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M C Johnson

Publications and source records attributed to M C Johnson.

At least 37 records · Page 2Linked to original sources
PubMed1999

Molecular characterization of the glycoproteins from two warm water rhabdoviruses: snakehead rhabdovirus (SHRV) and rhabdovirus of penaeid shrimp (RPS)/spring viremia of carp virus (SVCV).

We have determined the complete coding sequences for the glycoprotein (G) genes from two rhabdoviruses that infect warm water aquatic animals, the snakehead rhabdovirus (SHRV) and rhabdovirus of penaeid shrimp (RPS). Surprisingly, the G nucleotide sequence from RPS, a virus which has been isolated from diseased shrimp in Hawaii on numerous occasions, was over 99% identical to the G nucleotide sequence from spring viremia of carp virus (SVCV), a fish virus from Europe and Asia. This is the first report of SVCV isolation outside of Europe and Asia, and it is also the first report of SVCV infecting a non-vertebrate species. The G gene from SHRV was most closely related to the G genes from the three Novirhabdoviruses, viral hemorrhagic septicemia virus (VHSV), infectious hematopoietic necrosis virus (IHNV), and hirame rhabdovirus (HIRRV), with 47, 37, and 36% amino acid identity, respectively. In addition, a phylogenetic analysis using the amino acid sequence from rhabdovirus G genes indicated that SHRV should be classified within the Novirhabdovirus genus. Finally, the SHRV-G gene was successfully expressed in mammalian cells under the control of the cytomegalovirus (CMV) promoter, establishing that it can potentially be used in the production of pseudotyped retroviruses designed to infect fish.

Amino Acid Sequence↗
PubMed1999

Diastolic function and tachycardia in hypertensive children.

We investigated the prevalence and potential predictors of Doppler echocardiographic evidence of diastolic function in untreated hypertensive children. Doppler and M-mode echocardiographic values from 42 children (mean age 13, range 5-17 years) from a pediatric hypertension clinic were retrospectively reviewed and compared to data from 39 age and gender matched normotensive children in a control group. Compared to the participants in the control group, hypertensive patients had increased mean body mass index (29 v 19 kg/M2, P < .0001), peak mitral A velocity (57 v 42 cm/sec, P < .0001), isovolumic relaxation time (65 v 42 msec, P < .0001, resting heart rate (90 v 74 bpm, P < .0001), mitral E deceleration time (150 v 137 msec, P = .006), indexed left ventricular mass index (32 v 26 g/M2.7, P < .0001), relative left ventricular wall thickness (0.32 v 0.29, P = .02), and decreased ratio of peak mitral E velocity/peak mitral A velocity (1.7 v 2.1, P = .0001). Mean age, height, mitral E velocity, mitral A deceleration time, fractional shortening, and indexed left ventricular diastolic dimension were similar in patients and control group children. In the hypertensive patients, multivariate analysis demonstrated that heart rate (P = .0008) and systolic blood pressure (P = .03) were significant predictors of peak A velocity. In addition, heart rate (P = .0003), body mass index (P = .04), and indexed left ventricular diastolic dimension (P = .04) predicted the ratio of peak E/peak A velocity. None of the measures of diastolic function correlated with left ventricular mass index or relative wall thickness. Furthermore, none of the analyzed variables predicted isovolumic relaxation time or mitral E deceleration time. We conclude that untreated hypertensive children have Doppler indices suggestive of impaired left ventricular relaxation. Resting heart rate was the strongest predictor of abnormal diastolic indices.

Adolescent↗
PubMed1999

Mutations in the cardiac transcription factor NKX2.5 affect diverse cardiac developmental pathways.

Heterozygous mutations in NKX2.5, a homeobox transcription factor, were reported to cause secundum atrial septal defects and result in atrioventricular (AV) conduction block during postnatal life. To further characterize the role of NKX2.5 in cardiac morphogenesis, we sought additional mutations in groups of probands with cardiac anomalies and first-degree AV block, idiopathic AV block, or tetralogy of Fallot. We identified 7 novel mutations by sequence analysis of the NKX2.5-coding region in 26 individuals. Associated phenotypes included AV block, which was the primary manifestation of cardiac disease in nearly a quarter of affected individuals, as well as atrial septal defect and ventricular septal defect. Ventricular septal defect was associated with tetralogy of Fallot or double-outlet right ventricle in 3 individuals. Ebstein's anomaly and other tricuspid valve abnormalities were also present. Mutations in human NKX2.5 cause a variety of cardiac anomalies and may account for a clinically significant portion of tetralogy of Fallot and idiopathic AV block. The coinheritance of NKX2.5 mutations with various congenital heart defects suggests that this transcription factor contributes to diverse cardiac developmental pathways.

