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Biomedical subjects

M H Lin

Publications and source records attributed to M H Lin.

At least 19 recordsLinked to original sources
PubMed1995

Normal expression and the effects of ectopic expression of the Drosophila muscle segment homeobox (msh) gene suggest a role in differentiation and patterning of embryonic muscles.

Myogenesis is a several step process that requires genes involved in specifying mesoderm lineage and genes involved in determining muscle identity, differentiation, and patterning. We report here on the isolation, characterization, and expression pattern of a cDNA clone encoded by the previously uncharacterized Drosophila muscle segment homeobox (msh) gene and its possible role in myogenesis. The amino acid sequence of the msh homeobox domain is highly homologous to the homeodomains of the Drosophila S59 and empty spiracles genes and the Hox 7 and Hox 8 family of vertebrate homeobox genes. In addition, the 5' end of msh has 52% sequence identity to the 5' end of the empty spiracles gene and encodes several stretches of amino acids rich in serine, alanine, proline, glutamine, and acidic amino acids, indicating potential domains of regulatory activity. The expression of msh is initially detected at about stage 6 in the dorsal lateral ectoderm of the embryo and later in the developing central (CNS) and peripheral nervous systems. During germ band retraction (stage 12), msh continues to be expressed in cells of the nervous system as well as cells of the somatic mesoderm corresponding mostly to the developing dorsal and lateral somatic body wall muscles. These mesodermal cells, which continue to express msh in daughterless mutant embryos, undergo an increase in cell number in neurogenic mutants. By late stage 14 of embryonic development, msh expression is greatly reduced or absent in most or all mesoderm and muscle but continues in CNS until hatching. Ectopic expression of msh in the mesoderm results in altered expression of the S59 and nau/Dmyd genes leading to a loss of some muscles and defects in the patterning of others, suggesting that the muscle defects are at the level of recruitment and/or patterning of muscle precursor cells. Thus the similarity of Drosophila msh expression to that of the homologous vertebrate Hox 7 and Hox 8 genes together with the effects of ectopic expression of msh in the mesoderm suggest a role for the msh-like family of genes in mesodermal and muscle differentiation and patterning.

Amino Acid Sequence↗
PubMed1994

Intracellular calcium increase induced by GABA in visual cortex of fetal and neonatal rats and its disappearance with development.

To address the question of whether gamma-aminobutyric acid (GABA) induces a change in the concentration of Ca2+ in neurons of the developing visual cortex, and if so, to elucidate a developmental profile of such a GABA-induced change, we measured intracellular Ca2+ signals using microscopic fluorometry in visual cortical slices loaded with rhod-2. The slices were prepared from rat fetuses of embryonic day 18 (E18) and rat pups of postnatal days 0-30 (P0-P30). Application of GABA through the perfusate at 100 microM induced a marked rise in intracellular Ca2+ signals in the cortical plate and subplate at E18 and P0-P2. After P5 the GABA-induced rise in Ca2+ dramatically reduced, and at P20 and thereafter it became undetectable. At E18 and P0-P2 an agonist for GABAA receptor, muscimol, induced a Ca2+ rise in the same way as did GABA, while a GABAB receptor agonist, baclofen, did not induce any significant rise in Ca2+ signals. Also, a GABAA receptor antagonist, bicuculline, blocked the GABA-induced rise in Ca2+ signals. These results indicate that the Ca2+ rise is triggered by activation of GABAA receptors. The application of Ni2+ at a concentration high enough to block all types of voltage-dependent CA2+ channels prevented the Ca2+ signals from increasing in response to GABA application, suggesting that Ca2+ may be influxed through such channels following depolarization evoked by GABA.

Animals↗
PubMed1994

Sequential cytogenetic alterations in hamster oral keratinocytes during DMBA-induced oral carcinogenesis.

Using the hamster cheek pouch oral cancer model, we have performed a comprehensive analysis of the cytogenetic changes in hamster oral keratinocytes during 7,12-dimethylbenz[a]anthracene (DMBA)-induced carcinogenesis. Tumour induction in the hamster cheek pouch required repeated application of the carcinogen for 14 weeks. We have found that this hamster oral cancer model to be suitable for cytogenetic studies. Unlike human oral cancers where chromosome breaks have been shown, this is only infrequently observed in DMBA-treated hamster oral keratinocytes. Of importance is the finding that at the beginning of the second week of DMBA treatment, there is a significant increase of karyotypes demonstrating tetraploid or near-tetraploidy. We propose that the significant increase in hamster oral keratinocytes exhibiting tetraploidy be further evaluated as a marker of premalignancy/malignancy.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1994

Perinatal characteristics of low birthweight infants in postdate pregnancies.

