PubMed Health⌕ Search

Biomedical subjects

S T Chen

Publications and source records attributed to S T Chen.

At least 55 records · Page 3Linked to original sources
PubMed1999

Differential expression of beta-amyloid precursor and Bcl-2 proto-oncogene proteins in the developing dog retina.

Previous studies of rat retinas have not only provided evidence that beta-amyloid precursor (APP) and B-cell lymphoma proto-oncogene (Bcl-2) proteins are colocalized in retinal Müller glial cells, but have also indicated that common mechanisms regulate their expression in these cells (Chen, S.T., Garey, L.J., Jen, L.S., 1994. Bcl-2 proto-oncogene protein immunoreactivity in normally developing and axotomised rat retinas. Neurosci. Lett. 172, 11 14; Chen, S.T., Gentleman, S.M., Garey, L.J., Jen, L.S., 1996. Distribution of beta-amyloid precursor and B-cell lymphoma proto-oncogene proteins in the rat retina after optic nerve transection or vascular lesion. J. Neuropathol. Exp. Neurol. 55, 1073-1082; Chen, S.T., Garey, L.J., Jen, L.S., 1997. Expression of beta-amyloid precursor protein immunoreactivity in the retina of the rat during normal development and after neonatal optic tract lesion. NeuroReport 8, 713-717). This investigation attempts to resolve whether or not the pattern observed in rats also applies to other higher mammalian species by examining the expression of immunoreactivity to APP and Bcl-2 in developing as well as mature dog retinas using immunocytochemical methods. Experimental results indicate that the immunoreactivity of both APP and Bcl-2 is located primarily in the inner retina, particularly in the ganglion cells and their axons in late fetal and neonatal stages. From the second postnatal week (the time of eye opening) onwards, immunoreactivity to APP, but not Bcl-2, is localized primarily in the endfeet and proximal part of the radial process of retinal Müller glial cells. Although the findings show both APP and Bcl-2 are expressed in ganglion cells and their processes suggest that the molecules have a role in the differentiation of neurons in the central nervous tissue, the lack of Bcl-2 in the Müller glial cells in dog retinas further suggests that the two molecules may have different biological roles with respect to glial function.

Amyloid beta-Protein Precursor↗
PubMed1999

Effects of bFGF and TGFbeta on the expression of amyloid precursor and B-cell lymphoma protooncogene proteins in the rat retina.

The pattern of immunoreactivity for amyloid precursor (APP) and B-cell lymphoma protooncogene (Bcl-2) proteins in the rat retina was studied after intravitreal injection of basic fibroblast growth factor (bFGF) or transforming growth factor-beta (TGFbeta). In normal control retinas, intense immunostaining of APP and Bcl-2 was observed primarily in the endfeet and proximal part of radial processes of Müller glial cells. A dose-dependent reduction in immunostaining of APP and Bcl-2 in Müller cells was observed after injection of bFGF and TGFbeta. These results provide the first evidence that APP and Bcl-2 can be down-regulated by cytokines in vivo.

Amyloid beta-Protein Precursor↗
PubMed1999

Thoracic disc herniation mimicking acute lumbar disc disease.

STUDY DESIGN: Case report of a 49-year-old woman with a lower thoracic disc herniation mimicking acute lumbosacral radiculopathy. OBJECTIVE: To describe an unusual case of thoracic disc herniation mimicking acute lumbar disc disease. SUMMARY OF BACKGROUND DATA: Symptomatic thoracic disc herniation is rare and its clinical manifestations differ widely from those of cervical and lumbar disc herniations. Midline back pain and signs of spinal cord compression progressing over months or years are the predominant clinical features. Acute and subacute thoracic disc herniation occurs in less than 10% of patients, and isolated root pain is unusual. METHODS: A 49-year-old woman had acute low back pain radiation into the left buttock and the lateral aspect of the left leg and left foot. Magnetic resonance imaging study showed a bulging disc and posterior osteophytes at T11-T12. RESULTS: Surgical removal of the herniated disc and osteophytes rapidly relieved her symptoms and neurologic deficits. A follow-up neurologic examination 3 years later showed normal motor and sensory functions, although low back soreness was noted occasionally. CONCLUSION: A case of thoracic disc herniation mimicking an acute lumbosacral radiculopathy is presented. Compression of the lumbosacral spinal nerve roots at the lower thoracic level after exit from the lumbar enlargement may be the mechanism for this unusual presentation.

