PubMed Health⌕ Search

Biomedical subjects

K Chun

Publications and source records attributed to K Chun.

At least 37 records · Page 2Linked to original sources
PubMed1995

Gastroschisis: a simple technique for staged silo closure.

In conjunction with the Neonatology Department at Loma Linda University Children's Hospital, a new protocol has evolved for the management of infants with gastroschisis, which obviates both risks associated with primary and staged silo closure. After stabilization of the infant in the neonatal intensive care unit, under sterile conditions, a 5- or 7-cm SILASTIC silo with a spring-loaded ring is placed over the exposed viscera, under the fascial defect. No sutures are required. A fentanyl drip is given, and the bowel is gradually reduced over the next few days. The transparent material of the silo allows for continuous monitoring of the condition of the bowel. Second-stage closure in the operating room is performed using a purse-string suture in the fascia to create a pseudoumbilicus. From October 1992 to April 1994 the authors managed 10 infants using this protocol. The results are compared with those of infants with gastroschisis treated at the same institution between August 1982 and June 1993. Outcome parameters to be compared include time until closure, time on ventilation, days of total parenteral nutrition, time until start of oral feeding, time until toleration of full-volume oral feeding, and time until discharge. The authors conclude that silo closure in the neonatal intensive care unit is simple, quick, and effective. It eliminates multiple trips to the operating room, allows the natural accommodation of the bowel into the abdominal cavity with little edema and minimal vascular compromise, and has become the authors' treatment of choice for infants with gastroschisis.

Abdominal Muscles↗
PubMed1995

Nevus sebaceus: clinical outcome and considerations for prophylactic excision.

BACKGROUND AND OBJECTIVE: Nevus sebaceus is a hamartoma of the skin with the potential to develop benign and malignant neoplasms. Prophylactic surgical excision has been advocated, usually before puberty, to prevent their occurrence; however, it is the clinical impression of the authors that the development of cutaneous neoplasms is infrequent and, if they develop, they are usually benign and nonaggressive. Our objective was to investigate the clinical outcome and histopathologic findings of every single nevus sebaceus that had been excised in our institution in a five-year period. METHODS: Two hundred and twenty-five consecutive cases, coded as nevus sebaceus corresponding to 175 patients were submitted to our institution between September 1987 and May 1992, and were identified among a total of 64,827 specimens. All cases were reviewed histopathologically and clinical information was obtained from the records. Specimens from 10 patients were excluded. RESULTS: A total of nine benign neoplasms (5.4%) were identified in the 165 patients. Three patients were in their second decade of life, two in their third, two in the fifth and two in the sixth. There were five trichoblastomas, three specimens of syringocystadenoma papilliferum, and one aprocrine cystadenoma. No malignant neoplasms were found. Six of the tumors were removed either for prophylactic or cosmetic reasons and in only three cases were the neoplasms suspected clinically and excised. CONCLUSIONS: If this same tendency prevails in other prospective studies, we strongly believe that prophylactic excision of all nevus sebaceus is not warranted. Excision should be recommended only when benign or malignant neoplasms are clinically suspected or for cosmetic considerations.

Adolescent↗
PubMed1995

Caffeine-halothane accuracy in MH testing.

The accuracy and stability of caffeine and halothane concentrations in liquid Krebs medium were examined. Caffeine-Krebs Ringer's solution in incremental concentrations from 0.25 to 10 mM (N = 8 for each concentration) was serially assayed over a three-year period. Storage was at 4 degrees C. For serial testing of halothane during a five month period, halothane 1% or 3% in carbogen was bubbled through a Krebs solution, contained in muscle baths, either using a roller pump (to eliminate vaporizer back pressure) or using carbogen at a line pressure of 4-6 lbs/in2 (27-41 kPa). Halothane in Krebs was assayed by high pressure liquid chromatography. Caffeine concentrations did not vary for 20 weeks. From then, through 60 weeks, concentrations less than 2 mM steadily diminished; after that, through 156 weeks, only 4, 8, and 10 mM were stable. When compared to the halothane concentration in gas entering the muscle baths, halothane concentration in Krebs was predictable regardless of method delivery, as long as a gas analyzer indicated the proper concentration. We conclude that caffeine solutions are stable for 20 weeks when refrigerated, and for three years at concentrations 4 mM or greater.

Caffeine↗
PubMed1995

Mutations in the X-linked E1 alpha subunit of pyruvate dehydrogenase: exon skipping, insertion of duplicate sequence, and missense mutations leading to the deficiency of the pyruvate dehydrogenase complex.

