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Biomedical subjects

F C Chang

Publications and source records attributed to F C Chang.

At least 73 records · Page 4Linked to original sources
PubMed1995

The involvement of metabotropic glutamate receptors in long-term depression of N-methyl-D-aspartate receptor-mediated synaptic potential in the rat hippocampus.

The frequency-dependent long-term modifications of pharmacologically isolated N-methyl-D-aspartate (NMDA) receptor-mediated excitatory postsynaptic potential (EPSPNMDA) was studied. Intracellular recordings were obtained from CA1 cells of rat hippocampal slices and in the presence of 6-cyano-7-nitroquinoxaline-2,3-dione (10 microM) and bicuculline (20 microM) which block non-NMDA and GABAA receptors, respectively. Low-frequency stimulation at 5 Hz resulted in a long-term depression (LTD) of EPSPNMDA in 12 of 17 cells. However, when the stimulus frequency was increased to 30 Hz, a long-term potentiation (LTP) of EPSPNMDA was observed in 7 out of 9 cells. The LTD was not affected by pretreating the slices with okadaic acid (0.5-1 microM) suggesting that activation of endogenous protein phosphatase is not responsible for this process. In the presence of L-2-amino-3-phosphonopropionic acid (50 microM) or (RS)-alpha-methyl-4-carboxyphenylglycine (200 microM), 5 Hz tetanization resulted in LTP instead of LTD. These results suggest that activation of metabotropic glutamate receptor (mGluR) is necessary for the induction of EPSPNMDA LTD and blockade of mGluR unmasks a LTP.

Animals↗
PubMed1995

Spontaneous recanalization of the esophagus after exclusion using nonabsorbable staples.

Perforations of the thoracic esophagus can be fatal unless diagnosed promptly and treated effectively. Two patients in whom primary repair was not feasible were treated by esophageal exclusion and diversion using nonabsorbable stapling devices. Both patients had spontaneous recanalization of the esophagus without leakage or stricture formation. We conclude that nonabsorbable staples can be used safely to achieve effective esophageal exclusion, thereby allowing complete healing of the perforation. Furthermore, use of this technique may eliminate the necessity for another major procedure to reestablish esophageal continuity.

Adolescent↗
PubMed1995

Changing trends in the management of splenic injury.

BACKGROUND: A gradual change in the management of splenic injuries has occurred at our institution. This study was therefore undertaken to determine whether changes in management of splenic injury influenced outcomes during the past 30 years. PATIENTS AND METHODS: A retrospective study of patients admitted with splenic trauma between 1965 and 1994 was performed. Two hundred seven patients were identified and demographic and outcome data were recorded. Patients were then grouped based upon the period in which they received treatment (ie, Period I [1965 to 1974], Period II [1975 to 1984], and Period III [1985 to 1994]), and the type of treatment received (ie, splenectomy, splenorrhaphy, or observation). RESULTS: More patients were treated in Period III than in the other two periods, and Period III patients had shorter hospital stays. Splenectomy was solely used during Period I; splenorrhaphy and observation were occasionally performed during Period II; and splenectomy, splenorrhaphy, and observation were performed in near-equal numbers during Period III. Mortality was similar for each period, though Injury Severity Scores (ISS) were higher during later years. When compared by treatment modality, patients receiving splenectomy had higher ISS and splenic injury classifications. CONCLUSION: Patients treated by splenorrhaphy and observation for splenic injury have markedly increased over the past 30 years without adverse outcome.

Adult↗
PubMed1995

PASG: does it help in the management of traumatic shock?

A prospective, randomized study was designed to determine the efficacy of pneumatic antishock garment (PASG) in the treatment of traumatic shock in a medium-size urban community. A total of 291 traumatic shock patients were assigned to either the PASG or No-PASG treatment groups. Of these, data from 248 patients were analyzed in detail. Analysis of demographic factors--such as age, sex, and mechanism of injury--as well as prehospital evaluative tools--such as trauma and CRAMS scores, and injury severity scores--revealed that the two groups were well-matched. This study did not demonstrate significant differences in hospital stay or mortality between PASG and No-PASG patients. Similarly, in the subset of patients with blunt trauma, PASG was not found to be beneficial.

