Assessing the organizational climate in dental schools.
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Administrative Personnel↗
Biomedical subjects
J D Johnson
Publications and source records attributed to J D Johnson.
Contacts between 5 S DNA and Xenopus TFIIIA identified using 5-azido-2'-deoxyuridine-substituted DNA.
A highly photosensitive analogue of thymidine, 5-azidodeoxyuridine 5'-triphosphate, has been incorporated into 61-base pair (bp) DNA fragments corresponding to the central region of Xenopus somatic-type 5 S RNA genes such that 5-azidodeoxyuridine replaces some or all T residues in either the coding or noncoding strand of the TFIIIA binding site. Photolysis of TFIIIA.DNA complexes formed with these probes results in efficient, sequence-specific cross-linking to the Zn-finger protein providing direct evidence that this class of proteins have contacts in the major groove of their target sequence. Of the 20 T residues present in the 61-bp probes, greater than 90% of the cross-linking occurs from two sites in the 5 S RNA gene corresponding to T residues at positions 84 and 88 in the noncoding and coding strands, respectively. Digestion by V8 protease of the complex formed with the noncoding strand probe releases peptides not bound to the DNA. Amino acid sequence analysis of the remaining, cross-linked peptides indicates the region including zinc-finger 2 plus the finger 2-3 linker is in contact with position 84. The linker region between fingers 5 and 6 is also in close proximity to the major groove somewhere upstream from position 84.
Amino Acid Sequence↗
A continuous fluorescence assay for protein kinase C.
A 6-acryloyl-2-dimethylaminonapthalene (acrylodan)-labeled 25-amino acid peptide (acrylodan-CKK-KKRFSFKKSFKLSGFSFKKNKK-COO-), containing the protein kinase C (PKC) phosphorylation sites of brain myristoylated alanine-rich kinase C substrate protein, undergoes a 20% fluorescence decrease when it is phosphorylated by phospholipid/calcium-dependent protein kinase (PKC). This fluorescence decrease is dependent on the presence of PKC, calcium (half-maximal stimulation at pCa = 6.2), phosphatidylserine, diacylglycerol, or phorbol-12-myristate-13-acetate (half-maximal stimulation at 2 nM) and ATP, and correlates well (r = 0.997) with [32P]phosphate incorporation into the peptide. This fluorescence assay allows detection of 0.02 nM PKC, while similar concentrations of cyclic AMP-dependent or type II calmodulin-dependent protein kinases produced no change in peptide fluorescence. The method can be used to assay purified PKC as well as activity in crude brain homogenates. Incubation of PKC with staurosporine inhibits the fluorescence decrease with an IC50 of 2 nM. Thus the fluorescence decrease that occurs in the acrylodan-peptide provides a continuous fluorescence assay for PKC activity.
2-Naphthylamine↗
Phosphorylation-dependent binding of a synthetic MARCKS peptide to calmodulin.
A 25-amino acid peptide, containing the four protein kinase C (PKC) phosphorylation sites and the calmodulin (CaM) binding domain of the myristoylated alanine-rich C kinase substrate (MARCKS) protein, has been synthesized and used to determine the effects of phosphorylation on its binding and regulation of CaM. PKC phosphorylation of this peptide (3.0 mol of Pi/mol of peptide) produced a 200-fold decrease in its affinity for CaM. PKC phosphorylation of the peptide resulted in its dissociation from CaM over a time course that paralleled the phosphorylation of 1 mol of serine/mol of peptide. The peptide inhibited CaM's binding to myosin light chain kinase and CaM's stimulation of phosphodiesterase and calcineurin. PKC phosphorylation of the peptide resulted in a rapid release of bound CaM, allowing its subsequent binding to myosin light chain kinase (t1/2 = 1.6 min), stimulation of phosphodiesterase (t1/2 = 1.2 min) and calcineurin (t1/2 = 1.7 min). Partially purified MARCKS protein produced a similar inhibition of CaM-phosphodiesterase which was reversed by PKC phosphorylation. PKC phosphorylation of the peptide occurred primarily at serine 8 and serine 12, and phosphorylation of serine 12 regulated peptide affinity for CaM. Thus, PKC phosphorylation of the peptide and the MARCKS protein results in the rapid release of CaM and the subsequent activation of CaM-dependent enzymes. This process might allow for interplay between PKC and CaM-dependent signal transduction pathways.
2-Naphthylamine↗
Copy number and chromosomal location of Saccharomyces cerevisiae tRNA(Trp)-encoding genes.
Yeast tRNA(Trp)-encoding genes have been identified by Southern-blot analysis of chromosomal DNA. Seven copies of this gene are detected in blots of both restriction endonuclease digests and intact chromosomal DNA. Electrophoretic mapping of tDNA(Trp) indicates one copy is located on each of chromosomes X, XI, XIII, and XVI. The remaining three copies are localized to chromosomes VII and/or XV. Three different yeast strains gave identical results indicating this multi-gene family is relatively stable.
Base Sequence↗
Cytoplasmic calcium levels in protoplasts from the cap and elongation zone of maize roots.
