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Biomedical subjects

J D Johnson

Publications and source records attributed to J D Johnson.

At least 181 records · Page 10Linked to original sources
PubMed1990

Professional satisfaction among California general dentists.

Dentists' assessments of their jobs provide insights about issues in the dental profession needing attention. This study assessed professional satisfaction among 558 California general dentists using the 54-item, multi-faceted Dentist Satisfaction Survey (DSS). Although dentists tended to be satisfied with various facets of their jobs and careers, substantial variation in the levels of satisfaction was noted. The most satisfied dentists were older, reported higher incomes, attended more continuing education, and employed more dental auxiliaries than dentists who were the most dissatisfied. Fifty-eight percent of the variation in overall job satisfaction was explained by quality of nonwork life and satisfaction with five facets of the profession: respect received from being a dentist, the actual process of delivering care, income derived from dentistry, relationships with patients, and reduced levels of job-related stress. Dentists were most dissatisfied with the threat of malpractice, level of income, demands of managing the practice, and amount of personal time. Professional organizations should direct programs to address these issues. Dental educators should use these findings to counsel predoctoral students about the realities of dental practice and as an outcome measure of their programs. Moreover, these findings document the perceptions of the practicing profession and support several components of the SELECT recruitment strategy.

Adult↗
PubMed1989

Phosphorylation-regulated calmodulin binding to a prominent cellular substrate for protein kinase C.

We have evaluated the possibility that a major, abundant cellular substrate for protein kinase C might be a calmodulin-binding protein. We have recently labeled this protein, which migrates on sodium dodecyl sulfate-gel electrophoresis with an apparent Mr of 60,000 from chicken and 80,000-87,000 from bovine cells and tissues, the myristoylated alanine-rich C kinase substrate (MARCKS). The MARCKS proteins from both species could be cross-linked to 125I-calmodulin in a Ca2+-dependent manner. Phosphorylation of either protein by protein kinase C prevented 125I-calmodulin binding and cross-linking, suggesting that the calmodulin-binding domain might be located at or near the sites of protein kinase C phosphorylation. Both bovine and chicken MARCKS proteins contain an identical 25-amino acid domain that contains all 4 of the serine residues phosphorylated by protein kinase C in vitro. In addition, this domain is similar in sequence and structure to previously described calmodulin-binding domains. A synthetic peptide corresponding to this domain inhibited calmodulin binding to the MARCKS protein and also could be cross-linked to 125I-calmodulin in a calcium-dependent manner. In addition, protein kinase C-dependent phosphorylation of the synthetic peptide inhibited its binding and cross-linking to 125I-calmodulin. The peptide bound to fluorescently labeled 5-dimethylaminonaphthalene-1-sulfonyl-calmodulin with a dissociation constant of 2.8 nM, and inhibited the calmodulin-dependent activation of cyclic nucleotide phosphodiesterase with an IC50 of 4.8 nM. Thus, the peptide mimics the calmodulin-binding properties of the MARCKS protein and probably represents its calmodulin-binding domain. Phosphorylation of these abundant, high affinity calmodulin-binding proteins by protein kinase C in intact cells could cause displacement of bound calmodulin, perhaps leading to activation of Ca2+-calmodulin-dependent processes.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1989

Long-term clinical evaluation of toothpaste and oral rinse containing sanguinaria extract in controlling plaque, gingival inflammation, and sulcular bleeding during orthodontic treatment.

