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Biomedical subjects

K Johnson

Publications and source records attributed to K Johnson.

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

Side-to-side aorto-Gore-Tex central shunt.

BACKGROUND: This report details our experience in 13 patients with a technical modification of the standard central shunt. METHODS: The study was performed using a retrospective chart review approach. In our operation, the aorto-Gore-Tex (W.L. Gore & Assoc, Flagstaff, AZ) anastomosis is created in a side-to-side fashion with the free end of the Gore-Tex shunt being oversewn. RESULTS: All patients had echocardiographic evidence of shunt patency in the immediate postoperative period, and there have been no cases of late shunt occlusion at a mean follow-up period of 10 months. CONCLUSIONS: We believe this approach will yield patency rates equivalent to or better than those of the standard central shunt. The technique has the advantage of creating a short, straight-lying shunt that is less likely to kink or be injured on repeated sternotomy and in which flow may be more reliable.

Aorta↗
PubMed1998

Inhibition of nitric oxide synthase causes elevation of hearing thresholds.

OBJECTIVE: Nitric oxide mediates the effects of excitatory amino acids in the central nervous system. The excitatory amino acids are thought to be the neurotransmitters at the cochlear hair cell-afferent nerve synapse. Nitric oxide synthase is present in spiral ganglion cells. This study investigated the role of nitric oxide in cochlear neurotransmission. METHODS: In gerbils, cochlear compound action potential thresholds were recorded before and after cochlear perfusions with control solutions of artificial perilymph solution and test solutions of S-methyl-L-thiocitrulline (MTC), a competitive inhibitor of nitric oxide synthase. Cochleas were also preperfused with L-arginine before perfusion with a mixture of MTC/L-arginine (to overcome competitive inhibition by MTC with L-arginine, the natural substrate of nitric oxide synthase). RESULTS: Cochlear perfusion with MTC caused significant elevations of compound action potential threshold of 51 dB as opposed to insignificant elevations of only 10 dB in control animals. An insignificant threshold shift of 9 dB was observed when L-arginine was coperfused with MTC. CONCLUSIONS: Nitric oxide is involved in neurotransmission/neuromodulation in the cochlea. Because nitric oxide is both a mediator of neurotoxicity and an initiator of apoptosis in the central nervous system, nitric oxide may play a role in these processes in the cochlea.

Action Potentials↗
PubMed1998

Effects of a circumferentially vented mask on breathing patterns of women as measured by respiratory kinematic techniques.

Since pneumotachograph masks are commonly used in studies of speech breathing, the purpose of this study was to measure the differences in respiratory volumetric and frequency measures during speech under two conditions: with and without a circumferentially vented pneumotachograph mask coupled to the face. Thus we sought to identify whether changes in breathing patterns occur with the use of a specific face mask, because these patterns are accepted as representative of normal speech breathing. Subjects were 10 normal-speaking women, each of whom produced a syllable train and a connected speech task, both at comfortable intensity levels. Respiratory measures were made using linearized magnetometers during speech production. The measurements included lung volume, rib cage volume, and abdominal volume at utterance initiation and termination, volume excursions during the utterance, and the number of breath groups during the speech task. There were no significant differences between the mask-on and mask-off conditions in volumetric and frequency measures. A significant task difference for abdominal initiation was found. It was concluded that the use of a circumferentially vented pneumotachograph mask does not alter the reliability of respiratory volume and frequency measures for studies of voice.

Adult↗
PubMed1998

Neuronal overexpression of heme oxygenase-1 correlates with an attenuated exploratory behavior and causes an increase in neuronal NADPH diaphorase staining.

