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Biomedical subjects

J Kieffer

Publications and source records attributed to J Kieffer.

At least 19 recordsLinked to original sources
PubMed2003

Entropic phase separation in polymer-microemulsion networks.

We study theoretically a model system of a transient network of microemulsion droplets connected by telechelic polymers and explain recent experimental findings. Despite the absence of any specific interactions between either the droplets or polymer chains, we predict that as the number of polymers per drop is increased, the system undergoes a first-order phase separation into a dense, highly connected phase, in equilibrium with dilute droplets, decorated by polymer loops. The phase transition is purely entropic and is driven by the interplay between the translational entropy of the drops and the configurational entropy of the polymer connections between them. Because it is dominated by entropic effects, the phase behavior of the system is extremely robust and is independent of the detailed properties of either polymers or drops.

Emulsions↗
PubMed1996

Psychiatric and developmental disorders in families of children with attention-deficit hyperactivity disorder.

OBJECTIVE: To evaluate whether a pediatric family history obtained via a brief parent interview would reveal a high prevalence of psychiatric and developmental disorders in the family members of children with attention-deficit hyperactivity disorder (ADHD) compared with a group of children with another chronic developmental disability, Down syndrome (DS). DESIGN: A controlled cross-sectional group comparison study. SETTING: An interdisciplinary hyperactivity and learning problem clinic and a DS clinic located in a large, urban tertiary care teaching hospital in Chicago, Ill. PARTICIPANTS: A total of 140 children with ADHD and 163 children with DS of comparable socioeconomic status. MEASURES: Using a screening questionnaire and parent interview, the development pediatricians obtained a family history. RESULTS: By parent report, children with ADHD were significantly more likely than the control children with DS to have a parent affected by alcoholism (P = .007), other drug abuse (P < .001), depression (P < .001), delinquency (P < .001), learning disabilities (P < .001), and ADHD (P < .001). Similar patterns were evidenced in other first- and second-degree relatives. CONCLUSIONS: The high reported frequency of psychiatric and developmental disorders in the families of children with ADHD requires that the treating clinician explore the area of family psychiatric and developmental history and use the findings to formulate a comprehensive treatment plan that includes anticipatory guidance and psychosocial intervention.

Adolescent↗
PubMed1996

Relative effects of carbonic anhydrase infusion or inhibition on carbon dioxide transport and acid-base status in the sea lamprey Petromyzon marinus following exercise

In vivo experiments were carried out to determine the relative effects of carbonic anhydrase (CA) infusion or inhibition on carbon dioxide (CO2) transport and acid-base status in the arterial and venous blood of sea lampreys recovering from exhaustive exercise. Infusion of CA into the extracellular fluid did not significantly affect CO2 transport or acid-base status in exercised lampreys. In contrast, infusion of the CA inhibitor acetazolamide resulted in a respiratory acidosis in the blood of recovering lampreys. In acetazolamide-treated lampreys, the post-exercise extracellular pH (pHe) of arterial blood was significantly lower than that in the saline-infused (control) lampreys. The calculated arterial and venous partial pressure of carbon dioxide (PCO2) and the total CO2 concentration in whole blood (CCO2wb) and red blood cells (CCO2rbc) during recovery in the acetazolamide-infused lampreys were also significantly greater than those values in the saline-infused control lampreys. These results suggest that the CO2 reactions in the extracellular compartment of lampreys may already be in equilibrium and that the access of plasma bicarbonate to CA is probably not the sole factor limiting CO2 transport in these animals. Furthermore, endogenous red blood cell CA clearly has an important role in CO2 transport in exercising lampreys.

Journal Article↗
PubMed1995

Gastroesophageal reflux after repair of congenital diaphragmatic hernia.

Seventy-four survivors of congenital diaphragmatic hernia (CDH) repair were reviewed for gastroesophageal reflux (GER). Twenty-nine patients had a prenatal diagnosis of CDH, 31 had the diagnosis established during the first 60 minutes of life, and 14 had a late diagnosis. Fifty-seven of the 60 patients with a prenatal diagnosis or diagnosis at birth had their CDH repaired during the first 24 hours of life. Thirty-six of the 37 patients with clinical signs of GER and 10 patients without typical clinical signs had documented GER. The overall incidence of GER was 62% (46 of 74). The 46 comprised 22 of the 29 patients (75.8%) with a prenatal diagnosis of CDH, 21 of the 31 (67.7%) with a diagnosis at birth, and 3 of the 14 with a late diagnosis. Eleven patients had surgical treatment of GER. A significant correlation was found between GER and the preoperative thoracic position of the stomach (32 v 8, GER+ v GER-; P < .01) and GER and the prenatal diagnosis of CDH (22 v 7, GER+ v GER-; P < .01). Duration of artificial ventilation (68.97 +/- 15.33 days v 14.14 +/- 3.89 days, GER+ v GER-; P < .005) and duration of hospitalization (22.04 +/- 3.59 weeks v 3.9 +/- 0.88 weeks, GER+ v GER-; P < .0003) were significantly longer for the patients with pathological GER. To decrease the morbidity related to GER, we propose using diaphragmatic patches during hernia repair to lower the strain on the crus, and using parietal patches to lower intraabdominal pressure after reintroduction of the herniated viscera.

