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Biomedical subjects

R Johnson

Publications and source records attributed to R Johnson.

At least 145 records · Page 8Linked to original sources
PubMed1998

Interaction of cationic diamidines with Leishmania infantum DNA.

The interaction of a series of potent leishmanicidal aromatic diamidines resembling pentamidine, was studied with Leishmania infantum DNA and polynucleotides. The diamidines viz., CGP040215A, CGP033829A and CGP039937A, interacted with leishmania DNA as well as with the polynucleotides poly(dA)-poly(dT), poly(dA-dT) and poly(dG-dC). The thermodynamic analysis to determine the association constants and the binding enthalpy pointed toward binding of the diamidines at AT regions of the DNA. The results also indicate that the diamidines bind at the outside of the DNA double helix, probably to the minor groove regions, with hydrogen bonds connecting the amide nitrogen of the diamidine to carbonyl oxygen atoms of thymidine or adenosine bases. However, CGP040215A and CGP033829A, the bisaryl diamidines, showed higher affinity than CGP039937A, the monoaryl diamidine. The spectrophotometric analysis of the interaction of these diamidines to test their effects on the melting temperature of leishmanial DNA suggests non-intercalating binding. The diamidines also showed potent inhibition of DNA polymerase activity of L. infantum extracts in vitro.

Animals↗
PubMed1998

Reducing patient restraint use.

Here's an assessment tool to help nurses identify the reasons a patient may require restraint, and find alternative or less-restrictive measures. After using it for 13 months, the staff from one hospital reduced restraint use by 95%-less than 1% of total patient days.

Humans↗
PubMed1998

Gender differences in knee injury epidemiology among competitive alpine ski racers.

A questionnaire was sent in 1995 to all members of the Vermont Alpine Racing Association and several New England NCAA Division I ski racing programs. A total of 1010 surveys were sent and 404 responses were received. The survey included questions regarding the racer's age, gender, number of years spent ski racing, injury to knee(s), surgery to knee(s), and reinjury to a surgically reconstructed anterior cruciate ligament (ACL) requiring subsequent surgery. Only injuries that occurred during alpine skiing were included. One-quarter of respondents (27%) reported a history of a knee injury. Female racers were 2.3 times more likely to have sustained a knee injury than male racers. More impressively, one in five female alpine racers (22%) reported an ACL disruption, and females were 3.1 times more likely to sustain an ACL injury in comparison to their male counterparts. Of the athletes who had surgery to reconstruct their ACL, approximately one-third (36%) required subsequent surgery to the same knee. One in five (22%) ACL reconstructions failed, requiring additional surgery to the same ACL. Females reported a higher rate of reinjury to an ACL graft than males (27% vs. 13%), but this was not statistically significant.

Adult↗
PubMed1997

A baculovirus (Bombyx mori nuclear polyhedrosis virus) repeat element functions as a powerful constitutive enhancer in transfected insect cells.

It has been previously reported that baculovirus homologous regions, the regions of baculovirus genomes that contain the origins of DNA replication, can augment the expression of a small number of baculovirus genes in vitro. We are now reporting that a region of the genome of Bombyx mori nuclear polyhedrosis virus (BmNPV) containing the homologous region 3 (HR3) acts as an enhancer for the promoter of a nonviral gene, the cytoplasmic actin gene of the silkmoth B. mori. Incorporation of the HR3 sequences of BmNPV into an actin promoter-based expression cassette results in an augmentation of transgene expression in transfected cells by two orders of magnitude relative to the control recombinant expression cassette. This increase is due to a corresponding increase in the rate of transcription from the actin promoter and not to replication of the expression cassette and occurs only when the HR3 element is linked to the expression cassette in cis. A comparable degree of enhancement in the activity of the silkworm actin promoter occurs also in heterologous lepidopteran cells. Concomitant supplementation of transfected cells with the BmIE1 trans-activator, which was previously shown to be capable of functioning in vitro as a transcriptional co-activator of the cytoplasmic actin gene promoter, results in more than a 1,000-fold increase in the level of expression of recombinant proteins placed under the control of the actin gene promoter. These findings provide the foundation for the development of a nonlytic insect cell expression system for continuous high-level expression of recombinant proteins. Such a system should provide levels of expression of recombinant proteins comparable to those obtained from baculovirus expression systems and should also have the additional advantage of continuous production in a cellular environment that, in contrast to that generated by a baculovirus infection, supports continuously proper posttranslational modifications of recombinant proteins and the capability of expression of proteins from genomic as well as cDNA sequences.