BACKGROUND: Early literature discussed postdate pregnancy in relation to difficult delivery of mothers with an excessively large fetus; more recent reports imply that the risk of perinatal death exists especially for the small, growth-retarded fetus. However there is little in the literature concerning low birthweight infants in postdate pregnancies. METHODS: A 6-year retrospective review of 135 low birthweight infants with 40 or more weeks' gestation was conducted. Among the subjects, 19 cases had a gestational age greater than 42 weeks (Group 1), 26 cases, between 41 and 42 weeks (Group 2), and 90 cases, between 40 and 41 weeks (Group 3). Assess was made of the outcomes of low birthweight infants in postdate pregnancies, comparing Group 1 with Group 2 and Group 3. RESULTS: Group 1 infants had significantly higher rates of chromosomal (21.1%) and congenital (31.6%) abnormalities and perinatal mortality (21.1%) than either Group 2 or Group 3 infants. Also, in Group 1 there were two cases of polyhydramnios and they both had abnormal karyotypes. CONCLUSIONS: The outcome of low birthweight infants in postdate pregnancies appears to be worse than predicted. This finding could offer for managing the cases which have a high frequency of abnormal karyotype (21.1%), especially when combined with polyhydramnios.

Adult↗
PubMed1993

Involvement of amygdala N-methyl-D-asparate receptors in long-term retention of an inhibitory avoidance response in rats.

This study examined the involvement of amygdala N-methyl-D-aspartate (NMDA) receptors in long-term retention of an inhibitory avoidance response. Rats bearing chronic cannulae implanted into the basolateral amygdala were trained on a one-trial inhibitory avoidance task and tested for retention 21 days later. They received intra-amygdala injections of vehicle (Veh) or 0.25, 1.25 or 5.0 micrograms of a competitive NMDA antagonist-2-amino-5-phosphonopentoic acid (AP5) either 5 min before training, immediately after training or 5 min before testing. Results indicated that pretraining intra-amygdala injections of AP5 at all doses impaired retention performance profoundly. Intra-amygdala injections of AP5 immediately after training caused a dose-dependent retention deficit: 0.25 microgram induced no deficit and 5.0 micrograms induced a great deficit. Immediate posttraining intra-amygdala injections of a non-competitive NMDA antagonist MK-801, also impaired retention but MK-801 given 2 hrs after training had no significant effect. In contrast to the marked amnestic effect produced by pre- or posttraining intra-amygdala injections of AP5, intra-amygdala injections of AP5 given just before retention tests had no discernible effect on retention performance. The retention deficit induced by pretraining intra-amygdala injections of 1.25 micrograms AP5 was ameliorated completely by N-methyl-DL-aspartate (0.25 microgram), but also partially by norepinephrine (0.2 microgram) infused into the amygdala immediately after training. However, posttraining infusion 0.2 microgram norepinephrine failed to attenuate significantly the amnestic effect induced by 5.0 micrograms AP5. These findings, taken together, suggest that NMDA receptors in the amygdala are normally involved in memory formation processing of affective experience.

2-Amino-5-phosphonovalerate↗
PubMed1993

Measurements of urinary growth hormone in the assessment of its secretory status.

A highly sensitive enzyme immunoassay was used to measure urinary growth hormone (GH) levels in 29 children and 32 adults with different levels of GH secretion. The 24-hour urinary GH excretion of seven children with complete GH deficiency was 1.90 +/- 1.55 ng/g Cr (mean +/- SD), of 10 normal but short children was 19.04 +/- 14.11 ng/g Cr, of 12 children with normal height was 14.57 +/- 5.53 ng/g Cr, of 11 adults of normal height was 4.46 +/- 4.47 ng/g Cr, and of six adults with acromegaly was 366.75 +/- 349.95 ng/g Cr. The nocturnal urinary GH excretion of seven children with complete GH deficiency was 2.27 +/- 1.22 ng/g Cr, of 10 normal but short children was 22.74 +/- 12.76 ng/g Cr, of 12 children of normal height was 22.40 +/- 11.86 ng/g Cr, of 26 adults of normal height was 7.14 +/- 5.86 ng/g Cr and of six adults with acromegaly was 338.70 +/- 309.12 ng/g Cr. There was no overlap in the urinary GH excretion, either 24-hour or nocturnal values, between children with complete GH deficiency and children without GH deficiency, or between adults with acromegaly and normal adults. These data indicate that urinary GH measurements can reflect the endogenous GH secretory status and may be a promising tool for the diagnosis of complete GH deficiency in children and acromegaly in adults.

Adolescent↗
PubMed1992

The Taiwanese hepatitis C virus genome: sequence determination and mapping the 5' termini of viral genomic and antigenomic RNA.