DNA Mutational Analysis↗
PubMed1999

Antisteroidogenic action of nitric oxide on human corpus luteum in vitro: mechanism of action.

To analyze the mechanism by which nitric oxide (NO) exerts its antisteroidogenic action, human luteal cells were cultured during 24 and 48 h with L-arginine (L-Arg, 1 mmol/L); 1,2(2-trifluoromethylphenyl)imidazole (TRIM) (50 micromol/L and 1 mmol/L) and cyclic guanosine monophosphate (cGMP) analog (8-Br-cGMP, 1 mmol/L). Estradiol, nitrite, and P450 AROM activity were determined in culture media. Total cGMP concentration was evaluated in the cells and culture media by radioimmunoassay, and NADPH diaphorase was used as a histochemical marker for NO synthase (NOS) activity. During the corpus luteum (CL) life-span, NO affected estradiol secretion in an age-dependent manner, with an inhibition in mid-CL (37%; p < 0.05) in agreement with our previous results, and no significant modification in early and late CL. Basal nitrite concentration in 24 and 48 h of midluteal cell cultures (42 and 93 pmol/10(6) cells, respectively) was increased by L-Arg (53% and 88%) and inhibited by the two TRIM concentrations; also, an intense diaphorase reactivity was observed in endothelial cells and luteal parenchyma. Total cGMP was not detected in cell cultures and 8-Br-cGMP did not modify estradiol secretion, whereas aromatase activity was strongly inhibited by L-Arg (70%, p < .05). These results suggest that both NOS isoforms are active in midluteal cells, and the mechanism of action for NO on in vitro estradiol secretion may be an inhibition of P450 AROM activity.

Adult↗
PubMed1998

Presence of angiotensin II and expression of angiotensin II type-2 receptor in human fallopian tube.

OBJECTIVE: To determine the presence of angiotensin II and angiotensin II type-2 receptor subtype messenger RNA (mRNA) in human fallopian tube. DESIGN: Frozen fallopian tubes were used for all studies. SETTING: Procedures were performed at the Institute of Maternal and Child Research, School of Medicine, University of Chile and San Borja-Arriarán Clinical Hospital, National Health Service, Santiago, Chile. PATIENT(S): Eight patients (30-38 years) undergoing surgical sterilization or hysterectomy for benign gynecologic conditions. INTERVENTION(S): Surgery was scheduled in the proliferative or secretory stage of the menstrual cycle. MAIN OUTCOME MEASURE(S): Localization of angiotensin II by immunofluorescence studies, expression of angiotensin II type-2 receptor mRNA, and concentrations of angiotensin II receptor subtypes and binding characteristics. RESULT(S): Angiotensin II was immunolocalized mainly in blood vessel endothelium and, to a lesser extent, in stromal cells. Both binding and angiotensin II type-2 receptor mRNA were detected at high levels. No differences were seen in receptor concentration, dissociation constants or median inhibitory concentration in fallopian tubes ipsilateral or contralateral to the corpus luteum. CONCLUSION(S): Angiotensin II and angiotensin II receptor are present in human fallopian tube. Angiotensin II type-2 receptor was the main receptor subtype. These results suggest that the renin-angiotensin system may play a regulatory role in functions of the fallopian tube.

Adult↗
PubMed1998

Modulation of alloimmunity to major histocompatibility complex class I by cotransfer of cytokine genes in vivo.

Major histocompatibility complex (MHC) class I antigen is a potent stimulus for alloimmune responses and is the principal immunologic target mediating acute cellular rejection of allografts. Using a method of direct in vivo gene transfer of cDNA encoding donor type MHC class I, we showed in a rat model that recipient muscle could express the transferred MHC class I cDNA, resulting in alloimmunization of the recipient. This was most graphically demonstrated by accelerated rejection of cardiac allografts expressing the same MHC class I as encoded by the immunizing cDNA. We now report the use of the particle-mediated gene transfer via a gene gun (Geneva, Middleton, WI, USA) to transfer MHC class I, as well as cytokine gene expression vectors, into rat skin. Compared to intramuscular injection, gene gun transfer to skin resulted in more efficient immunization. Donor-specific cytotoxic T lymphocyte (CTL) responsiveness and antibody levels increased. Furthermore, coexpression of certain cytokine genes with the MHC class I cDNA modulated the immune response. Specifically, coimmunization with IL-10 cDNA abrogated immunity to allo-MHC class I, while coimmunization with GM-CSF cDNA enhanced it. The influence of expression of these genes in skin was demonstrated by alteration of donor cardiac allograft survival. This model is useful for induction and modulation of alloimmune responses and may be used to develop gene therapy strategies to modify them.

