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Biomedical subjects

Y C Lai

Publications and source records attributed to Y C Lai.

At least 55 records · Page 3Linked to original sources
PubMed1998

Difficult pulmonary artery catheterization in a patient with persistent left superior vena cava.

A persistent left superior vena cava is an uncommon congenital abnormality. It arises when the left anterior cardinal vein fails to regress during the embryonic period. Although such patients are usually asymptomatic, they may have associated cardiovascular abnormalities. The anaesthetist may encounter difficulty in the insertion of pulmonary artery catheters. Other implications in the management of these patients in the operating theatre or intensive care unit are discussed.

Aged↗
PubMed1998

Plasma levels of antioxidant vitamins, selenium, total sulfhydryl groups and oxidative products in ischemic-stroke patients as compared to matched controls in Taiwan.

The possible involvement of oxidative damage and antioxidant protection has been suggested in the pathogenesis of stroke which is the second-leading cause of death in Taiwan. In this study we investigated the relationship between ischemic stroke and plasma status of antioxidants and oxidative products. Plasma levels of vitamin A, alpha-tocopherol, carotenoids, selenium (Se), total SH groups (T-SH), thiobarbituric acid-reactive substances (TBARS) and protein carbonyl, a marker of protein damage, were determined in ischemic-stroke patients (n = 36, blood sampled within 24 hrs after the clinical event) in comparison with 21 matched controls. The cholesterol-adjusted carotenoids and vitamin E were significantly lower (P < 0.05) in the plasma of ischemic-stroke patients than those of the controls. TBARS were higher (P < 0.05) in the patients than in the controls but Se, T-SH and protein carbonyls were not significantly different between the two groups. Separation of the patients into small-artery ischemic stroke (SAIS, n = 17) and large-artery ischemic stroke (LAIS, n = 19) groups revealed that both carotenoids/cholesterol and vitamin E/cholesterol ratios were significantly lower in both LAIS and SAIS groups than the controls (n = 21) while vitamin A/cholesterol was not different among the three groups. TBARS were only significantly higher in the LAIS group. The results demonstrated that, within 24 hrs after the clinical event, the acute-ischemic stroke patients had lowered levels of cholesterol-adjusted carotenoids and alpha-tocopherol but elevated levels of TBARS in the plasma as compared to the matched controls. It remains to be resolved as to whether enhanced lipid peroxidation is a cause or a result of lowered antioxidants in ischemic stroke.

Adult↗
PubMed1998

Predictors of long-term outcome in severe head injury.

Severe head injury is associated with significant morbidity and mortality. We conducted a retrospective study to assess the long-term outcome of these patients using the Glasgow Outcome Score (GOS) and evaluate the variables that might predict outcome. Data were collected from all post-traumatic neurosurgical patients with severe head injury (Glasgow Coma Scale 8 or less) admitted to the Surgical Intensive Care Unit over a 29-month period. The long-term outcome was assessed one year after the injury by a telephone interview or a review of the hospital records. Seventy patients satisfied the criteria for the study. The male to female ratio was 9:1. The mean age of the patients was 37 (range 17 to 84) years. The overall mortality was 50%. Patients with a poor outcome (defined as GOS scores of 1 to 3) had a significantly higher mean age, higher Acute Physiology and Chronic Health Evaluation (APACHE) II score and a lower Glasgow Coma Scale than those with a good outcome (GOS 4 to 5). The APACHE II score correlated better with outcome than the Glasgow Coma Scale or age. The APACHE II score may be used to prognosticate the long-term outcome in severe head injury.

APACHE↗
PubMed1997

Surface wettability enhancement of silicone hydrogel lenses by processing with polar plastic molds.

In the quest for hydrogel contact lenses with improved extended wear capability, the use of siloxane moieties in the lens materials was investigated. However, the introduction of hydrophobic siloxane groups gave rise to wettability and lipidlike deposit problems. It was found that when polysiloxane-based compositions for hydrogels were processed with polar plastic molds, such as those fabricated from an acrylonitrile-based polymer, the hydrogel lenses fabricated were wettable, with minimized lipidlike deposits. These findings were supported by the wettability of silicone hydrogel films, silicon, and nitrogen element contents near lens surfaces, as well as the results from clinical assessment of silicone hydrogel lenses.

Contact Lenses, Extended-Wear↗
PubMed1996

The importance of the helix 2 region for the cis-cleaving and trans-cleaving activities of hepatitis delta virus ribozymes.