The complete nucleotide sequence of hepatitis C virus (HCV) cloned from the liver tissue of a Taiwanese patient with post-transfusion type C hepatitis was determined. The 5' end of HCV genomic RNA was located 341 nucleotides upstream from the initiation codon for the viral polyprotein open reading frame. The 5' end of the viral antigenomic RNA was shown to have 13 consecutive As. Thus the 3' terminus of the viral genome is a stretch of U which ends about 50 nucleotides downstream from the stop codon of the large open reading frame. The nucleotide sequence homology between this HCV strain and two Japanese isolates was 90.5 and 90.7%, respectively. Homology with the United States strain, however, was only 77.8%. Accordingly, the indigenous Taiwanese HCV strain is of the same subtype as the Japanese isolates. Novel features of the viral genome termini are possibly relevant to HCV genome replication.

Amino Acid Sequence↗
PubMed1992

Prenatal diagnosis of meconium peritonitis--a case report with literature review.

A case of meconium peritonitis that was diagnosed ultrasonographically in the second trimester is presented. Fetal ascites, intraabdominal calcification and polyhydramnios were detected on antenatal ultrasonography. Specks of calcification were also demonstrated on abdominal radiography postnatally. The obstetric and neonatal implications of meconium peritonitis are discussed with literature review.

Adult↗
PubMed1992

Clinical experience of octreotide in the treatment of acromegaly.

To evaluate the efficacy and safety of octreotide (a somatostatin analogue) in the treatment of acromegaly, 10 patients were injected subcutaneously with octreotide, 50 micrograms, thrice daily before each meal for two days, followed by 100 micrograms thrice daily for six months. One case dropped out at the initial stage because of diarrhea, and another quit due to a lack of improvement in headaches after treatment for three months. Eight patients completed the study. The results showed that the circumference of the fourth finger and hand volume significantly decreased after treatment. Laboratory data demonstrated that serum growth hormone (GH) and somatomedin-C levels also decreased significantly. However, in six patients without a history of trans-sphenoidal adenomectomy, the serum GH and somatomedin-C levels returned to normal in only one case who had a serum GH level < 20 mU/L before treatment. In the oral glucose tolerance test, paradoxic elevation of GH subsided after treatment. In the TRH test, paradoxic elevation of GH improved after treatment. In the bromocriptine test, octreotide had a synergistic effect on the suppression of GH. All cases had the side effect of injection pain, especially at the initial stage. An increase in intestinal peristalsis and bowel movement occurred in the first week, but symptoms later subsided. Two out of these eight patients had gallbladder sludge after six months of treatment. In conclusion, octreotide is effective in the treatment of acromegaly; however, it is better used in patients who have serum GH levels < 20 mU/L, or after a trans-sphenoidal adenomectomy, and may be combined with bromocriptine to treat the patient.(ABSTRACT TRUNCATED AT 250 WORDS)

Acromegaly↗
PubMed1991

Isolation of a complementary DNA fragment of hepatitis C virus in Taiwan revealed significant sequence variations compared with other isolates.

To clone and characterize hepatitis C virus strains present in Taiwan, RNA was extracted from liver tissue collected from a patient during the acute phase of posttransfusion non-A, non-B hepatitis. RNA was then subjected to complementary DNA synthesis and the polymerase chain reaction, using primers derived from the original nucleotide sequence of the United States hepatitis C virus strain. A complementary DNA clone, HCV-T3, containing 552 base pairs of hepatitis C virus complementary DNA sequences was isolated and characterized. The homologies in nucleotide sequence between the Taiwan isolate and either the United States or Japan isolate were 80.1% and 91.5%, respectively. However, most of the nucleotide changes occurred in the third base positions, resulting in much higher homologies in amino acid sequence of 91.8% and 97.3%, respectively. Amplification of the less conserved region of hepatitis C virus genome with the polymerase chain reaction was improved by use of primers with nucleotides matched to the local strain. Finally, in addition to the liver and serum, the viral genome was also demonstrated in the spleen tissue by similar methods, suggesting another possible target for hepatitis C viral infection. These findings indicate that there is considerable heterogeneity in hepatitis C virus genomes isolated from different areas of the world.

Adult↗
PubMed1991

Temporal aspects of major viral transcript expression in Hep G2 cells transfected with cloned hepatitis B virus DNA: with emphasis on the X transcript.

