Biomedical subjects

E A Fox

Publications and source records attributed to E A Fox.

48 records · Page 3Linked to original sources

PubMed1988

Primary structure of human placental ribonuclease inhibitor.

The primary structure of the human placental ribonuclease inhibitor (PRI), a tight-binding inhibitor of angiogenin and pancreatic ribonucleases, has been determined from the cDNA. The sequence of the mature protein is composed of 460 amino acids, yielding a molecular mass of 49,847 g/mol. Peptides comprising 92% of the predicted sequence were isolated from a tryptic digest of PRI, and direct sequence information obtained for 65% of the molecule agreed at all positions with the sequence predicted from the cDNA. The amino acid sequence of PRI contains seven direct internal repeat units, each 57 amino acids in length. These repeat units comprise 87% of the molecule. The average degree of identity between any two is 39%. A region within each repeat unit displays similarity to tandem, leucine-rich repeats found in six other proteins. Modification of PRI with iodoacetic acid, p-(hydroxymercuri)benzoate, and 5,5'-dithiobis(2-nitrobenzoic acid) reveals that at least 30 of the 32 cysteine residues of PRI are in the reduced form.

Amino Acid Sequence↗

PubMed1988

Expression of Met-(-1) angiogenin in Escherichia coli: conversion to the authentic less than Glu-1 protein.

A method for obtaining authentic human angiogenin utilizing an Escherichia coli recombinant expression system is described. A synthetic gene encoding angiogenin was placed into a vector for direct expression under the control of a modified E. coli trp promoter. The protein was produced by the bacteria in an insoluble form and purified to homogeneity by cation-exchange and reversed-phase HPLC following reduction/solubilization and reoxidation. The protein isolated was identified as Met-(-1) angiogenin by amino acid analysis and tryptic peptide mapping; the latter demonstrated that all three disulfide bonds had formed correctly. Both the enzymatic and angiogenic activities of the Met-(-1) protein were equivalent to those of native angiogenin. A Met-(-1) Leu-30 derivative of angiogenin was also isolated and found to be fully active. Conversion of Met-(-1) angiogenin to the authentic less than Glu-1 protein was achieved by treatment with Aeromonas aminopeptidase under conditions in which the new N-terminal glutamine readily cyclizes nonenzymatically. This aminopeptidase treatment may have more general applicability for removal of undesirable N-terminal methionine residues from foreign proteins expressed in bacteria.

Amino Acid Sequence↗

PubMed1987

Retrograde tracer technique for assessment of selective and total subdiaphragmatic vagotomies.

A new protocol that provides a sensitive, reliable, and practical test for completeness of selective as well as total subdiaphragmatic vagotomies is described. This protocol employs a microscopic inventory of retrogradely labeled neurons in topographically distinct regions of the dorsal motor nucleus to determine which vagal branches have been surgically destroyed. Physiological experiments for validation and observations on the use of the method with 243 rats indicate that the protocol described can assess total as well as at least 11 different types of selective subdiaphragmatic vagotomies, including surgeries for which no assays have existed. Furthermore, the technique can identify cases where a branch is only partially destroyed. Other strengths include the facts that the protocol provides a simultaneous inventory of the different branches in a single test, is not influenced by the general health of the animal, and does not interfere with concurrent behavioral or physiological tests. Limitations include the facts that the tracer inventory requires a minimal survival period, can only be done postmortem, and has low resolution for cuts of the vagal hepatic branch. Aspects of the protocol critical to its implementation, including specifics for using the fluorescent tracer true blue, are discussed. Other tracers with similar diffusion characteristics, such as fluoro-gold and fast blue, can be used with equal effectiveness with this protocol.

Animals↗

PubMed1986

Vagotomy does not alter circannual body weight cycles in the hibernator Citellus lateralis.

To evaluate a hypothesized role of the vagus in the circannual metabolic cycle of hibernators, measures of annual weight gain, weight loss and cycle period were taken for the ground squirrel, Citellus lateralis, maintained in constant environmental conditions before and after subdiaphragmatic vagotomy. The surgery did not alter the peak weights attained, the lowest weights reached, or the period of the circannual cycle.

Animals↗

PubMed1986

Tracer diffusion has exaggerated CNS maps of direct preganglionic innervation of pancreas.