Heme oxygenase isozymes, HO-1 (also known as hsp32) and HO-2, are the source for the formation of the putative messenger molecule carbon monoxide (CO), reactive iron, and the in vitro antioxidant bilirubin. We have developed and characterized transgenic (Tg) mice that overexpress the stress protein in neurons in various brain regions. The Tg mice were generated by the use of rat HO-1 cDNA under the control of the neuron-specific enolase promoter. Except for a tendency to have an enlarged spleen, Tg mice did not show gross anatomical changes. Increase in HO-1 mRNA, which was demonstrated by northern blot analysis and in situ hybridization, was accompanied by an increase in neuronal HO-1 protein expression, shown by immunohistochemistry and western blotting, and an increase in HO activity. Expression of the transgene correlated with an attenuation of exploratory behavior and increased circling activity and coincided with enhanced neuronal NADPH diaphorase staining. Those changes were not accompanied by an increase in DNA damage or significant change in whole-brain NO synthase activity. The HO-1 Tg mice potentially represent a good model to examine the function of CO as a neuromodulator, iron as a gene regulator, and bile pigments as in vivo antioxidants.

Animals↗
PubMed1998

Mammography use among women attending an inner-city clinic.

BACKGROUND: Low-income, minority, and inner city women have breast cancer screening rates that are below those of the general population. METHODS: The authors surveyed women who received primary care at Seattle's county hospital about their mammography behaviors in early 1995. Data were analyzed within the context of the PRECEDE framework. RESULTS: Only half (48%) of the women were obtaining regular screening. Breast cancer and mammography beliefs differed by racial group. The following factors differentiated between inner-city women who were and were not regular users: mammography beliefs concerning early detection of disease, pressure from the machine causing breast cancer, and cost (these were less important among white women than members of other racial groups); previous physician discussions, concerns about appointment scheduling, and transportation problems; and social support from physicians, family, and friends. CONCLUSION: Interventions to encourage regular screening among inner-city women should address predisposing, enabling, and reinforcing factors.

Black or African American↗
PubMed1998

Preventing and reducing alcohol and other drug use among high-risk youths by increasing family resilience.

This study examines the effects of a community-based program designed to delay onset and reduce the frequency of alcohol and other drug (AOD) use among high-risk youths, ages 12 to 14, through strengthening family resilience. It is part of a larger five-year demonstration project funded by the Center for Substance Abuse Prevention (CSAP). The program was implemented in multiple church communities in rural, suburban, and inner-city settings. Program components of this study included parent or guardian and youth training, early intervention services, and follow-up case management services. The results show that the program produced positive direct effects on family resilience. The evaluation also found positive moderating effects on delayed onset of alcohol and other drug use and frequency of alcohol and other drug use among youths in the form of conditional relationships with changes in those family resilience factors that were targeted by the program.

Adolescent↗
PubMed1998

Caprine mucopolysaccharidosis-IIID: clinical, biochemical, morphological and immunohistochemical characteristics.

Several animal models have been developed for the mucopolysaccharidoses (MPSs), a group of lysosomal storage disorders caused by lysosomal hydrolase deficiencies that disrupt the catabolism of glycosaminoglycans (GAG). Among the MPS, the MPS-III (Sanfilippo) syndromes lacked an animal counterpart until recently. In this investigation of caprine MPS-IIID, the clinical, biochemical, morphological, and immunohistochemical studies revealed severe and mild phenotypes like those observed in human MPS III syndromes. Both forms of caprine MPS IIID result from a nonsense mutation and consequent deficiency of lysosomal N-acetylglucosamine 6-sulfatase (G6S) activity and are associated with tissue storage and urinary excretion of heparan sulfate (HS). Using special stains, immunohistochemistry, and electron microscopy, secondary lysosomes filled with GAG were identified in most tissues from affected goats. Primary neuronal accumulation of HS and the secondary storage of gangliosides were observed in the central nervous system (CNS) of these animals. In addition, morphological changes in the CNS such as neuritic expansions and other neuronal alterations that may have functional significance were also seen. The spectrum of lesions was greater in the severe form of caprine MPS IIID and included mild cartilaginous, bony, and corneal lesions. The more pronounced neurological deficits in the severe form were partly related to a greater extent of CNS dysmyelination. These findings demonstrate that caprine MPS IIID is a suitable animal model for the investigation of therapeutic strategies for MPS III syndromes.