The sequence, secondary structure, and size requirements of the helix 2 region (H2) of a cis-acting hepatitis delta virus ribozyme Rz 1 were examined in this study. Mutational analysis was performed, and the cleavage rate of each H2 mutant of Rz 1 was assayed. We found that H2 could be elongated to twice its original size without affecting ribozyme folding while the shortening of H2 by one base pair severely decreased autolytic activity. In addition, the maintenance of the Watson-Crick base-pairing interactions of the last base pair of H2 (A16U58) was not critical for cis-cleavage reaction. Nevertheless, mutants with an AA, an AG, an AC, or a GG pair at the bottom of H2 were less active, and the sequence of the H2/H3 interface might affect the stability of the catalytic core. The negative effects on ribozyme folding, such as the destabilization of H2, the unfavorable sequences at the last base pair of H2 as well as the disruption of the continuity of H2 and H3, could be compensated for by elongating the H2 region of the corresponding mutants. The extension of H2 may alter the conformation of ribozyme molecules; in addition, it stabilized the catalytic core and enhanced the resistance to formamide. Finally, for a trans-acting ribozyme and its substrate that require the formation of H1, H2, and H4 to reconstitute the autocatalytic domain of HDV RNA, the extension of H2 stabilized the substrate/ribozyme complex and speeded up the cleavage rate but hindered the product release process.

Base Sequence↗
PubMed1996

Effects of circular permutation on the cis-cleavage reaction of a hepatitis delta virus ribozyme: application to trans-acting ribozyme design.

In this study we investigated the effects of the relocation of the wild type termini on the folding of a cis-cleaving RNA Rz 1 that was modified from the autolytic domains of hepatitis delta virus (HDV) RNA. Ten circularly permuted (CP) isomers of this ribozyme were synthesized. The structure homogeneity of RNA molecules, the molar ratio of the active species that undergoes cis-cleavage, and the rate of cis-cleavage were examined for each construct. CP isomers with new termini in H1 or at the junction of H2-H3, H1-J1/4, J1/4-H4, or H4-J4/2 of the proposed pseudoknot-like structure were inactive. The single breaks of phosphodiester bond in H2, J1/2, Lp4, and at the 3'-end of Lp3 decreased but did not abolish autolytic activity. The structural heterogeneity of RNA molecules may account for the limited cis-cleavage of the latter three isomers. The findings of circular permutation analysis were used as the basis for designing an active trans-cleaving ribozyme by dividing the cis-cleaving ribozyme into two subdomains at J1/2 and Lp4. The ribozyme subdomain catalyzed the site-specific cleavage of the circularly permuted composite substrate RNA in trans. Thus, the structure of HDV autolytic domain could be re-formed after two subdomains were associated through the base-pairing interactions of H1, H2, and H4.

Base Sequence↗
PubMed1994

Stenosis of pulmonary veins with ventricular septal defect: visualization of the pulmonary veins after pulmonary arterial banding.

A case of 'absent' left pulmonary vein with ventricular septal defect was diagnosed based on echocardiography, magnetic resonance imaging and cardiac catheterization at newborn stage. Pulmonary arterial banding was performed at the age of 1 month to ameliorate the pulmonary flow. At a cardiac catheterization 1 year later, the left pulmonary veins were visualized with moderate stenosis at their entrance into the left atrium. The patient has been stable after surgical repair of the ventricular septal defect and dilation of the pulmonary venous stenosis.

Cardiac Catheterization↗
PubMed1994

A model of selective processing of auditory-nerve inputs by stellate cells of the antero-ventral cochlear nucleus.

Stellate cells in the cat antero-ventral cochlear nucleus (AVCN) maintain a robust rate-place representation of vowel spectra over a wide range of stimulus levels. This rate-place representation resembles that of low threshold, high spontaneous rate (SR) auditory nerve fibers (ANFs) at low stimulus levels, and that of high threshold, low-medium SR ANFs at high stimulus levels. One hypothesis accounting for this phenomenon is that AVCN stellate cells selectively process inputs from different SR population of ANFs in a level-dependent fashion. In this paper, we investigate a neural mechanism that can support selective processing of ANF inputs by stellate cells. We study a physiologically detailed compartmental model of stellate cells. The model reproduces PST histograms and rate-versus-level functions measured in real cells. These results indicate that simple and plausible distribution patterns of excitatory and inhibitory inputs within the stellate cell dendritic tree can support level dependent selective processing. Factors affecting selective processing are identified. This study thus represents a first step towards the development of a computational model of the AVCN stellate cell receptive field.

Animals↗
PubMed1993

Prospective study of abdominal ultrasonography before laparoscopic cholecystectomy.

To investigate the role of abdominal ultrasonography (US) in predicting possible difficulties during laparoscopic cholecystectomy, we performed preoperative US evaluation prospectively in 82 consecutive patients. We correlated our predictions of "easy" and "difficult" with difficulties experienced at operation in surgery. The binary outcomes were analyzed by taking both easy category of US and surgical operation as positive results and both difficult category as negative results. We obtained satisfactory sensitivity (93.8%), accuracy (81.4%), and positive predictive value (84.7%), but low specificity (35.3%) and negative predictive value (60%). The highly positive results were the result of careful US examination. The low specificity and negative predictive value were attributed to the fact that most surgically difficult cases were due to adhesions around the gallbladder, difficult indeed to detect at US. We conclude that thorough abdominal US examination before laparoscopic cholecystectomy is useful in preoperative evaluation of patients undergoing laparoscopic cholecystectomy, even if it not infrequently fails to predict the surgically difficult cases mainly due to adhesions around the gallbladder.

