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Biomedical subjects

K F Lee

Publications and source records attributed to K F Lee.

At least 127 records · Page 7Linked to original sources
PubMed1990

Ca-ATPase isozyme expression in sarcoplasmic reticulum is altered by chronic stimulation of skeletal muscle.

Chronic stimulation of a predominantly fast skeletal muscle enhanced the expression of type I (slow muscle) Ca-ATPase and suppressed the expression of the type II (fast muscle) Ca-ATPase. Monoclonal antibodies IID8 and IIH11 against type I (slow) and type II (fast) isozymes respectively, were used to type the Ca-ATPases of the isolated SR (sarcoplasmic reticulum) by Western blots, and the Ca-ATPases of the muscle fibers by immunohistochemistry. Of the fibers from control muscles 80% stained for the type II isozyme and 20% for the type I isozyme. Following chronic stimulation all fibers stained for type I isozyme and none stained for type II isozyme. Ca-ATPase isozyme distribution in isolated SR confirmed this effect of chronic stimulation. The calcium uptake activities of homogenates of stimulated muscles were 22% of the control muscles. The Ca-ATPase and calcium-uptake activities of the isolated SR from stimulated muscles were, respectively, 32 and 45% of the control muscles.

Animals↗
PubMed1990

Superior myocardial preservation with modified UW solution after prolonged ischemia in the rat heart.

Cardiac transplantation remains constrained by poor graft tolerance of prolonged cold ischemia. University of Wisconsin solution has remarkably extended ischemic preservation in pancreas, kidney, and liver transplantation. To assess its efficacy in cardiac preservation, modified University of Wisconsin solution flush and storage were tested against St. Thomas' cardioplegia flush and normal saline solution storage after six hours of ischemia at 0 degrees C in 46 isolated rat hearts. After ischemia, groups were compared before and after reperfusion. After ischemia but before reperfusion, University of Wisconsin solution hearts had significantly less tissue water (3.8%), superior tissue sodium, potassium, calcium, and magnesium profiles, and elevated adenosine and inosine levels, and tended toward better histological preservation. After reperfusion, University of Wisconsin solution more effectively preserved left ventricular compliance (75% versus 35% of baseline), developed pressure (71% versus 45% of baseline), histological integrity, and tissue potassium and calcium profiles than St. Thomas' solution. The University of Wisconsin solution provided superior preservation of systolic and diastolic ventricular function, tissue histology, tissue water, and tissue electrolytes than did St. Thomas' cardioplegia and normal saline solution storage in this experimental model, and might result in improved graft tolerance of ischemia in clinical cardiac transplantation.

Adenine Nucleotides↗
PubMed1990

Altered contractile response in neonatal myocardium to citrate-phosphate-dextrose infusion.

The clinical use of citrate-phosphate-dextrose during blood-product transfusion is known to affect ionized calcium levels and can result in depression of myocardial contractility. The immature heart appears to have an intrinsic reduction in contractile state compared with the adult heart and may be more dependent on transsarcolemmal calcium flux for regulation of contraction. The myocardial contractile response to citrate infusion was compared in neonatal and adult rabbit hearts using clinically comparable citrate-phosphate-dextrose concentrations. Isovolumic left ventricular pressures were monitored in an isolated, crystalloid-perfused heart model before, during, and after 15 minutes of citrate-phosphate-dextrose infusion. Developed pressure decreased 42.1 +/- 4.9% from control within 1 minute in the neonatal group versus 24.3 +/- 4.3% in the adult group (p less than 0.02). The effect on diastolic function was paradoxical in the neonate with a 43.1 +/- 11.9% increase in end-diastolic pressure compared with a 9.7 +/- 7.8% decrease in the adult (p less than 0.01). These results indicate that the neonatal heart appears more sensitive to the myocardial effects of citrate infusion with impairment of both systolic and diastolic function. The decreased ventricular compliance in the neonate with citrate-phosphate-dextrose suggests that the myocardial effects may not be simply due to changes in ionized calcium concentration.

Animals↗
PubMed1990

Rapid cooling contracture of the myocardium. The adverse effect of prearrest cardiac hypothermia.