Animals↗
PubMed1998

Randomized, blinded, placebo-controlled trial of tissue factor pathway inhibitor in porcine septic shock.

This study tested the hypothesis that tissue factor pathway inhibitor (TFPI) would improve mortality and morbidity evoked by peritonitis-induced bacteremia in pigs. Secondarily, it sought to determine if TFPI treatment would attenuate cardiodynamic abnormalities produced by this septic model. 32 pigs were chronically instrumented with intracardiac transducers to measure left ventricular pressure and diameter, pulmonary and aortic pressures, and cardiac output. At least 5 days after surgery to implant transducers, basal cardiovascular readings and blood samples were obtained. Using a randomized, blinded study design, either purified, reconstituted TFPI (1 mg/kg bolus, 10 mg/kg/min for 48 h), placebo (arginine buffer), or saline was administered to pigs immediately after Escherichia coli 0111.B4 (3.0-11 x 10(9) colony-forming U/kg)-laden fibrin clots were implanted intraperitoneally, producing peritonitis and bacteremia. Pigs did not receive antibiotics or supportive therapy. No significant differences in primary or secondary endpoints were noted between the arginine and saline groups, so these data were combined into a control group (N = 20). 5 of 12 TFPI pigs survived (42%), while 5 of 20 control pigs survived (25%); this difference was not significant (p = .714, Fisher's exact test). TFPI treatment augmented cardiac output in surviving pigs, but did not affect any other cardiovascular performance variable (heart rate, % diameter shortening, or systemic and pulmonary vascular resistance). In controls, peritonitis induced rapid increase in plasma tumor necrosis factor-alpha (428 +/- 771 to 5,933 +/- 559 pg/mL at 2 h) and interleukin-8 (180 +/- 153 to 1,393 +/- 145 pg/mL at 2 h). TFPI treatment significantly attenuated cytokine responses to sepsis, reducing peak tumor necrosis factor-alpha to 2,103 +/- 813 pg/mL and reducing peak interleukin-8 levels to 534 +/- 211 pg/mL at 2 h (p < .05, Tukey test, two-way ANOVA). In conclusion, TFPI treatment attenuated important mediator components of the inflammatory response but did not provide significant survival benefit.

Animals↗
PubMed1998

Root-growth behavior of the Arabidopsis mutant rgr1. Roles of gravitropism and circumnutation in the waving/coiling phenomenon.

In this study we investigated the kinetics of the gravitropic response of the Arabidopsis mutant rgr1 (reduced root gravitropism). Although the rate of curvature in rgr1, which is allelic to axr4, was smaller than in the wild type (ecotype Wassilewskija), curvature was initiated in the same region of the root, the distal elongation zone. The time lag for the response was unaffected in the mutant; however, the gravitropic response of rgr1 contained a feature not found in the wild type: when roots growing along the surface of an agar plate were gravistimulated, there was often an upward curvature that initiated in the central elongation zone. Because this response was dependent on the tactile environment of the root, it most likely resulted from the superposition of the waving/coiling phenomenon onto the gravitropic response. We found that the frequency of the waving pattern and circumnutation, a cyclic endogenous pattern of root growth, was the same in rgr1 and in the wild type, so the waving/coiling phenomenon is likely governed by circumnutation patterns. The amplitudes of these oscillations may then be selectively amplified by tactile stimulation to provide a directional preference to the slanting.

Arabidopsis↗
PubMed1998

The politics of EPSDT policy in the 1990s: policy entrepreneurs, political streams, and children's health benefits.