Actins↗
PubMed1997

The differential effects of 12-O-tetradecanoylphorbol-13-acetate on the gap junctions and connexins of the developing mammalian lens.

Epithelial cells in primary ovine lens cultures express the gap junction proteins connexin43 (Cx43) and connexin49 (Cx49; a.k.a. MP70), a homologue of mouse connexin50. In contrast, lens cultures of differentiated, fiber-like cells (termed lentoid cells) express Cx49 and connexin46 (Cx46), but not Cx43. To investigate the regulation of lens cell gap junctions by protein kinase C (PKC), differentiating lens cultures were treated with the PKC activator 12-O-tetradecanoylphorbol-13-acetate (beta-TPA). Within 10 min, beta-TPA significantly inhibited the transfer of Lucifer Yellow dye between epithelial, but not lentoid, cells. This inhibition was correlated with the phosphorylation of Cx43 and was followed by the gradual disappearance of Cx43 from cell interfaces. The protein kinase inhibitor staurosporine prevented Cx43 phosphorylation and the loss of Cx43 from intercellular junctions. Following treatment of cultures with beta-TPA for 2-6 hr, Cx49 disappeared from epithelial cell interfaces, and by 24 hr of beta-TPA treatment, levels of Cx49 detected on immunoblots of purified epithelial membrane fractions had also diminished significantly. The beta-TPA-induced loss of Cx49 both from regions of epithelial cell contact and from isolated membranes was correlated with the disappearance of Cx49 mRNA. In contrast to the epithelial connexins, the lentoid connexins Cx49 and Cx46 were unaffected by even extended beta-TPA treatment. In spite of lentoid dye transfer being refractory to beta-TPA, significant levels of PKC-alpha (a beta-TPA-sensitive isoform) were detected in the lentoid cell. The response of lens gap junctions to beta-TPA depends upon the stage of differentiation and the complement of connexins expressed. The contrasting effects of beta-TPA on Cx43 and Cx49 in lens epithelial cells indicate a fundamental difference in the regulation of these connexin proteins in the developing mammalian lens.

Animals↗
PubMed1997

A system for mutation measurement in mammalian cells: application to gamma-irradiation.

Monitoring of mutagenesis by environmental agents for the purpose of preventing genetic disease including cancer must include quantitation of cell killing, sensitive measurement of mutation production by appropriate doses of each agent, and assessment of mutation repair effects in mammalian cells. A four-step procedure, in the presence and absence of a repair suppressor, is proposed: (i) determination of the survival curve; (ii) measurement of the mitotic index in cells collected after treatment with colcemid; (iii) construction of a mutagenesis yield curve in the presence and absence of a repair suppressor, like caffeine; and (iv) assessment of the effect of test agents on the repair of mutations produced by other mutagens. The procedure is quantitative, reproducible, and reasonably rapid. It involves measurement of mutations causing visible chromosomal aberrations. Numerical parameters are proposed defining quantitatively mutation, cell killing, and mutation repair capacity. The procedure is applied to gamma-irradiation and can detect the effects of doses as low as 2-5 cGy. Theoretical analysis of the underlying processes is presented, using the concept of D(0)E, the effective dose of mutagen after repair mechanisms and neutralizing agents have acted. Microscopically visible chromosome aberrations are due to mutations that distort the process of mitotic chromosome condensation, with or without actual chromosome breakage.

Caffeine↗
PubMed1997

Dehydroepiandrosterone (DHEA) treatment of depression.

