Radiographic guided epidural placement.
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Analgesia, Epidural↗
Biomedical subjects
T W Johnson
Publications and source records attributed to T W Johnson.
Recruitment of a foreign quinone into the A1 site of photosystem I. In vivo replacement of plastoquinone-9 by media-supplemented naphthoquinones in phylloquinone biosynthetic pathway mutants of Synechocystis sp. PCC 6803.
Interruption of the phylloquinone (PhQ) biosynthetic pathway by interposon mutagenesis of the menA and menB genes in Synechocystis sp. PCC 6803 results in plastoquinone-9 (PQ-9) occupying the A(1) site and functioning in electron transfer from A(0) to the FeS clusters in photosystem (PS) I (Johnson, T. W., Shen, G., Zybailov, B., Kolling, D., Reategui, R., Beauparlant, S., Vassiliev, I. R., Bryant, D. A., Jones, A. D., Golbeck, J. H., and Chitnis, P. R. (2000) J. Biol. Chem. 275, 8523-8530. We report here the isolation of menB26, a strain of the menB mutant that grows in high light by virtue of a higher PS I to PS II ratio. PhQ can be reincorporated into the A(1) site of the menB26 mutant strain by supplementing the growth medium with authentic PhQ. The reincorporation of PhQ also occurs in cells that have been treated with protein synthesis inhibitors, consistent with a displacement of PQ-9 from the A(1) site by mass action. The doubling time of the menB26 mutant cells, but not the menA mutant cells, approaches the wild type when the growth medium is supplemented with naphthoquinone (NQ) derivatives such as 2-CO(2)H-1,4-NQ and 2-CH(3)-1,4-NQ. Since PhQ replaces PQ-9 in the supplemented menB26 mutant cells, but not in the menA mutant cells, the phytyl tail accompanies the incorporation of these quinones into the A(1) site. Studies with menB26 mutant cells and perdeuterated 2-CH(3)-1,4-NQ shows that phytylation occurs at position 3 of the NQ ring because the deuterated 2-methyl group remains intact. Therefore, the specificity of the phytyltransferase enzyme is selective with respect to the group present at ring positions 2 and 3. Supplementing the growth medium of menB26 mutant cells with 1,4-NQ also leads to its incorporation into the A(1) site, but typically without either the phytyl tail or the methyl group. These findings open the possibility of biologically incorporating novel quinones into the A(1) site by supplementing the growth medium of menB26 mutant cells.
Alkyl and Aryl Transferases↗
Enantiospecific synthesis of the proposed structure of the antitubercular marine diterpenoid pseudopteroxazole: revision of stereochemistry.
An enantiospecific synthesis of structure 1, previously assigned to the antitubercular marine natural product pseudopteroxazole, has been accomplished as outlined in Scheme 1. Coupling of diene acid 3 and amino phenol 4 produced the amide 5, which was subjected to a novel oxidative intramolecular Diels-Alder reaction to generate the tricyclic lactam 6a stereoselectively. This product was transformed via intermediates 7-11 into the diene 13. Cationic cyclization of 13 afforded two diastereomeric tricyclic amphilectanes which were separated and transformed by parallel four-step sequences into 1 and 2, respectively. Neither 1 nor 2 were identical with pseudopteroxazole, indicating a need for revision of the structure, probably to 16.
Alkaloids↗
Syntheses and stereochemical revision of pseudopterosin G-J aglycon and helioporin E.
Revised structures are proposed for pseudopterosin G-J aglycon and helioporin E.
Anti-Inflammatory Agents, Non-Steroidal↗
Recruitment of a foreign quinone into the A(1) site of photosystem I. I. Genetic and physiological characterization of phylloquinone biosynthetic pathway mutants in Synechocystis sp. pcc 6803.
