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Biomedical subjects

A C Chang

Publications and source records attributed to A C Chang.

At least 163 records · Page 9Linked to original sources
PubMed1990

Accuracy of prospective two-dimensional/Doppler echocardiography in the assessment of reparative surgery.

Between January 1987 and January 1989, all 129 patients (aged 11 days to 25 years, median 39 months) undergoing both an echocardiographic examination and cardiac catheterization after reparative surgery were prospectively included in a study to assess the accuracy of combined two-dimensional and Doppler color flow imaging. The patient diagnoses were transposition of the great arteries (n = 20), tetralogy of Fallot (n = 38), coarctation of the aorta (n = 24), complete atrioventricular (AV) canal (n = 15), atrial septal defect (n = 8), ventricular septal defects (n = 3), pulmonary stenosis (n = 4), aortic stenosis (n = 8) and subaortic stenosis (n = 9). In arterial tract stenosis, there was high correlation between Doppler estimates and catheterization-derived measurements of residual right ventricular outflow tract obstruction in patients after the arterial switch operation for transposition of the great arteries (r = 0.95) as well as in patients after corrective repair of tetralogy of Fallot (r = 0.84). In semilunar/AV valve regurgitation, graded as none, mild, moderate or severe, echocardiographic estimates correlated exactly with angiographic grading in 84% and differed by one angiographic grade in the other 16%. In residual left to right shunting, no hemodynamically significant shunt was missed by echocardiography. For residual shunts at the ventricular level (n = 32), addition of Doppler color flow imaging improved the sensitivity (from 63% to 94%) and the negative predictive value (from 88% to 98%). In elevated right ventricular pressure, Doppler-derived right ventricular-right atrial pressure estimates in 24 patients correlated well with catheterization measurements (r = 0.93). Combined two-dimensional and Doppler color flow echocardiography was highly accurate in the prospective evaluation of these four types of postoperative residual.

Cardiac Catheterization↗
PubMed1990

Survival of primates in LD100 septic shock following therapy with antibody to tumor necrosis factor (TNF alpha).

The purpose of this study was to determine the efficacy of treatment with anti-TNF monoclonal antibody in preventing the deleterious effects of sepsis in a nonhuman primate. Experiments were carried out on anesthetized baboons intravenously infused with a lethal dose of Escherichia coli (E. coli). Twelve baboons (six control and six experimental) received 2 hr infusions of E. coli. The experimental group was administered a bolus of anti-TNF antibody, 15 mg/kg, 30 min after beginning the E. coli infusion. Control baboons lived an average of 19 hr (12-34 hr). All antibody-treated baboons survived more than 7 days with a significantly improved quality of life compared to the control group. Although some adverse changes occurred during the monitoring period in surviving baboons, they maintained nearly normal arterial pressures, and serum urea nitrogen and creatinine concentrations. The severe histopathologic changes in lungs, liver, adrenals, kidneys, and spleen documented at death in baboons receiving E. coli only were absent after 7 days in baboons given E. coli and early post-treatment with antibody to TNF.

Animals↗
PubMed1990

Hypoplastic left heart syndrome. Outcome after initial reconstruction and before modified Fontan procedure.

The outcome and clinical course before modified Fontan procedure were reviewed for 200 patients with hypoplastic left heart syndrome who underwent initial reconstructive surgery between August 1985 and March 1989. The median age at the time of initial reconstruction was 6 days (range, 1 day to 7.2 months). In 28 patients, a right modified Blalock-Taussig shunt was used; in 172 patients, a central shunt was placed. Additional procedures (n = 41) performed in 38 patients (median age, 5 months; range, 6 days to 17.5 months) were revision of systemic-to-pulmonary shunt (n = 15), arch reconstruction (n = 8), balloon angioplasty of arch obstruction (n = 7), atrial septectomy (n = 4), pulmonary artery angioplasty (n = 2), tricuspid valve annuloplasty or replacement (n = 4), and modified Glenn shunt (n = 1). There was no significant difference in the frequency of additional procedures performed more than 30 postoperative days in the survivors compared with the nonsurvivors. Actuarial survival rates were 0.66 (1 month), 0.48 (12 months), and 0.44 (18 months). Seventy percent of all deaths occurred during the initial admission, with 32% resulting from acute cardiovascular collapse during the first postoperative day. There was no statistical difference in actuarial survival when assessed by the type of shunt used or by anatomical subtype or when the influence of additional interventions was considered. Substantial improvement in outcome may be possible if immediate perioperative mortality can be reduced. We speculate that some of the intermediate mortality (30 days to 1 year) may be related to the effects of chronic exposure of the right ventricle to volume overload at systemic pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Actuarial Analysis↗
PubMed1989

