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Biomedical subjects

J Burris

Publications and source records attributed to J Burris.

15 recordsLinked to original sources

Diaphragm shortening and intrathoracic pressure during hypercapnia in rats.

The purpose of this study was to determine the relationship between intrathoracic pressure (delta ITP) and diaphragm shortening (DS) during the development of diaphragm fatigue. Fatigue of the diaphragm was produced by having rats breath 15% CO2 in O2. Diaphragm shortening increased significantly to 178% of control during the first 5 min of hypercapnia and then decreased to 86% of control at approximately 80 min. Twenty minutes after terminating hypercapnia, DS increased to 115% of the prehypercapnic value. delta ITP increased to 199% of control following 5 min of hypercapnia and continued to increase, reaching 267% of control at the end of the hypercapnic period. Twenty minutes later, delta ITP was 147% of control. These results illustrate that during increased respiratory work, DS can decrease while intrathoracic pressure remains increased. These findings suggest that intrathoracic pressure may not always reflect the contractile status of the diaphragm. These findings are consistent with other studies indicating that as the diaphragm fatigues, accessory respiratory muscle activity increases to maintain delta ITP.

Animals↗

The Human Genome Project after a decade: policy issues.

The Human Genome Project began a decade ago, its early momentum fueled by two reports. A report from the National Research Council (NRC) in February 1998 endorsed the project and provided the basis for the first joint plan by the National Institutes of Health (NIH) and the Department of Energy (DOE). A report from the Office of Technology Assessment (OTA) in April 1988, provided Congress with a means to assess the roles of NIH and DOE. Both reports highlighted the importance of genomics and emphasized the need for a concerted research program. The committees did not predict the large investment of private funds or the extensive patenting of sequences, and they underestimated the rate of progress. Overall, though, the consensus-building provided by the committees helped to set the blueprint for one of the great success stories in modern biology.

Advisory Committees↗

Comparison of commercial enzyme immunoassay kits with plaque reduction neutralization test for detection of measles virus antibody.

Four commercially available enzyme immunoassay (EIA) kits were evaluated in comparison with the plaque reduction neutralization (PRN) test for detection of measles virus antibody. The EIA kits, Enzygnost (Behring), Diamedix, Vidas (bioMerieux Vitek), and Measlestat (Biowhittaker), were assessed with two PRN cutoff titers: a PRN titer of 8, the lowest detectable antibody level by the PRN test under the test conditions, and a titer of 120, which has been shown to be the minimum protective antibody titer. At a PRN cutoff titer of 8, the sensitivity was 88.2, 91.1, 74.6, and 69.8% for Behring, Diamedix, Vidas, and Biowhittaker EIA tests, respectively, with negative predictive values ranging from 22.7 to 45.5%. The specificity was 93.8% for Diamedix and 100% for the rest. At a PRN cutoff titer of 120, the sensitivity and specificity, respectively, were 100 and 90.7% (Behring), 98.2 and 58.8% (Diamedix), 90.6 and 94.5% (Vidas), and 85.7 and 96.4% (Biowhittaker). At this PRN cutoff titer, the negative predictive values of all EIA tests improved considerably, ranging from 70.7 to 100%. The EIA results showed an excellent association with PRN results when the PRN titers of the test samples were either < 8 or > 1,052. Discrepancies occurred especially when testing samples having PRN titers in the range of 8 to 120, indicating lack of sensitivity of the EIA tests in detecting measles virus antibody at low levels. Maternally derived measles virus antibody at this level has been shown to interfere with measles vaccine response in children and hence has implications from the standpoint of measles immunization. The ready availability, ease of operation, and rapid turnaround time are strong plus points of the EIA kits, and they could be useful in a clinical laboratory setting for routine application, but they may have limited use in vaccine-related studies and seroepidemiological surveys.

Antibodies, Viral↗

Mass colorectal cancer screening: choosing an effective strategy.

1. Colorectal cancer is the third leading cause of cancer related death in the U.S. 2. Efforts to control this disease have focused primarily on early disease detection and treatment. 3. The occupational health nurse can assume the role of educating employees regarding known risk factors and disease signs and symptoms. 4. In those situations when employee risk factors justify mass screening, the occupational health nurse must work to identify the high risk individuals appropriate for screening and facilitate their understanding and compliance with screening and referral procedures.

