Biomedical subjects

S C Lin

Publications and source records attributed to S C Lin.

At least 109 records · Page 6Linked to original sources

PubMed1996

Management of severe pulmonary hypertension in an infant with obstructed total anomalous pulmonary venous return using magnesium sulfate.

Severe hypoxemia and pulmonary hypertension occurred in an infant with total anomalous pulmonary venous return. Though under hyperventilation with high fractional inspired oxygen and prostaglandin E1, hypoxemia remained intractable. Magnesium sulfate was used in view of its vasodilating effect. Significant clinical improvement was observed without causing systemic hypotension and the mechanism is discussed.

Alprostadil↗

PubMed1996

Complete nucleotide sequence and full-length cDNA clone of S.A.AR86 a South African alphavirus related to Sindbis.

S.A.AR86 and Girdwood S.A., two South African Sindbis-like arboviruses, are closely related antigenically to the Swedish isolate, Ockelbo82 [Lundström, J. O., Vene, S., Saluzzo, J. F., and Niklasson, B. (1993) Am. J. Trop. Med. Hyg. 49(5), 531-537]. Each of these viruses is associated with human disease, and Girdwood S.A. was isolated from a human case. In addition, S.A.AR86 is unique among Sindbis-like viruses in that adult mice remain sensitive to lethal infection with S.A.AR86. The complete genomic sequences of S.A.AR86 and Girdwood S.A. were determined. The S.A.AR86 RNA genome contained 11,663 nucleotides, excluding the 5' CAP structure and 3' poly(A) tail. In comparison to the consensus sequence of the prototype Egyptian Sindbis strain AR339, S.A.AR86 differed at 5.57% of the nucleotides, including a 54-nucleotide deletion, two insertions of 6 nucleotides each, and a 3-nucleotide insertion in the 3' terminal one-third of the S.A.AR86 nsP3 gene. S.A.AR86 is one of only three alphaviruses sequenced to date that does not have an opal termination codon between the nsP3 and the nsP4 genes. These genes are separated by a cysteine codon in the S.A.AR86 genome. The genome of Girdwood S.A. was 11,717 nucleotides in length, excluding the 5' CAP and 3' poly(A) tail. Girdwood S.A. contained an opal termination codon between nsP3 and nsP4 and did not have the large 54-nucleotide deletion in nsP3, although Girdwood S.A. did contain the remaining insertions and deletions characteristic of S.A.AR86. S.A.AR86 was more closely related to Girdwood S.A. than to the Egyptian isolate, and the South African isolates as a group were more closely related to the Swedish isolate. Comparison of the S.A.AR86 sequence to that of Ockelbo82, Girdwood S.A., and Sindbis virus AR339 revealed several codons where S.A.AR86 differed from the conserved amino acid encoded by the other three viruses. These changes may be related to the ability of S.A.AR86 to initiate a lethal central nervous system infection in adult mice. To fulfill a prerequisite for testing this hypothesis, a full-length cDNA clone of S.A.AR86 was constructed from which infectious genomic RNA replicas could be derived. The sequence of this clone differed from the S.A.AR86 genomic RNA sequence at four translationally silent positions, and virus derived from the clone reproduced the adult mouse neurovirulence phenotype of its biological progenitor.

Alphavirus↗

PubMed1996

Genomic aberrations of human papillomavirus recovered from cervical cancers.

Human papillomaviruses (HPV) contribute to the development of malignancies of the uterine cervix and the viral E6 and E7 oncogenes are invariably retained and expressed in cervical cancer tissues. Minor, but not major, structural aberrations have been found quite frequently in viral DNA recovered from cervical cancer tissues. We examined the presence of the DNA sequence of HPV type 18 in 33 cervical cancer tissues by polymerase chain reaction. HPV type 18 DNA sequences was found in 24 of these 33 cervical cancer tissue specimens, and at least 21 of these 24 specimens did not appear to retain all the region and open reading frames examined. Twelve of these 24 tissues seemed to harbor only the E6 and/or E7 genes. These results can be construed to suggest that the absence of viral genes other than E6 and E7 is quite frequent in HPV recovered from cervical cancer tissues and that the E6 and E7 genes are important in the carcinogenesis of cervical carcinoma. It is possible that the E6 and/or E7 alone may be sufficient to maintain the transformed phenotype of cervical cancer.