Dehydroepiandrosterone (DHEA) and its sulfate, DHEA-S, are plentiful adrenal steroid hormones that decrease with aging and may have significant neuropsychiatric effects. In this study, six middle-aged and elderly patients with major depression and low basal plasma DHEA f1p4or DHEA-S levels were openly administered DHEA (30-90 mg/d x 4 weeks) in doses sufficient to achieve circulating plasma levels observed in younger healthy individuals. Depression ratings, as well as aspects of memory performance significantly improved. One treatment-resistant patient received extended treatment with DHEA for 6 months: her depression ratings improved 48-72% and her semantic memory performance improved 63%. These measures returned to baseline after treatment ended. In both studies, improvements in depression ratings and memory performance were directly related to increases in plasma levels of DHEA and DHEA-S and to increases in their ratios with plasma cortisol levels. These preliminary data suggest DHEA may have antidepressant and promemory effects and should encourage double-blind trials in depressed patients.

Aged↗
PubMed1997

Urinary oxalate excretion and its role in vulvar pain syndrome.

OBJECTIVE: This study was undertaken to determine the urinary oxalate excretion patterns in patients with vulvodynia compared with controls and to evaluate antioxalate therapy in women with vulvar pain syndrome (vulvodynia). STUDY DESIGN: A total of 130 consecutive patients with vulvar pain syndrome and 23 volunteers without symptoms collected urine specimens for 24 hours; each voiding was saved in individual labeled containers and refrigerated. The specimens were analyzed individually for oxalate and calculated according to 24-hour concentration, volume, and peak oxalate by hour. A total of 59 patients were treated with low-oxalate diets and calcium citrate for 3 months and evaluated for objective relief of vulvar pain. RESULTS: The 24-hour excretion of oxalate was almost identical in controls and vulvodynia patients. The total 24-hour excretion was directly proportional to the volume of urine excreted (p < 0.001). No significant differences were found in peak oxalate excretion (95% confidence intervals). The number of voidings was higher in the vulvodynia cohort (p < 0.02). The 59 women with elevated oxalate concentrations (> 1 mg/40 dl) were treated with an antioxalate regimen. Fourteen (24%) demonstrated an objective response, but only 6 (10%) could have pain-free sexual intercourse. CONCLUSIONS: Urinary oxalates may be nonspecific irritants that aggravate vulvodynia; however, the role of oxalates as instigators is doubtful.

Circadian Rhythm↗
PubMed1997

Stimulus responses and amyloid precursor protein processing in DAMI megakaryocytes.

Platelets, when released as anuclear cells by their precursor megakaryocytes, already carry soluble proteolytic fragments of the amyloid precursor protein (APP) within their alpha-granules and intact APP in the alpha-granule membranes. In response to activation signals elicited by physiologic stimuli such as thrombin, platelets release their granules' soluble contents and translocate granule membrane-bound proteins to the plasma membrane. Because platelets carry >90% of the circulation's APP, activated platelets have been implicated as origins of the beta-amyloid peptide fragment of APP (A beta), whose deposition in the cerebrovasculature is characteristic of Alzheimer's disease. We have therefore studied the APP contents and proteolytic processing in resting DAMI human megakaryocytic cells, along with the consequences of the activation of these cells by thrombin, comparing the results in each case to those with human platelets. Resting and PMA-differentiated DAMI cell contents were examined by Western blotting, immunoprecipitation, or metabolic labeling with sulfur 35-labeled methionine during culture, while plasma membrane-bound APP was evaluated by flow cytometry. Activation was followed by changes in cytoplasmic calcium concentration ((Ca++)in) and in membrane potential. Like platelets, DAMI cells exhibited a thrombin dose-dependent delta(Ca++)in, and membrane potential change; in contrast to the surface of a platelet, the surface of an agranular resting DAMI cell expresses granule-membrane proteins (APP and CD63) that appear on platelets only after activation. DAMI cell culture with 35S-labeled methionine confirmed that megakaryocytes synthesize large amounts of APP, of slightly higher molecular weight, and degrade their APP extensively before platelets are formed.

Amyloid beta-Protein Precursor↗