Animals↗
PubMed1998

Rapidly progressive extensive subcutaneous emphysema associated with an implantable intratracheal oxygen catheter.

Localized subcutaneous emphysema is a recognized complication of transtracheal oxygen catheters. It usually occurs in the immediate postoperative period or in association with catheter tip migration. This is a case of rapidly progressive, extensive subcutaneous emphysema apparently resulting from paroxysms of coughing in a patient with a normally functioning implanted intratracheal oxygen catheter several weeks after placement.

Aged↗
PubMed1998

Regulation of human luteal steroidogenesis in vitro by nitric oxide.

To evaluate the effect of nitric oxide (NO.) in human corpus luteum (CL) function, we investigated the expression and the presence of NO. synthase (NOS) in the human CL and the action of NO. on the in vitro luteal steroid production. The expression of endothelial NOS (eNOS) in early, mid-, and late CL was assessed by reverse transcriptase polymerase chain reaction (RT-PCR) and the immunohistochemical study was performed in human CL histological sections by using monoclonal antibodies (MAbs) against the distinct NOS isoforms. In addition, seven human mid-CLs were enzymatically dispersed, and the cells were cultured with NO. donor compounds. Steroid production was measured in the culture media by specific radioimmunoassay. The results show that the expression of eNOS was highly detected in mid- and early CL, and to a lesser extent, in late CL. Meanwhile, the immunohistochemical study indicated that both isoenzymes of NOS were expressed in mid-human CL, eNOS being the more abundant isoform present. On the other hand, functional studies showed that NO. donors (L-arginine [L-Arg] and sodium nitroprusside) elicited an inhibitory action on steroid synthesis, preferentially on estradiol production by the luteal cell cultures (p < 0.05). In conclusion, the NO-NOS system is present in the human CL, and it may serve as a modulator of the in vitro human luteal steroidogenesis.

Adult↗
PubMed1998

[Membrane receptors and their enzymatic mechanisms of action. Associated endocrine diseases].

The cell, as a functional unit of a living individual, has the capacity to recognize signals from the extracellular compartment and to respond to these signals in a specific, precise and characteristic way. This review analyzes some membrane receptor mediated processes, characterized by a complex chain of events from the external signal to the induction of specific genes. Additionally, some endocrine diseases associated with molecular defects in some of these stages are analyzed.

Endocrine System Diseases↗
PubMed1997

A sensitive immunoassay to detect the alpha-chemokine GRO in rabbit blood and lung fluids.

GRO-alpha, GRO-beta and GRO-gamma are closely related peptides that stimulate growth of tumor cells and activate leukocytes in acute inflammatory reactions. In order to study the biology of GRO peptides in the lungs of experimental animals, we have developed and characterized a sensitive and specific immunoassay for rabbit GRO, and used this assay to measure GRO in rabbit lung fluids and plasma. GRO was cloned from a rabbit cDNA library and expressed in Escherichia coli. Specific goat polyclonal antibodies were used to create an antigen-capture immunoassay. The assay is sensitive to approximately 30 pg/ml GRO and does not crossreact with rabbit IL-8 or MCP-1, or human GRO. The assay accurately measures GRO in rabbit bronchoalveolar lavage fluid, plasma and serum. Rabbit erythrocytes bind little GRO and do not interfere with the detection of GRO in lung fluids. Circulating GRO was detected in the plasma of 4 of 6 pathogen-free rabbits, but the function of circulating GRO in normal animals is uncertain. This immunoassay will facilitate the study of the biology of GRO in rabbits with acute and chronic inflammation in the lungs and other tissues.

Animals↗
PubMed1997

Chromosome abnormalities in congenital heart disease.

Refinements in cytogenetic techniques have promoted progress in understanding the role that chromosome abnormalities play in the cause of congenital heart disease. To determine if mutations at specific loci cause congenital heart disease, irrespective of the presence of other defects, and to estimate the prevalence of chromosome abnormalities in selected conotruncal cardiac defects, we reviewed retrospectively cytogenetic and clinical databases at St. Louis Children's Hospital. Patients with known 7q11.23 deletion (Williams syndrome), Ullrich-Turner syndrome (UTS), and most autosomal trisomies were excluded from this analysis. Two groups of patients were studied. Over a 6.5-year period, 57 patients with chromosomal abnormalities and congenital heart disease were identified. Of these, 37 had 22q11 deletions; 5 had abnormalities of 8p; and 15 had several other chromosome abnormalities. The prevalence of chromosome abnormalities in selected conotruncal or aortic arch defects was estimated by analysis of a subgroup of patients from a recent 22-month period. Chromosome abnormalities were present in 12% of patients with tetralogy of Fallot, 26% in tetralogy of Fallot/pulmonary atresia, 44% in interrupted aortic arch, 12% in truncus arteriosus, 5% in double outlet right ventricle, and 60% in absent pulmonary valve. We conclude that chromosome analysis should be considered in patients with certain cardiac defects. Specifically, fluorescent in situ hybridization (FISH) analysis of 22q11 is indicated in patients with conotruncal defects or interrupted aortic arch. High resolution analysis should include careful evaluation of the 8p region in patients with either conotruncal or endocardial cushion defects.

