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Biomedical subjects

C J Johnson

Publications and source records attributed to C J Johnson.

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

Local norming of the test of adolescent/adult language-3 in the Ottawa Speech and Language Study.

The young adult norms for the Test of Adolescent/Adult Language-3 (TOAL-3; D. Hammill et al., 1994) are based only on individuals who pursued postsecondary education, a restriction that renders the norms inappropriate for many clinical and research purposes. This research note details the rationale, methods, and results of a local norming of the TOAL-3 spoken language subtests, based on participants from the Ottawa Speech and Language Study (C. J. Johnson et al., 1999). The resulting Ottawa norms represent the full range of young adult language abilities and, therefore, can be used with caution for some clinical and research purposes.

Adolescent↗
PubMed1999

Elevated tissue plasminogen activator antigen and stroke risk: The Stroke Prevention In Young Women Study.

BACKGROUND AND PURPOSE: Abnormalities in endogenous fibrinolysis are associated with an increased risk for stroke in men and older adults. We tested the hypothesis that elevated plasma tissue plasminogen activator (tPA) antigen, a marker for impaired endogenous fibrinolysis, is an independent risk factor for stroke in young women. METHODS: Subjects were 59 nondiabetic females ages 15 to 44 years with cerebral infarction from the Baltimore-Washington area and 97 control subjects frequency-matched for age who were recruited by random-digit dialing from the same geographic area. A history of cerebrovascular disease risk factors was obtained by face-to-face interview. Plasma tPA antigen was measured by enzyme-linked immunosorbent assay. RESULTS: Mean plasma tPA antigen levels were significantly higher in stroke patients than control subjects (4. 80+/-4.18 versus 3.23+/-3.67 ng/mL; P=0.015). After adjustment for age, hypertension, cigarette smoking, body mass index, and ischemic heart disease, there was a dose-response association between tPA antigen and stroke with a 3.9-fold odds ratio of stroke (95% CI, 1.2 to 12.4; P=0.03) for the upper quartile (>4.9 ng/mL) of tPA antigen compared with the lowest quartile. The dose-response relationship between tPA antigen and stroke was equally present in white and nonwhite women, and further adjustment for total and HDL cholesterol levels only modestly attenuated this association. CONCLUSIONS: This population-based case-control study shows that elevated plasma tPA antigen level is independently associated with an increased risk for ischemic stroke in nondiabetic females 15 to 44 years of age. These findings support the hypothesis that impaired endogenous fibrinolysis is an important risk factor for stroke in young women.

Adolescent↗
PubMed1999

Homocyst(e)ine and risk of cerebral infarction in a biracial population : the stroke prevention in young women study.

BACKGROUND AND PURPOSE: Genetic enzyme variation and vitamin intake are important determinants of blood homocyst(e)ine levels. The prevalence of common genetic polymorphisms influencing homocyst(e)ine levels varies by race, and vitamin intake varies by socioeconomic status. Therefore, we examined the effect of vitamin intake, race, and socioeconomic status on the association of homocyst(e)ine with stroke risk. METHODS: All 59 hospitals in the greater Baltimore-Washington area participated in a population-based case-control study of stroke in young women. One hundred sixty-seven cases of first ischemic stroke among women aged 15 to 44 years were compared with 328 controls identified by random-digit dialing from the same region. Risk factor data were collected by standardized interview and nonfasting phlebotomy. Plasma homocyst(e)ine was measured by high-performance liquid chromatography and electrochemical detection. RESULTS: Blacks and whites did not differ in median homocyst(e)ine levels, nor did race modify the association between homocyst(e)ine and stroke. After adjustment for cigarettes per day, poverty status, and regular vitamin use, a plasma homocyst(e)ine level of >/=7.3 micromol/L was associated with an odds ratio for stroke of 1.6 (95% CI, 1.1 to 2.5). CONCLUSIONS: The association between elevated homocyst(e)ine and stroke was independent not only of traditional vascular risk factors but also of vitamin use and poverty status. The degree of homocyst(e)ine elevation associated with an increased stroke risk in young women is lower than that previously reported for middle-aged men and the elderly and was highly prevalent, being present in one third of the control group.

