Search PubMed⌕ Search

Biomedical subjects

C Lincoln

Publications and source records attributed to C Lincoln.

At least 55 records · Page 3Linked to original sources
PubMed1996

Negative-pressure ventilation improves cardiac output after right heart surgery.

BACKGROUND: A low cardiac output state can complicate the postoperative course of patients undergoing Fontan-type operations and tetralogy of Fallot repair. METHODS AND RESULTS: We investigated the effect of negative-pressure ventilation on cardiac output in 11 children in the early postoperative period after right heart surgery. All patients were initially ventilated with volume-cycled intermittent positive-pressure ventilation, and negative-pressure ventilation was delivered with the Hayek external high-frequency oscillator. Cardiac output was calculated by the direct Fick method, oxygen consumption being measured by respiratory mass spectrometry. Cardiac output was measured during intermittent positive-pressure ventilation and after 15 minutes of negative-pressure ventilation. Negative-pressure ventilation improved the cardiac output by a mean of 46% (P = .005). Heart rate did not change, and stroke volume increased by a mean of 48.5% (P = .005). Mixed venous saturation increased by 4.6% (P < .02), and consequently arteriovenous oxygen content difference fell significantly (P = .01). The systemic and pulmonary vascular resistances were reduced significantly during negative-pressure ventilation (P < .05 and P < .03, respectively). CONCLUSIONS: Negative-pressure ventilation improves cardiac output in children after total cavopulmonary connection and tetralogy of Fallot repair and may prove to be an important therapeutic option in children with the low cardiac output state.

Adolescent↗
PubMed1996

Anomalous origin of left coronary artery. Evolution of surgical treatment.

OBJECTIVE: To evaluate contemporary surgical techniques in the correction of anomalous origin of the left coronary artery from the pulmonary artery. METHODS: Eleven infants were operated upon during a ten year period by one surgeon. The anomalous coronary artery arose from the main pulmonary artery in ten and the right pulmonary artery in one patient. Direct reimplantation used in eight and the intra-pulmonary artery tunnel technique in three. Delayed sternal closure was used in the immediate post-operative period in five patients. RESULTS: There were no deaths within the 30 day post-operative period. At cardiac catheterisation and coronary angiography in seven patients, six showed normal left ventricular function and serial improvement of left ventricular shortening fractions. Pulmonary artery obstruction and aortopulmonary communications were observed in two patients in which the tunnel technique was used. One patient has required transplantation of the heart. CONCLUSION: Direct reimplantation is probably always possible and is the operation of choice. In the short and intermediate term there is improvement of left ventricular function in most patients.

Cardiac Surgical Procedures↗
PubMed1996

KNAT1 induces lobed leaves with ectopic meristems when overexpressed in Arabidopsis.

Plant development depends on the activity of apical meristems, which are groups of indeterminate cells whose derivatives elaborate the organs of the mature plant. Studies of knotted1 (kn1) and related gene family members have determined potential roles for homeobox genes in the function of shoot meristems. The Arabidopsis kn1-like gene, KNAT1, is expressed in the shoot apical meristem and not in determinate organs. Here, we show that ectopic expression of KNAT1 in Arabidopsis transforms simple leaves into lobed leaves. The lobes initiate in the position of serrations yet have features of leaves, such as stipules, which form in the sinus, the region at the base of two lobes. Ectopic meristems also arise in the sinus region close to veins. Identity of the meristem, that is, vegetative or floral, depends on whether the meristem develops on a rosette or cauline leaf, respectively. Using in situ hybridization, we analyzed the expression of KNAT1 and another kn1-like homeobox gene, SHOOT MERISTEMLESS, in cauliflower mosaic virus 35S::KNAT1 transformants. KNAT1 expression is strong in vasculature, possibly explaining the proximity of the ectopic meristems to veins. After leaf cells have formed a layered meristem, SHOOT MERISTEMLESS expression begins in only a subset of these cells, demonstrating that KNAT1 is sufficient to induce meristems in the leaf. The shootlike features of the lobed leaves are consistent with the normal domain of KNAT1's expression and further suggest that kn1-related genes may have played a role in the evolution of leaf diversity.

