Biomedical subjects

T H Chen

Publications and source records attributed to T H Chen.

At least 91 records · Page 5Linked to original sources

PubMed1996

ATF3 gene. Genomic organization, promoter, and regulation.

ATF3 gene, which encodes a member of the activating transcription factor/cAMP responsive element binding protein (ATF/CREB) family of transcription factors, is induced by many physiological stresses. As a step toward understanding the induction mechanisms, we isolated the human ATF3 gene and analyzed its genome organization and 5'-flanking region. We found that the human ATF3 mRNA is derived from four exons distributed over 15 kilobases. Sequence analysis of the 5'-flanking region revealed a consensus TATA box and a number of transcription factor binding sites including the AP-1, ATF/CRE, NF-kappa B, E2F, and Myc/Max binding sites. As another approach to understanding the mechanisms by which the ATF3 gene is induced by stress signals, we studied the regulation of the ATF3 gene in tissue culture cells by anisomycin, an approach that has been used to study the stress responses in tissue culture cells. We showed that anisomycin at a low concentration activates the ATF3 promoter and stabilizes the ATF3 mRNA. Significantly, co-transfection of DNAs expressing ATF2 and c-Jun activates the ATF3 promoter. A possible mechanism implicating the C-Jun NH2-terminal kinase/stress-activated protein kinase (JNK/SAPK) stress-inducible signaling pathway in the induction of the ATF3 gene is discussed.

Activating Transcription Factor 3↗

PubMed1996

Cold requirement for maximal activity of the bacterial ice nucleation protein INAZ in transgenic plants.

The bacterial ice nucleation gene inaZ confers production of ice nuclei when transferred into transgenic plants. Conditioning of the transformed plant tissue at temperatures near 0 degrees C greatly increased the ice nucleation activity in plants, and maximum ice nucleation activity was achieved only after low-temperature conditioning for about 48 h. Although the transgenic plants contain similar amounts of inaZ mRNA at both normal and low temperatures, low temperatures are required for accumulation of INAZ protein. We propose that the stability of the INAZ protein and thus ice nucleation activity in the transgenic plants is enhanced by low-temperature conditioning.

Bacterial Outer Membrane Proteins↗

PubMed1996

Analysis of late-blight disease resistance and freezing tolerance in transgenic potato plants expressing sense and antisense genes for an osmotin-like protein.

The expression patterns of plant defense genes encoding osmotin and osmotin-like proteins imply a dual function in osmotic stress and plant pathogen defense. We have produced transgenic potato (Solanum commersonii Dun.) plants constitutively expressing sense or antisense RNAs from chimeric gene constructs consisting of the cauliflower mosaic virus 35S promoter and a cDNA (pA13) for an osmotin-like protein. Transgenic potato plants expressing high levels of the pA13 osmotin-like protein showed an increased tolerance to the late-blight fungus Phytophthora infestans at various phases of infection, with a greater resistance at an early phase of fungal infection. There was a decrease in the accumulation of osmotin-like mRNAs and proteins when antisense transformants were challenged by fungal infection, although the antisense transformants did not exhibit any alterations in disease susceptibility. Expression of pA13 sense and antisense RNAs had no effect on the development of freezing tolerance in transgenic plants when assayed under a variety of conditions including treatments with abscisic acid or low temperature. These results provide evidence of antifungal activity for a potato osmotin-like protein against the fungus P. infestans, but do not indicate that pA13 osmotin-like protein is a major determinant of freezing tolerance.

Agrobacterium tumefaciens↗

PubMed1996

Fractures of posterior wall of acetabulum.