Small injections of True Blue (TB) into 4 different segments of the pancreas of the rat resulted in characteristic and different numbers and distributions of labeled cells within the dorsal motor nucleus of the vagus (DMN). Composites of these patterns of labeled cells in the DMN closely matched the distributions previously reported for more extensive injections of retrograde tracers into the pancreas. However, the application of a diffusion barrier (formed with a plastic wound spray) on the outer surface of the stomach and intestines adjacent to the pancreas segment which contained the TB injection depot prevented virtually all of the labeling of DMN cells. Similarly, applying a diffusion barrier directly to the injected pancreas segment itself prevented all or most (mean greater than 99%) of the DMN labeling. In contrast to this effect on DMN label, the barrier reduced more modestly the labeling of celiac ganglion somata after pancreas injections. Several additional control experiments also suggest that the absence of DMN label after the barrier application resulted from interference with tracer diffusion from the injected organ and not from neurotoxic effects. These include the following demonstrations in the presence of the barrier: (1) observation of unimpaired vagally stimulated insulin secretion, (2) uncompromised cell labeling of DMN from other organs treated with TB plus the barrier, and (3) normal hematoxylin and eosin stained pancreas tissue which had received TB injections and barrier application. It was concluded that both the number of parasympathetic preganglionic neurons that project monosynaptically to the pancreas and their distribution in the medulla may have been very significantly overestimated in previous tracer studies.

Animals↗

PubMed1986

Molecular characterization and phylogenetic studies of a wound-inducible proteinase inhibitor I gene in Lycopersicon species.

A gene coding for proteinase inhibitor I, whose expression is induced in tomato leaves (Lycopersicon esculentum L. var. Bonny Best) in response to wounding or insect attacks, was isolated from a genomic library and characterized. The nucleotide sequence revealed that the gene is complete and encodes the sequence of an inhibitor I cDNA that was previously isolated from a cDNA library prepared from wound-induced mRNA from tomato leaves. This gene is located 13.1 kilobase pairs (kbp) upstream from an inhibitor II gene. The wound-inducible gene is interrupted by two intervening sequences of 445 and 404 bp, situated within the codons of amino acids 17 and 47, respectively, of the open reading frame. In addition to the presence of putative regulatory sequences, TATAAA and CCACT, two copies of an imperfect direct repeat approximately 100 bp long were identified in the 5'-flanking region. Phylogenetic comparisons of wound-inducible inhibitor I genes within the genomes of various Lycopersicon species revealed that the repeat is found in seven ancestral species of tomato.

Amino Acid Sequence↗

PubMed1985

Longitudinal columnar organization within the dorsal motor nucleus represents separate branches of the abdominal vagus.

To identify the distribution of central preganglionics associated with each branch of the subdiaphragmatic vagus, the fluorescent tracer True Blue (TB) was administered intraperitoneally to rats with 4 out of 5 branches cauterized, and then, after 72 h, the animals were sacrificed for histological analysis. Each vagal branch contained the axons of a topographically distinct column of cells within the dorsal motor nucleus of the vagus (DMN). The columns representing the 4 branches with the largest numbers of efferents are organized as paired, bilaterally symmetrical, longitudinal distributions on either side of the medulla. Each DMN side contains a column occupying the medial two-thirds or more of the nucleus and corresponding to one of the gastric branches (left DMN, anterior gastric; right DMN, posterior gastric). Also on each side, the lateral pole of the DMN consists of a coherent cell column corresponding to one of the celiac branches (left DMN, accessory celiac; right DMN, celiac). The fifth branch, the hepatic, is represented by a limited number of somata forming a diffuse column largely coextensive with that representing the anterior gastric branch. At some levels of the DMN, the columns overlap. Labeled cells observed in the reticular formation were correlated in number, left-right ratios and response to vagotomy with those in the DMN, which suggests that they are displaced cells of the nucleus. Distributions of labeled cells in the nucleus ambiguus and the retrofacial nucleus were not tightly correlated with those of the DMN. An analysis of cell counts obtained for each of the individual branches suggests that vagal axons do not generally send collaterals through more than one branch.

Animals↗

PubMed1985

A retrograde tracer strategy using True Blue to label the preganglionic parasympathetic innervation of the abdominal viscera.

A simple and reliable method for labeling the preganglionic neurons which innervate the abdominal viscera is described. Infusion of a True Blue (TB) suspension in several different concentrations directly into the peritoneal cavity consistently labeled the medullary vagal nuclei including the dorsal motor nucleus (DMN), nucleus ambiguus (NA), and retrofacial nucleus (RFN). Quantitative analysis of cell labeling after 30 microliters infusions of a large range of concentrations of TB (0.001-20.0%) showed that: (1) as little as 0.0075 mg of TB was sufficient to label DMN cells distinctly while only 0.075 mg (or larger) doses of TB were adequate for labeling cells of the NA and the RFN, and (2) doses of 3.0 mg (or greater) labeled the maximum number of cells in the DMN, NA, and RFN. Qualitative analysis suggested that medium range doses (0.075-0.75 mg) were optimal for discerning cell size and type throughout each of these nuclei.

Abdomen↗

PubMed1984

Regeneration may mediate the sparing of VMH obesity observed with prior vagotomy.