Adolescent↗
PubMed1999

Direct observation of stress response in Caenorhabditis elegans using a reporter transgene.

Transgenic Caenorhabditis elegans expressing jellyfish Green Fluorescent Protein under the control of the promoter for the inducible small heat shock protein gene hsp-16-2 have been constructed. Transgene expression parallels that of the endogenous hsp-16 gene, and, therefore, allows direct visualization, localization, and quantitation of hsp-16 expression in living animals. In addition to the expected upregulation by heat shock, we show that a variety of stresses, including exposure to superoxide-generating redox-cycling quinones and the expression of the human beta amyloid peptide, specifically induce the reporter transgene. The quinone induction is suppressed by coincubation with L-ascorbate. The ability to directly observe the stress response in living animals significantly simplifies the identification of both exogenous treatments and genetic alterations that modulate stress response, and possibly life span, in C. elegans.

Animals↗
PubMed1998

Body posture during simulated tracheal intubation.

Seventeen experienced anaesthetists and 15 novices were filmed intubating the trachea of a training manikin. Measurements were made of the distance from manikin's chin to subject's nose and of the angles at the elbow, the shoulder and of the forearm with the horizontal. Trained subjects stood further back (trained: median 43 cm, interquartile range 41-56 cm; novices 35 cm, 26-38 cm; Mann-Whitney U, p < 0.01), with a straighter arm (trained elbow angle: 108 degrees, 99-121 degrees; novices': 92 degrees, 88-102 degrees; Mann-Whitney U, p < 0.01). Trained subjects tended to hold the laryngoscope closer to the hinge, with a pincer grip; novices were more likely to use a full grip of the handle. Trainers should consider giving novices explicit instructions on how to stand and how to hold the laryngoscope.

Anesthesiology↗
PubMed1998

In vivo aggregation of beta-amyloid peptide variants.

Transgenic Caenorhabditis elegans animals have been engineered to express wild-type and single-amino acid variants of a long form of human beta-amyloid peptide (A beta 1-42). These animals express high levels (approximately 300 ng of A beta/mg of total protein) of apparently full-length peptide, as determined by quantitative immunoblot. Expression of wild-type A beta in these animals leads to rapid production of amyloid deposits reactive with Congo red and thioflavin S. This model system has been used to examine the effect of Leu17Pro, Leu17Val, Ala30Pro, Met35Cys, and Met35Leu substitutions on the in vivo production of amyloid deposits. We find that the Leu17Pro and Met35Cys substitutions completely block the formation of thioflavin S-reactive deposits, implicating these as key residues for in vivo amyloid formation. We have also constructed transgenic strains expressing a novel A beta variant, the single-chain dimer. Animals expressing high levels of this variant also fail to produce thioflavin S-reactive deposits.

Amino Acid Sequence↗
PubMed1998

Platelet glycoprotein receptor IIIa polymorphism P1A2 and ischemic stroke risk: the Stroke Prevention in Young Women Study.

