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Biomedical subjects

F C Chang

Publications and source records attributed to F C Chang.

At least 109 records · Page 6Linked to original sources
PubMed1988

Taste responses in the nucleus tractus solitarius of the chronic decerebrate rat.

The ingestive behavior of decerebrate rats has been studied for some time, yet little is known of its neural substrates. While taste fibers in rats proceed from hindbrain to thalamus and ventral forebrain, these regions return centrifugal fibers to the hindbrain by which lower-order taste activity may be influenced. We examined the functional characteristics of taste neurons in the nucleus tractus solitarii (NTS) of chronic decerebrate rats in which this reciprocal communication was disrupted and compared them with those of intact controls. Nine Wistar rats were decerebrated at the supracollicular level. After a minimum of one week recovery, they were immobilized with Flaxedil, anesthetized locally and prepared for recording. The responses of 50 taste cells were isolated bilaterally from the NTS of these animals, while the activity of 50 additional neurons was recorded from 12 intact rats under the same conditions. Taste stimuli included 7 Na-Li salts, 3 sugars, HCl and citric acids, quinine HCl and NaSaccharin. Mean spontaneous activity in decerebrates was 6.5 spikes/s, 36.0% lower than the level in intact animals. Mean evoked activity was reduced by 32.6%. Analyses of the effects of stimulus quality, intensity and time course of the responses all indicated that the decrease in activity was attributable to the inability of taste cells in decerebrate rats to respond to demands for high discharge rates. This deficit could be responsible for the failure of these animals to develop conditioned taste aversions. Neurons from decerebrate preparations did, however, retain the broad sensitivity across stimuli that characterized taste cells in intact preparations. It was also typical that most neuron response profiles from decerebrates could be grouped into 3 loose clusters with peak sensitivities to acid-salt, salt or sugar. An analysis of similarities among stimulus activity profiles indicated that Na-Li salts, sugars and an acid-quinine complex represented 3 groups of stimulus quality; in intact animals, the primary distinction was between sweet and non-sweet stimuli. Moreover, the response to sodium saccharin lost its bitter component in decerebrates. These findings were in general agreement with those derived from acute decerebrate rats.

Animals↗
PubMed1988

Methods of single unit recording from medullary neural substrates in awake, behaving guinea pigs.

An electrophysiological procedure that permits extracellular single neuronal recording in the medulla of unanesthetized, freely behaving animals is described. System components consist of 1) a flexible, single-strand microwire as recording electrode; 2) a miniature, skull-mounted miniature microdrive used for isolation of single unit activity; and 3) a head-mounted voltage follower that conditions and stabilizes the neuronal signals prior to amplification and transmission for further processing. A unique advantage of this procedure is the latitude and provision for microwire replacement in the event that multiple penetrations are desired or the tip of the microwire recording electrode is insulated as a result of gliomatosis. With minor modification, this technique can be used for single unit recording virtually anywhere along the supra-segmental neuraxis. Technical aspects of this procedure, together with details of design and fabrication of implantable devices, chronic instrumentation procedure, and potentials for other chronic applications, are discussed.

Action Potentials↗
PubMed1988

Hemoccult screening for colorectal cancer.

A community hemoccult screening project for colorectal cancer resulted in the processing of 18,198 specimens. Positive test results were reported in 3 percent of the total, which ultimately resulted in the identification of 20 colorectal malignancies (0.1 percent) and 53 benign polyps (0.3 percent). The number of malignancies and polyps identified was disappointingly low. Our findings would challenge the concept of unsupervised mass screening from the viewpoint of cost-effectiveness; however, because of the numerous voluntary services and supplies, this particular project was useful in educating the public about early colon cancer detection.

Aged↗
PubMed1988

CT of small pyogenic hepatic abscesses: the cluster sign.

Of 36 consecutive patients with pyogenic liver abscesses evaluated by CT, five (14%) had multiple small abscesses less than 2 cm in size. The CT appearance of the small pyogenic abscesses was compared with that of 10 patients who had either fungal or mycobacterial abscesses and with that of 50 patients who had hepatic metastases. In all five patients who had small pyogenic abscesses, the abscesses appeared to cluster, or aggregate, in a pattern that suggested the beginning of coalescence into a single, larger abscess cavity (cluster sign). This cluster appearance was not seen in in any of the patients who had fungal or mycobacterial microabscesses. It was present in only one of the patients who had confirmed hepatic metastasis. Despite the small size of the abscesses, guided needle aspiration was successful in recovering pyogenic organisms in four of the five patients. In our experience, the presence of the cluster sign suggests that the lesions are pyogenic abscesses.