Female↗
PubMed1994

Combined anterior and posterior convex epiphysiodesis for progressive congenital scoliosis in children aged < or = 5 years.

Six patients aged < or = 5 years with congenital scoliosis due to vertebral malformation were treated by anterior and posterior epiphysiodesis of the convexity. In all cases the pattern of deformity was a kyphoscoliosis. The average age at operation was 3 years 6 months, average follow-up was 4 years 6 months, and average preoperative angles were 42 degrees in the frontal and 36 degrees in the sagittal plane. The fusion included the malformative zone and the superior and inferior adjacent vertebrae. Two patients had a fusion effect, three patients had a true epiphysiodesis effect, and one patient had a postoperative progression of the deformity. Epiphysiodesis of the convexity is a treatment proper for the growing period, allowing the child either to reach skeletal maturity without needing further treatment or to achieve an adequate torso height to finish the treatment with a classical vertebral arthrodesis.

Child, Preschool↗
PubMed1994

EFFECTS OF ENVIRONMENTAL TEMPERATURE ON THE METABOLIC AND ACID-BASE RESPONSES OF RAINBOW TROUT TO EXHAUSTIVE EXERCISE

In vivo experiments were conducted to determine how the physiological response to exhaustive exercise in rainbow trout (Oncorhynchus mykiss) is affected by environmental temperature. The white muscle acid&shy;base status (e.g. pH, PCO2, HCO3- and deltaH+m) and metabolite (e.g. lactate, phosphocreatine, ATP and glycogen) content, and the acid&shy;base status and lactate concentrations in the blood, were measured at rest and during recovery from burst exercise in rainbow trout acclimated to either 5 or 18 &deg;C. Trout acclimated to the warmer temperature had higher resting levels of white muscle phosphocreatine (PCr) and also utilized a greater proportion of their muscle ATP and glycogen stores during burst activity compared with trout acclimated to the colder temperature. Recovery of muscle PCr and glycogen levels was independent of acclimation temperature, but muscle ATP levels recovered faster at 18 &deg;C. Exhaustive exercise resulted in a similar lactacidosis in the muscle of trout acclimated to either temperature. In contrast, temperature had a marked influence on the lactacidosis in the blood. Blood lactate and metabolic proton concentrations following exercise were about twofold greater in fish acclimated to 18 &deg;C than in fish acclimated to 5 &deg;C. Despite the more severe acidosis and the greater lactate accumulation in the plasma of fish acclimated to warmer temperatures, the time required for recovery of these variables was similar to that at 5 &deg;C. Taken together, these results suggest that acclimation temperature does not significantly affect anaerobic capacity in rainbow trout, but may account for much of the documented variability in the dynamics of the lactacidosis in blood following exhaustive exercise in fish.

Journal Article↗
PubMed1980

Intra-hepatic percutaneous deposition of radioactive xenon (133Xe) as a means of measuring hepatic blood flow.

Percutaneous deposition of radioactive xenon in the hepatic parenchyma is suggested as a technique for estimating the hepatic blood flow. The authors applied this procedure, which can be repeated at very short intervals, twice in 5 patients suffering from schistosomiasis, and in 6 controls. The percentage of deviation from the mean was calculated by means of two measurements performed in each individual, and was less than 10% in 63.6% of the cases. Higher variations up to 30% can be attributed either to irregular liver perfusion or to oscillations due to emotional distress of the waking subject. The mean value obtained in normal control subjects was 46.7 ml/min per 100 g liver weight. No significant difference was seen between the mean values obtained in patients suffering from schistosomiasis and in the controls. The use of inert gases presents considerable advantages such as rapid diffusion and immediate elimination. However, the varying degree of fatty degeneration with its corresponding changes in the distribution coefficient between gas and tissue, restricts the use of this method in hepatic disorders.

Adult↗
PubMed1978

Plasma insulin disappearance curve after intravenous insulin injection in human hyperthyroidism.

The disappearance curves of plasma insulin after intravenous injection of unlabelled pork insulin was studied in nine young female hyperthyroid subjects with Graves' disease and eleven young female normal subjects, who served as controls. Comparison of the curves by analysis of variance did not reveal statistical differences between them (F obtained = 2.8, F F 0.05 = 4.41), implying that there was no significant differences in the transference of injected insulin from plasma to the extra-vascular space between hyper- and euthyroid subjects. The results may suggest that the metabolism of insulin is not appreciably affected in hyperthyroidism.

Adolescent↗