Initiation of pro-opiomelanocortin mRNA from a normally quiescent promoter in a human small cell lung cancer cell line.

We describe the characteristics of pro-opiomelanocortin (POMC) mRNA synthesized by a human small cell lung cancer (SCLC) cell line that secretes a peptide immunoreactive with antibodies to the POMC-derived component, adrenocorticotropin. While no alteration in restriction endonuclease pattern or structure was found for the SCLC-derived pomc gene vs. the previously described human pomc gene cloned from a fetal liver library, Northern-blot analysis of SCLC RNA using pomc-derived probes showed a hybridizing transcript more than 300 nucleotides longer than POMC mRNA isolated from human pituitaries, as well as a pomc-gene-hybridizing mRNA the same length as pituitary-derived transcripts. 5' end mapping and primer extension analyses showed that the novel mRNA species is initiated at a site 371 bp upstream from the 5' end identified for pituitary-derived POMC mRNA. We conclude that synthesis of POMC transcripts occurs from an ordinarily quiescent promoter in the SCLC cell line we have studied, as well as from the pomc promoter normally used in pituitary cells.

Base Sequence↗
PubMed1989

Complementation of a Dictyostelium discoideum thymidylate synthase mutation with the mouse gene provides a new selectable marker for transformation.

A cDNA encoding mouse thymidylate synthase has been inserted 3' to the Dictyostelium discoideum actin 15 promoter in an E. coli-D.discoideum shuttle vector. When this construct was introduced into a D.discoideum thymidylate synthase mutant strain HPS400, stable transformants were obtained at high frequency. These transformants grew in standard axenic medium without requiring exogenous thymidine. This construct provides a second selectable marker for use in transformation of D.discoideum.

Animals↗
PubMed1989

Developmental expression of polypeptide PEP-19 in cerebellar cell suspensions transplanted into the cerebellum of pcd mutant mice.

Cerebellar cell suspensions were prepared from normal mouse embryos and implanted into the cerebellum of Purkinje cell degeneration (pcd) mutant mice, which are characterized by a virtually complete degeneration of Purkinje cells between postnatal day (P) 17 and P45. The expression of immunoreactivity for PEP-19, a developmentally-regulated brain-specific polypeptide, was analyzed in normal mouse cerebellum, as well as in pcd mutants with or without grafts. In the normal cerebellum, PEP-19 immunoreactivity was present in Purkinje cells. In unoperated mutants, 45 days of age or older, Purkinje cells were absent. In grafted pcd mice, numerous PEP-19 immunoreactive, neuroblast-like cells were seen in the graft at 5 days after transplantation. By 9 days, large PEP-19 immunoreactive neurons were found in the host molecular layer; by 17 days after transplantation, such neurons displayed an extensive dendritic tree and resembled differentiated Purkinje cells. The vast majority of PEP-19 immunoreactive cells was located in the molecular layer of the host at 9 days after transplantation and beyond; nonetheless, the same cells extended axonal processes toward the graft, indicating an affinity for co-grafted (possibly deep nuclei) neurons. These results point to the ability of donor Purkinje cells for survival, migration into the host brain and morphological and chemical differentiation following transplantation to the degenerated cerebellar cortex of the recipient mutants.