Colorectal Neoplasms↗

Diagnosis of birth asphyxia on the basis of fetal pH, Apgar score, and newborn cerebral dysfunction.

Imprecise diagnosis of birth asphyxia coupled with uncertainties about causal factors for neurologic abnormalities in the newborn have greatly fueled the current litigation crisis in obstetrics. Our goal was to more precisely define birth asphyxia based on fetal condition as measured by umbilical artery blood pH, Apgar scores, and neurologic condition of newborns. We selected for study 2738 patients with singleton pregnancies with cephalic presentations who were delivered of infants at term to avoid complications such as prematurity, which may affect infant outcome independent of birth condition. The basis for study of these particular patients were defined criteria for high risk and an indicated arterial cord pH value. A total of five infants demonstrated cerebral dysfunction as evidenced by seizures during the neonatal period. Infection was linked to seizures in three of these infants; one infant had neonatal asphyxia and only one infant's clinical course could be attributed solely to birth events (uterine rupture). Stratification of umbilical artery blood pH values, Apgar scores, and combinations of these dependent variables in relation to newborn clinical outcomes revealed that infants must be severely depressed at delivery before birth asphyxia can be reliably diagnosed. Such depression includes Apgar scores less than or equal to 3 at 1 and 5 minutes plus umbilical artery pH values less than 7.00.

Acid-Base Equilibrium↗

Nursing delivery of sublingual nifedipine.

Nifedipine is often administered sublingually, although the drug is not manufactured in this form. A group of 150 nurses were surveyed to determine how they deliver sublingual nifedipine to functionally independent and dependent patients. Functionally independent patients were most frequently instructed to place the capsule under their tongues or to perforate the capsule before placing it in their mouths. Nifedipine was administered to functionally dependent patients most frequently by cutting the capsule, squeezing its contents into the patient's mouth, and discarding the capsule. These findings raise several questions about the methods nurses commonly use to administer nifedipine.

Activities of Daily Living↗

Umbilical artery acid-base status in the preterm infant.

It is becoming increasingly apparent that Apgar scores are generally lower in otherwise uncomplicated preterm newborns than in term newborns. However, there is little information regarding normal values for umbilical artery blood gas measurements in the preterm infant. The present study included 77 otherwise uncomplicated preterm infants and 1292 uncomplicated term infants. Although preterm infants did have significantly lower 1- and 5-minute Apgar scores, there was no significant difference in the frequency of acidemia (umbilical artery pH below 7.20). The mean pH was 7.29 in preterm infants and 7.28 in term infants. Mean values for pCO2, pO2, HCO3, and base deficit were similar in each group. There were no significant differences in umbilical artery blood gas values in the 77 preterm infants according to birth weight groups. Umbilical cord blood acid-base determination may prove a useful adjunct in assessing the condition of the newborn preterm infant.

Acid-Base Equilibrium↗

Antibiotic concentration in maternal blood, cord blood, and placental membranes in chorioamnionitis.

Levels of five antibiotics used in treating chorioamnionitis were measured in maternal and cord blood and placenta. Ampicillin provided the highest ratio of cord to maternal blood (0.71). Gentamicin was also relatively high in this respect and also had the highest placenta to maternal blood ratio (3.97). Based on these findings, the commonly used combination of ampicillin and gentamicin seems appropriate, although additional anaerobic coverage may be needed.

Acute Disease↗

Enhanced renin secretion in adrenalectomized rats with glucocorticoid-induced hypertension.