A sanguinaria-containing toothpaste and oral rinse regimen was evaluated during a 6-month period to determine its effectiveness in controlling plaque, gingival inflammation, and sulcular bleeding. Oral hygiene instructions and a 1-month prestudy brushing period failed to produce a significant improvement in health among the 24 subjects as determined by the three evaluation parameters. After the oral hygiene period, the subjects were randomly assigned to the active treatment (marketed Viadent toothpaste and oral rinse) or the placebo treatment (same base formulas without sanguinaria). Treatments were evaluated using the Löe and Silness gingival index, the Silness and Löe plaque index, and the Mühlemann and Son sulcular bleeding index at baseline and monthly through 6 months. The sanguinaria regimen reduced plaque by 57%, gingival inflammation by 60%, and sulcular bleeding by 45% from baseline compared with placebo group reductions of 27% (plaque) and 21% (gingival inflammation), and an increase of 30% in bleeding index. Repeated-measures analysis of covariance with baseline scores used as covariates showed statistically significant differences at 6 months for plaque (active 0.39; placebo 0.68, p less than 0.01), gingival inflammation (active 0.32; placebo 0.76, p less than 0.001), and sulcular bleeding (active 0.34; placebo 0.70, p less than 0.002). Results of this study demonstrated that the combined use of the sanguinaria-containing toothpaste and oral rinse controls and reduces plaque and gingival inflammation in an orthodontic population.

Adolescent↗
PubMed1989

Suprabulbar palsy with pseudankylosis of the mandible: review and report of three cases.

Neonates with suprabulbar palsy present as extremely difficult and complex cases requiring the expertise of many different professionals over an extended period of time. The experience gained from the patients presented may serve as a guide for diagnosis and treatment for other patients with this problem. Precise early diagnosis is paramount to eventual levels of recovery and function attained.

Ankylosis↗
PubMed1989

Ganglioside modulation of cyclic AMP-dependent protein kinase and cyclic nucleotide phosphodiesterase in vitro.

Purified cyclic AMP-dependent protein kinase (cAK) catalytic subunit phosphorylated 180-, 49-, 31-, 19-, and 14-kilodalton (kDa) proteins of rabbit sciatic nerve membranes. The ability of cAK to phosphorylate these membrane substrate proteins was inhibited by gangliosides GM1, GD1a, and GT1b with half-maximal inhibitory concentration (I50) = 7-25 microM. Neutral glycolipids and lysophosphatidylcholine were much less effective. Cyclic AMP (cAMP) kinase phosphorylation of histone IIA was inhibited by GM1, GD1a, and GT1b (I50 = 115 microM, 75 microM, and 75 microM, respectively). Inhibition by GM1 was competitive with respect to histone (Ki = 108 microM). Autophosphorylation of cAMP kinase was inhibited by GM1 (I50 = 15 microM). GT1b, GD1a, and GM1 half-maximally stimulated calmodulin-dependent cyclic nucleotide phosphodiesterase at 0.1 microM, 0.2 microM, and 0.3 microM, respectively. Although GT1b stimulated phosphodiesterase by increasing Vmax and decreasing Km (similar to calmodulin), GD1a and GM1 produced only an increase in Vmax. These results suggest that ganglioside can modulate the activity of cAMP kinase by both direct inhibition of the enzyme and indirect reduction of cAMP levels through activation of phosphodiesterase. Through these mechanisms, gangliosides may alter cAMP-dependent protein phosphorylation and cell function within the nervous system.

Animals↗
PubMed1989

Assessment of immunoglobulin-M immunosorbent agglutination assay (ISAGA) for detecting toxoplasma specific IgM.

An immunoglobulin-M immunosorbent agglutination assay (ISAGA) was introduced to detect toxoplasma specific IgM. This assay incorporates mu chain capture and use of entire toxoplasma trophozoites as an antigen source. The performance of the ISAGA was compared with that of a double sandwich enzyme linked immunosorbent assay (DS-ELISA) currently used in the Public Health Laboratory Service Toxoplasma Reference Laboratories. The ISAGA was found to be more sensitive than DS-ELISA but there was no demonstrable difference in the specificity or reproducibility between the two assays. The ISAGA is suitable for the diagnosis of acute toxoplasmosis in immunocompetent patients and as a screening test for recent infection in pregnant women. The persistence of ISAGA reactivity, however, is such that additional serological assessment is required to define the risk of congenital infection.

Agglutination Tests↗
PubMed1989

T-Screw. A new bone fixation device.

The T-Screw was patented in 1984. A 5-year study was begun in 1980, and FDA approval was granted in 1985. Detailed results of this clinical study will be reported in a later paper. The purpose of this paper is to introduce the device. The authors have found that early return to normal function and wearing shoes has been possible when using T-Screws for fixation of podiatric osteotomies. The screw appears to accelerate bone healing and has numerous applications throughout the foot. The authors believe that its ease of application and removal as well as its ability to generate rigid, compressive fixation makes it an excellent alternative to current fixation devices.