DNA, Viral↗

PubMed1996

A CBP integrator complex mediates transcriptional activation and AP-1 inhibition by nuclear receptors.

Nuclear receptors regulate gene expression by direct activation of target genes and inhibition of AP-1. Here we report that, unexpectedly, activation by nuclear receptors requires the actions of CREB-binding protein (CBP) and that inhibition of AP-1 activity is the apparent result of competition for limiting amounts of CBP/p300 in cells. Utilizing distinct domains, CBP directly interacts with the ligand-binding domain of multiple nuclear receptors and with the p160 nuclear receptor coactivators, which upon cloning have proven to be variants of the SRC-1 protein. Because CBP represents a common factor, required in addition to distinct coactivators for function of nuclear receptors, CREB, and AP-1, we suggest that CBP/p300 serves as an integrator of multiple signal transduction pathways within the nucleus.

Animals↗

PubMed1996

Crystallization and preliminary X-ray analysis of chicken-liver glutathione S-transferase CL 3-3.

Five different crystal forms of recombinant chicken-liver glutathione S-transferase CL 3-3 have been obtained by the vapor-diffusion method. The form A crystals are monoclinic C2, a = 125.56, b = 85.81, c = 52.71 A and beta = 114.64 degrees, and diffract to 4 A resolution. The form B crystals are monoclinic P2(1), a = 105.13, b = 118.54, c = 62.62 A and beta = 124.74 degrees, and diffract to 2.8 A resolution. The form C crystals are orthorhombic C222(l), a = 101.69, b = 115.46, c = 95.40 A, and diffract to 2.8 A resolution. The form D crystals are tetragonal, P4(1)2(1)2 or P4(3)2(1)2, a = b = 115.31, c = 171.20 A and diffract to 3.5 A resolution. The form E crystals are hexagonal, P6(1) or P6(5), a = b = 104.23, c = 114.35 A, diffract to 3.5 A resolution. Forms A, C and E have one dimer of molecular weight 50 kDa, while forms B and D have two dimers per asymmetric unit, respectively.

Journal Article↗

PubMed1996

Crystallization and preliminary x-ray analysis of volvatoxin A2 from Volvariella volvacea.

Volvatoxin A2, an ion channel disturbed cardiotoxic and hemolytic protein from the edible mushroom, Volvarilla volvacea, has been crystallized by the vapor diffusion method using polyethylene glycol 4000 and ammonium sulfate in sodium acetate buffer pH 4.6. The best crystals belong to the monoclinic space group C2 with unit cell dimensions a = 155.25 angstroms, b = 58.06 angstroms, c = 116.92 angstroms, and beta = 119.5 degrees. These crystals diffract to at least 2.2 angstroms and there are four molecules of molecular weight 24 kDa per asymmetric unit with a solvent content of 48%.

Basidiomycota↗

PubMed1996

Stability and folding of the SH3 domain of Bruton's tyrosine kinase.

Bruton's tyrosine kinase (BTK) plays an important role in B cell development. Deletion of C-terminal 14 amino acids of the SH3 domain of BTK results in X-linked agammaglobulinemia (XLA), an inherited disease. We report here on the stability and folding of SH3 domain of BTK. Peptides corresponding to residues 216-273 (58 residues) and 216-259 (44 residues) of BTK SH3 domain were synthesized by solid phase methods; the first peptide constitutes the entire SH3 domain of BTK while the latter peptide lacks 14 amino acid residues of the C-terminal. The 58 amino acid peptide forms mainly a beta-barrel type folding unit. Although small and lacking disulfide bonds, this peptide is extremely stable to thermal denaturation. Based on circular dichroism measurements, its melting temperature was found to be high, 82 degrees C at pH 6.0. However, the Gibbs free energy (delta GH2O) of the intrinsic stability and thermodynamic spontaneity of unfolding were found to be low, 2.6 kcal/mol by Gdn.HCl denaturation experiments, as compared to 12 kcal/mol obtained for larger single domain proteins, indicating poor stability of SH3 domain. Addition of 500 mM of Na2SO4 increased the free energy change delta GH2O to 4.0 kcal/mol, suggesting an ionic strength effect. The truncated peptide fails to fold correctly and adopts random coil conformation in contrast to 58 amino acid beta-barrel peptide, which exhibits high thermal stability but normal or low stability at ambient temperature. These results, to our knowledge the first to delineate the importance of C-terminal in structural integrity of SH3 domains, indicate also that improper folding and/or poor stability of mutant SH3 domain in BTK likely causes XLA.