Adult↗
PubMed1995

Delayed hemothorax resulting from stab wounds to the internal mammary artery.

Massive delayed hemothorax as a result of stab wounds to the internal mammary artery have not recently been reported. A patient who died after such an injury prompted a 10-year retrospective review. During that time period, 88 patients with stab wounds to the chest were identified. Thirty-five of these involved injuries to the parasternal region. This region is described as being located below the clavicles, between the midclavicular lines, and above the costal margins. We identified 5 patients with internal mammary artery injuries: 4 had massive delayed bleeding and 2 died. Our current recommendations for managing stable patients with parasternal stab wounds include maintaining a high index of suspicion, intensive care monitoring, and placement of chest tubes for monitoring. Should delayed bleeding occur, a prompt thoracotomy is mandatory.

Adult↗
PubMed1995

Potential bile acid metabolites. 23. Syntheses of 3-glucosides of nonamidated and glycine- and taurine-amidated bile acids.

The 3-glucosides of nonamidated lithocholic, chenodeoxycholic, ursodeoxycholic, deoxycholic, and cholic acids, and their double conjugate forms with glycine and taurine were synthesized. The key reactions used were 1) beta-D- glucosidation at C-3 by the Koenigs-Knorr condensation reaction of 3 alpha-hydroxylated bile acid methyl (or p-nitrophenyl) esters with 1 alpha-bromo-1-deoxy-2, 3, 4, 6-tetra-O-acetyl-D-glucopyranose in the presence of cadmium carbonate in refluxing benzene; 2) indirect and direct amidations at C-24 by the activated p-nitrophenyl ester and by the diethylphosphorylcyanide methods, respectively, using glycinate ester and taurine as coupling agents; and 3) simultaneous alkaline hydrolysis of the hydroxyl-protecting and ester groups in both the sugar and aglycone moieties.

Amides↗
PubMed1994

Reversal of saxitoxin-induced cardiorespiratory failure by a burro-raised alpha-STX antibody and oxygen therapy.

Reversal of saxitoxin (STX; 10 micrograms/kg, ip) induced cardiorespiratory effects by oxygen ventilation and burro-raised alpha-STX antitoxin (60 mg/kg, i.v.) was studied in urethane-anesthetized guinea pigs acutely instrumented for concurrent monitoring of medullary respiratory-related single units, diaphragm EMG, Lead II electrocardiogram, arterial blood pressure (BP), arterial pH, and O2/CO2 tensions, electrocorticogram (ECoG), and end-tidal CO2. STX-induced cardiorespiratory effects included (1) a state of progressive bradypnea and hypercapnia; (2) a functional blockade of the diaphragm; (3) a prolongation of respiratory cycle duration; (4) an aberrant bulbar respiratory-related neuronal activity pattern; and (5) a decline in BP and heart rate. The therapeutic effect of artificial ventilation following STX-induced apnea was equivocal in that the cardiorespiratory activities, be they of central or peripheral nature, remained dysfunctional despite continued oxygen ventilation. Spontaneous breathing and cardiovascular performance following STX-induced apnea could all be promptly restored (typically in less than a minute) by combined oxygen/antitoxin therapy. Notable also was a state of uncompensated acidemia (as revealed by changes in arterial pH and CO2 tension) which persisted throughout the course of therapeutic intervention. Notwithstanding, the ventilatory frequency continued to be low, the central respiratory activity pattern remained aberrant, and the ECoG amplitudes were still depressed. In consideration of these findings, and of the large molecular weight of alpha-STX antitoxin (> 150,000 Da) which limits its entry into the CNS, we are of the opinion that the therapeutic effects of antitoxin are probably confined primarily to the periphery.

Adrenal Glands↗
PubMed1994

Kansas surgeons' attitudes toward immediate breast reconstruction: a statewide survey.