Human pyruvate dehydrogenase (PDH)-complex deficiency is an inborn error of metabolism that is extremely heterogeneous in its presentation and clinical course. In a study of 14 patients (7 females and 7 males), we have found a mutation in the coding region of the E1 alpha gene in all 14 patients. Two female patients had the same 7-bp deletion at nt 927; another female patient had a 3-bp deletion at nt 931. Another female patient was found to have a deletion of exon 6 in her cDNA. Two other female patients were found to have insertions, one of 13 bp at nt 981 and one of 46 bp at nucleotide 1078. Two male patients were found to have a 4-bp insertion at nucleotide 1163. The remaining six patients all had missense mutations. A male patient and a female patient both had an A1133G mutation. The other missense mutations were C214T, C615A, and C787G (two patients). Five of these mutations are novel mutations, five have been previously reported in other patients, and two were published observations in other patients in an E1 alpha-mutation summary. In the four cases where parent DNA was available, only one mother was found to be a carrier of the same mutation as her child.

Base Sequence↗
PubMed1994

Thumb duplication, 66 years' experience--a review of surgical complications.

Fifty-four supernumerary thumbs excisions were followed for an average of 9 years for results of their surgical management, which consisted of simple excision (16 patients), reconstructive procedures (33 patients), or central wedge resections (5 patients). Half of all simple excisions and reconstructive procedures gave unacceptable results, most were salvaged. These were primarily joint deviations, joint instabilities, and bony prominences. All of our central wedge resections gave unacceptable results that were not salvageable--short, stiff, fat thumbs with nail deformities. We feel this procedure should probably be reserved for cases where both digits of the supernumerary thumbs are severely hypoplastic.

Adolescent↗
PubMed1994

Microcirculatory failure determines lethal hepatocyte injury in ischemic/reperfused rat livers.

The contribution of microcirculatory failure to ischemia/reperfusion injury in isolated perfused rat livers was investigated using intravital epifluorescence videomicroscopy. The degree of microvascular shut-down during reperfusion was modulated by the reperfusion conditions: flow-controlled (10 ml/min), in which microcirculatory failure is minimized by maintenance of constant flow through the liver, and pressure-controlled, in which microvascular shut-down is allowed to occur. Livers underwent 60 min of ischemia, 90 min of ischemia, or no ischemia (control). Perfused sinusoids and dead hepatocytes were quantified in 10 standardized microscopic fields (9000 microns2) per liver during off-line video playback. With flow-controlled reperfusion, microvascular (sinusoid) shut-down was largely avoided; a maximum of 21% of the sinusoids failed to conduct flow. Pressure-controlled reperfusion, however, resulted in early and severe shut-down. A significant decrease of approximately 20-30% was found after 60 min of ischemia and 30 min of reperfusion, while, after 90-min ischemia and 90-min reperfusion, 90% of the sinusoids failed to conduct flow. The appearance of dead hepatocytes correlated well with the number of perfused sinusoids (r = -0.78 for flow controlled, r = -0.97 for pressure-controlled). Only an occasional dead hepatocyte was observed with control perfusion, while up to 50% stained with propidium iodide following 90-min ischemia and 90-min reperfusion under pressure-controlled conditions. These results indicate that loss of sinusoidal flow can be ameliorated by flow-controlled reperfusion; moreover, hepatocyte necrosis during reperfusion is highly dependent upon the integrity of the microcirculation.

Animals↗
PubMed1993

The relationships between transketolase, yeast pyruvate decarboxylase and pyruvate dehydrogenase of the pyruvate dehydrogenase complex.

The amino acid sequences of four thiamine pyrophosphate-requiring enzymes were aligned with the published amino acid sequence of the transketolase of Hansenula polymorpha. Sequences of the combined alpha and beta subunits of the E1 enzyme of the pyruvate dehydrogenase complexes of Homo sapiens and Bacillus stearothermophilus aligned well with the transketolase while the E1 of the pyruvate dehydrogenase complex of Escherichia coli aligned easily provided a non-aligning segment of 77 amino acids was omitted. The non-acetylating pyruvate decarboxylase of Saccharomyces cerevisiae could only be aligned if the sequence was cut in two with the C-terminus corresponding to the N-terminus of the other TPP-dependent enzymes. Using the published 2.5 A resolution of the X-ray crystal structure of Saccharomyces cerevisiae transketolase as a template we show that a hydrophobic region of the beta-subunit of the PDH E1 alpha beta enzymes likely contains a binding site for the thiazolium ring of TPP and key motifs are retained in common by all the TPP-dependent enzymes considered, which are essential for catalysis.

