflatoxin production

The relationship between nitrogen assimilation, metabolism and aflatoxin formation has been investigated in a toxigenic and a non-toxigenic strain of Aspergillus parasiticus. Ammonia from the medium is mainly assimilated via NADP-requiring glutamate dehydrogenase. During growth NAD-requiring glutamate dehydrogenase followed an inverse pattern of activity with respect to NADP glutamate dehydrogenase. Alpha-ketoglutarate, the product of NAD glutamate dehydrogenase, stimulated acetate incorporation into aflatoxins. Glutamine synthetase, ornithine transcarbamylase, both utilizing glutamate as substrate were assayed under different growth conditions. An important regulatory role for glutamine synthetase is suggested. The metabolic route of asparagine utilization was also investigated. Both the known pathways, glutamate oxaloacetate transaminase and glutamate pyruvate transaminase are operative simultaneously.

Pyridine nucleotides and redox state regulation of aflatoxin biosynthesis in Aspergillus parasiticus NRRL 3240

In vivo regulation of lipid and aflatoxin biosynthesis by pyridine nucleotides and their derived functions was studied in Aspergillus parasiticus NRRL 3240. Aflatoxins, total lipids and pyridine nucleotide content were estimated under different growth conditions. Aflatoxin formation was highest in cultures grown in sucrose-low salts medium followed by asparagine- and zinc-deficient media. The lipid content of the cultures followed an inverse pattern. The levels of oxidized nucleotides decreased with age under all culture conditions employed. Concentrations of NADPH peaked before the onset of aflatoxin biosynthesis. For each medium used, the estimated catabolite reduction charge was constant at all stages of growth whereas the anabolic reduction charge varied. A direct relationship between the level of extracellular ammonium ions and anabolic reduction charge was established. A high anabolic reduction charge was associated with increased lipid biosynthesis rather than aflatoxin biosynthesis.

Effects of morphine on sprouting of locus coeruleus fibers in the neonatal rat

Acutely (by 48 h), as well as after one month survival, morphine (20 mg/kg) significantly potentiated the extent of noradrenergic degeneration in the forebrain of newborn rats caused by 50 mg/kg of 6-hydroxydopamine (6-OHDA) s.c. This was associated with increased regenerative sprouting in the cerebellum and pons-medulla as determined by measurements of norepinephrine (NE) concentration and [3H]NE uptake. This potentiating effect of morphine was not seen in either forebrain, brainstem, or cerebellum if it was administered to newborn rats with a 24-h delay following 6-OHDA. Clonidine (0.1 mg/kg) which, like morphine, decreases locus coeruleus activity, acutely tended to enhance the acute degenerative effects of 6-OHDA, whereas yohimbine (5 mg/kg), an alpha 2-antagonist which increases locus coeruleus activity, significantly attenuated the acute effect of 6-OHDA in the forebrain. In order to determine whether morphine directly alters the regenerative growth of neurons independently of its acute interaction with 6-OHDA, we explored its effect on the collateral sprouting of locus coeruleus projections induced by midcollicular hemisection. Unilateral midcollicular hemisection in neonates resulted, at 2 months of age, in a 91% reduction of NE concentration in the ipsilateral forebrain and an increase in the ipsilateral cerebellar hemisphere to over 200% of control. Significant increases of a slightly smaller magnitude were found in the cerebellar vermis, pons-medulla and the colliculi. Morphine given simultaneously with the lesion significantly attenuated this collateral sprouting in the cerebellar hemisphere and colliculi. These results indicate that morphine potentiates the initial toxicity of 6-OHDA, perhaps by altering activity of locus coeruleus neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Cis- and trans-4-n-Propyl-1,2,3,4,4a,5,6,10b-octahydrobenzo(f)quinolines

Cis- and trans-4-n-Propyloctahydrobenzo(f)quinolines 4a,b were prepared for further assessment of dopaminergic effects of non-oxygenated dopamine congeners. The trans isomer 4b exhibited marked dopamine-like effects in the cat cardioaccelerator nerve assay and in a rat rotation model. Compound 4b produced dose-related lowering of blood pressure in the cat. The cis isomer 4a was inactive in these assays. Both compounds were inactive in a dopamine binding assay, but both appeared active in a spiroperidol binding assay. Both compounds are active alpha 1- and alpha 2-adrenoceptor antagonists. Compound 4b provides evidence that alpha 2-adrenoceptors and dopamine receptors are different entities, since this compound is an alpha 2 antagonist and a dopamine receptor agonist at presynaptic sites.