Acute Disease↗
PubMed1999

Current perception threshold testing in Fabry's disease.

We investigated 16 patients with Fabry's disease (eight hemizygous men and eight heterozygous women) in one family. We used constant current perception threshold (CPT) testing, which evaluated three major sensory nerve fiber populations, to assess subjective complaints of pain and paresthesias. We also examined clinical and biochemical features and compared the values of CPTs and nerve conduction studies (NCS) in detecting the sensory neuropathy. Our results showed that CPT testing at low frequencies (5 and 250 Hz) was significantly more sensitive than at a higher frequency (2 kHz) and NCS in detecting sensory neuropathy in patients with Fabry's disease. However, there was no correlation between CPT testing and clinical symptom scores, duration of disease, creatinine clearance (Ccr) values or alpha-galactosidase A (AGA) activities in either hemizygous or heterozygous patients. Hemizygous patients clinically demonstrated more severe symptom scores, poorer renal function, and higher prevalence of hypohidrosis and corpora angiokeratomas than did heterozygous patients, which indicates that detailed clinical examinations can differentiate the clinical status of hemizygous men from heterozygous women. There were no associations between the biochemical levels of serum AGA activity and renal function (Ccr values) or the symptom scores (grading of acroparesthesia), indicating that biochemical parameters do not predict clinical severity.

Adolescent↗
PubMed1999

The antioxidant melatonin reduces cortical neuronal death after intrastriatal injection of kainate in the rat.

The anti-excitotoxic efficacy of the pineal hormone melatonin was investigated in kainate-injured brains of rats. Kainate (a glutamate-receptor agonist, 2.5 nmol in 1 microl) was directly injected to unilateral striatum. Melatonin (10 mg/kg) was administrated intraperitoneally 1 h before and 1, 3, and 5 h after intrastriatal kainate injection in adult Sprague-Dawley rats. Three days after kainate injection, a significant neuronal damage was found, as determined by Nissl staining and the TUNEL method, not only in the injected striatum, but also in the ipsilateral neighboring cortex. The kainate-induced cortical apoptotic neuronal death was significantly attenuated by treatment with melatonin compared with the vehicle control group. However, no detectable changes were observed in the contralateral side of the brain in either vehicle- or melatonin-treated rats. Moreover, the biochemical results indicated that kainate can indeed induce oxidative stress, such as a decrease in the content of total glutathione (GSH), oxidized glutathione (GSSG), and an increase in the ratio of GSSG/GSH in the striatum and cortex compared with the contralateral brain regions. In the kainate-injected striatum, melatonin did not reduce the oxidative stress, but in the neighborhood of injected area-cortex, kainate-induced oxidative stress was significantly reduced by melatonin. Enhancement of glutathione-peroxidase activity was induced by intrastriatal kainate injection, not only in the cortical area of control and melatonin-treated rats, but also in striatum of control rats. However, a large elevation was found in the melatonin-treated cortex. Taking the morphological and biochemical data together, the present results suggest that melatonin functions as an antioxidant by upregulating the glutathione antioxidative defense system, thereby reducing neuronal death caused by excitotoxicity and preventing the kainate-induced damage from spreading to adjacent brain regions.

Animals↗
PubMed1999

Expression of beta-amyloid precursor and Bcl-2 proto-oncogene proteins in rat retinas after intravitreal injection of aminoadipic acid.