BACKGROUND AND PURPOSE: Platelet glycoprotein IIb/IIa (GpIIb-IIIa), a membrane receptor for fibrinogen and von Willebrand factor, has been implicated in the pathogenesis of acute coronary syndromes but has not been previously investigated in relation to stroke in young adults. METHODS: We used a population-based case-control design to examine the association of the GpIIIa polymorphism P1A2 with stroke in young women. Subjects were 65 cerebral infarction cases (18 patients with and 47 without an identified probable etiology) 15 to 44 years of age from the Baltimore-Washington region and 122 controls frequency matched by age from the same geographic area. A face-to-face interview for vascular disease risk factors and a blood sample for the P1A2 allele and serum cholesterol were obtained from each participant. Logistic regression was used to estimate the odds ratio for one or more P1A2 alleles after adjustment for other risk factors. RESULTS: Among cases and controls, the prevalence rates of one or more P1A2 alleles were 21% and 22% among blacks and 36% and 28% among whites, respectively. This genotype was significantly associated with hypertension only in black control subjects but otherwise not with any of the established vascular risk factors. The adjusted odds ratio for cerebral infarction of one or more P1A2 alleles was 1.1 (confidence interval [CI], 0.6 to 2.3) overall, 0.5 (CI, 0.1 to 7.1) among blacks, and 1.4 (CI, 0.5 to 3.7) among whites. For the cases with an identified probable etiology, the corresponding odds ratios were 3.0 (CI, 0.9 to 10.4) overall, 0.7 (CI, 0.1 to 7.1) among blacks, and 12.8 (CI, 1.2 to 135.0) among whites. CONCLUSIONS: No association was found between the P1A2 polymorphism of GpIIIa and young women with stroke. However, subgroup analyses showed that the P1A2 polymorphism of GpIIIa appeared to be associated with stroke risk among white women, particularly those with a clinically identified probable etiology for their stroke. Further work with an emphasis on stroke subtypes and with multiracial populations is warranted.

Adolescent↗
PubMed1998

Cerebral infarction in young adults: the Baltimore-Washington Cooperative Young Stroke Study.

BACKGROUND: Few reports on stroke in young adults have included cases from all community and referral hospitals in a defined geographic region. METHODS: At 46 hospitals in Baltimore City, 5 central Maryland counties, and Washington, DC, the chart of every patient 15 to 44 years of age with a primary or secondary diagnosis of possible cerebral arterial infarction during 1988 and 1991 was abstracted. Probable and possible etiologies were assigned following written guidelines. RESULTS: Of 428 first strokes, 212 (49.5%) were assigned at least one probable cause, 80 (18.7%) had no probable cause but at least one possible cause, and 136 (31.8%) had no identified probable or possible cause. Of the 212 with at least one probable cause, the distribution of etiologies was cardiac embolism (31.1%), hematologic and other (19.8%), small vessel (lacunar) disease (19.8%), nonatherosclerotic vasculopathy (11.3%), illicit drug use (9.4%), oral contraceptive use (5.2%), large artery atherosclerotic disease (3.8%), and migraine (1.4%). There were an additional 69 recurrent stroke patients. CONCLUSIONS: In this hospital-based registry within a region characterized by racial/ethnic diversity, cardiac embolism, hematologic and other causes, and lacunar stroke were the most common etiologies of cerebral infarction in young adults. Nearly a third of both first and recurrent strokes had no identified cause.

Adolescent↗
PubMed1998

Illicit drug-associated ischemic stroke in the Baltimore-Washington Young Stroke Study.

BACKGROUND: Limited information exists on the frequency, trends in occurrence, risk factors, mechanisms, and outcome of ischemic stroke associated with illicit drug use among young adults in a geographically defined population. METHODS: We reviewed ischemic stroke in young adults (aged 15 to 44 years) in 46 regional hospitals for 1988 and 1991. We examined stroke mechanisms and outcome in patients with recent drug use. RESULTS: Recent illicit drug use was noted in 51/422 (12.1%) stroke patients. Patients with drug use were more likely than other stroke patients to be black (p=0.01), aged 25 to 39 years (p=0.004), and smokers (p=0.006), and were less likely to have hypertension (p=0.004) or diabetes mellitus (p=0.004). Drug use was the probable cause of stroke in 20 (4.7%) patients. Among 31 (7.3%) patients with drug use as a possible stroke mechanism, more likely diagnoses included cardioembolic stroke in 18, hematologic/collagen vascular in 6, nonatherosclerotic vasculopathy in 5, and atherosclerosis in 3. There was no difference in outcome between drug-associated and non-drug associated stroke. CONCLUSIONS: Recent illicit drug use occurs in 12.1% of young adult stroke patients. Drug-associated young adult stroke seems to relate to vascular mechanisms other than those related to hypertension or diabetes. Case-control studies are needed.