Fractures of the posterior wall of the acetabulum form a special group in acetabular fractures. This study aims to evaluate the results in the management of such fractures. Thirty-two patients with fractures of posterior wall of acetabulum were reviewed retrospectively. The follow-up period was 7 (range 3-10) years. Twenty-four were associated with initial posterior dislocations. Twenty-seven were managed with open reduction and internal fixation, while the remainder were managed conservatively. Reductions were rated as congruent in 30 cases and as noncongruent in 2. The functional results were excellent in 16 cases, good in 10, fair in 2, and poor in 4. Two early complications were met, namely 1 iatrogenic sciatic nerve injury and 1 superficial wound infection. Sixteen late complications were noted, including 10 heterotopic ossifications, 3 avascular necroses of femoral head, and 3 symptomatic arthritides. The incidence of late complications was high, but the functional results were generally satisfactory. Congruent reduction was the key in obtaining satisfactory results in the management of these fractures.

Acetabulum↗

PubMed1996

Percutaneous pinning in undisplaced subcapital femoral neck fractures.

Three hundred and five undisplaced subcapital femoral neck fractures managed by pinning in situ with Knowles' pins were evaluated to elucidate the role and effect of such treatment. The protocol of management and follow up, and evaluation, both radiographically and functionally, were set up prospectively. The duration from injury to management was 3.5 (1-14) days, the operation time was 22 (9-48) min and most of the patients were discharged without hospitalization. The follow-up period was 75 (28-136) months. The final results showed 282 (92.5 per cent) fractures united without complications (mean union time: 20 weeks), 14 (4.6 per cent) limbs with non-union, and 9 (2.9 per cent) had implant problems. Twenty-two (7.2 per cent) developed avascular necrosis after union. Percutaneous pinning of undisplaced subcapital femoral neck fractures as day cases is a simple, safe, effective and economic method.

Adult↗

PubMed1996

Effects of caffeine on intracellular calcium release and calcium influx in a clonal beta-cell line RINm5F.

We studied the effects of caffeine on intracellular calcium in a clonal insulin-secreting cell line RINm5F. Caffeine (1-30 mM) induced a dose-dependent intracellular Ca2+ release and Ca2+ influx. Pretreatment with combination of ryanodine (10 microM) and caffeine (10 mM), but not ryanodine alone, abolished subsequent caffeine-induced release of intracellular Ca2+. Pretreatment with another ryanodine receptor blocker procaine (0.1, 0.3, and 1mM) antagonized the caffeine-induced release of intracellular Ca2+. Pretreatment with thapsigargin (2 microM), the endoplasmic reticular Ca2+-ATPase inhibitor, abolished both the caffeine- and arginine vasopressin (AVP)-induced Ca2+ release. AVP induces Ca2+ release by increasing the formation of IP3. Pretreatment with AVP greatly reduced caffeine-induced Ca2+ release whereas pretreatment with caffeine also reduced AVP-induced Ca2+ release. The L-type Ca2+ channel blocker nimodipine (1 microM) inhibited caffeine-induced Ca2+ influx. In addition, depletion of intracellular Ca2+ stores with thapsigargin did not affect caffeine-induced Ca2+ influx. These results suggested that: 1) the ryanodine- and caffeine-sensitive Ca2+ store exists in RINm5F cells, 2) most of these Ca2+ release channels in RINm5F cells are closed in the resting state, since pretreatment with ryanodine alone failed to block the caffeine-induced Ca2+ release, 3) there is a "cross-talk" between the caffeine- and IP3-sensitive pools in RINm5F cells, 4) caffeine increases Ca2+ entry in RINm5F cells through L-type voltage-dependent Ca2+ channels, and 5) the caffeine-induced Ca2+ influx is independent of the Ca2+ release from the intracellular Ca2+ stores.

Animals↗

PubMed1996

Effects of dietary nucleoside-nucleotide mixture on memory in aged and young memory deficient mice.