Genes encoding enzymes of the biosynthetic pathway leading to phylloquinone, the secondary electron acceptor of photosystem (PS) I, were identified in Synechocystis sp. PCC 6803 by comparison with genes encoding enzymes of the menaquinone biosynthetic pathway in Escherichia coli. Targeted inactivation of the menA and menB genes, which code for phytyl transferase and 1,4-dihydroxy-2-naphthoate synthase, respectively, prevented the synthesis of phylloquinone, thereby confirming the participation of these two gene products in the biosynthetic pathway. The menA and menB mutants grow photoautotrophically under low light conditions (20 microE m(-2) s(-1)), with doubling times twice that of the wild type, but they are unable to grow under high light conditions (120 microE m(-2) s(-1)). The menA and menB mutants grow photoheterotrophically on media supplemented with glucose under low light conditions, with doubling times similar to that of the wild type, but they are unable to grow under high light conditions unless atrazine is present to inhibit PS II activity. The level of active PS II per cell in the menA and menB mutant strains is identical to that of the wild type, but the level of active PS I is about 50-60% that of the wild type as assayed by low temperature fluorescence, P700 photoactivity, and electron transfer rates. PS I complexes isolated from the menA and menB mutant strains contain the full complement of polypeptides, show photoreduction of F(A) and F(B) at 15 K, and support 82-84% of the wild type rate of electron transfer from cytochrome c(6) to flavodoxin. HPLC analyses show high levels of plastoquinone-9 in PS I complexes from the menA and menB mutants but not from the wild type. We propose that in the absence of phylloquinone, PS I recruits plastoquinone-9 into the A(1) site, where it functions as an efficient cofactor in electron transfer from A(0) to the iron-sulfur clusters.
Alkyl and Aryl Transferases↗
Recruitment of a foreign quinone into the A(1) site of photosystem I. II. Structural and functional characterization of phylloquinone biosynthetic pathway mutants by electron paramagnetic resonance and electron-nuclear double resonance spectroscopy.
Electron paramagnetic resonance (EPR) and electron-nuclear double resonance studies of the photosystem (PS) I quinone acceptor, A(1), in phylloquinone biosynthetic pathway mutants are described. Room temperature continuous wave EPR measurements at X-band of whole cells of menA and menB interruption mutants show a transient reduction and oxidation of an organic radical with a g-value and anisotropy characteristic of a quinone. In PS I complexes, the continuous wave EPR spectrum of the photoaccumulated Q(-) radical, measured at Q-band, and the electron spin-polarized transient EPR spectra of the radical pair P700(+) Q(-), measured at X-, Q-, and W-bands, show three prominent features: (i) Q(-) has a larger g-anisotropy than native phylloquinone, (ii) Q(-) does not display the prominent methyl hyperfine couplings attributed to the 2-methyl group of phylloquinone, and (iii) the orientation of Q(-) in the A(1) site as derived from the spin polarization is that of native phylloquinone in the wild type. Electron spin echo modulation experiments on P700(+) Q(-) show that the dipolar coupling in the radical pair is the same as in native PS I, i.e. the distance between P700(+) and Q(-) (25.3 +/- 0.3 A) is the same as between P700(+) and A(1)(-) in the wild type. Pulsed electron-nuclear double resonance studies show two sets of resolved spectral features with nearly axially symmetric hyperfine couplings. They are tentatively assigned to the two methyl groups of the recruited plastoquinone-9, and their difference indicates a strong inequivalence among the two groups when in the A(1) site. These results show that Q (i) functions in accepting an electron from A(0)(-) and in passing the electron forward to the iron-sulfur clusters, (ii) occupies the A(1) site with an orientation similar to that of phylloquinone in the wild type, and (iii) has spectroscopic properties consistent with its identity as plastoquinone-9.
Alkyl and Aryl Transferases↗
Personality, job level, job stressors, and their interaction as predictors of coping behavior.
Hypotheses concerning the relationships among job stressors, job level, personality, and coping responses were investigated in a sample of 305 electrical contracting employees. Coping behaviors were measured with questionnaire items based on interviews conducted with a sample of the subjects. Neuroticism (N) and Extraversion (E) were the personality variables most strongly related to coping behavior. Overall, more coping variance was explained by personality than by job stressors; however, when the effects of job level and job stressors were combined, they explained more variance in complaining/quitting and seeking social support than did the personality variables. Both work situation and personality seem to be important variables in the choice of coping behaviors. There was no evidence of interactions among personality, stressors, and job level in explaining coping behavior.
Adaptation, Psychological↗
A case of Susac syndrome.
Susac syndrome is a readily recognized but often misdiagnosed disorder almost exclusively affecting women in the 20- to 40-year age range. Characterized by the clinical triad of encephalopathy, branch retinal artery occlusions, and sensorineural hearing loss, patients with Susac syndrome are often misdiagnosed with multiple sclerosis (MS). Unlike MS, however, the disease process extends over a 1- to 2-year period and then goes into remission. This presentation describes the progression of symptoms of a patient eventually diagnosed with Susac syndrome.
Adult↗
First total synthesis of xestobergsterol A and active structural analogues of the xestobergsterols.