Hypothermic total circulatory arrest for repair of congenital heart lesions in neonates requires a period of rapid core cooling on cardiopulmonary bypass during which the myocardium is also exposed to hypothermic perfusion. Myocardial hypothermia in the nonarrested state results in an increase in contractility due to elevation of intracellular calcium levels. This study was designed to test the hypothesis that rapid myocardial cooling before cardioplegic ischemic arrest results in damage, with impaired recovery during reperfusion. Two groups of 10 rabbit hearts were perfused on an isolated Langendorff apparatus. Group N (normothermia) was perfused at 37 degrees C before 2 hours of cardioplegic ischemic arrest at 10 degrees C. Group C (cooling) was perfused at 15 degrees C in the unarrested state for 20 minutes before the same cardioplegic arrest conditions as group N. Left ventricular isovolumic pressure measurements, biochemical measurements from right ventricular biopsy specimens, and ventricular necrosis as defined by tetrazolium staining were used to compare the groups at 30 and 60 minutes of normothermic reperfusion. Developed pressure at a constant volume was preserved in group N at 90.7 +/- 4.5 mm Hg versus 76.9 +/- 6.3 in group C after reperfusion (p less than 0.05). Diastolic compliance showed significant deterioration in group C, with marked elevation of diastolic pressure during reperfusion (group N = 6.8 +/- 2.5 mm Hg versus group C = 38.9 +/- 6.1 after reperfusion; p less than 0.001). Adenosine triphosphate levels were significantly higher in group N both at end-ischemia and after reperfusion versus group C (group N = 17.0 +/- 1.1 nmol/mg protein versus group C = 7.7 +/- 1.0 after reperfusion; p less than 0.001). Group N had 0.4% +/- 0.4% necrosis of ventricular mass versus 19.3% +/- 2.2% with prearrest cooling in group C (p less than 0.0001). These results indicate that, when combined with cardioplegic ischemic arrest, rapid myocardial cooling in the unarrested state results in significant damage. The mechanism may be related to the cytosolic calcium loading effect of hypothermia that is not relieved during the subsequent period of cardioplegic arrest. Although hypothermia is an essential component to ischemic preservation, rapid cooling contracture can adversely influence cardioplegic myocardial protection.

Animals↗
PubMed1989

Differential regulation of rat beta-casein-chloramphenicol acetyltransferase fusion gene expression in transgenic mice.

Previous studies in our laboratory have demonstrated the mammary-specific expression of the entire rat beta-casein gene with 3.5 kilobases (kb) of 5' and 3.0 kb of 3' DNA in transgenic mice (Lee et al., Nucleic Acids Res. 16:1027-1041, 1988). In an attempt to localize sequences that dictate this specificity, lines of transgenic mice carrying two different rat beta-casein promoter-bacterial chloramphenicol acetyltransferase (cat) fusion genes have been established. Twenty and eight lines of transgenic mice carrying two fusion genes containing either 2.3 or 0.5 kb, respectively, of 5'-flanking DNA of the rat beta-casein gene along with noncoding exon I and 0.5 kb of intron A were identified, most of which transmitted the transgenes to their offspring in a Mendelian pattern. CAT activity was detected predominantly in the lactating mammary gland of female transgenic mice but not in the male mammary fat pad. A several-hundred-fold variation in the level of cat expression was observed in the mammary gland of different lines of mice, presumably due to the site of integration of the transgenes. CAT activity was increased in the mammary gland during development from virgin to midpregnancy and lactation. Unexpectedly, the casein-cat transgenes were also expressed in the thymus of different lines of both male and female mice, in some cases at levels equivalent to those observed in the mammary gland, and in contrast to the mammary gland, CAT activity was decreased during pregnancy and lactation in the thymus. Thus, 0.5 kb of 5'-flanking DNA of the rat beta-casein gene along with noncoding exon I and 0.5 kb of intron A are sufficient to target bacterial cat gene expression to the mammary gland of lactating mice.

Animals↗
PubMed1989

Relative contribution of promoter and intragenic sequences in the hormonal regulation of rat beta-casein transgenes.

In order to identify DNA sequences responsible for the regulation beta-casein gene expression, lines of transgenic mice bearing the entire rat beta-casein gene and two rat beta-casein promoter chloramphenicol acetyltransferase (CAT) fusion genes have been established. All three transgenes have been shown previously to be regulated in a tissue- and stage specific manner. To investigate the relative contribution of promoter and intragenic sequences in the hormonal regulation of the beta-casein gene, mammary explant cultures derived from these lines of mice have now been performed, and the effects of PRL and glucocorticoids on transgene as compared with endogenous beta-casein gene expression have been quantified. After the addition of PRL to cultures performed in the presence of insulin and glucocorticoids, a 25- to 40-fold induction of endogenous mouse beta-casein mRNA was observed after 48 hr. A comparable greater than 25-fold induction of transgene expression after PRL addition was observed in explant cultures derived from a line of mice expressing the entire rat beta-casein gene. In contrast, PRL addition elicited only a 1- to 4.5-fold increase in CAT activity in cultures derived from two lines of mice bearing casein-CAT fusion genes with either 524 or 2300 base pairs of 5'-flanking DNA. In the presence of insulin, glucocorticoid or PRL addition alone increased endogenous beta-casein gene expression 2- to 2.5-fold and 5- to 10-fold, respectively, but only a 1.2- to 2.5-fold induction of CAT activity was observed for each hormone.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Tissue-specific expression of the rat beta-casein gene in transgenic mice.