Adolescent↗
PubMed1988

A facile one-step synthesis of delta 1,4-3-keto bile acid esters by iodoxybenzene and benzeneselenic anhydride.

A facile one-step conversion of stereoisomeric methyl 3-hydroxycholanoates to 1,4-dien-3-one, by treatment in boiling toluene with iodoxybenzene catalyzed by benzeneselenic anhydride, is described. The direct oxidation-dehydrogenation at C-3 is applicable to other cholanoates (hyodeoxycholic, chenodeoxycholic, ursodeoxycholic, deoxycholic, and cholic) when the hydroxyl groups at C-6, C-7, or C-12 are protected. Without protection at C-6 and C-7, the products from hyodeoxycholic, chenodeoxycholic, ursodeoxycholic, and cholic esters are complex mixtures, whereas, methyl deoxycholate yields the 1,4-dien-3,12-dione cleanly.

Benzene Derivatives↗
PubMed1988

Potential bile acid metabolites. 13. Improved routes to 3 beta, 6 beta- and 3 beta, 6 alpha-dihydroxy-5 beta-cholanoic acids.

New synthetic routes to three possible stereoisomers of hyodeoxycholic (3 alpha, 6 alpha-dihydroxy-5 beta-cholanic) acid are described. The principal reactions involved were inversion at C-3 of 3 alpha-hydroxy-6-oxo derivatives with diethyl azodicarboxylate-triphenylphosphine-formic acid and with N,N-dimethylformamide, without allomerization to the more stable 5 alpha form. On the basis of physical and chromatographic data, previously reported 3 beta, 6 alpha-dihydroxy-5 beta-cholanic acid and its methyl ester are shown to be C-3 epimeric mixtures. The 13C nuclear magnetic resonance spectra were of key importance in characterizing the stereoisomers and estimating their purity.

Chemical Phenomena↗
PubMed1987

Capillary gas chromatography of hydroxylated bile acid stereoisomers of the allo and normal series.

Relative retention times and methylene unit (MU) values were determined for 56 bile acids of the allo (5 alpha, A/B-trans) and normal (5 beta, A/B-cis) series, which differ from one another in the number, position and configuration of the hydroxyl groups at positions C-3, C-6, C-7 and/or C-12. The bile acids were derivatized to their methyl ester O-trimethylsilyl ethers (Me-TMS) and methyl ester O-dimethylethylsilyl ethers (Me-DMES), and chromatographed on fused-silica capillary columns, chemically bonded with non-selective OV-1 and selective PEG-20M liquid phases. Of the four possible combinations of derivatives and columns examined, Me-DMES on OV-1 and Me-TMS on PEG-20M were most suitable. The differences in the MU values between the 5 alpha- and 5 beta-series, and between the Me-DMES and Me-TMS ether derivatives, are also summarized. These retention data would be helpful in the identification of closely related bile acid stereoisomers or for estimation of their structures. photolysis.

Bile Acids and Salts↗
PubMed1987

Is nasogastric intubation necessary in colon operations?

Fifty-six patients undergoing elective colonic resection were prospectively randomized into two groups either with or without postoperative nasogastric decompression. The results demonstrated only minimal differences between the two groups. Postoperative abdominal distention was more common in patients without nasogastric tubes, whereas pulmonary complications were more common in patients with nasogastric tubes. Other morbidity and mortality and hospital stay were the same in both groups. We conclude that in elective colon operations, the routine use of postoperative nasogastric decompression is unnecessary and can safely be omitted.

Aged↗
PubMed1986

Traumatic rupture of the aorta: still a lethal injury.

A 10 year retrospective review of a community experience with blunt trauma of the aorta has been presented. We found that an overall mortality of 84 percent was associated with this injury. Fourteen patients reached the emergency department with stable vital signs. Of these patients, 10 underwent successful treatment (71 percent). Despite advances in many areas of trauma care, blunt trauma of the aorta remains a highly lethal injury. However, this review has demonstrated that with prompt diagnosis and treatment, a significant number of these patients can be salvaged. It is for this reason that we have adopted an aggressive approach toward victims of blunt trauma. We now proceed with diagnostic aortography in any patient who has undergone a significant deceleration injury.