Calcium has been implicated as a key component in the signal transduction process of root gravitropism. We measured cytoplasmic free calcium in protoplasts isolated from the elongation zone and cap of primary roots of light-grown, vertically oriented seedlings of Zea mays L. Protoplasts were loaded with the penta-potassium salts of fura-2 and indo-1 by incubation in acidic solutions of these calcium indicators. Loading increased with decreasing pH but the pH dependence was stronger for indo-1 than for fura-2. In the case of fura-2, loading was enhanced only at the lowest pH (4.5) tested. Dyes loaded in this manner were distributed predominantly in the cytoplasm as indicated by fluorescence patterns. As an alternative method of loading, protoplasts were incubated with the acetoxymethylesters of fura-2 and indo-1. Protoplasts loaded by this method exhibited fluorescence both in the cytoplasm and in association with various organelles. Cytoplasmic calcium levels measured using spectrofluorometry, were found to be 160 +/- 40 nM and 257 +/- 27 nM, respectively, in populations of protoplasts from the root cap and elongation zone. Cytoplasmic free calcium did not increase upon addition of calcium to the incubation medium, indicating that the passive permeability to calcium was low.
Calcium↗
New methods in the diagnosis and management of cerebral toxoplasmosis associated with the acquired immune deficiency syndrome.
Cerebral toxoplasmosis is a life-threatening condition associated with the acquired immune deficiency syndrome (AIDS). Current diagnostic and therapeutic methods have serious limitations. The diagnosis of cerebral toxoplasma infection in a patient with AIDS was assisted by the detection of specific IgM in a highly sensitive immunosorbent agglutination assay and by the demonstration of Toxoplasma gondii nucleic acid in a brain biopsy specimen by means of the polymerase chain reaction. Following initial failure of the patient to respond to treatment with sulphadiazine and pyrimethamine, clinical improvement was observed during treatment with clindamycin followed by dapsone. Further assessment of novel methods in the management of cerebral toxoplasmosis is required.
Acquired Immunodeficiency Syndrome↗
Slash pine bud dormancy as affected by lifting date and root wrenching in the nursery.
Bud dormancy of root wrenched and unwrenched slash pine (Pinus elliottii Engelm.) seedlings growing in a forest nursery was measured on five lifting dates. Determination of bud dormancy was based on days to budbreak (DBB) under optimal growing conditions, mitotic activity in the apical meristem, chilling hours accumulated, and bud morphology. Based on DBB, seedlings were most dormant at Lift 2 on November 24 after exposure to 189 hours below 10 degrees C and 93 hours below 6.7 degrees C. Mitotic activity in the apical meristem was at its lowest 23 days later at Lift 3, possibly indicating the period when seedlings are most resistant to transplanting stresses. Multiple wrenching resulted in a slight shift in the dormancy cycle as wrenched seedlings set bud sooner in the nursery and broke bud sooner at the planting site in the spring than control seedlings. This implies that wrenched seedlings can be successfully lifted from the nursery earlier and will initiate spring shoot growth earlier than control seedlings.
Journal Article↗
Elevated myocardial calcium and its role in sudden cardiac death.
The contribution of intracellular calcium to ventricular fibrillation (VF) was investigated using chronically instrumented dogs with healed myocardial infarctions. A 2-minute coronary occlusion was initiated during the last minute of exercise. Fourteen animals developed ventricular fibrillation (susceptible) whereas the remaining 12 did not (resistant) during this exercise plus ischemia test. The test was then repeated for the susceptible animals after pretreatment with the intracellular calcium chelator BAPTA-AM (1.0 mg/kg). BAPTA-AM significantly reduced left ventricular dp/dt max and prevented VF in 8 of 12 susceptible animals. Conversely, myocardial cytosolic calcium levels were increased in resistant animals using the calcium channel agonist Bay K 8644 (30 micrograms/kg) or phenylephrine (10 micrograms.kg-1.min-1 3-5 min before occlusion). Bay K 8644 induced VF in all 5 resistant animals tested whereas phenylephrine induced VF in 8 of 12 resistant animals. BAPTA-AM pretreatment attenuated the hemodynamic effects of Bay K 8644 or phenylephrine and prevented VF in five of five Bay K 8644- and four of seven phenylephrine-treated animals. Finally, the endogenous level of calcium/calmodulin (Ca-CaM)-dependent phosphorylation of 170- and 55-kDa substrate proteins was measured (as an index of intracellular free calcium concentration). In the susceptible dog heart, the endogenous level of Ca-CaM-dependent phosphorylation was estimated to be two- to threefold higher than that observed in resistant dog heart. Treatment of resistant dog tissue with the calcium ionophore A23187 increased the level of Ca-CaM-dependent phosphorylation of these two proteins to the level observed in susceptible dog heart. These data suggest that elevated cytosolic calcium facilitates development of malignant arrhythmias and that elevated cytosolic calcium levels may be present in animals particularly susceptible to ventricular fibrillation.
3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
Difficulties in the diagnosis of congenital toxoplasmosis by cordocentesis. Case report.
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Acute Disease↗
Parvalbumin content and Ca2+ and Mg2+ dissociation rates correlated with changes in relaxation rate of frog muscle fibres.