The rat beta-casein gene is a member of a small gene family, encoding the principal milk proteins. In order to understand the mechanisms by which its stage- and tissue-specific expression are regulated, initially, a 14 kb genomic clone containing the entire 7.5 kb rat beta-casein gene with 3.5 kb of 5' and 3.0 kb of 3' flanking DNA was microinjected into the germline of mice. Eight F0 transgenic mice were generated with copy numbers ranging from 1-10; five transmitted the transgene to their offspring in a Mendelian pattern. A specific RNase protection assay was developed to quantitate the level of expression of the rat beta-casein transgene as compared to the endogenous mouse beta-casein gene. Using this assay expression was demonstrated predominantly in the lactating mammary gland of transgenic mice at a level of 0.01-1% of the endogenous mouse beta-casein gene. The transgene employed the authentic transcription initiation site observed previously in the analogous rat beta-casein gene. In one line, a reduced level of expression of the transgene was also observed in the brain. The site of integration, therefore, plays an important role in influencing the level of expression of the transgene, but not its general pattern of tissue-specificity. The transgene appears to be developmentally-regulated in accordance with the endogenous mouse beta-casein gene. These lines of mice generated carrying the rat beta-casein transgene should provide useful models for studying the developmental and hormonal regulation of milk protein gene expression.

Animals↗
PubMed1988

The role of three-dimensional computed tomography in the management of maxillofacial trauma.

Open reduction and internal fixation of facial fractures demand a detailed understanding of the three-dimensional pattern of injury. This is difficult if not impossible to obtain with present radiographic methods. The purpose of this study was to define the role of three-dimensional computerized tomography (3DCT) in surgical management of facial fractures. The two-part investigation: 1) compared the diagnostic accuracy of 3DCT with conventional CT and plain film studies; and 2) examined the clinical usefulness of 3DCT to surgeons. Twenty-four acute trauma patients suspected of having facial fractures were examined radiographically with analysis of every facial bone and specific facial regions. Particular attention was directed to the course of the fracture lines and the number, size, and displacement of fracture fragments. The surgeons were then asked to conceptualize the reported and the personally observed radiographic information and document their impressions on preprinted diagrams of the facial skeleton. They also completed questionnaires designed to indicate whether patient management would be influenced by the 3DCT. The radiographic findings were correlated with intraoperative observations. The 3DCT provided superior definition of fracture lines (especially horizontal) and the extent of comminution was better appreciated. This additional information improved the surgeons' ability to plan placement of interfragmentary wires and/or plates. Surgeons were also able to more accurately predict those patients requiring immediate bone grafting. Large, life-size 3D images of the facial skeleton made intraoperative conceptualization of the injury pattern easier. The accuracy of the 3DCT images corroborated the intraoperative findings in all cases. The following conclusions are offered: 1) The diagnosis of most mandibular fractures can be made equally well with conventional and 3DCT techniques. 2) Improved diagnosis of fracture lines and the specific patterns of comminution in midface fractures is made possible with 3DCT. 3) If open reduction and internal fixation is the mode of treatment, 3DCT is desirable because the added information makes preoperative planning more accurate and thereby facilitates surgical intervention.

Facial Injuries↗
PubMed1988

The pseudodelta sign in acute head trauma.

The "delta sign" is a triangular area of high density with a low-density center seen on contrast-enhanced computerized tomography (CT) scans in the location of the superior sagittal sinus. It indicates thrombosis of the sinus. The authors describe the "pseudodelta sign," which is similar but is seen on non-contrast-enhanced CT scans and which has a high correlation with hemorrhage secondary to acute head trauma.

Acute Disease↗
PubMed1988

Immediate versus delayed coronary grafting after streptokinase treatment. Postoperative blood loss and clinical results.

Of all patients with acute evolving myocardial infarction treated surgically at Duke University Medical Center between 1984 and 1986, 27 patients given high doses (greater than 1.5 million units) of streptokinase preoperatively were studied. Eleven patients who received streptokinase had coronary bypass grafting 12 hours after thrombolytic therapy (early hours), eight patients between 12 and 72 hours (delayed), and eight patients beyond 72 hours (late hours). Seventeen patients who underwent coronary bypass grafting within 6 hours of the onset of symptoms, without preoperative streptokinase, were included as control patients. Only the patients having early operation had significantly greater postoperative blood loss; postoperative use of red blood cells; fresh-frozen plasma; cryoprecipitate; prolonged postoperative prothrombin time; and prolonged partial thromboplastin time. Patients having delayed or late operations did not differ significantly from patients not receiving streptokinase. Only the interval between time of streptokinase administration and operation could account for the coagulopathy and the postoperative bleeding complications in the early group. Patients in the early group had a higher in-hospital mortality (27% versus 6% for the non-streptokinase group) and major noncardiac morbidity (36% versus 12% for the non-streptokinase group). Patients in the delayed and late groups had minimal postoperative complications and no mortality. Observations were not explained by differences in total ischemic time, number of angioplasty failures, or number of patients with cardiogenic shock between the early group and the non-streptokinase group. Postoperative bleeding and massive use of blood products seemed to be contributory factors: Two of three deaths in the patients having early operations were associated with clinical suspicion of tamponade. Patients undergoing coronary bypass grafting within 12 hours of streptokinase therapy appear to be a high-risk group in a more emergent, uncontrolled clinical setting and require aggressive monitoring and correction of coagulopathy.