Arabidopsis↗
PubMed1995

Three-dimensional echocardiography can simulate intraoperative visualization of congenitally malformed hearts.

BACKGROUND: The new technique of three-dimensional echocardiography can display the studied anatomy in any desired view plane. We sought to establish whether the reconstructions produced could provide views of the heart comparable with those obtained by the surgeon in the operating room. METHODS: Ninety-four patients, aged 1 day to 19 years (mean, 4.3 years), were examined. The ultrasound probe was placed either on the chest or subcostally and acquired 80 to 100 perpendicular parallel images of the heart with electrocardiographic and respiratory gating. Any plane, in particular oblique planes, within the data set can be analyzed. Whenever possible, the arrangement as seen by the surgeon was photographed, or heart specimens with similar intracardiac lesions were cut to simulate the view of the surgeons, to validate the echo-cardiographic reconstructions. RESULTS: Three-dimensional reconstruction of perimembranous ventricular septal defects, atrial septal defects, or anomalies of the atrioventricular valves could be displayed as viewed through an atriotomy. In similar fashion, reconstructions of muscular or doubly committed ventricular septal defects, along with obstruction of the right ventricular outflow tract, could be prepared as seen through a right ventriculotomy. Obstruction of the left ventricular outflow tract was shown as viewed through an aortotomy. Transthoracic three-dimensional echocardiography provided additional information in the prospective diagnosis of supravalvar mitral membrane, doubly committed subarterial ventricular septal defect, and subaortic stenosis caused by a restrictive ventricular septal defect in double inlet left ventricle. CONCLUSIONS: Three-dimensional echocardiography can simulate the display of the heart as seen by the surgeon in the operating room, and therefore can aid in better planning of surgical repair.

Adolescent↗
PubMed1995

The AXR1 and AUX1 genes of Arabidopsis function in separate auxin-response pathways.

The recessive mutations aux1 and axr1 of Arabidopsis confer resistance to the plant hormone auxin. The axr1 mutants display a variety of morphological defects. In contrast, the only morphological defect observed in aux1 mutants is a loss of root gravitropism. To learn more about the function of these genes in auxin response, the expression of the auxin-regulated gene SAUR-AC1 in mutant and wild-type plants has been examined. It has been found that axr1 plants display a pronounced deficiency in auxin-induced accumulation of SAUR-AC1 mRNA in seedlings as well as rosette leaves and mature roots. In contrast, the aux1 mutation has a modest effect on auxin induction of SAUR-AC1. To determine if the AUX1 and AXR1 genes interact to facilitate auxin response, plants which are homozygous for both aux1 and axr1 mutations have been constructed and characterized. The two mutations are additive in their effects on auxin response, suggesting that each mutation confers resistance by a different mechanism. However, the morphology of double mutant plants indicates that there is an inter-action between the AXR1 and AUX1 genes. In mature plants, the aux1-7 mutation acts to partially suppress the morphological defects conferred by the axr1-12 mutation. This suppression is not accompanied by an increase in auxin response, as measured by SAUR-AC1 expression, suggesting that the interaction between the AUX1 and AXR1 genes is indirect.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1994

Anatomic correction for post-mustard pulmonary venous obstruction.

Pulmonary artery banding and arterial switch operation as a two-stage approach have offered a surgical solution to the failing right ventricle after intraatrial repair of the transposition of the great arteries. Banding of the pulmonary artery increases the resistance to the left ventricular output and, therefore, "prepares" the left ventricle for supporting the systemic circulation and arterial switch operation. We report a case of anatomic correction for transposition of the great arteries after intraatrial repair (Mustard's operation) in which the left ventricle was retrained serendipitously as a consequence of pulmonary venous obstruction complicating Mustard's procedure.

Child↗
PubMed1994

Thromboembolism after the Fontan procedure and its modifications.

