Biomedical subjects

D G Johnson

Publications and source records attributed to D G Johnson.

At least 73 records · Page 4Linked to original sources

PubMed1995

Rectal irrigations for the prevention of postoperative enterocolitis in Hirschsprung's disease.

The purpose of this clinical trial was to examine the role of rectal irrigations in the prevention of postoperative enterocolitis in children with Hirschsprung's disease. Over the past 22 years 177 children had surgical treatment for Hirschsprung's disease at a single pediatric hospital. Five children have died of other causes. Of the remaining 172 patients, follow-up clinical information was obtained from 135 (78%). In 1989, all of the children undergoing surgical reconstruction for Hirschsprung's disease were placed on routine postoperative rectal irrigations with normal saline. The parents were instructed in the irrigation technique before leaving the hospital. Irrigations were started 1 to 2 weeks postoperatively and were performed two times a day for 3 months, then once a day for an additional 3 months. There were no complications from the irrigations themselves. A previous report from the authors' institution has documented five sudden deaths over the past 22 years from fulminant postoperative enterocolitis. These five children all had an unremarkable postoperative recovery, then developed a rapidly progressive diarrheal illness. All of these deaths occurred before the institution of routine postoperative irrigations. Of the 135 patients in this review, 40 had the postoperative rectal irrigations. The remaining 95 children serve as historical controls. Data analysis showed that 34 of the 95 children in the nonirrigation cohort developed postoperative enterocolitis compared with 3 of 40 in the rectal irrigation cohort; P < .001 using Fisher's exact test. In the authors' experience, routine postoperative rectal irrigations have significantly decreased the incidence and severity of enterocolitis in children after surgical correction of Hirschsprung's disease.

Child↗

PubMed1995

Gastrointestinal function after surgical correction of Hirschsprung's disease: long-term follow-up in 135 patients.

This study is a retrospective review of all children treated for Hirschsprung's disease over the past 22 years at a single pediatric institution. During this time 177 patients had definitive surgical reconstruction. Five children died of causes unrelated to Hirschsprung's disease, and five children died from enterocolitis after an uneventful postoperative course. Clinical follow-up information was obtained from 135 (78%). Demographic data includes the following: sex ratio 74% male, 26% female; current mean age 9.9 years; mean length of follow-up 7.9 years (range, 3 months to 21.5 years). Mean age at surgical reconstruction was 1.6 years. Definitive surgical procedures included endorectal pull-through (Soave), 21%; modified Duhamel, 67%; extended side-to-side ileocolic anastomosis, 8%; rectal myomectomy, 4%. Transition zone was within rectum or rectosigmoid region in 86%. Overall, 32% (43/135) report difficulty with fecal soiling, and 12.6% (17/135) identify this as a severe problem. These numbers include patients with trisomy 21 and total colonic aganglionosis. Severe fecal soiling was reported in 7.1% (2/28) after an endorectal pull-through, and in 12.1% (11/91) after the modified Duhamel. The difference in incidence of soiling after these two procedures is not statistically significant. However, 40% (4/10) of the patients after the long side-to-side anastomosis for total colonic aganglionosis report severe problems with fecal soiling (P = .03). Surgical reconstruction for Hirschsprung's disease provides near-normal gastrointestinal function for the majority of children, but long-term follow-up shows significant residual problems with soiling in 12.6% of the patients. This is consistent with reported experience worldwide.

Adolescent↗

PubMed1995

Analysis and localization of cyclophilin A found in the virions of human immunodeficiency virus type 1 MN strain.

Previous reports have shown that cyclophilin A (CyPA) is found to be specifically associated with human immunodeficiency virus type-1 (HIV-1) virions and is required for infectivity (Franke et al. Nature 372:359; Thali et al. Nature 372:363). We have examined CyPA associated with HIV-1MN virions. Virions from infected human lymphoid cells were analyzed by high-pressure liquid chromatography (HPLC), protein sequence, and immunoblot analysis. At least three forms of CyPA were found: an unmodified form, an N-terminally modified form, and an N-terminally modified form that migrates as a larger isoform on a reducing-SDS polyacrylamide gel. Using a protease digestion procedure, CyPA that is associated with virions was found to be located inside the viral membrane. Similar examination of SIVMne produced by HUT-78 human T cells did not detect specific incorporation of CyPA into SIV virions. Our results are consistent with the role of CyPA acting early in the infectious process of HIV-1.

Amino Acid Isomerases↗

PubMed1995

Cardiovascular, plasma norepinephrine, and thermal adjustments to prolonged exercise in young and older healthy humans.