In order to investigate the role of glia in relation to factors that affect the expression of beta-amyloid precursor protein (betaAPP) and B cell lymphoma oncogene protein (Bcl-2) in the central nervous tissue, the patterns of expression of betaAPP and Bcl-2 in developing and mature rat retinas were studied immunocytochemically after intravitreal injection of alpha-aminoadipic acid (alpha-AAA), a glutamate analogue and gliotoxin that is known to cause injury of retinal Müller glial cells. In normal developing retinas, betaAPP and Bcl-2 were expressed primarily but transiently in a small number of neurons in the ganglion cell layer during the first postnatal week. Immunoreactivity of betaAPP and Bcl-2 appeared in the endfeet and proximal part of the radial processes of Müller glial cells from the second postnatal week onwards. In rats that received intravitreal injection of alpha-AAA at birth, there was a loss of immunoreactivity to vimentin, and a delayed expressed on betaAPP or Bcl-2 in Muller glial cells until 3-5 weeks post-injection. Immunoreactive neurons were also observed in the inner retina especially in the ganglion cell layer from 5 to 35 days after injection. A significant reduction in numerical density of cells with large somata in the ganglion cell layer was observed in the neonatally injected retinas at P56, which was accompanied by an increased immunostaining in radial processes of Müller glial cells. In contrast, no detectable changes in the expression of betaAPP and Bcl-2 were observed in retina that received alpha-AAA as adults. These results indicate that the gliotoxin alpha-AAA has long lasting effects on the expression of betaAPP and Bcl-2 in Müller glial cells as well as neurons in the developing but not mature retinas. The loss of vimentin and delayed expression of betaAPP and Bcl-2 in developing Müller glial cells suggests that the metabolic integrity of Müller cells was temporarily compromised, which may have adverse effects on developing neurons that are vulnerable or dependent on trophic support from the Müller glial cells.

2-Aminoadipic Acid↗
PubMed1999

Effect of NGF and anti-NGF on neuropathic pain in rats following chronic constriction injury of the sciatic nerve.

The systemic administration of anti-nerve growth factor (NGF) antibodies can prevent local sensory hypersensitivity and block nociceptive fibers from sprouting into denervated adult rat skin. However, in the case of chronic constriction injury (CCI) in a rat, there is evidence that NGF reverses some effects of axotomy and alleviates thermal hyperalgesia. It is with this in mind that we investigated the influence of local anti-NGF and NGF on neuropathic pain and collateral sprouting caused by CCI. In our study, we looked at the effects to the ligated nerves after 30 consecutive days of local injections of anti-NGF and NGF. A high-dose of anti-NGF (1800 ng) was found to eradicate heat and cold hyperalgesia during postoperative days 16-28 and from days 8 to 34 after CCI, respectively. Our results show that a low-dose anti-NGF (18 ng) only mildly alleviates heat hyperalgesia but not cold hyperalgesia. There is evidence that a rebound phenomenon occurs for a short period of time after the anti-NGF injections cease. Results show that anti-NGF injections, whether in a high or low dose, significantly reduces the severity of autotomy or prevents the spread of collateral sprouting from the saphenous nerve into the sciatic innervation territory. In contrast, when a NGF (0.75 ng/g body weight) was applied to the ligated nerve immediately after the ligation, heat and cold hyperalgesia were eradicated during postoperative days 4-68 and from days 4 to 28, respectively. The results show that the effect of anti-NGF is delayed at the onset, is short in duration, and is dependent on the dosage. However, anti-NGF but not NGF blocked collateral sprouting and decreased the severity of autotomy, suggesting that anti-NGF may be a better potential alternative analgesic for the treatment of neuropathic pain in humans. The different initiation times to abolish thermal hyperalgesia by anti-NGF (delayed onset) and NGF (early onset) suggests that alterations in neurotrophic factors contribute to the development of behavioral hyperalgesia via a complex mechanism in CCI rats.

Animals↗
PubMed1999

Direct solid-phase synthesis of octreotide conjugates: precursors for use as tumor-targeted radiopharmaceuticals.

Somatostatin analogues, such as octreotide, are useful for the visualization and treatment of tumors. Unfortunately, these compounds were produced synthetically using complex and inefficient procedures. Here, we describe a novel approach for the synthesis of octreotide and its analogues using p-carboxybenzaldehyde to anchor Fmoc-threoninol to solid phase resins. The reaction of the two hydroxyl groups of Fmoc-threoninol with p-carboxybenzaldehyde was catalyzed with p-toluenesulphonic acid in chloroform using a Dean-Stark apparatus to form Fmoc-threoninol p-carboxybenzacetal in 91% yield. The Fmoc-threoninol p-carboxybenzacetal acted as an Fmoc-amino acid derivative and the carboxyl group of Fmoc-threoninol p-carboxybenzacetal was coupled to an amine-resin via a DCC coupling reaction. The synthesis of protected octreotide and its conjugates were carried out in their entirety using a conventional Fmoc protocol and an autosynthesizer. The acetal was stable during the stepwise elongation of each Fmoc-amino acid as shown by the averaged coupling yield (> 95%). Octreotide (74 to 78% yield) and five conjugated derivatives were synthesized with high yields using this procedure, including three radiotherapy octreotides (62 to 75% yield) and two cellular markers (72 to 76% yield). This novel approach provides a strategy for the rapid and efficient large-scale synthesis of octreotide and its analogues for radiopharmaceutical and tagged conjugates.