Agammaglobulinaemia Tyrosine Kinase↗

PubMed1996

Genes in the RB pathway and their knockout in mice.

The retinoblastoma susceptibility gene (RB), the first identified human tumor suppressor gene, has been shown to be directly involved in the genesis of a variety of human cancers. RB is actually one of a family of three closely related genes including p107 and p130. Many elegant biochemical studies have demonstrated that RB is a critical component of the cell cycle regulatory machinery and have characterized the downstream effectors which the RB gene product regulates. More recent advances have demonstrated that the function of RB and RB-related genes is positively and negatively regulated by an intricate network of cell cycle regulatory proteins, some of which have also been implicated as tumor suppressor genes. Despite the detailed understanding of these biochemical and genetic pathways, the full function of genes in the RB pathway in the context of a whole organism is only now being addressed. Using gene knockout technology, it is now known that RB, and RB-related proteins p107 and p130, have important functions during early mouse development. Furthermore, despite its ubiquitous expression, RB has tissue- and cell-type specific effects which account for its function as a tumor suppressor but may also be independent of its role as a cell cycle regulator. Analysis of mice lacking regulatory genes upstream of RB and effector genes downstream of RB have confirmed that other genes in this pathway have tissue-specific effects on development and tumor susceptibility in mice.

Animals↗

PubMed1996

The impact of gender on alpha-methyl-para-tyrosine mediated changes in prolactin secretion and 6-hydroxymelatonin sulfate excretion.

Prolactin (PRL) and melatonin (ML) secretion are mediated by dopamine (DA) and norepinephrine (NE), respectively. Alpha-methyl-para-tyrosine (AMPT) inhibits the production of CNS catecholamines (CA). The purpose of the study is to determine: (1) if AMPT inhibition of ML has the same gender-dependent effect as on PRL secretion; (2) if there is a post AMPT-induced NE depletion mood change in men and/or women. In a randomized, double-blind cross-over fashion, five healthy young males and five females were either given five doses of AMPT 1 g (active) or promethazine 50 mg (placebo) over a 28 h period, separated by 4-6 weeks. The PRL and ML concentrations were collected at regular intervals via an indwelling venous catheter and concurrently, two 12 h urinary 6-hydroxymelatonin sulfate (6-MS) measurements were made. Mood and anxiety states of subjects at baseline and post drug were assessed with appropriate rating scales at regular intervals. Light exposure beginning at dusk and lasting until dawn was controlled to no more than 200 lux during all phases of the study. The PRL secretion showed a significant interaction of drug x time (p = .0001) in women and a non-significant trend (p = .056) in men. No difference in PRL secretion was found between the two genders in the placebo condition, whereas the PRL secretion was significantly higher in the AMPT condition in women when compared to men (df 17,119, F = 1.9, p = .021). Total 24 h urinary 6-MS secretion highly correlated with ML secretion expressed as area under the curve (AUC) during both active and placebo experiments (r = 0.8, p < .01) and (r = 0.86, p < or = .01), respectively. The ANOVA reveals a significant interaction of drug x time for 6-SM excretion. There was no gender difference in AMPT suppression of 6-MS excretion. No mood changes were detected in men or women. We conclude that urinary 6-MS is a reliable indirect measure of the degree of AMPT-induced decrease in CNS NE activity as part of overall AMPT-induced reduction of central catecholamine activities. The pre and post AMPT-induced changes in 6-MS are not gender dependent, dissimilar to the AMPT-induced changes in PRL secretion. Therefore, 6-MS, in addition to PRL, should be measured when applying the AMPT paradigm in future research.

Adult↗

PubMed1996

Examining serotonin function: a modified technique for rapid tryptophan depletion.