We tested the hypothesis that the whole body energy expenditure, plasma norepinephrine, cardiovascular, and internal body temperature adjustments to prolonged submaximal exercise (i.e., 'cardiovascular drift') performed at the same per cent of peak oxygen uptake (per cent VO2peak) under thermoneutral ambient conditions would be smaller in older compared to young non-physically trained men. Healthy young (25 +/- 1 years; VO2max = 49.3 +/- 1.6 ml kg-1 min-1; n = 6) and older (66 +/- 2 years; VO2max = 31.5 +/- 2.3 ml kg-1 min-1; n = 6) untrained men with similar levels of chronic physical activity were studied during pre-exercise standing rest and serially during 45 min of constant load treadmill walking at approximately 65% VO2peak (Ta = approximately 23 degrees C; approximately 40 RH). There were no group differences at rest. From rest to 5 min of exercise, the increases in heart rate were less (P < 0.05), the changes in arterial blood pressure and per cent delta blood volume were not different, and the rise in plasma norepinephrine concentration was greater (P < 0.05) in the older men vs. young controls. Consistent with our hypothesis, the increases in rectal temperature and plasma norepinephrine concentrations from 5 to 45 min of exercise were smaller in the older men (1.06-0.18 vs. 1.46 +/- 0.16 degrees C and 110 +/- 132 vs. 443 +/- 189%, respectively, P < 0.05). In contrast, the progressive increases in VO2, heart rate, and perceived effort, as well as the time-dependent reductions in systolic, mean and diastolic arterial blood pressure and per cent delta blood volume, were not different in the two groups. Thus, the whole body energy expenditure and selected cardiovascular adjustments to prolonged submaximal treadmill exercise performed at the same per cent VO2peak under comfortable ambient conditions are not different in healthy, physical activity-matched young and older men, despite a smaller elevation in internal body temperature in the latter.

Adult↗

PubMed1995

Early lactation responses of Holstein cows fed a rumen-inert fat prepartum, postpartum, or both.

Primiparous (n = 22) and multiparous (n = 41) cows were randomly assigned by calving date and parity to one of four dietary sequences of supplemental fat from 14 d prepartum to 151 d postpartum. Partially hydrogenated tallow was added to diets at 0% prepartum and postpartum (control); 1% prepartum and 2% postpartum; 0% prepartum and 2% postpartum; and 0% prepartum, 0% from 1 to 34 d postpartum, and 2% from 35 to 151 d postpartum. Inclusion of partially hydrogenated tallow did not influence yields of milk or 3.5% FCM, milk composition, or DMI during the first 151 d postpartum. During the first 35 d postpartum, cows receiving partially hydrogenated tallow starting at parturition yielded milk with a higher fat content than those receiving fat prepartum and postpartum. Addition of partially hydrogenated tallow to diets starting 35 d postpartum resulted in cows being more persistent in yields of milk and 3.5% FCM from 60 to 151 d postpartum. Reproduction parameters measured were unaffected by time of fat addition to diets. Our data suggest that delaying the addition of partially hydrogenated tallow to diets until 35 d postpartum may improve the persistency of lactation.

Animals↗

PubMed1995

Unexpected death from enterocolitis after surgery for Hirschsprung's disease.

Unanticipated death from enterocolitis occurred in five children 3 weeks to 20 months after uncomplicated reconstruction for Hirschsprung's disease. In each case the presenting symptoms of enterocolitis were mild and were misinterpreted by examining physicians. Within 2 to 12 days of onset of symptoms, unexpected death occurred. Although fatal enterocolitis is a well-known complication of Hirschsprung's disease, emphasis is usually placed on preoperative enterocolitis. Fatal postoperative enterocolitis is not a new entity associated with Hirschsprung's disease, but physician awareness of this possibility is obviously deficient. We strongly recommend extensive parent education and better postoperative communication between the surgeon and the referring physician.

Diagnostic Errors↗

PubMed1994

Oncogenic capacity of the E2F1 gene.

Previous experiments have identified the E2F transcription factor as a potential downstream target for the action of cellular regulatory activities, such as the Rb tumor suppressor protein, that control cell growth and that, when altered, contribute to the development of human tumors. In light of these findings, we have assayed the ability of the E2F1 and DP1 genes, which encode heterodimeric partners that together create E2F activity, to act in an oncogenic fashion. We find that E2F1, particularly in combination with the DP1 product, cooperates with an activated ras oncogene to induce the formation of morphologically transformed foci in primary rat embryo fibroblast cultures. In addition, an E2F1 chimeric protein, in which sequences involved in Rb binding have been replaced with the herpesvirus VP16 activation domain, exhibits increased transformation activity. Cells transfected with E2F1 and DP1 or the E2F1-VP16 chimera form colonies in soft agar and induce tumor formation in nude mice. We conclude that deregulated E2F1 expression and function can have oncogenic consequences.