Blood Coagulation Disorders↗
PubMed1987

Acute spinal cord injury: MR imaging at 1.5 T.

Thirty-seven magnetic resonance (MR) imaging studies were performed with a 1.5-T magnet and surface coils in 27 patients with suspected spinal cord injuries. Imaging was performed 1 day to 6 weeks after injury. Cord abnormalities were seen with MR in 19 patients, while skeletal and/or ligamentous injuries were seen in 21 (78%). Three types of MR signal patterns were seen in association with cord injuries. Acute intraspinal hemorrhage was seen in five patients with cord injuries and demonstrated decreased signal intensity on T2-weighted images obtained within 24 hours of injury. Cord edema and contusion had high signal intensity on T2-weighted images and were observed in 12 cases with cord injury. Neurologic recovery, determined in 16 patients, was insignificant in patients with intraspinal hemorrhage; however, patients with cord edema or contusion recovered significant neurologic function. MR at 1.5 T is extremely useful in the diagnosis of acute cord injury and also demonstrates potential in predicting neurologic recovery.

Acute Disease↗
PubMed1987

The impact-absorbing effects of facial fractures in closed-head injuries. An analysis of 210 patients.

A series of 210 patients with facial fractures sufficiently severe to require cranial computerized tomography (CT) to evaluate suspected closed-head injury (CHI) was studied. The injuries were separated into five grades of severity based on neurological examination, including cranial CT. The injuries were also grouped into three categories based on facial regional involvement, using chi-square contingency table analysis. The data demonstrated that patients with upper facial fractures were at greatest risk for serious CHI. Injuries to both the mandibular and the midfacial regions with no upper facial involvement more frequently resulted in mild CHI with a modest likelihood of no neurological deficits. Trauma to only the mandibular region or to only the midfacial region was least likely to involve CHI.

Adult↗
PubMed1986

Interpeduncular fossa sign: CT criterion of subarachnoid hemorrhage.

A retrospective study of 100 cerebral computed tomography scans interpreted as displaying subarachnoid hemorrhage was undertaken to determine the frequency of blood in the interpeduncular fossa as a useful radiographic sign. The results indicate that the interpeduncular fossa sign is second only to blood in the Sylvian fissure-circular sulcus area as a reliable indicator of subarachnoid hemorrhage on CT scans.

Humans↗
PubMed1986

Gunshot wounds to the head: a perspective.

Craniocerebral gunshot wounds are a significant cause of injury and death in the United States. However, despite reports of occasional unexpectedly favorable outcome in surgically treated patients, these injuries have been viewed pessimistically and indeed have generally been excluded from modern studies of head injuries, which have concentrated on closed head injuries. A review of 143 victims of craniocerebral gunshot wounds admitted to Hermann Hospital, Houston, Texas, during a recent 30-month period confirmed that a few apparently neurologically devastated patients can be saved. A detailed analysis of these patients, including demographic details, general and neurological condition, anatomic injuries, laboratory findings, surgical care, neurological course, and neurological and functional outcome follows. The helpfulness of early resuscitation and appropriate criteria for surgery need to be studied using historic or randomized controls.

Adolescent↗
PubMed1985

Unilateral pupillary distortion: a case report.

A 29-year-old white man who complained of episodic pupillary distortion in his right eye brought on by strenuous exercise was found to have a segmental Horner's syndrome in association with a hypoplastic internal carotid artery.

Adult↗
PubMed1983

Chiasmal syndrome in sarcoidosis.

Four patients had involvement of the anterior visual pathway by sarcoidosis. In two cases recognition of the systemic disease was delayed because only visual symptoms were present. Three cases had evidence of hypothalamic-pituitary axis dysfunction, with histologically proved granulomatous infiltration of this region. The chiasmal syndrome in sarcoidosis is characterized by a pattern of blindness in one eye, atrophy of the optic discs, and temporal visual field loss in the contralateral eye with variable degrees of pituitary dysfunction. The condition is medically treatable and simulates the clinical and even the roentgenographic appearance of a pituitary tumor.

Adult↗