Bone Screws↗
PubMed1989

Increasing breast milk production for premature infants with a relaxation/imagery audiotape.

Many women whose premature infants are hospitalized in a newborn intensive care unit choose to express breast milk for their babies. Yet anxiety, fatigue, and emotional stress are powerful inhibitors of lactation. To facilitate the breast-feeding experience, intervention mothers were given a 20-minute audio cassette tape based on relaxation and visual imagery techniques. At a single follow-up expression of milk at the hospital approximately 1 week after enrollment, they expressed 63% more breast milk than a randomized group of control mothers. The fat content of the breast milk in the two groups was not significantly different. Among a small group of mothers whose infants were receiving mechanical ventilation, the increase in milk volume compared with that of control mothers was 121%. Longer-term effects of the relaxation/imagery approach (such as extending the duration of breast-feeding or reducing parental stress after hospital discharge) and the physiologic basis for the increased volume of expressed milk (improved milk production v more efficient milk ejection) are appropriate topics for future research.

Female↗
PubMed1988

Inhibition of cyclic nucleotide phosphodiesterase and calcineurin by spermine, a calcium-independent calmodulin antagonist.

Spermine binding to calmodulin and its effects on two calmodulin-dependent enzymes were studied. Spermine bound to dansylated calmodulin with an apparent Ki of 0.7 mM, and to native calmodulin with a Kd of 1.1 mM in equilibrium dialysis experiments. Its binding was found to be independent of calcium. Spermine inhibited calmodulin-activated cyclic nucleotide phosphodiesterase noncompetitively with respect to calcium (Ki = 1.1 mM). Calmodulin activation of calcineurin was inhibited at similar concentrations (Ki = 1.2 mM). Spermine had little effect on basal phosphodiesterase activity or nickel-activated calcineurin activity. Inhibition of both enzymes correlated well with spermine binding to dansylcalmodulin. These findings suggest that spermine might modulate calcium-dependent events in the cell by inactivation of calmodulin via a novel calcium-independent mechanism.

Animals↗
PubMed1988

Large-scale isolation of covalently closed circular DNA using gel filtration chromatography.

The isolation of covalently closed circular (ccc) DNA free of contamination by RNA and other forms of DNA is fundamental to molecular biology. A variety of methods have been explored but CsCl density-gradient centrifugation remains the method most widely used for preparative scale resolution. The process is expensive, time-consuming, requires the use of large amounts of the carcinogen ethidium bromide, and is subject to considerable variation in yield and purity. To avoid these problems, we have devised a procedure for the preparation of cell lysates which results in consistently good yields of biologically active ccc DNA minimally contaminated with chromosomal DNA fragments and RNA. Lysates are deproteinized, precipitated with CaCl2 to remove rRNA, concentrated by ethanol precipitation, and applied to a Sephacryl S-1000 column which resolves chromosomal fragments, open circular plasmid DNA, and residual RNA from the ccc DNA. We have found that substituting the gel filtration column for CsCl density-gradient centrifugation results in substantially better purification as well as reducing processing time, cost, and degree of difficulty. The time required from harvest of cells to final recovery of DNA is about 16 h. We have used the method to isolate plasmids from 4.4 to 12 kb and, with slight modifications, recombinant M13 replicative form DNAs.

Acrylic Resins↗
PubMed1988

Complementary oligodeoxynucleotide mediated inhibition of tobacco mosaic virus RNA translation in vitro.