Chromosome Deletion↗
PubMed1997

Endothelial cell injury in cardiovascular surgery: the systemic inflammatory response.

Many of the components currently used to perform cardiovascular operations lead to systemic insults that result from cardiopulmonary bypass circuit-induced contact activation, circulatory shock, and resuscitation, and a syndrome similar to endotoxemia. Experimental observations have demonstrated that these events have profound effects on activating endothelial cells to recruit neutrophils from the circulation. Once adherent to the endothelium, neutrophils release cytotoxic proteases and oxygen-derived free radicals, which are responsible for much of the end-organ damage seen after cardiovascular operations. Recently the cellular and molecular mechanisms of endothelial cell activation have become increasingly understood. It is conceivable that once the molecular mechanisms of endothelial cell activation are better defined, therapies will be developed allowing the selective or collective inhibition of vascular endothelial activation during the perioperative period.

Cardiac Surgical Procedures↗
PubMed1997

Regulatory role of angiotensin II on progesterone production by cultured human granulosa cells. Expression of angiotensin II type-2 receptor.

The role of angiotensin II (AngII) in ovarian steroidogenesis is not clearly understood. In order to study its action on progesterone synthesis and to determine which receptor subtype is involve, granulosa cells obtained from women undergoing in-vitro fertilization were cultured for 2 or 4 days and then incubated in the presence of AngII (10(-7) M) with or without human chorionic gonadotrophin (HCG, 10 IU/ml) for 3 or 18 h. In cells cultured for 2 days, incubation with AngII decreased progesterone secretion by 36%, and inhibited activity of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) by 87% (P < 0.05), although its expression was not significantly reduced. However, in cells cultured for 4 days, progesterone production was enhanced by incubation with AngII (38%), and no change was observed in 3 beta-HSD expression. Both inhibitory and stimulatory effects were dose-dependent. Progesterone secretion was increased (93%) by incubation with HCG of cells cultured for 4, but not for 2 days, and no potentiation was observed with AngII. Treatment with PD123177 completely blocked the action of AngII and decreased the HCG-stimulated secretion of progesterone by 27%. Angiotensin type-2 (AT2) receptor mRNA was expressed in cells cultured for 4 days. In conclusion, AngII showed a regulatory role in in-vitro progesterone production by human granulosa luteinized cells, modulating the activity of 3 beta-HSD. It is likely that these actions may be mediated via membrane receptors, possibly of the AT2 receptor family.

Angiotensin II↗
PubMed1997

Pulmonary and systemic inflammatory responses in rabbits with gram-negative pneumonia.

The major goals of this study were to define the relationships between intrapulmonary and systemic inflammatory responses in animals with gram-negative pneumonia. We treated rabbits with intrapulmonary Escherichia coli (1 x 10(7) to 1 x 10(10) cfu/ml), and then measured physiologic, cellular, and molecular events in the lungs and systemic circulation for 24 h. The treatment protocols resulted in groups of animals that mimicked the stages of the septic inflammatory response in humans. Animals treated with low inocula had systemic changes consistent with systemic inflammatory response syndrome and cleared the bacteria and inflammatory products from the lungs. Animals treated with high inocula failed to clear bacteria from the lungs, had severe intrapulmonary inflammatory responses, and developed septic shock. Intrapulmonary leukocyte recruitment was directly related to the size of the bacterial inoculum, but lung protein accumulation was not. Tumor neurosis factor-alpha (TNF-alpha), interleukin-8 (IL-8), and GRO were detectable in lung lavage fluid at 4 h and declined by 24 h in animals that cleared intrapulmonary E. coli. In contrast, lavage TNF-alpha, IL-8, and GRO increased over 24 h in animals that failed to clear intrapulmonary bacteria. MCP-1 increased between 4 h and 24 h in the lungs of all of the animals as the histologic response evolved from neutrophilic to mononuclear cell predominance. Thus, the intensity of systemic inflammatory and physiologic responses to intrapulmonary gram-negative infection depends on the inoculum size and whether the bacteria are cleared from or proliferate in the lungs. The results provide experimental support for the recently proposed classification of septic responses in humans.