Amino Acid Sequence↗
PubMed1993

Gastroschisis in successive siblings: further evidence of an acquired etiology.

In recent years, we have treated two families that had successive siblings with gastroschisis. In the first family, the delivery of their second child, a boy with gastroschisis, was followed 11 months later by the delivery of a girl also with gastroschisis. The mother admitted to use of tobacco, alcohol, and marijuana during both pregnancies; the father was the same for both children. In the other family, the second child was a boy with gastroschisis, and the third, born 6 years later, was also a boy with gastroschisis. The mother denied any use of tobacco, alcohol, or recreational drugs; these two boys had different fathers. Gastroschisis in siblings has been reported only rarely, and has been noted in both identical and dizygotic twins. Our second set of siblings is the first documented case involving paternity by different fathers. Although a genetic factor cannot be excluded completely, teratogenic factors operative through the mother seem most probable. In conjunction with other reports of "epidemics" of gastroschisis, these two families amid our own recent outbreak of gastroschisis strongly suggest that the teratogenic factors may be environmental.

Abdominal Muscles↗
PubMed1993

Mutations in the X-linked E1 alpha subunit of pyruvate dehydrogenase leading to deficiency of the pyruvate dehydrogenase complex.

Human PDH complex deficiency is an extremely heterogeneous disease in its presentation and clinical course. In an investigation at the level of the gene into ten cases of PDH complex (E1) deficiency, we found that all had mutations in the coding sequence of the X-linked E1 alpha gene while the E1 beta coding sequence was normal. Six of these patients (three males, three females) had missense mutations resulting in a changed amino acid residue in the E1 alpha subunit at positions amino acid 148 (in two siblings), 170, 202, 234 and 263 of the mature protein. Two of the females had one normal E1 alpha gene and one with a deletion at the sites of tandem repeats of AGTAAGA and TAT respectively. The two remaining females also had one normal E1 alpha gene and one with an insertion. Both insertions, one of 2 bp and one of 4 bp, occurred in DNA hotspots normally associated with deletions. Only two of these ten mutations have been reported in other patients previously. In the five cases (including the two siblings) where parent DNA was available, only in one case could the same mutation be found in the patient as well as the maternal genomic DNA.

Amino Acid Sequence↗
PubMed1993

Malignant melanoma in children.

BACKGROUND: While significant risk factors for malignant melanoma may initially develop or are first seen in childhood, the actual occurrence of this neoplasm in prepubertal children is uncommon. METHODS: A retrospective study of malignant melanoma in Puerto Ricans up to 16 years of age occurring from 1973 to 1990 was carried out by identifying those cases in the Puerto Rico Cancer Registry. RESULTS: A total of seven cases were found consisting of three boys and four girls with ages ranging from 22 months to 16 years and comprising 0.94% of the total melanomas. In three of the seven cases, there was a history of a previously existent small congenital melanocytic nevus on the area. Three cases were Clark's level I, two level II, and in two cases with proved metastatic disease, Clark's level of invasion were not reported. Those cases with Clark's level I and II had a 100% 5-year survival. CONCLUSIONS: Although rare, malignant melanoma in children can be as aggressive as in adults. Among the known factors predisposing to malignant melanoma, three out of seven cases developed within a small congenital nevus, two of which occurred during the first decade of life. Due to the rarity of this event in our population, it appears unreasonable to excise all small congenital nevi during the first decade of life. Even for those who advocate excision of all small congenital nevi, the evidence at present suggests that such small nevi very rarely undergo malignant change before puberty and therefore a policy of observation in childhood and offering excision around the time of puberty is perfectly logical.

Adolescent↗
PubMed1992

Mutations and polymorphisms in the pyruvate dehydrogenase E1 alpha gene.

We present an update on mutations and polymorphisms in the human X chromosome located pyruvate dehydrogenase E1 alpha gene. A total of 20 different mutations are tabulated. The mutations include deletions, insertions, and point mutations. Certain sequences seem particularly prone to mutation. Most of the mutations are found in exons 10 and 11. Furthermore, four of the mutations are seen in unrelated patients. Little is known about how the mutations affect the structure or function of the pyruvate dehydrogenase complex.

Amino Acid Sequence↗
PubMed1992

Diagnosis and management of congenital vascular rings: a 22-year experience.