Adolescent↗
PubMed1998

Thermolabile methylenetetrahydrofolate reductase polymorphism (C677T) and total homocysteine concentration among African-American and white women.

A polymorphism associated with a thermolabile variant (C677T) of the enzyme methylenetetrahydrofolate reductase has been associated with both elevated total homocysteine (tHcy) levels and risk for cardiovascular disease. Data from the Stroke Prevention in Young Women Study were used to determine the prevalence of the C677T genotype and to assess whether environmental factors modified the association between genotype and tHcy concentration. The C677T genotype prevalence was 80% -/-, 20% +/-, and 0% +/+ among 46 African-American women; and 39% -/-, 53% +/-, and 8% +/+ among 77 white women (P < 0.01). There was a trend toward higher tHcy levels in African-American women with the +/- genotype when compared with the -/- genotype (6.9 mumol/L vs 5.3 mumol/L respectively, p = 0.10); no association was found among the white women (6.0 mumol/L, -/-; 4.5 mumol/L, +/-; and 6.2 mumol/L, +/+; p = 0.67). Among African American women, those who smoked and were +/- genotype had the highest tHcy levels (8.0 mumol/L); while among white women, those who smoked and were -/- had the highest tHcy levels (8.1 mumol/L). Despite being hampered by a limited sample size, the thermolabile allele is significantly less common among African-American than white women. The association between genotype and tHcy concentration is influenced by smoking and multivitamin use.

Adolescent↗
PubMed1997

Homeless youths and young adults in Los Angeles: prevalence of mental health problems and the relationship between mental health and substance abuse disorders.

Although understanding of the subsistence patterns, service utilization, and HIV-risk behaviors of homeless youths and young adults in increasing, relatively little is known about the epidemiology of mental health problems in this group or the relationships between mental health problems and substance use. This study measured symptoms of depression, low self-esteem, ADHD, suicidality, self-injurious behavior (SIB), and drug and alcohol use disorder in a sample of homeless youth and young adults living in Hollywood, CA. Results indicated extremely high prevalences of mental health problems as compared with corresponding rates of mental health problems found among housed youths in previous studies. Prevalence of mental health problems differed by age and ethnicity. African Americans were at lower risk of suicidal thoughts and SIB than were those of other ethnicities. Older respondents and females were at increased risk of depressive symptoms, and younger respondents were at increased risk of SIB. Previous history of sexual abuse and/or assault was associated with increased risk of suicidality and SIB. Risk factors for drug abuse disorders included ethnicity other than African American, homelessness for 1 year or more, suicidality, SIB, depressive symptoms, and low self-esteem. Risk factors for alcohol abuse disorder included male gender, white ethnicity, homelessness for 1 year or more, suicidality, and SIB. Extremely high rates of mental health problems and substance abuse disorders in this sample suggest the need for street-based and nontraditional mental health services targeted toward these youths and young adults.

Adolescent↗
PubMed1996

Pregnancy and the risk of stroke.

BACKGROUND: It is widely believed that pregnancy increases the risk of stroke, but there are few data available to quantify that risk. METHODS: We identified all female patients 15 through 44 years of age in central Maryland and Washington, D.C., who were discharged from any of 46 hospitals in the study area in 1988 or 1991. Two neurologists reviewed each case, using data from the women's medical records. We determined whether the women had been pregnant at the time of the stroke or up to six weeks before it occurred. For purposes of this analysis, the six-week period after pregnancy could begin with an induced or spontaneous abortion or with the delivery of a live or stillborn child. RESULTS: Seventeen cerebral infarctions and 14 intracerebral hemorrhages occurred in women who were or had recently been pregnant (pregnancy-related strokes), and there were 175 cerebral infarctions and 48 intracerebral hemorrhages that were not related to pregnancy. For cerebral infarction, the relative risk during pregnancy, adjusted age and race, was 0.7 (95 percent confidence interval, 0.3 to 1.6), but it increased to 8.7 for the postpartum period (after a live birth or stillbirth) (95 percent confidence interval, 4.6 to 16.7). For intracerebral hemorrhage, the adjusted relative risk was 2.5 during pregnancy (95 percent confidence interval, 1.0 to 6.4) but 28.3 for the postpartum period (95 percent confidence interval, 13.0 to 61.4). Overall, for either type of stroke during or within six weeks after pregnancy, the adjusted relative risk was 2.4 (95 percent confidence interval, 1.6 to 3.6), and the attributable, or excess, risk was 8.1 strokes per 100,000 pregnancies (95 percent confidence interval, 6.4 to 9.7). CONCLUSIONS: The risks of both cerebral infarction and intracerebral hemorrhage are increased in the six weeks after delivery but not during pregnancy itself.