Animals↗
PubMed1988

Evaluation of naloxone therapy for Escherichia coli sepsis in the baboon.

This study evaluated the effects of naloxone hydrochloride in the treatment of Escherichia coli-induced shock in baboons. The baboons were studied for 12 hours and monitored for survival times. All baboons were intravenously infused for two hours with E coli and treated as follows: group 1, E coli (control); group 2, E coli plus naloxone hydrochloride, 0.5 mg/kg bolus plus 0.5 mg/kg/h for 9.5 hours; and group 3, E coli plus naloxone hydrochloride, 2.0 mg/kg bolus plus 2.0 mg/kg/h for 3.8 hours. Naloxone was administered after arterial pressure had reached the nadir (more than two hours following initiation of E coli infusion). Mean arterial pressure was supported by the lower dose of naloxone; however, sustained leukopenia and neutropenia were not reversed by its infusion. Naloxone prevented the increase in plasma beta-endorphin level and blunted the increase in plasma cortisol level. Despite these effects, naloxone did not prevent multiple-organ disease and did not decrease mortality.

Animals↗
PubMed1988

Staphylococcus aureus-induced shock: a pathophysiologic study.

The purpose of the present study was to determine the effects of lethal intravenous infusions of Staphylococcus aureus (SA) in adult dogs. Animals were maintained under anesthesia for 6 hr and observed until death following the 1-hr infusions of SA organisms. Findings unique to SA administration compared to those with Escherichia coli were the absence of significant necrosis of the mucosal intestinal glands of the small and large intestines; widespread intravascular colonization of bacteria in lung, heart, kidney and adrenal tissues often associated with neutrophil sequestration, microabscess formation, and necrosis; relative constant blood pressure, fibrinogen, fibrin degradation products (FDP), serum glutamic pyruvic transaminase (SGPT), blood (serum) urea nitrogen (BUN), creatinine, pH, and PO2, all of which remained relatively unchanged for 6 hr. Rapid early increases were observed in temperature, respiration rate, lactate, and hematocrit, while PCO2, platelet and white blood cell concentrations decreased. Results suggest unique qualitative differences in responses to Staphylococcal-induced shock compared to those caused by gram-negative bacteria.

Animals↗
PubMed1987

Erythrocyte deformability in canine septic shock and the efficacy of pentoxifylline and a leukotriene antagonist.

Decreased microcirculatory flow in the case of endotoxic shock has been extensively reported. The flexibility of the red blood cell plays an important role in tissue perfusion. The present study with a canine shock model was designed to investigate the changes in erythrocyte flow properties during septic shock. Deformabilities of canine erythrocytes were found to decrease considerably 6 hr after infusion of Escherichia coli organisms (P less than 0.05). Pretreatment of dogs with pentoxifylline reduced the effect by improving erythrocyte deformability significantly and by increasing animal survival times. The leukotriene antagonist LY171883 also increased survival time, but did not change red cell filterability. The mortality of the dogs was not affected by either pentoxifylline or the leukotriene antagonist. Both drugs aided the concentration recovery of circulating leukocytes by 6 hr post-E. coli infusion.

Acetophenones↗
PubMed1986

Sequence of the cDNA encoding porcine pro-opiomelanocortin.

Messenger RNA was extracted from porcine pituitary pars intermedia and cloned as cDNA by standard methods. The nucleotide sequence encoding porcine pro-opiomelanocortin was established from analysis of two separate cDNA segments having an overlap of 420 bases. The amino acid sequence for the porcine pro-opiomelanocortin protein, which was inferred from the cDNA sequence, was found to correspond exactly to the sequence determined by direct amino acid analysis of the component peptides of pro-opiomelanocortin; namely, the porcine hormones ACTH, beta-lipotropin, gamma-MSH and the connecting peptide. We thus find no evidence for the existence of two porcine pro-opiomelanocortin genes that differ in their coding sequences, as was suggested by the in vitro protein synthesis results of others using mRNA obtained from porcine pituitaries.