Animals↗

PubMed1994

Autoregulatory control of E2F1 expression in response to positive and negative regulators of cell cycle progression.

Both positive and negative signals govern the progression of cells from G1 into S phase, and a variety of data implicate the E2F transcription factor as a target for the action of one class of negative regulators, the Rb family of growth suppressors. We now find that the E2F1 gene, which encodes one of the components of E2F activity, is subject to autoregulatory control during progression from G0 to S phase and that this primarily reflects a negative control in G0 and early G1, a time when the majority of E2F activity exits as a complex with Rb family members. In addition, we find that deregulated expression of G1 cyclins in quiescent cells stimulates the E2F1 promoter and that this is augmented by coexpression of cyclin-dependent kinases in an E2F-dependent manner. We conclude that the E2F1 gene is a downstream target for G1 cyclin-dependent kinase activity, most likely as a consequence of phosphorylation of Rb family members, and that the autoregulation of E2F1 transcription may provide a sensitive switch for regulating the accumulation of E2F activity during the transition from G1 to S phase.

Base Sequence↗

PubMed1994

Treatment of overt isolated testicular relapse in children on therapy for acute lymphoblastic leukemia. A report from the Childrens Cancer Group.

BACKGROUND: Fifty-seven children with acute lymphoblastic leukemia (ALL) receiving therapy who experienced overt isolated testicular relapse while in bone marrow remission were entered into a study that featured an intensive retreatment regimen. METHODS: The objective was to determine whether a change in chemotherapy and local irradiation would prevent subsequent marrow relapse and increase the survival rate. The regimens used (modified Berlin-Frankfurt-Munster or modified New York) delivered acceptable therapy based on analyses of toxicity data. RESULTS: Overall survival at 5 years from the time of testicular relapse was 47%, with an event-free survival of 43%. Events have been documented in 28 of 55 evaluable children. Analysis of these patients revealed that 23 children had bone marrow relapse, 4 children had central nervous system relapse, and 1 child had testicular relapse. In addition, two patients were removed from the study for toxicity, one child for infection (mucormycosis), and five children had a bone marrow transplantation while in remission and became ineligible to continue in the study. Two children were removed at the request of their parents, and nine children were lost to follow-up. CONCLUSION: Because of their high risk of developing systemic relapse, boys with ALL who experience isolated overt testicular relapse during active therapy should be retreated with intensive treatment.

Adolescent↗

PubMed1994

Bronchoscopic removal of aspirated foreign bodies in children.

Foreign body aspiration is the cause of death for more than 300 children each year in the United States. Tracheobronchial inhalation of foreign bodies may result in acute respiratory distress, atelectasis, chronic pulmonary infections, or death. A review of the records of 548 children (aged 4 months to 18 years) was undertaken to identify factors important in diagnosis, to illustrate the effectiveness of current endoscopic techniques and equipment, and to evaluate the results and complications of management. Coughing, choking, and wheezing were the presenting symptoms seen for 95% of the patients. Results of inspiratory and expiratory chest radiographs were positive in 83% of the 440 children who had foreign bodies removed. Fluoroscopy findings were positive for 67 patients, 90% of whom had foreign bodies removed. Foreign bodies were successfully identified and removed in 440 patients (80%). A wide variety of objects was recovered, the most common being peanuts, organic material, other nuts, popcorn, seeds, plastic objects, and pins. The foreign bodies were in the right bronchus in 49%, the left in 44%, and the trachea and hypopharynx in 4%. Two thirds of the objects were lodged in the mainstem bronchi, on either side, and the remainder were in the distal bronchi. Bronchoscopy is required for treatment, and with experience this procedure can be simple and safe. Ninety-nine percent of the foreign bodies identified during bronchoscopy were removed successfully. Minor complications occurred in 5%, and there were no deaths.

Adolescent↗

PubMed1994

Characterizing nutrient intakes of adolescents by sociodemographic factors.