The extent to which the vagus nerve is involved in mediating the development of obesity in animals with lesions of the ventromedial hypothalamus (VMH) was determined. Female rats were given either VMH lesions or sham lesions 100 days after they had received vagotomy with pyloroplasty, sham vagotomy with pyloroplasty, or sham vagotomy with sham pyloroplasty. For the first 7 postlesion wk, the animals were fed a wet mash diet, then they were maintained on a high-fat diet for 10 wk, and finally they were fed a highly palatable supermarket diet for 4 wk. VMH-lesioned animals with prior vagotomy and pyloroplasty displayed 65% of the obesity observed in lesioned animals with prior sham vagotomy. This expression was increased to 72% of the full VMH obesity during the supermarket diet phase. Assessment of vagotomy suggested that vagal regeneration and, in some cases, recovery of vagally stimulated insulin secretion had occurred. This reorganization may have contributed to the residual obesity expressed in VMH-lesioned animals with prior vagotomy.

Animals↗

PubMed1983

Automatic query formulations in information retrieval.

Modern information retrieval systems are designed to supply relevant information in response to requests received from the user population. In most retrieval environments the search requests consist of keywords, or index terms, interrelated by appropriate Boolean operators. Since it is difficult for untrained users to generate effective Boolean search requests, trained search intermediaries are normally used to translate original statements of user need into useful Boolean search formulations. Methods are introduced in this study which reduce the role of the search intermediaries by making it possible to generate Boolean search formulations completely automatically from natural language statements provided by the system patrons. Frequency considerations are used automatically to generate appropriate term combinations as well as Boolean connectives relating the terms. Methods are covered to produce automatic query formulations both in a standard Boolean logic system, as well as in an extended Boolean system in which the strict interpretation of the connectives is relaxed. Experimental results are supplied to evaluate the effectiveness of the automatic query formulation process, and methods are described for applying the automatic query formulation process in practice.

Computers↗

PubMed1983

Anatomical considerations for surgery of the rat abdominal vagus: distribution, paraganglia and regeneration.

In order to provide a detailed surgical anatomy of the rat abdominal vagus, we examined pyridine silver-stained tissue from one group of normal animals and a second group that survived 9 months after vagotomy. In the normal sample, as has been established for man, there was considerable variability in the levels at which each of the vagal branches separated from the main trunks. Contrary to reports from dissection studies, most of the branches were not single fiber bundles but rather consisted of two or more separate bundles. At the extreme, the posterior gastric and coeliac branches each consisted of as many as 15 individual bundles. Even the main trunks of the subdiaphragmatic vagus were occasionally observed to have multiple components (anterior trunk, 13% of the cases; posterior, 25%). In addition to the classically recognized hepatic, anterior gastric, coeliac, and posterior gastric branches, we also observed an accessory coeliac branch of the anterior trunk in all animals. This accessory coeliac division originated just caudal to the hepatic branching and extended first laterally and then dorsally while running caudally to exit from the esophagus just before the separation of the coeliac branch from the posterior trunk. The vagi were observed to contain paraganglia consisting of islands of glomus cells, neurons, and extensive capillary beds, all situated within the perineurium. The paraganglia occurred in greatest frequency at the sites where the hepatic and coeliac branches divide from their respective trunks. Paraganglia were also observed peripherally within vagal branches; there they were most numerous within the coeliac branch and least numerous in the accessory coeliac. Other studies yielded evidence that regeneration had occurred after complete vagotomy. First, stumps of the branches distal to the resection scar contained axons. Central to the scar, axons grew out in all directions from the neuroma; some of them appeared to cross the scar and to reinnervate the distal stumps. Secondly, 30% of the animals in which regeneration was thought to be possible increased their insulin secretion in response to electrical stimulation of the cervical vagus. The implications of the above findings for experiments that involve manipulation or recording of the vagus are discussed.

Abdomen↗

PubMedDate not supplied

False-positive artifacts of tracer strategies distort autonomic connectivity maps.

The widespread use of new axonal transport tracing techniques in the ANS has resulted in substantially revised and amended descriptions of ANS organization. The present review suggests, however, that at least some of the results on which proposed revisions of ANS anatomy have been based have incorporated artifacts and therefore should be cautiously interpreted. The peripheral nervous system and viscera are composed in part of connective and endothelial tissues that are porous or 'leaky' to solutes with appropriate chemical characteristics, including the major tracer compounds. As a result, several extra-axonal routes for redistribution of label from the application site into other tissues are present. These include (1) diffusion through tissue membranes to enter directly adjacent tissues and (2) leakage into extracellular fluids within the body cavity, vasculature, lymphatics, exocrine ducts, or organ lumens to migrate to more distant tissues. As a consequence of the extreme sensitivity of the methods used, such redistribution of even minute amounts of label can produce false positives. Review of autonomic neuroanatomy suggests additional mechanisms, including tracer uptake by fibers of passage, can produce artifactual staining. Based on these surveys of tissue composition, tracer characteristics and sources of artifact, experimental controls and criteria for identifying and avoiding labeling artifacts are described. Since no single procedure is foolproof for ANS experimentation, the routine application of multiple controls, particularly ones which restrict or prevent tracer diffusion, are needed.

Animals↗