The Early and Periodic Screening, Diagnosis and Treatment (EPSDT) program, which was designed to ensure that Medicaid-eligible children receive comprehensive health services, is the only national attempt to provide a right to these services. The political factors that have shaped national EPSDT policy during the past decade are described, based on a conceptual framework developed by John W. Kingdon. The analysis focuses on the roles of two distinct sets of policy entrepreneurs: child health advocates and fiscally conservative governors. Their activities are described in relation to the larger political environment, or "political stream," from the period of the expansion of Medicaid eligibility for pregnant women and children in the late 1980s to the enactment of a new State Children's Health Insurance Program (SCHIP) in 1997. The relative saliency of eligibility and benefit issues in children's health policies had a major influence on the politics and outcomes.

Child↗
PubMed1998

The circulating common gamma chain (CD132) in inflammatory bowel disease.

OBJECTIVE: Inflammatory bowel disease (IBD) is characterized by T cell activation. Activated T cells shed interleukin-2 receptors (IL-2R) in a soluble form. A positive correlation between sIL-2Ralpha (CD25) and disease activity is well documented in IBD, whereas IL-2Rgamma (CD132) has not been investigated in this respect. Sera from 42 patients with ulcerative colitis (UC), 34 with Crohn's disease (CD), 31 healthy volunteers, and 12 patients with infectious enterocolitis were obtained. METHODS: Disease activity was scored according to a semiquantitative score for UC and CD. sIL-2R alpha chain and gamma chain were assessed by sandwich ELISA techniques using monoclonal antibodies specific for CD25 and CD132, respectively. RESULTS: The concentration of IL-2Ralpha chain (CD25) was found to be median 3.8 ng/ml in healthy volunteers versus 7.0 ng/ml in UC patients (p < 0.001), and 9.6 ng/ml in CD patients (p < 0.001). With respect to IL-2Rgamma (CD132), significantly higher amounts were found in CD patients: 6.6 ng/ml as compared with healthy controls <1.0 ng/ml (p < 0.004). A Kruskal-Wallis test revealed a significant correlation between alpha chain and disease activity in CD (p < 0.001), and further significantly higher gamma chain levels were found in active CD (p = 0.03). For UC patients, a statistically significant increase of the alpha chain with increasing disease activity (p < 0.01) was observed, whereas no significant changes of the gamma chain levels were found (p > 0.05). A difference of gamma chain levels were found between CD and UC in moderate and severe disease activity (p < 0.05). Further analyses revealed that mesalazine did not influence the IL-2Ralpha or -gamma concentration either in UC or in CD patients. CONCLUSION: An increased circulating level of the soluble common gamma chain (CD132) seems to be found in CD, and an overlap exists between CD and UC.

Adult↗
PubMed1998

A supported relationships intervention to increase the social integration of persons with traumatic brain injuries.

A supported relationships intervention was used to increase the integrated social contacts (ISCs) of 3 persons with traumatic brain injury (TBI) who were each matched with 4 community participants. The intervention consisted of asking participants to meet with their matched counterpart to engage in leisure activities once per week for 4 weeks. Additionally, community participants were provided with a brief training session on TBI, were given specific suggestions on interacting with the persons with TBI with whom they were matched, and received weekly phone calls from the researcher. Frequency of ISCs were analyzed with a multiple baseline design across participants. All 3 participants with TBI increased the frequency of ISCs after implementation of the supported relationships intervention and continued to experience more than baseline levels of ISCs during 8 weeks of follow-up. These data suggest that social integration can be enhanced with a procedure requiring limited staff intervention.

Adult↗
PubMed1998

Tobacco, alcohol, and drug use in a primary care sample: 90-day prevalence and associated factors.