The frequency of thromboembolism after the Fontan procedure has not been specifically addressed. Seventy patients underwent this operation between 1987 and 1992, and complete information was available on 64. Forty-five had a right atrium-pulmonary artery anastomosis, 17 had a total cavopulmonary connection, and 2 had a right atrium-right ventricle anastomosis. No patient received anticoagulants for more than 8 months postoperatively. Seven patients died in the early postoperative period (< 30 days). Ten cases of thromboembolism were identified in the follow-up, which ranged from 6 to 55 months (mean follow-up, 24.5 +/- 17 months). They occurred 7 days to 4.5 years after the Fontan repair. Seven thombi were on the systemic venous or pulmonary aspect of the circulation and three, on the systemic arterial aspect. Freedom from thromboembolism was 75% at 4 years. We conclude that thromboembolism is common after the Fontan procedure; it can occur several days to years postoperatively; it is an important cause of morbidity; and it may partly explain late death after the Fontan operation. Our data suggest that all patients undergoing this procedure require long-term anticoagulant therapy.

Anticoagulants↗
PubMed1994

A knotted1-like homeobox gene in Arabidopsis is expressed in the vegetative meristem and dramatically alters leaf morphology when overexpressed in transgenic plants.

The homeobox gene knotted1 (kn1) was first isolated by transposon tagging a dominant leaf mutant in maize. Related maize genes, isolated by virtue of sequence conservation within the homeobox, fall into two classes based on sequence similarity and expression patterns. Here, we report the characterization of two genes, KNAT1 and KNAT2 (for knotted-like from Arabidopsis thaliana) that were cloned from Arabidopsis using the kn1 homeobox as a heterologous probe. The homeodomains of KNAT1 and KNAT2 are very similar to the homeodomains of proteins encoded by class 1 maize genes, ranging from 78 to 95% amino acid identity. Overall, the deduced KNAT1 and KNAT2 proteins share amino acid identities of 53 and 40%, respectively, with the KN1 protein. Intron positions are also fairly well conserved among KNAT1, KNAT2, and kn1. Based on in situ hybridization analysis, the expression pattern of KNAT1 during vegetative development is similar to that of class 1 maize genes. In the shoot apex, KNAT1 transcript is localized primarily to the shoot apical meristem; down-regulation of expression occurs as leaf primordia are initiated. In contrast to the expression of class 1 maize genes in floral and inflorescence meristems, the expression of KNAT1 in the shoot meristem decreases during the floral transition and is restricted to the cortex of the inflorescence stem. Transgenic Arabidopsis plants carrying the KNAT1 cDNA and the kn1 cDNA fused to the cauliflower mosaic virus 35S promoter were generated. Misexpression of KNAT1 and kn1 resulted in highly abnormal leaf morphology that included severely lobed leaves. The expression pattern of KNAT1 in the shoot meristem combined with the results of transgenic overexpression experiments supports the hypothesis that class 1 kn1-like genes play a role in morphogenesis.

Amino Acid Sequence↗
PubMed1994

Spatiotemporal relation between gap junctions and fascia adherens junctions during postnatal development of human ventricular myocardium.