Abdomen↗
PubMed1993

Surgical treatment of infantile cardiac tumor: report of a case.

We herein report on a male infant who was diagnosed as having a cardiac tumor at the age of four days. This baby was quite well after birth, with the exception of a heat murmur heard by the pediatrician in a routine physical examination. Echocardiograms disclosed a tumor located in the muscular portion of the interventricular septum, almost occupying the whole right ventricular chamber. The patient underwent near total excision of the tumor to relieve the right ventricular outflow obstruction when he was 54 days old. The pathologic report revealed a rhabdomyoma.

Heart Neoplasms↗
PubMed1991

Cysteine-86 is not needed for the enzymic activity of glutathione S-transferase 3-3.

Recombinant glutathione S-transferase 3-3 expressed in Spodoptera frugiperda (SF9) cells with the use of a baculovirus expression system was modified with 1 mM-iodoacetamide. Amino acid analysis indicated that 0.79 +/- 0.15 cysteine residue was modified per enzyme subunit. The S-carbaminomethylated protein retains the GSH-conjugating activity. Glutathione S-transferase 3-3 modified with iodo[14C]acetamide was digested with Achromobacter proteinase I and the resulting peptides were separated by h.p.l.c. The modified peptides were pooled and further digested with Staphylococcus aureus V8 proteinase. Isotope-labelled peptides were isolated and collected for N-terminal sequence analysis. By this procedure, cysteine-86 was identified as the major S-carbaminomethylated residue. Verification of this findings came from the use of site-directed mutagenesis in which this cysteine was replaced by serine (C86S mutant). The C86S mutant is enzymically active. Therefore cysteine-86 is not needed for the conjugation of GSH with electrophilic compounds on glutathione S-transferase 3-3.

Amino Acid Sequence↗
PubMedDate not supplied

Portal blood flow in acute hepatitis with and without ascites: a non-invasive measurement using an ultrasonic Doppler.

To evaluate the role of portal blood flow in severe acute hepatitis leading to the formation of ascites, we studied the portal blood flow of 30 patients with severe acute hepatitis (20 without ascites and 10 with ascites), 20 patients with mild acute hepatitis and 20 healthy normal volunteers using duplex sonography. The portal blood flow of patients with severe acute hepatitis and ascites (421 +/- 94 mL/min) was lower than that of the volunteers (725 +/- 131 mL/min), the mild acute hepatitis (658 +/- 148 mL/min), and the severe acute hepatitis (633 +/- 108mL/min) without ascites (P < 0.001). The congestion index of severe acute hepatitis and ascites (0.16 +/- 0.04 cm.s) was higher than that of the volunteers (0.09 +/- 0.03 cm.s, P < 0.001), the mild acute hepatitis (0.09 +/- 0.02 cm.s, P < 0.001), and the severe acute hepatitis (0.12 +/- 0.04 cm.s, P < 0.02) without ascites. Portal blood flow was negatively correlated with prolonged prothrombin time (P < 0.001) and serum total bilirubin level (P = 0.002) and congestion index was positively correlated with heart rate (P = 0.006), prolonged prothrombin time (P < 0.001) and serum total bilirubin level (P = 0.001). Our study shows that in severe acute hepatitis, portal blood flow was reduced in patients with ascites. The non-invasive ultrasonic Doppler is a safe and helpful method in the clinical evaluation of portal hypertension in severe acute hepatitis.

Acute Disease↗
PubMedDate not supplied

Eczema herpeticum in children with atopic dermatitis.

Eczema herpeticum (EH), a form of disseminated cutaneous herpes simplex virus (HSV) infection, is a potentially life-threatening disease. It usually occurs in individuals with atopic dermatitis (AD) or other preexisting dermatosis. The resulting disruption of the skin barrier decreases the ability of such individuals to localize an HSV infection. We report eight AD cases with eczema herpeticum, seen from February 1989 to January 1996. Their ages ranged from 5 months to 6 years (mean age 2.5 years), There were 5 boys and 3 girls. Their laboratory data showed: IgE: 39 to 474, mean 197 IU/ml; eosinophil count 139 to 560, mean 314/mm3; Tzanck smear positive in 6 out of 6 patients; vesicle fluid culture positive for Herpes simplex type I in 4 out of 4 patients. All patients were treated with acyclovir and recovered.

Child↗