Intestinal mucosa, bone marrow hematopoietic cells and brain have limited capacity for the de novo synthesis of nucleosides (NSs) and nucleotides (NTs). Whereas the role of dietary NS and NT in the former two tissues is known, it is not known in the brain. Therefore we studied the effect of dietary NS and NT mixture on memory in aged mice (Experiment 1) and young memory deficient mice (Experiment 2). Memory retention was studied by step-through type passive avoidance performance (maximum 180 seconds). In Experiment 1 aged (7 month old) senescence accelerated mice (SAM) were fed 20% casein diet (control) or this diet supplemented with 0.5% NS/NT mixture for 12 weeks. Memory was studied 1, 2 and 3 days after the electric shock (punishment). In Experiment 2, young (1 month old) memory deficient mice (Dull mice) and normal mice (ddY mice) were fed the same diets as those in Experiment 1 for 12 weeks. Memory retention was studied 1 and 3 days after the punishment. In the aged SAM the average time of avoidance and also the percentages of successful memory 2 and 3 days after the punishment were significantly higher in the NS/NT diet group than the control diet group (P < 0.05). In the Dull mice percentage of successful memory was higher in the NS/NT diet group than in the control group 3 days after the punishment, however, such an effect was not observed in the normal mice. These results suggest that insufficient endogenous supply of NSs and NTs may be responsible for the factor of memory deficiency with aging or of genetical memory deficiency, which can be improved by the dietary administration of NSs and NTs.

Aging↗

PubMed1996

Incidence and toxigenicity of Aeromonas hydrophila in seafood.

Three selective media, Oxoid Aeromonas agar (OA), blood ampicillin agar (BA) and starch ampicillin agar (SA) were used to evaluate the presence of Aeromonas hydrophila in 66 samples of oyster, shrimp, fish and surimi products. Oyster had the highest incidence, with 50% positive, whilst no A. hydrophila was found in the surimi. Of the three selective media, BA displayed the highest recovery rate of A. hydrophila from seafood. Forty-eight isolates from this survey were tested for their capability to produce hemolysin and cytotoxin. Hemolysin was produced by 79.2% of the isolates and cytotoxin was produced by 91.7% of the isolates in brain heart infusion broth. One of the toxin-producing isolates from oyster, strain 8-169, was further tested for growth and toxin production in oyster, shrimp and fish at various temperatures. This particular isolate grew best and had highest toxin production in oyster. Hemolysin and cytotoxin were produced earlier at 28 degrees C than at 37 degrees C, and titers of hemolysin were also higher at 28 degrees C. At 5 degrees C, it was able to grow and produce hemolysin in oyster.

Aeromonas hydrophila↗

PubMed1996

Structure of pp32, an acidic nuclear protein which inhibits oncogene-induced formation of transformed foci.

pp32 is a nuclear protein found highly expressed in normal tissues in those cells capable of self-renewal and in neoplastic cells. We report the cloning of cDNAs encoding human and murine pp32. The clones encode a 28.6-kDa protein; approximately two-thirds of the N-terminal predicts an amphipathic alpha helix containing two possible nuclear localization signals and a potential leucine zipper motif. The C-terminal third is exceptionally acidic, comprised of approximately 70% aspartic and glutamic acid residues; the predicted pI of human pp32 is 3.81. Human and murine pp32 cDNAs are 88% identical; the predicted proteins are 89% identical and 95% similar. Although the structure of pp32 is suggestive of a transcription factor, pp32 did not significantly modulate transcription of a reporter construct when fused to the Gal4 DNA-binding domain. In contrast, in cotransfection experiments, pp32 inhibited the ability of a broad assortment of oncogene pairs to transform rat embryo fibroblasts, including ras + myc, ras + jun, ras + E1a, ras + mutant p53, and E6 + E7. In related experiments, pp32 inhibited the ability of Rat 1a-myc cells to grow in soft agar, whereas it failed to affect ras-induced focus formation in NIH3T3 cells. These results suggest that pp32 may play a key role in self-renewing cell populations where it may act in the nucleus to limit their sensitivity to transformation.

3T3 Cells↗

PubMed1996

Extended open-tip rhinoplasty with three V-flaps for secondary correction of bilateral cleft lip nasal deformity.