Amino Acid Sequence↗
PubMed1999

Mutation analysis of the putative tumor suppression gene PTEN/MMAC1 in sporadic breast cancer.

PTEN/MMAC1, a potential human tumor suppressor gene, has been found to have inactivating mutations in several types of cancer, including breast cancer. The incidence of breast cancer in Chinese is quite low in comparison with Caucasians, and genetic factors may play some roles. To further determine the role of PTEN/MMAC1 in breast cancer in Chinese, we used loss of heterozygosity (LOH), single strand conformation polymorphism (SSCP) with direct sequencing of variant bands, and Southern blot analysis methods to analyze mutations in PTEN/MMAC1 in 52 cases of breast cancer. None had LOH at chromosome 10q23.3. One mutation was identified, a somatic 3-base deletion, in one case. Our results suggest PTEN/MMAC1 does not play a major role in the development of sporadic breast cancer.

Adult↗
PubMed1999

NADPH-diaphorase activity in normally developing and intracranially transplanted retinas.

The activity and distribution of nicotinamide dinucleotide phosphate diaphorase (NADPH-d), an enzyme that is widely distributed in the central nervous system and involved in the production of the free radical nitric oxide, were investigated histochemically in the normal developing and intracranially transplanted retinas. In the normal rat retina, NADPH-d activity was first detected in cells in the ganglion cells layer (GCL) and blood vessels on the first postnatal day (P0). A small but distinct population of NADPH-d positive cells were observed along the inner border of the inner nuclear layer at P7. NADPH-d positive sublaminae began to appear in the inner plexiform layer during the second postnatal week, and several strongly reactive sublaminae resembling those observed in the adult were observed by the fourth postnatal week. The overall spatio- temporal sequence of development of NADPH-d positive cells in the transplanted retina was similar to that of the normal retina, except a lack of reactive in the inner plexiform layer in more mature transplants as compared with normal retinas of corresponding ages. These results indicate that the time course of development and distribution of NADPH-d cells in early postnatal retina requires signals mainly of intraretinal origin and is independent of influence from the surroundings. While this finding is supportive to the notion that neurons that are rich in NADPH-d are resistant to injury or perturbation, the observation of a lack of well organized NADPH-d reactive sublaminae in the inner plexiform layer in older transplants suggests a possible alteration in the synaptic circuitry in the inner retina with increasing postgrafting survival time.

Animals↗
PubMed1999

Olfactory function in patients with nasopharyngeal carcinoma following radiotherapy.

The aim of this study was to examine the impact of radiation treatment on olfactory function in patients with nasopharyngeal carcinoma (NPC). An olfactory function test battery was administered to 25 adult NPC patients having received radiotherapy, 24 adult nasopharyngeal carcinoma patients awaiting to receive radiation treatment, and 36 adult normal control subjects. Members of the three groups were matched in terms of age, educational level, and full-scaled IQ score. Comparing the test results revealed that the NPC patients with radiotherapy had olfactory information processing impairments including absolute threshold, odour-tactile cross-modality matching, verbal identification of odours, and recall and recognition of identity of odours. The deficits of suprathreshold olfactory functioning in these patients did not seem to arise from impaired absolute threshold sensitivity. Provided that the results are reproducible, an evaluation of olfactory functioning in NPC patients during the period of radiotherapy may be useful for detecting or even avoiding side effects of radiation.

Adult↗
PubMed1999

Acute bacterial meningitis in adults: a hospital-based epidemiological study.