Accidents, Traffic↗
PubMed1985

High performance liquid chromatographic separation of stereoisomeric bile acids as their UV-sensitive esters.

High performance liquid chromatographic separation of a series of mono-, di- and trihydroxylated 5 beta-cholanic acids, which differ only in position and configuration of hydroxyl groups at positions C-3, C-7 and/or C-12, is reported. The C-24 free acids were derivatized to four different classes of UV-sensitive esters, i.e., p-bromophenacyl (BP), m-methoxyphenacyl (MP), 4-nitrophthalimidemethyl (NPM) and 9-anthrylmethyl (AM) esters, and chromatographed on two variants of C18 reversed-phase columns (Nova-Pak C18 and Zorbax ODS) with methanol-water systems as mobile phase. Separation efficiency and elution order of some isomeric pairs were influenced by both the structure of the C-24 ester groups and the nature of the columns used. Excellent chromatographic properties were found for those derivatives, particularly for the NPM esters.

Bile Acids and Salts↗
PubMed1985

Incidence and associated mortality of retained common bile duct stones.

A hundred consecutive patients who underwent cholecystectomy and exploration of the common bile duct were studied. The traditional indications for exploration resulted in a yield of 55 percent positive explorations. There were nine patients with retained stones, three of whom died. The high mortality rate of patients with retained stones stresses the importance of systematic and thorough exploration of the biliary tree during initial operation. Choledochoscopy, when combined with cholangiography, may decrease the incidence of retained stones.

Adolescent↗
PubMed1985

Complications of the Angelchik antireflux prosthesis. A community experience.

The use of the Angelchik antireflux prosthesis has increased rapidly in our community since its introduction in 1979. Our experience with two patients who had serious complications associated with this prosthesis led us to review all 76 patients in our community who had undergone implantation of the device. Complications developed in 20 patients after placement of the prosthesis, and 12 of them required subsequent laparotomy for removal of the prosthesis. The complications observed were persistent dysphagia, late-onset dysphagia, transient dysphagia, persistent vomiting, esophageal obstruction, early gas bloat syndrome, gastric erosion, slippage of the prosthesis over the gastric fundus, disruption of the prosthesis, and migration of the prosthesis. Because of the frequency of potentially serious complications, we cannot recommend its use in the surgical treatment of esophageal reflux.

Adult↗
PubMed1985

Potential bile acid metabolites. 9. 3,12-Dihydroxy- and 12 beta-hydroxy-5 alpha-cholanoic acids.

Syntheses of the heretofore unreported 3 alpha, 12 beta-, 3 beta, 12 beta-dihydroxy-, and 12 beta-hydroxy-5 alpha-cholanic acids of the 5 alpha-series, their methyl esters, and some related derivatives are described. In addition, allodeoxycholic (3 alpha, 12 alpha-dihydroxy) acid was prepared by a new route. The principal reactions involved were the stereoselective reduction of C-12 ketones with an amino-borane reagent and of a C-3 ketone with K-Selectride, and inversion of a 3 beta-tosylate derivative with N,N-dimethylformamide.

Bile Acids and Salts↗
PubMed1984

Acute diverticulitis. Comparison of treatment in immunocompromised and nonimmunocompromised patients.

The clinical course and required treatment of diverticulitis were reviewed in 76 nonimmunocompromised patients and 10 immunocompromised patients. The immunocompromised patients presented with either minimal or no symptoms and findings. Therefore, to make the diagnosis of acute diverticulitis in this group, a high index of suspicion must be maintained. The required treatment varied considerably between the two groups. In 45 nonimmunocompromised patients (76 percent), medical therapy was successful. Medical treatment failed in the other 14 patients (24 percent). However, the compromised group had no patients in whom medical therapy was successful (100 percent failure rate). Thirty-one of the nonimmunocompromised patients (41 percent) required an operation, whereas 100 percent of the immunocompromised patients with acute diverticulitis required an operation. By relating postoperative complications, we were unable to determine the initial operative procedure of choice in the nonimmunocompromised group; however, in the immunocompromised group, colostomy and resection had fewer surgical complications than colostomy and drainage. The immunocompromised patient with acute diverticulitis requires operation. We believe the operation of choice is colostomy and resection of the involved segment.

Acute Disease↗