BACKGROUND: The growing postnatal human heart maintains electromechanical function while undergoing substantial changes of cellular topology and myocardial architecture. The capacity for growth and remodeling of ventricular myocardium in adaptation to the hemodynamic changes of early infancy later declines. This decline is associated with changes in electromechanical properties of the myocardium, which suggest that the electrical and mechanical interactions between the myocytes may change in an age-dependent manner. Thus, reduction in the capacity for myocardial growth and adaptability may relate to age-dependent alterations in the patterns of the intercellular junctions that mediate electrical and mechanical coupling. We therefore examined the hypotheses that (1) age-dependent changes in the distribution patterns of gap junctions and fasciae adherentes, the intercellular junctions responsible, respectively, for electrical and mechanical coupling, accompany postnatal development in the human heart and that (2) such changes continue into the first few years of childhood. Further, the spatial relation between the two types of junction, for which a close association has been hypothesized as necessary, was explored. METHODS AND RESULTS: Ventricular myocardial gap-junction distribution was investigated in 23 pediatric surgical patients (4 weeks to 15 years old) by quantitative immunohistochemical localization of the principal cardiac gap-junctional protein, connexin43, using confocal microscopy. Immunolocalization of fascia adherens junctions by labeling N-cadherin, and correlative immunogold and standard electron microscopy, were performed in parallel. In the neonate, connexin43 gap junctions have a punctate distribution over the entire surface of the ventricular myocytes. With advancing age, gap junctions become progressively confined to the transverse terminals of the cell, ie, toward the distribution within the intercalated disk characteristic of the adult ventricle. The transversely arrayed proportion of gap-junctional label showed a linear increase with age (R = .88, P < .001), reaching the adult pattern at about 6 years, and the fascia adherens junctions showed a similar progression. Electron microscopy confirmed the changing pattern of junctional contacts and demonstrated that initially gap junctions and adhering junctions are frequently not closely adjacent but become increasingly so with maturation of the intercalated disk. CONCLUSIONS: Changes in the spatiotemporal patterns of the intercellular junctions responsible for electrical and mechanical coupling are closely coordinated in postnatal human ventricular myocardium and continue to about 6 years of age. Over this period there is a close and increasing association between the gap junctions and fascia adherens junctions. These changes in the distribution of intercellular electrical and adhering junctions may parallel the changing functional requirements of the ventricle, from a distribution that facilitates the remodeling necessitated by rapid growth and changing hemodynamics to that of the relatively stable and rapidly conducting adult myocardium. These age-related changes may also diminish the ability for appropriate myocardial remodeling in response to physiological, pathological, or surgical hemodynamic alterations.

Adolescent↗
PubMed1993

Cerebral lactate release after circulatory arrest but not after low flow in pediatric heart operations.

Arteriovenous (jugular bulb) differences in blood lactate were followed throughout the procedure and until 18 hours postoperatively in 17 children undergoing congenital heart operations during profound hypothermia. Transcranial Doppler sonography was used to monitor changes in blood flow velocity in the middle cerebral artery. Ten children had a period of total circulatory arrest (39 +/- 6 minutes) during profound hypothermia (arrest group). Another 7 children had continuous but reduced pump flow (0.6 to 1.2 L/m2) throughout hypothermic cardiopulmonary bypass (low-flow group). The mean age was 7.3 +/- 1.3 months in the arrest group and 7.9 +/- 2.2 months in the low-flow group. The mean time on bypass was 90 +/- 10 minutes in the arrest group and 75 +/- 9 minutes in the low-flow group. The velocity of blood flow in the middle cerebral artery decreased significantly (p < 0.05) in both groups to less than 50% of the preoperative level during hypothermia and increased during and after rewarming. Differences in blood lactate level were significantly less than zero (p < 0.05) from the start of rewarming until 3 hours after the end of cardiopulmonary bypass in the arrest group, whereas differences in blood lactate level remained close to zero in the low-flow group. We conclude that circulatory arrest during profound hypothermia is followed by a period with release of lactate from the brain, indicating anaerobic cerebral metabolism and possibly disturbed cerebral aerobic metabolism. This study argues for the avoidance of circulatory arrest whenever possible.

Blood Flow Velocity↗
PubMed1993

Cytokine production and hemofiltration in children undergoing cardiopulmonary bypass.

Multiorgan dysfunction still occurs after cardiopulmonary bypass and remains a major cause of morbidity and mortality, especially in the pediatric age group. This is consequent upon the so-called systemic inflammatory response to bypass with an increase in inflammatory mediators. Hemofiltration may be able to attenuate the effects of this response by elimination of some or all of these mediators. We undertook a prospective, randomized study to investigate the effect of hemofiltration on plasma levels of the cytokines tumor necrosis factor alpha, interleukin-8, and interleukin 6 in 18 infants and children undergoing deep hypothermic bypass. Serial plasma samples were taken before, during, and after bypass. Assay of the plasma samples revealed presence of the cytokines in a number of subjects in both groups, in some cases before operation. There were significant reductions in levels of tumor necrosis factor after hemofiltration, with no reduction noted in the group not undergoing hemofiltration. A similar difference (p < 0.05) was detected in the levels of interleukin-6 between the two groups after bypass, although this was largely due to changes in 2 subjects. Interleukin-8 was detected in a small number of subjects insufficient for statistical analysis, but with higher values in the group undergoing hemofiltration. We conclude that hemofiltration has the potential to remove cytokines from the circulation, with consequent beneficial effects.

