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Biomedical subjects

C C Johnson

Publications and source records attributed to C C Johnson.

At least 145 records · Page 8Linked to original sources
PubMed1989

Childhood nervous system tumours: an assessment of risk associated with paternal occupations involving use, repair or manufacture of electrical and electronic equipment.

Parental occupational exposures to chemical carcinogens have been associated with malignancies in offspring. Recent studies have raised the issue that electromagnetic fields may play a role in carcinogenesis. We conducted a population-based case-control study testing for an association between the occurrence of a nervous system tumour in a child and paternal employment at the time of the child's birth in occupations involving potential exposure to low frequency electromagnetic fields, primarily in the electrical and electronics industries. Birth certificate data, including parental occupation information, of 499 children who died in Texas from intracranial and spinal cord tumours were compared with 998 controls randomly selected from Texas livebirths. The odds ratio for paternal employment in industries involving potential electromagnetic field exposure was 1.6 (p less than 0.07). A risk of 3.5 (p less than 0.05) was detected for fathers who were electricians. The additional presence of chemical exposures in these diverse occupations and industries must also be considered.

Case-Control Studies↗
PubMed1989

Cell-wall-defective variants of Fusobacterium.

The activity of antimicrobial agents against Fusobacterium species has been reported as variable in the literature. For some strains, the inconsistency arises from difficulty in determining the endpoint of growth in agar dilution susceptibility tests. Certain strains persist as a subtle haze beyond the levels of antibiotic that permit conventional colonial growth. We have determined by light and electron microscopy that this haze represents the colonial growth of cell-wall-defective (CWD) variants of the parent Fusobacterium. The CWD forms could be propagated indefinitely in hypertonic medium containing the antibiotic inducing agent. However, when the antibiotic was eliminated, the organisms would revert to their native morphology. Formation of CWD variants was observed in the presence of cell-wall-active drugs (e.g., beta-lactam agents) but not with drugs that work by a different mechanism (e.g., clindamycin or chloramphenicol). Fourteen of 22 F. varium strains, 8 of 11 F. mortiferum strains, 2 of 10 F. gonidiaformans strains, and 1 of 4 of F. necrophorum strains could be induced to a CWD form in vitro in the usual agar dilution susceptibility test. Although the clinical significance of CWD variants of Fusobacterium is unknown, they may be a source of confusion in interpreting agar dilution susceptibility tests.

Anti-Bacterial Agents↗
PubMed1989

Season-of-birth and acute leukemia of infancy.

Because of its short and clearly delineated latency period, acute leukemia of infancy is particularly suited to etiologic analysis. From 1950 to mid-1985, 31 infants with acute leukemia (less than 1 year of age) were registered at the University of Texas, M.D. Anderson Cancer Center at Houston. The medical records of these infants were reviewed for demographic and birth information. Of the 31 infants, 14 (45%) were Hispanic. The sex ratio was 3:1 male/female) for white infants and 5:9 for Hispanic infants. Of the white infants, half had acute lymphocytic leukemia, compared with all but one of the Hispanic infants. There was a significant excess of winter births among the infants diagnosed with acute leukemia (P less than 0.05). The significant association between season-of-birth and the occurrence of leukemia cases is suggestive of periodicity of an environmental etiologic agent, perhaps acting in concert with endogenous rhythmicities in susceptibility to that agent. This finding is deserving of further study.

Acute Disease↗
PubMed1989

Newer penicillins and beta-lactamase inhibitors.

The penicillins continue to be important antibiotics for the treatment and prophylaxis of many infectious diseases. The emergence of resistant microorganism has led to the development of newer penicillin compounds that have extended spectrums of antimicrobial activity. Beta-lactamase production by many pathogenic bacteria is the most common and clinically relevant mechanism of antibiotic resistance. The addition of beta-lactamase inhibitors to penicillin antibiotics has proven to be successful in preventing the inactivation of the parent penicillin compound by the more commonly produced beta-lactamase enzymes.

Chemical Phenomena↗
PubMed1988

A dynamic family approach for the prevention of cardiovascular disease.

Social and behavioral learning methods, combined with nutrition counseling and innovative education modules, provide a well-rounded approach to eating behavior intervention. Dietitians can apply this multifaceted approach in various settings to maximize eating behavior change.

Adolescent↗
PubMed1988

In vitro inactivation of aminoglycosides by cephalosporin antibiotics.