Amino Acid Sequence↗
PubMed1986

Tobramycin therapy for lethal sepsis in the dog.

Antimicrobial effectiveness and effect on survival of single-dose vs. multiple-dose aminoglycoside antibiotic therapy (with and without steroid) for lethal sepsis were evaluated. Adult dogs of either sex were anesthetized, divided into five groups, and infused iv for one hour with Escherichia coli. Group A was given no drug. Group B was given a 45-mg/kg, 10-min iv injection of tobramycin (TOB) at 65 min. Group C was given a 3-mg/kg, 10-min TOB injection at 65 min, followed by an 8.25-mg/kg iv infusion for 285 min, and three 11.25-mg/kg intramuscular injections at 6, 12, and 18 h (total 45 mg/kg). Group D was given the same TOB regimen as B, plus a 30-mg/kg iv injection and 30-mg/kg iv infusion of methylprednisolone sodium succinate (MPSS) from 15 to 360 min. Group E was given the same TOB regimen as C, plus the same MPSS regimen as D. Treated dogs also received 11.25 mg/kg of TOB daily for 4 days. The percent surviving more than 7 days was 0, 0, 17%, 83%, and 83%, for groups A through E, respectively. By 4 h, TOB-treated groups had significantly (p less than .05) lower E. coli blood levels than group A. Also E. coli levels in group B were significantly (p less than .05) lower than those in groups C, D, or E. High trough serum TOB concentrations were associated with death and very low levels with recovery. Serum urea nitrogen and creatinine concentrations increased in all groups, but returned to normal by 7 days in survivors.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Effects of prior administration of steroids upon recovery from lethal sepsis.

The effects upon survival of large doses of steroid administered to dogs prior to challenging them with lethal sepsis was evaluated in this study. Dogs were given 30 milligrams per kilogram of body weight per day of methylprednisolone sodium succinate for one, two or eight days and then were infused with 9.72 +/- 0.35 X 10(9) Escherichia coli per kilogram of body weight. All dogs in group 1 (n equals six) not given steroid died within 25 hours. Of the dogs in group 2 (n equals 12) given one or two doses of steroid previously, 42 per cent permanently survived (more than seven days). All dogs in group 3 (n equals five) given eight daily doses of steroid prior to infusion of Escherichia coli died within 17 hours. Dogs in group 4 (n equals six) were given eight daily doses of steroid prior to infusion of Escherichia coli and treated on the day of infusion of Escherichia coli with a regimen of methylprednisolone and gentamicin sulfate which results in a 100 per cent survival rate when given to dogs that have not received prior treatment with steroid. Thirty-three per cent of the dogs in group 4 permanently survived. One or two daily large doses of steroid did not detrimentally affect survival of the dogs. Eight days of steroid administration suppressed endogenous cortisol production. When the dogs were treated with six hours of steroid-antibiotic therapy, survival benefits were limited.

Adrenal Cortex Hormones↗
PubMed1985

Monoclonal antibodies to pseudorabies virus produced by mouse hybridomas.

Monoclonal antibodies to pseudorabies viral capsid protein were prepared by fusing Sp2/0-Ag14 myeloma cells with pseudorabies virus (PrV)-primed Balb/c splenocytes. These monoclonal antibodies were specific for PrV. No crossreaction with Herpes Simplex Virus (HSV, type I) or infectious bovine rhinotrachitis virus (IBR) was found. The reaction between these monoclonal antibodies and PrV was demonstrated by immunofluorescent staining technique and enzyme-linked immunoblotting assay. These antibodies could be a useful diagnostic reagent for PrV as well as a good tool for the study of the capsid protein of PrV.

Animals↗
PubMed1985

Corticosteroid/antibiotic treatment of adrenalectomized dogs challenged with lethal E. coli.