Many procedures have been developed to correct the secondary cleft lip nasal deformity, including the depressed nasal tip, flaring nasal aperture, and a very short columella. The forked flap, cartilage graft, or strut and bony graft have been applied for many years. We propose the extended open-tip rhinoplasty with three V-flaps, which we have performed on 12 patients during the past 3 years. An extended incision for the nasal skin flap exposes all deformities to direct vision, makes the advancement and rotation of the nasal skin flap complete, and makes the corrective procedures easy and accurate. A large V-flap (with V-Y advancement for columellar lengthening) and two small V-flaps (with back-cut incisions on the nasal lining) are used to elevate and suspend the alar domes and cartilage to create two symmetrical and piriform apertures, and to ensure adequate columellar length. Columellar lengthening averaged from 2.5 mm preoperatively to 10 mm postoperatively. A protruded nasal tip with two delicate and small dimples over the alar rims, and a piriform aperture of the nasal nares were achieved in our series. No hypertrophic scar, nasal obstruction, or exposure of hairy nares were noted. No cartilage graft or strut and bone graft were required.

Adolescent↗

PubMed1996

Unstable closed tibial shaft fractures: a prospective evaluation of surgical treatment.

OBJECTIVE: To define the roles of the rigid interlocking nail and the semirigid Ender nail in the treatment of closed unstable tibia] shaft fractures. DESIGN: Randomized, clinical, prospectively study with detailed comparison of parameters. MATERIALS AND METHODS: Data on 116 unstable closed tibial shaft fractures were collected. Randomly, 60 tibiae were fixed with interlocking nails and 56 tibiae were fixed with Ender nails. The follow-up period was 24 (16-32) months. MEASUREMENTS AND MAIN RESULTS: In the interlocking nail group, the average blood loss was 189 cc, operation time was 51 minutes, length of hospital stay was 7 days, and union time was 14.2 weeks. In the Ender nail group, the average blood loss was 95 cc, operation time was 30 minutes, length of hospital stay was 5.0 days, and union time was 16.9 weeks. Student's t test was used for statistical significance. CONCLUSIONS: For more comminuted unstable tibial shaft fractures, an interlocking nail is undoubtedly a better choice, but an Ender nail still is effective in some aspects of treatment in the less comminuted unstable tibial shaft fractures.

Adolescent↗

PubMed1996

Treatment of unstable tibial fractures with interlocking nail versus Ender nail: a prospective evaluation.

BACKGROUND: For unstable tibial fractures, there are many methods of surgical treatment. The efficacy of the Ender nail and the interlocking nail in the treatment of such fractures is examined. METHODS: One hundred and seven cases of unstable tibial shaft fractures were collected for the prospective study. Randomly, 61 tibia were fixed with interlocking nails and 46, with Ender nails. The mean follow-up period was 30.5 (23 to 40) months. The results of the different treatments were compared. RESULTS: In the group with interlocking nails, the average blood loss was 265 cc; operation time was 61 minutes; hospital days were 10.4; and union time was 15.1 weeks for closed fractures and 17 weeks for Winquist-Hansen type III and IV fractures. In the group with Ender nails, the average blood loss was 135 cc, operation time was 32 minutes, hospital days were 8.3 days, and union time was 17.6 weeks for closed fractures and 22.5 weeks for Winquist-Hansen type III and IV fractures. Student t-test revealed statistically significant difference between the groups in all of the data described above. However, treatment with the different nails showed no significant difference in results for open type I and II fractures. CONCLUSIONS: Ender nail still has its superior usefulness in some aspects of treatment of less comminuted unstable tibial shaft fractures, but for the more comminuted unstable tibial shaft fractures, the interlocking nail is undoubtedly better used.

Adolescent↗

PubMed1996

Treatment of open tibial fracture with Ender nail.

BACKGROUND: This retrospective study aims to evaluate the effect of Ender nail in management of open type I and II unstable tibial fractures. METHODS: From 1984 to 1993, 30 cases of open unstable tibial shaft fracture (with fibular fracture) were collected in the retrospective study. All were fixed with Ender nails. The followup period was 99 (24-135) months. RESULTS: The average of blood loss was 140 cc, operation time 45 minutes, hospital day 10 days, and union time 20.5 weeks. Student t-test revealed statistically significant difference between open type I cases and type II cases in some parameters described above. CONCLUSIONS: Ender nail is effective in the treatment of open type I and II unstable tibial shaft fractures, but it should be used carefully, especially in cases with more comminution.