Animals↗
PubMed1996

Sensitive and specific immunoassays to detect rabbit IL-8 and MCP-1: cytokines that mediate leukocyte recruitment to the lungs.

The alpha- and beta-chemokines such as IL-8 and MCP-1 direct the recruitment of neutrophils and monocytes into the lungs and other tissues. In order to study the roles of IL-8 and MCP-1 in animals models, specific reagents are required that provide accurate measurements of these cytokines in biological fluids. Here we describe the development of sensitive and specific immunoassays for rabbit IL-8 and rabbit MCP-1, and the validation of these assays in rabbit plasma and bronchoalveolar lavage fluid. The sensitivity of each assay in 0.25 ng/ml for IL-8 and 0.1 ng/ml for MCP-1. The rabbit IL-8 assay does not crossreact with rabbit GRO, another alpha-chemokine, and crossreacts only weakly with human IL-8. The rabbit MCP-1 assay does not crossreact with human MCP-1. Anticoagulants interfere with the detection of IL-8 and MCP-1 in plasma, although. EDTA has the least inhibitory effect. Heat-sensitive inhibitors in normal rabbit serum interfere with the detection of IL-8 and MCP-1, although autoantibodies to IL-8 and MCP-1 were not detected. Rabbit erythrocytes bind IL-8 and MCP-1, but erythrocyte contamination of bronchoalveolar lavage fluid causes only a small error in the detection of IL-8 and MCP-1, unless the number of erythrocytes approaches the number found in blood. These assays provide sensitive and specific means to detect IL-8 and MCP-1 in rabbit plasma and bronchoalveolar lavage fluid, and demonstrate the importance of using species-specific reagents in animal studies.

Animals↗
PubMed1996

Synthesis and activity of a novel series of 3-biarylquinuclidine squalene synthase inhibitors.

Quinuclidines with a 3-biaryl substituent are a new class of potent, orally active squalene synthase (SQS) inhibitors. Variants around these rigid structures indicate key structural requirements for cationic SQS inhibitors. Thus the lower in vitro potency found for quinuclidines bearing 3-substituents, which did not overlay the biphenyl group of 3-(biphenyl-4-yl)-3-hydroxyquinuclidine (2) (IC50 = 16 nM, rat microsomal SQS), implied a directional requirement for the 3-substituent. Similarly, the lower potency of the 3-terphenyl analogue 6 (IC50 = 370 nM) indicated size constraints for this substituent. In compounds with a linking group between the quinuclidine and biphenyl ring, linking groups of lower lipophilicity were less well tolerated (e.g., 17, CH2CH2, IC50 = 5 nM vs 19, NHCO, IC50 = 1.2 microM). Replacement of the distal phenyl ring of 2 with a more polar pyridine heterocycle caused a reduction in in vitro potency. In general, good in vivo activity in the rat was restricted to 3-hydroxy analogues, with the 3-[4-(pyrid-4-yl)phenyl] derivative 39 (IC50 = 161 nM) showing the best inhibition (following oral dosing) of cholesterol biosynthesis from mevalonate (ED50 = 2.7 mg/kg).

Animals↗
PubMed1996

Molecular expression of the alpha-chemokine rabbit GRO in Escherichia coli and characterization of its production by lung cells in vitro and in vivo.

GRO proteins are alpha-chemokine cytokines that attract neutrophils and stimulate the growth of a variety of cells. Previously, we observed that rabbit alveolar macrophages transcribe the genes for at least two GRO homologues. In order to study the role of GRO cytokines in lung inflammation, we cloned the predominant rabbit GRO cDNA (RabGRO) from alveolar macrophages, expressed bioactive recombinant protein (rRabGRO) in Escherichia coli, and developed a sensitive and specific enzyme-linked immunosorbent assay for RabGRO protein. We found that rabbit AM express and secrete GRO in vitro in response to both exogenous (e.g. lipopolysaccharide, heat-killed Staphylococcus aureus, and crystalline silica) and endogenous inflammatory stimuli (e.g. tumor necrosis factor-alpha) as determined by both radioimmunoprecipitation and enzyme-linked immunosorbent assay. Biologically significant amounts of GRO are present in vivo in the bronchoalveolar lavage fluid of rabbits with E. coli pneumonia; by in situ hybridization, GRO mRNA is detectable in infiltrating pulmonary leukocytes and bronchial epithelial cells. These results indicate that GRO chemokines are likely to be important mediators of the inflammatory response that accompanies acute infectious processes in the lungs.

Animals↗