Adrenalectomized animals are extremely sensitive to endotoxin and die quickly when given small doses. A six hour administration of the corticosteroid, methylprednisolone sodium succinate (MPSS), combined with the antibiotic, gentamicin sulfate (GS), promotes complete recovery of dogs with intact adrenals administered LD100 E. coli. The aim of the present study was to determine if this early administered treatment would protect adrenalectomized dogs from overwhelming lethal doses of E. coli. Dogs were infused with MPSS from fifteen minutes to six hours after the onset of E. coli administration and with GS after administration of all E. coli. Animals given only E. coli died in 2.6 (+/- 0.3) hours, while those given no E. coli, or E. coli plus steroid/antibiotic, survived longer than 100 hours. Arterial pressure, pH, pO2, hematocrit, lactate, and glucose concentrations were maintained near control values in animals receiving steroid/antibiotic infusions. Adrenalectomized dogs infused with corticosteroid/antibiotic recovered completely from shock even though the treatment period was limited to the first 6 hours after lethal E. coli infusion. Findings indicate that animals treated with MPSS/GS after E. coli ultimately succumbed to adrenal insufficiency rather than from the E. coli insult and thus recovery from shock itself was complete.

Adrenal Cortex Hormones↗
PubMed1984

Evaluation of naloxone for therapy of Escherichia coli shock. Species differences.

Dogs and baboons were infused intravenously (IV) with Escherichia coli and treated with the opiate antagonist, naloxone hydrochloride, and the antibiotic, gentamicin sulfate, to determine the therapeutic efficacy of naloxone. Naloxone hydrochloride (2 mg/kg) was injected IV when one fourth of the E coli had been infused and then infused at 2 mg/kg/hr (six hours for dogs and 12 hours for baboons). Four of five naloxone-treated dogs survived permanently (greater than seven days), while all dogs that were given only E coli died. Arterial BP, blood glucose levels, PCO2, and PO2 were supported at higher levels and lesions of the gastrointestinal tract were prevented in naloxone-treated dogs. A steady decline in blood glucose levels after an initial hyperglycemia was observed in naloxone-treated baboons, indications of peripheral vasoconstriction were noted, and all baboons died within 42 hours.

Animals↗
PubMed1984

A fine structural study of the formation of temporary swellings (Herring bodies) and reversible degeneration of neurosecretory axons following microiontophoretic ejection of vinblastine into the hypothalamo-neurohypophysial tract of the frog (Rana pipiens).

The microiontophoretic ejection of vinblastine into the median eminence effectively blocked axonal transport in the hypothalamoneurohypophysial system of the frog. Proximal to the ejection site, large axon swellings (Herring bodies) were found that contained mainly abundant neurosecretory granulated vesicles and axonal smooth endoplasmic reticulum. At advanced post ejection times, autophagic events were obvious. Subsequently, preexperimental conditions were reestablished, indicative of the resumption of axonal transport. Distal to the ejection site, i.e. in the neural lobe, the relatively long block of axonal transport subsequent to the vinblastine ejection caused most axons to degenerate and to be phagocytized by pituicytes. The degenerative process was reversible since upon reestablishment of the axonal transport regeneration of the neurosecretory fibers occurred.

Animals↗
PubMed1984

Musculoskeletal sporotrichosis.

Sporotrichosis is a chronic, indolent, fungal infection that rarely involves the musculoskeletal system. The etiologic agent, Sporothrix schenckii, is ubiquitous in nature and has been isolated from soil, timber, decaying vegetation, and a variety of foliage. The organism gains entrance to the body through trauma to the skin or, in rare instances, by inhalation. The vast majority of infections in humans is characterized by nodular or ulcerated lesions of the cutaneous tissues and adjacent lymphatics. Osteoarticular involvement may occur either by contiguous spread from a cutaneous focus, through direct inoculation of tissue by the organism, or by hematogenous dissemination. The rarity of musculosketetal sporotrichosis often causes a delay in diagnosis which leads to inappropriate therapy and permanent deformity in some patients. Three cases which show a spectrum of bone and joint involvement are presented.

Aged↗