Adult↗

PubMed1996

Ender nail in unstable closed tibial fractures.

BACKGROUND: This retrospective study aims to evaluate the effect of Ender nail in management of unstable closed tibial fractures. METHODS: From January 1985 to May 1992, 99 cases of unstable closed tibial shaft fractures (with fibular fractures) were collected for retrospective study. All the 99 tibiae were fixed with Ender nails. The mean follow up period was 80 (26-115 months). RESULTS: The clinical results were evaluated with special charts. The average blood loss was 126 ml. Operation time was 45 minutes. Hospital day was 10.2 days. Union time was 16.8 weeks for Winquist-Hansen (WH) type I-II fractures and 20.5 weeks for VVH type III-V fractures. Student t test revealed statistically significant differences between the clinical results of WH type I-II cases and those of WH type III-V cases. The postoperative complications included superficial infection in 1 case (1%), nail protrusion in 13 (13%), malunion in 10 (10%), aseptic nonunion in 2 (2%) and infected nonunion in 1 (1%) (overall 18% in the 99 cases). CONCLUSIONS: Ender nail is no doubt effective in treatment of less comminuted unstable tibial shaft fractures, but should be used carefully for more comminuted unstable tibial shaft fractures.

Adolescent↗

PubMed1996

Oxytocin-stimulated insulin release in a clonal beta-cell line RINm5F: involvement of phospholipase C-dependent and -independent pathways.

AIM: To study the mechanisms underlying oxytocin (Oxy)-induced insulin release. METHODS: In a clonal pancreatic beta-cell line, RINm5F cells. RESULTS: Oxy increased insulin release and [Ca2+]i in a concentration-dependent manner. Oxy-induced insulin release was not altered by pretreatment with pertussis toxin (PT). U-73122 (2-8 mumol.L-1), a phospholipase C (PLC) inhibitor, concentration-dependently inhibited Oxy-induced increases in [Ca2+]i with IC50 value of 2.8 +/- 0.2 mumol.L-1. In addition, U-73122 diminished the Oxy-induced increase in intracellular concentration of inositol 1, 4, 5-triphosphate (IP3). U-73122 at 8 mumol.L-1 totally abolished the Oxy-induced increases in [Ca2+]i and IP3; however it reduced the Oxy-induced increase in insulin release only by 36% and 63% in the monolayer and suspended cell preparations, respectively. CONCLUSION: Oxy increases insulin release through both PLC and non-PLC mediated signal transduction mechanisms.

Animals↗

PubMed1995

Thapsigargin stimulates intracellular calcium mobilization and inhibits parathyroid hormone release.

Ca2+ and other divalent cations like Sr2+, Ba2+, and Mg2+ stimulate rapid and sustained increases in intracellular Ca2+ ([Ca2+]i) and 1,4,5-inositol trisphosphate (1,4,5-InsP3) presumably by interacting with recently identified parathyroid cell membrane Ca2+ receptors. We used thapsigargin (THAPS), an inhibitor of the microsomal Ca(2+)-ATPase, to deplete InsP3-sensitive intracellular Ca2+ stores to determine whether sustained increases in [Ca2+]i due to divalent cations require intact cytosolic Ca2+ pools. In Fura 2-loaded parathyroid cells, THAPS produced a gradual increase in [Ca2+]i which reached a steady-state level by 2-3 minutes. The effect of THAPS (3 x 10(-6) M) was substantial with [Ca2+]i, rising from 281 +/- 27 nM at 0.5 mM Ca2+ to a peak value of 684 +/- 30 nM (p < 0.0001). The addition of Sr2+ to cells at 0.5 mM extracellular Ca2+ induced an immediate 2- to 3-fold increase in [Ca2+]i which stabilized at a [Ca2+]i above baseline for > or = 10 minutes. THAPS (3 x 10(-6) M) pretreatment for > or = 5 minutes blocked this sustained-phase increment in [Ca2+]i due to Sr2+. In the absence of extracellular Ca2+, there was a slight but nonsignificant effect of THAPS on [Ca2+]i. Incubation of cells with THAPS did not change the levels of 3H-inositol phosphates (InsP3, InsP2, and InsP1) or alter Sr(2+)-induced accumulation of InsP3, InsP2, and InsP1.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗

PubMed1995

Oxytocin induced a biphasic increase in the intracellular Ca2+ concentration of porcine myometrial cells: participation of a pertussis toxin-insensitive G-protein, inositol 1,4,5-trisphosphate-sensitive Ca2+ pool, and Ca2+ channels.

This study investigated the underlying mechanisms of oxytocin (OT)-induced increases in intracellular Ca2+ concentrations ([Ca2+]i) in acutely dispersed myometrial cells from prepartum sows. A dose-dependent increase in [Ca2+]i was induced by OT (0.1 nM to 1 microM) in the presence and absence of extracellular Ca2+ ([Ca2+]e). [Ca2+]i was elevated by OT in a biphasic pattern, with a spike followed by a sustained plateau in the presence of [Ca2+]e. However, in the absence of [Ca2+]e, the [Ca2+]i response to OT became monophasic with a lower amplitude and no plateau, and this monophasic increase was abolished by pretreatment with ionomycin, a Ca2+ ionophore. Administration of OT (1 microM) for 15 sec increased inositol 1,4,5-trisphosphate (IP3) formation by 61%. Pretreatment with pertussis toxin (PTX, 1 microgram/ml) for 2 hr failed to alter the OT-induced increase in [Ca2+]i and IP3 formation. U-73122 (30 nM to 3 microM), a phospholipase C (PLC) inhibitor, depressed the rise in [Ca2+]i by OT dose dependently. U-73122 (3 microM) also abolished the OT-induced IP3 formation. Thapsigargin (2 microM), an inhibitor of Ca(2+)-ATPase in the endoplasmic reticulum, did not increase [Ca2+]i. However, it did time-dependently inhibit the OT-induced increase in [Ca2+]i. Nimodipine (1 microM), a voltage-dependent Ca2+ channel (VDCC) blocker, inhibited the OT-induced plateau by 26%. La3+ (1 mM), a nonspecific Ca2+ channel blocker, abrogated the OT-induced plateau. In whole-cell patch-clamp studies used to evaluate VDCC activities, OT (0.1 microM) increased Ca2+ current (ICa) by 40% with no apparent changes in the current-voltage relationship.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

Expression of three osmotin-like protein genes in response to osmotic stress and fungal infection in potato.

We have characterized three cDNAs encoding osmotin-like proteins from potato (Solanum commersonii) cell cultures. These cDNAs (pA13, pA35, and pA81) have extensive nucleotide identity in the coding regions but low homology in the 3' non-coding sequences, and may encode three isoforms of potato pathogenesis-related (PR) type 5 proteins. Using gene-specific probes, RNA gel blot analyses showed constitutive accumulation of osmotin-like protein mRNAs in cell cultures, leaves, stems, roots and flowers, with high abundance in the roots and mature flowers. Treatments with abscisic acid (ABA), low temperature, and NaCl increased the accumulation of all three mRNAs in S. commersonii cell cultures and plants grown in vitro. Salicylic acid (SA), and wounding resulted in a moderate increase in the levels of pA13 and pA81 but not pA35 mRNAs. Infection with the fungus Phytophthora infestans activated strong and non-systemic expression of all three osmotin-like protein genes. The accumulation of osmotin-like proteins, however, was detected only in P. infestans-infected tissues but not in plants treated with ABA, SA, NaCl, low temperature, or wounding.

Adaptation, Biological↗