BACKGROUND: Primary care settings are an ideal system in which to identify and treat substance use disorders. OBJECTIVE: To ascertain the prevalence of tobacco, alcohol, and drug use in the office of 88 primary care clinicians by gender, age and ethnicity. METHOD: 21,282 adults ages 18-65 completed a self-administered Health Screening Survey while participating in a trial for early alcohol treatment. RESULTS: The period prevalence of tobacco use was 27%. For alcohol: abstainers 40%, low risk drinkers 38%, at-risk drinkers 9%, problem drinkers 8%, and dependent drinkers 5%. Twenty percent of the sample reported using illicit drugs five or more times in their lifetime and 5% reported current illicit drug use. There were marked differences in alcohol use disorders by age and ethnicity. The majority of persons who smoked reported the desire to cut down or stop using tobacco. SIGNIFICANCE: This is the first report on the combined prevalence of tobacco, alcohol and drug disorders in a large sample of persons attending community-based non-academic primary care clinics. This report confirms the high prevalence of these problems and suggests that patients will accurately complete a self-administered screening test such as the Health Screening Survey. The office procedures developed for this study provide Managed Care Organizations with a system of care that can be used to screen all persons for tobacco, alcohol and drug use disorders.

Adolescent↗
PubMed1998

Bone morphogenetic proteins and bFGF exert opposing regulatory effects on PTHrP expression and inorganic pyrophosphate elaboration in immortalized murine endochondral hypertrophic chondrocytes (MCT cells).

A fundamental question in endochondral development is why the expression of parathyroid hormone-related protein (PTHrP), which inhibits chondrocyte maturation and mineralization, becomes attenuated at the stage of chondrocyte hypertrophy. To address this question, we used clonal, phenotypically stable SV40-immortalized murine endochondral chondrocytes that express a growth-arrested hypertrophic phenotype in culture (MCT cells). Addition of individual cytokines to the medium of MCT cells revealed that bone morphogenetic protein (BMP)-6, which commits chondrocytes to hypertrophy, markedly inhibited PTHrP production. This activity was shared by three other osteogenic bone morphogenetic proteins (BMP-2, BMP-4, and BMP-7) and by transforming growth factor beta (TGF-beta), which all inhibited the level of PTHrP mRNA. In contrast, basic fibroblast growth factor (bFGF), an inhibitor of chondrocyte maturation to hypertrophy, induced PTHrP in MCT cells and antagonized the effects of BMP-2, BMP-4, BMP-6, and BMP-7 and TGF-beta on PTHrP expression. Opposing effects of bFGF and BMPs also were exerted on the elaboration of inorganic pyrophosphatase (PPi), which regulates the ability of hypertrophic chondrocytes to mineralize the matrix. Specifically, BMP-2 and BMP-4, but not BMP-6 and BMP-7, shared the ability of TGF-beta to induce PPi release, and this activity was inhibited by bFGF in MCT cells. Our results suggest that effects on PTHrP expression could contribute to the ability of BMP-6 to promote chondrocyte maturation. BMPs and bFGF exert opposing effects on more than one function in immortalized hypertrophic chondrocytes. Thus, the normal decrease in bFGF responsiveness that accompanies chondrocyte hypertrophy may function in part by removing the potential for bFGF to induce PTHrP expression and to oppose the effects of BMPs. MCT cells may be useful in further understanding the mechanisms regulating the differentiation and function of hypertrophic chondrocytes.

Animals↗
PubMed1998

At-risk drinking in an HMO primary care sample: prevalence and health policy implications.

OBJECTIVES: This study was designed to determine the prevalence of at-risk drinking using varying alcohol use criteria. METHODS: A period prevalence survey was conducted in 22 primary care practices (n = 19372 adults). RESULTS: The frequency of at-risk alcohol use varied from 7.5% (World Health Organization criteria) to 19.7% (National Institute on Alcohol Abuse and Alcoholism criteria). A stepwise logistic model using National Institute on Alcohol Abuse and Alcoholism criteria found male gender, current tobacco use, never married status, retirement, and unemployment to be significant predictors of at-risk alcohol use. CONCLUSIONS: Public health policy needs to move to a primary care paradigm focusing on identification and treatment of at-risk drinkers.

Adult↗