Two different "antisense" oligodeoxynucleotides and their RNA analogues, each complementary to non-overlapping sequences of 51 bases near the 5' end of TMV RNA, inhibit in vitro translation of the genomic RNA in a rabbit reticulocyte lysate. Inhibition is dependent upon complementarity, concentration, and hybridization of the oligomers with TMV RNA. Inhibition is observed at molar ratios of TMV RNA to antisense oligomers as low as 1:1.5. A plateau of inhibition at which 10-25% of the control signal remains is achieved by molar ratios of TMV RNA:antisense DNA or RNA greater than or equal to 1:15. The extent of inhibition is not increased by the simultaneous presence of both complementary fragments. Oligodeoxynucleotides and their RNA analogues identical to the same regions of TMV RNA have no direct effect on translation, however, they can block inhibition by the antisense fragments. Translation of BMV RNA is not affected by any of the oligodeoxynucleotides. Polyacrylamide gel electrophoresis shows translation of TMV p126 is selectively inhibited. We conclude that the observed inhibition of translation is due to direct interference with ribosome function.

Base Sequence↗
PubMed1988

Biologically active fluorescent derivatives of spinach calmodulin that report calmodulin target protein binding.

Spinach calmodulin (CaM) has been labeled at cysteine-26 with the sulfhydryl-selective probe 2-(4-maleimidoanilino)naphthalene-6-sulfonic acid (MIANS) to produce MIANS-CaM. The interaction of MIANS-CaM with CaM binding proteins was studied by fluorescence enhancement accompanying the protein-protein interactions. MIANS-CaM bound to smooth muscle myosin light-chain kinase with a Kd of 9 nM, causing a 4.6-fold fluorescence enhancement. Caldesmon bound with a Kd of 250 nM, causing a 2-fold fluorescence enhancement. Calcineurin (CaN) bound to MIANS-CaM with a Kd less than 5 nM, causing an 80% increase in fluorescence. On the other hand, binding of the CaM antagonist drugs prenylamine and calmidazolium or the potent peptide antagonist melittin did not alter MIANS fluorescence. MIANS-CaM activated brain cGMP phosphodiesterase and CaN as effectively as unlabeled CaM. Spinach CaM was also labeled with three other sulfhydryl reagents, 6-acryloyl-2-(dimethylamino)naphthalene, (2,5-dimethoxy-4-stilbenyl)maleimide, and rhodamine X maleimide. CaN bound to the highly fluorescent rhodamine X maleimidyl-CaM with a Kd of 1.4 nM, causing a 25% increase in polarization. Both MIANS-CaM and rhodamine X-CaM were used to monitor the Ca2+ dependence of the interaction between CaM and CaN. Half-maximal binding occurred at pCa 6.7-6.8 in the absence of Mg2+, or at pCa 6.3 in the presence of 3 mM Mg2+. In both cases, the dependence of the interaction was cooperative with respect to Ca2+ (Hill coefficients of 1.7-2.0). Use of these fluorescent CaMs should allow accurate monitoring of CaM interactions with its target proteins and perhaps their localization within the cell.

Anilino Naphthalenesulfonates↗
PubMed1988

Cyanide-induced neurotoxicity: mechanisms of attenuation by chlorpromazine.

Chlorpromazine (CPZ) is an effective cyanide antidote, with its greatest efficacy displayed when combined with the antidotes, sodium nitrite and sodium thiosulfate. Since the central nervous system is a primary target organ in cyanide toxicity, the objective of the present study was to determine the mechanisms by which CPZ prevents cyanide-induced damage in neural systems. KCN (10 mM) increased cytosolic free calcium in rat pheochromocytoma (PC12) cells as indicated by the fluorescent dye quin 2. This was blocked by addition of CPZ (0.1 mM) to the cells 15 min prior to addition of KCN. Incubation of cells with KCN (0.1 mM) increased the levels of lipid conjugated dienes and this was blocked by addition of CPZ (1 microM). Peroxidation of brain lipids in mice administered KCN (7-15 mg/kg, sc) was also attenuated by pretreatment with CPZ. Furthermore, production of lipid peroxidation in fresh mouse brain slices, following incubation with 0.1 mM KCN, was blocked by simultaneous addition of CPZ. These observations indicate CPZ prevents cyanide-induced calcium influx and decreases peroxidation of membrane lipids. Thus the antidotal activity of CPZ in cyanide toxicity appears to be related to maintenance of cellular calcium homeostasis and membrane integrity.

Adrenal Gland Neoplasms↗