BACKGROUND: Immediate reconstruction following mastectomy provides patients the benefit of emerging from their operation with a reconstructed breast mound. METHODS: A survey was distributed to 197 Kansas surgeons to determine the frequency of breast reconstruction and to identify factors that may influence them to refer patients for immediate reconstruction. RESULTS: A response of 78.2% was obtained. Ten percent of mastectomy patients had breast reconstruction. Significant findings were that younger surgeons were more likely to discuss reconstruction with all patients and were more likely to preoperatively refer their patients to a plastic surgeon; surgeons in larger communities had more patients who had undergone immediate reconstruction; surgeons who discussed reconstruction with all patients had more patients who underwent immediate reconstruction; and frequency of immediate reconstruction increased along with increased time spent discussing reconstruction preoperatively. CONCLUSION: Our survey indicated that immediate breast reconstruction was rarely performed; however, when it was, a number of factors were correlated. These included the surgeon's age and practice location, attitude toward reconstruction, and time spent preoperatively with patients.

Adult↗
PubMed1993

Use-dependent modification of a slow NMDA receptor-mediated synaptic potential in rat amygdalar slices.

A single stimulus applied to the endopyriform nucleus evoked in 35 of the 101 basolateral amygdaloid (BLA) neurons a slow excitatory postsynaptic potential (s-EPSP) of varying latencies. The s-EPSP could be graded by changing the stimulus intensity and, on reaching the threshold, triggered action potentials. At stimulus intensity just subthreshold for evoking a spike, the s-EPSP has an average amplitude of 16.3 +/- 1.4 mV, a time to peak of 25.7 +/- 3.8 ms, and a duration of 124 +/- 14 ms. The s-EPSP was reversibly blocked by DL-2-amino-5-phosphonovaleate (DL-APV) or ketamine, indicating its mediation through N-methyl-D-aspartate (NMDA) receptor activation. However, the s-EPSP was not able to follow stimulus frequency of 1 Hz, suggesting that APV-sensitive s-EPSP is probably generated by a polysynaptic pathway. The s-EPSP was greatly enhanced by synaptic stimulation in the presence of bicuculline or in Mg(++)-free solution leading to the genesis of paroxysmal depolarizing shift (PDS). The s-EPSP can undergo robust long-term potentiation (LTP) following tetanic stimulation. These results suggest that the NMDA receptor-mediated s-EPSP may play an important role in epileptogenesis and synaptic plasticity in the amygdala.

2-Amino-5-phosphonovalerate↗
PubMed1993

Potential bile acid metabolites. 20. A new synthetic route to stereoisomeric 3,6-dihydroxy- and 6-hydroxy-5 alpha-cholanoic acids.

An improved procedure for the syntheses of stereoisomeric 3,6-dihydroxy- and 6-hydroxy-5 alpha-cholanoic acids (and their methyl esters) is described. The principal reactions employed are those reported in the preceding paper of this series, with the commercially available hyodeoxycholic acid as starting material. The final step in the procedure is the reduction of the key 5 alpha C-6 ketones with either the stereoselective equatorial reagent, Li/NH3/MeOH, or the axial reagent, Zn(BH4)2. The results of analysis of the prepared 6-monohydroxylated and 3,6-dihydroxylated stereoisomers by thin-layer chromatographic, high performance liquid chromatographic and gas-liquid chromatographic mobilities, and 1H and 13C nuclear magnetic resonance spectra are discussed along with the data for the corresponding compounds in the 5 beta-series.

Bile Acids and Salts↗
PubMed1993

Potential bile acid metabolites. 19. The epimeric 3 alpha,6,7 beta-trihydroxy- and 3 alpha,6,7 beta,12 alpha-tetrahydroxy-5 alpha-cholanoic acids.