[formula: see text] A novel pentacyclic polyhydroxylated sterol, xestobergsterol A (1a), has been synthesized in 24 steps and in good overall yield from stigmasterol 17. The key steps of the synthesis are the Breslow remote functionalization of the polyoxygenated steroid derived from 25 and the base-catalyzed epimerization-aldol condensation of the dione derived from 27.
Carbohydrate Sequence↗
Prolonged loss of consciousness and elevated porphyrins following propofol administrations.
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Adult↗
Hypermelanotic nevus: clinical, histopathologic, and ultrastructural features in 316 cases.
We report on a series of benign melanocytic nevi that have unique clinical, histopathologic, and ultrastructural features. Between March 1993 and February 1994, 316 examples of hypermelanotic nevi were received by the dermatopathology laboratory at Denver General Hospital. Our study identified the clinical characteristics, histopathologic criteria, and ultrastructure of this lesion. Clinically, the lesions were dark brown to black macules or papules. The most common location was the back. There was a slight female predominance, and the mean age of our patients was 40 years. Histopathologically, the nevus showed the following characteristics: (a) melanin within a compact stratum corneum, (b) small nests of nevus cells at the dermal-epidermal junction and (in 52% of the cases), nests within the papillary dermis, (c) heavy melanin within keratinocytes in the lower epidermis, (d) a sparse to moderate lymphocytic infiltrate and melanophages in the superficial dermis, and (e) an absence of cytologic atypia. Electron microscopy revealed that abundant melanin was packaged in melanosome complexes within keratinocytes. Less pigmented melanocytes and nevus cells contained well-developed dendritic processes and golgi, indicative of efficient melanin transfer. According to our retrospective case control analysis, patients with hypermelanotic nevi were older and more likely to be male than those with ordinary nevi. Hypermelanotic nevi were more likely than controls to be junctional nevi; they were smaller, dark brown or black in color, and clinically suspicious for melanoma. We propose the name "hypermelanotic nevus" to describe this benign lesion, which is often biopsied to exclude melanoma.
Adolescent↗
An inexpensive, self-assembly pressure algometer.
We have developed a simple instrument for pressure algometry. It can be made easily using components found in most anaesthetic rooms. Ten students were able to make the device using written instructions. All the resulting algometers performed within 10% accuracy limits for values up to 4 kg.cm-2.
Calibration↗
Patient-controlled analgesia--who benefits?
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Analgesia, Patient-Controlled↗
Pedigree analysis in families with febrile seizures.
Febrile seizures are the most common form of seizures, occurring in an estimated 2-5% of North American children. We carried out a systematic pedigree study of febrile seizure probands. Forty of 52 probands (77%) in a referral population selected for increased severity had more than one case per family: one family had 10 cases, one family had 7, 3 families had 6, 2 had 5, 3 had 4, 13 had 3, and 17 had 2 cases. Mode of inheritance in the multicase families best fit the hypothesis of autosomal dominance with reduced penetrance. Polygenic inheritance could not be excluded for some of the smaller families. There was no support for X-linked or mitochondrial inheritance. Penetrance was calculated to be 0.64. Because the cases were selected for increased severity, this represents a useful estimate of the upper limit of penetrance and is in agreement with twin studies. Simulated lod scores showed adequate power for a linkage study in the absence of heterogeneity. Individual families had simulated average lod scores as high as 2.1. However, with potential heterogeneity, assuming only 70% of families share the same disease locus, average lod scores were marginal, and a high density map of marker loci and additional families would be required to document linkage.
Databases, Factual↗
DOPA-negative melanocytes in the outer root sheath of human hair follicles express premelanosomal antigens but not a melanosomal antigen or the melanosome-associated glycoproteins tyrosinase, TRP-1, and TRP-2.
It is believed that DOPA-negative melanocytes in the outer root sheath of the human hair follicle are activated, become identifiable by DOPA staining, and migrate into the epidermis during the repigmenting phase of vitiligo. These cells are difficult to identify, however, and otherwise have not been characterized. These cells are readily identified by immunofluorescence, immunohistochemistry, and immunoelectronmicroscopy using the antibodies NKI/beteb and A4F11, which recognize premelanosome-related antigens. The majority of the outer root sheath melanocytes were found in the mid to the upper portion of the hair follicle. Double staining revealed that these cells were distinct from HLA-DR-bearing dendritic cells. Further immunohistochemical investigation using alpha-PEP-7, alpha-PEP-1, or TMH-1 and alpha-PEP-8 antibodies revealed that outer root sheath melanocytes cannot be identified by antibodies to tyrosinase, TRP-1, or TRP-2, respectively. These cells also did not react with HMB45 antibody, which recognizes a melanosome-associated cytoplasmic antigen. We believe that the inactive outer root sheath melanocytes contain some of the early structural proteins but not any of the enzymatic proteins necessary for melanogenesis. Therefore, activation is the process whereby outer root sheath melanocytes acquire all of the structural and enzymatic proteins necessary for melanogenesis.