Tryptophan (TRP) depletion was used to study serotonin because the ratio of TRP to large neutral amino acids (TRP/LNAA) determines the quantity of TRP that enters the brain. Because TRP is not universally available, a modified technique of TRP depletion was developed where a 1/4 strength preparation of an amino acid mixture (AAM) replaces TRP as the placebo. Seven healthy subjects could not differentiate between the preparations in this double-blind, placebo-controlled study. Urinary 6-hydroxymelatonin sulfate (6-MS) was monitored as a biochemical marker of serotonin. The TRP/LNAA ratio (GG = 0.001) and 6-MS secretion (GG = 0.024) were decreased, but placebo TRP levels (GG = 0.062) were not altered significantly. This modified technique facilitates the use of TRP depletion in clinical research.

Adult↗

PubMed1996

p53 and Ha-ras mutations in chemically induced hamster buccal pouch carcinomas.

Well-differentiated squamous cell carcinomas were induced in hamster buccal pouch epithelium by twice weekly topical applications of N-methyl-N-benzylnitrosamine (MBN) or 7,12-dimethylbenz[a]anthracene (DMBA) over a period of 15 weeks. Each of the 22 tumors induced (14 MBN and eight DMBA) were evaluated by single-strand conformation polymorphism and DNA sequencing to identify mutations in conserved exons (E5-E8) of the p53 tumor suppressor gene and codons 12/13 and 61 of Ha-ras. In addition, Northern blot analysis of 10 MBN tumors and five DMBA tumors was performed to determine whether the mdm-2 gene was overexpressed, p53 mutations were detected in five of 14 (35%) MBN-induced carcinomas and in two of eight (25%) DMBA-induced carcinomas. Ha-ras mutations were detected in three of 14 (21%) MBN-induced carcinomas and in three of eight (37%) DMBA-induced carcinomas. One MBN-induced carcinoma exhibited a mutation in both the p53 and Ha-ras genes. The majority (five of seven of p53/Ha-ras mutations induced by MBN were G->A transitions and two of these occurred at hamster p53 codon 248, which corresponds to human p53 codon 245, a known mutational tumor 'hot spot'. A->T transversion at Ha-ras codon 61 accounted for three of five (60%) DMBA-induced mutations. There was no evidence of mdm-2 overexpression in any of the tumors evaluated. Overall, the results provide additional support for the validity of the hamster buccal pouch model of oral carcinogenesis, as applied to sequential cellular and molecular analysis and cancer chemoprevention studies.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed1996

Deduced consensus sequence of Sindbis virus strain AR339: mutations contained in laboratory strains which affect cell culture and in vivo phenotypes.

The consensus sequence of the Sindbis virus AR339 isolate, the prototype alphavirus, has been deduced. THe results presented here suggest (i) that a substantial proportion of the sequence divergence evident between the consensus sequence and sequences of laboratory strains of AR339 has resulted from selection for efficient growth in cell culture, (ii) that many of these changes affect the virulence of the virus in animal models, and (iii) that such modified genetic backgrounds present in laboratory strains can exert a significant influence on genetic studies of virus pathogenesis and host range. A laboratory strain of Sindbis virus AR339 was sequenced and cloned as a cDNA (pTRSB) from which infectious virus (TRSB) could be derived. The consensus sequence was deduced from the complete sequences of pTRSB and HRsp (E. G. Strauss, C. M. Rice, and J. H. Strauss, Virology 133:92-110, 1984), from partial sequences of the glycoprotein genes of three other AR339 laboratory strains, and by comparison with the sequences of the glycoprotein genes of three other AR339 sequence. HRsp differed form the consensus sequence by eight coding changes, and TRSB differed by three coding changes. In the 5' untranslated region, HRsp differed from the consensus sequence at nucleotide (nt) 5. These differences were likely the result of cell culture passage of the original AR339 isolate. At three of the difference loci (one in TRSB and two in HRsp), selection of cell-culture-adaptive mutations was documented with Sindbis virus or other alphaviruses. Selection in cell culture often results in attenuation of virulence in animals. Considering the TRSB and HRsp sequences together, one noncoding difference from the consensus (an A-for-G substitution in the 5' untranslated region at nt 5) and six coding differences in the glycoprotein genes (at E2 amino acids 1, 3, 70, and 172 and at E1 amino acids 72 and 237) were at loci which, either individually or in combination, significantly affected alphavirus virulence in mice. Although the levels of virulence of isogenic strains containing either nt 5 A or nt 5 G did not differ significantly in neonatal mice, the presence of nt 5 A greatly enhanced the effect of a second attenuating mutation in the E2 gene. These results suggest that minimal differences in the "wild type" genetic background into which an additional mutation is introduced can have a dramatic effect on apparent virulence and pathogenesis phenotypes. A cDNA clone of the consensus AR339 sequence, a sequence devoid of occult attenuating mutations introduced by cell culture passage, will allow the molecular genetic examination of cell culture and in vivo phenotypes of a virus which may best reflect the sequence of Sindbis virus AR339 at the time of its isolation.