Syntheses by a new procedure of the known 3 alpha,6 alpha,7 beta- and 3 alpha,6 beta,7 beta-trihydroxy-5 alpha-cholanoic acids, and of the once-reported analog 3 alpha,6 alpha,7 beta,12 alpha-, as well as the new 3 alpha,6 beta,7 beta,12 alpha-tetrahydroxy-5 alpha-cholanoic acids, are described. Key intermediates of the syntheses are the 6-oxo-7 beta-ols of the respective 5 alpha-cholanoic acids (and their methyl esters) prepared by allomerization at C-5 of appropriate 6-bromo-7-oxo derivatives of the corresponding 5 beta-acids. Successful reduction of the 6,7-ketols to the desired products depended on the proper choice of reagents, either Zn(BH4)2 or Li/NH3/MeOH.

Ammonia↗
PubMed1993

Central and peripheral cardio-respiratory effects of saxitoxin (STX) in urethane-anesthetized guinea-pigs.

Effects of saxitoxin (STX; 10 micrograms/kg; i.p.) on cardio-respiratory activities were evaluated in urethane-anesthetized guinea-pigs. Concurrent recordings were made of electrocorticogram (ECoG), bulbar respiratory-related unit activities, diaphragmatic electromyogram (DEMG), electrocardiogram (Lead II ECG), blood pressure, heart rate, end-tidal CO2, arterial O2/CO2 tensions, and arterial pH. The average time to STX-induced respiratory failure was about 10 min. The most striking effect prior to apnea was a state of progressive bradypnea which emerged 5-7 min after the toxin administration. Other noteworthy responses included (i) a time-dependent decrease in ECoG amplitudes which typically began before the development of a bradypneic profile; (ii) an increasing degree of diaphragm neuromuscular blockade; (iii) a state of combined hypercapnia and uncompensated acidemia; (iv) a declining blood pressure; (v) an incrementally dysfunctional myocardial performance; and (vi) an increasingly degenerative central respiratory activity profile which ultimately culminated in a complete loss of central respiratory drive. The therapeutic effect of intratracheally administered oxygen was equivocal in that the cardio-respiratory activities, be they of central of peripheral nature, remained conspicuously dysfunctional and precarious despite 100% oxygen ventilation. What can be inferred from this study is two-fold. First, STX-induced ventilatory insufficiency can be attributed to a loss of functional integrity of both central and peripheral respiratory system components. That is, although diaphragm blockade contributes significantly to STX-induced respiratory failure, analyses of single respiratory unit activity data revealed that the central respiratory rhythmogenic mechanism also appeared to play a pivotal role in the development of a bradypneic profile which promotes, and directly causes, a complete loss of respiratory drive. Second, a state of unabating depression of central respiratory activities, which seemed to be refractory to the effect of O2, suggests STX has a direct and persistent action on medullary rhythmogenic mechanisms. In conclusion, these findings indicate that both central and peripheral cardio-respiratory components are critically involved in STX-induced apnea, dysfunctional cardiovascular performance, and lethality.

Anesthesia↗
PubMed1993

Long-term enhancement of EPSP and NMDA receptor-mediated synaptic transmission in the amygdala.

An in vitro slice preparation of rat amygdala was used to study the long-term modifications of synaptic efficacy following high-frequency stimulation of the ventral endopyriform nucleus. Delivery of brief tetani to the afferent fibers led to a long-term potentiation (LTP) of the amplitude and the initial slope of excitatory postsynaptic potential (EPSP). Pretreatment the slices with DL-2-amino-5-phosphonovaleate (DL-APV, 50 microM) blocked the induction of LTP, indicating that N-methyl-D-aspartate (NMDA) receptor activation is required for induction. NMDA receptor-mediated component of synaptic response (EPSPNMDA) was isolated by application of a solution containing 6-cyano-7-nitro-quinoxaline-2,3-dione (CNQX, 10 microM) and bicuculline (20 microM). Tetanic stimulation led to a lasting potentiation of the EPSPNMDA. These results suggest that brief repetitive stimulation of afferent pathway produces forms of LTP that share many properties of LTP seen in the CA1 region of the hippocampus.

2-Amino-5-phosphonovalerate↗
PubMed1993

Hemolytic disease of the newborn caused by maternal anti-Dib: a case report in Taiwan.