Bacterial meningitis, a world-wide disease, has to be reviewed periodically because the specific micro-organisms responsible for the infection vary with time, geography and patient age. To determine its incidence and clinical features in Taiwan, we reviewed the microbiological records for cerebrospinal fluid (CSF) and blood cultures, and the medical records of patients with bacterial meningitis admitted between 1981 and mid-1998. Bacterial micro-organisms were demonstrated in the CSF and/or blood in 395 patients with 418 episodes of bacterial meningitis. Streptococcus species were the most common causative micro-organism group, at 23. 21% of all episodes. Its prevalence rate significantly decreased from the first 7 years of study (41.9%) to the last 10.5 years (19. 2%). However, Klebsiella meningitis and Staphylococcal meningitis were more frequently noted after 1987. More than 70% of patients had at least one underlying disease or condition. Poor prognostic factors indicated by univariable analysis were: age >60 years; diabetes mellitus; severe neurological deficits on the first day of treatment; infection with Gram-negative bacilli; CSF WBC count >5000x10(6)/l; malignancy; seizure; and bacteraemia. The overall mortality rate was 29.4%, 29.7% in the first 7 years of study and 29. 4% in the last 10.5 years. The use of new antibiotics has not reduced the mortality rate in our patients with bacterial meningitis.

Acute Disease↗
PubMed1999

A double-blind placebo controlled trial of oral midazolam as premedication before flexible sigmoidoscopy.

OBJECTIVE: We aimed to determine the efficacy of oral midazolam as premedication to improve tolerance of flexible sigmoidoscopy. METHODS: Ninety-nine patients were randomized to receive 7.5 mg of oral midazolam solution mixed with apple juice or placebo (apple juice), 20 min before sigmoidoscopy. Patients' anxiety and pain experienced before sedation, before the procedure, and during the procedure were assessed using a 10-cm visual analog scale (VAS) by both patients and physicians (0 = no pain, anxiety, 10 = severe pain, anxiety). Extent of sedation, amnesia, overall tolerance, adequacy of sedation, and willingness to repeat the procedure were assessed, and changes in vital signs and oximetries were recorded. RESULTS: Fifty-one patients received midazolam and 48 patients received placebo. Patients reported less pain and anxiety (VAS 2.56, 1.64) compared with placebo (VAS 4.62, 4.16) during the procedure (p < 0.005, p < 0.0005). Physicians observed less pain and anxiety (VAS 2.19, 1.52) with midazolam than placebo (VAS 5.00, 3.97) during the procedure (p < 0.0001, p < 0.0001). A significantly greater number of patients judged tolerance of the procedure to be "excellent" using midazolam (p < 0.005) compared with placebo. A majority of patients in both groups was willing to repeat the procedure if recommended. Two patients in the midazolam group had transient asymptomatic hypotension during sigmoidoscopy, but no patients were observed to have desaturation by oximetry. CONCLUSIONS: Oral midazolam significantly reduces anxiety and pain during flexible sigmoidoscopy as assessed by both patients and physicians. Oral midazolam is a safe and effective premedication before flexible sigmoidoscopy in patients who require or prefer sedation.

Administration, Oral↗
PubMed1999

Requirements for efficient production and transduction of human immunodeficiency virus type 1-based vectors.

A number of human immunodeficiency type 1 (HIV-1)-based vectors have recently been shown to transduce nondividing cells in vivo as well as in vitro. However, if these vectors are to be considered for eventual clinical use, a major consideration is to reduce the probability of unintended generation of replication-competent virus. This can be achieved by eliminating viral genetic elements involved in the generation of replication-competent virus without impairing vector production. We have designed a system to transiently produce HIV-1-based vectors by using expression plasmids encoding Gag, Pol, and Tat of HIV-1 under the control of the cytomegalovirus immediate-early promoter. Our data show that the best vector yield is achieved in the presence of the Rev/Rev-responsive element (RRE) system. However, the constitutive transport element of Mason-Pfizer monkey virus can substitute for RRE and Rev at least to some extent, whereas the posttranscriptional regulatory element of human hepatitis B virus appeared to be inefficient. In addition, we show that high-titer virus preparations can be obtained in the presence of sodium butyrate, which activates the expression of both the packaging construct and the vector genome. Finally, our results suggest that efficient infectivity of vectors defective in the accessory proteins Vif, Vpr, Vpu, and Nef depends on the nature of the target cells.

Butyric Acid↗
PubMed1999

Memory self-appraisal in middle-aged and older adults with the apolipoprotein E-4 allele.