Alphavirus Infections↗

PubMed1996

Activation of NF-kappaB/Rel by CD40 engagement induces the mouse germ line immunoglobulin Cgamma1 promoter.

Interaction between CD40 on B cells and CD40 ligand (CD40L) on T cells has been shown to mediate T-cell contact help for B-cell proliferation, differentiation, and immunoglobulin isotype switching. It has recently been shown that cross-linking CD40 on mouse B cells induces germ line gamma1 and epsilon transcripts and that interleukin-4 synergizes with CD40 signaling to further induce these germ line transcripts. Germ line transcripts have been shown to be required for class switch recombination. Here we show that signaling via CD40 increases expression of a transiently transfected luciferase reporter plasmid driven by the germ line Cgamma1 promoter in M12.4.1 B-lymphoma cells. By linker-scanning mutation analysis of the promoter, we have identified a CD40-responsive region (CD40RR) which is able to confer inducibility by CD40L to a minimal c-fos promoter. The CD40RR contains three binding sites for NF-kappaB/Rel proteins which are each required for maximal induction of CD40RR activity by CD40L. Binding of the NF-kappaB/Rel proteins p50, p65, c-Rel, and RelB to the CD40RR is induced by CD40 signaling in M12.4.1 cells and in splenic B cells. Cotransfection of expression plasmids for p50 and p65 or p50 and RelB, but not c-Rel, into M12.4.1 cells transactivates the CD40RR and the germ line gamma1 promoter. These data demonstrate that NF-kappaB Rel proteins activated by CD40 ligation play an important role in induction of the germ line Cgamma1 promoter.

Animals↗

PubMed1996

The protective effect of Alstonia scholaris R. Br. on hepatotoxin-induced acute liver damage.

The hepatoprotective effect of Alstonia scholaris R. Br. on liver injuries induced by carbon tetrachloride (CCl4). beta-D-galactosamine, acetaminophen and ethanol were investigated by means of serum-biochemical and histopathological examinations. Post treatment of A scholaris reduced dose-dependently the elevation of serum transaminases level and histopathological changes such as cell necrosis, inflammatory cell infiltration, which were caused by the single administration of 32 microliters/kg CCl4 or 600 mg/kg acetaminophen in mice. A. scholaris significantly lowered 288 mg/kg beta-D-galactosamine induced serum transaminases elevation in the serum-biochemical analysis in rats. A tendency was also shown to inhibit cell necrosis and inflammatory cell infiltration caused by beta-D-galactosamine in histopathological examination. All serological and histopathological effects of A. scholaris were compared with those of Bupleurum chinense, which has been reported previously as a treatment criteria of hepatitis.

Acetaminophen↗

PubMed1996

Protective and therapeutic effects of huanglian-jie-du-tang on hepatotoxin-induced liver injuries.

The hepatoprotective effect of Huanglian-Jie-Du-Tang (HLJDT), a Chinese medicinal prescription, was investigated in three kinds of experimental models. The animals were treated with HLJDT (300 mg/kg, p.o.) thrice at 2, 4 and 10 hours after administration with carbon tetrachloride (32 microliters/kg, i.p.), acetaminophen (600 mg/kg, i.p.) and beta-D-galactosamine (188 mg/kg, i.p.). Significant hepatoprotective effects on carbon tetrachloride and acetaminophen induced liver injuries were noted, but no significant effect on beta-D-galactosamine induced liver injury was observed. These hepatoprotective effects were evidenced by comparing the serum glutamate oxaloacetate transaminase (SGOT) and serum glutamate pyruvate transaminase (SGPT) levels in HLJDT treated and untreated groups. Serum enzyme activities in the carbon tetrachloride and acetaminophen experiments were significantly lower in the treated groups while the herbal prescription has no effect on the beta-D-galactosamine experiment. These results demonstrated that Huanglian-Jie-Du-Tang has a hepatoprotective effect against experimental liver injuries induced by specific hepatotoxins, and therefore may be useful in treating some, but not all, liver injuries.