Cardiopulmonary Bypass↗
PubMed1993

Absent diastolic cerebral blood flow velocity after circulatory arrest but not after low flow in infants.

It is controversial whether profound hypothermia (15 degrees C) provides adequate cerebral protection during a limited period of total circulatory arrest during pediatric cardiac surgery. In the present study, transcranial Doppler echography was used to monitor the blood flow velocity (BFV) pattern in the middle cerebral artery (MCA). The purpose of the study was to investigate the influence of a period of circulatory arrest on MCA BFV, as judged from the reperfusion flow velocity pattern. The MCA BFV was studied in 22 small children undergoing profound hypothermic cardiac operations after induction of anesthesia. Twelve of the children had a period of profound hypothermic circulatory arrest (15 to 74 minutes; arrest group). Circulation was maintained in the remaining 10 children (nonarrest group). Time-averaged MCA BFV was decreased and diastolic BFV was absent immediately after cardiopulmonary bypass in 10 of 12 children in the arrest group. In contrast, only 1 of 10 patients in the nonarrest group (p < 0.05) showed this pattern. Diastolic BFV normalized 54 to 328 minutes after the arrest in the arrest group. Circulatory arrest during profound hypothermia is followed by a period of low cerebral perfusion, whereby time-averaged MCA BFV is decreased and MCA BFV is absent during diastole. We speculate that this can be explained by an increase in intracranial pressure after brain edema.

Blood Flow Velocity↗
PubMed1992

Morphology of the posterior junctional area in atrioventricular septal defects.

The location and size of the coronary sinus in hearts with atrioventricular septal defect were investigated in relation to the known disposition of the atrioventricular conduction axis. We examined the morphology in 40 hearts and supplemented this series with two other hearts that had been serially sectioned previously. The coronary sinus received drainage from a persistent left superior caval vein in 5 hearts. Six cases of 40 had malalignment of the septal structures relative to the crux of the heart. In these, the conduction axis was anticipated to course in the position where the inlet ventricular septum met the atrioventricular junction. The coronary sinus terminated in the left atrium in 4 hearts: 2 in the morphological series and 2 that were sectioned for histological studies. The sectioned hearts showed the atrioventricular conduction axis in the usual position for the defect, unrelated to the coronary sinus. The principle that the node and penetrating bundle are located at the intersection of the ventricular septum with the atrioventricular junction holds good despite the variability of the coronary sinus.

Adolescent↗
PubMed1992

Hormone-resistant mutants of Arabidopsis have an attenuated response to agrobacterium strains.

We have examined the response of the hormone-resistant mutants axr1 and axr2 of Arabidopsis thaliana to inoculation by Agrobacterium tumefaciens and Agrobacterium rhizogenes. Our results indicate that recessive mutations in the axr1 gene affect the frequency of tumor formation after inoculation with either Agrobacterium strain. In addition, tumors produced on axr1 plants were smaller than those growing on wild-type plants. These results indicate that the product of the AXR1 gene is important for both crown gall and hairy root tumor formation. In contrast, the dominant axr2 mutation has a more severe effect on the development of crown gall tumors than on hairy root tumors. Crown gall tumors produced on axr2 plants had a different morphology than wild-type tumors and did not grow when they were removed from the explant. In contrast, a large number of hairy root tumors were produced on wild-type and axr2 plants, and both types of tumors grew when they were removed from the explant. Like the roots of axr2 plants, roots produced on axr2 explants lacked root hairs.

Journal Article↗
PubMed1992

Prenatal pericardiocentesis: its role in the management of intrapericardial teratoma.

A fetus with intrapericardial teratoma had a large pericardial effusion diagnosed by echocardiography. Cardiac tamponade, a common cause of fetal death, was averted by intrauterine pericardiocentesis. Planned obstetric and neonatal management permitted surgical treatment before cardiorespiratory distress developed. The tumor was completely excised and the infant is asymptomatic.

Adult↗