The role of circulating epinephrine in the regulation of renin release was studied in unanesthetized rats with glucocorticoid-induced hypertension. Biadrenalectomized Wistar rats were made hypertensive with methylprednisolone (20 mg/kg s.c. weekly) for 2 weeks and supplemented with deoxycorticosterone pivalate (10 mg/kg s.c. weekly). Sham-operated controls received the same treatment. Baseline weight, mean intra-arterial blood pressure and heart rate of the groups were the same. In both adrenalectomized and sham-operated rats plasma renin activity was determined after a 30 min infusion of the beta-adrenoceptor stimulant isoproterenol (40 ng/min) or its vehicle. Isoproterenol had no blood pressure effect and accelerated heart rate to a similar extent in rats with and without adrenals. Plasma renin activity was significantly higher in epinephrine-deficient than in sham-operated rats. Renin secretion was significantly enhanced by isoproterenol in both groups of rats. These data therefore indicate that in rats with glucocorticoid-induced hypertension the renin-angiotensin system is activated by adrenalectomy, despite the fact that adrenal insufficiency cannot develop. It also appears that rats lacking of circulating epinephrine for a prolonged period do not exhibit an abnormal responsiveness of renin secretion to the stimulation of renal beta-adrenoceptors.

Adrenalectomy↗

Effectiveness of potassium chloride or triamterene in thiazide hypokalemia.

Potassium chloride was compared with triamterene in a crossover trial involving 16 hypertensive patients with overt diuretic-induced hypokalemia. Potassium chloride, 24 to 96 mEq/day, normalized the plasma potassium (PK) level at 3.5 mEq/L or more in only eight of the patients. The average increase in PK level was 0.58 mEq/L. Triamterene, 50 to 200 mg daily, normalized PK level in ten of the patients. The average increase in PK level was 0.72 mEq/L, which was not significantly different than that with potassium therapy. Some patients who responded to potassium did not respond to triamterene, and vice versa. Most of the administered potassium was excreted in the urine even with persisting hypokalemia. Addition of triamterene to diuretic therapy resulted in a small but statistically significant increase in plasma creatinine level.

Adult↗

Blood pressure and heart rate response to central beta-blockade in conscious rats with glucocorticoid-induced hypertension.

The beta-adrenergic antagonist propranolol, administered subcutaneously to conscious adrenalectomized rats made hypertensive by exogenous glucocorticoids, has been shown to induce acutely a marked fall in blood pressure and heart rate. These animals almost completely lacked circulating epinephrine. Because both changes were closely related, it was suggested that in this model of hypertension propranolol acts via a central mechanism. To test this hypothesis, we now administered sotalol (300 micrograms) intracerebroventricularly to unanesthetized adrenalectomized rats with glucocorticoid-induced hypertension (this hydrophilic beta-blocking agent does not cross the blood-brain barrier). The same experiments were also performed in sham-operated glucocorticoid-hypertensive rats. On the day of the study, there was no significant difference between adrenalectomized and sham-operated groups of rats in intraarterial pressure and heart rate. Sotalol increased blood pressure and significantly slowed heart rate during the 60-min observation period, both in adrenalectomized and sham-operated rats. Sotalol's vehicle had no blood pressure effect and caused a transient heart rate acceleration in rats with, as well as without, circulating epinephrine. These results therefore suggest that the previously observed enhanced effect of peripherally administered propranolol in the absence of detectable circulating epinephrine, in this model, is not mediated centrally.

Adrenalectomy↗

Measles immunization strategy: measles antibody response following MMR II vaccination of children at one year of age.

Measles antibody levels were determined by the plaque reduction neutralization (PRN) test in 580 one-year-old children before vaccination and four to six weeks after MMR II vaccination. Fifty-one (8.8%) had maternally derived measles antibody at prevaccination, and this was more common among children of women born before 1967 (10.6%) vs. 4.3%; p < 0.01). Among those with maternal antibody, only 22 (43.1%) responded with a protective PRN titre of over 120, in contrast to 463 (87.5%) of the 529 without maternal antibody at prevaccination (p < 0.0001). Also, the geometric mean titre was significantly lower for the former (114.1 vs. 378.5; p < 0.0001). Overall, 15 (2.6%) of the 580 children had no antibody response after vaccination, and a further 80 (13.8%) had a subprotective response (PRN titre < 120). This lack of response could not be attributed entirely to the presence of maternal measles antibody at the time of vaccination. The MMR II vaccine may not be sufficiently immunogenic in inducing adequate measles antibody response after a single dose given at one year of age.

Age Factors↗