Possibly the first case of hemolytic disease caused by anti-Dib in a Chinese infant is reported. The infant developed jaundice soon after birth; based on study, the jaundice has been diagnosed as a result of maternal anti-Dib which was most likely induced by previous pregnancies. The phenotype of the mother's red cells was Di (a+b-). The frequency of the Dia antigen among Chinese in Taiwan is 3.2%. In Orientals, hemolytic disease of the newborn caused by maternal anti-Dib is likely to be more severe than that caused by anti-Dia.

Blood Group Antigens↗
PubMed1992

Modification of medullary respiratory-related discharge patterns by behaviors and states of arousal.

The modulatory influences of behaviors and states of arousal on bulbar respiratory-related unit (RRU) discharge patterns were studied in an unanesthetized, freely behaving guinea pig respiratory model system. When fully instrumented, this model system permits concurrent monitoring and recording of (i) single units from either Bötzinger complex or nucleus para-ambiguus; (ii) electrocorticogram; and, (iii) diaphragmatic EMG. In addition to being used in surveys of RRU discharge patterns in freely behaving states, the model system also offered a unique opportunity in investigating the effects of pentobarbital on RRU discharge patterns before, throughout the course of, and during recovery from anesthesia. In anesthetized preparations, a particular RRU discharge pattern (such as tonic, incrementing or decrementing) typically displayed little, if any notable variation. The most striking development following pentobarbital was a state of progressive bradypnea attributable to a significantly augmented RRU cycle duration, burst duration and an increase in the RRU spike frequencies during anesthesia. In freely behaving states, medullary RRU activities rarely adhered to a fixed, immutable discharge pattern. More specifically, the temporal organization (such as burst duration, cycle duration, and the extent of modulation of within-burst spike frequencies) of RRU discharge patterns regularly showed complex and striking variations, not only with states of arousal (sleep/wakefulness, anesthesia) but also with discrete alterations in electrocorticogram (ECoG) activities and a multitude of on-going behavioral repertoires such as volitional movement, postural modification, phonation, mastication, deglutition, sniffing/exploratory behavior, alerting/startle reflexes. Only during sleep, and on occasions when the animal assumed a motionless, resting posture, could burst patterns of relatively invariable periodicity and uniform temporal attributes be observed. RRU activities during sniffing reflex is worthy of further note in that, based on power spectrum analyses of concurrently recorded ECoG activities, this particular discharge pattern was clearly associated with the activation of a 6-10 Hz theta rhythm. These findings indicated that bulbar RRU activity patterns are subject to change by not only behaviors and sleep/wakefulness cycles, but also a variety of modulatory influences and feedback/feedforward biases from other central and peripheral physiological control mechanisms.

Animals↗
PubMed1992

Pharmacological characterization of excitatory synaptic potentials in rat basolateral amygdaloid neurons.

The pharmacological properties of synaptic responses in rat basolateral amygdaloid (BLA) neurons were studied using intracellular recording techniques. Three distinct types of synaptic potential were evoked by stimulation of the adjacent ventral endopyriform nucleus: 1) a fast excitatory postsynaptic potential (f-EPSP); 2) a late EPSP (1-EPSP) following the f-EPSP; and 3) a multiphasic hyperpolarization following the initial depolarizing potential. Superfusion of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), a selective non-N-methyl-D-aspartate (non-NMDA) receptor antagonist, blocked the f-EPSP in a concentration-dependent manner. The ED50 for this effect was around 4 microM. In the presence of CNQX, however, a small depolarizing potential remained. This residual depolarizing component was markedly enhanced on removing Mg++ from the perfusing medium and could subsequently be abolished by DL-2-amino-5-phosphonovaleate (DL-APV, 50 microM) indicating its mediation via NMDA receptor-coupled ionophore. The l-EPSP was reversibly blocked by DL-APV. These results suggest that the pyriform cortex-amygdala pathway is mediated through excitatory amino acids acting on non-NMDA as well as NMDA receptors located on the BLA neurons.

2-Amino-5-phosphonovalerate↗