Adult↗
Avian telencephalon and body weight.
The neurological mechanisms associated with weight gain in animals have been extensively studied in mammals, but relatively little investigation has been carried out in birds. As in mammals, it has been shown that lesion of the ventromedial nucleus of the hypothalamus leads to hyperphagia and obesity in several species of birds. Likewise, bilateral lesions of the lateral hypothalamus result in aphagia and weight loss. Therefore, at the level of the hypothalamus, control of body weight appears to be controlled by similar neurological mechanisms in all homeothermic species via modulation of the sympathetic nervous system. Because of the role of the mammalian striatum in body weight regulation, body weight data from various manipulative studies in chickens were analyzed to see if these areas play a role in avian body weight regulation. In the first study, cycloheximide, glutamate, or saline was injected intracerebrally into 1-day-old chicks. In the second study, 3-day-old chicks received surgical ablation of the neocortex or kainic acid-induced lesions of the paleostriatum. Decreased body weight was noted in chicks that received injections of cycloheximide or glutamate, or kainic acid-induced lesions. The disruption in body weight in Experiment 1 might have been due to neurochemical pathology thought to occur in the paleostriatum. In the second experiment, lesions of the neostriatum or hyperstriatum, analogous to the neocortex in mammals, did not produce a difference in weight gain compared to controls. This preliminary work with kainic acid lesions in the chicken paleostriatum demonstrates a significant long-term decrease in body weight. As in mammals, the basal ganglia may have a role in body weight regulation.
Animals↗
Substitution of aromatic and nonaromatic amino acids for the Phe3 residue in the delta-selective opioid peptide deltorphin I: effects on binding affinity and selectivity.
Deltorphins I and II (Tyr-D-Ala-Phe-Asp-Val-Val-Gly NH2 and Tyr-D-Ala-Phe-Glu-Val-Val-Gly NH2) display a high degree of delta-opioid receptor selectivity. Since they lack the intervening Gly3 residue found between the Tyr and Phe aromatic moieties in pentapeptide enkephalins, deltorphins I and II resemble a previously described series of cyclic tetrapeptides based on Tyr-c[D-Cys-Phe-D-Pen] (JOM-13). With the goal of development of structure-activity relationships for deltorphins and comparison with that of the cyclic tetrapeptides, ten analogs of deltorphin I were synthesized in which Phe3 was replaced with specific aromatic and nonaromatic amino acids with varying physicochemical properties. Results indicated that analogs containing the bicyclic aromatic amino acids 3-(1-naphthyl)-L-alanine [1-Nal; Ki(mu) = 767 nM, Ki(delta) = 7.70 nM], 3-(2-naphthyl)-L-alanine [2-Nal; Ki(mu) = 1910 nM, Ki(delta) = 49.2 nM], tryptophan [Ki(mu) = 1250 nM, Ki(delta) = 23.9 nM], and 3-(3-benzothienyl)-L-alanine [Bth; Ki(mu) = 112 nM, Ki(delta) = 3.36 nM] were fairly well tolerated at mu- and delta-receptors, though affinity was compromised to varying degrees relative to deltorphin I. Shortening the Phe side chain by incorporation of phenylglycine (Pgl) was detrimental to both mu (Ki = 4710 nM) and delta (Ki = 15.6 nM) binding, while extension of the side chain with homophenylalanine (Hfe) enhanced mu binding (Ki = 67.8 nM), leaving delta affinity unaffected (Ki = 2.64 nM). Substitution with nonaromatic amino acids valine and isoleucine led expectedly to poor opioid binding [Ki(mu) = > or = 10,000 nM for each, Ki(delta) = 160 and 94.7 nM, respectively], while peptides containing cyclohexylalanine (Cha) and leucine surprisingly retained affinity at both mu (Ki = 322 and 1240 nM, respectively) and delta (Ki = 10.5 and 12.4 nM, respectively) sites. In general, these trends mirror those observed for similar modification in Tyr-c[D-Cys-Phe-D-Pen].
Amino Acid Sequence↗