Between 1968 and 1990, we operatively treated 39 patients (19 boys, 20 girls) with congenital aortic arch anomalies. Median age was 7 months (range, 1.5 months to 23 years). Thirty-seven patients (95%) had respiratory symptoms. Barium swallow was diagnostic in 95%. Right arch with aberrant left subclavian artery and double aortic arch were the most common types (11 each). Treatment of an aortic diverticulum was documented in 19 patients; the aortic diverticulum was excised (9), managed by aortopexy (7), or left in situ (3). Postoperative recovery was rapid, with a median intensive care unit stay of 2 days, time to oral feeding of 1 day, and postoperative time to discharge of 7 days. Two deaths occurred: 1 infant had undergone emergent operation for control of hemorrhage from an aortotracheal fistula due to tracheostomy tube erosion, and the other had multiple associated congenital heart defects. Postoperative complications included bleeding (1), pneumonia (5), and chylothorax (4). One boy had persistent severe symptoms due to an untreated aortic diverticulum and underwent subsequent excision of the aortic diverticulum with complete relief of symptoms. Median length of follow-up was 12.5 months, with at least 97% of survivors completely or nearly completely free of symptoms from the vascular ring. These results suggest that early repair of congenital aortic vascular rings, including fixating or excising an associated serious aortic diverticulum, is safe and effective and allows for normal tracheal growth.

Adolescent↗
PubMed1992

Intestinal villus microcirculatory response to hemorrhage in adult and immature rats.

The response of the villus microcirculation to moderate hemorrhage was compared in adult and immature rats. As an estimate of villus blood flow, flux of red blood cells through the terminal arteriole loop at the villus tip was quantified in vivo using fluorescence epilumination videomicroscopy. Baseline red blood cell flux and mean arterial pressure (MAP) of immature rats (973 cells/s, 84 mm Hg) were significantly less than that of adults (1,435 cells/s, 131 mm Hg). Following hemorrhage of 30% of estimated blood volume, MAP of immature rats was still 24% less than that of adults; however, villus flux was not significantly different (578 cells/s immature, 640 cells/s adult; P = .63). Thus, as indicated by changes in villus flux, immature rats do not appear to be more susceptible to acute intestinal blood flow reduction induced by a single moderate hemorrhage. Immaturity of villus microvascular anatomy and of intestinal vasoregulatory mechanisms may account for the differential response.

Age Factors↗
PubMed1991

Pyruvate dehydrogenase deficiency due to a 20-bp deletion in exon II of the pyruvate dehydrogenase (PDH) E1 alpha gene.

A 20-bp deletion in the last exon of the pyruvate dehydrogenase (PDH) E1 alpha gene was found in a severely affected female patient diagnosed with PDH deficiency. PDH-complex activity in the patient's fibroblasts was 22% of that in normal controls. The mutation was characterized using PCR techniques with both patient cDNA and genomic DNA, followed by sequencing of the products. E1 beta cDNA sequence was found to be the same as that in controls. The deletion causes a frameshift and the occurrence of a premature stop codon. Western blot analysis revealed an extra band migrating just above the PDH E1 beta band. Northern blot analysis showed normal levels of both E1 alpha and E1 beta message when probed with the respective cDNAs. However, a larger intermediate-size transcript was observed for this patient in the E1 beta blot. The 20-bp deletion was not found in either parent's genomic DNA, and hence we conclude that the mutation must have occurred de novo, either in the germ-line cells or immediately following fertilization.

Amino Acid Sequence↗
PubMed1990

Isolation, characterization and chromosomal localization of cDNA clones for the E1 beta subunit of the pyruvate dehydrogenase complex.

A full-length cDNA clone for the E1 beta subunit of the human pyruvate dehydrogenase (PyrDH) complex was isolated from a human skin fibroblast cDNA library. When sequenced, it showed differences from the nucleotide sequence already published [Koike, K., Ohta, S., Urata, Y., Kagawa, Y. & Koike, M. (1988) Proc. Natl Acad. Sci. USA 85, 41-45], such that 19 amino acids were different in the translated open reading frame. Northern blotting of human fibroblast cell lines revealed a major mRNA species of 1.6 kb and a weaker band of 5.5 kb. In a series of nine PyrDH-complex-deficient cell lines from patients with this deficiency, no patients had severely reduced amounts of mRNA, but there was one patient cell line with an increased amount of abnormal-size mRNA. Chromosome localization carried out with DNA blots from man-mouse hybrid cell lines indicated that the E1 beta subunit of pyruvate dehydrogenase is located on chromosome 3. A motif AXGXXXXGL(R/K)X15(D/E)Q was found in common with a variety of other oxo-acid oxidoreductases, but its function is not known.

Amino Acid Sequence↗