Cerebral Hemorrhage↗
PubMed1996

Cognitive components of picture naming.

A substantial research literature documents the effects of diverse item attributes, task conditions, and participant characteristics on the case of picture naming. The authors review what the research has revealed about 3 generally accepted stages of naming a pictured object: object identification, name activation, and response generation. They also show that dual coding theory gives a coherent and plausible account of these findings without positing amodal conceptual representations, and they identify issues and methods that may further advance the understanding of picture naming and related cognitive tasks.

Adult↗
PubMed1996

Clinical evidence of efficient tumor targeting based on single-chain Fv antibody selected from a combinatorial library.

We present a system for cancer targeting based on single-chain Fv (scFv) antibodies selected from combinatorial libraries, produced in bacteria and purified by using an engineered tag. Combinatorial libraries of scFv genes contain great diversity, and scFv antibodies with characteristics optimized for a particular task can be selected from them using filamentous bacteriophage. We illustrate the benefits of this system by imaging patients with carcinoembryonic antigen (CEA)-producing cancers using an iodine-123 labeled scFv anti-CEA selected for high affinity. All known tumor deposits were located, and advantages over current imaging technology are illustrated. ScFvs are produced in a cloned form and can be readily engineered to have localizing and therapeutic functions that will be applicable in cancer and other diseases.

Adult↗
PubMed1996

Utility of a verbal reasoning test in indicating vocational readiness following traumatic brain injury.

Present tests are often inadequate to assess subtle aspects of cognitive-communicative functioning following traumatic brain injury (TBI), making it difficult to predict vocational readiness, particularly for those in professional occupations. This study examined the viability of the Ross Test of Higher Cognitive Processes (RTHCP) as a measure of verbal reasoning deficits following TBI. The verbal reasoning performance of a 43-year-old lawyer with TBI was compared, at two stages in his rehabilitation, to that of a peer group of lawyers (n = 43). The RTHCP detected noticeable differences in speed and accuracy of performance at different stages of recovery. The RTHCP also revealed individual differences among the peer group, who presumably were competent in verbal reasoning. Thus, the RTHCP may be an effective tool to measure subtle deficits in verbal reasoning post-TBI. Some cautions in using this test for the TBI population are presented, as well as suggestions for further test development and validation.

Adult↗
PubMed1996

Aging increases the cardiotoxicity of daunorubicin and daunorubicinol in the rat.

This study examined effects of aging on the cardiac response in vitro to daunorubicin, a cancer chemotherapeutic agent that causes cardiotoxicity. Left ventricular trabeculae carneae from adult (aged 6-9 months) and old (aged 24-28 months) Fischer 344 rats were placed in oxygenated, physiological buffer. Preparations were treated with daunorubicin (175 microM) or saline (controls) over a 210-minute study period. Daunorubicin-induced decline in contractility (DS and dS/dt) was greater in old compared to adult myocardium (p < .02). Similarly, cardiac relaxation (90% relaxation time) was more impaired by daunorubicin in older preparations (p < 01). Although daunorubicin concentrations were unaffected by age, daunorubicinol concentrations in ventricular strips increased with time to a greater extent in the older group (p < .05). This study suggests that senescence increases the acute in vitro cardiotoxicity of daunorubicin and that the metabolite, daunorubicinol, may contribute to this toxicity.

Aging↗