PURPOSE: The purpose of this study was to provide a description of the current dietary intake of a large sample of U.S. adolescents and to identify sociodemographic risk factors for nutrient intakes that did not meet recommended levels. METHODS: The 1987-88 USDA Nationwide Food Consumption Survey was used to assess the nutrient intake of 933 adolescents aged 11 to 18 years. Analysis of covariance was used to determine the effect of the following on the nutrient intakes of males and females: household income and size, race, geographic region, degree of urbanization, and head of household status. Subject age was entered as a control variable. RESULTS: Vitamin A, vitamin E, calcium, magnesium, and zinc were the nutrients most often consumed below recommended levels. In addition the females consumed low levels of phosphorus and iron. Percent calories from total fat and saturated fat and mean sodium intakes were above recommended levels for the majority of the sample. Females were more likely to meet cholesterol recommendations than males. Race and region affected the most nutrient intake variables. For the females, living in the south was a significant predictor for low intakes of several essential vitamins and minerals. CONCLUSIONS: On average, the adolescents consumed diets that were low in several essential vitamins and minerals and high in some nutrients related to increased incidence of chronic disease. There were groups of teens who had dietary patterns that placed them at especially high risk, in particular the black and Southern females.

Adolescent↗

PubMed1994

Treatment of myopic astigmatism with the 193 nm excimer laser utilizing aperture elements.

In this paper, we examine the 193 nm excimer laser's efficacy and safety in treating myopic astigmatism. The VISX Twenty/Twenty excimer laser uses aperture elements to effect astigmatic photorefractive keratectomy. In 70 patients with six months follow-up, the average postoperative sphere was -0.14 and the average postoperative cylinder was -0.54. Seventy-one percent of these patients had uncorrected visual acuity of 20/40 or better at six months. In 12 patients with one year follow-up, the average postoperative sphere was -0.05 and the average postoperative cylinder was -0.59. Eighty-three percent of these patients had uncorrected acuities of 20/40 or better; none had a clinically significant loss of best corrected acuity. This investigation demonstrates that the excimer laser can be used to treat myopic astigmatism successfully.

Astigmatism↗

PubMed1994

Regulation of pancreatic amylase and lipase gene expression by diet and insulin in diabetic rats.

Although insulin has been proposed to mediate the dietary regulation of pancreatic amylase, its interaction with diet in the regulation of amylase and lipase is not well understood and was examined in diabetic rats fed diets high in carbohydrate (HC), protein (HP), or fat (HF) and treated with insulin. Diabetes, independent of diet, decreased amylase content (97%; P < 0.0001) and mRNA (90%; P < 0.0001), but insulin only restored amylase content and mRNA to respective dietary control values. Diabetes, independent of diet, also increased lipase mRNA 1.6-fold (P < 0.004) but interacted (P < 0.0003) with diet on lipase content, resulting in opposite effects in HC- (increased 202%) and HF-diabetic rats (decreased 40%). Insulin partially restored lipase content and mRNA to respective dietary control values. Diet, independent of diabetes, regulated amylase content (P < 0.0001) and mRNA (P < 0.0003), which were three- to fourfold greater in HC- than in HF-fed rats, and lipase content (P < 0.001) and mRNA [rat pancreatic lipase 1 (rPL-1), P < 0.04; rPL-3, P < 0.0001], which were 1.8-fold greater in HF- than in HC- or HP-fed rats. Insulin failed to stimulate maximal amylase gene expression in HP- or HF-fed diabetic rats, suggesting that it is necessary, but not sufficient, for this dietary regulation. Differential regulation of lipase activity and mRNA by diet and insulin raises the possibility that lipase gene expression is regulated by a complex interaction of diet and insulin.

Amylases↗

PubMed1994

Sympathetic neural reactivity to stress does not increase with age in healthy humans.

Sympathetic nervous system reactivity to stress is though to increase with age in humans. We tested this hypothesis by recording postganglionic sympathetic nerve activity to skeletal muscle (MSNA) (peroneal microneurography) and by measuring plasma norepinephrine concentrations (PNE), heart rate, and arterial pressure before (prestress control) and during cognitive challenge (mental arithmetic and colored word test), thermal stress (i.e., the cold pressor test), and exhaustive isometric handgrip exercise (40% of maximum voluntary force)/postexercise ischemia in 15 older (60-74 yr, mean +/- SE = 64 +/- 1) and 15 young (19-30 yr, mean +/- SE = 25 +/- 1) healthy men and women (8 males, 7 females each). The initial prestress control level of MSNA was higher in the older subjects (P < 0.01 vs. young), but there were no significant differences for PNE, heart rate, or arterial pressure. The MSNA and PNE responses to mental stress were small and not different in the two groups. MSNA and PNE increased markedly in response to the cold pressor test and isometric handgrip exercise/post exercise ischemia in both groups. The absolute unit increases in MSNA were similar in the two groups, but the relative (percentage) increases were actually smaller in the older subjects (P < 0.05 vs. young) due to their elevated baseline levels. The stress-evoked increases in arterial pressure were similar in the groups, but the older subjects tended to demonstrate smaller increases in heart rate. In general, no gender differences were noted in either age group. These findings fail to support the long-held concept that stress-induced sympathetic nervous system stimulation becomes exaggerated with age. Thus, sympathetic neural hyperreactivity does not appear to be a fundamental property of the aging process in humans.