1. Experiments were done to test the hypothesis that parvalbumin (PA) promotes relaxation in frog skeletal muscle. Single fibres and purified PA from Rana temporaria skeletal muscle were used to determine the relationship between PA concentration ( [PA] ), Ca2+ and Mg2+ dissociation rates from PA and changes in rate of relaxation as a function of tetanus duration at 0 degrees C. 2. Total [PA] in fibres from tibialis anterior muscles is 0.76 +/- 0.20 mmol PA l-1 myoplasmic water (mean +/- S.D., n = 25) with 65% PA IVa and 35% PA IVb, where PA IVa and PA IVb are PA isoforms. 3. Relaxation rate from an isometric tetanus shows progressively as a function of tetanus duration with an exponential time course and a rate constant of 1.18 +/- 0.35 s-1 (n = 17). Time course of recovery of relaxation rate after a prolonged tetanus is exponential with a rate constant of 0.12 +/- 0.02 s-1 (n = 14). 4. The extent of recovery of relaxation rate after a prolonged tetanus was correlated with total [PA] in fibres (correlation coefficient (r) = 0.80, n = 7; P less than 0.05). 5. Dissociation rate constants for Mg2+ and Ca2+ from purified PA are 0.93 +/- 0.02 s-1 (n = 5) and 0.19 +/- 0.01 s-1 (n = 5), respectively. Dissociation rate constants were not significantly different for PA isoforms IVa and IVb. These rate constants are similar to the rate constants determined for the time courses of slowing and recovery of relaxation rate, respectively. 6. Results suggest that the time courses of slowing and recovery of relaxation rate may be controlled, to a large extent, by Mg2+ and Ca2+ dissociation from PA, respectively. This evidence supports a role for PA in facilitating relaxation during a tetanus in frog skeletal muscle at 0 degrees C.
Animals↗
Serological investigation of ocular toxoplasmosis.
The limitations of serological assessment in toxoplasma infection of the eye are well recognised, but the predictive value of clinical examination is not defined. We undertook a prospective investigation into the role of clinical examination and of serological findings in cases of suspected toxoplasma infection of the eye by means of the dye test and multiple IgM assays. Seventy-four cases of retinal disease and 202 control patients were studied. Patients with retinal disease had a significantly higher incidence of toxoplasma seropositivity than the control group. This was because some patients with retinal disease had acquired the infection congenitally. Half the patients investigated for toxoplasmosis were seronegative. Possible explanations for these findings included misdiagnosis, clinical uncertainty, or, the use of serology testing in the confirmation of other diseases. An excess of IgM reactivity among the retinal disease group may indicate low level immunoglobulin-M production associated with an acute exacerbation of ocular toxoplasmosis. There is a need to consider invasive procedures in cases of ocular infection and for novel techniques to aid the diagnosis of toxoplasma retinochoroiditis.
Adolescent↗
Duration of toxoplasma infection.
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Animals↗
Cubonavicular coalition.
The cubonavicular coalition is a rare form of tarsal coalition that probably accounts for less than 1% of all coalitions. The authors present a new case of cubonavicular coalition as well as the findings of the 17 previously published accounts. Etiology, clinical presentation, diagnosis, and treatment of the condition are discussed.
Adolescent↗
The distal saphenous vein cutdown procedure.
Distal saphenous vein cutdown is an excellent method for intravenous access. It allows for a rapid infusion of fluids. Although the saphenous vein cutdown is not commonly performed, the podiatrist should be familiar with this procedure, as it may be necessary during an emergency situation.
Education, Medical, Continuing↗
Cancer information: women's source and content preferences.
The authors examine the preferences of women who have undergone mammography for specific cancer-related information content from four information sources: doctors, friends/family, organizations, and media. Statistical analyses reveal significant interactions between content and sources and significant main effects for sources and for content. These findings raise important issues for health-related marketing campaigns.
Analysis of Variance↗
Growth retardation during the suckling period in expanded litters of rats: observations of growth patterns and protein turnover.
Postnatal patterns of growth and protein turnover were studied in suckling rats derived from expanded (EL) as compared to contracted (control) suckling rats (Widdowson and McCance, 1960). Maximum deviation of body weight growth velocity in EL vs. control litters of animals occurred early in the postnatal period (days 3-9). Fractional protein synthesis (Ks) in heart, diaphragm and gastrocnemius at 15 postnatal days were not significantly different in animals from expanded vs. control litters (e.g., Ks in heart 35.5 +/- 3.8% per day in control and 36.1 +/- 9.2% in expanded litters). Fractional growth rates in these 3 tissues were comparable in EL and controls, while fractional rates of protein breakdown (Kd) were somewhat reduced in diaphragm and gastrocnemius from EL animals (e.g., Kd in diaphragm 10.4% per day in control and 6.1% per day in EL). Absolute rates of protein synthesis and degradation were lower in EL animals, with rates of degradation reduced more than rates of synthesis. RNA activity of striated muscle tissues at 15 postnatal days in EL animals was not reduced vs. controls in contrast to results obtained in malnourished weanling and adult rats.
Aging↗