The in vitro inactivation of aminoglycoside antibiotics by semisynthetic penicillins complicates antibiotic assays. Due to the increasing number of new cephalosporins and use of aminoglycoside-cephalosporin combinations, we determined the in vitro stability of 28 aminoglycoside-cephalosporin combinations (gentamicin sulfate, tobramycin sulfate, netilmicin sulfate [10 micrograms/mL], and amikacin [20 micrograms/mL] in combination with cefazolin sodium, cefoxitin sodium, cefoperazone sodium, cefotaxime sodium, ceftazidime acid pentahydrate, cefsulodin sodium, or cefpiramide sodium at 100, 200, and 300 micrograms/mL). These mixtures were incubated at 37 degrees C and sampled at 0, 8, and 24 hours. Amikacin and tobramycin were most stable and netilmicin was the least stable of the aminoglycosides. Cefoxitin, ceftazidime, and cefotaxime were the least inactivating of the cephalosporins. When combined with first- and second-generation cephalosporins, aminoglycosides are relatively stable, but some laboratory precautions may be necessary when determining aminoglycoside levels in the presence of third-generation cephalosporin compounds.

Aminoglycosides↗
PubMed1987

Ciprofloxacin for eradication of methicillin-resistant Staphylococcus aureus colonization.

Ciprofloxacin (750 mg orally twice a day) was used to treat 22 episodes of methicillin-resistant Staphylococcus aureus (MRSA) colonization among 20 patients. Most patients had serious, progressive underlying medical diseases and had multiple sites of colonization. Eleven had previously received parenteral vancomycin therapy. Duration of ciprofloxacin therapy was from seven to 28 days. Therapy was discontinued in eight patients because of minor adverse reactions (two patients) or serious events attributed to underlying diseases (six patients). These serious events included seizures in two patients with known seizure disorders. Of the remaining 14 courses of therapy, 11 (79 percent) were associated with eradication of MRSA colonization. For the 18 patients who received at least two weeks of therapy, results of cultures from 47 of the 56 colonized sites became negative. Recolonization with MRSA occurred in four patients within one month. Increased resistance to ciprofloxacin was observed in seven of the 22 treatment episodes; this was associated with treatment failure in three patients and successful therapy in one patient; therapy was discontinued for other reasons in three patients. For comparison, medical records of 31 patients whose clinical specimens revealed MRSA but who did not receive ciprofloxacin were reviewed. MRSA colonization (as opposed to infection) was not eradicated in any patient who received only a single drug or no specific therapy directed against MRSA; four of seven patients given combination therapy had colonization eradicated. Although there is the potential for increased resistance, ciprofloxacin is an important new option that can be used as a single agent for eradication of MRSA colonization. Additional study is needed to define the optimum use of ciprofloxacin as a single agent and in combination therapy for MRSA colonization and infection.

Adult↗
PubMed1987

The relationship between cynical hostility and blood pressure reactivity.

It is hypothesized that high levels of hostility stimulate blood pressure hyperresponsivity to challenge. Seventy-six normotensive adults completed the MMPI hostility subscale, and blood pressure reactivity to, and recovery from, cold pressor and mental arithmetic stressors were measured on two occasions. Only one of twenty Pearson correlations between Cook-Medley hostility and blood pressure reactivity was significant. Analyses of variance revealed that blood pressure reactivity was influenced by sex and family history of cardiovascular disease, but neither factor interacted with hostility. There was no evidence from the present study that cynical hostility as measured by the Cook-Medley was associated with blood pressure reactivity.

Adult↗
PubMed1987

Childhood nervous system tumors--an evaluation of the association with paternal occupational exposure to hydrocarbons.

Paternal occupational exposures to hydrocarbons have been associated with childhood nervous system cancer, but study results have not been consistent. This population-based case-control study was designed to examine this association using a large sample size to increase the precision of risk estimates. The birth certificates of 499 children who died in Texas from intracranial and spinal cord tumors were compared with 998 control certificates randomly selected from all Texas live births. Information on parental job title and industry at the time of birth was obtained from the birth certificates. No significant associations were identified for the dichotomized variable of all hydrocarbon-related occupations combined, as variously defined in previous studies, or for most of the specific jobs affiliated with exposures to hydrocarbons. Significant, relatively stable odds ratios (OR) were found for printers and graphics arts workers (OR = 4.5; 95% confidence interval (CI) = 1.4-14.7) and chemical and petroleum workers with high exposure levels (OR = 3.0; CI = 1.1-8.5). A discussion of the biases involved in this type of study design is presented.