Adult↗

PubMed1994

Endurance exercise training is associated with elevated basal sympathetic nerve activity in healthy older humans.

We tested the hypothesis that endurance training is associated with altered basal levels of muscle sympathetic nerve activity (MSNA) and responses to acute stress in healthy older adults. MSNA (peroneal microneurography) and plasma norepinephrine (NE) concentrations were measured during supine rest, a cold pressor test, and isometric handgrip (40% maximal voluntary force to exhaustion) in 16 older masters endurance athletes [10 men, 6 women; 66 +/- 1 (SE) yr] and 15 healthy normotensive untrained control subjects (9 men, 6 women; 65 +/- 1 yr). The athletes had higher levels of estimated daily energy expenditure and maximal oxygen uptake and lower levels of resting heart rate and body fat than the control subjects (all P < 0.05). MSNA during supine rest was elevated in the athletes whether expressed as burst frequency (43 +/- 2 vs. 32 +/- 3 bursts/min, respectively; P < 0.05) or burst incidence (75 +/- 4 vs. 52 +/- 5 bursts/100 heartbeats, respectively; P < 0.01). These whole group differences were due primarily to markedly higher levels of MSNA in the athletic vs. untrained women (48 +/- 4 vs. 25 +/- 3 bursts/min, 82 +/- 3 vs. 38 +/- 3 bursts/100 heartbeats, respectively, P < 0.001). In contrast, basal plasma NE concentrations were not significantly different in the athletes vs. control subjects. The MSNA and plasma NE responses to acute stress tended to be greater in the athletes. These findings indicate that vigorous regular aerobic exercise is associated with an elevated level of MSNA at rest and a tendency for an enhanced response to acute stress in healthy normotensive older humans.

Aged↗

PubMed1994

Evaluation of calf starters containing different amounts of crude protein for growth of Holstein calves.

Holstein calves (n = 110) were used to evaluate the effect of calf starters containing 15, 16.8, 19.6, or 22.4% CP, DM basis (diets A, B, C, and D, respectively), on calf performance from d 4 to 56 of life. Preweaning daily gain tended to increase linearly as protein content of diets increased, averaging .37, .39, .38, and .44 kg/d for diets A, B, C, and D, respectively. After weaning, calves fed diet C gained the most (.86 versus .71, .75, and .79 kg/d for A, B, and D, respectively). Overall BW gains from d 4 to 56 averaged .54, .56, .62, and .61 kg/d for A, B, C, and D, respectively. Throughout the experiment, starter consumption tended to increase as CP content of diet increased. Under these conditions, maximum growth was supported by diet C (19.6% CP); no advantage was gained from higher (22.4%) protein content. Calf growth was moderate when calf starters of lower protein contents (15 or 16.8%) were fed.

Aging↗

PubMed1994

Tracheal reconstruction.

Treatment of stenosing malformations of the pediatric airway has progressed from dilatation and occasional localized resection to radical resection or extended tracheoplastic reconstruction. Current preoperative evaluation includes high-contrast radiography, bronchography, often magnetic resonance imaging (MRI) or computed tomography (CT), and intraoperative bronchoscopy. Cardiopulmonary bypass may be essential for complicated reconstructions involving the carina and bronchi, but most other stenoses can be corrected without bypass. Balloon dilatation directed toward forceful posterior split of complete cartilage rings has shown recent promise in small infants. Segmental resection with anastomosis is preferred for localized lesions. Incision tracheoplasty with interposition cartilage grafting is the current choice for long stenoses.

Child↗

PubMed1994

Head and neck malformations of the pediatric airway.

The authors describe the head and neck malformations that can affect the upper aerodigestive tract. The article is organized so that it begins with the nose and extends through the larynx. A diagnostic table for the localization for an airway lesion is given. Medical and surgical treatment regarding various malformations including choanal atresia, Pierre Robin sequence, laryngomalacia, laryngeal edema, and subglottic stenosis are discussed.

Airway Obstruction↗