Animals↗

PubMed1996

Correlation of toxic signs, ultrasonographic findings and pathological changes in cholecystitis.

BACKGROUND: Cholecystitis is a frequently encountered clinical problem. What parameters are reliable in helping predict its severity? METHODS: One hundred and forty-nine cholecystectomized cases of cholecystitis were analysed of which 99 (95 calculous) cases were pathologically diagnosed as chronic cholecystitis and 50 acute (43 calculous) cholecystitis. Medical records were reviewed to determine the frequency of toxic signs. Sonographic findings (performed within three days prior to operation), and final pathological changes with respect to the thickness and echotexture of the gallbladder wall were compared. RESULTS: Of 99 chronic cholecystitis patients, 13 cases showed toxic signs. Sonography detected an abnormal wall in 64, but made a correct diagnosis in only 34 cases. A great discrepancy was found in wall thickness as measured by sonography and pathology. A discrepancy > or = 2mm was noted in 19 cases. Of 50 patients with acute cholecystitis (20 cases had complications, defined as severe acute cholecystitis), 31 cases (14 of the 20 severe acute cases) showed toxic signs. Sonographic findings demonstrated an abnormal wall in 46 cases (19 of the severe acute cases) and an accurate diagnosis in 28 cases (13 of the severe acute cases). A difference in the measurement of gallbladder wall thickness > or = 2mm was noted in 26 patients. CONCLUSIONS: Clinical toxic signs and sonographic findings could not offer sufficient information to quickly identify lifethreatening gallbladder diseases.

Acute Disease↗

PubMed1995

Is Kaposi's-sarcoma-associated herpesvirus detectable in semen of HIV-infected homosexual men?

We explored a possible route of transmission of Kaposi's-sarcoma-associated herpes virus (KSHV) with nested and unnested PCR techniques. We looked for KSHV DNA sequences in semen of HIV-positive homosexual men and HIV-negative healthy semen donors. With unnested primers we found KSHV sequences in 21 of 33 (64%) homosexual men and in none of 30 healthy donors. With a nested PCR assay, 30 of 33 (91%) specimens from the homosexual men and 7 of 30 (23%) specimens from healthy donors had detectable KSHV sequences. Over 5 years of follow-up, 13 of 30 KSHV-positive homosexual men (43%) developed KS compared with none of the 3 KSHV-negative homosexual men.

DNA, Viral↗

PubMed1995

Geographic sequence variation of latent membrane protein 1 gene of Epstein-Barr virus in Hodgkin's lymphomas.

To assess the role of the Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) gene in the development of Hodgkin's lymphoma (HL), the polymorphism of this gene in EBV isolates from different geographic locations was analyzed. A 497 bp fragment spanning LMP1 gene exons 1 and 2 was amplified by polymerase chain reaction (PCR), using a primer pair bracketing a Xhol restriction site. PCR products were subjected to Xhol digestion and to DNA sequencing analysis. Twenty-five HL biopsy specimens from the United States and five HL and four non-Hodgkin's lymphoma (NHL) biopsy specimens from Italy were examined. Eighty percent of LMP1-positive samples (12 of 15) from the United States maintained the Xhol restriction site and the remaining 20% partially lost the Xhol site. One of four EBV-positive HL and one of the three EBV-positive NHL specimens from Italy lost the restriction site. The other three EBV-positive HL DNAs were partially cut by Xhol. Direct DNA sequencing analysis revealed that those Italian samples not digested by Xhol were due to a G to C transversion at the first base of codon 18, resulting in the change of glycine to arginine. Those DNA samples partially cut by Xhol were due to a mixture of G/C at the same location. In contrast, those partially digested American HL DNAs had a mixture of G/T at the second base of codon 17.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