The major transcripts of hepatitis B virus (HBV) and the kinetics of their expression were studied in a transient expression system by transfecting partially duplicated copies of HBV genome into Hep G2 cells. By Northern blotting, six species of HBV-specific transcripts could be identified. They were the pregenomic (3.6 kb), the preS1 (2.6 kb), the preS2/S (2.2 kb), the X (0.8 kb), and two spliced (2.2 kb) RNAs, respectively. The preS2/S RNA and the spliced RNAs could be distinguished when a core gene-specific probe, which could not hybridize with the former, was used. Kinetic analysis of the expression of these RNAs revealed that the X transcript exhibited a pattern different from that of other viral transcripts. Amounts of all RNAs peaked at 24-48 hr post-transfection and then gradually declined. However, the X transcript became undetectable on Day 4 post-transfection while other viral RNAs persisted for at least 10 days. The unique expression profile of the X transcript suggested that it probably behaves as an early gene and this is consistent with its proposed role as a transactivator. Nevertheless, frameshift mutations within the X ORF had no obvious effects on the activities and temporal pattern of HBV transcription in this transient expression system.

Base Sequence↗
PubMed1991

Characterization and genetic analysis of alternatively spliced transcripts of hepatitis B virus in infected human liver tissues and transfected HepG2 cells.

The transcriptional map of hepatitis B virus (HBV) has been expanded recently by the discovery of a singly spliced transcript in hepatoma cell lines transfected with cloned viral DNA and a doubly spliced one in naturally infected human liver tissues. By the use of reverse transcription and a subsequent polymerase chain reaction, the two spliced HBV RNAs were shown to be present in both types of cells. As further evidence, an HBV mutant was constructed and found to exclusively express the singly spliced RNA. This mutant was also used to quantitate the two spliced species in transfected HepG2 cells; they were found to be equally abundant, and each represented about 30% of the pregenomic RNA. The HBV mutant could still produce replication-competent HBV virions when transfected into HepG2 cells, indicating that the doubly spliced transcript, just like the singly spliced one, was not essential for HBV replication. However, the two abundant spliced HBV transcripts were detected in most naturally infected human liver tissues, suggesting that they may have biologic functions in vivo.

Base Sequence↗
PubMed1990

Reliability and validity of using a Brief Psychiatric Symptom Rating Scale in clinical practice.

To develop a reliable and valid psychiatric self-rating scale for use in medical practice, the authors modified Derogatis' Symptom Check List-90-R (SCL-90-R) and designed a shorter form, named Brief Symptom Rating Scale (BSRS). The BSRS comprises 50 items, which best reflect the original ten symptom dimensions and three indices of psychopathology from the SCL-90-R. The BSRS has been proven in different populations to have an excellent split-half reliability as well as good internal structure according to factor analysis. In addition, BSRS scores are highly correlated with the parental form SCL-90-R among medical populations for each symptom dimension and the three indices. The rate of accurate classification for BSRS between psychiatric and nonpsychiatric cases was 75.8%, with a sensitivity of 66.7% and a specificity of 86.7% by discriminant analysis based on 10 dimensional scores obtained from 1,638 subjects, randomly selected from the Psychiatric Outpatient Clinic, the Family Medicine Clinic and nonpsychiatric medical inpatients. Therefore, the BSRS is a satisfactory global measure and case-finding screening instrument for psychopathology in both psychiatric and nonpsychiatric medical settings.

Adult↗
PubMed1990

Antiplatelet action of dehydrokawain derivatives isolated from Alpinia speciosa rhizoma.

5,6-Dehydrokawain (DK) and dihydro-5,6-dehydrokawain (DDK) inhibited the aggregation and ATP release of rabbit platelets induced by arachidonic acid and collagen, without affecting those induced by ADP, PAF and thrombin. This inhibition was reversible and in a concentration-dependent manner. The IC50 of DK and DDK on arachidonate-induced platelet aggregation were calculated to be about 10 and 60 micrograms/ml, respectively. Thromboxane B2 formation caused by arachidonic acid was also suppressed by both antiplatelet agents. DK inhibited the intracellular calcium concentration rised by arachidonic acid, but not that by collagen or thrombin. DK also inhibited the secondary, but not the primary aggregation of human platelet-rich plasma induced by ADP and epinephrine. It is concluded that the antiplatelet effect of both DK and DDK is due to the inhibition of thromboxane A2 formation.

Adenosine Triphosphate↗
PubMed1989

Dimerization of hepatitis B viral X protein synthesized in a cell-free system.

Hepatitis B viral X protein (HBx), a 17-kDa polypeptide, has been demonstrated as a trans-acting factor. In this study, we report that the HBx was able to form a dimer, a feature very similar to many well known trans-acting factors. In vitro synthesized HBx, after immunoprecipitation and analysis by SDS-PAGE, appeared as one prominent 17-kDa band (monomer) and a faint 34-kDa band (dimer). The amount of dimer increased if the sample of immunoprecipitated HBx was not treated with 2-mecaptoethanol, indicating the dimer was held together by the disulfide linkage. Dimerization of a truncated HBx established that the four cysteine residues close to the N-terminus are sufficient for the dimerization process.

Cell-Free System↗