Adolescent↗
PubMed1987

Treatment and long-term follow-up of foot infections in patients with diabetes or ischemia: a randomized, prospective, double-blind comparison of cefoxitin and ceftizoxime.

The efficacy and safety of ceftizoxime and cefoxitin were compared in a randomized, double-blind study of therapy for lower extremity infections in patients with diabetes mellitus or peripheral vascular disease. Overall clinical responses were satisfactory in 82% (23/28) of patients treated with ceftizoxime and in 68% (17/25) of patients treated with cefoxitin. The difference was not statistically significant. Ceftizoxime had superior in vitro activity against Enterobacteriaceae, especially Enterobacter cloacae, whereas cefoxitin had better activity against the Bacteroides fragilis group. Relapses of infection were common in both groups during long-term follow-up; only about one third of patients in either group maintained satisfactory outcomes after one year. More than half of the patients in both groups responded to one or more courses of medical therapy and avoided major amputations for one year following entry into the study.

Aged↗
PubMed1987

Cardiovascular risk in parents of children with elevated blood pressure. "Heart Smart"--family health promotion.

The Heart Smart Family Health Promotion identified elementary-school-age children with elevated blood pressure (BP), based on sex-, race-, height-specific 90th percentiles, and ponderal index (wt/ht3), based on sex-, race-, and age-specific 90th percentiles (norms developed in the Bogalusa Heart Study). These children and their parents were recruited into a behavioral program aimed at reducing cardiovascular (CV) risk factors for both children and parents and preventing "tracking" of children's elevated risk factors into adulthood. Cardiovascular screening consisted of BP, anthropometric evaluation, serum lipids, and 24-hour urinalysis. Self-reported assessments were personal and family medical history, eating, exercise, smoking, and alcohol behaviors. Both child and parent subjects were predominantly black and female. Data were stable over two baseline measurements and indicated CV risk factor abnormalities in one or both of the parents selected: 67% of the black parents and 25% of the white parents were hypertensive; 91% had positive familial CV history; 41% had total cholesterol greater than or equal to 220 mg/dl; 50% had LDL-C levels greater than or equal to 140 mg/dl; 74% were overweight; 44% were smokers; and 91% were completely sedentary. Using percentile grids to identify children with elevated BP also identifies families with hypertension and associated risk factors.

Adolescent↗
PubMed1986

In vitro activities of 17 antimicrobial agents against the formate/fumarate-requiring, anaerobic gram-negative bacilli.

The in vitro activities of 17 antimicrobial agents were evaluated against 46 clinical isolates of formate/fumarate-requiring anaerobic gram-negative bacilli. Strains of Bacteroides ureolyticus (23) were almost uniformly susceptible to the tested antimicrobials, whereas strains of Bacteroides gracilis (18) showed some striking resistance with penicillin active against only 67%, the cephalosporins active against 67%-89%, and clindamycin active against 67%. Although few strains of Wolinella species/C. concisus (5) were available for testing, these isolates tended to be more resistant than B. ureolyticus but less resistant than B. gracilis.

Anti-Bacterial Agents↗
PubMed1986

Ethnic patterns of Hodgkin's disease incidence among children and adolescents in the United States, 1973-82.

The descriptive epidemiologic findings were summarized on 1,109 patients (white, black, and Hispanic) under 20 years of age who were diagnosed with Hodgkin's disease as reported to the Surveillance, Epidemiology, and End Results ("SEER") Program of the National Cancer Institute from 1973 to 1982. Across all ethnic strata, incidence rates increased with advancing age at diagnosis, with white adolescents 15-19 years old exhibiting the highest rates (male, 3.67; female, 4.18). Gender difference among children 0-14 years of age was most evident in blacks (male:female ratio: 4.0 for blacks, 1.0 for whites). Highest adolescent:childhood ratios of incidence rates were noted for females (5.81 for whites and 8.29 for New Mexico Hispanics) and lowest, for Hispanic males (1.25, New Mexico; 2.15, Puerto Rico). Whites exhibited the highest percentage of the nodular sclerosis histologic subtype (65%) and Hispanics, the lowest (45%). Conversely, Hispanics had higher rates of histologic types associated with a poorer prognosis (mixed cellularity and lymphocyte depletion). These differing age and histologic patterns were consistent with previously described international patterns of disease occurrence. Analysis of secular trends for whites from 1969 to 1982 revealed relatively stable rates for youngest ages and male adolescents. Rates increased over time for white female adolescents, but the trend was not statistically significant.

Adolescent↗