OBJECTIVE: Because subjective memory complaints may indicate subtle functional brain abnormalities, the authors studied the influence of the major genetic risk for Alzheimer's disease, the apolipoprotein E-4 (APOE-4) allele, on self-reports of memory performance in middle-aged and older adults. METHOD: Subjective and objective assessments of memory performance were compared in relation to the presence or absence of the APOE-4 allele in 39 cognitively intact persons with mild memory complaints. RESULTS: Subjects with the APOE-4 allele had lower scores on objective verbal memory and on the subjective memory measure for retrospective functioning. Among the subjects in the age range where APOE-4 has its greatest influence on the risk of Alzheimer's disease (55-74 years), the APOE-4 group had lower scores on the subjective memory measure for frequency of forgetting. Moreover, the standardized difference in retrospective functioning scores between the two genetic risk groups increased when the mid-age-range group was examined rather than the whole study group. CONCLUSIONS: The APOE-4 allele is associated with increased subjective memory impairment in middle-aged and older adults. Longitudinal studies of age-related memory loss should include genetic risk and subjective memory measures as potential predictors of decline.

Adult↗
PubMed1999

Efficacy of lithium vs. valproate in the treatment of mania in the elderly: a retrospective study.

BACKGROUND: This retrospective study was conducted to assess the efficacy of lithium and valproate and associated serum levels in the treatment of mania in elderly patients. METHOD: Records of 59 patients aged 55 years and older with minimal or no neurologic impairment, hospitalized for mania, and discharged on lithium (N = 30) or valproate (N = 29) therapy were reviewed. Data on mood stabilizer choice, serum levels, and type of mania were recorded. A clinician blinded to medications rated improvement in each case with Clinical Global Impressions (CGI) scores based on abstracted notes. RESULTS: Overall, the percentage of patients improved was significantly greater in the lithium group than in the valproate group (67% vs. 38%, chi2 = 4.88, p = .027). Patients taking lithium with serum levels > or =0.8 mmol/L were more improved at discharge than those outside this range (> or =0.8, CGI 2.0+/-0.6 vs. <0.8, CGI 2.6+/-0.8, t = 2.15, p = .043). Patients taking valproate with serum levels between 65-90 microg/mL were more improved at discharge than those outside this range (65-90, CGI 2.1+/-0.6 vs. <65, >90, CGI 3.3+/-0.8, t = 3.73, p = .002). When response rates among only patients with these "therapeutic" levels were assessed, they were similar for lithium (82%) and valproate (75%). The difference in efficacy between drugs was maintained in classic mania, but the 2 drug groups were similar when only mixed mania was analyzed (lithium 63% vs. valproate 67% improved). CONCLUSION: Results suggest that lithium may be more efficacious than valproate overall, but response rates for the 2 drugs were similar when "therapeutic" serum levels were achieved. For lithium, levels similar to those reported for younger adults were associated with response. For valproate, a "therapeutic window" different from that in younger adults was found. While the retrospective and naturalistic design of this study has limitations, these data may help direct further studies and treatment of mania in the elderly.

Age Factors↗
PubMed1999

Protein gene product 9.5-immunoreactive neurons in the retina of striped dolphin (Stenella coeruleoalba) and Fraser dolphin (Lagenodelphis hosei).

This study demonstrates immunocytochemically that protein gene product 9.5 (PGP 9.5), a neuronal marker, is expressed by various populations of retinal cells in Stenella coeruleoalba (striped dolphin) and Lagenodelphis hosei (Fraser dolphin): one in the retinal ganglion cells and the other in the inner nuclear layer, resembling horizontal and amacrine cells. The specific distribution of PGP 9.5 in a dolphin closely resembles that in rodents and carnivores; however, some differences arise among these animals. In a dolphin's retina, for example, only a few of giant ganglion cells are immunoreacted while almost all the small ganglion cells are stained strongly. The processes of horizontal cells, identified according to their localization, appear not to connect entirely in a dolphin. Instead, PGP 9.5 positive cells are widely distributed in the small to moderate ganglion cells and have distinct processes which are ramified extensively in the outer plexiform layer in rodents and carnivores. The high levels of PGP 9.5 expressing in the inner part of dolphin retina, including ganglion cells and their axons as well as distinct sublamination in the inner plexiform layer, indicate that this molecule markedly influences the retinal system, possibly in visual connection. Although mammals have various visual behavior, i.e., living marine vs. terrestrial environment, and active during daytime vs. in the night, the retina is a common model to characterize the neurochemical properties.

Adaptation, Ocular↗